EP2024701A1

EP2024701A1 - Dryer for free-flowing material to be dried and a method for operating a dryer

Info

Publication number: EP2024701A1
Application number: EP07722957A
Authority: EP
Inventors: Willem Westerveld
Original assignee: Ijzerlo Holding BV
Current assignee: Ijzerlo Holding BV
Priority date: 2006-05-22
Filing date: 2007-02-28
Publication date: 2009-02-18
Anticipated expiration: 2027-02-28
Also published as: DE102006024144A1; EP2024701B1; DK2024701T3; WO2007134656A1

Abstract

The present invention relates to a dryer (1) for free-flowing material to be dried (6), comprising a conveyor track which the material to be dried (6) is to pass through with at least one rotatable conveyor worm (2) in which a gas can be passed through the material to be dried (6), wherein the minimum of at least one rotatable conveyor worm (2) forming the conveyor track is surrounded over its entire circumference with a gas-permeable and material-impermeable casing (20). The new dryer (1) is characterized in that during operation of the dryer (1), the free-flowing material to be dried (6) fills only partially the cross section of the conveyor worm (2) inside the casing (20), in that the gas in a lower area of the conveyor worm (2) can be fed through the casing (20) into the inside of the conveyor worm (2) with the formation of a fluidized bed in the material to be dried (6), and in that the gas, after passing through the material to be dried (6) forming the fluidized bed, can be discharged into a top area of the conveyor worm (2) through the casing (20) thereof. The invention also relates to a method for operating a dryer (1).

Description

Description :

Dryer for pourable drying material and method for operating a dryer

The invention relates to a dryer for pourable Trocknungsgut, with a to be traversed by the drying material conveying path with at least one rotatable screw conveyor, in which the drying material is flowed through by a gas, wherein the conveying path forming at least one rotatable screw conveyor over its full extent with a gas-permeable and well-impermeable Coat is surrounded. Moreover, the invention relates to a method for operating a dryer.

From EP-BI 110 047 a method and an apparatus for drying mushy substances are known. This method is used to dry fibrous pulp, such as chemical pulp, mechanical pulp, thermo-mechanical pulp, TMP, deinked pulp or fibrous slurry, ie, pulp-forming materials. In this case, the wet pulp is first dewatered mechanically, for example by means of a drum or screw press. Thereafter, the pulp passes through a dryer in which drying gas is blown through a sheet of the pulp to evaporate water from the pulp. In the dryer, the pulp passes through a gap-like drying space, which is defined by a first and a second cyclic drying chamber. limb surface, both of which are apertured, with the pulp pushed forward along the first or second surface by a wing-like device in the gap-like drying space. The pulp forming the material to be dried is here of mushy consistency and fills the gap space between the cylindrical surfaces during the drying process. So that the drying gas can pass through the pulp, the thickness of the layer of the pulp must not be too large; Therefore, a gap-like drying room is used here.

A disadvantage of this known dryer, the energy consumption is relatively high because the material to be dried forms a compact mass with relatively high flow resistance in the gap, so that large pressure differences must be generated. Nevertheless, the efficiency of such a drying process and dryer remains limited because the compact mass of the material to be dried in the gap space provides the drying gas flowing through only a relatively small surface, where evaporation and entrainment of moisture can take place. Due to the compactness of the material to be dried in its passage through the dryer, there is also the danger of overdrying or overheating of parts of the material to be dried, in particular the parts of the material to be dried located radially outside in the gap, where the drying gas flows in. This problem does not occur only when drying to a still relatively high residual moisture, which is sufficient for an application in papermaking, but is not sufficient for many other applications, since there often higher drying with very low residual moisture must be achieved. Another dryer is known from CH-A-485 993. This dryer has a plurality of mutually parallel, horizontally extending augers, each auger lies in a trough-shaped tray. The lower area of each trough is rounded off to the outer diameter of the auger and provided with openings. About one or more input devices with dosing the material to be dried is fed to the screw conveyor. By rotating the screw conveyors, the drying material to be dried is conveyed through the dryer. At the same time, a gas is passed from the outside through the perforations in the lower region of the trough-shaped troughs, through which the drying material flows and thereby dries it.

