Process simulation of a lignite-fired circulating fluidized bed boiler integrated with a dryer and a pyrolyzer

A process model using Aspen Plus was established to simulate the performance of a lignite-fired 1,025 t/h circulating fluidized bed boiler integrated with a dryer and a pyrolyzer for improving the energy efficiency. The combustion module of the proposed model was first verified by design data and the system characteristics of the circulating fluidized bed boiler combined with the coal dryer and the pyrolyzer were then investigated. The most suitable case for the retrofit of existing 1,025 t/h CFB boilers is that 35% of the coal was dried and then pyrolyzed with the energy efficiency of 95.3% and exergy efficiency of 50.2%. The results demonstrate the lignite-fired circulating fluidized bed boiler integrated with a dryer and a pyrolyzer facilitates the system performances effectively.