Title of Invention	A PROCESS FOR PRODUCTION OF MIXED CARBIDE OF SILICON AND IRON (SIC-FE3C) FROM FLY ASH
Abstract	A process for production of mixed carbide of silicon ana iron (SiC- Fe3C) from fly ash wnich comprises heating a mixture of fly ash and carbon in an electrically conducting crucible that forms the anode employing carbon cathode and argon as plasmagen gas in a plasma reactor operating in extended arc mode at temperature 1600-2200°C in a time of 10-30 min and recovering SiC-Fe3C by conventional leaching methods.

Title of Invention

A PROCESS FOR PRODUCTION OF MIXED CARBIDE OF SILICON AND IRON (SIC-FE3C) FROM FLY ASH

Abstract

A process for production of mixed carbide of silicon ana iron (SiC- Fe3C) from fly ash wnich comprises heating a mixture of fly ash and carbon in an electrically conducting crucible that forms the anode employing carbon cathode and argon as plasmagen gas in a plasma reactor operating in extended arc mode at temperature 1600-2200°C in a time of 10-30 min and recovering SiC-Fe3C by conventional leaching methods.

Full Text	The invention relates to a process for production of mixed carbide of silicon and iron (SiC-Fe3C) from fly ash. Silicon carbide (SiC) and iron carbide (fe3C) are used as abrasive compounds for grinding and lapping of metals, ceramics, plastic, leather etc. in machine tool, automobile and engineering industries. The range of application of these two carbides includes coated abrasives and bonded abrasives, composites, mould wall paints in foundry and additive in cast iron. Mixed carbide of silicon and iron is a new product that combines the advantageous properties of both phases and therefore has a greater application. The industrial process to produce silicon carbide (SiC) is Acheson's process which has been in operation from 1901 up till now. A reference can be made to (i) R. I. Fuentes, 'Silicon Carbide: Advanced Material Application and Preparation' Chemistry and Industry, 2nd Nov. 1992, pp 806; & (ii) R. Helberg, 'SiC Recent Developments: Materials, technology, Devices', Phys. Ser. Vol.T35, 1991, pp, 194. In this process Si02 in the form of quartzite is reduced by carbon in a resistance heated furnace. The charge consisting of quartzite lumps and petroleum coke is heated in the said furnace and the reaction is completed at about 2200°C. The batch operated process takes 48-72 hours depending on the scale of operation for a single batch to complete. High performance low volume production of SiC makes use of different methods such as chemical vapour deposition (CVD), plasma CVD, laser derived CVD involving silicon monoxide and particulate carbon ,and carbothermic reduction of rice husk/hull in thermal plasma. This has been well documented in the following papers (a) N.N. Ault and J.T. Crowe, 'Silicon carbide', Am. Cer. Soc. Bull. Vol 69(5), 1990, pp 878 ; (b) A. Mitsue and A. Kato, 'Preparation of SiC by the CVD method using RF plasma' Yogyo Kyokaishi (Jap.), Vol. 94(5), 1986, pp 517; (c) M. Cauchetier, 0. Croix, M. Luce, M. Michon, J. Paris and J. Tistcheuko, 'Laser synthesis of ultrafine powders', Ceram. Int., Vol.13, 1987, pp 13; (d) B. Haigis and M. Pickering, 'CVD scale up for economic production of bulk SiC', Am. Ceram. Soc. Bull., Vol. 72(3), 1993, pp.74; (e) P. Kennedy and B. North The production of fine silicon carbide powders by reaction of gaseous silicon minoxide with particulate carbon', Proc. Br. Ceram. Soc. Vol.33, 1983, pp.1; (f) J.G. Lee and B. Cutler 'Formation of silicon carbide from rice hulls', Am. Ceram. Soc. Bull., Vol.54, 1975, pp.195; (g) B.B. Nayak, B.C. Mohanty and S.K. Singh, J. Am. Ceram. Soc. Vol.79(5), 1996, pp.1197. Essentially all the processes involve the reaction of silicon or silicon containing compound with carbon/carbonaceous compound at high temperatures between 500-2200°C to synthesize SiC. Iron carbide (Fe3C) is a metastable compound which is industrially produced by fluidised bed reaction of iron oxide (Fe2O3) with natural gas at 1.8 bar pressure as illustrated in A. Ganguly, RHG Rau and V.S. Shah , Metal News, Vol. 19(2), 1997, pp 13. It is also prepared when carbon in solid form (coke/graphite) reacts with liquid iron at high temperature (>1540°C) [Engineering physical metallurgy and heat treatment Author : Yu. M. Lakhtin, Mir Publ. Moscow, First Edn. Third printing , 1986, pp 14]. The production of mixed carbide of silicon and iron (SiC-Fe3C) by a jingle step process is not reported so far. The main object of this process is to prepare the mixed carbide of silicon and iron from fly ash (generated from coal based thermal power plants) in a dc extended arc plasma. It is also the object of this invention to produce high-valued abrasive carbide at lower cost by utilizing a virulent