This invention relates to a method- of sealing at a fluidized bed and to a device for carrying out the method. Said sealing refers 5 primarily to openings between zones or sections in the bed or between the bed and its surrounding.

.. A fluidized bed consists in principle of a container, which part-

• ially is filled with scϋd small particles, of which by-injection of gas, usually through the container bottom, the major part is

• ^Q maintained suspended, in such a manner, that the suspended part¬ icles and the gas together constitute a system, which owns many properties of a fluid. In order to bring about and maintain fluid- ization, of course, certain conditions must be met.

^• -It was found that a very good and uniform heat transfer can be ^• 5 achieved between the bed, i.e. the suspended particles and the gas, and objects occurring in the bed and having a temperature different from that of the bed. Therefore, fluidized beds are utilized a.o. for the heat treatment of, for example, large work¬ pieces of steel, which require efficiently controlled and uniform 0 heating and cooling in order a.o. not to get distorted.

Fluidized beds also can be used as "cooling beds" for the cooling of cast or hot-worked, for example hot-rolled products in conn¬ ection, for example, with steel manufacture. Fluidized_b§dε_σf£er in this respect a number of advantages, such as reduced bed size ^■■ and improved environment in connection to the bed, compared with cooling beds using free or forced air cooling as in conventional cooling beds.

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, For controlling the cooling, it may be expedient in many cases to divide the bed into several zones or sections, through which the workpieces to be cooled in the bed are to pass.

One problem in connection therewith, of course, is to effect seal- ing between said zones. The workpieces namely are to be transport¬ ed between the zones, i.e. are to be transferred from a certain zone to an adjacent zone after having stayed for a certain period in said firstmentioned zone, and for this reason there..must: be . openings between the zones. A corresponding problem prevails in connection with the introduction of workpieces into the bed and their removal out of the same. Transfer of bed material between the zones can be tolerated only to a small degree, because other¬ wise the possibility of adjusting and controlling would be poor. Bed material must not leak out from the bed, either, when the workpieces are being fed in and discharged, because such leakage" would yield .a.o. an unsatisfactory environment about the bed and increase operation costs.

It was found very difficult at the infeed and discharge to effect sealing between the zones by applying conventional technique. The difficulty is due to several factors, a.o. high temperature as well as clogging and wear caused by the bed material. The cooling bed has to meet very high requirements on relia-ble oper¬ ation, because the bed mostly must be capable to receive workpiec¬ es at the rate and time at which the workpieces are delivered from the equipment, for example a rolling mill in which they have been worked.

The present invention relates to a method and a device for sealing, ^• at which a.o. the bed material is utilized, and the sealing is not stationary, but is built up partially during operation.

The invention, thus, relates to a method of sealing an opening between two zones in a fluidized bed and/or between the bed and its surrounding, in which bed particles are intended to be maint¬ ained suspended by means of a carrier gas, which is introduced into the bed bottom beneath the level of said opening, through

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> which primarily workpieces to be treated in the bed are intended to pass, and which opening, for example, is a horizontal gap in a vertical partition wall between the zones or between the bed and its surrounding.

5 The method is characterized in that a heap or several heaps of particles, by utilizing the movements of the particles and carrier gas in the bed, are caused to build up at said opening to such a height, that the opening is covered or substantially covered by

^• the heap/heaps of particles, and that workpieces at their passage • ^Q through the opening, and therewith through the sealing, demolish the heap/heaps, whereafter said heap/heaps is/are built up again during and/or after the passage of the workpieces.

The invention also relates to a device for sealing an opening betw¬ een two zones in a fluidized bed and/or between the bed and its

1 surrounding,- in which bed particles are intended to be maintained suspended by means of a carrier gas intended to be introduced in . the bed bottom beneath said opening, through which opening prim¬ arily workpieces to be treated in the bed are intended to pass, and which opening is, for example, a horizontal gap ina partition 0 wall between the zones or between the bed and the surrounding and

• where, by utilizing the movements of the particles and carrier gas in the bed, one or several heaps are intended to be built up to cover or substantially cover said opening.

