The Cold Experimental Study Of Combined Fluidized Bed Waste Heat Recovery Device For Wide Slag Particle Size Distribution

Blast furnace slag is the main by-product during the process of iron and steel production.Large amount of blast furnace slag is emitted with extremely high discharge temperature,and it is a significant high-grade waste heat resource.Nowadays,blast furnace slag is treated by water quenching,which has many remarkable shortcomings as large water consumption and low heat recovery.Therefore,it is urgent to develop dry slag granulation technology.Among the dry slag granulation technologies,centrifugal granulation integrated with heat recovery has been recognized as the most promising method for slag treatment.Thus,the research on the centrifugal granulation integrated with heat recovery is of great significance to realize the energy saving and industrial upgrading for iron and steel industry.The centrifugal granulated particles have the characteristics such as wide particle size distribution,different particle size with difference quality and large particles etc.Therefore,a technical idea of particle separation and stepped cooling process has been proposed.And the combined fluidized bed waste heat recovery device has been designed and constructed.In this work,the hydrodynamic characteristics and particle separation characteristics on quasi-rectangular spouted bed,which is the basic component of gas-solid heat exchange device,were experimentally studied.The effects of static bed height,taper angle,particle size distribution on the hydrodynamic characteristics were studied.And the effects of separation partition height and the operating air speed on particle separation and distribution characteristics have also been experimentally studied.Besides,the ability of the combined fluidized bed gas-solid heat exchange device in the continuous operation conditions have been studied.The main contents and conclusion of this paper include:(1)Study on the fluidization characteristics of wide slag particle size distribution in quasi-rectangular spouted bed.It can be seen that three flow regimes,fixed bed regime,partially fluidized bed regime,spouting bed regime,successively appear.It is found that Umf,and U sp increased with the increasing of static bed height,taper angle and mean particle dimeter.Based on the results,the calculation model and empirical correlations have been established.The proposed model and empirical correlation have a good capability to predict the experimental values.(2)Study on the distribution characteristics of slag particles separated by quasi-rectangular spouted bed.For operational conditions,it can be found that the slag particles entering the subsequent bubbling bed were more likely to accumulate in the vicinity of the spouted bed.When the height of the baffle increases,the maximum mass concentration of the slag will move further.The average particle size distribution of the slag particles showed a certain randomness,and the average particle size of the slag particles at 6 cm was the maximum,and the mass percentage of the coarse slag decreased with the increase of the transverse distance.While the height of the partition and the operating wind speed have little effect on the change of the mass percentage of the coarse slag.(3)Study on the of combined fluidized bed gas-solid heat exchange device in the continuous operation conditions.the separation mass flow rate decreased with the increase of the height of the partition and the decrease of the operating air speed,and the average particle size of the slag retained in the spouted bed bin are larger than that of slag particles entering the subsequent bubbling.Besides,with the decrease the height of the partition and the increase in operating air speed,the separation efficiency increases.The separation efficiency of each particle size particle increases with the increase of air speed and the decrease of the height of the partition.The efficiency of classification with particle size greater than 4 mm is very low,and the slag with particle size less than 1 mm is large.And the particle size of slag emitted in the spouted bed is larger than that of the left and right bubbling beds.The results showed that the combined fluidized bed gas-solid heat exchange device can realize particle separation and stepped discharge process.