polluting agent like fly ash. The composition of the fly ash used in the process is shown in Table-l given below : TABLE-I (Table Removed) It is evident that due to above constituents, fly ash is mainly an oxide ceramic which requires high temperatue (>1300°C) endothermic carbon based reaction for synthesis of carbides. In the industrial Acheson process SiC preparation takes about more than 48 hours to complete the synthesis reaction. Fe3C, being a metastable phase, is prepared at 1.8 bar pressure in fluidised bed reactor using Fe203, H2 and CH4/C2H2 gas. It is also prepared by interaction of liquid iron with carbon (solid) at temperature above 1540°C. These processes are not only time consuming but also cost intensive. There is so far no process existing today to prepare SiC-Fe3C at a time in a single step process as the reaction kinetics of the two carbides are different. The plasma process involving ionic reaction, high temperature (>10,000°C in dc extended arc), very fast reaction kinetics, higher throughput and low cost of production does not face the above problems, shortcomings. The said plasma is formed using argon as plasmagen gas which also prevents oxidation of carbides at high temperatures. The main findings of the process are : 1. For the first tune mixed carbide of silicon and iron (SiC-Fe3C) has been produced in a single step process by thermal plasma using fly ash as the starting raw material. 2. The process makes use of low cost do extended arc plasma formed by arcing between two graphite electrodes and the heat generated by the arc plasma brings about the carbothermic reduction to synthesize SiC-Fe3C. 3. The process directly makes use of fly ash as charge without making any agglomeration pelletization. thereby saving a considerable amount of energy and cost. 4. The process produces mixed carbide SiC- Fe3C which is hard and abrasive, thus a good grinding and lapping compound has been developed. Accordingly, the present invention provides a process for production of mixed carbide of silicon and iron (SiC- Fe3C) from fly ash which comprises heating a mixture of fly ash and carbon in an electrically conducting crucible that forms the anode employing carbon cathode and argon as plasmagen gas in a plasma reactor operating in extended arc mode at temperature 1600-2200°C in a tune of 10-30 min and recovering SiC-Fe3C by conventional leaching methods. A process for preparation of SiC- Fe3C by thermal plasma involves heating a mixture of fly ash and carbon kept in a electrically conducting crucible that forms the anode wherein the carbon cathode having provision for vertical movement and passing argon gas through an axial hole is made to contact the anode and then slowly withdrawn to form the arc plasma in non-transferred mode which subsequently changes to the transferred mode of operation soon after the charge becomes conducting at elevated temperature (>1000°C) and the carbothermic reduction is carried out at high temperature (1600-2200°C) generated by arc plasma and the reaction of oxide to carbide conversion is completed in a short time ( The following plasma process conditions are adopted to prepare the above mixed carbide : Arc current : 300-600A Arc voltage : 30-60 V Argon flow rate : 1-2 litres/minute Time of plasma : 10-30 minutes synthesis (arc operation) Characterisation of the above product by x-ray diffraction identified the carbide as mixed carbide of silicon and iron i.e. SiC-Fe3C along with the presence of very small amount Al-SiC. The following typical examples will illustrate how the process of the present investigation is carried out in actual practice and should not be construed to limit the scope of the investigation. Exartiple - 1 A graphite crucible was placed inside the hearth of the plasma furnace. The crucible was vertically supported on the base of the hearth where a graphite electrode (anode) introduced through a central hole maintained contact with the crucible for electrical connection. Another graphite electrode (cathode) was introduced from the upper end of the crucible having provision for vertical movement by rack and pinion arrangement. To start with, the electrodes were brought very close to each other (at a separation of 1-2 mm), 100g of charge was then placed inside the crucible and lightly rammed. Argon gas was passed into the arc zone through axial hole in the cathode at a rate of 1.5 litre per minute. Arc was struck in non-transferred mode and was allowed to continue in that position for 2 minutes to heat up the surrounding charge for conducting electricuty. The arc length was then gradually increased and fixed at 5-7 cms. After 4 minutes, the entire charge in the furnace became conducting and the plasma arc started