Microporous silica membrane manufacturing technology has been scaled-up and tubes with several hundred cm(2) of membrane surface area have been prepared. Practical problems in applying high-temperature ceramic membrane technology, such as sealing and ceramic metal joining, have been solved successfully on pilot scale. Experiments show that membranes developed are capable of selectively separating hydrogen from a gas mixture containing hydrogen at elevated pressures and temperatures. Permselectivity values for H-2/CH4 Separation are as high as 28. The gas separation performance of membranes is influenced by the flow conditions at both the feed and permeate side of the membrane. Non-ideal flow conditions can decrease the separation efficiency and strongly influence the performance of ceramic membrane separators. By performing high-temperature high-pressure separation experiments and simulation of the non-ideal flow effects around the membrane, the influence of the flow effects is predicted. The operation of the pilot scale membrane separator is simulated by a two-dimensional, one-phase mathematical model which predicts the basic features of the separator from an engineering point of view. A comparison between the experimental data and the modelling results yields the conclusion that the dispersion model predicts much better the membrane separator performance than the simplified model which assumes plug flow on both sides of the membrane separator.