WO1989012207A1 - Process and device for drying a particulate material - Google Patents

Abstract

To dry a particulate material formed, for example, in the interior (23) of a container (1) by spraying a solution and/or suspension and freezing the droplets produced in a fluidized bed, said material is removed by a current of gas, in particular air, from the lower limiting element (17) of the inner space (23) and subjected during the turbulence to the action of waves and, after or instead of the latter, is raised to a gas-permeable filter (21) with which it is placed in contact. When the particulate material is placed on the filter, vibrations and/or waves which act on the particulate material can again be produced. The vibrations and/or waves may be in the form of sound with a frequency in the audible or ultrasonic range, microwaves or infrared light waves. As a result of the action of the vibrations and/or waves and/or by raising the material to the filter (21), drying can be carried out in a relatively short time without detriment to the material.

Description

Method and device for drying a particulate material

DESCRIPTION

Technical field of the invention

The invention relates to a method and a device for drying a particulate material.

The material to be dried can, for example, have granules and / or serve to form them and, after drying and any additional processing operations, can be used, for example, as a remedy and / or as a food.

It is known to use a device with a container for drying a particulate material, which has a sieve bottom at the bottom and a filter at the top, the particulate material to be dried in the container interior present between the sieve bottom and the filter with these from bottom to top lifting air flowing through from the sieve bottom and swirling it in such a way that a fluidized bed is formed. The air supplied is normally heated, so that what is present in the particulate material and is to be extracted from it during drying

Material - normally water and / or an organic solvent - is in the liquid state and evaporates during the drying process and / or evaporates. With different goods, however, heating to temperatures above normal room temperature can cause damage. In addition, with certain goods even drying at normal room temperature is disadvantageous because the structure of the particles is changed in an unfavorable manner during a drying process that takes place by evaporation and / or evaporation. These disadvantages and problems with drying a good in a fluidized bed device can be remedied by the particulate good according to US Pat. No. 4,608,764 before the actual drying process to a temperature below the freezing of the water or the other good material to be extracted during drying is cooled and the temperature of the air used to swirl the material and the other process parameters are determined in such a way that the water or said other material is extracted from the material by sublimation. The goods can be gently dried by such freeze drying.

However, drying a particulate material which is swirled to form a fluidized bed requires a comparatively large amount of time even at temperatures approximately the same as room temperature. If the drying takes place at temperatures of the goods below the freezing temperature, the time requirement becomes even greater.

Drying processes are already known per se, in which a particulate material is subjected to the action of mechanical vibrations and / or waves, ie sound vibrations or waves, and / or the action of electromagnetic fields and radiation during the drying process . For example DE-A-3 204 690 discloses a device with a container, a base and means for shaking the container together with the goods located on its base during operation. Furthermore, this device has an electrode arranged above the floor in order to generate an electromagnetic high-frequency alternating field in the space between it and the floor. However, this device, in which the good lies on a floor and is subjected to mechanical vibrations, has the disadvantage that the particles of the good are subject to a relatively high degree of abrasion. In addition, the material that is located between the electrode and the base that serves as the counterelectrode and, in the water-containing state, depending on its composition, may be relatively electrically conductive, may cause electrical discharges that in turn can trigger dust explosions. Due to this risk of discharges and dust explosions, the permissible field of application of the device known from DE-A-3 204 690 is severely restricted.

Presentation of the invention

The invention has for its object to provide a method and a device for drying a particulate material and thereby avoid disadvantages of the known methods and devices. On the basis of the known fluidized bed processes or devices, in which the material to be dried is swirled by an upward air or other gas flow, the aim is in particular to gently dry a particulate material and then to dry the time required for drying as much as possible to keep short if the material to be dried during the Drying process has a relatively low temperature, which is, for example, at most a little above the normal room temperature or approximately in the size of this or even below the freezing temperature of the water and / or other material to be removed from the material during drying. The method and the device should therefore enable drying which is sufficiently gentle to achieve the desired properties of the dried material, but nevertheless can be carried out quickly and economically.

According to the invention, this object is achieved by a method having the features of claim 1 and by a device having the features of claim 8.

An object of the invention therefore consists of a method for drying a particulate material in the interior of a container, gas being passed from a limiting element delimiting the interior space through the interior space, the particulate material and a filter delimiting the interior space at the upper end, wherein the method is characterized in that at least the majority of the material is subjected to the action of vibrations and / or waves and / or brought to rest on the filter during at least part of the drying process when the gas is lifted from the limiting element.