working in transferred mode. The high plasma (or ion) temperature (>10,000°C at, the arc point) and high enthalpy generated by the arc in its vicinity caused Si02 and Fe2O3 available in the fly ash to undergo carbothermic reduction by graphite, thus producing the synthesis of their carbides in mixed form. The time taken for completing the plasma synthesis was 10-15 minutes. Voltage and current in this operation were 30 V dc and 300 A respectively at full arcing condition. The product was cooled in the furnace upto room temperature and collected in the form of loosely gglomerated powder. Leaching of the product was carried out in a mixture of 40% HF and HCI followed by thorough washing in water. The final product was obtained in powder form showing greyish black colour. X-ray diffraction of the product identified the product to be SiC-Fe3C (mixed carbide of silicon and iron) with presence of very small amounts of Al-SiC. Yield of the mixed carbide was found in the range of 65-70% (by wt). Example - 2 A graphite crucible was kept inside the hearth of the plasma furnace. Two graphite electrodes (anode and cathode) fitted in vertical configuration were properly arranged inside the graphite crucible having provision for vertical up and down movement of the cathode actuated by rack and pinion arrangement. The electrodes were at first brought very close to each other (1-2 mm arc length). 1 kg of charge was then filled into the crucible in this position with light ramming of the charge. Argon gas at a rate of 2 litre / minute was passed into the arc zone through an axial hole in the cathode. Arc was struck between anode and cathode by impressing electric filed (dc) on the electrodes in non-transferred mode. After 2 minutes when the charge surrounding the arc got sufficiently heated to conduct electricity, the arc length was increased gradually and fixed at 5-7 cms. After 4 minutes when the entire charge in the crucible started conducting, the plasma arc worked in transferred mode. Carbothermic reduction of SiQ2 and Fe2O3 was carried out by graphite at high plasma temperature (>10,000°c)yand high enthalpy available in the plasma furnace (reactor) which resulted in synthesis of carbides of silicon and iron. The time for completing the synthesis reaction in plasma condition was 25-30 minutes. Voltage and current in this operation were maintained at 50 V dc and 550 A respectively at full arcing condition. The product was furnace cooled, leached with 40% HF + HCI to remove unreacted oxides and then thoroughly washed with water. The final product was obtained in the form of powder with greyish black colour. X-ray diffraction of the final product in the form of powder identified the material to be SiC-FesC (mixed carbide of silicon and iron) along with the presence of very small amounts of Al-SiC. Yield of the product was found in the range of 65-72% (wt%). The main advantages are : 1 . The polluting fly ash waste can be used to prepare a high valued abrasive 2. Mixed carbide SiC-Fe3C is produced in a single process step although individual reaction kinetics are known to be different. 3. The process accepts both powdery as well as agglomerated fly ash for production of 4. The process makes use of low cost extended arc thermal plasma formed by arcing between graphite electrodes (non transferred) and graphite electrode and charge (transferred) while argon is continuously fed through the cathode. 5. By the plasma process only SiC-Fe3C and small amounts of Si-AIC are produced; thus elimination of carbides of other constituent oxides is possible. claim ; 1. A process for production of mixed carbide of silicon and iron (SiC- Fe3C) from fly ash which comprises heating a mixture of fly ash and carbon in an electrically conducting crucible that forms the anode employing carbon cathode and argon as plasmagen gas in a plasma reactor operating in extended arc mode at temperature 1600-2200°C in a time of 10-30 min and recovering SiC-Fe3C by conventional leaching methods. 2. A process as claimed hi claim 1 wherein carbon used in the form of graphite. 3. A process as claimed in claims 1 and 2 wherein weight ratio of fly ash to carbon is maintained at 3:2 and less. 4. A process as claimed in claims 1 to 3 wherein the extended arc plasma used has an arc current in the range 300-600A. arc voltage in the range 30-60V, plasmagen gas flow in the range 1 to 2 litres per minute. 5. A process as claimed hi claims 1-4 wherein leaching of the product is carried out by a mixture of 40% HF and HC1 to remove un-reacted oxides in the product for improving purity. 6. A process for production of mixed carbide of silicon and iron (SiC-Fe3C) from fly ash substantially as herein described with reference to the examples.

