Gas Raman Enhanced Detection System Based On Atomization Extraction

In the fields of national security,factory production and personal health,it is of great significance to detect harmful substances and trace components in gases.The gas composition in the actual environment is complex and the concentration of the target gas is low,which makes it difficult to apply it in the field of gas detection.However,gas chromatography mass spectrometry as the current mainstream gas analysis method limits its application in the field of gas detection due to its large size,high cost,and complicated detection process.Raman spectroscopy is a spectroscopic technique based on molecular vibration and rotation.For each kind of molecule,it has its own characteristic spectral information.Raman spectroscopy can realize the integration of the detection system,has good timeliness,and has better application prospects in samples detection.However,Raman detection sensitivity is low and it is not easy to detect complex samples.In this dissertation,a Raman enhanced gas detection system based on atomization extraction was designed to detect highly complex gases with high sensitivity.The gas pretreatment system achieves the purification and enrichment of the target trace gas components in the mixed gas by means of atomization extraction,and further increases the concentration of the target substance component in the sample to be measured through the gas circulation and the liquid circulation.The Raman back-end detection system achieves the binding of excitation light and Raman light through the silver plating on the inner wall of the capillary,and inserts a reflective gold film at the end of the capillary to enhance the collection efficiency of Raman light.The Raman back-end detection system can achieve Raman enhanced detection of the target material composition in the sample to be measured.The system designed in this paper can realize the detection of complex gas in the factory workshop.In this dissertation,two sets of gas pre-treatment systems,the gas atomizing-condensing circulation extraction system and the enrichment device of electrospinning filter based on PAN and PVP materials were designed.In the gas atomizing-condensing circulation extraction system,the mixture gas atomizes the extraction liquid sufficiently,and the extraction liquid extracts the target trace gas components.On the one hand,the area of contact between the target gas component and the extract is increased by atomization extraction,and on the other hand,the concentration of the target substance in the solution to be measured is increased by gas circulation and liquid circulation,and enrichment of the target trace gas component is achieved.In an enrichment device for electrospinning filters based on PAN and PVP materials,gas circulation is filtered through PAN and PVP electrospinning filters to achieve enrichment of fine particles in the air.The PAN and PVP materials are easily hydrolyzed in water and cannot adapt to the large amount of water vapor in the factory's production plant.Therefore,the first option was selected as the gas pretreatment system.At the same time,a Raman enhanced detection system based on the silver plating on the inner wall of the capillary and the reflection of the gold film was designed to measure the Raman spectrum of the mixed solution containing the target substance.In the Raman enhanced detection system designed in this paper,Raman light and excitation light are bound by silver plating on the capillary wall.At the same time,a gold film is inserted at the end of the capillary to reflect excitation light and Raman light.The excitation light travels back and forth within the capillary for one week,increasing the interaction distance between the light and the sample.At the same time,the forward Raman light and the backward Raman light are both collected by the Raman probe,which increases the Raman light collection efficiency of the Raman probe.In experiments,when the capillary length was 2.5 cm,the gain coefficient of the reflective gold film to Raman signal intensity was 2,which was in accordance with theoretical calculations.The relationship between the Raman intensity and the concentration of the ethanol solution with different concentrations was further verified.In order to realize the detection of complex gas in the workshop,a simulation workshop concentration detection demonstration system was designed to verify the detection performance of the gas circulation atomization extraction condensation system.First,the relationship between the concentration ratio of ethanol and isopropanol mixed solution and the intensity of the Raman peak was calibrated.On this basis,the isopropanol component of the mixed gas is atomized and extracted by the ethanol extract.The gas circulation and the liquid circulation increase the isopropanol concentration in the test liquid.At the same time,the performance of the gas pre-treatment system was verified by experiments.The extraction effect of ethanol on isopropyl alcohol in the gas-phase atomization extraction condensation system was 3.3 times that of the isopropanol gas directly introduced into the ethanol solution.This reduces the requirement for the detection sensitivity of the back-end Raman enhanced detection system so that the Raman enhanced detection system based on atomized extraction can detect lower concentrations of gas.In view of the situation in actual factory production,on the one hand,it is necessary to improve the detection sensitivity of the system.It can be achieved by improving the airtightness of the gas circulation atomization extraction system in order to improve the extraction efficiency of the system.On the other hand,it can be achieved by improving the transmission characteristics of the capillary tube and reducing the transmission loss,which improves the detection sensitivity of the Raman detection system.When the gas atomizing-condensing circulation extraction system extracts about two times more isopropanol,and the detection sensitivity of the Raman enhanced detection system reaches 0.14%,a concentration of 1000 ppm of isopropanol gas can be detected to meet the need for safe production requirements of the factory floor.At the same time,the integration of the gas Raman detection system is improved.A multi-metal tube condensation structure is designed to replace the glass condenser,where metal materials are used to increase the heat exchange efficiency,and the multi-metal tube structure is further utilized to increase the heat exchange surface area.The condensing system is designed as a complete chassis and a package structure is designed for the rear Raman enhanced detection system.The gas Raman enhanced detection system based on atomization extraction enriches the target gas in the gas pretreatment system and achieves a higher detection sensitivity in the rear Raman detection system.The detection system has a wide range of application for it can uses different extraction fluids for different target gases.It can be integrated into products for use in actual production and life,and thus has a broad potential market.