Impact of measures adopted to reduce Specific Heat Consumption in Reheating Furnaces of Hot Strip Mill, Roukela Steel Plant, SAIL

摘要

Hot Strip Mill of Rourkela Steel Plant is provided with two Walking Beam Re-heating Furnaces having slab handling capacity of 225 t / hr each. These furnaces were commissioned in the year 1999 and they were designed for cold slab charging. The average Specific Heat Consumption (SHC) of the furnaces was about 376 Mcal /tof cold slab in the year 2000-01 against the international norm of 310 Mcal/t. This paper analyses the impact of different changes adopted like increase in slab thickness, length and width, reduction in mill delays, increase in rolling rate etc. on the reduction in SHC of the furnaces. From the analysis, it was found that every 10 t / mill utilisation hr increase in rolling rate resulted in reduction of SHC by at least 7.7 Mcal /t slab. For increasing the slab rolling rate, the decreasing mill delays (mill unutilised hours/total furnace available hours) played a major role. The mill delays decreased from 37% in 2000-01 to 24% in 2009-10. It was found that for every 1 % reduction in mill delay, the mill rolling rate increases by at least 6t / mill utilisation hr and correspondingly the SHC decreases by at least 4.74 Mcal /t slab. The second most important parameter is the furnace throughput. For every 10t/ mill utilisation hr / furnace increase in furnace throughput, the SHC decreases by at least 12.3 Mcal /t slab. For increasing the furnace throughput, the slab thickness was increased gradually from 206 mm in 200-01 to 218 mm in 2007-08. It was found that for every 1 mm increase in slab thickness, the furnace throughput increases by at least 1.4 t / mill utilisation hr / furnace and the SHC decreases by at least 2 Meal /t slab. However both are not additive as increase in Rolling rate directly influences the Furnace throughput and vice versa. The above measures along with improvement in SOP & SMP resulted in reduction of SHC and the same could be reduced to 344 Mcal /t slab by the year 2011-12.