介质阻挡放电等离子体脱除硫化氢的能效优化研究

为提高介质阻挡放电(DBD)系统降解H2S的能量利用效率,以同轴DBD反应系统为对象,从谐振特性和功率特性两方面研究了DBD放电系统的电气参数和反应器几何参数对反应器能量输入和H2S脱除效果的影响。研究发现,放电频率与负载电压之间的谐振特性直接影响H2S脱除效率,在谐振频率点脱除效率最大。谐振频率的大小受负载电压和反应器几何参数的影响,其原因可以归结于介质层等效电容的变化。DBD放电有效功率与放电频率、负载电压和反应器几何参数间存在量化规律P=A·L·f·Vn,且在相同的负载电压下,谐振频率点的能量输入效率ηP最大。其他条件不变的情况下,放电区域长度越大,H2S脱除效率越高;放电气隙的大小存在最优值,本文中最优的放电气隙为5 mm。     

介质阻挡放电裂解CO_2的实验研究

考察了CO_2进气流量、放电功率、放电频率对介质阻挡放电(DBD)裂解CO_2反应的影响。结果表明,CO_2转化率随着CO_2进气流量的增加而减小,随着放电功率的增加而增加,随着放电频率的增大略微减小,但变化幅度不大。DBD转化CO_2能量效率几乎不随CO_2进气流量和放电功率改变,仅随放电频率有所改变。     

基于VSP2的放热反应失控紧急泄放特性

基于VSP2绝热量热仪,通过增加泄放物收集罐、快速响应气动阀及泄放孔板,开展了放热反应失控泄放实验,详细探讨了输入热功率、初始填充率、泄放压力、泄放直径以及反应物发泡性对泄放能力及泄放物质量的影响。结果表明:二相流泄放能力随输入热功率增大而降低,随初始填充率增大先增大后减小,随泄放压力增大先快速降低后缓慢增加,随泄放直径增大而增大。泄放物质量随输入热功率、初始填充率、泄放压力和泄放直径的增大而增大。发泡性材料能显著降低泄放装置的泄放能力,但能增大泄放物质量。     

高温DBD系统的研制及其放电特性研究

为探究高温条件下介质阻挡放电特性,采用氮化硅陶瓷为绝缘介质的同轴管式结构研制了一套可在800℃高温下运行的DBD放电系统,研究了在氮气气氛中不同温度条件下的DBD放电性能。结果表明,研制的DBD系统可在室温到800℃范围内实现稳定放电。随着电压逐步提升,内电极附近区域最先发生细丝放电,强度优于外电极;随着温度的升高,放电逐步变得均匀;在维持外加电压不变时升高温度,有效电流和放电功率显著增大;高温环境DBD性能稳定,600℃时系统运行1 h后能量变化方差仅为0. 81。     

介质阻挡放电降解VOCs的能效特性研究

挥发性有机物（VOCs）已经严重威胁了城市居民的生活环境,介质阻挡放电技术最高可使VOCs的降解率达到95%以上。本研究选择甲苯作为目标污染物,进行介质阻挡放电（DBD）降解VOCs的能效研究。考察放电电压、电源频率、气体流量和初始浓度对能量密度（SED）和能量效率的影响。研究结果表明：能量效率随放电电压的升高而降低,随电源频率的升高而升高。且能量效率随气体流量的增大先升高后降低,随甲苯初始浓度的增大而提高。     

O2介质阻挡放电微等离子体制备O3

介质阻挡放电(DBD)是工业生产臭氧(O₃)最有效的方法。研究以O₂为原料气采用DBD微等离子体放电制备O₃,研究了放电间距、放电长度、放电功率以及停留时间对产生O₃的影响。此外,通过向正弦AC等离子体电源中叠加调制脉冲,探讨了脉冲占空比与调制频率对O₃生成的影响。结果表明：O₃浓度与DBD反应器的放电间距呈负相关,与O₂的停留时间呈正相关,放电功率及有效放电长度对O₃浓度的影响呈现火山形变化趋势。综合考虑O₃浓度及能量产率确定了适宜的参数。与普通正弦交流电源相比,在其基础上叠加脉冲调制电源有利于O₃的产生,而能量产率与占空比呈正相关,与调制频率呈负相关,据此确定了合适的占空比与调制频率。     

