"DRYER AND FILTER/DRYER"

DESCRIPTION

The present invention relates to a dryer possibly also capable of filtration under pressure, particularly for chemico-pharmaceutical products, of the type comprising a main body internally forming a collection chamber adapted internally to collect a quantity of product to be dried and first fluid supply means adapted to supply a fluid to the collection chamber.

The present invention also relates to a drying method.

A unit of this type is known, for instance, from US Patent Specification 5 564 350, in the name of Peplinski.

These types of unit are widely used in the chemical and pharmaceutical industry for the production of active principles or other chemical substances in powder form.

Since the final result of the processes in which they are used, the dry residue, has a high added value, it is therefore particularly important to keep the content of the batch as homogeneous as possible and to reduce to a minimum any contamination between one batch and the following batch and to enable simple and thorough cleaning of all the dry residue from the unit.

In the units known at present, the semi-liquid mixture (generally containing up to 40% of solvent) supplied to the filter/dryer is agitated, filtered under pressure and vacuum dried by heating means.

During the stage of filtration under pressure, gas, for instance dry air or nitrogen, is blown into the unit so that this gas exerts a pressure on the mass to be filtered and urges it toward the filter baffle, thus adding a further force to the pressure of a mechanical type brought about by the action of the agitator blades.

The agitator is actuated both in rotation and with an alternating ascending/descending movement along its axis so as to ensure that the product mass is constantly being mixed.

Drying is generally assisted by the heating of the collection chamber, or by causing steam or another heating fluid to pass through appropriate external jackets.

When the mass is sufficiently dry, the output duct for the dry product is opened and the dry product is urged towards this duct by the mechanical action of the agitator.

In order to prevent the arms of the agitator from damaging the filter baffle by sliding thereon, there is always play, normally of a few millimetres, between them.

As a result of this play, a hard heel which is compact and difficult to remove is formed during the filtration and drying process.

In general, the heel is removed by connecting an apparatus to the dryer which makes it possible for an operator to break up and manually remove the heel, while at the same time maintaining the required sterile conditions; this process is nevertheless very time-consuming and the apparatus required is expensive. It does not, moreover, make it possible to increase the homogeneity of the batch as it merely recovers the finished product forming the heel, but does not — and could not — prevent its formation. The filter/dryer disclosed in the Peplinski patent has a bell-shaped collection chamber, a circular filter baffle disposed in the lower part of the collection chamber, an agitator disposed along the longitudinal axis of the collection chamber, a supply duct for the product to be filtered and/or dried and an output duct for the dry product and fixed upper nozzles for the supply of gaseous nitrogen. These fixed nozzles, whose purpose is to increase the turbulence within the

filtration/drying chamber, nevertheless leave untouched zones in the volume in which they act. In addition to the heel, a certain amount of dry residue is therefore left in the collection chamber and also has to be manually removed.

Moreover, in cases in which it is necessary consecutively to dry and/or filter two product batches which are not compatible with one another, it is essential for all the dry residue to be cleaned from the collection chamber in order to prevent any contamination of the subsequent batch.

In such cases, the machine down time needed to carry out appropriate operations to clean and/or wash the collection chamber is obviously greater than that required for the simple removal of the powder product, and therefore entails higher costs.

As the technology has become more refined and the quality specifications for the finished product have become less flexible, two requirements are becoming increasingly pressing: first, cleaning of the collection chamber between one batch and the next in order to improve performance without any lack of homogeneity of the product and, second, washing of the collection chamber between one cycle and the next, i.e. when a different chemico-pharmaceutical product is to be produced.

In view of the prior art described, the object of the present invention is to provide a dryer or a filter/dryer and a drying or filtration/drying method which remedies the problems described above, enabling the dry residue to be removed and the chamber to be cleaned more rapidly and more thoroughly than in the prior art, while at the same time ensuring that there is less risk of a batch being contaminated by a previous incompatible batch than has been the case up to now.

In accordance with the present invention, this object is achieved by a dryer as claimed in claim 1 and by a method of drying as claimed in claim 6 or in claim 7.

The characteristic features and advantages of the present invention are set out in the following detailed description of a practical embodiment thereof, given purely by way of non-limiting example, made with reference to the accompanying drawings, in which: Fig. 1 is a perspective view, partly in section, of a filter/dryer according to a preferred embodiment;

Fig. 2 is a view, partly in section, of the filter/dryer of Fig. 1;

Fig. 3 is a partial perspective view of a detail of the filter/dryer of Fig. 1 ;

Figs. 4 and 5 are perspective views, partly in section, of the filter/dryer of Fig. 1 in a sequence of operating instants during the stage of breaking up of the dry heel.

As will also be clarified below, although the description is made with reference to a unit able to filter and to dry the chemico-pharmaceutical product with which it is loaded, the salient characteristic features of the present invention apply equally to a simple dryer or to a unit not provided with filtration means.

