Title of Invention

A IMPROVED PROCESS FOR THE SIMUTTANEOUS PREPARATION OF TITANIA RICH SLAG AND PIG IRON

Abstract A process has been developed for simultaneous preparation of titania rich slag and pig iron from ilmenites. The present invention is a two step process wherein ilmenite is first reduced with coal to high degree of metallisation in a rotary kiln and then the reduced ilmenite is melted in a plasma furnace. In the plasma furnace, use of high enthalpy of thermal plasma generated in the extended arc with a plasma forming gas such as argon is made which results in very high through put by rapid melting with reduced heat loss.
Full Text The present invention relates to an improved process for the simultaneous preparation of titania rich slag and pig iron from ilmenites. Titania rich slag containing about 80-85% TiOa is one of the major feed stock for the production of TiO2 pigment or TiCU which is further reduced to titanium metal. Titanium dioxide finds extensive application as pigments, welding electrode flux and also used in paper, plastics, rubber and textile industries.
This invention relates to an improved process for the production of titania rich slag and pig iron from pre-reduced ilmenite in a more environmentally friendly route and recovering all the iron values from the ilmenite in the form of value added pig iron. The mentioned process can widely be used in industries such as TiOa pigment manufacturing, Titanium metal production and ilmenite processing industries.
An ever increasing gap between the demand and supply of TiO2 pigment in the recent years, has pushed up the utilization of abundantly available ilmenite for the production of synthetic rutile. Production of alternate feedstocks for TiO2 pigment production has gained significance owing to the limited reserves of natural rutile and over exploitation of these minerals. Hence there is every need to switch over to abundantly available minerals such as ilmenite to bridge the demand - supply gap.
Production of synthtic rutile from ilmenite has been attempted by many routes though, a very few of them had been of industrial relevance. Production of synthetic rutile from the beneficiation of ilmenite has been reviewed by S.k.Jain et al. (Ind. J.Technol.15(9), 1977, 398-402; P.K.Jena et.al. (Ban. Met.,5,
1973,107-117; J . A . Kalm , J . Metal s , July 1984,33-38; Moldran luliu er al . Chem,Abstr. ,84 (1970} , 76-j-7(vp ; S.Yamada, Lnd.Miner. , (London) , 100(197G) , 33-40 .
Based on the physical and chemical principles employed for the preferential chemical reaction of iron oxide in ilrnenite, the following classification could be made for .the preparation of synthetic rutile from i linen ite.
In the fusion method, various alkali metal compounds such as
Na CO , NaHSO , Na SO and ZnS are used to convert ilmenite to a
23 424 more leachable product. The fused products are subsequently
leached with acids and titanium and iron values are recovered from the solution (E.M.Khairy, M.K.Hussain and K.A.Baraway, NML Tech.J,10(4),1968; K.V.V.Nair,Bull.Central Res.Instt.,Uni.Travan-core, 11 (1952) , 106; A.K.Sharova and A.A.Fotiyev,Izev.Sibirskogo. Otd.Akad.Nauk.SSSR,4,(1959)52; Y.Tokimoto and H.Hattori,J.Chem. Soc.Jpn.Ind.Chem.Soc.58(1955)654; S.Prasacl and J.B . P .Tripathi , Ind, J.Appl.Chem.,21(1958),162; A.S.Gaskin and A.E.Ringwood.Australian Patent 222517 (1959); G.Jabsen,Norwegian Patent 21693 (1910),Chem Abstr.6, (1912) ,2153; L.E.Barton,US Patent 1201541,(1917) ,Chem. Abstr.ll (1917),279; Fr.Patent 483780 (1917),Chem.Abstr . 12 (1918) 1000; Br.Patent 106585 (1916),Chem.Abstr.11 (1917) , 2575;Norwegian Patent 29194 (1918),Chem.Abstr.14 (1920) 1418; Belgian Patent 447709 (1942), Chem.Abstr.41,(1947),7064; H.H.Hoekje and R.A.Kearley.Ger.Patent 1058463 (1959),Chem.Abstr.55,(1961),5892; T.Tshino,T.Tanaka,Y.Tanaka and Y.Takimoto, Jap.Patent 8771 (1950); A.K.Sharora and A.A.Fotipev,Chem.Abstr . 53 , (1959),20717).
However, the processes employinq the abovp pv\;:ciple suffej. y from problems associated with effluents and corrosion besides, being uneconomical owing to high cost of alkali and other fu.-:io;: ma teriaJ s .
Direct acid leaching of ilmeni tre with HC1 and K SO has )>•;
2 4 widely used in the preparation of synthetic rutile..Digestion of
