PROSPECTS OF USING ALTERNATIVE FUELS FOR HEATING OF REGENERATIVE AIR HEATERS FOR BLASТ FURNACES

Abstract

Landfill gas as one of the promising artificial gaseous fuels is analyzed for use in heating system of regenerative air heaters for blast furnaces. Increasing the temperature of blast is one of the most effective ways for metallurgical coke saving and increase the productivity of blast furnaces. To increase this temperature, a mixture of blast-furnace and coke oven gases is used as fuel for regenerative heat exchangers. Considering the current shortage of coke oven gas, landfill gas, the main combustible element of which is methane, is proposed as a high-calorie additive to the main fuel. Calculations were made for the combustion of a mixture of gaseous fuels in three combinations: blast-furnace gas, blast-furnace and coke gases mixture, blast-furnace and landfill gases mixture. The possibility of increasing the temperature of the hot blast to 1250 °C for the air supply system of a blast furnace with a volume of 1033 m³ was considered. Calculations showed that in order to achieve such a temperature, the adiabatic combustion temperature should be 1423 °C, and the flue gas temperature in the crown should be 1300 °C. Such temperatures cannot be reached using only blast-furnace gas, so two possible options were considered. The first option is the use of a coke and blast furnace gases mixture with a coke gas content of 6.3 % and combustion air heating to 180 °C by exhaust gases from blast furnace air heaters. The second option is combustion of a mixture of blast-furnace and landfill gas with combustion air heating to 180 °C (the content of landfill gas is 7.6 %). The flow rate of the fuel mixture for the second option is 68,523 m³ /h, and the required amount of landfill gas is 5208 m³ /h. The volumes of gas output from landfills in large cities are reported to be 5–10 MCM a year, which is less than the amount of biogas required to heat an air heater. Therefore, to achieve the required temperature it makes sense to consider a tree gas mixture that is blast-furnace, coke and landfill gases an appropriate proportions. The use of landfill gas contributes to the solution of an important environmental problem of land and atmosphere pollution during the accumulation of municipal solid waste.