Study On The Biogas Project Based On The Analysis Of Exergy Consumption

In northern cold regions,due to the low natural environment temperature,in order to ensure the normal and continuous operation of biogas projects all year round,it is necessary to consume energy,and heating the fermentation raw materials and anaerobic fermentation reactor through the heating system to maintain the required temperature for fermentation.How to utilize energy sources and improve the energy utilization rate of biogas project heating system in an effective and rational way is a realistic problem for biogas engineering to achieve low energy consumption and high production capacity,which is also in urgent need of being solved.Comprehensively analyzing the thermal energy loss of biogas projects throughout the year and exploring their distribution rules are the basic conditions for achieving the energy saving goals of the biogas project heating system.In this paper,based on the effective heat transfer coefficient method,a calculation model of heat loss of biogas project is established,and the model is applied to a anaerobic fermentation biogas project in Harbin City,Heilongjiang Province.On the basis of the monthly heat loss of the biogas project,using the exergy analysis method and the energy level analysis method,from the aspects of the use of energy value and whether the energy quality is reasonable,analyzing the energy consumption of the five types of biogas heating systems including: coal-fired boiler heating,biogas boiler heating,groundwater source heat pump heating,solar heating and electric heating film heating.The subject overcomes the research method in the calculation of energy consumption of anaerobic fermentation reactor,without taking into account the heat loss of solar radiation heat and sky radiation,making the calculation inaccurate.As well as,in the past biogas engineering heating system energy consumption analysis,only based on the first law of thermodynamics,the thermal efficiency as an index of energy consumption evaluation,did not consider the defects in energy quality utilization.On these basis,the conclusions obtained in this study are as follows:Through the calculation and analysis of the biogas project,I obtained the thermal energy loss of the fermentation liquor temperature rise and the thermal energy loss of the anaerobic fermentation reactor in the whole year of the biogas project.In the total thermal energy loss of anaerobic fermentation reactors,the proportion of heat transfer and heat consumption of the anaerobic fermentation reactor envelope structure is about 70%~90% of the total heat consumption.The key to energy saving of anaerobic fermentation reactor is the energy saving of the envelope structure.In the total heat loss of biogas projects,the ratio of heating energy consumption to the total energy consumption of biogas projects in each month is about 85%~95%.It showed that the energy consumption accounts for the vast majority of the total energy consumption of the biogas engineering,the weak link in the energy consumption process of the biogas engineering heating system,and the recovery of the waste heat from the biogas engineering to discharge the biogas liquid,which is beneficial to the energy saving and consumption reduction of the biogas engineering.Through the comparison and analysis of the production capacity and total heat energy loss of the biogas project for each month,the results showed that the proportion of the energy consumption of the biogas project in Harbin is about 15%~37%.Under the condition of normal medium temperature anaerobic fermentation,the capacity of biogas engineering is far greater than the loss of heat energy,which indicated that it is possible to realize the positive output of the biogas project in the cold regions of the north.Based on the theoretical analysis of exergy analysis and energy level analysis of biogas projects and the calculation of annual heat loss of biogas project,conducting exergy analysis and energy level analysis for different biogas projects.The results showed that the efficiency of the heating system of the five biogas projects is about 2%~7%,and the exergy efficiency between the heating system of the biogas project and the user system is between 0.39~0.85.The efficiency of the heating system of biogas engineering is low.The reason is that the energy level difference between the heating system of biogas engineering and the user system of biogas engineering is larger,and the task of using high grade can be used to complete a low grade heat energy,which makes the process of energy supply and energy use between the two sides unreasonable.Compared with the other 4 heating methods,the underground water source heat pump heating system has the largest efficiency and energy saving advantages.