Any reference to the filter/dryer shown in the Figures should therefore be understood as a reference both to a filter/dryer and a dryer as alternatives to one another.

Fig. 1 shows a filter/dryer 1 , comprising a collection chamber 2 of circular section, which is pressure and vacuum resistant, closed by a cover 4 which is generally dished and by a base with a filter baffle 5 which is generally plane. The collection chamber 2 as shown extends along a longitudinal axis X-X which, when the device 1 is installed, is disposed in a vertical direction.

The filter/dryer 1 comprises a charging opening 6 for the product to be filtered and dried, a discharge opening 7 for the dry powder filtrate and a discharge opening 8

for the removed liquid solvent, all provided in a known manner with means controlling their opening and closing.

It may also comprise pressurised gas supply means (not shown) for the rapid supply, in a known manner, of a quantity of drying gas, air or nitrogen, sufficient to bring the collection chamber 2 to the correct operating pressure in a relatively fast period of time.

A filter baffle 5 is borne by a structure 10 and operationally divides the collection chamber 2 from a lower portion 12 provided with mains connections 13.

The collection chamber 2 contains an agitator 14 which comprises a shaft 16 disposed along an axis generally coincident with the longitudinal axis X-X of the collection chamber 2 and a certain number of radial arms 15, generally two, rigid with the shaft 16.

A jacket 17 adapted to maintain the collection chamber 2 at the desired temperature is shown diagrammatically about the collection chamber 2. Further means for supplying fluid to the collection chamber 2 are shown by

18 and 19 in Fig. 1.

In a preferred embodiment, the fluid in question is a gas, preferably inert, for instance air, dry air or nitrogen.

The collection chamber 2 is bounded at least partly by a reference surface α, which is substantially defined by the surface of the filter baffle 5 facing this collection chamber 2.

The agitator 14 may be moved in rotation in both the clockwise and anticlockwise directions and may possibly also be moved in translation towards the lower portion 12 or towards the upper cover 4 of the filter/dryer 1 as shown in Figs. 1 and 2 by the arrow V.

In this way, the agitator 14 has its own working volume within the collection chamber 2 which is substantially coincident with its central zone; there are nevertheless two zones of the collection chamber 2 which may not be reached by the action of the arms 15 of the agitator 14: an upper and a lower zone; the latter, in particular, prevents any damage to the filter baffle 5.

The filter/dryer 1 comprises first supply means 18 for the supply of a fluid, disposed in the lower zone of the filter/dryer 1 and more particularly on the side of the reference plane α opposite the collection chamber 2; they are also disposed so that the path of the conveyor fluid towards the collection chamber 2 passes through the reference plane α.

This arrangement has the. advantageous effect that the product disposed in the vicinity of the filter baffle 5, and therefore also the heel 20 of dry residue, is provided with a force which, as it is not opposed by any support, generates a lifting action urging the product into the working volume of the agitator. In this way, when the fluid is supplied via the first supply means 18, the heel

20 is firstly lifted and is then broken up by the movement of the agitator 14.

Alternatively, when the fluid supply means 18 are actuated during the stage of filtration/drying, they create a turbulence in the product mass which prevents the heel

20 from forming. In this way, the entire batch is efficiently fluidised by keeping it in constant movement, thereby obtaining a more homogeneous mass of product than has been possible up to now.

In a particular embodiment, the fluid path comprises one or more fluid branches ending in one or a plurality of respective openings 21, for instance calibrated holes or nozzles, disposed on the side of the reference plane α opposite the collection chamber 2 and oriented such that the conveyor fluid is supplied to the

collection chamber 2 by passing though the reference plane α.

The openings 21 may be disposed along at least one of the radial directions with respect to the longitudinal axis X-X of the main body 3, and are preferably disposed in one or more arms 11 which form, overall, a radiate structure 10. This structure 10 comprises a certain number of hollow arms 11 , for instance eight, twelve, sixteen or twenty, preferably equally angularly spaced, so as to define therein at least part of the fluid path branches. The number of arms 11 may be selected such that the distance between the outermost openings 21 of two adjacent arms 11 is approximately 30-40 centimetres. This makes it possible substantially completely to break up the heel 20: the localised supply of fluid through the surface α manages locally to lift the heel 20 in a_ zone, called the effective zone, solely around this opening 21.

Because of its poor mechanical resistance, it would break up only in an zone, called the effective zone, solely around the fluid supply point. The radiate structure 10, with the openings 21 disposed along the arms 11, makes it possible to distribute the effective zones of the openings 21 in a substantially uniform manner and thus makes it possible substantially completely to break up the heel 20.

The fluid path branches may be provided with valve control means (not shown), for instance automatic three-way valves actuated by solenoids able selectively to open and/or close them.

