Description:[0017] The preferred embodiments of the present invention will now be explained in detail. It should be understood however that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. The following description and drawings are not to be construed as limiting the invention and numerous specific details are described to provide a thorough understanding of the present invention, as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. However in certain instances, well-known or conventional details are not described in order not to unnecessarily obscure the present invention in detail.

[0018] The preferred embodiment of the present invention teaches a process involving the reduction of acidic iron oxide to produce sponge iron by Direct reduced iron method. The acidic iron oxide waste is the by-product of Ilmenite beneficiation by Benelite Corporation of America (BCA) process. Chemically, ilmenite is FeTiO3 (Iron titanate) that contains approximately 30% of Fe2O3. In BCA process, ilmenite is leached with 20% hydrochloric acid and therefore, the spent acid containing iron is highly acidic. Said spent HCl acid is spray dried to recover the Fe2O3, which is also highly acidic. The approximate composition of iron oxide is shown in the tabular column:
Sr no.
Elements
%
1 Fe2O3 87.1
2 TiO2 0.80
3 V2O5 0.90
4 Al2O3 1.78
5 Cr2O3 0.13
6 SiO2 1.00
7 Total chlorides 2.90
8 Moisture 5.10
9 pH of 10% slurry 1.4
10 Conductivity of 10% slurry(mMho) 8.62

[0019] In the major titanium dioxide industries using the BCA process for Ilmenite beneficiation, this acidic iron oxide is either stored in ponds or discarded to environment. Hence, this acidic iron oxide is a major concern for titanium dioxide industries using BCA process for Ilmenite beneficiation. Due to the acidity, this iron oxide cannot be directly used in blast furnace or DRI (direct reduced iron) method for metallic iron manufacture. The iron oxide fines has a particle size of 2-10 micrometer and this was mixed with water, borax and ammonium chloride and made to pellets of size 3 mm to 15 mm and reduced with petroleum coke. Trials were also tried by powdering petcoke and also incorporating in the pellets. However, the reduction was found to be not good.

[0020] As per the preferred embodiment of the present invention, the acidic iron oxide, which has crystalline structure of alpha Fe2O3, is reduced with borax and ammonium chloride mixture, and petroleum coke in a rotary kiln. The reduction was performed at 1000oC for different durations ranging from 1 hour to 6 hours, wherein the optimum duration for sponge iron formation was found to be 5 hours. Also different compositions of ammonium chloride and borax mixture were tried, wherein the optimum composition was observed to be 3% each of ammonium chloride and borax respectively in the mixture.

[0021] Different set of trials were also performed by varying the concentration of petroleum coke from 10 % to 50 %. A combination of 25% pet coke and 3% each of ammonium chloride and borax mixture was found to provide good quality sponge iron at 1000o C. In other words, as per the preferred embodiment of the present invention, acidic iron oxide is reduced with a combination of 25% pet coke and 3% each of ammonium chloride and borax mixture at 1000oC for 5 hours in a rotary kiln.

[0022] Petroleum coke used has the following specification: free moisture 5%, inherent moisture 1%, ash 2%, volatile matter 15%, and fixed carbon 85%.After reduction, the percentage of metallic iron and degree of metallisation etc was calculated as per IS standards No: IS 15774:2007. Sponge iron produced was within standard IS specification. The total iron content in the iron oxide was 87.1%. The metallic iron content was in the range of 86.52%. And the degree of metallisation percentage was 99.67%. The metallic iron content was analysed by bromine-methanol titrimetric method (IS 5416:2006).

[0023] The DRI /sponge iron produced has no additional binder addition like bentonite and CaCO3 / dolomite addition for desulphurisaton etc. Hence, during steel manufacture, the slag formed is substantially reduced. Waste generation is also less. The carbon, sulphur and phosphorus content of the DRI/sponge iron was also within IS specifications.

[0024] Iron oxide cakes is also directly reduced as such without pelletisation, but the reduction was good. But for industrial scale production pelletisation before reduction was found to be feasible.

Example 1

[0025]The acidic iron oxide waste after ilmenite beneficiation was used for this work.1 kg of acidic iron oxide was mixed with 30 gm borax and 30 gm ammonium chloride and little water and made to pellets of size 3 mm to 20 mm .Said pellets were then reduced with 250 gm of pet coke at 1000oC for 5 hours in a rotary kiln. The sponge iron/DRI produced was found to be within specifications.

