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Raceway Flame Temperature With Pulverized Carbon Injection
C H A P T E R
16 Raceway Flame Temperature With Pulverized Carbon Injection O U T L I N E 16.1 Impact of Pulverized Carbon Injection on Raceway Flame Temperature
151
16.2 Matrix Setup
152
16.3 Raceway Injectant Quantity Specification
152
16.4 Raceway O2-in-Blast Air Input Specification
152
16.5 Raceway N2-in-Blast Air Input Specification
154
16.6 Raceway Carbon Balance Equation With Pulverized C Injection
154
16.7 Oxygen and Nitrogen Balances
154
16.8 Raceway Matrix Results
155
16.9 Input Enthalpy Calculation 16.9.1 Automated Input Enthalpy Calculation
155 155
16.10 Raceway Output Enthalpy
156
16.11 Raceway Flame Temperature Calculation
156
16.12 Effect of C Injection on Raceway Flame Temperature
156
16.13 Summary
157
Exercise
157
16.1 IMPACT OF PULVERIZED CARBON INJECTION ON RACEWAY FLAME TEMPERATURE
temperature (RAFT) without tuyere injectants (Fig. 14.1). This chapter calculates RAFT with tuyere injection of pulverized carbon (Fig. 16.1). The objectives of this chapter are to;
Chapter 14, Raceway Flame Temperature, and Chapter 15, Automating Matrix Calculations, calculate raceway adiabatic flame
1. show how injected pulverized carbon is included in our raceway flame temperature calculations,
Blast Furnace Ironmaking DOI: https://doi.org/10.1016/B978-0-12-814227-1.00016-6
151
© 2020 Elsevier Inc. All rights reserved.
152
16. RACEWAY FLAME TEMPERATURE WITH PULVERIZED CARBON INJECTION
3. input and output enthalpies from these input masses and their H T =MW 4. output gas (flame) temperature from the raceway’s output masses, output enthalpy, and H T =MW versus temperature equations of Table J.4. flame
The matrices and their results are shown in Table 16.1. Explanations follow.
FIGURE 16.1
Sketch of blast furnace raceway with tuyere injection of pulverized C(s). The C(s) is a simplified stand-in for pulverized coal. All the blast furnace’s blast air and injected C enter the furnace through its raceways. All the injectants are oxidized to CO(g) in the raceway. The sketch is a vertical slice through the center of a pear-shaped raceway.
16.3 RACEWAY INJECTANT QUANTITY SPECIFICATION The raceway calculation begins by specifying that the raceway injectant C input mass is 100 kg, as shown in Cell C12 of matrix Table 16.1. It is;
2. indicate how injected pulverized carbon affects raceway flame temperature, and 3. explain this effect.
mass C in tuyere 5 100 ðin this caseÞ injected carbon
or in matrix form; 100 5
16.2 MATRIX SETUP Our carbon injection raceway calculations start with the matrix of the calculated results of the bottom-segment carbon injection of Table 8.1 (Table 16.1). We then prepare a tuyere raceway calculation matrix with these results by; 1. specifying that all the matrices of tuyereinjected carbon, O2-in-blast air, and N2-inblast air, of Fig. 16.1, enter blast furnace through its raceways, and 2. developing raceway oxygen, nitrogen, and carbon balances. The matrix’s spreadsheet then calculates the raceway’s; 1. mass input C-in-falling-coke particles; 2. mass output CO(g) and N2(g);
mass C in tuyere 1 injected carbon
(16.1)
where 100 is the kg of injected pulverized carbon per 1000 kg of Fe in product molten iron. For flexibility, this injection quantity is put into Cell C38 of matrix Table 16.1 by the instruction 5 C12. This instruction causes any prescribed amount of injected carbon to be automatically updated in the raceway matrix.
16.4 RACEWAY O2-IN-BLAST AIR INPUT SPECIFICATION The bottom-segment matrix results of matrix Table 16.1 show that 310 kg of O2-in-blast air per 1000 kg of Fe in product molten iron is required for steady-state bottom-segment operation, see Cell C21. This is also the amount of O2 entering the blast furnace raceways per 1000 kg of Fe in product molten iron.
