FORM 2
THE PATENTS ACT,1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)


//
A PROCESS FOR PRODUCING DIRECTLY REDUCED IRON AND IRON-STEEL SCRAP"
ELECTROTHERM (INDIA)LTD, an Indian company, of 72, Palodia, Via Thaltej, Ahmedabad-382 115, India
The following specification particularly describes the invention and the manner in which it is to be performed.

PROCESS FOR PRODUCING DIRECTLY REDUCED IRON AND
IRON-STEEL SCRAP
Field of Invention:
The present invention relates to a method of producing directly reduced iron (DRI) and/or iron-steel scrap utilizing the waste heat of the slag.
Background of the Invention:
In iron or steel making industries directly reduced iron (DRI) or sponge iron is produced by reduction of iron oxide source material. There are number of processes available for production of directly reduced iron (DRI) or sponge iron. The conventional processes for producing DRI can be divided into the following three categories:
Gas based process: In this process iron ore pellets/ lump ore is charged into a vertical shaft and a reducing gas normally containing a mixture of carbon monoxide, hydrogen and carbon-di-oxide etc. is passed through the lower part of the shaft at a temperature in the range of 750°C to 950°C. Due to counter current gas solid reaction the pellets/lump ore gets reduced to DRI. There are number of gas based processes, such as, Midrex, HYL-III etc. In this process normally natural gas is used as a source of reducing gas and energy.
Coal based process: In this process iron ore pellets/lump and coal fines/lumps are charged into an inclined kiln. During descent of the burden the pellet/lump ore gets reduced to DRI. In this process coal is the only sources of reductant and energy. Due to the external heat source this process involves high energy consumption.
Rotary hearth process: In this process carbon and iron bearing materials are mixed together and formed pellets. These pellets are charged inside a rotary hearth furnace, where the pellets get reduced at a temperature over 1350°C. Since this process involve external heat source it is not an energy intensive process.
2

All of the above indicated processes are time consuming, require large amount of energy due to the need of external heat source for reduction of iron ore and also involves large capital expenditure. Therefore, there exists a need to develop a process which requires comparatively less energy and less time to produce directly reduced iron.
Object of the Present Invention:
The main object of the present invention is to provide a process for producing directly reduced iron (DRI) and/or iron-steel scrap from iron ore.
Summary of the Invention:
The present invention provides a process for producing a directly reduced iron. The DRI thus produced can be melted using the surplus heat available in the slag bath producing iron or steel scrap depending upon the amount of carbon available in the process. The Applicant(s) have named the DRI produced by the process of the present invention as 'slag DRI'.
Detailed description of the present invention:
Accordingly, the present invention provides a process for producing a directly reduced iron (DRI) or iron/steel scrap in the absence of external heat source comprising a step of contacting a iron oxide source material with liquid slag in the presence of carbon source material for a predetermined exposure time, wherein the temperature of the liquid slag is in the range of 1400 to 1750° C.
In an aspect of the present invention the directly reduced iron (DRI) thus produced in the process of the present invention can be melted to liquid iron or liquid steel depending upon the amount of carbon available in the process (carbon < 2.0% called steel, carbon >2.0% called iron), which subsequently produces iron or steel scrap after solidification as the case may be. Thus, the present invention can be used for the production of either DRI or iron/steel scrap by means of controlling the slag temperature and the exposure time between the mixture of iron oxide- carbon source material and the slag.
3

iron and steel making process slag is generated as a by-product and thrown out as a waste material. The slag is mostly a mixture of inert oxides, such as, CaO, MgO, Si02, Al2O3 etc. The slag generated in iron and steel making process is tapped out of the furnace in the liquid form, at a temperature of about 1450°C to 1750°C.
In many cases, the slag is processed in cold condition, where heat of slag is not utilized. The present invention relates to the utilization of waste heat of slag for the production of directly reduced iron (DRI) or sponge iron. The Applicant(s) have named the DRI produced by the process of the present invention as 'Slag DRI'. Subsequently, the process also allows to melt this DRI for the production of iron-steel scarp.
In iron ore 'iron' is present in the form of oxides (i.e. iron combined with oxygen). During directly reduced iron (DRI) production it is required to separate the oxygen from the iron. Removal of oxygen or reduction of iron is done by carbon which combines with oxygen at high temperature and forms carbon monoxide. However, it is practically not possible to remove all the oxygen from iron ore. For this reason inside the DRI there would be both metallic iron and iron oxide. Effectiveness of reduction can be indicated by degree of metallization which can be described as follows:
Degree of Metallization = (wt. of Metallic iron in DRI) x 100/(wt. of total iron in DRI)
By the process of the present invention the degree of metallization of the DRI could be over 90%.
As it can be clearly understood, the slag is at a higher temperature than the mixture of carbon source material and iron oxide source material. Heat of the slag can be transferred to the mixture with help of heat transfer mechanism selected from the group comprising conduction, convection, radiation or combination thereof. At higher temperature, combustion of carbon produces carbon monoxide gas which ultimately utilizes iron oxide to form metallic iron.
4