Example 2

[0026]1 kg of haematite ore was mixed with 30 gm borax and 30 gm ammonium chloride and little water and made to pellets of size 3 mm to 20 mm .This pellets were then reduced with 250 gm of pet coke at 1000oC for 5 hours in a rotary kiln. The sponge iron/DRI produced was found to be within specifications.

Example 3

[0027]1 kg of magnetite ore was mixed with 30 gm borax and 30 gm ammonium chloride and little water and made to pellets of size 3 mm to 20 mm .This pellets were then reduced with 250 gm of pet coke at 1000oC for 5 hours in a rotary kiln. The sponge iron/DRI produced was found to be within specifications.

Example 4

[0028]The acidic iron oxide waste after ilmenite beneficiation was used for this work.1 kg of acidic iron oxide was mixed with 20 gm borax and 20 gm ammonium chloride and little water and made to pellets of size 3 mm to 20 mm .This pellets were then reduced with 250 gm of pet coke at 1000oC for 5 hours in a rotary kiln. The sponge iron/DRI produced was found to be within specifications.

Example 5

[0029]The acidic iron oxide waste after ilmenite beneficiation was used for this work.1 kg of acidic iron oxide was mixed with 20 gm borax and 20 gm ammonium chloride and little water and made to pellets of size 3 mm to 20 mm .Here 10 gm calcium silicate flux was also added. The quantity of flux added is 0.5% of iron oxide quantity. These pellets were then reduced with 250 gm of pet coke at 1000oC for 5 hours in a rotary kiln. The sponge iron/DRI produced was found to be within specifications.

Example 6

[0030]The acidic iron oxide waste after ilmenite beneficiation was used for this work.1 kg of acidic iron oxide was mixed with 20 gm borax and 20 gm ammonium chloride and little water and made to pellets of size 3 mm to 20 mm .Here 6gm calcium silicate flux was also added. These pellets were then reduced with 250 gm of pet coke at 1000oC for 5 hours in a rotary kiln. The sponge iron/DRI produced was found to be within specifications.

Example 7

[0031]The acidic iron oxide waste after ilmenite beneficiation was used for this work.1 kg of acidic iron oxide was mixed with 20 gm borax and 20 gm ammonium chloride and little water and made to pellets of size 3 mm to 20 mm .Here 10gm calcium aluminate flux was also added. The quantity of flux added is 0.5% of iron oxide quantity. The pellets were then reduced with 250 gm of pet coke at 1000oC for 5 hours in a rotary kiln. The sponge iron/DRI produced was found to be within specifications.

[0032] Although the present invention has been described in connection with the preferred embodiments thereof, it is to be noted that various changes and modifications are possible and are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention unless they depart there from.
, Claims:WE CLAIM

1. A process for manufacturing sponge iron from acidic iron oxide, and ores of iron, said process characterized by:
• pelletizing the iron ores powder to 3mm to 20mm size pellets by mixing with borax and ammonium chloride; and
• reducing said pelletized iron ores using petroleum coke and mixture of 3% of ammonium chloride and 2% borax in a rotary kiln at temperature of 10000C for 5 hours.

2. The process as claimed in claim 1, wherein the petroleum coke used is 25% of iron oxide.

3. The process as claimed in claim 1, wherein the petroleum coke comprises of free moisture (5%), inherent moisture (1%), ash (2%), volatile matter (15%), and fixed carbon (85%).

4. The process as claimed in claim 1, wherein calcium silicate or calcium aluminate flux is added, wherein the quantity of said flux is 0.5% of the iron oxide quantity.

5. The process as claimed in claim 1, wherein the slag generated is less.

6. The process as claimed in claim 1, wherein the degree of metallisation percentage attained is 99.67%.

7. The process as claimed in claim 1 is for hazardous waste management of acidic iron oxide, which has been categorized in schedule 2 Class C2.

8. The process as claimed in claim 1, wherein the pH of the 10% solution of iron oxide is 1.4.

23/05/2022 Prasanth S
IN/PA 2954

Agent for the Applicant