FORM 2
THE PATENT ACT 197 0 (39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See Section 10, and rule 13)
1. TITLE OF INVENTION
GAS BASED DIRECT REDUCTION PROCESS FOR PRODUCING SPONGE IRON
2. APPLICANT(S)
a) Name : ISPAT INDUSTRIES LIMITED
b) Nationality : INDIAN Company
c) Address : CASABLANCA, PLOT NO. 45,
SECTOR -11,
CBD BELAPUR,
NAVI MUMBAI-4 0 0 614
MAHARASHTRA, INDIA
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

Field of the Invention:
The present invention relates to process for producing direct reduced iron. More particularly it relates to gas based direct reduction process for producing sponge iron from iron oxide.
Prior Art:
Direct reduced iron (DRI) also known as sponge iron is a metallic product which is produced when iron ore is reduced in the solid state by removing oxygen as an impurity. The production of direct reduction of iron ore is carried out without reaching the melting point of the iron ore as compared to the blast furnace process where the process is completed in molten state. In the DRI processes the maximum temperature obtained is less than 1000°C, a temperature at which iron remains solid whereas in blast furnace the temperature of the liquid iron is around 1450 Deg. C.
In the process of direct reduction there is thorough mixing of screened iron ore feed (Lump or Pellet). The sensible heat of reducing gas is used for heating the ore bed to a temperature which is required for achieving the desired rate of reaction. Higher the favor the reduction reaction, however, there are other problems associated with increase in furnace bed temperature. The reductants used are Hydrogen & Carbon Mono-oxide produced by reforming reactions inside Reformer by passing Natural gas & recycled spent gas from the furnace through Nickel catalyst filled alloy reformer tube at temperature @ 1100 Deg.C . In case of gaseous reductant, natural gas suits best for the direct reduction process, other gases being used are Corex gas, coke oven gas and the gas generated by the gasification of coal or oil. However, whichever the reductant used the reduction of the iron ore takes place by means of either hydrogen or carbon mono-oxide or both.
The raw material used for sponge iron production consists a combination of lumps & pellets (generally in the ratio of 50:50 as specified by the technology supplier). The feed mix containing lumps & pellets is charged from the top of the furnace and then it

goes through a series of reduction reactions inside the furnace in different zones at different heights before being transformed into DRI (Direct Reduced Iron). The product is called Direct Reduced Iron as it is produced by direct contact of Hydrogen & Carbon mono-oxide called as reductants in the shaft Furnace. The reduction reactions occurring inside the shaft furnace in reduction zone are as mentioned below:
Fe2O3 + 3CO → 2Fe + 3CO2 Iron Oxide reduction with Carbon mono-oxide
Fe2O3 + 3H2 → 2Fe + 3H2O Iron Oxide reduction with Hydrogen
The CO & H2 are known as the reductants and CO2 & H2O are known as the oxidants. The reducing potential of reducing gas is measured by taking the ratio of percentage of reductants (Hydrogen + Carbon mono-oxide) to the percentage of oxidants (to Water + Carbon Di-oxide ) in reducing gas gas. The other reactions occurring within the furnace includes carburization reactions which are as follows:
3Fe + CH4 → Fe3C + 2H2 3Fe + 2CO → Fe3C + CO2
3Fe + CO + H2 → Fe3C + H2O
The majority of the carbon in DRI is in cementite form and some is in loose form on the surface of surface of DRI. The carbon percentage in the product is essential for the most efficient use of the DRI in Steel making and output from its conversion during melting.
The use of pellets as a raw material for production of DRI leads to increase in the manufacturing cost of iron. Also there is limitation for adequate availability of good quality pellets. On the other hand, increasing of lump ore in the raw material to reduce the overall cost of raw material leads to following problems:

a. Since lump ore contains higher fines / dust percentage than pellet ore, there
is high carryover of fines to the furnace as feed even after screenings, which
results in poor furnace bed permeability and hence increase in chances of
channeling inside the furnace.
b. The chances of cluster formation inside the furnace due to sticking of lump
ore by locking with each other due to high surface area and further
deteriorating the bed permeability.
c. Lump ore are prone to generates more fines during reduction due to thermal
degradation and lowers the bed permeability which leads to less solid to gas
contact & affects the quality.
d. There is higher percentage of classifier fines and sludge generation while
using higher percentage of lump ores which occurred as result of the natural
property of lump ore to generates more fines during reduction due to thermal
degradation during reduction.
Hence it is necessary to provide a solution to aforesaiid problem which occurs during direct iron reduction process.
Object of the Invention:
The main object of the present invention is to provide a gas based direct reduction process for producing sponge iron which will be free from aforementioned problems. More specifically it is to decrease the percentage of pellet ore and increase the percentage of lump ore to decrease the overall cost of the raw material without compromising with the quality of the product
Another object of the invention is to provide a gas based direct reduction process for producing sponge iron efficiently.
Another object of the invention is to reduce the raw material cost in direct reduction process for producing sponge iron.
Another object of the invention is to provide a gas based direct reduction process for producing sponge iron economically without compromising with quality of the final product.

