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Top-Segment Calculations With Moisture in Blast Air
C H A P T E R
28 Top-Segment Calculations With Moisture in Blast Air O U T L I N E 28.1 Incorporating Blast Moisture Into Top-Segment Balances
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28.2 Bottom-Segment Results
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28.3 Top-Segment Calculations
250
28.4 Top Gas Temperature Results
253
28.5 Summary
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Exercises
254
Reference
254
28.1 INCORPORATING BLAST MOISTURE INTO TOP-SEGMENT BALANCES
Fig. 28.1 shows steady-state flows across a blast furnace’s conceptual division—with through-tuyere input H2O(g). They are the same as with CH4(g) injection, that is;
Chapters 25 27 determined top gas composition, enthalpy, and temperature with tuyereinjected CH4(g). This chapter does the same with through-tuyere input H2O(g). Our objectives are to;
• descending Fe0.947O(s) and C(s)-in-coke, and • ascending CO(g), CO2(g), N2(g), H2(g), and H2O(g). We now calculate the steady-state mass flows of these substances with: • 15 g of H2O(g) in blast per Nm3 of dry air in blast.
1. show how to calculate top gas masses, enthalpies, and temperatures with H2O(g) in blast, and 2. indicate the effect of this H2O(g) on top gas temperature.
Blast Furnace Ironmaking DOI: https://doi.org/10.1016/B978-0-12-814227-1.00028-2
Matrix Table 28.1 is used. Note that the H2O(g) always enters the furnace at blast temperature, which is 1200 C throughout this chapter.
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© 2020 Elsevier Inc. All rights reserved.
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28. TOP-SEGMENT CALCULATIONS WITH MOISTURE IN BLAST AIR
FIGURE 28.1 Conceptually divided blast furnace with H2O(g) in blast. The blast’s H2O(g) is from humid air topped up with injected steam. Note the flows of Fe0.947O(s), C(s)-in-coke, CO(g), CO2(g), N2(g), H2(g), and H2O(g) across the conceptual division.
28.2 BOTTOM-SEGMENT RESULTS Table 28.1 shows that the steady-state crossdivision mass flows with 15 g of H2O(g) per Nm3 of dry air in blast are; • mass Fe0.947O into bottom segment 5 mass Fe0.947O out of top segment 5 1302 kg; Cell C18 • mass C-in-coke into bottom segment 5 mass C-in-coke out of top segment 5 399 kg; Cell C19 • mass CO out of bottom segment 5 mass CO into top segment 5 569 kg; Cell C24 • mass CO2 out of bottom segment 5 mass CO2 into top segment 5 395 kg; Cell C25 • mass N2 out of bottom segment 5 mass N2 into top segment 5 995 kg; Cell C26 • mass H2 out of bottom segment 5 mass H2 into top segment 5 1.1 kg; Cell C27 • mass H2O out of bottom segment 5 mass H2O into top segment 5 5.8 kg; Cell C28
all per 1000 kg of Fe in product molten iron. These are the only values that will keep Fig. 28.1 furnace steadily producing 1500 C molten iron with: • 15 g of H2O(g) in blast per Nm3 of dry air in blast.
28.3 TOP-SEGMENT CALCULATIONS Cross-division flows of Section 28.1 are now inserted into column AC of top-segment matrix Table 28.2. The insertions can be manual, or more usefully by the instructions:
BLAST FURNACE IRONMAKING
Cell AC3 5 C18
(28.1)
Cell AC8 5 C24
(28.2)
Cell AC9 5 C25
(28.3)
Cell AC10 5 C26
(28.4)
TABLE 28.1
Matrix for Calculating Bottom-Segment Steady-State Inputs and Outputs of Fig. 28.1 With 15 g of H2O(g) per Nm3 of Dry Air in Blast
Table 28.1 is a copy of Table 12.1. It calculates the amounts of O2-in-blast air and C-in-coke charge that will keep Fig. 28.1 blast furnace steadily producing 1500 C molten iron. It also calculates the equivalent steady-state Fe0.947O, C-in-coke, CO, CO2, N2, H2, and H2O flows across conceptual division of Fig. 28.1. Eqs. (7.9), (11.8), and (12.2) are explained in Chapters 7, 11, and 12.
