【作者】 王波；

【导师】 孙冰；

【作者基本信息】 大连海事大学 ， 环境科学， 2014， 博士

【摘要】 微波液相放电技术是一项新兴等离子体产生技术,由于其较大的空间分布和较高的等离子体密度越来越备受关注。目前,世界上对微波液相放电基本特性及其在环境和制氢领域的应用研究鲜有报道。本文对微波液相放电电极设计方法、电极结构特性、液相放电机理及特性、放电光谱特性、微波液相放电技术在污染物处理和氢气制取领域的应用等方面进行了研究。所取得的主要研究成果如下：第一,设计了一种匹配良好的微波液相放电电极,电极由内到外依次为内导体、陶瓷管、硅胶和外导体。同时,对反应器内理化环境对电极匹配的影响特性进行研究证明：水的电导率、pH值、外界压强对驻波比(SWR)的影响不明显,而随着温度的增加,SWR不断增大；电极所处液体相对介电常数对SWR的影响最大。第二,对微波液相放电特性研究结果表明：等离子体区域面积和OH自由基发射光谱强度的变化趋势具有良好的对应关系。微波功率的增大和温度的提高有利于维持等离子体的持续产生,而外界压强和电导率的增大会使等离子体淬灭现象越来越明显；悬浮电极能够有效增强放电强度；OH自由基光谱相对强度随外界压强的增大而减弱,随功率的增大而增强；在温度为25℃时,OH自由基光谱相对强度出现最大值；OH自由基光谱相对强度随着电导率的增大出现先增强后减弱的趋势。第三,通过研究损耗因子对微波液相放电的影响机理得出：在微波频率一定的条件下,介质相对介电常数、温度、电导率是影响微波与液体耦合的三个主要因素。HFSS模拟结果发现当有气泡存在时,原位于内电极尖端与陶瓷管之间间隙处的最强电场区域已经转移至气泡底部。通过调整放电电极的放置方式,发现气泡走向对放电有一定影响,结合软件模拟和理论分析得出微波液相放电过程实际为电极内导体尖端气泡被强电场击穿过程。第四,利用微波液相放电技术对亚甲基蓝溶液进行了脱色实验研究。结果发现：亚甲基蓝的脱色率随着功率的增大而增大；在pH值为6-8范围内,亚甲基蓝的脱色率随pH值的增大而减小,在酸性溶液条件下亚甲基蓝的脱色效果最好,处理12min,即可达到97.81%;当亚甲基蓝的初始浓度为12.5mg/L时,亚甲基蓝获得了最大脱色率,最大能量效率为120mg/kWh。第五,利用微波液相放电技术对低碳醇(甲醇和乙醇)进行了分解制氢。结果显示：甲醇和乙醇溶液放电气相产物主要包括氢气、一氧化碳、乙炔和二氧化碳。随着功率的增大,放电产生的总气体流量和氢气流量都显著增加,而随着醇溶液浓度的增大,放电产生的总气体流量和氢气流量都出现先增加后减小趋势。随着功率的增大,氢气比例和一氧化碳比例都有所提高,其它气体的比例有明显的下降；当醇溶液浓度为8%时,氢气比例和一氧化碳比例都出现了最大值,而其它气体的比例则出现最低值。随着功率的增大,放电产氢能量效率都有显著地提高,且在同一功率下,乙醇的制氢能量效率都要高于甲醇的制氢能量效率。随着醇溶液体积分数的增大,制氢能量效率则出现先增大后减小趋势,且在8%体积分数时获得最大值。本文中微波液相放电醇类制氢最大氢气流量、最大氢气纯度及最大能量效率分别为215nL/min,64.55%和74.26NL/kWh。更多还原

【Abstract】 Microwave discharge in liquid is a new plasma technology and becomes more and more concerned due to its large spatial distribution and high density of plasma. At present, there are few reports about the characteristics of plasma and application in the field of pollution treatment and hydrogen production. In this paper, the design method of electrode of microwave discharge in liquid, characteristic of electrode structure, mechanism and characteristic of microwave discharge in liquid, spectral characteristic of discharge, application of microwave discharge in liquid in the field of pollution treatment and hydrogen production are studied. The main results are as follows:First, a new style electrode of microwave discharge in liquid is designed, which consists of inner electrode, ceramic tube, silicone and outer electrode in turn from inside to outside. At the same time, the effects of physical and chemical properties of liquid in the reactor on matching properties of microwave discharge are studied. The results show that the SWR increases as the water temperature rise, while the pH, pressure and conductivity have no effects on the SWR. The main cause for the change of the SWR is the change of the relative dielectric constant of liquid.Second, the characteristic of microwave discharge in liquid is studied. The results show that:the change of plasma area is well corresponding with that of the emission intensity of OH radicals. The increase of microwave power and temperature is beneficial to maintain the generation of plasma, while the increase of external pressure and conductivity make the quenching of plasma more and more frequent. Suspension electrode can enhance the intensity of discharge effectively. The emission intensity of OH radicals decreases with the increase of pressure, but increases with the increase of power. The emission intensity of OH radicals is seen to attain the maximum value at the temperature of25℃. The emission intensity of OH radicals increases firstly and then decreases gradually with the increasing conductivity.Third, by studying the influence mechanism of loss factor on microwave discharge in liquid, it can be got that:when the microwave frequency is fixed, the relative dielectric constant of medium, temperature, conductivity are main factors of injection efficiency of microwave energy. The results of HFSS simulation show that when there is a bubble, the area of strongest electric field is located at the bottom of the bubble, instead of the gap between the inner electrode tip and the ceramic tube. By adjusting placed mode of the electrode, it is found that the movement of bubble has influence on the discharge. Combined with the simulation and theoretical analysis, it is concluded that the process of microwave discharge in liquid is actual the breakdown of bubble over the electrode tip by strong electric field.Fourth, in the paper, methylene blue is decolorized using plasma which is generated by microwave discharge in liquid. The results show that the decolorization rate of methylene blue increases with increasing of microwave power, but decreases with increasing pH in the range of6-8. A maximum decolorization rate of97.81%is obtained in the acidic solution with12minutes treatment. When the initial concentration is12.5mg/L, the decolorization of methylene blue reaches the maximum value, and the max energy efficiency can reach120mg/kWh.Fifth, hydrogen is produced from low carbon alcohol (methanol and ethanol) by microwave discharge in liquid. The results show that the gaseous product of discharging in methanol and ethanol solution mainly includes hydrogen, carbon monoxide, acetylene and carbon dioxide. The flow rates of total gaseous product and hydrogen in the process of discharge increase with the increase of power, while that increase firstly and then decrease with the increase of concentration of low carbon alcohol solution. The proportions of the hydrogen and carbon monoxide increase with the increase of power, but the proportion of other gases decreases significantly. When the concentration of low carbon alcohol solution is8%, the proportions of the hydrogen and carbon monoxide reach a maximum value, while the proportion of other gases have a minimum value. The energy efficiency of hydrogen production improves significantly as the power increase, and the energy efficiency of hydrogen produced from ethanol is higher than that from methanol in the condition of same power. The energy efficiency of hydrogen production increases firstly and then decreases with the increase of concentration of low carbon alcohol solution. When the concentration of low carbon alcohol solution is8%, the energy efficiency of hydrogen production reaches the maximum value. In this paper, the maximum flow rate of hydrogen, the maximum proportions of hydrogen and the maximum energy efficiency are215mL/min,64.55%and74.26NL/kWh respectively.更多还原