Taking Huaneng Pingliang bituminous coal as the design coal

a polygeneration system for 2×350 MW circulating fluidized bed (CFB) pyrolysis and combustion staged conversion process was built up

which comprises of coal pyrolysis unit

combustion furnace

steam and water system

coal gas cooling and purification unit

tar hydrogenation unit

water-gas conversion unit and methanation unit.The coal is sent to the fluidized pyrolyzer by the coal feeder

then it is quickly heated to 700 ℃ to generate coal gas

tar and char through a series of pyrolysis reactions.The coal gas is further utilized to generate synthetic natural gas (SNG)

the tar is upgraded to oil through tar hydrogenation technology

while the char residues are sent to the supercritical circulating fluidized bed boiler to generate electricity.The technical and economic performances of this polygeneration system is calculated and analyzed using the Aspen Plus software.The results reveal that the energy conversion efficiency of the whole system is up to 50.02%

and the internal rate of return and the discounted payback period is 21.63% and 8.29 a respectively.This paper provides a thorough analysis of the polygeneration plant and the results indicate the proposed plant has a promising market prospects.