Claims:We Claim:

1. A system for pellet induration using 100% Coke Oven Gas(COG) comprising

indurating furnace having a plurality of dual fired burners having selective nozzle opening installed therein to carry out firing of green iron ore pellets carried on pellet cars to produce full fired pellets of desired quality parameters;

fuel gas circuit comprising modified pipe line comprising interconnection of mixed gas header and Natural Gas header by two parallel pipes with flow control means for supplying COG to said burners through natural gas header;

booster compressor to supply COG at desired pressure and flow rate to ensure sufficient gas flow to achieve firing zone temperature set point of 1330 deg C;

combustion air blowers to supply combustion air at desired pressure at burner tip to generate required burner flame length with firing temperature of 1330 deg C.

2. A system as claimed in claim 1 wherein said indurating furnace comprising 34 number of dual fired burners in firing zone each havingnozzle diameter in the range of 27 to 31 mm preferable 31mm.

3. A system as claimed in anyone of claim 1 or 2 wherein said fuel gas circuit comprising said interconnecting pipes are DN300 pipes connecting between DN 1200 mixed gas header and DN 800 natural gas header and are provided with NRV valve, vent valve and stop valves for flow control.

4. A system as claimed in anyone of claim 1 to 3 wherein said booster compressor supply COG at a discharge pressure of 0.9 bar for introducing into natural gas header through the modified pipe line.

5. A system as claimed in anyone of claim 1 to 4 wherein said combustion air blower involves more than one blower to increase combustion air pressure at burner tip from 400 mm WC to 800 mm WC for desired increase in burner flame length to attain firing temperature of 1330 deg C.

6. A process for pellet making involving pellet induration using 100% Coke Oven Gas(COG) involving the system as claimed in claims 1 to 5 comprising
(i) Providing green pellets on pellet cars for firing of pellets in indurating furnace;
(ii) Supplying 100% COG through natural gas header of modified fuel gas circuit at desired flow rate and pressure by booster compressor;
(iii) Supplying combustion air at desired flow rate and pressure by air combustion blower;
(iv) Firing said fuel and air mixture through said dual fired burners disposed inside indurating furnace to generate desired flame length to achieve desired firing temperature of 1330C in combustion zone to produce fully fired pellet of desired quality.
7. A process as claimed in claim 6 wherein the flowrate of COG is at arate of 9000 to 16000 m3/hr preferably 16000 m3/hr and the supply pressure is 0.6 to 0.9 preferably 0.9 bar.

8. A process as claimed in anyone of claims 6 or 7 wherein flow rate of combustion air is 25000 to 35000 m3/hrprefereably35000 m3/hr and the supply pressure at burner tip is 400 to 800 mm WC preferably 800 mm WC.

9. A process as claimed in anyone of claims 6 to 8 capable of producing fired pellets at production rate of 7000 to 8600 preferably 8600MT/day.

10. A process as claimed in anyone of claims 6 to 9 adapted to produce full fired pellets with quality parameters comprising CCS 280 to 315 kg/pellet, TI 94.5 to 96.2%, AI 3 to 4.5%, Porosity 22 to 24.5% etc.

Dated this the 2nd day of January, 2017
Anjan Sen
Anjan Sen & Associates
(Applicants Agent)

, Description:FIELD OF THE INVENTION
The present invention relates to a system for operating pellet plant with 100% Coke Oven Gas(COG) and a method of such operation. More particularly, the present invention is directed to a system for using 100% Coke Oven Gas for pellet induration eliminating the dependency on blast furnace gas or mixed gas used conventionally, with increased COG flow rate and supply pressure along with increased combustion air pressure at burner tip from 400 mm WC to 800 mm WC involving additional combustion air blower as well as COG supplied through modified gas supply line having interconnected mixed gas header of 1200 mm dia and 800 mm dia Natural Gas header with booster compressor discharge pressure at 0.9 barand increased burner nozzle diameter so as to supply sufficient gas flow to achieve firing zone temperature set point of 1330°C, resulting in fully fired pellet with excellent pellet quality parameter.

