Title of Invention	A PROCESS FOR THE REDUCTION OF CHROMITE ORE FINES IN SOLID STATE IN A FLUIDISED BED REACTOR
Abstract	A process for the reduction of chromite ore fines in solid state in fluidised bed reactor whereby the Cr2O3 and FeO content of the said ore is reduced to Cr2C3 and Fe2C3, comprising the steps of loading chromite ore was into the reactor and lowering the same into the fluidised bed furace at ambient temperature; heating the furnace to 1200 degree C over a 7- hour period; decreasing the fluidising gas flow as the temperature inside the reactor increased, to maintain a constant linear velocity; replacing the nitrogen by the process gas (a combintaion of methane, hydrogen and nitrogen (30/ 20/50 %).when the bed temperature reached 1100 degree C; running the reactor under these conditions for 100 minutes; increasing the concentration of the methane to 33 % (hydrogen concentration decreased to 17%); passing twice the calculated quantity of methane after 75 minutes and reducing the concentration of methane to 20% in the mixture before completelycutting off methane and hydrogen; maintaining the reactor under these conditions for 25 minutes; returning the fluidising gas to full nitrogen and removing from the furnace; maintaining the bed under foil nitrogen flow for approximately 2 hours to result in the reduction of Cr2O3 and FeO in the said ore to Cr2C3 and Fe2C3-

Title of Invention

A PROCESS FOR THE REDUCTION OF CHROMITE ORE FINES IN SOLID STATE IN A FLUIDISED BED REACTOR

Abstract

A process for the reduction of chromite ore fines in solid state in fluidised bed reactor whereby the Cr2O3 and FeO content of the said ore is reduced to Cr2C3 and Fe2C3, comprising the steps of loading chromite ore was into the reactor and lowering the same into the fluidised bed furace at ambient temperature; heating the furnace to 1200 degree C over a 7- hour period; decreasing the fluidising gas flow as the temperature inside the reactor increased, to maintain a constant linear velocity; replacing the nitrogen by the process gas (a combintaion of methane, hydrogen and nitrogen (30/ 20/50 %).when the bed temperature reached 1100 degree C; running the reactor under these conditions for 100 minutes; increasing the concentration of the methane to 33 % (hydrogen concentration decreased to 17%); passing twice the calculated quantity of methane after 75 minutes and reducing the concentration of methane to 20% in the mixture before completelycutting off methane and hydrogen; maintaining the reactor under these conditions for 25 minutes; returning the fluidising gas to full nitrogen and removing from the furnace; maintaining the bed under foil nitrogen flow for approximately 2 hours to result in the reduction of Cr2O3 and FeO in the said ore to Cr2C3 and Fe2C3-

