Title of Invention	PROCESS AND EQUIPMENT FOR THE RECOVERY OF VALUABLE PRODUCTS FROM LEACH LIQUOR
Abstract	A process for the recovery of valuable products from leach liquor, namely yellow iron oxide pigment ammonia and calcium chloride. Leach liquor is reacted with iron to convert free hydrochloric acid and ferric chloride in the leach liquor to ferrous chloride. The impurities in the leach liquor are precipitated by treating the leach liquor with an aqueous ammonia solution containing 8-12%ammonia at a pH of 2.5 to 5 under agitation. The precipitated impurities are flocculated by treating the leach liquor with a flocculating agent and separated from the leach liquor to obtain a purified ferrous chloride solution. The pH of the ferrous chloride solution is optionally adjusted between 1.5 to 2 by treatment with hydrochloric acid. The ferrous chloride solution containing a ferrous iron (Fe++) concentration of 2.0 to 4.0% is reacted with an aqueous solution of ammonia containing 8-12% ammonia in the presence of 8-15% ammonium chloride and chilled water under agitation to convert ferrous chloride to ferrous hydroxide. The ferrous hydroxide is oxidized with air at a temperature between 18-35°C and a pH between 3 to 5 to form hydrated ferric oxide pigment seeds (yellow pigment seeds) which are further oxidized with oxygen mixed with steam in the presence of an aqueous ammonia solution containing 8-12% ammonia at 60-85°C under agitation and at pH at 3 to 5 to allow the seeds to grow to the require size. The pigment slurry is filtered to separate the pigment cake from the mother liquor containing ammonium chloride. The pigment cake is washed with water, dried and pulverized. Ammonia and calcium chloride in the mother liquor are also recovered. Also an equipment for the recovery of the valuable products.

Title of Invention

PROCESS AND EQUIPMENT FOR THE RECOVERY OF VALUABLE PRODUCTS FROM LEACH LIQUOR

Abstract

A process for the recovery of valuable products from leach liquor, namely yellow iron oxide pigment ammonia and calcium chloride. Leach liquor is reacted with iron to convert free hydrochloric acid and ferric chloride in the leach liquor to ferrous chloride. The impurities in the leach liquor are precipitated by treating the leach liquor with an aqueous ammonia solution containing 8-12%ammonia at a pH of 2.5 to 5 under agitation. The precipitated impurities are flocculated by treating the leach liquor with a flocculating agent and separated from the leach liquor to obtain a purified ferrous chloride solution. The pH of the ferrous chloride solution is optionally adjusted between 1.5 to 2 by treatment with hydrochloric acid. The ferrous chloride solution containing a ferrous iron (Fe++) concentration of 2.0 to 4.0% is reacted with an aqueous solution of ammonia containing 8-12% ammonia in the presence of 8-15% ammonium chloride and chilled water under agitation to convert ferrous chloride to ferrous hydroxide. The ferrous hydroxide is oxidized with air at a temperature between 18-35°C and a pH between 3 to 5 to form hydrated ferric oxide pigment seeds (yellow pigment seeds) which are further oxidized with oxygen mixed with steam in the presence of an aqueous ammonia solution containing 8-12% ammonia at 60-85°C under agitation and at pH at 3 to 5 to allow the seeds to grow to the require size. The pigment slurry is filtered to separate the pigment cake from the mother liquor containing ammonium chloride. The pigment cake is washed with water, dried and pulverized. Ammonia and calcium chloride in the mother liquor are also recovered. Also an equipment for the recovery of the valuable products.

