| The energy from solar and biomass is the renewable energy which can be widelyavailable in the rural areas and play an important role to improve the rural living environment,ecological environment and to meet the rural multi-level energy requirements by through thecost effective use.Based on the character that the economics of the collection temperature(30℃) from thesolar energy and the temperature(30℃、37℃and52℃) from the efficient and thermostaticanaerobic fermentation are match, the team put forwarded the new system-the solar heating ofthree levels thermostatic anaerobic fermentation system and analysised the systemperformance at preliminary work. Research findings that:1) the heat losing of thefermentation system had a part of from the heat dissipation of the system, but the more partwas removed from the system with the biogas slurry and residues;2) the biogas slurry andresidues contain water more than90%which cause losses with the system discharging;3) thefermentation materials needed to dilute the fermentation concentration(the subject offermentation concentration is8%) before enter into the fermentor, and then heating to thefermentation temperature(30℃,37℃and52℃) using the solar energy.In order to make full use of the solar energy at the same time recycle and utilize water,the subject put forwarded the system that add the heat and mass recovery equipment in thesolar heating of three levels thermostatic anaerobic fermentation system and analysised thesystem performance. Its principle was that use biogas slurry from the system dischargingreplaces the tap water to dilute the fermentation materials, and used the remaining to heat thematerials replace the solar energy through the heat and mass recovery equipment. The mainresearch contents and the results were as follows:The experimental studied the thermostatic anaerobic fermentation mechanism under thecondition of the temperature are30℃,37℃and52℃respectively, with the materials wascow dung which the total solid is8%, and combined with the dates about the temperature andsolar radiation intensity in Lanzhou’s typical year, we simulated the heat losing of the yearabout the three levels thermostatic anaerobic fermentation system, and studied the systemperformance after adding the heat and mass recovery equipment. The finally section we usedthe similarity principle to simulate the1/5times the actual equipment to study the heat transferperformance and designed the heat and mass recovery equipment model diagram. The thermostatic anaerobic fermentation experiment results showed that: the cumulativegas production were153.41L,187.59L,173.12L under the condition of30℃,37℃and52℃respectively; the gas production reached the peak(7.32L) in the tenth day in30℃,while37℃and52℃fermentor reached the peak in the third and sixth day respectively, and the gasproduction were17.02Land13.91L. The biogas yield decreased gradually due to thenutrients decreased. Compared to the normal temperature anaerobic fermentation, thehydrogenogens activities were the best when the temperature was30℃, so the biogasproduction were relatively good, while the methanobacters activities were good at52℃,thebiogas production were the best. When the anaerobic fermentation temperature was37℃, ithad the both characteristics of30℃and52℃. Based on the above characteristics, the firstchoice was52℃when the fermentation materials were sufficient because they had a fastergas production rate and higher gas production peak. From the view of energy consumption ofthe system, it was necessary to choose the appropriate temperature combined with the climatefeatures with the different seasons and different regions.For new and old system year-round heat loss simulation results show that:1) the workingof the heat and mass recovery equipment is relatively stable although the average annualtemperature fluctuations are range from-11.8℃to26.9℃. Under the conditions of30℃,37℃and52℃fermentation temperature, the time different of the heat recovery is not morethan five seconds everyday, and the heat transfer time of the three fermentation temperaturesare determined to be41minutes,38minutes and27minutes at the three temperatures. Theinitial temperature of the raw materials from5℃to17.5℃,21.0℃and28.5℃, and thetemperature of the discharging section from the30℃,37℃and52℃correspondingdecrease to17.5℃,21.0℃and28.5℃;2) The heat losing of the solar thermostatic anaerobicfermentation system in the condition of30℃,37℃and52℃is45948.4MJ,44230.1MJ and74143.3MJ within a year respectively, correspondingly, the heat and mass recovery equipmentcan recover28711.2MJ,36750.5MJ and53972.9MJ one a year. And the energy saving rate ina day can reach30.3%~48%,31.8%~44.8%and33.8%~41.6%, the full-year energy savingrate is39%,38.3%and37.7%respectively;3) The three levels thermostatic anaerobicfermentation system require71m~2solar collectors to maintain the normal operation of thethree fermentor and can keep the fermentation temperature with30℃in cold season and52℃in summer-time. The fermentation temperature can keep37℃in the first month in springseason and52℃in the second month for the three fermentors. In autumn season, the threefermentor temperature can keep30℃,37℃and52℃separately. When adding theheat and mass recovery equipment, the fermentation system can keep52℃around a year as the solar collectors remain unchanged. While keep the normal operation just need47.4㎡solar collectors.The innovative points of this subject were: designed the heat and mass recoveryequipment, put forwarded the solar heating of three levels thermostatic anaerobicfermentation system, and reveal its thermodynamic economy.The result of this study has a instruction function to reduce the cost of production anduse, especially in cold and dry areas, such as Gansu province, and has a great significance toensure the normal operation of the biogas project in winter.This work was supported by National Natural Science Foundation of China (51166008/E0607), Key Technologies R&D Program of China (2011BAD15B03), China Spark Program (2010GA860004), Research Foundation of Education Bureau of Gansu (0803-06), Longyuan Youth Innovative Support Program (09-0165), Construction Science and Technology Development Program of Gansu (JK2010-29),Tamarisk Outstanding Talent Program of Lanzhou University of Technology (Q201101). |
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