This work shows the application of a validated mathematical model for gas permeation at high temperatures focusing on demonstrated scale-up design for H
2 processing. The model considered the driving force variation with spatial coordinates and the mass transfer across the molecular sieve cobalt oxide silica membrane to predict the separation performance. The model was used to study the process of H
2 separation at 500 °C in single and multi-tube membrane modules. Parameters of interest included the H
2 purity in the permeate stream, H
2 recovery and H
2 yield as a function of the membrane length, number of tubes in a membrane module, space velocity and H
2 feed molar fraction. For a single tubular membrane, increasing the length of a membrane tube led to higher H
2 yield and H
2 recovery, owing to the increase of the membrane area. However, the H
2 purity decreased as H
2 fraction was depleted, thus reducing the driving force for H
2 permeation. By keeping the membrane length constant in a multi-tube arrangement, the H
2 yield and H
2 recovery increase was attributed to the higher membrane area, but the H
2 purity was again compromised. Increasing the space velocity avoided the reduction of H
2 purity and still delivered higher H
2 yield and H
2 recovery than in a single membrane arrangement. Essentially, if the membrane surface is too large, the driving force becomes lower at the expense of H
2 purity. In this case, the membrane module is over designed. Hence, maintaining a driving force is of utmost importance to deliver the functionality of process separation.
Full article
