The two-fluid model and kinetic theory of granular flow coupled with a local structure-dependent drag model and improved reaction kinetics are used to simulate the heat removal in a fluidized bed methanation reactor from coke oven gas using immersed horizontal tubes. By implementing the equilibrium calculation and the computational fluid dynamics simulations based on isothermal flow assumptions, the optimal operating temperature range of the methanation system is determined as 400-420 degrees C. The adiabatic simulations show that the temperature in the reactor will increase rapidly if the heat released by the reactions is not removed, thereby resulting in poor reactor performance. The performance and, in particular, the temperature of the reactor can be controlled at the desired condition by introducing the immersed horizontal tubes in the reactor for heat removal. The analysis of various geometric parameters indicates that the heat removal efficiency of a single tube is a function of its position in the reactor.