Another object of the invention consists of a device for drying a particulate material, with a container which contains an interior serving to receive the material, which at its lower end by a limiting element allowing gas to be introduced and at its upper end by a that Filter allowing gas to flow out is limited, and with at least one pump in order to allow gas to flow from the limiting element through the interior to the filter and thereby to lift at least most of the material above the limiting element during drying, the device thereby is marked that a vibration and / or wave generating device for generating vibrations and / or waves acting on the material is present and / or that the container and the pump are designed to bear at least the majority of the material to bring on the filter.

The method and the device can be used, for example, for drying, in particular freeze-drying, a particulate material which contains at least one active pharmaceutical ingredient and / or auxiliary substance, is intended for use as a medicament and after drying, for example in for the oral ingestion capsules are filled in or made available for dissolution in water or another liquid. In addition, particulate goods intended for use as soluble foods can also be dried.

The method and the invention are particularly advantageous when drying thermolabile goods. The good particles to be dried can be formed, for example, by freezing a solution and / or suspension. Such particles can be freeze-dried to produce a porous and highly soluble granulate.

Normally, the items to be dried are placed in the same container in which they are to be dried is subsequently dried, subjected to another treatment which takes place under swirling, and is produced at least in part or in full in said container. For example, an at least partially liquid substance, such as a solution or

Spray the suspension into the interior of the container and convert the resulting droplets to their solid state by cooling below their freezing or melting temperature, so that a particulate material is formed. Its particles can be dried immediately thereafter or agglomerated to larger particles before the drying process and / or coated with coatings by spraying with another solution and / or suspension. Of course, there is also the possibility of introducing the material to be dried into the said container in the form of solid, dry or moist particles and subjecting it to a treatment, such as an agglomeration and / or coating treatment, for example with an at least partially liquid substance is sprayed, which serves as a binder and / or to form a coating. With all these variants for the formation of the material to be dried, it is dried during drying at normal room temperature, i.e. at about 20 ° C to 25 ° C, liquid material contained therein, normally water and / or another, for example organic solvent and or suspending agent, at least in part and preferably for the most part or completely by sublimation withdrawn.

For further possible variants and details on the provision of freeze-drying particulate goods and their uses, reference is made to the already cited US-A-4 608 764 and WO-A-88/10150, to which reference is hereby expressly made is taken During the drying process, the gas, which often consists of air, flows upwards through the container and lifts the particulate material from the lower boundary element of the interior, which consists, for example, of a sieve bottom. The amount of gas flowing through the container per unit of time can be determined during the drying process - for example depending on the type of particulate material - in such a way that the particulate material is either completely or at least largely raised to the filter and brought to bear on it or swirled and fluidized in the interior. For the sake of clarity, it should also be noted that the previously used term "the largest part" means a part which amounts to more than 50% of the total quantity of the goods. However, the drying process can also be subdivided into different parts or steps, the particulate material being swirled in the interior of the container during part of the drying process and being raised to the filter during another part of the drying process

Example, the material is swirled in a first step of the drying process and raised to the filter in a second step of the drying process.

If the particulate good throughout

Drying process applied to the filter 21, the good can be dried with or without the action of vibrations and / or waves on the good. If the material is swirled during part of the drying process and is brought to rest against the filter during another part, the latter part of the drying process or even the entire drying process can possibly be carried out without the action of vibrations and / or waves on the material be performed. If the goods are partly in a swirled state and partly in a state of contact with the filter Condition is dried and if the entire drying process is carried out without the action of vibrations and / or waves, the drying process part in which the material is in contact with the filter should take up a relatively large proportion of the total drying time and should preferably take a minimum at least extend over 50% of this. At least in the event that the particulate material is swirled during the entire drying process and is therefore not brought into contact with the filter, the material should be exposed to the action of vibrations and / or waves during at least part of the drying process and, for example, during the entire drying process. The vibrations and / or waves acting on the particulate material can be caused by sound vibrations and / or

Waves with frequencies lying in the audible sound range or in the ultrasound range are formed. However, electromagnetic vibrations and / or waves, namely microwaves and infrared light waves, can also act on the particles.

The method and the device according to the invention are particularly advantageous for freeze drying, but not limited to them, but also suitable for "normal" drying, in which the material to be removed from the material during the drying process evaporates from the material and / or evaporation is withdrawn.

The time required for drying a good can be considerably reduced by the action of vibrations and / or waves on the good pushed by gas from the limiting element and / or by bringing the good into contact with the filter located above the limiting element. This applies in particular to freeze drying or when drying at most about 30 ° C or even only at most about 25 ° C and for example in the range of normal room temperature.