BACKGROUND OF THE INVENTION

4 million MT Iron Ore Pelletizing Plant of Amba River Coke Limited (ARCL), a 100% subsidiary of the applicants (JSW Steel Limited), producing Iron oxide pellets for in-house consumption by Sponge Iron Plant and Blast Furnace. Iron ore fines of 100% less than 10 mm size is ground to -45 micron size in wet grinding ball mills. Subsequent process of dewatering at thickener and pressure filter will produce iron ore concentrate, to which, ground additives like limestone, coke breeze, bentonite is added and fed into pelletizing discs to produce green pellets. Green Pellets of 8 to 18 mm are screened and fired in the Indurating Furnace of 116 mtr length, at 1330 deg C temperature to produce fired pellets. 34 Nos Dual fired burners are installed in indurating furnace for this purpose.Fired pellets having cold crushing strength(CCS) of minimum 250 kg/pellet and tumble index more than 94% are dispatched downstream to in-house consumer Sponge Iron Plant and Blast Furnace Plant.

Dual fired burners in Indurating machine uses either Natural Gas or Mixed gas (Combination of Blast Furnace Gas (BF Gas) + Coke Oven Gas (COG) in 2.8:1 ratio by volume). BF gas at suction pressure of 1000 mmWC is mixed with Coke Oven Gas of 1440 mmWC in suction header of 2 Nos. booster compressors. Booster compressor discharge pressure is set at 0.6 bar. Mixed gas at 0.6 bar is supplied to burners, combustion air is introduced into burner at 400 mmWC for optimum firing. Mixed gas is fired in 34 Nos. of burners to achieve firing temperature set point of 1340 deg C.

LIMITATIONS OF EXISTING PROCESS:

1. Pellet plant of ARCL operates with 100% mixed gas as fuel in the Indurating Furnace. Thus, prior to the implementation of this invention, operation of pellet plant was 100% dependent on availability of Blast Furnace Gas.

2. In the event of non-availability of BF gas, pellet plant would have shutdown, resulting of flaring (wastage) of Coke Oven Gas which is a useful energy resource.

Applicants’ existing Pellet Plant used to operate with 100% mixed gas and was totally dependent on availability of Blast Furnace Gas. Any interruption in supply of blast furnace gas used to result in stoppage of pellet plant. Such a situation occurred in the past during planned Blast Furnace Plant shutdown for renovation work for 2 months, during which, it was decided to cutoff supply of BF gas to pellet plant.
There has been thus a continuing need in the existing pellet plant to develop a system and method to avoid exclusive reliance on BF gas and provide alternative less costly fuel gas based process for pellet induration which would be operative even when BF gas is not available. Accordingly, to keep pellet plant in running condition and to utilize the Coke Oven Gas (which otherwise would have been flared), applicants explored an innovative thought process to operate the indurating furnace with 100% Coke Oven gas for the first time. Thus an implementation plan was finalized and modifications carried out, to develop a facility to utilize 100% COG for pellet induration.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to provide a system for operating pellet plant involving pellet induration with 100% Coke Oven Gas(COG) and a method of such operation.

A further object of the present invention is directed to provide a system and method for operating pellet plant and particularly pellet induration with 100% COG whereby there would not be any dependence on availability of blast furnace gas and pellet induaration would continue even when Blast Furnace undergoes shutdown and maintenance for long period to enable protecting production and business continuation.

A still further object of the present invention is directed to provide a system and method for operating pellet plant with 100% COG which would need minor less expensive modifications of existing plant/facilities to allow use of 100% COG for pellet induration which is totally developed and implemented inhouse.

