A dynamic model is developed of the fluidized-bed desulfurizer/regenerator system for the hot-gas desulfurization (HGD) process as part of the integrated gasification combined cycle. The efforts of model development, simulation, control structure exploration and evaluation of design changes are described in this paper. The desulfurizer and regenerator are modeled as bubbling fluidized beds with perfectly mixed solid phases and plug flow gas phases. Six alternative control structures are tested dynamically for load disturbance rejection. The control schemes in which the H2S concentration is controlled by changing the level of solids in the desulfurizer perform poorly because they give large swings in solid circulation rates. For throughput changes, O-2 concentration is controlled very well by the use of a ratio controller with time lag. The dynamic studies indicate that the HGD process can be controlled, but that trade-offs between design and control must be carefully considered.