Title of Invention

"A PROCESS FOR THE PREPARATION OF DIRECTLY REDUCED IRON (DRI) BLOCKS FROM IRON ORE AND COAL OR COKE FINES"

Abstract

A process for the preparation of Directly Reduced Iron (DRI) blocks from iron ore and coal or coke fines which comprises: a), mixing iron ore and coal or coke fines along with binderin the range of 5-15 W% , wherein the said binder used is a mixture of pyrophilite and cement in the range of 1.2 : 1 to 1 : 1.2 b). preparing the composite blocks of the above said mixture, at a vertical compaction pressure ranging between 200 to 450 kg/cm and curing them for about 5 days, c). roasting the above said composite blocks at a temperature in the range of 1000 - 1100°C for a period of 60 to 90 minutes under non-oxidising or mild-reducing condition to obtain the desired product.

Full Text

This invention relates to a process for the preparation of Directly Reduced Iron (DRI) blocks from iron ore and coal or coke fines. More particularly, the present invention relates to a process for the preparation of Directly Reduced Iron (DRI) blocks using iron ore and coal or coke fines generated at plant and during mining. The DRI blocks with more than 90% iron metallisation could be directly used for steel making. The process of present invention is to make composite blocks using iron ore fines and coal/coke fines generated at DRI plant/ Steel plant. The aim of the process is to reduce more than 90% of iron oxide in the block to iron metal, which can be charged for steel making. Coal based DRI plants employing technologies like SL/RN process (jointly developed by steel company of Canada, Lugri Chemie, Republic steel company and National Lead corporation in 1964), Allis-Chalmers Atmospheric Reduction (ACCAR), TISCO Direct Reduction (TDR) process etc., generates approximately 20-30% iron and coal fines as rejects. In all above processes Direct Reduction of iron ore is accomplished using rotary kiln as the reactor and coal as reductant. Besides the above, huge quantity of iron ore fines are generated during mining. In Iron and Steel industry large quantities of iron ore fines and coke fines are also rejected as wastes. At present, part of these fines are sold at throw away price, resulting in substantial financial loss but bulk of these wastes are stock piled causing waste disposal and environmental problems. There is no information available on the present invention of a process for the preparation of direct reduced iron (DRI) from the composite blocks of iron ore and coal or coke fines. The main objective of the present invention is to provide a process to bring the iron oxide to iron metal. Another object is to make composite blocks of iron ore fines and coal/coke fines by using a suitable binder combination Yet another objective is to reduce the composite blocks in non-oxidising/mildly-reducing condition to obtain more than 90% iron metallisation. Accordingly the present invention provides a process for the preparation of Directly Reduced Iron (DRI) blocks from iron ore and coal or coke fines which comprises: a). mixing iron ore and coal or coke fines along with binder in the range of 5-15 W% , wherein the said binder used is a mixture of pyrophilite and cement in the range of 1.2 : 1 to 1 : 1.2, b). preparing the composite blocks of the above said mixture, at a vertical compaction pressure ranging between 200 to 450 kg/cm2 and curing them for about 5 days, c). roasting the above said composite blocks at a temperature in the range of 1000 - 1100°C for a period of 60 to 90 minutes under non-oxidising or mild-reducing condition to obtain the desired product. In an embodiment of the present invention the weight % of coal fines used is in the range of 25 to 40 W% of iron ore. In yet another embodiment the weight % of coke fines used is in the range of 20 - 30 W% of iron ore. In yet another embodiment the weight % of binder used is in the range of 5-15 W% of iron ore, preferably 7-9 W% of iron ore. In yet another embodiment the binder used is a mixture of pyrophilite and cement in a proportion of 1.2 : 1- 1 : 1.2, preferably 1:1 . In still another embodiment the vertical compaction pressure used is preferably in the range of 200 to 400 kg/cm2. The size of iron ore used in the study is -6 mm and coal fines/coke fines -3 mm. The composite blocks are roasted in the temperature range of 1000° to 1100°C to obtain more than 90% iron metallisation. The following examples are given to illustrate how the process of present invention is carried