炉排型垃圾焚烧炉燃烧过程的数值模拟

针对城市生活垃圾焚烧发电厂运行优化的需要,采用计算流体力学的方法建立了垃圾焚烧炉燃烧过程的数值计算模型,通过联合求解质量方程、动量方程、k-ε方程、能量方程,模拟得到了炉内热解气体组分分布、炉内温度场等参数。利用该模型计算得出了炉膛温度、NO_x排放浓度随过量空气系数、生物质掺混比变化的特性曲线,并与实验结果进行了对比。结果表明：该模型能够预测炉内焚烧过程的变化趋势,且计算值与实验值吻合较好,模型误差在8%以内。     

Design consideration for cross jet air mixing in municipal solid waste incinerators

In mass-burning municipal solid waste incinerators, overfire air injection plays a key role in the improvement of mixing and reaction between oxygen and incomplete combustion products and/or pollutants. However, the design parameters of overfire air nozzles are not well understood and sometimes confusing. In this paper, major design parameters concerning cross jet air nozzles are discussed along with flow simulation results for simplified furnace geometry. The overall performance of jet air mixing and the effects of design parameters are quantitatively evaluated. The flow simulation results are interpreted in terms of the penetration depth of the jet into the main flow, the size of the recirculation zone and the ratio of the unmixed portion of the gas flow. The momentum flux ratio J of the jet to the cross flow strongly affects the penetration depth of the jet and the mixing of two flow streams. As the inter-nozzle distance S (in non-dimensional form) decreases, the penetration depth decreases but the size of the recirculation zone increases and the resultant mixing deteriorates. The degree of mixing of the jet with the cross gas stream is evaluated in terms of the mass-averaged probability distribution of the relative concentration. Fresh air disperses more efficiently into the gas stream as J and S increase. The momentum flux ratio and the inter-nozzle distance are considered as important design parameters, and optimum values of these variables can be chosen for the given furnace conditions. This numerical evaluation also provides a basis for similarity considerations in cold flow model tests and the validity of the two-dimensional idealization. © 1997 by John Wiley & Sons, Ltd.     

城市生活垃圾等高热值废弃物资源化利用技术

针对我国城市生活垃圾、废塑料等高热值废弃物,采用比较成熟的焦炉炼焦、蓄热式火焰炉等热解技术,开发高热值城市生活垃圾外热式固定床热解技术、共焦化技术与设备,可以发挥钢铁企业的技术设备优势,减少高热值废弃物热解工艺的研究周期.实现废弃物处理过程的无害化和资源化利用的最大化.     

Experimental Studies on Combustion Characteristics of Mixed Municipal Solid Waste

In our country, municipal solid wastes (MSW) are always burnt in their original forms and only a few pretreatments are taken. Therefore it is vital to study the combustion characteristics of mixed waste. In this paper, thermogravimetric analysis and a lab scale fluidized bed facility were used as experimental means. The data in two different experimental systems were introduced and compared. It took MSW 3-3.5 min to burn out in FB, but in thermogravimetric analyzer, the time is 20-25 min. It can be concluded that, in general, the behavior of a mixture of waste in TGA can be expressed by simple combination of individual components of the waste mixtures. Only minor deviations from the rule were observed. Yet, in Fluidized Bed, it was found that, for some mixtures, there was interference among the components during fluidized bed combustion.     

Environmental analysis of municipal solid waste combustion in a fluidized bed

A steady-state Aspen Plus model of municipal solid waste (MSW) combustion has been developed to simulate the influence of operating conditions and hydrodynamic parameters on the concentrations of air pollutants and performance indicators. To simulate the hydrodynamic characteristics, a FORTRAN subroutine was coupled to Aspen Plus software. Model validated against the experimental data is available in the literature and found to be in good agreement. Results showed that the operating pressure has a negligible influence on gas composition and performance indicators, but it plays a major role in the commercialization of thermal conversion of carbon-based fuels due to a significant reduction in the capital costs. It was also concluded that as the U_mf increases from 1.2 to 2.5, the concentrations of pollutants released increase, probably due to a considerable decrease in the rate of reactions involved, especially at the end of combustor.     

