Energetic and environmental performance of three biomass upgrading processes integrated with a CHP plant

In order to react on future expected increased competition on restricted biomass resources, communal combined heat and power (CHP) plants can be integrated with biomass upgrading processes that add valuable products to the portfolio. In this paper, outgoing from a base case, the retrofit integration of production of wood pellets (WPs), torrefied wood pellets (TWPs) and wood fast pyrolysis slurry (PS) with an existing wood-fired CHP plant was simulated. Within the integration concept, free boiler capacity during times of low district heat demands is used to provide energy for the upgrading processes. By detailed part-load modelling, critical process parameters are discussed. With help of a multiperiod model of the heat duration curve, the work further shows the influence of the integration on plant operating hours, electricity production and biomass throughput. Environmental and energetic performance is assessed according to European standard EN 15603 and compared to the base case as well as to stand-alone production in two separate units. rk shows that all three integration options are well possible within the operational limits of the CHP plant. Summarising, this work shows that integration of WP, TWP and PS production from biomass with a CHP plant by increasing the yearly boiler workload leads to improved primary energy efficiency, reduced CO2 emissions, and, when compared to stand-alone production, also to substantial fuel savings.