ITMI20111125A1 - FLUID BED SYSTEM FOR TREATMENT OF SOLID PARTICLES AND FLUIDIZATION GAS DISTRIBUTOR DISC FOR SUCH EQUIPMENT - Google Patents

Description

Title: Fluidized bed apparatus for the treatment of solid particles and fluidizing gas distributor disc for this apparatus

DESCRIPTION

Background of the invention

The present invention relates to a fluidized bed apparatus for the treatment of solid particles, in particular comprising a containment casing in which a chamber for the treatment of such particles is defined.

The invention also refers to a distributor disc for a fluidization gas for this apparatus.

In the following description and in the subsequent claims, with the term: treatment, it is intended to indicate at least one of the following operations to which the solid particles can be subjected: mixing, drying, granulation, coating / stratification.

In particular, with the term: mixing, it is intended to indicate an operation by which solid particles of different types, for example in size and / or composition, are intimately mixed together.

With the term: drying, we mean both a process by which the solid particles incorporating an aqueous or non-aqueous solvent are dried, or the solvent content is reduced (humidity in the case of an aqueous solvent), and a process by which a liquid coating material is dried so as to form a film on the solid particles.

The term: granulation is intended to indicate any process by which a powdered material is subjected to agglomeration with suitable granulation substances to form granular material.

With the term: coating / stratification, it is finally meant to indicate any process by which the solid particles are covered with a film of an appropriate coating material, liquid or powder; in the first case, the solid particles coated by the liquid coating material are also subjected to drying to dry the previously deposited film and form a uniform coating around each solid particle.

In the following description and in the subsequent claims, with the expression of: treatment material, it is intended to indicate any material used in the treatment of solid particles (drying, granulation, coating / stratification), and can be either in powder form (for for example, a pharmaceutical active ingredient in the case of coating a substantially inert substance used as a support core), and liquid (for example a suitable coating film-forming substance in the case of coating a pharmaceutical active ingredient in powder or pellet).

Related art

Fluid bed apparatuses for the treatment of solid particles are known in the pharmaceutical and food industries. For example, fluid bed apparatuses are known for coating / layering solid particles such as a pharmaceutical active ingredient or a food substance with a suitable coating substance.

Fluidized bed apparatuses typically include a treatment chamber, in which the solid particles to be treated, loaded in the form of a bulk mass, are kept in suspension by a flow of a suitable fluidization gas. The solid particles suspended in the treatment chamber can thus be subjected to mixing, drying, granulation or coating / stratification processes. For example, in the case of coating / stratification, the solid particles in suspension are covered with an appropriate coating liquid and are at the same time subjected to drying by the action of the fluidization gas (for example air) which is heated to a suitable temperature in order to consolidate the coating film previously deposited on the solid particles.

US patent US 4 970 804 discloses a fluidized bed apparatus for the production and / or further treatment of a granular material. This fluidized bed apparatus comprises a vessel with approximately rotational symmetry with respect to a vertical axis, of which it is made up of:

an inlet chamber crossed from bottom to top by a fluidization gas,

a vortex chamber traversed from bottom to top by the fluidization gas placed above the inlet chamber and formed to fluidize the granular material,

- a ring formed by guide plates, inclined with respect to the vertical axis and superimposed on each other, which give a spiral movement to the flow of fluidization gas directed into the vortex chamber, and

- nozzles for introducing treatment materials into the vortex chamber as suitable granulation substances.

A mechanism is provided for tilting the guide plates substantially orthogonally with respect to the vertical axis of the apparatus, so as to position the guide plates in a first operating position in which they form an angle of approximately 75 ° with respect to the The vertical axis of the container and in a second non-operative position in which they are substantially horizontal and in tight contact with each other, so that the granular material produced can collect above them and be subsequently discharged.

In recent times, the Oystar Huttlin company has marketed fluidized bed apparatuses equipped with a fluidizing gas distributor disk called "Diskjet". This distributor disk is placed at the base of the respective treatment chamber and is provided with a plurality of thin radial slits to distribute in the treatment chamber a flow suitable for keeping the solid particles to be treated in suspension. For this purpose, the radial slots are made in the thickness of the distributor disc with a predetermined inclination with respect to the plane of the disc itself. In this way, the radial slots channel the fluidization gas and generate a substantially spiral fluidization gas flow downstream of the distributor disc.

