Characteristics of gaseous product from municipal solid waste gasification with hot blast furnace slag

Possibility of combustible gas production from municipal solid waste （MSW） using hot blast furnace （BF） slag has been studied.The objective of this work is to generate combustible gas from MSW using heated BF slag.In this experiment,the thermal stability of the MSW was analyzed by thermogravimetric analysis,and effects of temperature,gasifying agent （air,N2,steam） and BF slag on the gas products were investigated at 600？900 ？C.The thermogravimetric analysis indicates that the weight loss of MSW includes four stages：evaporation of the moisture,combustion of volatile materials,burning of carbon residue and burnout of ash.The contents of the combustible gas increase with increasing temperature,and the lower calorific value （LCV） increases rapidly at 600？900 ？C.It is found that volume fraction of CO,H2 and CH4 at different atmospheres increases in the order N2〈air〈steam.It is believed that BF slag acts as the catalyst and the heat carrier,which promotes the gasification reactivity of MSW.

Thermodynamic Analysis of the Gasification of Municipal Solid Waste

This work aims to understand the gasification performance of municipal solid waste （MSW） by means of thermodynamic analysis. Thermodynamic analysis is based on the assumption that the gasification reactions take place at the thermodynamic equilibrium condition, without regard to the reactor and process characteristics. First, model components of MSW including food, green wastes, paper, textiles, rubber, chlorine-free plastic, and polyvinyl chloride were chosen as the feedstock of a steam gasification process, with the steam temperature ranging from 973 K to 2273 K and the steam-to-MSW ratio （STMR） ranging from 1 to 5. It was found that the effect of the STMR on the gasification performance was almost the same as that of the steam temperature. All the differences among the seven types of MSW were caused by the variation of their compositions. Next, the gasification of actual MSW was analyzed using this thermodynamic equilibrium model. It was possible to count the inorganic components of actual MSW as silicon dioxide or aluminum oxide for the purpose of simplification, due to the fact that the inorganic components mainly affected the reactor temperature. A detailed comparison was made of the composition of the gaseous products obtained using steam, hydrogen, and air gasifying agents to provide basic knowledge regarding the appropriate choice of gasifying agent in MSW treatment upon demand.

Experimental study on combustion characteristics of municipal solid waste

As incineration provides a relatively safe means of disposal, significant reduction of weight and volume, and energy recovery from the waste, it was adopted by many countries. For the experimental investigation on the combustion characteristics of municipal solid waste(MSW), a lab scale fluidized bed facility was constructed. Many kinds of combustion runs were conducted in this fluidized bed combustion facility. The examined parameters were bed temperature(773 to 1143K), form of fuels (scrap or whole), moisture of fuels and so on. Concentration of CO 2,CO,SO 2, O 2 and NOx in the flue gas were monitored and recorded every 5 seconds. The temperatures along the reactor are recorded every 10 seconds. Experimental results were given and analyzed.

Exploring Enablers and Barriers to Municipal Solid Waste (MSW) Management Technologies Adoption in the Kingdom of Bahrain

Municipal Solid Waste (MSW) becomes a point of focus globally due to its harmful effects on the environment and human health if it is not managed properly. MSW was proved globally to be used as a resource, and it has a major opportunity in the realm of conversion technologies. Accordingly, this study aims to explore the enablers and barriers to six different MSW management (MSWM) technologies adopted in the Kingdom of Bahrain, in order to ensure the successful adoption of these technologies that are Anaerobic Digestion (AD), Incineration, Pyrolysis, Gasification, Composting and Refused Derived Fuel (RDF). This study provides sufficient information to the decision and policy-makers for the processes of selection and adoption of the MSWM technologies in Bahrain, using a qualitative approach “mainly semi-structured interviews” with experts and then Thematic Analysis using nvivo12 software. The results show that the main themes that enablers and barriers fall under are: political (e.g. national waste management strategy), technical (e.g. segregation at source), managerial (e.g. capacity building), social (e.g. public awareness), economic (e.g. incentives to investment) and environmental (e.g. air quality). This study concluded that in order to succeed in the MSWM technologies adoption, the resulted barriers should be overcome. Furthermore, Incineration was recommended as the best solution to manage MSW which has the least barriers and most enablers in Bahrain as per the experts.

Research on municipal solid waste composting with coal ash

Considering the fact that there is much coal ash in the municipal solid waste (MSW) in some cities of China, the feasibility of composting in this situation was studied and the effect of content of the coal ash on the composting process and some basic relative technological parameters were investigated. The values of the moisture, the total organic matter, the content of coal ash, the C/N ratio and the ventilation were suggested to be 50%60%, 40%60%, 40%60%, (25∶1)(35∶1) and 0.050.20 m 3/(min·m 3), respectively.

Experimental study on MSW gasification and melting technology

In order to develop municipal solid waste （MSW） gasification and melting technology, two preliminary experiments and a principle integrated experiment were fulfilled respectively. The gasification characteristics of MSW were studied at 500-750℃ when equivalence ratio （ER） was 0.2--0.5 using a fluidized-bed gasifier. When temperature was 550-700℃ and ER was 0.2--0.4, low heat value （LHV） of syngas reaches 4000-12000 kJ/Nm^3. The melting characteristics of fly ash were investigated at 1100-1460℃ using a fixed-bed furnace. It was proved that over 99.9% of dioxins could be decomposed and most heavy-metals could be solidified when temperature was 1100-1300℃. The principle integrated experiment was carried out in a fluidized-bed gasification and swirl-melting system. MSW was gasified etticiently at 550-650℃, swirl-melting furnace maintains at 1200-1300℃ stably and over 95% of fly ash could be caught by the swirl-melting furnace. The results provided much practical experience and basic data to develop MSW gasification and melting technology.

Development of catalytic combustion and CO_(2)capture and conversion technology

Changes are needed to improve the efficiency and lower the CO_(2)emissions of traditional coal-fired power generation,which is the main source of global CO_(2)emissions.The integrated gasification fuel cell(IGFC)process,which combines coal gasification and high-temperature fuel cells,was proposed in 2017 to improve the efficiency of coal-based power generation and reduce CO_(2)emissions.Supported by the National Key R&D Program of China,the IGFC for nearzero CO_(2)emissions program was enacted with the goal of achieving near-zero CO_(2)emissions based on(1)catalytic combustion of the flue gas from solid oxide fuel cell(SOFC)stacks and(2)CO_(2)conversion using solid oxide electrolysis cells(SOECs).In this work,we investigated a kW-level catalytic combustion burner and SOEC stack,evaluated the electrochemical performance of the SOEC stack in H2O electrolysis and H2O/CO_(2)co-electrolysis,and established a multiscale and multi-physical coupling simulation model of SOFCs and SOECs.The process developed in this work paves the way for the demonstration and deployment of IGFC technology in the future.

Breakthrough Technologies for the Biorefining of Organic Solid and Liquid Wastes

Organic solid and liquid wastes contain large amounts of energy, nutrients, and water, and should not be perceived as merely waste. Recycling, composting, and combustion of non-recyclables have been practiced for decades to capture the energy and values from municipal solid wastes. Treatment and disposal have been the primary management strategy for wastewater. As new technologies are emerging, alternative options for the utilization of both solid wastes and wastewater have become available. Considering the complexity of the chemical, physical, and biological properties of these wastes, multiple technologies may be required to maximize the energy and value recovery from the wastes. For this purpose, biorefin- ing tends to be an appropriate approach to completely utilize the energy and value available in wastes. Research has demonstrated that non-recyclable waste materials and bio-solids can be converted into usable heat, electricity, fuel, and chemicals through a variety of processes, and the liquid waste streams have the potential to support crop and algae growth and provide other energy recovery and food production options. In this paper, we propose new biorefining schemes aimed at organic solid and liquid wastes from municipal sources, food and biological processing plants, and animal production facilities. Four new breakthrough technologies-namely, vacuum-assisted thermophilic anaerobic digestion, extended aquaponics, oily wastes to biodiesel via glycerolysis, and microwave-assisted thermochemical conversion-can be incorporated into the biorefining schemes, thereby enabling the complete utilization of those wastes for the production of chemicals, fertilizer, energy （biogas, syngas, biodiesel, and bio-oil）, foods, and feeds, and resulting in clean water and a significant reduction in pollutant emissions.