A still further object of the present invention is directed to provide a system and method for operating pellet plant with 100% COG which would avoid flaring (wastage) of useful energy resource like Coke Oven Gas and thus ensuring conservation of energy resources.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a system for pellet induration using 100% Coke Oven Gas(COG) comprising

indurating furnace having a plurality of dual fired burners having selective nozzle opening installed therein to carry out firing of green iron ore pellets carried on pellet cars to produce full fired pellets of desired quality parameters;

fuel gas circuit comprising modified pipe line comprising interconnection of mixed gas header and Natural Gas header by two parallel pipes with flow control means for supplying COG to said burners through natural gas header;

booster compressor to supply COG at desired pressure and flow rate to ensure sufficient gas flow to achieve firing zone temperature set point of 1330 deg C;

combustion air blowers to supply combustion air at desired pressure at burner tip to generate required burner flame length with firing temperature of 1330 deg C.

A further aspect of the present invention is directed to said system wherein said indurating furnace comprising 34 number of dual fired burners in firing zone each having nozzle diameter in the range of 27 to 31 mm preferable 31mm.

A still further aspect of the present invention is directed to a system wherein said fuel gas circuit comprising said interconnecting pipes are DN300 pipes connecting between DN 1200 mixed gas header and DN 800 natural gas header and are provided with NRV valve, vent valve and stop valves for flow control.

A still further aspect of the present invention is directed to a system wherein said booster compressor supply COG at a discharge pressure of 0.9 bar for introducing into natural gas header through the modified pipe line.

Another aspect of the present invention is directed to a system wherein said combustion air blower involves more than one blower to increase combustion air pressure at burner tip from 400 mm WC to 800 mm WC for desired increase in burner flame length to attain firing temperature of 1330 deg C.

Yet another aspect of the present invention is directed to a process for pellet making involving pellet induration using 100% Coke Oven Gas(COG) involving the system comprising
(i) Providing green pellets on pellet cars for firing of pellets in indurating furnace;
(ii) Supplying 100% COG through natural gas header of modified fuel gas circuit at desired flow rate and pressure by booster compressor;
(iii) Supplying combustion air at desired flow rate and pressure by air combustion blower;
(iv) Firing said fuel and air mixture through said dual fired burners disposed inside indurating furnace to generate desired flame length to achieve desired firing temperature of 1330°C in combustion zone to produce fully fired pellet of desired quality.

A further aspect of the present invention is directed to a process wherein the flowrate of COG is at arate of 9000 m3/hr to 16000 m3/hr preferably 16000 m3/hr and the supply pressure is 0.6 bar to 0.9 bar preferably 0.9 bar.

A still further aspect of the present invention is directed to aprocess wherein flow rate of combustion air is 25000 m3/hr 35000 m3/hrpreferably 35000m3/hr and the supply pressure at burner tip is400 mm WC to 800 mm WCpreferably 800 mm WC.

A still further aspect of the present invention is directed to aprocess capable of producing fired pellets at production rate of 7000 to 8600 MT/day preferably 8600 MT/day.

An yet further aspect of the present invention is directed to said process adapted to produce full fired pellets with quality parameters comprising CCS 280 to 315 kg/pellet, Ti 94.5 to 96.2%, AI 3 to 4.5%, Porosity 22 to 24.5% etc.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to the following non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 : shows the process flow sheet for wet grinding & filtration unit of pellet plant.

Figure 2:Process Flow Sheet for Pelletization Unit.

Figure 3: shows the schematic view of modifications carried out in fuel gas circuit of pellet plant.

Figure 4: shows the schematic view of modifications carried out in burner nozzle.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS

The present invention is directed to provide a system and method for operating pellet plant involving pellet induration with 100% Coke Oven Gas(COG) avoiding dependence on BF gas.

In conventional pellet making process, ground iron ore fines are processed through dewatering at thickener and pressure filter to produce iron ore concentrate, to which, ground additives like limestone, coke breeze, bentonite is added and fed into pelletizing discs to produce green pellets. Green Pellets of 8 to 18 mm are screened and fired in the Indurating Furnace of 116 mtr length, at 1330 deg C temperature to produce fired pellets. 34Nos. Dual fired burners are installed in indurating furnace for this purpose.

