低温等离子体催化处理汽车尾气

针对汽车尾气控制和防治,自制了同轴管介质阻挡放电催化反应器,并采用石英玻璃作为绝缘介质层处理了汽油机尾气。研究脉冲放电频率、脉冲电压、气体流量qV、NO初始体积分数0φ(NO)等对NO、HC和CO去除率影响的结果表明,NO、HC和CO的去除率随脉冲电压、脉冲频率的增加而增加,随φ0(NO)及qV的增加而减小。当脉冲频率为15 kHz、脉冲电压为15 kV、0φ(NO)=100×10-6、工作气体qV=0.05m3/h,并以γ-Al2O3小球作为催化剂时,NO、HC和CO的去除率分别为82.3%,83.2%和48.6%;而若不加γ-Al2O3小球,NO、HC和CO的去除率在相同条件下分别只能达到68.1%、76.0%和41.9%。可见,-γAl2O3小球的加入有利于提高污染物的去除率。研究表明,介质阻挡放电产生的低温等离子体在催化剂的协同作用下处理汽车尾气效果较好。     

介质阻挡放电产生低温等离子体除去NO_x的实验研究

低温等离子体技术对氮氧化物(NOx)及多种污染物实现同步净化已成为尾气净化方面的研究热点。为此,针对国内外大多数研究采用模拟气体放电的现状,以实际柴油机尾气中NOx为研究对象,采用介质阻挡放电技术,实验研究了电压幅值、电源频率、高压电极直径、反应器体积、放电间隙对NOx去除的影响。实验结果证明,采用该研究所建立的低温等离子体处理装置,柴油机尾气中的NOx的除去率随着电压幅值及其频率的增加先升高后降低,即出现一个最大值,随电压幅值的增加其能耗增加;NOx除去率随放电间隙的减小和高压电极直径的增加而升高,随着反应器体积增加而增加。该研究成果对低温等离子处理NOx装置的车载化应用有一定的指导意义。     

线板脉冲放电对罗丹明B脱色的实验研究

为了提高脉冲放电对罗丹明B染料废水的脱色率η,采用线-板式脉冲放电反应器实验研究了脉冲电压Up、脉冲频率f、线板间距d、线线间距s、曝气量Q等对η的影响。研究表明,当Up为35kV、f为60Hz、d为8mm、s为5mm、Q为15L/h时,处理50min后,η达99.43%,溶液中总有机碳质量浓度ρ(TOC)由70mg/L降到17.3mg/L。最佳实验条件下,在放电反应器中投放Fenton试剂对罗丹明B废水进行联合处理,研究Fenton的投放量在放电过程中的作用及对脱色的影响,结果表明投放Fe2+的量为0.05mmol和H2O2的量为88.2mmol时能有效地发挥Fenton和脉冲放电低温等离子体的协同作用,提高了η,处理30min时η达99.87%。     

双极性高压脉冲介质阻挡放电降解甲醛及臭氧生成质量浓度控制

为进一步提高介质阻挡放电(DBD)降解甲醛的效率,并控制副产物的生成量,采用正负双极性高压脉冲电源对同轴式介质阻挡反应器供电,系统地研究了脉冲电压、脉冲重复频率、放电间隙、气体体积流量及甲醛初始质量浓度等影响因素对甲醛降解率及臭氧生成质量浓度的影响。实验结果表明:升高脉冲电压有利于甲醛的降解,当脉冲电压达到19 k V时,脉冲电压继续升高对甲醛降解率的影响不大,而臭氧生成质量浓度随着脉冲电压的增加而不断增大;放电间隙对甲醛降解率有很大的影响,随着放电间隙的减小,甲醛降解率增大,但放电间隙过小时,臭氧生成质量浓度较大;随着气体体积流量的增大,甲醛降解率降低;随着脉冲重复频率的增大,甲醛降解率增大,当脉冲重复频率达到60 Hz时,继续增加脉冲重复频率,甲醛降解率增大不明显;在一定实验条件下,甲醛初始质量浓度越大,甲醛降解率降低,而甲醛去除质量浓度增大并趋近于反应器的最大处理量。     

