|Title of Invention||
AN IMPROVED PROCESS FOR THE PREPARATION OF TITANIA RICH SLAG AND METALLIC IRON FROM METALLIZED ILEMINITE IN AN IMPROVED INFLIGHT THERMAL PLASMA REACTOR
|Abstract||The present provides a process for the preparation of titania rich slag and metallized iron from the metallized ilmenite using an extended arc plasma reactor. Thermal plasma technology is emerging as one of the eco-friendly route for processing of ilmenite. Production of TiO2 rich slag from metallized ilmenite by thermal plasma is gaining importance due to increased demand for slag as feed material in the pigment industry. A modified thermal plasma process has been developed using in-flight techniques wherein a closed graphite bed reactor has been used for making TiO2 rich slag from metallized ilmenite. Using this process power consumption is reduced considerably.|
|Full Text||Field of the invention
The present invention relates to an improved process for preparation of titania rich slag and metallic iron from metallized ilmenite. Titania rich slag contains about 75-85% Ti02 which is one of the major feedstock for the production of TiO2 pigment. TiOa is an excellent material for its white luster, which is used in paints, papers, plastics, rubber, ceramics and printing ink and in the manufacture of corrosion resistant as well as heat resistant materials.
Background and prior art of the invention
The invention relates to a modified process for the production of Titania rich slag and metallic iron from metallized ilmenite in a static bed thermal plasma reactor using in-flight process. To reduce the energy consumption a process has been developed to melt separates the metallized ilmenite in an in-flight extended transferred arc thermal plasma reactor. The mentioned process can widely be used in ilmenite processing industries for making Titania rich slag and high value of iron. More particularly, the present invention relates to a process using a static bed plasma reactor with in-flight processing for continuous production of titania rich slag and iron ingot from metallized ilmenite. The product titania rich slag can be used for production of TiO2 pigment. Slag can also be used to produce synthetic rutile containing more than 90% TiO2.
Synthetic rutile is primarily produced by chemical treatment of ilmenite with hydrochloric acid or sulphuric acid to upgrade TiC2content to more than 90%. Direct acid leaching of ilmenite with sulphuric acid brings both TiO2 and iron oxide into solution while HCI digestion brings only iron into solution. [E.N. Kramer, U.S. patent 2437164 (1948); British Titan Products Co. Ltd., British patent 1085359(1967); Ching-Lung Lo and T.S. Muckey, Wah Chang Corp. U.S. patent 3193376 (1965); G.S.Davar, Ind. Patent 124558 (1969); Kenzo Ishihara, outline of Ishihara Sangyo kaisha Ltd. (1970); Columbia Southern Chemical Corp. Br. Pat. 795164, (1958); N.N. Murach and LG. povedskaya, USSR patent 116155 (1958); N.A. Aawal, M. Rehman, S.A. Rarafder and A.M.S. Huq, chem. Abs. 85, (1976), 14632]. The disadvantage of these processes is that it generates large quantities of effluents. During such
processing for every pound of TiO2 1.2 pounds of iron chloride or 4 pounds of iron sulphate were produced [chemical week, 116(1975) 26]. These wastes are difficult to handle and create pollution problems.
Alternatively, Titania rich slag is produced by smelting the ilmenite in an electric arc furnace where the iron oxide is reduced by carbon and separated as pig iron leaving TiO2 in the slag. [T. Noda, J. Metals, (1965) 1728].
Reduction of ilmenite and melting are simultaneously carried out in the arc furnace. The process was very well commercialized at Sorel, Canada for production of titania rich slag, (G.W. Elger, D.E. Kishy, S.C. Rhoads, USBM Rl 8140, (1976), 31; D-J. Swinden and D.G.Jones, Trans. Inst. Min. metal. Sec. C, 87, (1978), 83-87; A.J.Mercahnt and M.A.Warner, Trans. Inst. Min metal. C, 101, (1992) 177-182; R.H.Nafziger, Trans. Inst. Min. metal. C 87, (1978), 120, P.K. Mishra, S.K.Singh, B.C.Acharya, B.C.Mohanty and P.K.Sahoo, Min. processing, Recent Advances and Future trends, Conf. Proc. (1995), 875-878, (Eds) S.P. Mehrotra and Shekar Rajeev, Allied publ, New Delhi; G.M. Denton, A. Schoukens and S. Francois, European patent 583126 (1994). However, this process for the production of Titania rich slag is very much energy intensive and as such quite uneconomical for countries where electrical energy is scarce and expensive.