If, for example, the particulate material is swirled and fluidized in the interior with air flowing upward, sound waves can be radiated into the interior, for example, which propagate through the air present in the latter and act on the swirled particles. This significantly accelerates the drying process. The acceleration of the drying process is probably caused, at least in part, by the sound waves causing a vacuum or at least a decrease in pressure on one side of the particles and an increase in pressure on the other side of the particles, these changes in pressure changing with the frequency of the waves. The vacuums or cavitations that occur as a result of the sound waves in particle surface areas can disrupt and tear open a thin air boundary layer, which is probably around the particles in the absence of sound waves, and at least largely saturated with water vapor, and thereby accelerate the vapor waves of the particles .

If the particles are in contact with the surface of the filter adjacent to the interior during at least part of the drying process, this contact already accelerates the drying process without sound vibrations or sound waves or other vibrations or waves acting on the particles. For example, tests were carried out in which a solution was sprayed in such a way that the particulate material present after drying had particle sizes, that is to say particle diameters of at least 0.01 mm and at most 0.1 m in the case of an approximately spherical particle shape would have. In these experiments, for example, batches of the same size of a particulate material formed by spraying a solution and freezing the droplets were either freeze-dried in a known manner without the action of vibrations and / or waves with air in the fluidized bed or else - also without them Exposure to vibrations and / or waves - freeze-dried in such a way that the particulate material formed a layer adjacent to the filter during the drying process. For example, tests have been carried out with frozen solutions of mannitol, glycine or urea. In the case of medicinal products, these three substances often serve as auxiliary substances, namely carrier substances, to which the actual active ingredient is then added. According to these experiments, the time required to dry the material in contact with the filter is 3 to 10 times less than if the material is dried in the fluidized bed without the effect of sound or other waves. Tests have also been carried out on freeze-drying solutions of a very thermolabile pharmaceutical active substance, namely interferon. In the case of freeze-drying in a fluidized bed not according to the invention without the action of sound waves or electromagnetic waves, only about 10% by weight of the water contained in the particles could be removed during drying times of 5 to 6 hours. If, on the other hand, the particles consisting of a frozen interferon solution were dried in contact with the filter in accordance with the invention, the particles were able to dry approximately 70 to 80% by weight of the original during 5 to 6 hours without the effects of vibrations or waves water present in the particles are removed.

Now of course there is a larger one for lifting the material to the filter, at least in the initial phase Air flow rate in the container is required as for swirling the material. Increasing the flow rate tends to accelerate the drying process. However, the test results provide strong indications that the flow velocity in the flow velocity range used as such has only a relatively small influence on the time required for drying and that the shortening of the drying time given when the material is in contact with the filter drying in the fluidized bed is actually largely effected by the filter. The acceleration of the drying process through the filter without the action of vibrations and / or waves may be at least partly due to the fact that the air boundary layer enclosing the particles, more or less saturated with water vapor, by the particles passing through the filter and / or touching each other, disturbed and to a certain extent broken open, so that the particle surfaces come into contact with dry air and / or the filter. In addition, the metallic fibers present in the wetted filter result in good heat conduction, so that heat is supplied to the particles adjacent to the filter not only by the air flowing past them, but also additionally by the heat conduction of the filter, which may also be beneficial accelerates the drying process.

If sound vibrations and / or waves and / or microwaves or infrared light waves also act on the particulate material in contact with the filter, the drying process is of course accelerated even more

It should be noted here that the method according to the already cited DE-A-3 204 690, the material to be dried, lying on a floor, is also flowed through by air and vibrated. The drying process taking place in the method according to the invention, in which the material lies against the filter and in the latter

Sound vibrations and / or waves are generated, but differs in various respects from the method known from DE-A-3 204 690. First of all, drying in the latter does not take place by sublimation, but rather by passing warm air through the material and thus by evaporation and / or evaporation of the water to be extracted during drying. Furthermore, however, there are very different effects if the material to be dried - as in the known method - rests on the upper surface of a vibrating floor or - as in the method according to the invention - by an air or other gas flow of approximately raised from a sieve bottom, lower boundary element of the container interior and to lie on the underside of a

Filters is brought. In the latter case, namely, the drying process can be carried out with a substantially higher air flow rate, which increases the drying speed and prevents gravity from pressing the material onto the support. The avoidance of the material pressing against a vibrating floor due to gravity contributes to the prevention or at least to a strong reduction of the abrasion and is particularly advantageous if the particles of the material have a loose, porous structure, as is the case with particles applies, which were prepared by freezing a solution or suspension. Brief description of the drawing

The invention will now be explained on the basis of an exemplary embodiment of a device shown in the drawing and on the basis of the methods and variants of the device and method which can be carried out with it. In the drawing shows

1 shows a schematic vertical section through a device for producing and drying a particulate material,

FIG. 2 shows an oblique view from below of the filter and of the exciter of the device according to FIGS

3 shows a section of the filter on a larger scale.

