静电除尘极配方式对烧结机头微细粉尘收集效率的影响分析

为了寻找烧结机头烟气中微细颗粒物超低排放的方法,实验采用圆线、芒刺电晕线和传统、开孔型收尘极板进行组合,构成多种极配结构。通过分析不同极配结构下的收集效率及粉尘粒径分布,研究了影响烧结烟气中微细颗粒物捕集效果的因素。结果表明:粉尘粒径分布、流场结构是影响除尘效果的重要因素;开孔型收尘极板改变了放电空间的气流分布,实现了对PM2.5、PM10等超微细粉尘的高效捕集。其中,芒刺-孔板极配结构的除尘效率可达99.00%,可使烧结机头除尘机组末级电场颗粒物的排放密度低至5 mg/m3以下,达到了超低排放。     

空间介质颗粒对交流导线电晕特性影响规律

为了研究空间介质颗粒对导线交流电晕特性的影响,基于小电晕笼,应用Fi Lin?6紫外成像仪记录存在介质颗粒时模拟导线交流电晕放电发生、发展的过程,实验结果表明:空间介质颗粒会对导线交流电晕发生、发展过程产生影响,球径越大、距离导线越近则导线的起晕电压越低;存在多球时,由于颗粒间的相互影响,导线的起晕电压和放电过程会受到影响,其中垂直排列的颗粒之间对放电发展过程和起晕电压影响相对较大。将偏心偶极子模型应用到存在介质颗粒时电场计算中,结合模拟电荷法对导线周围存在颗粒时空间电场分布进行分析,仿真结果表明:导线表面的最大场强以及导线和颗粒间场强的均值随着颗粒尺寸的增大、颗粒导线距离的降低和颗粒相对介电常数的增大而增大;空间存在多个颗粒时,由于球间的相互影响使导线表面场强进一步增大,其中球间连线和电场方向一致时的影响更大。     

The performance of an integrated air purifier for control ofaerosol, microbial, and odor

A new type of an air purifier has been developed for a simultaneous control of aerosol, microbial, and odor in living environments using ozone, corona precharger, an electrified minipleats filter, and an ozone-decomposing catalyzer as well as a semiconductor ozone sensor for safety control. Ozone is generated in the corona precharger by enhancing negative corona with the application of a higher-than-ordinary voltage. This device, which is named AIP, indicates 85% one-through number collection efficiency for aerosol particles in the size range of 0.1-1.0 mm. AIP shows a very satisfactory deodorizing performance for man-originated and living environment-originated odors, such as ammonia, hydrogen sulfide,methylmercaptane, etc. The AIP also effectively kills, through long exposure to low-concentration ozone, most bacteria, fungi, viruses, and other microbials and small insects collected in its filter     

Metallic particle movement, corona, and breakdown in compressed gasinsulated transmission line systems

A simplified computational algorithm has been developed to study the behavior of metallic particles in gas insulated transmission line (GITL) systems. The model provides an estimate of the effectiveness of particle trapping for a particular trap design at a given commissioning voltage. Results of measured breakdown probabilities of particle contaminated SF₆ show fair agreement with calculated values. A computational model was developed to calculate the corona inception voltage due to conducting particle motion in GITL systems. The computed results for various parameters were in fair agreement with the measured values. A corona pulse pattern is computed and plotted using the same algorithm. Oscillographic records of the transient corona show that particle discharge is larger for long particles, and its magnitude increases with voltage level. Corona patterns obtained in the laboratory indicate that conducting particles can be detected in GITL systems and that the particle size can be determined through partial discharge measurements with AC voltage at different gas pressures     

氨法脱硫过程烟气中细颗粒物的变化特性

采用电称低压冲击器(electrical low pressure impactor,ELPI)对氨法脱硫前后的细颗粒进行测量,获得烟气中细颗粒的数浓度和粒径分布特性,分析了氨法脱硫过程细颗粒的生成机制及洗涤塔对细颗粒的捕集特性。结果表明,氨法脱硫后细颗粒的数浓度明显增加,在SO2浓度为1 767 mg/m3和氨水浓度为5%,平均粒径由洗涤前的0.07 mm增大到0.09 mm;常规洗涤对细颗粒的脱除效率很低且几乎不受液气比影响;而氨水脱硫时,洗涤塔出口的颗粒数浓度随液气比的增大而提高,特别是氨水浓度较高的情况;氨水浓度为10%,液气比从2 L/m3增加到5 L/m3,颗粒数浓度增加了10%;此外,随氨水浓度和烟气中SO2浓度的增大,洗涤后颗粒的数浓度增加。     

Distribution of electric field strength around a large-scalecharged particle cloud

