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
A PROCESS FOR REDUCING IRON ORE IN A BLAST FURNACE TO OBTAIN IRON BY CO-INJECTING NATURAL GAS WITH COAL AS SUPPLEMENTARY
2. APPLICANT(S)
a) Name : ISPAT INDUSTRIES LIMITED
b) Nationality : INDIAN Company
c) Address : CASABLANCA, PLOT NO. 45,
SECTOR -11,
CBD BELAPUR,
NAVI MUMBAI-400 614
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 a process for reducing iron ore in a blast furnace. More particularly it relates to a process for chemically reducing and physically converting iron oxides into liquid iron in blast furnace using natural gas as a supplementary fuel co-injected with coat for combustion.
Prior Art:
The purpose of a blast furnace is to reduce and physically convert iron oxides into liquid iron called "hot metal". The blast furnace is a huge, steel stack lined with refractory brick, where iron ore and coke are dumped into the top, and preheated air is blown into the bottom. The raw materials require 6 to 8 hours to descend to the bottom of the furnace where they become the final product of liquid slag and liquid iron. These liquid products are drained from the furnace at regular intervals, the hot air that was blown into the bottom of the furnace ascends to the top in 6 to 8 seconds after going through numerous chemical reactions.
Iron oxides can come to the blast furnace plant in the form of raw ore, pellets or sinter. The raw ore is removed from the earth and sized into pieces that range from 0.5 to 1.5 inches. This ore is either Hematite (Fe203) or Magnetite (Fe304) and the iron content ranges from 50% to 70%. This iron rich ore can be charged directly into a blast furnace without any further processing.
All of the raw materials are stored in an ore field and transferred to the stock house before charging. Once these materials are charged into the furnace top, they go through numerous chemical and physical reactions while descending to the bottom of the furnace.
The iron ore, pellets and sinter are reduced which simply means the oxygen in the iron oxides is removed by a series of chemical reactions. These reactions occur as follows:

1) 3 Fe203 + CO = C02 + 2 Fe304 Begins at 850° F
2) Fe304+ CO = C02+ 3 FeO Begins at 1100° F
3) FeO + CO = C02 + Fe or Begins at 1300° F FeO + C = CO + Fe
At the same time the iron oxides are going through these purifying reactions, they are also beginning to soften then melt and finally trickle as liquid iron through the coke to the bottom of the furnace.
The coke descends to the bottom of the furnace to the level where the preheated air or hot blast enters the blast furnace. The coke is ignited by this hot blast and immediately reacts to generate heat s follows:
C+ 02 = C02 + Heat
Since the reaction takes place in the presence of excess carbon at a high temperature the carbon iron oxide is reduced to carbon monoxide as follows:
C 02+ C = 2CO
The product of this reaction, carbon monoxide, is necessary to reduce the iron ore as seen in the previous iron oxide reactions.
The main problem associated with such iron making process is high cost as the cost of coke is very high. It ultimately affects productivity of the blast furnace.
Hence it is an urgent need to find out another fuel which can replace coke to considerable extent in iron making process.

Objects of the Invention:
The main object of the present invention is to provide an iron making process using blast furnace which overcomes all the problems associated with prior art processes.
Another object of the invention is to provide iron making process which uses another fuel along with coal to reduce the production cost by further reducing coke.
Another object of the invention is to provide iron making process which increases efficiency of the blastfurnace by improved permeability.
Another object of the invention is to provide iron making process which required lowest capital and operating cost.
Another object of the invention is to provide iron making process which simple and reliable.
Another object of the invention is to provide iron making process which reduces green house gas generation.
Summary of the Invention:
1. A process for manufacturing liquid iron (hot metal) from iron ore in a blast furnace having plurality of tuyere located in the bustle zone wherein each tuyere is provided with two lances (injector) 1, for coal and other for natural gas injection, said process comprising:
Charging iron ore and coke into the blast furnace from top of the furnace;
injecting pulverized coal into the furnace through tuyere using a first injector, the first injector being provided in a blow pipe of the furnace; and