The device is characterized in that a plane, such as a metal sheet 5 or similar object is located in connection to the lower edge of said opening, that said metal sheet/sheets is/are arranged so that said workpieces are allowed to pass through the opening, and so ^" that said heap/heaps is/are allowed to be built up on said metal sheet/sheets, which is/are arranged horizontally in connection to

30 •said lower edge and project from said partition wall, so that the width of the projecting sheet portion/portions at least extends to the height of said opening.

The invention is described in greater detail in the following,

with reference to the accompanying drawing, in which Fig. 1 shows schematically an embodiment of a fluidized bed for the cooling of workpieces, where sealing between the zones of the bed and at infeed and discharge is effected by embodiments of sealings according to the present invention, which Figure is a vertical section through the bed in parallel with the intended feed direction of the workpieces, Fig. 2 is a section corresponding to that in Fig. 1 through a _. first embodiment of a sealing according to the invent ion between two zones in the bed, Fig. 3 is a section corresponding to that in Fig. 1 through a second embodiment of a sealing according to the inven ion between two zones in the bed, and Fig. k is a section corresponding to that in Fig. 1 through a sealing according to the invention at an infeed or discharge opening of the bed.

The fluidized bed shown schematically in Fig. 1 comprises a cont ainer 1, which encloses the main part cf the bed. The bed has substantially rectangular or square horizontal cross-section.

The said container 1 is substantially parallelepipedic and parti filled with solid small particles 2, which are intended to be maintained suspended by means of a carrier gas, which usually is introduced at the bottom 3 of the bed, container, as indicated by arrows in Fig. 1. Preferably ir- the roof h of the container 1 outlets 5 for carrier gas having passed through the bed as indic ated by arrows in Fig. 1 are located.

For the transport of workpieces 6 to be treated in the bed, a ^• conveying means 7 of a suitable kind is provided so that at an opening 8, for example in the form of a horizontal gap δ in one of the vertical outer walls 9 of the container 1 , workpieces 6 are introduced into the bed, transported through the bei and re¬ moved therefrom through an opening 10, corresponding to the open¬ ing 8, in a second corresponding outer wall 9, preferably the one which includes the opening 8, as shown in Fig. 1.

1 ^' 1 designates vertical partition walls in the bed which in this case are two in number and arranged so as to divide the bed into three zones 12,13 and 1*f, respectively. Each partition wall 11 includes at least one opening 15 ₅ each having the form of, for example, a horizontal gap of a definite height, through which the workpieces 6 are intended to pass.

In Fig. 2 the opening 15 between the zones 12 and 13 in the partit¬ ion wall 11 is shown in greater detail. In connection to the lower edge 16 of the opening 15 a plane 17 _ι such as a metal sheet 17, is located horizontally and projects from the partition wall 11 so that the width of the projecting portion cr portions at least amounts to the height of the opening 15 _> i.e. the distance between its lower edge 16 and its upper edge 18. In Fig. 2 an embodiment is shown, where said plane or metal sheet 17 projects substantially an equal distance in each zone 12,13- In Fig. 3 an embodiment is shown, where' the metal sheet 17 projects a substantially longer distance in the zone 13 than in the zone 12.

On said plane or metal sheet 17 one or several heaps 19 of particl¬ es 2 are intended to be built up by utilizing the movements of the particles 2 and carrier gas in the bed. Said heap/heaps 19 are •built up on the upper surface 20 of said metal sheet. The width of said metal sheet portions projecting from the partition wall 11 should be at least a distance, which approximately corresponds to the height of said opening 15 or exceeds said distance so that the heap/heaps 19 being built up assume such a height,that the opening iε covered by the heap/heaps. The height assumed by the heap/heaps depends, in addition to said width, also on the operation characteristics of the bed, such as fluidization degree, gas rate etc. The width, therefore, must be adjusted to these characteristics.

