Dehydration and concentration gas circuit system and method for volatile organic compounds in atmosphere

Abstract

The invention discloses a water removal and concentration gas path system and a method for volatile organic compounds in atmosphere. The system comprises a first-stage high-carbon trap, a second-stagelow-temperature water removal cold trap and a third-stage low-temperature adsorption cold trap, the first-stage high-carbon trap, the second-stage low-temperature water removal cold trap and the third-stage low-temperature adsorption cold trap are fixedly communicated through six-way valves; the method is scientific and reasonable, safe and convenient use, the gas path passes through a first-stage high-carbon trap; high boiling components are trapped, water vapor is removed through a secondary low-temperature water removal cold trap; then the gas enters a third-stage low-temperature adsorption cold trap to adsorb and trap the gas penetrating through the second-stage cold trap; according to the method, high-boiling-point components intercepted by the first-stage high-carbon trapping trap can be transferred into the third-stage low-temperature adsorption cold trap along with carrier gas; according to the method, the condensation of the high-carbon component in the water removal cold trap is avoided while water is removed, the recovery rate of the high-boiling-point component is improved, and the content of the tested high-boiling-point component is closer to an actual value, so thatthe authenticity and the accuracy of data are greatly improved.

Description

technical field [0001] The invention relates to the technical field of water removal in the pretreatment process of the analysis and detection of volatile organic compounds in the atmosphere, in particular to a water removal and concentration gas circuit system and method for volatile organic compounds in the atmosphere. Background technique [0002] At present, when sampling and analyzing VOCs in the atmosphere in the industry, in order to increase the detection limit, it is necessary to enrich and concentrate the VOCs in the atmosphere, then desorb and send them to the subsequent stage chromatography and mass spectrometry for analysis and detection. In terms of gas concentration pretreatment In the method, the first stage of freezing and dewatering is generally used, and the second stage of low-temperature adsorption concentration is adopted. This method has obvious defects in that: freezing and dewatering will trap a lot of high-boiling VOC in the atmosphere in the water r...

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Problems solved by technology

[0002] At present, when sampling and analyzing VOCs in the atmosphere in the industry, in order to increase the detection limit, it is necessary to enrich and concentrate the VOCs in the atmosphere, then desorb and send them to the subsequent stage chromatography and mass spectrometry for analysis and detection. In terms of gas concentration pretreatment In the method, the first stage of freezing and dewatering is generally used, and the second stage of low-temperature adsorption concentration is adopted. This method has obvious defects in that: freezing and dewatering will trap a lot of high-boiling VOC in the atmosphere in the water removal pipe, even if dry blowing is added. function, it can only bring out a small amount of high boiling point components that are intercepted, and the content of high boiling point components tested is obviously less than the actual value, which affects the authenticity and accuracy of the data. The traditional atmospheric pre-concentration method: first pass The first-stage water removal cold trap filters the water vapor in the air at low temperature, and at the same time intercepts the VOC substances with high boiling point under freezing. The low-boiling point components will enter the secondary cold trap along the flow path for capture, and the sampling ends Finally, the temperature is raised by purging the first-stage water-removing cold trap with the carrier gas, and part of the high-boiling point components are desorbed at low temperature and enter the secondary cold trap with the carrier gas to be trapped. However, the recovery rate of the high-boiling point components of this method is It is very low, which affects the authenticity and accuracy of the data, and will bring water vapor into the next-stage adsorption tube, so people need a water removal and concentration gas system and method for volatile organic compounds in the atmosphere to solve the above problems

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