WO2005038371A1 - Method for drying a particularly liquid or pasty material for drying - Google Patents

Abstract

The invention relates to method from drying a particularly liquid or pasty material for drying, whereby the material for drying (1a) is introduced into a drying container (2), pressurised with a hot gas and/or through which a hot gas flows. The method is characterised in that a filling material made up of a number of filling bodies (3) is introduced into the drying container (2), whereby the filling bodies (3) are kept in motion during the drying process and come into contact with each other and/or with the material for drying (1a) and/or with the container wall.

Description

 Method and device for drying a particular liquid or pasty dry material

The invention relates to a method for drying a particular liquid or pasty material, after which the material to be dried is introduced into a drying container, which is acted upon by a hot gas and / or flows through a hot gas, and then in the drying container one of a plurality of Packing existing filler is introduced.

The liquid or pasty material regularly contains a high proportion of a solvent before treatment, Σ. B. water, which should be reduced in the course of the drying process by a predetermined amount.

For drying such moist goods a variety of methods are known. When drying unsouched, flowable materials in particular the problem arises that they stick in the course of the drying process, pasty or agglomerate in other forms and can adhere to surfacesi For this reason, liquid to pasty goods are processed so far with special methods, eg. B. in fluidized bed dryers or by way of spray drying. These processes ₍ are technically very complex and energetically.

In the generic state of the art according to JP 01004201 A, a drying column is used as the drying container into which the material to be dried is introduced on the head side. Starting from the bottom of the drying column, hot gas flows in. At the top of the drying column, the powdery substance thus produced is withdrawn. It can not be excluded in principle that not individual grains still are wet. In addition, the distribution of commissions can not be influenced practically.

The same applies to the teaching of JP 07116491 A, in which a horizontally lying and rotating drying container is heated by means of a peripheral heating coil. As a result, the heat transfer takes place from the wall of the drying container and is therefore not necessarily suitable for ensuring a uniform drying of the filled material can.

The invention is based on the technical problem of further developing such a method so that a proper and cost-effective drying is made possible with low equipment and energy expenditure, while at the same time providing for a small grain size of the dried material. In addition, a particularly suitable device is to be specified, which is particularly suitable for carrying out the method.

To solve this problem, the invention proposes in a generic method, that the packing be kept in motion during the drying process and come into contact with each other and / or with the material to be dried or drying material and / or with the container wall of the drying container.

The invention is initially based on the recognition that the problems occurring in connection with the drying of particular liquid or pasty substances can be avoided if a loose bed of rollfähigem filler kept constantly in motion and against each other in a traversed by a hot gas drying tank is rubbed without the filling material is smashed thereby.

In such a drying container, in which the rollable filling material is kept in motion, the liquid to pasty product to be dried is added. By the movement of the filling material and / or the container wall, both the container wall and the filling material is wetted. As a result, the surfaces are made available for evaporation z. B. the water are required (namely in the form of the container wall and additionally in the form of the surface of the packing).

The surface coverings that form in the course of drying are constantly being removed and the surfaces rewetted. As a result, the adhesion of the dry material is continuously broken on the surfaces and renewed so that no thick layers can form. It has been found that even very firmly adhering materials that can form during the course of drying, are constantly removed and reapplied. After a given treatment time, solid, powdery to granular particles with sufficiently low humidity are made available. These can be z. B. are separated by means of a screening device from the filler. The filling material is then available for further drying operations.

Of particular importance in the context of the invention is that the filling material is kept constantly in motion in the drying container. There are various possibilities for this. Thus, the drying container itself can be made to move, z. For example, by ^"rotating. The filler material is thus held in place by rotating the Trockriungsbehälters, including a drum in motion. The mixing of the filler material can be effected by installations having low surface, for example, by coaxially installed in a predetermined distance from the drum wall rods, to be improved. Alternatively, there is the possibility that the filling bodies are set in motion with at least one agitator arranged in the drying vessel or

