Ceramic packing with channels for thermal and catalytic beds

Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness

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Details

428120, 428166, 428172, 156 8922, 156290, 156292, 165166, B32B 328, F28F 300

Patent

active

060715936

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to processes utilizing beds of ceramic packing to heat and/or react a body of fluid or act as a carrier for a catalyst and, more particularly, this invention relates to such processes utilizing improved ceramic packings for the beds.


BACKGROUND OF THE INVENTION

Regenerative thermal beds are used to capture and store heat from a first hot stream of fluid and then to transfer the heat to a second cold body of fluid before it is reacted such as by combustion, oxidation, reduction or other chemical process whether reacted in the presence or absence of a catalyst.
Originally gravel was used as the packing for the bed. Ceramic saddles and Raschig rings have been utilized for decades. As the saddles and Raschig rings randomly pack into the heat exchanger shell, they may locally stack in an orientation that will block flow. The flow is non-uniform throughout the bed of material and the pressure drop through a heat exchanger containing saddles, gravel or rings is relatively high, usually about 10 inches of water. Furthermore, the locally blocked areas may trap fluid which can contaminate the flow of second fluid or can be exhausted to the environment.
Recently, the use of monolithic columns of ceramic material for the heat exchanger columns in a regenerative thermal oxidizer system for cleaning combustion gas has been disclosed in U.S. Pat. No. 5,352,115. The monolithic columns have a lower pressure drop and reduce contamination experienced with random packing of saddles or rings.
Monolithic columns carrying a layer of catalyst are also used in catalytic processes to synthesize or convert gaseous streams to other products and in the treatment of exhaust gases from combustion engines or from industrial processes. The ceramic columns are coated with catalyst materials, such as rare earth metals. However, it is expensive to manufacture monolithic columns. Furthermore, monolithic columns are rigid and brittle. After repeated cycles of heating and cooling, the column can develop stress cracks and break or shatter into small pieces. The column becomes inoperative requiring replacement of the monolithic element. This can be quite expensive in the case of columns coated with noble or rare earth metals or metallic compounds containing platinum or palladium, rhodium, etc. Also, the channels in monolithic columns are gas-tight leading to no lateral dispersion of the gas flowing in the channels.


STATEMENT OF THE INVENTION

A column having similar architecture to a monolithic column is provided by the invention at a fraction of the cost of manufacturing a monolithic column. Instead of manufacturing the column as a homogenous, unitary body, the column is formed by stacking a plurality of ceramic plates. The ceramic plates may be cured or may be in the green, uncured state. The plates have grooves formed between ribs. When the plates are stacked with the ribs and grooves parallel to the ribs and grooves on an opposing plate, an element is formed having a plurality of channels extending through the element.
The ribs on the plate can be adhered to the opposed surface. If the opposed surface is planar and the ribs have the same elevation, the opposing surface contacts the end faces to form channels. The channels can be gas tight or can allow fluid to transfer laterally depending on the continuity of the bond between opposed surfaces. The volume and cross-section of the channel will be defined by the volume and cross-section of the groove. The plates can have one flat side and one grooved side. The plates can be flat and have regular or irregular polygonal shapes such as a square, rectangular, triangular, pentagonal, hexagonal or circular. The plates can have a regular undulating cross-section or a repeating polygonal cross-section. The plates can be the same size or can increase in size and/or decrease in size in the stack. The plates can be curved into a closed cylinder and each plate will have a diameter larger than the preceding plate by the thickness of the preceding plate. All

REFERENCES:
patent: 4705097 (1987-11-01), Mita et al.
patent: 4771826 (1988-09-01), Grehier et al.
patent: 5310593 (1994-05-01), Tsujimoto et al.
patent: 5658537 (1997-08-01), Dugan
patent: 5851636 (1998-12-01), Lary et al.

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