EP0606810A1 - Drying device - Google Patents

Abstract

Device for drying materials which are in solution, in suspension, pasty, divided up in various forms or pulverulent, by means of the flow of a desiccative fluid brought into the presence of the material to be dried, consisting of a closed enclosure (1) equipped with a turning agitator (6) comprising a hollow shaft which communicates with a plurality of hollow radial agitating elements (8) pierced with orifices (10) which allow the admission of the desiccative fluid into said enclosure (1) via the hollow shaft and the agitating elements (8), characterised in that the agitating elements (8) mounted on said hollow shaft are in the form of tubulures extending to the inner wall (1a) of the enclosure (1), the majority of which are hollow and are equipped at their end adjacent to said wall (1a) with an orifice (10), the axis of which can be oriented between two predetermined angular positions, in two perpendicular planes, the first of these planes being perpendicular to the axis of the agitator (6), the second being parallel to the axis of the agitator (6) and perpendicular to the axis of the tubulure (8). According to one possibility, the shaft consists of at least two hollow pipes (7) with parallel axes positioned symmetrically in relation to the axis of the turning agitator (6), on which said agitating elements are mounted.

Description

The present invention relates to a device for drying or drying materials in solution, in suspension, pasty, broken up into various forms or powders. Desiccation is carried out by means of the flow of a desiccant fluid brought into contact with the material to be dried in a closed enclosure provided with a rotating agitator.

The shaft of this agitator is hollow, communicating with a plurality of hollow agitator elements of generally radial appearance pierced with orifices allowing the admission of the desiccant fluid into the enclosure via the shaft and the agitator elements.

The latter allow mixing of the material to be dried and consequently improve the conditions of heat and material transmission between said material and the desiccant fluid.

Drying devices corresponding to the characteristics which have just been stated are already known in the state of the art.

In particular, there is a French patent obtained by a Czech company VYZKUMNY USTAV ORGANICKYCH SYNTEZ, issued on May 23, 1972 under No. 2,019,344, which relates to an installation of this type.

This patent relates simultaneously to a method and to an apparatus for the physical or chemical treatment of bodies in any condition, by introduction at relatively high speed of fluid agents, that is to say liquid or gaseous, into an enclosure.

The apparatus performing this treatment comprises said closed enclosure provided with inlet and outlet ports and at least one agitator. It is essentially characterized in that the agitator consists of a shaft provided with one or more hollow agitator elements pierced with holes for the admission of the fluid body into the enclosure.

The agitator elements have several possible shapes, but their basic geometry is generally circular. These are discs or hollow cylinders, complete or truncated, which may have various cross sections, communicating with the shaft and whose position relative to said shaft may be centered, eccentric and / or have an angle which is not straight.

The inlet ports are therefore radial or positioned on one of the substantially planar faces of the discs.

This document also mentions the use of radial arms from the central shaft, but without describing it precisely. A more precise description on the other hand relates to the use of radial arms connecting to the central shaft of the longitudinal tubes, parallel to the axis of the device. In this configuration, the intake orifices are also positioned in a radial mode.

• la transmission de chaleur,
• le transfert de masse, et
• la surface de contact entre le matériau à sécher et le moyen dessiccatif.

In the case of agitator dryers, the determining factors in the drying operation are:

• heat transmission,
• mass transfer, and
• the contact surface between the material to be dried and the desiccant.

The values of these parameters directly influence the speed of drying as well as the intensity of the mixture which takes place between the material to be treated and the desiccant fluid.

The trade-off between speed and efficiency of drying must also take into account economic parameters. In other words, it is necessary to arrive at high values for the determining factors of drying, without excessive consumption of the desiccant, which would result in a high energy expenditure.

Access to the drying fluid from inside the drying device - because it increases the speed of the drying fluid and improves the quality of the mixture with the material to be treated - theoretically constitutes a good technical approach, because it allows better heat transmission and increases the contact surface between the two phases.

The positioning of the orifices is also an important point. In the prior art, these orifices are fixed or mobile, positioned both on the rotating agitator and on the casing of the device, for example on fins interposed between the agitating discs. When they are mobile, their movement can be pendulum or rotary.

The desiccant fluid takes part in the preparation of the mixture, while carrying out the drying: it is therefore important that the orifices are placed with particular care allowing the fluid to achieve its double function.