Summary of the Invention

The Applicant has verified that the aforesaid known type fluidized bed apparatuses have a series of drawbacks to which an adequate solution has not yet been given. In relation to the fluidized bed apparatus disclosed in US 4 970 804, the Applicant has found that it has at least the following drawbacks:

- a high manufacturing cost correlated to the need to realize numerous structurally independent guide plates, to mount them in partial reciprocal overlap ensuring the seal when they are in mutual support in the aforementioned non-operative position and to provide control mechanisms to vary the inclination of the guide plates;

- a high operating cost, correlated to the high pressure drops that are generated upon crossing the gas passages defined between the partially overlapping guide plates; And

- significant practical difficulties in cleaning the plates.

The Applicant has also found that the fluidized bed apparatus disclosed in US 4 970 804 has the further drawbacks of an imperfect seal between the guide plates in their operating position with undesirable product losses, and of allowing an unwanted deposit of particles between the radially external end of the guide plates and the internal wall of the vortex chamber, all with a further unwanted loss of product and with an aggravation of cleaning operations subsequent to the treatment of the solid particles.

In relation to the fluidized bed apparatus marketed by Oystar Huttlin and equipped with the distributor disk called "Diskjet" and structured in the manner described above schematically, the Applicant has found that it has at least the following drawbacks:

- a high manufacturing cost correlated to the need to make the aforementioned numerous thin radial slots in the thickness of the disc;

- a high operating cost, correlated to the high pressure drops that are generated when passing through the thin radial slits; And

- significant practical difficulties in cleaning the slits themselves at the end of the treatment operations.

The Applicant therefore perceived the possibility of overcoming the drawbacks highlighted above and, more particularly, the possibility of providing a fluidized bed apparatus for the treatment of solid particles capable of achieving an efficient treatment of solid particles, both from qualitative and process point of view, with a simplified structure and with lower operating and maintenance costs compared to the prior art cited.

The invention therefore relates, in a first aspect, to a fluidized bed apparatus for the treatment of solid particles according to claim 1.

In particular, the invention relates to a fluidized bed apparatus for the treatment of solid particles, comprising:

- a containment envelope in which a chamber for treating said particles is defined;

- a disc for distributing a fluidization gas adapted to keep the solid particles in suspension in said treatment chamber,

- a net positioned above said distributor disc to retain the solid particles to be treated inside the treatment chamber;

in which:

i) the distributor disk is located at the base of said treatment chamber, is substantially formed of a single piece and is provided with a plurality of radial slots to distribute respective flows of the fluidization gas in the treatment chamber;

ii) the distributor disc is equipped with a plurality of deviating fins, each extending below the disc near a corresponding slot, to direct the fluidization gas flows from the slots towards the treatment chamber according to respective ascending paths. substantially spiral;

iii) the gas passage section defined by each radial slot is equal to or greater than 1100 mm <2>; And

iv) the overall gas passage section defined by the radial slits is between 15% and 25% of the total area of the disc.

In the context of this description and in the subsequent claims, all numerical quantities indicating quantities, parameters, percentages, and so on are to be understood in all circumstances preceded by the term â € œaboutâ € unless otherwise indicated. Furthermore, all ranges of numerical quantities include all possible combinations of the maximum and minimum numerical values indicated and all possible intermediate ranges, in addition to those specifically indicated below.

In the context of the present description and in the subsequent claims, with the expressions: "above", "below", "above", "below", "vertical", "horizontal", "upstream" and " downstream ", refer to the configuration of the fluidized bed apparatus for the treatment of solid particles in the operating conditions of use.

In the context of this description and in the subsequent claims, with the expression: "single piece format", it is intended to indicate both an element that is formed in a single piece, and an element formed by rigidly joining a plurality of portions making up the single piece as a whole.

In a first preferred embodiment, the fluidized bed apparatus of the invention can be devoid of dispensing nozzles; in this case, the fluidized bed apparatus can carry out mixing and drying treatments, achieving the advantageous technical effects illustrated below.

In a second preferred embodiment, the fluid bed apparatus of the invention comprises a plurality of dispensing nozzles for delivering a treatment material into the treatment chamber; in this case, the fluidized bed apparatus can carry out both mixing and drying treatments, as well as granulation and coating / stratification treatments, that is to say also treatments in which it is necessary to dispense a suitable treatment material on the solid particles. Also in this case, the advantageous technical effects illustrated below are achieved.

In accordance with the invention and thanks to the aforementioned single-piece conformation of the distributor disc provided with a plurality of radial slots defining a gas passage section as indicated above and a corresponding plurality of deviating fins extended below the disc in proximity of each slot, it is advantageously possible to impart the desired substantially spiral path to the fluidization gas flows, with the consequent advantages in terms of fluidization efficiency and turbulence in the motion imparted to the particles to be treated, with a mechanically simple structure, easy to manufacture and with reduced manufacturing and operating costs.

