Three-Dimensional CFD simulation of waste plastic (SRF) gasification in a bubbling fluidized bed with detailed kinetic chemical model

The utilization of municipal solid waste combustible fractions as a fuel is generally preferred over landfilling. Fuels derived from waste materials, such as solid refuse fuel (SRF), can be utilized for energy generation using pyrolysis, gasification, and combustion. A three-dimensional computational fluid dynamics (CFD) model was developed for the simulation of SRF gasification process in a bubbling fluidized bed (BFB). The gas phase and solid phase were studied using the large eddy simulation (LES) approach and the multiple particle-in-cell (MP-PIC) method, respectively. The simulation included the chemical kinetic model of SRF drying, pyrolysis, gas-solid reactions, and homogeneous reactions. The kinetic chemistry model was expanded to reflect a higher yield of C-2-C-3 gases and tars evolved from SRF. The simulation results were compared with the gas composition obtained from experiments conducted on a lab-scale reactor having a capacity, height, and internal diameter of 1 kg/h, 1 m, and 0.114 m, respectively. The independence of the accuracy of the model on the mesh resolution and computational particle number was examined. Varying air-to-fuel equivalence ratio (ER) to 0.20, 0.25, and 0.30 changed syngas LHV to 25.40, 16.86, and 14.30 kJ(gas)/g(fuel) respectively and changed C-2-C-3 hydrocarbons yield to 0.30, 0.18, and 0.16 g/g(fuel) respectively. Changing the SRF feed location to below the bed at ER = 0.25, increased the gas LHV to 19.85 kJ(gas)/g(fuel) and increased C-2-C-3 hydrocarbons yield to 0.21. SRF BFB gasification reactor model can be exploited for simulation of low ER autothermal decomposition of SRF to C-2-C-3 hydrocarbons or high LHV gas production.