Local percolation of non-spherical particles in moving bed waste heat recovery unit for hydrogen production by methanol steam reforming

Abstract

To study the local percolation of non-spherical particles in a moving bed waste heat recovery unit (MBWHRU) for hydrogen production, the discrete element method (DEM) was applied to simulate the discharge. A local method was applied to determine the location and local intensity of percolation. The percolation maps were presented. Moreover, the effects of structural parameters of MBWHRU, fine particle parameters, and friction parameters on local percolation were also considered. Percolation mainly occurs at the bottom, flow mechanism transition region, and near the vertical segment wall. Among them, percolation above the orifice is the most intense. The velocity gradient (or shear) is not the only condition under which percolation occurs. Percolation is closely related to changes in multiple parameters. The effects of fine particle parameters and friction parameters relative to structural parameters on percolation are significant. Percolation can be effectively avoided by increasing the mass percentage and particle size of fine particles, which is beneficial to hydrogen production. Especially, for the particle size ratio of fine particles to coarse particles greater than 0.5, percolation is no longer evident. The percolation near the vertical segment wall is particularly sensitive to particle-wall friction (>0.45). Reducing particle-particle friction and wall roughness is also beneficial to hydrogen production.