玉米秸秆与猪粪两阶段厌氧消化反应机理及关键参数研究

发布时间：2018-01-19 00:23

本文关键词： 玉米秸秆猪粪产甲烷潜力挥发性有机酸两阶段厌氧消化微生物群落分析　出处：《天津大学》2016年博士论文　论文类型：学位论文

【摘要】：目前,我国秸秆理论资源量为8.4亿吨,可收集资源量约为7亿吨。由于缺乏有效的处理方式,约有2.47亿吨的秸秆被废弃或直接焚烧,不仅污染了环境,更是对资源的极大浪费。我国同时也是生猪养殖大国,2012年统计数据显示,生猪粪污产生量近30亿吨,合理有效地处置秸秆及畜禽粪便已成为当务之急。本论文选择玉米秸秆和生猪粪便为混合原料,采用固态产酸和液态产甲烷两阶段厌氧消化新工艺,研究了两阶段厌氧消化的反应机理、影响因素、关键工艺参数及微生物群落结构动态变化规律。论文研究成果可为玉米秸秆与猪粪混合原料固-液两阶段厌氧发酵工艺开发与应用提供理论依据和技术支撑。论文分析了13种木质纤维素原料的理化特性和产甲烷潜力,研究发现累积沼气产量、累积甲烷产量与木质纤维素类原料的半纤维素含量呈显著的正相关关系(p0.05);与木质素含量呈显著的负相关关系(p0.05);而与原料的可溶性糖含量、VS/TS含量、TOC含量、TC含量以及C/N无明显的相关关系。其中玉米秸秆的产沼气潜力最高,其沼气产率与甲烷产率分别为478.6Nml/gVS与252.2Nml/gVS。猪粪的沼气产率与甲烷产率分别为617 Nml/gVS和337Nml/gVS,最大产甲烷速率为39.7 Nml/(g·d)VS。玉米秸秆与猪粪混合后,可使发酵原料C/N和含水率更适合厌氧消化。论文得出固体产酸发酵的工艺优化条件为:猪粪与秸秆原料配比为2:1,沼液回流量25%,沼液回流间隔时间12~24h。静态固体产酸过程在6~10d为高峰期,20d以后维持在较低水平。固体产酸消化为乙酸型发酵,消化产物VFA中乙酸占有机酸60%以上,丙酸浓度低于1.0g/L,适合于产甲烷厌氧消化。液态产甲烷反应的实验结果显示,在相同pH水平下,35℃厌氧消化的沼气产率高于55℃;相同消化温度下,当pH高于7.0时,沼气产率随pH的升高而降低。实验结果得出,pH为7.0,35℃为液态产甲烷发酵的最适参数。中温消化中,乙酸营养型甲烷鬃毛菌属Methanosaeta为优势菌属,主要通过乙酸氧化生产甲烷,在中低pH(6.5~7.5)下相对丰度高于70%;高温消化中,Methanosarcina甲烷八叠球菌属为优势菌属,在pH为7.0~7.5时相对丰度在60%以上,除可利用乙酸合成甲烷外,还可利用H2和CO2生成CH4,但速率较低,使高温消化甲烷产量低于中温消化甲烷产量;游离氨的增加是甲烷产率降低的主要原因,对于高含氮有机废弃物厌氧消化,不宜采用高温厌氧消化。通过连续动态试验,得出两阶段厌氧混合发酵的最佳猪粪与秸秆原料比、沼液回流比、沼液回流间隔时间、固体产酸反应器有效容积与液体产甲烷反应器有效容积比、固体消化停留时间,液态消化阶段的有机负荷、水力停留时间等最佳工艺参数。试验结果还显示,沼液回流对调节产酸消化体系pH具有明显作用,沼液回流量和回流间隔时间是调控固体产酸消化的重要参数。沼液回流参数也受液体产甲烷消化参数影响,是耦合两阶段厌氧消化,减少沼液排放的关键;通过对两阶段厌氧消化过程中不同阶段种群结构的分子生物学试验检测发现,固态产酸阶段细菌和古菌优势种群随着消化时间的延长存在明显的演替,其中厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)与浮霉菌门(Planctomycetes)为细菌中优势种群;古菌以氢营养型的甲烷细菌属为优势种群。产甲烷阶段,细菌和古菌群落结构较稳定。其中厚壁菌门为细菌中的优势种群;氢营养型的甲烷杆菌属、甲烷囊菌属与乙酸营养型的甲烷八叠球菌属为优势种群。论文采用的固态物料的产甲烷潜力压力测定法,具有操作简单,结果稳定的特点;采用的车库式固体酸化反应器和改进CSTR高效耦合的两阶段厌氧消化工艺,有利于提高反应器容积产气率,减少沼液排放。利用玉米秸秆和猪粪混合厌氧消化,能够提高沼气产量和反应器运行稳定性。试验结果显示通过工艺参数优化,可实现两阶段沼气厌氧消化稳定运行。
[Abstract]:At present, the theory of straw resources in China is 8.4 tons, can collect resources is about 7 tons. Due to the lack of effective treatment, about 2.47 tons of straw were abandoned or burned directly, not only pollute the environment, it is a tremendous waste of resources. China is also the pig breeding country, 2012 statistics data show that the pig manure produced nearly 30 tons, a reasonable and effective disposal of straw and animal manure has become a pressing matter of the moment. This paper choose corn straw and pig manure mixed raw materials by solid acid production and liquid methane two stage anaerobic digestion process, factors influencing the reaction mechanism of two stage anaerobic digestion the key process parameters, and the microbial community structure dynamics changes. The research results for corn straw and pig manure mixed solid raw material development and application of anaerobic fermentation liquid two phases to provide the theory basis and Technical support. This paper analyzes the physical and chemical properties of 13 kinds of lignocellulosic materials and methane production potential, the study found that the cumulative biogas yield, there was a significant positive correlation between the content of hemicellulose and the cumulative methane production of lignocellulosic raw materials (P0.05); a negative significant correlation with lignin content (P0.05); and the content of soluble sugar and raw materials, VS/TS content, TOC content, no significant correlation between the content of TC and C/N. The biogas production potential of corn straw is the highest, the biogas yield and methane yield were 478.6Nml/gVS and 252.2Nml/gVS. of pig dung biogas yield and methane yield were 617 Nml/gVS and 337Nml/gVS, the maximum methane production rate was 39.7 Nml/ (G - D) VS. of corn straw and pig manure mixed, the fermentation raw material and water content of C/N is more suitable for anaerobic digestion. The optimum conditions obtained for solid acid fermentation of pig manure and straw The ratio of raw materials was 2:1, the back