EP0626550A1

EP0626550A1 - Apparatus for carrying out a physical and/or chemical process, such as a heat exchanger

Info

Publication number: EP0626550A1
Application number: EP94201509A
Authority: EP
Inventors: Dick Gerrit Klaren
Original assignee: Bronswerk Heat Transfer BV
Current assignee: Bronswerk Heat Transfer BV
Priority date: 1993-05-27
Filing date: 1994-05-27
Publication date: 1994-11-30
Anticipated expiration: 2014-05-27
Also published as: EP0626550B1; NL9300915A; ES2110690T3; DE69404756D1; DE69404756T2

Abstract

An apparatus for carrying out a physical and/or chemical process, such as a heat exchanger, comprising a reservoir provided with upwardly-directed tubes, which tubes 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. The invention further comprises means for feeding fluidized bed particles back from the top box to the bottom box. At the bottom end, the bottom box is provided with a bottom pot (6) having a deepened bottom (9) for collecting thereon pollutions from the main flow fed via a feed line (5, 5A) laterally extending into the bottom pot (6), the collected pollutions being removable from the bottom pot (6) by means of a conduit system (10, 14) which discharges a portion of the main flow.

Description

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 and capable of being held in a quasi-stationary, fluidised condition by means of a medium to be treated or heated or cooled which is supplied via the bottom box and flows through the tubes, 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 EP-B-0.065.333. In this known apparatus, the means for feeding fluidized bed particles back from the top box to the bottom box consist of downcomers arranged within the reservoir of the apparatus, via which downcomers a portion of the fluidized bed particles can be brought into, and maintained in, circulation. This 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 or cooled, may undergo a strong pollution. In this connection, the internal circulation and vortex action of the solid particles provide for the cleaning of the riser pipes.
Although this known apparatus is highly satisfactory in a large number of cases, one drawback can be pointed out which needs improvement. This drawback is the following:
Hereinabove, it is observed that on the pipe side, the known apparatus generally involves a very strongly polluted medium. This means that the medium itself may contain solid parts of considerable dimensions, or that the feed lines upstream of the heat exchanger may be subject to pollution due to, for instance, incrustation, which crusts may break off from the walls of these conduits, for instance due to temperature changes in the process, to be subsequently carried along to the heat exchanger. This heat exchanger contains, in the bottom box thereof, at least one distribution plate for supporting the fluidized bed, and although the distribution plates are provided with large holes in a specific pattern or with spray heads which are reasonably well permeable, there is still the danger that the above-mentioned pollutions may stop up the distribution plates, so that the proper operation of the heat exchanger is obstructed.
The object of the invention is to provide an elegant solution to the above-described problem. According to the invention, this object is realized by altering the bottom box of the heat exchanger and also providing it with suitable means such that the above-mentioned pollutions are removed from the flowing medium before the distribution plates are reached. Provisions integrated with the bottom box should cause these pollutions to be eventually carried along and sequestered in a partial flow, which is only a fraction of the main flow to the heat exchanger. Subsequently, the pollutions are regularly removed from this small partial flow. Obviously, a small partial flow can be treated with constructive means of small dimensions. This may be a great advantage in the case where the process of which the heat exchanger is a part takes place at high pressures.
One embodiment of the apparatus according to the invention will be further explained hereinafter with reference to the accompanying drawings. In these drawings:

Fig. 1 shows a bottom box comprising means for removing large pollutions from the flowing medium before the distribution plates are reached; and
Fig. 2 shows a variant of the embodiment shown in Fig. 1.

