汽车维修行业挥发性有机物排放特征及大气化学反应活性

汽车维修行业挥发性有机物排放是臭氧前体物VOCs的重要来源,但目前汽车维修行业的VOCs减排政策主要基于VOCs的排放量,而没有考虑其化学反应活性,这将影响VOCs减排对改善空气质量的效果.通过分析汽车维修企业不同工段VOCs的产排污节点,结合各工段油漆用量及其VOCs质量分数,采用物料衡算法获得不同工段VOCs产生量...

Emission Characteristics and Atmospheric Chemical Reactivity of Volatile Organic Compounds(VOCs) in Automobile Repair Industry

Volatile organic compounds (VOCs) emitted by the automobile repair industry are an important source of ozone precursors. However, the current reduction policy generally focuses on the emissions of VOCs, without considering their chemical reactivity. Based on an investigation of the development status of China''s automobile repair industry, this study analyzes VOCs emission nodes in different sections of automobile repair enterprises. The amount and VOCs content of paint in each section was determined, and a material balance algorithm was used for sections with different VOCs quantities and compositions to analyze the emission characteristics of exhaust VOCs. The atmospheric reactivity of VOCs components was evaluated by calculating ozone generation potential (OFP). The results show that VOCs components produced by automobile repair paint are mainly benzene homologues, with butyl acetate and xylene the highest. Varnish is the largest contributor to VOCs emissions in automobile repair industries (92%), due to its high VOCs content and high dosage. The VOCs content of solvent-based coatings (22%) is higher than that of water-based coatings (3%). The application of water-based coatings leads to a remarkable reduction in VOCs emissions in automobile repair industries. A total of 49 VOCs components have been detected in gas from exhaust cylinders, with the top 10 VOCs components accounting for 97.9% of the total emissions. The main pollutants are aromatic hydrocarbons (10 types, 30.90%-69.30%), and OVOC (12 types) and halogenated hydrocarbons (22 types) were the second-highest contributors, with contribution rates of 8.82%-43.71% and 2.40%-25.00%, respectively. Aromatic hydrocarbon is the largest VOCs component emitted by automobile repair industries, but the main types of VOCs vary greatly in different studies. VOCs discharged by automobile repair industries have an average OFP value of 194.04 mg ·m^-3 and an average SR value of 3.37 g ·g^-1. The m/p-xylene component contributes the most to OFP (70.24%) and is the preferred pollutant in automobile repair industry. Aromatic hydrocarbons contribute a maximum of 99.29% to the OFP value and are also the most chemically reactive component. Although esters account for a large proportion of VOCs, their contribution to OFP is relatively low. Therefore, the automobile repair industry should focus on controlling the emission of aromatic hydrocarbons.