Preferred embodiments of the invention

The device shown in FIG. 1, used to manufacture and / or dry a particulate material, has a container 1 held by a frame (not shown), the wall 3 of which, from bottom to top, has a base part 5, a conical jacket 7 that widens upwards , a cylindrical jacket 9 and a cover part 11. The different parts of the wall 3 of the container 1 are provided with flanges at their mutually facing edges, releasably connected to one another by connecting means such as screws and / or quick-action locking members and with sealing means sealed against each other. At least the bottom part 5, and the coats 7 and 9 and for example, the cover part 11 of the wall 3 is also heat-insulating and has, for example, a shell made of stainless steel on the inside and a heat insulation arranged on the outside thereof. In addition, at least the base part 5 and the two jackets 7, 9 of the wall 3 can also be provided with a cooling / heating device, not shown, which has, for example, a channel for a liquid and / or gaseous cooling / heating fluid.

The bottom part 5 is provided with a connection serving as a gas inlet 15 and, when it is connected to the conical jacket 7, contains a limiting element 17 which is horizontal during operation and allows gas to be introduced, namely a sieve bottom 17. In the cylindrical jacket 9 is, for example, an annular one Bracket 19 releasably held a filter 21, the design of which can be seen particularly clearly from FIGS. 2 and 3 ^* . The filter 21 has a horizontal filter section 21a, which extends at least approximately - namely apart from the cross-sectional area occupied by the holder 19 - over the entire interior cross-section of the jacket 9. The filter 21 has a number of hollow tufts 21b distributed over the horizontal cross section of the interior of the container 1 and projecting downward from the horizontal filter section 21a, for example circular in cross section, the upper ends connected to the horizontal filter section 21a are open and closed at the end facing away from the filter section 21a. The filter 21 is formed from a fiber material, namely a fabric, but could also consist of a fleece or the like. The individual threads of the fabric consist of fibers spun together. These fibers consist of various materials, namely partly of an artificial Fabric such as polyester and partly made of a metallic material such as stainless steel. The proportion of plastic fibers is larger by volume and, for example, also by weight than the proportion of metallic fibers. The interior of the container 1, which is delimited at the bottom by the delimiting element 17, ie sieve plate 17, and at the top by the filter 21, is used for the treatment and in particular for drying the particulate material.

The device also has an oscillation and / or wave generating device, designated as a whole with 31, with excitation and / or radiating means in order to generate such oscillations and / or waves during drying and / or to radiate into the interior 23 that these vibrations and / or waves act on the material to be dried which is present in the interior 23. The vibration and / or wave excitation device 31 is for example for generating mechanical vibrations and / or elastic waves, i.e. Sound vibrations and / or waves formed. The generating device 31 has, for example, at least one sound exciter 33 arranged in the area of the conical jacket 7 and namely several sound exciters 33 distributed around the container axis and / or arranged at different heights and / or having different radiation directions, to radiate sound waves into the interior 23. In the present case there are, for example, three sound exciters 33 distributed uniformly around the container axis. The

Vibration and / or wave generating device 31 also has a sound exciter 35 which is arranged on the upper side of the filter 21 and faces away from the interior 23, in order to excite and possibly sound vibrations in the filter additionally radiate sound waves into the interior 23 from above.

The sound exciter 33, 35 can depend on the size of the container and the type of to be dried

Good can be designed to generate sound vibrations and / or waves with frequencies in the audible range or in the ultrasound range. The frequency of the vibrations and / or waves that can be generated is expediently at least 100 Hz, preferably at least 500 Hz and, for example, at least 20 kHz or even at least 30 kHz and is therefore in the last two cases in the inaudible ultrasonic range. However, it can also be provided that the frequency of the excitable by the exciters 33, 35

Vibrations and / or waves less than 18 kHz and even less than 10 kHz. and is in the audible range. The vibrations and / or waves generated by the exciters 33, 35 during operation can all be at least approximately or even exactly the same

Frequency or different frequencies. In addition, the wall 3 of the container 1 can be provided with sound insulation if necessary.