being held. Particularly advantageous in this context, if the moving parts of the agitator have a low total surface area and z. B. consist of an array of rods. The filling material is kept in motion in a similar manner as this is effected by appropriate installations of a rotating drum. Of course, it is also possible to combine the various possibilities in which the drying container is both rotated and provided with an internal agitator. Characterized in that the filling bodies are kept in motion during the drying process, they hit each other and / or to the container wall, so that their surfaces are constantly renewed and then optionally crusting of the liquid or pasty material are broken up. In this case, the liquid or pasty material in any form in the drying container is given, that is as a liquid, as a pasty mass or as a more or less solid, but moist substance, for example in the form of raw or cooked fish, meat etc. In this case, all substances have in common or is the liquid or pasty material to be dried characterized by the fact that the material in question forms a so-called glue phase during drying and consequently has strongly adhesive properties in this phase.

This means that the material to be dried, which is at least slightly flowable when it is introduced into the drying container, changes into a sticky state as a result of the drying process, adheres to the filling bodies and eventually forms a crust at this point. As a result of this, running through the drying glue phase there is a risk that the drying container is clogged overall and on the output side not as desired a powdery consistency is achieved.

The invention now meets this problem by the fact that the filling bodies are constantly kept in motion during drying and thus can not stick together or already formed crusts are broken up. In this case, the hot gas is provided for drying either directly available, in which a hot air generator is used or is obtained indirectly, for example by means of a heat exchanger using other processes.

As a filler body preferably rollable filler, for example, spherical, rounded or cylindrical packing are used. In this case, spherical packing or rolling bodies have proven in the form of steel balls with several centimeters in diameter particularly suitable. Because they not only have a large surface, which is important for the drying process, but are easy to keep in motion during the drying process. In most cases, the density or grain density of the filler is greater than the density of the material to be dried or the dried material.

It is also important that the fillers are not destroyed during the drying process or break. Further, it is advantageous if the filler bodies are formed so that the dry material adheres only slightly to the packing. In this context, a particularly advantageous variant of the method is characterized in that gravel, z. B. natural gravel, preferably granite gravel is used. But it can also (artificial) filler metal, plastic or ceramic can be used. In this case, the filler, a coating, for. B. have a hydrophobic coating, so that a total of water-repellent packing are provided.

The packing can have a grain size of 20 to 80 mm, z. For example, 25 to 70 mm. Preferably, a grain size of 32 to 64 mm is used. The

Grain density of the filler should substantially exceed the density of the (dried) dry material substantially.

As a hot gas preferably hot air of a predetermined temperature is used, which preferably flows through the drying vessel. In this case, the hot gas is preferably introduced with the proviso in the drying vessel, that its partial pressure of the solvent to be dried is lower than the vapor pressure of the solvent in the dry material. Consequently, the hot gas quantity, the hot gas flow rate and / or the hot gas temperature are set. The hot gas may be directly or indirectly heated air. With solvent is meant in the context of the invention of the dry matter in the course of the drying process to be withdrawn and solvent. This may in particular be water.

According to a further proposal of the invention, the inlet temperature and / or the outlet temperature of the hot gas are regulated during the current drying process. Preferably, the inlet temperature and / or the outlet temperature are kept constant during the initial drying process so as to obtain an energy efficiency that is optimum in economic terms. If only a small amount of solvent can be evaporated off, the inlet temperature is regulated down accordingly so as not to unnecessarily heat the dry material. For this purpose, air or gas can be passed by a controllable fan to a controllable burner or other heater, wherein the fan power is controlled by the measured outlet temperature of the hot gas from the dryer and the heat output of the burner / heater to the inlet temperature of the hot gas in the dryer. At the end of the drying process, which z. B. can be seen on the basis of the temperature-power curve, can advantageously with the heat storage of the contents with the burner off

or heater and further blower the remaining drying can be made.

Alternatively or additionally, the invention proposes that the vessel wall of the drying container is completely or at least partially heated.

The invention also provides a device for drying a particular liquid or pasty material, which is particularly suitable for carrying out the method described. This device has a drying container, in which the material to be dried and a filling material consisting of a plurality of filler material is introduced, and further has a hot gas supply, wherein the packing in the drying container in motion and held.