The development of an efficient and economical drying apparatus represents a set of rather complicated problems, due to the interaction between the parameters mentioned. A bad compromise between said parameters results in poor performance.

The objective of the present invention is to propose a set of technical solutions optimizing the use of the determining factors of drying, and usable for a wide range of materials. These solutions offer a high specific yield, with relatively low energy requirements.

The problem of energy consumption is mainly linked to that of the consumption of desiccant fluid, the other energy inputs necessary for the operation of the device being less significant. The nature of the fluid used therefore constitutes another element of the global problem, insofar as said fluid must be both the least expensive possible for production and the most effective possible for drying. The invention incorporates the choice of a fluid achieving a good compromise between these two requirements.

The devices of the invention in practice substantially improve the yields allowed by devices of this type existing to date.

According to a first essential characteristic, the tree consists of at least two hollow ducts with parallel axes positioned symmetrically with respect to the axis of the rotary agitator, on which are placed agitator elements of generally radial shape in the form of tubing extending to the wall of the enclosure, most of which are hollow, in communication with one of the hollow conduits, and provided at their end near said wall with an orifice for admitting the desiccant fluid into the pregnant. According to one second essential characteristic, said orifices have an axis which can be oriented in two perpendicular planes between two predetermined angular positions. The first of these planes is perpendicular to the axis of the conduit, while the second is parallel to the axis of the conduit and perpendicular to the axis of the tubing.

Finally, according to a third major technical characteristic, the flow rate of the desiccant fluid passing through each hollow conduit and through the hollow tubes which converge therein is controlled by a cover placed at the end of the shaft, the shape of which is intended to obstruct more or less completely the opening at the inlet of the conduit, as a function of the angular position of said conduit in the rotary stroke of the shaft, so that the conduit and its associated pipes are crossed by desiccant fluid only between two predetermined angular positions .

This particular feature of the device plays a role in particular in moderating energy expenditure, since it prevents the fluid from rushing into all the conduits of the shaft at all times. It also makes it possible to feed preferably the most favorable area of the enclosure in terms of drying and stirring. In fact, the supplied conduits correspond to pipes located in a certain area of the dryer. It then suffices to determine the most suitable space for the treatment in order to deduce therefrom the conduits which must be supplied with desiccant fluid.

Given that in most cases the rotary movement of the agitator is uniform, the conduits are either open, or completely blocked, or even partially blocked. Consequently, the fluid flow follows a sinusoidal curve which must be taken into account in the positioning of the cover.

The container forming the enclosure of the dryer can of course take various forms, cylindrical, conical, trough, etc. The inclination of its axis is however limited between two angular positions located at -15 ° and + 15 ° by compared to the horizontal.

Inside the enclosure, the end orifices of the tubes are orientable in two orthogonal planes.

In each of these, the axis of said tubes is orientable between two predetermined angular positions. Outside these limits, the dryer performance becomes poor.

In the first plane, perpendicular to the axis of the duct, the possible angle is noted γ. This is the angle between the axis of the intake port and the perpendicular to the axis of the agitator located in said first plane and passing through the point of intersection between the axis of the orifice and the surface which is perpendicular to it situated at the level of the outlet of said orifice in the enclosure, that is to say the surface which connects the edges of the orifice.

This angle γ is between 30 ° and 120 °.

The orientation in the second plane is carried out at an angle β. This second plane is perpendicular to the previous one, parallel to the axis of the conduit, and perpendicular to the axis of the tubing. This angle β is measured relative to the vector V of the movement.

β is between 45 ° and 315 °.

To promote mixing and increase the contact surface between the desiccant and the product to be dried, a plurality of tubes are provided with additional agitating devices, consisting of two thin flat plates forming an angle δ between them, the direction of the plate the closer to the wall of the enclosure and the tangent to said wall at the point of intersection between said direction and the wall forming an angle ε.

These additional agitating devices are fixed to prismatic heads placed at the ends of the tubes, near the wall of the enclosure, and comprising the intake orifices. They are then placed opposite said orifices, on the face which can be considered to be the front face with respect to the direction of movement V.

The angle δ is between 70 ° and 165 ° and the angle ε is between 10 ° and 70 °.

All the internal elements of the drying device obey fairly precise criteria of shape, positioning and / or orientation. The different angular intervals are those in which the modifiable components can be adapted without departing from the initial requirement of good efficiency combined with moderate energy expenditure. They result from the experience acquired during numerous tests.