Full Text	FORM 2 THE PATENTS ACT, 1970 (39 of 1970) As amended by the Patents (Amendment) Act, 2005 & The Patents Rules, 2003 As amended by the Patents (Amendment) Rules, 2006 COMPLETE SPECIFICATION (See section 10 and rule 13) TITLE OF THE INVENTION Process and equipment for the recovery of valuable products from leach liquor INVENTOR Name : Yadav Baburam Nationality : Indian National Address : DCW Limited, Sahupuram 628 229, Thoothukudi Dist, Tamil Nadu, India APPLICANTS Name : DCW LIMITED Nationality : Indian Company Address : Nirmal, 3rd Foor, Nariman Point, Mumbai 400 021,Maharashtra, India PREAMBLE TO THE DESCRIPTION The following specification parTiCl4larly describes the nature of this invention and the manner in which it is to be performed: TECHNICAL FIELD OF INVENTION This invention relates to a process and equipment for the recovery of valuable products from leach liquor. The valuable products recovered from leach liquor according to the invention are yellow iron oxide pigment, ammonia and calcium chloride. BACKGROUND OF THE INVENTION Several processes are known and reported for the manufacture of yellow iron oxide pigment having a goethite crystalline structure, also known as alpha ferric oxide hydrate (alpha Fe OOH or a Fe203. H2O), the oldest being the Penniman - Zoph process (US 1327061, 1368748, 5032180 and 5076848). Ferrous sulphate solution is reacted with sodium hydroxide to precipitate alpha-FeOOH seeds (nuclei). On oxidizing the ferrous sulphate solution containing the nuclei and scrap iron immersed in it, with air mixed with steam, hydrated ferric oxide gets deposited on the nuclei. Crystal growth is allowed to continue until the desired colour is achieved. Martin process also known as precipitation process as taught in US 2939767 comprises passing free oxygen containing gas through ferrous salt solution containing alpha -FeOOH seeds. Ferric oxide formed is hydrolysed with evolution of hydrogen ions which are neutralized and oxidised with ammonia premixed with the free oxygen containing gas. In order to economize the process, ferrous sulphate formed as a byproduct in the manufacture of titanium dioxide by the sulphate process is used. 2 US 6042642 relates to iron oxide yellow pigments prepared by intensively admixing an alkaline component to an acidic 50 - 450 g/1 FeCl2 solution to adjust the pH of the solution between 3 and 5. A flocculation aid is optionally added to the FeCl2 solution before, after or concurrent with the addition of the alkaline component and the solution is optionally exposed to oxidation. The solution, after separation of the solids, is added to an a-FeOOH nuclei suspension produced by the precipitation process. The suspension is heated to 30 to 95°C with thorough mixing and oxidized while increasing the pH 3.0 to 5.0 by adding alkaline component. The oxidation is optionally continued while maintaining the pH at a constant between 3.0 and 5.0. The oxidation is stopped when the Fe(II) content of the suspension is less than 1 mole % and the oxide yellow pigment is separated, washed, dried and ground. US 6179908B1 describes iron oxide red pigments produced by calcining iron oxide yellow pigments or iron oxide black pigments. The iron oxide yellow pigments are prepared from ferrous chloride by treating it with an alkali to adjust the pH between 3 and 5. The solution is flocculated and oxidized optionally and the solid formed is separated from the solution. The solution is then added to an a- or b-FeOOH seed suspension produced by the precipitation process. The suspension formed is heated to 30 to 95°C and oxidized with air and at the same time the pH is adjusted to 3.0 to 5.0 with an alkali. The oxidation is stopped as soon as the ferrous content of the suspension is less than 1 mole %. The solid formed is separated, washed, dried and ground. In order to render the process economical, the ferrous chloride used is obtained from steel pickling industry or from plants manufacturing TiO2 using the chloride process. In the chloride process, titanium rich feed stocks like natural rutile, leucoxene minerals or upgraded ilmenite like synthetic rutile or titanium slag is chlorinated with chlorine gas in a 3 fluidized bed reactor to make titanium tetra chloride (TICI4). The iron content in the feed stock (2.0 - 6.0%) also gets chlorinated to form ferrous chloride in the fluidized bed reactor along with titanium tetra chloride. Ferrous chloride is separated from TiC14 by condensation. TiCl4 is oxidised to form the pigments. US 5916360 relates to preparation of yellow iron oxide from ferrous chloride solution containing at least one organic aliphatic amine in the ratio of organic carbon to ferrous chloride about 0.05 mg/g to about 0.5 mg/g. The iron (11) compound is precipitated in about 30% to about 80% with an alkali followed by oxidation. US 6689206 describes preparation of yellow iron oxide by adding precipitated ferrous chloride solution to alpha-FeOOH seeds produced by the alkaline process. The suspension is then oxidised in two stages with continuous addition of alkali. US 6530987B1 describes a process for the preparation of iron oxide pigment from the waste acid resulting from the preparation of titanium dioxide by the sulfate process. The sulfuric acid contained in the waste acid is partially neutralized with metallic iron and/or an iron compound having a manganese content of US 6534032B2 describes a process for the production of yellow iron oxide comprising adding an iron component comprising FeSO4 or FeCl2 with an Fe (III) content of 0.5 to 1.5 mol % Fe (III) 4 and a Mn content of up to 0.7 wt. %, based on the Fe content of FeSO4 or FeCl2, to a solution or suspension of an alkaline component that has been heated between 42 and 75°C and oxidizing the suspension formed with an oxidizing agent at 42 to 75°C until all iron (II) has been converted into iron (III) as a-FeOOH. US 2005/0045066 Al relates to iron oxide pigment prepared by precipitation method from iron (11) chloride or iron (11) sulphate and calcium carbonate precipitant. Use of calcium carbonate leads to contamination of the pigment with calcium carbonate. Leach liquor (containing ferrous and ferric chlorides and residual hydrochloric acid) is a waste from synthetic rutile plant formed during leaching out of iron from ilmenite ore using hydrochloric acid. Leach liquor is also contaminated with several of the metallic impurities present in the ilmenite ore such as oxides of aluminium, silica, chromium, vanadium, manganese, calcium, magnesium, sodium, potassium, zirconium or titanium. Leach liquor is generally used for regeneration of hydrochloric acid in about 16-18% concentration by hydrothermal decomposition of the ferrous and ferric chloride in a spray roaster. Iron oxide contaminated with the impurities present in the leach liquor, is left behind and is a waste creating disposal and environmental problems. Preparation of yellow iron oxide pigment using the ferrous chloride and ferrous sulfate routes involves precipitation of ferrous hydroxide with alkali. Depending upon the alkalis generally used, this generates ammonium chloride and sodium chloride or ammonium sulphate and sodium sulphate which are normally disposed of creating waste disposal and environmental problems. Due to the presence of ferric chloride and hydrochloric acid and also the impurities, leach liquor 5 cannot be directly used for making yellow iron oxide pigment. Presence of the impurities and ferric chloride will reduce the colour quality of the pigment from yellow to redish. Excess alkali also will be required to neutralise the acid. OBJECTS OF INVENTION An object of the invention is to provide a process for the recovery of valuable products from leach liquor namely yellow iron oxide pigment, ammonia and calcium chloride, thereby practically converting the entire waste leach liquor into useful and valuable products and eliminating waste disposal and environmental problems and realizing economy. Another object of the invention is to provide an equipment for the recovery of valuable products from leach liquor namely yellow iron oxide pigment, ammonia and calcium chloride, thereby practically converting the entire waste leach liquor into useful and valuable products and eliminating waste disposal and environmental problems and realizing economy. DETAILED DESCRIPTION OF INVENTION According to the invention there is provided a process for the recovery of valuable products from leach liquor, namely yellow iron oxide pigment, ammonia and calcium chloride, the process comprising : a) reacting the leach liquor with iron to convert free hydrochloric acid and ferric chloride in the leach liquor to ferrous chloride; 6 b) precipitating the impurities in the leach liquor by treating the leach liquor with an aqueous ammonia solution containing 8-12%ammonia at a pH of 2.5 to 5 under agitation; c) flocculating the precipitated impurities by treating the leach liquor with a flocculating agent; d) separating the flocculated impurities from the leach liquor to obtain a purified ferrous chloride solution; e) adjusting optionally the pH of the ferrous chloride solution between 1.5 to 2 by treatment with hydrochloric acid; f) reacting the ferrous chloride solution containing a ferrous iron (Fe++) concentration of 2.0 to 4.0% with an aqueous solution of ammonia containing 8-12% ammonia in the presence of 8-15% ammonium chloride and chilled water under agitation to convert ferrous chloride to ferrous hydroxide, oxidizing the ferrous hydroxide with air at a temperature between 18-35°C and a pH between 3 to 5 to form hydrated ferric oxide pigment seeds (yellow pigment seeds) and further oxidizing the pigment seeds with oxygen mixed with steam in the presence of an aqueous ammonia solution containing 8-12% ammonia at 60-85°C under agitation and at pH at 3 to 5 to allow the seeds to grow to the require size; filtering the pigment slurry to separate the pigment cake from the mother liquor containing ammonium chloride, washing the pigment cake with water, drying the pigment cake and pulverizing the cake; and recovering ammonia and calcium chloride from the mother liquor. 7 In order to render the process economical, the reaction of leach liquor in step (a) is carried out with carbon steel scraps such as cuttings, punchings and / or trimmings of cold rolled carbon steel. The leach liquor used in step (a) is generally at about 60 - 85°C. Exothermeric heat of the reaction of the leach liquor with iron (carbon steel scraps) maintains the temperature of the reaction. Dissolution of the iron in the leach liquor at high temperatures of 60-85°C dilutes the hydrogen concentration with water vapours below ignitable limit. Due to agitation of the leach liquor during the precipitation step (b) formation of black iron oxide is avoided and the colour quality of the pigments is maintained. The flocculating agent used in step (c) is selected from polyelectrolytes, preferably polyacrylate. The separation of the flocculated impurities from the leach liquor in step (d) is preferably carried out by clarification. To avoid oxidation of the ferrous chloride during storage, pH of the solution is optionally adjusted between 1.5-2 by treatment with hydrochloric acid. Preferably the drying of the pigment in step (g) is carried1 out at 110- 130°C. According to an embodiment of the invention the step (h) of recovering ammonia and calcium chloride from the mother liquor comprises i) reacting the mother liquor containing ammonium chloride with lime to form ammonia and calcium chloride; ii) recovering the ammonia from the reaction mixture by subjecting the reaction mixture to steam distillation; iii) dissolving the distilled off ammonia in water to form aqueous ammonia solution; iv) cooling the distiller liquid containing calcium chloride; v) filtering the distiller liquid to remove lime grits; 8 vi) concentrating the clear solution of calcium chloride by exporation; and vii) and converting the concentrated calcium chloride to the required form followed by calcination and cooling. Calcination of the calcium chloride is carried out to reduce the moisture content thereof. According to an embodiment of the invention the concentrated calcium chloride is converted into flakes by viia) flaking it at 170- 175°C; viib) calcining the flakes at 200 to 220 °C; and viic) cooling the calcined flakes to 40 - 45°C. According to the invention there is also provided an equipment for recovering valuable products from leach liquor namely yellow iron oxide pigment, ammonia and calcium chloride, the equipment consisting of an yellow iron oxide pigment recovering unit, an ammonium recovering and recycling unit and a calcium chloride recovering unit. According to an embodiment of the invention, the equipment consists of a scrap iron reactor provided with a scrap iron inlet, leach liquor inlet and leach liquor recirculation line having a first pump and a first valve, an impurities precipitation tank provided with a leach liquor inlet line connected across the leach liquor recirculation line between the first pump and first valve and having a second valve, the precipitation tank being further provided with an agitator and an aqueous ammonia solution supply line connected to the outlet of an aqueous ammonia storage tank and provided with a second pump, a flocculation tank provided with an ammonia treated leach liquor inlet line connected to the outlet of the precipitation tank and having a third pump, the flocculation tank being further provided with a flocculant inlet line and an agitator, a clarifier 9 connected to the outlet of the flocculation tank through a fourth pump, a ferrous chloride solution storage tank connected to the launder of the clarifier, a pigment formation reactor provided with a ferrous chloride solution inlet line connected to the ferrous chloride solution storage tank through a fifth pump, the pigment formation reactor being further provided with an air inlet, chilled water inlet, aqueous ammonia solution inlet connected across the aqueous ammonia solution supply line, oxygen inlet, steam inlet and mother liquor (ammonium chloride) inlet line, the pigment formation reactor being further provided with an agitator, a first filter comprising a pigment slurry inlet line connected to the outlet of the pigment formation reactor through a sixth pump, a solid outlet line connected to a dryer and a mother liquor (filtrate) outlet line connected to a mother liquor storage tank, a mother liquor supply line connected to the inlet of a mother liquor and lime reactor and to the outlet of the mother liquor storage tank through a seventh pump, the mother liquor inlet line being connected across the mother liquor supply line past the seventh pump, the dryer being connected to a pulviser having an outlet line, the mother liquor and lime reactor being provided with a lime inlet line and ammonia gas outlet line connected to the ammonia gas outlet line of a distiller, the mother liquor and lime reactor being further provided with a reaction liquid outlet line connected to the reaction liquid inlet of the distiller at the top thereof through an eight a pump, the mother liquor and lime reactor being further provided with an agitator, the distiller being provided with a steam inlet line at the bottom thereof, the ammonia gas outlet line of the distiller being connected to the ammonia gas inlet of a gas scrubber at the bottom thereof, the gas scrubber being provided with a water inlet line and an air outlet at the top and an aqueous ammonia solution recirculation line provided with a ninth pump and a heat exchanger, the inlet of the aqueous ammonia storage tank being connected across the said aqueous ammonia recirculation line past the heat exchanger, a second filter 10 comprising a calcium chloride solution inlet line connected to the calcium chloride solution outlet of the distiller at the bottom thereof through a tenth pump and a lime stone grits outlet line, a lime stone grits collection trolley disposed below the lime stone grits outlet line, a calcium chloride solution collection tank comprising a calcium chloride inlet line connected to the outlet of the second filter, an evaporator comprising a calcium chloride solution inlet line connected to the calcium chloride solution outlet of the calcium chloride collection tank through an eleventh pump, a vapour separator comprising a vapor inlet line at the top thereof connected to the vapor outlet at the top of the evaporator, the vapour separator further comprising a steam outlet line at the top and a concentrated calcium chloride solution outlet line at the bottom thereof connected to the inlet of a water cooled flaker and a calciner comprising a flakes inlet line connected to the outlet of the flaker and a calcined flakes outlet line connected to the flakes inlet line of a cooler. The following is a detailed description of the invention with reference to the accompanying drawings in which the sole Fig 1 is a flow diagram of the equipment used for recovering valuable products from leach liquor according to an embodiment of the invention. The equipment 1 as illustrated in Fig 1 of the accompanying drawings consists of a scrap iron reactor 2 provided with a scrap iron inlet 3, leach liquor inlet 4 and leach liquor recirculation line 5 having a first pump 6a and first valve 7a. 8 is an impurities precipitation tank provided with a leach liquor inlet line 9 connected across the leach liquor recirculation line 5 between pump 6a and valve 7a. 7b is a second valve provided in line 9. Tank 8 is further provided with an agitator 10 and an aqueous ammonia solution supply line 11 connected to the outlet of an aqueous ammonia storage tank 12 and provided with a second pump 6b. 13 is a flocculation tank provided with an ammonia treated leach liquor inlet line 13a connected to the precipitation tank outlet and having a third 11 pump 6c. The flocculation tank is further provided with a flocculant inlet line 14 and an agitator 15. 