介质阻挡放电等离子体特性及其在化工中的应用

阐述了介质阻挡放电（DBD）等离子体的基本特性、放电机理、理论模型、反应器类型及存在问题。评述了介质阻挡放电在物质合成、挥发性有机物处理、汽车尾气净化、材料表面处理、催化剂改性、沉积制膜以及等离子体催化协同作用在环境化工中的应用等方面的研究进展,分析了传统方法在这些方面应用的优缺点,指出通过与催化剂协同可以更好地发挥等离子体的优势。DBD等离子体技术在节约能源、降低成本、安全操作和环境保护等方面都有很大改进,是一种很有前途的新技术,并展望了DBD等离子体技术的发展前景和研究方向。     

基于钙镁二元盐的热化学储能反应器的性能优化

水合盐热化学储能技术储能密度高、再生温度与太阳能集热器的温度一致，在提高太阳能的利用和缓解能源紧张方面具有很好的应用前景，其中热化学储能反应器的设计优化则是重要环节。本文针对硅藻土(WSS)+MgCl₂/2CaCl₂热化学储能系统，对填充床反应器建立了二维数值模型，对填充床的放热过程进行了研究，分析了钙镁二元盐含量、粒径大小、填充床高度对填充床放热过程的影响。数值模拟结果表明，填充床出口空气温升随粒径减小而增大；填充床出口空气温升的衰减速度随钙镁二元盐含量增大而减小，随粒径减小而增大，随填充床高度增大而减小；填充床的放热功率和储能密度随盐含量增大而增大，随粒径减小而增大，填充床高度增大时，填充床放热功率增大，而储能密度则减小。采用粒径为2mm的WSS20颗粒，填充高度为10cm的填充床反应器储能密度达到0.985GJ/m³，几乎是水的4倍。     

三维上流式反应器床层流动和返混特性

采用内径为280 mm的上流式反应器,以空气模拟气相、甘油和水混合溶液模拟渣油。用3种不同粒径的氧化铝球形工业催化剂颗粒为填充颗粒,考察了不同模拟物系的颗粒粒径、颗粒密度、液相黏度、不同床层的高径比和不同操作条件对上流式反应器内床层压降及其波动、床层轴向返混的影响规律。得到模拟工业运行物系和操作条件的上流式反应器床层总压降关联式,相对误差在12%以内。床层总压降均随床层高径比、颗粒密度和液相黏度增加而增大,但随颗粒粒径的增大而减小,床层压降波动随表观气速增加而增大。填充颗粒粒径越小、颗粒密度越小、高径比越大,床层内轴向返混越严重;床层内压降和轴向返混均随表观气速的增加而增大。     

三维上流式反应器床层流动和返混特性

采用内径为280 mm的上流式反应器,以空气模拟气相、甘油和水混合溶液模拟渣油。用3种不同粒径的氧化铝球形工业催化剂颗粒为填充颗粒,考察了不同模拟物系的颗粒粒径、颗粒密度、液相黏度、不同床层的高径比和不同操作条件对上流式反应器内床层压降及其波动、床层轴向返混的影响规律。得到模拟工业运行物系和操作条件的上流式反应器床层总压降关联式,相对误差在12%以内。床层总压降均随床层高径比、颗粒密度和液相黏度增加而增大,但随颗粒粒径的增大而减小,床层压降波动随表观气速增加而增大。填充颗粒粒径越小、颗粒密度越小、高径比越大,床层内轴向返混越严重;床层内压降和轴向返混均随表观气速的增加而增大。     

Rapid growth of particles by coagulation between particles in silane plasma reactor

The changes of particle size distribution were investigated during the rapid growth of particles in the silane plasma reactor by the discrete-sectional model. The particle size distribution becomes bimodal in the plasma reactor and most of the large sized particles are charged negatively, but some fractions of small sized particles are in a neutral state or even charged positively. As the mass generation rate of monomers increases or as the monomer diameter decreases, the large sized particles grow more quickly and the particle size distribution becomes bimodal earlier. As the mass generation rate of monomers decreases, the electron concentration in the plasmas increases and the fraction of particles charged negatively increases. With the decrease in monomer diameter, the electron concentration decreases in the beginning of plasma discharge but later increases.     