The heap/heaps 19 are built up, in tϋat the upper surface of the metal sheet 17 partially iε shielded off from the flow of gas and particles which is directed upward from the bottom 3 as indicated by the arrows in Figs. 2 and 3. When said metal sheet 17 projects

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' substantially an equal distance in each zone, as in Fig. 2, a sub¬ stantially symmetric heap is formed, its "top" being at the partit ion wall 11 and inclining therefrom down to the metal sheet 17* When the metal sheet, as in Fig. 3, projects substantially only in one of the zones, the grsater part of the heap will be found in this zone.

When in each zone a metal sheet 17 projects which is long in relat ion to the gap height, the build-up of a heap 19 in each zone can ^: be imagined.

The metal sheet 17, of course, is arranged so that said workpieces are allowed to pass through the opening 15, nd, for example, is arranged horizontally as shown in Figs. 1-3*

The function of the sealing is as follows. Workpieces 6, shown in Fig. 2 but hot in Fig. 3, are transported through the bed by a conveying means (not shown in Figs. 2 and 3) and are caused to pas ■ through the openings 15» Hereby, the sealing heap/heaps 19 at each opening are demolished at the passage of each workpiece 6. During and after the passage of each workpiece 6 the heap/heaps 19 are built up again by the particle and gas movements in the bed.

in Fig. the zone 14 of the bed and the opening 10 are shown. 22 designates the surrounding of the bed. In connection to the lower edge 23 of said opening 10 a metal sheet 2h or the like is located which includes a substantially horizontal portion 25 corr¬ esponding to the metal sheets 17, and a longitudinal upward angled portion 26 located substantially in the surrounding 22of the bed, i.e. on the outside of the bed.

The function of the sealing between the bed and its surrounding 22 is substantially the same as at the sealing between zones in the bed, i.e. one/several hejvp/heaps 27 of particles are built up to such a height that the opening 10 is covered. The angular metal sheet portion 26 forms a pocket, in which particles are collected which have accumulated on the workpieces 6 and drop down when the workpieces are removed from the bed through the opening 10. The

particles are hereby returned to the sealing heap/heaps 27-

For sealing between the bed and the surrounding 22 according to above at the feed opening 8 or discharge opening 10, the opening can be arranged either below the upper surface 28 of the bed as in Fig. 1 or above the upper surface 28 of the bed as in Eάg. . When the opening is located above the upper surface 28 of the bed, the heap/heaps are built up of particles torn off from the bed and of particles taken along by the workpieces 6. In this connection the particle amount can be completed, for example by returning torn-off particles.

The method according to the invention and some embodiments of a device for carrying out the method have been described above.

It should have been understood therefrom that sealing according to • the invention can be carried out simply, cheaply and without any such problems as they normally arise at sealing in the environment ' here concerned. The sealing,- thus, is substantially maintenance- -free and completely reliable in operation.

It is, of course, possible to imagine a plurality of embodiments of a sealing according to the invention, without abandoning the invention idea. The metal sheet 17, for example, cay consist of several parts, for example two, and the portion projecting in each zone may be arranged, for example, slightly below the lower edge 16 of the opening 15 and be angled upward in order, when necessary, to improve the retention capacity of particle heaps. Alternatively, an outer portion of each-projecting portion can be angled upward.

^• The said openings 8,10,15 need not be designed as horizontal gaps, but sealing according to the invention is applicable to any opening form, for example circular.

When sealing a feed opening or a discharge opening, the sealing can be made still more effective by controlling the difference in pressure between the bed and the surrounding. The pressure differ-

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ence should be small above the opening. Preferably a certain vacuu should prevail in the bed portion adjacent the opening relative to the suroounding.

The invention, thus, must not be regarded restricted to the embod- iments described above, but can be varied within the scope of the attached claims.

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