BLAST FURNACE IRONMAKING
TABLE 16.1
Bottom Segment Matrix, Raceway Matrix, and Flame Temperature Calculation With C(s) Injection
Cell E53 5 E52 Cell E52 5 C48 0 1 C43 2 F11 1 C44 2 G11 1 C45 2.488 Cell F55 5 (E53 2 C46 2 4.183 2 C47 2 0.2488)/(C46 0.001310 1 C47
0.001301)
154
16. RACEWAY FLAME TEMPERATURE WITH PULVERIZED CARBON INJECTION
Oxygen is included in the raceway matrix by the O2 specification equation;
mass O2 entering 5 310 raceway in blast air
With pulverized C injection, the raceway carbon balance equation of Chapter 14, Raceway Flame Temperature, becomes;
or in matrix terms 310 5
mass O2 entering 1 raceway in blast air
16.6 RACEWAY CARBON BALANCE EQUATION WITH PULVERIZED C INJECTION
(16.2a)
mass C in tuyere
100 mass% C
in pulverized C 100% 100 mass% C mass C entering in in pulverized C 1 100% falling coke particles
Of course, this numerical value will change with different amounts of injected C. This is automatically taken care of in Table 16.1 by inserting the instruction 5 C20
injected carbon
(16.2b)
5
into raceway matrix Cell C33.
mass CO in raceway ½42:9 mass% C in CO 100% output gas
or
16.5 RACEWAY N2-IN-BLAST AIR INPUT SPECIFICATION The bottom-segment matrix of Table 16.1 shows that 1024 kg of N2 accompany 310 kg of O2-in-blast air by Eqs. (16.2a) and (16.2b). This is also the amount of N2 entering the blast furnace raceways per 1000 kg of Fe in product molten iron. It is included in the raceway matrix by means of the specification equation;
mass C in tuyere
05
mass C in tuyere
1
mass N2 entering 1 raceway in blast air
(16.3a)
This numerical value will also change with different amounts of injected pulverized carbon. This is automatically taken care of in Table 16.1 by inserting the instruction 5 C21
into raceway matrix Cell C34.
11
mass C entering in
1
injected carbon mass CO in raceway output gas
mass C entering in falling coke particles
1
0:429 (16.4)
or in matrix terms
1 injected carbon falling coke particles mass CO in raceway 5 0:429 output gas mass C in tuyere 1 or, subtracting injected carbon ) mass C entering in from both sides: 1 falling coke particles
mass N2 entering 5 1024 raceway in blast air
1024 5
(16.3b)
where the coal and coke are (for now) specified as pure carbon. The effects of real coal and real coke are described in the later chapters.
16.7 OXYGEN AND NITROGEN BALANCES Oxygen and nitrogen balances of Chapter 14, Raceway Flame Temperature, are not altered by pulverized C injection. They are as shown in Table 16.1.
BLAST FURNACE IRONMAKING
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16.9 INPUT ENTHALPY CALCULATION
H
16.8 RACEWAY MATRIX RESULTS
25 C
CðsÞ MWC
05
The raceway matrix results are shown in Cells C45C47 of Table 16.1. The calculated masses are:
H 1200 C O2 g 1:239 5 MWO2
• 133 kg of C in falling coke particles, • 543 kg CO in departing raceway gas, and • 1024 kg N2 in departing raceway gas.
H 1200 C N2 g 1:339 5 MWN2 H 1500 C
16.9 INPUT ENTHALPY CALCULATION
2:488 5
The above-calculated 133 kg of C in falling coke particles now permits calculation of the raceway’s input enthalpy. It is: 2
raceway
3
6 7 4 input 5 1 enthalpy
5
mass C in tuyere injected carbon H
CðsÞ MWC
Eq. (16.5) can be put in final automated form by replacing;
1200 C mass O2 entering O2 g 1 MWO2 raceway in blast air
mass C entering
or
raceway
(16.5)
by F11
and H 1200 C N2 g MWN2
3 H 1500 C
6 7 1 4 raceway in falling 5 coke paricles 2
H 1200 C O2 g MWO2
H 1200 C mass N2 entering N2 g 1 MWN2 raceway in blast air 2
all MJ per kg of substance, Table J.1.