大气压介质阻挡放电及协同催化剂脱硝研究进展

受绿色生态和可持续发展战略理念的驱动,废气排放对环境造成的危害备受关注。NO _x 作为废气的主要污染物之一,是废气污染物控制的重点与难点。基于此,本文介绍了传统后处理脱硝技术的优缺点及应用现状,回顾了介质阻挡放电（DBD）基础研究,分析了DBD脱硝性能,重点阐述了DBD协同催化剂脱硝及脱硝机理。分析指出：①DBD驱动电源与反应器结构是制约脱硝性能的关键因素;②单独DBD技术脱硝性能较差,而DBD协同催化填充床技术展现出优异的脱硝性能和较高的N₂选择性;③等离子体协同催化脱硝机理研究主要包括等离子体特征参数诊断、流体模型验证、等离子体传播机制分析以及原位表征,而在等离子体催化理论计算方面的研究较为缺乏。因此,未来DBD协同催化脱硝技术应立足如下几个方面发展：研发高功率、低能耗电源,提升废气NO _x 处理量;优化反应器结构,提升脱硝的效率与选择性;设计与构筑适宜于DBD环境的脱硝催化剂;深入全面分析DBD协同催化剂脱硝机理。     

Plug Flow Modeling of Particle Formation and Growth Combined with Plasma Chemistry in NO x Removal by a Pulsed Corona Discharge Process

We analyzed the plasma chemistry, particle formation, and growth in the pulsed corona discharge process (PCDP) to remove NO x and investigated the effects of several process variables (initial concentrations of NO, NH 3 , and H 2 O and electron concentration). In the PCDP, most of NO is converted into NO 2 and, later, HNO 3 , which reacts with NH 3 to form NH 4 NO 3 particles. As the initial NO concentration increases or as the initial H 2 O concentration and the electron concentration decrease, it takes longer reactor lengths to remove the NO x . With the increase of initial NO concentration, more NH 3 is consumed to remove the NO supplied initially and NH 3 disappears more quickly in the PCDP. In the beginning of the reactor, the particle concentration and the standard deviation of particle size distribution increase quickly because of fast particle formation from the NO supplied initially. The particle concentration and the standard deviation decrease in the PCDP, where the NO initially supplied is all consumed. Later, the particle concentration decreases slowly because the disappearance rate of particles is slightly faster than the generation rate from the NO newly formed and the NO 2 by N 2 O 5 decomposition reaction, but the standard deviation increases slowly. New particle formation stops after the NH 3 is all consumed, and the particle concentration and the standard deviation drop quickly by coagulation between particles, but the average particle diameter starts to grow quickly. As the initial concentrations of NO and H 2 O increase or as the electron concentration increases, new particle formation stops earlier in the PCDP and the average particle diameter starts to increase earlier and becomes larger and the standard deviation drops more quickly to reach an asymptotic value. As the initial NH concentration increases, the average particle diameter starts to increase later, but particle concentration increases and the average particle diameter becomes larger by faster coagulation in the end of the reactor. The information on the particle characteristics can be the basic raw materials to develop more efficient PCDP and particle collection equipments.     

Analysis of particle contamination in plasma reactor by 2-sized particle growth model

Rapid particle growth in the silane plasma reactor by coagulation between 2-sized particles was analyzed for various process conditions. The particle coagulation rate was calculated considering the effects of particle charge distribution based on the Gaussian distribution function. The large size particles are charged more negatively than the small size particles. Some fractions of small size particles are in neutral state or charged positively, depending on the plasma conditions. The small size particle concentration increases at first and decreases later and reaches the steady state by the balance of generation rate and coagulation rate. The large size particles grow with discharge time by coagulation with small size particles and their size reaches the steady state, while the large size particle concentration increases with discharge time by faster generation rate and reaches the steady state by the balance of generation and disappearance rates. As the diameter of small size particles decreases, the diameter of large size particles increases more quickly by the faster coagulation with small size particles of higher concentration. As the residence time increases, the concentration and size of large size particles increase more quickly and the average charges per small size and large size particle decrease.     

