Research On The Analysis And Utilization Method Of Waste Heat In Vehicle Biogas Plant

The vehicle biogas plant,that has aroused attention from all walks of life,has a broad development prospect,because it can dispose organic waste and produce clean Bio-CNG at the same time.However,it still has problems such as higher energy-consuming and higher operation cost.Higher utilization efficiency of waste heat can effectively reduce the energy-consuming and operational cost.There are less research on analysis and utilization of waste heat in vehi cle plant.Therefore,this paper build a set of research method of waste heat analysis,calcul ation and utilization based on investigation and literature.On the basis of this method,a 10000m3/d engineering model is analyzed.The main research contents and results are as follows:(1)For the engineering analysis of waste heat,this paper firstly introduced general situation,processes,the basic energy using and heat resources and heat users,and so on,pointed out waste heat distribution.Secondly,the comprehensive statistical analysis of the systemic waste heat resource was conducted,the main statistical contents included medium of waste heat,distribution,temperature and flow rate.Finally,the waste heat characteristic of vehicle biogas plant were summarized,and its availability of waste heat was evaluated.Results show that the waste heat mainly include waste heat of stripper top gas,waste heat of poor liquid,waste heat of compressor cooling water,waste heat of biogas slurry and waste heat of boiler exhaust gas.(2)For the engineering calculation of waste heat,on the basis o f industrial waste heat calculation model,calculation model of waste heat potential was established in vehicle biogas plant.Calculation model of waste heat energy-saving potential was established combining with the systemic requirement heat.Calculation model of recycling waste heat was set up by analyzing the way of waste heat recovery,which lay a foundation for establishment of waste heat utilization plans.The analysis of waste heat showed five kinds of waste heat could be recycled by heat exchanger and heat pump.(3)For the engineering utilization of waste heat,the utilization plan of waste heat was established by using the pinch analysis method which mainly add or reduce heat exchanger for the current heat exchange network,the energy-saving rate could be calculated.Secondly,the heat exchange network was optimized through the heat pump technology,which could recycle the unemployed waste heat.Finally,combined with the optimization of waste heat utilization plan,the target model of energy-saving analysis and economic analysis were established.(4)A 10000m3/d bio-CNG engineering model was established by investigated domestic typical vehicle biogas plant.Applied the established method of waste heat analysis,calculation and utilization,analysis of waste heat showed that this kind of project need consume a lot of energy,accounts for 30.01% ~ 36.44% of total capacity.These low grade waste heat was mainly composed of waste heat of decarbonizing stripper top gas,waste heat of poor liquid,waste heat of compressor,waste heat of biogas slurry and waste heat of boiler exhaust.Calculation of waste heat showed that systemic potential of waste heat were respectively 5.87×104MJ/d,4.79×104MJ/d,the largest energy-saving potential of 74.81% and 73.92% at hottest and coldest month respectively.The utilization plan of waste heat was established by using the pinch analysis method and heat pump integration.The results of pinch point analysis showed pinch point temperature was 50?,the minimum heating load was 234.02 k W,the minimum cooling load was 201.25 k W,maximum energy-saving rate was 60.19%.Energy-saving rate after heat exchange network optimization was 19.75%,energy-saving rate after heat pump integration was 16.25%,the total energy-saving rate was 36.00%.Economic analysis showed that the maximum energy-saving income was 661.82 thousand RMB/y,the minimum extra cost was 2.71 million RMB/y,the minimum investment recovery period was 4.1 years after the system was reformed.The innovation of subject lies in:1)In order to improve the waste heat utilization efficiency,reduce the energy consumption and running cost of the vehicle biogas project,a set of research methods of waste heat analysis,calculation and utilization was set up,which can provide reference for the related research.2)Combined with engineering research,a engineering model of daily biogas production of 10000 m3 was built.Through the analysis and calculation of waste heat,the distribution and potential of waste heat were clarified,and the waste heat utilization scheme was designed by using pinch analysis and heat pump technology.The economic and feasibility of the scheme were researched for the sake of ensuring this scheme rightness.