- Email: [email protected]
Top-Segment Calculations With Multiple Injectants
C H A P T E R
40 Top-Segment Calculations With Multiple Injectants O U T L I N E 40.1 Understanding the Top Segment With Multiple Injectants
355
40.2 Top-Segment Equations With Gangue, Ash, Fluxes, and Slag Plus Injection of Coal, Oxygen, H2O(g), and Natural Gas
356
40.3 Top-Segment Input Enthalpy
362
40.4 Top-Segment Output Enthalpy
362
40.5 Top Gas Enthalpy
362
40.6 Top Gas Temperature
363
In this chapter, we calculate top gas composition, enthalpy, and temperature with tuyere injection of;
Blast Furnace Ironmaking DOI: https://doi.org/10.1016/B978-0-12-814227-1.00040-3
364
40.8 List of Top-Segment Equations of Table 40.2
364
40.9 Matching the model to Commercial Blast Furnace Data
366
40.10 Summary
367
Exercises
368
Reference
368
• H2O(g)-in-blast (from humid air and injected steam), and • natural gas.
40.1 UNDERSTANDING THE TOP SEGMENT WITH MULTIPLE INJECTANTS
• pulverized coal, • pure oxygen,
40.7 Results
It is important to understand how top gas temperature is affected by these injectants. Top gas must be warm enough to; 1. efficiently evaporate the top charge’s moisture content so that iron ore reduction begins quickly,
355
© 2020 Elsevier Inc. All rights reserved.
356
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
FIGURE 40.1 Conceptual bottom segment of blast furnace with moist blast air, injection of oxygen into the blast, and injection of pulverized coal and natural gas into the furnace. The flows descending from the top segment and ascending into the top segment are notable. Fig. 40.2 shows the equivalent conceptual top segment with its topcharged inputs and the same cross-segment flows.
2. avoid unwanted condensation of moisture in the charge that can move down the furnace walls and damage hearth refractory, and 3. purge undesirable minor elements, especially zinc in the burden materials but not so warm as to; 4. increase the fuel rate due to excessive energy lost to the top gas and 5. damage the top-charging equipment 110 C140 C appears to be the optimum range. The objectives of this chapter are to; 1. build a top-segment matrix based on bottom-segment cross-division flows of Chapter 38, Bottom-Segment Calculations with Multiple Injectants (Fig. 40.1), and top charged inputs of Fig. 40.2; 2. use the matrix to calculate top gas composition of Fig. 40.2; 3. develop equations to calculate top-segment input enthalpy, top-segment output enthalpy, and top gas enthalpy of Fig. 40.2; and; 4. develop an equation that calculates top gas temperature of Fig. 40.2 from (1)’s top gas composition and (3)’s top gas enthalpy.
FIGURE 40.2 Conceptual blast furnace top segment and the flows between it and the bottom segment, Fig. 40.1.
These steps finish the development of our blast furnace model. When connected to the automatic flame temperature calculation and automatic inclusion of blast temperature of Chapter 39, Raceway Flame Temperature with Multiple Injectants, in the bottom-segment calculations, these calculations form the basis for our blast furnace optimization analysis.
40.2 TOP-SEGMENT EQUATIONS WITH GANGUE, ASH, FLUXES, AND SLAG PLUS INJECTION OF COAL, OXYGEN, H2O(g), AND NATURAL GAS Fig. 40.2 shows that; 1. the top segment’s top-charged inputs are; a. FeSiO2 ore; b. Al2O3CSiO2 coke; c. Al2O3, CaO, MgO, SiO2 fluxes; and d. MnO2 ore, and; 2. its ascending-from-bottom-segment inputs are a. CO; b. CO2; c. H2; d. H2O(g); and e. N2.
BLAST FURNACE IRONMAKING
TOP-SEGMENT EQUATIONS WITH GANGUE, ASH, FLUXES, AND SLAG PLUS INJECTION
The top-segment outputs are; 3. Fe0.947OSiO2 partially reduced ore, Al2O3CSiO2 coke, Al2O3, CaO, MgO fluxes, and MnO (partially reduced MnO2) descending into the bottom segment, and; 4. CO, CO2, H2, H2O, and N2 departing in top gas. Notice that tuyere injectants are not part of our top-segment calculations—except as they affect the bottom segment’s cross-division mass flows, Table 40.1.
357
Table 40.2 shows our top-segment matrix, based in part on Table 31.2. The relevant equations are listed at the end of the chapter. Table 40.3 shows the calculated input and output quantities. These are now used to calculate; • • • •
top-segment input enthalpy, top-segment output enthalpy, top gas enthalpy, and top gas temperature (Table 40.4).
TABLE 40.1 Bottom-Segment Matrix Results With Through-Tuyere Injection of Pulverized Coal, Oxygen, H2O(g), and Natural Gas
This is a copy of Table 38.2.
