Multiphase Flow Numerical Simulation And Energy Consumption Prediction In Anaerobic Fermentation Plant

With the development and utilization of biomass energy,biogas projects are becoming more and more important.The energy consumption analysis of biogas projects can make more rational use of energy and solve the problem of high energy consumption in biogas projects.The anaerobic fermentation process is an important part of biogas engineering.In the anaerobic fermentation process,the most influential factor on biogas production is the control of the temperature of the feed liquid during the fermentation process.Therefore,based on this problem,this study uses the fluid simulation software Fluent to numerically simulate the biogas fermentation unit when analyzing the internal heat transfer problem of the fermentation unit.To simplify the calculation,the study simplified the interior of the fermentation unit into gas and liquid phases,and the biogas slurry(Ts=8%)is regarded as a uniform fluid.The heating method of the biogas fermentation device is simplified to upper and lower insulation,and the sidewall is isothermally heated.The temperature field in the biogas fermentation device is studied and compared by the combination of experiment and numerical simulation.The test determines the temperature distribution of the fermentation process by measuring the temperature data of different height layers during the heating process,and then obtains the temperature distribution field of the fermentation device.The turbulence characteristics of the feed liquid are described by using the Fluent numerical simulation software to select the k~? turbulence model.The Mixture model in the double Euler model is used to describe the multiphase flow in the fermentation.The solution method of SIMPLEC is used to solve the discrete equations,and the temperature field and velocity flow field in the static fermentation process are simulated.The simulation results are compared with the experimental data,then we analyze and determine the actual internal heat transfer of the biogas fermentation in the static fermentation process.On this basis,the energy consumption analysis software is used to predict the energy consumption of the enclosing structure and the liquid heating process of the fermentation plant in the biogas project,and explore the key aspects of energy saving in the biogas project.The main findings of this paper are as follows:(1)Based on the previous simulation of biogas fermentation,the fermentation mo del was further optimized,and the static fermentation in the fermentation process was numerically simulated.The temperature field results showed that during the biogas fe rmentation process,the edge was high,the middle was low,and the temperature diffe rence of the same section does not exceed 2K,and the temperature difference in the whole fermenter does not exceed 3K;(2)Build the same proportion of fermentation equipment,use the cow dung of a cattle farm in Harbin as the fermentation raw material,and carry out temperature detection.The test temperature monitoring results are consistent with the simulated temperature distribution results,and the temperature difference at the same position is compared.The results showed that there was no significant difference at the significant level of 0.005,indicating that the Fluent software is feasible in simulating the biogas fermentation process,and in the static fermentation process,the temperature difference in the whole fermentation device is small and the flow speed is very slow;(3)Based on the simulation results,a heat transfer model was established for the heating process of the feed liquid in the biogas project and the enclosure structure of the anaerobic fermentation device.For a biogas fermentation project in the cold northern region,the simulated energy consumption analysis software was used to simulate the energy consumption.The results show that the heat loss of the feed liquid is much greater than the heat loss of the enclosure structure of the fermentation plant,accounting for more than 80%of the energy consumption of the entire biogas project,indicating that the temperature rise process of the control liquid is the key link for energy conservation of the biogas project.