Sweep gases oxygen separation

Catalytic testings have been performed using the same rig and a conventional fixed-bed placed in the inner volume of the tubular membrane. The catalyst for isobutane dehydrogenation [9] was a Pt-based solid and sweep gas was used as indicated in Fig. 2. For propane oxidative dehydrogenation a V-Mg-0 mixed oxide [10] was used and the membrane separates oxygen and propane (the hydrocarbon being introduced in the inner part of the reactor). 

Figure 16.4 Oxygen separation from air using inert sweep gases Oxygen flux through a BCFZ hollow fiber membrane as a function of temperature for steam (O) and He (O) as sweep gases (after Tablet et al. ). Experimental details Air flow rate on the core side = 150 mL min steam or He flow rate on the shell side= 10 mL min 0.35 cm effective membrane area. For comparison, different sweep gas flows of 5 ( ) and 20 (A) mL min He.

Another NG-fired OTM-based oxy-fuel plant is the zero emission ion transport membrane oxygen power (ZEITMOP) cycle (Fig. 10.11) proposed by Yantovski and co-authors. The cycle is based on a supercritical CO2 cycle, where CO2 is compressed in an intercooled compressor to over 200 bar, heated in a recuperative heat exchanger and expanded in a high pressure turbine to 15 bar. It is then used as sweep gas in an OTM, where it is enriched with O2 separated from a stream of compressed air. The CO2/O2 flow is used as oxidant in a NG combustor which produces high temperature oxidized gas to be expanded to nearly ambient temperature in a low pressure turbine. Efficiencies of 50.4-52.0% with virtually zero CO2 emissions are reported. " A reactive membrane configuration can also be adopted to reduce the required membrane surface area. In this case, cycle efficiency... 

Figure 4.16 An illustration of a counter-flow module for the separation of nitrogen from air. Directing the permeate to flow counter to the feed sweeps the permeate side of the membrane with a flow of oxygen-depleted gas. This increases the oxygen flux and decreases the nitrogen flux through the membrane...

A carrier gas, such as nitrogen, helium, or a helium/ hydrogen mixture, sweeps the pyrolysis gases into any of four downstream systems of reactors, scrubbers, separators, and detectors for the determination of the carbon monoxide content, hence of the oxygen in the original fuel sample. The result is reported as mass % oxygen in the fuel. 

---