out in actual practice and should not be constructed to limit the scope of the invention. Example-1: 1.5 kg of iron ore fines having total iron content of 66% is mixed with 375g (25% by weight of iron ore fines) of coal fines and mixed with 120g (8% by weight of iron ore fines) of binder containing pyrophilite and cement in the proportion 1:1. Composite blocks of these materials are prepared under vertical compaction pressure of 400kg/cm2. The composite block obtained is of the size 25cm x 10cm x 3.5 cm. The block, after curing for 5 days, is subjected to roasting at 1100°C for 90 minutes to reduce iron oxide to metallic iron in a non-oxidizing condition. Iron metallisation to the extent of 92.5% is achieved. Example-2: 1.5 kg of iron ore fines having total iron content of 66% is mixed with 600g (40% by weight of iron ore fines) of coal fines and mixed with 120g (8% by weight of iron ore fines) of binder containing pyrophilite and cement in the proportion 1:1. Composite blocks of these materials are prepared under vertical compaction pressure of 400kg/cm . The composite block obtained is of the size 25cm x 10cm x 3.5 cm. The block, after curing for 5 days, is subjected to roasting at 1100°C for 90 minutes to reduce iron oxide to metallic iron in a non-oxidizing condition. Iron metallisation to the extent of 93% is achieved. Example-3: 1.5 kg of iron ore fines having total iron content of 66% is mixed with 300g (20% by weight of iron ore fines) of coke fines and mixed with 120g (8% by weight of iron ore fines) of binder containing pyrophilite and cement in the proportion 1:1. Composite blocks of these materials are prepared under vertical compaction pressure of 400kg/cm . The composite block obtained is of the size 25cm x 10cm x 3.5 cm. The block, after curing for 5 days, is subjected to roasting at 1100°C for 90 minutes to reduce iron oxide to metallic iron in a non-oxidizing condition. Iron metallisation to the extent of 91% is achieved. Example-4: 1.5 kg of iron ore fines having total iron content of 66% is mixed with 450g (30% by weight of iron ore fines) of coke fines and mixed with 120g (8% by weight of iron ore fines) of binder containing pyrophilite and cement in the proportion 1:1. Composite blocks of these materials are prepared under vertical compaction pressure of 400kg/cm2. The composite block obtained is of the size 25cm x 10cm x 3.5 cm. The block, after curing for 5 days, is subjected to roasting at 1100°C for 90 minutes to reduce iron oxide to metallic iron in a non-oxidizing condition. Iron metallisation to the extent of 93% is achieved. Example-5: 1.5 kg of iron ore fines having total iron content of 66% is mixed with 375g (25% by weight of iron ore fines) of coke fines and mixed with 120g (8% by weight of iron ore fines) of binder containing pyrophilite and cement in the proportion 1:1. Composite blocks of these materials are prepared under vertical compaction pressure of 400kg/cm2. The composite block obtained is of the size 25cm x 10cm x 3.5 cm. The block, after curing for 5 days, is subjected to roasting at 1000°C for 90 minutes to reduce iron oxide to metallic iron in a non-oxidizing condition. Iron metallisation to the extent of 90% is achieved. Example-6: 1.5 kg of iron ore fines having total iron content of 66% is mixed with 375g (25% by weight of iron ore fines) of coke fines and mixed with 120g (8% by weight of iron ore fines) of binder containing pyrophilite and cement in the proportion 1:1. Composite blocks of these materials are prepared under vertical compaction pressure of 400kg/cm . The composite block obtained is of the size 25cm x 10cm x 3.5 cm. The block, after curing for 5 days, is subjected to roasting at 1100°C for 90 minutes to reduce iron oxide to metallic iron in a non-oxidizing condition. Iron metallisation to the extent of 93.5% is achieved. Example-7: 1.5 kg of iron ore fines having total iron content of 66% is mixed with 375g (25% by weight of iron ore fines) of coke fines and mixed with 120g (8% by weight of iron ore fines) of binder containing pyrophilite and cement in the proportion 1:1. Composite blocks of these materials are prepared under vertical compaction pressure of 400kg/cm . The composite block obtained is of the size 25cm x 10cm x 3.5 cm. The block, after curing for 5 days, is subjected to roasting at 1100°C for 60 minutes to reduce iron oxide to metallic iron in a non-oxidizing condition. Iron metallisation to the extent of 91% is achieved. Example-8: 1.5 kg of iron ore fines having