IMECH-IR  > 高温气体动力学国家重点实验室
船舶厨余垃圾的热等离子体气化研究
李慧鑫
导师魏小林
2015-05-24
学位授予单位中国科学院大学
学位授予地点北京
学位类别硕士
学位专业流体力学
关键词热等离子体 厨余垃圾 气化 化学平衡
摘要

随着城市规模和人口的快速发展,城市固体垃圾,包括厨余垃圾的产生量也呈现逐渐上升趋势,同时,对垃圾处理技术及其污染排放标准的要求也越来越高。船舶生活垃圾由于船舶的结构特殊性和流动性较大,同样有大量垃圾需要处理。因此根据船舶配套设备需要体积小、效率高以及操作性强的特点,本文设计和搭建等离子体气化处理船舶厨余垃圾的实验系统。根据需求,将船舶厨余垃圾的有机成分分为米面主食类、纤维素类和油脂类,主要使用热等离子体发生器,对厨余垃圾的主食替代物(如面粉、米等)进行气化处理,涉及少量纤维素类生物质气化实验。

通过自行设计和搭建的1 kW、35 kW热等离子体气化实验系统完成空气、水蒸气气化剂和物料自身属性对热等离子体气化效果影响的实验。在1 kW的实验系统上,研究结果表明,过量空气系数(ER)对于合成气和低位热值的影响有两种效应:当 ER小于0.095时,化学反应热在气化室中占据主导;而当ER大于0.095,合成气由于空气含量的增加而导致其被消耗,一氧化碳和氢气的产量有所下降,二氧化碳含量升高。水蒸汽作为气化剂的气化过程,水煤气反应会增强,进而促进合成气的产量和气化效率提升。整个热等离子体气化实验过程中的热效率和㶲效率最大值均出在水蒸汽物料比(SFR)等于0.084时,分别为28.2%和       23.0%。

在35 kW热等离子体气化实验系统,研究结果表明,40目和10目的物料颗粒粒径均会引起一氧化碳和氢气的产量降低。等离子体能量比(PER)小于0.26较有利于等离子体气化进行,效率较高,而过高的等离子体能量长时间工作容易造成气化室高温,不利于设备的实际安全运行。不同物料下,面粉和米的气化产物主要以一氧化碳和氢气为主,而甘蔗渣这种纤维素生物质,由于水煤气反应占主导,气化产物中一氧化碳浓度在三种物质中最低,而二氧化碳浓度为最高。碳酸钾盐负载对于等离子体气化过程促进效果有限,不如传统气化过程的催化效果明显。残渣为气化反应的终止产物,对于气化反应过程有一定的反馈作用。因此实验结束后对残渣使用X射线衍射(XRD)和Raman光谱两种表征手段,表明热等离子气化处理后的米、面和甘蔗渣均会有轻微的石墨微晶,甘蔗渣的残渣石墨化进程最高,而碳酸钾会抑制物料残渣的石墨化进程。

此外,本文通过吉布斯自由能最小化原理,应用Aspen Plus软件对热等离子体气化过程进行建模和模拟,模拟和能量需求分析指出物料在进入气化室前,应该尽量控制含水率在36%以下;采用流体力学的经典公式将气化室内的颗粒受力分解为沿轴向的流体作用力和沿径向的热泳力,对实验中出现残渣堆积和小粒径进料易堵塞的问题给出了定量的分析。

英文摘要

With the rapid development of the city's scale and population, the amount of municipal solid waste (MSW) and kitchen waste has also increased gradually. However, the standards for waste disposal and pollution emission are more stricter rather than reduced. Ships also have a large amount of domestic garbage that needs to be disposed of, due to their small space and mobility. Therefore, this study mainly focuses on designing and setting up an experimental system for plasma gasification treatment of ship kitchen waste, according to the small bulk, high efficiency and strong operability of ship equipment. Considering the ship kitchen waste is classified into staple food, celluloses, and oil and fats, this study is carried out by a thermal plasma generator to gasify the staple food wastes, involving a small amount of gasification experiments related to cellulosic biomass.

The gasification experiments of air, water gasification agents and raw materials properties were carried out through the self-designed and constructed 1 kW, 35 kW thermal plasma gasification experimental systems. The results under 1 kW generator indicate that two effects induced by the equivalence ratio (ER) appear on the syngas and low heating value: When the ER is less than 0.095, the chemical reaction heat dominates in the gasification chamber; When the ER is greater than 0.095, the syngas is consumed by the rise of air, resulting in a decrease in the production of carbon monoxide and hydrogen and an increase in the carbon dioxide concentration. As for the process of steam gasification, the water gas reaction enhanced in turn promotes the production and gasification efficiency of syngas. During the entire thermal plasma gasification, the maximum thermal and exergy efficiencies were obtained at the steam-to-material ratio (SFR) of 0.084, corresponding to 28.2% and 23.0%, respectively.

The experimental results under the 35 kW plasma generator demonstrate that the material with different particle sizes plays an important role for the gasification: the materials, 40 and 10 mesh, cause a decline in the yield of carbon monoxide and hydrogen. A plasma energy ratio (PER) less than 0.26 is more favorable for plasma gasification in order to obtain the higher efficiency. Since excessively high plasma energy is likely detrimental to the gasification chamber and actual safe operation of the equipment, which results from the high temperature caused by long time work. As to different materials, the gasification production of flour and rice mainly consist of carbon monoxide and hydrogen. However carbon monoxide concentration in the bagasse gasification products is the lowest among three materials, while the carbon dioxide concentration is the highest, due to the water vapor reaction. The Potash carbonate loading in rice has limited promotion effects on the plasma gasification process and is not as good as the catalytic effect of the traditional gasification process. The residue can reflect the process of gasification in extent. Thus, X-ray diffraction (XRD) and Raman spectroscopy were employed in the residues after plasma gasification, with results demonstrating that the residues have slightly microcrystalline graphite, among which the residue of bagasse has the highest process of graphite, while potassium carbonate can inhibit the process of graphite of material residue.

In addition, through the Gibbs free energy minimum principle, the Aspen Plus software is employed to model and simulate the thermal plasma gasification process. The simulation and energy demand analysis indicate that the moisture content of raw material should be controlled below 36% before the material enter. The classical empirical formula of fluid mechanics is used to analysis the force of particles during the plasma gasification. And the force in the gasification chamber was broke into the hydrodynamic force along the axial direction and the thermophoresis force along the radial direction, which are conducive to realizing the reason that the residue is accumulate in the chamber and the small particle size feed are apt to be blocked in the inlet. From the calculation results, the equivalent model employed in the study is relatively reasonable.

语种中文
文献类型学位论文
条目标识符http://dspace.imech.ac.cn/handle/311007/73146
专题高温气体动力学国家重点实验室
作者单位1.中国科学院力学研究所高温气体动力学国家重点实验室
2.中国科学院大学工程科学学院
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李慧鑫. 船舶厨余垃圾的热等离子体气化研究[D]. 北京. 中国科学院大学,2015.
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