脉冲介质阻挡放电脱除N_2/NO体系中NO的模拟研究EI北大核心CSCD

NO是重要的大气污染物之一,为了深入了解脉冲介质阻挡放电去除N2/NO体系中NO的机理,采用一维自洽的流体力学模型对N2/NO中大气压脉冲放电进行了模拟研究,并分析讨论了各种放电参数对NO去除效率的影响。模拟结果表明:NO的去除主要通过还原反应N+NO→N2+O来实现;N原子是脱除NO的主要活性粒子,它来源于电压上升沿和下降沿的2次放电,并主要通过电子直接碰撞解离N2分子产生;放电中产生的N原子体积分数的高低直接决定NO的脱除效率;电压脉冲幅度越大,上升和下降时间越短,介质层越薄,或放电间隙越小,则脉冲放电产生的N原子体积分数就越高,越有利于NO的脱除;在其他参数不变时,存在1个最佳脉冲宽度,在此脉冲宽度下NO的脱除率最高。     

脉冲介质阻挡放电脱除N_2/NO体系中NO的模拟研究

NO是重要的大气污染物之一,为了深入了解脉冲介质阻挡放电去除N2/NO体系中NO的机理,采用一维自洽的流体力学模型对N2/NO中大气压脉冲放电进行了模拟研究,并分析讨论了各种放电参数对NO去除效率的影响。模拟结果表明:NO的去除主要通过还原反应N+NO→N2+O来实现;N原子是脱除NO的主要活性粒子,它来源于电压上升沿和下降沿的2次放电,并主要通过电子直接碰撞解离N2分子产生;放电中产生的N原子体积分数的高低直接决定NO的脱除效率;电压脉冲幅度越大,上升和下降时间越短,介质层越薄,或放电间隙越小,则脉冲放电产生的N原子体积分数就越高,越有利于NO的脱除;在其他参数不变时,存在1个最佳脉冲宽度,在此脉冲宽度下NO的脱除率最高。     

新型复合静电除尘器脱硝性能研究

NO是燃烧产生的重要气体污染物之一。脉冲放电与直流放电相结合的新型除尘方式在有效提高对粒径小于 2.5 mm的颗粒物(PM2.5)脱除效率的同时,还具有氧化NO的能力。高压脉冲放电产生的高能电子可以产生强氧化性的自由基,对NO进行氧化,同时还可以直接打断N-O键,游离态的N原子大部分生成了N2分子。线筒式放电结构氧化NO的能力明显优于线板式放电,与除尘能力具有一致性。氧化效率随着电压的升高而升高,由于一定电压下对NO的处理量趋于定值,氧化效率与NO的初始浓度具有重要的关系,同时也受NO2浓度的影响。在该文讨论的反应器中,当脉冲峰值电压达到50kV,NO初始体积分数低于10-4时,NO的氧化率可以达到90%以上。氧化产物NO2可以在湿法脱硫设备中脱除。     

大气压空气中纳秒脉冲介质阻挡放电均匀性的研究

为了实现大气压空气中纳秒脉冲均匀介质阻挡放电(DBD),利用上升沿15ns,半高宽30～40ns的正极性纳秒脉冲激发DBD,并由电压电流和放电图像研究DBD的特性,分析均匀放电实现的条件和特征。实验结果表明放电电流呈双极性,且电气参数要比交流及微秒脉冲DBD的高,在一定条件下可获得均匀模式放电。通过重复频率和气隙距离对放电均匀性的影响研究发现,2mm空气间隙中,双层介质阻挡时重复频率对放电均匀性影响不明显,但当间隙距离从2～8mm延长时,放电明显由均匀模式向丝状模式过渡。此外,对纳秒脉冲DBD放电均匀性与施加脉冲上升沿的关系进行了探讨。     

