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类型 综合研究 预答辩日期 2017-12-05
开始(开题)日期 2015-06-19 论文结束日期 2017-10-27
地点 动力楼420 论文选题来源 中央、国家各部门项目     论文字数 8.5 (万字)
题目 农村废弃生物质太阳能辅热中温两相厌氧产沼技术研究
主题词 农作物秸秆,微需氧预处理,两相厌氧消化,太阳能辅热,相变蓄热
摘要 本论文针对农作物秸秆在厌氧消化过程中存在难生物降解和产甲烷易受温度影响等问题,在厌氧消化之前对秸秆进行微需氧生物预处理以提高其水解酸化性能,同时利用秸秆与其他废弃物之间的营养互补和协同作用,构建了以难降解秸秆为主要底物的混合底物两相厌氧消化产沼系统。并以此为基础构建了太阳能光热-相变蓄热与混合底物两相厌氧消化耦合的中试系统,实现了厌氧消化产沼系统在冬季的中温发酵。本文主要研究工作和研究结果包括以下内容。 针对传统物理-化学预处理方法和生物预处理方法带来的副产物问题和菌种成本等问题,开展了以两相厌氧消化中水解酸化液作为接种物的微需氧生物预处理研究。发现氧气负荷的升高能提高微需氧预处理过程对油菜木质纤维素的降解率,但过量的氧会降低预处理后秸秆的水解产酸性能。在氧气负荷为20mL/ gVS秸秆/d,接种液中有机酸浓度为4g/L,预处理时间为10d的条件下预处理的油菜秸秆,经过水解产酸发酵,VFAs和sCOD比未处理油菜秸秆分别提高了88.43%和75.50%。通过对预处理过程中秸秆形貌结构、化学基团和晶体结构变化的研究,发现微生物破坏了秸秆中原本规整的结构、降低了秸秆中纤维素结晶度、减少了木质素相关的化学基团。此外,微需氧预处理前后的微生物群落,尤其是与木质素降解密切相关的微生物菌群发生明显变化,在预处理之后细菌菌群中放线菌门(Actinobacteria)的相对丰度提高了84.5倍,真菌菌群中的黑曲霉(Aspergillus niger)和橘青霉(Penicillium citrinum)的相对丰度分别提高了4.4倍和1.2倍。 农村地区除农作物秸秆外还存在的厨余垃圾及禽畜粪便等生物质,可以将它们与秸秆进行混合,利用底物之间的协同作用展开混合底物两相厌氧消化研究。研究结果表明(1)通过对水解酸化过程的研究,发现油菜秸秆与其他两种底物混合后能增加水解酸化阶段产生VFAs的浓度,VFAs中乙酸的含量随着鸭粪比例的增加或厨余垃圾的降低而升高,而丙酸的含量显示出相反的规律。(2)通过对产甲烷过程的研究,发现混合底物两相厌氧消化具有明显的协同促进效应,比单独秸秆的总产甲烷量提高了29.3-183.1%。不同混合底物在两相厌氧消化中产甲烷量的增加,一方面与底物中易生物降解物质的增加和C/N比的降低有关,另一方面源于多种混合底物之间的协同作用。实验还发现易水解的厨余垃圾和高含氮的鸭粪与秸秆混合后进行两相厌氧消化,可以提高秸秆的生物降解率。综合水解酸化特性、产甲烷特性和秸秆的生物降解特性,确定油菜秸秆、厨余垃圾和鸭粪的最适宜混合比例为50:25:25。(3)通过对两相厌氧消化中温度对水解酸化特性和产甲烷特性的影响研究,发现在20°C~35°C温度范围内,水解产酸发酵的产VFAs能力会随发酵温度的升高而提高,在35°C时最高产酸量达到9270.1mg/L。同时,实验还发现产甲烷过程对温度较敏感,从35°C降低2°C~5°C均会降低其产甲烷能力,在35°C条件下累计产气量比33°C和30°C时分别增加了31.07%和169.88%,但从产气速率角度考虑,产甲烷反应器可以接受短期内从35°C降低不超过2°C的情况。 在混合底物两相厌氧消化的基础上构建了太阳能辅热的中温两相厌氧产沼中试系统,利用太阳能集热-相变蓄热(PCTS)系统收集和储存太阳能为两相厌氧消化系统供热,减小太阳辐射波动和低温气候造成的发酵温度波动。实验研究了不同供热方式对两相厌氧反应器在冬季产甲烷效能的影响,发现采用太阳能集热- PCTS系统收集和储存太阳能为两相厌氧消化装置供热,可以减小发酵温度的波动并将其保持在中温范围,两相厌氧消化总产气量达到20.48m3,其底物能量转化率比传统太阳能供热和不供热的两相厌氧消化装置分别增加了1.01倍和5.65倍;采用修正Gompertz模型可以很好地拟合太阳能-PCTS系统供热的两相厌氧消化系统甲烷产率变化情况,预测值与实验值误差为1.49%。 通过对冬季典型工况条件下各子系统的热力性能和热利用效率的研究,发现太阳能辅热的两相厌氧产沼系统在冬季的热利用效率为42.0%,研究表明,可以通过进一步提高换热盘管传热系数,优化管道和反应器的外部保温层等方式提高系统的热利用效率。采用计算流体动力学(CFD)软件对产甲烷反应器内部温度场分布情况进行数值模拟,模拟结果显示供热温度的升高会提高反应器内部升温速率,但同时也会加剧反应器内部的温度分层,综合考虑温度场分布、换热效率和相变蓄热材料的成本,选取55°C作为太阳能辅热装置的供热温度。增加水力搅拌可以提升反应器内温度场分布的均匀程度,当搅拌速度增大到0.27m/s后,反应器内部最大温度差从2.3°C减小到0.2°C。
英文题目 MESOPHILIC TWO-PHASE ANAEROBIC DIGESTER COMBINED WITH SOLAR HEATING SYSTEM FOR BIOGASIFICATION OF BIOMASS WASTES IN RURAL AREAS
英文主题词 crop straw; micro-aerobic pretreatment; two-phase anaerobic digestion; solar auxiliary heat; phase change thermal storage
英文摘要 There exist some problems in anaerobic digestion of crop straw, including hard biodegradation and easy to be affected by temperature in methane production process. This study improved the hydrolysis-acidification of straw by micro-aerobic bio-pretreatment before anaerobic digestion. At the same time, this study utilized the nutrients complementarily and synergistic effect between straw and other biomass wastes, built a two-phase anaerobic digestion (TPAD) system which used hard-degraded straw as main substrate. On that basis, this study built a pilot system which was composed by the solar thermal-phase change thermal storage (PCTS) and TPAD. It has succeeded in applying mesophilic anaerobic digestion of biogas production system in winter. The main research works and results include the following content. Concerning the by-products accompanied with traditional physical-chemical pretreatment method, and cost of microbial strains of biological pretreatment. The