16.9.1 Automated Input Enthalpy Calculation
H 25 C
CðsÞ MWC
CðsÞ MWC
by G11
which changes Eq. (16.6a) to: 2
3
6 7 4 input 5 5 C48 0 1 C43 1:239 1 C44 1:339 enthalpy 1 C45 2:488 5 2087 MJ per 1000 kg of Fe in product
3 raceway 6 7 4 input 5 5 C48 0 1 C43 F11 1 C44 G11 enthalpy 1 C45 2:488 5 2087 MJ per 1000 kg of Fe in product molten iron (16.6b)
molten iron (16.6a)
where Cell C48 and Cells C43C45 refer to Table 16.1 and where;
This equation is now inserted into Cell E52 by the instruction: 5 C48 0 1 C43 F11 1 C44 G11 1 C45 2:488
BLAST FURNACE IRONMAKING
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16. RACEWAY FLAME TEMPERATURE WITH PULVERIZED CARBON INJECTION
(
16.10 RACEWAY OUTPUT ENTHALPY
2
Raceway output enthalpy is needed to calculate our raceway adiabatic flame temperature (RAFT). RAFT is calculated by the following equation; 2
3
2
raceway output
ðflameÞ enthalpy mass CO in raceway
2 ("
3
output gas mass N2 in raceway
mass CO in raceway
1
output gas mass N2 in raceway output gas
ð 24:813Þ )
output gas
"
Raceway Raceway 4 output 5 1 zero 5 4 input 5 enthalpy enthalpy
ð 20:2488Þ 5 Tflame ; C
# 0:001310 #
) 0:001301 (14.16)
assuming zero conductive, convective, and radiative heat loss from the raceway to its surroundings. From Section 16.9, the raceway input enthalpy is 2087 MJ so that: 3 3 2 Raceway Raceway 7 6 7 6 4 output 5 5 4 input 5 5 E52 2
enthalpy
where the numerical values are from our enthalpy versus flame temperature equations of Table J.4, that is, H
Tflame CO g 5 0:001310 Tflame 4:183 MJ per kg of CO g MWCO (14.14)
enthalpy
5 2087 MJ per 1000 kg of Fe in product molten iron: (16.7)
This equation is inserted into Cell E53 by the instruction; 5 E52
H
Tflame N2 g 5 0:001301 Tflame 0:2488 MJ per kg of N2 g MWN2 (14.15)
For the numerical example in Table 16.1, the raceway flame temperature is: Tflame 5
16.11 RACEWAY FLAME TEMPERATURE CALCULATION Our raceway flame temperature calculations use; 1. raceway CO and N2 output masses, 543 and 1024 kg (from Cells C46 and C47), and 2. raceway output enthalpy, 2087 MJ from Cell E53 of matrix Table 16.1 all per 1000 kg of Fe in product molten iron. The flame temperature equation is the same as in Section 14.11, that is;
E53 C46 ð4:183Þ 2 C47 ð0:2488Þ 5 2258 C C46 0:001310 1 C47 0:001301 (16.8a)
This is inserted into Cell F55 by the instruction: 5
E53 2 C46 2 4:183 2 C47 2 0:2488 C46 0:001310 1 C47 0:001301
(16.8b)
16.12 EFFECT OF C INJECTION ON RACEWAY FLAME TEMPERATURE Table 16.1 is now used to determine the effect of pulverized C injection on raceway flame temperature (Fig. 16.2).
BLAST FURNACE IRONMAKING
157
EXERCISE
6. calculate raceway output gas (flame) temperature, also using enthalpy versus flame temperature equations of Table J.4.
FIGURE 16.2
Effect of injected C on blast furnace raceway temperature. Raceway temperature decreases with increasing C injection. This is a consequence of all the equations of Table 16.1. We may speculate that it is mainly due to replacing hot (high enthalpy) falling C-in-coke with cool (low enthalpy) tuyere-injected pulverized carbon. A quantity of 100 kg carbon injection per 1000 kg Fe in product molten iron lowers flame temperature by B120 C. The line segments are not quite straight. This is because Eq. (16.18a) is not linear.