The drying container may be a substantially horizontal or inclined drying drum. According to another proposal of the invention, the drying drum is provided with a drive unit, so that the drying drum is movable, for. B. can be rotated. The rotation of the drying drum then allows the packing arranged in the drying drum to be set in motion. It is advantageous in this context, if in the drying container Mischeinbauten, z. As rods are installed, which improve the mixing of the filler. A cylindrical drum can be, for example, coaxially extending rods or rods or webs which are arranged directly at or at a predetermined distance from the drum wall.

In an alternative embodiment, the invention proposes that in the drying vessel at least one agitator is arranged, with which the

Fill material can be kept in motion. The agitator may be a rod agitator made up of a plurality of rods, for example coaxially disposed in the container. Again, it is of particular importance that the moving parts of the agitator have the lowest possible total surface area. By a suitably designed agitator, the packing can be kept in motion in a similar manner, as this is done with a rotating drum with corresponding internals. The drying container can be designed as a multi-chamber drying container having a plurality of drying chambers, so that the drying can be carried out in a batch process. In this case, the drying drum by annular discs in several, z. B. be divided into three chambers. These chambers are successively flowed through by the hot gas, so that it is possible to work in the successive chambers at different, descending temperature levels. In this way, an improved energy yield can be achieved. Conveniently, the chambers are filled depending on the respective temperature level with different amounts of Füllmateriäl and dry matter, so that the drying process in all chambers can be completed at the same time.

A comparable effect can also be achieved with a single-chamber drying container, if this - as already mentioned - is operated in an inclined position, that is, when the longitudinal axis of the drying drum is arranged inclined at a predetermined angle to the horizontal. Then there is a higher amount of material during operation in the lowered portion of the container than in the non-lowered portion. The hot air is preferably supplied in this embodiment from the direction of the lowered end side of the container. The hot air thus flows through and

to areas of the container with decreasing capacity. In this way, the fact is taken into account that the temperature of the hot gas in the course of flowing gradually decreases and at the same time the water vapor content increases, so that the hot gas during passage through the drum can absorb different amounts of water vapor.

According to an advantageous development, the drying container has one or more closable screen openings. In a multi-chamber container sieve openings are provided in the region of each chamber. Sieböffnüng means a covered with a sieve or filled opening or opening in the container wall. Closable means that the sieve opening can be closed with at least one lid, at least one flap, at least one slide or the like.

Due to the (unclosed) sieve opening, the dried powdery or granular dry material or dried material passing by the continuous movement can be discharged at the sieve opening, the filling material (filling material or filler plus still moist material) remaining in the drum. It is useful if the mesh size of the sieves in the sieve openings is set up so that only the dry material and not the filling bodies are discharged. The heat stored in the packings can thus be used for subsequent drying processes. In the course of the drying process, the screen openings remain closed as long as the drum wall liquid or pasty dry material is passed. Only then are the sieve openings released, so that the discharge of the material to be dried can begin. In this connection, the invention proposes that a collecting container for the dried material emerging from the sieve openings be arranged below the drying container. But it is also possible to operate the system according to the invention continuously, so that a continuous drying process is performed, in which the

Feeding the material to be dried and the discharge of the dried material done continuously.

The hot air supply preferably has at least one heater, for. As a burner, and at least one fan. The blower is preferably a controllable blower. Likewise, the burner is preferably designed as a controllable burner. In addition, the container walls of the drying container can be heated.

In an advantageous embodiment, additional installations are provided in the Trocknungsbeh older, z. B. may be formed helical, and on the one hand support mixing on the other hand facilitate the loading and unloading of the dryer with filler and / or dry material.

In embodiments with an arranged in the drying vessel agitator, it is advantageous if this agitator z. B. by screw-like arrangement of the internals allows the transport of the filler to allow loading and unloading of the dryer with filler or to facilitate. Preferably, the drying container has an inlet opening and an outlet opening with a large cross section, which allow a virtually resistance-free flow through the drying container with hot gas. There is also the possibility that the drying tank has only one opening with a large cross-section for gas exchange. Then the hot gas can be blown into the vessel by means of a lance with a significantly smaller cross-section. Overall, the arrangement of the ^' internals of the drying container should be designed so that there are no blind spots in which the dry material can collect, without being able to be abraded by the filler can.