Accompanying Figure 1 shows the process flow sheet for wet grinding and filtration unit of pellet plant and Figure 2 shows process Flow Sheet for Pelletization Unit.

As already explained that the existing pellet induration process carried out in applicants’ pellet plant made use of Mixed gas either Natural Gas or Mixed gas (Combination of Blast Furnace Gas (BF Gas) + Coke Oven Gas (COG) in 2.8:1 ratio by volume) through dual fired burners. BF gas at suction pressure of 1000 mmWC is mixed with Coke Oven Gas of 1440 mmWC in suction header of 2 Nos. booster compressors. Booster compressor discharge pressure is set at 0.6 bar. Mixed gas at 0.6 bar is supplied to burners, combustion air is introduced into burner at 400 mmWC for optimum firing. Mixed gas is fired in 34 Nos. of burners to achieve firing temperature set point of 1340 deg C.

Following table I gives the composition of BF gas, Coke Oven Gas, Natural Gas and Mixed Gas for which the dual fired burners of pellet plant are designed.

Table I:
COMPOSITION % BY VOLUME
BLAST FURNACE GAS COKE OVEN GAS NATURAL GAS MIXED GAS
H2 4.5 56 21
N2
Balance 9 0.32 35
CH4 (Methane)
0.14 to 0.16 25 93.26 8.6
CO 24 8 19
CO2 21 2.2 0.13 15
O2 0.6 0.5
Ethane 4.85
CmHn 2
Net Calorific Value (kcal/Nm3) 850 4200 8630 1850

Following table II & III illustrates the design parameters of Mixed Gas & Natural Gas burners is as mentioned below:

Table II: DESIGN PARAMETERS OF MIXED GAS BURNERS

FURNACE CONNECTED THERMAL LOAD 307 Mbtu/hr 77 Mkcal/hr
TOTAL MIXED GAS FLOW (Nm3/Hr) 42700
TOTAL NUMBER OF MIXED GAS BURNERS 34 Nos.
MIXED GAS (BFG+COG) PRESSURE AT BURNER TIP 0.6 bar (NOMINAL) 1 bar (DESIGN)
CALORIFIC VALUE OF MIXED GAS 1850 Kcal/m3
COMBUSTION AIR BLOWER: 132 kW 1490 RPM
COMBUSTION AIR FLOW (DESIGN) 28800 m3/hr
COMBUSTION AIR PRESSURE AT BURNER TIP 400 mmWC

Table III: DESIGN PARAMETERS OF NATURAL GAS BURNERS:

FURNACE CONNECTED THERMAL LOAD 307 Mbtu/hr 77 Mkcal/hr
TOTAL NATURAL GAS FLOW (Nm3/Hr) 9468
TOTAL NUMBER OF NATURAL GAS BURNERS 34 Nos.
NATURAL GAS PRESSURE AT BURNER TIP 0.8 bar (NOMINAL) 1 bar (DESIGN)
CALORIFIC VALUE OF NATURAL GAS 8500 Kcal/m3
COMBUSTION AIR BLOWER: 132 kW 1490 RPM
COMBUSTION AIR FLOW (DESIGN) 28800 m3/hr
COMBUSTION AIR PRESSURE AT BURNER TIP 600 mmWC

Since the Mixed gas comprising Combination of Blast Furnace Gas (BF Gas) + Coke Oven Gas (COG) in 2.8:1 ratio by volume has a calorific value of 1850kCal/Nm3 and COG has a calorific value of 4200kcal/Nm3, which is more than Mixed gas but much less than Natural Gas(8630kCal/Nm3), several trials have been made to modify the existing system to ascertain the required flow rate and pressure of gas and combustion air directed to use 100% COG to generate appropriate flame at the combustion zone to attain the required firing temperature set point of 1330degree C. Accordingly, following step wise modifications have been implemented.

