燃煤电厂WESP颗粒物脱除机制及排放特征研究

从强化荷电和促进细颗粒团聚两方面对湿式电除尘器（WESP）细颗粒强化脱除机制进行了分析。并基于调研和现场实测方式,对国内投运的WESP颗粒物排放特征进行了系统研究。采用ELPI测定WESP进出口粉尘粒径分布,采用滤筒方法测定总尘,采用ELPI、PM-10或DGI测定PM₁₀、PM_2.5浓度,采用冷凝法测定SO₃。对调研及实测数据进行统计分析：ELPI将PM₁₀从0.03~10 μm被分为12等级,WESP对PM₁₀各级粒径均有明显的去除效率,数浓度、质量浓度去除效率均在40%以上,最高可达90%以上;WESP出口颗粒物浓度0.43~12.5 mg/m³,绝大部分在5 mg/m³以下,除尘效率均在70%以上,最高可达90%以上;WESP出口PM_2.5浓度0.35~1.59 mg/m³,大部分数据低于1 mg/m³,且脱除效率大部分在60%以上,最高可达90%以上;WESP出口SO₃浓度0.10~3.21 mg/m³,脱除效率均大于60%,最高可达90%以上。调研某350 MW机组WESP出口连续3个月CEMS数据,颗粒物小时浓度达标率为100%,系统实现了长期稳定运行。

Research of PM Removal Mechanism and Emission Characteristics for WESP in a Coal-Fired Power Plant

In this paper, the WESP fine particle strengthening removal mechanism is analyzed for the first time from the aspects of strengthened charging and promoted fine particle coalescence. Then through further investigation and on-site measurement, the PM emission characteristics of WESP are studied comprehensively. The inlet and outlet particle size distribution, total dust concentration, PM₁₀/PM_2.5 concentration and SO₃ concentration of WESP were measured by virtue of ELPI, filter cartridge, ELPI/PM-10 or DGI and condensation method, respectively. Based on the statistical analysis of the research and measured data, it is shown that PM₁₀ is divided into 12 levels ranged from 0.03 μm to 10 μm by using ELPI and dust particles in each level are removed significantly using WESP with the removal efficiency of both number concentration and mass concentration exceeding 40%, and the maximum even reaching more than 90%. The outlet dust concentration of WESP is between 0.43 mg/m³ and 12.5 mg/m³, most of which is lower than 5 mg/m³. Moreover, dust removal efficiency is above 70%, with the maximum over 90%. The outlet PM_2.5 concentrations of WESP are limited in the range between 0.35 mg/m³ and 1.59 mg/m³ while most of them are lower than 1 mg/m³ and PM_2.5 removal efficiency is above 60%, with the maximum more than 90%. The outlet SO₃ concentration of WESP is within the range between 0.10 mg/m³ and 3.21 mg/m³. SO₃ removal efficiency is achieved above 60% with the maximum more than 90%. The outlet CEMS data for three months of continuous operation of WESP of a 350 MW unit was studied and the result showed that hourly concentration control rate reached 100%. Therefore long term stable operation of the system is realized.