Another dryer is known from EP-A-0 165 916. Here, a dryer is disclosed in which a screw conveyor for conveying the material to be dried is used, which is arranged above a perforated bottom. Through the bottom of a gas is passed, which flows through the drying material and this dries. The screw conveyor here consists of a relatively narrow helix, which is mounted radially on the outside of a tube assembly. The tube arrangement can be flowed through by a heat transport medium in order to additionally introduce heat as drying energy into the material to be dried in this way.

A disadvantage of both known dryers last described that there is a relatively high risk that undesirably parts of the material to be dried are taken from the gas stream and entrained by the gas outlet, which leads to problems especially with light drying. To avoid this, the gas velocity must be limited to relatively low values, which is a good efficiency of the dryer, however, detrimental. In the third prior art dryer is also disadvantageous that the auger is expensive because it requires sealing rotary unions for the supply and discharge of the heat transfer medium. These rotary unions are wear parts that require regular maintenance or replacement and lead to increased costs.

For the present invention, therefore, the object is to provide a dryer of the type mentioned, which avoids the disadvantages mentioned above and provides a reliable function with high efficiency in a simple construction and in which an undesirable entrainment of parts of the material to be dried with the the gas stream flowing through the material to be dried is avoided. In addition, a method for operating a dryer should be specified, with the good and reproducible drying results are achieved with high efficiency.

The solution of the first part of this task, relating to the dryer, according to the invention succeeds with a dryer of the type mentioned, which is characterized

- That during operation of the dryer, the pourable drying material only partially fills the cross section of the screw conveyor within the shell,

- That the gas in a lower region of the screw conveyor through the shell in the interior of the screw conveyor with the formation of a fluidized bed in the drying material is introduced and

that the gas, after flowing through the material forming the fluidized bed, flows through an upper rich of screw conveyor through the jacket through which can be discharged.

With the dryer according to the invention a simple construction is advantageously achieved, because it does not require vulnerable rotary unions for a heat transfer medium. The casing surrounding the screw and the only partial filling of the screw conveyor with the pourable Trocknungsgut ensure that the drying material within the screw conveyor for forming the fluidized bed sufficiently large range of motion, in particular upwards, and that no entrainment of the drying material occurs, even if the material to be dried is light and / or the gas used for drying flows through the material to be dried at high speed. At the same time relatively high gas temperatures are possible because the fluidized bed leads to a high evaporation of moisture from the material to be dried and thus to a cooling of the material to be dried. This allows a very high efficiency of the dryer, while at the same time the risk of entrainment of parts of the material to be dried is avoided with the gas stream.

Preferably, the dryer is a continuous dryer with a continuously running screw conveyor. This enables a continuous drying operation, which is advantageous for many applications in continuously operating production or processing plants.

Alternatively, the dryer may be a batch dryer with a feed screw running during filling and emptying of the dryer, wherein during a drying of the material to be dried the conveyor screw is stationary or rotates back and forth. The back and forth turning of the screw conveyor is used here, the drying material during the Dry to move without promoting it, which can be favorable for the drying process, in particular for a uniform drying of all parts of the drying material.

At standstill of the screw conveyor a weighing process for determining the weight or a change in weight of the Trocknungsgutcharge is particularly simple, because there are no disturbing influences by moving dryer parts. Even with a running screw conveyor such weighing processes are possible, in which case movements of the screw can interfere with, but which, for example. can be sufficiently eliminated by averaging.

It is possible that the dryer is operated with identical design, either alternatively or alternately in one of two modes of operation, ie continuous drying or batch drying, whereby it can be used flexibly.

In a further development of the dryer according to the invention is preferably provided that the jacket is attached to the screw conveyor and rotatable with this. In this way, any relative movement and any friction caused thereby between the screw conveyor on the one hand and the jacket on the other hand completely avoided. Unwanted, leading to damage of the drying material leading grinding effects can not occur. Thus, the material to be dried is transported particularly gently by the conveyor screw, which is surrounded by the co-rotating mantle, which also makes the dryer particularly sensitive to drying goods, such as e.g. Seeds, suitable.

