The invention discloses a multistage continuous overheated steam
drying system and method of low-rank
coal. The multistage continuous overheated steam
drying system comprises at least two stages of
fluidized bed drying devices, wherein a discharging port of the first stage of
fluidized bed drying device is connected with a feeding port of the second stage of
fluidized bed drying device, and an air outlet at the top of the second stage of
fluidized bed drying device is connected with an air inlet at the bottom of the first stage of the
fluidized bed drying device; a feeding hole of the first stage of
fluidized bed drying device is connected with a raw
coal feeding device, an air outlet at the top of the first stage of fluidized
bed drying device is connected with a dust removing device, an air outlet of the dust removing device is connected with a circulating fan, and an air outlet of the circulating fan is connected with a
heating furnace; and a
discharge port of the last stage of fluidized
bed drying device is connected with a dry
coal warehouse, and an air inlet at the bottom of the last stage of the fluidized
bed drying device is connected with the
heating furnace. Overheated steam and raw coal are dried by adopting a countercurrent operation, and partial purified steam can be recycled, therefore
high heat utilization rate is achieved; and the multistage continuous overheated steam drying
system and method disclosed by the invention have the advantages of simple whole drying process,
continuous operation capability in an anaerobic environment, safety and reliability.