Heat exchange – With cleaning means for heat exchanger
Patent
1996-01-30
1997-10-14
Flanigan, Allen J.
Heat exchange
With cleaning means for heat exchanger
16510416, 422143, 422146, F28D 1300
Patent
active
056762011
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an apparatus for carrying out a physical and/or chemical process, such as a heat exchanger, comprising a reservoir provided with upwardly-directed tubes accommodated, at the top and bottom ends thereof, in tube plates, and which are in open communication with a top box and a bottom box, in which bottom box at least one distribution plate is arranged for supporting a fluidized bed consisting of granular material, capable of being held in a quasi-stationary, fluidized condition by means of a medium to be treated or heated, supplied via a feed line, which medium can flow, via the tubes provided in and above the fluidized bed with openings, to the top box while entraining fluidized bed particles, and which apparatus further comprises means for feeding fluidized bed particles back from the top box to the bottom box.
Such an apparatus is disclosed in GB-A-2 087 534. In this known apparatus, the internal circulation of fluidized bed particles serves for cleaning the inner surfaces of the riser pipes, which, in the case where a strongly polluted medium is treated or heated, may undergo a strong pollution.
Although this known apparatus is highly satisfactory in a large number of cases, drawbacks can be indicated which need to be removed. For a proper distribution of fluid and fluidized bed particles over the riser pipes, a reasonably heavy particle bed, i.e. a fluidized bed having a porosity of approximately 65%, is desirable. When the volume flow in the feed line increases, it is possible that the medium rate above the distribution plates becomes too high, as a consequence of which all particles of the fluidized bed would be blown away from the bottom box. These problems may be prevented by enlarging or expanding the apparatus, but this involves a considerable increase in costs. This is in particular disadvantageous in the case of a fluctuating medium flow, because this sometimes requires additional capacity and sometimes does not. If additional capacity is not required but nevertheless present, this may moreover lead to an a fluidized bed which is insufficiently fluidized and to an irregular distribution of the entrained fluidized bed particles over the riser pipes.
The object of the invention is to provide an apparatus of the type described hereinabove, wherein the drawbacks mentioned have been overcome. According to the invention, this object is realized through the presence of a bypass line having an adjustable flow rarer the arrangement being such that a portion of the medium fed via the feed line can directly be brought above the fluidized bed and flow into the tubes via the openings located above the fluidized bed.
In this manner, an apparatus is obtained wherein the amount of medium fed to the fluidized bed optionally be reduced by causing a portion of the flow to pass the fluidized bed via the bypass line, i.e., relatively large amounts of medium can be processed without involving the danger of a fluidized bed being blown away. Further, it will be understood that as an additional advantage, these features involve the possibility of an optimally functioning fluidized bed by keeping the amount of medium which is conducted through the fluidized bed more or less constant. It is observed that this solution of the above-described problems is based on the inventive insight that the fluidized bed particles should act on the walls of the riser pipes rather than on the medium, while it has further been proved that a reduction of the number of fluidized bed particles per medium unit which is fed through annuls the desired cleaning effect.
Further elaborated embodiments of the apparatus according to the invention relating to an external and an internal bypass line have been laid down in the subclaims.
Embodiments of the apparatus according to the invention are further explained with reference to the accompanying drawings. In these drawings:
FIG. 1 shows a heat exchanger with external circulation of fluidized bed particles;
FIG. 2 shows a detail of the separating device, used in the apparatus
REFERENCES:
patent: 4398594 (1983-08-01), Klaren
patent: 4426958 (1984-01-01), Hosek et al.
patent: 4554963 (1985-11-01), Goodwin et al.
patent: 5033413 (1991-07-01), Zenz et al.
Bronswerk Heat Transfer B.V.
Flanigan Allen J.
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