垃圾填埋场填埋气竖井收集系统设计优化

目前实际工程中通常采用现场抽气试验的方法确定垃圾填埋气收集系统的相关技术参数。这种方法不能对影响抽气效果的因素综合分析并加以优化，本文利用竖井抽气条件下填埋气压力分布模型，分析讨论了抽气系统各参数对对抽气效果的影响，提出了垃圾填埋场填埋气竖井收集系统的抽气量，抽气井影响半径，抽气井埋深的优化设计方法，可为填埋气污染控制与回收利用系统的规划设计及运行管理提供技术支持。     

城市污泥填埋气集气井收集系统的优化研究

对城市污泥填埋场填埋气集气井收集系统进行了优化研究,考察了城市污泥水平方向的渗透系数(以下简称污泥渗透系数)对集气井影响半径的影响、集气井抽气负压随填埋时间的变化规律、填埋气的经济收集年限。结果表明,当抽气负压为25000～30000Pa时,污泥渗透系数分别取1.04×10-7、2.60×10-8、1.04×10-8m2/(Pa.s)时,集气井的影响半径分别为10.0～11.0、6.0～7.0、5.0～5.5m,过小的污泥渗透系数会严重影响集气井的集气效率,因此污泥渗透系数最好不应小于1.00×10-8m2/(Pa.s);随城市污泥填埋时间的增加,集气井抽气负压总体呈指数型降低趋势,从第8年起,抽气负压由起初的25000Pa降低到5000Pa以下,此时CH4产率约为2kg/(m3.a),到第20年时CH4产率接近于零,故从城市污泥填埋后第8年起,对填埋气继续进行收集的意义已经不大。     

垃圾填埋气收集控制的CFD数值模拟应用研究

基于多孔介质渗流理论,给出了填埋气在填埋场内流动控制方程组及其定解条件,但实际填埋场的不规则边界使其很难求得解析解。建立填埋场竖井抽气物理模型,采用计算流体力学数值模拟软件PHONEICS求得控制方程的数值解,并用相关文献的结论进行校验,结果与前人结论相吻合。将该方法应用于实际填埋场抽气系统的设计,通过PHONEICS软件编程接口二次开发计算负压抽气条件下流入抽气系统的外部空气量,由此引入抽气效率做为抽气效果的评价指标,模拟了传统等边三角形布置竖井抽气系统的运行效果,并根据模拟结果对传统竖井抽气系统进行优化。     

苏州市生活垃圾两种处置方法的生命周期影响评价

采用生命周期评价的方法,比较了苏州市垃圾填埋和垃圾焚烧2种处置方法对环境的影响。研究的系统范围主要包括垃圾收集、垃圾运输、垃圾填埋或焚烧以及发电等几个部分。采用收集的垃圾组分数据,利用IPCC推荐的模型等,计算了垃圾填埋和垃圾焚烧时CO₂等气体污染物的排放量。根据对垃圾渗滤液的实测数据,计算了水污染物的排放量。环境影响评价采用日本开发的AIST-LCA Ver4计算机软件进行。计算结果表明：垃圾填埋的生态币值要大得多,可见垃圾焚烧对环境的影响比垃圾填埋的影响要小。所获得的结论较为客观地反映了对环境的影响,可以作为中国城市垃圾处置决策的参考依据。     

西南地区某已封场非规范垃圾填埋场垃圾稳定化进程分析

以重庆某非规范填埋场为例,针对西南地区已封场非规范垃圾填埋场的稳定化进程进行了分析。按照场地布局选取4个采样点,在垃圾体上进行钻孔取样,分析不同深度的垃圾样pH值、有机质、含水率、生物可降解度以及垃圾样浸出液和填埋气组成以及各个指标随着填埋深度的变化规律,确定不同深度垃圾体的稳定化程度。结果表明,场内垃圾已呈现矿化垃圾特征;有机质、BDM、浸出液COD以及填埋气CH4含量等4个指标与填埋深度均较好地符合一级降解反应,可以预测垃圾体稳定化临界填埋深度。根据有机质、BDM、浸出液COD以及填埋气CH4含量等4个指标与填埋深度一级降解反应函数预测临界稳定化深度为15 m,与实测值判定的稳定化填埋深度相一致性。在对非规范垃圾填埋场场地利用过程中,需要先对未稳定的上层垃圾进行清理,并在已稳定的底层垃圾体上充填其他稳定介质后利用该地块。     

模拟成藏地质填埋及诱导填埋有机质生气的理论初探

填埋处理和垃圾生物气的开发利用是实现城市生活垃圾资源化、无害化、减量化处理的有效途径,引入模拟生物气成藏和含气系统的思路,开展地质填埋与诱导填埋有机质生气研究是对能源地质学和填埋设计理念的新探索.通过对比研究地质填埋结构与地质学中生物气藏系统的异同点、生气机理和影响因素的共性与差异,初步论证了将模拟生物气藏理论引入地质填埋设计、优化地质填埋结构、提高填埋有机质生物气化效率和抽排利用效率的可行性;探讨了生物气藏理论在构建地质填埋结构中的可能应用和启示.研究表明:模拟生物气藏地质填埋设计和非常规生物气开发理念具有理论依据和现实基础;生物气藏生、储、盖要素和运、圈、保过程的模拟可应用于垃圾地质填埋场的构建,微生物地球化学理论有助于对诱导填埋有机质生气条件优化的认识.     

非规范生活垃圾填埋场填埋气横向迁移规律及控制

我国城市中尚有大量非规范生活垃圾填埋场存在,对其进行污染整治消除填埋气导致的环境安全隐患刻不容缓.以重庆某垃圾填埋场为例,研究重庆市主城区的非规范生活垃圾填埋场填埋气的横向迁移问题,在垃圾场周边区域布设36个监测井,对监测井中的填埋气进行分析监测,以填埋气特征组分CH4气体的体积浓度变化研究填埋气的横向迁移规律.结果表明,监测井到填埋场边界的距离为监测井中CH4气体浓度的主要影响因素;垃圾场周边距离填埋场场界50 m以外的区域,填埋气的横向迁移已经相当微弱;但是距离填埋场边界50 m以内区域的填埋气的横向迁移明显,需要在距离填埋场边界50 m范围内采取措施与场内填埋气的导排措施配合,进行填埋气的污染控制.     

模拟生物反应器加速产甲烷过程研究

渗滤液原液回灌易导致填埋垃圾产甲烷过程的滞后,从而对甲烷收集利用产生不利影响。通过3根实验室模拟生物反应器,研究了原液回灌(C1)、渗滤液好氧预处理后回灌(C2)和原液回灌+垃圾层上部通风曝气(C3)3种填埋方式下的填埋气产气规律。结果表明,C1甲烷浓度经历短暂上升,达到19.5%后开始逐渐降低,产甲烷速率和产甲烷总量均很低;C2甲烷浓度逐渐上升,在第121天时甲烷浓度达到50%,产甲烷最高速率和产甲烷总量分别为0.31 L/(kg·d)和25.2 L/kg。在停止上部垃圾层通风曝气后,C3甲烷浓度迅速上升,在81 d时甲烷浓度便达到50%以上,最大产甲烷速率和产甲烷总量分别为0.22 L/(kg·d)和16.0 L/kg。对各模拟柱填埋气可回收性评价结果表明,C3填埋气可回收利用比例最高,C2略低,C1在实验期间内则无可回收利用气体产生。     

垃圾填埋气火焰稳定特性试验研究

针对大气式燃烧器在燃烧垃圾填埋气时的火焰稳定特性进行了实验研究,设计了一种结构简单、效果明显的填埋气火焰稳定装置.这种装置对于低热值燃气的稳定燃烧能起到较好的作用.     

北京市垃圾填埋气体排放模拟及CDM现状分析

为了理清北京固废系统潜在的环境影响及相关机制发展状况,本研究基于填埋气逸出模拟对北京市固废系统中的填埋气排放和CDM项目进行研究分析。将中国垃圾填埋气模型应用到北京市,预测其潜在垃圾填埋气排放总碳当量达0.97亿t,2026年左右迎来产气高峰,排放量为54 367 m3/h,碳当量达228万t,2015—2040年间的碳当量占比约53.3%;北京市CDM数据分析显示,2010年以来北京市CDM项目发展良好,但较全国水平稍显滞后,其垃圾填埋气回收利用项目占北京市获批CDM项目总量的11.1%,签发数比例约33.3%,远低于全国水平的41.82%。研究表明:北京市固废系统即将步入产气高峰期,潜在碳排放量巨大,势必将给北京市的温室气体减排工作带来切实压力,但是相关CDM项目发展不适应当前的减排需求,急需加强和改善北京市的城市固体废物管理,推进相关CDM项目在北京的良性发展。     

Surface emission of landfill gas from solid waste landfill

The surface emission of landfill gas (LFG) was studied to estimate the amount of LFG efflux from solid waste landfills using an air flux chamber. LFG efflux increased as atmospheric temperature increased during the day, and the same pattern for the surface emission was observed for the change of seasons. LFG efflux rate decreased from summer through winter. The average LFG efflux rates of winter, spring and summer were 0.1584, 0.3013 and 0.8597 m³ m⁻² h⁻¹ respectively. The total amount of surface emission was calculated based on the seasonal LFG efflux rate and the landfill surface area. From the estimates of LFG generation, it is expected that about 30% of the generated LFG may be released through the surface without extraction process. As forced extraction with a blower proceeded, the extraction well pressure decreased from 1100 to –100 mm H₂O, and the LFG surface efflux decreased markedly above 80%. Thus, the utilization of LFG by forced extraction would be the good solution for global warming and air pollution by LFG.     