TABLE 28.2
Top-Segment Matrix With 15 g of H2O(g) per Nm3 of Dry Air in Blast
All masses are per 1000 kg of Fe in product molten iron. The column AC matrix values have been forwarded from Table 28.1. The contents of Cells AG16 and AL16 are explained in Section 25.7.
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28.5 SUMMARY
Cell AC11 5 C19
(28.5)
Cell AC14 5 C27
(28.6)
Cell AC15 5 C28
(28.7)
28.4 TOP GAS TEMPERATURE RESULTS The top segment (column AC) of Table 28.2 calculated masses show that steady-state top gas temperature of Fig. 28.1 with; • 15 g of H2O(g) in blast per Nm of dry air in blast entering the furnace at 1200 C is 196 C. 3
This and other top gas temperatures are plotted in Fig. 28.2, which shows that; • top gas temperature increases by 0.95 C for each additional gram of H2O(g) per Nm3 of dry air in blast. This is comparable to the 10.9 C value suggested by Geerdes et al.1 Fig. 28.2 shows that top gas temperature increases with increasing concentration of H2O(g)
FIGURE 28.3 Effect of H2O(g) concentration in blast on mass hot N2 rising into top segment of Fig. 28.1. The increase in mass N2 with increasing H2O(g)-in-blast concentration is notable. We postulate that increasing top gas temperature of Fig. 28.2 is at least partially due to this extra N2.
in blast. This is due to all our equations - but we may postulate that it is mainly due to; • an increasing amount of hot (930 C) N2 ascending from the bottom segment into the top segment with an increasing H2O(g) concentration in blast (Fig. 28.3).
28.5 SUMMARY
FIGURE 28.2 Blast furnace top gas temperature with H2O(g) entering the furnace in blast (Fig. 28.1). Top gas temperature increases with increasing H2O(g) concentration in blast.
The top-segment matrix with through-tuyere H2O(g) input is the same as with CH4(g) injection. Only the bottom-segment top-segment cross-flow values (Column AC) vary - as calculated by their respective bottom-segment matrices. Top gas temperature increases with increasing H2O(g) concentration in blast. This is due to all our equations—but we speculate that it is largely due to a greater amount of hot N2 rising into the top segment with increasing H2O(g). This increase may be offset by raising blast temperature and/or oxygen injection, Chapter 22, Top Gas Temperature Calculation,
BLAST FURNACE IRONMAKING
254
28. TOP-SEGMENT CALCULATIONS WITH MOISTURE IN BLAST AIR
and Chapter 24, Top Segment Calculations with Oxygen Enrichment.
EXERCISES All masses are in kg per 1000 kg of Fe in product molten iron. 28.1. Fig. 28.1 blast furnace’s Engineering team plans to raise the moisture content of its blast to 25 g/Nm3 of dry air. They wish to know what its furnace’s top gas temperature will be with this increased moisture content. Please calculate this for them. 28.2. However, the blast furnace’s Research department now believes that Exercise 28.1 furnace operators should restrict
their top gas temperature to 200 C or below. Please calculate the blast moisture level that will give 200 C top gas. 28.3. Exercise 28.2 Research team also wants to know how much steam they will have to add to Fig. 28.1 humid air to obtain blast moisture level of Exercise 28.2. Humid air of Fig. 28.1 contains 10 g of H2O(g) per Nm3 of dry air. Please express you answer in g per Nm3 of dry air and kg per kg of dry air.
Reference 1. Geerdes M, Chaigneau R, Kurunov I, Lingiardi O, Ricketts J. Modern blast furnace ironmaking, an introduction. 2nd ed. Amsterdam: IOS Press BV; 2015. p. 195.