If the sound exciters 33 are to be used to generate sound with frequencies in the upper, audible frequency range or in the ultrasound range, each of them can be designed, for example, as a pneumatic exciter operating on the principle of the Galton whistle. Such an exciter can have a nozzle with an annular gap-shaped mouth opening, a cutting edge, a resonance tube enclosing the nozzle mouth and a sound cone which widens conically away from the nozzle mouth at its end. The inlet of the nozzle is equipped with a gas supply Device connected, which in the present case consists of a suction pump 37 from the environment and for compressing this air 37 and a reservoir 39 for the compressed air. The end of the horn of the exciter 33 facing away from the nozzle mouth faces the interior 23. While the sound funnel in known exciters of this type is open on its end face facing away from the nozzle mouth, each exciter 33 has at its end facing the interior 23 a membrane 33a which enables sound transmission into the interior 23, but which is gastight against the resonance. Closes the cavity of the exciter 33 so that the compressed air used to operate the exciter 33 does not get into the interior 23. The sound funnel of the exciter 33 can have lateral openings through which the compressed air required for operating the exciter can flow into the environment. The exciters 33 can also be equipped with an adjusting device for adjusting the frequency of the sound generated.

The or each exciter 35 can be designed, for example, for the electrostrictive, namely piezoelectric conversion of electrical energy into sound and a piezoelectric transducer with at least one disk-shaped and / or foil-shaped element 35a made of piezoelectric ceramic and at least two elements have electrodes 35b, 35c arranged on both sides facing away from each other. The electrode 35c located closer to the filter 21 can, for example, rest at least in places on the horizontal filter section 21a and possibly be firmly connected to it. The sound exciter 35 has a through hole 35d in the region of each villi 21b. Furthermore, the sound exciter 35 can also be in the areas of the horizontal filter which are not occupied by the villi. section 21a have holes 35e. The electrodes of the sound exciters 33, 35 are connected in an electrically conductive manner to an electrical oscillator 41, which is designed to generate an electrical, for example sinusoidal voltage, but could also provide a periodic sequence of pulses of any shape. The oscillator 41 can also have control and / or regulating means in order to enable manual, gradual or continuous adjustment of the frequency and / or the frequency of the electrical signals generated

To regulate voltage to one of the resonance frequencies of the mechanical resonator formed by the exciter 35 in cooperation with the filter 21. Advantageously, the or each electrode 35c of the exciter 35 facing the interior 23 is electrically conductively connected to the electrical mass and the metallic parts of the container wall 3.

On the upper side of the filter 21 there is a shaking device 45 which serves to shake and clean it. The cover part 11 is provided with a gas outlet 51, which is connected to the cavity of the container 3 present above the filter 21. A spray member 53 has at least one spray nozzle opening into the interior around 23 and is connected by a line to a liquid supply device 55. A coolant inlet 57 opening into the interior 23 is connected to a coolant supply device 59.

The gas outlet 51 of the container 1 is connected via a line 65, a valve 67, a pump 69 formed by a blower, a filter 71, a vapor / liquid separator 73, a gas cooling device 75 and a valve 77 to the gas inlet 15 of the Container 1 connected. There is a branch between the valve 67 and the pump 69 is present, from which a bypass line 79, ie a "bypass" with a valve 81 leads to a branch of the connection connecting the cooling device 75 to the valve 77, the bypass line 79 possibly also having a thermally insulated gas reservoir (not shown) can. The gas outlet 51 of the container 1 is still via a line 85, with a valve 87, a pump 89 consisting of a blower, a filter 91, a vapor / liquid separator 93, a gas heating device 95 and a valve 97 with the container -Gas inlet 15 connected. The inlet of the pump 89 is connected to the outlet of the gas heating device 95 via a bypass line 99 containing a valve 101. The container 1 and the lines 65, 79, 85, 99 enable the formation of various circuits. These are also provided with gas supply / gas discharge means in order to supply and remove gas, namely air, from them. The gas supply / discharge means can, for example, two air intake openings, which are connected via a valve 103 or 105 to the inlet of the pump 69 or 89, and one via a valve 107 to the gas outlet 51 of the container 1, into the environment have opening air outlet.

The pump 69 and / or at least one of the valves 67, 77 are designed such that, during the operation described below, the amount of gas conveyed through the container 1 by means of the pump 69 per unit of time and thus the gas flow rate resulting in the container changes and can be adjusted. Otherwise, temperature, pressure and humidity sensors (not shown), measuring and display devices connected to them, and electronic control and / or regulating means can be present at various points in order to enable manual and / or to enable automatic control and / or regulation of the various processes taking place during operation.

