Optimization Design Of Thermal Insulation Layer Thickness For Solar Biogas Fermenter In Xuzhou Area

Temperature is the main factor affecting the fermentation rate of biogas.In cold regions,the low outdoor temperature during winter leads to a decrease in gas production,which affects the normal operation and economic benefits of biogas projects.Heating and insulation are important technical measures to maintain the appropriate temperature in fermentation tanks during winter.The current methods for determining the optimal insulation thickness for fermentation tanks are not yet perfect and require further indepth research.By comprehensively applying theoretical analysis,field measurements,and numerical simulations,we have obtained the rules of temperature variation in solar biogas projects’ daylight greenhouses and biogas tanks and proposed a calculation method for the heat dissipation of biogas tanks,established an insulation thickness optimization model,and calculated the optimal insulation thickness for three insulation schemes of biogas tanks in Xuzhou area.The main research results and conclusions are as follows:1)The heat dissipation calculation model of biogas fermenter was established.According to the actual project,the heat balance equation of solar greenhouse and the heat balance equation of biogas fermenter are established on the basis of reasonable simplification of the hypothesis of solar greenhouse.The calculation method of solar radiation of solar greenhouse and biogas fermenter and the calculation method and solution method of heat dissipation of biogas fermenter based on the coupling solution of internal temperature of solar greenhouse and biogas fermenter are given.2)The rules of temperature variation in daylight greenhouses and internal biogas fermentation tanks have been obtained.Field measurements and numerical simulation calculations have been used to study the temperature variation rules in daylight greenhouses and internal biogas fermentation tanks.During the day,the stronger the solar radiation and the higher the outdoor temperature,the higher the air temperature in the greenhouse;at night,without solar radiation and with lower outdoor temperature,the air temperature in the greenhouse decreases accordingly.The temperature of each point on the wall surface varies with solar radiation intensity and outdoor temperature in the same way as indoor air.During the day,the temperature of the soil surface in the greenhouse increases with the increase of solar radiation intensity;at night,without solar radiation and dissipating heat to indoor air,the temperature decreases.The deeper the soil,the less affected the temperature is by outdoor temperature and solar radiation,and the more stable the temperature change.The temperature inside the fermentation tank is related to outdoor temperature and solar radiation intensity;the higher the outdoor temperature and solar radiation intensity,the higher the temperature inside the tank.The numerical simulation calculation and field measurement results show the same trend,with an average error between 5.9% and 8.2%,meeting the engineering accuracy requirements,and verifying the scientific and rational nature of the numerical simulation calculation scheme.3)A multi-objective optimization model for the insulation thickness of biogas fermentation tanks has been established.Calculation methods for the whole life cycle cost and savings rate of biogas fermentation tank insulation,whole life cycle carbon emissions and emission reduction rate,and energy consumption and energy-saving rate have been given.By considering the economy,environmental protection,and energysaving,a multi-objective optimization model for the insulation thickness of biogas fermentation tanks has been established,and the weights of each evaluation index have been determined.4)The optimum insulation thickness of different insulation materials in two insulation schemes of biogas fermenter was obtained.The heat dissipation of two insulation schemes for biogas fermenter with different insulation layer thickness and different insulation materials was obtained by numerical simulation,and the corresponding life-cycle cost and saving rate,life-cycle carbon emission and emission reduction rate,energy consumption and energy-saving rate were calculated.The functional relationship between the superiority degree of insulation schemes and the thickness of insulation layer was obtained by fitting.The optimum insulation thickness of different insulation materials in two insulation schemes of biogas fermenter was calculated This thesis includes 50 figures,16 tables,and 98 references.