The discharge of the dried material can be done hydraulically, for example by means of air flow. It must of course be ensured that the air velocity is high enough to be able to transport the fines or the powdered dried material to the outlet or from the inlet opening to the outlet opening. In this way it is ensured that the dried product with the desired degree of drying and in the required consistency immediately discharged and removed from the heating zone.

In this case, the largest part of the dried material can be discharged via a separator, such as a cyclone, wherein the need for the discharge air or the gas, which is warmed up as a result of the drying process, are returned to energy optimization. In other words, the air flow used for the discharge of the dried material is used through the drying tank through to the outlet in three ways.

First, the air flow is adjusted so that only dried material is transported with the desired powder fineness, which therefore has as a result of the grinding process through the packing on the desired grain size. Secondly, the air flow ensures that only dried material is discharged which has the desired moisture content. Both can be controlled with the speed of the air flow, in that only particles of a certain size and an associated weight are (can) be transported by the air flow at all. Third, the air flow ensures that the already dry and present in the desired consistency Good is not unnecessarily further dried and subjected to the hot gas. It is understood that the air flow for discharge usually coincides with the hot gas for the drying process, although of course different air currents on the one hand for drying and on the other hand for the

Discharge be covered by the invention. If the hot gas is used both for the drying process and for the discharge of the dried material, it will be provided in any case a return to the inlet after separation of the dried material for reasons of energy efficiency.

The use of the method according to the invention is recommended, for example, in the case of a protein concentrate which also contains fractions of oils. Such protein concentrates may be produced in the course of fishmeal processing. After the drying process has been carried out with the process according to the invention, powdery to granular particles with sufficiently low moisture are obtained.

In the following the invention will be explained in more detail with reference to a drawing showing only one exemplary embodiment.

The single FIGURE shows a schematic side view of an apparatus according to the invention for drying a liquid or pasty material 1a. This comprises a drying container 2, in which the material to be dried a and a filling material 3 consisting of a plurality of filling material is introduced. To the drying tank 2, a hot air supply 4 is connected, which has a hot air generator 5. The hot air generator 5 is connected to the drying container 2 via a hot air duct 6. According to the packing 3 are brought in the Trocknungsbeh age 2 in motion and kept in motion during the drying process. For this purpose, the drying container 2 is designed as a rotatably mounted drying drum 2, whose longitudinal axis α is inclined at a predetermined angle to the horizontal. The angle α may for example be 1 ° to 10 °, preferably 1 ° to 5 °. In the exemplary embodiment, the angle is approximately

3 °. There is the possibility that the angle α is adjustable via a suitable adjusting mechanism. This is not shown in the figure.

Further, a drive unit 7 is connected to the drying drum or the drying container 2, with which the drying drum 2 can be set in rotation. For this purpose, a suitable sprocket 8 is placed on the front side of the drying drum 2, which is in operative connection with the drive shaft. The drive can also be connected in other ways with the drying drum 2.

By the rotation of the drying container 2, the packing 3 are set in motion. In the packing 3 is rollable filler, z. For example, steel balls. These fillers or rolling bodies 3 initially provide an additional surface (in addition to walls of the drying container 2). In addition, however, it is crucial that the filler 3 represent a quasi-continuous mill, in which the surfaces are constantly renewed by rotation and friction. In addition, the container walls are constantly scraped. The adhesion of the moist material 1a to the surfaces is consequently continuously broken and renewed so that no thick layers can form. The effect is improved by arranging mixing installations in the form of rods or webs 9 in the drying container 2. In the exemplary embodiment, such webs are shown as a driver 9, which extends in the container longitudinal direction and z. B. are connected directly to the drum inner wall.

The supply of the material to be dried 1 a via a supply line 10th Der

Discharge of the dried material 1b takes place via at least one sieve opening 11.

This is designed as a closable sieve opening 11. A corresponding cover 12 for closing the sieve opening 11 is shown in the single figure.

indicated. In the course of the drying process, the sieve opening 11 initially remains closed. If the sieve opening 11 is then released, the discharge of the dried product 1b can take place. For this purpose, a collecting container for the emerging from the sieve opening 11 dried material 1 b may be disposed below the drying container 2, in the figures, this collecting container 13 is merely indicated. The screen disposed within the screen opening 11 has a mesh size such that the discharge of the packing 3 is prevented. At the same time, however, the discharge of the dried product 1b is made possible, which is finely ground by the constant movement.

Incidentally, it can be seen in the figure that the drying container 2 flows through the hot air in the course of the drying process. For this purpose, an exhaust air line 14 is connected to the hot air supply 4 opposite side of the drying tank 2. The material supply via the supply line 10 also takes place from the side opposite the Heißiuftzuführung side of the drying drum 2. The support of the drying drum 2 can be done via a plurality of bearings 15, which may be formed as a rolling bearing or plain bearings. In addition, a pressure bearing 16 is indicated in the figures, which may be formed, for example, as a sliding bearing. Against this thrust bearing 16, the inclined drying drum 2 is supported from the front side.

The figure also shows that with inclined drying drum 2, the hot air supply 4 from the direction of the lowered end side of the drying drum 2 takes place. This is important because when operating in an inclined position in the lowered (right) area of the drum 2 regularly higher amounts of material are present as in the not lowered or raised (left) portion of the drum 2. In this case, the amount of material to be dried 1a from the not lowered end of the drying drum 2 to the lowered end of the drying drum 2, as it were

continuously too. Consequently, the hot air gradually flows through different filling regions of the drying container 2.

Since the temperature of the hot gas in the course of passage through the drying drum 2 decreases and the water vapor content increases at the same time, so that the hot gas during passage through the drying drum 2 can absorb different amounts of water vapor, it comes to simultaneous drying of the entire moist material 1a, which for dried good 1b becomes. The drying process can therefore be completed with a uniform degree of drying at the same time. Due to the inclination of the system at the same time corresponding hot air supply 4, a batchwise, simultaneous drying is thus possible.

Claims

claims: 1. A method for drying a particular liquid or pasty material (1a), after which the material to be dried (1a) is introduced into a drying container (2), which is charged with a hot gas and / or through which a hot gas flows, and after which in the drying container (2) is introduced from a plurality of filler bodies (3) existing filling material, d a d u r c h e c e n c i n e s that the filling bodies (3) are kept in motion during the drying process and come into contact with each other and / or with the material to be dried (1a) and / or with a container wall of the drying container (2). 2. The method according to claim 1, characterized in that the drying container (2) for moving the filling body (3) is moved, for Example rotates. 3. The method according to claim 1 or 2, characterized in that the filling body (3) with at least one in the drying container (1) arranged agitator are set in motion and / or held. 4. The method according to any one of claims 1 to 3, characterized in that as filler (3) rollable packing can be used. 5. The method according to any one of claims 1 to 4, characterized in that the hot gas with the proviso in the drying vessel (2) is introduced, the partial pressure of which is to be dried solvent is lower than the vapor pressure of the solvent in the dried material (1b). 6. The method according to any one of claims 1 to 5, characterized in that the input temperature and / or the outlet temperature of the hot gas are controlled during the drying process, preferably each kept constant. 7. The method according to any one of claims 1 to 6, characterized in that the at least one ßehälterwand the drying container (2) is heated at least partially. 8. An apparatus for drying a liquid or pasty material (1 a), in particular for carrying out the method according to one of claims 1 to 7 with a drying container (2), in which the material to be dried (1 a) and one of a plurality of filling bodies (3) existing filling material are introduced, and with a hot air supply (4), characterized in that the packing (3) in the drying container (2) during the drying in motion and held. 9. The device according to claim 8, characterized in that the drying container (2) is designed as a substantially horizontally or inclined arranged Trocknungstrommei (2). 10. Device according to claim 8 or 9, characterized in that the drying container (2) has one or more closable screen openings (11).