Abstract
Problem Statement (Relevance): Considering the short supply and high prices for coke it would be reasonable to minimize the consumption of coke in the production of cast iron in blast furnaces by substituting it with natural gas as much as practicable. As the higher gas flow rate changes the blast furnace process, it can create the risk of the burden suspended within the upper heat transfer stage making it necessary to take measures to prevent any irregularities in burden movement. Objectives: The objective is to develop operating modes that would ensure a lower specific consumption of coke together with a higher consumption of natural gas within the top zone limiting the interaction of counterflows. Methods Applied: Blast Furnaces ##2 and 10 of MMK with the top zone limiting the interaction of counterflows of stock and gas provided a ground for research into finding ways to reduce the specific consumption of coke by increasing the consumption of natural gas. Low hearth drainage was observed in Blast Furnace #10 during the reference period. For this reason manganese ore was added at the rate of 650 kg/charge in order to improve the filtration conditions. For experiments, the natural gas flow rate was increased by 800 m3/h, and the wind rate was increased from 3328 to 3491 m3/min. To compensate for the impacted burden movement a number of heat parameters were modified. Thus, the top gas pressure was increased from 133 to 142 kPa, the stockline was lowered from 1.2 to 1.36 m, the pellet concentration was increased from 31 to 34 %. For Blast Furnace #2, the raise of the gas flow rate by 1900 m3/h became possible due to the top gas pressure increase by 4 kPa and a partial substitution of pellets from Sokolovsk-Sarbaysk Mining and Processing Plant with those from Mikhailovsky GOK. The hot strength of the pellets increased by 16.4% abs. under LTD+6,3. Originality: The authors identified ways to improve the blast furnace process and decrease the specific consumption of coke by raising the natural gas flow rate under the conditions when the interaction of counterflows within the upper heat exchange stage is a crucial factor. Findings: A number of measures which compensated the impact of natural gas flow rate increase on the gas dynamics in Blast Furnace #10 helped bring down the burden resistance to gas flow at the top of the furnace and improved the H2 and CO utilization. The coke-to-gas substitution rate amounted to 0.76 kg/m3. For Blast Furnace #2, the H2 and CO utilization rates were raised by 5.9 and 0.7 % rel. correspondingly. The reduced rate of coke was decreased by 7.0 kg per ton of cast iron. The coke-to-gas substitution rate amounted to 0.78 kg/m3. Further increase of the gas flow rate by 1000 m3/h without compensating its impact on gas flow at the top of the furnace would result in a 7.3 % rel. increase in burden resistance in that zone and irregular stock movement. To eliminate irregular stock movement the wind rate was reduced from 3210 to 3138 m3/min. Increasing the gas flow rate without accounting for its impact on the blast furnace process resulted in the increase in the specific consumption of coke of 8.3 kg per ton of cast iron. The production rate of the furnace dropped by 88 t/day. Practical relevance: A decrease of 4.5 kg per ton of cast iron in the average specific consumption of coke was obtained through the efficient use of the higher natural gas flow rate in Blast Furnaces ##2 and 10 of MMK during the experimental period.
Keywords
Blast furnace, coke, natural gas, pellets, hot strength, LTD indicator, top gas pressure, the resistance coefficient of charge.
1. Bahgat, M., Abdel Halim, K.S., El-Kelesh, H.A., Nasr, M.I. Blast furnace operating conditions manipulation for reducing coke consumption and CO 2 emission. Steel Research International. 2012, no. 83(7), pp. 686–694.
2. Sibagatullin S.K. The optimum degree of the direct reduction of iron from oxides. Stal' [Steel]. 1997, no. 4, pp. 1–5. (In Russ.)
3. Lyalyuk V.P., Tovarovskyi I.G. Selecting the smelting modes for a blast furnace with a fuel enriched blast while analyzing the tuyere zone parameters. Chernye metally [Ferrous metals]. 2003, no. 11, pp. 13–16. (In Russ.)
4. Tovarovskyi I.G., Lyalyuk V.P., Merkulov A.E. The analysis of the blast furnace melting process with an oxygen enriched blast. Byulleten'. Chernaya metallurgiya [Bulletin. Ferrous Metallurgy]. 2011, no. 5, pp. 20–33. (In Russ.)
5. Mansheng Chu, Zhenggen Liu. Mathematical modeling and exergy analysis of blast furnace operation with natural gas. Steel Research International. 2013, no. 84 (4), pp. 333–343.
6. Gostenin V.A., Pishnograev S.N., Chevychelov A.V. et al. Intensificying the blast furnace operation through an optimum combination of natural gas and oxygen flow rates. Stal' [Steel]. 2012, no. 2, pp. 7–11. (In Russ.)
7. Gostenin V.A., Pishnograev S.N., Shtafienko N.S. et al. Intensificying the blast furnace operation through an optimum combination of natural gas and oxygen flow rates. Byulleten'. Chernaya metallurgiya [Bulletin. Ferrous Metallurgy]. 2011, no. 6, pp. 16–22. (In Russ.)
8. Tovarovskyi I.G., Merkulov A.E. The analysis of the blast-furnace processes with largely varying blast air temperatures. Byulleten'. Chernaya metallurgiya [Bulletin. Ferrous Metallurgy]. 2011, no. 4, pp. 36–49. (In Russ.)
9. Sibagatullin S.K. Zakonomernosti dvizhenija shihty i gaza v domennoj pechi: monografija [Blast furnace charge material and gas movement patterns: Monograph]. Magnitogorsk: Nosov Magnitogorsk State Technical University, 2011, 161 p. (In Russ.)
10. Khaled S Abdel-Halim, V. N. Andronov, M. I. Nasr. Blast furnace operation with natural gas injection and minimum theoretical flame temperature. Ironmaking & Steelmaking. 2009, no. 36(1), pp. 12–18.
11. Khaled S Abdel-Halim. Effective utilization of using natural gas injection in the production of pig iron. Materials Letters. 2007, no. 61(14–15), pp. 3281–3286.
12. Spirin N.A., Gileva L.Yu., Lavrov V.V. et al. Optimizing the natural gas distribution in a blast furnace shop following a change in the smelting parameters. Izvestija vysshih uchebnyh zavedenij. Chernaja metallurgija [Proceedings of Russian Universities. Ferrous Metallurgy]. 2014, no. 6, pp. 45–49. (In Russ.)
13. Spirin N.A., Fedulov Yu.V., Ovchinnikov Yu.N. The distribution of the process oxygen between the blast furnaces within a single shop]. Izvestija vysshih uchebnyh zavedenij. Chernaja metallurgija [Proceedings of Russian Universities. Ferrous Metallurgy]. 1993, no. 11–12, pp. 68–72. (In Russ.)
14. Feshchenko S.A., Pleshkov V.I., Lizunov B.N. et al. Improving the blast furnace process by injecting natural gas due to it being heated. Metallurg [Metallurgist]. 2007, no. 11, pp. 44–48. (In Russ.)
15. Ovchinnikov Yu.N., Moykin V.I., Spirin N.A. Nestacionarnye processy i povyshenie jeffektivnosti domennoj plavki. Monografija [Non-stationary processes and optimized blast furnace operation: Monograph], Chelyabinsk, 1989. 120 p. (In Russ.)
16. Sibagatullin S.K., Kharchenko A.S., Kharchenko E.O., Sibagatullina M.I., Minikaev S.R. Improving blast furnace short-term reduction in natural gas consumption. Byulleten'. Chernaya metallurgiya [Bulletin. Ferrous Metallurgy]. 2017, no. 2(1406), pp. 16–20. (In Russ.)
17. Sibagatullin S.K., Kharchenko A.S., Polinov A.A. et al. Stabilizing the ratios of natural gas and wind flow rates by tuyere. Teorija i tehnologija metallurgicheskogo proizvodstva [Metallurgical theory and technology]. 2014, no. 1(14), pp. 26–26. (In Russ.)
18. Andronov V.N., Belov Yu.A. Analysing the efficiency of blast and natural gas distribution by tuyere. Stal' [Steel]. 2002, no. 9, pp. 15–17. (In Russ.)
19. Sibagatullin S.K., Kharchenko A.S., Beginyuk V.A. Technological solutions for the blast furnace process. Metallurg [Metallurgist]. 2014, no. 4, pp. 64–71. (In Russ.)
20. Donskov E.G., Lyalyuk V.P. Blast consumption and the role of high pressure in modern blast furnaces]. Stal' [Steel]. 2012, no. 12, pp. 2–6. (In Russ.)
21. Sibagatullin S.K., Mayorova T.V. Intensified gas flow in a blast furnace with an increased overall differential pressure. Vestnik Magnitogorskogo gosudarstvennogo tehnicheskogo universiteta im. G.I. Nosova [Vestnik of Nosov Magnitogorsk State Technical University]. 2011, no. 1, pp. 14–16. (In Russ.)
22. Sibagatullin S.K., Mayorova T.V. On the calculation of process indicators for a blast furnace with an increased overall differential pressure of gases. Vestnik Magnitogorskogo gosudarstvennogo tehnicheskogo universiteta im. G.I. Nosova [Vestnik of Nosov Magnitogorsk State Technical University]. 2010, no. 3, pp. 16–18. (In Russ.)
23. Tarasov V.P., Tarasov P.V. Teoriya i tekhnologiya domennoy plavki [Blast furnace theory and technology]. Moscow: Intermet Inzhiniring, 2007. 384 p. (In Russ.)