Ceramic membrane tubes

Fig. 4. Configuration of a ceramic membrane reactor for partial oxidation of methane. The membrane tube, with an outside diameter of about 6.5 mm and a length of up to about 30 cm and a wall thickness of 0.25-1.20 mm, was prepared from an electronic/ionic conductor powder (Sr-Fe-Co-O) by a plastic extrusion technique. The quartz reactor supports the ceramic membrane tube through hot Pyrex seals. A Rh-containing reforming catalyst was located adjacent to the tube (57).

A proper sealing system to link the ceramic membranes tubes to the steel module is required. 

Fig. 9.10 (a) Concept for closed-one-ended ceramic tubes bundled for cermet membrane applications, (b) Bundle of ceramic membrane tubes produced by CoorsTek for an earUer industried separation application (Courtesy R. Kleiner, J. Stephan, and F. Anderson, CoorsTek)... 

A prototypic design for a tubular membrane reactor can be found in linde AG s patent appUcation shown in Fig. 8.9 [24]. This design uses a bundle of ceramic membrane tubes that are inside a pressure vessel. The tubes are closed at one end with the air fed to the tubes in the annulus between the ceramic tube, labeled 32,... 

Figure 8.9 Figure 1 from DE 10 114 173 A1 [24], showing the ceramic membrane tube 33. Fresh syngas is supplied at port 36 and syngas product is withdrawn at port 6. 

Praxair has also filed patent applications on a syngas reactor incorporating tubular membranes, as shown in Fig. 8.11 [26]. Similar to the Unde AG design of Fig. 8.9, this design uses tubular membranes oriented with the axes of the tubes parallel to the axis of the cylindrical pressure vessel. High pressure syngas flows on the exterior of the ceramic membrane tubes, and low pressure air is fed into... 

Lattner and Harold [56] performed autothermal reforming of methanol in a relatively big fixed-bed reactor carrying 380 g BASF alumina-supported copper/zinc oxide catalyst modified with zirconia. The 01C ratio was set to 0.22 while the SIC ratio varied from 0.8 to 1.5. The axial temperature profile of the reactor, which had a length of 50 cm, was rather flat, the hot spot temperature did not exceed 280° C which was achieved by the air distribution system through porous ceramic membrane tubes. More than 95% conversion was achieved. Very low carbon dioxide formation was observed for this reactor only 0.4 vol.% was found in the reformate. However, the WHSV calculated from the data of Lattner and Harold [56] reveals a low value of only 6 l/(h gcat) for the highest CHSV of 10 000 h reported. 

The use of a dead-end ceramic membrane tube can make the assembly of the membrane reactor much simpler. As shown in Fig. 7.12(b), a dead-end ceramic membrane tube is sealed onto the muUite tube in which a smaller dense alumina tube is coaxially placed. The whole system is sited in a quartz tube, which serves as the shell side in the reactor operation. The short step in the mullite tube serves as a holder for both the seal material and the membrane. For the Bii jYojSnio 2O3 (BYS) membrane mounted to the mullite tube, the sealant consisting of 45 wt% BYS, 25 wt% SrCeo.95Tbo.05O3,10 wt% Pyrex glass, 10 wt% NaA102 and 10 wt% B2O3 can be used (Akin and Lin, 2002). 

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