Experimental Study On Gas-solid Two-phase Flow And Drying Characteristics In Spouted Bed With Swirl Nozzle

This paper focuses on the influence of inlet gas swirl effect on the flow field of spouted bed.The swirl nozzle is installed at the inlet of spouted bed to accumulate the gas-solid two-phase contact area,increase the radial disturbance between two phases in the bed,and ensure the regular three-zone flow.Meanwhile it can significantly improve the overall drying efficiency of the bed and reduce energy loss.In order to compare the material handling efficiency more comprehensively between two structures spouted bed,the experimental verification through two stages will be carried out in this paper.First,using PIV(Particle Image Velocimetry)technology to carry out the cold model experiment of the bed.The high-energy laser highlights the transparent particles in a cross section of a fountain area.Then the software records and analyzes the movement behavior of astigmatic particles.The results show that: after the improvement of conventional spouted bed,that is,installed a swirl nozzle at the entrance,the height of the fountain zone is reduced under the same working condition,but its radial range is significantly increased.The velocity distribution on the plane is more uniform,and the energy loss due to bed vortex and internal friction is reduced.The smaller the spouted bed burden,the greater the strengthening effect.But at the same time,energy consumption increases.Furthermore,combined with the hot air-drying technology,this experiment will research the different performance,the drying efficiency change between the swirling bed and the conventional bed under different particle diameters,different filling heights and different gas temperatures.The results shows that: within the temperature scale studied in this paper,the drying efficiency of the bed increases with the increase of the gas temperature,and reaches the highest level when T=70 ℃;the drying effect reach the best when d=1.5 mm,increasing or decreasing particle diameters have a negative effect on drying efficiency;with the increase of bed filling mass,drying time increases.But it can be observed that when m=66 g,the material treatment efficiency per unit time in spouted bed is higher,the average drying efficiency is higher,and the drying energy consumption is lower.So appropriately increasing the bed filling load in the swirling spouted bed can promote the overall drying effect.In summary,no need to complicatedly modify the structure,the spouted bed with swirl nozzle can preserve the basic three-zone flow.The inlet gas rotates in the swirl nozzle,introduced swirling effect into the spouted bed.It changes the velocity and volume distribution of the inlet gas in the three-dimensional space,increases the gas-solid interfacial radial disturbance,and optimizes the mass transfer,heat transfer,and momentum transfer efficiency between three phases in the bed.Under the same conditions,compared with the conventional spouted bed,the activation energy of the drying process in the swirling spouted bed increases,the drying time shortens,the drying rate increases,the water diffusion in the bed accelerates,and the unit energy consumption decreases.