What are the common online monitoring methods for VOCs?

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What are the common online monitoring methods for VOCs? VOCs refer to various organic compounds with volatile organic properties and boiling points ranging from 50 to 260°C at room temperature. They are generated during industrial production processes, have a significant impact on human health, and can cause bodily abnormalities or cancer; therefore, they need to be monitored and controlled. The VOCs online monitoring system can continuously monitor the emission of such pollutants 24/7, providing real-time data at all times. All data is transmitted to the environmental protection agency’s monitoring platform through system software and data acquisition devices, enabling data sharing and making environmental supervision faster, more accurate, and more intelligent. There are four methods for online VOC monitoring: gas chromatography, which first uses a chromatographic column to separate the components to be analyzed, and then a selected detector (FID/MSD/ECD) is used to determine the identity of the components based on their retention time, while the peak height (or peak area) is used for quantitative analysis. Fourier Transform Infrared Spectroscopy (FTIR) works by using infrared light with continuously varying wavelengths to illuminate the target compound molecules; infrared light of specific wavelengths that match the inherent vibration frequencies of the molecules is absorbed. The infrared light incident on the molecules is dispersed using a monochromator, so that the different wavelengths are arranged in sequence, and the intensity of absorption for each wavelength is measured, thereby producing an infrared absorption spectrum. Qualitative assessment is based on the degree of fit between the infrared absorption spectrum of the sample and that of the standard substance, while semi-quantitative evaluation is conducted based on the intensity of the characteristic absorptions. PID photoionization detection: When the gas to be analyzed absorbs ultraviolet light with high energy, the gas molecules are excited by this ultraviolet light and temporarily lose their electrons, becoming positively charged particles. Once these gas ions are detected at the electrodes of the detector, they quickly recombine with electrons to form the original gas molecules. It is a non-destructive type of detector. FID hydrogen flame ionization detection uses a hydrogen flame as an ionization source to ionize organic molecules into positive and negative ions. Under the electric field created by a polarization voltage, these positive and negative ions move toward their respective opposite electrodes; the resulting ion stream is collected by the collector electrode and sent out. After impedance conversion, the amplifier generates a measurable electrical signal. The above are the methods for online VOC monitoring, totaling four types. I hope this information is useful to everyone. Those who wish to learn more about this topic can consider the VOC online monitoring devices produced by Yichang Shengda Technology. These devices use high-precision PID sensors of Chinese origin, and feature an 8-inch large touch screen. The accuracy of the measurement data is very high and stable. They enable digital management of hazardous waste gases across various processes, from collection and transmission to analysis and processing, as well as output and sharing, thus ensuring that corporate production can proceed safely, smoothly, and continuously.