16 is a clarifier comprising a leach liquor inlet line 16a connected to the outlet of the flocculation tank through a fourth pump 6d. 16b is precipitate outlet line of the clarifier. 17 is a ferrous chloride solution storage tank connected to the launder 18 of the clarifier through line 16c. 19 is a pigment formation reactor provided with a ferrous chloride solution inlet line 19a connected to the ferrous chloride solution storage tank through a fifth pump 6e. The pigment formation reactor is further provided with an air inlet 20, chilled water inlet 21, aqueous ammonia solution inlet line 22, oxygen inlet 23, steam inlet 24, mother liquor (ammonium chloride) inlet line 25 and an agitator 26. The ammonia solution inlet line 22 is connected across the ammonia solution supply line 11. 27a is a first filter comprising a pigment slurry inlet line 28 connected to the outlet of the pigment formation reactor through a sixth pump (f), a solid outlet line 29 connected to a dryer 30 and a mother liquor (filtrate) outlet line 31 connected to a mother liquor storage tank 32. The dryer 30 is a tray dryer but can be any other type of dryer also. 33 is a mother liquor supply line connected to the outlet of the mother liquor storage tank through a seventh pump 6g and further connected to the inlet of a mother liquor and lime reactor 34. The mother liquor inlet line 25 is connected across the mother liquor supply line 33 past the seventh pump 6g. The tray dryer is connected to a pulveriser 35 having outlet one 35a. The mother liquor and lime reactor is provided with a lime inlet line 36 and an ammonia gas outlet line 37 connected to the ammonia gas outlet line 38 of a distiller 39. The mother liquor and lime reactor is further provided with a reaction liquid outlet line 40 connected to the reaction liquid inlet of the distiller at the top thereof through an eighth pump 6h. Tthe mother liquor reactor is further provided with an agitator 41. The distiller is provided with a steam inlet line 42 at the bottom thereof. The ammonia gas outlet line of the distiller is connected to the ammonia gas 12 inlet of a gas scrubber 43 at the bottom thereof. The gas scrubber is provided with a water inlet line 44 and air outlet 45 at the top and an aqueous ammonia solution recirculation line 46 provided with a ninth pump 6i and a heat exchanger 47. Cold water inlet and hot water outlet of the heat exchanger are marked 47a and 47b, respectively. The inlet of the aqueous ammonia storage tank 12 is connected across the aqueous ammonia recirculation line 46 past the heat exchanger 47 through cross line 48. 49 is a second filter comprising calcium chloride solution inlet line 50 connected to the outlet of the distiller at the bottom thereof through a tenth pump 6j. 51 is a lime stone grits collection trolley disposed below the lime stone grits outlet line 52 of the second filter. 53 is a calcium chloride solution collection tank comprising a calcium chloride inlet line 54 connected to the outlet of the second filter. 55 is an evaporator comprising a calcium chloride solution inlet line 56 connected to the calcium chloride solution outlet of the calcium chloride collection tank through an eleventh pump 6k. Steam inlet and steam condensate outlet of the evaporator are marked 57 and 58, respectively. 59 is a vapour separator comprising a vapour inlet line 60 at the top thereof connected to the vapour outlet at the top of the evaporator. The vapour separator also comprises a steam outlet line 61 at the top and a concentrated calcium chloride outlet line 62 at the bottom thereof connected to the inlet of a water cooled flaker 63. 64 is a calciner comprising a flakes inlet line 65 connected to the outlet of the flaker and a calcined flakes outlet line 66 connected to the flakes inlet of a cooler 67. The cooler outlet line is marked 68. The calciner 64 is a rotary calciner but can also be any other type of calciner. The scrap iron reactor 2 is loaded with iron scraps (not shown), valve 7a is kept open and valve 7b is kept closed. Leach liquor (not shown) at about 60 to 80°C is pumped into the reactor 2 via 13 inlet line 4 and recirculated in the reactor 2 via the recirculation line 5 by operating the pump 6a. The acid concentration in the leach liquor is monitored and when the acid concentration drops very low say 0.1% HCL or less as indicated by a pH of about 1, the recirculation of the leach liquor is stopped. The reaction temperature of the leach liquor with iron scrap is maintained between 60-80°C due to the exhothermic nature of the reaction. Valve 7a is closed and valve 7b is opened and the leach liquor is pumped into the precipitation tank by pump 6a. Aqueous ammonia solution is pumped into the precipitation tank 8 via the supply line 11 by the pump 6b. The p of the leach liquor in the precipitation tank is maintained between 2.5 to 5 under agitation to precipitate the impurities in the leach liquor. The agitator 10 is switched off and the leach liquor in the precipitation tank is pumped into the flocculation tank 13 by pump 6c via the inlet line 13a. The leach liquor in the flocculation tank is dosed with a flocculent via the inlet line 14 under agitation so as to flocculate the precipitated impurities. The agitator 15 is switched off and the leach liquor is pumped into the clarifier 16 by pump 6d via the inlet line 16a. The flocculated impurities in the leach liquor settle at the bottom of the clarifier and are drained out via the precipitate outline 16b of the clarifier. The clarified (purified) ferrous chloride solution rises in the launder 17 thereof and flows down into the ferrous chloride solution storage tank 18. The pH of the ferrous chloride solution in the tank 18 is adjusted optionally with hydrochloric acid and it is pumped into the pigment formation reactor 19 by pump 6e via inlet line 19a. Part of the mother liquor (ammonium chloride solution) from storage tank 32 pumped by pump 6g and part of the aqueous ammonia solution from storage tank 12 pumped by pump 6b and chilled water are fed into the reactor 19 via line 25, line 22 and line 21, respectively. Air is also supplied into the reactor 19 via line 20. The reaction is agitated and the pH is maintained between 3 to 5. Ferrous chloride gets converted into ferrous hydroxide and ammonium chloride. The ferrous hydroxide 14 is oxidized to ferric hydroxide seeds. Because of the chilled water the reaction temperature is maintained between 18-35°C during this time. Air supply is discontinued and instead oxygen and steam are supplied into the reactor 19 via inlet lines 23 and 24, respectively. Agitation is continued and pH is maintained between 3-5 with continued supply of ammonia so as to allow the seeds to grow to the required sizes ie colour values by further oxidation. The reaction temperature in the reactor 19 rises to 65 to 85°C because of the steam and the temperature is maintained due to the exhothermic nature of the reaction. The agitator 26 is switched off and the pigment slurry is pumped into the filter 27a by pump 6f via line 28. Yellow iron oxide pigment cake from the filter is fed into the dryer 30. The dried pigment cake is pulverized in the pulveriser 35 and discharged for bagging or packing via outlet line 35a of the pulveriser. The mother liquor (filtrate containing ammonium chloride) from the filter 27a flows into the storage tank 32 via line 31. A major quantity of the mother liquor in the storage tank 32 is pumped into the mother liquor and lime reactor 34 by pump 6g. The remaining quantity of the mother liquor is recycled into the pigment formation reactor 19 via the line 25. The mother liquor is reacted with lime in the reactor 34 under agitation. Ammonia gas evolved flows into the ammonia gas outlet line 38 of the distiller via line 37. The agitator 41 is switched off and reaction liquid in the reactor 33 is pumped into the distiller 39 and is subjected to distillation by steam fed through line 42. Ammonia gas being formed flows into the ammonia gas outlet line 38 and from there into the gas scrubber 43. Ammonia gas dissolves in the water being supplied into the gas scrubber and the aqueous ammonia solution is recirculated through the recirculation line 46 by pump 6i to increase the concentration thereof. The aqueous ammonia solution being recirculated through the recirculation line 46 is cooled in the heatexchanger by passing cooling 15 water therethrough. Cooling water enters the heat exchanger through inlet 47a and hot water leaves the heat exchanger via outlet 47b. Air in the reaction liquid are let out through the air outlet line 45. Aqueous ammonia solution is collected in the storage tank 12 and is recycled into the precipitation tank 8 and pigment formation reactor 19 via the lines 11 and 22. The calcium chloride solution in the distiller is pumped into the filter 49 by pump 6j via line 50 and is filtered in the filter 49. Lime stone grits are discharged into the trolley underneath the filter and are disposed of. The filtrate comprising calcium chloride solution flows into the calcium chloride collection tank 53 via the line 54. The calcium chloride solution is pumped into the evaporator 55 by pump 6k via line 56 and evaporated in the evaporator by steam supplied through the inlet line 57 thereof. The steam condensate flows out through the outlet line 58 of a.. the evaporator. The vapours flow into the vapour separator 59 via line 60 thereof. Water vapours ie steam flow out via the outlet line 61 of the vapour separator. Concentrated calcium chloride solution flows into the water cooled flaker 63 via the inlet line 62, where they are flaked. Calcium chloride flakes flow into the calciner 64 via the inlet line 65 where theysare calcined. The calcined flakes are cooled in the cooler 67 and discharged via the outlet line 68 of the cooler for bagging or packing. It is to be clearly understood that the construction and configuration of the equipment in terms of the individual units like reactors, filters, precipitation tank or flocculation tank and their layout can vary depending upon the process requirements. The type of the agitators used in the reactors, precipitation tank or flocculation tank will depend upon the process requirements and can be single or double impeller types. There can be equipment configurations comprising more than one of such units. Instead of the clarifier a filter can be used to separate the flocculated 16 impurities from the ferrous chloride solution. Instead of clarification, other known techniques like filtration can be used to separate the impurities from the leach liquor. The concentrated calcium chloride can be converted into forms other than flakes like powder or granules. The equipment need not have a flaker. Instead, it can comprise spray dryer or granulator depending upon the forms into which the concentrated calcium are to be converted. Such variations in the process and equipment configuration and construction are obvious to those skilled in the art and are to be construed and understood to be clearly within the scope of the invention. Yellow iron oxide pigment has a variety of uses, its main use being in paint industry for coating formulations and in construction industry for colouring of concrete. It also finds applications in food and pharmaceutical industries, paper and plastics industries or printing industry or as catalyst. Calcium chloride also has a variety of uses, for instance, as desicant for drying out moisture in various industries, in cement paint industry, construction industry, oil well drilling, petroleum industry, paper industry, or refrigerating industry or as a snow thawing agent, or as additive in ferrous metallurgy. Besides being recycled and used in the process and equipment of the invention ammonia being recovered can also be used as ammonium hydroxide alkali or ammonia gas to make nitrogenous fertilizers or other ammonium salts. According to the invention, leach liquor, a waste from a synthetic rutile plant, is practically entirely recovered as useful and valuable products namely yellow iron oxide pigment, calcium chloride and ammonia. Therefore, waste disposal and resultant environmental problems are practically eliminated and significant economical benefits are realized. 17 The following examples are illustrative of the invention but not limitative of the scope thereof. Example 1 Carbon steel scraps (cuttings, punchings and trimmings of cold rolled carbon steel) were loaded in a 15 KL reactor tank. Ten kilo litre (KL) leach liquor at 70°C was pumped into the tank upto the level of the scraps. The leach liquor was recirculated through the scraps for 12 hours until the pH of the leach liquor dropped to 1 indicating completion of the reaction. Due to the exothermic nature of the reaction, reaction temperature remained at 70°C without any external heating. The leach liquor composition before and after the scrap treatment was as in the following Table 1: Table 1 Before treatment After treatment Ferrous chloride (FeC12) % 26.814 32.11 Ferric chloride (FeC13) % 2.013 Nil Hydrochloric acid % 2.163 0.07 (pH about 1) Aluminium (Al) 960 ppm 975 ppm Chromium (Cr) 68 ppm 73 ppm Cadmium (Cd) 2.5 ppm 3.0 ppm Silicon (Si) 115 ppm 120 ppm Magnesium (Mg) 1350 ppm 1370 ppm Manganese (Mn) 952 ppm 975 ppm The scraps treated leach liquor (9KL) was taken in a precipitation tank and aqueous ammonia solution of 10% concentration was added into the tank to raise the pH to 4 under agitation. The agitation was continued for 10 minutes to precipitate the impurities after which the leach liquor was taken in a flocculation tank and 0.1% solution of poly acrylate was added into the tank under agitation. The agitation was stopped after 30 minutes to allow the precipitated impurities to 18 flocculate. The leach liquor was pumped into a clarifer to separate a clear solution of ferrous chloride having the composition as in the following Table 2: Table 2 Ferrous chloride (FeC12) % 30.1 Ferric chloride (FeC13) % Nil Hydrochloric acid pH 4.0 Aluminium (Al) 15 ppm Chromium (Cr) 2 ppm Cadmium (Cd) lppm Silicon (Si) 7 ppm Magnesium (Mg) 1285 ppm Manganese (Mn) 930 ppm The pH of the ferrous chloride solution was adjusted to 2 with hydrochloric acid. Ammonium chloride solution of 10.95% concentration at 21°C and 6 KL chilled water at 12°C were pumped into a 60KL pigment formation reactor. To this, the ferrous chloride solution (5.5 KL) containing a ferrous iron (Fe++) concentration of 3.06% was added under agitation. 