Method and device for recycling ammonia-containing tail gas in LNG co-production ammonia synthesis process

The invention relates to a method and a device for recycling ammonia-containing tail gas in an LNG co-production ammonia synthesis process, and belongs to the technical field of gas recovery. According to the invention, the ammonia-containing tail gas is introduced into the raw material gas, so that energy waste and nitrogen oxide pollution caused by air combustion of NH3 are eliminated. Flash steam generated after synthesis of liquid ammonia and ammonia-containing methane gas (the methane content is about 20%) are collected and conveyed to the front of a purification device through a pipeline, and methanation is carried out after purification. The invention further comprises a device for implementing the recycling method. The ammonia gas does not enter the methanation process and the cryogenic liquefaction process, so that the problems of insufficient ammonia washing in the methanation process and ammonia freezing blockage caused by the ammonia gas entering the cold box can be fundamentally restrained, and t