ZA200203795B - "A fluidized bed apparatus." - Google Patents

Description

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A FLUIDIZED BED APPARATUS

THIS INVENTION relates to a fluidized bed apparatus. More particularly, the invention relates to a spouting fluidized bed apparatus

Known fluidized bed apparatus have many different applications including the drying of particulate products, the gasification of particulate products, the combustion of particulate fuels, the drying and roasting of nuts and seeds, and the like. All the above applications involve the passage of a gas through a bed of particles and thereby creating a fluidized bed of particles, within which required physical and/or chemical reactions can occur, as is determined by the particular application of the apparatus.

Each spouting fluidized bed apparatus known to the Applicant generally comprises a hollow body that defines an internal space including a downwardly tapering lower section, the hollow body defining a gas inlet opening at its operative lower end which leads into the internal space and which communicates, directly or indirectly, with a gas feed duct. From the operative upper end of the tapering lower section of the internal space defined by the hollow body, the walls of the hollow body define an upper section of the internal space that extends upwardly, leading to a gas outlet duct which extends from the hollow body and which provides for the passage of gases from the internal

CONFIRAMTION COPY

- 2 - Co * space defined by the hollow body. The apparatus provides also for the feed of particulate product into the internal space defined by the hollow body and for the discharge of particulate product from the hollow body, which can take place in various different modes.

In operation, for example for drying a particulate product, the particulate product to be dried can be fed into the hollow body via the gas outlet duct, the particles forming the product effectively dropping under gravity into the tapering lower section of the internal space defined by the hollow body. Heated gas is fed into the hollow body via a gas feed duct leading to the gas inlet opening defined at the operative lower end of the hollow body, the heated gas thus passing through the bed of particles formed in the said lower section of the internal space defined by the hollow body. As the gas flow rate:increases through the bed of particles, a point is reached where the gas pressure drop marginally exceeds the mass of the particles forming the particulate product bed, the ‘particles thereby becoming partially suspended in the air stream. As gas flow } increases even further, an expansion of the bed of particles takes place, a vigorous boiling action being created similar to a boiling liquid. Thereby, the bed of particles is said to be fluidized.

The flow pattern of gas through the bed of particles results in a spouting action of particles in the upper region of the fluidized bed, this region being referred to as the free-board space from which spouted particles will drop back into the bed of particles.

In its fluidized state, the particles behave like a fluid insofar as a specific particle level can be detected, this level being controllable and facilitating also the removal of particles from the hollow body via overflow weirs, or the like, in order to be conveyed to a following process stage. Insofar as the exact operation and functioning of a spouting fluidized bed apparatus is well known and as this does not constitute a part of the present invention, this is not described in further detail herein.

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It is an object of this invention to provide a fluidized bed apparatus which is particularly " suitable for fluidized bed applications where feed material and dried product material i. vary in size and density. Clearly, although the fluidized bed apparatus of the invention is considered particularly suitable for the above applications, it can be utilized also for other conventional applications, or such applications that are considered specifically suitable in conjunction with the apparatus of the invention.

According to the invention there is provided a spouting fluidized bed apparatus, which includes a hollow body that defines an internal space including a downwardly tapering lower section defining a longitudinal axis and a truncated V-shaped profile in cross : section along the length thereof and terminating in an elongate slot-like gas inlet opening , defined at the operative lower end of the hollow body, and an upper section

LL extending‘operatively upwardly from the upper end of the lower section, leading to a gas outlet defined by the hollow body near the operative upper end of the internal space, the hollow body defining a particulate product inlet opening connectable to a particulate product supply source for feeding product into the lower section of the internal space defined by the hollow body; an elongate tray formation which is positioned operatively beneath the gas inlet opening defined at the operative lower end of the hollow body, the tray formation having a base platform spaced from the operative lower end of the hollow body and side walls extending upwardly in an overlapping spaced configuration with respect to the walls of the hollow body that define the tapering lower section of the internal space defined by the hollow body, providing for slot-like passages to be defined between the side walls of the tray formation and the said walls of the hollow body through which gases can pass to enter the said gas inlet opening defined at the operative lower end of the hollow body;

- 4 - Co ¥ a plenum chamber body that defining a chamber that surrounds at least partially the lower section of the hollow body including the tray formation and that defines a gas inlet opening connectable to a gas supply, permitting a gas to enter the chamber and pass into the hollow body via the said slot-like passages and the said gas inlet opening; and a particulate product discharge means for discharging particulate product from the hollow body.