To investigate an electrical discharge occurring from or in a space-charge cloud, a large-scale charged particle cloud was formed by using a cloud generator consisting of a blower and corona charger. The distribution of the electric field strength around a charged particle cloud has been investigated to determine the behavior of charged particles. The soil-conditioning particles were charged by corona charging and blown by high-speed air flow in a test room, 5 m wide, 10 m long, and 3 m high. The average charge-to-mass ratio of the particles blown by this method was 170 μC/kg. The space-charge density of the cloud was calculated at the order of 10 μC/m³ from the electric field strength outside of the cloud. While the electric field strength at the outside of the cloud increased up to 52 kV/m within 2 m downstream from the cloud generator, it decreased below 25 kV/m farther than 2 m away from the cloud generator due to dispersion of charged particles. The change in the electric field strength due to dispersion of charged particles can be qualitatively explained by a simple cloud model. The velocity of charged particles transported by air flow and mobility of charged particles are found to be effective factors increasing the electric field strength around the large-scale charged particle cloud     

Electrostatic Precipitation of Submicron Particles using a DBD in Axisymmetric and Planar Configurations

The aim of the present work has been to quantify the efficiency of Dielectric Barrier Discharges (DBDs) for the collection of submicron particles. The experiments were performed with incense smoke particles having a mean size of about 0.3 mum. An aerosol spectrometer was employed for characterizing the size distribution of these particles at the outlet of Wire-to-Cylinder (WC) and Plate-to-Plate (PP) DBD reactors. The collection efficiency was estimated for various applied voltages (6 - 26 kV, 1 - 2000 Hz), and airflow rates of 1.6 - 24 L/min. The discharge mode was diffuse, in the case of the axisymmetric configuration, and filamentary, in the case of the planar configuration. When flow rate increases, the discharge current and the electric power decrease in both cases. This effect is less pronounced with the planar configuration. Results obtained with the aerosol spectrometer show that the particle collection efficiency of both reactors is higher at high applied voltage and low flow rate; it decreases at high frequency because of particle oscillations, and at low frequency due to the intermittent nature of the discharge. The frequency range for which the collection efficiency is higher than 90% is wider in the case of WC reactor.     

Pilot-plant testing of a novel electrostatic collector for submicrometer particles

A novel electrostatic collector CAROLA (Corona Aerosol Abscheider) for gas cleaning from submicrometer particles is described. The CAROLA concept is based on particle charging by corona discharge and subsequent particle removal in the grounded part of the collector. CAROLA collectors for fine oil mists and for fly ash were tested. The influence of the operation conditions on corona discharge was studied. It is shown that the CAROLA electrostatic collectors have high fractional removal efficiencies (>98% for particles >1 /spl mu/m and 95%-98% for particles with sizes 0.3-1 /spl mu/m), low operating voltages (10-20 kV), and low pressure drop (<200 Pa). The collection of charged particles without external electric field and the compact design provide a cost-effective solution for the removal of submicrometer particles from industrial off gases.     

离子风对静电除尘器中颗粒物脱除的影响机制研究

静电除尘器中电晕放电产生的离子风是影响颗粒迁移和沉积的重要因素,通过建立多过程耦合的静电除尘器数值模型,研究了不同极配型式静电除尘器的电场分布特性及离子风对空间流场和颗粒物脱除的影响规律。结果表明,针刺电极电场强度和离子电荷密度的最高值均略高于芒刺电极,但是芒刺电极的静电场分布更加均匀。在外加电压为60k V时,针刺电极和芒刺电极的离子风最高流速分别可达7.91m/s和4.62m/s,离子风会促进荷电颗粒向收尘极板运动,同时也会形成近壁高速区造成堆积颗粒的不均匀分布并导致二次扬尘。由此,针对不同形式静电除尘器提出了合理调整放电电极结构方法,进行离子风调控以强化颗粒物脱除。     

磁增强电晕放电及其对颗粒荷电的研究

介绍磁增强电晕放电的特性及其对颗粒荷电的性能.在负电晕放电中,磁场可提高极间自由电子的能量,增加带电粒子的浓度,增大放电电流.在放电极雾化负电晕放电中,磁场可显著提高微小颗粒的凝并效能.采用永久磁铁形成放电极附近较强的非均匀磁场,比均匀磁场对负电晕放电有更好的增强效果.     

Particle-triggered pre-breakdown phenomena in atmospheric air gap under AC voltage

Corona discharge mechanism and breakdown voltage characteristics of air gaps in the presence of metallic particles were investigated including the relationship between the corona discharge mechanism and the phase resolved partial discharge patterns. These results are of interest for detection of foreign particles in gas insulated systems (GIS). The results with different shaped particles show that the corona mechanism depends on the particle shape and applied voltage. Moreover the corona discharges on both sides of the particle interfere with each other by inflow of charge carriers into the particle. The breakdown voltage is a minimum when the particle is in the vicinity of the electrode due to active interference of coronas. The phase-charge characteristics as the phase resolved partial discharge patterns vary with the particle shape. This suggests that the corona discharge mechanisms for all types of particles should be considered in the particle-detection method for GIS based on the phase resolved partial discharge patterns.     

