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.

Automated summary

A three-dimensional computational fluid dynamics (CFD) model was developed to simulate the gasification process of solid refuse fuel (SRF). The model was validated by comparing the simulation results with experimental data. The study found that changing the air-to-fuel equivalence ratio and SRF feed location can impact the yield of syngas and C-2-C-3 hydrocarbons.