Advective-diffusive Mass Transport in PBMR

In contrast to FBR, local concentrations of the components in a PBMR are affected additionally by mass transport through the membrane. In order to illustrate how the dosing of a component influences the local concentration distribution in 

Advective-diffusive transport was simulated by the moment-propagation method (Lowe and Frenkel, 1995 Merks et ah, 2002). In this method, a scalar quantity P(x,t), e.g. species concentration, is released in the lattice. At each itera- 

A halfway bounce-back boundary condition was imposed at the spheres/fluid interface. Gas particles (molecules) which are propagated into a solid point bounce back immediately and stay where they were. The flux through the membrane depended on the local pressure (advective contribution) and local concentration gradient (diffusive contribution) across the membrane. 

In this chapter a specific type of membrane reactor, the so-called distributor was analyzed theoretically. In contrast to conventional tubular fixed-bed reactors (FBR), where all reactants are introduced together at the reactor inlet (cofeed mode), packed-bed membrane reactors (PBMR) allow dosing of one or several reactants via membranes over the reactor wall along the axial coordinate (distributed-feed mode). 

The distributor -type membrane reactor possesses different residence-time characteristics and different local concentration profiles compared to the conventional FBR. The additional degrees of freedom allow in complex networks of consecutive and parallel reactions, the selectivity and the yield to be enhanced with respect to a certain target product. The concept can be considered as an interesting option in the current attempts to improve and intensify reaction processes. 

---