In this study, the 6.7-MWe solid fuel in Hatyai, Thailand was modeled and operational data were used to verify the simulated results. A steady-state model was used with a transient fluid environment during solid iteration implementation in UN. An environmental energy limit was introduced to facilitate keeping the fuel bed's energy absorption in equilibrium with the energy released from particles in the local fluid, with energy transferring from fluid convection and energy releasing from volatile combustion. The volatile species were obtained from a pyrolysis experiment using a lab-scale fixed-bed reactor equipped with micro GC. Tar was assumed to be CH3CHO for compatibility with GRI3.0. Simulated results showed that the usage of a simplified transported equation and the environmental energy limit could help the model to converge. The results of the solid fuel bed were reasonable and go along with fluid behavior. The simulated temperatures of the fluid at the sensors' locations had a discrepancy of approximately 30%. The pattern of the simulated temperatures was in line with the measurement. Simulated results also showed solid fuel to be combusted too early, which caused the temperature in the combustion zone to be higher than the measured temperature. The high temperature in the combustion zone could come from assuming tar as CH3CHO, which was combusted early inside the fuel bed. (C) 2019 Elsevier Ltd. All rights reserved.