Co-production of gasification based biofuels in existing combined heat and power plants - Analysis of production capacity and integration potential

Solid fuel fired fluidized bed (FB) boilers are common in combined heat and power (CHP) plants in district heating- and process industry. In this study, utilization of such FB boilers for production of syngas in dual fluidized bed gasifiers and subsequent catalytic biofuel production to substitute natural gas (SNG), methanol (MeOH) and Fischer-Tropsch fuel (FT) has been examined. Based on the hypothesis that waste-heat and tail gas from the biofuel processes can be utilized in the CHP plant, process configurations aiming for operationally robustness and low investment cost rather than maximum stand-alone efficiency have been explored and implemented in actual industrial cases and over the full operating range of the boilers. The results of the study show that significant improvements of overall efficiency can be achieved by integration of the biofuel processes in the CHP plants and that a relatively high biofuel production capacity can be achieved. SNG showed the highest obtainable efficiency and production capacity of the studied biofuels, whereas the FT process showed largest increase in terms of efficiency when integrated in the CHP plant, compared to its stand-alone efficiency.