16.13 SUMMARY This chapter shows how to calculate raceway flame temperature with tuyere injection of pulverized carbon. The steps are to; 1. calculate the bottom-segment C-in-coke and O2-in-blast air requirements for steady-state blast furnace operation with pulverized C injection; 2. calculate the corresponding amount of N2-in-blast air; 3. preparation of a raceway matrix including pulverized carbon injection; 4. calculate the raceway’s mass input C-infalling-coke particles, mass output CO(g) and mass output N2(g); 5. calculate raceway input and output enthalpies, using the enthalpy versus temperature equations of Table J.4; and
These steps can all be automated as described in Table 16.1. Raceway flame temperature decreases with increasing C injection. This is mainly due to the replacement of hot (high enthalpy) falling C-in-coke particles with cool (low enthalpy) injected pulverized C-in-coal. As it will be shown later, this decrease in flame temperature can be offset by; 1. simultaneous injection of pure oxygen into the furnace’s blast air, and 2. higher temperature blast air.
EXERCISE 16.1. Please give your calculated masses in kg per 1000 kg of Fe in product molten iron. The blast furnace management team of Table 16.1 plans to increase its tuyereinjected pulverized carbon to 175 kg/ 1000 kg of Fe in product molten iron. They want to know how this increase will affect their raceway flame temperature. Please calculate this for them. 16.2. Please also calculate how much topcharge C-in-coke will be required with this injection of 175 kg pulverized carbon. The blast furnace engineering team of Table 16.1 believes that it shouldn’t let its raceway flame temperature fall below 2200 C. What is the maximum amount of pulverized carbon that they can inject without cooling the flame below this
BLAST FURNACE IRONMAKING
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16. RACEWAY FLAME TEMPERATURE WITH PULVERIZED CARBON INJECTION
set-point? Please use two calculation methods. Suggest several ways that pulverized carbon injection can be increased further without lowering the raceway flame temperature flame below 2200 C?
16.3. As we will see later, coal always contains Al2O3 1 SiO2 ash. So, tuyere-injected pulverized coal always brings these oxides into a blast furnace’s raceways. What effect do you think will they have on flame temperature?
BLAST FURNACE IRONMAKING
16 Raceway Flame Temperature With Pulverized Carbon Injection O U T L I N E 16.1 Impact of Pulverized Carbon Injection on Raceway Flame Temperature
151
16.2 Matrix Setup
152
16.3 Raceway Injectant Quantity Specification
152
16.4 Raceway O2-in-Blast Air Input Specification
152
16.5 Raceway N2-in-Blast Air Input Specification
154
16.6 Raceway Carbon Balance Equation With Pulverized C Injection
154
16.7 Oxygen and Nitrogen Balances
154
16.8 Raceway Matrix Results
155
16.9 Input Enthalpy Calculation 16.9.1 Automated Input Enthalpy Calculation
155 155
16.10 Raceway Output Enthalpy
156
16.11 Raceway Flame Temperature Calculation
156
16.12 Effect of C Injection on Raceway Flame Temperature
156
16.13 Summary
157
Exercise
157
16.1 IMPACT OF PULVERIZED CARBON INJECTION ON RACEWAY FLAME TEMPERATURE
temperature (RAFT) without tuyere injectants (Fig. 14.1). This chapter calculates RAFT with tuyere injection of pulverized carbon (Fig. 16.1). The objectives of this chapter are to;
Chapter 14, Raceway Flame Temperature, and Chapter 15, Automating Matrix Calculations, calculate raceway adiabatic flame
1. show how injected pulverized carbon is included in our raceway flame temperature calculations,
Blast Furnace Ironmaking DOI: https://doi.org/10.1016/B978-0-12-814227-1.00016-6
151
© 2020 Elsevier Inc. All rights reserved.
152
16. RACEWAY FLAME TEMPERATURE WITH PULVERIZED CARBON INJECTION
3. input and output enthalpies from these input masses and their H T =MW 4. output gas (flame) temperature from the raceway’s output masses, output enthalpy, and H T =MW versus temperature equations of Table J.4. flame
The matrices and their results are shown in Table 16.1. Explanations follow.