The cover placed at the end of the tree can also have several possible shapes. Depending on the case, the simplest is simply a solid angular sector.

In the context of a variant for which the flow rate is never zero in any of the conduits, the solid angular sector is hollowed out with a portion of the crown.

According to another variant, the cover takes the form of a solid disc, from which is also cut a portion of the crown, with a larger surface area than previously.

The crown portions can have a constant or variable width. In all cases, the cover is never animated by a rotary movement. The adjustment of the flow rate simply results from the movement of the shaft placed downstream of said cover in the course of the desiccant fluid. On the other hand, it is possible to animate this cache with an alternating linear movement of axis parallel to the axis of the rotary agitator.

As a result, the cover obstructs the opening of the conduits also according to a sinusoidal curve. The combination of the two movements, that of the shaft and that of the cover, makes it possible to refine the adjustment of the flow rate.

The shaft of the rotary agitator has several conduits arranged symmetrically with respect to the axis of said agitator. In particular, it is possible to create a configuration with an additional central duct coaxial with the agitator.

This central duct is provided with at least one orifice opening into the enclosure. This can be carried out directly in the duct, or be placed at the end of a tubular agitating element of radial appearance, exactly as for the other ducts of the shaft.

Said central duct can have the same function as the others or serve as additional heating means, possibly in combination with an additional jacket fitted to the enclosure and also intended for heating.

The enclosure may also include parts fixed to its internal wall, positioned between the rotating parts of the agitator and also intended for additional heating and / or for the crumbling of particularly compact materials.

These heating means can be connected. Thus, the peripheral jacket and the central hollow duct are connectable by means of hollow connections, so as to form a heating circuit covering a maximum surface.

The numerous variants mentioned above can be combined in a large number of possibilities. Several different combinations can even coexist in a single drying device: depending on the needs, the configuration of the installation places or the material to be treated, a dryer can be designed cylindrical on a first section and conical on a second, have pieces of unpacking on only part of the total volume and / or be provided with a central duct shaft provided with orifices only in one place to orient the desiccant fluid more precisely.

The inlet / outlet pipes of the material to be dried can be positioned on the side façades or on the peripheral envelope of the enclosure. Other conduits for supplying the desiccant fluid can open out at various locations in the enclosure, so as to possibly reinforce the flow rate of said fluid passing through the conduits of the agitator shaft.

The desiccant fluid can borrow the same conduits as the material leaving the device. The exact configuration of the drying chamber determines, with the nature of the material to be treated, the angles used for the axes of the intake orifices of the agitating elements. Depending on the location of the radial pipes in said enclosure, said angles may be different.

Likewise, the additional agitator devices fixed to said tubes are not necessarily systematically installed. Insulated tubing or groups of well localized tubing can be fitted, while all the others do not. The shape of said devices can also vary from one tubular agitating element to another.

Certain drying operations are very specific and require special conditions as to the quality of the desiccant, the treatment temperature, or even the means of application of the flow of desiccant fluid. It may be advantageous to supply the central hollow duct independently of the other ducts of the shaft, so that a hotter fluid, or more generally endowed with other physical and / or chemical properties, can be injected there. By combining this with a precise arrangement of the intake orifices, it is possible to inject a particular fluid, at a determined flow rate, at a precise location, if the treatment requires it.

According to a preferred mode, the drying is carried out with superheated steam, according to a technique known per se and which is already used in this field.

The exchange which takes place in the dryer makes it possible to recover, at the outlet of the device, the water vapor obtained during the desuperheating of the superheated steam entering during the treatment in the dryer as well as the water vapor resulting from evaporation of the water contained in the product.

It is possible to improve the efficiency of the system by recompressing the water vapor generated by the evaporation of the humidity contained in the product. This vapor is then treated by a compressor which raises its temperature to a value much higher than that required for drying. The steam then gives up its enthalpy in an exchanger of the condenser / superheater type which overheats the steam recovered at the outlet of the dryer, which is then reinjected into the latter.

