Planar-type seals

FIGURE 5.3 Schematic of typical planar-type seal, illustrating p ... 

Taniguchi, S., Kadowaki, M., Yasuo, T, Akiyama, Y, Miyake, Y. and Nishio, K. (20(K)), Improvement of thermal cycling characteristics of a planar-type solid oxide fuel cell by using ceramic fibre as sealing material, J. Power... 

The gas sealing at the side of anode substrate is a serious problems in the anode supported type SOFCs as well as in the conventional planar type SOFCs. The lower operation temperature makes it difficult to select an appropriate sealing agent. Moreover, a large oxide ion flux through the thin electrolyte may cause a rise of oxygen partial pressure in the anode side. The degradation and dimensional instability on start-up and shutdown of the anode supported type cell stacks due to the oxidation of the nickel component in the anode substrate. 

There are currently two main types of plate-based planar patch instmments those which produce giga-Ohm seals, as in conventional patch clamp (e.g., PatdiXpress, QPatch) and those producing <100mega-Ohm seals as a compromise to allow a higher throughput (e.g., lonWorks HT, lonWorks Quattro) [57, 58]. 

In contrast, tube-and-shell type membrane modules do not have these engineering challenges with deflection and compromise of seal integrity. For this reason, tubular membrane modules will generally be lighter in construction relative to stacked planar membrane modules of comparable membrane area. However, a drawback to the tubular membrane module is that the packing density of the membrane is often substantially less than that which can be achieved with the stacked planar designs. 

From the structure point of view, there are two types of structures of SOFC tubular and planar. Tubular SOFCs have shown some desirable characteristics over systems with planar SOFCs [4]. Tubular SOFCs can alleviate the sealing problem arose by CTE mismatch of planar SOFC therefore, they are robust for repeated cycling under rapid changes in electrical load and in cell operating temperatures. The large form factor tubular SOFC built by Siemens Westinghouse has successfully conducted long-term operation over 70,000 h. Small-scale tubular SOFCs could... 

At its simplest, an onlap trap may be a blanket sand that pinches out up-dip (Fig. 8D). It is sealed by impermeable rocks beneath and by an onlapping shale (generally the source rock, as well as the cap). Many unconformities are old land surfaces, however, and sands may be deposited in old topographic lows. Alternating hard and soft sediments may have been weathered and eroded to form scarps, dip slopes, and strike valleys. Fluvial or shallow marine sands may have been deposited along the old valleys and sealed by marine muds. Stratigraphic traps of this type are known as the Mississippian Pennsylvanian imconformity of Oklahoma. Alternatively, the unconformity may have been a planar land surface that was locally incised by alluvial valleys. These may have been sand filled and drowned by... 

Figure 6.13.1 Different shapes of ultramicroelectrodes (UMEs). (A) A perfect microdisk electrode. (B) A conical disk-type planar UME due to sealing of the tnicrowire at an angle relative to the insulating shroud. (C) An irregular cylindrical protruding from the insulator. (D) A recessed microdisk electrode. (E) A recessed electrode in which the cavity in the insulator is large than the...

Figure 7-6 Possible Seal Types in a Planar SOFC (from (29))...

The requirements, material choices, and general sealing concepts are common to most planar SOFC stack designs. Fundamentally, two different types of seals are being developed for SOFC bonded and compressive seals. 

Sealless planar Electrochemical cells made up of electrolyte, cathode, and anode are stacked with metal interconnects without using sealing materials. For example, disk-type planar sealless stacks have been constructed by Mitsubishi Materials Corporation. For this purpose, fuel and air are introduced through the central part of the respective cells. Outside the cells, the remaining fuel becomes combusted with air. Self-supporting cells are usually used for this design. 

The flat tube design (fig. 3c) was proposed to improve the sealing problems in the anode supported planar SOFCs without losing its high performance. The 1 kW SOFC stack of flat-type design was recently demonstrated by Kyocera Co. Japan in 2004. 

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