Shell-side composition profile

Thus far, only binary mixtures have been separated in the total membrane column. Results of this work have been discussed elsewhere (28,29). A sample shell-side composition profile from a total column experiment with a CO2-O2 mixture is shown in Figure 2. Table I summarizes the total column data obtained to date. 

Figure 3. Shell-side composition profiles for the COt-CHi,-Nt mixture in a stripper at total reflux...

Shell-side composition profiles jor the COf,-CHii-Ni mixture in a stripper with bottom product... 

Figure 9. Shell-side composition profile minimum for the CO2—N2 mixture in the...

Figure 10. Sensitivity of the stripper shell-side composition profile to the bottom...

Figure 13. Shell-side composition profile variation with a comparable cut and a...

Usually in an enricher or the enriching section of the membrane column, the more permeable component is steadily concentrated from the feed inlet to the compressor. However, some of the results show that the shell-side and even the tube-side composition profiles can pass through a minimum. Note the experimental data in Figures 7 and 8. In these cases the feed flow is relatively slow and reflux action, rather than bulk flow, is predominant. Figure 8 Illustrates that a composition minimum can also occur dinring operation of the total column when the residue flow rate from the enriching section is too slow. 

Figures 7 and 8 incorporate calculated tube- and shell-side concentration profiles for the unique CO2-N2 and O2-N2 (air) data, and also Illustrate local permeate composition variation. Each figure shows that the concentration of more permeable gas steadily decreases in the direction of flow along the high-pressure (tube)...

Figure 3 shows the steady-state radial temperature profiles for the two adiabatic catalytic beds operating at conditions of the optimal point. The corresponding axial temperature profiles in the interbed heat exchanger are also included in Fig. 3, for the tube side (Tt) and shell side (Tsh). The simulation results have been compared with industrial data corresponding to a large scale ammonia converter. The deviations at the reactor outlet were less than 0.2% (relative error) in composition and 14 °C in temperature (Toutz)-... 

The conditions are substantially more favorable for the microporous catalytic membrane reactor concept. In this case the membrane wall consists of catalyti-cally active, microporous material. If a simple reaction A -> B takes place and no permeate is withdrawn, the concentration profiles are identical to those in a catalyst slab (Fig. 29a). By purging the permeate side with an inert gas or by applying a small total pressure difference, a permeate with a composition similar to that in the center of the catalyst pellet can be obtained (Fig. 29b). In this case almost 100% conversion over a reaction length of only a few millimeters is possible. The advantages are even more pronounced, if a selectivity-limited reaction is considered. This is shown with the simple consecutive reaction A- B- C where B is the desired product. Pore diffusion reduces the yield of B since in a catalyst slab B has to diffuse backwards from the place where it was formed, thereby being partly converted to C (Fig. 29c). This is the reason why in practice rapid consecutive reactions like partial oxidations are often run in pellets composed of a thin shell of active catalyst on an inert support [30],... 

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