• la température est généralement plus élevée qu'avec de l'air chaud. Il y a donc une augmentation importante du coefficient de transmission de chaleur, la vitesse d'écoulement ayant une influence décisive sur sa valeur, d'où l'importance de la conception vue auparavant ;
• le transfert de matière se fait directement, sans passage à travers un film de gaz inerte, comme c'est par exemple le cas pour l'air chaud au contact de l'eau évaporée. Le mouvement de la vapeur ne dépend que de la différence entre les pressions partielles de celle-ci dans le film et dans les pores du matériau ;
• seule l'eau évaporée pendant le processus de séchage est éliminée du sécheur, la vapeur étant recyclée ;
• la vapeur surchauffée est très performante dans le séchage de matériaux pulvérulents, qui peuvent être séparés et totalement récupérés, après la condensation de la vapeur.

For drying wet materials, the use of superheated steam has a number of advantages:

• the temperature is generally higher than with hot air. There is therefore a significant increase in the heat transfer coefficient, the flow speed having a decisive influence on its value, hence the importance of the design seen previously;
• the material is transferred directly, without passing through a film of inert gas, as is the case for hot air in contact with evaporated water, for example. The movement of the vapor depends only on the difference between the partial pressures of the latter in the film and in the pores of the material;
• only the water evaporated during the drying process is removed from the dryer, the steam being recycled;
• superheated steam is very effective in drying pulverulent materials, which can be separated and completely recovered, after condensation of the steam.

The exchange between the superheated steam and the product to be dried is cross-current with percolation of the steam through the layer of said product.

Such an installation is also very advantageous economically and by its favorable impact on the environment.

It requires two times less primary energy than current products, hence an energy expenditure reduced by half.

There are no discharges of fumes saturated with water vapor: all the discharges are condensed and discharged in the form of liquids after cooling. Thermal discharges are also twice as low as with traditional installations, since they are reduced in the same proportions as primary energy.

Finally, it should be noted that the product is no longer percolated except by water vapor, which allows treatments without oxygen.

• la figure 1 est une coupe longitudinale d'un exemple de dispositif de séchage selon l'invention,
• la figure 2 en est une coupe transversale simplifiée,
• la figure 3 montre l'orientation possible des orifices d'admission dans le second plan,
• la figure 4 fait de même pour le premier plan,
• la figure 5 représente deux types de dispositifs agitateurs additionnels installés sur leurs tubulures agitatrices radiales,
• la figure 6 concerne un cache,
• la figure 7 en montre une variante,
• la figure 8 représente une variante du dispositif comprenant un conduit creux central dans l'arbre,
• la figure 9 montre schématiquement le positionnement d'un agitateur dans une installation,
• la figure 10 illustre une variante avec un arbre à deux conduits creux, et
• la figure 11 est un schéma du circuit de recyclage de la vapeur surchauffée.

We will now proceed to a more detailed description of the drying device or dryer according to the invention, using the attached figures, for which:

• FIG. 1 is a longitudinal section of an example of a drying device according to the invention,
• FIG. 2 is a simplified cross section thereof,
• FIG. 3 shows the possible orientation of the intake orifices in the second plane,
• FIG. 4 does the same for the foreground,
• FIG. 5 represents two types of additional agitator devices installed on their radial agitator pipes,
• FIG. 6 relates to a cover,
• FIG. 7 shows a variant,
• FIG. 8 represents a variant of the device comprising a central hollow duct in the shaft,
• FIG. 9 schematically shows the positioning of an agitator in an installation,
• FIG. 10 illustrates a variant with a shaft with two hollow conduits, and
• FIG. 11 is a diagram of the circuit for recycling superheated steam.

If FIG. 1 only represents an example of a device according to the invention, it nevertheless includes the basic elements, which are also found in FIG. 2.

The enclosure (1) is provided with flanges or covers (2, 3) in which the inputs / outputs are made in the form of tubes (4,5). The outlet pipe (5) serves simultaneously to evacuate the material after treatment and the desiccant fluid.

The rotary agitator (6) comprises a shaft which is formed by four hollow cylindrical conduits (7) with parallel axes symmetrical with respect to the axis of the rotary agitator. These conduits (7) each comprise a row of radial agitator elements (8), which can be offset from one row to another. Near the internal wall (1a) of the enclosure (1), the tubular agitating elements (8) comprise a prismatic head (9) in which an orifice (10) is drilled.

This orifice (10) appears on one of the faces of said head (9) oriented perpendicular to the direction of the rotary movement, on the face which can be described as rear face with respect to the direction of rotation (see particularly in Figure 2) .