Thus, smelting of ilmenite for the production of titania rich slag is very much energy intensive and as such quite uneconomical for countries where electrical energy is scare and expensive. Further, titania rich slag so produced by electrical smelting is tailor made only to sulphate route of TiO2 pigment manufacture and it needs further processing to enable to employ it in chloride process. [Mohandas, P.N.; Bhat, K.H.; Janaki, MEK; Sasibhushanan, S.; Mukherjee, P.S.; Mohanty, B.C.; Ray, H.S. USPA NO. 6,306, 195, Oct. 23,2001].
Plasma smelting of ilmenite have also been investigated for production of TiO2 rich slag and iron ingot [A.D. Brent, The smelting of ilmenite in a d.c. transferred arc plasma furnace with a molten anode configuration, Report No. M304, Randburg Mintek, 15 July, 1987; P.K.Sahoo, R.K.Galgali, S.K.Singh, S. Bhattacharjee, P.K.Mishra and B.C. Mohanty, Sc. J. Metell., 28 (1999) 243]. Reference may be made to US patent 6,306, 195 (2001), where it has been described for the
preparation of high-grade synthetic rutile and pig iron by plasma using metallized ilmenite wherein energy requirement can be reduced considerably. [Mohandas, P.N.; Bhat, K.H.; Janaki, MEK; Sasibhushanan, S.; Mukherjee, P.S.; Mohanty, B.C.; Ray, H.S. USPA NO. 6,306, 195, Oct. 23,2001]. Reference may be made to US patent 5,244,488 (1993) where direct smelting process with thermal plasma has been described. (Safo; Ryoda; Shoji, kichino suke; Takemura; Naoshi, US pat 5, 244, 488, September14, 1993).
The smelting of ilmenite to produce Titania rich slag and iron is energy intensive process and hence it may not be suitable for commercial production in the countries where electrical energy is expensive. To reduce the overall energy consumption, a process has been developed to melt the pre-reduced metallized ilmenite in a transferred arc plasma to produce titania rich slag and pig iron [P.N.M Das, K.H, Bhat, P.S.Mukherjee, B.C. Mohanty, H.S. Ray, US Patent No. 6,306, 195 B 7, oct. 23, 2001]. However the disadvantage of the process is that the plasma melting is carried out in a fixed bed plasma reactor and is a batch process. To overcome the above drawback. A patent is filed by R.K.Galgali, P.S. Mukherjee, S.K.Singh, S. Bhattacharjee, & V.N.Mishra where in a moving bed plasma reactor is used for processing of metallized ilmenite in a continuous manner. However, the disadvantages of the process is that a substantial amount of heat is lost in the surroundings by
ii) Splashing of the heated powders.
iii) Heat loss by residue of unreacted powders.
Object of the invention
The main object of the present invention is to provide a process for the preparation of titania rich slag and iron metal from ilmenite by using static bed plasma reactor with inflight processing, which obviates the drawbacks of the prior art as detailed above.
Another objective of the invention is to provide an improved in-flight process for processing metallized ilmenite for the preparation of Titania rich slag and metallic iron with reduced energy consumption.
Yet another object is to provide an improved process for the preparation of titania rich slag and iron metal from metallized ilmenite in a well heat insulated plasma reactor to avoid heat losses.
Yet another objective is to reduce the splashing heated powders in a closed reactor.
Still another object is to eliminate heat loss & material loss due to un reacted powder in the plasma reactor.
Summary of the invention
Accordingly the present invention provides a process for the preparation of titania rich slag and metallized iron from the metallized ilmenite using an extended arc plasma reactor which comprises treating metallic ilmenite in an arc plasma reactor by passing it through an inner hollow vertical graphite electrode, at a feed rate of 70-500 gm/min, in the presence of plasmagen gas passing through an axial opening of graphite crucible, at a flow rate of 1-100 Its/min, at an arc voltage of 30-90 V and at an arc current of 100-500 amp, for a period of at least 1 minute to obtain the resultant molten mass in the form of lumps followed by cleaning and crushing it by known method to obtain the desired titania rich slag.
In an embodiment of the present invention the metallized ilmenite used has a composition of about total iron (39.61%), metallic iron (33.45), TiO2 (56.5%), phosphorus (0.01%), carbon (0.91%) and sulphur (0.11%).
In an embodiment of the present invention the inner hollow vertical graphite electrode used is a cathode.
In yet another embodiment of the present invention the graphite crucible used is acted as an anode.
In yet another embodiment the plasmagen gas used is Argon.
In yet another embodiment the metallic iron get separated from the resultant molten mass obtained due to the difference in their melting point.
In yet another embodiment the metallic iron obtained has iron content of 98-99%.
