- Email: [email protected]
Top Segment Calculations With Oxygen Enrichment
C H A P T E R
24 Top Segment Calculations With Oxygen Enrichment O U T L I N E 24.1 Impact of Blast Oxygen Enrichment on the Top Segment and Top Gas Conditions
219
24.2 Cross-Division Flows With Pure Oxygen Injection
219
24.3 Top-Segment Calculations
220
24.1 IMPACT OF BLAST OXYGEN ENRICHMENT ON THE TOP SEGMENT AND TOP GAS CONDITIONS
24.4 Summary
223
Exercises
224
Reference
224
Our primary objective is to show how injection of pure oxygen affects top gas temperature. Secondary objectives are to determine top gas composition and enthalpy.
Chapter 23, Top Gas Calculations With Pulverized Carbon Injection, determined top gas; • composition, • enthalpy, and • temperature with pulverized carbon injection. This chapter does the same with pure oxygen injection, Fig. 24.1.
Blast Furnace Ironmaking DOI: https://doi.org/10.1016/B978-0-12-814227-1.00024-5
24.2 CROSS-DIVISION FLOWS WITH PURE OXYGEN INJECTION Fig. 24.1 shows the steady-state flows across our oxygen-injected blast furnace’s conceptual division. The steady-state material flows, but not their rates, are the same as with carbon injection, that is;
219
© 2020 Elsevier Inc. All rights reserved.
220
24. TOP SEGMENT CALCULATIONS WITH OXYGEN ENRICHMENT
FIGURE 24.1 Conceptually divided blast furnace with pure oxygen injection. The oxygen is mixed with blast air, heated, and then blown into the blast furnace. Note the flows of Fe0.947O(s), C(s)-in-coke, CO(g), CO2(g), and N2(g) across the conceptual division.
• Fe0.947O(s) and C(s)-in-coke descending, and • CO(g), CO2(g), and N2(g) ascending. We now calculate the steady-state mass flows of these substances, per 1000 kg of Fe in product molten iron using the bottom segment matrix of Chapter 9, Bottom Segment With Oxygen Enrichment of Blast Air, Table 24.1. With 30 kg of pure oxygen injection, the masses are; • mass Fe0.947O into bottom segment 5 mass Fe0.947O out of top segment 5 1302 kg, • mass C-in-coke into bottom segment 5 mass C-in-coke out of top segment 5 394 kg, • mass CO out of bottom segment 5 mass CO into top segment 5 561 kg, • mass CO2 out of bottom segment 5 mass CO2 into top segment 5 389 kg, and • mass N2 out of bottom segment 5 mass N2 into top segment 5 894 kg all per 1000 kg of Fe in product molten iron.
These are the only values that will keep the blast furnace of Fig. 24.1 steadily producing 1500 C molten iron with 30 kg of pure oxygen injectant.
24.3 TOP-SEGMENT CALCULATIONS The above five values are now forwarded to the top segment matrix of Fig. 24.1, Table 24.2 as shown in Cells AC3 and AC8AC11. The forwarding instructions are; Cell AC3 5 C18 Cell AC8 5 C24 Cell AC9 5 C25 Cell AC10 5 C26 Cell AC11 5 C19
where C Cells refer to Table 24.1.
BLAST FURNACE IRONMAKING
TABLE 24.1
Matrix for Calculating Bottom-Segment Inputs and Outputs of Fig. 24.1 With 30 kg of Pure Oxygen Injection
This is a copy of Table 9.1. It calculates the amounts of O2-in-blast air and C-in-coke charge that will keep the blast furnace of Fig. 24.1 steadily producing molten iron, 1500 C. It also calculates the equivalent steady-state Fe0.947O, C-in-coke, CO, CO2, and N2 flows across conceptual division of Fig. 24.1. All masses are per 1000 kg of Fe in product molten iron.
TABLE 24.2 Spreadsheet for Blast Furnace Top-Segment of Fig. 24.1 With 30 kg of Pure Oxygen Injection
The values in Cells AC3 and AC8AC11 are from bottom segment calculated values of Table 24.1. Except for column AC, the matrix is the same as Fig. 23.2.
Cell AG33 5 AC18 ð2 5:169Þ 1 AC19 0 1 AC20 ð2 2:926Þ 1 AC21 ð2 7:926Þ 1 AC22 1:008 Cell AG34 5 AG33 2 80 Cell AG37 5 AG34 2 AC23 ð2 3:152Þ 2 AC24 1:359 Cell AH40 5
ðAG37 2 AC25 ð2 3:972Þ 2 AC26 ð2 8:966Þ 2 AC27 ð2 0:02624ÞÞ ðAC25 0:001049 1 AC26 0:0009314 1 AC27 0:001044Þ
(21.2) (21.5b) (22.2)
(22.4)
223
24.4 SUMMARY
FIGURE 24.2 Top gas temperature falls with increasing pure oxygen injection - by about 1.3 C/kg of oxygen. The line is not quite straight because Eq. (22.4) is not linear.
FIGURE 24.3 Mass of hot nitrogen rising into a blast furnace’s top segment as a function of mass tuyere-injected pure oxygen. The decrease is notable. It is due to the replacement of air with pure oxygen in the bottom segment. The smaller amount of hot nitrogen brings less enthalpy into the top segment lowering top gas enthalpy and hence top gas temperature. The line is straight.
Insertion of the above oxygen-injection cross-division values into Table 24.2 automatically calculates the equivalent top gas; • CO, CO2, and N2 masses, Cells AC25, 26, and 27; • enthalpy, Cell AG37; and • temperature, Cell AH40. Top gas temperature of Table 24.2 is plotted in Fig. 24.2 - along with other oxygen injection results. Top gas temperature is seen to decrease with increasing pure oxygen injection. This fall in temperature is a consequence of all equations of Tables 24.1 and 24.2. We may speculate that it is mainly due to; • the decreased amount of hot, high enthalpy N2 rising into the top segment, Fig. 24.3, and • the increased amount of cool, low enthalpy top charged C-in-coke, Fig. 24.4, with increasing pure oxygen injection.
FIGURE 24.4 Effect of pure oxygen injection on the amount of top charge C-in-coke needed for steady production of 1500 C molten iron. Oxygen injection increases C-in-coke requirement but the effect is small. The line is straight. The cause of the increase is detailed in Section 9.4.
24.4 SUMMARY Tuyere injection of pure oxygen into the blast furnace is readily included in our top gas;
BLAST FURNACE IRONMAKING
224
24. TOP SEGMENT CALCULATIONS WITH OXYGEN ENRICHMENT
• composition, • enthalpy, and • temperature
EXERCISES All masses are per 1000 kg of Fe in product molten iron
calculations. The top gas calculations entail; 1. bottom segment calculation of blast furnace C-in-coke and O2-in-blast air requirements for steady 1500 C molten iron production with pure oxygen injection, Chapter 9, Bottom Segment With Oxygen Enrichment of Blast Air, and 2. top segment calculation of top gas composition, enthalpy, and temperature from the equivalent; a. steady-state cross-division mass flows, Fig. 24.1 and Table 24.1, and b. top segment mass and enthalpy balances, Table 24.2. The calculations show that top gas temperature falls with increasing pure oxygen injection—confirmed by the industrial data of Geerdes et al1.
24.1. What is the top gas temperature with 60 kg of injected pure oxygen? 24.2. What are the top gas masses with 30 kg and 60 kg of injected pure oxygen? 24.3. The top gas temperature must be greater than 160 C while simultaneously having the tuyere raceway flame temperature lower than 2400 C. Over what oxygen injection range are these requirements both met?
Reference 1. Geerdes M, Chaigneau R, Kurunov I, Lingiardi O, Ricketts J. Modern blast furnace ironmaking, an introduction. 2nd ed BV, Amsterdam: IOS Press; 2015. p. 195.
BLAST FURNACE IRONMAKING
24 Top Segment Calculations With Oxygen Enrichment O U T L I N E 24.1 Impact of Blast Oxygen Enrichment on the Top Segment and Top Gas Conditions
219
24.2 Cross-Division Flows With Pure Oxygen Injection
219
24.3 Top-Segment Calculations
220
24.1 IMPACT OF BLAST OXYGEN ENRICHMENT ON THE TOP SEGMENT AND TOP GAS CONDITIONS
24.4 Summary
223
Exercises
224
Reference
224
Our primary objective is to show how injection of pure oxygen affects top gas temperature. Secondary objectives are to determine top gas composition and enthalpy.
Chapter 23, Top Gas Calculations With Pulverized Carbon Injection, determined top gas; • composition, • enthalpy, and • temperature with pulverized carbon injection. This chapter does the same with pure oxygen injection, Fig. 24.1.
Blast Furnace Ironmaking DOI: https://doi.org/10.1016/B978-0-12-814227-1.00024-5
24.2 CROSS-DIVISION FLOWS WITH PURE OXYGEN INJECTION Fig. 24.1 shows the steady-state flows across our oxygen-injected blast furnace’s conceptual division. The steady-state material flows, but not their rates, are the same as with carbon injection, that is;
219
© 2020 Elsevier Inc. All rights reserved.
220
24. TOP SEGMENT CALCULATIONS WITH OXYGEN ENRICHMENT
FIGURE 24.1 Conceptually divided blast furnace with pure oxygen injection. The oxygen is mixed with blast air, heated, and then blown into the blast furnace. Note the flows of Fe0.947O(s), C(s)-in-coke, CO(g), CO2(g), and N2(g) across the conceptual division.
• Fe0.947O(s) and C(s)-in-coke descending, and • CO(g), CO2(g), and N2(g) ascending. We now calculate the steady-state mass flows of these substances, per 1000 kg of Fe in product molten iron using the bottom segment matrix of Chapter 9, Bottom Segment With Oxygen Enrichment of Blast Air, Table 24.1. With 30 kg of pure oxygen injection, the masses are; • mass Fe0.947O into bottom segment 5 mass Fe0.947O out of top segment 5 1302 kg, • mass C-in-coke into bottom segment 5 mass C-in-coke out of top segment 5 394 kg, • mass CO out of bottom segment 5 mass CO into top segment 5 561 kg, • mass CO2 out of bottom segment 5 mass CO2 into top segment 5 389 kg, and • mass N2 out of bottom segment 5 mass N2 into top segment 5 894 kg all per 1000 kg of Fe in product molten iron.
These are the only values that will keep the blast furnace of Fig. 24.1 steadily producing 1500 C molten iron with 30 kg of pure oxygen injectant.
24.3 TOP-SEGMENT CALCULATIONS The above five values are now forwarded to the top segment matrix of Fig. 24.1, Table 24.2 as shown in Cells AC3 and AC8AC11. The forwarding instructions are; Cell AC3 5 C18 Cell AC8 5 C24 Cell AC9 5 C25 Cell AC10 5 C26 Cell AC11 5 C19
where C Cells refer to Table 24.1.
BLAST FURNACE IRONMAKING
TABLE 24.1
Matrix for Calculating Bottom-Segment Inputs and Outputs of Fig. 24.1 With 30 kg of Pure Oxygen Injection
This is a copy of Table 9.1. It calculates the amounts of O2-in-blast air and C-in-coke charge that will keep the blast furnace of Fig. 24.1 steadily producing molten iron, 1500 C. It also calculates the equivalent steady-state Fe0.947O, C-in-coke, CO, CO2, and N2 flows across conceptual division of Fig. 24.1. All masses are per 1000 kg of Fe in product molten iron.
TABLE 24.2 Spreadsheet for Blast Furnace Top-Segment of Fig. 24.1 With 30 kg of Pure Oxygen Injection
The values in Cells AC3 and AC8AC11 are from bottom segment calculated values of Table 24.1. Except for column AC, the matrix is the same as Fig. 23.2.
Cell AG33 5 AC18 ð2 5:169Þ 1 AC19 0 1 AC20 ð2 2:926Þ 1 AC21 ð2 7:926Þ 1 AC22 1:008 Cell AG34 5 AG33 2 80 Cell AG37 5 AG34 2 AC23 ð2 3:152Þ 2 AC24 1:359 Cell AH40 5
ðAG37 2 AC25 ð2 3:972Þ 2 AC26 ð2 8:966Þ 2 AC27 ð2 0:02624ÞÞ ðAC25 0:001049 1 AC26 0:0009314 1 AC27 0:001044Þ
(21.2) (21.5b) (22.2)
(22.4)
223
24.4 SUMMARY
FIGURE 24.2 Top gas temperature falls with increasing pure oxygen injection - by about 1.3 C/kg of oxygen. The line is not quite straight because Eq. (22.4) is not linear.
FIGURE 24.3 Mass of hot nitrogen rising into a blast furnace’s top segment as a function of mass tuyere-injected pure oxygen. The decrease is notable. It is due to the replacement of air with pure oxygen in the bottom segment. The smaller amount of hot nitrogen brings less enthalpy into the top segment lowering top gas enthalpy and hence top gas temperature. The line is straight.
Insertion of the above oxygen-injection cross-division values into Table 24.2 automatically calculates the equivalent top gas; • CO, CO2, and N2 masses, Cells AC25, 26, and 27; • enthalpy, Cell AG37; and • temperature, Cell AH40. Top gas temperature of Table 24.2 is plotted in Fig. 24.2 - along with other oxygen injection results. Top gas temperature is seen to decrease with increasing pure oxygen injection. This fall in temperature is a consequence of all equations of Tables 24.1 and 24.2. We may speculate that it is mainly due to; • the decreased amount of hot, high enthalpy N2 rising into the top segment, Fig. 24.3, and • the increased amount of cool, low enthalpy top charged C-in-coke, Fig. 24.4, with increasing pure oxygen injection.
FIGURE 24.4 Effect of pure oxygen injection on the amount of top charge C-in-coke needed for steady production of 1500 C molten iron. Oxygen injection increases C-in-coke requirement but the effect is small. The line is straight. The cause of the increase is detailed in Section 9.4.
24.4 SUMMARY Tuyere injection of pure oxygen into the blast furnace is readily included in our top gas;
BLAST FURNACE IRONMAKING
224
24. TOP SEGMENT CALCULATIONS WITH OXYGEN ENRICHMENT
• composition, • enthalpy, and • temperature
EXERCISES All masses are per 1000 kg of Fe in product molten iron
calculations. The top gas calculations entail; 1. bottom segment calculation of blast furnace C-in-coke and O2-in-blast air requirements for steady 1500 C molten iron production with pure oxygen injection, Chapter 9, Bottom Segment With Oxygen Enrichment of Blast Air, and 2. top segment calculation of top gas composition, enthalpy, and temperature from the equivalent; a. steady-state cross-division mass flows, Fig. 24.1 and Table 24.1, and b. top segment mass and enthalpy balances, Table 24.2. The calculations show that top gas temperature falls with increasing pure oxygen injection—confirmed by the industrial data of Geerdes et al1.
24.1. What is the top gas temperature with 60 kg of injected pure oxygen? 24.2. What are the top gas masses with 30 kg and 60 kg of injected pure oxygen? 24.3. The top gas temperature must be greater than 160 C while simultaneously having the tuyere raceway flame temperature lower than 2400 C. Over what oxygen injection range are these requirements both met?
Reference 1. Geerdes M, Chaigneau R, Kurunov I, Lingiardi O, Ricketts J. Modern blast furnace ironmaking, an introduction. 2nd ed BV, Amsterdam: IOS Press; 2015. p. 195.
BLAST FURNACE IRONMAKING