Exploration Of Gas-powder Flow Granulated Blast Furnace Slag And Waste Heat Recovery Process

Due to energy shortage and environmental problems,it became inevitable for the steel industry to reduce energy consumption as a circular economy.Blast furnace slag is a by-product of the steel industry which has high value of waste heat recovery and product utilization.But now blast furnace slag is mainly treated by the method of water quenching what discharges harmful gas and causes waste of water resources.Although the existing dry granulation method is feasible in principle,it has not been put into large-scale use because of the unstable granulation effect.This paper breaks the bondage of breaking molten slag with water or air as a single granulation media.The gas-powder two-phase impingement flow as the granulation media is proposed,Slag crushing can depend on the greater impact force of powder and the blowing effect of air.In this paper,a method of gas-powder flow injection is established,and a complete process of gas-powder quenching and waste heat recovery is designed.The new method is expected to provide ideas for technological innovation in iron and steel industry,to guide more energy-saving and effective development of production.In the dynamic and economic analysis of the process of gas-powder flow conveying,spraying and slag crushing,the optimum design parameters of 300t/h melting blast furnace slag to 5 mm particle size were determined as follows:the particle size of 0.8-1.2 mm,the mass flow rate of 16.8 t/h,the outlet pressure of compressed air of 1.0 mPa,the air flow rate of 117 Nm3/h,and the power consumption of air compressor of 12.44 kW.To achieve the same effect of slag crushing,the air pressure of 1.5 mPa and air flow rate of 6700Nm3/h are required for air quenching.The power consumption of air quenching is about 68 times that of gas-powder quenching.In the thermodynamic analysis of slag cooling,the heat transfer in the process of slag droplet cooling,slag droplet solidification and slag particle cooling is completed.Mathematical model of slag and air temperature following is established.900?as the heat transfer boundary temperature of molten slag is determined.The air flow rates of360 Nkm~3/h and 440 Nkm~3/h as primary and secondary heat exchange are determined.It is found that compared with the air quenched slag,the heat transfer thickness of gas-powder flow quenched slag is thinner,and the heat transfer time can be shortened by above 10%,which is conducive to improving the vitreous content of the granulated slag and reducing the cost of the equipment.