A study of gas and solid mixing behaviors in a three partitioned fluidized bed

• The partitioned fluidized bed has been developed for efficient gasification.
• The concept is dividing a gasifier and a combustor by a partitioned wall.
• Maximizing solid mixing and minimizing gas mixing are essential preconditions.

A previously unknown partitioned fluidized bed gasifier (PtFBG) has been developed for improving coal gasification performance. The basic concept of the PtFBG is a fluidized bed divided into two parts, a gasifier and a combustor, by a partitioned wall. Char is burnt in the combustor and the generated heat is supplied to the gasifier along with the bed materials. During that time, highly concentrated CO2 is inevitably generated in the combustor. Therefore, vigorous solid mixing is an essential precondition as well as minimizing horizontal gas mixing. In this study, gas and solid mixing behaviors were verified in a cold model three partitioned fluidized bed (3-PtFB). Glass beads with an average diameter of 150 μm and a particle density of 2500 kg/m3 were used as bed materials. For the gas mixing experiments, CO2 and N2 were introduced into the beds through each distributor. Then, outlet gas flow rates and concentrations were measured by gas flow meters and an IR gas analyzer respectively. The calculated gas exchange ratios ranged from 3% to 10% with varying gas flow rates. For the solid mixing experiments, 1000 μm polypropylene particles with a density of 883 kg/m3 were continuously fed into the reactor. Then, the polypropylene particles were distributed to the entire beds evenly. Solid mixing behaviors were very analogous to liquid mixing behaviors in a continuous stirred tank reactor (CSTR).

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