The whole with a treatment efficiency equal to or higher than that of known type fluid bed systems.

The Applicant has in fact experimentally verified that thanks to the specific distribution of the passage section of the fluidization gas indicated above, with a minimum passage section defined by each radial slot equal to or greater than 1100 mm <2> and with a distribution of the overall gas passage defined by the radial slots as a whole comprised between 15% and 25% of the total area of the disc, it is advantageously possible, with the same flow rate of the fluidization gas, to have both a pressure drop lower than that required by the fluidized bed apparatuses of the known art, is a lower delivery speed of the fluidization gas in the treatment chamber.

These technical effects entail both an advantageous reduction in operating costs and an advantageous increase in the efficiency of the treatment operations, in particular when performing a treatment of granulation or coating / stratification of solid particles, since a delivery speed lower than the fluidization gas allows to reduce the height of the particle fluid bed and therefore reduce the distance between the dispensing nozzles that deliver the treatment material and the particles, which can thus be invested more uniformly and in their all of the treatment material dispensed by the nozzles.

This last technical effect translates in practice into an advantageous reduction of the treatment times at the same flow rate of the fluidization gas and of the treatment material and in an advantageous reduction of the quantity of treatment material supplied by the dispensing nozzles at the same flow rate of the fluidization gas.

In accordance with the invention and thanks to the presence of the mesh positioned above the distributor disc to retain the solid particles to be treated inside the treatment chamber, it is also possible to achieve significant technical advantages in the loading and unloading phases. of the solid particles to be treated.

Contrary to what happens for the known type fluidized bed apparatuses described above, in fact, the solid particles to be treated can be loaded into the treatment chamber of the fluidized bed apparatus even in the absence of any fluidization gas flow since they are retained in the chamber by the net.

The net also allows the solid particles treated at the end of the operations carried out in the fluidized bed apparatus to be discharged in a very simple way without necessarily having to use suction and discharge systems but simply by pouring the particles into a collection container.

In this regard and as will be illustrated in more detail below, the fluidized bed apparatus of the invention is advantageously provided in a particularly preferred embodiment with a removable base portion which at least partially defines the treatment chamber. and which facilitates both the loading and unloading operations of the particles, and the cleaning operations of the treatment chamber, the mesh and the distributor disc.

Further preferred characteristics of the fluidized bed apparatus according to the invention are also defined in the attached dependent claims 2-19, the content of which is incorporated herein by reference.

The invention relates, in a second aspect thereof, to a distributor disc for a fluidization gas for a fluidized bed apparatus for the treatment of solid particles according to claim 20.

In particular, this distributor disc comprises:

- a plurality of radial slots for distributing respective flows of the fluidization gas; - a plurality of deviating fins, each extending below the disc in proximity to a corresponding slot, to direct said fluidization gas flows downstream of the slits according to respective substantially spiral ascending paths; in which:

- the distributor disc is essentially made up of a single piece,

- the gas passage section defined by each radial slot is equal to or greater than 1100 mm <2>; And

- the overall gas passage section defined by the radial slits is between 15% and 25% of the total area of the disc.

Advantageously, the aforesaid distributor disc allows to achieve - thanks to the aforesaid structural characteristics - the advantageous technical effects illustrated above with reference to the fluidized bed apparatus incorporating the disc itself.

Preferred characteristics of the distributor disc according to the invention are defined in the attached dependent claims 21-24, the contents of which are incorporated herein by reference.

Brief description of the figures

Further characteristics and advantages of the present invention will become clearer from the following description of a preferred embodiment thereof, made with reference to the attached drawings, given by way of non-limiting example. In these drawings: - Figure 1 is a schematic perspective view, partially in section, of a fluidized bed apparatus for the treatment of solid particles, according to a preferred embodiment of the invention;

- figure 2 is a schematic perspective view, partially in section, of a detail of the fluidized bed apparatus of figure 1, which shows a top view of a lower portion of a treatment chamber of the apparatus same;

- figure 3 is an exploded perspective schematic view of three components of the fluid bed apparatus of figure 1, and precisely - starting from the bottom - of a distributor disc, a net and a disc deflector cone;

- figure 4 is a schematic perspective view from above, on an enlarged scale, of the distributor disk of figure 3 in a configuration of use thereof;

- figure 5 is a schematic perspective view of the distributor disc of figure 4, in an inverted configuration with respect to the configuration of use, which shows the elements of the disc extended below from it;

- figure 6 is a schematic perspective view from above, on an enlarged scale, of a detail of the distributor disc in inverted configuration illustrated in figure 5, which shows in particular the deviating fins of the distributor disc itself;

- figure 7 is a side elevation view, on an enlarged scale, of some details of the distributor disk of figure 4;

- figure 8 is a schematic top view, on an enlarged scale, of a detail of the distributor disc of figure 4, which shows in particular a radial slot of the distributor disc itself.

