磁旋转弧等离子体温度诊断及其在甲烷重整反应的应用

发布时间：2018-03-29 00:19

本文选题：发射光谱诊断技术　切入点：热等离子体　出处：《浙江大学》2017年硕士论文

【摘要】：热等离子体具有电热转化效率高、反应温度高、能量密度集中、气氛环境可调控等特点,是一种前沿的化工强化手段,被广泛应用于乙炔、合成气的制备及固体废弃物处理等方面。热等离子体反应器内的温度分布情况是影响反应效率的关键性因素,然而热等离子体的温度可达2000～20000 K,同时反应器往往要求具有良好的气密性,这使得反应器内的温度分布难以通过常规检测手段获得。本文首次采用发射光谱诊断技术对磁旋转弧等离子体炬内纯气体进料状况下以及涉及化学反应进料状况下的温度分布进行实验研究,结合计算机模拟研究结果,阐明了操作条件对温度分布和产物组成的影响规律,揭示了磁旋转弧等离子体炬这类热等离子体反应器的独特优势和发展潜力。采用发射光谱诊断技术对纯氩气进料条件下的磁旋转弧等离子体进行诊断,探究了不同操作条件对等离子体温度的影响。研究表明,等离子体温度与电子温度近似相等,在10000K以上。提高输入功率以及减小进气量均可以提高等离子体温度,增加磁感应强度有利于形成均匀的热等离子体。采用Fluent软件对该体系的温度分布进行计算流体力学模拟,所得结果与实验符合良好。利用磁旋转弧等离子炬重整甲烷二氧化碳制取合成气,采用发射光谱诊断技术研究等离子炬内的温度分布信息。研究表明,随着原料中CH_4浓度的增加,CH_4转化率和CO选择性持续降低,H_2选择性持续上升,而CO_2的转化率则先增后减,等离子体温度随之下降;随着输入功率的增加,CH_4转化率、CO_2转化率、CO选择性都呈现上升趋势,而H_2选择性则先上升后下降,等离子体温度随之上升;随着磁感应强度增加,原料转化率和产物选择性上升,热等离子体温度分布更加均匀。通过Chemkin-PRO软件对磁旋转弧等离子炬重整甲烷二氧化碳的转化率、收率和温度进行数值模拟,不同CH_4/CO_2比例下CH_4转化率和H_2收率的模拟结果与实验符合良好,CO_2转化率及CO收率在变化趋势上与实验较为一致。随着输入功率、体系压力以及阳极内径的增加,CH_4转化率、CO_2转化率、H_2收率以及CO收率均随之增加,但过高的输入功率对反应进行程度的促进作用有限。模拟得到的温度与发射光谱法诊断所得的温度存在约1000K的偏差,但其变化趋势非常吻合。
[Abstract]:Thermal plasma has the characteristics of high efficiency of electrothermal conversion, high reaction temperature, concentration of energy density and controllable atmosphere, etc. It is a kind of advanced chemical strengthening method, which is widely used in acetylene. The temperature distribution in the hot plasma reactor is the key factor that affects the reaction efficiency, such as the preparation of syngas and the treatment of solid waste. However, the temperature of hot plasma can reach 2000 ~ 20000 K, and the reactor often requires good airtightness. This makes it difficult to obtain the temperature distribution in the reactor by conventional means of detection. In this paper, the emission spectrum diagnosis technique is used for the first time in the case of pure gas feed in the magnetic rotating arc plasma torch and the chemical reaction feed condition. The temperature distribution is studied experimentally. Based on the results of computer simulation, the effects of operating conditions on temperature distribution and product composition are illustrated. The unique advantages and development potential of magnetic rotating arc plasma torch are revealed. The magnetic rotating arc plasma under the condition of pure argon gas feed is diagnosed by using the emission spectrum diagnostic technique. The effect of different operating conditions on plasma temperature is investigated. The results show that the plasma temperature is approximately equal to electron temperature, above 10000K. The plasma temperature can be increased by increasing input power and reducing air intake. Increasing the intensity of magnetic induction is beneficial to the formation of homogeneous thermal plasma. The temperature distribution of the system is simulated by computational fluid dynamics (CFD) with Fluent software. The results are in good agreement with the experimental results. The temperature distribution in the plasma torch is studied by using the emission spectrum diagnostic technique to study the temperature distribution in the plasma torch by reforming methane carbon dioxide with magnetic rotating arc plasma torch to produce syngas. With the increase of CH_4 concentration in feedstock, the conversion of CH4 and the selectivity of CO continued to decrease, while the conversion of CO_2 increased first and then decreased, and the plasma temperature decreased. With the increase of the input power, the CO selectivity of Ch _ 4 conversion and CO _ 2 conversion increased, while the H _ S _ 2 selectivity first increased and then decreased, and the plasma temperature increased, and with the increase of magnetic induction intensity, the conversion of raw material and the selectivity of the product increased. The temperature distribution of thermal plasma is more uniform. The conversion, yield and temperature of methane carbon dioxide reforming by magnetic rotating arc plasma torch are simulated by Chemkin-PRO software. The simulated results of the conversion of CH_4 and the yield of Hap2 at different CH_4/CO_2 ratios are in good agreement with the experimental results, and are consistent with the experimental results with the input power, and the CO yield and the conversion of CO2 are in good agreement with the experimental results. The pressure of the system and the inside diameter of the anode increased with the increase of the conversion of CHS _ 4 and the yield of CO _ (2) and H _ (2) as well as the yield of CO. However, the effect of high input power on the degree of reaction is limited. The simulated temperature has a deviation of about 1000K from the temperature diagnosed by the emission spectrometry, but the variation trend is very consistent.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE665.3;O657.3

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