To ensure capability of using 100% COG for pellet induration in the existing pellet plant set up, following step by step implementation of modifications were carried out:

Step 1:
Directly introducing 100% COG into mixed gas line (1200 mm dia) at 0.6 bar pressure:

Coke Oven Gas was introduced directly into mixed gas burners. Attempt failed due to uncontrolled rise in firing zone temp, resulting in pellet cluster formation at firing zone, as Calorific Value of Coke oven gas in higher than Mixed gas. This has led to uncontrolled temperature rise in firing zone.

Step 2:
Introduce 100% COG into Natural Gas line (800 mm dia) at 0.6 bar pressure:

From step 1, it was evident that, operating pellet plant with 100% Coke Oven Gas is possible only by using natural gas line and natural gas burners. Hence, modifications were carried out in the next stepto interconnect mixed gas header of 1200 mm dia to 800 mm Natural Gas header by parallel interconnecting DN 300 pipes with NRVs, vent valves and stop valves. This modification in fuel gas circuit is as illustrated in accompanying Figure 3.

With this modification, 100% Coke Oven Gas is introduced into natural gas header at booster compressor discharge pressure of 0.6 bar.Attempt Failed due to restricted COG flow as firing zone temperature too low (1200 deg C), as low CV gas is introduced in Natural gas line. Natural Gas(NG) header being of smaller size, was not able to supply sufficient gas flow to achieve firing zone temperature set point of 1330 deg C.

Based on the above observation, it was decided to carry out the following plan of action to increase the Coke Oven Gas flow through NG header and achieve firing zone temperature of 1330 deg C:
a) Introducing Coke Oven Gas in NG header at higher pressure by increasing booster compressor discharge pressure from 0.6 bar to design pressure of 0.9 bar.
b) Increasing burner nozzle tip diameter from existing 27 mm to 31 mm.
Accordingly following modifications were made in next steps.

Step 3:
Follow fuel gas parameters as in STEP 2, but with increased booster compressor discharge pressure (0.9 bar):

Booster compressor discharge pressure was increased from 0.6 bar to 0.9 bar and introduced into natural gas header through the modified pipe line. With this, it was possible to achieve firing zone temp. of 1280 deg C against set point of 1330 deg C. Since the actual temperature is less than the optimum indurating temperature of 1330 deg C, unfired pellets reported at pellet car bottom bed and sides, which was not acceptable. Hence this attempt did not succeed to yield desired results in respect of pellet quality parameters.

Step 4:
Modifying Natural Gas Burner Nozzle Diameter (20.10.2015 TO 23.10.2015):

It was then decided to increase the COG flow rate further by increasing the firing zone burnernozzle diameter from 27 mm to 31 mm in steps involving a total of 18 burners out of 34 Nos. The burner nozzle modification has been illustrated in accompanying Figure 4 which show an increase of burner tip diameter from existing 27mm to 31mm. With this modification, even though optimum indurating temperature set point of 1330 deg C was achieved, side layer pellets were still unfired due to shorter burner flame length. Hence thought process was initiated towards increasing the flame length of the burner in next step.

Step 5:
Increase burner flame length by increasing combustion air pressure at burner tip:

A second combustion air blower also started and increased combustion air pressure at burner tip from 400 mm WC to 800 mm WC. This resulted in increase in burner flame length, with firing temperature of 1330 deg C. Indurating machine output was fully fired pellet with best quality.

Thus with all the stated innovative work undertaken in steps, it was possible to consistently operate pellet plant with 100% Coke Oven Gas for the first time, achieving excellent pellet quality parameter.
Pellet quality parameters prior to modification and post modification are as presented in following Tables IV & V.

