Sparge pipe assembly for fluidised bed

Details Sparge pipe assembly for fluidised bed Sparge pipe assembly for fluidised bed

1986-10-02

1988-11-01

Schwartz, Larry I.

Drying and gas or vapor contact with solids

Apparatus

With apparatus using centrifugal force

34 57B, 34 57E, F26B 1710

Patent

active

047809663

DESCRIPTION:

BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION(S)

This United States application stems from PCT International Application No. PCT/GB86/00082 filed Feb. 19, 1986.


FIELD OF THE INVENTION

This invention relates to a fluidised bed containing a mass of particulate material which can for example be in the form of granulated solid fuel or ash that results from combusting solid fuel. Alternatively the bed may consist of refractory particles used, inter alia, for the heat treatment of a component or components immersed in the bed, for removal of plastics or paints or contaminants from such components or for any other purpose in which said component or components are required to be immersed in a predetermined atmosphere and within a predetermined temperature range. Further uses are in connection with various chemical reactions or where the aforementioned components are of such a size that they may themselves be fluidised in order to achieve a chemical reaction or heat treatment. A further application is where refractory particles are used to transfer heat from a hot fluidising gas to a heat exchanger so that heat is transferred from the fluidising gas to a separate gas or liquid. In all the aforementioned cases however it is to be understood that, in use, the aforementioned particulate material or refractory particles are fluidised by means of a fluidising gas which is admitted into the bed.


BACKGROUND ART

Hitherto, the particulate fluidising media have been supported on a diffusion tile, which tile may be made from a porous ceramic or porous metal, or from a metal plate punched or machined with a plurality of apertures. Difficulties can, however, arise in using such diffusion tiles. For example, all such tiles are difficult to seal around their periphery and it is not easy to replace damaged or worn tiles. Furthermore, problems arise from differential thermal expansions which may give rise to cracked ceramic tiles or buckled metal tiles. Also holes or apertures in metal tiles are frequently clogged by the fluidising media or by solid residues in some fluidising gases. Yet another disadvantage of using diffusion tiles is that it is not possible to keep separate different components of the fluidising gas before it enters the bed. Such separation is necessary if the gaseous components form an ignitable or explosive mixture because light-back may occur through the diffusion tile or the tile may be overheated as a result of flame burning on its surface.
To overcome some of the aforementioned disadvantages it has previously been proposed to make an apertured tube or sparge pipe assembly located within the container adjacent to its base and connected to a source of fluidising gas disposed outside the container. Such an arrangement possesses disadvantages. When in a non-fluidising or rest condition some of the particulate fluidising material may enter the sparge pipe via the apertures and thereby subsequently impair the efficiency of the distribution of fluidising gas and in some cases actually block all or part of the sparge pipe. Another disadvantage results from the fact that, in order to avoid lateral pressure drops in the length of the sparge pipe, the fluidising gases are introduced to said pipes at a plurality of points along their length by supply tubes which are fixed to the relatively cool base of the container, and this arrangement results in differential thermal movements of the sparge pipe relative to the supply pipes which, in turn, gives rise to distortion and cracking of the assembly. Yet another problem is that the sparge pipe is usually unevenly heated so that, for example, the top of the pipe in the fluidising area of the bed becomes hotter than the bottom of the pipe adjacent to the cooler container base. This causes distortion of the sparge pipe along its lateral axis. Yet another disadvantage is that particulate fluidising material in a deep bed suffers from a hysteresis effect at the onset of fluidisation. This is caused by initial differential pressures along the length of the sparge pipe, so that ga

REFERENCES:
patent: 3740865 (1973-06-01), Laguilharre
patent: 4032300 (1977-06-01), Packer
patent: 4241021 (1980-12-01), Skrzec
patent: 4606135 (1986-08-01), Morin

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