便携式飞行时间质谱仪的研制及其在石化污水系统挥发性有机物监测中的应用

近年来，国内的大气污染问题越来越严重，挥发性有机物（VOCs）的排放是其中一个重要原因。VOCs是臭氧和气溶胶的前驱物之一，在大气化学反应过程中扮演着极其重要的角色。本实验自行研制了一台基于真空紫外（VUV）灯的高分辨光电离飞行时间质谱仪（TOF MS），建立了一种新的VOCs稀释采样方法，并将其应用于石化行业污水处理系统VOCs的采样与分析。结果表明：隔油系统的3个池子基本没有测到高浓度的挥发性有机物，其中溶气气浮甲苯物质的质量浓度最高，为50.41 mg/L，其余组分的质量浓度大多数在0.1~1.0 mg/L之间；1#加氢和2#加氢隔油池有着类似的组分浓度，以1#加氢隔油池为例，二甲苯物质的质量浓度为10.60 mg/L，乙苯为52.33 mg/L，苯为59.80 mg/L；由于罐区隔油池没有加盖，处于露天状态，挥发性有机物气体容易向大气中扩散，并没有检测出较高浓度组分。可以看出，新式采样方法可有效地稀释定量样品，操作简便，减少了样品因闪蒸过程造成的VOCs损失，检出物质更丰富；同时，使用自行研制的TOF MS仪器能够快速检测不同装置污水处理系统的VOCs种类，将该仪器用于实际样品检测，发现化工企业大多数密闭的池子都含有苯系物、醚类等，但不同工艺的污水处理系统VOCs存在明显差异。该质谱仪适用于石化企业污水系统VOCs监测。

Development of Portable Time-of-Flight Mass Spectrometer and Application in the Monitoring of VOCs in Petrochemical Sewage System

Air pollution has become more and more serious in China recently, and the volatile organic compounds (VOCs) is a main cause of air pollution. The VOCs also play an important role as the precursors of the ozone and the secondary organic aerosol (SOA). A high-resolution photoionization time-of-flight mass spectrometer (TOF MS) based on the vacuum ultraviolet (VUV) lamps was developed, and a new method for dilution sampling of VOCs was established. The developed dilution sample method directly fed the sewage discharged from the high temperature and high pressure vessel into the sampling bottle after buffering. Firstly, an analysis and research was carried out for the process of the wastewater of a refinery in transport, storage and emissions, and then this method was used in the sampling and analysis of VOCs in the petrochemical industry sewage treatment system. According to the layout of the sewage treatment system in the petrochemical enterprise, general environmental protection sampling points were selected. In addition, sampling points were set up upstream and downstream of the plant area, and then sampling points were determined according to field investigation. The results showed that no high-concentration VOCs were detected in the three tanks of oil separation system. Among them, dissolved air flotation toluene had the highest mass concentration (50.41 mg/L), while the mass concentration of other components ranged mostly from 0.1 to 1.0 mg/L. Similar component concentrations were found in 1# hydrogenation and 2# hydrogenation oil separation tanks. Take 1# hydrogenation oil separation tank as an example, the mass concentration of toluene is 10.60 mg/L, ethylbenzene is 52.33 mg/L, and benzene is 59.80 mg/L and so on. Because the oil separating tank in tank area was not capped and in open air, the VOCs was easy to diffuse into the atmosphere, and no higher concentration components were detected. The results also showed that new sampling method effectively diluted the quantitative sample, the operation was simple, and the loss of the VOCs due to the flashing process was reduced, so the detected substances were more abundant. At the same time, the self-developed TOF MS can be used to detect the sewage treatment system of different devices quickly. The results showed that most of the closed cells of chemical enterprises contained benzene series and ethers, but there were significant differences in the VOCs from different processes. Mass spectrometer can be well applied to the monitoring of VOCs in the petrochemical enterprises’ sewage systems.