Table IV

PELLET QUALITY PARAMETERS OPERATING WITH 100% MIXED GAS
Day Day Production (CaO+MgO)/ (Al2O3+SiO2) CCS
Kg/Pellet %T.I. %A.I. Feed mix ratio % Flux + Coke Addition Ratio Lime + Coke Addition (%) Bentonite Addition (%) ESP DUST (%) Porosity %

Norms MT > 220 > 94 < 5 22-28
1 10383 0.36 293 94.16 4.60 NMDC 80 +South Africa 20 2:1 2.73 0.50 - 20.13
2 10055 0.36 291 94.36 4.80 NMDC 80 +South Africa 20 2:1 2.60 0.47 - 20.95
3 10075 0.34 296 94.48 4.42 NMDC 80 +South Africa 20 2:1 2.60 0.49 - 21.80
4 4007 0.37 293 94.67 4.33 NMDC 80 +South Africa 20 2:1 2.60 0.55 - -
5 8168 0.35 303 94.16 4.84 NMDC 80 +South Africa 20 2:1 2.60 0.48 - 21.63
6 10000 0.29 309 94.13 4.80 NMDC 70 +South Africa 30 2:1 2.60 0.50 - 21.28
7 10075 0.34 305 94.66 4.34 NMDC 70 +South Africa 30 2:1 2.63 0.45 - 20.43
8 5893 0.33 297 95.13 3.80 NMDC 70 +South Africa 30 2:1 2.60 0.45 - 20.59
9 8320 0.34 306 95.06 3.76 NMDC 70 +South Africa 30 2:1 2.43 0.45 - 19.37
10 8136 0.33 332 95.59 3.49 NMDC 70 +South Africa 30 2:1 2.37 0.46 - 18.74
11 10084 0.29 292 94.64 4.31 NMDC 100 2:1 2.53 0.50 0.50 19.88
12 7823 0.29 294 93.66 5.28 NMDC 100 2:1 2.60 0.57 0.50 23.26
13 9929 0.29 287 93.54 5.38 NMDC 100 2:1 2.60 0.71 0.50 23.54
14 10140 0.33 291 93.71 5.27 NMDC 100 2:1 2.60 0.72 0.50 23.69
15 8933 0.36 290 94.40 4.47 NMDC 100 2:1 2.70 0.72 0.43 24.10
16 10196 0.34 297 94.36 4.62 NMDC 100 2:1 2.70 0.70 0.30 24.83
17 10829 0.28 285 93.48 5.36 NMDC 100 2:1 2.70 0.61 - -
18 10282 0.30 287 94.27 4.78 NMDC 100 2:1 2.73 0.67 0.40 23.94
19 10175 0.30 296 93.98 5.03 NMDC 100 2:1 2.80 0.72 0.40 25.23
20 10138 0.29 291 93.99 4.96 NMDC 100 2:1 2.80 0.72 0.42 24.98
21 10111 0.30 297 93.80 5.20 NMDC 100 2:1 2.80 0.74 0.48 24.33
22 10201 0.28 292 94.00 5.02 NMDC 100 2:1 2.80 0.75 0.50 24.36
23 10201 0.33 295 94.20 4.96 NMDC 100 2:1 2.80 0.78 0.50 25.69
24 10260 0.32 292 93.57 5.37 NMDC 100 2:1 2.73 0.81 0.70 26.15
25 9619 0.38 312 94.20 4.84 NMDC 100 2:1 2.77 0.81 0.65 24.82
26 8534 0.36 303 94.29 4.64 NMDC 100 2:1 2.77 0.80 0.50 25.10
27 9053 0.34 305 94.62 4.42 NMDC 100 2:1 2.70 0.82 0.60 24.93
28 3588 0.37 294 94.80 4.33 NMDC 100 2:1 2.70 0.80 0.57 24.83
29 PLANT SHUTDOWN
30 PLANT SHUTDOWN

Table V
PELLET QUALITY PARAMETERS OPERATING WITH 100% COKE OVEN GAS
Day Day Production (CaO+MgO)/ (Al2O3+SiO2) CCS
Kg/Pellet %T.I. %A.I. Feed mix ratio % Flux + Coke Addition Ratio Lime + Coke Addition (%) Bentonite Addition (%) ESP DUST (%) Porosity %

