黄土导气性与甲烷氧化能力测试及在覆盖层中的应用

发布时间：2018-06-23 08:17

本文选题：填埋场覆盖层 + 黄土　；参考：《浙江大学》2014年硕士论文

【摘要】：黄土在我国干旱和半干旱的西北地区广泛分布,是当地垃圾填埋场覆盖层的主要材料,该材料的气体渗透特性和甲烷氧化能力直接影响了覆盖层对填埋气释放控制和甲烷减排的效果。因而研究覆盖黄土气体渗透特性和甲烷氧化能力,以及覆盖层中气体运移和甲烷氧化的相关规律,对于甲烷氧化功能覆盖层的设计具有重要的现实意义。本文通过室内单元体试验和模型试验、数值模拟和解析法等手段,系统研究了覆盖黄土的气体渗透特性和甲烷氧化能力,以及黄土覆盖层中气体运移和甲烷氧化的相关规律,并探讨了覆盖层的甲烷氧化能力。本文所做的主要工作和相应的研究成果如下： (1)利用自制的气体渗透系数测量装置测试了非饱和黄土的气体渗透系数,分析了压实度、压实含水量和土样结团状况、服役含水量对压实黄土气体渗透系数的影响。测试结果表明,压实含水量相同时,黄土的气体渗透系数随干密度的增大而呈指数型减小；干密度相同时,黄土气体渗透系数受到压实含水量和土样结团状况的共同影响；当黄土土体结构一定时,其气体渗透系数随服役含水量的增大而减小,且压实程度越高,气体渗透系数减小得越快。 (2)通过22天的培养瓶试验测试了覆盖黄土的甲烷氧化能力,研究了覆盖时间、含水量和堆肥掺量等因素对黄土甲烷氧化能力的影响,分析了甲烷氧化过程中气体组分变化关系。测试结果表明,覆盖时间不同的黄土的甲烷氧化能力相差很大,未用作覆盖的新鲜黄土几乎没有甲烷氧化能力；在新鲜黄土中掺入堆肥能有效提高新鲜黄土的甲烷氧化能力；含水量对覆盖土的甲烷氧化能力有很大影响,黄土甲烷氧化的最适宜含水量为20%～30%；甲烷氧化过程中,甲烷氧化菌将甲烷中约44%的碳氧化为二氧化碳,其余碳转化为甲烷氧化菌胞内物质。 (3)利用自制的模拟覆盖层土柱试验装置开展了模拟黄土覆盖层的土柱试验,研究了土柱中气体运移和甲烷氧化规律,以及降雨对覆盖层中气体运移和甲烷氧化的影响。试验结果表明,土柱两层土中的气压分别沿深度线性增大,空气扩散传入土中的深度约为30～40cm；经过5天的培养后,土柱才逐渐具有甲烷氧化能力,试验中土柱的最大甲烷去除率和甲烷氧化速率分别为27.8%和68.4g CH4·m-2·d-1,甲烷氧化活动最为强烈的区域为5～25cm；模拟降雨使得土柱表层土体的导气性急剧减小,甲烷氧化活动迅速减弱至近乎停止,随着土柱表层水分逐渐下渗,导气性逐渐恢复,甲烷氧化能力也随之恢复。 (4)通过建立填埋气在垃圾体和覆盖层中的一维稳态运移模型,分析了覆盖层气体渗透系数和抽气速率对填埋气释放控制效果的影响,并探讨了覆盖层的甲烷氧化能力,提出了一些甲烷氧化功能覆盖层设计参数确定的建议。分析和试算结果表明,在一定的产气速率条件下,覆盖层底部气压随覆盖层气体渗透系数的减小而增大,当该气压超过警戒气压时,需要采取抽气等措施减小气压以保证覆盖层的安全稳定性；从覆盖层的气体扩散层抽气等措施可有效减小覆盖层底部气压和减少填埋气的释放；通过在覆盖层的植被层中掺入堆肥等高有机质含量的材料来提高覆盖层的甲烷氧化能力时,需要根据填埋场的产气速率和覆盖层的气体渗透系数确定与之匹配的覆盖土甲烷氧化速率,进而得到合理的堆肥掺量。
[Abstract]:Loess is widely distributed in arid and semi-arid northwest areas of China. It is the main material for the cover layer of local landfill. The gas permeability and methane oxidation capacity of the material directly affect the effect of the cover layer on the release control of landfill gas and the methane emission reduction. As well as the law of gas migration and methane oxidation in the overburden layer, it has important practical significance for the design of methane oxidation functional coverage.
In this paper, through the laboratory unit test and model test, numerical simulation and analytical method, the gas permeability and methane oxidation capacity of the covered loess, the gas migration and methane oxidation in the loess cover layer are systematically studied, and the methane oxidation capacity of the covering layer is discussed. The main work and corresponding work of this paper are done in this paper. The results of the research are as follows:
(1) the gas permeability coefficient of unsaturated loess is tested by the self-made gas permeability coefficient measuring device, and the influence of compaction degree, compacted water content and soil sample formation and water content on the permeability coefficient of compacted loess is analyzed. The test results show that the permeability coefficient of loess increases with the dry density when the compacted water content is the same. When the dry density is the same, the permeability coefficient of the loess is affected by the compacted water content and the state of the soil sample. When the structure of the loess soil is certain, the gas permeability coefficient decreases with the increase of the service water content, and the higher the degree of compaction, the faster the gas permeability coefficient decreases.