Full Text

The invention relates to a process for production of mixed carbide of silicon and iron (SiC-Fe3C) from fly ash.
Silicon carbide (SiC) and iron carbide (fe3C) are used as abrasive compounds for grinding and lapping of metals, ceramics, plastic, leather etc. in machine tool, automobile and engineering industries. The range of application of these two carbides includes coated abrasives and bonded abrasives, composites, mould wall paints in foundry and additive in cast iron. Mixed carbide of silicon and iron is a new product that combines the advantageous properties of both phases and therefore has a greater application.
The industrial process to produce silicon carbide (SiC) is Acheson's process which has been in operation from 1901 up till now. A reference can be made to (i) R. I. Fuentes, 'Silicon Carbide: Advanced Material Application and Preparation' Chemistry and Industry, 2nd Nov. 1992, pp 806; & (ii) R. Helberg, 'SiC Recent Developments: Materials, technology, Devices', Phys. Ser. Vol.T35, 1991, pp, 194. In this process Si02 in the form of quartzite is reduced by carbon in a resistance heated furnace. The charge consisting of quartzite lumps and petroleum coke is heated in the said furnace and the reaction is completed at about 2200°C. The batch operated process takes 48-72 hours depending on the scale of operation for a single batch to complete. High performance low volume production of SiC makes use of different methods such as chemical vapour deposition (CVD), plasma CVD, laser derived CVD involving silicon monoxide and particulate carbon ,and carbothermic reduction of rice husk/hull in thermal plasma. This has been well documented in the following papers (a) N.N. Ault and J.T. Crowe, 'Silicon carbide', Am. Cer. Soc. Bull. Vol 69(5), 1990, pp 878 ; (b) A. Mitsue and A. Kato, 'Preparation of SiC by the CVD method using RF plasma' Yogyo Kyokaishi (Jap.), Vol. 94(5), 1986, pp 517; (c) M. Cauchetier, 0. Croix, M.