Summary of the Invention:
Accordingly to achieve the aforesaid objects the present invention provides a gas based direct reduction process for producing sponge iron comprising:
Screening of lump ore & iron ore pellets.
Feeding of a mixture of the lump iron ore, iron ore pallets after the effective coating
with limestone powder from the top of a shaft furnace;
Blowing in a reducing gas from the bottom of the furnace so to produce reduced
iron;
Maintaining the temperature inside the reduction furnace just below the clustering
temperature for efficient use of reducing gas for maximum output.
characterized in that
the mixing is carried out in following proportion:
lump iron ore in 75-80 percent by weight,
iron ore pellets in 25-20 percent by weight,
Limestone powder coating @ 3.0 to 3.50 Kg/Mt of Iron ore charged
feeding rate of the iron ore for screening @ 300 TPH,
the screen size for screening is 8 x 8 mm for lump ore to remove the smaller
size materials
blowing with reduced gas at temperature between 910°c - 915°C and
Generating the reductants inside the reformer in the presence of Nickel
catalyst by adding Natural gas @ 180 NM3/Mt-185 NM3/Mt of DRI Produced.
Brief Description of the Drawings:
Fig. 1 : Shows a screen used in prior art direct iron reduction process.
Fig. 2 : Shows a screen used in direct iron reduction process in accordance to
present invention.
Fig. 3 : Shows iron lumps to be sued in direct iron reduction process in
accordance to present invention.

Fig. 4 : Shows iron pellets to be sued in direct iron reduction process in
accordance to present invention.
Fig. 5 : Shows final reduced iron cluster produced by direct iron reduction
process in accordance to present invention.
Detailed Description of the Drawings:
The features, nature, and advantages of the disclosed subject matter will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference numerals identify correspondingly throughout.
Pellet ore are costlier than lump ore which are required as raw material for the production of sponge iron. Previously they were fed in the ratio of 1:1. The invention is to decrease the percentage of pellet ore and increase the percentage of lump ore to decrease the overall cost of the raw material without compromising with the quality of the product.
The present invention provides a gas based direct reduction process for producing sponge iron. The process comprising the following steps:
a. Screening of each lump & pellets with proper size screen to minimize the fines
carryover to the furnace.
b. Feeding a mixture of the lump iron ore & iron ore pellets after coating with
limestone powder at the top of a shaft furnace.
c. Blowing with reducing gas from the bottom of the furnace so as to produce
direct reduced iron with maximum quality.

The lump iron ore is present in 75-80 percent by weight in the mixture. The iron ore pellets are present in 25-20 percent by weight. The blend of raw material is coated with 3.0 to 3.50 Kg/Mt of limestone powder. The limestone powder coating on oxide reduces the sticking problem of lump iron ores inside the furnace and hence overcome the clustering problem.
The feeding rate of each lump & pellets feeding rate for screening is 300TPH to increase the screening efficiency. The screen size is changed for present invention from 6x6 mm to 8x8 mm so that the fines percentage carryover to the furnace became less. The screen used in present invention is shown in figure 2. The mixture of the lump iron ore, iron ore pellets and oxides are fed to the shaft furnace from the top.
Thereafter the reduced gas is blown at temperature between 910°C - 915°C. This range of temperature and flow rate ensures increase in the rate of reaction of CO and H2 with Iron Oxide to produce Metallic iron.
The following examples must be taken for only illustration purpose. These examples by no way restrict the scope of invention. Other possibilities are also there apart from those mentioned in following examples.
Example 1:
lump iron ore in 80 percent by weight, iron ore pellets in 20 percent by weight
The mixture of the lump iron ore, iron ore pellets after limestone powder coating is fed to the shaft furnace from the top.
Example 2:
lump iron ore in 90 percent by weight, iron ore pellets in 10 percent by weight

The mixture of the lump iron ore, iron ore pellets after limestone powder coating is fed to the shaft furnace from the top.
Example 3:
lump iron ore in 75 percent by weight, iron ore pellets in 25 percent by weight
The mixture of the lump iron ore, iron ore pellets after limestone powder coating is fed to the shaft furnace from the top.
Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and acope of the invention as described in the following claims

WE CLAIM:
1. A gas based direct reduction process for producing sponge iron comprising:
Screening of lump iron ore and pellets with proper screen size to minimize the
fines carry over to Furnace.
Feeding a blend of lump ore & pellets after limes tone powder coating in dry
form at the top of the Furnace.
Blowing with reducing gas from the bottom of the furnace so as to produce
reduced iron;
characterized in that
the mixing is carried out in following proportion:
lump iron ore in 75-80 percent by weight,
iron ore pellets in 25-20 percent by weight,
feeding rate of the mixture to the screen for screening is 300TPH,
the screen size for screening is 8 x 8 mm;
blowing in the reduced gas at temperature between 910°C - 915°C and
Increasing the Process Natural gas consumption @ 180Nm3/min -185
Nm3/Mt
2. A gas based direct reduction process for producing sponge iron as claimed in
claim 1 wherein the mixing is carried out in following proportion:
lump iron ore in 80 percent by weight, iron ore pellets in 20 percent by weight
3. A gas based direct reduction process for producing sponge iron as claimed in
claim 1 wherein the mixing is carried out in following proportion:
lump iron ore in 90 percent by weight, iron ore pellets in 10 percent by weight

4. A gas based direct reduction process for producing sponge iron as claimed in
claim 1 wherein the mixing is carried out in following proportion:
lump iron ore in 75 percent by weight, iron ore pellets in 25 percent by weight
5. A gas based direct reduction process for producing sponge iron as claimed in claim 1 wherein the coating materials used is natural lime stone powder of certain size.
6. A gas based direct reduction process for producing sponge iron as claimed in claim 1 wherein the reducing gas is natural gas used for production of Hydrogen & Carbon mono-oxide.