Modeling and Simulation of Interconnected CFB-boiler and Fast Pyrolysis Processes – Control Design Case

The fast pyrolysis process is developed to produce liquid bio oil from biomass. In the discussed process the required thermal energy is extracted from a circulating fluidized bed boiler (CFB) as hot sand fed into the pyrolysis reactor. Residual char and uncondensed gases from the pyrolysis process are fed back and combusted in the boiler. Thus, the pyrolysis and the boiler processes are interconnected together both via energy and mass balances. Dynamic simulation is used to analyze how start ups, stops, and disturbances in the pyrolysis process effect on the operation of the boiler. According to the results of the analysis the boiler control system is modified to be able to stabilize the operation of the boiler with the interconnected pyrolysis process. The trouble free operation of the boiler must be guaranteed during all possible situations of the pyrolysis process. This project is a part of a R&D project by Metso Power where fast pyrolysis process is developed and commercialized as a new liquid bio fuel production process which can be integrated e.g. as a part of a paper mill.