Full Text	This invention relates to a process for the reduction of chromite ore fines in solid state in fluidised bed reactor. Conventionally high carbon ferro chrome is produced in submerged electric arc smelting fuenace using chrome ores/agglomerates, flux and carbonaceous reductants. About 2.5 tonnes of chrome ores are required for production of 1 .0 MT of ferro chrome. About 85 % of the chromite ore reserves occur in the form of fines. These ore fines cannot be directly charged to submerged electric arc smelfing fuueace and therefore these fines have to be agglomerated either bv briquetting or pelletising or sintering and then charged along with carbonaceous reductants such as coal, coke, anthracite along with fluxes to the submerged arc electric furnace for production of ferro chrome. For every tonne of ferro chrome (depending upon the ore analysis, and ash content of the coke and coal) about 1 to 1.2 tonnes slag are produced. The recovery of chromium in ferro chrome is about 80 to 85 %. The known process has got a limitafion of recovery of only 85% of chrome besides involvement of additional cost of electric power for smelting and agglomeration cost of chromite ore fines. An object of this invention is therefore to reduce naturally occurring chromite ore fines and beneficiated chrome ore concentrate directly in solid state in fluidised bed reactor with natural gas (methane). The target was to achieve at least 90 % reduction of chromium oxide and 100% reducfion of iron oxide in chromite ore fines at temperature below 1200 degrees C, say, between 1050 to 1100 degree C to ensure that ore fines remain in solid state without any fusion on the surface of the ore grains in order to keep the fines in a fluidised state to promote the reductipn reaction to completion. Maintaining this temperature below 1200 degree C compared to about 1650 degrees in a smelting fiimace would also result in substantial saving of electric energy apart from saving in cost for agglomeration of fines required to be done in the conventional process. The output from the fluidised bed reactor can be directly used for the production of alloy and stainless steel unlike the case of the conventional process followed in the arc melting furnace. In the process proposed herein for the reduction of chromite.in its solid state, the chromium and iron oxides in the ore are reduced to chromium and iron carbides using methane (natural gas) along with nitrogen and hydrogen in a fluidised bed reactor. The chromium and iron carbides produced in the reactor can either be charged to an electric arc furnace producing stainless steel where foaming slag practice is in vogue and slag forming impurities in the chrome ore are tolerated or itcan be melted in an arc furnace with flux using much lower (almost half) electric power to produce normal ferro chrome free of slag forming impurities. Apart from the object of this invention stated above, another object of this invention to conserve (1) non-replenishable mineral resources such as chromite fines (2) electric power up to 60 % of the conventional method (3) avoid import of low ash, low phos and low sulphur coke (4) achieve overall cost reduction in production of High Carbon Ferro Chromium. Though hydrogen is used in the initial test work, it is expected that in would not be required in regular production since it is produced during the chemical reaction between oxide of chromium in the ore with methane. Cr 2O3 + 13/3 CH4 = 2/3 Cr 3C 2 + 3CO + 26/3 H2 According to this invention, the process for the reduction of chromite ore fines in solid state in fluidised bed reactor whereby the Cr203 and FeO content of the said ore is reduced to Cr2C3 and Fe2C3, comprises the steps of loading chromite ore into the reactor and lowering theisame into the fluidised bed furnace at ambient temperature; heating the furnace to 1200 degree C over a 7- hour period; decreasing the fluidising gas flow as the temperature inside the reactor increased, to maintain a constant linear velocity; replacing the nitrogen by the process gas (a combintaion of methane, hydrogen and nitrogen (30/ 20/50 %).when the bed .temperature reached 1100 degree C; running the reactor under these conditions for 100 minutes; increasing the concentration of the methane to 33 % (hydrogen concentration decreased to 17%); passing twice the calculated quantity of methane after 75 minutes and reducing the concentration of methane to 20% in the mixture before completely cutting off methane and hydrogen; maintaining the reactor under these conditions for 25 minutes; returning the fluidising gas to full nitrogen and removing from the furnace; maintaining the bed under full nitrogen flow for approximately 2 hours to result in the reduction of Cr2O3 and FeO in the said ore to Cr2C3 and Fe2C3. This invention will now be described in further detail with referemce to the accompanying charts which illustrate by way of example, and not by way of limitation, In Fig. 1 test run temperature history And In Fig. 2 an analysis of reduced material EXAMPLE Bench scale test was performed in a 6" diameter batch fluid bed unit equipped with a screw plate gas distributor. The vessel was heated in a fluidised bed furace, with a maximum temperature of 1200 degree C. Thermocouples inside the reactor monitored the temperature of the material as well as the off-gas and the furnace. A gas train and pre-heater were assembled to supply the desired fluidising gases, namely, nitrogen, natural gas and hydrogen. The system set up included the capability for change-over of one gas to another during any particular run and/or the use of a mixture of gases during any particular run. The off-gas from the process was filtered through sintered metal filters, a cyclone and finally a scrubber before release to the atmosphere. For the run 12.5 pound of chromite ore was loaded into the unit. Nitrogen was used to fluidise the material at a linear velocity of 20 ft./min. The reactor was lowered into the fluidised bed furnace at ambient temperature. The furnace was then heated to 1200 degree C over a 7- hour period. As the temperature inside the reactor increased, the fluidising gas flow was decreased to maintain a constant linear velocity. During the heat-up, the temperature reading of the bed diverged around 570 degree C. The lowest thermocouple in the bed idled at around 570 degree C. for several minutes while the other thermocouples continued to increase in temperature. Generally, this divergence of temperature in the material bed is an indicator of non- ideal fluidisation of the particulate material. Nevertheless the test run was continued. When the bed reached 1100 degree C, the nitrogen was replaced by the process gas, a combintaion of methane, hydrogen and nitrogen (30/ 20/50 ;%). The reactor under these conditions for approximately 100 minutes. The concentration of the methane was then increased to 33 % (hydrogen concentration decreased to 17%). After another 75 minutes when twice the calculated quantity of methane was passed and the reaction was expected to have been completed the concentration of methane was reduced to 20% in the mixture before completely cutting off methane and hydrogen. The reactor was held under these conditions for another 25 minutes. The fluidising gas was then returned to full nitrogen and removed from the furnace, The bed was maintained under full nitrogen flow for approximately 2 hours. The temperature profile of the test run including fluidised bed temperatures, heating furnace temperature and inlet gas plenum and freeboard temperatures is given in Fig. 1. The reactor was opened and emptied the next morning. The majority of the material inside was free-flowing powder. There were a few chunlcs of materials on the distributor plate. The weight of the product recovered from the reactor was 4.6 kg equal its to 14. The terms and expressions herein are of description and not of limitation having regard to the scope and ambit of this invention. We Claim: 1. A process for the reduction of chromite ore fines in solid state in fluidised bed reactor whereby the Cr2O3 and FeO content of the said ore is reduced to Cr2C3 and Fe2C3, comprising the steps of loading chromite ore was into the reactor and lowering the same into the fluidised bed furace at ambient temperature; heating the furnace to 1200 degree C over a 7- hour period; decreasing the fluidising gas flow as the temperature inside the reactor increased, to maintain a constant linear velocity; replacing the nitrogen by the process gas (a combintaion of methane, hydrogen and nitrogen (30/ 20/50 %).when the bed temperature reached 1100 degree C; running the reactor under these conditions for 100 minutes; increasing the concentration of the methane to 33 % (hydrogen concentration decreased to 17%); passing twice the calculated quantity of methane after 75 minutes and reducing the concentration of methane to 20% in the mixture before completelycutting off methane and hydrogen; maintaining the reactor under these conditions for 25 minutes; returning the fluidising gas to full nitrogen and removing from the furnace; maintaining the bed under foil nitrogen flow for approximately 2 hours to result in the reduction of Cr2O3 and FeO in the said ore to Cr2C3 and Fe2C3- 2. A process as claimed in Claim 1 wherein the linear velocity of nitrogen is 29ft./min. 3. A process as claimed in Claim 1 or Claim 2 wherein hydrogen is produced during the reaction between the oxide of chromium in the ore and methane.' ' 4. A process for the reduction of chromite ore fines in solid state in fluidised bed reactor substantially as herein described with reference to, and as illustrated by, the Example and the Charts.

