Study On Themostatic Biogas Production Plant Heated By Solar Energy And Waste Heat Of Exhaust Gas

For the sake of solving the shortage of heating which leads to the reduction of overall capacity in the biogas production of large and medium-sized biogas plants in winter of the north, a themostatic biogas production plant heated by solar energy and waste heat of exhaust gas has been constructed. The plant utilizes solar energy and waste heat of exhaust gas to realize complementary warming for biogas plany with the link of heat and mass recycling of biogas slurry to recycle the heat in biogas slurry warming feedstock. The construction of the system can provide a reference solution for the problem of low yield and high heating cost existed in large and medium-sized methane plant during the cold season of northern winter. The topic main research contents and results are as follows:(1) Choosing Huazhuang biogas CHP plant which has run for 10 years in Honggu District of Lanzhou city, Gansu Province as a topic. It can be found through analysis of its operating data that the generator efficiency of biogas plant is about 30%, the waste heat utilization rate is almost 33% which is 17% lower than the design condition of 50%. Low temperature in winter leads to the decrease of temperature of feedstock and the increase of heating load for fermentation. The heating of waste heat of exhaust gas cannot only maintain thermostatic fermentation and the drop of fermentation temperature may seriously affect the system production. Building themostatic biogas production plant heated by solar energy and waste heat of exhaust gas combining with heat and mass recycling can maintain the themostatic fermentation to improve productivity.(2) To study the heating effect of solar thermal collector arrays of plant in winter, Choosing collector arrays consisted of 55 all glass vacuum tube solar thermal collectors. Thermal performance tests for single collector covered by dust and daily average efficiency and average heat loss factor have been done. The results show that heat-collecting temperature and daily useful energy of single collector covered by dust one day is 5.6℃ and 2.135 MJ lower than collector covered without dust; The influence of accumulated dust to efficiency of collectors is a negative correlation. As dust accumulated for 6 days, the daily useful energy of collector without dust is 2.53 times as much as the collector covered by dust for 6 days. Collector located in the front row may shade the collector area in the back to reduce the daily useful energy. So dust and shade will double influence the daily average efficiency. Daily useful energy of the collector not influenced by dust and shade is 3.23 times as much as the collector affected by these two factors. Thermal properties of solar thermal collector arrays have been tested as low ambient temperature below-10℃ in 17 days. It can be found that the daily average efficiency of solar thermal collector arrays is 41.96% and average heat loss factor is 1.64W/m2·℃.(3) Designing biogas slurry heat-recovery pool to realize heat exchanging between feedstock from acidifying pool and slurry from fermentation tank. As the 30% of biogas slurry has been flowed back into feedstock, the heat recycle efficiency of the link of heat and mass recycling of biogas slurry is ranging from 40% to 41%. According to operating data of plant to assume related initial conditions and thermal performance has been analyzed. The results show that the recycling of heat from biogas slurry can increase the feedstock temperature from 5℃ to 24.0℃.(4) Economic analysis of the system adding solar thermal collector and the link of heat and mass recycling of biogas slurry have been calculated. The results show that deploying 14 solar thermal collectors on the basis of heating of exhaust waste heat can maintain biogas system fermentation processing at 35 ℃ constantly. Transforming the Huazhuang biogas production plant into the system in this paper can save water 14.4t everyday and the pay-back period is 1.76 year.The innovation of subject lies in: built a themostatic biogas production plant heated by solar energy and waste heat of exhaust gas with the link of link of heat and mass recycling of biogas slurry and thermal properties and economic analysis have been done.