介质阻挡放电常压低温等离子体转化甲烷制C2及高碳烃的研究

对介质阻挡放电(DBD)反应器用于甲烷常压低温等离子体转化过程,分别就停留时间、输入功率、内电极材料及温度、介质厚度等对反应的影响进行了研究。实验结果表明,甲烷转化率随停留时间、输入功率的增加而增加,但增加的幅度逐渐减小。内电极材料对反应积炭有很大的影响。紫铜和紫铜(镀银)材料能够有效地抑制积炭的产生,从而可以增加反应寿命,还对甲烷转化率有很大的影响。较低的内电极温度可以抑制积炭,但是甲烷转化率有所降低,同时液态高碳烃选择性增加。在甲烷流量较低时介质厚度对反应的影响很小,但随着甲烷流量的提高会逐渐增大,并且介质厚度越小,甲烷转化率越高。     

Herstellung von metallischen Nanopartikeln in einem asymmetrischen Dielectric Barrier Discharge‐Plasma bei Atmosphärendruck

This paper focuses on the production of metal nanoparticles in a dielectric barrier discharge (DBD) reactor at atmospheric pressure. In the developed reactor only one electrode is provided with a dielectric (alumina), while the point‐shaped counter electrode is not covered and is accessible to the filamentary discharges (asymmetrical DBD). The metallic particles are formed from the material of the open counter electrode, on which the filamentary discharges lead to the formation of craters. A high number of larger nanoparticles (with diameter of some tens of nanometers) are observed in the cold reactor at the beginning of the discharges. After the achievement of the thermal equilibrium in the reactor mainly very small metallic nanoparticles are produced with constant size and number concentration. The produced metallic particles in thermal equilibrium are crystalline and not agglomerated. The mean diameter of the produced particles is about 4 nm. For given operating conditions of the reactor (fixed electrode gap and gas flow rate) the electrode material has almost no influence on the size of the produced particles, but it determines the number concentration.     

Enhancement of VOCs removal using a novel double-tube packed bed catalytic dielectric barrier discharge (DPDBD) reactor

We developed a novel double-tube packed bed catalytic dielectric barrier discharge (DPDBD) reactor to degrade toluene. The DPDBD reactor contains four discharge cells with one power supply, namely, A–D. NiO/γ-Al₂O₃ is packed in cell A to effectively destroy the branched chains in toluene. TiO₂/γ-Al₂O₃ is packed in cell B owing to its high catalytic oxidation activity to weaken the benzene rings and mineralize the generated partial aromatic compounds. Cell C is a pure DBD process without any catalyst packed to thoroughly mineralize all the generated aromatic compounds and convert CO into CO₂ and NO into NO₂. γ-Al₂O₃ is packed in cell D to reduce the concentrations of byproducts, including O₃ and NO generated by air through oxidation. The combinations of the four discharge cells are optimized by the treatment of −3000 mg m⁻³ of toluene at 11 kV. In comparison with a double-tube dielectric barrier discharge (DDBD) reactor without catalyst packing and with a total discharge length of 6 cm, the selectivity of CO₂ was significantly improved from 45% to 57% when the discharge lengths of A, B, C, and D are 2, 4, 4, and 2 cm, respectively. Furthermore, the concentrations of O₃ and NO in the outlet can also be effectively reduced from 2.80 and 210 mg m⁻³ to 1.30 and 60 mg m⁻³, respectively. We also investigated the effects of applied voltage and styrene initial concentration.     

Solid–liquid mass transfer studies in trickle bed reactors

Solid–liquid mass transfer was studied in a trickle bed reactor packed with copper cylindrical particles. Diffusion-controlled dissolution of copper in acidified dichromate solution was used to study the solid–liquid mass transfer. The effect of liquid and gas throughputs and particle diameter on solid–liquid mass transfer was investigated.     

采用多相放电反应技术加氢精制生物油的试验研究

针对目前生物油加氢技术中存在的催化剂易结焦、工艺过程不能连续等问题,采用多相放电反应对生物油进行加氢精制。构建了生物油/固体催化剂/H₂的多相放电体系,研究了催化剂类型、工作电压、气体流量、反应时间等条件对精制生物油的加氢脱氧效果的影响。研究结果表明：随着工作电压和气体流量的增大,多相放电催化加氢精制生物油的脱氧率（R）呈现出先增加后减少的趋势;随着反应时间的延长,呈现出先增加后稳定的趋势。在工作电压为22kV,气体流量为60mL/min,反应时间为120min的工艺条件下,脱氧率最高可达41%。与生物原油相比,多相放电催化加氢精制的生物油中醇类、酚类、酮类等物质的含量相对较低,而碳氢类物质显著增多。