A method for determination of the amount of solid particles reaching the wall of a coal gasifier was developed in order to predict the adhesion phenomena of particles to the furnace wall. In this study, experimental measurements of the rate of arrival (adhesion) at the wall of particles flowing in a straight tube were compared with our numerical results. The experimental arrival rate could be represented numerically, by analyzing the simplified two-fluid model. In this study, a system having a thermal gradient in the flow field near the wall was numerically analyzed using this simplified two-fluid model, and it was confirmed by comparing the calculated result with the result of Direct Numerical Simulation that the thermophoretic force increased the amount of solid particles reaching the wall.