Offgas Treatment Approaches By Focusing On Biofiltration Methods in Asphalt Factories

In the considered foundry emits offgas containing VOCs (especially ethanol). In order to reduce the VOC content, a compost based biofilter has been installed. In this approach, the polluted air stream enters a pre-conditioning chamber where temperature and humidity is adjusted for asphalt factories. Biofilteration has already been well established as an air pollutant control alternative. There are some physical, chemical and biological parameters which influence biofilter performance such: filter media , oxygen availability , moisture content , pH and etc. . In the considered factory emits offgas containing VOCs (especially ethanol) . It shows that may be there are still some VOCs in offgas which are not degraded by biofiltration. Biofiltration is not a suitable choice for treating the offgas of the certain foundry. Optimum off-gas temperature is between 25 and 37 DC but in this case, the bed temperature is less/more than the optimum range. In considered situation, it may be necessary to substitute biofiltration by another technology which can remove VOCs and odoriferous compounds completely. Different factors may affect the decision on application of these technologies, and also the effectiveness and cost of these technologies: VOC concentration, VOC species, and presence of halogenated VOCs, presence of catalyst poisons, particulate loading, moisture content, gas flow rate, and ambient temperature.