Keywords: Double vortexes; Transport properties; Ion Concentration; Charge capacity

Transcription

1 Applied Mechanics and Materials Online: ISSN: 166-7, Vol. 7, pp doi:1./ 1 Trans Tech Publications, Switzerland Study On the Experiment of Ion Transport Properties in Single Area Double Vortexes Plate ESP Hong Liu 1,a, Minyi Zhou 1,b, ChengwuYi 1,c, YanshengDu 1,d, HuijuanWang 1,e, Tian Yin 1, f 1 1 Xuefu Rd., Jiangsu University, Jingkou Dist., Zhenjiang, Jiangsu Prov.,China a hliu@ujs.edu.cn, b mimiao@16.com, c yichengwu9@16.com, d dys@16.com, e wendyjuaner@16.com, f yt111@16.com Keywords: Double vortexes; Transport properties; Ion Concentration; Charge capacity Abstract. This paper explores the effect of factors on the ion concentration n e in single area double vortexes plate ESP. For example, the distance L between the export and the discharge electrode, applied electric field voltage U, the interval of collecting plates d, gas velocity υ, etc. Then the experimental results and data has been analyzed, and it is concluded that n e becomes maximum under the circumstance of U=1kV, L=1mm, d=1mm, υ=m/s. The increasing charge capacity of fine particles can improve charging efficiency, and enhance the particles velocity and removal efficiency so as to provide a basis for the application of this type of dust removal equipment. 1. Introduction China has become a major country of production and application of ESP. The number of ESP comprises about 75% of the total domestic market. The maximum allowable emission standard of coal-fired boiler is mg/nm according to the new Coal-fired power plant air pollutants emission standards (GB 1-11).The vast majority of existing ESP is hardly to meet the new standard [1]. The main reason is that ion concentration produced in discharging electric field of existing ESP is low (only about /cm ). The probability of fine particles agglomeration is small which causes the low fine particles migration velocity ( ~ cm/s) and capture efficiency []. At present, studies on the ion productivity and transport rate also come to academic attention of the international plasma physics academia, some scholars have conducted some researches to improve the ion transport properties by increasing the momentum of particles [-6]. Zhou JG, et al. [7] found that when the driving force is nearly 9.6fN and.9pn, the transport rate of strong electric field ionization discharge plasma source reaches about 1 1 /(cm s) and 1 1 /(cm s) respectively. Bai MD,et al. [] did some experimental study on the effect of factors like energy density and υ in corona discharge electric field on ion transport rate at atmospheric pressure. They found that when the energy density is. mj/cm, with υ increased from 1.5 to 5 m/s, the ion transport rate increased from 5. 1 to 1 1 /cm. Bai MD, Qiu XM, et al. [9] indicated that the plasma concentration produced by non-equilibrium plasma source at atmospheric pressure increased along with applied electric field and momentum of particles. The n e might exceed 1 1 /cm when the applied electric field was 56 kv/cm and the momentum of particles was g m/s. Mao CQ, et al. [1] mentioned in experimental study of transportation characteristic of charged particle in ESP that when corona discharge electric field intensity was Td, ion transporting increased two orders of magnitude with the momentum of particles increased from 7 to 1195 g m/s. These researches showed that it is expected to solve high ion recombination rate in the discharge channel and low ion transporting by increasing the momentum of particles, it will provide theoretical and methodological support to solve the problem of low ion generation rate. The technology of dust removal in this paper uses the double vortexes collecting plates which are installed perpendicularly with airflow direction. The discharge setup is settled on the exit of the interstice between collecting plates. The velocity of airflow flowed past discharge electric field, up to 5m/s-m/s, which increases the momentum of charged particles greatly, makes ions get rid of electric field efficiently, and then increases ion transport rate. As a result, n e increases exponentially. In this paper, the change rule of ion transport rate will be confirmed by changing different parameters, which will provide a basis for this type of removal equipment. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (#696, Pennsylvania State University, University Park, USA-19/9/16,6:1:5)

