Numerical Simulation Of Flow And Heat Transfer Characteristics Of Blast Furnace Slag Particles

In the production of electricity,steel,nonferrous metals,coal coking and so on,a large amount of waste heat will be generated.This part of the waste heat resources that could be utilized but abandoned is a secondary energy source.Rational use of waste heat resources can accelerate the realization of industrial energy conservation and emission reduction strategic goals.As the main waste in the steel industry,high-temperature slag has a temperature of up to 1400～1500℃,and its high-grade sensible heat resources have great recycling value.At present,the main treatment method of slag in domestic steel mills is used as raw material for cement after water quenching treatment,but the rest of the heat has not been recycled,and the treatment method will pollute the atmosphere and waste water resources.Therefore,the dry granulation waste heat recovery process has become the research focus in the field of slag treatment.Among them,the waste heat recovery device is a key part of the process system.The design of the process parameters of the self-flowing bed waste heat boiler has a decisive influence on the sensible heat recovery effect of the blast furnace slag.In this paper,the flow and heat transfer mechanism of blast furnace slag particles in a self-flowing bed waste heat boiler are studied.The essence of the process is the process of blast furnace slag particles around the tube bundle,including heat exchange between high temperature slag particles,high temperature slag particles and water wall,high temperature slag particles and gas.This paper establishes the flow and heat transfer model of the slag system.The EDEM-Fluent bidirectional coupling technology was used to simulate the flow and heat transfer of particles in a self-flowing bed waste heat boiler.The simulation results were compared with the experimental data in the literature to verify the accuracy of DEM-CFD coupling method to simulate flow and heat transfer characteristics.This paper focuses on the effects of tube type,slag particle diameter,tube bundle arrangement,model exit size and initial slag particle temperature on slag flow and heat transfer.The simulation results show that:(1)By arranging the half tube at the wall surface,the flow environment of the slag particles is changed,thereby improving the Coanda effect of the slag particle flow.The elliptical tube is beneficial to the mixing between the slag particles to improve the motion state,the overall cooling amount,cooling rate at the first three rows of tubes and the comprehensive heat transfer coefficient are the best,which is the best choice for improving the movement state and enhancing the heat transfer effect.(2)The decrease of the slag particle diameter has no effect on the trajectory curve of the slag particle and the dead zone,but increases the coordination number of the slag particle and the contact area with the pipe wall and reduces the film thickness,thereby enhancing the heat transfer effect.(3)The tube arrangement mainly affects the trajectory curve and flow pattern of the slag particles.When the fork rows are arranged,the S-shaped motion enhances the mixing among slag particles and increases the probability of contact with the tube wall surface,and the residual heat recovery effect is better.(4)The size of the outlet mainly affects the flow velocity of the slag particles.The larger the outlet size,the faster the flow rate of the slag particles,and the worse slag particles flow and heat transfer.(5)The initial temperature of the slag particles mainly affects the amount of radiant heat exchange.From the perspective of heat transfer effect,under the premise of ensuring granulation of blast furnace slag,increasing the slag particle temperature entering the waste heat boiler is beneficial to improve the recovery of waste heat.