Development of an internally circulating fluidized bed for catalytic methanation of syngas

Abstract

In this work, an internally circulating fluidized bed reactor was proposed and designed for the catalytic methanation of syngas from the 100 kWth dual fluidized bed gasification reactor at TU Wien. Additionally, first fluid dynamic investigations were carried out in order to determine characteristic pressures and the gas slip between in the internally circulating fluidized bed. The results from the design of the reactor showed that a volume contraction in the reactor between 30-50 % and a heat generation between 0.16 to 0.25 kW per kW of exit gas need to be considered in the thermodynamic equilibrium for a low temperature methanation process at 300 °C and 1 bara. Further technical and economic considerations resulted in the design of a fluidized bed with an outer diameter of 164 mm, which corresponds to a maximum feed gas volume flow of 6 m3stp/h and a maximum chemical energy of 15 kW in the exit gas for the chosen catalyst properties. The fluid dynamic investigations with an inert bed material showed that there is a clear correlation between the pressure difference between the draft tube and the annular region and the fluidization ratio. Additionally, the gas slip was shown to increase with a higher fluidization ratio as well as higher absolute fluidization velocities. Furthermore, the gas slip from the annular region to the draft tube was shown to be by an order of magnitude higher than the gas slip from the draft tube to the annular region.