BLAST FURNACE IRONMAKING
TABLE 40.2
Matrix for Top-Segment of Fig. 40.2
(Continued)
TABLE 40.2 (Continued)
The related equations are listed at the end of this chapter. Numerical values of Column BC are from Table 40.1
360
TABLE 40.3
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
Top-Segment Mass Flows Calculated From Matrix Table 40.2
BLAST FURNACE IRONMAKING
TABLE 40.4
Equations for Automatically Calculating Top-Segment Input Enthalpy, Top-Segment Output Enthalpy, Top Gas Enthalpy and Top Gas Temperature
362
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
40.3 TOP-SEGMENT INPUT ENTHALPY
40.4 TOP-SEGMENT OUTPUT ENTHALPY
Top-segment input enthalpy is calculated by the following equation;
Top-segment output enthalpy (MJ per 1000 kg of Fe in product molten iron) is calculated by Eq. (21.4);
top segment input enthalpy
5 ½1431 kg of Fe2 O3 in top-charged ore 5:169 1 ½75 kg of SiO2 in top-charged ore 15:16
top segment output enthalpy
1 ½326 kg of C in top-charged coke 0 1 ½11 kg of Al2 O3 in top-charged coke 16:43 1 ½25 kg of SiO2 in top-charged coke 15:16
5
top segment
input enthalpy 2 3 80 MJ conductive; convective 6 7 and radiative heat loss 4 5 from the top segment
1 ½12 kg of top-charge Al2 O3 flux 16:43
(21.4)
1 ½100 kg of top-charged CaO flux 11:32
which in the present case is:
1 ½24 kg of top-charged MgO flux 14:92
1 ½9 kg of top-charge MnO2 ore 5:98
top segment output enthalpy
1 ½600 kg of CO ascending into the top segment 2:926
5 2 15; 34580 5 2 15; 425 MJ=1000 kg of Fe in product molten iron
1 ½416 kg of CO2 ascending into the top segment 7:926 1 ½12 kg of H2 ascending into the top segment 13:35 1 ½67 kg of H2 O ascending into the top segment 11:49
(40.3)
1 ½1146 kg of N2 ascending into the top segment 1:008 (40.1)
where the masses are from Table 40.3 and the enthalpies (on the right) are for temperatures of Fig. 40.2, Appendix J. With these values, Eq. (40.1) gives:
top segment input enthalpy
5 15; 345 MJ=1000 kg of Fe in product molten iron
In automatic spreadsheet form, the equation is: 5 BC72 ð2 5:169Þ 1 BC73 ð2 15:16Þ 1 BC74 0 1 BC75 ð2 16:43Þ 1 BC76 ð2 15:16Þ 1 BC77 ð2 16:43Þ 1 BC78 ð2 11:32Þ 1 BC79 ð2 14:92Þ 1 BC80 ð2 5:98Þ 1 BC90 ð2 2:926Þ 1 BC91 ð2 7:926Þ 1 BC92 13:35 1 BC93 ð2 11:49Þ 1 BC94 1:008 (40.2)
as shown in Table 40.4.
40.5 TOP GAS ENTHALPY Top gas enthalpy is a portion of topsegment output enthalpy of Section 40.4. The other portion is the enthalpy of the 930 C; • • • • • • • • •
Al2O3-in-coke, Al2O3 flux, C-in-coke, CaO flux, Fe0.947O (partially reduced Fe2O3) , MgO flux, MnO (partially reduced MnO2) , SiO2-in-coke, and SiO2-in-ore
descending out of the top segment. In the present case, the equation is;
BLAST FURNACE IRONMAKING
363
40.6 TOP GAS TEMPERATURE
½top gas enthalpy 5 ½top-segment output enthalpy ½mass Al2 O3 -in-coke 2 15:41 ½mass Al2 O3 flux 2 15:41
40.6 TOP GAS TEMPERATURE As in Chapter 27, Top Gas Temperature with CH4(g) Injection, we calculate our top gas temperature by the equation;
½mass C-in-coke 1:359 ½mass CaO flux 2 10:50 ½mass Fe0:947 O 2 3:152
(
½mass MgO flux 2 13:84 ½mass MnO 2 4:770 ½mass SiO2 -in-coke 2 14:13 ½mass SiO2 -in-ore 2 14:13 (40.4)
where all the enthalpies are at 930 C. With top-segment output enthalpy of Section 40.4 and masses of Table 40.4, the equation becomes; ½top gas enthalpy 5 2 15; 425 2 ½11 kg of Al2 O3 in descending coke 2 15:41 2 ½12 kg of descending Al2 O3 flux 2 15:41 2 ½326 kg of C in descending coke 1:359 2 ½100 kg of descending CaO flux 2 10:50 2 ½1302 kg of descending Fe0:947 O 2 3:152 2 ½24 kg of descending MgO flux 2 13:84 2 ½7:6 kg of descending MnO 2 4:770 2 ½25 kg of descending SiO2 -in-coke 2 14:13 2 ½75 kg of descending SiO2 -in-ore 2 14:13
which totals to; ½top gas enthalpy 5 2 8570 MJ=1000 kg of Fe in product molten iron:
½top gas enthalpy 5 BC113 2 BC81 ð2 15:41Þ 2 BC82 ð2 15:41Þ 2 BC83 1:359 2 BC84 ð2 10:50Þ 2 BC85 ð2 3:152Þ 2 BC86 ð2 13:84Þ 2 BC87 ð2 4:770Þ
2
mass CO out
ð2 3:972Þ enthalpy in top gas mass CO2 out 2 ð2 8:966Þ in top gas mass H2 out ð2 0:3616Þ 2 in top gas mass H2 O out ð2 13:47Þ 2 in top gas ) mass N2 out 2 ð2 0:02624Þ in top gas (27.2) Ttop gas 5 ( mass CO out 0:001049 in top gas mass CO2 out 0:0009314 1 in top gas mass H2 out 0:01442 1 in top gas mass H2 O out 0:001902 1 in top gas ) mass N2 out 1 0:001044 in top gas
or with mass flows of Table 40.3
As shown in Table 40.4, the automatic spreadsheet version of Eq. (40.4) is:
top-gas
8570 2 ð422 ð2 3:972ÞÞ 2 ð695 ð2 8:966ÞÞ
2 ð8:6 ð2 0:3616ÞÞ 2 ð99 ð2 13:47ÞÞ 2 ð1146 ð2 0:02624ÞÞ Ttop gas 5 422 0:001049 1 695 0:0009314 1 8:6 0:01442 1 99 0:001902 1 1146 0:001044 5 273 C
2 BC88 ð2 14:13Þ 2 BC89 ð2 14:13Þ
(40.6)
5 2 8570 MJ=1000 kg of Fe in product molten iron: (40.5)
In automatic spreadsheet form, this equation is;
BLAST FURNACE IRONMAKING
364
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
0
1 BJ116 2 BC95 ð2 3:972Þ 2 BC96 ð2 8:966Þ B C B C B 2 BC97 ð2 0:3616Þ 2 BC98 ð2 13:47Þ C @ A 2 BC99 ð2 0:02624Þ 1 Ttop gas 5 0 BC95 0:001049 1 BC96 0:0009314 1 BC97 @ A 0:01442 1 BC98 0:001902 1 BC99 0:001044 5 273 C
40.8 LIST OF TOP-SEGMENT EQUATIONS OF TABLE 40.2 Mass CO ascending into top segment:
600 5
mass CO2 ascending 1 into top segment
416 5
The above calculations show that the top gas temperature produced with the injection of; of of of of
(40.9)
Mass H2 ascending into top segment:
40.7 RESULTS
60 kg 30 kg 18 kg 60 kg
(40.8)
Mass CO2 ascending into top segment: (40.7)
• • • •
mass CO ascending 1 into top segment
pulverized coal, oxygen, H2O(g) in moist blast, and natural gas
is 273 C. This temperature and others are plotted in Fig. 40.3 for the injectants shown above.