Experimental studies of free conducting wire particle behavior between nonparallel plane electrodes with AC voltages in air

When a spherical conducting particle exists in an electrode system where electrical gradient force acts along the electrode surface, the particle tends to move towards the high field region. The possibility of appearance of this phenomenon is experimentally investigated with wire particles, which can easily produce the corona discharge on their ends resulting the action of a reactive force on the particle by a corona wind. The results show that a hovering particle travels deeper into the high electric field regions regardless of the corona discharge. Moreover, it is found that wire particle with corona discharge hovers near the negative electrode under DC voltage in atmospheric air due to different characteristics of corona discharge by the polarity. But under the AC voltage, the particle hovers near the bottom electrode only and invades in the high field region deeper than under the DC voltage.     

均匀磁场中燃煤可吸入颗粒物聚并实验研究

在均匀磁场中分别对东胜、大同和徐州烟煤燃烧产生的3种飞灰细微粒子进行了聚并实验，研究了粒径、外磁场强度、粒子在磁场中停留时间以及粒子质量浓度对聚并脱除效率的影响。实验结果表明：在相同条件下，东胜烟煤飞灰粒子的聚并脱除效率最高，大同烟煤次之，徐州烟煤最小；在0.098~9.314mm粒径范围内，0.576~3.758mm粒径的3种飞灰粒子聚并脱除效率最高；聚并总脱除效率随磁感应强度、粒子在磁场中停留时间以及粒子质量浓度的增加而增大，粒子饱和磁化时，聚并总脱除效率达到最大值，不再随外磁场的增强而变化。采用二元碰撞聚并模型计算了粒子在均匀磁场中的聚并系数，在此基础上求解了粒子聚并动力学方程，预测了粒子的聚并脱除效率。数值模拟结果与实验结果相一致，在粒子质量浓度为40g×m-3时，东胜烟煤、大同烟煤和徐州烟煤燃烧产生的3种飞灰粒子聚并总脱除效率分别为52.6%、43.1%、14.4%。     

Discharge occurring at a grounded electrode located in a charged particle cloud

Electrical discharge phenomena from a grounded electrode located in a charged particle cloud have been investigated. Soil conditioning particles charged by corona charging were blown to form a space charge cloud. A grounded sphere electrode was placed at the center of the charged cloud to produce an electrical discharge. A positive pulse discharge extended from the sphere electrode toward the charged cloud with a strong luminescence. A brushlike streamer with a maximum length of 170 mm appeared at an interval of 30 ms. The maximum pulse height of the discharge was 2.4 A. The distribution of the electric field around the sphere electrode was obtained from field analysis using a concentric spherical model. It was found that the magnitude of the discharge depends on the radius of the grounded electrode and the size and charge density of the clouds. © 2001 Scripta Technica, Electr Eng Jpn, 136(4): 7–14, 2001     

Semipilot plant pulse energized cold-precharger electrostaticprecipitator tests for collection of moderately high resistivity flyashparticles

The performance of an electrostatic precipitator (ESP) to collect moderately high resistivity flyash has been tested under pulse/precharger energization using the semipilot scale integrated electrostatics combustion flue gas (IECFG) cleaning system at Ontario Hydro's 640 MJ/h Combustion Research Facility Center. The pulse energization enhanced the performance of the existing de-energized wire-plate electrostatic precipitator in collecting moderately high resistivity (ρ~10¹⁰ Ω·cm) flyash. A 26% improvement in particle collection efficiency and 30% energy saving were obtained with pulse energization, with moderately high resistivity flyash generated by burning high-sulfur (3.7%) Nova Scotia coal with limestone conditioning. The cold precharger specially designed to suit the three-stage wire-plate ESP has also been tested for its ability to improve the performance of ESP in reducing the back corona. With an additional 30% of energy supplied to the precharger it was possible to obtain up to 40% enhancement in collection efficiency. In general an enhancement factor of 1.8-2.8 was obtained with dust loading ~2 g/m³. A thyratron switched pulse power supply was used for the ESP     

