Article pubs.acs.org/EF
Experimental Study on Electrostatic Precipitation of Low-Resistivity High-Carbon Fly Ash at High Temperature Chenghang Zheng, Zhiyang Shen, Qianyun Chang, Qiufeng Su, Xinbo Zhu, and Xiang Gao* State Key Lab of Clean Energy Utilization, State Environmental Protection Center for Coal-Fired Air Pollution Control, Zhejiang University, Hangzhou 310027, China ABSTRACT: A high-temperature electrostatic precipitator (ESP) is a good solution for hot gas cleaning to ensure the long-term stability of the production system in many energy-consuming industries. The high-carbon fly ash particles in the gasification of coal pyrolysis process are typical particles with low resistivity. In this paper, the characteristics of the coal pyrolysis furnace fly ash (ash A) were compared with coal-fired power plant fly ash (ash B). The effects of their characteristics on particle removal were compared in a wire-plate ESP. The particle collection efficiency was found to decrease with increasing temperature. From 363 to 523 K, the collection efficiencies of both ash samples were as high as above 95%. However, at 623 and 723 K, the collection efficiency of ash A was obviously lower than ash B. A method of enhancing particle removal was proposed by particle conditioning to reduce the occurrence of particle re-entrainment, and the fine calcium carbonate powders were used as the conditioning particles to improve the collection efficiency. When the ratio in mass was 1:1, the particle collection efficiency of ash A increased from 93.5% to 99.2% at 623 K by particle conditioning in the ESP. The optimal effect of conditioning occurred compared with different mix proportion because the resistivity of mixing particles was 1.01 × 108 Ω·cm, within the scope of normal resistivity for good operation of ESP.
1. INTRODUCTION Energy-consuming industries, such as the integrated gasification combined cycle (IGCC) and pressured fluidized bed combustion (PFBC), contain high-temperature flue gas with large amounts of particles, which could cause wear in downstream devices and affect the quality of coal chemical production (such as Tar, alcohols, and aldehydes). In order to reduce the particle concentration in the flue gas and avoid wear in downstream devices, the hot gas cleaning device is necessary to ensure the long-term stability of the production system. Moreover, the sensible heat and latent heat of clean gas could be used for electricity generation, and the quality of high-valueadded products could be promoted after particle removal.1−5 Several hot gas cleaning methods have been proposed, including cyclone separation,6,7 ceramic filtration,8−10 granular bed filtration,11,12 and electrostatic precipitation. An electrostatic precipitator (ESP) can remove suspended particles from a gas stream through electrostatic force with low pressure drop (
