Experimental Study On Continuous Separation Technology Of Catalyst Fine Powder In Slurry Bed Reactor For Fischer Tropsch Synthes

In the production and operation of Fischer-Tropsch slurry bed reactor,some catalyst particles with very small particle size will be generated due to wear and breakage of catalyst,which not only affects the filtration process in the reactor,but also increases the operation cost.In order to ensure the smooth separation process between catalyst and liquid paraffin,it is imperative to separate harmful catalyst fine powder in advance and recover effective coarse catalyst.At present,filtration method is often used to achieve this purpose,but in the actual process,the surface of the filter element will be blocked,so that the process is not continuous.Therefore,a continuous separation technology of hydrocyclone fine powder is proposed to solve the above problems.The main core of this technology is hydrocyclone.Firstly,the feasibility of the technology was verified,and the optimal structure parameters of hydrocyclone were obtained after the feasibility was verified.Secondly,the influence of the change of operating conditions on the separation performance of hydrocyclone fine powder was studied.Finally,the experimental study on the separation performance of medium physical parameters was carried out.In order to obtain the optimal structure of hydrocyclone separation performance,based on the characteristics of the hydrocyclone classification according to the plan in the feed flow rate Q is 4 m³/h,R_f bottom flow rate for 30%of the operating conditions,including 22μm as the critical particle diameter,inlet diameter di,the overflow tube diameter,do shell height h and the cone Angle of theta four structural parameters as the optimization goal,Three horizontal values were taken for each structure parameter,and the maximum Newton classification efficiencyη_N was used as the main evaluation index to carry out the orthogonal experiment.The optimal structure combination of hydrocyclones was determined by comprehensive range and variance analysis of the experimental results,that is,DN75 hydrocyclones had the best classification performance under the current experimental conditions when d_i=0.267d,d₀=0.373d,H=4d,θ=15°.The classification performance of hydrocyclones will be affected because the operating conditions will change with the production.After the optimal structure combination of hydrocyclones was determined,the optimal structure was verified by changing the feed flow Q of 2,4 and 6 m³/h and the bottom flow rate R_f of 20%and 30%under the operating conditions.The experimental results show that the Newton fractional efficiency increases first and then decreases with the increase of feed flow rate and bottom flow rate.When Q=4 m³/h and R_f=20%,the Newton fractional efficiency reaches the highest 58.9%.Finally,the effects of solid concentration（10%,15%,20%）and liquid viscosity（1cp,6cp,11cp）on the classification effect of hydrocyclones were tested by using this experimental device.Through the verification of the effect of physical properties,it was found that with the increase of viscosity and concentration,the removal of fine powder increased,but the recovery of coarse powder decreased significantly.By comparison,it was found that viscosity had a more significant impact on the classification efficiency than concentration.The pressure drop is also one of the important indexes to measure the classification performance of hydrocyclones,and the pressure drop is about 0.03 MPa in the experiment of the influence of operating conditions on the classification performance of hydrocyclones.The increase of concentration and viscosity had a slight effect on the pressure drop of the cyclone,while the change of underflow rate had no obvious effect on the pressure drop.The pressure drop varied from 0.017 to 0.077 MPa in the range of3-6 m3/h feed flow.This suggests that the technology is feasible in terms of reduced pressure,compared with the existing filter catalyst powder classification scheme,based on the optimization of the structure of the hydrocyclone separation scheme can successfully implement invalid catalyst powder for highly efficient separation,and realize the most effective catalyst recycling,economic benefit is remarkable.