Detailed description of the currently preferred embodiments

With initial reference to Figure 1, the numerical reference 10 generally indicates a fluidized bed apparatus according to a preferred embodiment of the invention for the treatment of solid particles 11, for example particles of a pharmaceutical active ingredient in powder form, for example solid particles 11 having an average particle size of about 160 µm.

The fluidized bed apparatus 10 comprises a containment casing 12 in which a treatment chamber 14 is defined, which extends along a substantially vertical longitudinal axis A-A of the fluidized bed apparatus 10.

At the base of said treatment chamber 14 there is a distributor disc 16 for a fluidization gas (for example hot air), which is more clearly illustrated in Figures 2-8. In the preferred embodiment illustrated, the distributor disc 16 is of the static type, ie it is mounted at the base of the treatment chamber 14 without the possibility of relative movement with respect to the chamber itself.

The distributor disc 16 is preferably made of metallic material, for example stainless steel suitable for contact with pharmaceutical or food substances, and is substantially formed of a single piece.

In accordance with the invention, the distributor disc 16 is provided with a plurality of radial slots 18 to distribute in the treatment chamber 14 respective flows of fluidization gas which are designed to keep the solid particles 11 to be treated in suspension.

The fluidization gas exits from the top of the apparatus 10, after being filtered by a filtration unit 15 comprising a plurality of bag filters 8, per se known, of substantially tubular shape.

In the preferred embodiment illustrated, the fluid bed apparatus 10 comprises two dispensing nozzles 30 for delivering a suitable treatment material into the treatment chamber 14.

In an alternative preferred embodiment, not shown, the dispensing nozzles 30 can be in a greater number, for example between two and four.

The treatment material can for example be an aqueous suspension including at least one filming substance.

Preferably, the dispensing nozzles 30 are mounted on the distributor disc 16, preferably on diametrically opposite sides thereof.

For this purpose, the distributor disc 16 comprises respective through openings 16a which are crossed by the dispensing nozzles 30, or by supporting elements thereof.

Preferably, the distributor disc 16 in this case comprises a pair of radial slots 18a, 18b, respectively radially external and radially internal, extending from radially opposite parts of each of said dispensing nozzles 30 or, better, from radially opposite parts of each of the openings pass-throughs 16a formed in the distributor disc 16 and intended to accommodate the dispensing nozzles 30 (see Fig. 3).

In a further preferred alternative embodiment, not shown, the dispensing nozzles 30 can be mounted on the containment casing 12, preferably in correspondence with a base portion 20 of the casing 12, which will be discussed below. Preferably, the dispensing nozzles 30 extend in an inclined direction with respect to the plane of the distributor disc 16 and deliver the treatment material in this inclined direction, so as to facilitate the motion along substantially spiral paths of the fluidization gas and of the particles 11 to be it kept in suspension in the treatment chamber 14.

Preferably, the dispensing nozzles 30 (both in the preferred embodiment in which they are mounted on the distributor disc 16, and in the preferred embodiment in which they are mounted on the containment casing 12) are inclined with respect to the plane of the distributor disc 16. an angle comprised between 30 ° and 50 °, more preferably equal to about 45 °.

Preferably, the distributor disc 16 comprises from 10 to 30, more preferably, from 14 to 24 and, even more preferably, from 16 to 18 radial slots 18.

In the preferred embodiment illustrated, the radial slots 18 are arranged circumferentially equidistant from each other.

In this way, it is advantageously possible to distribute the fluidization gas as uniformly as possible inside the treatment chamber 14, achieving the desired substantially spiral paths of the fluidization gas and of the particles 11 held in suspension by it in the chamber. treatment 14.

For the purposes of the invention, the number of radial slots 18 can be determined as a function of the diameter of the distributor disc 16 and of the gas passage section defined by them and which must be kept within the range of the numerical values described herein. In the preferred embodiment illustrated, the distributor disc 16 has a total number of eighteen radial slots divided as follows:

- 14 radial slots 18 circumferentially equidistant and positioned between the two dispensing nozzles 30; And

- 4 radial slots 18a, 18b extended in pairs on opposite sides of each of the dispensing nozzles 30.

In accordance with the invention, the gas passage section defined by each radial slot 18 is equal to or greater than 1100 mm and, more preferably, between 1100 mm and 1800 mm <2>, while the passage section of overall gas defined by the radial slots 18 is between 15% and 25% and, more preferably, between 18% and 22% of the total area of the disc.