In yet another embodiment the titania rich slag obtained has TiOa content in the range 80-85%.
Brief description of drawings
Figure 1 represents the schematic diagram of the static bed reactor along with the powder feeder in accordance with the embodiment of the present invention for producing titania rich slag and iron ingot from metallized ilmenite.
The detail description explaining various parts of the arc plasma reactor is given below against their numericals as given in the drawing:
1. Alumina block
2. Water cooled MS casing
3. Bubble alumina
4. Graphite crucible cum electrode
5. In-flight particles
6. Melted charge
7. Thermal Plasma arc
8. Viewing port
9. Exhaust outlet
10. Top graphite electrode
11. Water inlet
12. Electrode with gas flow and water cooling facilities
13. Gas inlet
14. Screw feeder
15. Water outlet
16. Insulated strip
17. Rack and pinion system
18. Supporting structure
Detailed description of the invention
The present invention is essentially a development of static bed reactor with in-flight process for the preparation of titania rich slag and iron metal from metallized ilmenite in an extend arc plasma reactor. More specifically it relates to an extended plasma arc furnace having one electrode with an axial hole through which an appropriate gas, such as argon is introduced. Still more specifically the furnace embodies a vertical graphite electrode with an inner hollow through which a particulate charge is fed by gravity into the extended plasma arc zone. The in-flight arrangement has facility to vary the feed rate of the charge (metallized ilmenite), which is passed through hollow cathode. The melted charge is collected inside the crucible which acts as anode. Argon as plasmagen gas is passed through the hollow cathode along with the powder feed. The plasma arc is initiated by shorting the two electrodes instantaneously and then lifted to a particular arc length, which is directly proportional to the voltage. A fixed current is set to pass through the arc. The powder feeder stopper is then opened by fixing a particular feed rate of the metallized ilmenite. Both feed rate & time were varied for a particular metallized ilmenite. Keeping feed rate and duration of smelting constant ilmenite with various degree of metallization was treated by inflight processing. The observations were analyzed with respect to yield rate, energy consumption and metallic iron yield (%). The percentage of iron separated i.e. the metal yield % is directly proportional to the slag quality. Energy consumption was measured using an energy meter placed in the electrical circuit.
In accordance with this invention it has been found that improvements in operation and in economy for the process can be effected by the inflight extended arc plasma reactor design and parameters of operation, which are described herein. The improved design is based on the extended arc plasma which is stabilized with one electrode having an axial opening through which an appropriate gas is passed. Such as argon is fed into the arc. The reactor design also features a vertical powder feeder positioned in the top electrode which is above the extended arc so that the particulate charge may be fed by gravity directly into the stabilized extended arc plasma zone.
It has been found that this operation results in.
(1) Reduced energy consumption.
(2) Improved heat transfer.
(3) Reduced heat loss.
(4) Improved power control.
(5) Reduced acoustical and electrical noise.
The preparation of TiO2 rich slag by this process is beneficial in many ways .The process is eco-friendly and creation of large amount of effluent by chemical route can be avoided while producing synthetic TiOa using titania rich slag. Secondly, energy consumption can be reduced considerably in comparison to the conventional processes and the by-product viz-high value iron known as Sorel metal is an equally important and marketable product.
In the present invention, the apparatus includes three major functional component systems.
(i) Static bed plasma reactor assembly (ii) Master control unit, (iii) Plasma power supply.
In the present invention the graphite electrode is held in a water-cooled holder having facility to connect DC terminal (cathode). The electrode has an axial hole to pass plasma forming argon gas. The electrode is mounted on a rack and pinion mechanism for up and down movement of the electrode.
In yet another feature of the present invention, the reactor is equipped with master control unit for regulating voltage & current.
This unit comprises main electrical switch for switching power on or off to the reactor. Gas flow meters for precise control of the gas to the electrodes, volt meter for measuring the on load voltage, Ammeter for measuring the arc current and energy meter for measuring the input power to the reactor, safety switch for switching off electrical supply to the unit in the event of water supply to the reactor assembly is stopped.
Supply of water and gas to plasma reactor is ensured and the plasma power supply switch is put on to provide power to the reactor before the beginning of the
experiment while keeping both electrodes in contact with each other. Plasma is generated by moving top electrode away and stabilizing the arc.
The process of the invention generally involves the following sequential steps.
