Development of a particle-based reactor network model for pressurized entrained flow gasifiers

A novel particle-based reactor network model (PRNM) was developed as a design-screening tool to predict performance of pressurized, single-stage, oxygen-fired, entrained flow gasifiers (EFGs). PRNM is based on the reactor network concept, but provides improved detail of particle reactions not available in standard reactor network models (RNMs). Three plug-flow reactors (PFRs) are used to prescribe gas flow patterns within the gasifier a priori based on gasifier geometry and classical turbulent jet theory and recirculating flow theory. Multiple particle types and sizes are tracked using a Lagrangian approach. Cantera PFR and WSR reactor modules with a modified GRI-Mech 3.0 kinetic mechanism are used to calculate gas phase properties. Particle devolatilization rates are defined by the Ubhayakar two-step method; single-step char oxidation and gasification reactions are used. Heat transfer rates are calculated for the particles, gas, and refractory wall. An optically thick assumption is used for inter-particle and particle–wall radiative transfer. PRNM performance metrics include gas, particle and refractory temperature profiles, axial gas composition, and particle conversion. Predicted gas temperature profiles, exit gas compositions and particle conversions compared well with results from a laboratory-scale, pilot-scale and commercial-scale gasifiers. The main limitation was calculating the gas and wall temperature profiles near the burner where the radiation model is dimensionally limited, but inaccuracies were not found to impact exit gas temperature, composition, and particle conversion. Although developed for EFGs, PRNM techniques for coupling reacting particles to PFRs and WSRs in reactor networks are well-suited for other chemically reacting systems.