Research On Combustion Adjustment And Energy-Saving Optimization Of Low Heat Value Gas/Pulverized Coal Combined Combustion Boiler

The BFG (Blast Furnace Gas) effective use as the main secondary energy is an important way of energy saving in steel industry. The problem of a 75t/h gas/pulverized coal combined combustion boiler in an iron & steel enterprise in Guizhou caused by unreasonable BFG blending ratio would be discussed in this paper, such as high carbon content in fly ash, high exhaust gas temperature, and low thermal efficiency. By analyzing the combustion characteristics of BFG, COG (Coke Oven Gas), and pulverized coal, the boiler combustion process would be studied under the conditions of co-firing of the practical pulverized coal with different BFG blending ratio, and co-firing of different kinds of pulverized coal with the designed blending ratio. The results showed the co-firing of pulverized coal with BFG would lead to the decrease of furnace temperature, the rise of flame center position, and the increase of exhaust gas temperature, especially for co-firing of inferior coal with BFG. The blending is harmful for the pulverized coal burnout and the exhaust gas temperature decrease. Meanwhile, the combustion adjustment test under the different conditions was investigated according to the actual operation. The results showed the boiler had high thermal efficiency under the conditions of co-firing of pulverized coal and COG or co-firing of BFG and COG. However, the operating modes are not economical for the gas balance of plant. The mode of the 35% BFG heat value, the 35% COG heat value and the 30% pulverized coal heat value has been applied in the boiler, which improves the problems of high exhaust gas temperature, high carbon content of fly ash and low thermal efficiency, and increases the BFG blending ratio and the operation economy of the boiler.