BLAST FURNACE IRONMAKING
28 Top-Segment Calculations With Moisture in Blast Air O U T L I N E 28.1 Incorporating Blast Moisture Into Top-Segment Balances
249
28.2 Bottom-Segment Results
250
28.3 Top-Segment Calculations
250
28.4 Top Gas Temperature Results
253
28.5 Summary
253
Exercises
254
Reference
254
28.1 INCORPORATING BLAST MOISTURE INTO TOP-SEGMENT BALANCES
Fig. 28.1 shows steady-state flows across a blast furnace’s conceptual division—with through-tuyere input H2O(g). They are the same as with CH4(g) injection, that is;
Chapters 25 27 determined top gas composition, enthalpy, and temperature with tuyereinjected CH4(g). This chapter does the same with through-tuyere input H2O(g). Our objectives are to;
• descending Fe0.947O(s) and C(s)-in-coke, and • ascending CO(g), CO2(g), N2(g), H2(g), and H2O(g). We now calculate the steady-state mass flows of these substances with: • 15 g of H2O(g) in blast per Nm3 of dry air in blast.
1. show how to calculate top gas masses, enthalpies, and temperatures with H2O(g) in blast, and 2. indicate the effect of this H2O(g) on top gas temperature.
Blast Furnace Ironmaking DOI: https://doi.org/10.1016/B978-0-12-814227-1.00028-2
Matrix Table 28.1 is used. Note that the H2O(g) always enters the furnace at blast temperature, which is 1200 C throughout this chapter.
249
© 2020 Elsevier Inc. All rights reserved.
250
28. TOP-SEGMENT CALCULATIONS WITH MOISTURE IN BLAST AIR
FIGURE 28.1 Conceptually divided blast furnace with H2O(g) in blast. The blast’s H2O(g) is from humid air topped up with injected steam. Note the flows of Fe0.947O(s), C(s)-in-coke, CO(g), CO2(g), N2(g), H2(g), and H2O(g) across the conceptual division.
28.2 BOTTOM-SEGMENT RESULTS Table 28.1 shows that the steady-state crossdivision mass flows with 15 g of H2O(g) per Nm3 of dry air in blast are; • mass Fe0.947O into bottom segment 5 mass Fe0.947O out of top segment 5 1302 kg; Cell C18 • mass C-in-coke into bottom segment 5 mass C-in-coke out of top segment 5 399 kg; Cell C19 • mass CO out of bottom segment 5 mass CO into top segment 5 569 kg; Cell C24 • mass CO2 out of bottom segment 5 mass CO2 into top segment 5 395 kg; Cell C25 • mass N2 out of bottom segment 5 mass N2 into top segment 5 995 kg; Cell C26 • mass H2 out of bottom segment 5 mass H2 into top segment 5 1.1 kg; Cell C27 • mass H2O out of bottom segment 5 mass H2O into top segment 5 5.8 kg; Cell C28
all per 1000 kg of Fe in product molten iron. These are the only values that will keep Fig. 28.1 furnace steadily producing 1500 C molten iron with: • 15 g of H2O(g) in blast per Nm3 of dry air in blast.
28.3 TOP-SEGMENT CALCULATIONS Cross-division flows of Section 28.1 are now inserted into column AC of top-segment matrix Table 28.2. The insertions can be manual, or more usefully by the instructions:
BLAST FURNACE IRONMAKING
Cell AC3 5 C18
(28.1)
Cell AC8 5 C24
(28.2)
Cell AC9 5 C25
(28.3)
Cell AC10 5 C26
(28.4)
TABLE 28.1
Matrix for Calculating Bottom-Segment Steady-State Inputs and Outputs of Fig. 28.1 With 15 g of H2O(g) per Nm3 of Dry Air in Blast
Table 28.1 is a copy of Table 12.1. It calculates the amounts of O2-in-blast air and C-in-coke charge that will keep Fig. 28.1 blast furnace steadily producing 1500 C molten iron. It also calculates the equivalent steady-state Fe0.947O, C-in-coke, CO, CO2, N2, H2, and H2O flows across conceptual division of Fig. 28.1. Eqs. (7.9), (11.8), and (12.2) are explained in Chapters 7, 11, and 12.