co-injecting natural gas inside tuyeres at a predetermined distance from the tuyere nose, the natural gas is injected using a second injector, the second injector being provided in a blow pipe of the furnace;
wherein
natural gas is injected at ambient temp with 3.5 bars;
after injection with hot air at 1125°C the temperature inside the furnace raises up to 2150°C thus natural gas gets spitted and the hydrogen obtained from splitting is used as a reducing agent for obtaining liquid iron (hot metal).
Brief Description of the drawing:
Fig.1: shows a device used for injecting coal and natural gas into blast furnace.
Detailed Description of the Invention:
The present invention provides a process for reducing iron ore in a blast furnace to obtain iron. First the iron ore and coke are charged into the blast furnace from top of the furnace. The iron ore are mainly in the form of sinter, pallets or combination of the both. The pulverized coal is injected into the furnace through tuyere using a coal injection lance. The coal injection lance is provided in a blow pipe of the furnace. Then natural gas is injected inside tuyeres at a predetermined distance from the tuyere nose. The natural gas is injected using a natural gas injection lance. The natural gas injection lance is provided in a blow pipe of the furnace.
The process is carried out in following specific conditions:
i. natural gas is injected along with preheated air at a pressure higher than hot blast by 0.3 bars;

ii. after injection with hot air at 1125X this temperature of inside the furnace raised upto 2150°C; natural gas get splitted and the hydrogen obtained from splitting is used as a reducing agent for obtaining liquid iron.
According to an embodiment of the invention natural gas is injected at a pressure of 3.5 bars. The mixture of coal and natural gas meets oxygen entering through blow pipe, just before entering the tuyere's nose. In this process burning of natural gas starts before blast exits the tuyeres and hence CO and H2 are introduced at the early
stage of the process.
Theoretical background
The Natural Gas consists of almost 100% methane (CH4), the chemical reaction corresponding to natural gas combustion occurs in a single stage as shown below:
CH4+202+2[(1-w)/w]N2 = C02 + 2H20+2[(1-w)/w]N2
Where w is the relative content by (by volume) of oxygen in the blast.
Key Chemical Reactions:
The following table shows the benefit of using NG injection in the blast furnace as compared to traditional coal process.

SN Chemical Reaction Remark
1 CH4 + 4.67 106 J/kg = C + 2H2 Splitting of methane made possible by the high temperature of the blast (RAFT)
2 H2 + 3Fe203 = H20 + 2Fe304 Apart from carbon, Hydrogen from methane, also acts as a potent reducing agent as per the reactions on the left.
3 H2 + Fe304= H20 + 3FeO

4 H2 + FeO = H20 + Fe

5 H20 + C = H2 + CO Water Gas shift, to recover H2 from water (high temp reaction)
6 C02 + H2 = CO + H2O H2 produced from reaction 5 helps to recover CO from C02

The use of natural gas has invariably shown a much more extensive combustion zone than with the normal blast. The oxygen content of the blast decreases even before emerging out of the tuyere since the natural gas is introduced inside the tuyeres at some distance from the tuyere nose . The oxygen reaches as low as 3 percent within 250mm from the tuyere nose. The oxygen disappears and CO appears earlier in the case of normal blast which can be traced to the burning of methane according to,
CH4 + 1 1/2 02 = 2CO + H20
When injecting hydrogen-bearers, the depth of the combustion zone is not determined by the oxygen or C02 contents but by the reduction of water vapor by carbon,
C + H20 = CO + H2 AH (1400°C) = +3270 kcal/ kg C
The above reaction is accelerated in the presence of hydrogen.
The reduction of moisture apparently starts almost after the disappearance of C02 by carbon gasification. Hydrogen appears in considerable quantities at the outer surface of the C02 zone which suggests that the endothermic reaction occurs preferentially at the outer surface of the oxidizing zone, thus extending the zone much further (2-2.5m from the tuyere nose). The sharp cooling effect of this reaction also reduces the volume and velocity of the gas in the axial neighborhood. This, combined with an extensive penetration of the raceway towards the axis, promotes a smooth ascent of the gas and descent of the charge materials over a wide area. Any hanging or retarded movement caused by the resistance to flow of gases in this region may therefore disappear.
The gas in front of the tuyeres is much more reducing in case of natural gas injection and this has a great influence on the re-oxidation of iron and metalloids in the oxidizing zone, reduction of slag iron oxides in the central zone and the maintenance of hearth temperatures. Although the above reaction is highly endothermic, the

temperature level even deep in the central zone is sufficiently high to keep the smelting products in a molten state and for the normal occurrence of metallurgical processes.
The injection process of coal and natural gas is carried out by a device as shown in figure 1. Referring to Fig. 1, the device consists of separate injection lances for coal and natural gas.

