直流电晕自由基簇射脱除烟气中的NOX

研究了直流电晕放电诱导自由基簇射脱除烟气中的NOx。该技术特点是以NH3为吸收剂的气流通过喷嘴电极电晕区域，分解产生自由基，氧化（或还原）NO。研究发现：通入喷嘴电极的气体成分和流量对放电的V－I特性有影响。通过调节两股气流量，可得到稳定的帘状流光电晕；烟气中水蒸汽对电晕放电的V－I特性有影响，并为NOx脱除过程提供更多的OH脱除量，实验结果表明，此项技术可有效脱除烟气中的NOx，并且能耗较低。     

等离子体过程结合化学吸收脱除烟气中的NOx

研究用等离子体过程诱导H2O－O2自由基簇射技术，结合化学吸收脱除烟气中NOx。研究表明，通过调节喷嘴电极氧气流量，可得到稳定的流光电晕；氧气中水蒸汽对电晕放电的V－I特性有影响；在反应器内同时有HNO2和NHO3生成，NOx脱除率可达70％以上，NaOH溶液对NO吸收率较低，而对NO2的吸收率很高，经NaOH吸收液吸收后总NOx脱除率最高可达90％。     

地下气化煤气作为多组分还原性气体脱硝的实验研究

为了揭示再燃过程中地下气化煤气作为多组分还原性气体(H2、CO等)降低还原NO的影响规律,在气体反应器实验台上进行了多组分还原性气体脱硝的实验研究。实验结果表明：反应温度不变时,化学当量比增大,NO脱除率逐渐降低;化学当量比较低时,随着反应温度的升高,NO脱除率逐渐升高;化学当量比较高时,再燃区存在一个最佳反应温度条件;停留时间对多组分气体再燃脱硝的影响规律表明,为提高再燃过程的脱硝效率,在锅炉设计时应尽量增加再燃燃料在再燃区的停留时间;再燃燃料比的增加使再燃区还原性气体浓度增加,这必然提高NO与还原性气体的反应速率,有利于进一步提高NO脱除。实验结果有利于了解多组分还原性气体再燃降低还原NO特性,组织良好的燃烧条件,可为理论研究提供参考依据。     

O3液相氧化脱除SO2试验研究

臭氧氧化SO2溶于水形成的SO2×H2O、HSO3-、SO32-产生SO42-,这使利用O3氧化脱除烟气SO2副产硫酸或硫酸盐成为可能。含SO2的氮气与臭氧分2路进入置于45 ℃水浴中的洗气瓶反应。研究臭氧施加量、溶液的PH值、氧气含量、臭氧浓度、SO2浓度、金属离子的催化作用对硫酸根产量的影响。当PH=7,O3与SO2摩尔比为1时可以达到70%左右的硫酸根产率。随着PH降低,硫酸根的产率降低,同时影响SO2的吸收效率。氧气含量不影响硫酸根的产率。当施加的臭氧量不变,加大气相臭氧浓度,有利于气液传质,因而增加硫酸根的产量。O3与SO2的摩尔比不变,SO2浓度增加,因臭氧的气液传质较差使硫酸根产率下降。铁、锰离子对O3/O2混合气氧化S(IV)有明显的促进作用。     

反应器电极布置对NO电晕氧化过程影响的试验研究

使用湿空气作为自由基源物质,研究反应器中电极布置变化对电晕放电特性和NO电晕氧化过程的影响。试验结果显示,NOx在电晕反应器中的氧化时间不超过3．3s,多电极布置的电极间距可为100mm,电极数增加NOx转化率明显提高。     

填充石英球对DBD等离子体转化NO的影响

放电等离子体辅助选择催化还原两段法脱除NOx是一项很有前景的氮氧化物治理技术.介质阻挡放电(DBD)是一种常见的等离子体产生方法,在DBD等离子体反应器中填入电介质小球可进一步增强放电.本文考察了有无石英填充球的DBD等离子体反应器对NO的转化和能量利用效率的影响,借助ANSOFT软件对DBD等离子体反应器内的电场进行了仿真分析.实验结果表明,在较低的放电电压下,填充石英球的DBD等离子体反应器虽然能耗略有提高,但在NO的转化和能量利用效率上都优于无填充情况,其原因归结为,填充石英球有利于反应器在更低电压下实现局部放电,同时促进反应器内的电场和气流在空间更均匀地分布,增加了反应气流与放电等离子体的接触机会.     

