Membranes total flow rates

Itoh [1990] simulated a Pd membrane reactor coupling the cyclohexane dehydrogenation reaction on the feed side with oxidation of hydrogen on the permeate side. Given in Figure 11.35 is the predicted conversion of the dehydrogenation reaction as a function of the total flow rate of the sweep gas with the Damkbhler number for the permeate side as a parameter... 

The mole fraction compositions yt and %, are therefore to be uniform on each side of the membrane, where the subscript i denotes components 1, 2, 3,..., k. The respective steady-state molar stream rates are denoted by F, L, and V. These may designate the total flow rate of the each stream, or may be a flux rate based on the membrane area. 

Prior to each experimental trial, the reactor is externally preheated to 200°C with inert flow on both the reaction side and the sweep side of the membrane at the desired total flow rate of the experimental trial. The reactants are then introduced to the reaction side maintaining the desired total flow rate. The net reaction that occurs is exothermic causing the reactor temperature (measured by an alumel-chromel thermocouple) to increase. At steady-state, the reactor temperature measures between 400 and 650°C depending on the iC4Hio 02 feed ratio and the level of dilution. This is not an isothermal reactor at steady state, sizable temperature gradients exist within the catalyst bed. The temperature reported here is the temperature at the axis of the reactor where the feed stream meets the catalyst bed. 

Figure 3 Selectivity, iC4H o conversion, and reaction temperature for the oxidative dehydrogenation of 1C4H10 over Pt/o-Al203 in a Pd membrane reactor as pictured in Figure 2 as a function of the iC4H o 02 ratio. The reaction side contained 30% N2 dilution, had a total flow rate of 1 sipm, and was maintained at a pressure of 2 psig. The sweep side (N2) had a total flow rate of 4 slpm and was maintained at a pressure of 1 psig.

Figure 5 Selectivity, conversion, and reaction temperature with and without a Pd membrane for continuous H2 removal. The striped bars correspond to the data for the membrane reactor (H2 removal). The solid bars correspond to data collected when the membrane is replaced by an impermeable disk (without H2 removal). In all cases, the total flow rate on the reaction side was 1 slpm at a pressure of 2 psig. Data is shown for iC4Hio 02 ratios of 1.0 and 1.5 at 10%, 20%, and 30% N2 dilution. For the trials with the Pd membrane, the flow rate on the sweep side was 4 slpm of N2 at a pressure of 1 psig.

The effect of increased membrane permeability is depicted in Fig. 5.14. The material properties considered now correspond to that of a sintered metallic macrofiltration membrane (Bq = 8.6 x 10" m, mean ipor = 100 pm). In this calculation, the same total flow rate and the same Fts/Fss ratio was applied as in Fig. 5.13. As can be seen, both profiles of the axial and radial velocity differ significantly at different axial positions (Fig. 5.14). 

Figure 16.15 Improved C2 selectivities and C2 yields by feeding diluted oxygen on core side while feeding 10% methane on shell side of the hollow fiber membrane at a total flow rate of 25 mL min Methane conversion, product selectivities and C2 yield as a function of the oxygen concentration on the core side of the membrane at 1 bar and T = 800 °C. Experimental details Flow rate on the shell side = 5 mL min methane + 20 mL min helium on the core side Ftotai = 50 mL min air diluted with helium 0.78 cm effective membrane surface 0.25 g of catalyst WHSV = 0.86...

The small intestine is assumed to be a cylindrical tube with a surface area of 2kRL, where R is the radius and L is the length of the tube (Fig. 4). The rate at which the drug enters the tube is the product of the inlet concentration, C0, and the volumetric flow rate, Q. The rate at which it exits the tube is the product of the outlet concentration, Cout, and the volumetric flow rate, Q. The absorption flux across the small intestinal membrane, , is the product of the effective permeability, Peff, and concentration, C. The total drug loss by absorption from the... 

FIGURE 8 Arrangement of multiple radial flow modules to increase capacity and flow rate. Two 8 m2 modules were connected in parallel, with one 4 m2 module in series, in conjunction with a final I m2 module in series. Total membrane area is 21 m2. (Adapted from Journal of Chromatography, Vol. 852, W. Demmer and D. Nussbaumer, Large-scale membrane adsorbers, 73-81. Copyright 1999 with... 

Since the first reports on microdialysis in living animals, there have been efforts to estimate true (absolute) extracellular concentrations of recovered substances (ZetterstrOm et al., 1983 Tossman et al., 1986). Microdialysis sampling, however, is a dynamic process, and because of a relatively high liquid flow and small membrane area, it does not lead to the complete equilibration of concentrations in the two compartments. Rather, under steady state conditions, only a fraction of any total concentration is recovered. This recovery is referred to as relative or concentration recovery, as opposed to the diffusion flux expressed as absolute or mass recovery. The dependence of recovery on the perfusion flow rate is illustrated in Figure 6.2. As seen, relative recovery will exponentially decrease with increasing flow as the samples become more... 

Preparation of membranes with pores having non-uniform catalyst distributions. It has been indicated that special, non-uniform catalyst distributions inside the membrane pores offer optimal reaction performance indices such as the total conversion, product purity and product molar flow rate. Specifically, surface step distributions near the pore mouths or subsurface step distributions inside the membrane pore channels are preferred. 

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