Validation of the improvements using NG co-injection with Coal
Hypothesis test and graphs has been used as tools to carry out the validation of before and after scenarios for the parameters given in above point no-6.
1) Improvement in BF gas CV value

The above graph shows that the BF gas CV value has significantly increased with usage of NG co-injection with Coal. The same has been statistically validated using Hypothesis test. The 0.00 p-value (for alpha= 0.05) indicates that there is significant difference in CV of BF gas after using NG.
One-way ANOVA: BF Gas CV versus condition
Source DF SS MS F P
condition 1 18934 18934 27.64 0.000 Error 14 9589 685 Total 15 28523
S = 26.17 R-Sq = 66.38% R-Sq(adj) = 63.98%
Individual 95% CIs For Mean Based on
Pooled StDev
Level N Mean StDev
Coal with NG 8 925.55 11.68
With Coal 8 856.75 35.12
840 870 900 930

2) Improvement in Hot metal product quality; Sulphur and Silicon %

The above graph shows that the Silicon % in hot metal has significantly reduced with usage of NG co-injection with Coal. The same has been statistically validated using Hypothesis test. The 0.00 p-value (for alpha= 0.05) indicates that there is significant difference in Silicon % in hot metal after using NG. Reduction in S% is desirable in hot metal product.
One-way ANOVA: Si versus condition



The above graph shows that the Sulphur % in hot metal has significantly reduced with usage of NG co-injection with Coal. The same has been statistically validated using Hypothesis test. The 0.001 p-value (for alpha= 0.05) indicates that there is significant difference in Sulphur % in hot metal after using NG. Reduction in S% is desirable in hot metal product.
One-way ANOVA: S versus condition
Source DF SS MS F P
condition 1 0.0009923 0.0009923 17.09 0.001
Error 14 0.0008127 0.0000581
Total 15 0.0018050
S = 0.007619 R-Sq = 54.97% R-Sq(adj) = 51.76%
Level N Mean StDev
Coal with NG 8 0.036875 0.008043
Coal without NG 8 0.052625 0.007170
Individual 95% CIs For Mean Based on Pooled StDev Level
Coal with NG
Coal without NG
0.0350 0.0420 0.0490 0.0560

WE CLAIM:
1. A process for manufacturing liquid iron (hot metal) from iron ore in a blast
furnace having plurality of tuyere located in the bustle zone wherein each
tuyere is provided with two lances (injector), one for coal and other for natural
gas injection. The said process comprises of
Charging iron ore and coke into the blast furnace from top of the furnace;
Injecting pulverized coal into the furnace through tuyere using a first injector,
the first injector being provided in a blow pipe of tuyere stock assembly in the
furnace; and
Co-injecting natural gas inside tuyeres at a predetermined distance from the
tuyere nose, the natural gas is injected using the second injector, the second
injector being provided in a blow pipe of tuyere stock assembly in the furnace
Wherein
Natural gas is injected at ambient temp with 3.5 bars pressure
after injection with hot air at 1125°C the temperature inside the furnace raises
up to 2150°C thus natural gas gets spitted and the hydrogen obtained from splitting is works as a reducing agent for obtaining liquid iron (hot metal) form
iron ore.
2. The process for reducing iron ore in a blast furnace to obtain iron as claimed in claim 1 wherein natural gas is injected at a pressure of 3.5 bars.
3. The process for reducing iron ore in a blast furnace to obtain iron as claimed in claim 1 wherein the mixture of coal and oxygen injected through one lance and natural gas injected through other lances.
4. The process for reducing iron ore in a blast furnace to obtain iron as claimed in claim 1 wherein burning of natural gas starts before blast exits the tuyeres and hence CO and H2are introduced at the early stage of the process.

5. The process for reducing iron ore in a blast furnace to obtain iron as claimed in claim 1 where in iron ore is in the form of sinter and ore / pallets.
6. NG co-injection with coal has resulted in the following benefits to the BF

> Increased calorific value of BF gas.
> Improving hot metal product quality.
> Improved furnace permeability.
> Reduction in stove heating cycle time thereby increasing hot blast temp which further reduces the fuel rate of the furnace.
> Improving combustion efficiency of coal being injected with NG.