FIGURE 16.1
Sketch of blast furnace raceway with tuyere injection of pulverized C(s). The C(s) is a simplified stand-in for pulverized coal. All the blast furnace’s blast air and injected C enter the furnace through its raceways. All the injectants are oxidized to CO(g) in the raceway. The sketch is a vertical slice through the center of a pear-shaped raceway.
16.3 RACEWAY INJECTANT QUANTITY SPECIFICATION The raceway calculation begins by specifying that the raceway injectant C input mass is 100 kg, as shown in Cell C12 of matrix Table 16.1. It is;
2. indicate how injected pulverized carbon affects raceway flame temperature, and 3. explain this effect.
mass C in tuyere 5 100 ðin this caseÞ injected carbon
or in matrix form; 100 5
16.2 MATRIX SETUP Our carbon injection raceway calculations start with the matrix of the calculated results of the bottom-segment carbon injection of Table 8.1 (Table 16.1). We then prepare a tuyere raceway calculation matrix with these results by; 1. specifying that all the matrices of tuyereinjected carbon, O2-in-blast air, and N2-inblast air, of Fig. 16.1, enter blast furnace through its raceways, and 2. developing raceway oxygen, nitrogen, and carbon balances. The matrix’s spreadsheet then calculates the raceway’s; 1. mass input C-in-falling-coke particles; 2. mass output CO(g) and N2(g);
mass C in tuyere 1 injected carbon
(16.1)
where 100 is the kg of injected pulverized carbon per 1000 kg of Fe in product molten iron. For flexibility, this injection quantity is put into Cell C38 of matrix Table 16.1 by the instruction 5 C12. This instruction causes any prescribed amount of injected carbon to be automatically updated in the raceway matrix.
16.4 RACEWAY O2-IN-BLAST AIR INPUT SPECIFICATION The bottom-segment matrix results of matrix Table 16.1 show that 310 kg of O2-in-blast air per 1000 kg of Fe in product molten iron is required for steady-state bottom-segment operation, see Cell C21. This is also the amount of O2 entering the blast furnace raceways per 1000 kg of Fe in product molten iron.
BLAST FURNACE IRONMAKING
TABLE 16.1
Bottom Segment Matrix, Raceway Matrix, and Flame Temperature Calculation With C(s) Injection
Cell E53 5 E52 Cell E52 5 C48 0 1 C43 2 F11 1 C44 2 G11 1 C45 2.488 Cell F55 5 (E53 2 C46 2 4.183 2 C47 2 0.2488)/(C46 0.001310 1 C47
0.001301)
154
16. RACEWAY FLAME TEMPERATURE WITH PULVERIZED CARBON INJECTION
Oxygen is included in the raceway matrix by the O2 specification equation;
mass O2 entering 5 310 raceway in blast air
With pulverized C injection, the raceway carbon balance equation of Chapter 14, Raceway Flame Temperature, becomes;
or in matrix terms 310 5
mass O2 entering 1 raceway in blast air
16.6 RACEWAY CARBON BALANCE EQUATION WITH PULVERIZED C INJECTION
(16.2a)
mass C in tuyere
100 mass% C
in pulverized C 100% 100 mass% C mass C entering in in pulverized C 1 100% falling coke particles
Of course, this numerical value will change with different amounts of injected C. This is automatically taken care of in Table 16.1 by inserting the instruction 5 C20
injected carbon
(16.2b)
5
into raceway matrix Cell C33.
mass CO in raceway ½42:9 mass% C in CO 100% output gas
or
16.5 RACEWAY N2-IN-BLAST AIR INPUT SPECIFICATION The bottom-segment matrix of Table 16.1 shows that 1024 kg of N2 accompany 310 kg of O2-in-blast air by Eqs. (16.2a) and (16.2b). This is also the amount of N2 entering the blast furnace raceways per 1000 kg of Fe in product molten iron. It is included in the raceway matrix by means of the specification equation;
mass C in tuyere
05
mass C in tuyere
1
mass N2 entering 1 raceway in blast air
(16.3a)
This numerical value will also change with different amounts of injected pulverized carbon. This is automatically taken care of in Table 16.1 by inserting the instruction 5 C21
into raceway matrix Cell C34.