1680 litres of aqueous ammonia solution of concentration 8.56% was also added into the reactor in ten minutes. Ferrous hydroxide formed in the reaction is oxidized to hydrated ferric oxide seeds or Alpha FeOOH nuclei (yellow seeds) by allowing air into the reactor at a flow rate of 60 m3 / hour and pressure 3.5 kg/cm2. Oxidation was continued for three hours until the seed formation was complete. Because of the chilled water the reaction temperature remained at 20-22°C. The pH of the reaction was retained at 3.5-4 with the use of the ammonia. Air flow was stopped and oxygen flow at a rate 12 m / hr at pressure 3.8 kg / cm was started. Simultaneously steam was introduced into the reactor. Addition of aqueous ammonia solution was started to maintain the pH at 3.4. After 5 hours, the reactor temperature rose to 70°C and the steam supply was stopped. The reaction temperature was maintained 73 - 75°C by the exothermic heat of the reaction. After 5 hours of pigment crystal growth, steam supply was discontinued. The reaction was dosed with 19 the remaining ferrous chloride solution (5.5 KL) for about 20 hrs to maintain Fe++ concentration in the reaction mixture between 1.0 -1.5%. Dosing of ferrous chloride was stopped 5 hrs before the completion of the reaction to consume almost all the Fe++ present. The reaction was terminated after 30 hours of crystal formation. The pigment slurry containing 62.67 kg/KL solids was filtered and the filter cake containing 48% moisture was dried in tray dryers at 110-130°C to get a final moisture content below 0.5%. The dried cake (weight 2977 kgs) was pulverized and bagged. The physical and chemical characteristics of the pigment were as in the following Table 3. Table 3 Volatile matter % 0.25 Residue on sieve - 300 0.05 Matter soluble in water % 0.25 p" 3.98 Loss of Ignition % 11.63 Oil absorption gm /100 gm pigment 31.0 Conductivity mmho 132 The colour values (CIELAB UNITS) of the pigments were as in the following Table 4 measured in draw down made in acrylic resin : Table 4 Mass Tone L 59.07 A 15.44 B 44.53 Reduced Tone (1 : 3) L 76.43 A 10.59 B 35.07 It is quite clear from the Table 4 that the pigments were of good quality. 20 The mother liquor (28 KL) containing ammonium chloride of concentration of 12.2% was treated with lime to form ammonia and calcium chloride. Ammonia was recovered from the reaction mixture by steam distillation. Ammonia gas was dissolved in water to make 10% solution for recycling to pigment production. Ammonia recovery was 98 %. The distillar liquid containing calcium chloride solution was cooled and filtered to remove lime stone grits. The clear solution was concentrated by evaporation. The concentrate containing 71% calcium chloride was flaked at 172°C. The flakes were calcined at 210°C and cooled to 45°C. Calcium chloride recovery was 95%. The composition of the calcium chloride flakes were as in the following Table 5 : Table 5 CaC12 % 78 MgC12 % 0.3 Alkali Chlorides as NaCl % 1.0 Sulphate as CaS04 % 0.1 Water Insolubles % 0.2 pH of 10% solution 9.0 Flakes size 1.5-3.0 mm The flakes were of good quality as can be seen in Table 5. Example 2 Twelve KL leach liquor at 80°C was treated with carbon steel scraps in the same manner as stated in Example 1. The reaction temperature was maintained at 80°C and the recirculation was carried out for 9 hours. Leach liquor composition before and after treatment with scraps was as given in the following Table 6 21 Table .6 Before Treatment After Treatment Ferrous chloride (FeC12) % 26.08 34.32 Ferric chloride (FeC13) % 2.4 Nil Hydrochloric acid % 3.1 0.08 (pH about 1) Aluminium (Al) 890 ppm 905 m Chromium (Cr) 75 ppm 78ppm Cadmium (Cd) 3.5 ppm 40 ppm Silicon (Si) 105 ppm 110 ppm Magnesium (Mg) 1030 ppm 1060 ppm Manganese (Mn) 535 ppm 545 ppm Table 7 Ferrous chloride (FeC12) % 32.1 Ferric chloride (FeC13) % Nil Hydrochloric acid pH pH4.5 Aluminium (Al) 20 ppm Chromium (Cr) 3 ppm Cadmium (Cd) Not detectable Silicon (Si) 9 ppm Magnesium (Mg) 980 ppm Manganese (Mn) 515 ppm The clear ferrous chloride solution without acidification with HCL was used for seed formation and crystal growth in a 60 KL pigment formation reactor. 16 KL mother liquor (ammonium chloride solution) at 19°C and concentration 12.2% NH4C1, 8 KL chilled water at 14°C and 5 KL ferrous chloride solution containing ferrous concentration of 3.26% Fe++ were pumped into the reactor. The reaction temperature remained at 20°C. 1600 litres Ammonia solution of 22 concentration of 10.5% was added in the reactor in 10 minutes to precipitate ferrous hydroxide. Air at 65 M3 per hour and pressure 3.5 kg/cm2 was introduced to oxidize ferrous hydroxide to yellow iron oxide seeds. Air flow was stopped and oxygen flow at 14 M3 / hour at a pressure of 3.8 kg/cm2 was started with simultaneous steam introduction for four hours to raise the reaction temperature to 65°C. Thereafter the reaction temperature rose to 72°C due to the exothermic heat of the reaction and remained steady in the range 72 to 78°C. Due to the high rate of reaction crystal growth was over in 26 hours when the reaction was terminated. The pigment slurry containing 62.18 kg/KL solids was processed as in Example 1. The dried cake weighed 2985 kgs. The physical and chemical characteristics of the pigments were as in the following Table 8 : Table 8 Volatile matter % 0.42 Residue on sieve - 300 0.06 Matter soluble in water % 0.18 PH 3.75 Loss of Ignition % 11.91 Oil absorption gm / 100 gm pigment 27.31 Conductivity mmho 236 The colour values (CIELAB Units) of the pigments were as in the following Table 9 : Table 9 Mass Tone L 58.78 A 15.40 B 45.27 Reduced Tone L 77.136 A 11.13 B 37.91 Table 9 clearly shows that the pigments were of good quality. 23 The mother liquor 30 KL containing ammonium chloride concentration of 12.2% was processed in the same manner as in Example 1. 98.5 % of ammonia content in NH4CI was recovered as ammonia. The calcium chloride concentrate had 12% calcium chloride. Ammonia recovery was 98.5 %. Calcium chloride recovery was 94.0%. The composition of the calcium chloride flakes were as in the following Table 10: Table 10 CaC12 % 80.0 MgC12 % 0.4 Alkali Chlorides as NaCl % 1.2 Sulphate as CaS04 % 0.12 Water Insolubles % 0.15 pH of 10% solution 8.3 Flakes size 1.5 -3.5mm The flakes were of good quality as can be seen in Table 10. 24 We claim 1. A process for the recovery of valuable products from leach liquor, namely yellow iron oxide pigment ammonia and calcium chloride, the process comprising : a) reacting the leach liquor with iron to convert free hydrochloric acid and ferric chloride in the leach liquor to ferrous chloride; b) precipitating the impurities in the leach liquor by treating the leach liquor with an aqueous ammonia solution containing 8-12%ammonia at a p of 2.5 to 5 under agitation; c) flocculating the precipitated impurities by treating the leach liquor with a flocculating agent; e) separating the flocculated impurities from the leach liquor to obtain a purified ferrous chloride solution; e) adjusting optionally the pH of the ferrous chloride solution between 1.5 to 2 by treatment with hydrochloric acid; f) reacting the ferrous chloride solution containing a ferrous iron (Fe++) concentration of 2.0 to 4.0% with an aqueous solution of ammonia containing 8-12% ammonia in the presence of 8-15% ammonium chloride and chilled water under agitation to convert ferrous chloride to ferrous hydroxide, oxidizing the ferrous hydroxide with air at a temperature between 18-35°C and a pH between 3 to 5 to form hydrated ferric oxide pigment seeds (yellow pigment seeds) and further oxidizing the pigment seeds with oxygen mixed with steam in the presence 25 of an aqueous ammonia solution containing 8-12% ammonia at 60-85°C under agitation and at pH at 3 to 5 to allow the seeds to grow to the require size; g) filtering the pigment slurry to separate the pigment cake from the mother liquor containing ammonium chloride, washing the pigment cake with water, drying the pigment cake and pulverizing the cake; h) and recovering ammonia and calcium chloride from the mother liquor. 2 A process as claimed in claim 1, wherein the reaction of leach liquor in step (a) is carried out with carbon steel scraps. 3 A process as claimed in claim 1, wherein the flocaulating agent used in step (c) is polyacrylate. 4 A process as claimed in claim 1, wherein the separation of the flocculated impurities from the leach liquor in step (d) is carried out by clarification; 5 A process as claimed in claim 1, wherein the drying of the pigment cake in step (g) is carried out atllO-130°C. 6. A process as claimed in claim 1,wherein the step(h) of recovering ammonia and calcium chloride from the mother liquor comprises i) reacting the mother liquor containing ammonium chloride with lime to form ammonia and calcium chloride; ii) recovering the ammonia from the reaction mixture by subjecting the reaction mixture to steam distillation; iii) dissolving the distilled off ammonia in water to form aqueous ammonia solution; 26 iv) cooling the distiller liquid containing calcium chloride; v) filtering the distiller liquid to remove lime grits; vi) concentrating the clear solution of calcium chloride by exporation; and vii) and converting the concentrated calcium chloride to the required form followed by calcination and cooling; 7 A process as claimed in claim 6, wherein in the concentrated calcium chloride is converted into flakes by viia) flaking it at 170 - 175°C; viib) calcining the flakes at 200 to 220 °C; and viic) cooling the calcined flakes to 40 - 45°C. 8 An equipment for recovery of valuable products from leach liquor namely yellow iron oxide pigment, ammonia and calcium chloride, the equipment consisting of an yellow iron oxide pigment recovering unit, an ammonium recovering and recycling unit and a calcium chloride recovering unit. 9 An equipment as claimed in claim 9, consisting of a scrap iron reactor provided with a scrap iron inlet, leach liquor inlet and leach liquor recirculation line having a first pump and a first valve, an impurities precipitation tank provided with a leach liquor inlet line connected across the leach liquor recirculation line between the first pump and first valve and having a second valve, the precipitation tank being further provided with an agitator and an aqueous ammonia solution supply line connected to the outlet of an aqueous 27 ammonia storage tank and provided with a second pump, a flocculation tank provided with an ammonia treated leach liquor inlet line connected to the outlet of the precipitation tank and having a third pump, the flocculation tank being further provided with a flocculant inlet line and an agitator, a clarifier connected to the outlet of the flocculation tank through a fourth pump, a ferrous chloride solution storage tank connected to the launder of the clarifier, a pigment formation reactor provided with a ferrous chloride solution inlet line connected to the ferrous chloride solution storage tank through a fifth pump, the pigment formation reactor being further provided with an air inlet, chilled water inlet, aqueous ammonia solution inlet connected across the aqueous ammonia solution supply line, oxygen inlet, steam inlet and mother liquor (ammonium chloride) inlet line, the pigment formation reactor being further provided with an agitator, a first filter comprising a pigment slurry inlet line connected to the outlet of the pigment formation reactor through a sixth pump, a solid outlet line connected to a dryer and a mother liquor (filtrate) outlet line connected to a mother liquor storage tank, a mother liquor supply line connected to the inlet of a mother liquor and lime reactor and to the outlet of the mother liquor storage tank through a seventh pump, the mother liquor inlet line being connected across the mother liquor supply line past the seventh pump, the dryer being connected to a pulviser having an outlet line, the mother liquor and lime reactor being provided with a lime inlet line and ammonia gas outlet line connected to the ammonia gas outlet line of a distiller, the mother liquor and lime reactor being further provided with a reaction liquid outlet line connected to the reaction liquid inlet of the distiller at the top thereof through an eight a pump, the mother liquor and lime reactor being further provided with an agitator, the distiller being provided with a steam inlet line at the bottom thereof, the ammonia gas outlet line of the 28 distiller being connected to the ammonia gas inlet of a gas scrubber at the bottom thereof, the gas scrubber being provided with a water inlet line and an air outlet at the top and an aqueous ammonia solution recirculation line provided with a ninth pump and a heat exchanger, the inlet of the aqueous ammonia storage tank being connected across the said aqueous ammonia recirculation line past the heat exchanger, a second filter comprising a calcium chloride solution inlet line connected to the calcium chloride solution outlet of the distiller at the bottom thereof through a tenth pump and a lime stone grits outlet line, a lime stone grits collection trolley disposed below the lime stone grits outlet line, a calcium chloride solution collection tank comprising a calcium chloride inlet line connected to the outlet of the second filter, an evaporator comprising a calcium chloride solution inlet line connected to the calcium chloride solution outlet of the calcium chloride collection tank through an eleventh pump, a vapour separator comprising a vapor inlet line at the top thereof connected to the vapor outlet at the top of the evaporator, the vapour separator further comprising a steam outlet line at the top and a concentrated calcium chloride solution outlet line at the bottom thereof connected to the inlet of a water cooled flaker and a calciner comprising a flakes inlet line connected to the outlet of the flaker and a calcined flakes outlet line connected to the flakes inlet line of a cooler. An equipment as claimed in claim 10, wherein the dryer is a tray dryer. An equipment as claimed in claim 10 or 11, wherein the calciner is a rotary calciner. 29 12 Valuable products namely yellow iron oxide pigment, ammonia and calcium chloride obtained by the process as claimed in any one of claims 1 to 7. Abstract A process for the recovery of valuable products from leach liquor, namely yellow iron oxide pigment ammonia and calcium chloride. Leach liquor is reacted with iron to convert free hydrochloric acid and ferric chloride in the leach liquor to ferrous chloride. The impurities in the leach liquor are precipitated by treating the leach liquor with an aqueous ammonia solution containing 8-12%ammonia at a pH of 2.5 to 5 under agitation. The precipitated impurities are flocculated by treating the leach liquor with a flocculating agent and separated from the leach liquor to obtain a purified ferrous chloride solution. The pH of the ferrous chloride solution is optionally adjusted between 1.5 to 2 by treatment with hydrochloric acid. The ferrous chloride solution containing a ferrous iron (Fe++) concentration of 2.0 to 4.0% is reacted with an aqueous solution of ammonia containing 8-12% ammonia in the presence of 8-15% ammonium chloride and chilled water under agitation to convert ferrous chloride to ferrous hydroxide. The ferrous hydroxide is oxidized with air at a temperature between 18-35°C and a pH between 3 to 5 to form hydrated ferric oxide pigment seeds (yellow pigment seeds) which are further oxidized with oxygen mixed with steam in the presence of an aqueous ammonia solution containing 8-12% ammonia at 60-85°C under agitation and at pH at 3 to 5 to allow the seeds to grow to the require size. The pigment slurry is filtered to separate the pigment cake from the mother liquor containing ammonium chloride. The pigment cake is washed with water, dried and pulverized. Ammonia and calcium chloride in the mother liquor are also recovered. Also an equipment for the recovery of the valuable products.