In this regard, it should be noted that in the context of the present description and in the subsequent claims, the additional slots 18a, 18b are not taken into consideration and do not contribute to the definition of the gas passage sections through the distributor disc 16 indicated above.

Thanks to the aforementioned division of the gas passage section, it is advantageously possible, at the same flow rate of the fluidization gas, to have both a pressure drop lower than that required by the fluidized bed apparatuses of the known art, and a lower delivery speed. of the fluidization gas in the treatment chamber 14. As stated above, these technical effects entail both an advantageous reduction in operating costs and an advantageous increase in the efficiency of the treatment operations since a lower gas delivery rate of fluidization allows to reduce the height of the fluid bed of particles 11 and therefore to reduce the distance between the dispensing nozzles 30 for distributing the treatment material and the particles, which can thus be invested more uniformly and in their entirety from the treatment material delivered by the dispensing nozzles 30.

This last technical effect translates in practice into an advantageous reduction of the treatment times at the same flow rate of the fluidization gas and of the treatment material and in an advantageous reduction of the quantity of treatment material supplied by the dispensing nozzles 30 to equal flow rate of the fluidization gas.

Preferably, the radial slots 18, 18a, 18b are formed in the distributor disc 16 within a circular crown defined between two internal circumferences of the disc 16 and respectively having a first radius RI having a value between 15% and 25% of the radius R of the distributor disc and a second radius R2 having a value between 85% and 95% of the radius R of the distributor disc 16 (see Fig. 3).

In this way, it is advantageously possible to confine most of the mass of particles 11 held in suspension by the fluidization gas in the radially innermost area of the treatment chamber 14, increasing the exposure of the particles 11 to the material delivered by the dispensing nozzles 30. and consequently increasing the efficiency of the treatment operations (for example coating with a filming substance). Furthermore, it is advantageously possible to strongly limit the deposits of solid particles 11 on the internal walls of the treatment chamber 14 in proximity to the radially external portion of the distributor disc 16 thanks to the presence of an external circular crown 16c of the disc 16, between the circumference of radius R2 and the outer perimeter edge of the disc 16, without openings and acting as a sealing element against the internal walls of the treatment chamber 14.

In turn, the radius R of the distributor disc 16 is preferably between 400 and 1200 mm as a function of the diameter of the treatment chamber 14 of the fluidized bed apparatus 10 which in turn is a function of the treatment capacity of the apparatus 10.

In accordance with a preferred embodiment and as shown in particular in Figures 3, 4 and 8, the radial slots 18, 18a and 18b formed in the distributor disc 16 are radially tapered towards the center of the disc 16.

In this way, it is advantageously possible to distribute the fluidization gas as evenly as possible along the radial development of the slots 18.

Preferably, the taper angle Î ± of the radial slots 18 is between 2 ° and 10 ° and, more preferably, between 4 ° and 8 °.

In the context of the present description and in the subsequent claims, the term: "taper angle" of the radial slots 18, 18a and 18b is intended to indicate the angle formed by the longitudinal edges 19 of the slots 18, 18a and 18b ( those extended radially) and the longitudinal axis X-X of the slots 18, 18a and 18b themselves.

In this way, it is advantageously possible to optimize the distribution along the radial extension of the slots 18, 18a and 18b of the fluidization gas.

In accordance with the invention, the distributor disc 16 is equipped with a plurality of deviating fins 32, 33, 34 each extending below the disc 16 in proximity to a corresponding slot 18, 18a and 18b to direct the fluidization gas flows from the slots 18, 18a, 18b towards the treatment chamber 14 according to respective substantially spiral ascending paths (in Figure 1, this flow is schematised with the dashed line V).

In particular, the deviating fins 32, 33 and 34 extend substantially at a respective longitudinal edge 19 of the radial slots 18, 18a, 18b. In a preferred embodiment, the deviating vanes 32-34 are inclined with respect to the plane of the distributor disc 16 by an angle γ comprised between 30 ° and 50 ° and, more preferably, an angle comprised between 35 ° and 45 ° (see Fig. 7).

In this way, it is advantageously possible to correctly channel the fluidization gas into the slots 18, 18a and 18b and to impart to the fluidization gas flows exiting the slots 18, 18a and 18b an inclination such as to obtain the desired substantially spiral ascending paths of the gas and the particles 11 kept in suspension therefrom.

Preferably, the deviating fins 32-34 are radially tapered towards the center of the disc 16 (as shown in particular in Figures 5 and 6).

In this way, it is advantageously possible to distribute the fluidization gas as uniformly as possible along the radial development of the slots 18, 18a and 18b.