11
mass C entering in
1
injected carbon mass CO in raceway output gas
mass C entering in falling coke particles
1
0:429 (16.4)
or in matrix terms
1 injected carbon falling coke particles mass CO in raceway 5 0:429 output gas mass C in tuyere 1 or, subtracting injected carbon ) mass C entering in from both sides: 1 falling coke particles
mass N2 entering 5 1024 raceway in blast air
1024 5
(16.3b)
where the coal and coke are (for now) specified as pure carbon. The effects of real coal and real coke are described in the later chapters.
16.7 OXYGEN AND NITROGEN BALANCES Oxygen and nitrogen balances of Chapter 14, Raceway Flame Temperature, are not altered by pulverized C injection. They are as shown in Table 16.1.
BLAST FURNACE IRONMAKING
155
16.9 INPUT ENTHALPY CALCULATION
H
16.8 RACEWAY MATRIX RESULTS
25 C
CðsÞ MWC
05
The raceway matrix results are shown in Cells C45C47 of Table 16.1. The calculated masses are:
H 1200 C O2 g 1:239 5 MWO2
• 133 kg of C in falling coke particles, • 543 kg CO in departing raceway gas, and • 1024 kg N2 in departing raceway gas.
H 1200 C N2 g 1:339 5 MWN2 H 1500 C
16.9 INPUT ENTHALPY CALCULATION
2:488 5
The above-calculated 133 kg of C in falling coke particles now permits calculation of the raceway’s input enthalpy. It is: 2
raceway
3
6 7 4 input 5 1 enthalpy
5
mass C in tuyere injected carbon H
CðsÞ MWC
Eq. (16.5) can be put in final automated form by replacing;
1200 C mass O2 entering O2 g 1 MWO2 raceway in blast air
mass C entering
or
raceway
(16.5)
by F11
and H 1200 C N2 g MWN2
3 H 1500 C
6 7 1 4 raceway in falling 5 coke paricles 2
H 1200 C O2 g MWO2
H 1200 C mass N2 entering N2 g 1 MWN2 raceway in blast air 2
all MJ per kg of substance, Table J.1.
16.9.1 Automated Input Enthalpy Calculation
H 25 C
CðsÞ MWC
CðsÞ MWC
by G11
which changes Eq. (16.6a) to: 2
3
6 7 4 input 5 5 C48 0 1 C43 1:239 1 C44 1:339 enthalpy 1 C45 2:488 5 2087 MJ per 1000 kg of Fe in product
3 raceway 6 7 4 input 5 5 C48 0 1 C43 F11 1 C44 G11 enthalpy 1 C45 2:488 5 2087 MJ per 1000 kg of Fe in product molten iron (16.6b)
molten iron (16.6a)
where Cell C48 and Cells C43C45 refer to Table 16.1 and where;
This equation is now inserted into Cell E52 by the instruction: 5 C48 0 1 C43 F11 1 C44 G11 1 C45 2:488
BLAST FURNACE IRONMAKING
156
16. RACEWAY FLAME TEMPERATURE WITH PULVERIZED CARBON INJECTION
(
16.10 RACEWAY OUTPUT ENTHALPY
2
Raceway output enthalpy is needed to calculate our raceway adiabatic flame temperature (RAFT). RAFT is calculated by the following equation; 2
3
2
raceway output
ðflameÞ enthalpy mass CO in raceway
2 ("
3
output gas mass N2 in raceway
mass CO in raceway
1
output gas mass N2 in raceway output gas
ð 24:813Þ )
output gas
"
Raceway Raceway 4 output 5 1 zero 5 4 input 5 enthalpy enthalpy
ð 20:2488Þ 5 Tflame ; C
# 0:001310 #
) 0:001301 (14.16)
assuming zero conductive, convective, and radiative heat loss from the raceway to its surroundings. From Section 16.9, the raceway input enthalpy is 2087 MJ so that: 3 3 2 Raceway Raceway 7 6 7 6 4 output 5 5 4 input 5 5 E52 2
enthalpy
where the numerical values are from our enthalpy versus flame temperature equations of Table J.4, that is, H
Tflame CO g 5 0:001310 Tflame 4:183 MJ per kg of CO g MWCO (14.14)
enthalpy
5 2087 MJ per 1000 kg of Fe in product molten iron: (16.7)
This equation is inserted into Cell E53 by the instruction; 5 E52
H
Tflame N2 g 5 0:001301 Tflame 0:2488 MJ per kg of N2 g MWN2 (14.15)
For the numerical example in Table 16.1, the raceway flame temperature is: Tflame 5