In Fig. 1, reference numeral 1 designates the casing of the known apparatus including the distribution plates 2 which support the fluidized bed in the heat exchanger. The flowing medium, which may contain pollutions in the form of solid parts of considerable dimensions, is fed to the heat exchanger via the conduits 3, 3A and 3B. The pump 4 provides the required lift and the amount of flowing medium fed is regulated by means of the regulating valve 7. In a normal operating situation, as is discussed hereinafter, the valve 8 is closed. By means of a tangential connection 5, the flowing medium is fed to an enlarged bottom pot 6 via conduit 3B. As a result of the rotation of the flowing medium due to the tangential connection 5, the larger solid pollutions are slung from the flowing medium and collected in the bottom portion 9 of the bottom pot 6. In the bottom pot 6, the cleaned flowing medium is deflected in upward direction toward the distribution plates 2, supporting the fluidized bed.
From the lowest point 9 of the bottom pot 6, the pollutions are carried along with a partial flow, which is fed to the suction side of the pump 4 via the conduit 10, the vale 11, which is completely open, the settler or filter 12, the regulating valve 13 and the conduit 14. Meanwhile, in the settler or filter 12, the separation of the solid parts has taken place. Because the partial flow from the settler or filter 12 to the suction side of the pump 4 is cleaned of coarse solid parts, the regulating valve 13 for adjusting the partial flow is located in conduit 14. Normally, the partial flow will be less than 10% of the main flow. Consequently, the conduits 10 and 14 can have a slighter diameter and the dimensions of the settler or filter 12 can be limited, which limits the investment costs, in particular in the case of high system pressures and/or the use of costly materials. Due to the slight diameter of conduit 14, it is not a prohibitive objection when the pump 4 is disposed at a considerable distance from the heat exchanger 1.
Obviously, the settler or filter 12 has to be cleaned at regular times. For this purpose, this settler or filter is isolated from the arrangement by closing the valves 11 and 13, after which the settler or filter can be opened and the solid parts can be removed. The settler or filter can be used continuously (except for the short cleaning periods) but also intermittently.
It is possible that when the solid parts are sucked up from the bottom pot 6 by means of conduit 10, blockage of the inlet opening of conduit 10 occurs. This can be remedied by changing the direction of the flow in conduit 10 for a short period, by closing valve 11 and opening valve 8 and closing regulating valve 7 slightly further so as to cause a partial flow from conduit 3A to conduit 10. The reversed partial flow will undo the blockage of the inlet of conduit 10 and, moreover, loosen the heaped-up solid parts in the bottom pot 6 somewhat, so that when the partial flow is reversed again to the normal situation (i.e., when the valve 11 is open and the valve 8 is closed), the solid parts are carried along by the partial flow more easily.
Fig. 2 shows a variant with an altered bottom pot. Instead of an enlarged bottom pot 6 with tangential supply 5 of the main flow, the bottom pot has the same diameter as the bottom box of the heat exchanger wherein the distribution plates 2 are mounted, and the main flow is centrally supplied to the bottom pot 6 by means of supply 5A. The separation of the solid parts is less effective, which is compensated by using distribution plates with slightly larger openings, if necessary in combination with a slightly higher bottom pot 6. However, the constructive advantages of this variant are substantial, in particular in the case where existing installations are converted.
The above-discussed situation is based on the assumption that the partial flow does not leave the total installation. This is important in particular in the case where the flowing medium is dangerous or harmful. Of course, there may be cases where the partial flow is not supplied to the suction side of the pump 4 via conduit 14, but is drained off toward the surroundings without involving any danger to the surroundings.

Claims

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, at least one distribution plate being arranged in said bottom box for supporting a fluidized bed consisting of granular material and capable of being held in a quasi-stationary, fluidized condition by means of a medium to be treated or heated or cooled which is supplied via the bottom box and flows through the tubes, said apparatus further comprising means for feeding fluidized bed particles back from the top box to the bottom box, characterized in that the bottom box, at the bottom end thereof, is provided with a bottom pot (6) having a deepened bottom (9) for collecting thereon pollutions from the main flow supplied via a feed line (5, 5A) laterally extending into the bottom pot (6), the collected pollutions being removable from the bottom pot (6) by means of a conduit system (10, 14) discharging a portion of the main flow and having connected thereto a settling reservoir or filter (12), of which conduit system one end (10) ends at a distance above the deepened bottom (9) and the other end (14) is connected to the main feed line (3) at the suction side of the main flow supply pump (4).
An apparatus according to claim 1, characterized in that the bottom pot (6) is enlarged relative to the bottom box (5), the feed line for the main flow extending tangentially into the bottom pot (6).
An apparatus according to claim 1, characterized in that the bottom pot (6) has the same diameter as the bottom box (5), the feed line (5A) for the main flow extending centrally into the bottom pot (6), having a downwardly directed mouth.
An apparatus according to any one of claims 1-3, characterized in that between the main flow feed line (3, 3A, 3B) and the conduit system (10, 14) discharging a portion of the main flow, a bypass with a valve (8) is arranged for periodically conducting a partial flow to the end (10) of the conduit system (10, 14) in a direction opposite to the usual direction of flow, for remedying blockages, if any, in said end (10).