雾霾对冲击放电路径影响特性的分析

由于经济规模的迅速扩大和城市化进程的加快,雾霾现象日趋严重,这些雾霾多发地区是我国输电走廊或用电高负荷密度地区。为研究雾霾对放电发展的影响,利用水雾、粉煤灰等模拟雾霾天气,采用雷电冲击电压进行了雾霾对击穿电压和放电路径影响的实验研究。研究结果表明:当雾霾的粒径范围<0.01mm时,雾霾间隙的击穿电压始终较空气间隙的高,放电路径选择雾霾的概率<50%;当粒径范围为0.01～0.1mm时,正电压下选择概率<50%,雾霾间隙的击穿电压较空气间隙的高,而负电压下选择概率>50%,雾霾间隙的击穿电压较空气间隙的低。雾霾中放电发展是电场的畸变和雾霾颗粒与粒子间作用联合影响的结果。     

供电方式对介质阻挡放电-催化降解苯的影响

为研究能量注入方式对等离子体降解有机污染物的影响,分别将交流高压和双极性脉冲高压引入介质阻挡放电反应器,结合Mn催化剂对苯进行降解,研究供电方式对放电特性、苯去除率和产物选择性的影响。结果发现,与交流电源相比,脉冲电源供电下能量在极短的时间里注入到反应器内,产生瞬间大功率放电和高能活性粒子,可以实现对苯的高效降解和较高的CO2选择性。此外,相同功率下脉冲介质阻挡放电(DBD)的臭氧质量浓度更多,更有利于与Mn催化剂结合对苯进行降解。在电压为18.8kV的条件下,对苯的去除率最高可达98%,CO2转化率可达77%。     

改性粉煤灰在水处理方面的应用

粉煤灰因其具有多孔性、比表面积大、吸附能力强等特性,同时其结构中具有Al2O3、CaO等活性组分,目前在国内已被应用于废水处理方面。通过酸改性、碱改性、盐改性等方法对粉煤灰的表面结构进行装饰,可以增强其吸附性能,提高其对污染物的处理效果;在其表面引入活性基团,还可以拓宽其在污水处理方面的应用范围。在最优试验条件下,改性粉煤灰对印染废水、造纸废水、有机物废水中的色度以及COD的去除率可达85%以上,对废水中重金属离子的去除率可达95%以上,对废水中总磷和氨氮也有明显的去除效果;在藻类废水以及含油废水、生活污水、工业混合废水、矿井水等综合性废水处理方面,改性粉煤灰对其中的多种污染物也有较好的去除作用。同时指出对于改性粉煤灰在水处理方面的应用目前多数局限于试验室研究阶段,提出了可将改性粉煤灰应用于火电厂脱硫废水处理的建议。     

等离子体协助InZSM-5选择性催化还原贫燃NOx

为了解等离子体协助选择性催化还原(SCR)贫燃NOx的效果及相关因素,以NO模拟尾气中NOx,C2H4为还原剂,InZSM-5为催化剂,空速为32000h-1,试验研究了NO/O2/N2/C2H4系统中,单独等离子体、单独SCR及等离子体协助SCR 3种技术路线下NOx的去除率,并考察了等离子体电压、电源频率及空速对NOx去除的影响。试验发现:单独等离子体作用时NOx无法被有效的还原成N2,但等离子体在一定电压下可显著提高CH-SCR活性;较低空速下,等离子体协助InZSM-5效果明显提高;在2.5-4 kHz内,电源频率对等离子体协助SCR影响不大。     

Energy Efficiency of Corona Discharge Reactor Driven by Inductive Energy Storage System Pulsed Power Generator