12 5
mass H2 ascending 1 into top segment
(40.10)
Mass H2O ascending into top segment: 67 5
mass H2 O ascending 1 into top segment
(40.11)
Mass N2 ascending into top segment: 1146 5
mass N2 ascending 1 into top segment
(40.12)
Mass Al2O3-in-coke descending out of top segment:
11 5
mass Al2 O3 -in-coke 1 descending out of top segment
(40.13)
Mass Al2O3 flux descending out of top segment:
12 5
mass Al2 O3 flux descending 1 out of top segment
(40.14)
Mass C-in-coke descending out of top segment: 326 5
mass C-in-coke descending 1 out of top segment
(40.15)
Mass Fe0.947O descending out of top segment: 1302 5
mass Fe0:947 O descending 1 out of top segment
(40.16)
Mass CaO descending out of top segment:
FIGURE 40.3 The effect of increasing individual tuyere input quantities, while holding all other injectants constant, on top gas temperature. Oxygen decreases top gas temperature. Coal, H2O(g), and natural gas increase top gas temperature. The trends are confirmed by Geerdes et al. (see Ref. [1], p 115).
100 5
mass CaO descending 1 out of top segment
(40.17)
Mass MgO descending out of top segment:
24 5
BLAST FURNACE IRONMAKING
mass MgO descending 1 out of top segment
(40.18)
365
40.8 LIST OF TOP-SEGMENT EQUATIONS OF TABLE 40.2
Mass MnO descending out of top segment:
7:6 5
CaO mass balance:
mass MnO descending 1 out of top segment
(40.19)
mass CaO descending mass top charged 05 11 1 out of top segment CaO flux (40.25)
Mass SiO2-in-coke descending out of top segment:
25 5
mass SiO2 -in-coke 1 descending out of top segment
(40.20)
Mass SiO2-in-reduced ore descending out of top segment:
75 5
mass SiO2 -in-reduced ore 1 descending out of top segment
mass Al2 O3 in top
052 1
1
mass top charged
out of top segment
mass C in
out of top segment
(40.22) 1
(40.23) 1
(40.26) 0:768
mass H2 ascending
1 into top segment mass H2 O ascending 0:112 into top segment mass H2 departing top 1 1 segment in top gas mass H2 O departing top 0:112 1 segment in top gas
(40.27)
MgO mass balance: mass top charged mass MgO descending 05 11 1 MgO flux out of top segment
C mass balance: 05
0:699 top-charged ore mass Fe0:947 O descending
05
1 Al2 O3 flux mass Al2 O3 flux descending
H mass balance:
Al2O3-in-flux mass balance:
mass Fe2 O3 in
(40.21)
1
descending out of top segment
052
charged coke mass Al2 O3 -in-coke
05 1
Al2O3-in-coke mass balance:
Fe mass balance:
1 top-charged coke mass CO ascending 2 0:429 into top segment mass CO2 ascending 0:273 into top segment mass C-in-coke descending 1 1 out of top segment mass CO departing top 1 0:429 segment in top gas mass CO departing top 1 0:273 segment in top gas
(40.28)
Mn mass balance:
mass top charged
0:621 MnO2 ore mass MnO descending 1 0:774 out of top segment
05
(40.24)
N mass balance:
05 1
BLAST FURNACE IRONMAKING
mass N2 ascending
(40.29)
1 into top segment mass N2 departing top segment in top gas
(40.30) 1
366
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
O balance:
where from Section 25.5
mass Fe2 O3 in 0:301 top-charged ore mass top-charged 0:368 2 MnO2 ore mass CO ascending 2 0:571 into top segment mass CO2 ascending 0:727 2 into top segment mass H2 O ascending 0:888 2 into top segment mass Fe0:947 O descending 1 0:232 into bottom segment mass MnO descending 1 0:226 into bottom segment mass CO departing top 1 0:571 segment in top gas mass CO2 departing top 0:727 1 segment in top gas mass H2 O departing top 1 0:888 segment in top gas
0
1 mass H2 ascending B from bottom segment C C 0:117 5 B @ mass CO ascending A 5:7 from bottom segment
052
(40.31)
mass SiO2 in top-
1
1 charged coke mass SiO2 -in-coke
05
(40.32) 1
descending out of top segment
SiO2-in-iron-ore mass balance:
05 1
mass SiO2 in top-
1 charged iron ore mass SiO2 -in-reduced ore descending out of top segment
(40.33) 1
C oxidation in top-segment equation:
mass C in 1 top-charged coke mass C-in-coke descending 1 1 out of top segment
05 2
(40.34)
Top-segment CO/H2 relative reaction extent:
mass CO2 ascending
0:117 from bottom segment mass CO2 out 0:117 1 in top gas mass H2 O ascending mass H2 O out 1 1 1 from bottom segment in top gas
05
40.9 MATCHING THE MODEL TO COMMERCIAL BLAST FURNACE DATA When the matrix model prepared in this book is used to simulate a commercial blast furnace, the user may find it challenging to get a precise match of the key operating parameters. While the model describes most aspects of the blast furnace process, some changes must be considered to match industrial data. Through experience, the authors have found that the following parameters may need adjustment:
SiO2-in-coke mass balance:
(25.12)
(25.13)