an aspect of the present invention the ratio of iron oxide source material or iron ore and the carbonaceous material can be in the range of 5:1 to 1:1. Preferably, the ratio of iron ore and carbonaceous material is 4:1.
The ratio of liquid slag to the mixture of carbon source material and iron oxide source material can be selected in the range of 10:1 to 2:1. Preferably, the ratio of liquid slag and the mixture (of iron ore and carbon source material) is 5:1.
The slag generated from the COREX, blast furnace or any other iron making units can be used in the process of the present invention. Also, for the process of the present invention the source of the liquid slag can be selected from the group comprising but not limited to basic oxygen furnaces, Electric Arc furnace (EAF), Argon Oxygen Decarburization (AOD), CONARC furnace, Energy optimizing furnace (EOF), induction furnace and any other steel making/ stainless steel making unit etc.
In the process of the present invention the Iron oxide source material can be selected from the group comprising but not limited to iron ore, iron ore lump and fines, mill scale, de-dusting dust in iron and steel making process, iron ore slimes and tailings generated during benefication and sinter fines etc.
In an aspect of the process of the present invention the carbon source material can be selected from the group comprising but not limited to coal,, crushed coal, coal fines, coke fines, iron and steel making sludge, petroleum coke, Calcined petroleum coke, tar, charcoal and charcoal fines etc.
In the process of the present invention when the liquid slag at a high temperature comes in contact with the mixture of iron oxide source or iron ore and carbon source material, the heat of the slag metallize the mixture of iron ore and carbon mixture. It can be clearly understood that in the process of the present invention heat of the slag and carbon source mixed with iron ore are only two sources of energy. Other than this no other source of energy is used. Since, the process of the present invention does not need any other energy
5

source therefore in the absence of the external heat/energy source the present process saves lots of energy.
In the process of the present invention the mixtures of iron bearing materials or iron oxide source material and carbon source material can be in the form of briquettes, pellets, lumps and fines.
The process of the present invention utilizes heat of the liquid slag generated from conventionally known furnaces. However, production of slag DRI and/or iron-steel scrap by the process of the present invention does not require any furnace; it is done in the slag pot outside the furnace.
In a preferred aspect of the process of the present invention a predetermined amount of mixture of iron ore and coal in the form of briquettes is added into the predetermined amount of liquid slag. After a predetermined time the briquettes are transferred to another slag pot. This action avoids any kind of segregation inside the slag pot. The size of the iron ore and coal briquettes can be made smaller so that heat transfer is effective. As indicated earlier, depending upon the product requirement (i.e. either DRI or iron-steel scrap), the contacting time of the slag and iron-carbon source materials is selected. Slag temperature also plays a vital role in the same.
In the process of the present invention the slag is removed from the slag pot in liquid state. Therefore, the reduced briquettes can be easily removed from the slag without creating any logistical problems. However, in case of iron or steel scrap production, slag is allowed to solidify first and then it is crushed and through magnetic separation iron-steel scrap is separated from the slag.
The process of the present invention takes very less time as compared to conventional processes to produce directly reduced iron (DRI). For example, a normal coal based DRI takes about 5-8 hrs for conversion of iron ore to DRI. Whereas the process of the present invention takes about 10-30 minutes to convert the same amount of iron to DRI and even melt the same to form iron-steel scrap.
6

In the process of the present invention during production of DRI using liquid slag, some amount of steel also produces through reduction of Ferrous Oxides (FeO), also known as wustite) present in the slag.
Example 1:
1 ton of briquettes of iron oxide source material and carbon source material in the ratio which may be in the range of 5:1 to 1:1 are prepared. The iron oxide source material may be iron ore lump and fines, mill scale, de-dusting dust produced in iron and steel making process, tailing generated during beneficiation and sinter fines; and carbon source material may be coal, crushed coal, coal fines, coke, coke fines, iron and steel making sludge, petroleum coke, calcined petroleum coke , tar, charcoal and charcoal fines. The briquettes are supplied to a slag pot having liquid slag at a temperature which may be in the range of 1400°C to 1750°C and in the quantity ranging from 2 tons to 10 tons. The liquid slag may be obtained from COREX, blast furnace, basic oxygen furnaces, Electric Arc Furnace (EAF), Argon Oxygen Decarburization (AOD), CONARC furnace, Energy Optimizing Furnace (EOF), induction furnace and any other steel making/ stainless steel making unit. The briquettes may be kept in contact with the hot liquid slag in the slag pot for duration in the range of 5 minutes to 30 minutes. In this process due to the heat of the liquid slag the iron oxide gets reduced and is converted into DRI or iron/steel scrap. Example 2:
1 ton briquettes of iron ore and coal in the ratio of 4:1 is prepared. The briquettes are supplied to a first slag pot having 5 tons of liquid slag at a temperature of 1700° C. After 5 mins duration the briquettes and liquid slag is transferred to a second empty slag pot. After another 5 mins duration the slag is separated from the briquettes present in the second pot. In this process the briquettes get converted to DRI.
Example 3:
1 ton briquettes of iron ore and coal in the ratio of 4:1 is prepared. The briquettes are supplied to a first slag pot having 5 tons of liquid slag at a temperature of 1750° C. After l0mins duration the briquettes and liquid slag is transferred to a second empty slag pot. After another
7