Full Text

FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003 As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
Process and equipment for the recovery of valuable products from leach liquor
INVENTOR
Name : Yadav Baburam
Nationality : Indian National
Address : DCW Limited, Sahupuram 628 229,
Thoothukudi Dist, Tamil Nadu, India
APPLICANTS
Name : DCW LIMITED
Nationality : Indian Company
Address : Nirmal, 3rd Foor, Nariman Point,
Mumbai 400 021,Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification parTiCl4larly describes the nature of this invention and the manner in which it is to be performed:

TECHNICAL FIELD OF INVENTION
This invention relates to a process and equipment for the recovery of valuable products from leach liquor.
The valuable products recovered from leach liquor according to the invention are yellow iron oxide pigment, ammonia and calcium chloride.
BACKGROUND OF THE INVENTION
Several processes are known and reported for the manufacture of yellow iron oxide pigment having a goethite crystalline structure, also known as alpha ferric oxide hydrate (alpha Fe OOH or a Fe203. H2O), the oldest being the Penniman - Zoph process (US 1327061, 1368748, 5032180 and 5076848). Ferrous sulphate solution is reacted with sodium hydroxide to precipitate alpha-FeOOH seeds (nuclei). On oxidizing the ferrous sulphate solution containing the nuclei and scrap iron immersed in it, with air mixed with steam, hydrated ferric oxide gets deposited on the nuclei. Crystal growth is allowed to continue until the desired colour is achieved. Martin process also known as precipitation process as taught in US 2939767 comprises passing free oxygen containing gas through ferrous salt solution containing alpha -FeOOH seeds. Ferric oxide formed is hydrolysed with evolution of hydrogen ions which are neutralized and oxidised with ammonia premixed with the free oxygen containing gas. In order to economize the process, ferrous sulphate formed as a byproduct in the manufacture of titanium dioxide by the sulphate process is used.
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US 6042642 relates to iron oxide yellow pigments prepared by intensively admixing an alkaline component to an acidic 50 - 450 g/1 FeCl2 solution to adjust the pH of the solution between 3 and 5. A flocculation aid is optionally added to the FeCl2 solution before, after or concurrent with the addition of the alkaline component and the solution is optionally exposed to oxidation. The solution, after separation of the solids, is added to an a-FeOOH nuclei suspension produced by the precipitation process. The suspension is heated to 30 to 95°C with thorough mixing and oxidized while increasing the pH 3.0 to 5.0 by adding alkaline component. The oxidation is optionally continued while maintaining the pH at a constant between 3.0 and 5.0. The oxidation is stopped when the Fe(II) content of the suspension is less than 1 mole % and the oxide yellow pigment is separated, washed, dried and ground.
US 6179908B1 describes iron oxide red pigments produced by calcining iron oxide yellow pigments or iron oxide black pigments. The iron oxide yellow pigments are prepared from ferrous chloride by treating it with an alkali to adjust the pH between 3 and 5. The solution is flocculated and oxidized optionally and the solid formed is separated from the solution. The solution is then added to an a- or b-FeOOH seed suspension produced by the precipitation process. The suspension formed is heated to 30 to 95°C and oxidized with air and at the same time the pH is adjusted to 3.0 to 5.0 with an alkali. The oxidation is stopped as soon as the ferrous content of the suspension is less than 1 mole %. The solid formed is separated, washed, dried and ground. In order to render the process economical, the ferrous chloride used is obtained from steel pickling industry or from plants manufacturing TiO2 using the chloride process. In the chloride process, titanium rich feed stocks like natural rutile, leucoxene minerals or upgraded ilmenite like synthetic rutile or titanium slag is chlorinated with chlorine gas in a
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fluidized bed reactor to make titanium tetra chloride (TICI4). The iron content in the feed stock (2.0 - 6.0%) also gets chlorinated to form ferrous chloride in the fluidized bed reactor along with titanium tetra chloride. Ferrous chloride is separated from TiC14 by condensation. TiCl4 is oxidised to form the pigments.
US 5916360 relates to preparation of yellow iron oxide from ferrous chloride solution containing at least one organic aliphatic amine in the ratio of organic carbon to ferrous chloride about 0.05 mg/g to about 0.5 mg/g. The iron (11) compound is precipitated in about 30% to about 80% with an alkali followed by oxidation. US 6689206 describes preparation of yellow iron oxide by adding precipitated ferrous chloride solution to alpha-FeOOH seeds produced by the alkaline process. The suspension is then oxidised in two stages with continuous addition of alkali.
US 6530987B1 describes a process for the preparation of iron oxide pigment from the waste acid resulting from the preparation of titanium dioxide by the sulfate process. The sulfuric acid contained in the waste acid is partially neutralized with metallic iron and/or an iron compound having a manganese content of US 6534032B2 describes a process for the production of yellow iron oxide comprising adding an iron component comprising FeSO4 or FeCl2 with an Fe (III) content of 0.5 to 1.5 mol % Fe (III)
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and a Mn content of up to 0.7 wt. %, based on the Fe content of FeSO4 or FeCl2, to a solution or suspension of an alkaline component that has been heated between 42 and 75°C and oxidizing the suspension formed with an oxidizing agent at 42 to 75°C until all iron (II) has been converted into iron (III) as a-FeOOH. US 2005/0045066 Al relates to iron oxide pigment prepared by precipitation method from iron (11) chloride or iron (11) sulphate and calcium carbonate precipitant. Use of calcium carbonate leads to contamination of the pigment with calcium carbonate.
Leach liquor (containing ferrous and ferric chlorides and residual hydrochloric acid) is a waste from synthetic rutile plant formed during leaching out of iron from ilmenite ore using hydrochloric acid. Leach liquor is also contaminated with several of the metallic impurities present in the ilmenite ore such as oxides of aluminium, silica, chromium, vanadium, manganese, calcium, magnesium, sodium, potassium, zirconium or titanium. Leach liquor is generally used for regeneration of hydrochloric acid in about 16-18% concentration by hydrothermal decomposition of the ferrous and ferric chloride in a spray roaster. Iron oxide contaminated with the impurities present in the leach liquor, is left behind and is a waste creating disposal and environmental problems.
Preparation of yellow iron oxide pigment using the ferrous chloride and ferrous sulfate routes involves precipitation of ferrous hydroxide with alkali. Depending upon the alkalis generally used, this generates ammonium chloride and sodium chloride or ammonium sulphate and sodium sulphate which are normally disposed of creating waste disposal and environmental problems. Due to the presence of ferric chloride and hydrochloric acid and also the impurities, leach liquor
5

cannot be directly used for making yellow iron oxide pigment. Presence of the impurities and ferric chloride will reduce the colour quality of the pigment from yellow to redish. Excess alkali also will be required to neutralise the acid.
OBJECTS OF INVENTION
An object of the invention is to provide a process for the recovery of valuable products from leach liquor namely yellow iron oxide pigment, ammonia and calcium chloride, thereby practically converting the entire waste leach liquor into useful and valuable products and eliminating waste disposal and environmental problems and realizing economy.
Another object of the invention is to provide an equipment for the recovery of valuable products from leach liquor namely yellow iron oxide pigment, ammonia and calcium chloride, thereby practically converting the entire waste leach liquor into useful and valuable products and eliminating waste disposal and environmental problems and realizing economy.
DETAILED DESCRIPTION OF INVENTION
According to the invention there is provided a process for the recovery of valuable products from leach liquor, namely yellow iron oxide pigment, ammonia and calcium chloride, the process comprising :
a) reacting the leach liquor with iron to convert free hydrochloric acid and ferric chloride in the leach liquor to ferrous chloride;
6

b) precipitating the impurities in the leach liquor by treating the leach liquor with an aqueous ammonia solution containing 8-12%ammonia at a pH of 2.5 to 5 under agitation;
c) flocculating the precipitated impurities by treating the leach liquor with a flocculating agent;
d) separating the flocculated impurities from the leach liquor to obtain a purified ferrous chloride solution;
e) adjusting optionally the pH of the ferrous chloride solution between 1.5 to 2 by treatment with hydrochloric acid;
f) reacting the ferrous chloride solution containing a ferrous iron (Fe++) concentration of 2.0 to 4.0% with an aqueous solution of ammonia containing 8-12% ammonia in the presence of 8-15% ammonium chloride and chilled water under agitation to convert ferrous chloride to ferrous hydroxide, oxidizing the ferrous hydroxide with air at a temperature between 18-35°C and a pH between 3 to 5 to form hydrated ferric oxide pigment seeds (yellow pigment seeds) and further oxidizing the pigment seeds with oxygen mixed with steam in the presence of an aqueous ammonia solution containing 8-12% ammonia at 60-85°C under agitation and at pH at 3 to 5 to allow the seeds to grow to the require size; filtering the pigment slurry to separate the pigment cake from the mother liquor containing ammonium chloride, washing the pigment cake with water, drying the pigment cake and pulverizing the cake;
and recovering ammonia and calcium chloride from the mother liquor.
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In order to render the process economical, the reaction of leach liquor in step (a) is carried out with carbon steel scraps such as cuttings, punchings and / or trimmings of cold rolled carbon steel. The leach liquor used in step (a) is generally at about 60 - 85°C. Exothermeric heat of the reaction of the leach liquor with iron (carbon steel scraps) maintains the temperature of the reaction. Dissolution of the iron in the leach liquor at high temperatures of 60-85°C dilutes the hydrogen concentration with water vapours below ignitable limit. Due to agitation of the leach liquor during the precipitation step (b) formation of black iron oxide is avoided and the colour quality of the pigments is maintained. The flocculating agent used in step (c) is selected from polyelectrolytes, preferably polyacrylate. The separation of the flocculated impurities from the leach liquor in step (d) is preferably carried out by clarification. To avoid oxidation of the ferrous chloride during storage, pH of the solution is optionally adjusted between 1.5-2 by treatment with hydrochloric acid. Preferably the drying of the pigment in step (g) is carried1 out at 110- 130°C.
According to an embodiment of the invention the step (h) of recovering ammonia and calcium chloride from the mother liquor comprises
i) reacting the mother liquor containing ammonium chloride with lime to form ammonia and calcium chloride;
ii) recovering the ammonia from the reaction mixture by subjecting the reaction mixture to steam distillation;
iii) dissolving the distilled off ammonia in water to form aqueous ammonia solution;
iv) cooling the distiller liquid containing calcium chloride;
v) filtering the distiller liquid to remove lime grits;
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vi) concentrating the clear solution of calcium chloride by exporation; and
vii) and converting the concentrated calcium chloride to the required form followed
by calcination and cooling. Calcination of the calcium chloride is carried out to reduce the moisture content thereof. According to an embodiment of the invention the concentrated calcium chloride is converted into flakes by
viia) flaking it at 170- 175°C;
viib) calcining the flakes at 200 to 220 °C; and
viic) cooling the calcined flakes to 40 - 45°C. According to the invention there is also provided an equipment for recovering valuable products from leach liquor namely yellow iron oxide pigment, ammonia and calcium chloride, the equipment consisting of an yellow iron oxide pigment recovering unit, an ammonium recovering and recycling unit and a calcium chloride recovering unit.
According to an embodiment of the invention, the equipment consists of a scrap iron reactor provided with a scrap iron inlet, leach liquor inlet and leach liquor recirculation line having a first pump and a first valve, an impurities precipitation tank provided with a leach liquor inlet line connected across the leach liquor recirculation line between the first pump and first valve and having a second valve, the precipitation tank being further provided with an agitator and an aqueous ammonia solution supply line connected to the outlet of an aqueous ammonia storage tank and provided with a second pump, a flocculation tank provided with an ammonia treated leach liquor inlet line connected to the outlet of the precipitation tank and having a third pump, the flocculation tank being further provided with a flocculant inlet line and an agitator, a clarifier
9