The production of a particulate material from an aqueous solution and / or suspension which contains at least one dissolved and / or suspended pharmaceutical active ingredient and / or auxiliary substance will now be explained. The solution and / or suspension is first introduced into a reservoir of the liquid supply device 55 and sprayed into the interior 23 with the spray element 53 during a manufacturing phase of the method. At the same time, a coolant, namely dry ice powder, is introduced into the interior 23 from the coolant supply device. Furthermore, gas, namely air, is circulated through the line 65, the filter 71, the vapor / liquid separator 73, the gas cooling device ^* 75 and the container 1 simultaneously with the pump 69. This the interior 23 with at least generally directed upwards

Air flowing through the flow swirls the liquid droplets sprayed into the interior 23 with the spray element, as well as the dry ice particles above the sieve tray 17, as is indicated by tracks 111. The liquid droplets are cooled below their freezing temperature by the air cooled in the cooling device 75 and the dry ice powder likewise swirled by the latter and thereby solidified. The dry ice particles absorb heat during this process, so that they are converted into gaseous carbon dioxide, which is circulated together with the air.

When the intended amount of the good formed by freezing liquid droplets in the interior 23 is located and forms a fluidized bed in it, the spraying of liquid and the introduction of dry ice powder is stopped. Thereafter, the batch of particulate material present in the container begins to dry or, if one takes into account that some liquid has possibly been removed from the particles during the freezing process, at least the main phase of the drying process. This is carried out as freeze drying. Accordingly, the air circulated for drying by the pump 69 is brought to a temperature with the cooling device 75 at which the temperature of the particles present in the interior 23 remains below their freezing or melting temperature. The air conveyed by the pump 69 and introduced into the container 1 through the gas inlet 15 lifts the particulate material from the sieve tray 17 during drying. The amount of air conveyed through the container 1 by the pump 69 per unit of time can be adjusted during the drying process, for example depending on the type of the particulate material, such that the particulate material is at least for the most part or completely either up to the filter 21 is raised and brought to bear against it or is swirled and fluidized in the interior 23. However, the drying process can also be divided into different parts and carried out step by step. When drying, the air conveyed by the pump 69 through the container can be adjusted, for example, at least in a first part or step of the drying process in such a way that the particles of the material to be dried or at least most of it swirls above the sieve plate 17 in the interior become. In a subsequent, second part or step of the drying process, the amount of air passed through the container per unit of time can are increased so much that the particulate material or at least the major part of it is lifted up to the filter 21 and forms a layer lying on the side or surface of the filter 21 facing the interior 27. Because of the villi 21b, the surface of the filter 21 is considerably larger than the horizontal cross-sectional area of the interior of the jacket 9. This means that the layer of the particulate material in contact with the filter 21 in the second part of the drying process remains relatively thin even when it is is formed by a relatively large amount of particulate material.

If the particulate material is swirled during the entire drying process and, for example, also in the event that the material is swirled during part of the drying process, the sound exciters 33 and possibly additionally the sound exciter 35 and above are also used during the swirling of the goods the filter 21 connected to this radiated sound waves into the interior 23. The sound waves radiated into the interior 23 are then transmitted to the swirled particles by the air present in the interior.

If the particulate material is in contact with the filter 21 during at least part of the drying process or during the entire drying process, at least during this part of the drying process or during the entire drying process, the

Sound exciter 35 sound vibrations are generated which cause 21 vibrations and / or waves in the filter. The filter 21 then transfers its oscillating movements to the particles in contact with it. It goes without saying that when the material is in contact with the filter 21, sound waves can also enter the sound exciter 23 Interior 23 are irradiated. These waves are then transmitted through the air to the particles on the filter.

After the goods have dried, the supply of cooled air to the gas inlet 15 of the container 1 is ended. If the dried particulate material hanging on the filter 21 does not fall off automatically when the air supply is interrupted, the filter 21 can be shaken with the shaking device 45 in order to detach the particles from the filter. The vibrating movements of the filter 21 generated by the vibrating device can also be perceived as sound vibrations, but normally have substantially lower frequencies than the vibrations generated with the exciter 35 and therefore larger amplitudes than these.