等离子体辅助催化还原NO_x系统的优化

为研究等离子体辅助催化系统的优化,以NO/NO2/C2H4/O2/N2为模拟反应气体系,介质阻挡放电(DBD)反应器为等离子体反应器,Ag/γ-Al2O3为催化剂,实验考察了DBD反应器内填充石英介质小球对等离子体辅助催化系统的NOx脱除效率影响。结果表明:DBD反应器内填充石英介质小球,有利于DBD反应器在较低的放电能量密度下产生更多低温催化活性高的含氮有机物,促使等离子体辅助催化系统在较低的催化温度250°C时获得>80%的NOx脱除效率。     

结构及供电电源对沿面介质阻挡放电装置放电特性及臭氧生成的影响

沿面介质阻挡放电(SDBD)等离子体能够高效生成反应活性物质,在生物医学、环保等应用领域得到广泛研究。SDBD装置的结构和供电电源参数是影响其放电特性及反应活性物质生成的主要因素,为此,以具有螺环线形高压电极的管状沿面放电装置为对象,研究了装置结构及供电电源对其放电特性及臭氧生成的影响。结果表明:在相同的供电电压下,螺环线形高压电极的螺距、介质厚度影响电极间的电场强度和分布、放电功率和臭氧生成量,但螺环线形高压电极的线径对放电功率和臭氧生成量几乎没有影响;螺环线形高压电极的螺距存在一个优化值,在螺距低于25mm时,放电功率和臭氧产生量随着螺距的增加而增加,当螺距大于25mm时,放电功率和臭氧产生量基本不再变化;当绝缘介质管厚度由3mm减小到1.6mm时,放电功率提高约2倍,臭氧产生量提高约3倍。同采用50Hz交流电源供电相比,SDBD装置采用9.6k Hz高频电源供电时,在较低的电压下即可获得较大的放电功率及臭氧产量,且臭氧生成的能量效率提高约25%。     

介质阻挡放电特性与臭氧合成的实验研究

采用线管结构反应器与管管结构反应器进行介质阻挡放电(DBD)产生臭氧。通过测量放电电气参数和观察辐射发光现象来研究两种反应器的介质阻挡放电特性。结合对比不同电场强度下的臭氧浓度和臭氧的生成效率,讨论两种反应器在生成臭氧应用方面的性能,实验发现线管结构介质阻挡放电特性不同于管管结构,同时臭氧浓度和臭氧生成效率取决于外加在两种反应器上的折合电场强度峰值。     

煤粉热解气还原NO的数值研究

基于详细的化学动力学模型Dagaut机理(1 006个反应,145种组分),利用Chemkin4.1软件中柱塞流反应器模型模拟了煤粉热解气再燃还原NO的反应过程,揭示了影响热解气还原NO 2种主要因素(温度和当量比)的作用规律,并研究了热解气中含硫组分对NO还原的影响。结果表明：当量比一定时,温度高于1 100 K后不利于热解气还原NO,当量比为1.25时热解气还原NO的最佳温度是1 100 K;温度一定时,随着当量比增加NO还原效率升高,1 200 K时热解气还原NO最佳当量比范围为1.2~1.6,且随着当量比增加反应器中HCN和NH3浓度增大,而N2浓度减少;在模拟的工况中,热解气中的H2S和SO2对NO还原效率的影响不超过5%,且H2S对NO脱除的影响大于SO2。     

Wide-range two-dimensional imaging of NO density profiles by LIF technique in a corona radical shower Reactor

Planar laser-induced fluorescence was employed during the process of NO/sub x/ removal in a corona radical shower system. Using the wide-range imaging (image size: 240 mm in width and 160 mm in height), two-dimensional distributions of ground-state NO could be observed not only in the discharge zone but also both in the downstream and the upstream regions of the reactor. The obtained results showed that the density of NO molecules decreased not only in the plasma region formed by the corona streamers and the downstream region of the reactor but also in the upstream region of the reactor. The effect of the gas injection through the nozzles electrode on the NO profile in the reactor was negligible. The NO removal rate was almost the same for both cases with and without the injection gas once the streamer discharge was produced. In the present reactor at low main gas flow rate, it was considered that electrohydrodynamic flow became to be dominant, and the flow toward the upstream affected the decrease of NO in the upstream region. This fact is important for optimizing the performance of the nonthermal plasma reactor.     