connected to the outlet of the flocculation tank through a fourth pump, a ferrous chloride solution storage tank connected to the launder of the clarifier, a pigment formation reactor provided with a ferrous chloride solution inlet line connected to the ferrous chloride solution storage tank through a fifth pump, the pigment formation reactor being further provided with an air inlet, chilled water inlet, aqueous ammonia solution inlet connected across the aqueous ammonia solution supply line, oxygen inlet, steam inlet and mother liquor (ammonium chloride) inlet line, the pigment formation reactor being further provided with an agitator, a first filter comprising a pigment slurry inlet line connected to the outlet of the pigment formation reactor through a sixth pump, a solid outlet line connected to a dryer and a mother liquor (filtrate) outlet line connected to a mother liquor storage tank, a mother liquor supply line connected to the inlet of a mother liquor and lime reactor and to the outlet of the mother liquor storage tank through a seventh pump, the mother liquor inlet line being connected across the mother liquor supply line past the seventh pump, the dryer being connected to a pulviser having an outlet line, the mother liquor and lime reactor being provided with a lime inlet line and ammonia gas outlet line connected to the ammonia gas outlet line of a distiller, the mother liquor and lime reactor being further provided with a reaction liquid outlet line connected to the reaction liquid inlet of the distiller at the top thereof through an eight a pump, the mother liquor and lime reactor being further provided with an agitator, the distiller being provided with a steam inlet line at the bottom thereof, the ammonia gas outlet line of the distiller being connected to the ammonia gas inlet of a gas scrubber at the bottom thereof, the gas scrubber being provided with a water inlet line and an air outlet at the top and an aqueous ammonia solution recirculation line provided with a ninth pump and a heat exchanger, the inlet of the aqueous ammonia storage tank being connected across the said aqueous ammonia recirculation line past the heat exchanger, a second filter
10

comprising a calcium chloride solution inlet line connected to the calcium chloride solution outlet of the distiller at the bottom thereof through a tenth pump and a lime stone grits outlet line, a lime stone grits collection trolley disposed below the lime stone grits outlet line, a calcium chloride solution collection tank comprising a calcium chloride inlet line connected to the outlet of the second filter, an evaporator comprising a calcium chloride solution inlet line connected to the calcium chloride solution outlet of the calcium chloride collection tank through an eleventh pump, a vapour separator comprising a vapor inlet line at the top thereof connected to the vapor outlet at the top of the evaporator, the vapour separator further comprising a steam outlet line at the top and a concentrated calcium chloride solution outlet line at the bottom thereof connected to the inlet of a water cooled flaker and a calciner comprising a flakes inlet line connected to the outlet of the flaker and a calcined flakes outlet line connected to the flakes inlet line of a cooler.
The following is a detailed description of the invention with reference to the accompanying drawings in which the sole Fig 1 is a flow diagram of the equipment used for recovering valuable products from leach liquor according to an embodiment of the invention. The equipment 1 as illustrated in Fig 1 of the accompanying drawings consists of a scrap iron reactor 2 provided with a scrap iron inlet 3, leach liquor inlet 4 and leach liquor recirculation line 5 having a first pump 6a and first valve 7a. 8 is an impurities precipitation tank provided with a leach liquor inlet line 9 connected across the leach liquor recirculation line 5 between pump 6a and valve 7a. 7b is a second valve provided in line 9. Tank 8 is further provided with an agitator 10 and an aqueous ammonia solution supply line 11 connected to the outlet of an aqueous ammonia storage tank 12 and provided with a second pump 6b. 13 is a flocculation tank provided with an ammonia treated leach liquor inlet line 13a connected to the precipitation tank outlet and having a third
11

pump 6c. The flocculation tank is further provided with a flocculant inlet line 14 and an agitator 15. 16 is a clarifier comprising a leach liquor inlet line 16a connected to the outlet of the flocculation tank through a fourth pump 6d. 16b is precipitate outlet line of the clarifier. 17 is a ferrous chloride solution storage tank connected to the launder 18 of the clarifier through line 16c. 19 is a pigment formation reactor provided with a ferrous chloride solution inlet line 19a connected to the ferrous chloride solution storage tank through a fifth pump 6e. The pigment formation reactor is further provided with an air inlet 20, chilled water inlet 21, aqueous ammonia solution inlet line 22, oxygen inlet 23, steam inlet 24, mother liquor (ammonium chloride) inlet line 25 and an agitator 26. The ammonia solution inlet line 22 is connected across the ammonia solution supply line 11. 27a is a first filter comprising a pigment slurry inlet line 28 connected to the outlet of the pigment formation reactor through a sixth pump (f), a solid outlet line 29 connected to a dryer 30 and a mother liquor (filtrate) outlet line 31 connected to a mother liquor storage tank 32. The dryer 30 is a tray dryer but can be any other type of dryer also. 33 is a mother liquor supply line connected to the outlet of the mother liquor storage tank through a seventh pump 6g and further connected to the inlet of a mother liquor and lime reactor 34. The mother liquor inlet line 25 is connected across the mother liquor supply line 33 past the seventh pump 6g. The tray dryer is connected to a pulveriser 35 having outlet one 35a. The mother liquor and lime reactor is provided with a lime inlet line 36 and an ammonia gas outlet line 37 connected to the ammonia gas outlet line 38 of a distiller 39. The mother liquor and lime reactor is further provided with a reaction liquid outlet line 40 connected to the reaction liquid inlet of the distiller at the top thereof through an eighth pump 6h. Tthe mother liquor reactor is further provided with an agitator 41. The distiller is provided with a steam inlet line 42 at the bottom thereof. The ammonia gas outlet line of the distiller is connected to the ammonia gas
12

inlet of a gas scrubber 43 at the bottom thereof. The gas scrubber is provided with a water inlet line 44 and air outlet 45 at the top and an aqueous ammonia solution recirculation line 46 provided with a ninth pump 6i and a heat exchanger 47. Cold water inlet and hot water outlet of the heat exchanger are marked 47a and 47b, respectively. The inlet of the aqueous ammonia storage tank 12 is connected across the aqueous ammonia recirculation line 46 past the heat exchanger 47 through cross line 48. 49 is a second filter comprising calcium chloride solution inlet line 50 connected to the outlet of the distiller at the bottom thereof through a tenth pump 6j. 51 is a lime stone grits collection trolley disposed below the lime stone grits outlet line 52 of the second filter. 53 is a calcium chloride solution collection tank comprising a calcium chloride inlet line 54 connected to the outlet of the second filter. 55 is an evaporator comprising a calcium chloride solution inlet line 56 connected to the calcium chloride solution outlet of the calcium chloride collection tank through an eleventh pump 6k. Steam inlet and steam condensate outlet of the evaporator are marked 57 and 58, respectively. 59 is a vapour separator comprising a vapour inlet line 60 at the top thereof connected to the vapour outlet at the top of the evaporator. The vapour separator also comprises a steam outlet line 61 at the top and a concentrated calcium chloride outlet line 62 at the bottom thereof connected to the inlet of a water cooled flaker 63. 64 is a calciner comprising a flakes inlet line 65 connected to the outlet of the flaker and a calcined flakes outlet line 66 connected to the flakes inlet of a cooler 67. The cooler outlet line is marked 68. The calciner 64 is a rotary calciner but can also be any other type of calciner.
The scrap iron reactor 2 is loaded with iron scraps (not shown), valve 7a is kept open and valve 7b is kept closed. Leach liquor (not shown) at about 60 to 80°C is pumped into the reactor 2 via
13

inlet line 4 and recirculated in the reactor 2 via the recirculation line 5 by operating the pump 6a. The acid concentration in the leach liquor is monitored and when the acid concentration drops very low say 0.1% HCL or less as indicated by a pH of about 1, the recirculation of the leach liquor is stopped. The reaction temperature of the leach liquor with iron scrap is maintained between 60-80°C due to the exhothermic nature of the reaction. Valve 7a is closed and valve 7b is opened and the leach liquor is pumped into the precipitation tank by pump 6a. Aqueous ammonia solution is pumped into the precipitation tank 8 via the supply line 11 by the pump 6b. The p of the leach liquor in the precipitation tank is maintained between 2.5 to 5 under agitation to precipitate the impurities in the leach liquor. The agitator 10 is switched off and the leach liquor in the precipitation tank is pumped into the flocculation tank 13 by pump 6c via the inlet line 13a. The leach liquor in the flocculation tank is dosed with a flocculent via the inlet line 14 under agitation so as to flocculate the precipitated impurities. The agitator 15 is switched off and the leach liquor is pumped into the clarifier 16 by pump 6d via the inlet line 16a. The flocculated impurities in the leach liquor settle at the bottom of the clarifier and are drained out via the precipitate outline 16b of the clarifier. The clarified (purified) ferrous chloride solution rises in the launder 17 thereof and flows down into the ferrous chloride solution storage tank 18. The pH of the ferrous chloride solution in the tank 18 is adjusted optionally with hydrochloric acid and it is pumped into the pigment formation reactor 19 by pump 6e via inlet line 19a. Part of the mother liquor (ammonium chloride solution) from storage tank 32 pumped by pump 6g and part of the aqueous ammonia solution from storage tank 12 pumped by pump 6b and chilled water are fed into the reactor 19 via line 25, line 22 and line 21, respectively. Air is also supplied into the reactor 19 via line 20. The reaction is agitated and the pH is maintained between 3 to 5. Ferrous chloride gets converted into ferrous hydroxide and ammonium chloride. The ferrous hydroxide
14

is oxidized to ferric hydroxide seeds. Because of the chilled water the reaction temperature is maintained between 18-35°C during this time. Air supply is discontinued and instead oxygen and steam are supplied into the reactor 19 via inlet lines 23 and 24, respectively. Agitation is continued and pH is maintained between 3-5 with continued supply of ammonia so as to allow the seeds to grow to the required sizes ie colour values by further oxidation. The reaction temperature in the reactor 19 rises to 65 to 85°C because of the steam and the temperature is maintained due to the exhothermic nature of the reaction. The agitator 26 is switched off and the pigment slurry is pumped into the filter 27a by pump 6f via line 28. Yellow iron oxide pigment cake from the filter is fed into the dryer 30. The dried pigment cake is pulverized in the pulveriser 35 and discharged for bagging or packing via outlet line 35a of the pulveriser.
The mother liquor (filtrate containing ammonium chloride) from the filter 27a flows into the storage tank 32 via line 31. A major quantity of the mother liquor in the storage tank 32 is pumped into the mother liquor and lime reactor 34 by pump 6g. The remaining quantity of the mother liquor is recycled into the pigment formation reactor 19 via the line 25. The mother liquor is reacted with lime in the reactor 34 under agitation. Ammonia gas evolved flows into the ammonia gas outlet line 38 of the distiller via line 37. The agitator 41 is switched off and reaction liquid in the reactor 33 is pumped into the distiller 39 and is subjected to distillation by steam fed through line 42. Ammonia gas being formed flows into the ammonia gas outlet line 38 and from there into the gas scrubber 43. Ammonia gas dissolves in the water being supplied into the gas scrubber and the aqueous ammonia solution is recirculated through the recirculation line 46 by pump 6i to increase the concentration thereof. The aqueous ammonia solution being recirculated through the recirculation line 46 is cooled in the heatexchanger by passing cooling
15