Advantageously, the interior of the container 1 is fluidly separated from the pump 69, the filter 71, the vapor / liquid separator 73 and in particular the gas cooling device 75 by closing the valves 67, 77 by closing the valves 67, 77 and therefore by opening the previously closed Valves 87, 97 are fluidly connected to the pump 89, the filter 91, the vapor / liquid separator 93 and the gas heating device 95. With the pump 89, the container can then be supplied with air heated by the gas heating device and circulated until the inner surface of the container wall, the sieve plate 17, the filter 21, the other parts of the device inside the container and the like Particulate goods are heated to approximately the ambient temperature. Thereafter, the supply of air conveyed by the pump 89 to the container 1 is stopped and this is temporarily opened at the lower end in order to remove the batch of the dried, particulate material. The warming up of the inner parts of the container and the good before the removal of the good can prevent the ambient air coming into contact with the good when the good is being removed and inside and outside of it, the inner surfaces of the container and the good moistened by condensation of the water vapor normally contained in it.

In the period in which the container with the pump

89 warm air is supplied for warming up and the material is then removed, the valve 81 can be opened and, when the valves 67, 77 are closed, air can be pumped 69 via the filter 71, the vapor / liquid separator 73, the gas cooling device 75 and the bypass line 79 circulated, dried and cooled and thereby conditioned for the production of the next batch of the particulate material. When the batch of the produced particles is removed from the container 1 and this is closed again, the pump 69 can be reconnected to the container 1 by opening the valves 67, 77, the valve 81 closed and almost immediately the production of a new batch of particulate Start well. During the period of time required for producing and drying the new batch of the particulate material, or at least for part of it, the pump 89 can circulate air through the filters 91, the steam / with the valves 87, 97 and the valve 101 open. Circulate, dry and heat the liquid separator 93 and the gas heating device 95 and thereby condition it for the next necessary heating of the container and the goods. Moreover, in the various operating phases, gas or air can be passed between the valves 103, 105, 107 as needed different circuits and the environment can be exchanged.

The procedure and setup can be changed in a number of ways.

The device described with reference to FIGS. 1 to 3, according to the preceding description, makes it possible, for example, to swirl the particulate material during the entire drying process and at the same time to subject it to the action of sound waves, without dispensing with the particulate material or at least its raise most of the filter 21. The filter would then, as in known fluidized bed devices, only have the purpose of undesirably preventing particles coming up through the region of the container interior intended for swirling, such as dust particles created by abrasion, from escaping from the container. In another possible method variant, on the other hand, after the desired amount of solid particles has been formed by freezing liquid droplets, the particles are immediately raised to the filter 21 by increasing the flow rate and then dried. If the device is provided exclusively for carrying out one of these two process variants, either the sound exciter 33 or the sound exciter 35 can be omitted. If the particulate material is dried while in contact with the filter 21, this can also be done with or without the generation of sound vibrations in the filter. In the latter case, it is even possible to omit both the sound exciter 33 and the sound exciter 35.

The training of the sound exciter can also be based on varied ways can be varied. For example, the pneumatic sound exciter 33 could be replaced by an appropriate number of piezoelectric sound exciters or a single piezoelectric sound exciter encircling the container axis. Conversely, the piezoelectric sound exciter 35 could be replaced by at least one pneumatic sound exciter replace. Furthermore, to generate the sound vibrations and / or waves, sound exciters could also be provided with transducers which convert electrical energy into movements of a membrane using electromagnetic induction and are designed, for example, in the manner of electrodynamic or electromagnetic loudspeakers . In order to excite vibrations in the filter 21, the force effect of electrical fields between the two electrodes of an electrical capacitor could also be used, one electrode of the capacitor being formed by the filter and the other electrode of the capacitor being formed by an electrode arranged above the filter. In this case, the filter would of course be designed in such a way that all of its areas are connected to one another in an electrically conductive manner.

Furthermore, you can the vibration and / or

Equip wave generating devices instead of with sound exciters or additionally with at least one exciter in order to excite vibrations and / or waves of the electromagnetic field, such as microwaves and / or infrared light waves, and to radiate them into the container interior. A microwave exciter can, for example, have a klystron connected to the interior of the container. An infrared exciter can be, for example, a predominantly incandescent lamp that generates infrared light, a high-pressure xenon lamp, a quartz mercury lamp, a dark radiator plate and / or a semiconductor radiator exhibit. At least in the case that freeze drying is provided, the or each infrared exciter is preferably designed and arranged in such a way that it heats the gas flowing through the container interior as little as possible by heat conduction. The particulate material can then be exposed to the effects of electromagnetic field vibrations and / or waves during drying, when it is swirled and / or when it rests on the filter.

