Study On Drying Of Heat Pipe Assisted Heat Transfer In Pneumatic Spouted Bed

China is rich in oil shale reserves.As an alternative energy material for oil,oil shale has great application potential in the future,which has great strategic significance for the efficient development and utilization of oil shale.Due to the large water content of oil shale,it is not conducive to its large-scale development and utilization,so the dehydration pretreatment of oil shale has become the focus of attention.Based on the traditional combined drying of pneumatic spouted bed,the heat pipe structure was added to the drying equipment,and the pneumatic spouted bed heat pipe assisted heat transfer drying equipment was developed.With the combined action of spouted gas and heat pipe structure,the material flow and drying in the annular gap of spouted bed are enhanced.In this paper,the hydrodynamic characteristics and drying characteristics of the pneumatic spouted bed assisted by heat pipe were studied experimentally and numerically.The experimental results of hydrodynamic characteristics show that the pressure drop of the flow spouted bed assisted by heat pipe is lower than that of the traditional pneumatic spouted bed.The influence of heat pipe on the low bed is great,and the traditional spouted bed stability law can not be formed under the condition of multiple heat pipes.The maximum spouting pressure drop and minimum spouting velocity decrease with increasing the number of heat pipes.When 12 or less heat pipes are added,the sudden change of pressure drop shows that the pressure drop increases twice,but decreases gradually,and the transition gas velocity of sudden change of pressure drop increases gradually.When the number of heat pipes is more than 12,the sudden change of pressure drop becomes a secondary decrease,and the spouting becomes more unstable.When the number of heat pipes is 12,the bed pressure drop is small and stable,which is conducive to spouted bed operation.There is no sudden change of pressure drop when the bed is low,and the pressure drop decreases gradually when the gas velocity is high.There is no obvious secondary sudden change of pressure drop for small particles in different beds.The difference of the maximum spouting pressure drop under different air intake modes is 280 pa.The results show that the maximum spouting pressure drop of intermittent feeding is 17.6% higher than that of continuous feeding,and the apparent gas velocity of 0.88m/s is the change point of flow pattern under the two feeding modes.The results of numerical simulation show that the circulation of particles in the flow field is affected by the heat pipe,and the particle velocity is higher when the particles enter the annulus in the fountain area.The results show that the wall condition of the heat pipe has a great influence on the flow field.The increase of the specularity coefficients increase the diameter of the injection zone,and the particle velocity in the annulus changes obviously.The elastic coefficient of restitution between particles has a significant effect on the vertical distribution of solid phase in the bed,and the granular temperature increases with the increase of the coefficient of restitution.With the increase of restitution coefficient,the granular temperature increases.The experimental results of drying characteristics show that the dehydration efficiency of oil shale is improved by heat pipe.The drying time of 12 heat pipes was shortened by 14.29%and the moisture removal rate was increased by 4.25%.Bed height,gas temperature and particle size have great influence on the drying of oil shale,while gas velocity and initial moisture content have relatively small influence.Under the condition of continuous cross domain circulation,it takes about 90 minutes to dry all materials without heat pipe,and the heat pipe assisted drying time is reduced by about 11.11% under the same conditions.