Preferably, the deviating fins 32-34 are tapered substantially in a linear manner starting from a first radially external end 32a, 33a and 34a towards a radially internal end 32b, 33b and 34b.

Preferably, the tapering angle β of the deflector fins 32-34 is between 2 ° and 10 °, more preferably, between 4 ° and 8 °.

In the context of the present description and in the subsequent claims, with the term: "tapering angle" of the deviating fins 32-34, it is meant to indicate the angle formed by a longitudinal edge 32c, 33c and 34c of the deviating fins 32 -34 and the longitudinal edge 19 of the slots 18, 18a and 18b from which the deviating fins 32-34 extend.

In this way, it is advantageously possible to optimize the guiding action of the fluidization gas towards the slots 18, 18a and 18b.

In accordance with the preferred embodiment shown in the figures, the deviating fins 32-34 are substantially flat and extend integrally from the longitudinal edge 19 of the slots 18, 18a and 18b.

Preferably, the deviating fins 32-34 are obtained by means of the steps of:

- laser cutting of the distributor disc 16,

- bending of the solid part thus formed to the angular values defined above, and - extension of the length of each of the fins 32-34 to suitable values, for example by welding a plate of suitable width to the free longitudinal edge of the solid part obtained after bending.

Preferably, the length of the deviating fins at the radially outer end 32a and 33a is comprised between 30 and 40 mm, more preferably between 32 and 38 mm.

Preferably, the length of the deviating fins at the radially internal end 32b and 34b is comprised between 15 and 25 mm, more preferably between 18 and 22 mm.

In this way, it is advantageously possible to optimize the guiding action of the fluidization gas towards the slots 18, 18a and 8b.

In the preferred embodiment illustrated, the fluidized bed apparatus 10 comprises a fine mesh net 22, positioned above the distributor disc 16 to retain the solid particles 11 to be treated inside the treatment chamber 14. Preferably , the net 22 rests directly on the distributor disc 16.

Preferably, the mesh 22 has a thickness comprised between 80 and 100 µm and is preferably formed by a metal mesh having a passage section of the openings preferably comprised between 50 and 150 µm, and more preferably, comprised between 80 and 100 µm.

The mesh 22 is substantially shaped like a ring and is mounted between an internal reinforcement ring 24 and an external reinforcement ring 26, which has a diameter substantially consistent with that of the distributor disc 16.

In the preferred embodiment illustrated, the distributor disc 16 further comprises a deviator element 28, preferably substantially shaped like a cone, positioned in the center of the distributor disc 16 to which it is fixed in a per se known manner, for example by screwing onto a pin. thread 17 extending in the center of the distributor disc 16 above it.

The cone-shaped diverter element 28 advantageously performs the dual function of facilitating the direction of the fluidization gas flows and of the solid particles 11 along substantially spiral paths inside the treatment chamber 14 and of locking the mesh 22 in position on the distributor disc 16 by acting with its base portion 29 on the inner ring 24 of the mesh itself.

The network 22 preferably comprises a plurality of through openings comprising, in the preferred embodiment illustrated:

- two through openings 22a corresponding to the through openings 16a of the distributor disc 16, which are crossed by the respective dispensing nozzles 30, or by supporting elements thereof, and

- a through opening 25 for the insertion of the cone-shaped diverter element 28. Preferably, the through openings 22a and 25 are defined by respective rings 27 and, respectively, by the ring 24 described above.

In a preferred embodiment and as described above, the containment casing 12 of the fluidized bed apparatus 10 comprises a base portion 20 which defines a lower portion of the treatment chamber 14.

Preferably, the base portion 20 is advantageously associated in a removable way with the containment casing 12 in such a way as to form, together with the assembly consisting of the distributor disc 16 and the mesh 22, a removable collection container for the solid particles 11 to be treated (before the treatment operated by the apparatus) and treated (after the treatment).

In the preferred embodiment illustrated, the removable base portion 20 is substantially shaped like a hopper (for example in the form of a spherical segment with two bases), while the assembly consisting of the distributor disc 16 and the mesh 22 forms a wall of bottom of the removable collection container consisting of the base portion 20 substantially not permeable to solid particles 11.

Advantageously, the base portion 20 is removably associated with the containment casing 12 by means of suitable fastening means, for example by means of a plurality of bolts, schematized with 13 in figure 1, which allow the removal of the base portion 20 to facilitate the loading / unloading operations of the solid particles 11 to be treated / treated.

With reference to the fluidized bed apparatus 10 described above and to Figure 1, a preferred embodiment of a method for treating solid particles, for example coating / layering them with a filming substance, will now be described. In a first step of the method, the mass of solid particles 11 is charged in bulk form to the interior of the base portion 20 of the containment casing 12.