• The model assumes that all iron ore is hematite, Fe2O3. Blast furnace sinter contains 510% FeO, this will need to be considered in the iron and oxygen balances. • Adjust CO2/CO equilibrium mass ratio leaving the bottom segment, which has been assumed to be 0.694, to match the observed coke rate. This may represent gas flow issues/short circuiting in the bottom segment that creates inefficiency as the reducing gases cannot react with the descending iron oxides. A blast furnace operating with a central coke chimney for permeability reasons is a good example as there is no iron ore to react with the rising CO at the center of the blast furnace. • Adjust H2O/H2 equilibrium mass ratio leaving the bottom segment, which has been assumed to be 5.44, to match the observed H2 top gas production/analysis. H2 conversion to H2O may be under reported due to inefficient gas flow in the bottom segment as described earlier. • Adjust top/bottom segment heat loss rates, 320 and 80 MJ/1000 kg Fe in product
BLAST FURNACE IRONMAKING
367
40.10 SUMMARY
molten iron, respectively, to match top gas temperature. Actual heat losses may be understated. When matching your model calculations to industrial data, take a note that the following measuring errors could impact your ability to make a good match: • Accurate measurement of the blast air volume can be challenging due to the large quantity to be measured and need for a long straight pipe section between the turbo blower and blast furnace to take a precise measurement. A viable blast furnace model may not match the measured air volume, the latter of which could be in error. • Measurement of the total carbon input can be in error. Ability to measure the coke moisture content and charge coke on a dry basis can lead to an input carbon measurement error. Injected pulverized coal can have a variable carbon content depending on quality control at the coal mine. • Errors in top gas temperature measurement. The model calculates the top gas temperature leaving the charged burden surface. The actual measurement in the furnace uptakes is about 10 m higher, this could lead to a small difference in top gas temperature. Above burden probes or newer systems like TMT—Tapping Measuring Technologies’ SOMA system provide a better indication of the top gas temperature leaving the charged burden surface. While the difference in top gas temperature may not be large, it can impact the model accuracy as a large volume of gas leaves the blast furnace. • Not all heat losses may be measured. Some blast furnaces do not measure the heat losses to all cooling systems. The reported values may understate the actual cooling losses. • Reported raceway adiabatic flame temperature may not match the matrix model calculation. Many producers use empirical equations that may be inaccurate.
The model calculated flame temperature is more comprehensive and defendable. Armed with this knowledge, adjustments can be easily made to the matrix calculations to match the model to the available industrial data. Knowing what adjustments are needed can help identify measurement errors that may be present at the industrial blast furnace. Once the model has been calibrated to the observed measurements, the blast furnace engineer can extrapolate to future conditions/scenarios with confidence and accuracy.
40.10 SUMMARY In this chapter, we completed our matrix development by including the effects of multiple through-tuyere inputs in our top gas calculations. Through-tuyere inputs don’t appear in our top-segment matrix because they are not present in top segment of Fig. 40.2. They do, however, influence the masses of CO, CO2, H2, H2O(g), and N2 rising into the top segment. This changes the top-segment input, output, and top gas enthalpies and hence top gas temperature, Fig. 40.3. Our automatic top gas calculations are nearly complete. We must, however, consider the effects of moisture in the top-charged ores, coke, and fluxes. This is done in Chapter 41, Top-Segment Calculations with Raw Material Moisture, by adding top-charge moisture to matrix Table 40.2. The top gas temperatures in Fig. 40.3 are higher than industrial top gas temperatures; 110 C140 C. This is because in this chapter, we did not include several top-segment endothermic reactions, that is, moisture-in-top charge evaporation and carbonate flux dissociation. These are added to our calculations in Chapter 41, Top-Segment Calculations with Raw Material Moisture, and Chapter 42, Top Segment with Carbonate Fluxes.
BLAST FURNACE IRONMAKING
368
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
EXERCISES
injection will give them this temperature. Please calculate this for them.
40.1. Please predict for the management of Exercise 38.1 what their top gas temperature will be with 20 kg of 25 C oil injection of Exercise 38.1 (plus all the other injectants). Can you suggest a trend before you do the calculation? 40.2. The blast furnace operators of Exercise 40.1 want a top gas temperature of 280 C. They wish to know how much oil
Caution: make sure that your bottomsegment calculated values transfer automatically to the top-segment matrix.
Reference 1. Geerdes M, Chaigneau R, Kurunov I, Lingiardi O, Ricketts J. Modern blast furnace ironmaking (an introduction). 3rd ed IOS Press BV: Amsterdam; 2015.