ilmenite with sulphuric acid brings both TiC) and Iron Oxide into
2 solution while HC1 digestion selectively brings only iron into
solution.(E.N.Kramer,U.S.Patent 2437164 (1948); British Titan Products Co.Ltd. ,British Patent 1085359 (19?7TT*CHTng-Lurig Lo and T.S.Mac-key, Wah Chang Corp . U. S . Patent 3193376 (1965); G.S.Davar, Ind.Patent 124558 (1969); Kenzo Ishihara,Outline of Ishihara Sangyo Kaisha Ltd. (1970) ;Colurnbia Southern Chemical Corp,Br.Pat. 795164, (1958) ; N.N.Murach arid L.G.Povedskaya,USSR Patent 116155 (1958); N.A.Aawal,M.Rehman, S.A.Tarafder and A.M. S .Huq, Chern . Abs . 85, (1976) ,146321g.
Partial reduction of iron oxide in Ilmenite to ferrous state and its subsequent removal by acid leaching has been successful in many of the industrial ventures for producing synthetic rutile. The processes falling to the above category include:Murso (R.I.Jaffe and I!.M.Burte,Titanium Sci.and Technol.Vol.1,(Eds)R.1. Jaffe and H.M.Burte;Plenum Press,New York,Londonl973), Burastero (J .Burastero,Chem.Abstr.89 (1978) , 26787z) , Kurata ( T. Kurata , Frni Satoshi,O.KunihikorT.Tstutomu and S.Isanm,Jpn.Kokai,7693714 (1976) Pre oxidation of some ilmenites prior to reduction i^/as found advantageous for the reduction. A process similar to above was also employed to Sri Lankan Ilmneites for the production of
synthetic rutile ( M.G.Mu.Ismail, J.Amarasekara and J.S.N.Kumara-singho, Int 1 . J . Miner . Process . 1 0 {'A } ,1983,161-164) . A careful reoxi elation and reduction of ilmenite followed by acid leaching wa.s suggested by Ken . Me . Corp ( Raclo T heodore A, C . Kerr . Me . Corp . U . S . Pa t 4199552,(1980). In another process, synthetic rutile was prepared by the complete reduction of J imonite to metallic iron state and the metallic iron was later removed by aqueous aeration rusting in presence of a catalyst (B.F.Bracanin,R.J.Clements and U. John,Proc.Austr.Inst.Win.Metal1.,275 (1980) ,33-42) . Synthetic rutile with about 2-3% iron was prepared from Indian ilmenites by the reduction of ilraenite followed by acid leaching (Annie Goerge, V.S.Kelukutty, L.G.Radhika, P.N.Mohan Das and P.K.Rohtagi,J.Mater. Sci.,19 (5)(1984),1522). Metallic iron from the reduced ilmenite was also extracted by electrolytic dissolution to produce synthetic rutile high in TiO2 content (Allan Benjamin Wilson,Ger. Offen.2557411 (1977), Mori Taday Oshi, Kato Akemi and Kawakami Naboru, Jpn.Kokai, 77 128817,(1977)). A process based on the coal reduction of ilmenite followed by acid leaching before or after aeration rusting was patented by Grey et. al (I.E.Grey,M.J.Hollit, A.Brian, B.O'Brien, Australian Patent 9346047, (1993), Austr. Patent 649946 (1994), U.S.Patent 5427749 (1995)). In another patented process, reduced ilmenite was subjected to aqueous oxidation and then high temperature acid leaching (Ishihara,Sangic Kaisha, Japn.Patent 58199720 (1983). Synthetic rutile was also prepared by the reduction of ilmenite followed by the oxidation of metallic iron in aqueous solution in presence of ozone or oxygen. The oxidised product was subsequently leached with acid. (H.Walter,European Patent,612654 (1994). High grade synthetic
riii.il>- from Indian ilmenit. e wd:.. also p-'-'~'"3'iced by employing solid state reduction, oxidation and acid leaching ( P.N.Mohan Das,A.I). Damodaran , S . Velusamy and S . Sasibhushanan , Ind . Patent , 1 033/01.i. (1991). A better quality synthetic rutile with brownish yellow colour was prepared from Indian ilmenite by subjecting ilmenrte to metallisation, aeration runt ing,rutilation and acid J each ing (P.N.Mohan Das, A. D . Dam'odaran , K.H.Bhat,S.Velusamy and G.L^as ibhushanan, Ind.Patent,1262/DEL (1997).
o Chlorination of ilmenite in presence of Carbon at 850-950 C
produces Iron chloride and Titanium tetrachloride (D Wendel D.C.Jr. U.S.Patent 4332615 (1982), U.S.Patent 4085189 (1978); J.K.Heyrner, G.Stephan and H.Werner, Ger .Of fen, 3203482 (1983)) which were separated and titanium dioxide was obtained by the oxidation of pure titanium tetrachloride.
