Cold model experimental and dynamic modeling studies on the slag flow and heat transfer at the slag tap hole region of Shell gasifier have been carried out. The cold model experiment was set up to observe the simulated slag deposition. The dynamic model was proposed to clarify the slag accumulation on the wall of slag screen. The results show that the simulated slag can be broken up to slender liquid filaments by the high-speed swirling gas flow, and a part of the filaments can deposit on the slag screen wall. When the surface temperature is below the critical temperature, the slag is totally solidified to solid slag layer. At equilibrium, a liquid slag layer covers the solid slag layer and its surface temperature is higher than the critical temperature. The solid slag layer thickness increases along the slag flow. In addition, the solid slag thickness can be decreased by increasing the operating load and operating temperature. (c) 2012 Elsevier B.V. All rights reserved.