Cold model study of a dual fluidized bed system for the gasification of solid fuels

Sorption-enhanced reforming (SER) is a process that couples steam gasification with carbonation/calcination reaction of limestone to enhance the hydrogen concentration in a product gas. Inspired from lab scale results a 200 kWth pilot plant is constructed at IFK, University of Stuttgart. This pilot plant is a dual fluidized bed (DFB) system comprised of a bubbling fluidized bed (BFB) gasifier and a circulating fluidized bed (CFB) regenerator. These two fluidized beds are coupled with an L valve and a lower loop seal located at the bottom of the gasifier. This paper delineates the cold model studies of this pilot plant carried out during the design phase. The cold model is based on the Glicksman's simplified scaling ratios, which determine the particle properties and operating conditions of the cold model. Results of the cold model can be extrapolated to the pilot plant using the scaling ratios. The results validate long term stable operation is possible with the planned DFB system. The solid circulation patterns in the BFB are studied and results show that the proposed BFB design is suitable for the gasifier. The parameters such as gasifier inventory, riser velocity and riser entrainment rates are tested under scaled conditions to prove the feasibility of the pilot plant. The results show that the required design criteria of the 200 kWth DFB pilot plant are fulfilled and the proposed DFB pilot plant is feasible.