Luce, M. Michon, J. Paris and J. Tistcheuko, 'Laser synthesis of ultrafine powders', Ceram. Int., Vol.13, 1987, pp 13; (d) B. Haigis and M. Pickering, 'CVD scale up for economic production of bulk SiC', Am. Ceram. Soc. Bull., Vol. 72(3), 1993, pp.74; (e) P. Kennedy and B. North The production of fine silicon carbide powders by reaction of gaseous silicon minoxide with particulate carbon', Proc. Br. Ceram. Soc. Vol.33, 1983, pp.1; (f) J.G. Lee and B. Cutler 'Formation of silicon carbide from rice hulls', Am. Ceram. Soc. Bull., Vol.54, 1975, pp.195; (g) B.B. Nayak, B.C. Mohanty and S.K. Singh, J. Am. Ceram. Soc. Vol.79(5), 1996, pp.1197. Essentially all the processes involve the reaction of silicon or silicon containing compound with carbon/carbonaceous compound at high temperatures between 500-2200°C to synthesize SiC.
Iron carbide (Fe3C) is a metastable compound which is industrially produced by fluidised bed reaction of iron oxide (Fe2O3) with natural gas at 1.8 bar pressure as illustrated in A. Ganguly, RHG Rau and V.S. Shah , Metal News, Vol. 19(2), 1997, pp 13. It is also prepared when carbon in solid form (coke/graphite) reacts with liquid iron at high temperature (>1540°C) [Engineering physical metallurgy and heat treatment Author : Yu. M. Lakhtin, Mir Publ. Moscow, First Edn. Third printing , 1986, pp 14].
The production of mixed carbide of silicon and iron (SiC-Fe3C) by a jingle step process is not reported so far. The main object of this process is to prepare the mixed carbide of silicon and iron from fly ash (generated from coal based thermal power plants) in a dc extended arc plasma. It is also the object of this invention to produce high-valued abrasive carbide at lower cost by utilizing a virulent polluting agent like fly ash.
The composition of the fly ash used in the process is shown in Table-l given below :
TABLE-I
(Table Removed)
It is evident that due to above constituents, fly ash is mainly an oxide ceramic which requires high temperatue (>1300°C) endothermic carbon based reaction for synthesis of carbides. In the industrial Acheson process SiC preparation takes about more than 48 hours to complete the synthesis reaction. Fe3C, being a metastable phase, is prepared at 1.8 bar pressure in fluidised bed reactor using Fe203, H2 and CH4/C2H2 gas. It is also prepared by interaction of liquid iron with carbon (solid) at temperature above 1540°C. These processes are not only time consuming but also cost intensive. There is so far no process existing today to prepare SiC-Fe3C at a time in a single step process as the reaction kinetics of the two carbides are different. The plasma process involving ionic reaction, high temperature (>10,000°C in dc extended arc), very fast reaction kinetics, higher throughput
and low cost of production does not face the above problems, shortcomings. The said plasma is formed using argon as plasmagen gas which also prevents oxidation of carbides at high temperatures. The main findings of the process are :
1. For the first tune mixed carbide of silicon and iron (SiC-Fe3C) has been
produced in a single step process by thermal plasma using fly ash as the
starting raw material.
2. The process makes use of low cost do extended arc plasma formed by
arcing between two graphite electrodes and the heat generated by the arc
plasma brings about the carbothermic reduction to synthesize SiC-Fe3C.
3. The process directly makes use of fly ash as charge without making any
agglomeration pelletization. thereby saving a considerable amount of
energy and cost.
4. The process produces mixed carbide SiC- Fe3C which is hard and
abrasive, thus a good grinding and lapping compound has been developed.
Accordingly, the present invention provides a process for production of mixed carbide of silicon and iron (SiC- Fe3C) from fly ash which comprises heating a mixture of fly ash and carbon in an electrically conducting crucible that forms the anode employing carbon cathode and argon as plasmagen gas in a plasma reactor operating in extended arc mode at temperature 1600-2200°C in a tune of 10-30 min and recovering SiC-Fe3C by conventional leaching methods.
A process for preparation of SiC- Fe3C by thermal plasma involves heating a mixture of fly ash and carbon kept in a electrically conducting
crucible that forms the anode wherein the carbon cathode having provision for vertical movement and passing argon gas through an axial hole is made to contact the anode and then slowly withdrawn to form the arc plasma in non-transferred mode which subsequently changes to the transferred mode of operation soon after the charge becomes conducting at elevated temperature (>1000°C) and the carbothermic reduction is carried out at high temperature (1600-2200°C) generated by arc plasma and the reaction of oxide to carbide conversion is completed in a short time ( The following plasma process conditions are adopted to prepare the above mixed carbide :
Arc current : 300-600A
Arc voltage : 30-60 V
Argon flow rate : 1-2 litres/minute
Time of plasma : 10-30 minutes
synthesis (arc operation)
Characterisation of the above product by x-ray diffraction identified the carbide as mixed carbide of silicon and iron i.e. SiC-Fe3C along with the presence of very small amount Al-SiC.
The following typical examples will illustrate how the process of the present investigation is carried out in actual practice and should not be construed to limit the scope of the investigation.
Exartiple - 1
A graphite crucible was placed inside the hearth of the plasma furnace. The crucible was vertically supported on the base of the hearth
where a graphite electrode (anode) introduced through a central hole maintained contact with the crucible for electrical connection. Another graphite electrode (cathode) was introduced from the upper end of the crucible having provision for vertical movement by rack and pinion arrangement. To start with, the electrodes were brought very close to each other (at a separation of 1-2 mm), 100g of charge was then placed inside the crucible and lightly rammed. Argon gas was passed into the arc zone through axial hole in the cathode at a rate of 1.5 litre per minute. Arc was struck in non-transferred mode and was allowed to continue in that position for 2 minutes to heat up the surrounding charge for conducting electricuty. The arc length was then gradually increased and fixed at 5-7 cms. After 4 minutes, the entire charge in the furnace became conducting and the plasma arc started working in transferred mode. The high plasma (or ion) temperature (>10,000°C at, the arc point) and high enthalpy generated by the arc in its vicinity caused Si02 and Fe2O3 available in the fly ash to undergo carbothermic reduction by graphite, thus producing the synthesis of their carbides in mixed form. The time taken for completing the plasma synthesis was 10-15 minutes. Voltage and current in this operation were 30 V dc and 300 A respectively at full arcing condition. The product was cooled in the furnace upto room temperature and collected in the form of loosely gglomerated powder. Leaching of the product was carried out in a mixture of 40% HF and HCI followed by thorough washing in water. The final product was obtained in powder form showing greyish black colour. X-ray diffraction of the product identified the product to be SiC-Fe3C (mixed carbide of silicon and iron) with presence of very small amounts of Al-SiC. Yield of the mixed carbide was found in the range of 65-70% (by wt).
Example - 2
A graphite crucible was kept inside the hearth of the plasma furnace. Two graphite electrodes (anode and cathode) fitted in vertical configuration were properly arranged inside the graphite crucible having provision for vertical up and down movement of the cathode actuated by rack and pinion arrangement. The electrodes were at first brought very close to each other (1-2 mm arc length). 1 kg of charge was then filled into the crucible in this position with light ramming of the charge. Argon gas at a rate of 2 litre / minute was passed into the arc zone through an axial hole in the cathode. Arc was struck between anode and cathode by impressing electric filed (dc) on the electrodes in non-transferred mode. After 2 minutes when the charge surrounding the arc got sufficiently heated to conduct electricity, the arc length was increased gradually and fixed at 5-7 cms. After 4 minutes when the entire charge in the crucible started conducting, the plasma arc worked in transferred mode. Carbothermic reduction of SiQ2 and Fe2O3 was carried out by graphite at high plasma temperature (>10,000°c)yand high enthalpy available in the plasma furnace (reactor) which resulted in synthesis of carbides of silicon and iron. The time for completing the synthesis reaction in plasma condition was 25-30 minutes. Voltage and current in this operation were maintained at 50 V dc and 550 A respectively at full arcing condition. The product was furnace cooled, leached with 40% HF + HCI to remove unreacted oxides and then thoroughly washed with water. The final product was obtained in the form of powder with greyish black colour. X-ray diffraction of the final product in the form of powder identified the material to be SiC-FesC (mixed carbide of silicon and iron) along with the presence of very small amounts of Al-SiC. Yield of the product was found in the range of 65-72% (wt%).