micro-aerobic pretreatment which used hydrolysis-acidogenesis liquid from TPAD as inoculum were studied. The results show that, the degradation rate of the lignocellulose in rape straw was increased with improvement of oxygen load. However, excess oxygen loads may decrease hydrolysis-acidification performance of pretreated straw. The optimal pretreatment conditions were as following: oxygen load 20 mL/ gVS/d, VFAs concentration of inoculum liquid 4 g/L, pretreat time 10 d. The VFAs and sCOD concentration of hydrolysis-acidification fermentation of the pretreated straw were improved 88.43% and 75.50%, respectively, compared with un-treated straw. After investigating the morphology, functional groups and crystal structure variations of the rape straw, it is found that the regular structure was destroyed, the crystallinity of cellulose was decreased and the functional groups related to lignin was decreased after micro-aerobic pretreatment. In addition, the microbial community structures have varied, especially the microbial flora closely related to lignin degradation. After the pretreatment, the abundance of Actinobacteria was increased 84.5 times, and the abundance of Aspergillus niger and Penicillium citrinum were increased 4.4 fold and 1.2 times, respectively. There are kitchen waste and livestock manure existing in rural area besides crop straw, which can be mixed together. The study on TPAD based on synergistic effects between different substrates was conducted. The results show that(1)The VFAs production was promoted when rape straw was mixed with other two substrates in hydrolysis-acidification process. The acetic acid content in VFAs showed increasing trend when the DD content increased and KW content decreased. While the content of propionic acid showed a contrary tendency.(2)The promoting synergistic effects of co-substrates anaerobic digestion can be found in research on methane producing process. The total methane yields of co-digestions were increased 29.3-183.1% compared with mono-digestion of rape straw. The promotion of methane yield was on account of two reasons. On the one hand, it was due to the increasing of easily degradable organic matter and the decreasing of C/N ratio. On the other hand, it was due to the synergistic effects between different substrates. The experimental results also revealed that the biodegradation rate of rape straw was improved when kitchen waste and duck dung was mixed with the rape straw in two-phase anaerobic digestion. The optimal mixture ratio of the rape straw, kitchen waste and duck dung was 50:25:25.(3)The influence of fermentation temperature on hydrolytic acidification and methanogenesis were studied. The results showed that, the VFAs production capacity was improved with the fermentation temperature in 20°C~35°C range. The VFAs concentration of the fermentation was reached 9270.1mg/L at 35°C. Additionally, it can be found that the methanogenesis was very sensitive to the temperature variation. The methane production capability was reduced when fermentation temperature reduced 2°C~5°C from 35°C. The cumulative biogas yield of the anaerobic digestion in 35°C was improved 31.07% and 169.88%, respectively, compared with that in 33°C and 30°C. Considering the perspective of biogas production rate, the fermentation temperature reduced 2°C from 35°C in a short time is considered acceptable. In this study, a pilot