Reduction smelting of ilmenite in electric arc furnace capable of processing all grades of ilmenites had been also in practice in places where cheap and abundant electrical energy is available. Reduction of ilmenite and melting are simultaneously carried out in the arc furnace. The process was very well commercialised at Sorel, canada and the titania rich slag obtained was subsequently used in sulphuric acid digestion for Ti02 pigment production (G.W.E.lger, D . E . Ki shy, S . C . Rhoads , USBM RI 81 40, (1976) , 31;D.J.Swinden and D.G.Jones, Trans.Inst. Min.Metall. sec.C,87, (1978) ,83-87; A,J.Merchant and N.A.Warner,Trans.Inst.Min Metall.C,101,(1992),177-182; R.H.Nafziger,Trans.Inst.Min.Metall.C 87, (1978),120) Simultaneous reduction melt separation of ilmenite using plasma containing hydrogen,methane or argon were also
reported for the production of titania rich slag and pig iron. (J.D.Chast- and J . F . Skirvan , AIChE Symp. Series 75:186,38 (1978).. R.Ishizuka and K.Aka.shi, J.Jap.Inst. Metals,45, 1229 (1981); P.K,Mishra, S . K . 3 ingli, B . C . Achai ya , B . C . Mohanty and P . K . Hahoo , Min. Processing,Recent Advances and Future trends,Conf.proc.(1995), 875-878, (EdiO 3 . P . Mehrot i~a and Shekar Rajeev,Allied Publ.Mev Delhi; G.M.Denton, A.Schoukens and S.Francois,European Patent 583126 (1994) .
However,reduction smelting of ilmenite for the production of titania rich slag is very much energy intensive and as such is quite uneconomical for countries where electrical energy is scarce and expensive.Further,titania rich slag so produced by electrical smelting is tailor made only to sulphate route of
TiO pigment manufacture and it^needs further processing to
2 enable to employ it in chloride process.
Compared to many of the commercial wet chemical processes for the production of synthetic rutile, electro smelting or plasma smelting of ilmenite however,scores high owing to its environment friendly nature and byproduct utilisation. All the iron metal values from ilmenite are recoverd in the form of valuable pig iron which finds direct application in foundries.
However, when compared to plasma smelting, reduction smelting in electric arc furnaces tends to be highly energy intensive. Further,owing to longer time required for the smelting in electrical smelting,through puts are very low compared to plasma smelting. The process under invention however, makes use of pre-reduced ilmenite as the feed stock and plasma for smelting. Use of pre-reduced ilmenite considerably decreases theenergy requirement while plasma renders the process clean and more productive with high through puts and minimum energy loss.
The main object of the present invention is to provide an improved process for the preparation of titania rich slag and pig iron from ilmenite.
Accordingly the present invention provides an improved process for the simultaneous preparation of titania rich slag and pig iron from ilmenites which comprises: subjecting ilmenite to reduction with 30-100% coal at a temperature in the range of 850-1250°C for a period in the range of 2-6 hours, cooling and removing unreacted coal by conventional methods such as herein described to obtain the product of 80-95% metallisation, smelting the metallised ilmenite mixed with less than 10% carbon in the transferred arc plasma using arc current in the range of 100-400 amps, arc voltage of 20-60 volts, under flow of inert gas at a rate in the range of 0 to 2 lit/min, getting solid metal as pig iron and titanium oxide as the slag, the said process characterized in using arc plasma with current in the range of 100-400 amps, arc voltage of 20-60 volts, under flow of inert gas.
The present invention is a two step process wherein ilmenite is first reduced with coal to high degree of metallisation in a rotary kiln and then the reduced ilmenite is melted in a plasma furnace. In the plasma furnace, use of high enthalpy of thermal plasma generated in the extended arc with a plasma forming gas such as argon is made which results in very high through put by rapid melting with reduced heat loss. Thermal efficiency of arc plasma melting was further enhanced by generating this plasma in the transferred mode.
Sequential steps followed in the process are as follows:
Commercially available Indian ilmenite is subjected to
reduction with 30-100% of coal in a rotary kiln at about 850-
o 1250 C for about 2-6 hours. It is then cooled and sieved t r.-
