Modelling of Cost Optimized HTL Fuel Production by Process Integration

Advanced biofuel production via hydrothermal liquefaction (HTL) can contribute to the mitigation of greenhouse gases from the transport sector. The HTL process is suitable for the conversion of a broad variety of organic feedstock including wet waste streams. The potential of transportation fuel production via sub-critical HTL of primary sewage sludge with integrated biocrude upgrading via hydrotreatment, and an energetic valorization of the aqueous phase via catalytic hydrothermal gasification is assessed. The thermal management of an integrated biofuel plant is optimized with respect to subsystem cost based on in-depth process modelling to quantify mass and energy flows and principles of pinch analysis to design a heat exchanger network. The cost optimized configuration has an installed heat exchanger surface of 1.32 m2 related to 1 kg of processed sewage sludge and results in an overall process efficiency of 58.3 %