In this way, it is possible precisely to control those fluid path branches which need to be opened and those which need to be closed at any given instant.

These valve means are able to open the fluid branches, acting upstream of the fluid branches or directly on the openings 21 , so that they emit pulses of fluid having

a duration of some tenths of a second.

Figs. 4 and 5 show a graphical representation of the breaking-up effect: Fig. 4 shows how the heel 20, subject to the lifting action of the gas emitted from the openings 21 disposed along one of the arms 11 of the structure 10 which makes up the lower supply means 18, is in practice lifted slightly before the arm 15 of the agitator 14, rotating in an anticlockwise direction, urges it forward and breaks it up.

In Fig. 5, which shows a subsequent instant, the arm 15 of the agitator 14 has been displaced by a certain angle and the arm 11 of the gas emission structure 10 which is operational is the adjacent arm in the direction of rotation of the agitator 14. As before, the heel 20 is lifted and brought into the working volume of the agitator

14 which breaks it up.

The operating pressures are approximately 6-8 bar; since the filter baffle 5 is interposed between the radiate structure 10 and the collection chamber 2, it must be able to withstand the fluid pulses emitted by the fluid supply means 18. The filter baffle 5 is generally composed of one or a plurality of drilled drainage plates on which one or a plurality of actual multi-layer filter webs are disposed.

The multi-layer webs are metal webs generally formed by three to seven layers, preferably sintered with one another. In an example of a five-layer web, the first and third layers are protective and the second defines the porosity of the means (for instance 20 micrometers), and the fourth and fifth layers are support layers adapted to provide it with the necessary resistance.

The filter baffle 5 has a section such that it coincides substantially with the section of the collection chamber 2 in which it is disposed. This surface is generally

circular.

In order for the filter baffle 5 to be able to withstand the counter-pressures generated by the fluid supply means 18 described above, it is advantageous to divide the filter baffle 5 into a plurality of segments 9. The number of circular segments 9 is, for instance, equal to the number of arms 11 of the support structure 10; the segments 9 preferably all have the same angular extension.

They are preferably disposed in an offset manner with respect to the arms 11 of the radiate structure 10, for instance so that the arms 11 are disposed in a substantially aligned manner with the bisectors of the segments 9 of the filter baffle

5; in this way, the filter baffle 5 protects the openings 21 against the entry of dry powder residue.

According to a preferred embodiment of the invention, the filter/dryer 1 further comprises control means to control the opening of the fluid path branches in relation to the rotation of the agitator 14 or in relation to its position and/or its angular speed.

These control means, for instance driven by PLC, are programmed to open the fluid path branches when the arm 15 of the agitator 14 is in the vicinity of these fluid branches. By "in the vicinity of it is understood that the angular distance is such as to provide for the breaking-up effect discussed above; the precise angular and/or time offset values depend, inter alia, on the density, thickness and mechanical strength of the heel.

At the end of the process of drying or of filtration/drying, there is always a certain quantity of dry powder product which it has not been possible to remove,

even when using the lower fluid supply means 18 described above.

Zones such as the upper side of the arms 15, the bellows structure which covers the shaft 16 of the agitator 14 and the junctions between the segments 9 of the filter baffle 5 are in practice untouched zones which cannot be reached by the action of the fluid supply means 18.

To remedy this drawback, the filter/dryer of the present invention may further comprise upper fluid supply means 19 connected to the upper portion of the main body 2, for instance connected to the cover 4, and able to supply fluid in at least one direction which may be varied over time, by rotation about at least two axes Y-Y and Z-Z inclined with respect to one another.

The fluid supplied by these, supply means 19 may be the same type of fluid supplied by the lower fluid supply means 18.

The upper means 19 comprise one or a plurality of devices 23, an embodiment of which is shown in Fig. 3, each provided with a main body 24 comprising a first elongate portion 25 extending along a first rectilinear axis Y-Y and a second portion 26, connected to the first portion 25, which has a free end; in this way, the second portion 26 defines a second axis Z-Z at an angle with respect to the first axis Y-Y.

The first axis Y-Y may be disposed parallel to the longitudinal axis X-X of the collection chamber 2, as shown in Figs. 1 and 2, or, more advantageously, perpendicular to the cover 4, or with an inclination with respect to the axis X-X of some 20°-30° to dispose the free end of the second portion 26 in a more central manner with respect to the wall of the main body 3.

Fig. 3 shows a cone of the possible orientations of the first axis Y-Y of the device 23 with respect to an axis parallel to the longitudinal axis X-X of the

collection chamber 2.

If it is assumed that the first portion 25 and the second portion 26 define the sides of the angle comprised between them, it may be considered that the angle has an aperture of between 45° and 135°, preferably between 60° and 120°, with an optimum value of some 90°.

A rotary support 27 is provided on the free end of the second portion and is able to rotate about the second axis Z-Z.

