Heat exchange – Intermediate fluent heat exchange material receiving and... – Solid fluent heat exchange material
Patent
1992-01-23
1993-10-12
Davis, Jr., Albert W.
Heat exchange
Intermediate fluent heat exchange material receiving and...
Solid fluent heat exchange material
110263, 110347, 122 4D, F28C 316, F23D 100
Patent
active
052516911
DESCRIPTION:
BRIEF SUMMARY
Indirect heating of large flows of air with high pressure (10-30 bars) to high temperature (750.degree.-850.degree. C.) is of interest in connection with power generation based on solid fuels, especially coal, comprising combinations of gas and steam turbines in purpose of reaching high efficiency.
The present invention relates to a device advantageous for said heating comprising a specially designed heat exchanger submerged in a fluid bed of classical type through which fine-grained hot bed material, as an example coal ash, is flowing, which material has been heated to a high temperature by combustion of pulverized coal in mixture with the bed material.
The fluidized bed is maintained at 0.6<.epsilon.<0.7 (.epsilon.=voidage) in a chamber with a preferably rectangular horizontal section, which is supplied with hot bed material, preferably below the bed surface, in the vicinity of one of the chamber walls and from which chamber the bed material flows over a weir in the opposite chamber wall.
According to the invention the heat exchanger surface consists of an adapted number of hairpin bent tubes, which for reason of strength and cost preferably have an inner diameter of 20-80 mm. The "hairpins" have straight vertically downward pointing legs of differing length which are fastened to separate disc shaped pressure chambers--one upper inlet chamber and one lower outlet chamber--each with horizontal between themselves connected plane parallel walls and sides with preferably half circular section. The short leg of the "hairpins" opens into the upper wall of the inlet chamber while the long leg extends down through a tube shaped conduit between the horizontal walls of the inlet chamber and opens into the upper horizontal wall of the outlet chamber.
According to the invention the tube shaped conduit is fastened to the horizontal walls of the inlet chamber concentrically with the long leg and has such a length that it extends to an adapted level above the upper horizontal wall of the inlet chamber and has such an inner diameter that an annular channel with suitable width is formed between the tube leg and the conduit. The latter acts simultaneously as a fortifying element between the horizontal walls of the inlet chamber.
Another characteristic feature of the device according to the invention are bubblecaps with a suitably toothed lower edge which are fastened-to the long leg at an adapted level above the upper edge of the conduits. Together the bubblecaps and the annular channels form suitable distributors for the feeding of the fluidizing air to the fluid bed in which the heat exchanger is submerged.
The device according to the invention has a low space between the pressure chambers separated from the fluid bed preferably by a "skirt" that extends from the sides of the inlet chamber past the sides of the outlet chamber and ends somewhere at approximately the level of the lower horizontal wall of the outlet chamber. The fluidizing of the bed, in which the heat exchanger is submerged, is done with a small adapted flow of gas that is fed into the space between the pressure chambers and flows up through the annular channels and out below the toothed lower edge of the bubblecaps, thereby fluidizing the bed.
A simple way of feeding a fluidizing flow of air to the space between the pressure chambers is by tapping an adapted flow from the inlet chamber through one or more small holes with adapted diameter in the lower horizontal wall of the chamber.
Because of the high temperature of the bed material (>800.degree. C.) and the outlet air together with the high pressure, a large part of the tube's surface and the whole outlet chamber reaches a high temperature. This means that only walls made of heat-resistant alloys, i.e. Incoloy 800 H, match the strains with reasonable wall thickness.
By using tubes with comparatively small diameter (20-80 Mm) the wall thickness will be very reasonable, which is of importance because of the high specific material cost.
The outlet chamber, where the hot air from the "hairpins" is
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patent: 3982901 (1976-09-01), Steever et al.
patent: 4287156 (1981-09-01), DeFeo
patent: 4292023 (1981-09-01), DeFeo et al.
patent: 4377072 (1983-03-01), Campbell, Jr. et al.
patent: 4530290 (1985-07-01), Comparato
Collin Mans
Collin Per
Davis Jr. Albert W.
Meller Michael N.
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