Characteristics of a pulse corona reactor driven by an inductive energy storage (IES) pulsed power generator are described in this paper with focusing on the influence of streamer-to-glow transition on NO removal efficiency. A pulsed high voltage with a short rise time of under 30 ns is employed to generate streamer discharges homogeneously in whole the discharge region. Fast recovery diodes are used as semiconductor opening switch (SOS) to shorten the rise time. The various resistors are employed as dummy load to clarify a suitable circuit parameter such as the capacitance of a primary energy storage capacitor and/or the inductance of a secondary energy storage inductor. The energy transfer efficiency of the pulsed power generator has a maximum value of 50% at 714 Omega dummy load resistance. A co-axial cylinder type discharge chamber was used as the corona discharge plasma reactor driven by the IES pulsed power generator. The pulsed power generator supplies 30 kV pulse with 300 pps repetition rate. The co-axial cylinder plasma reactor consists of 1 mm diameter tungsten wire and 19 mm i.d. copper tube with 30 cm length. NO removal from the simulated diesel engine exhaust gas (N₂:O₂=9:1, Initial NO concentration=200 ppm) increased with input energy into the reactor. The energy efficiency for NO removal was obtained to be 25 g/kWh at 30 % removal in gas flow rate of 2 L/min. However, the energy efficiency decreased to 5 g/kWh with increasing capacitance of the primary capacitor from several hundreds pF to several nF. This decrease was caused by a streamer-to-glow transition. The efficiency was affected by oxygen concentration in the gas mixture.     

含油污泥流化床焚烧试验研究

含油污泥是石油开采、运输和石油化工行业中常见的废弃物。对某油田油泥的物化特性进行了分析,并在流化床中试炉上进行了焚烧试验。试验结果表明:油泥可以在不添加辅助燃料的情况下稳定燃烧,燃烧效率达到了96.8%;二恶英的原始排放为0.07ng/Nm3,NO2的原始排放为387.45mg/Nm3,SO2原始排放为778.05mg/Nm3,在添加一定的脱酸设备下,含油污泥流化床焚烧污染物排放可以达到国家危险废物焚烧污染控制标准;飞灰中重金属Cd含量高于《土壤环境质量标准》三级标准中的限值,建议对飞灰按危险废物固化填埋处理。从试验结果分析,用流化床焚烧技术来处理油泥是一种较为可行的方法。     

循环流化床锅炉汞排放和吸附实验研究

选取一台有代表性的440 t/h循环流化床锅炉,运用美国环保署推荐的安大略法,现场测定了入炉煤、底渣、飞灰和烟气中的各种汞形态浓度,获得了循环流化床锅炉汞排放特性。结果表明,循环流化床锅炉烟气中主要是颗粒汞,静电除尘装置的脱汞效率达98%,烟气汞排放浓度为0.062 mg/m3,底渣中汞小于总汞的1%。飞灰对汞强烈的吸附作用主要归因于其较高的含碳量,其次与飞灰中碳的结构形式和烟气温度有关。大幅度提高飞灰含碳量并不能提高其汞吸附量。     

烟气成分对燃煤飞灰汞吸附的影响

在小型固定床试验台上开展了烟气成分对燃煤飞灰汞吸附影响的试验研究。结果表明：在CO2-O2-N2的体系中,单独加入SO2,飞灰的汞吸附能力表现出与SO2的浓度有密切的关系;单独加入0~100′10-6 HCl,随着HCl浓度的增加,飞灰的汞吸附能力逐渐增加,在50′10-6左右达到最佳吸附效果,而后飞灰的汞吸附能力有所降低,但影响不大;单独加入NO,大大促进了飞灰对汞的吸附。HCl和SO2共同作用时,飞灰对汞的吸附效果要好于SO2单独存在时,但比HCl单独存在时要差一些;再加入NO后飞灰的汞吸附效率与吸附量都得到很大的提高。飞灰对Hg0的吸附是物理吸附与化学吸附双重作用的结果。     

Performance evaluation of nonthermal plasma reactors for NO oxidation in diesel engine exhaust gas treatment