BLAST FURNACE IRONMAKING
40 Top-Segment Calculations With Multiple Injectants O U T L I N E 40.1 Understanding the Top Segment With Multiple Injectants
355
40.2 Top-Segment Equations With Gangue, Ash, Fluxes, and Slag Plus Injection of Coal, Oxygen, H2O(g), and Natural Gas
356
40.3 Top-Segment Input Enthalpy
362
40.4 Top-Segment Output Enthalpy
362
40.5 Top Gas Enthalpy
362
40.6 Top Gas Temperature
363
In this chapter, we calculate top gas composition, enthalpy, and temperature with tuyere injection of;
Blast Furnace Ironmaking DOI: https://doi.org/10.1016/B978-0-12-814227-1.00040-3
364
40.8 List of Top-Segment Equations of Table 40.2
364
40.9 Matching the model to Commercial Blast Furnace Data
366
40.10 Summary
367
Exercises
368
Reference
368
• H2O(g)-in-blast (from humid air and injected steam), and • natural gas.
40.1 UNDERSTANDING THE TOP SEGMENT WITH MULTIPLE INJECTANTS
• pulverized coal, • pure oxygen,
40.7 Results
It is important to understand how top gas temperature is affected by these injectants. Top gas must be warm enough to; 1. efficiently evaporate the top charge’s moisture content so that iron ore reduction begins quickly,
355
© 2020 Elsevier Inc. All rights reserved.
356
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
FIGURE 40.1 Conceptual bottom segment of blast furnace with moist blast air, injection of oxygen into the blast, and injection of pulverized coal and natural gas into the furnace. The flows descending from the top segment and ascending into the top segment are notable. Fig. 40.2 shows the equivalent conceptual top segment with its topcharged inputs and the same cross-segment flows.
2. avoid unwanted condensation of moisture in the charge that can move down the furnace walls and damage hearth refractory, and 3. purge undesirable minor elements, especially zinc in the burden materials but not so warm as to; 4. increase the fuel rate due to excessive energy lost to the top gas and 5. damage the top-charging equipment 110 C140 C appears to be the optimum range. The objectives of this chapter are to; 1. build a top-segment matrix based on bottom-segment cross-division flows of Chapter 38, Bottom-Segment Calculations with Multiple Injectants (Fig. 40.1), and top charged inputs of Fig. 40.2; 2. use the matrix to calculate top gas composition of Fig. 40.2; 3. develop equations to calculate top-segment input enthalpy, top-segment output enthalpy, and top gas enthalpy of Fig. 40.2; and; 4. develop an equation that calculates top gas temperature of Fig. 40.2 from (1)’s top gas composition and (3)’s top gas enthalpy.
FIGURE 40.2 Conceptual blast furnace top segment and the flows between it and the bottom segment, Fig. 40.1.
These steps finish the development of our blast furnace model. When connected to the automatic flame temperature calculation and automatic inclusion of blast temperature of Chapter 39, Raceway Flame Temperature with Multiple Injectants, in the bottom-segment calculations, these calculations form the basis for our blast furnace optimization analysis.
40.2 TOP-SEGMENT EQUATIONS WITH GANGUE, ASH, FLUXES, AND SLAG PLUS INJECTION OF COAL, OXYGEN, H2O(g), AND NATURAL GAS Fig. 40.2 shows that; 1. the top segment’s top-charged inputs are; a. FeSiO2 ore; b. Al2O3CSiO2 coke; c. Al2O3, CaO, MgO, SiO2 fluxes; and d. MnO2 ore, and; 2. its ascending-from-bottom-segment inputs are a. CO; b. CO2; c. H2; d. H2O(g); and e. N2.
BLAST FURNACE IRONMAKING
TOP-SEGMENT EQUATIONS WITH GANGUE, ASH, FLUXES, AND SLAG PLUS INJECTION
The top-segment outputs are; 3. Fe0.947OSiO2 partially reduced ore, Al2O3CSiO2 coke, Al2O3, CaO, MgO fluxes, and MnO (partially reduced MnO2) descending into the bottom segment, and; 4. CO, CO2, H2, H2O, and N2 departing in top gas. Notice that tuyere injectants are not part of our top-segment calculations—except as they affect the bottom segment’s cross-division mass flows, Table 40.1.
357
Table 40.2 shows our top-segment matrix, based in part on Table 31.2. The relevant equations are listed at the end of the chapter. Table 40.3 shows the calculated input and output quantities. These are now used to calculate; • • • •
top-segment input enthalpy, top-segment output enthalpy, top gas enthalpy, and top gas temperature (Table 40.4).
TABLE 40.1 Bottom-Segment Matrix Results With Through-Tuyere Injection of Pulverized Coal, Oxygen, H2O(g), and Natural Gas
This is a copy of Table 38.2.