Full Text

This invention relates to a process for the reduction of chromite ore fines in solid state in fluidised bed reactor.
Conventionally high carbon ferro chrome is produced in submerged electric arc smelting fuenace using chrome ores/agglomerates, flux and carbonaceous reductants. About 2.5 tonnes of chrome ores are required for production of 1 .0 MT of ferro chrome. About 85 % of the chromite ore reserves occur in the form of fines. These ore fines cannot be directly charged to submerged electric arc smelfing fuueace and therefore these fines have to be agglomerated either bv briquetting or pelletising or sintering and then charged along with carbonaceous reductants such as coal, coke, anthracite along with fluxes to the submerged arc electric furnace for production of ferro chrome. For every tonne of ferro chrome (depending upon the ore analysis, and ash content of the coke and coal) about 1 to 1.2 tonnes slag are produced. The recovery of chromium in ferro chrome is about 80 to 85 %.
The known process has got a limitafion of recovery of only 85% of chrome besides involvement of additional cost of electric power for smelting and agglomeration cost of chromite ore fines.
An object of this invention is therefore to reduce naturally occurring chromite ore fines and beneficiated chrome ore concentrate directly in solid state in fluidised bed reactor with natural gas (methane). The target was to achieve at least 90 % reduction of chromium oxide and 100% reducfion of iron oxide in chromite ore fines at temperature below 1200 degrees C, say, between 1050 to 1100 degree C to ensure that ore fines remain in solid state without any fusion on the surface

