US-12618817-B2 - Compact dehydration and trap module

US12618817B2US 12618817 B2US12618817 B2US 12618817B2US-12618817-B2

Abstract

Gas detection devices comprise a dehydration unit a concentration unit, and a temperature control unit for controlling a temperature. The gas detection device includes a sampling mode in which sample gas flows into and out of the dehydration unit through a first port and a second port, respectively, wherein the volatile organic compounds in the sample gas are concentrated in the concentration unit. The temperature control unit may be configured such that the temperature of the sample gas after flowing out from the dehydration unit and before flowing into the concentration unit is not greater than a first preset temperature. Generation of condensed substances in the sample gas can be effectively avoided in a simple manner after the sample gas flows into the concentration unit, thereby further preventing ice blockage. Methods for detecting volatile organic compounds in a sample gas are also disclosed.

Inventors

Te Yu HUNG
Chien Kuo Chang
Colin Zou
Rong Hua Chen
Jun Fang

Assignees

THERMO FISHER (SHANGHAI) INSTRUMENT CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20230922
Priority Date: 20220927

Claims (11)

1 . A gas detection device for detecting volatile organic compounds in a sample gas, comprising: a dehydration unit configured to dehydrate the sample gas flowing into the dehydration unit by condensation, the dehydration unit comprising a first port; a concentration unit arranged downstream of the dehydration unit in a flow direction of the sample gas and in fluid communication with the dehydration unit, the concentration unit comprising a second port; and a temperature control unit for controlling a temperature, wherein the gas detection device includes a sampling mode, in which the sample gas flows into the dehydration unit through the first port and flows out of the concentration unit through the second port, wherein the volatile organic compounds in the sample gas are concentrated in the concentration unit, and the temperature control unit is configured such that the temperature of the sample gas after flowing out from the dehydration unit and before flowing into the concentration unit is not greater than a first preset temperature set by the temperature control unit for the concentration unit, wherein the gas detection device further comprises an analysis unit for analyzing the volatile organic compounds, and includes a desorption mode, in which a carrier gas flows into the concentration unit from the second port, such that the volatile organic compounds desorbed from the concentration unit flows to the analysis unit with the carrier gas, wherein the dehydration unit comprises a reduced-diameter portion that has a reduced diameter in the flow direction of the sample gas, and in the sampling mode, the sample gas flows out of the dehydration unit through the reduced-diameter portion, and in the desorption mode, a part of the carrier gas can flow into the dehydration unit through the reduced-diameter portion for branch-off.
2 . The gas detection device according to claim 1 , wherein the temperature control unit comprises a cooling apparatus that can cool an entire sample gas flow path from the dehydration unit to the concentration unit.
3 . The gas detection device according to claim 2 , wherein the temperature control unit comprises a first heating apparatus for heating the dehydration unit and/or a second heating apparatus for heating the concentration unit.
4 . The gas detection device according to claim 3 wherein the second heating apparatus comprises a heat generating mechanism arranged around the concentration unit and an insulating sleeve arranged outside of the heat generating mechanism and configured to fix the heat generating mechanism.
5 . The gas detection device according to claim 1 , wherein the temperature control unit is configured to make the first preset temperature greater than a second preset temperature set for the dehydration unit by a first temperature difference, wherein the first temperature difference is 0° C. to 10° C., and the second preset temperature is in a range of −45° C. to −35° C.
6 . The gas detection device according to claim 1 , wherein the gas detection device comprises a capillary tube which includes a first open end and a second open end, wherein the first open end is in communication with the analysis unit, and the second open end is in fluid communication with an interior of the concentration unit, and wherein in the desorption mode, the carrier gas loaded with the volatile organic compounds can flow to the analysis unit through the capillary tube.
7 . The gas detection device according to claim 6 , wherein the second open end is located inside the dehydration unit, such that in the desorption mode, the carrier gas containing the volatile organic compounds flows into the capillary tube inside the dehydration unit, wherein a part of the carrier gas can be branched off by means of at least one of the first port and another port of the dehydration unit.
8 . The gas detection device according to claim 1 , wherein the gas detection device further includes a purge mode, in which the temperature control unit can heat the dehydration unit to convert condensed substances therein into water vapor, such that the water vapor can be blown out from the dehydration unit.
9 . A method for detecting volatile organic compounds in a sample gas by using a gas detection device, the gas detection device comprising a dehydration unit with a first port and a concentration unit with a second port, wherein the method comprises a sampling step, in which the sample gas flows into the dehydration unit through the first port and flows out of the concentration unit through the second port, wherein the sampling step comprises: dehydrating the sample gas by condensation in the dehydration unit; concentrating the volatile organic compounds in the sample gas within the concentration unit; and controlling a temperature of the sample gas, such that the temperature of the sample gas after flowing out from the dehydration unit and before flowing into the concentration unit is not greater than a first preset temperature set for the concentration unit, wherein the gas detection device further comprises an analysis unit for analyzing the volatile organic compounds, the method further comprises a desorption step performed after the sampling step, wherein said desorption step includes heating the concentration unit to desorb the volatile organic compounds, making a carrier gas flow through the concentration unit, to carry the desorbed volatile organic compounds out of the concentration unit and to the analysis unit, wherein the dehydration unit comprises a reduced-diameter portion that has a reduced diameter in the flow direction of the sample gas, and in the sampling step, the sample gas flows out of the dehydration unit through the reduced-diameter portion, and in the desorption step, a part of the carrier gas can flow into the dehydration unit through the reduced-diameter portion for branch-off.
