Systems and methods for producing synthetic natural gas are provided. The method can include gasifying a carbonaceous feedstock within a gasifier to provide a raw syngas. The raw syngas can be cooled to provide a cooled raw syngas. The cooled raw syngas can be processed in a purification system to provide treated syngas. The purification system can include a flash gas separator in fluid communication with the gasifier and a saturator. The treated syngas can be converted to synthetic natural gas to provide steam, a methanation condensate, and a synthetic natural gas. The methanation condensate can be introduced to the flash gas separator.