电厂湿法脱硫系统对烟气中细颗粒物脱除作用的实验研究

采用Andersen 8级撞击器对某300 MW燃煤电厂湿法烟气脱硫(wet flue gas desulphurization,WFGD)系统前后的飞灰颗粒物进行采集,获得了烟气中飞灰颗粒物的质量浓度和粒径分布特性。采样工况分别为100%和70%锅炉负荷。使用场发射扫描电镜-能谱分析,X射线荧光分析和电感耦合等离子体-原子发射光谱分析法对颗粒物进行了形貌分析和主、次量元素含量的检测。结果表明,WFGD系统入口飞灰质量粒径呈典型的双峰分布,峰值分别在1和3 mm处,颗粒多呈规则球形,PM2.5与PM10质量比为0.434,飞灰总浓度约为85 mg/m3标准状态;出口处飞灰质量粒径分布也呈现双峰性,其中细颗粒比例增大,PM2.5与PM10质量比为0.764,细颗粒间相互聚集粘连形成不规则的块状结构,飞灰总浓度在23 mg/m3(标准状态)以下,总飞灰的脱除效率为74.5%,分级脱除效率随粒径减小而明显下降。经过WFGD系统后,细颗粒上S和Ca元素含量增大,而Al,Ba,Fe,Mn和Si元素的含量降低。计算表明,WFGD出口烟气中新增的石灰石与石膏颗粒分别占颗粒物质量的47.5%和7.9%。     

复合式电旋风除尘器中颗粒的凝聚机理与实验研究

针对特定的反转式电旋风除尘器中的固体颗粒,把颗粒的整个收集过程分成4个区域,分别进行颗粒的凝聚机理分析,并通过冷态实验证实颗粒凝聚的规律性。理论分析与实验证明,电旋风除尘器中颗粒的凝聚存在如下结论:不同种类颗粒凝聚规律有所不同;处于除尘器不同区域颗粒的凝聚机理也不尽相同;荷电电压提高和给粉浓度增加能使颗粒凝聚作用加大,收尘效率提高;颗粒的强烈凝聚加强了离心分离作用,成为电旋风除尘器高效除尘的重要原因。     

应用蒸汽相变机理脱除燃煤可吸入颗粒物实验研究

应用蒸汽相变机理促进细颗粒凝结长大，然后用湿式洗涤塔脱除长大后的含尘液滴，对燃煤可吸入颗粒物作为凝结核在过饱和蒸汽中凝结长大及湿式洗涤塔对凝结长大颗粒的脱除效果进行了实验研究，考察了蒸汽添加量、颗粒粒径及洗涤塔操作条件的影响。用电称低压冲击器(ELPI)实时测量凝结洗涤脱除前后的颗粒数量浓度和粒径分布。实验结果表明：蒸汽添加量的增加，能够迅速提高小粒径颗粒的脱除效率，蒸汽添加量为0.17kg/m3时，对平均粒径为0.3μm的颗粒的脱除效率超过80%；随着颗粒粒径增大，脱除效率提高；此外，洗涤塔液气比的增加，有利于燃煤可吸入颗粒物的脱除。研究表明蒸汽相变是脱除燃煤可吸入颗粒物的重要预调节措施之一。     

An EHD Gas Pump Utilizing a Wet Porous Point Electrode

A point-to-mesh type electrohydrodynamic (EHD) gas pump, utilizing a wet porous point electrode, has been proposed, and the effect of the wet porous point electrode on the gas flow velocity and flow generation yield of the EHD gas pump was investigated. The wet porous point is used as a corona discharge electrode, and the mesh is used as an ion collecting electrode. It was observed that the EHD gas pump with the wet porous point electrode can generate a higher gas flow velocity and flow generation yield than the same design EHD gas pump with a non-porous metal point electrode. As a result with the wet porous electrode, a peak gas flow velocity of V_W=2.54, 2.74, and 1.93 m/s has been obtained for positive, negative, and ac corona discharges. This is 1.95, 1.31, and 1.30 times higher than the velocity V_W =1.30, 2.09, and 1.49 m/s measured with the same design EHD gas pump and a non-porous) metal point electrode. At 0.1 W of input corona power for dc and ac powers, the flow generation yields of Y=13.88, 12.80, and 11.70 m/s/W were obtained with the wet porous point electrode for the positive, negative, and ac corona discharges, which are 1.23, 1.24, and 1.15 times higher as compared with those of the metal point electrode with Y=11.32, 10.29, and 10.20 m/s/W, respectively. These enhancements may be due to the elevated input corona powers and the water particles generated from the wet porous point electrode.     

梯度磁场中燃煤PM10聚并动力学数值模拟

提出了求解梯度磁场中燃煤PM10聚并动力学方程的三分区算法，应用该算法模拟了0.023~9.314μm粒径范围内大同煤灰在永磁环梯度磁场中的聚并动力学过程，并与实验结果进行了比较。结果表明：数值模拟结果与实验结果相一致，三分区算法具有较好的适用性；中间粒径粒子的聚并脱除效率高于小粒子和大粒子的聚并脱除效率；增大粒子质量高，数目中位直径减小，单粒径聚并脱除效率最大值对应的浓度、延长粒子在磁场中聚并时间，粒子的聚并脱除效率提粒径减小；增大平均气流速度，粒子的聚并脱除效率降低，数目中位直径增大，单粒径聚并脱除效率最大值对应的粒径增大。