Energy Recovery from MSW Treatment by Gasification and Melting Technology

The increase of waste production, joined to the difficulties concerning both the identification of new disposal sites and the construction of big conventional incinerators, led in recent years to the development of new technologies for waste management such as gasification and melting treatments. The possibility to introduce in the Italian context the DMS （direct melting system） technology, designed and manufactured by Nippon Steel Engineering Co. Ltd., has been taken into account for the scope of proposed work. DMS technology consists in MSW gasification, slags melting and combustion of the syngas produced, with the consequent generation of electric energy through a steam cycle. The system minimizes environmental impact, thanks to an effective recycling of useful resources such as inert melted slags and metals, featuring high flexibility in terms of treatment capacity due to its modular design. The aim of this article is to consider different plant configurations in order to optimize the energy recovery downstream the DMS module. As a case study, landfill gas exploitation integrated in the DMS plant will be considered as a typical situation that could occur in the Italian scenario. The energetic input provided by the biogas allows improving the thermo-economic performances according to market incentives.

In-situ catalytic decomposition of emitted ammonia from municipal solid waste gasification by Ni–M bimetallic catalysts supported on sewage sludge-derived biochar

Gasification technology can effectively realize energy recovery from municipal solid waste(MSW)to reduce its negative impact on the environment.However,ammonia,as a pollutant derived from MSW gasification,needs to be treated because its emission is considered harmful to mankind.This work aims to decompose the NH3 pollutant from MSW gasification by an in-situ catalytic method.The MSW sample is composed of rice,paper,polystyrene granules,rubber gloves,textile and wood chips.Ni–M(M=Co,Fe,Zn)bimetallic catalysts supported on sewage sludge-derived biochar(SSC)were prepared by co-impregnation method and further characterized by X-ray diffraction,N2 isothermal adsorption,scanning electron microscopy,transmission electron microscopy and NH3 temperature programmed desorption.Prior to the experiments,the catalysts were first homogeneously mixed with the MSW sample,and then in-situ catalytic tests were conducted in a horizontal fixed-bed reactor.The effect of the second metal(Co,Fe,Zn)on the catalytic performance was compared to screen the best Ni-M dual.It was found that the Ni–Co/SSC catalyst had the best activity toward NH3 decomposition,whose decomposition rate reached 40.21%at 650℃.The best catalytic performance of Ni–Co/SSC can be explained by its smaller Ni particle size that facilitates the dispersion of active sites as well as the addition of Co reducing the energy barrier for the associative decomposition of NH species during the NH3 decomposition process.Besides,the activity of Ni–Co/SSC increased from 450℃to 700℃as the NH3 decomposition reaction was endothermic.

不同含水率下的生活垃圾气化特性模拟

我国不同地区的垃圾含水率有很大差异,为了探究垃圾含水率对气化特性的影响,更进一步地实现生活垃圾资源化利用,本文基于Aspen Plus建立了垃圾气化的工艺流程模型,分析了不同含水率下的温度对气化合成气组分、碳转化率(CCE)、低位热值(LHV)、气体产率的影响,气化温度提高促进CCE、LHV先降低后升高。结果表明升温和增加含水率可提高CCE、降低LHV,温度小于650℃时,增加含水率可促进气体产率,温度大于650℃时,增加含水率会降低气体产率;通过诸多气化指标得出垃圾含水率为25%、气化温度为850℃时为最优工况,在此基础上,40.63%的产气燃烧比例放热可以为干燥、热解、气化阶段提供热量,实现系统的热量自给。当气化温度和产气燃烧比例不变时,随着垃圾含水率的提高,气化系统对外界放出的热量先增加后减小。

基于Aspen Plus的MSW气化熔融工艺全流程模拟研究

城市固体废物(MSW)气化熔融工艺能够减少二噁英的生成和熔融固化重金属,是一种清洁高效的固体废物处理方式。已有研究多针对MSW的热解特性以及污染物的生成与排放,而对气化熔融工艺系统模块之间的影响和各反应器间物质流、能量流的联动变化过程研究不足。利用Aspen Plus模拟平台,基于吉布斯自由能最小化原理,对MSW气化熔融工艺进行了全流程模拟研究,分析了垃圾干燥温度、垃圾含水率、气化温度、气化介质以及灰熔点对工艺流程节点参数、物质流和能量流的影响,并提出了优化的工艺流程和运行参数。结果表明:在垃圾热解模拟时,垃圾含水率为9%,通过烟气循环能达到能量自给;在相同条件下,以水蒸气作为气化介质的气化效率最高,且在气化温度为850℃,水蒸气当量比为50%时,达到最佳工艺效果;当气化后产生的焦炭在熔融炉内燃烧刚满足灰熔点温度时,灰熔点的升高使气化剂比例、气化气有效气体摩尔流量和碳转化率不断降低。不同工况下的物质流、能量流的变化对实际工程具有指导意义。

基于仿真机理和改进回归决策树的二噁英排放建模

城市固废焚烧(Municipal solid waste incineration,MSWI)过程是“世纪之毒”二噁英(Dioxin,DXN)的重要排放源之一.截止目前为止,DXN的演化机理和实时检测仍是尚未解决的难题.现有研究主要基于离线化验数据构建数据驱动模型,DXN的检测未有效结合燃烧过程机理.针对该问题,本文提出基于仿真机理和改进线性回归决策树(Linear regression decision tree,LRDT)的DXN排放建模.首先,采用基于床层固废燃烧模拟软件FLIC(Fluid dynamic incinerator code)和过程工程先进系统软件(Advanced system for process engineering Plus,Aspen Plus)耦合的数值仿真模型,获取蕴含多运行工况的虚拟机理数据;接着,利用虚拟机理数据构建基于改进LRDT的CO_(2)、CO和O_(2)燃烧状态表征变量模型;然后,以真实CO_(2)、CO、O_(2)作为输入和以DXN真值作为输出,构建多入单出LRDT的过程映射模型(Process mapping model,PMM),再利用该模型进行半监督学习和结构迁移得到机理映射模型1(Mechanism mapping models1,MMM1);最后,通过结构增量学习获得基于半监督迁移学习的MMM2模型.在实验室的半实物平台和北京某MSWI厂的边侧验证平台对所提方法进行了工业应用验证.实验结果证明了所提方法与研发的软测量系统可有效实现二噁英排放浓度在线检测.

生活垃圾气炭分离燃烧污染物排放特性研究

为了研究生活垃圾挥发分和热解碳分离燃烧污染物排放特性,探索通过改变燃烧方式来降低生活垃圾燃烧污染物排放,利用固定床装置对生活垃圾直接燃烧和热解后的挥发分、热解炭单独燃烧进行了试验对比。结果表明:与直接燃烧相比,气炭分离燃烧生成CO、HCl、SO_(2)、NO_(2)、NH_(3)、HCN、HNCO等污染物的总量明显减少,NO和N_(2)O生成量略有增加;不同的燃烧方式产生的NO_(x)组分有较大的区别,直接燃烧产生的NO_(x)主要是NO和NO_(2),气炭分离后燃烧产生的NO主要是NO不同燃烧方式下,过量空气系数α对污染物的生成量均有影响,随着α的增加,直接燃烧时产生的CO、N_(2)O、SO_(2)、NH_(3)有所减少,NO、NO_(2)、HCN、HNCO有所增加,挥发分燃烧产生NO明显增加,HCN和HNCO略有减少,HCl、N_(2)O、NO_(2)、NH_(3)生成量很小变化不明显;热解炭燃烧时各污染物生成量均较低。

基于混合数据增强的MSWI过程燃烧状态识别

国内城市固废焚烧(Municipal solid waste incineration, MSWI)过程通常依靠运行专家观察炉内火焰识别燃烧状态后再结合自身经验修正控制策略以维持稳定燃烧,存在智能化水平低、识别结果具有主观性与随意性等问题.由于MSWI过程的火焰图像具有强污染、多噪声等特性,并且存在异常工况数据较为稀缺等问题,导致传统目标识别方法难以适用.对此,提出一种基于混合数据增强的MSWI过程燃烧状态识别方法.首先,结合领域专家经验与焚烧炉排结构对燃烧状态进行标定;接着,设计由粗调和精调两级组成的深度卷积生成对抗网络(Deep convolutional generative adversarial network, DCGAN)以获取多工况火焰图像;然后,采用弗雷歇距离(Fréchet inception distance, FID)对生成式样本进行自适应选择;最后,通过非生成式数据增强对样本进行再次扩充,获得混合增强数据构建卷积神经网络以识别燃烧状态.基于某MSWI电厂实际运行数据实验,表明该方法有效地提高了识别网络的泛化性与鲁棒性,具有良好的识别精度.

基于等离子气化的城市固废制备乙酰丙酸系统及性能评估

提出了一种利用城市固体废弃物制备乙酰丙酸(Levulinic Acid,LA)的系统,并通过Aspen Plus进行建模。通过回收LA的催化剂与萃取剂并使用固体残留物(生物质碳)、沼气和固废中的衍生燃料作为热源,最大限度地减少废物产生。通过等离子气化技术耦合厌氧发酵技术为系统供热。对所提出系统的性能进行了评估。结果表明:该系统在技术上是可行的,有较高能源转化效率和较低的环境污染,等离子气化效率为69.94%,净现值达189483万元,动态回收周期为5.04 a,拥有0.37的内部收益率。

基于可视化大尺寸快速升温热重分析装置的混合固废热解和燃烧特性的实验研究

城市固体废弃物(municipal solid waste,MSW)的燃烧依次经历干燥和热解、挥发分燃烧、焦炭燃烧三个阶段,描述样品热解、燃烧动力学特性的主要参数包括样品质量、温度、尺寸和点火特性等。实际固废焚烧处理过程的主要特征包括升温速率高(400 K/min以上)、样品尺寸大、组分复杂和样品体积收缩等。然而,常规用于测量固废热解、燃烧的实验设备如TGA、macro TGA和沉降炉等存在升温速率或样品尺寸受限、难以同时获取样品的质量和温度及图像信息等缺陷。为此,搭建了可视化大尺寸快速升温热重分析装置,测量了打印纸、PET塑料、松木和厨余垃圾及其混合样品在慢速升温(10 K/min,15 K/min,25 K/min)和快速升温(约500 K/min)工况下热解和燃烧的质量、温度和图像信息。结果表明:升温速率对混合样品的热解和燃烧动力学特性影响较大。慢速升温模式下,混合样品燃烧DTG曲线呈现多峰特征,且这些峰的出现时间与其四种组分的燃烧DTG曲线峰值具有对应关系;快速升温模式下,混合样品各组分的热解区间趋于重叠,燃烧DTG曲线的峰减少为一个。温度和图像信息表明,15 K/min慢速升温模式下,混合样品内部和表面的点火时间基本一致,点火时样品中心温度为191℃,燃烧发生在样品表面。快速升温模式下,升温开始后样品表面可以立即观察到挥发分的燃烧火焰,随后燃烧逐步向样品内部扩展。随着燃烧的进行,样品尺寸持续收缩,直至燃尽。

“双碳”目标下城市生活垃圾制氢技术研究进展

在全球碳减排的背景下,中国提出了实现“碳达峰碳中和”的“双碳”目标。利用城市生活垃圾中的生物质能制氢符合“双碳”目标要求。目前,城市生活垃圾制氢技术包括热化学转化、生物转化等直接制氢技术和结合甲烷重整制氢技术与城市生活垃圾厌氧发酵技术的间接制氢技术两大类。间接制氢技术因成熟可靠而成为当下城市生活垃圾制氢的主流工程化应用方向。城市生活垃圾前端分类、中端收运及末端处置系统的完善,将对生活垃圾制氢技术发展起到积极推动作用。

生活垃圾热解气化炉结构与污染物控制研究

随着污染物排放要求的日益严格,焚烧成本进一步提高,热解气化技术以其投资小、运行成本低、污染物排放少的特点,成为焚烧的有效补充并受到了广泛关注。主要通过介绍热解炉的结构特点、技术原理、生成物特性来研究生活垃圾热解炉的技术优势,并通过分析生活垃圾热解炉产物的生成环境及生成量来研究生活垃圾热解工艺污染物的排放情况。

城市固废焚烧过程燃烧线极端异常火焰图像对抗生成

燃烧线是表征城市固废焚烧(municipal solid waste incineration,MSWI)过程燃烧稳定性的关键参数之一。完备的火焰图像模板库是实现燃烧线量化以从检测视角代替依靠运行专家“人工看火”,进而通过实时反馈提升MSWI过程控制的智能化水平的基础。针对燃烧线极端异常火焰图像缺失问题,该文提出基于机理知识和对抗网络的燃烧线极端异常火焰图像生成方法。首先,基于焚烧炉内三维空间位置到图像像素点的机理映射关系分析燃烧线极端异常火焰图像,通过对正常火焰图像像素点的平移、拼接和组合等方式获取伪标记的燃烧线极端异常火焰图像;然后,采用循环生成对抗网络(cycle generative adversarial networks,CycleGAN)获得符合真实火焰图像分布的候选图像;最后,提出组合基于弗雷歇距离(Fréchet inception distance,FID)评估最优模型参数和根据伪标记筛选最终燃烧线极端异常火焰图像的2级评估与筛选策略。针对北京某MSWI厂的实验结果表明:依据燃烧线可划分图像为51%~73.6%正常、47%~51%和73.6%~100%异常、0%~47%极端异常;当第2级评估阈值设定为0.4时,所提方法生成合格极端异常火焰图像的比例为85.7%,优于传统评估方法。