BLAST FURNACE IRONMAKING
TABLE 40.2
Matrix for Top-Segment of Fig. 40.2
(Continued)
TABLE 40.2 (Continued)
The related equations are listed at the end of this chapter. Numerical values of Column BC are from Table 40.1
360
TABLE 40.3
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
Top-Segment Mass Flows Calculated From Matrix Table 40.2
BLAST FURNACE IRONMAKING
TABLE 40.4
Equations for Automatically Calculating Top-Segment Input Enthalpy, Top-Segment Output Enthalpy, Top Gas Enthalpy and Top Gas Temperature
362
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
40.3 TOP-SEGMENT INPUT ENTHALPY
40.4 TOP-SEGMENT OUTPUT ENTHALPY
Top-segment input enthalpy is calculated by the following equation;
Top-segment output enthalpy (MJ per 1000 kg of Fe in product molten iron) is calculated by Eq. (21.4);
top segment input enthalpy
5 ½1431 kg of Fe2 O3 in top-charged ore 5:169 1 ½75 kg of SiO2 in top-charged ore 15:16
top segment output enthalpy
1 ½326 kg of C in top-charged coke 0 1 ½11 kg of Al2 O3 in top-charged coke 16:43 1 ½25 kg of SiO2 in top-charged coke 15:16
5
top segment
input enthalpy 2 3 80 MJ conductive; convective 6 7 and radiative heat loss 4 5 from the top segment
1 ½12 kg of top-charge Al2 O3 flux 16:43
(21.4)
1 ½100 kg of top-charged CaO flux 11:32
which in the present case is:
1 ½24 kg of top-charged MgO flux 14:92
1 ½9 kg of top-charge MnO2 ore 5:98
top segment output enthalpy
1 ½600 kg of CO ascending into the top segment 2:926
5 2 15; 34580 5 2 15; 425 MJ=1000 kg of Fe in product molten iron
1 ½416 kg of CO2 ascending into the top segment 7:926 1 ½12 kg of H2 ascending into the top segment 13:35 1 ½67 kg of H2 O ascending into the top segment 11:49
(40.3)
1 ½1146 kg of N2 ascending into the top segment 1:008 (40.1)
where the masses are from Table 40.3 and the enthalpies (on the right) are for temperatures of Fig. 40.2, Appendix J. With these values, Eq. (40.1) gives:
top segment input enthalpy
5 15; 345 MJ=1000 kg of Fe in product molten iron
In automatic spreadsheet form, the equation is: 5 BC72 ð2 5:169Þ 1 BC73 ð2 15:16Þ 1 BC74 0 1 BC75 ð2 16:43Þ 1 BC76 ð2 15:16Þ 1 BC77 ð2 16:43Þ 1 BC78 ð2 11:32Þ 1 BC79 ð2 14:92Þ 1 BC80 ð2 5:98Þ 1 BC90 ð2 2:926Þ 1 BC91 ð2 7:926Þ 1 BC92 13:35 1 BC93 ð2 11:49Þ 1 BC94 1:008 (40.2)
as shown in Table 40.4.
40.5 TOP GAS ENTHALPY Top gas enthalpy is a portion of topsegment output enthalpy of Section 40.4. The other portion is the enthalpy of the 930 C; • • • • • • • • •
Al2O3-in-coke, Al2O3 flux, C-in-coke, CaO flux, Fe0.947O (partially reduced Fe2O3) , MgO flux, MnO (partially reduced MnO2) , SiO2-in-coke, and SiO2-in-ore
descending out of the top segment. In the present case, the equation is;
BLAST FURNACE IRONMAKING
363
40.6 TOP GAS TEMPERATURE
½top gas enthalpy 5 ½top-segment output enthalpy ½mass Al2 O3 -in-coke 2 15:41 ½mass Al2 O3 flux 2 15:41
40.6 TOP GAS TEMPERATURE As in Chapter 27, Top Gas Temperature with CH4(g) Injection, we calculate our top gas temperature by the equation;
½mass C-in-coke 1:359 ½mass CaO flux 2 10:50 ½mass Fe0:947 O 2 3:152
(
½mass MgO flux 2 13:84 ½mass MnO 2 4:770 ½mass SiO2 -in-coke 2 14:13 ½mass SiO2 -in-ore 2 14:13 (40.4)
where all the enthalpies are at 930 C. With top-segment output enthalpy of Section 40.4 and masses of Table 40.4, the equation becomes; ½top gas enthalpy 5 2 15; 425 2 ½11 kg of Al2 O3 in descending coke 2 15:41 2 ½12 kg of descending Al2 O3 flux 2 15:41 2 ½326 kg of C in descending coke 1:359 2 ½100 kg of descending CaO flux 2 10:50 2 ½1302 kg of descending Fe0:947 O 2 3:152 2 ½24 kg of descending MgO flux 2 13:84 2 ½7:6 kg of descending MnO 2 4:770 2 ½25 kg of descending SiO2 -in-coke 2 14:13 2 ½75 kg of descending SiO2 -in-ore 2 14:13
which totals to; ½top gas enthalpy 5 2 8570 MJ=1000 kg of Fe in product molten iron:
½top gas enthalpy 5 BC113 2 BC81 ð2 15:41Þ 2 BC82 ð2 15:41Þ 2 BC83 1:359 2 BC84 ð2 10:50Þ 2 BC85 ð2 3:152Þ 2 BC86 ð2 13:84Þ 2 BC87 ð2 4:770Þ
2
mass CO out
ð2 3:972Þ enthalpy in top gas mass CO2 out 2 ð2 8:966Þ in top gas mass H2 out ð2 0:3616Þ 2 in top gas mass H2 O out ð2 13:47Þ 2 in top gas ) mass N2 out 2 ð2 0:02624Þ in top gas (27.2) Ttop gas 5 ( mass CO out 0:001049 in top gas mass CO2 out 0:0009314 1 in top gas mass H2 out 0:01442 1 in top gas mass H2 O out 0:001902 1 in top gas ) mass N2 out 1 0:001044 in top gas
or with mass flows of Table 40.3
As shown in Table 40.4, the automatic spreadsheet version of Eq. (40.4) is:
top-gas
8570 2 ð422 ð2 3:972ÞÞ 2 ð695 ð2 8:966ÞÞ
2 ð8:6 ð2 0:3616ÞÞ 2 ð99 ð2 13:47ÞÞ 2 ð1146 ð2 0:02624ÞÞ Ttop gas 5 422 0:001049 1 695 0:0009314 1 8:6 0:01442 1 99 0:001902 1 1146 0:001044 5 273 C
2 BC88 ð2 14:13Þ 2 BC89 ð2 14:13Þ
(40.6)
5 2 8570 MJ=1000 kg of Fe in product molten iron: (40.5)
In automatic spreadsheet form, this equation is;
BLAST FURNACE IRONMAKING
364
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
0
1 BJ116 2 BC95 ð2 3:972Þ 2 BC96 ð2 8:966Þ B C B C B 2 BC97 ð2 0:3616Þ 2 BC98 ð2 13:47Þ C @ A 2 BC99 ð2 0:02624Þ 1 Ttop gas 5 0 BC95 0:001049 1 BC96 0:0009314 1 BC97 @ A 0:01442 1 BC98 0:001902 1 BC99 0:001044 5 273 C
40.8 LIST OF TOP-SEGMENT EQUATIONS OF TABLE 40.2 Mass CO ascending into top segment:
600 5
mass CO2 ascending 1 into top segment
416 5
The above calculations show that the top gas temperature produced with the injection of; of of of of
(40.9)
Mass H2 ascending into top segment:
40.7 RESULTS
60 kg 30 kg 18 kg 60 kg
(40.8)
Mass CO2 ascending into top segment: (40.7)
• • • •
mass CO ascending 1 into top segment
pulverized coal, oxygen, H2O(g) in moist blast, and natural gas
is 273 C. This temperature and others are plotted in Fig. 40.3 for the injectants shown above.