The desiccant fluid, at the inlet, is first sent to a distribution chamber (11) via an inlet pipe (11a). This chamber is located in the axial extension of the shaft of the rotary agitator (6) and it contains the cover (12) placed at the end of the shaft. The fluid passes from the chamber (11) into the shaft, that is to say into the hollow conduits (7) of the shaft, goes to the inlet (18) and after possible filtering by the cover (12) .

Then, said fluid escapes to the radial pipes (8) which communicate with one of the hollow conduits (7), and exits in the enclosure (1) through the orifices (10) located in the prismatic heads (9). In this configuration, the desiccant fluid is additionally introduced into the enclosure (1) by means of the fixed conduits (13) and (14), in order to reinforce the drying effect due to the central flow.

Figure 2 shows the shape chosen for the elements of the rotating agitator (6). Other configurations are of course quite possible. Thus, the transverse profiles of the conduits (7) can be square, rectangular, oval, etc. Similarly, the tubular agitating elements (8) can be drawn according to another profile, be straight or curved, oblique with respect to the 'axis of the tree, etc ... Even the shape of the orifices can undergo variations.

The inner wall (1a) of the enclosure (1) is provided with fixed parts (15) whose function here is essentially the crumbling of the material, although they also influence the dynamics of the fluid in the enclosure.

Alternatively, these parts could be hollow and connected to the heating jacket (16) serving as additional heating means.

In FIG. 1, an example of an additional mixing device (17) placed on the front face (in the direction of movement) of the head (9) of a tubular element (8) has been placed: an additional illustration of these additional elements (17) appears in FIG. 5, in longitudinal section.

Figure 3 illustrates the positioning of the angle β. The direction of rotation being represented by V, we can visualize the different values taken by β, between 45 °
and 315 °. β is never parallel to the direction of movement, and never enters a right angle of which this direction is the bisector. In the figure, β has a value of approximately 135 °, a value adjusted according to the material to be treated and the requirements due to the architecture of the rest of the configuration of the enclosure (1).

Figure 4 shows the positioning of the angle γ. This is between a value of 30 °, equivalent to an orifice (9) generally oriented towards the shaft and a value of 120 ° for which the orientation of said orifice (9) is substantially orthogonal to the axis of the tubing (8).

Figure 5 shows two types of additional agitator devices (17). In both cases, these devices are composed of two thin flat plates forming an angle δ between them, without this being an intangible rule. Multiple forms of additional agitators can indeed do the trick.

The first includes two plates (19, 20) forming an angle δ approximately equal to 120 °, while in the second plate (21, 22), δ is almost 180 °. The angle ε between the plate (19; 21) closest to the internal wall (1a) and the tangent to the wall (1) at the point of intersection of the straight line (D; D '), extending said plate (19; 21) and said wall (1a) is substantially equal in both cases and is approximately 30 °.

In both cases, this additional device (17) is fixed to the front face (in the direction of movement V), although this is indirect as far as the plate (22) is concerned.

A possible positioning and shape of the cover (12) appear in the following figures, also applied to a configuration with four hollow ducts (7).

In the first case (Figure 6), the cover is a solid angular sector cut from a portion of crowns (23). In the representation plane, the cover (12) is fixed, while the hollow conduits (7) are movable in rotation according to V. It can be made mobile, according to a linear reciprocating movement which takes place in the third dimension (not shown).

In the second case (Figure 7), the cover is geometrically a little different and very similar to a completely closed angular sector. The obstructed sector covers, as in the previous case, an angle of approximately 90 °. Its complement in the disc is a cut crown portion (24). It would have been equivalent to provide only a single solid angular sector. The same remark as before concerning the mobility of the cache is true.

The cover (12) can be in contact with the inlet (18) of the hollow conduits (7) or at a short distance.

FIG. 8 schematically shows the variant with a central hollow duct (25) in the middle of the peripheral ducts (7). The overall symmetry of the system is respected, since this central shaft (25) is coaxial with the shaft of the rotary agitator (6).

The central duct (25) comprises at least one orifice (26) opening directly into the enclosure (1) and / or at least one tubular agitating element (8) provided with an inlet orifice (27) located - in this configuration - opposite the internal wall (1a) of the enclosure (1), that is to say on the face of the prismatic head (9) facing said wall (1a).

A variant of the cylindrical device of FIG. 1 is shown in FIG. 9, in which the enclosure takes the form of an asymmetrical trough (1). In this type of device, the desiccant means and the material to be dried do not have a common outlet tube. The desiccant fluid escapes through the piping (28), while the treated material exits through the tubing (5).