The number, shape and size of the villi of the gas-permeable filter 21 can also be varied. Furthermore, the villi could be provided with metallic, helical spring-like coils to reinforce and improve the vibration or wave propagation. Furthermore, instead of the villi 21a, which are circular in the horizontal cross section, a villus having another cross-sectional shape could be provided. In addition, the villi could be omitted and the filter provided with other sections that form an angle with a horizontal plane. For example, the filter could be wavy and / or zigzag in a vertical section. The filter 21 could contain fibers made of a natural, organic material instead of the plastic fibers. Instead of using a filter which is formed from a mixture of fibers made of organic material and metallic fibers, one could also provide a filter made of fibers which have a metallic core and a coating of plastic enveloping it. A filter made exclusively of metallic fibers could possibly also be used.

As already mentioned in the introduction, particles can be swirled in the container before the drying process and thereby agglomerate into larger particles and / or coat so that the particulate to be dried is then formed by the agglomerated and / or coated particles. If such treatments are provided before drying, it may be advantageous in certain cases to provide a rotatable rotor disk which rotates during agglomeration and / or coating of the particles instead of the sieve tray 17 which is stationary during operation. The air intended for passage through the container can then be introduced through an annular gap between the container wall and the rotor disk into the interior serving to treat and dry the material.

In the device shown in FIG. 1, the air conveyed by the pump 89 can flow through the container 1 from bottom to top. However, the pump 89, the filter 91, the vapor / liquid separator 93 and the gas heating device 95 could also be connected to one another and to the container 1 in such a way that the pump 89 can convey air through the container 1 from top to bottom. The air conveyed by the pump 89 through the container 1 could then also serve, in addition to the described heating of the container inner parts and the dried material, to blow the latter away from the filter 21, so that the vibrating device 45 could then possibly be dispensed with .

Furthermore, another gas, for example nitrogen, could be passed through the container to swirl and / or dry the particulate material instead of air.

Claims

PATENT CLAIMS 1. A method for drying a particulate material in the interior (23) of a container (1), wherein gas from a limiting element (17) delimiting the interior (23) below through the interior (23), the particulate material and the interior (23) is passed through the filter (21) delimiting at the upper end, characterized in that at least most of the material is at least during part of the drying process in the state of the action of vibrations and / or lifted off by the gas from the limiting element (17). or subjected to waves and / or brought to bear on the filter (21). 2. The method according to claim 1, characterized gekenn¬ characterized in that the material is kept during at least part of the drying process at a temperature at which the material present in the material and to be removed during drying, for example water, at least partially and preferably is completely in the solid aggregate state and is removed from the good by sublimation. 3. Device according to claim 1, characterized in that the particulate material to be dried is produced by spraying a solution and / or suspension into the interior (23) and by swirling and freezing the droplets formed during spraying in the interior (23) . 4. The method according to any one of claims 1 to 3, characterized in that the vibrations and / or waves acting on the particulate material are acoustic vibrations and / or waves, which in the Interior (23) existing gas and / or the filter (21) are transferred to the particulate material and their frequency is expediently at least 100 Hz, preferably at least 500 Hz, for example at least 20 kHz and / or possibly less than 18 kHz. 5. The method according to claim 4, characterized in that the sound vibrations and / or waves are at least partially pneumatically excited, wherein the pneumatic excitation is preferably carried out without the gas used for excitation, for example previously compressed air, in reaches the interior (23) containing the particulate material. 6. The method according to claim 4 or 5, characterized gekenn¬ characterized in that the sound vibrations and / or waves at least in part by electrostriction, for example using the piezoelectric effect, and / or at least in part by moving a membrane by means of electromagnetic induction are generated. 7. The method according to any one of claims 1 to 6, characterized in that the vibrations and / or waves acting on the particulate material are at least partially formed by vibrations and / or waves of an electromagnetic field, such as microwaves and / or infrared light waves. 8. Device for drying a particulate material, comprising a container (1) which contains an interior (23) for receiving the material, which at its lower end by a gas-permitting limiting element (17) and at its upper end is limited by a filter (21) which allows gas to flow out, and by at least one Pump (69) for flowing gas from the limiting element (17) through the interior (23) to the filter (21) and thereby lifting at least most of the material above the limiting element (17) during drying, characterized in that that a vibration and / or wave generating device (31) for generating vibrations and / or waves acting on the material is present and / or that the container (1) and the pump (69) are designed to at least the largest part to bring the goods to rest against the filter (21).