A preferred embodiment of the invention provides for the side walls of the elongate tray formation to extend in a substantially parallel, spaced, overlapping relationship with 0 respect to the walls of the hollow body defining the tapering lower section of the “internal space defined by the hollow body and providing for slot-like passages between the said side walls of the tray formation and the said walls of the hollow body. The said slot-like passages accordingly will guide gases passing through these passages . onto the base platform of the tray formation, to be deflected towards a central region 5 disposed intermediate between opposite sides of the tray formation, where the gases willimpinge and be directed operatively upwardly through the gas inlet opening defined at the operative lower end of the hollow body into the internal space defined by the holiow body.

In use, the upwardly directed gases will flow through particulate products within the 0 lower section of the internal space defined by the hollow body, providing for the formation of a fluidized bed. The particulate product simultaneously will be lifted from the tray formation to a raised level above which the fluidized bed will be defined. The motion of the particles forming the fluidized bed otherwise will be essentially conventional, with spouting particles dropping back into the fluidized bed, as is 5 commonly associated with a spouting fluidized bed apparatus.

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The fluidized bed apparatus, in accordance with the invention, also can be associated

CC with any further features commonly associated with a spouting fluidized bed apparatus of the type herein envisaged and insofar as the configuration of the fluidized bed apparatus of the invention in this regard is greatly variable, the invention extends also to such alternative configurations fluidized bed apparatus which incorporate the principles of the invention as herein defined.

Further features of the invention, including the operation of the invention, are described hereinafter, by way of example, with reference to the accompanying diagrammatic drawing which illustrates schematically in end view a segment of the hollow body of a spouting fluidized bed apparatus, in accordance with the present invention. : Referring to the drawing, a segment of the hollow body of a spouting fluidized bed apparatus, in accordance with the invention, is designated generally by the reference ] numeral 10. The hollow body defines an internal space 11 including a downwardly tapering lower section 12 that defines a longitudinal axis and a truncated V-shaped profile in cross section along the length thereof, the lower section 12 of the space 11 thus terminating in an elongate slot-like gas inlet opening 14 defined by the hollow body at the lower end thereof. The internal space defined by the hollow body further includes an upper section 16 extending operatively upwardly from the lower section 12, the upper section leading to a gas outlet (not shown), also defined by the hollow body.

The hollow body defines also a particulate product inlet (not shown) through which particulate products can be fed into the hollow body, to drop under gravity into the lower section 12 of the internal space defined by the holiow body.

Operatively beneath the gas inlet opening 14 defined by the hollow body at the lower end thereof, there is provided an elongate tray formation 18, the tray formation 18 having a base platform 20, disposed operatively beneath the opening 14, and side walls 22 extending from the base platform 20 in a parallel, spaced, overlapping relationship with respect to the operative bottom segments of the walls 24 that define the lower

Le WO 01/36082 PCT/IB00/01649 - 6 - CT section 12 of the internal space defined by the hollow body. Passages 30 for gases therefore are defined between the walls 24 of the hollow body and the side walls 22 of the tray formation 18, which gases can then enter the internal space defined by the hollow body via the gas inlet opening 14, as is described in more detail hereafter.

The lower section 12 of the internal space defined by the hollow body is surrounded by a plenum chamber body 26 which is formed of walls 28 defining a chamber, the plenum chamber body having a gas inlet opening through which gases can be fed into the chamber to pass from the chamber into the internal space defined by the hollow body of the fluidized bed apparatus.

The “apparatus also includes a particulate product discharge means for discharging - particulate product from the hollow body, this discharge means not being illustrated in the ‘drawing and comprising essentially conventional discharge means as is commonly associated with spouting fluidized bed apparatus of the type herein envisaged. The . discharge means accordingly may comprise an overflow weir, or suitable feed pipes, that can feed particulate product from the hollow body to a required destination where further processing, or the like, can occur.

With the apparatus connected in line with other components and parts associated with a typical spouting fluidized bed apparatus, which typically may provide for drying of a particulate product, the product can be fed into the internal space defined by the hollow body to fill the lower section 12 of the space. It will be appreciated that without fluidizing gases entering the hollow body, the particles forming the particulate product will rest on the tray formation 12.

