The Study Of Influencing Factors On Dust Removal Efficiency Of Oil Shale Retorting Gas In Spray Scrubber

Oil shale retorting process will produce a lot of dust,while the traditional spray washing process is backward,which has the disadvantages of large energy consumption,large amount of circulating water and large amount of wastewater.Based on the traditional spray washing tower,this project has designed a multi-layer spray dust removal experimental device for water washing and oil washing.Compared with the traditional spray washing tower,the spray scrubber has high dust removal efficiency.It has the advantages of simple structure,small footprint,low investment and operating cost,and saving liquid working fluid.This paper took the spray scrubber as the research object.Firstly the characteristics of the dust particles used in the experiment were tested.Then the effects of inlet gas flow,inlet dust concentration,liquid gas volume ratio and nozzle layout on the washing efficiency of different size of dust particles were studied.Finally using the CFD numerical simulation method to study the spray scrubber under different working conditions,such as velocity distribution,pressure distribution and turbulence intensity distribution,while the impact of nozzle arrangement on the droplet size distribution was also studied.In the study of powder properties,the experimental dust particles had good fluidity,jet flow and wettability,and belonged to moderately hydrophilic dust.The particle size distribution was between 1μm to100μm,and the average particle size was 15.23μm.The surface morphology of dust particles was mainly spherical,and accompanied by other irregular shapes.In the experimental study of spray scrubber,inlet gas flow was the most important factor influencing the overall pressure drop of spray scrubber.The change of inlet dust concentration and liquid gas volume ratio had little effect on the pressure drop.The total dust removal efficiency of the spray scrubber was increased with the increase of inlet gas flow rate,inlet dust concentration and liquid gas volume ratio.When the inlet gas flow rate was 158.3m~3/h,the inlet dust concentration was 32g/m~3and the liquid gas volume ratio was 16.3L/m~3,the dust removal efficiency can reach to 98.7%.The washing efficiency of dust particles which size was less than3μm was decreased with the increase of inlet gas flow and inlet dust concentration,and was increased with the increase of liquid gas volume ratio.The cleaning efficiency of dust particles with a particle size of 3μm to 5μm was less affected by inlet gas flow and inlet dust concentration,while was increased with the increase of liquid gas volume ratio.The washing efficiency of dust particles with a particle size of 5μm to 15μm was increased with the increase of the inlet gas flow,inlet dust concentration and liquid gas volume ratio.In the CFD numerical simulation of spray scrubber,the velocity,pressure drop,and turbulence intensity in the spray scrubber were increased with the increase of the inlet gas flow.The increase of the inlet gas flow made the dust particles more evenly distributed in the washing zone,while the degree of mixing of the dust particles and the droplets was improved,and the collision probability of the dust particles and the droplets was also improved.When the double nozzle sprayed radially along the spray scrubber,it not only enhanced the disturbance and mixing between the dust particles and the droplets,but also prolonged the residence time of the dust particles in the washing zone,and could effectively improve the inertial effect,diffusion and interception of dust particles too.Compared with the single-nozzle arrangement,the Sauter mean diameter(SMD)of droplets was reduced about 10μm by the double-nozzle symmetrical arrangement at the same injection pressure,and the atomization uniformity was also improved.