flow of 25% biogas slurry, biogas slurry reflux time interval 12~24h. static solid acid process at 6~10d peak, 20d remained at a low level. The solid acid digestion for acetic acid fermentation, digestion products of VFA acetic acid 60% share above machine, low concentration of propionic acid in 1.0g/L, suitable for anaerobic methane production liquid methane reaction to digestion. The experimental results show that under the same level of pH under 35 DEG C anaerobic digestion biogas yield of higher than 55 DEG C; the same digestion temperature, when the pH is higher than 7, the biogas yield decreased with the increase of pH. The experiment results, pH is the most suitable parameters for liquid methane fermentation 7.0,35 C the mesophilic digestion, nutrition acetate Methanosaeta Methanosaeta dominant bacteria, mainly through the production of methane oxidation in acetic acid, pH (6.5~7.5) under low relative abundance is higher than 70%; high temperature digestion, Methanosarcina ch eight stacked coccus Was predominant genus, pH in 7.0~7.5 relative abundance in more than 60%, in addition to the use of acetic acid synthesis of methane, can also use H2 and CO2 to generate CH4, but the rate is low, the high temperature digestion methane production methane production in lower temperature digestion; increase of free ammonia is the main reason for the methane yield decreased. High content of organic waste anaerobic digestion of nitrogen, not by thermophilic anaerobic digestion. Through continuous dynamic test, the two stage anaerobic fermentation of pig manure and straw best raw material ratio, slurry recirculation ratio, slurry recirculation interval, solid acid producing reactor with effective volume of liquid methane producing reactor effective volume ratio, solid residence time of digestion, the liquid phase digestion of organic load, hydraulic retention time optimal parameters. The experimental results also showed that biogas slurry reflux has a significant effect on the regulation of acid digestion system pH, biogas back flow and reflux interval Time is an important parameter to control solid acidogenic digestion. The biogas slurry reflux parameters by liquid methane digestion parameters, is the coupling of two stage anaerobic digestion, biogas key to reduce emissions; through the discovery of molecular biology test in different stages of population structure of two stage anaerobic digestion process, solid acid producing bacteria and archaea population stage with the advantages of prolonged digestion time has obvious succession, including Firmicutes, Proteobacteria (Firmicutes) (Proteobacteria), Bacteroidetes (Bacteroidetes) and planctomycetes (Planctomycetes) for the population of bacteria in the Archaea to bacteria; methane hydrogen nutrition type genus is the dominant species. The methanogenic phase bacterial and archaeal community structure was stable. The Firmicutes were the dominant species in bacteria; methane bacteria hydrogen nutrition type genus of bacteria and methane sac nutrition acetate methane eight fold for Staphylococcus aureus The dominant population. Determination of the solid material of methane production potential pressure, has the advantages of simple operation, stable characteristics; garage type solid acidification reactor used and improved CSTR coupling efficiency of two stage anaerobic digestion process, is conducive to the improvement of reactor volume gas production rate, reduce emissions of biogas slurry. Using corn straw and pig manure anaerobic digestion, biogas can improve the yield and stability of reactor operation. Test results show that by optimizing the process parameters, can realize the stable operation of the two stage of biogas anaerobic digestion.

【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：X71

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