TABLE 28.2
Top-Segment Matrix With 15 g of H2O(g) per Nm3 of Dry Air in Blast
All masses are per 1000 kg of Fe in product molten iron. The column AC matrix values have been forwarded from Table 28.1. The contents of Cells AG16 and AL16 are explained in Section 25.7.
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28.5 SUMMARY
Cell AC11 5 C19
(28.5)
Cell AC14 5 C27
(28.6)
Cell AC15 5 C28
(28.7)
28.4 TOP GAS TEMPERATURE RESULTS The top segment (column AC) of Table 28.2 calculated masses show that steady-state top gas temperature of Fig. 28.1 with; • 15 g of H2O(g) in blast per Nm of dry air in blast entering the furnace at 1200 C is 196 C. 3
This and other top gas temperatures are plotted in Fig. 28.2, which shows that; • top gas temperature increases by 0.95 C for each additional gram of H2O(g) per Nm3 of dry air in blast. This is comparable to the 10.9 C value suggested by Geerdes et al.1 Fig. 28.2 shows that top gas temperature increases with increasing concentration of H2O(g)
FIGURE 28.3 Effect of H2O(g) concentration in blast on mass hot N2 rising into top segment of Fig. 28.1. The increase in mass N2 with increasing H2O(g)-in-blast concentration is notable. We postulate that increasing top gas temperature of Fig. 28.2 is at least partially due to this extra N2.
in blast. This is due to all our equations - but we may postulate that it is mainly due to; • an increasing amount of hot (930 C) N2 ascending from the bottom segment into the top segment with an increasing H2O(g) concentration in blast (Fig. 28.3).
28.5 SUMMARY
FIGURE 28.2 Blast furnace top gas temperature with H2O(g) entering the furnace in blast (Fig. 28.1). Top gas temperature increases with increasing H2O(g) concentration in blast.
The top-segment matrix with through-tuyere H2O(g) input is the same as with CH4(g) injection. Only the bottom-segment top-segment cross-flow values (Column AC) vary - as calculated by their respective bottom-segment matrices. Top gas temperature increases with increasing H2O(g) concentration in blast. This is due to all our equations—but we speculate that it is largely due to a greater amount of hot N2 rising into the top segment with increasing H2O(g). This increase may be offset by raising blast temperature and/or oxygen injection, Chapter 22, Top Gas Temperature Calculation,
BLAST FURNACE IRONMAKING
254
28. TOP-SEGMENT CALCULATIONS WITH MOISTURE IN BLAST AIR
and Chapter 24, Top Segment Calculations with Oxygen Enrichment.
EXERCISES All masses are in kg per 1000 kg of Fe in product molten iron. 28.1. Fig. 28.1 blast furnace’s Engineering team plans to raise the moisture content of its blast to 25 g/Nm3 of dry air. They wish to know what its furnace’s top gas temperature will be with this increased moisture content. Please calculate this for them. 28.2. However, the blast furnace’s Research department now believes that Exercise 28.1 furnace operators should restrict
their top gas temperature to 200 C or below. Please calculate the blast moisture level that will give 200 C top gas. 28.3. Exercise 28.2 Research team also wants to know how much steam they will have to add to Fig. 28.1 humid air to obtain blast moisture level of Exercise 28.2. Humid air of Fig. 28.1 contains 10 g of H2O(g) per Nm3 of dry air. Please express you answer in g per Nm3 of dry air and kg per kg of dry air.
Reference 1. Geerdes M, Chaigneau R, Kurunov I, Lingiardi O, Ricketts J. Modern blast furnace ironmaking, an introduction. 2nd ed. Amsterdam: IOS Press BV; 2015. p. 195.
BLAST FURNACE IRONMAKING