Improvement And Optimization Of VOCs On-line Monitoring System

Volatile organic compounds(VOCs)are organic compounds having a boiling point of 50 ° C to 260 ° C or a saturated vapor pressure of greater than 71 Pa at room temperature,which are one of the main pollutants causing atmospheric pollution.They can pose a greater hazard to humans,animals and plants.Due to the complex composition of the VOCs in the atmosphere,the concentration is very low,it is necessary to enrich and concentrate at the front of instrumental analysis.Under the ultra-low temperature environment below-150 °C,all the VOCs can be effectively captured and concentrated without using any adsorbent by Ultra-low temperature hollow tube enrichment technology,which is highly efficient,non-polluting and non-component discrimination.At present,there has been a small amount of research on this technology,but it is still not mature enough.There are still more content related technologies that need further research,such as the design and optimization of the principle structure of cold trap,gas path,temperature and process.The main content of this research is to improve and optimize the prototype of the VOCs adsorption and concentration online monitoring system developed by our team in the gas path structure,cold trap structure and experimental conditions to improve instrumental performance.The specific contents are as follows:1.Designing the supply device during the secondary focusing process to improve the response of high carbon VOCs.Improving the design of the cold trap structure by replacing the material of the capture trap and the focus trap and improving heating device to improve performance of the cold trap.2.The parameters of the VOCs adsorption and concentration online monitoring system such as secondary focusing temperature,analytical temperature,injection volume,injection pressure and carrier gas flow rate are optimized to improve performance of include compound characterization,standard curve linearity,repeatability,detection limits,and recovery.3.Monitoring 108 kinds of VOCs in outdoor ambient air by VOCs adsorption concentration online monitoring system,we researched the impact of carbon dioxide and hydrone on monitoring of VOCs in the atmosphere and analyze the concentration of various VOCs.The test results show that the instrument has good performance and long-term stable operation,95% of the compound linear coefficient can reach 0.99,97% of the compound RSD is below 10%,which can meet the online monitoring for qualitative and quantitative analysis of VOCs in the atmosphere.