Fatal flaws in measuring landfill gas generation rates by empirical well testing

Well testing procedures, such as the Tier 3 methodology specified in the U.S. Code of Federal Regulations (CFR) Subtitle D, are commonly used for directly estimating landfill gas (LFG) emissions at municipal solid waste (MSW) landfills. Similar procedures are also used to estimate LFG generation rates for the design of LFG-to-energy projects. These methodologies assume that the LFG generation rate equals the extraction rate of a test gas well within its radius of influence (ROI). The ROI is defined as the distance from the extraction well at which the induced pressure drop is immeasurable by some standard of precision. Based on fluid dynamic principles, Tier 3 and similar methodologies are demonstrated to be incapable of providing reliable estimates of the LFG generation rate. These tests may either over- or underestimate the LFG generation rate depending on the precision with which the ROI is determined, but they will only coincidentally produce an estimate that accurately represents the actual LFG generation rate. Fluid dynamic principles dictate that the actual LFG generation rate can only be estimated if the pneumatic properties of the refuse and cover materials as well as the excess pressure in the refuse caused by LFG generation are known or can be estimated.     

Removal characteristics of trace compounds of landfill gas by activated carbon adsorption

The removal characteristics of trace compounds and moisture in raw landfill gas (LFG) were studied. The LFG from the extraction well was saturated with water and moisture was eliminated by physical methods including cyclone-type dehydrator and compressor. The moisture removal efficiency of dehydrator and compressor was above 80%. As the moisture contents of LFG decreased, the toxic compounds like aromatics and chlorinated compounds were effectively removed by using the granular activated carbon. The breakthrough time and adsorption capacity of benzene, toluene, and ethyl benzene decreased rapidly when the relative humidity is over 60%. The effect of moisture was more pronounced at lower adsorbate concentrations tested than at higher concentrations. The breakthrough curves for multi-component mixtures show displacement effects. In the course of competing adsorption, adsorbates with strong interaction force to displace weakly bounded substances. Adsorption by activated carbon is in descending order of xylene, ethylbenzene, toluene, tri or tetrachloroethylene, benzene, carbon tetrachloride and chloroform in LFG, respectively.     

Effect of biogas generation on radon emissions from landfills receiving radium-bearing waste from shale gas development

Dramatic increases in the development of oil and natural gas from shale formations will result in large quantities of drill cuttings, flowback water, and produced water. These organic-rich shale gas formations often contain elevated concentrations of naturally occurring radioactive materials (NORM), such as uranium, thorium, and radium. Production of oil and gas from these formations will also lead to the development of technologically enhanced NORM (TENORM) in production equipment. Disposal of these potentially radium-bearing materials in municipal solid waste (MSW) landfills could release radon to the atmosphere. Risk analyses of disposal of radium-bearing TENORM in MSW landfills sponsored by the Department of Energy did not consider the effect of landfill gas (LFG) generation or LFG control systems on radon emissions. Simulation of radon emissions from landfills with LFG generation indicates that LFG generation can significantly increase radon emissions relative to emissions without LFG generation, where the radon emissions are largely controlled by vapor-phase diffusion. Although the operation of LFG control systems at landfills with radon source materials can result in point-source atmospheric radon plumes, the LFG control systems tend to reduce overall radon emissions by reducing advective gas flow through the landfill surface, and increasing the radon residence time in the subsurface, thus allowing more time for radon to decay. In some of the disposal scenarios considered, the radon flux from the landfill and off-site atmospheric activities exceed levels that would be allowed for radon emissions from uranium mill tailings.

Implications: Increased development of hydrocarbons from organic-rich shale formations has raised public concern that wastes from these activities containing naturally occurring radioactive materials, particularly radium, may be disposed in municipal solid waste landfills and endanger public health by releasing radon to the atmosphere. This paper analyses the processes by which radon may be emitted from a landfill to the atmosphere. The analyses indicate that landfill gas generation can significantly increase radon emissions, but that the actual level of radon emissions depend on the place of the waste, construction of the landfill cover, and nature of the landfill gas control system.     

Modelling methane and vinyl chloride in soil surrounding landfills

Sanitary landfilling is used in many countries as a preferred method for disposal of household wastes for reasons of simplicity and economics. Immediately following its deposition within a landfill, most of the organic fraction of waste will begin to undergo degradation through chemical and bacterial action. Landfill gas (LFG) is a product of biodegradation and consists of primarily methane (explosive) and carbon dioxide, with trace amounts of other volatiles that are often toxic gases (for example, vinyl chloride). LFG can migrate through the soil away from the landfill site and appear at the surface away from where it started. Since methane presents a fire or explosive threat, LFG must be controlled to protect property and public safety. To aid this, consideration must be given to models. Therefore, this study was undertaken to develop a simple numerical model by using a finite difference method in order to predict gas migration through the soil surrounding the landfill. The model construction was described as well as the landfill and its surrounding soil. The model was applied to predict methane and vinyl chloride concentrations at different distances from the landfill. Comparison between the predicted and measured values was calculated to evaluate the validity of the model. The agreement between measured and predicted concentrations was found, and this agreement is sufficiently good     

Feasibility of Landfill Gas as a Liquefied Natural Gas Fuel Source for Refuse Trucks

Abstract

The purpose of this paper is to develop a methodology to evaluate the feasibility of using landfill gas (LFG) as a liquefied natural gas (LNG) fuel source for heavy-duty refuse trucks operating on landfills. Using LFG as a vehicle fuel can make the landfills more self-sustaining, reduce their dependence on fossil fuels, and reduce emissions and greenhouse gases. Acrion Technologies Inc. in association with Mack Trucks Inc. developed a technology to generate LNG from LFG using the CO₂ WASH process. A successful application of this process was performed at the Eco Complex in Burlington County, PA. During this application two LNG refuse trucks were operated for 600 hr each using LNG produced from gases from the landfill. The methodology developed in this paper can evaluate the feasibility of three LFG options: doing nothing, electricity generation, and producing LNG to fuel refuse trucks. The methodology involved the modeling of several components: LFG generation, energy recovery processes, fleet operations, economic feasibility, and decision-making. The economic feasibility considers factors such as capital, maintenance, operational, and fuel costs, emissions and tax benefits, and the sale of products such as surplus LNG and food-grade carbon dioxide (CO₂).

Texas was used as a case study. The 96 landfills in Texas were prioritized and 17 landfills were identified that showed potential for converting LFG to LNG for use as a refuse truck fuel. The methodology was applied to a pilot landfill in El Paso, TX. The analysis showed that converting LFG to LNG to fuel refuse trucks proved to be the most feasible option and that the methodology can be applied for any landfill that considers this option.     

填埋场沼气发电的温室气体减排效益分析

填埋场沼气是垃圾卫生填埋场产生的可利用资源.以深圳下坪垃圾填埋场为例,定量分析垃圾填埋气体发电的温室气体减排效益.结果表明,填埋场沼气发电具有很好的经济效益和环境效益,可作为与发达国家进行CDM(清洁发展机制)项目合作的优先技术领域.     

Gas emission into the atmosphere from controlled landfills: an example from Legoli landfill (Tuscany,Italy)

Background, aim and scope  

Landfill gas (LFG) tends to escape from the landfill surface even when LFG collecting systems are installed. Since LFG leaks are generally a noticeable percentage of the total production of LFG, the optimisation of the collection system is a fundamental step for both energy recovery and environmental impact mitigation. In this work, we suggest to take into account the results of direct measurements of gas fluxes at the air–cover interface to achieve this goal.     

Feasibility of landfill gas as a liquefied natural gas fuel source for refuse trucks

The purpose of this paper is to develop a methodology to evaluate the feasibility of using landfill gas (LFG) as a liquefied natural gas (LNG) fuel source for heavy-duty refuse trucks operating on landfills. Using LFG as a vehicle fuel can make the landfills more self-sustaining, reduce their dependence on fossil fuels, and reduce emissions and greenhouse gases. Acrion Technologies Inc. in association with Mack Trucks Inc. developed a technology to generate LNG from LFG using the CO2 WASH process. A successful application of this process was performed at the Eco Complex in Burlington County, PA. During this application two LNG refuse trucks were operated for 600 hr each using LNG produced from gases from the landfill. The methodology developed in this paper can evaluate the feasibility of three LFG options: doing nothing, electricity generation, and producing LNG to fuel refuse trucks. The methodology involved the modeling of several components: LFG generation, energy recovery processes, fleet operations, economic feasibility, and decision-making. The economic feasibility considers factors such as capital, maintenance, operational, and fuel costs, emissions and tax benefits, and the sale of products such as surplus LNG and food-grade carbon dioxide (CO2). Texas was used as a case study. The 96 landfills in Texas were prioritized and 17 landfills were identified that showed potential for converting LFG to LNG for use as a refuse truck fuel. The methodology was applied to a pilot landfill in El Paso, TX. The analysis showed that converting LFG to LNG to fuel refuse trucks proved to be the most feasible option and that the methodology can be applied for any landfill that considers this option.