INERT GAS PURGING OF ANAEROBIC DIGESTERS AND DIGESTER GAS SYSTEMS

Inert gas purging is critical to safe start-up and maintenance of anaerobic digesters and their associated gas handling and storage systems. Implementation of inert gas purging as a step in anaerobic digester and gas system start-up or maintenance results in additional labor requirements and costs. However, when the potential for personal injuries and structural and equipment damage resulting from a digester gas explosion are considered, the additional time and costs are well justified.This paper discusses National Fire Protection Association (NFPA) code requirements related to purging of fuel gas systems, purging reference sources, “inert” gases commonly used for purging, and basic purging procedures. Results of inert gas purging of anaerobic digesters at two POTWs are also presented.