Norms MT > 220 > 94 < 5 22-28
1 8187 0.39 300 94.56 4.58 NMDC 100 2:1 2.78 0.80 0.75 24.53
2 7406 0.42 301 91.80 7.19 NMDC 100 2:1 2.87 0.80 - 23.72
3 7228 0.36 310 92.67 6.33 NMDC 100 2:1 2.77 0.80 - 24.16
4 6993 0.41 296 93.07 6.07 NMDC 100 2:1 2.93 0.80 0.50 24.85
4 7970 0.40 289 92.68 6.27 NMDC 100 2:1 3.10 0.78 0.50 24.79
5 7437 0.36 282 93.21 5.75 NMDC 100 2:1 3.30 0.85 23.58
6 7605 0.41 287 95.04 4.27 NMDC 100 2:1 3.30 0.58 23.02
7 8000 0.42 310 95.19 4.13 NMDC 100 2:1 3.30 0.58 22.67
8 7503 0.36 283 94.19 4.89 NMDC 100 2:1 3.30 0.62 0.53 24.51
9 7850 0.39 284 94.28 4.90 NMDC 100 2:1 3.23 0.67 0.43 23.80
10 7549 0.32 297 94.36 4.78 NMDC 85 + S.A. 15 2:1 3.20 0.70 0.35 23.29
11 7113 0.32 299 95.02 4.13 NMDC 85 + S.A. 15 2:1 3.30 0.70 0.35 22.25
12 6038 0.36 284 95.65 3.52 NMDC 85 + S.A. 15 2:1 3.30 0.64 0.35 22.84
13 7520 0.34 292 95.53 3.69 NMDC 85 + S.A. 15 2:1 3.30 0.50 0.40 23.35
14 7187 0.33 294 95.34 3.77 NMDC 85 + S.A. 15 2:1 3.30 0.52 - 22.45
15 7501 0.45 302 95.89 3.31 NMDC 100 2:1 3.30 0.47 - 24.28

It is observed from above data that the fired pellet produced using 100% COG having cold crushing strength (CCS) of more than 220 kg/pellet and tumble index more than 94% are consistently produced meeting the requirement of Sponge Iron Plant and Blast Furnace Plant. Also the attributes like % A.I. and Porosity is within acceptable range.

It was also observed that the average specific heat consumption with 100% COG operation for average production rate of 7500MT/day is oof the order of about 2,50,000kCal/MT, as compared to Mixed gas based pellet making operation having average specific heat consumption of 2,08,000 for a production rate of 9000-10,000MT per day. Also the coke breeze consumption is of the order of 9.5kg/Ton for Mixed Gas and 10.5kg/MT for the respective production rates. With increase in pellet production rate to 9500 MT/ day, both specific coke consumption and specific heat consumption are expected to be within normal range of 9.5 kg/MT & 2,10,000 kCal/MT.

It was further observed that by utilizing 100% COG for pellet induration, apart from totally avoiding wastage of useful energy resources (flaring of Coke Oven Gas), following monetary benefit have been achieved:

Business continuation ensured continuity of pellet plant operation at 8000 TPD. Assuming profit of Rs.1500 per MT of pellet, daily profit by operating pellet plant with 100% COG is:
8000 TPD X Rs.1500/MT = Rs.12 million per day.

It is thus possible by way of the present invention to provide a system and method for using 100% Coke Oven Gas for pellet induration eliminating the dependency on blast furnace gas or mixed gas used in existing process, with increased COG flow rate and supply pressure alongwith increased combustion air pressure at burner tip from 400 mm WC to 800 mm WC involving additional combustion air blower and COG supplied through interconnected gas circuit and increased burner nozzle opening diameter so as to supply sufficient gas flow to achieve firing zone temperature set point of 1330°C, resulting in fully fired pellet with excellent pellet quality parameter.