건·습식 혼합형 전기 다층 다단 임팩션 시스템의 집진특성

Abstract

The fine dust reduction policy was introduced recently and air environment criteria on PM 2.5 were applied from January 1, 2015. As such related regulation has been reinforced, which requires the development of low cost and high efficient dust collector. Among dry type dust collection systems, filter dust collector and electrostatic precipitator are widely used in the industrial field with its excellent dust collection performance. While the filter dust collector has excellent dust collection performance with stable high collection efficiency (over 99%), It has problem of discontinuity of operation by filter clogging and filter maintenance problem. Electrostatic precipitator can handle a exhaust gas without significant pressure drop and is very simple in terms of structure with easy maintenance and repair. But, it requires high initial installation cost. To obtain high collection efficiency (over 99%), it must ensure wide installation area, which results in the large size of device. Existing scrubber include venturi scrubber, packed tower and spraying tower. Among them, venturi scrubber has high collection efficiency among cleaning dust collectors, it has high pressure drop compared with others (over 300 mmH2O) and large cleansing solution is required that resulted in high operating cost. Generally, scrubber is not restricted much by temperature and humidity and It can handle particle and gas pollutants at the same time. But, it is highly possible for fine droplet to be discharged outside. To solve the problem, demister must be installed at outlet to minimize droplet discharge. But, when demister is installed, periodic replacement of demister is required because the pore of demister is closed by dust. Firstly, as for dry type dust collection system, to overcome problem of the filter dust collector and electrostatic precipitator, this study attempted to develop electrostatic multi-layered multi-staged impaction system that is combined with electrostatic precipitator to the front part of multi-layered multi-staged porous plate of dry type which introduced black box and block hole concept to increase dust collection efficiency and to obtain more than 99% efficiency. This study carried out experimental studies to interpret electrostatic multi-layered multi-staged porous plate system pressure drop, dust collection efficiency, voltage and current characteristics by physical variables such as inflow speed, number of stage, tube diameter, applied voltage and shape and location of discharge electrode. As a result, if voltage is not applied within flow rate 1.63 m3/min (tube velocity = 15 m/s), tube diameter 12mm, it is 96.2%, and if applied voltage is 30 kV, it has 99.7% dust collection efficiency. Thus, it can keep within 5% of electric power dependency. And, it is determined to be a system for stable operation with suitable pressure drop (148 mm H2O) and high collection efficiency (99.7%) without use of filter. Secondly, to handle particle and gas pollutant at the same time, it is required to introduce wet type dust collection system. As mentioned above, existing wet scrubber such as venturi scrubber or packed tower had high pressure drop (300 mmH2O) to obtain high collection efficiency and it needs to install demister to prevent fine droplet discharge. Accordingly, this study attempted to overcome the above problem by developing high collection efficiency electrostatic multi-layered multi-staged impaction system of mixed dry and wet type that does not need installation of demister. The system consists of electrostatic dust collecting part in the front and wet type electrostatic multi-layered multi-staged impaction system in the rear. The 1st stage is single layer and 2nd stage is multi-layer system included black box type and 3rd ~ 5th stage is the type where tube is inserted into black box to prevent discharge of droplet. To solve spray nozzle block problem in the inflow of dust of high concentration (10g/m3) into wet system and to solve short replacement cycle of spray droplet by high turbidity, electrostatic dust collection part is combined to the front of the system to introduce water spray system at the rear part of the system which is followed by maximum decrease of dust concentration introduced to multi-layered multi-staged impaction system. Dust not collected by dry type electrostatic dust collecting part in the front is collected by condensation by water spray, direct block and impaction effect. The study attempted to develop and commercialize compact electrostatic multi-layered multi-staged impaction system of mixed dry and wet type that prevents fine droplet discharge from external device without installation of demister having suitable pressure drop (150 mmH2O) and high efficiency (over 99%) while keeping simultaneous treatment of particle and gas pollutant. Through lab scale(1.63 m3/min) device, pressure drop, dust collection efficiency characteristics, current - voltage curve characteristics and NO2 and SO2 removal efficiency characteristics were interpreted by means of experiments based on physical variables. Based on the lab scale experiment result, Pilot. scale (50 CMM), Real. scale (800 CMM) dust collection system was designed and manufactured. With the system, pressure drop and dust collection efficiency were interpreted by physical variables such as flow rate, number of stage, water spray amount and applied voltage. Real scale (800 m3/m) for simultaneous treatment of particle and gas pollutant can make zero discharge of droplet without installation of demister to prevent droplet discharge. And, it showed high collection efficiency (99.38%) of dust collection performance with low liquid/gas ratio (0.82 L/m3) at suitable pressure drop (125 mmH2O). It is expected that this can be a basic model for commercialization of dust collection system in the industrial field.