remove unreacted coal followed by a magnetic separation to sepai'ate coal fines and ash. The product containing about 20% tola] iron had a metallisation of about 90-95%.
Pro-reduced ilmen.it e if. then mixed with less than 10% of carbon depending on the pre reduction step.
The above charge is then taken in a graphite crucible either in loose form or in the form of pellets. The said crucible has a side tap hole at its bottom which is plugged by a high melting compound material and attached with a graphite rod for releasing the hole as and when required.
An arc is struck on to the charge and an extended arc argon plasma in transferred mode is formed. The charge is melted in the said extended arc plasma where graphite crucible along with the charge forms one of the electrode. The said graphite electrode has provision for introducing plasamagen gas such as argon into the arc zone to form extended/expanded arc plasma in transferred mode.
Once the melting starts, iron gets separated due to melting point difference and settles at the bottom of the crucible owing to its higher density.
After a specified time depending on the charge, the tap hole made out of a graphite hollow tube is opened and pig iron is
separated resulting in enrichment of the slag with TiO content.
2 The invention is described in the following examples which
are provided by way of illustrations only and should not be construed to limit the scope of the invention.
Under the given following plasma condition::; typical f \i>oi j merit s are described wiili varying carbon content with the pre reduced cahrge. The raw material for the plasma exper imenm t , vi z . pre reduced llinen Lte had the following composition as determined by the chemical analysis.
Total Iron - 28-32% Sulphur - 0.113%
TiO - 6M-640,-, Phosphorous - 0.012%
2 Carbon - 1.0%
Plasma Conditions :
Arc current - 200-300 amps
Arc Voltage - 40-50 V
Argon Flow - 0 to 2 lit/min.
About 1% carbon is mixed with the pre reduced ilmenite and then granulated. 500 gms of granulated powder was taken in a graphite crucible. At the centre of the graphite crucible, a cylindrical graphite rod (-ve electrode) with a central hole for purging the plasmagen gas was placed and a good contact with the graphite crucible (+ve electrode) was established. The granulated mixture was then poured into the space between the electrode and the graphite reactor. Arc was struck with flow of argon gas under the upper electrode and the electrode was slowly raised. The mixture then melts slowly and the heavier molten iron settles at the bottom of the crucible. After a specified time, the side plug of the crucible was opened for tapping the metal. The metal and slag was then washed and analysed as per the standard
procedure. The results aro as follows: Total charge taken - 500 gms . Weight of iron separated - 118 gm.(] - 345 grns .
Chemical analysis of Metallic1 portion ;
+ Total iron content - 92%
Metallic iron - 89%
TiO content- 1%
2 Chemical analysis of Slag portion :
Total iron content - 7% Metallic iron - 4%
TiO content - 85% 2
A mixture containing Pre reduced ilmenite mixed with 5% (w/w) carbon was granulated. 500 gms of granulated powder was taken in the graphite crucible. A cylindrical graphite rod with central hole for purging the plasmogen gas was placed at the centre of the crucible with good contact. Granulated powder for smelting was loaded in the space between the graphite electrode and the crucible. An arc was struck with argon flow and the electrode was slowly raised as the charge started melting. Metal separated at the bottom of the crucible was removed through the tap hole. The metal and slag after washing were analysed. The results are as follows: Results :
Total charge taker, - 500 gmt;. W e i g 11t o f i r o n s e p a r a t r; d - 10 0 g rn s . Weight- of slag -- 285 gins. Cliem lea 1 analysis:
M e t. a 111 o 1J :-t c t i. n 11 :
Total iron content - 86% Met all ic i i .>ri - 84%
TiO content - 3%
2 Slag fraction ;
Total iron - 13% Metallic iron - 11%
TiO content - 80%
2 Effect of Power Input:
A number of experiments were carried out to find the effect of plasma power input onto smelting of fixed charge and smelted for a fixed time. The results are tabulated as under:

(Table Removed) It is clear from the above table that for a fixed charge and smelting time, increase in power does not lead to any increase in separation of iron from the charge. Further,both metal as well as slag became contaminated at higher power loading. Hence an optimium power is necessary for a better separation of metal and slag.
Further to the above,a number of experiments wore also carried out to :-.>•.:udy the- effect: of time, power and nature of the ilrnenite feed on the chemistjv of the slag produced. The results are tabulated lie low:

(Table Removed) Chemical analysis of the pig iron separated in experiment 1-30 is shown below:
Total Iron - 95.39%
Metallic iron - 95.17%

TiO

- 0.65%


Metallisation - 99.76%
1. The main advantages of the process are:
Simple and eco friendly method to separate more than 90% of
iron in'the pre reduced ilmenite.
2. The byproduct of the process is pig iron which is having
high value and very good demand.
3. Utilisation of high enthalpy argon thermal plasma results in
high throughput.
4. The process makes use of low cost extended plasma termed by
arcing between graphite electrode and the charge resulting
in low cost of production.
5. The titania rich slag obtained is of good quality for use as
a starting material for further processing.






We Claim:
1. An improved process for the simultaneous preparation of titania rich slag
and pig iron from ilmenites which comprises: subjecting ilmenite to
reduction with 30-100% coal at a temperature in the range of 850-1250°C
for a period in the range of 2-6 hours, cooling and removing unreacted
coal by conventional methods such as herein described to obtain the
product of 80-95% metallisation, smelting the metallised ilmenite mixed
/vith less than 10% carbon in the transferred arc plasma using arc current
in the range of 100-400 amps, arc voltage of 20-60 volts, under flow of
inert gas at a rate in the range of 0 to 2 lit/min, getting solid metal as pig
iron and titanium oxide as the slag, the said process characterized in
using arc plasma with current in the range of 100-400 amps, arc voltage of
20-60 volts, under flow of inert gas.
2. An improved process as claimed in claim 1 wherein unreacted coal and
ash are removed by conventional methods such a ssieving and magnetic
separation.
3. An improved process for the simultaneous production of pig iron and
titania rich slag substantially as herein described with reference to the
examples.

Documents:

804-del-1997-abstract.pdf

804-del-1997-claims.pdf

804-del-1997-complete specificaation (granted).pdf

804-del-1997-correspondence-others.pdf

804-del-1997-correspondence-po.pdf

804-DEL-1997-Description (Complete).pdf

804-DEL-1997-Description (Provisional).pdf

804-del-1997-form-1.pdf

804-del-1997-form-19.pdf

804-DEL-1997-Form-2.pdf

804-del-1997-form-3.pdf

804-del-1997-form-5.pdf

804-del-1997-form-6.pdf


Patent Number 246958
Indian Patent Application Number 804/DEL/1997
PG Journal Number 12/2011
Publication Date 25-Mar-2011
Grant Date 23-Mar-2011
Date of Filing 27-Mar-1997
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG,NEW DELHI-110001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 PAWVATHU NARAYANAN REGIONAL RESEARCH LABORATORY(CSIR)THIRUVANANTHPURAM-695019,KERALA,INDIA.
2 KARVAL HARIKRISHNA BHAT REGIONAL RESEARCH LABORATORY(CSIR)THIRUVANANTHPURAM-695019,KERALA,INDIA.
3 BISHNU CHARANA RABINDHA MOHANTY REGIONAL RESEARCH LABORATORY(CSIR)BHUBANESWAR-751013,INDIA.
4 ALATHUR DAMODARAN DAMODARAN REGIONAL RESEARCH LABORATORY (CSIR),THIRUVANANTHAPURAM-695019 KERALA
5 NAIR MOHAN DAS REGIONAL RESEARCH LABORATORY(CSIR)THIRUVANANTHPURAM-695019,KERALA,INDIA.
6 PARTHASARATHI MUKHERJEE REGIONAL RESEARCH LABORATORY(CSIR)BHUBANESWAR-751013,INDIA.
PCT International Classification Number C21B 013/14
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA