SO2 Emission Characteristics and BP Neural Networks Prediction in MSW/Coal Co-Fired Fluidized Beds

The SO_2 emission characteristics of typical MSW components and their mixtures have been investigated in aΦ150mm fluidized bed.Some influencing factors of SO_2 emission in MSW fluidized bed incinerator were foundout in this study.The SO2 emission is increasing with the growth of the bed temperature,and it is rising with theincreasing oxygen concentration at furnace exit.When the weight percentage of auxiliary coal is being raised,theconversion rate of S to SO_2 is largely going up.The SO_2 emission decreases if the desulfurizing agent (CaCO_3) isadded during the incineration process,but the desulfurizing efficiency is weakened with the enhancement of thebed temperature.The fuel moisture content has a slight effect on the SO_2 emission. Based on these experimentalresults, a 12×6×1 three-layer 13P neural networks prediction model of SOR emission in MSW/coal co-firedfluidized bed incinerator was built.The prediction results of this model give good agreement with theexperimental results,which indicates that the model has relatively high accuracy and good generalization ability.It was found that BP neural network is an effectual method used to predict the SO_2 emission of MSW/coalco-fired fluidized bed incinerator.     

Hazardous organic compounds in urban municipal solid waste from a developing country

Fresh and partially decomposed municipal solid waste (MSW) collected from three places in Chennai city, viz., a residential collection point and two dumping grounds (Kodungaiyur and Perungudi) were screened for hazardous organic pollutants. Toxicity Characteristics Leaching Procedure (TCLP) using a Zero Headspace Extractor (ZHE) followed by further extraction by solvent separation using n-hexane containing 15% di-ethyl ether was performed and the organic extract obtained was qualitatively screened by GC-MS. 28 different types of higher alkanes and their derivatives, 7 types of C6-C8 fatty acids and their esters, 7 different phenolic compounds including alkylated phenols and degradation products and 5 phthalate compounds occurred in a majority of the analysed samples. 17 other organic compounds such as carboxylic acids, chloroform, phosphate, pharmaceutical chemicals etc. were also detected. Among these compounds, phenolics and phthalates are highly hazardous in nature and occurred in relatively higher concentrations. Hazardous compounds like p-cresol, di-butyl, mono butyl and di-ethyl pthalates were found in concentrations more than 200mg/kg in MSW.     

An investigation of MSW gasification in a spout-fluid bed reactor

This paper presents the experimental results of MSW gasification in a spout-fluid bed reactor. Municipal solid waste (MSW) modeled based on compositions of Bangkok waste transfer station “On-nuch” was used as the fuel. Three scenarios were investigated in this study. In the base case scenario, only primary air of equivalence ratios (ER) 0.35, 0.3, 0.25, 0.2, and 0.15 were used. The other two scenarios investigated the influence of secondary air in the free board, and the effect of the recirculation of carryover captured by the cyclone inside the reactor's free board at an ER of 0.25. In the base case, higher heating values of 2.40–5.05 MJ/Nm³ were obtained with the ER values of 0.35–0.15, respectively. However, opposite trend was observed for the tar content. At ER of 0.35, a value of 11.37 g/Nm³ was found compared to 20.76 g/Nm³ at ER of 0.15. The tar content in the producer gas was reduced from 14.47 to 10.98 g/Nm³ when secondary air was supplied in the freeboard due to an increase in temperature. The gasification efficiency was increased from the base case which was 35.78 to 38.99% with the recirculation of carryover. Higher heating value of producer gas was found to be 4.4–4.9 MJ/Nm³ in this case.     

城市生活垃圾的气体渗透性试验研究

采用填埋场钻孔获得的垃圾样,用自制导气试验装置,测试垃圾的气体渗透系数,分析孔隙比、饱和度和垃圾组分对气体渗透性的影响。测试结果表明:所测试垃圾的气体渗透系数为(10-8～10-5)m2.Pa-1.s-1量级,固有渗透系数为(10-13～10-10)m2量级。垃圾试样的孔隙比、饱和度和组分均对气体渗透性均有显著的影响。当垃圾组分和饱和度(Sr=0%或40%)给定时,气体渗透系数随孔隙比(e=1.5～3.0)增加呈指数递增;当试样组分和孔隙比(e=2.0)给定时,气体渗透系数与饱和度呈双线性关系,其分界点所对应的饱和度(Sr=50%)略低于该垃圾田间持水量所对应饱和度值;当饱和度高于该界限值时,气体渗透系数随饱和度增加呈指数递减,而在低饱和度阶段,气体渗透系数受其影响相对较小。在控制试样孔隙比与饱和度均相同的特定条件下,气体渗透系数随填埋龄期(t=0～11 a)的增加而增大。     

气压和温度变化共同作用下垃圾填埋场边坡稳定性研究

城市生活垃圾填埋场在高渗沥液水位情况下发生边坡失稳滑坡的工程事故已多次发生,初步分析认为滑坡由渗沥液水位、垃圾降解产气和温度升高等因素共同引起。目前尚未见考虑渗沥液水位、气压和温度共同影响填埋场边坡稳定性研究的报道。通过简化垃圾填埋场气压和温度分布的计算,利用瑞典条分法进行考虑渗沥液水位、气压和温度共同影响的填埋场边坡稳定性分析。计算结果表明:考虑气压和温度的影响使得填埋场边坡稳定安全系数降低24.7%～43.0%;建议在同时考虑渗沥液水位、气压和温度的影响进行填埋场边坡稳定分析时,控制最小安全系数大于1.0可保证填埋场安全运行。本研究可为垃圾填埋场的设计、施工和运行管理提供理论支撑。     

生活垃圾燃烧特性实验研究

选取了城市生活垃圾中的厨余、纸张、织物、含氯塑料和不含氯塑料，进行元素分析、工业分析和热重分析，并在此基础上进行了几种垃圾混合物的燃尽实验。实验结果表明：生活垃圾的着火温度、活化能明显低于混合烟煤。而且塑料的燃烧规律与其它垃圾样品有显著区别。实验发现，随条件的不同，垃圾燃烧过程中会不同程度地产生CO、SO2和NOx，因此需要合理的燃烧组织，以降低污染的排放。     

垃圾焚烧发电厂渗沥液处理优化组合工艺

介绍目前国内外垃圾焚烧厂渗沥液处理的主要工艺方法,指出各种处理方法的优缺点和适用范围,提出一种将斜板沉淀、水解酸化、SBR、混凝沉淀及消毒杀菌技术相结合的垃圾焚烧厂渗沥液处理工艺。     

浅议生活垃圾压缩机的研制及前景

简单介绍了我国生活垃圾的现状,并根据垃圾的构成,分析了垃圾压缩机研制的必然性和可行性及垃圾压缩的原理,说明垃圾压缩机结构、分类和特点,对我国垃圾压缩机的发展前景进行了技术预测。     

基于土水特征曲线预测城市固体废弃物（MSW）非饱和渗透系数研究

基于对人工配制的城市固体废弃物（ MSW ）的土水特征试验,研究了不同有机含量、不同孔隙比下 MSW 的非饱和渗透系数,得到了 MSW 非饱和渗透系数随有机含量和孔隙比变化的定量关系式。研究结果表明在双对数坐标系下, MSW 的气相和液相非饱和渗透系数和吸力几乎为线性关系;对于相同的吸力作用,孔隙比越大,其液相和气相非饱和渗透系数也越大;总体上液相非饱和渗透系数的变化范围为 10 ^{- 11} ～ 10 ^{- 5} cm/s ,气相非饱和渗透系数的变化范围为 10 ^{- 5} ～ 10 ^{- 2} cm/s 。与有机含量的变化相比,孔隙比的变化对 MSW 非饱和渗透特性的影响较为明显。公式验证表明,利用该方法预测已知成分和孔隙比的 MSW 的非饱和渗透系数是可行的。     

生活垃圾典型可燃组分的热解产气特性

在接近实际生活垃圾热解处理工况的升温条件下,对垃圾中典型可燃组分如橡胶、塑料、竹木、废纸进行了热解产气特性的研究.结果显示,4种物料的热解过程存在较大的差异,塑料在热解过程中存在很强的吸热效应,致使其升温速率明显下降;塑料、橡胶热解的可燃产气以甲烷、乙烯为主,而废纸、竹木则以一氧化碳为主;各物料的产气速率及产气总量受其挥发分含量、氧含量及气相分解速率的影响.