بررسي كارآيي سيستم هاي كنترل كننده ذرات معلق و تعيين ميزان انتشار در كارخانجات آسفالت مشهد

Investigation on dust control systems and determination of emission rate in Mashhad asphaltplants

Asphaltplants are a group of air pollutants sources that have effective role in dust emissions in the atmosphere. There are 5 asphaltplants in the mashhad near suburb area which may rise the city air pollution and cause problems for natural and residential environment. In this reaserch necessary data depend on subject such as factories dust collector specifications, production rates and duration of activity in day and in a year as well as their situations near the Mashhad city and wind direction have collected. Four factories had wet scrubbers and the other one had no any industrial treatment system. The dust control systems of factories have assessed by gravimeteric method by sampling of dust from entrance as well as the exhaust air of the wet scrubbers using Gravimat SHC 502. For better achievement, 3 samples befor and 3 samples after wet scrubber were taken . Results of samplings have showed that the final exhaust air were still polluted with high concentrated dust. The concentration of Total Suspended Particulates (TSP) in the stacks were in the 260-345mglmJ range. In the same time, results of samplings before control systems showed the TSP concentration of 270-485mg/m3 range. Calculation of treatment systems efficiencies have showed %31.1, %32.2, %23 .1and %26.8 efficiency in Mashhad Municipality, Neumooneh, Rahban and Astan e Ghods Razavi factories respectively. Above the numbers showed very low efficiency which were mainly due to some what wrong desighn in wet scrubber and watering system as well as weak maintenance of the systems. Comparing the emissions with national emission standard have revealed that all of the factories were not in the allowable range. The emission factors have also calculated as 54.8, 62 .1, 70.5, 75.7 and 179.3 gr /tons of production in Neumooneh, Mamarbeton, Mashhad Municipality, Rahban and Astan e Ghods Razavi factories respectively only for emission from the stack of process activities except for fuel burning.