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为了实现在线大气汞分析仪的自动标定,本文选用商用的汞渗透管,自主设计了渗透恒温装置(控温精度为0.1℃),搭建了大气汞分析仪的标定模块,利用该模块建立了3种标定方法.与本实验组研发的在线大气汞分析仪联用对3种方法进行对比研究.①稀释气法:与经典的渗透管动态配气法相同,通过改变稀释气体流量(1~5 L,精度为20 mL)实现发生不同浓度的标准气(0~99 n.gm-3),所建立的工作曲线线性良好(R2=0.9968).②固定浓度时间调控法:发生一个固定浓度的汞标准气,通过改变采样时间使富集量不同进而建立工作曲线(R2=0.9968);③补气法:去掉稀释气路,渗透管载气流量保持不变,补给零空气以达到分析仪的采样流量,改变采样时间实现汞的梯度富集(R2=0.9972).方法2和3主要适用于富集效率不受样品浓度影响的预富集型汞分析仪的标定.3种标定方法所得结果吻合较好(回归直线的总体斜率无差异).稀释气法与环境大气的实际情况最接近,通过改变采样时间调控富集量的方法标定用时较短.该标定模块成本低,稳定性好,操作简易.
In order to realize the automatic calibration of on-line atmospheric mercury analyzer, a commercial mercury permeation tube was chosen to design an infiltration thermostat (temperature control accuracy of 0.1 ℃), and a calibration module of atmospheric mercury analyzer was established. Using this module, a 3 The calibration method was compared with the on-line atmospheric mercury analyzer developed by the experimental group.①Dilution gas method: By the same method as the classic permeation tube dynamic gas distribution method, by changing the diluent gas flow rate (1-5 L, with a precision of 20 mL), a good linearity (R2 = 0.9968) was obtained for the calibration curves of different concentrations of standard gas (0 ~ 99 n.gm-3) Mercury standard gas, by changing the sampling time so that the enrichment of different concentrations and then set up a working curve (R2 = 0.9968); ③ gas method: remove the diluent gas path, permeate tube carrier gas flow remains unchanged, zero air supply to reach the analyzer (R2 = 0.9972) .Methods 2 and 3 are mainly suitable for the calibration of pre-enrichment mercury analyzers whose enrichment efficiency is not affected by the sample concentration.The results of the three calibration methods Good agreement (regression line total No difference in slope). Method actual dilution air closest to the ambient atmosphere, by changing the sampling time is short calibration method for enrichment of regulation. The calibration module low cost, good stability, easy operation.