of the ore grains in order to keep the fines in a fluidised state to promote the reductipn reaction to completion. Maintaining this temperature below 1200 degree C compared to about 1650 degrees in a smelting fiimace would also result in substantial saving of electric energy apart from saving in cost for agglomeration of fines required to be done in the conventional process.
The output from the fluidised bed reactor can be directly used for the production of alloy and stainless steel unlike the case of the conventional process followed in the arc melting furnace.
In the process proposed herein for the reduction of chromite.in its solid state, the chromium and iron oxides in the ore are reduced to chromium and iron carbides using methane (natural gas) along with nitrogen and hydrogen in a fluidised bed reactor. The chromium and iron carbides produced in the reactor can either be charged to an electric arc furnace producing stainless steel where foaming slag practice is in vogue and slag forming impurities in the chrome ore are tolerated or itcan be melted in an arc furnace with flux using much lower (almost half) electric power to produce normal ferro chrome free of slag forming impurities.
Apart from the object of this invention stated above, another object of this invention to conserve (1) non-replenishable mineral resources such as chromite fines (2) electric power up to 60 % of the conventional method (3) avoid import of low ash, low phos and low sulphur coke (4) achieve overall cost reduction in production of High Carbon Ferro Chromium.

Though hydrogen is used in the initial test work, it is expected that in would not be required in regular production since it is produced during the chemical reaction between oxide of chromium in the ore with methane.
Cr 2O3 + 13/3 CH4 = 2/3 Cr 3C 2 + 3CO + 26/3 H2
According to this invention, the process for the reduction of chromite ore fines in solid state in fluidised bed reactor whereby the Cr203 and FeO content of the said ore is reduced to Cr2C3 and Fe2C3, comprises the steps of loading chromite ore into the reactor and lowering theisame into the fluidised bed furnace at ambient temperature; heating the furnace to 1200 degree C over a 7- hour period; decreasing the fluidising gas flow as the temperature inside the reactor increased, to maintain a constant linear velocity; replacing the nitrogen by the process gas (a combintaion of methane, hydrogen and nitrogen (30/ 20/50 %).when the bed .temperature reached 1100 degree C; running the reactor under these conditions for 100 minutes; increasing the concentration of the methane to 33 % (hydrogen concentration decreased to 17%); passing twice the calculated quantity of methane after 75 minutes and reducing the concentration of methane to 20% in the mixture before completely cutting off methane and hydrogen; maintaining the reactor under these conditions for 25 minutes; returning the fluidising gas to full nitrogen and removing from the furnace; maintaining the bed under full nitrogen flow for approximately 2 hours to result in the reduction of Cr2O3 and FeO in the said ore to Cr2C3 and Fe2C3.

This invention will now be described in further detail with referemce to the accompanying charts which illustrate by way of example, and not by way of limitation, In Fig. 1 test run temperature history And
In Fig. 2 an analysis of reduced material
EXAMPLE Bench scale test was performed in a 6" diameter batch fluid bed unit equipped with a screw plate gas distributor. The vessel was heated in a fluidised bed furace, with a maximum temperature of 1200 degree C. Thermocouples inside the reactor monitored the temperature of the material as well as the off-gas and the furnace. A gas train and pre-heater were assembled to supply the desired fluidising gases, namely, nitrogen, natural gas and hydrogen. The system set up included the capability for change-over of one gas to another during any particular run and/or the use of a mixture of gases during any particular run. The off-gas from the process was filtered through sintered metal filters, a cyclone and finally a scrubber before release to the atmosphere.
For the run 12.5 pound of chromite ore was loaded into the unit. Nitrogen was used to fluidise the material at a linear velocity of 20 ft./min. The reactor was lowered into the fluidised bed furnace at ambient temperature. The furnace was then heated to 1200 degree C over a 7- hour period. As the temperature inside the reactor increased, the fluidising gas flow was decreased to maintain a constant linear velocity. During the heat-up, the temperature reading of the bed diverged around 570 degree C. The lowest thermocouple in the bed idled at around 570 degree C. for several minutes while the other thermocouples continued to increase in temperature. Generally, this divergence of temperature in the material bed is an indicator of non-

