基于国内实测燃煤电厂烟气汞排放估算的不确定度

摘要

According to the technical specification of the evaluation and expression of uncertainty in measurement,a method to estimate the uncertainty of flue gas mercury emissions for China's coal-fired power plants (CFPPs) has been preliminarily established.We used the concentration data of mercury in China's raw coal of each province and the domestic field measurements of co-benefit mercury removal efficiency through conventional air pollution control devices (APCDs).Concentration data were collected from literatures and measured in this study.The uncertainty of mercury emissions from CFPPs in 2010 was calculated according to the coal-production-weighted mercury content in raw coal and the actual configuration of APCDs.The overall uncertainty of flue gas mercury emissions from CFPPs was 48.8 t,accounting for 34.3％ of the total emissions.A proportion of 60.2％ of the total uncertainty is attributable to the uncertainty of mercury removal efficiency of APCDs,and 39.8％ is attributable to that of the mercury content in coal.In addition,ESP,ESP + WFGD,SCR + ESP + WFGD and FF units brought 6.0,32.2,9.7 and 0.9 t uncertain mercury emissions,respectively,or represented 19.3％,32.8％,84.6％ and 53.6％ of their own emissions estimated,indicating that the SCR + ESP + WFGD units involved relatively more emission uncertainty than others (note:ESP-electrostatic precipitator,WFGD-wet flue gas desulfurization,SCR-selective catalytic reduction for De-NOx) due to the insufficient field measurements for this APCD style.With full implementation of CFPP flue gas De-NOx policy in China,the share of SCR + ESP + WFGD units will increase to over 66％ of the total after 2015.This implies that greater uncertainty on mercury emissions will arise,which suggests an urgent need to obtain new measurements for SCR + ESP + WFGD units.%参照测量不确定度评定与表示的国家技术规范,基于近年来我国燃煤电厂常规污控设备协同脱汞的现场测试数据(文献报道和实测值)及各省原煤w(汞)的实测值,初步构建了国内燃煤电厂烟气汞排放不确定度的计算方法,并以2010年的燃煤量、污控方式布局为基础,计算了该年度汞排放的不确定度.结果表明:2010年我国燃煤电厂烟气汞排放的总不确定度为48.8 t,占平均排放总量的34.3％；其中60.2％源于污控设备脱汞效率的不确定度,39.8％源于原煤w(汞)的不确定度；采用ESP(静电除尘)、ESP+ WFGD(静电除尘+湿法脱硫)、SCR+ ESP+ WFGD(选择性催化还原脱硝+静电除尘+湿法脱硫)和FF(袋式除尘)大气污控组合的机组各存在6.0、32.2、9.7和0.9t的烟气汞排放不确定度,分别占各对应机组烟气汞排放量的19.3％、32.8％、84.6％和53.6％,其中SCR+ ESP+ WFGD污控组合烟气汞排放的相对不确定度最大.随着我国烟气脱硝工作全面推行,2015年以后,SCR+ ESP+ WFGD污控措施(组合)的机组所占比例将会提高到66％以上,如果仍以现有数据为基础,则来自SCR+ ESP+WFGD污控措施(组合)机组的烟气汞排放不确定度将会大幅增加,因此急需增加对该类装置脱汞效率的实测样本数量.