Membrane gas permeation

In the simulation of the HMD process, the gas-permeation membrane used is assumed to be an asymmetric hollow-fiber membrane. For this type of membrane, gas permeation does not depend on the flow pattern on the permeate side as the porous supporting layer prevents mixing of the permeate fluxes (Pan, 1986). A schematic of the flow pattern in an asymmetric hollow-fiber membrane is shown in Figure 10.2. Hence, a simple cross-flow model is sufficient to describe the membrane behavior. 

PIMs Ladder-like structure with sites of contortion, hindered packing inside lattice 5 to 15 450 to 1760 Membrane gas permeation, gas storage, heterogeneous catalysis... 

In this section, we will briefly describe two membrane processes, ultrafiltration and membrane gas permeation, using configurations where we can assume that the feed mixture region is well-mixed its composition equals that of the concentrate stream. 

In a membrane gas permeator, both the feed side and the permeate side may be well-stirred. Sometimes this is identified as the complete mixing case. As shown in Figure 6.4.10, a binary feed gas mixture of species A and B (mole fraction of A, Xyy) enters the feed side at a pressure Pf and molar flow rate W,f The feed side is assumed to be well-mixed, therefore the gas composition of the exiting stream (/ = 2) Xa2 (reject mole fraction of A) is present everywhere in the feed side of the permeator. The reject gas stream exits at a molar flow rate Wa. The permeate side may be similarly well-mixed the permeate molar flow rate is W,i and the mole fraction of the permeate stream leaving the separator, Xai, is also present throughout the permeate side of the permeator of membrane area A ,. Assume that the pressures on both sides of the permeator are uniform. 

In earlier chapters we have studied gas separation via gas permeation in two permeator configurations in a completely mixed membrane gas permeation cell (Section 6.4.2.2) in crossflow membrane permeators (Section 7.2.1.1). In the shell-side fed hollow fiber gas permeator of Figure 7.2.1(d), if the permeate is withdrawn from the fiber bore at the feed end only (the other end is closed), then we have countercurrent flow between the feed side and the permeate side. We consider such a gas permeator configuration here via Figure 8.1.51(a) this figure does not show a hollow fiber. However, one could easily model a hollow fiber permeator with the permeate side being the fiber bore (I.D., dj O.D. do). We wiU now develop the governing balance equations for the countercurrent gas... 

There are a number of other aspects of significant importance in membrane gas permeator analysis and design. 

Figure 8.1.4(b) illustrates two membrane gas permeation devices coupled together with a compressor at the top. Suppose the whole system is filled with a binary gas mixture and the two sides of the membrane are at two different pressures as shown. No permeate product is being withdrawn, however, so there is... 

Minimum energy required for membrane gas permeation, distillation, extraction and other separation... 

In this section, we wiU illustrate the calculation of the minimum energy required for a variety of separation processes, e.g. membrane gas permeation, distillation, extraction and adsorption. 

Composite top layer with a non-metallic-based film (Nanosil membrane, etc.) In the case of Nanosil membranes, gas permeation occurs through windows Very high High Low... 

---