Research On Flow Filed And Kinetic Model Of Dynamic Aerobic Fermentation Equipment Based On Microbial Degradation

Among the many ways to disposal of kitchen waste,aerobic compost is the cheapest way to recovery of nutrient resource,which with the simple operation,well reduction effect,lowest pollution to environment.Now day many researchers pay more attentions to the development of small scale of aerobic compost to avoid the problem of large scale of aerobic compost.The topic builds a small scale aerobic composting reactor basing on the novel compound microbial agent for degradation of kitchen waste,which was isolate by our group.In the otherwise,in order to optimize the stirrer structure,mixing speed,a stirred model and porous medium model has been established to study the performance of flow filed.In this paper,aerobic compost kinetic model which base on microbial growth kinetics,stoichiometry and mass-heat conservation,has been established to control and optimize the ventilation and initial moisture of compost.The topic is derived from Shandong provincial Key Research and development project in 2019,which is "The development of efficient degradation kitchen waste disposal equipment based on the novel compound microbial agent".In this study,a small aerobic compost reactor is used as research object,in which apparent viscosity and the power-law model are used to describe physicochemical properties and the fluid properties of kitchen waste in the mixing model.The results show that the proportion of dead zone,mixing effect,average velocity of double helical ribbon-screw structure is better than double helical ribbon structure.In the same structure,with the stirring speed increasing,the proportion of dead zone is reducing,the average velocity of substrate and the power consumption is increasing.Therefore,50rpm and the double helical ribbon-screw structure are chosen as experimental and simulation parameter in this paper.The structure of reactor and the physicochemical characteristics of the compost substrate are incorporated into the compost kinetic model by porous medium model in this paper.The oxygen correction models have been detailed described to choose the best model,which can take the higher consistency and predictability accuracy in the whole composting process.In order to correct and optimize the oxygen correction in the compost kinetic model,the CFD software FLUENT is chosen to solve performance of oxygen concentration diffused filed in porous medium with different ventilation process.In order to get the satisfactory fittings of kinetic model to experimental data,our group has built a satisfied small scale aerobic composting equipment,in which many experiences will be carried out.The temperature of composting equipment is monitored during composting,then it will be compared with the results of the kinetic composting model.The accuracy of the aerobic composting model is quantitatively described using the root mean square error,the coefficient of determination,and the standard root mean square difference.The results show that the root mean square error is RMSE=1.9932K,the coefficient of determination is R2=0.89,and the standard root mean square error is NRMSE=0.0420,which meet the accuracy requirements.Based on the kinetic model of aerobic compost,the ventilation rate and the initial moisture content of the substrate are simulated.The results show that due to the high initial moisture content of kitchen waste,it is beneficial to diffuse oxygen and increase the composting rate when the ventilation rate increase appropriately.But when the ventilation is so high that the composting lost a lot of heat,the water content of substrate loses rapidly and the substrate degradation rate,composting rate reduce rapidly.On the other hand,when the moisture content was so high that the ventilation and oxygen supply were hindered,the fermentation temperature is difficult to rise,and the reactor is in a low oxygen environment,resulting in anaerobic fermentation,which is not conducive to the metabolism of aerobic microorganisms and reduces the quality of compost products.It is important that adjusting the parameters such as the moisture content of the substrate with bulk agent,before the moisture content of the substrate reach an appropriate range satisfied to aerobic compost.The results show that the optimal range of moisture content is 55-65%,and the optimal range of ventilation rate is 0.9L/min/kgOM.