印刷厂清洗过程中VOCs的恶臭污染及消失

Odor pollution and elimination of volatile organic compounds during the cleaning process in printing plant

分析印刷行业清洗过程VOCs排放特征及其恶臭指数,运用阈稀释倍数法对VOCs的恶臭产生及消失进行研究.结果表明,印刷行业清洗过程VOCs排放以芳香烃类组分为主,其中1,2,4-三甲基苯、间-二甲苯、1,2,3-三甲基苯、1,3,5-三甲基苯、邻-二甲苯、甲苯、乙苯为主要排放物种;BTEX(苯∶甲苯∶乙苯∶二甲苯)比值为0.05∶1.07∶1.00∶5.60,B/T值为0.04,可用于定性判断印刷厂清洗过程VOCs的来源;清洗过程中,恶臭贡献(阈稀释倍数)较大的VOCs物种为间-二甲苯(67.4)、1,2,4-三甲基苯(33.1)、对-二甲苯(9.5)、1,3,5-三甲基苯(5.5)、乙苯(4.1),其阈稀释倍数均远大于1,表明会产生明显的恶臭污染;在一般通风情况下(0.9 h-1),清洗过程开始5 min及清洗结束后4.7 h内,车间内恶臭污染明显,通风率越高越有益于消除恶臭,在清洗过程及清洗结束后,至少需增大车间内通风率至5.1 h-1,可有效消除车间内恶臭污染;因此,若清洗后快速投入正常生产,则优先选取低VOCs含量的环保型清洁剂,有效降低二甲苯、三甲苯、乙苯等恶臭化合物的排放,同时提高车间内通风率,是有效防治印刷行业清洗过程中恶臭污染的重要途经.

VOCs emission characteristics and odor index were investigated during the cleaning process in a printing plant.Thresholds of the diluted multiple was also used for analyzing the generation and elimination of odor pollution caused by VOCs.The results showed that aromatic hydrocarbon was the most abundant VOC group during the cleaning process,while the major compounds were 1,2,4-trimethylbenzene,m-xylene,1,2,3-trimethylbenzene,1,3,5-trimethylbenzene,o-xylene,toluene and ethylbenzene.As the qualitative index of VOCs source,BTEX(Benzene∶Toluene∶Ethylbenzene∶Xylene)ratio was 0.05∶1.07∶1.00∶5.60 and the B/T value was 0.04 with a unique characteristic,which can be used to qualitatively identify the source of VOCs during the cleaning process.The major odorant VOCs species were m-xylene,1,2,4-trimethylbenzene,p-xylene,1,3,5-trimethylbenzene and ethylbenzene,with the thresholds of the diluted multiple of 67.4,33.1,9.5,5.5,and 4.1,respectively,indicating the obvious odor pollution occurred during the cleaning process due to the thresholds of the diluted multiple was higher than 1.Odor pollution occurred evidently within 5 min after the cleaning process starts and lasted 4.7 h after cleaning finished under the general ventilation condition(0.9 h-1).Results showed that the higher the ventilation rate,the more beneficial to eliminate odor,and the ventilation rate in the workshop should be increased to at least 5.1 h-1 to eliminate the odor during and after the cleaning process.Therefore,if it put into normal production immediately after cleaning,it is an available way to effectively prevent and control the odor pollution during the cleaning process in printing plant by prioritizing the selection of environmental cleaning solvents with low VOCs content which can effectively reduce xylene,trimethylbenzene,ethylbenzene and other odor substances,and the ventilation rate in the workshop should be increased as much as possible.