water therethrough. Cooling water enters the heat exchanger through inlet 47a and hot water leaves the heat exchanger via outlet 47b. Air in the reaction liquid are let out through the air outlet line 45. Aqueous ammonia solution is collected in the storage tank 12 and is recycled into the precipitation tank 8 and pigment formation reactor 19 via the lines 11 and 22. The calcium chloride solution in the distiller is pumped into the filter 49 by pump 6j via line 50 and is filtered in the filter 49. Lime stone grits are discharged into the trolley underneath the filter and are disposed of. The filtrate comprising calcium chloride solution flows into the calcium chloride collection tank 53 via the line 54. The calcium chloride solution is pumped into the evaporator 55 by pump 6k via line 56 and evaporated in the evaporator by steam supplied
through the inlet line 57 thereof. The steam condensate flows out through the outlet line 58 of
a.. the evaporator. The vapours flow into the vapour separator 59 via line 60 thereof. Water
vapours ie steam flow out via the outlet line 61 of the vapour separator. Concentrated calcium
chloride solution flows into the water cooled flaker 63 via the inlet line 62, where they are
flaked. Calcium chloride flakes flow into the calciner 64 via the inlet line 65 where theysare
calcined. The calcined flakes are cooled in the cooler 67 and discharged via the outlet line 68 of
the cooler for bagging or packing.
It is to be clearly understood that the construction and configuration of the equipment in terms of the individual units like reactors, filters, precipitation tank or flocculation tank and their layout can vary depending upon the process requirements. The type of the agitators used in the reactors, precipitation tank or flocculation tank will depend upon the process requirements and can be single or double impeller types. There can be equipment configurations comprising more than one of such units. Instead of the clarifier a filter can be used to separate the flocculated
16

impurities from the ferrous chloride solution. Instead of clarification, other known techniques like filtration can be used to separate the impurities from the leach liquor. The concentrated calcium chloride can be converted into forms other than flakes like powder or granules. The equipment need not have a flaker. Instead, it can comprise spray dryer or granulator depending upon the forms into which the concentrated calcium are to be converted. Such variations in the process and equipment configuration and construction are obvious to those skilled in the art and are to be construed and understood to be clearly within the scope of the invention.
Yellow iron oxide pigment has a variety of uses, its main use being in paint industry for coating formulations and in construction industry for colouring of concrete. It also finds applications in food and pharmaceutical industries, paper and plastics industries or printing industry or as catalyst. Calcium chloride also has a variety of uses, for instance, as desicant for drying out moisture in various industries, in cement paint industry, construction industry, oil well drilling, petroleum industry, paper industry, or refrigerating industry or as a snow thawing agent, or as additive in ferrous metallurgy. Besides being recycled and used in the process and equipment of the invention ammonia being recovered can also be used as ammonium hydroxide alkali or ammonia gas to make nitrogenous fertilizers or other ammonium salts.
According to the invention, leach liquor, a waste from a synthetic rutile plant, is practically entirely recovered as useful and valuable products namely yellow iron oxide pigment, calcium chloride and ammonia. Therefore, waste disposal and resultant environmental problems are practically eliminated and significant economical benefits are realized.
17

The following examples are illustrative of the invention but not limitative of the scope thereof.
Example 1
Carbon steel scraps (cuttings, punchings and trimmings of cold rolled carbon steel) were loaded in a 15 KL reactor tank. Ten kilo litre (KL) leach liquor at 70°C was pumped into the tank upto the level of the scraps. The leach liquor was recirculated through the scraps for 12 hours until the pH of the leach liquor dropped to 1 indicating completion of the reaction. Due to the exothermic nature of the reaction, reaction temperature remained at 70°C without any external heating. The leach liquor composition before and after the scrap treatment was as in the following Table 1:
Table 1

Before treatment After treatment
Ferrous chloride (FeC12) % 26.814 32.11
Ferric chloride (FeC13) % 2.013 Nil
Hydrochloric acid % 2.163 0.07 (pH about 1)
Aluminium (Al) 960 ppm 975 ppm
Chromium (Cr) 68 ppm 73 ppm
Cadmium (Cd) 2.5 ppm 3.0 ppm
Silicon (Si) 115 ppm 120 ppm
Magnesium (Mg) 1350 ppm 1370 ppm
Manganese (Mn) 952 ppm 975 ppm
The scraps treated leach liquor (9KL) was taken in a precipitation tank and aqueous ammonia solution of 10% concentration was added into the tank to raise the pH to 4 under agitation. The agitation was continued for 10 minutes to precipitate the impurities after which the leach liquor was taken in a flocculation tank and 0.1% solution of poly acrylate was added into the tank under agitation. The agitation was stopped after 30 minutes to allow the precipitated impurities to
18

flocculate. The leach liquor was pumped into a clarifer to separate a clear solution of ferrous chloride having the composition as in the following Table 2:
Table 2

Ferrous chloride (FeC12) % 30.1
Ferric chloride (FeC13) % Nil
Hydrochloric acid pH 4.0
Aluminium (Al) 15 ppm
Chromium (Cr) 2 ppm
Cadmium (Cd) lppm
Silicon (Si) 7 ppm
Magnesium (Mg) 1285 ppm
Manganese (Mn) 930 ppm
The pH of the ferrous chloride solution was adjusted to 2 with hydrochloric acid. Ammonium chloride solution of 10.95% concentration at 21°C and 6 KL chilled water at 12°C were pumped into a 60KL pigment formation reactor. To this, the ferrous chloride solution (5.5 KL) containing a ferrous iron (Fe++) concentration of 3.06% was added under agitation. 1680 litres of aqueous ammonia solution of concentration 8.56% was also added into the reactor in ten minutes. Ferrous hydroxide formed in the reaction is oxidized to hydrated ferric oxide seeds or Alpha FeOOH nuclei (yellow seeds) by allowing air into the reactor at a flow rate of 60 m3 / hour and pressure 3.5 kg/cm2. Oxidation was continued for three hours until the seed formation was complete. Because of the chilled water the reaction temperature remained at 20-22°C. The pH of the reaction was retained at 3.5-4 with the use of the ammonia. Air flow was stopped and oxygen flow at a rate 12 m / hr at pressure 3.8 kg / cm was started. Simultaneously steam was introduced into the reactor. Addition of aqueous ammonia solution was started to maintain the pH at 3.4. After 5 hours, the reactor temperature rose to 70°C and the steam supply was stopped. The reaction temperature was maintained 73 - 75°C by the exothermic heat of the reaction. After 5 hours of pigment crystal growth, steam supply was discontinued. The reaction was dosed with
19

the remaining ferrous chloride solution (5.5 KL) for about 20 hrs to maintain Fe++ concentration in the reaction mixture between 1.0 -1.5%. Dosing of ferrous chloride was stopped 5 hrs before the completion of the reaction to consume almost all the Fe++ present. The reaction was terminated after 30 hours of crystal formation.
The pigment slurry containing 62.67 kg/KL solids was filtered and the filter cake containing 48% moisture was dried in tray dryers at 110-130°C to get a final moisture content below 0.5%. The dried cake (weight 2977 kgs) was pulverized and bagged.
The physical and chemical characteristics of the pigment were as in the following Table 3.
Table 3

Volatile matter % 0.25
Residue on sieve - 300 0.05
Matter soluble in water % 0.25
p" 3.98
Loss of Ignition % 11.63
Oil absorption gm /100 gm pigment 31.0
Conductivity mmho 132
The colour values (CIELAB UNITS) of the pigments were as in the following Table 4 measured in draw down made in acrylic resin :
Table 4

Mass Tone L 59.07
A 15.44
B 44.53
Reduced Tone (1 : 3) L 76.43
A 10.59
B 35.07
It is quite clear from the Table 4 that the pigments were of good quality.
20

The mother liquor (28 KL) containing ammonium chloride of concentration of 12.2% was treated with lime to form ammonia and calcium chloride. Ammonia was recovered from the reaction mixture by steam distillation. Ammonia gas was dissolved in water to make 10% solution for recycling to pigment production. Ammonia recovery was 98 %. The distillar liquid containing calcium chloride solution was cooled and filtered to remove lime stone grits. The clear solution was concentrated by evaporation. The concentrate containing 71% calcium chloride was flaked at 172°C. The flakes were calcined at 210°C and cooled to 45°C. Calcium chloride recovery was 95%. The composition of the calcium chloride flakes were as in the following Table 5 :
Table 5

CaC12 % 78
MgC12 % 0.3
Alkali Chlorides as NaCl % 1.0
Sulphate as CaS04 % 0.1
Water Insolubles % 0.2
pH of 10% solution 9.0
Flakes size 1.5-3.0 mm
The flakes were of good quality as can be seen in Table 5.
Example 2
Twelve KL leach liquor at 80°C was treated with carbon steel scraps in the same manner as stated in Example 1. The reaction temperature was maintained at 80°C and the recirculation was carried out for 9 hours. Leach liquor composition before and after treatment with scraps was as given in the following Table 6
21

Table .6
Before Treatment After Treatment
Ferrous chloride (FeC12) % 26.08 34.32
Ferric chloride (FeC13) % 2.4 Nil
Hydrochloric acid % 3.1 0.08 (pH about 1)
Aluminium (Al) 890 ppm 905 m
Chromium (Cr) 75 ppm 78ppm
Cadmium (Cd) 3.5 ppm 40 ppm
Silicon (Si) 105 ppm 110 ppm
Magnesium (Mg) 1030 ppm 1060 ppm
Manganese (Mn) 535 ppm 545 ppm
Table 7

Ferrous chloride (FeC12) % 32.1
Ferric chloride (FeC13) % Nil
Hydrochloric acid pH pH4.5
Aluminium (Al) 20 ppm
Chromium (Cr) 3 ppm
Cadmium (Cd) Not detectable
Silicon (Si) 9 ppm
Magnesium (Mg) 980 ppm
Manganese (Mn) 515 ppm
The clear ferrous chloride solution without acidification with HCL was used for seed formation and crystal growth in a 60 KL pigment formation reactor. 16 KL mother liquor (ammonium chloride solution) at 19°C and concentration 12.2% NH4C1, 8 KL chilled water at 14°C and 5 KL ferrous chloride solution containing ferrous concentration of 3.26% Fe++ were pumped into the reactor. The reaction temperature remained at 20°C. 1600 litres Ammonia solution of
22

concentration of 10.5% was added in the reactor in 10 minutes to precipitate ferrous hydroxide. Air at 65 M3 per hour and pressure 3.5 kg/cm2 was introduced to oxidize ferrous hydroxide to yellow iron oxide seeds. Air flow was stopped and oxygen flow at 14 M3 / hour at a pressure of 3.8 kg/cm2 was started with simultaneous steam introduction for four hours to raise the reaction temperature to 65°C. Thereafter the reaction temperature rose to 72°C due to the exothermic heat of the reaction and remained steady in the range 72 to 78°C. Due to the high rate of reaction crystal growth was over in 26 hours when the reaction was terminated.
The pigment slurry containing 62.18 kg/KL solids was processed as in Example 1. The dried cake weighed 2985 kgs. The physical and chemical characteristics of the pigments were as in the following Table 8 :
Table 8

Volatile matter % 0.42
Residue on sieve - 300 0.06
Matter soluble in water % 0.18
PH 3.75
Loss of Ignition % 11.91
Oil absorption gm / 100 gm pigment 27.31
Conductivity mmho 236
The colour values (CIELAB Units) of the pigments were as in the following Table 9 :
Table 9

Mass Tone L 58.78
A 15.40
B 45.27
Reduced Tone L 77.136
A 11.13
B 37.91
Table 9 clearly shows that the pigments were of good quality.
23

The mother liquor 30 KL containing ammonium chloride concentration of 12.2% was processed in the same manner as in Example 1. 98.5 % of ammonia content in NH4CI was recovered as ammonia. The calcium chloride concentrate had 12% calcium chloride. Ammonia recovery was 98.5 %. Calcium chloride recovery was 94.0%.
The composition of the calcium chloride flakes were as in the following Table 10:
Table 10

