基于CEMS(连续排放监测系统)监测数据的火电厂SO_(2)达标判定方法研究

Assessment Method of Compliance with SO_(2)Emission Limits of Thermal Power Plants Based on CEMS Data

我国重点大气排放源多已安装连续排放监测系统(Continuous Emissions Monitoring System,CEMS),而现行大气污染物排放标准中的达标判定主要依据手工监测数据.为研究制定基于CEMS监测数据的达标判定方法,以火电厂为例,从全国范围内的363台机组中筛选出满足数据有效性条件且具有代表性的68台机组,分析其2015年SO_(2)小时浓度、日均浓度和月均浓度的统计分布,建立了由严到宽的5种情景,每种情景都包含对应的3种排放限值,并与欧盟相关规定进行了对比.结果表明:①68台火电机组对数正态分布线性拟合决定系数(R 2)均大于0.90.②基于CEMS监测数据的达标判定方法中,不同时段排放限值存在关联.该研究采用95%预测上限对应的限值倍数关系作为研究结果,即在全年SO_(2)小时浓度的95%分位数、日均浓度、月均浓度均满足对应限值的前提下,当要求90%的机组达标时,SO_(2)小时浓度限值应分别为日均浓度限值和月均浓度限值的1.5和1.7倍;当要求95%的机组达标时,SO_(2)小时浓度限值应分别为日均浓度限值和月均浓度限值的1.6和2.0倍;当要求99%的机组达标时,SO_(2)小时浓度限值应分别为日均浓度限值和月均浓度限值的1.6和2.2倍.③不同时段排放限值之间的比例关系适用于各种装机规模的火电机组.研究显示:68台火电机组均符合对数正态分布;重点源大气污染物排放标准应增加基于CEMS监测数据的达标判定方法,同时对小时浓度、日均浓度和月均浓度进行规定,并明确其定量比例关系;各种装机规模的火电机组可采用统一的达标判定方法进行规定.

Although the Continuous Emissions Monitoring System(CEMS)has been installed for most key sources of air pollutants emission in China,the current assessment of compliance with emission limits of air pollutants is based on manual monitoring data.In order to study and develop emission limit assessment methods based on CEMS data,68 typical thermal power generation units that meet the validity conditions are selected from 363 units distributed all across China.The 2015 CEMS data of these units are used to analyze the statistical distribution of the hourly,daily average and monthly average SO_(2)values.The study establishes five scenarios ranging from strict to lenient,each of which contains three corresponding emission limits,and compares them with those of the EU.The results show that:(1)The determination coefficients of the lognormal distribution of 68 thermal power units all satisfy R 2>0.90.(2)In the assessment method of compliance with emission limits based on CEMS data,there is a correlation between the emission limits in different average periods.Finally,the research uses the limit multiple relationship corresponding to the 95%upper prediction as the research result.When 95%of SO_(2)hourly values,the daily average values and monthly average values meet the corresponding limits simultaneously in a calendar year.If 90%of the units are required to meet the limits,the hourly limit values can be set to 1.5 times the daily limit values and 1.7 times the monthly limit values.If 95%of the units are required to meet the limit values,the hourly limit values can be set to 1.6 times the daily limit values and 2.0 times the monthly limit values.If 99%of the units are required to meet the limit values,the hourly limit values can be set to 1.6 times the daily limit values and 2.2 times the monthly limit values.(3)The above-mentioned correlation between the emission limits for different average periods is independent of capacity scale of thermal power generation units.The study shows that the CEMS data of 68 units form a log-normal distribution.The assessment method of compliance with emission limits based on CEMS data should be included in the emission standards of the key sources of air pollutants.The method should stipulate hourly values,daily average values and monthly average values at the same time,and clarify their ratio.Thermal power units of various installation scales can be stipulated by the same assessment method of compliance with emission limits.