An experimental study on a novel shredder for municipal solid waste (MSW)

Based on composition and volume-mass properties of MSW (i.e., unit weight, void ratio, and water content), a new way for the breakage of the organic MSW is presented to effectively convert MSW to heat and fuel gas. A lab-scale shredder consisting of compaction and shredding chambers is designed and the breakage process of MSW in the shredder can be divided into three successive phases: deformation, further deformation, compressive shearing. The performances of the shredder, such as the effect of the rotor velocity and hydraulic pressure on product size distribution and specific energy are investigated. The results show that with hydraulic pressure the specific energy is reduced, and size distribution of product is finer. When hydraulic pressure is constant, the specific energy decreases with increasing rotor velocity, while the products size distribution is coarser.     

Nonisothermal particle modeling of municipal solid waste combustion with heavy metal vaporization

A particulate model was developed for municipal solid-waste incineration in a fluidized bed combining solid-waste-particle combustion and heavy metal vaporization from the burning particles. Based on a simpler, isothermal version presented previously, this model combines an asymptotic-combustion model for carbonaceous-solid combustion and a shrinking-core model to describe the heavy metal vaporization phenomenon, in which the particle is now considered nonisothermal. A parametric study is presented that shows the influence of temperature on the global metal-vaporization process. The simulation results are compared to experimental data obtained with a lab-scale fluid bed incinerator and to the results of the simpler isothermal model. It is shown that conduction in the particle strongly affects the variation of the vaporization rate with time and that the present version of the model well fits both the shape of the plots and the maximum heavy metal vaporization rates for all bed temperatures.     

Assessing the power generation,pollution control,and overall efficiencies of municipal solid waste incinerators in Taiwan

This paper evaluates the productivity of municipal solid waste incinerators (MSWIs) by addressing the following questions: (1) to what extent should one further increase the production of power generation while maintaining the emission of noxious air at the current level?; (2) To what extent should one further decrease the emission of noxious air while maintaining the production of power generation at the current level?; and (3) To what extent should one increase the production of power generation and decrease the emission of noxious air simultaneously? To effectively address these questions to improve performance, the power generation and pollution control efficiencies are evaluated using TODEA (two-objective data envelopment analysis), as well as the overall efficiency evaluated using Tone’s NS-overall model (slacks-based measure with non-separable desirable and undesirable outputs for evaluating overall efficiency). A MSWI case study in Taiwan with the panel data covering the period of 2004–2008 reveals that the power generation and overall efficiencies of build-operate-transfer are more efficient, on average, than those of public-own-operate and build-own-operate. However, the three building and operation types do not significantly differ in pollution control efficiency.     

The oxidation of benzene under conditions encountered in waste incinerators

The oxidation of benzene was studied as a function of residence time (τ_res=0–2.5 s), temperature (850–960 K), and oxygen concentration (O₂=0.2–2.3%) in a heated laminar flow reactor at atmospheric pressure. Nitrogen, doped with 350 ppm benzene, was injected downstream of the burned gas from a near stoichiometric flame of methane + air. Gas samples were taken at different heights up the reactor and analyzed using GC-FID/TCD and HPLC techniques. Phenol and partially oxidized hydrocarbons such as acetaldehyde, formaldehyde, and acrolein were found with concentrations up to 50 ppm. At relatively low temperatures, the conversion of benzene was observed to proceed considerably more slowly at higher oxygen concentrations. Measured concentration profiles were modeled using detailed reaction schemes. A modified mechanism for the oxidation of benzene called BenWas was constructed from the mechanism of Zhang and McKinnon (Combust. Sci. Technol. 107 (1995) 261) by incorporating a submechanism for benzoquinone (OC₆H₄O) and by updating and enlarging the reaction scheme of cyclopentadiene (C₅H₆). The agreement between observed and predicted concentration profiles, e.g., of phenol (C₆H₅OH), acetylene (C₂H₂), and carbon monoxide (CO), was considerably improved by the use of the BenWas mechanism for rich and lean conditions, mainly due to the introduction of an additional pathway for phenyl oxidation (C₆H₅ + O₂ = OC₆H₄O + H) and due to the changed kinetics of the oxidation of cyclopentadienyl (C₅H₅) in C₅H₅ + O₂ = C₅H₄O + OH. The measured retardation of benzene oxidation with higher amounts of oxygen can be explained by the formation and reactions of peroxy radicals.     

城市生活垃圾焚烧处理工艺的研究

针对我国城市生活垃圾的特点,对现有的垃圾焚烧处理工艺进行了深入的研究。结果表明:机械炉排焚烧炉技术比较适合国内的高水分、低热值垃圾,是目前垃圾焚烧发电行业应大规模推广的技术;烟气净化采用半干法脱酸塔加布袋除尘器的组合工艺为较佳方案。该研究成果对今后城市生活垃圾焚烧发电工程的建设和运营具有一定的参考价值。     

Effect of excess air on grate combustion of solid wastes and on gaseous products

An experimental study has been conducted in a fixed bed reactor to simulate, in a laboratory scale, industrial municipal waste incineration using moving grates. Carbon monoxide, nitrogen oxide, temperatures and mass loss rate measurements have been used to establish the importance of the operating parameters of a municipal waste incinerator in the characteristics of the combustion process. The present work is concerning the study of the impact of primary and secondary airs of combustion. Two different regimes have been identified that are controlled by the airflow through the fuel (primary airflow). These combustion regimes have indicated the impact of primary and secondary air flow on the combustion behavior and the resulting concentrations of carbon monoxide and nitrogen oxide: the production of NO seems to be controlled only by the oxygen concentration in the secondary zone of combustion. An increase in total airflow, thus, results in an increase in the yield of NO.     

昆明市春季生活垃圾分析及处理

对昆明市不同生活水平地区的5个垃圾中转站进行抽样分析,将样分带回实验室进行多种实验.分析结果表明,昆明市春季生活垃圾易腐成分含量及其含水率均为最高,分别为60.59%和78.49%;计算了垃圾焚烧的年发电量为4.80x108 kWh,可燃物比率为22.59%,并与秋季数据进行了比较;根据对测定数据的分析并计算各种垃圾焚烧所发的电量,可知昆明市春季生活垃圾的最优处理方法为焚烧发电.     

生活垃圾与柳树枝共热解研究

在热重分析仪和固定床热解炉上进行柳树枝对生活垃圾热解特性影响研究,考察了柳树枝对生活垃圾热解失重率、热解活化能、热解产物产率、热解气组成的影响。热重分析结果表明,生活垃圾(M)、柳树枝(W)及生活垃圾和柳树枝混合物(MW)在265~600℃时失重最明显,当热解温度为600℃时,3种样品的失重率分别为61.41%,57.81%和70.31%;热解动力学分析表明,MW的热解活化能低于M和W,且低于MW理论活化能;固定床热解实验表明,当MW混合比例为4∶1时,热解产物理论值与实验值差距最大,M和W热解过程中存在明显协同作用;对MW热解气组成分析发现,随着W添加比例的增大,热解气体中CO_2产率下降,CH_4,H_2产率增加,当MW混合比例为4∶4时,CH_4和H_2产率分别提高1.13 m L/g和2.53 m L/g,CO_2产率降低1.68 m L/g。     

城市固体废弃物典型组分的快速热解产气特性研究

选取城市固体废弃物中的常见六种组分(纸屑、厨余、织物、木屑、塑料、橡胶)作为实验物料进行快速热解实验。在所得实验数据的基础上对热解气体产物的组成以及变化情况进行了分析，并研究了热解混合气的热值随时间变化的情况。通过研究有助于对热解产物进行预测，且能够深入地了解热解机理。     

Optimizing the operating conditions for hydrogen-rich syngas production in a plasma co-gasification process of municipal solid waste and coal using Aspen Plus

The plasma gasification process is one of the newest and most innovative approaches to meet the needs of waste management but requires assessment and research on operational conditions prior to installation. In this work, a model based on Gibbs free energy minimization was developed and implemented in Aspen Plus®. A combination of municipal solid waste (MSW) and coal has been used as feedstocks. The model's performance was compared with the results of the literature and found to be in good agreement. The effect of various parameters such as temperature, equivalence ratio, MSW/coal blending ratio, and steam-to-feedstock ratio on the composition of syngas and hydrogen production were assessed. Very interesting results were obtained concerning the mixture of the feedstocks that maximize the hydrogen production besides that using steam as a gasifying agent allows higher hydrogen production than using air. When using high amounts of coal in the feedstock mixture, low steam ratios are preferred. When using high amounts of MSW in the feedstock mixture high steam ratios are preferred. The use of pure oxygen as the gasifying agent increases the hydrogen percentage but requires an air separation unit to be included in the process. The results obtained in this study are particularly relevant for countries with coal reserves.     

城市生活垃圾焚烧发电厂的垃圾前处理系统的设计

垃圾前处理系统,即在垃圾进入锅炉之前对垃圾进行处理的系统,是城市生活垃圾焚烧发电厂的重要的组成部分,也是工程设计中的重点和难点。结合在工程设计中的学习和实践,简要介绍了使用炉排炉的垃圾电厂中的垃圾前处理系统;针对使用CFB焚烧锅炉的电厂,对目前已经出现的几种形式的处理系统,进行了简单的阐述和比较分析,根据不同的情况给出推荐方案和建议：在需要全量破碎的情况下,推荐采用四列式布置,否则,推荐采用两列式布置,无论采用哪种布置形式,应设置人工分拣工序。     

上海市生活垃圾处理问题的系统动力学分析

与日俱增的人口产生了越来越多的生活垃圾.面对垃圾围城的严峻形势,城市生活垃圾处理变得越来越迫切.为了预测上海市未来的垃圾产生量,探讨合适的处置方法和调控措施,利用系统动力学的方法建立了上海市城市生活垃圾产生和处理系统的动力学模型.通过查阅大量文献并收集数据,预测未来生活垃圾的产生总量和处理总量,对各种处理方式的收益进行了对比,并利用系统动力学模型模拟软件VENSIM进行了模拟.结果表明:在调控措施下,未来上海市垃圾产生量能得到控制和更加环保的处理;同时,需要控制人口,提高环保投资占GDP比重,实行垃圾收费制度.     

Combined-gasification of biomass and municipal solid waste in a fluidized bed gasifier

Due to the environmental problems associated with burning of fossil fuels and population growth, more attention has been paid to develop renewable energies in recent years. Among all options for renewable energy utilization, biomass gasification is more popular because of environmental benefits and economic issues. In the present study, a series of experiments were carried out to study the influence of blending ratio, reaction temperature, equivalence ratio (ER) on co-gasification characteristics of pine sawdust (SD) and municipal solid waste (MSW). By increasing the blending ratio from 100% SD to 100% MSW, CO and CH₄ respectively increased from 16.7 to 18.8 vol% and from 4.1 to 5.1 vol%, while an opposite trend was found for H₂ and CO₂. Over the ranges of the experimental conditions used, the tar content and gas yield varied from 5.4 to 10.1 g/Nm³ and 1.34 to 1.15 Nm³/kg, respectively.     

Hydrogen as a transportation fuel produced from thermal gasification of municipal solid waste: an examination of two integrated technologies

Innovative technologies are required to offset increasing consumption and declining stocks of non-renewable resources. This study examines a possible enhancement of waste management and transportation by integrating two emerging technologies: municipal solid waste (MSW) gasification and fuel cell vehicles (FCVs), by fueling FCVs with hydrogen produced from gasified MSW. Material and energy flows were modeled in four MSW management scenarios (incineration, landfill, gasification, gasification with recycling) and four transportation scenarios (hybrid gasoline-electric, methanol FCVs, hydrogen FCVs using hydrogen from natural gas or municipal solid waste). Technological performance deemed feasible within 2010–2020 was assumed. Greenhouse gas emissions and non-renewable energy use were used to assess overall system performance. Gasification with hydrogen production performs as efficiently as incineration, but is advantageous compared to landfilling. Taking into account additional environmental criteria, the model suggests that hydrogen from MSW gasification for FCVs may provide benefits over conventional MSW treatment and transportation systems.     

城市有机垃圾车库式干发酵技术

城市有机垃圾处理和资源再生利用已成为我国建设资源节约型和环境友好型社会中迫切需要解决的问题。欧洲国家中以德国为代表的车库式干发酵技术(Garage-type dry anaerobic digestion)已经成熟,可进行规模化的沼气生产。文章着重介绍了车库式干发酵沼气工程的技术要点,并以德国Loock TNS工艺和黑龙江宾县车库式干发酵项目为例,介绍了有机垃圾车库式干发酵喷淋回流、系统密封等关键技术,以期为我国车库式干发酵工程的工艺设计提供参考。