FIG. 10 represents another particular case, with two hollow conduits (7) per shaft. The advantage of this figure is to schematically show the possible course of a hollow duct without being even partially obstructed. In this configuration with two conduits (7), the possible angular deviation, taking into account the full angular sector of approximately 90 ° materialized by the cover (12) is 195 °. Beyond that, there is partial or even total obstruction for a short time.

In this case, in a cross section, in the direct trigonometric direction, opposite to the direction of V, the obstruction ceases between the angular positions of values 135 ° and 330 °. The position of the cover is therefore provided so that the desiccant fluid flow rate is maximum at the bottom of the enclosure, and less, or even zero at the top of the volume.

A small change in this position changes the flow rates from the orifices, which can therefore be directed more specifically in certain zones of the enclosure. Such a choice obviously depends on the nature and the shape of the material to be treated.

Figure 11 shows the diagram of the superheated steam recycling circuit.

At the inlet of the dryer, superheated steam is available, at a flow rate Q, at a pressure close to atmospheric pressure and at a temperature of 140 ° C. or more.

The drying results in that at the output of the device (S), we are left with a flow rate Q + q, q being steam close to saturation, the whole being brought to a temperature very close to 100 ° C. and always at a pressure close to atmospheric pressure.

The flow q is derived from the main circuit to a compressor (W), which increases its pressure to a value such that the corresponding temperature allows the steam to heat up.

This flow q passes through the condenser - superheater (C), where its condensation, by the heat which it releases, allows the superheating of the flow Q of saturated steam which also enters said condenser - superheater (C) coming from the main circuit .

At the outlet, there is the flow rate Q of superheated steam at approximately 140 ° C. and at substantially atmospheric pressure, which a fan (T) re-injects into the dryer (S).

The cycle can start again.

The saturation of the vapor is very fast for humidity contents up to 75% of the dry matter, and the drying time in the meantime
[25%, 75%] is approximately three times faster than with air under normal conditions.

In practice, drying takes place at low temperature and in the absence of oxygen, there is no longer any risk of fire.

This system using the mechanical recompression of the steam leaving the drying device makes it possible to recover the latent heat of the evaporated water, and therefore participates in the savings mentioned above.

The cost is further reduced by the absence of risk resulting from the use of steam at low temperature and without oxygen, since the insurance premiums are for example substantially reduced.

The economic advantage brought about by the combination of the drying device according to the invention and the use of superheated steam is therefore particularly convincing.

Claims (25)