Improvement of the energy efficiency in the decomposition of dilute trichloroethylene by the barrier discharge plasma process

In order to improve the energy efficiency in the dilute trichloroethylene (TCE) removal by the nonthermal plasma process, the barrier discharge reactor was studied experimentally. It is investigated by combining it with catalyst of manganese dioxide at the downstream of the barrier discharge reactor. Decomposition efficiency by the barrier discharge reactor was about 83% at the gas flow rate 2 L/min, where the dilute TCE concentration is 250 ppm. Decomposition efficiency with passing through manganese dioxide was improved about 99% at the specific energy of 40 J/L. However, other by-products including ozone and oxidation by-products such as DCAC and TCAA were detected by the gas chromatograph mass spectrometry or the Fourier transform infrared spectroscope measurement. DCAC is generated at the plasma reactor, but TCAA is generated at catalyst during ozone decomposition. CO/sub x/ yield increased about twice with passing through catalyst in the Direct Process. Nitric oxides such as NO, NO/sub 2/, and N/sub 2/O did not generate so much in this barrier discharge process. The dielectric barrier discharge process combined with manganese dioxide is considered as a very desirable way to improve the energy efficiency.     

气体成分对介质阻挡放电脱除NO影响试验研究

为实现电厂排放达标,通过研究用柱筒型介质阻挡反应器对烟气成分对NO脱除率的影响,主要分析了烟气温度、氧气,二氧化硫和水蒸气含量对脱除率的影响。结果表明:烟气温度对脱除率影响不大。O2的加入使得脱除率降低,氧量越多,脱除率越低。同时NO2的生成量随着含氧量增加而增大。SO2抑制NO的脱除,SO2体积分数越大,脱除率越低。加入水蒸气后,脱除率有明显下降,且水量越高,脱除率越低。水蒸气也会促进NO2的生成。     

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.     

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。     

不同O2浓度下NH3选择非催化还原NO的实验和模型研究

NO的选择性非催化还原反应是燃烧过程重要的脱硝途径。文中在800~1 200 ℃,初始浓度CNO,ini=200 mmol/mol、CO2,ini=0%~10%、氨氮比CNH3/CNO=1.2的情况下,进行了NH3/NO/O2的均相流反应器的实验和化学动力学模拟研究,着重研究不同氧浓度对NO和N2O浓度变化规律的影响。实验结果表明,在微量氧气杂质(CO2"50 mmol/mol)条件下,脱硝温度更高,而脱硝率达到了95%。化学动力学模型预测的NO和N2O浓度变化规律与实验结果非常吻合：氧浓度的升高使NH3/NO的最佳反应温度下降,同时降低脱硝的效果;N2O生成浓度随着氧浓度的升高而降低,对应N2O最大浓度的温度也降低。微氧工况的N2O最大生成浓度比低氧浓度下更低,而生成温度更高。     

Time dependence of NOx removal rate by a corona radicalshower system

In this paper, the effects of flue gas flow rate and seed gas on the dynamics of corona discharge current-voltage characteristics and NO _x removal characteristics are experimentally investigated for a corona radical shower system. The corona discharge current-voltage characteristics have two operating modes which have a significant influence on NO_x removal characteristics, where the threshold value of the treatment gas to seed gas flow rate ratio is about 8. The hysteresis of corona current-voltage characteristics is observed in this system. For longer operational time, corona current and NO_x removal rate significantly changes with time. When the operation of the apparatus starts at relatively low applied voltage, the corona current under constant applied voltage increases with time to reach a maximum value, then decreasing with time to reach a steady state. At this condition, high NO_x removal efficiency can be achieved     

空气放电产生臭氧的研究

在臭氧产生机理分析的基础上 ,实验研究了功率、气量、气压和气体湿度对臭氧和NOx 产生的影响。结果表明 ,在一定范围内随着功率增加或气体流量减少 ,臭氧体积分数增加 ,臭氧产生效率降低 ,NOx 和NOx/O3 相对体积分数增大 ;一定条件下 ,随着气压增加 ,臭氧体积分数降低 ,NOx/O3 相对体积分数先减少后增加 ;湿度降低 ,臭氧产生体积分数提高 ,NOx/O3 相对体积分数减少。     

Two-dimensional distribution of ground-state NO density by LIFtechnique in DC needle-to-plate positive streamer coronas during NOremoval processing

Two-dimensional distribution of the ground-state NO molecules density was investigated using a laser-induced fluorescence (LIF) technique in a DC positive streamer corona reactor (needle-to-plate electrode geometry) during NO removal from a flue gas simulator (NO/air). NO density in the corona discharge reactor was monitored under the steady-state DC corona discharge condition. It was found that NO molecules density decreased due to the corona discharge processing not only in the discharging region but also in the upstream vicinity of the discharge     

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.