污泥气化合成气生成特性及其BP神经网络预测模型研究

发布时间：2018-09-14 09:40

【摘要】：发展新型、绿色、环保、资源化的污水污泥处理技术,是我国国民经济发展要求和顺应历史发展潮流的大势所趋。我国城市污水污泥中有机物含量和热值日渐增高,使其具备热化学转化等能源化处理的潜力。本文主要针对污泥水蒸气、水蒸气-空气混合气化合成气生成特性及其预测模型等展开研究,旨在全面分析高产出、低污染的污泥气化工艺特性,为污泥能源化处理装置的工程设计和工业运行提供有价值理论指导。主要研究工作和结论如下:(1)通过污泥水蒸气气化实验研究,着重分析了温度和水蒸气质量与污泥含碳量比(S/C比值)等对气化合成气生成特性以及污泥能源转化效率的影响规律,可以发现:温度对气化合成气特性影响是绝对性的,提高气化温度有利于高品质合成气的生成和污泥能源转化效率的提高。随着温度从650℃增加至1050℃,合成气中H2和CO含量分别增加了12.1%和6.2%,CO2和CH4含量分别降低了4.8%和3.2%;污泥气化冷煤气效率ηl、碳转化效率ηc以及有机相转化效率ηv分别增加了近40%、18%和34%;综合考虑气化过程的能耗和产气效率,污泥气化制取富氢合成气最佳温度是850℃左右。S/C比值对合成气生成特性影响是双重的,过大和过小的S/C比值将造成合成气品质和能源转化效率降低,当S/C值为4.74时,合成气产率及热值、氢气含量及其产率、气化冷煤气效率ηl均达到最优值。(2)基于污泥空气气化与水蒸气气化工艺的各自优势,实验分析了污泥空气-水蒸气混合气化合成气生成特性。研究发现:与水蒸气气化相比,不同温度下混合气化H2产率、CO+H2产率、合成气热值及冷煤气效率ηl的最佳值分别为0.38 m3/kg、0.46 m3/kg、6.24 MJ/m3和59%,显著低于水蒸气气化合成气的相应最佳值,但前者能耗低于后者近5 MJ/kg;与热解相比,混合气化合成气品质仍较高,尤其H2产率、合成气热值及冷煤气效率ηl显著高于相同温度下热解气的相应各值。另外,混合气化气化过程中气化介质与污泥样品量比值(Agent/SS)和H2O/O2质量比应严格控制。(3)污泥气化过程主要是自由基生成反应、含氧官能团分解反应、脂肪侧链断裂反应、裂解反应、脱氢反应、加氢反应、缩合等综合热化学反应过程;随着气化温度增加,污泥残渣表面化学结构发生了显著变化,O-H键和N-H键、-CH2和-CH3基团、C=O基团及C-O和C-Har键逐渐消失,而原样污泥中其它基团或键结构在650℃时已基本分解。(4)建立污泥高温水蒸气气化和水蒸气-空气混合气化特性的BP神经网络模型,其中污泥水蒸气气化模型预测精度较高,相对误差小于9%;混合气化预测模型预测精度较差,可通过增加样本量、改善网络等方法提高预测精度。
[Abstract]:The development of new, green, environmentally friendly and resource-based sewage sludge treatment technology is the trend of the development of our national economy and conforms to the trend of historical development. The content and calorific value of organic matter in municipal sewage sludge in China are increasing day by day, which makes it have the potential of energy treatment such as thermochemical conversion. In this paper, the characteristics of sludge steam, steam / air mixture gasification syngas and its prediction model are studied in order to analyze the characteristics of sludge gasification process with high yield and low pollution. It provides valuable theoretical guidance for the engineering design and industrial operation of sludge energy treatment plant. The main research work and conclusions are as follows: (1) through the experimental study of sludge steam gasification, the effects of temperature, water vapor mass and sludge carbon content ratio (S / C ratio) on gasification syngas generation characteristics and sludge energy conversion efficiency are analyzed. It can be found that the influence of temperature on gasification syngas characteristics is absolute, and the increase of gasification temperature is beneficial to the production of high quality syngas and the improvement of sludge energy conversion efficiency. As the temperature increases from 650 鈩，

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