Experimental Study On The Performance Characteristics Of Cyclone In Biomass Pyrolysis System

This paper first introduces the importance of developing the new energy, biomass energy development and utilization, then introduces studies on the biochar removal technologies from the biomass pyrolysis vapours. Cyclone is one of the most widely used dust removal devices in many applications, for the pyrolysis of biomass process, however, the working conditions are quite different from others. The operation temperature is high, usually higher than400℃, the concentration of biochar in the pyrolysis vapor is high, particle sizes are small ranging from2to300μ m, and the pyrolysis vapours are sticky, etc. All of these will affect the quality of the final product biooil.In order to determining the optimal operation parameters of cyclone used for biochar removal in the pyrolysis of biomass, a cyclone experimental apparatus was developed and tested in the laboratory. The experimental apparatus consists of an air blower, electric heater, biochar feeder and two cyclones connected in series. In order to simplify the study, heated air was used as the flow media instead of pyrolysis vapours and the biochar powder obtained from the pyrolysis of corn stalk powder in a fluidized bed pyrolysis reactor in our lab was added into the air for the experiment. Factors studied include air temperature (20℃,100℃), inlet air velocity (8-25m/s), concentration of biochar (40-200g/m3), shape of cleaned air outlet (cylindrical, horn-shaped), cleaned air outlet length to gas inlet height ratio (S/A)(1.23,1.96),and order of two cyclones (standard-diffusion, diffusion-standard) were considered in this study.Biochar, the solid product from biomass pyrolysis, was used in this study. In order to control the concentration of biochar in the air, a preliminary experiment about biochar feeder were conducted before the experiment and the relation curve between biochar feeding rate and the feeder rotating speed was determined.The experiment results showed that1) the separation efficiency of the first cyclone was higher than that of the second cyclone; the mean particle sizes collected in the first cyclone, second cyclone, and the air bag were90.29μ m,9.57μ m and3.09μ m separately;2) the separation efficiency of and pressure lose of first cyclone at the inlet gas temperature of20℃were a little higher than that of100℃;3) the separation efficiency of first cyclone increased in the beginning and then decreased as the increase of inlet gas concentration of biochar, while the pressure loss remained constant. When the concentration was140g/m3, the separation efficiency reached the maximum.4) the separation efficiency of first cyclone increased in the beginning and then decreased as the increase of inlet gas velocity, while the pressure loss increased too. When the velocity was20m/s, the separation efficiency reached the maximum;5) the separation efficiency of cyclone with cylindrical cleaned air outlet was higher than that with horn-shaped. The pressure loss of cyclone with cylindrical cleaned air outlet was higher than that with horn-shaped;6) when the cleaned air outlet length to inlet height ratio (S/A) was1.23, a higher separation efficiency of cyclone was observed.