【作者】 王飞；

【导师】 邱凌；

【作者基本信息】 西北农林科技大学 ， 农业生物环境与能源工程， 2020， 硕士

【摘要】 我国每年农作物秸秆产生量大、畜禽粪污排放量大,综合处理率低,已经严重制约了有关产业的发展。另一方面,处理农牧业废弃物所使用的传统的厌氧消化技术,存在运行周期长、进料浓度低、容易产生抑制现象。针对以上问题,有学者提出向厌氧消化系统中添加生物炭来提高系统的处理效率和稳定性。而大部分对生物炭在厌氧消化中的研究集中于单一物料,且关注生物炭吸附作用和微生物富集等微观作用机理,并未对混合原料,尤其是对混合原料主要成分的降解有较为深入的研究。对此,本研究选取了年产生量最高的两种农牧业废弃物:猪粪与玉米秸秆作为研究对象,在添加热解颗粒生物炭后,利用响应面方法确定添加底物的比例;并利用动力学方程分析沼气中甲烷变化以及底物中主要成分的变化规律;最后分析底物变化对产甲烷变化的影响。主要内容与结论如下:（1）生物炭介导猪粪玉米秆混合厌氧消化特性。本章节选取猪粪与玉米秸秆作为研究对象,并利用划分水平、控制单一变量的原则进行试验,分别探索了混合原料总固体含量、碳氮比、生物炭添加量对混合厌氧消化的影响,并从日产甲烷量、甲烷含量百分比、累积产甲烷量、消化液溶解性化学需氧量四个方面进行分析。研究结果表明:随着原料总固体浓度的增加,累积产甲烷量出现先增高后下降的趋势,合适的物料总固体浓度会增加第一个产甲烷峰值并提前峰值的出现时间,而过高的总固体浓度导致厌氧消化中后期溶解性化学需氧量浓度升高并降低厌氧消化初期沼气中甲烷含量百分比。原料碳氮比的增大导致日产甲烷量的第一个峰值减小,第二个峰值提高,但对甲烷含量百分比无显著影响,而碳氮比的降低会导致消化液溶解性化学需氧量的增加。添加合适比例的生物炭会增加日产甲烷的第一个峰值,同时缩短产甲烷停滞期,而较低的生物炭添加量会导致反应初期甲烷含量百分比降低,同时消化液溶解性化学需氧量升高。因此,过高的总固体含量以及低碳氮比会大幅提升消化液溶解性化学需氧量,从而降低产甲烷效率;而添加生物炭则能够有效地提升厌氧消化初期甲烷含量。（2）生物炭介导猪粪玉米秆混合厌氧消化工艺参数优化。本章节利用多因素旋转组合设计的方法,确定以甲烷产率（y）为响应变量,总固体含量（x₁）、热解炭添加量（x₂）和碳氮比（x₃）为自变量的回归模型:y=267.22+10.08x₁+10.37x₂+7.96x₃-42.90x₁²-14.09x₂²-16.03x₃²。结果表明,通过拟合优度分析、残差分析、扰动性分析等多种统计学评价,所得模型拟合效果良好。对独立因素、交互因素分析得到了三因素重要性排序为:总固体含量>碳氮比>生物炭添加量。通过模型寻优,得到最优总固体含量、生物炭添加量和碳氮比分别为:6.18%、8.73%和21.69,所得产甲烷率为269m L/g VS。通过验证试验得到的数据,其相对误差占试验值的0.6%,且试验值与模型预测值的偏差小于5%。因此可以认为本章得到的模型具有可靠性,可以用于描述甲烷产率随总固体含量、生物炭添加量和碳氮比变化的规律。（3）生物炭介导猪粪玉米秆混合厌氧消化动力学分析。本章将以总固体含量为6.18%,碳氮比为21.69的条件下,添加8.73%生物炭的试验组与没有添加生物炭的对照组最优组的气相、液相产物为研究对象,进行日产甲烷量、四种主要成分降解的变化时序关系和趋势分析,结果表明:在置信水平α=0.1时,添加生物炭的试验组的累积产甲烷量、淀粉类降解率均显著高于无生物炭的对照组;试验组的主要降解分成呈现出半纤维素与淀粉类先降解,粗蛋白后降解的次序关系;修正的Gompertz方程能够较好地对试验组与对照组全过程累积产甲烷量进行拟合;修正的Gompertz方程与Logistics方程均能较好地对试验组与对照组主要降解成分进行拟合;通过动力学方程参数求解,添加生物炭能够缩短产甲烷、主要成分降解的停滞期;同时能够提高最大单日产甲烷量、最大单日降解率。因此,通过分析动力学方程的各项参数,明确了添加生物炭缩短停滞期、并提升厌氧消化效率的根本原因是,生物炭促进了底物中淀粉类成分的降解速率。更多还原