This rotary support 27 comprises one or a plurality of nozzles 28, possibly equally angularly spaced so as to balance the forces resulting from the emission of fluid.

The devices 23 comprise motor means adapted to rotate the main body 24 about the first axis Y-Y, preferably using at least part of the fluid itself.

The nozzles 28 may be disposed on the outer circumference of the rotary support 27, about the axis of rotation and with their openings facing in the peripheral direction with respect to the second axis Z-Z, as shown in Fig. 3.

In this way, the rotary support 27 is caused to rotate about the second axis Z-Z simply by the supply of fluid.

In an alternative arrangement, the openings of the nozzles 28 are oriented in the radial direction, towards the exterior of the rotary support 27; in this alternative arrangement, separate motor means may be needed to cause the rotary support 27 to rotate about the second axis Z-Z.

The devices 23 which form these fluid supply means 19 are preferably fixed in the direction of the first axis Y-Y in order to facilitate stability at the point at which they supply the collection chamber 2. These devices 23 are disposed so as not to interfere with the working volume

of the agitator 15 during its working operations.

If there are two or more fluid supply devices 23, it is possible, bearing in mind the combined action of the rotation with which the nozzles 28 are provided and the rotation of the agitator 14, in practice to eliminate any untouched area within the collection chamber 2.

Consequently, by blowing in fluid, in this case gas, it is possible to move the whole mass of dry residue contained in the collection chamber 2.

By adapting these fluid supply devices 23 in order to supply liquid, for instance solvent or water, it is possible to provide the filter/dryer 1 with upper gas supply means 19a and/or upper liquid supply means 19b, connected to two independent circuits, as shown diagrammatically in Fig. 2.

Since liquids possess lubricating properties which are generally better than those of gases, the friction between the rotary support 27 and the second portion 26 of the main body 24 is generally lower when liquid is supplied than when gas is supplied. The liquid supply means 19b may not necessarily, therefore, require separate motor means for the rotation of the rotary support 27 about the second axis Z-Z.

An example of the operation of the filter/dryer 1 in accordance with one of the preferred embodiments will now be examined. In the description of this example of operation, reference will be made both to the operation of the fluid supply means 18 adapted to lift the heel 20 and to the operation of the upper fluid supply means 19.

It will be appreciated that these two systems may be actuated independently from one another and that they do not both have to be included in a filter/dryer. A filter/dryer without the upper fluid supply means 19 may, for instance, be envisaged. The material to be filtered/dried is firstly loaded into the collection chamber

2. During the operating phase, the agitator 14 is actuated, possibly at the same time as the lower and/or upper fluid supply means 18 and 19.

The agitator 14 is caused to rotate about its longitudinal axis X-X and/or is moved in translation along this axis. The first fluid supply means 18 may also be actuated only partially: in this case, at any given instant, only some (one or more) of the fluid path branches are active and supply fluid to the collection chamber 2, while the remainder are inactive; the active branches change, moreover, over time.

It is advantageous, for instance, for all the openings 21 disposed along the same radius to be active or inactive at the same instants; the openings 21 along the radii are preferably actuated in sequence in one of the two directions of rotation, possibly in a manner synchronised with the direction of rotation of the arms 15 of the agitator 14.

At the end of the filtration/drying operation, if it is necessary to break up the residual heel 20, the fluid is supplied for a very short period, immediately before the arms 15 of the agitator 14 are superimposed on the fluid outlet openings 21, or with an advance, for instance of between approximately 20° and approximately 40°.

Alternatively, it is possible to actuate all the openings 21 of the lower supply means 18 to emit fluid. It has been observed that the formation of the panel 20 is effectively prevented, thereby obtaining a finished product homogeneity never achieved up to now, by actuating the lower fluid supply means 18 directly during the filtration and/or drying process, according to one of the operating methods described above.

The upper fluid supply means 19 may be actuated during the filtration and/or drying operations, but it is more advantageous to actuate them during the successive

operations to dry clean the collection chamber 2 to remove the dry powder residue.

In practice, supplying fluid, or more particularly gas, during the dry cleaning phase, prevents powder from being deposited on the zones which cannot be reached by the lower fluid supply means 18 which may also be active during this phase. After a number of cycles of filtration/drying operations, it may be necessary to wash the interior of the filter/dryer. In such cases, it is simply possible to actuate further upper supply means 19b, when provided, to supply liquid, water or solvent in order to carry out a wet washing cycle of the collection chamber 2.

The washing cycle may be carried out, for instance, before a different product is placed in the collection chamber 2 (or at the end of each cycle) and makes it possible further to reduce the risk of contamination between two different products without the need for long and costly operations normally carried out manually with long machine down times.

It will be appreciated that a person skilled in the art, in order to satisfy allied and specific requirements, could modify and vary the arrangements described above in many ways without thereby departing from the scope of protection of the invention as set out in the following claims.