The discharge plasma-chemical hybrid process for NO/sub x/ removal from the flue gas emissions is an extremely effective and economical approach in comparison with the conventional selective catalytic reduction system. In this paper we bring out a relative comparison of several discharge plasma reactors from the point of NO removal efficiency. The reactors were either energized by AC or by repetitive pulses. Ferroelectric pellets were used to study the effect of pellet assisted discharges on gas cleaning. Diesel engine exhaust, at different loads, is used to approximately simulate the flue gas composition. Investigations were carried out at room temperature with respect to the variation of reaction products against the discharge power. Main emphasis is laid on the oxidation of NO to NO/sub 2/, without reducing NO/sub x/ concentration (i.e., minimum reaction byproducts), with least power consumption. The produced NO/sub 2/ will be totally converted to N/sub 2/ and Na/sub 2/SO/sub 4/ using Na/sub 2/SO/sub 3/. The AC packed-bed reactor and pelletless pulsed corona reactor showed better performance, with minimum reaction products for a given power, when the NO concentration was low (/spl sim/100 ppm). When the engine load exceeds 50% (NO>300 ppm) there was not much decrease in NO reduction and more or less all the reactors performed equally. The total operating cost of the plasma-chemical hybrid system becomes $4010/ton of NO, which is 1/3-1/5 of the conventional selective catalytic process.     

AC energized ferroelectric pellet bed gas cleaner

The basic performance of an AC energized ferroelectric pellet bed gas cleaner has been studied. A stable partial discharge can be formed inside the pellet bed due to polarization of the ferroelectric pellet. Dust particles are precharged by a DC corona discharge in front of the pellet bet and are collected on the pellet surface. The dust penetration became minimum at the voltage at which the partial discharge was taking place. The minimum value was about 0.001% using particles larger than 2 μm in diameter. Partial discharge can be used for sterilization, or the gas phase plasma chemical reactions can be used for deodorization. Survivability of yeast cells deposited on the pellet surface decreased with the exposure to the partial discharge. The deodorization performance was also measured using a mixture of ammonia with air. One hundred twenty PPM of ammonia could be removed with a detention time of 0.7 s inside the partial discharge     

Nitric oxide decomposition in air by using nonthermal plasmaprocessing with additives and catalyst

Catalyst (copper-coated zeolite catalyst, i.e., Cu-ZSM-5) was used to enhance NO_x removal plasma chemical reactions. Two kinds of hydrocarbons (2-propane-1-ol, 2-propanol) were added to the synthesized flue gas before the nonthermal plasma process, and their effects on NO_x removal characteristics were investigated. Enhancement effects of NO_x removal by the nonthermal plasma process with hydrocarbons as the additives were confirmed. Usually, the catalyst's working temperature is much higher than the room temperature. A catalytic reactor was installed after the plasma reactor. Catalytic effects on NO_x removal characteristics disappeared when the synthesized flue gas temperature was increased (~250°C). When the synthesized flue gas temperature was at room temperature, about 90% NO _x removal efficiency was realized with a combination of hydrocarbons, the catalytic reactor, and the pulsed discharge plasma     

改性粉煤灰吸收剂对单质汞的脱除研究

利用粉煤灰、石灰和少量氧化性添加剂制备了不含添加剂和含有不同添加剂的高活性吸收剂A、M和N,含氧化性添加剂的吸收剂外覆一层氧化性活性物质,具有催化氧化性能。利用汞蒸气发生器产生的单质汞和其他烟气主要气体成分模拟烟气条件,在固定床实验台上进行了同时脱硫脱硝脱汞的实验研究。实验结果表明,吸收剂A的脱硫脱硝和脱汞效率分别为84%,0%和18%;吸收剂M对3种污染物脱除效率分别为86%,64%和39%;吸收剂N对3种污染物脱除效率分别为100%,98%和43%。改性后的粉煤灰吸收剂M和N具有较好的同时脱硫脱硝和脱汞性能,其中N更为理想。