Research On A Novel Waste Heat Recovery Equipment For Blast Furnace Slag And Heat Transfer Numerical Simulation

Blast furnace slag is the main by-product during the process of steel production. It contains rich resources of high-grade sensible heat. As blast furnace slag is discharged at the temperature of about 1450℃, there is (1.26~1.88)×106kJ/ton sensible heat can be recovered if it is cooled to room temperature. It is obvious that the recovery of the sensible heat can save a lot of energy. How to recover the sensible heat will be a major research topic of energy reserving.Nowadays most of the steel enterprises at home adopt water quenching process to treat blast furnace slag, and then use the treated slag as aggregate for concrete making. There are many shortcomings during the course of processing. Firstly, the sensible heat have not been recovered, secondly, the water quenching process discharges harmful gases into the air ,such as hydrogen sulfide, sulfur dioxide and others which finally cause environment pollution, thirdly, the water quenching process would be a waste of a large amount of new water.Compared to water quenching process, the advantages of dry slag waste heat recovery technology is obvious. First, less consumption of water resources, second, less emissions of air-pollution gas, third, high-grade heat can be recovered, fourth, a huge water quenching system can be omitted and replacing it with an economical dry slag waste heat recovery system.Although it is far from industrial applications, it meets the steel industry development trend of energy-saving and environmental protection. It is of important significance for domestic water and energy shortage station.In response to the status quo, a high recovery efficiency technique which is based on the fluidized bed for blast furnace slag waste heat recovery is put forward in this paper.Main contents discussed in this paper are as follows: Firstly, a novel type of fluidized bed structure used for heat transfer process in the technology of blast furnace slag waste heat recovery is proposed. It is designed to use minimal amount of air flow state so as to raise the air temperature at the exit.Secondly, dense gas-solid two phases flow mechanism based on the fluidized bed is discussed. This paper focuses on the mechanism of momentum transfer and heat transfer between air and high-concentration granulated slag particles by means of CFD numerical simulation (using Eulerian multiphase model). By changing the three control parameters of the slag exit size, slag flow rate and air flow velocity, we aim at exploring the control parameters' relationship with the slag volume fraction, fluid height, heat transfer coefficient, and their impact on the air outlet temperature, heat recovery amount and heat recovery efficiency.Thirdly, a prototype was produced for the experimental study of blast furnace slag waste heat recovery.The results show that when the width of slag outlet between 0.005m and 0.015m, the slag flow amount between 3.3912ton/h and 10.1736ton/h, air flow amount between 6.12m3/h and 8.16m3/h. That is, the slag velocity between 0.1m/s and 0.3m/s, and the air velocity between 3m/s and 4m/s, the heat recovery efficiency can be above 60%.