Theoretical And Experimental Research On The Air-Cooled Waste Heat Recovery For Furnace Slag

In the blast furnace ironmaking process, the furnace slag is discharged at the temperature up to about 1350℃-1450℃, containing a lot of high-temperature sensible heat. Per ton of slag contains about (1.26 ~ 1.88)×10~6kJ of the sensible heat, which is equivalent to the heat released by 45-60kg standard coal. Nowadays, most of the steel enterprises adopt water to flush slag, which leads to the waste of the heat reserved by the slag, result in the consumption of the fresh water and the air pollution; additionally, the temperature of the gas supply is still maintained at the low level of 1000℃in our country, it is the pinch of exotic gas that confines the temperature improvement, so it is imminent to put forward a scheme to preheat the gas preceding the hot-air furnace to advance the temperature of the gas, which will improve the smelting furnace intensity and reduce the focal ratio.In response to the status, based on the research in the field of the slag waste heat recovery at home and abroad, the scheme that recover the slag waste heat to preheat the gas based on the fluidized bed was put forward in the paper. The scheme not only could recover the slag waste heat to heat the gas, but also make up the current disadvantage of the single heat source and low-temperature gas supply, and avoid the consumption of fresh water and air pollution.Theoretical and experimental research were carried out in the paper to work out the key basic theory of this program, which focuses the heat and mass transfer accompanied by the process that high-temperature blast furnace slag particles are cooled by air stream, and the key issue is resolved. The contents of the paper are followed.(1) Based on the research at home and abroad, the scheme that recovers the slag waste heat to preheat the gas based on the fluidized bed was put forward in the paper, the scheme and the structure of the fluidized bed heat exchanger were designed. The special structure can recover the waste heat efficiently and also could avoid the disadvantage emerged in the flush slag process, with high economic and environmental benefits. (2) The key equipments of the scheme were designed and calculated for the special high-temperature characteristic of the slag, and the accessories ,include the cyclone separating device and so on were designed in the scheme.(3) The physical model of slag particle of different stage was builded to analyze the spatial distribution of slag particle and the interaction force of particle- particle and particle-gas; the flow,heat transfer and mass transfer model for dense gas-solid multiphase was established to research the heat transfer process under a specific flow field.(4) Based on the numerical calculation, a high precision multi-function test bench for fluidized bed was built. The experimental measurement and control hardware and software systems were designed based on virtual instrument (LabVIEW).(5) Carry out the experimental research based on the platform, both cold and hot conditions were studied respectively for each condition, according to the factor both flow velocity and particle size, and obtain the best combination.