system of two-phase anaerobic digester heated by solar energy has been constructed based on two-phase anaerobic co-substrates digestion. The solar thermal and PCTS system can collect and store solar energy to heat the two-phase anaerobic digester, and reduce the fluctuation of fermentation temperature which was caused by solar radiation fluctuation. A set of comparative field studies were carried out on different heating mode in winter. The comparison shows that, the PCTS system can reduce the fluctuation of fermentation temperature and maintain the fermentation temperature within the mesophilic range. The total biogas yield reached 20.48 m3, the energy conversion rate of the substrate increased by 1.01 times and 5.65 times, respectively, than that of TPAD heated by only solar thermal collector and without heating, respectively. The modified Gompertz model model had a good precision and fitting with the methane production rate changes of two-phase anaerobic digestion heated by solar thermal-PCTS system. The errors between model predictions and measured results was 1.49%。 The thermal performances and heat utilizing efficiency of subsystems under typical working condition in winter were analyzed. The results show that, heat utilizing efficiency of solar heated two-phase anaerobic biogas production system is 42.0% in winter. The heat utilizing efficiency could potentially be improved by optimizing the external insulation layer or improving heat transfer coefficient of the heat exchange coil. This study use computational fluid dynamics software to build the physical and mathematical models of the methanogenic reactor. Simulation results show that the heating rates increased with the increasing heating temperature, but also intense the temperature stratification in reactor. Considering overall the temperature distribution, heat exchange efficiency and cost of phase change material, this study can choose 55°C as heating temperature of solar auxiliary heating device. The uniformity degree of temperature distribution can be improved by hydraulic agitation. The maximum temperature difference inside reactor reduced from 2.3°C to 0.2°C when stirring velocity increased to 0.27m/s.
学术讨论
主办单位时间地点报告人报告主题
李先宁课题组 2014年12月16日 东南大学五五楼 汪楚乔 秸秆两相厌氧消化特性研究
李先宁课题组 2015年3月19日 东南大学五五楼 汪楚乔 两相厌氧产沼技术研究(实验进展汇报)
李先宁课题组 2016年7月8日 东南大学五五楼 汪楚乔 Micro-aerobic pretreatment of rape-straw and two-phase co-digestion of rural biomass waste
李先宁课题组 2017年1月12日 东南大学五五楼 汪楚乔 研究阶段汇报
李先宁课题组 2015年3月31日 东南大学五五楼 王辉 土壤微生物燃料电池的构建及预实验结果
李先宁课题组 2015年9月13日 东南大学五五楼 曹羡 实验阶段汇报
李先宁课题组 2016年1月2日 东南大学五五楼 曾学良 太阳能辅热两相厌氧消化中试系统的构建以及实验结果
李先宁课题组 2016年3月17日 东南大学五五楼 程思超 不同共基质对CW-MFC中偶氮染料脱色与产电特性的影响
     
学术会议
会议名称时间地点本人报告本人报告题目
东北大学 2014年3月18日至22日 日本仙台 Mesophilic two-phase anaerobic digester combined with solar heating system for biogasification of biomass wastes in rural areas
清华大学 2015年10月24日 北京 Remove algae in eutrophic lake water using a diatomite porous ceramic membrane
     
代表作
论文名称
宜兴典型村落不同下垫面降雨径流污染物排放特征
Two-Phase Anaerobic Digester Combined with Solar Thermal and Phase Change Thermal Storage System in
Improved biogas production and biodegradation of oilseed rape straw by using kitchen waste and duck
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
杨林军 正高 教授 博导 东南大学
荆肇乾 正高 教授 博导 南京林业大学
宋海亮 正高 教授 博导 南京师范大学
仲兆平 正高 教授 博导 东南大学
余冉 正高 教授 博导 东南大学
陆勇 副高 副研究员 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
王沛 其他 讲师 东南大学