16.11 RACEWAY FLAME TEMPERATURE CALCULATION Our raceway flame temperature calculations use; 1. raceway CO and N2 output masses, 543 and 1024 kg (from Cells C46 and C47), and 2. raceway output enthalpy, 2087 MJ from Cell E53 of matrix Table 16.1 all per 1000 kg of Fe in product molten iron. The flame temperature equation is the same as in Section 14.11, that is;
E53 C46 ð4:183Þ 2 C47 ð0:2488Þ 5 2258 C C46 0:001310 1 C47 0:001301 (16.8a)
This is inserted into Cell F55 by the instruction: 5
E53 2 C46 2 4:183 2 C47 2 0:2488 C46 0:001310 1 C47 0:001301
(16.8b)
16.12 EFFECT OF C INJECTION ON RACEWAY FLAME TEMPERATURE Table 16.1 is now used to determine the effect of pulverized C injection on raceway flame temperature (Fig. 16.2).
BLAST FURNACE IRONMAKING
157
EXERCISE
6. calculate raceway output gas (flame) temperature, also using enthalpy versus flame temperature equations of Table J.4.
FIGURE 16.2
Effect of injected C on blast furnace raceway temperature. Raceway temperature decreases with increasing C injection. This is a consequence of all the equations of Table 16.1. We may speculate that it is mainly due to replacing hot (high enthalpy) falling C-in-coke with cool (low enthalpy) tuyere-injected pulverized carbon. A quantity of 100 kg carbon injection per 1000 kg Fe in product molten iron lowers flame temperature by B120 C. The line segments are not quite straight. This is because Eq. (16.18a) is not linear.
16.13 SUMMARY This chapter shows how to calculate raceway flame temperature with tuyere injection of pulverized carbon. The steps are to; 1. calculate the bottom-segment C-in-coke and O2-in-blast air requirements for steady-state blast furnace operation with pulverized C injection; 2. calculate the corresponding amount of N2-in-blast air; 3. preparation of a raceway matrix including pulverized carbon injection; 4. calculate the raceway’s mass input C-infalling-coke particles, mass output CO(g) and mass output N2(g); 5. calculate raceway input and output enthalpies, using the enthalpy versus temperature equations of Table J.4; and
These steps can all be automated as described in Table 16.1. Raceway flame temperature decreases with increasing C injection. This is mainly due to the replacement of hot (high enthalpy) falling C-in-coke particles with cool (low enthalpy) injected pulverized C-in-coal. As it will be shown later, this decrease in flame temperature can be offset by; 1. simultaneous injection of pure oxygen into the furnace’s blast air, and 2. higher temperature blast air.
EXERCISE 16.1. Please give your calculated masses in kg per 1000 kg of Fe in product molten iron. The blast furnace management team of Table 16.1 plans to increase its tuyereinjected pulverized carbon to 175 kg/ 1000 kg of Fe in product molten iron. They want to know how this increase will affect their raceway flame temperature. Please calculate this for them. 16.2. Please also calculate how much topcharge C-in-coke will be required with this injection of 175 kg pulverized carbon. The blast furnace engineering team of Table 16.1 believes that it shouldn’t let its raceway flame temperature fall below 2200 C. What is the maximum amount of pulverized carbon that they can inject without cooling the flame below this
BLAST FURNACE IRONMAKING
158
16. RACEWAY FLAME TEMPERATURE WITH PULVERIZED CARBON INJECTION
set-point? Please use two calculation methods. Suggest several ways that pulverized carbon injection can be increased further without lowering the raceway flame temperature flame below 2200 C?
16.3. As we will see later, coal always contains Al2O3 1 SiO2 ash. So, tuyere-injected pulverized coal always brings these oxides into a blast furnace’s raceways. What effect do you think will they have on flame temperature?
BLAST FURNACE IRONMAKING