Enhancement of Cathode Dust Collection and its Application in Improving the Efficiency of Dry Electrostatic Precipitator

As the main equipment of flue gas dedusting in coal fired boiler, electrostatic precipitator (ESP) can meet the requirements of emission standard for air pollutants from coal-fired power plants through improving the efficiency of ESP and combining with desulfurization system while not installing wet ESP (WESP). This paper introduces the modifications of ESP cathode structure to improve the efficiency of dust collection by reducing the secondary dust loss at cathode. The application of cathode dust collection provides a reference for the improvement of ESP dust collection efficiency.

Pengaruh Ukuran Partikulat Hasil Gasifikasi Batubara Terhadap Efisiensi Wet Scrubber

Syngas dari gasifikasi batubara mengandung komponen pengotor seperti tar, char, H2O, ash, NH3, H2S dan COS. Zat-zat pengotor tersebut dibagi mejadi dua fase, yaitu fase gas (uap) dan fase padatan (partikulat). Selanjutnya, syngas akan dibersihkan dari pengotornya menggunakan cyclone, wet scrubber dan wet ESP. Dalam penelitian ini, jenis wet scrubber yang digunakan adalah venturi scrubber. Efisiensi dari venturi scubber ini ditentukan oleh ukuran partikulat pengotor dalam syngas. Syngas dari cyclone dianalisa ukuran partikulatnya menggunakan Particle Size Analyzer dan didapatkan grup ukuran partikulat dalam mikrometer (%vol), yaitu 0 – 1 (8,81%), 1 – 2 (12,51%), 2 – 4 (27,33%), 4 – 6 (15,94%), 6 – 8 (10,25%), 8 – 10 (6,7%), 10 – 20 (10,66%), 20 – 40 (4,96%), 40 – 60 (2,6%), dan 60 – 80 (0,17%). Lalu, data tersebut dianalisa dengan debit (flow rate) dan fraksi massa umpan venturi scrubber, maka didapatkan hasil efisiensi venturi scrubber sebesar 97,48%.Syngas from coal gasifiation consist of various impurities such as tar, char, H2O, ash, NH3, H2S and COS. Those impurities can be classified into two phase groups, which are gas phase (includes vapor) and solid phase (particulates). After gasification, syngas will be purified or cleaned from its impurities with some equipments such as cyclone, wet scrubber and wet ESP. The wet scrubber type that is used in this research is venturi scrubber. The scrubber efficiency is determined by the amount of particulate in syngas. Particulate size in syngas from cyclone is analyzed using Particle Size Analyzer, to obtain data of particulate sizes in micrometer (%vol), which are yaitu 0 – 1 (8,81%), 1 – 2 (12,51%), 2 – 4 (27,33%), 4 – 6 (15,94%), 6 – 8 (10,25%), 8 – 10 (6,7%), 10 – 20 (10,66%), 20 – 40 (4,96%), 40 – 60 (2,6%), dan 60 – 80 (0,17%). Then, those data are calculated together with the flow rate and mass fraction of scrubber feed, to get venturi scrubber effficiency 97,48%.

Removal of Coal-Fired Pollutants Using a Novel Composite Collector in a Wet Electrostatic Precipitator

Rigorous new regulations in coal-fired pollutants emissions from power plant strengthen the requirements for electrostatic precipitator (ESP) technology. The study was inspired by the requirement to use the new composite collectors as substitutes for typical steel collector to save energy and structural materials. A bench scale and a pilot scale experimental system have been set up to investigate the performance of the novel wet composite collector. Contrastive collection efficiencies of different assembled modes were investigated. The removals of coal-fired pollutants including acid aerosol, ammonia aerosol, slurry droplets and fine particles were performed in new wet ESP, as well as to quantify the key properties of the new wet ESP. The results show that the collection efficiency of the new composite collector was higher than that by typical collectors using a thimbleful of water penetrating the surface via capillary flow. The new wet ESP device acts in synergy with WFGD and SCR systems for controlling coal-fired pollutants emissions and solves the adverse impacts caused by wet flue gas desulfurization (WFGD) and selective catalytic reduction (SCR) systems at the same time.

Simulation of Air Distribution on Inlet Section of Wet-ESP

Based on the theory of two-phase flow, the flow field of dust particles inside the wet electrostatic precipitator with SIMPLE algorithm was modeled used a standard turbulence model and simulated numerically. Establishment of finite element model for the entity porous plate was done with grid refined locally. The number and installation position of porous plates, the diverging angle of the horn inlet and the opening rate of air distribution plates were changed in this simulation. And the studies on the airflow distribution of the inlet section were performed, in which the flow of key parameters for air flow uniform distribution are given. The experimental verification of optimal results of simulation model suggested that the simulation results and the experimental results were coincident.

Removal of Particulate Matter in a Tubular Wet Electrostatic Precipitator Using a Water Collection Electrode

As one of the effective control devices of air pollutants, the wet electrostatic precipitator (ESP) is an effective technique to eliminate acid mist and fine particles that are re-entrained in a collection electrode. However, its collection efficiency can deteriorate, as its operation is subject to water-induced corrosion of the collection electrode. To overcome this drawback, we modified the wet ESP system with the installation of a PVC dust precipitator wherein water is supplied as a replacement of the collection electrode. With this modification, we were able to construct a compact wet ESP with a small specific collection area (SCA, 0.83 m2/(m3/min)) that can acquire a high collection efficiency of fine particles (99.7%).