| Volatile Organic Compounds(VOCs)are important environmental pollutants.With the rapid development of industrialization,the current situation of VOCs pollution is becoming more and more serious.The petrochemical industry is the main industry for national pollution control,and its VOCs emissions rank first among industrial sources.Petrochemical VOCs emissions are characterized by complex components,large concentration spans,and large differences in on-site humidity.Accurate online monitoring of them is a major problem in the current detection technology.Aiming at the major demands and technical challenges of online monitoring of petrochemical VOCs emissions,this paper proposed a Nafion-UV-FAIMS method for online monitoring of petrochemical VOCs emissions.Utilizing the characteristics of vacuum ultraviolet(UV)lamp ion source for VOCs,such as high ionization efficiency and wide linear range,combined with the advantages of high-field asymmetric waveform ion mobility spectrometry(FAIMS),such as high sensitivity,rapidity,and easy miniaturization,as well as the characteristics of the Nafion tube to quickly filter water vapor,this paper carried out demonstration research on petrochemical VOCs emission online monitoring technology and application.The specific innovative work is as follows:(1)An accurate acquisition method of VOCs characteristic spectrum based on glass-based monolithic tandem FAIMS is proposed.Using Micro-Electro-Mechanical System processes such as through glass via(TGV),multi-region electrode photolithography coating,multi-layer bonding,etc.,the single-chip tandem FAIMS analyzer was fabricated with high precision.Studied the separation and loss characteristics of VOCs ions in tandem FAIMS under the action of multi-stage dispersion voltage and compensation voltage,realized separation of VOCs overlapping peaks and discovery of weak peaks under large concentration differences,and solved the problem of obtaining complete spectra of the VOCs in traditional FAIMS under multi-component and large concentration differences.(2)A wide-range quantitative method for VOCs is proposed.By studying the transmission characteristics of ions in ionization,transmission,separation,and detection regions,an ion transmission loss model was constructed.By studying the influence of sample concentration,transit time,and ion species on the signal response,a UV-FAIMS quantitative detection model was constructed.Further,based on this model,a quantitative linear region preservation strategy based on sample dilution is proposed,and an adaptive detection method for VOCs is developed,which solves the problem of accurate quantification under the condition of large differences in VOCs concentration.(3)A method of eliminating water vapor interference in a petrochemical site based on the Nafion tube is proposed.The FAIMS spectral characteristics of typical petrochemical VOCs and hydrogen sulfide interferences under different humidity are studied,and the optimal humidity range for FAIMS detection is found.The Nafion tube technology is introduced into FAIMS,and the separation loss studies of VOCs and water vapor in Nafion-UV-FAIMS were carried out.The results proved that Nafion-UV-FAIMS technology has a strong anti-interference ability to water vapor,which solves the problem of humidity interference in petrochemical sites.(4)Demonstration of high-precision online monitoring of petrochemical VOCs based on Nafion-UV-FAIMS technology is carried out.Through the development of key modules such as separation voltage source,weak signal detection circuit,and measurement and control system,a Nafion-UV-FAIMS prototype for high-precision online monitoring of petrochemical VOCs is built,and a spectral library of benzene,styrene,xylene,and other VOCs are constructed.Sinopec Yanshan Petrochemical Company was selected as the demonstration unit,and the application demonstration was carried out in two key VOCs emission areas of the refinery and the storage and transportation plant,and the on-site monitoring data of petrochemical VOCs for two consecutive months is successfully obtained,which proves the effectiveness of the method in petrochemical field application. |
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