2 71 Mechanical Engineering, Materials Science and Civil Engineering II. Experimental procedure and setup The experimental procedure is designed as shown in Fig.1. The BF-7 centrifugal fan with self-made discharge device was used as the ion concentration test experimental system. The dust production system consisted of the VW-./7 oil-free air compressor and JJPT- dust static spraying device. The power supply system adopted the CGAj high voltage silicon rectifier dc, the maximum output voltage and current was7kv/.5a. Voltage value was measured by Q static high voltage meter. Parameters like airflow velocity and temperature were real-time measured by testo5m/xl gas multifunction analyzer. DLY- ion concentration was used for detecting ion videlicet anion concentration. A charge capacity counter with Faraday cylinder was used for detecting particles charge capacity. There were two sizes of ω type collecting plates in the discharge device. Collecting plate 1, which was mm wide, 17.5mm high and mm long. While the other was 9mm wide, 17.5mm high and mm long. The interval of adjacent plates was variable, ranging from -1mm Fig.1 The procedure of single area double vortexes plate ESP: 1. Oil-free air compressor;. Dust static spraying device;.ion concentration detector;. The dust concentration tester computer; 5. The dust collection plate; 6. The discharge electrode; 7. Gas multifunction analyzer;. Grounding; 9. High voltage power supply; 1. The ion concentration detecter; 11. The induced draft fan; 1. The wind speed distribution board;. Results and discussion Ion concentration [1 /cm ] The distance between the export and the discharge electrode [mm] Fig. Effect of the distance between the export and the discharge electrode on ion concentration Ion concentration [cm ] Applied electric field voltage [kv] Fig. Effect of the applied electric field voltage on ion concentration Ion concentration [1 9 /cm ] The interval of collecting plates [mm] Fig. Effect of the interval of collecting plates on ion concentration Ion concentration [1 9 /cm ] 气体速度 Gas velocity [m/s] Fig.5 Effect of gas velocity on ion concentration.1 Effect of the distance between the export and the discharge electrode on n e Experimental conditions: d = 1 mm, U = 1. kv, temperature is. Fig. shows that with the increase of L, n e is reduced. L downs slowly during 6-1 mm, and then falls faster after 1 mm. The maximum concentration cm - appears in 6mm, while

3 Applied Mechanics and Materials Vol it is only cm - in mm. Therefore, in the practical process of designing ESP, L should be controlled within a certain range, which would make airflow pass as close to discharge electrode, the bigger particles charge capacity, the higher dust removal efficiency.. Effect of the applied electric field voltage on n e Experimental conditions: d = 1 mm, L = 1 mm, the airflow velocity υ=.9 m/s, temperature is. Fig. shows that the U has a remarkable effect on n e. The n e rises six orders of magnitude from /cm to /cm with the increase of U from kv to 16kV. When U rises from16kv to 19.6kV, there is less remarkable effect on n e, n e increases to /cm. To sum up, when designing ESP, the U of dust removal system should be kept during 1-19 kv, so that it can guarantee the normal work of ESP, achieve higher dust removal efficiency.. Effect of the interval of collecting plates on n e Experimental conditions: L = 1 mm, U = 1. kv, υ=.9 m/s, temperature is. Fig. shows that d has a significant effect on n e. The n e rises from to /cm, with the increase of d from mm to mm. The maximum concentration /cm appears in mm. Then the n e decreases to /cm, with d increases to 1mm.When d is mm, it is small, resistance increases, then υ is reduced between the gaps, which causes ions are unable to get rid of the bondage of the electric field completely due to the small momentum. While when d outnumbers 1 mm, airflow turbulence happens in discharge field area due to the large plate interval, which causes lower concentration. Therefore, in order to obtain a high n e, the d can be designed for -1 mm.. Effect of gas velocity on n e The gas velocity measured in this experiment is the gas velocity between ω type collecting plates. The experiment aims to investigate the effect of υ on the n e.. Experimental conditions: d = 1 mm, L = 1 mm, U = 1 kv, temperature is. Fig.5 shows that the υ in dust removal tunnel has a significant effect on n e. When the velocity is.5m/s, n e in discharge electric field is. 1 7 /cm. The n e rises continually until the maximum concentration /cm appears in 6.1m/s. Then the n e decreases to /cm, with υ increases to 7. m/s. It can concluded that the increasing of υ would rise the momentum of ions, so that the ionic recombination in discharge area will be avoided effectively and the n e increased greatly which leads to the increase of ion transport rate in ESP. As a result, the new type of ESP can realize a higher dust remove efficiency by being combined with own structure advantage under the circumstance of high gas velocity, and smaller volume, lower cost of production. Table 1. Table of factor level Table. The orthogonal experiment result Level U[kV] υ[m/s] d[mm] mc/kg) Charge mass ratio( Ion concentration(1 /cm ) Fig.6 Experimental analysis of the effect of ion concentration on particles charge capacity NO. U[kV] υ[m/s] d[mm] n e [cm - ] K K K R