10 mins when all the DRI gets melted to iron/steel the liquid slag is poured into a slag pit, where it is cooled to room temperature. Subsequently, the solid slag is crushed and through magnetic separation the iron-steel scrap is separated from the slag.
Some of the advantages of the present invention are as follows:
1. The cost of production of DRI or iron-steel scrap produced by the process of the present invention is substantially lesser compared to the conventional processes presently used commercially. This is because amount of carbon source required for the process is much lesser compared to the conventional processes. This process uses the thermal energy of the liquid slag for its balance energy requirement. As carbon requirement is lesser the process is cheaper.
2. Slag is a waste product of iron making and steel making units. Utilization of heat of slag is considered as waste heat utilization.
3. The process of the present invention has potential to use various iron bearing fines and carbon sources, which are also a waste product of iron making and steel making plant.
4. Utilization of waste heat and requirement of low carbon in production of directly reduced iron (DRI) or iron/steel scrap of the present invention enables the process to qualify for 'Carbon Credit' in the international market,
5. Production of Slag DRI or iron/steel scrap by the process of the present invention is capable of improving production capacity of any steelmaking or iron making unit.
6. By the process of the present invention In-House production of directly reduced iron (DRI) with very less capital expenditure is possible.
7. The directly reduced iron (DRI) or iron/steel scrap produced by the process of the present invention can be used in any steel making units as a replacement of purchased DRI.
8. The production Cost of slag DRI by the process of the present invention is nearly half of the prevailing market price.
9. Production of slag DRI or iron/steel scrap requires very less quantity of coal (say, only 25%) compared to the coal needed for the production of DRI through Rotary kiln (coal based route). This is because amount of carbon source required for the
8

process is much lesser compared to the conventional processes. This process uses the thermal energy of the liquid slag for its balance energy requirement.
10. Slag DRI production by the process of the present invention enhances the steel scrap recovery from the slag. The scrap recovery is likely to be higher than normal due to partial reduction of FeO in the slag.
11. The cost of installing a 100 TPD Rotary kiln for the production of coal based DRI is about 20 crores and it requires 18-20 months time to install the facility. Whereas, the process of the present invention can be carried out using the available facilities inside a steel mill.
9

We Claim:
1. A process for producing a directly reduced iron (DRI) or iron/steel scrap comprising a step of contacting a iron oxide source material with liquid slag in the presence of carbon source material for a predetermined exposure time, wherein the temperature of the liquid slag is in the range of 1400 to 1750°C.
2. A process for producing a directly reduced iron (DRI) or iron/steel scrap as claimed in claim 1, wherein the iron ore source material and the carbon source material is contacted with the slag for a time in the range of 5 to 30 minutes.
3. A process for producing a directly reduced iron (DRI) or iron/steel scrap as claimed in claims 1 and 2, wherein the ratio of slag and the mixture of iron oxide source material-carbon source material is in the range of 10:1 to 2:1
4. A process for producing a directly reduced iron (DRI) or iron/steel scrap as claimed in claims 1 to 3, wherein the carbon source material is selected from the group comprising coal, crushed coal, coal fines, coke, coke fines, iron and steel making sludge, petroleum coke, calcined petroleum coke , tar, charcoal and charcoal fines.
5. A process for producing a directly reduced iron (DRI) or iron/steel scrap as claimed in claims 1 to 4. wherein the ratio of iron ore and carbon source material is in the range of 5:1 to 1:1.
6. A process for producing a directly reduced iron (DRI) or iron/steel scrap as claimed in any one of the preceding claims 1 to 5, wherein iron oxide source materia! is selected from the group comprising iron ore lump and fines, mill scale, de-dusting dust produced in iron and steel making process, tailing generated during beneficiation and sinter fines.
10

7. . {A process for producing a directly reduced iron (DRI) or iron/steel scrap as claimed in
any one of the preceding claims, wherein the liquid slag is obtained from COREX, blast furnace, basic oxygen furnaces, Electric Arc Furnace (EAF), Argon Oxygen Decarburization (AOD)3 CONARC furnace, Energy Optimizing Furnace (EOF), induction furnace and any other steel making/ stainless steel making unit.
8. A process for producing a directly reduced iron (DRI) or iron/steel scrap as claimed in any one of the preceding claims, wherein mixture of iron oxide source material and carbon source material is in the form of briquettes, pellets, lumps or fines.
9. A process for producing a directly reduced iron (DRI) or iron/steel scrap substantially as herein described with reference to the foregoing examples.

$
Dated this September 12, 2008
ANAND CHOUBEY
OF K & S PARTNERS
AGENT FOR THE APPLICANT(S)
11