Modelling of an integrated fast pyrolysis process with Aspen Plus

The integrated pyrolysis has a higher efficiency than conventional stand-alone units. VTT has developed a concept where a fast pyrolysis process has been integrated into a fluidized bed power boiler. An integrated fast pyrolysis process can be more efficient as it utilizes heat from the fluidized bed boiler for the pyrolysis reaction. Simultaneously, the char and non-condensable gases produced during the pyrolysis reaction can be combusted in the boiler. In this way, the overall efficiency penalty of the fluidized bed boiler process is minimized. We have built a simulation model with the Aspen Plus software where the fast pyrolysis process has been integrated into a power plant process. The simulation enables us to investigate the effect that the fast pyrolysis process has on the performance of the power plant. The model simulation is based on tests done in a pyrolysis process development unit (PDU). The model has been run with different feedstock such as hardwood and forest residue and with different moisture content of the pyrolysis raw material. We were able to confirm the earlier assessments that the integration can bring about several technical and economic advantages, such as a high overall efficiency compared to stand-alone fast pyrolysis concepts, lower investment costs and lower operating costs than for a stand-alone concept. Also the operating flexibility improves due to full exploitation of by-products in the power boiler. In addition, it has been shown that even low-value biomass such as forest residue can have a positive impact on the plant performance in an integrated fast pyrolysis concept