The Research On Performance Of Biogas Production Reactor Heated By Solar Energy

Environment and energy are the global issue of common concern to the international community today. The ecological environments of human and the human society to develop sustainedly were threatened by energy consumption based on the Non-renewable fossil fuels. Thus the development and utilization of environment-friendly renewable energy becomes indispensable.Solar energy and bio-mass energy which are abundant resource and also the most widespread, are two sorts of renewable energy resource. Both the biogas fermentation technology and the low-temperature solar energy heating technology are the advanced and matured technologies. Due to the biogas fermentation technology can effectively solve the problem of fuel shortages in rural areas, realize innocuous treatment and utilization of organic manure, it has been drawn attention to many countries. However the anaerobic fermentation process are strongly influenced by fermentation temperature, the lower temperature or larger fluctuation of fermentation temperature influence the rate of gas production and methane content of anaerobic fermentation .At present, parts of the current methods of raising temperature and keeping warm of biogas pools, some methods utilize bio-mass ,coal, electric, etc ,low conversion rate of thermal energy, high pollution; other are less effect and hard to control the anaerobic fermentation process. The relationship between the low-temperature solar energy heating temperature and the anaerobic fermentation temperature, it provide with a base for integrations of solar collector and biogas pool. Therefore, we designed and developed a biogas production reactor heated by solar energy. It uses hot water of solar collector to heat fermentation liquid, make it broke through the constraint of the adverse factors, such as day and night, season, climate and so on, and achieves continuous and stable energy supply.In order to study the factors which affect fermentation temperature and fermentation raw material on biogas production characteristics of the anaerobic fermentation, and the research on performance and comprehensive benefit of biogas production reactor heated by solar energy. This article has done the jobs as follow:1. To study the influence of temperature on biogas components of thermostatic anaerobic fermentation with cattle manure. Four parallel anaerobic digesters of 11.5L were operated in batch mode at temperature of 19℃, 30℃, 37℃and 52℃, respectively. And the real-time analysis was carried out to determine the biogas composition with Biogas Check instrument. The results shows that (1) When the concentration of fermentation were 8%, the cumulative biogas production were 173.12L,187.59L,153.41L and 39.12L , the fermentation period were 22, 22 and 27 days, the cumulative methane production were 90.44L,100.47L,79.35L and 13.90L, the volumetric biogas production rate were 0.71 m3/m3·d, 0.76 m3/m3·d and 0.51 m3/m3·d at the 52℃, 37℃and 30℃, respectively. The highest cumulative biogas and the highest methane production was under 37℃. (2) When the concentration of fermentation were 4%, the cumulative biogas production was 41.69L, 52.30L and 55.57L, the fermentation period were 16,15 and 14 days, the volumetric biogas production rate were 0.23m3/m3·d, 0.32m3/m3·d and 0.36 m3/m3·d, the cumulative methane production were 19.07L, 24.49L and 25.22L,the average methane content were 51.07%,51.76% and 50.63% at the 52℃, 37℃and 30℃, respectively. Compared with the situations under other temperature, although under 52℃the fermentation period is shorter, and the volumetric biogas production rate is higher, the quality of biogas is worst. So the highest methane production are under 37℃.(3) When the cattle manure and cabbage leaves with the mass ratio of 3 and the concentration of fermentation were 8%, the cumulative biogas production were 201.83L,225.18L and 195.76L; the fermentation period were 31, 42 and 58 days, the volumetric biogas production rate were 0.65m3/m3·d,0.54m3/m3·d and 0.34m3/m3·d; the cumulative methane production were 99.31L,117.96L and 102.10L,the average content of methane were 49.20%,52.38% and 52.16%, the biogas production yield were 0.42 m3/kg,0.47 m3/kg and 0.41 m3/kg. And the co-digestions with cattle manure and cabbage leaves has more biogas production potential than the digestion with cattle manure or cabbage leaves alone, the cumulative biogas production were increased by 7.00%, 34.08% and 22.16% at 30℃, 37℃and 52℃, respectively. When the mass ratio was 3, the most proper temperature for anaerobic fermentation was under 37℃. Moreover, when lower temperature could not start anaerobic co-digestion, the content of cabbage should be decreased. And because of decreasing the content of VFA will inhibit the methane bacteria, the PH need be adjusted in real-time.2. When the average ambient temperature was 8.6℃, solar thermostatic biogas reactor could steady run under 30±2℃. And when the concentration of fermentation was 7%, the peak values of daily biogas production was measured to be 2.059 m3/d at the eleventh day , the maximum material capacity production rate of biogas was 0.86 m3/m3·d, the fermentation period was 28d. For a family of 4～5, if this system runs regularly, capable of biogas pool about 3 m3 could satisfy the demand of boiling water and cooking food. Its net present value (NPV) was 8573 Yuan (RMB), its benefit-cost ratio was 2.80, its financial internal ration of return (FIRR) was 43.64% and its dynamic pay-off period was 2.9 year. Under such condition, which was taking into account all household biogas digesters in Gansu province, the annual emission reduction of carbon dioxide was about 2.35×107t. When the output of biogas is used to reduce the output of straw, firewood and coal for livelihood, the contribution of emission reduction of CO2 were 47.47%, 40.80% and 11.73%, respectively.The innovation of the work in this paper can be listed as follows:(1)Experimental Studied on effect of fermentation temperature on biogas production characteristics of the anaerobic fermentation,and found that the highest cumulative methane production and the highest methane content were appeared at 37℃.(2)We designed and developed a biogas production reactor heated by solar energy, and it could steady steady produce biogas in Lanzhou under winter conditions.A biogas production reactor heated by solar energy could break through the constraint of the adverse factors, such as day and night, season, climate and so on, and solve the problems of low production rate of biogas in winter and unstable production. Compared with traditional anaerobic fermentation, it come true thermostatic and high-efficient products biogas. These results could popularized a biogas production reactor heated by solar energy to larger area in north part of countries, promoted the construction new village, reduced dependence on traditional energy sources, expanded the scope of the use of renewable energy, increased the proportion of utilization of regenerated energy, achieved the sustainable development of energy and environment.