total iron content of 66% is mixed with 375g (25% by weight of iron ore fines) of coke fines and mixed with 120g (8% by weight of iron ore fines) of binder containing pyrophilite and cement in the proportion 1:1. Composite blocks of these materials are prepared under vertical compaction pressure of 200kg/cm2. The composite block obtained is of the size 25cm x 10cm x 3.5 cm. The block, after curing for 5 days, is subjected to roasting at 1100°C for 90 minutes to reduce iron oxide to metallic iron in a non-oxidizing condition. Iron metallisation to the extent of 94% is achieved. Example-9: 1.5 kg of iron ore fines having total iron content of 66% is mixed with 375g (25% by weight of iron ore fines) of coke fines and mixed with 120g (8% by weight of iron ore fines) of binder containing pyrophilite and cement in the proportion 1:1. Composite blocks of these materials are prepared under vertical compaction pressure of 450kg/cm . The composite block obtained is of the size 25cm x 10cm x 3.5 cm. The block, after curing for 5 days, is subjected to roasting at 1100°C for 90 minutes to reduce iron oxide to metallic iron in a non-oxidizing condition. Iron metallisation to the extent of 91% is achieved. The main advantages of the process are: 1. The process wherein, coal based DRI plant employing rotary kiln rejects can be utilised. 2. The process wherein, iron ore fines from the mine site can be utilised. 3. The process wherein, coal fines generated at plant, mines and coal washeries can be utilised. 4. The process wherein, the ore fines and coke fines generated in steel plants as wastes can be utilised. 5. The process wherein, the composite block making is simple. 6. The process wherein, the process is flexible as regard to size range of raw materials. 7. The process wherein, the materials are waste from the plants/mines. 8. The process wherein, the reduction of iron oxide to metallic iron is possible under non-oxidising/mild- reducing conditions. 9. The process wherein, handling of DRI in the form of blocks is easier for melting. 10. The process wherein conditions for conversion of iron ore to metallic iron is cost effective. 11. The process wherein, slow re-oxidation of the DRI product takes place as compared to conventional DRI making, resulting in less power consumption and high yield during melting. 12. The process wherein the fines generated can be effectively utilised by making composite blocks. We claim: 1. A process for the preparation of Directly Reduced Iron (DRI) blocks from iron ore and coal or coke fines which comprises: a), mixing iron ore and coal or coke fines along with binderin the range of 5-15 W% , wherein the said binder used is a mixture of pyrophilite and cement in the range of 1.2 : 1 to 1 : 1.2 b). preparing the composite blocks of the above said mixture, at a vertical compaction pressure ranging between 200 to 450 kg/cm2 and curing them for about 5 days, c). roasting the above said composite blocks at a temperature in the range of 1000 - 1100°C for a period of 60 to 90 minutes under non-oxidising or mild-reducing condition to obtain the desired product. 2. A process as claimed in the claim 1, wherein the weight % of coal fines used is in the range of 25 to 40 W % of iron ore. 3. A process as claimed in the claims 1&2, wherein the weight % of coke fines used is in the range of 20 - 30 W% of iron ore. 4. A process as claimed in the claims 1-3, wherein the weight % of binder used is preferably in the range 7-9 W% of iron ore. 5. A process as claimed in claims 1-4, the binder used is a mixture of pyrophilite and cement preferably in a proportion of 1:1 . 6. A process as claimed in claims 1-5, wherein the vertical compaction pressure used is preferably in the range of 200 to 400 kg/cm2. 7. A process for the preparation of Directly Reduced Iron (DRI) blocks from iron ore and coal or coke fines, substantially as herein described with reference to the examples.

Documents:

796-DEL-2002-Abstract-(12-10-2010).pdf

796-del-2002-abstract.pdf

796-DEL-2002-Claims-(12-10-2010).pdf

796-del-2002-claims.pdf

796-DEL-2002-Correspondence-Others-(12-10-2010).pdf

796-del-2002-correspondence-others.pdf

796-del-2002-correspondence-po.pdf

796-DEL-2002-Description (Complete)-(12-10-2010).pdf

796-del-2002-description (complete).pdf

796-DEL-2002-Form-1-(12-10-2010).pdf

796-del-2002-form-1.pdf

796-del-2002-form-18.pdf

796-DEL-2002-Form-2-(12-10-2010).pdf

796-del-2002-form-2.pdf

796-DEL-2002-Form-3-(12-10-2010).pdf

796-del-2002-form-3.pdf