Power input to plasma reactor and powder feed rate arc prefixed and melting of metallized ilmenite is carried out and duration of melting is varied. After a fixed time the crucible was taken out and the molten product, which is collected inside the graphite crucible in the form of a lump was separated out. The iron gets separated due to melting point difference and settles at the bottom because of its higher density. The solidified lump was then cleaned and crushed in order to separate the titania rich slag and the pig iron. Both the slag & metal were weighted separately to find the yield and the % iron separated. Energy consumption was recorded by the energy meter. The raw material for the plasma experiment i.e. metallized ilmenite (85%) has the following major composition.
Total iron-39.61% Metallic iron - 33.45% Ti02 - 56.5% Phosphorus-0.01% Carbon-0.91% Sulphur-0.11%
Thermal Plasma parameters can be varied as given below Arc Currents 100-500 amp Arc Voltage = 30 - 90 V Argon flow = 0 to 10 Itr/min Feed rate = 70 to 500 gm/min
Following experimental parameters were fixed for the thermal plasma as typical examples.
Arc Current = 200 amps.
Arc Voltage = 60 V Argon flow = 2 lit/min
The following examples are given by way of illustrates of the working of the invention in actual practice and therefore shouldn't be read or construed to limit the scope of the present invention.
Periodical taping of metal-slag 1st set
1st set of Expt. gives a set of four experiments which was carried out with charge material having varying degree of metallization. Both feed rate and duration of melt separation in these experiments were kept fixed. Feed rate -110 to 120 gm/min Time - 2 minutes.
The experimental details and the results of four are tabulated in Table. 1 along with the slag analysis
The batch of 2nd set of experiments are similar to that described in 1st setl except that duration of experiments was varied. Keeping the feed rate and
metallization of charge constant. Table 2 gives the experimental details along with
Feed rate-140 gm/min
(Table Removed)This set of experiments is also similar to that described earlier. Here the feed rate was varied keeping degree of metallization of charge and duration of experiment same. Tables gives the experimental details and results. Degree of metallization- 84 %
Advantages of the invention
The main advantages of the process are: -
1. A modified energy efficient process to melt separate iron from the metallized
2. The by-product of the process is metallic iron know as Sorel metal which is
having high value and very good demand.
3. The static bed plasma reactor uses low cost transferred arc thermal plasma
formed by arcing between graphite electrodes compared to be expensive DC
torches and RF thermal plasma.
4. The Titania rich slag obtained is of good quality for use as a starting material
for further processing in the pigment industry.
5. The process can be used for continuous production with periodic taping of slag
6. IN-FLIGHT processing of ilmenite is technically feasible and has certain
advantages over either static bed transferred arc or moving transferred arc-
7. The flow of argon gas through plasma and particulates through hollow graphite
enables a rapid propagation of heat into larger volume of the charge without
significant enthalpy loss and enables intensive, rapid and localized heating.
1. A process for the preparation of titania rich slag and metallized iron from the
metallized ilmenite using an extended arc plasma reactor which comprises
treating metallic ilmenite in an arc plasma reactor by passing it through an
inner hollow vertical graphite electrode, at a feed rate of 70-500 gm/min, in the
presence of plasmagen gas passing through an axial opening of graphite
crucible, at a flow rate of 1-100 Its/min, at an arc voltage of 30-90 V and at an
arc current of 100-500 amp, for a period of at least 1 minute to obtain the
resultant molten mass in the form of lumps followed by cleaning and crushing
it by known method to obtain the desired titania rich slag.
2. A process as claimed in claim 1, wherein the metallized ilmenite used has a
composition of about total 39.61 %iron, 33.45metallic iron, 56.5% TiO2, 0.01%
phosphorus, 0.91% carbon and 0.11%.sulphur.
3. A process as claimed in claim 1 wherein, the inner hollow vertical graphite
electrode used is acted as a cathode.
4. A process as claimed in claim 1, wherein the graphite crucible used is acted
as an anode.
5. A process as claimed in claim 1, wherein the plasmagen gas used is Argon.
6. A process as claimed in claim 1, wherein the metallic iron get separated from
the resultant molten mass obtained due to the difference in their melting point.
7. A process as claimed in claim 1, wherein the metallic iron obtained has iron
content of 98-99%.
8. A process is claimed in 1, wherein titania rich slag obtained has TiC>2 content
in the range 80-85%.
9. A process for the preparation of titania rich slag and metallized iron from the
metallized ilmenite using an extended arc plasma reactor, substantially is
herein described with reference to the examples and drawing accompanying
|Indian Patent Application Number||909/DEL/2006|
|PG Journal Number||01/2014|
|Date of Filing||30-Mar-2006|
|Name of Patentee||COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH|
|Applicant Address||ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI - 110 001, INDIA.|
|PCT International Classification Number||C22B 4/00|
|PCT International Application Number||N/A|
|PCT International Filing date|