12 5
mass H2 ascending 1 into top segment
(40.10)
Mass H2O ascending into top segment: 67 5
mass H2 O ascending 1 into top segment
(40.11)
Mass N2 ascending into top segment: 1146 5
mass N2 ascending 1 into top segment
(40.12)
Mass Al2O3-in-coke descending out of top segment:
11 5
mass Al2 O3 -in-coke 1 descending out of top segment
(40.13)
Mass Al2O3 flux descending out of top segment:
12 5
mass Al2 O3 flux descending 1 out of top segment
(40.14)
Mass C-in-coke descending out of top segment: 326 5
mass C-in-coke descending 1 out of top segment
(40.15)
Mass Fe0.947O descending out of top segment: 1302 5
mass Fe0:947 O descending 1 out of top segment
(40.16)
Mass CaO descending out of top segment:
FIGURE 40.3 The effect of increasing individual tuyere input quantities, while holding all other injectants constant, on top gas temperature. Oxygen decreases top gas temperature. Coal, H2O(g), and natural gas increase top gas temperature. The trends are confirmed by Geerdes et al. (see Ref. [1], p 115).
100 5
mass CaO descending 1 out of top segment
(40.17)
Mass MgO descending out of top segment:
24 5
BLAST FURNACE IRONMAKING
mass MgO descending 1 out of top segment
(40.18)
365
40.8 LIST OF TOP-SEGMENT EQUATIONS OF TABLE 40.2
Mass MnO descending out of top segment:
7:6 5
CaO mass balance:
mass MnO descending 1 out of top segment
(40.19)
mass CaO descending mass top charged 05 11 1 out of top segment CaO flux (40.25)
Mass SiO2-in-coke descending out of top segment:
25 5
mass SiO2 -in-coke 1 descending out of top segment
(40.20)
Mass SiO2-in-reduced ore descending out of top segment:
75 5
mass SiO2 -in-reduced ore 1 descending out of top segment
mass Al2 O3 in top
052 1
1
mass top charged
out of top segment
mass C in
out of top segment
(40.22) 1
(40.23) 1
(40.26) 0:768
mass H2 ascending
1 into top segment mass H2 O ascending 0:112 into top segment mass H2 departing top 1 1 segment in top gas mass H2 O departing top 0:112 1 segment in top gas
(40.27)
MgO mass balance: mass top charged mass MgO descending 05 11 1 MgO flux out of top segment
C mass balance: 05
0:699 top-charged ore mass Fe0:947 O descending
05
1 Al2 O3 flux mass Al2 O3 flux descending
H mass balance:
Al2O3-in-flux mass balance:
mass Fe2 O3 in
(40.21)
1
descending out of top segment
052
charged coke mass Al2 O3 -in-coke
05 1
Al2O3-in-coke mass balance:
Fe mass balance:
1 top-charged coke mass CO ascending 2 0:429 into top segment mass CO2 ascending 0:273 into top segment mass C-in-coke descending 1 1 out of top segment mass CO departing top 1 0:429 segment in top gas mass CO departing top 1 0:273 segment in top gas
(40.28)
Mn mass balance:
mass top charged
0:621 MnO2 ore mass MnO descending 1 0:774 out of top segment
05
(40.24)
N mass balance:
05 1
BLAST FURNACE IRONMAKING
mass N2 ascending
(40.29)
1 into top segment mass N2 departing top segment in top gas
(40.30) 1
366
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
O balance:
where from Section 25.5
mass Fe2 O3 in 0:301 top-charged ore mass top-charged 0:368 2 MnO2 ore mass CO ascending 2 0:571 into top segment mass CO2 ascending 0:727 2 into top segment mass H2 O ascending 0:888 2 into top segment mass Fe0:947 O descending 1 0:232 into bottom segment mass MnO descending 1 0:226 into bottom segment mass CO departing top 1 0:571 segment in top gas mass CO2 departing top 0:727 1 segment in top gas mass H2 O departing top 1 0:888 segment in top gas
0
1 mass H2 ascending B from bottom segment C C 0:117 5 B @ mass CO ascending A 5:7 from bottom segment
052
(40.31)
mass SiO2 in top-
1
1 charged coke mass SiO2 -in-coke
05
(40.32) 1
descending out of top segment
SiO2-in-iron-ore mass balance:
05 1
mass SiO2 in top-
1 charged iron ore mass SiO2 -in-reduced ore descending out of top segment
(40.33) 1
C oxidation in top-segment equation:
mass C in 1 top-charged coke mass C-in-coke descending 1 1 out of top segment
05 2
(40.34)
Top-segment CO/H2 relative reaction extent:
mass CO2 ascending
0:117 from bottom segment mass CO2 out 0:117 1 in top gas mass H2 O ascending mass H2 O out 1 1 1 from bottom segment in top gas
05
40.9 MATCHING THE MODEL TO COMMERCIAL BLAST FURNACE DATA When the matrix model prepared in this book is used to simulate a commercial blast furnace, the user may find it challenging to get a precise match of the key operating parameters. While the model describes most aspects of the blast furnace process, some changes must be considered to match industrial data. Through experience, the authors have found that the following parameters may need adjustment:
SiO2-in-coke mass balance:
(25.12)
(25.13)
