Design Of Vertical Aerobic Composting Reactor And Study On Composting Performance

A vertical aerobic composting reactor with forced ventilation was designed to solve the problems of poor uniformity of compost maturity caused by uneven agitation of aerobic composting reactor and the lack of thorough research on the rule of microbial evolution in composting process,fluent was used to simulate and verify the material flow field in the course of mixing.The spatial distribution characteristics of compost maturity and the evolution of microbial community during composting were analyzed to provide reference for practical composting of organic solid waste.The effective volume of the vertical aerobic composting reactor was 1 m3,with three paddle blades(the middle of the blades is inclined to the end 45°),a 50 mm insulation layer on the outer wall and a 10 mm aeration screen at the bottom.The diameter of the reactor was 1100 mm and the height was 1350 mm,the diameter of stirring shaft was 50mm,the diameter of stirring blade was 850mm,the diameter of feeding port was 400mm,the diameter of discharging port was 260mm,the diameter of sampling port was 60mm.The flow field in the reactor was simulated by Fluent software,and the results showed that the movement state of the material was consistent with the actual situation,and the reverse axial circulation movement of the material could be improved at 45° inclination of the blade,and the material homogenization could be realized in the process of composting.The reactor performance test was carried out with the mixture of Lentinus edodes residue and fresh chicken manure with the mass ratio of 4:1.The temperature of the middle-layer compost reached above 55℃ in the high-temperature period firstly,followed by the upperlayer compost and the lower-layer compost,the duration of the high temperature period was up to GB7959-2012,the content of O2 was between 13.1%and 20.02%,and the germination index of lettuce seeds in the upper and lower layers reached 80%first than that in the middle layers,at the end of composting,the germination index of the upper,middle and lower layers was 112.03%,112.03%and 109.46%,respectively There were no significant differences in pH,VS,TN,TC,P,K,EC,C/N,temperature,O2 content and CO2 concentration of the three-layer reactor(p>0.05).In addition,the pH value of each layer was between 5.5 and 8.5,and the contents of heavy metals(Cu,Zn,Cr,Pb and Cd)met the national agricultural organic fertilizer standard.In the composting process of mushroom residue and chicken manure,the dominant bacteria of upper layer are Tuberbacillus,Parapedobacter,Paenibacillus,the dominant bacteria of middle layer are Tuberibacillus,Parapedobacter,Pseudoxanthomonas,and the dominant bacteria of lower layer are Kurthia,Parapedobacter and Sphingobacterium,all of them were Methanobravacter,Methanocorpusculum and Candidatus_Methanoplasma.The archaea of upper layer were not detected after 13 days,middle layer was not detected after 19 days,and lower layer was not detected after 28 days.Parapedobacter and Moheibacter were positively correlated with O2,pH,GI and TN,Bordetella was most correlated with pH,Paenibacillus was most correlated with pH,Weissella,Bacillus and Lysinibacillus were most correlated with CO2 and temperature.At genus level,Bacillus is most closely related to EC,CO2 and TEMP,and Acinetobacter was most closely related to VS,MC,TC and C/N.