The invention relates to the technical field of exploitation and utilization of
coal bed gases, and in particular relates to a device and a method for purifying and concentrating a
coal bed gas and treating
produced water. The device comprises a wet
flame arrester, a water ring
vacuum pump, a gas flow meter, a one-way gas valve, a separator, a fireproof and explosion-proof compressor, a
safety valve, a
hydrate generating unit, a gas-liquid two-phase valve, a
gas concentration monitor, a stop valve, a filter, a one-way liquid valve, a
slurry pump, a three-phase separator, a granulating
machine, a stop valve, an outer transportation vehicle, a
hydrate decomposing unit, a water pump, an ice making device, a
grinding device, a liquid flow meter, a Laval spray valve and a
clarifier. Two
hydrate reactors are adopted to fix CO2 and
methane in the
coal bed gas respectively, and the CO2 released after regeneration is used as a gas-driving raw gas for improving the
recovery ratio of the coal bed gas, so that the release of CO2 of a gas field is reduced, and high-concentration
methane hydrate is granulated and transported outwards for application; and a salt draining effect during formation of the hydrate is used to ensure that a lot of salt-containing
produced water during exploitation of the coal bed gas can be treated to meet requirements for reinjection to a stratum layer, so that resources are saved, and the environment is protected.