10 . The method according to claim 9 , wherein the sampling step further comprises: controlling the temperature of the sample gas to make the first preset temperature greater than a second preset temperature set for the dehydration unit by a first temperature difference, wherein the first temperature difference is 0° C. to 10° C., and the second preset temperature is in a range of −45° C. to −35° C.
11 . The method according to claim 10 , wherein the method comprises a purge step performed after the sampling step, wherein the purge step comprises: heating the dehydration unit to convert condensed substances therein into water vapor, and blowing the water vapor out from the dehydration unit.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority from China Application No. 202211178331.5, filed on Sep. 27, 2022, which is incorporated herein by reference in its entirety. TECHNICAL FIELD The present invention relates to a gas detection device for detecting volatile organic compounds (VOCs) in a sample gas. The present invention further relates to a method for detecting volatile organic compounds in a sample gas by using a gas detection device. BACKGROUND ART Currently, volatile organic compounds (VOCs) in the ambient atmosphere, especially in the lower troposphere, has attracted increasing and extensive attention. Definitions of volatile organic compounds are not completely consistent among different organizations around the world. For example, the World Health Organization (WHO) defines a large class of organic compounds whose boiling point ranges from 50° C. to 260° C., whose saturated vapor pressure exceeds 13.33 Pa at room temperature, and which exist in the air in the form of vapor at room temperature as volatile organic compounds. As another example, the U.S. Environmental Protection Agency defines any carbon compound that participates in atmospheric photochemical reactions except carbon monoxide, carbon dioxide, carbonic acid, metal carbide, metal carbonate and ammonium carbonate as volatile organic compounds. The American Society for Testing and Materials directly defines any organic compound that can participate in atmospheric chemical reactions as volatile organic compounds. Overall, volatile organic compounds mainly include alkanes, olefins, halogenated hydrocarbons, oxygen-containing hydrocarbons, aromatic hydrocarbons, and other volatile substances. In addition, according to Code for indoor environmental pollution control of civil building engineer (GB50325-2001), volatile organic compounds refer to organic compounds that can participate in gas-phase photochemical reactions. Volatile organic compounds participate in a series of complex reactions in the atmosphere to generate ozone. Specifically, after the volatile organic compounds are oxidized in the atmosphere, the reaction between O3 and NO is inhibited, and free radicals are generated to accelerate conversion of NO to NO2, thereby leading to rapid accumulation of O3 and the deterioration of air quality. In addition, the volatile organic compounds may also be converted into secondary organic aerosols (SOAs) under certain conditions. The SOAs may also affect the atmospheric visibility and affect a regional environment through long-distance conveying. In addition, most of the volatile organic compounds are greenhouse gases, which may lead to global warming. The volatile organic compounds are also harmful to human health. When exceeding a certain concentration, the volatile organic compounds may stimulate people's eyes and respiratory tract, causing skin allergies, sore throat, and fatigue. The volatile organic compounds can very easily damage a central nervous system by means of blood-brain disorders. The volatile organic compounds harm people's liver, kidneys, brain and nervous system. The volatile organic compounds also have carcinogenicity, teratogenicity, and reproductive system toxicity. With the implementation of China's environmental protection policy in 2018, municipalities directly under the central government, provincial capitals and cities specifically designated in the state plan among key cities successively performed automatic monitoring of volatile organic compounds. In the monitoring scheme, it is stipulated that the volatile organic compounds to be monitored manually include 117 components, and there is no mandatory requirement for the components to be monitored automatically. Currently, with the development of technology, automatic monitoring will gradually be included in the scope of supervision, which lays a solid foundation for achieving the vision of “blue sky dream”. However, the volatile organic compounds themselves in the ambient atmosphere have a low concentration, a wide range, many types and rapid concentration changes, and are likely to be affected by weather and climate changes such as wind power, wind direction, rain and snow, and thus there are high requirements on analysis. Currently, the technical principle of monitoring volatile organic compounds is gas chromatography, and a detector includes a flame ionization detector (FID), a mass spectrometry detector (MSD), etc. Since the volatile organic compounds in the ambient atmosphere have a very low concentration, it is necessary to first concentrate and enrich the volatile organic compounds into an adsorption apparatus at a low temperature by means of a thermal desorption instrument, then desorb the concentrated volatile organic compounds from the adsorption apparatus by heating, and finally introduce the volatile organic compounds into a gas chromatography-mass spectrometry (GC-MS) combined system for detection. During the low-tempera