(2) the methane oxidation capacity of loess covered with loess was tested by a 22 day culture bottle test. The effects of covering time, water content and the amount of composting on the oxidation capacity of methane were studied. The variation of gas components in the process of methane oxidation was analyzed. The test results showed that the difference of methane oxidation capacity of loess with different coverage time was very different. Large, fresh loess not used as cover almost has no methane oxidation capacity; adding compost in fresh loess can effectively improve the methane oxidation capacity of fresh loess; water content has a great influence on the methane oxidation capacity of the covered soil, and the optimum water content of methane oxidation is 20% to 30%; methane oxidizing bacteria in the process of methane oxidation About 44% of the carbon in methane is oxidized to carbon dioxide, and the remaining carbon is converted into intracellular substances of methanogenic bacteria.
(3) the soil column test of simulated loess covered layer was carried out by the self-made simulated covering soil column test device. The gas migration and methane oxidation in the soil column and the effect of rainfall on the gas migration and methane oxidation in the cover layer were studied. The experimental results showed that the air pressure in the two layers of soil column increased linearly along the depth, and the air diffused in the soil column. The depth of the afferent soil is about 30 ~ 40cm. After 5 days of culture, the soil column gradually has the capacity of methane oxidation. The maximum methane removal rate and methane oxidation rate of the soil column in the test are 27.8% and 68.4g CH4 m-2. D-1 respectively. The most intense area of methane oxidation is 5 to 25cm, and the simulated rainfall leads to the air conduction in the surface of the soil column. The activity of methane oxidation decreased rapidly to nearly stop, with the gradual infiltration of water in the surface of the soil column, the gas conductivity gradually resumed, and the methane oxidation capacity resumed.
(4) through the establishment of one dimensional steady migration model of landfill gas in the waste and cover layer, the influence of the gas permeability coefficient and the pumping rate on the control effect of the landfill gas release is analyzed, and the methane oxidation capacity of the cover layer is discussed. Some suggestions for determining the design parameters of the methane oxidation energy cover layer are put forward. The results show that the bottom pressure of the cover layer increases with the decrease of the permeability coefficient of the cover layer under certain gas production rate. When the pressure exceeds the warning pressure, the air pressure should be taken to reduce the pressure to ensure the safety and stability of the cover layer, and the cover layer can effectively reduce the cover layer from the gas diffusion layer of the cover layer. At the bottom of the air pressure and reducing the release of the landfill gas, the methane oxidation rate of the covered soil should be determined according to the gas production rate of the landfill and the gas permeability coefficient of the cover layer by adding the high organic matter content of the compost in the cover layer to improve the methane oxidation capacity. The amount of composting.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU444

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