Device for drying materials in solution, in suspension, pasty, broken up into various forms or powders, by means of the flow of a desiccant fluid placed in the presence of the material to be dried, composed of a closed enclosure (1) provided with a rotary agitator (6) comprising a hollow shaft communicating with a plurality of hollow radial-agitating elements (8) pierced with orifices (10) allowing the admission of the desiccant fluid into said enclosure (1) via the hollow shaft and the agitator elements (8), characterized in that the agitator elements (8) mounted on said hollow shaft are in the form of tubes extending to the internal wall (1a) of the enclosure (1), of which most are hollow and are provided at their end near said wall (1a) with an orifice (10) whose axis is orientable between two predetermined angular positions, in two perpendicular planes, the first of these planes being perpendicular to l axis of the agitator ( 6), the second being parallel to the axis of the agitator (6) and perpendicular to the axis of the tubing (8). Device for drying materials in solution, in suspension, pasty, broken up into various forms or powders, by means of the flow of a desiccant fluid placed in the presence of the material to be dried, composed of a closed enclosure (1) provided with a rotary agitator (6) comprising a hollow shaft communicating with a plurality of hollow radial-agitating elements (8) pierced with orifices (10) allowing the admission of the desiccant fluid into said enclosure (1) via the hollow shaft and the agitator elements (8), characterized in that the shaft consists of at least two hollow conduits (7) with parallel axes positioned symmetrically with respect to the axis of the rotary agitator (6), on which said agitating elements (8) are mounted in the form of tubes extending to the internal wall (1a) of the enclosure (1). Drying device according to claim 2, characterized in that the agitating elements (8) in the form of tubes are provided at their end near said wall (1a) with an orifice (10) whose axis is orientable between two positions predetermined angulars, in two perpendicular planes, the first of these planes being perpendicular to the axis of the agitator (6), the second being parallel to the axis of the agitator (6) and perpendicular to the axis of the tubing (8). Drying device according to claim 1, characterized in that the shaft consists of at least two hollow conduits (7) with parallel axes positioned symmetrically with respect to the axis of the rotary agitator (6), on which the agitator elements (8) are mounted. Drying device according to one of claims 2 to 4, characterized in that the flow rate of the desiccant fluid passing through each hollow duct (7) and through the hollow tubes (8) which converge therein is controlled by a cover (12) placed at the end of the shaft, the shape of which is intended to more or less completely obstruct the opening at the inlet (18) of the duct (7), as a function of the angular position of said duct (7) in the rotary stroke of the 'shaft, so that the conduit (7) and its associated stirring pipes (8) are crossed by the drying fluid only between two predetermined angular positions. Drying device according to claim 5, characterized in that the cover (12) takes the form of a solid angular sector. Drying device according to claim 5, characterized in that the cover (12) consists of a solid angular sector in which is cut a portion of the crown (23). Drying device according to claim 5, characterized in that the cover (12) has the shape of a solid disc cut out from a portion of the crown (24). Drying device according to one of Claims 5 to 8, characterized in that the cover (12) is driven by a linear reciprocating movement of axis parallel to the axis of the rotary agitator (6). Drying device according to one of the preceding claims, characterized in that the axis of the closed enclosure (1) in which the material to be treated is located makes an angle between the horizontal and between +15 and -15 °. Drying device according to one of claims 1 and 3 to 10, characterized in that the axis of each orifice (10) makes an angle γ with the perpendicular to the axis of the agitator (6) located in said first plane and passing through the point of intersection between the axis of the orifice (10) and the surface which is perpendicular to it situated at the level of the outlet of said orifice in the enclosure, that is to say the surface connecting the edges of the orifice, γ being between 30 ° and 120 °. Drying device according to one of Claims 1 and 3 to 11, characterized in that the axis of each orifice (10) forms an angle β with the vector defining the movement (V), β being between 45 ° and 315 °. Drying device according to any one of the preceding claims, characterized in that the pipes (8) have prismatic heads (9) at their ends close to the wall (1a), the inlet orifice (10) being drilled in said head (9). Drying device according to any one of the preceding claims, characterized in that a plurality of pipes (8) are provided with additional agitating devices (17), consisting of two thin flat plates (19, 20; 21, 22) forming between them an angle δ, the direction (D; D ') of the plate (19; 21) closest to the wall (1a) of the enclosure (1) and the tangent to said wall at the point of intersection between said direction and the wall (1a) forming an angle ε. Drying device according to claim 14, characterized in that said additional agitating devices (17) are fixed on the heads (9) of the pipes (8), opposite the orifices (10). Drying device according to one of claims 14 and 15, characterized in that the angle δ is between 70 ° and 165 °. Drying device according to one of claims 14 to 16, characterized in that the angle ε is between 10 ° and 70 °. Drying device according to any one of the preceding claims, characterized in that the agitator shaft (6) comprises a central hollow duct (25), coaxial with said shaft, provided with at least one opening (26) opening out. in the enclosure (1). Drying device according to the preceding claim, characterized in that said central hollow duct (25) comprises at least one tubular agitating element (8) comprising an orifice (27). Drying device according to any one of the preceding claims, characterized in that the enclosure (1) has on its internal wall (1a) parts (15) placed between the rotating parts of the agitator (6), intended to additional heating and / or to quench and / or to disintegrate the material to be treated. Drying device according to any one of the preceding claims, characterized in that the enclosure (1) is equipped with an additional heating jacket (16). Drying device according to the preceding claim, characterized in that the heating jacket (16) is connected to the central hollow duct (25) of the shaft by hollow fittings. Drying device according to one of claims 2 to 22, characterized in that it consists of a shaft comprising two hollow conduits (7) symmetrical with respect to the axis of the rotary agitator (6), each provided of a plurality of tubular agitating elements (8) with heads (9) pierced with an orifice (10), with a cover (12) formed by an angular sector full of approximately 90 °, so that the angular deviation during which the conduits (7) are completely disengaged from the cover (12) is 195 °. Drying device according to any one of the preceding claims, characterized in that the desiccant fluid is superheated steam. Drying device according to the preceding claim, characterized in that the superheated steam is at a temperature of 140 ° C and at substantially atmospheric pressure.

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