【Abstract】 China has produced volumes of straw and livestock manure wastes every year,at the same time,the comprehensive treatment efficiency is low,which has seriously restricted the development of related industries.In contrast,the traditional anaerobic digestion（AD）technology used in the treatment of agricultural and animal husbandry wastes,has long operation time,low total solid（TS）concentration and easy to cause inhibition.To solve above problems,some scholars proposed to add biochar to AD in order to improve the treatment efficiency as well as enhance stability of the system.However,most researchers focused on mono-digestion with biochar,and paid attention to the micro-mechanism of biochar adsorption and microbial enrichment.In this study,two kinds of wastes:swine manure and corn straw,were selected.After adding biochar,response surface method was used to determine the proportion of added substrates,and kinetic models were used to analyze the change of methane and main components in the substrate.Finally,the change of main components in substrates along with the methane production was analyzed.The main contents and conclusions are as follows:（1）The characteristics of co-digestion of swine manure and corn stalks with biochar added.In this chapter,swine manure and corn straw were selected as substrates,and experiments were carried out based on the principle of single variable.The effects of TS of mixed raw materials,carbon nitrogen（C/N）ratio and biochar addition on co-digestion were explored respectively.Besides,the daily methane production,the methane content,the cumulative methane production and the solvable chemical oxygen demand（s COD）of digestate were analyzed.The results showed that:with the increase of TS in substrates,the cumulative methane production first increased and then decreased.High TS leads to the increase of s COD in the middle and later stages.The first peak of daily methane production will increase and its arriving time will be advanced if TS in substrates is suitable.The increase of C/N ratio of feedstock results in the decrease of the first peak value and the increase of the second peak value,but the rising C/N has no significant effect on the methane content.Therefore,high TS and low C/N ratio will reduce the methane production efficiency and greatly improve the s COD of digestate,while adding biochar can effectively improve the initial methane content.（2）The parameter optimization of co-digestion of swine manure and corn stalks with biochar added.This chapter uses the method of Central Composition Design（CCD）,taking the TS（x₁）,the amount of pyrolytic carbon added（x₂）and the C/N ratio（x₃）as independent variables,the regression model of methane yield（y）at the confidence levelα=0.1 is y=267.22+10.08x₁+10.37x₂+7.96x₃-42.90x₁²-14.09x₂²-16.03x₃².The results show that the fitting effect of the model is good through the goodness of fit analysis,residual analysis,disturbance analysis and other statistical evaluation.Additionally,the order of importance of three factors was TS>C/N>biochar addition.The optimal TS,biochar addition and C/N were 6.18%,8.73%and 21.69,respectively,and the methane production rate was 269ml/g VS.The relative error of the data obtained from the validation test accounts for 0.6%of the test value,and the deviation between the test value and the predicted value of the model is less than 5%.Therefore,the model obtained in this chapter is reliable and can be used to describe the variation of methane yield with the total solid content,the amount of biochar added and the ratio of carbon to nitrogen.（3）The kinetic analysis of co-digestion of swine manure and corn stalks with biochar added.In this chapter,under the condition of TS of 6.18%and C/N ratio of 21.69,several samples of biogas and digestate were selected in both of the experimental group（with 8.73%biochar）and the control group（without biochar）.In addition,the degradation sequences and trend analysis of methane and four main components are carried out.The results showed that:at the confidence level ofα=0.1,the cumulative methane production and starch degradation rate of the experimental group with biochar were significantly higher than those of the control group without biochar.The main degradation of the experimental group showed that the sequence of degradation was hemicellulose and starch degradation firstly,crude protein degradation later.The modified Gompertz equation can fit the cumulative methane production better in both the experimental group and the control group;the modified Gompertz equation and Logistics equation can fit the main degradation components better in both the experimental group and the control group.Therefore,by analyzing the parameters of the kinetic equation,it is clear that adding biochar can shorten the lag time and improve the efficiency of AD,furthermore,biochar also can promote the degradation rate of starch components largely in substrate.更多还原