Thermo-fluid model of a batch hydrothermal carbonization reactor

The work presented is a part of a wider project with the target to realize in­deep studies on the applicability of the hydrothermal carbonization process to the treatment of high moisture biomass. To get this challenging objective, a batch reactor has been built to perform preliminary tests to get insights on the thermochemical process. Several substrates have been carbonized, obtaining interesting results, useful for the modelling stage. A numerical model of a batch hydrothermal carbonization reactor have been developed. The model integrates both mass, momentum and heat equations within the reactor domain by means of finite volumes method (f.v.m.) approach. Convective and radiative exchange between the reactor and the fluid within the reactor have been implemented in the f.v.m. model. To calibrate the model, experimental tests have been performed to collect data referred to temperature profiles (outside and inside the reactor) and pressures. Under two strong assumptions (mono­component and mono­phase fluid, which fulfils the reactor), it has been possible to estimate the behaviour of an equivalent fluid (eq_fluid), in terms of thermal properties of the fluid (thermal capacity, thermal conductivity and thermal diffusivity). The foreseen upgrading of the model can help to obtain a better description of the process.