This phase can be carried out by removing the base portion 20 from the containment casing 12, pouring the solid particles 11 into the removable collection container constituted by the base portion 20 of the containment casing 12 and reassembling the base portion 20 in the Containment casing 12, ie by feeding the solid particles 11 into the base portion 20 in a pneumatic way using a loading opening not shown.

Subsequently, a predetermined flow rate of the fluidization gas is fed into the treatment chamber 14 of the fluidized bed apparatus 10 by means of suitable feeding means, for example comprising one or more fans conventional per se, not shown.

More specifically, the fluidization gas, for example dry air heated to a temperature between 60 and 80 ° C, is directed through suitable ducts, not shown, towards the distributor disc 16 located at the base of the treatment chamber 14 which directs fluidization gas flows from the slots 18, 18a and 18b towards the treatment chamber 14 according to respective substantially spiral ascending paths, so as to keep the solid particles 11 in suspension, which are also moved in accordance with these paths.

For this purpose, the deviating fins 32-34 extended below the distributor disc 16 perform the advantageous function of guiding the fluidization gas towards the slots 18, 18a and 18b imparting to it a direction substantially tangential to the disc 16 which facilitates the formation of substantially spiral ascending paths of the gas flows exiting the slots 18, 18a and 18b.

Once the fluid bed of the solid particles 11 has been created, the dispensing nozzles 30 deliver, according to methods known to those skilled in the art, a suitable treatment material, for example a filming substance, which can be easily selected by an expert in the field in operation. the type of coating to be obtained.

In the treatment chamber 14 are therefore carried out substantially simultaneously: a step of fluidization of the solid particles 11 by the fluidization gas, a step of dispensing a suitable coating material by the dispensing nozzles 30 and a step of drying the material of coating deposited on the solid particles 11 by the hot fluidization gas.

Optionally, the step of dispensing the coating material can be carried out in a discontinuous manner so as to achieve the desired characteristics of the coating layer of the solid particles 11.

The step of feeding the coating substance preferably also provides a step for controlling the quantity of substance fed into the treatment chamber 14 by means of the dispensing nozzles 30.

This control is preferably carried out by adjusting the flow rate of the coating substance according to methods known to those skilled in the art.

When the coating is completed, the supply of the coating substance and the supply of the fluidization gas are interrupted and the coated solid particles 11 are discharged from the fluidized bed apparatus 10 by removing the base portion 20 of the treatment chamber 14 and pouring the solid particles 11 coated therein into a further collection container (not shown).

In an alternative preferred embodiment, the coated solid particles 11 can be discharged from the base portion 20 of the treatment chamber 14 in a pneumatic way according to methods known to those skilled in the art.

In a series of experimental tests carried out, the Applicant has been able to find that the fluidized bed apparatus 10 and the distributing disc 16 according to the invention advantageously allow both to obtain a treatment efficiency equal to or higher than that of the bed apparatuses. fluid of a known type with the same flow rate of the fluidization gas, and to facilitate the subsequent cleaning operations, in particular of the treatment chamber 14, of the network 22 and of the various elements that make up the distributor disc 16 (slots 18, 18a and 18b , diverter vanes 32-34).

From the above, it is finally clear that the fluidized bed apparatus 10 of the invention is advantageously capable of achieving the aforementioned improved technical effects in the context of a multiplicity of treatments of solid particles, with or without dispensing of a treatment material by means of the dispensing nozzles 30, that is to say in the context of mixing, drying, granulating or coating / layering processes.

Obviously, a person skilled in the art, in order to meet specific and contingent needs, can make numerous modifications and variations to the fluid bed apparatus and the distributor disc described above, all of which are contained within the scope of protection of the present invention as defined by the following claims.

Claims (24)

