Experimental and computational study on the effect of ash deposition on fluid dynamic behavior in a bubbling fluidized bed gasifier

The effect of ash deposition on fluid dynamic behavior in a fluidized bed gasification reactor has been studied using experimental and computational methods. The experiments were carried out using sand particles as bed material and air as a fluidizing agent. A 3D computational model has been developed for a bubbling fluidized bed gasification reactor. First, the model was simulated using only sand particles and air. The results are compared with the experimental results. The comparison shows good agreement between the two sets of the results. The model was further used to study the effect of ash accumulation on the fluid dynamic properties of a biomass gasification reactor. The bed material was mixed with 2 and 4vol% of ash and simulated in cold conditions. Pressure drop increases and minimum fluidization velocity decreases with increasing the ash deposition in the bed. The model was also simulated for 2, 4, and 6 vol% of ash at a temperature of 800ºC. The minimum fluidization velocity was decreased in all the cases. The particle species concentration shows the ash particles start to segregate at the minimum fluidization condition and are totally separated at higher velocities. The bubble behavior of the bed is not effected by ash deposition.