Abstract: Unpowered adsorption technology has the advantages of low activated carbon consumption and low investment and operation and maintenance costs. The sewage tank of a project discharges gas only 60% of the time during normal operation and 40% of the time at the maximum discharge of sewage, so it is more appropriate to adopt unpowered adsorption process. According to the tail gas composition and flow rate in sewage tank, a calculation method is established and the parameters including activated carbon loading amount, basic dimension, alarm and interlock temperature and emergency gas flow rate are determined, providing a basis for the design of unpowered adsorption system. The process is further analysed, and some safety recommendations are put forward, such as good gas distribution structure, high-efficiency dewatering device, overpressure protection measures, electric heat tracing anti-freezing system, check valve and flame arrester, measures to maintain the gas flow in activated carbon bed and insulation measures.

Key words: unpowered adsorption, tail gas from sewage tank, volatile organic compounds/VOCs, safety design