4 7 Mechanical Engineering, Materials Science and Civil Engineering II.5 Design and analysis of multifactor orthogonal experiment affecting ion transport rate By feasibility study on self-made ion transport properties experimental device, the single factor experiment results shows that three factors- U, υ, d- have great effect on n e. In order to get reasonable design parameters in the removal efficiency experiment, a three levels orthogonal experiment should be designed on the basis of single factor experiment to determine the best experimental conditions. Experimental level and factor is shown in Table 1. Repeat this for each experimental group three times, and take average. According to the result of orthogonal experimental design, determine the best design parameters. Other experimental conditions: L = 1 mm, temperature is. The orthogonal experiment results are shown in Table. It can be concluded that the best experimental conditions of new type plates ESP experiment is: U=1kV,υ=m/s,d=1mm. The result of orthogonal experimental design corresponds with determination result of experiment. Learn from this, the biggest influencing factor of ion transporting in ESP is υ, secondly d and U respectively. The ion produced by corona discharge is proportional to the inlet gas velocity and U in ESP system..6 Experimental analysis of the effect of ion concentration on particles charge capacity The purpose of improving the ion transport properties is to improve n e in the discharge area of electric field, increase the particles discharge capacity, especially fine particles, improve the migration velocity and dust removal efficiency of ESP. The effect of n e on particles charge capacity as shown in Fig.6. Experimental conditions: d = 1 mm, U = 1. kv, υ=.5 m/s, temperature is. In Fig.6 particles charge capacity is proportional to n e basically. With the increase of n e, the charge capacity is also increasing. When the n e is /cm, dust charge-mass ratio is.6 mc/kg. When the n e is /cm, dust charge-mass ratio as high as.6 mc/kg. This is because when the air, the more number of ions transported by airflow from the experiment device, the greater chance of particles collision charged by ions, particles charge capacity will also increase, eventually improve the effect of charging. It follows that the final way to rise the charging effect of experimental device is to increase ion transport rate..conclusions (1)Through the experiments and the data above, parameters like L, U, d, υ, all of them have a great effect on n e. In design of ESP, stabilize these parameters of ESP system within a proper range. The new type of ESP can realize a higher dust removal efficiency by being combined with own structure advantage under the circumstance of high gas velocity, and smaller volume, lower cost of production. ()Combined with the result of single factor experiment, a three factors and three levels orthogonal experiment is designed. By analyzing the table of orthogonal experiment result, it can be concluded that the result of orthogonal experimental design corresponds with determination result of experiment. That is to say, under the condition of appropriate interval of collecting plates, the faster airflow velocity and the higher operating voltage is, the higher n e produced. These results has been well prepared for the next experimental research of the new type single area double vortexes plate ESP, it also suggests that the ESP is feasible technically. ()In the experiment of the effect of n e on particles charge capacity, particles charge capacity is proportional to n e basically. With the increase of n e, the charge capacity is also increasing, especially fine particles, which causes the improvement of the migration velocity and dust removal efficiency of ESP as well. Acknowledgements This work was supported financially by National Natural Science Foundation of China (Project No. 5179) and Science & Technology Support Project Plan and Social Deployment of Jiangsu Province (Project No.BE117 and No.SH11). Corresponding Author: Yi chengwu, 61155, yichengwu9@16.com.

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