Hot fluidizing gases can then be displaced into the chamber defined by the plenum chamber body 26 and from there via the passages 30 into the space beneath the inlet opening 14 defined by the hollow body. Gases so entering the said space will be deflected along the base platform 20 of the tray formation 18 towards a central region

! intermediate between the opposite sides of the base platform 20, where the gases will impinge on one another and be directed operatively upwardly to pass through the bed of particulate product formed above the base platform 20. By increasing the flow rate of gases entering the hollow body 12, a fluidized bed of particles will be generated in a conventional manner, further increasing of the flow rate of gases simultaneously providing for the entire body of particles to be lifted from the base platform 20, forming a virtual bed 32, above which the fluidized bed of particles will be defined. A proportion of the gases entering the hollow body 12 via the opening 14 will follow a circulating path within the space 34 beneath the virtual bed 32, to generate the configuration of the fluidized bed of particles as shown, the heated gases directed through the bed of particles also causing spouting of particles, particularly in the central region of the bed. Such particles will drop back into the bed in a location towards the - outer sides of the bed. The arrows illustrated in the drawing illustrate both the direction of gas flow through the fluidized bed, as well as the direction of particle movement, which in combination will provide for an extremely effective fluidized bed operation for drying the particles within the apparatus. In particular, the velocity profile of gases passing through the bed of particles will provide for a maximum velocity in the centre region between opposite sides of the inlet opening 14 and decreasing velocities on opposite sides of this centre region, towards the side edges by the opening 14, thus inducing the spouting action while permitting also the required circulation of particles within the bed of particles. This velocity profile clearly will be substantially constant along the entire length of the hollow body 12.

Clearly, other fluidized bed applications can be similarly carried out, it being envisaged that the fluidized bed apparatus as described will be particularly suitable for applications where feed material and dried product material vary in size and density. The applications of the fluidized bed apparatus, however, is not restricted to such applications and can be employed also for various other conventional and special applications.

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It will be appreciated that the segment of the hollow body of the spouting fluidized bed apparatus of the invention as shown will be combined with features associated with conventional spouting fluidized bed apparatus of the type herein envisaged and insofar as these features may be greatly variable, this is not described in further detail herein.

Clearly, the features to be associated with the apparatus will be determined particularly by‘the intended applications of the apparatus and particularly also by required operating capacities, the particulate products involved, and the like.

Claims (3)

. . 9g. CLAIMS

1. A spouting fluidized bed apparatus, which includes a hollow body that defines an internal space including a downwardly tapering lower section defining a longitudinal axis and a truncated V-shaped profile in cross section along the length thereof and terminating in an elongate slot-like gas inlet opening, defined at the operative lower end of the hollow body, and an upper section extending operatively upwardly from the upper end of the lower section, leading to a gas outlet defined by the hollow body near the operative upper end of the internal space, the hollow body defining a particulate product inlet opening connectable to a particulate product supply source for feeding product into the lower section of the internal space defined by the hollow body; ] an elongate tray formation which is positioned operatively beneath the gas inlet opening defined at the operative lower end of the hollow body, the tray formation having a base platform spaced from the operative lower end of the hollow body and side walls extending upwardly in an overlapping spaced configuration with respect to walls of the hollow body that define the tapering lower section of the internal spacers defined by the hollow body, providing for slot-like passages to be defined between the side walls of the tray formation and the said walls of the hollow body through which gases can pass to enter the said gas inlet opening defined at the operative lower end of the hollow body; a plenum chamber body defining a chamber that surrounds at least partially the lower section of the hollow body including the tray formation and that defines a gas inlet opening connectable to a gas supply, permitting a gas to enter the chamber and pass into the hollow body via the said slot-like passages and the said gas inlet opening; and

- 10 - oe Y a particulate product discharge means for discharging particulate product from the hollow body.

2. An apparatus as claimed in Claim 1, in which the side walls of the elongate tray formation extend in a substantially parallel, spaced, overlapping relationship with respect to the walls of the hollow body defining the tapering lower section of the internal space defined by the hollow body and providing for the slot-like passages between the said side walls of the tray formation and the said walls of the hollow body.

3. A spouting fluidized bed apparatus substantially as described in the specification with reference to and as illustrated in the accompanying drawings.