ideal fluidisation of the particulate material. Nevertheless the test run was continued.
When the bed reached 1100 degree C, the nitrogen was replaced by
the process gas, a combintaion of methane, hydrogen and nitrogen
(30/ 20/50 ;%). The reactor under these conditions for
approximately 100 minutes. The concentration of the methane was then increased to 33 % (hydrogen concentration decreased to 17%). After another 75 minutes when twice the calculated quantity of methane was passed and the reaction was expected to have been completed the concentration of methane was reduced to 20% in the mixture before completely cutting off methane and hydrogen. The reactor was held under these conditions for another 25 minutes. The fluidising gas was then returned to full nitrogen and removed from the furnace, The bed was maintained under full nitrogen flow for approximately 2 hours.
The temperature profile of the test run including fluidised bed temperatures, heating furnace temperature and inlet gas plenum and freeboard temperatures is given in Fig. 1.
The reactor was opened and emptied the next morning. The majority of the material inside was free-flowing powder. There were a few chunlcs of materials on the distributor plate. The weight of the product recovered from the reactor was 4.6 kg equal its to 14.
The terms and expressions herein are of description and not of limitation having regard to the scope and ambit of this invention.

We Claim:
1. A process for the reduction of chromite ore fines in solid state in
fluidised bed reactor whereby the Cr2O3 and FeO content of the said
ore is reduced to Cr2C3 and Fe2C3, comprising the steps of loading
chromite ore was into the reactor and lowering the same into the
fluidised bed furace at ambient temperature; heating the furnace to
1200 degree C over a 7- hour period; decreasing the fluidising gas flow as the temperature inside the reactor increased, to maintain a constant linear velocity; replacing the nitrogen by the process gas (a combintaion of methane, hydrogen and nitrogen (30/ 20/50 %).when the bed temperature reached 1100 degree C; running the reactor under these conditions for 100 minutes; increasing the concentration of the methane to 33 % (hydrogen concentration decreased to 17%); passing twice the calculated quantity of methane after 75 minutes and reducing the concentration of methane to 20% in the mixture before completelycutting off methane and hydrogen; maintaining the reactor under these conditions for 25 minutes; returning the fluidising gas to full nitrogen and removing from the furnace; maintaining the bed under foil nitrogen flow for approximately 2 hours to result in the reduction of Cr2O3 and FeO in the said ore to Cr2C3 and Fe2C3-
2. A process as claimed in Claim 1 wherein the linear velocity of nitrogen is 29ft./min.
3. A process as claimed in Claim 1 or Claim 2 wherein hydrogen is produced during the reaction between the oxide of chromium in the ore and methane.' '
4. A process for the reduction of chromite ore fines in solid state in fluidised bed reactor substantially as herein described with reference to, and as illustrated by, the Example and the Charts.

Documents:

2010-CHE-2007 AMENDED PAGES OF SPECIFICATION 24-02-2012.pdf

2010-CHE-2007 AMENDED CLAIMS 16-07-2012.pdf

2010-CHE-2007 CORRESPONDENCE OTHERS 24-02-2012.pdf

2010-CHE-2007 CORRESPONDENCE OTHERS 16-07-2012.pdf

2010-CHE-2007 POWER OF ATTORNEY 24-02-2012.pdf

2010-che-2007 claims.pdf

2010-CHE-2007 CORESPONDENCE-OTHERS 15-10-2009.pdf

2010-che-2007 correspondence others.pdf

2010-che-2007 description (complete).pdf

2010-che-2007 drawing.pdf

2010-che-2007 form-1.pdf

2010-che-2007 form-18.pdf

2010-che-2007 form-26.pdf

2010-che-2007-claims.pdf

2010-che-2007-correspondnece-others.pdf

2010-che-2007-description(complete).pdf

2010-che-2007-drawings.pdf

2010-che-2007-form 1.pdf

2010-che-2007-form 26.pdf

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Patent Number

258000

Indian Patent Application Number

2010/CHE/2007

PG Journal Number

48/2013

Publication Date

29-Nov-2013

Grant Date

26-Nov-2013

Date of Filing

07-Sep-2007

Name of Patentee

FACOR ALLOYS LIMITED

Applicant Address

SHREERAMNAGAR 535101 DISTRICT VIZIANAGARAM ANDHRA PRADESH

Inventors:

#	Inventor's Name	Inventor's Address
1	C.N. HARMAN	TECHNICAL DIRECTOR FACOR ALLOYS LIMITED SHREERAMNAGAR 535101 DISTRICT VIZIANAGARAM ANDHRA PRADESH

PCT International Classification Number

C22B 5/10

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA