Comprehensive Mathematical Model and Optimum Process Parameters of Nitrogen Free Blast Furnace

Abstract

According to different energy utilization in different regions, blast furnace is divided into raceway zone, bottom heat exchange zone (BHZ), thermal reserve zone (TRZ), and top heat exchange zone (THZ), and a mathematical model of nitrogen free blast furnace (NF-BF) is established. The optimum process parameters of two kinds of nitrogen free blast furnaces are calculated by the new mathematical model. The results show that for the nitrogen free blast furnace with a single row of tuyeres, the optimum process parameters are coke ratio of 220 kg/t, coal ratio of 193 kg/t, and volume of recycling top gas of 577 m3/t; for two rows of tuyeres, the process parameters are coke ratio of 202 kg/t, coal ratio of 211 kg/t, volume of recycling top gas in upper area of 296 m3/t, and volume of recycling top gas in lower area of 295 m3/t. Energy balances are reached in different regions. Theoretical combustion temperature (TCT) in raceway zone is largely affected by different processes, and a lower TCT should be adopted for the single row of tuyeres, but for two rows of tuyeres, a higher TCT should be maintained. Compared with traditional blast furnace, in NF-BF, the emission of CO2 would be reduced by 45.91% and 49.02% for a single row of tuyeres and two rows of tuyeres, respectively, and combined with CO2 sequestration technology, zero emission of CO2 could be realized.