CaC12 % 80.0
MgC12 % 0.4
Alkali Chlorides as NaCl % 1.2
Sulphate as CaS04 % 0.12
Water Insolubles % 0.15
pH of 10% solution 8.3
Flakes size 1.5 -3.5mm
The flakes were of good quality as can be seen in Table 10.
24

We claim
1. A process for the recovery of valuable products from leach liquor, namely yellow iron oxide pigment ammonia and calcium chloride, the process comprising :
a) reacting the leach liquor with iron to convert free hydrochloric acid and ferric chloride in the leach liquor to ferrous chloride;
b) precipitating the impurities in the leach liquor by treating the leach liquor with an aqueous ammonia solution containing 8-12%ammonia at a p of 2.5 to 5 under agitation;
c) flocculating the precipitated impurities by treating the leach liquor with a flocculating agent;
e) separating the flocculated impurities from the leach liquor to obtain a purified ferrous chloride solution;
e) adjusting optionally the pH of the ferrous chloride solution between 1.5 to 2 by treatment with hydrochloric acid;
f) reacting the ferrous chloride solution containing a ferrous iron (Fe++) concentration of 2.0 to 4.0% with an aqueous solution of ammonia containing 8-12% ammonia in the presence of 8-15% ammonium chloride and chilled water under agitation to convert ferrous chloride to ferrous hydroxide, oxidizing the ferrous hydroxide with air at a temperature between 18-35°C and a pH between 3 to 5 to form hydrated ferric oxide pigment seeds (yellow pigment seeds) and further oxidizing the pigment seeds with oxygen mixed with steam in the presence
25

of an aqueous ammonia solution containing 8-12% ammonia at 60-85°C under
agitation and at pH at 3 to 5 to allow the seeds to grow to the require size; g) filtering the pigment slurry to separate the pigment cake from the mother liquor
containing ammonium chloride, washing the pigment cake with water, drying the
pigment cake and pulverizing the cake; h) and recovering ammonia and calcium chloride from the mother liquor.
2 A process as claimed in claim 1, wherein the reaction of leach liquor in step (a) is carried out with carbon steel scraps.
3 A process as claimed in claim 1, wherein the flocaulating agent used in step (c) is polyacrylate.
4 A process as claimed in claim 1, wherein the separation of the flocculated impurities from the leach liquor in step (d) is carried out by clarification;
5 A process as claimed in claim 1, wherein the drying of the pigment cake in step (g) is
carried out atllO-130°C.
6. A process as claimed in claim 1,wherein the step(h) of recovering ammonia and calcium chloride from the mother liquor comprises
i) reacting the mother liquor containing ammonium chloride with lime to
form ammonia and calcium chloride; ii) recovering the ammonia from the reaction mixture by subjecting the reaction
mixture to steam distillation; iii) dissolving the distilled off ammonia in water to form aqueous ammonia solution;
26

iv) cooling the distiller liquid containing calcium chloride; v) filtering the distiller liquid to remove lime grits; vi) concentrating the clear solution of calcium chloride by exporation; and vii) and converting the concentrated calcium chloride to the required form followed by calcination and cooling;
7 A process as claimed in claim 6, wherein in the concentrated calcium chloride is converted
into flakes by
viia) flaking it at 170 - 175°C;
viib) calcining the flakes at 200 to 220 °C; and
viic) cooling the calcined flakes to 40 - 45°C.
8 An equipment for recovery of valuable products from leach liquor namely yellow iron oxide pigment, ammonia and calcium chloride, the equipment consisting of an yellow iron oxide pigment recovering unit, an ammonium recovering and recycling unit and a calcium chloride recovering unit.
9 An equipment as claimed in claim 9, consisting of a scrap iron reactor provided with a scrap iron inlet, leach liquor inlet and leach liquor recirculation line having a first pump and a first valve, an impurities precipitation tank provided with a leach liquor inlet line connected across the leach liquor recirculation line between the first pump and first valve and having a second valve, the precipitation tank being further provided with an agitator and an aqueous ammonia solution supply line connected to the outlet of an aqueous
27

ammonia storage tank and provided with a second pump, a flocculation tank provided with an ammonia treated leach liquor inlet line connected to the outlet of the precipitation tank and having a third pump, the flocculation tank being further provided with a flocculant inlet line and an agitator, a clarifier connected to the outlet of the flocculation tank through a fourth pump, a ferrous chloride solution storage tank connected to the launder of the clarifier, a pigment formation reactor provided with a ferrous chloride solution inlet line connected to the ferrous chloride solution storage tank through a fifth pump, the pigment formation reactor being further provided with an air inlet, chilled water inlet, aqueous ammonia solution inlet connected across the aqueous ammonia solution supply line, oxygen inlet, steam inlet and mother liquor (ammonium chloride) inlet line, the pigment formation reactor being further provided with an agitator, a first filter comprising a pigment slurry inlet line connected to the outlet of the pigment formation reactor through a sixth pump, a solid outlet line connected to a dryer and a mother liquor (filtrate) outlet line connected to a mother liquor storage tank, a mother liquor supply line connected to the inlet of a mother liquor and lime reactor and to the outlet of the mother liquor storage tank through a seventh pump, the mother liquor inlet line being connected across the mother liquor supply line past the seventh pump, the dryer being connected to a pulviser having an outlet line, the mother liquor and lime reactor being provided with a lime inlet line and ammonia gas outlet line connected to the ammonia gas outlet line of a distiller, the mother liquor and lime reactor being further provided with a reaction liquid outlet line connected to the reaction liquid inlet of the distiller at the top thereof through an eight a pump, the mother liquor and lime reactor being further provided with an agitator, the distiller being provided with a steam inlet line at the bottom thereof, the ammonia gas outlet line of the
28

distiller being connected to the ammonia gas inlet of a gas scrubber at the bottom thereof, the gas scrubber being provided with a water inlet line and an air outlet at the top and an aqueous ammonia solution recirculation line provided with a ninth pump and a heat exchanger, the inlet of the aqueous ammonia storage tank being connected across the said aqueous ammonia recirculation line past the heat exchanger, a second filter comprising a calcium chloride solution inlet line connected to the calcium chloride solution outlet of the distiller at the bottom thereof through a tenth pump and a lime stone grits outlet line, a lime stone grits collection trolley disposed below the lime stone grits outlet line, a calcium chloride solution collection tank comprising a calcium chloride inlet line connected to the outlet of the second filter, an evaporator comprising a calcium chloride solution inlet line connected to the calcium chloride solution outlet of the calcium chloride collection tank through an eleventh pump, a vapour separator comprising a vapor inlet line at the top thereof connected to the vapor outlet at the top of the evaporator, the vapour separator further comprising a steam outlet line at the top and a concentrated calcium chloride solution outlet line at the bottom thereof connected to the inlet of a water cooled flaker and a calciner comprising a flakes inlet line connected to the outlet of the flaker and a calcined flakes outlet line connected to the flakes inlet line of a cooler.
An equipment as claimed in claim 10, wherein the dryer is a tray dryer.
An equipment as claimed in claim 10 or 11, wherein the calciner is a rotary calciner.
29

12 Valuable products namely yellow iron oxide pigment, ammonia and calcium chloride obtained by the process as claimed in any one of claims 1 to 7.

Abstract
A process for the recovery of valuable products from leach liquor, namely yellow iron oxide pigment ammonia and calcium chloride. Leach liquor is reacted with iron to convert free hydrochloric acid and ferric chloride in the leach liquor to ferrous chloride. The impurities in the leach liquor are precipitated by treating the leach liquor with an aqueous ammonia solution containing 8-12%ammonia at a pH of 2.5 to 5 under agitation. The precipitated impurities are flocculated by treating the leach liquor with a flocculating agent and separated from the leach liquor to obtain a purified ferrous chloride solution. The pH of the ferrous chloride solution is optionally adjusted between 1.5 to 2 by treatment with hydrochloric acid. The ferrous chloride solution containing a ferrous iron (Fe++) concentration of 2.0 to 4.0% is reacted with an aqueous solution of ammonia containing 8-12% ammonia in the presence of 8-15% ammonium chloride and chilled water under agitation to convert ferrous chloride to ferrous hydroxide. The ferrous hydroxide is oxidized with air at a temperature between 18-35°C and a pH between 3 to 5 to form hydrated ferric oxide pigment seeds (yellow pigment seeds) which are further oxidized with oxygen mixed with steam in the presence of an aqueous ammonia solution containing 8-12% ammonia at 60-85°C under agitation and at pH at 3 to 5 to allow the seeds to grow to the require size. The pigment slurry is filtered to separate the pigment cake from the mother liquor containing ammonium chloride. The pigment cake is washed with water, dried and pulverized. Ammonia and calcium chloride in the mother liquor are also recovered. Also an equipment for the recovery of the valuable products.

Documents:

1152-MUM-2006-ABSTRACT(24-4-2009).pdf

1152-mum-2006-abstract(granted)-(17-6-2010).pdf

1152-mum-2006-abstract.doc

1152-mum-2006-abstract.pdf

1152-MUM-2006-CANCELLED PAGES(24-4-2009).pdf

1152-MUM-2006-CLAIMS(24-4-2009).pdf

1152-mum-2006-claims(granted)-(17-6-2010).pdf

1152-mum-2006-claims.doc

1152-mum-2006-claims.pdf

1152-MUM-2006-CORRESPONDENCE 8-7-2008.pdf

1152-mum-2006-correspondence(21-2-2008).pdf

1152-MUM-2006-CORRESPONDENCE(24-4-2009).pdf

1152-MUM-2006-CORRESPONDENCE(31-12-2009).pdf

1152-MUM-2006-CORRESPONDENCE(5-11-2008).pdf

1152-mum-2006-correspondence(ipo)-(18-6-2010).pdf

1152-mum-2006-correspondence-received.pdf

1152-mum-2006-description (complete).pdf

1152-MUM-2006-DESCRIPTION(COMPLETE)-(24-4-2009).pdf

1152-mum-2006-description(granted)-(17-6-2010).pdf

1152-MUM-2006-DRAWING(24-4-2009).pdf

1152-mum-2006-drawings.pdf

1152-MUM-2006-FORM 1(24-4-2009).pdf

1152-mum-2006-form 18(31-8-2006).pdf

1152-mum-2006-form 2(24-4-2009).pdf

1152-mum-2006-form 2(granted)-(17-6-2010).pdf

1152-MUM-2006-FORM 2(TITLE PAGE)-(24-4-2009).pdf

1152-mum-2006-form 2(title page)-(granted)-(17-6-2010).pdf

1152-mum-2006-form 26(21-8-2006).pdf

1152-MUM-2006-FORM 3(24-4-2009).pdf

1152-MUM-2006-FORM 8(24-4-2009).pdf

1152-mum-2006-form-1.pdf

1152-mum-2006-form-2.doc

1152-mum-2006-form-2.pdf

1152-mum-2006-form-3.pdf

1152-MUM-2006-PUBLICATION REPORT(5-11-2008).pdf

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Patent Number

241113

Indian Patent Application Number

1152/MUM/2006

PG Journal Number

26/2010

Publication Date

25-Jun-2010

Grant Date

17-Jun-2010

Date of Filing

19-Jul-2006

Name of Patentee

DCW LIMITED

Applicant Address

NIRMAL, 3RD FLOOR, NARIMAN POINT, MUMBAI 400 021,

Inventors:

#	Inventor's Name	Inventor's Address
1	YADAV BABURAM	DCW LIMITED, SAHUPURAM 628 229, THOOTHUKUDI,

PCT International Classification Number

C01G49/02,C01G57/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA