Study On Optimization Design Of Biogas Fermentation Tank In Xuzhou Area

Vigorously developing biogas technology is one of the effective ways to accelerate the construction of modern rural energy system with the goal of green,low-carbon and clean.In cold regions,the outside temperature is low in winter,and the decrease of biogas fermentation temperature will lead to the reduction of biogas gas production rate,which will affect the normal operation and economic benefits of biogas projects.It is urgent to conduct in-depth research on the temperature increase technology of biogas fermenters to promote the promotion and application of biogas projects in cold regions.By combining theoretical analysis,field measurement and numerical simulation,the temperature variation law of solar greenhouse and biogas fermenter in solar greenhouse biogas project was obtained,the calculation method of hourly heating load of biogas fermenter was determined,the optimization model of biogas fermenter temperature increase mode was established,and the temperature increase mode suitable for solar greenhouse biogas fermenter in Xuzhou was determined.The main results and conclusions are as follows:1)The heat transfer model of air and biogas fermenter in solar greenhouse was established.According to the actual situation of solar greenhouse biogas project,the simplified conditions of heat transfer process between solar greenhouse and biogas fermenter are determined,the heat balance equation of solar greenhouse and biogas fermenter and the calculation formula of solar radiation intensity received by solar greenhouse wall surface,soil surface and biogas fermenter are established.2)The temperature variation rule in solar greenhouse and biogas fermenter was obtained by field measurement.The variation trend of air temperature,wall inner surface temperature and soil surface temperature in the solar greenhouse is basically the same as that of the outside air temperature,which is greatly affected by the outside air temperature and solar radiation intensity.The stronger the solar radiation during the day,the higher the outside air temperature,and the higher the air temperature in the greenhouse,wall inner surface temperature and soil surface temperature.At night,because there is no solar radiation and the outdoor temperature is low,the air temperature in the greenhouse,the inner surface temperature of the wall and the soil surface temperature also decrease.The greater the soil depth is,the less its temperature is affected by the outside air temperature and solar radiation,the more gentle the temperature change is,and the influence on the soil temperature of 1m or less is small.The temperature in the fermenter is related to the outside air temperature and solar radiation intensity.The higher the outside air temperature is,the greater the solar radiation intensity is,and the higher the temperature in the tank is.During the whole test cycle,the temperature fluctuation in the biogas fermenter is small,within2℃.3)The CFD numerical simulation model of solar greenhouse and biogas fermenter is established.The temperature variation rules in solar greenhouse and biogas fermenter were obtained by numerical simulation.The absolute error between the numerical simulation results and the field measured results is less than 5℃,and the relative error is about 10%.The numerical simulation results are in good agreement with the field measured results,indicating that the numerical model is accurate and reliable.4)Considering economy and environmental protection,an optimization model of biogas fermenter temperature increase in solar greenhouse was established by using improved entropy analysis method.The hourly heating load of the biogas fermenter in the typical meteorological heating season in Xuzhou area was calculated by numerical simulation.Three different heating modes of biogas fermenter,namely,biogas boiler hot water cycle heating system,air source heat pump hot water cycle heating system and electric heater hot water cycle heating system,were optimized.The comprehensive evaluation value of the three heating methods is 0.33,0.29 and 0.38,respectively.The three heating methods of hollow air source heat pump hot water circulation heating system is better.This thesis has 50 figures,18 tables and 128 references...