The main advantages are :
1 . The polluting fly ash waste can be used to prepare a high valued abrasive
2. Mixed carbide SiC-Fe3C is produced in a single process step although
individual reaction kinetics are known to be different.
3. The process accepts both powdery as well as agglomerated fly ash for
production of

4. The process makes use of low cost extended arc thermal plasma formed
by arcing between graphite electrodes (non transferred) and graphite
electrode and charge (transferred) while argon is continuously fed through
the cathode.
5. By the plasma process only SiC-Fe3C and small amounts of Si-AIC are
produced; thus elimination of carbides of other constituent oxides is
possible.

claim ;
1. A process for production of mixed carbide of silicon and iron (SiC- Fe3C)
from fly ash which comprises heating a mixture of fly ash and carbon in an
electrically conducting crucible that forms the anode employing carbon
cathode and argon as plasmagen gas in a plasma reactor operating in
extended arc mode at temperature 1600-2200°C in a time of 10-30 min and
recovering SiC-Fe3C by conventional leaching methods.
2. A process as claimed hi claim 1 wherein carbon used in the form of graphite.
3. A process as claimed in claims 1 and 2 wherein weight ratio of fly ash to
carbon is maintained at 3:2 and less.
4. A process as claimed in claims 1 to 3 wherein the extended arc plasma used
has an arc current in the range 300-600A. arc voltage in the range 30-60V,
plasmagen gas flow in the range 1 to 2 litres per minute.
5. A process as claimed hi claims 1-4 wherein leaching of the product is carried
out by a mixture of 40% HF and HC1 to remove un-reacted oxides in the
product for improving purity.
6. A process for production of mixed carbide of silicon and iron (SiC-Fe3C)
from fly ash substantially as herein described with reference to the examples.

Documents:

284-del-1999-abstract.pdf

284-del-1999-claims.pdf

284-del-1999-correspondence-others.pdf

284-del-1999-correspondence-po.pdf

284-del-1999-description (complete).pdf

284-del-1999-form-1.pdf

284-del-1999-form-19.pdf

284-del-1999-form-2.pdf

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Patent Number

221640

Indian Patent Application Number

284/DEL/1999

PG Journal Number

31/2008

Publication Date

01-Aug-2008

Grant Date

30-Jun-2008

Date of Filing

19-Feb-1999

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	BIJAN BIHARI NAYAK	REGIONAI RESEARCH LABOKATORY BHUVANESWAR, BHUBANESWAR,751013,
2	BHABANI SANKAR ACHARYA	REGIONAI RESEARCH LABOKATORY BHUVANESWAR, BHUBANESWAR,751013,
3	BISHNU CHARANARABINDA MOHANTY	REGIONAI RESEARCH LABOKATORY BHUVANESWAR, BHUBANESWAR,751013,

PCT International Classification Number

C01B 31/36

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA