可燃固体废弃物热解特性及其过程数值模拟研究

发布时间：2018-03-30 07:07

本文选题：可燃固体废弃物　切入点：动力学　出处：《东南大学》2017年博士论文

【摘要】：可燃固体废弃物(CSW)作为一种有机碳源,可用于开发替代部分石油的液体燃料与化学品,从而缓解我国能源短缺和废弃物处理困难两方面难题。在众多CSW高值化开发技术方法中,热解制备高品质液体产物技术具有良好的发展前景。本文从基础和应用两个方面出发,在CSW原料的热解动力学、热解产物高值化的机理和特征、热解产物性质和潜在利用途径以及热解过程数值模拟等方面开展了较全面的研究。在热重反应器中研究了两种常见CSW原料的热解失重特性及动力学。废纸板和废轮胎在约220～400℃和159 ～523℃范围内分别有一个主要失重峰,且受升温速率的影响比较明显。利用高斯分峰拟合方法对微分失重(DTG)曲线进行拟合,发现废纸板DTG曲线可用两个峰进行拟合,而废轮胎DTG曲线需要三个峰进行拟合,每一个拟合峰均可代表原料的不同失重机理。利用Coats-Redfern法计算动力学参数,随后联合使用Flynn-Wall-Ozawa法和Malek法筛选出最合适的机理函数,从而获得了两种原料在主要失重阶段的动力学模型及相关参数。利用裂解-气相色谱/质谱联用仪(Py-GC/MS)研究了催化剂及改性催化剂对废纸板快速热解制备芳香烃的影响。废纸板快速热解产物以糖类、醛类、酮类等含氧有机物为主,品质较低。添加微孔分子筛HY、HZSM-5 (HZ)和廉价矿石凹凸棒土(PA)促进了芳香烃的生成,提高了产物品质。为进一步提高催化剂活性,对效果良好的HZ进行碱处理改性,获得含微孔和介孔的分级孔道分子筛,其孔道扩散性能得到明显改善。经过温和碱改性(NaOH溶液浓度≤0.3M)的HZ显著增加了目标产物BTX (苯、甲苯和二甲苯)的产量,并有效减少了 HZ的结焦率,实现了废纸板热解产物高值化。利用Py-GC/MS探索了废轮胎催化快速热解制取芳香烃的机理。对废轮胎热解重要产物D-柠檬烯的降解过程进行了研究,发现其在600℃及更高温度下被芳构化。根据产物分布及文献报导,提出了 D-柠檬烯在不同温度下降解主要途径,并利用这些途径解释了废轮胎热解产物转化特性。对废轮胎及其中间产物的催化热解试验研究发现,HY、HZ和PA对芳香烃的催化机理各不相同:HY催化D-柠檬烯和聚丁二烯橡胶(BR)热解产物芳构化效果良好,而HZ仅对催化BR热解产物芳构化效果明显,PA则对芳香烃和烯烃产物均有一定促进效果。该结果解释了废轮胎催化快速热解产物向芳香烃转化的途径,从而有利于废轮胎热解产物高值化。在最大处理量为10 kg/h的流化床反应器内,进行了实际CSW混合原料的热解制油试验。采用多级冷凝系统,获得38.4～56.5 wt%热解油产物,分为水溶相和有机相。水溶相含水率高,主要有机组分为酸类、羰基类、酚类和糖类,可提质后加以利用。而有机相几乎不含水,主要由芳香烃和酚类组成,且重金属Cd、Pb和Zn含量低,燃料性质与原油相近。水溶相和有机相分层有利于CSW热解油的分级利用,二者可通过不同的方式加以利用。除热解油外,热解炭和热解气产物可通过燃烧为热解反应提供热量。在试验研究基础上,对CSW在流化床内的热解过程进行了数值模拟研究。采用双欧拉模型模拟多相流流动,多组分、多步反应模型模拟CSW原料的热解过程。编制了非均相反应的用户自定义函数(UDF)程序,利用计算流体力学(CFD)软件进行耦合计算。模拟结果表明,随着热解时间的增加,流化床内逐渐趋于稳定流化状态,出口产物流量在±10%范围内波动。模拟了工况对产物产率的影响,发现热解温度对产物产率影响最大,而初始床层高度对产物波动影响最明显。与试验结果相比,模拟获得的床内温度分布结果与产物产率随温度的变化规律结果基本一致。CSW热解过程的CFD模拟结果可为工艺设计和工况优化提供有价值的参考。
[Abstract]:Combustible solid waste (CSW) as an organic carbon source, can be used for liquid fuels and chemicals to develop alternative part of oil, so as to relieve the two aspects of China's energy shortage and waste disposal problems. In many CSW high value method developing technology, prepared by pyrolysis of high quality liquid product technology has good development prospects. This paper from two aspects. The foundation and application of the pyrolysis kinetics of CSW raw materials, pyrolysis mechanism and characteristics of high value, carry out a comprehensive study of the properties of pyrolysis products and the potential utilization of pyrolysis process and numerical simulation. In the thermal pyrolysis reactor of two kinds of CSW raw materials weightlessness characteristics and kinetics of waste paper and waste tires. At about 220~400 degrees and 159~523 degrees respectively within the scope of one of the main peaks, and affected by the heating rate is more obvious. By Gauss The peak fitting method of differential weight loss (DTG) curve fitting DTG curve can be found in waste cardboard two peaks were fitted, and waste tire DTG curve requires three peaks were fitted, different weight loss mechanism on each peak can be the representative materials. The kinetic parameters calculated by Coats-Redfern method, then the combined use of Flynn-Wall-Ozawa and Malek method to select the most appropriate function mechanism, dynamics model and related parameters to obtain two kinds of raw materials in the main weight loss stage. Using pyrolysis gas chromatography / mass spectrometry (Py-GC/MS) to study the effects of catalyst and preparation of waste paper fast pyrolysis of aromatic hydrocarbon catalyst modified by fast pyrolysis of waste paper. The product of sugars, aldehydes, ketones and other organic compounds containing oxygen, low quality. Adding zeolite HY, HZSM-5 (HZ) and cheap ore attapulgite (PA) promotes the formation of aromatic hydrocarbon, improve Product quality. In order to further improve the catalytic activity of HZ, good effect of alkali modification, to obtain hierarchical molecules containing microporous and mesoporous sieve pore diffusion, its performance is significantly improved. After mild alkali modification (NaOH concentration = 0.3M) HZ significantly increased the target product BTX (benzene, toluene and xylene) production, and effectively reduce the coking rate of HZ, realized the waste paper pyrolysis products of high value. The use of Py-GC/MS to explore the mechanism of the catalytic waste tires from fast pyrolysis of aromatic hydrocarbons. On pyrolysis product of important D- limonene degradation process was studied, which was found in aromatization 600 degrees and higher temperature. According to the distribution of products and literature, put forward D- limonene degradation at different temperatures are the main way, and use these ways to explain the transformation characteristics of waste tyre pyrolysis of waste tire and its intermediate products. Experimental study on catalytic pyrolysis of the discovery, HY, HZ and PA on the catalytic mechanism of aromatic hydrocarbon is different: HY catalytic D- limonene and polybutadiene rubber (BR) pyrolysis product of aromatization effect is good, but HZ only BR on the catalytic pyrolysis of aromatization effect is obvious, PA of aromatic hydrocarbons and olefins the product has a certain promoting effect. The result explains the transformation way of waste tire catalytic fast pyrolysis products to aromatic hydrocarbon, which is conducive to waste tyre pyrolysis of high value. The maximum throughput of 10 kg/h fluidized bed reactor, pyrolysis test of mixed raw materials. The actual CSW multistage condensation system from 38.4 to 56.5 wt% pyrolysis products, divided into aqueous phase and organic phase. Water soluble high water content, the main unit is divided into acids, carbonyl compounds, phenols and sugar, can be used after upgrading. The organic phase almost no water, mainly composed of aromatic hydrocarbons and phenols Class composition, and heavy metals Cd, Pb and Zn content is low, the fuel properties and crude oil are similar. Water soluble organic phase and a layered by grading for CSW pyrolysis oil, the two can be utilized by different ways. In addition to the pyrolysis oil, pyrolytic carbon and pyrolysis product can provide heat for pyrolysis by burning. Based on the experiment, the pyrolysis of CSW in fluidized bed was simulated. The simulation model of dual Euler multiphase flow, multicomponent, pyrolysis reaction model of CSW raw materials. The user defined function of heterogeneous reactions (UDF) program, the use of computational fluid mechanical (CFD) coupling calculation software. The simulation results show that with the increase of pyrolysis time, the fluidized bed tends to stable state flow, export product flow fluctuations in + 10% range. The effect of operating conditions on the yield of the simulation, it was found that the heat The solution temperature has the greatest influence on the product yield, and the initial bed height on product fluctuations most obvious. Compared with the experimental results, the simulation results and bed temperature distribution in the yield variation with temperature consistent with the results of.CSW during pyrolysis of CFD simulation results can provide valuable reference for the optimization of process design and operation.

【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.12;O625.1

【参考文献】