CLAIMS 1. Fluidized bed apparatus (10) for the treatment of solid particles (11), comprising: - a containment envelope (12) in which a treatment chamber (14) for said particles (11) is defined; - a distributor disk (16) for a fluidization gas able to keep the solid particles (11) in suspension in said treatment chamber (14), - a net (22) positioned above said distributor disk (16) to retain the solid particles (11) to be treated from the treatment chamber (14); in which: i) the distributor disk (16) is placed at the base of said treatment chamber (14), is substantially formed of a single piece and is provided with a plurality of radial slots (18) to distribute in the treatment chamber (14 ) respective flows of the fluidization gas; ii) the distributor disc (16) is equipped with a plurality of diverter fins (32), each extending below the disc (16) in proximity to a corresponding slot (18), to direct the gas flows in use fluidization from the slots (18) towards the treatment chamber (14) according to respective substantially spiral ascending paths; iii) the gas passage section defined by each radial slot (18) is equal to or greater than 1100 mm <2>; And iv) the overall gas passage section defined by the radial slots (18) is between 15% and 25% of the total area of the disc (16). Fluidized bed apparatus (10) according to claim 1, wherein the distributor disc (16) comprises from 10 to 30 radial slots (18). Fluid bed apparatus (10) according to any one of the preceding claims, in which said radial slots (18) are arranged circumferentially equidistant from each other. Fluid bed apparatus (10) according to any one of the preceding claims, wherein said radial slots (18) are formed in the distributor disk (16) in a circular ring defined between two circumferences inside the disk (16) and respectively having a first spoke R1 having a value between 15% and 25% of the radius R of the distributor disc (16) and a second spoke R2 having a value between 85% and 95% of the radius R of the distributor disc (16). Fluid bed apparatus (10) according to any one of the preceding claims, wherein said radial slots (18) are radially tapered towards the center of the disc (16). 6. Fluidized bed apparatus (10) according to claim 5, wherein the taper angle (a) of said radial slots (18) is comprised between 2 ° and 10 °. 7. Fluidized bed apparatus (10) according to any one of the preceding claims, in which the gas passage section defined by the radial slots (18) is comprised between 1100 and 1800 mm <2> - 8. Fluidized bed apparatus (10) according to any one of the preceding claims, in which said deviating fins (32) are inclined with respect to the plane of the distributor disk (16) by an angle (γ) comprised between 30 ° and 50 °. Fluid bed apparatus (10) according to any one of the preceding claims, wherein said deviating fins (32) are radially tapered towards the center of the disc (16). 10. Fluidized bed apparatus (10) according to claim 9, wherein the taper angle (β) of said deviating fins (32) is comprised between 2 ° and 10 °. 11. Fluidized bed apparatus (10) according to claim 9, wherein the length of the deviating fins (32) at a radially outer end (32a) is between 30 and 40 mm. Fluid bed apparatus (10) according to claim 9, wherein the length of the deviating fins (32) at a radially inner end (32b) is between 15 and 25 mm. Fluid bed apparatus (10) according to any one of the preceding claims, comprising a plurality of dispensing nozzles (30) for delivering a treatment material into said chamber (14). Fluid bed apparatus (10) according to claim 13, wherein said dispensing nozzles (30) are mounted on the distributor disc (16). Fluid bed apparatus (10) according to any one of claims 13 or 14, wherein said dispensing nozzles (30) are inclined with respect to the plane of the distributor disk (16) by an angle comprised between 30 ° and 50 °. Fluid bed apparatus (10) according to any one of claims 4-6 and 13-15, wherein the distributor disk (16) further comprises a pair of radial slots (18a, 18b) extended from radially opposite parts of each of said dispensing nozzles (30). Fluid bed apparatus (10) according to any one of the preceding claims, further comprising a deflector element (28) positioned in the center of the distributor disc (16). 18 Fluidized bed apparatus (10) according to claim 16 or 17, wherein said network (22) comprises a plurality of through openings (22a, 25) to accommodate said diverter element (28) and said dispensing nozzles (30). 19. Fluidized bed apparatus (10) according to any one of the preceding claims, wherein said containment casing (12) comprises a removable base portion (20) and in which the treatment chamber (14) is defined at least in part in said removable base portion (20) of the containment casing (12). 20. Distributor disc (16) of a fluidization gas for a fluidized bed apparatus (10) for the treatment of solid particles (11), comprising: - a plurality of radial slots (18) for distributing respective flows of the fluidization gas; - a plurality of deviating fins (32), each extending below the disc (16) in proximity to a corresponding slot (18), to direct said flows of fluidization gas downstream of the slots (18) in use according to respective paths substantially spiral ascending; in which: - the distributor disc (16) is basically made up of a single piece, - the gas passage section defined by each radial slot (18) is equal to or greater than 1100 mm <2>; And - the overall gas passage section defined by the radial slots (18) is between 15% and 25% of the total area of the disc. Distributor disc (16) as defined in any one of claims 2 to 12 and 16. Distributor disc (16) according to claim 21, comprising a plurality of openings (16a) for housing a corresponding plurality of dispensing nozzles (30) adapted to be mounted on the distributor disc (16). 23. Distributor disc (16) according to claim 22, further comprising a pair of radial slots (18a; 18b) extending from radially opposite parts of each of said openings (16a). Distributor disc (16) according to any one of claims 20-23, further comprising a deflector element (28) positioned in the center of the distributor disc (16).