• The model assumes that all iron ore is hematite, Fe2O3. Blast furnace sinter contains 510% FeO, this will need to be considered in the iron and oxygen balances. • Adjust CO2/CO equilibrium mass ratio leaving the bottom segment, which has been assumed to be 0.694, to match the observed coke rate. This may represent gas flow issues/short circuiting in the bottom segment that creates inefficiency as the reducing gases cannot react with the descending iron oxides. A blast furnace operating with a central coke chimney for permeability reasons is a good example as there is no iron ore to react with the rising CO at the center of the blast furnace. • Adjust H2O/H2 equilibrium mass ratio leaving the bottom segment, which has been assumed to be 5.44, to match the observed H2 top gas production/analysis. H2 conversion to H2O may be under reported due to inefficient gas flow in the bottom segment as described earlier. • Adjust top/bottom segment heat loss rates, 320 and 80 MJ/1000 kg Fe in product
BLAST FURNACE IRONMAKING
367
40.10 SUMMARY
molten iron, respectively, to match top gas temperature. Actual heat losses may be understated. When matching your model calculations to industrial data, take a note that the following measuring errors could impact your ability to make a good match: • Accurate measurement of the blast air volume can be challenging due to the large quantity to be measured and need for a long straight pipe section between the turbo blower and blast furnace to take a precise measurement. A viable blast furnace model may not match the measured air volume, the latter of which could be in error. • Measurement of the total carbon input can be in error. Ability to measure the coke moisture content and charge coke on a dry basis can lead to an input carbon measurement error. Injected pulverized coal can have a variable carbon content depending on quality control at the coal mine. • Errors in top gas temperature measurement. The model calculates the top gas temperature leaving the charged burden surface. The actual measurement in the furnace uptakes is about 10 m higher, this could lead to a small difference in top gas temperature. Above burden probes or newer systems like TMT—Tapping Measuring Technologies’ SOMA system provide a better indication of the top gas temperature leaving the charged burden surface. While the difference in top gas temperature may not be large, it can impact the model accuracy as a large volume of gas leaves the blast furnace. • Not all heat losses may be measured. Some blast furnaces do not measure the heat losses to all cooling systems. The reported values may understate the actual cooling losses. • Reported raceway adiabatic flame temperature may not match the matrix model calculation. Many producers use empirical equations that may be inaccurate.
The model calculated flame temperature is more comprehensive and defendable. Armed with this knowledge, adjustments can be easily made to the matrix calculations to match the model to the available industrial data. Knowing what adjustments are needed can help identify measurement errors that may be present at the industrial blast furnace. Once the model has been calibrated to the observed measurements, the blast furnace engineer can extrapolate to future conditions/scenarios with confidence and accuracy.
40.10 SUMMARY In this chapter, we completed our matrix development by including the effects of multiple through-tuyere inputs in our top gas calculations. Through-tuyere inputs don’t appear in our top-segment matrix because they are not present in top segment of Fig. 40.2. They do, however, influence the masses of CO, CO2, H2, H2O(g), and N2 rising into the top segment. This changes the top-segment input, output, and top gas enthalpies and hence top gas temperature, Fig. 40.3. Our automatic top gas calculations are nearly complete. We must, however, consider the effects of moisture in the top-charged ores, coke, and fluxes. This is done in Chapter 41, Top-Segment Calculations with Raw Material Moisture, by adding top-charge moisture to matrix Table 40.2. The top gas temperatures in Fig. 40.3 are higher than industrial top gas temperatures; 110 C140 C. This is because in this chapter, we did not include several top-segment endothermic reactions, that is, moisture-in-top charge evaporation and carbonate flux dissociation. These are added to our calculations in Chapter 41, Top-Segment Calculations with Raw Material Moisture, and Chapter 42, Top Segment with Carbonate Fluxes.
BLAST FURNACE IRONMAKING
368
40. TOP-SEGMENT CALCULATIONS WITH MULTIPLE INJECTANTS
EXERCISES
injection will give them this temperature. Please calculate this for them.
40.1. Please predict for the management of Exercise 38.1 what their top gas temperature will be with 20 kg of 25 C oil injection of Exercise 38.1 (plus all the other injectants). Can you suggest a trend before you do the calculation? 40.2. The blast furnace operators of Exercise 40.1 want a top gas temperature of 280 C. They wish to know how much oil
Caution: make sure that your bottomsegment calculated values transfer automatically to the top-segment matrix.
Reference 1. Geerdes M, Chaigneau R, Kurunov I, Lingiardi O, Ricketts J. Modern blast furnace ironmaking (an introduction). 3rd ed IOS Press BV: Amsterdam; 2015.
BLAST FURNACE IRONMAKING