The Performance Research On Solar And Power Waste Energy For Warming Biogas Plant Of Cogeneration System

The Sino-Dutch biogas plant combined heat and power supply system which the application of biogas internal combustion engine generates power at the same time applying waste heat power generation recovery warms and insulates the fermentation tower,gasholder and feedstock in the town of Gansu Holstein dairy cattle breeding center of Lanzhou City,Gansu Province.But the heat from the exhausted gas is not enough to preheat the feedstock and maintains the constant thermostatic anaerobic fermentation.In order to ensure the stability of biogas production for large and medium-sized biogas plant and solve the large span of temperature caused by the low ambient temperature in fermentation tower,in this paper,a solar energy and waste heat power generation recovery warming and insulation system have been carry out to guarantee the fermentation tower which can maintain s the constant temperature for anaerobic fermentation in different seasons.The principle of warming and insulation system has been elaborated and calculated the theoretical heat demand of the various parts of the system.After system improved,the recovery of the waste heat is used by applying the Organic Rankine Cycle(ORC)which enhances the overall efficiency of the system.The main contents and results are listed as follows:(1)Through the comprehensive analysis of the biogas plant,the analysis of the problem shows that the main heat loss in the biogas plant is the heat loss of the fermentation tower,the gasholder and the feedstock.In this process,the he at loss of the fermentation tower and the gasholder accounted for 5.9%-15.8% and others accounted for 84.2%-94.1%.The biogas plant at this stage only relies on the internal combustion engine power generation waste heat recovery system in the cold season can inadequately provide the required heat to the system.Only generator waste heat recovery system does ensure the biogas plant in the summer to maintain constant temperature anaerobic fermentation in 37℃,but biogas engine waste heat recovery system can inadequately meet the fermentation system at the appropriate temperatu re fermentation in other seasons.(2)After biogas fermentation system improved,adding a solar energy to the entire system for warming and insulation.The result shows that the biogas power generation plant needs 7531.9 MJ·d-1 for warming,while the solar energy and waste heat power generation recovery warming and insulation system generates 7623.4 MJ·d-1,which is total able to meet the heat demand of the whole system.Thus,the temperature of the fermentation tower could be maintained at 52 ℃ in summer and 37℃ in other seasons.The required solar energy area is 256m2 and the total solids content of fresh cow manure is 27.5%.The daily re quirement feedstock is 40 m3.When total solid of the fresh cow dung is diluted from 27.5% to 8%,the volume of water is 28.4 m3.The average temperature of water in Lanzhou is about 0.5℃ in January and the temperature of solar collector outlet water tempe rature is 50℃.In this situation,the volume of water from the solar energy collector is 3.6 m3 and the volume of water is 24.8 m3.(3)Based on the principle of temperature matched and cascade utilization,proposing to use the Organic Rankine Cycle for recycle the waste heat of low temperature exhaust gas.The result shows that power generation efficiency and exergy efficiency of the whole system are 8.17 % and 54.16%,respectively;when the whole system introduces the regenerative cycle,the power g eneration efficiency and exergy efficiency of the system are 9.42% and 62.61%,respectively;compared to the previous system,the power generation efficiency and exergy efficiency of the system increase by 1.25% and 8.45%,respectively.(4)Combined the solar energy with waste heat power generation recovery,this measure can not only enhance the sufficient heat for the biogas plant,but also using of low temperature exhaust gas by the Organic Rankine Cycle can make the system show environment-friendly,high efficiency and so on.The noverty of this paper are listed as follows:(1)The combined heat and power(CHP)system driven by solar energy and biogas and biogas internal combustion engine is as the center of t he thermal power supply system to solve the problem which heat supplement of large and medium-sized biogas plant is insufficient in northwest.(2)Based on the principle of "temperature matched and cascade utilization ",in this paper,using the Organic Rankine Cycle to recycle the waste heat power generation recovery in biogas plant which significantly improves the energy efficiency of the whole system.