Further, it is preferably provided that the sheath consists of a latticed or perforated material or a woven or braided material, wherein the material is preferably metal or plastic. Specifically, For example, a fine perforated plate suitable for the particular application or for the respective Trocknungsgut adapted hole sizes and shapes. In all embodiments, it can be achieved that the jacket is on the one hand sufficiently permeable to the fluid which generates the fluidized bed and, on the other hand, is sufficiently impermeable to the material to be dried. The design of the shell and the choice of materials depend on the requirements in each case, in particular on the size of the individual particles of the material to be dried and on the temperatures to be used during the drying.

It is further proposed that, at least in a peripheral region of the screw conveyor, in which the gas enters the screw conveyor, parallel to the casing of the screw conveyor, a non-rotating gas guide element in the form of a perforated channel, which is adapted to the casing, is arranged. This gas guide contributes to a favorable for the formation of the fluidized bed in the drying material flow formation, distribution and - management of the gas, which is introduced through the jacket into the screw conveyor.

Preferably, the channel is provided with holes spaced apart in a regular grid for the gas guided into the conveyor screw. In this way, the gas in particular the speed, directivity and distribution imparted to ensure a homogeneous fluidized bed.

According to a further embodiment, the channel is preferably flexible so that it fits and engages well with the outer circumference of the conveyor screw or of the surrounding jacket. For the most cost-effective production, the channel is preferably formed from a plate or sheet of plastic or a metal sheet.

The material to be dried can be taken along in the direction of rotation, depending on its Schütteigenschaften in the rotation of the screw conveyor, whereby then during the drying process, the fluidized bed occupies a position which is slightly twisted from the horizontal plane in the direction of rotation of the screw conveyor. In order to be able to adapt the supply of the gas in the screw conveyor, it is provided that the channel as a whole in the circumferential direction of the screw conveyor can be rotated and fixed in desired positions.

Another embodiment proposes that the channel in its seen in the circumferential direction of the auger extension is adjustable and can be fixed in different directions in the circumferential direction. Thus, the gas supply to the screw conveyor with respect to the size of the peripheral region through which the gas enters the screw conveyor, can be varied and optimized for the respective application.

To avoid disturbing and efficiency-reducing erroneous flows of the gas is provided that the groove rests at its circumferentially spaced apart from the conveyor screw longitudinal edges by means of sliding seals on the outer circumference of the shell of the screw conveyor. With a gutter made of plastic, the material of the gutter itself can also form the seals.

Preferably, it is further provided that the screw conveyor with the jacket in a substantially gas-tight housing with at least one gas inlet and at least one Gas outlet is arranged and that the housing is divided in its interior into a connected to the gas inlet Gaszuführbereich and connected to the gas outlet Gasabführbereich, wherein the gas supply and the Gasabführbereich are fluidly interconnected only through the screw conveyor. Through the housing, the screw conveyor with the shell is completely encapsulated, so that an accurate and targeted gas flow without gas losses is made possible and at the same time a threat to the environment is excluded.

A concrete development provides that the gas supply and the Gasabführbereich are radially separated from each other outside the auger by two oppositely arranged in the housing separation and / or guide walls. In order that the gas flow can only extend in the desired manner through the screw conveyor, the separating and / or guide walls suitably extend as close as possible to the outer circumference of the screw conveyor or the surrounding jacket on its edge facing the conveyor screw. By means of the separation and / or baffles, the gas in a suitable manner, preferably in cross-flow, through the Trocknungsgut feasible. With the walls so a particularly accurate flow control is guaranteed, which avoids gas and energy losses and ensures a consistently high efficiency and a consistently good, reproducible drying result.

For the separation and / or guide walls is preferably provided to adapt to different drying properties that they are seen in the circumferential direction of the screw conveyor together and / or individually adjustable and fixed in selected positions. A particularly gas-tight connection of the separation and / or baffles to the outer periphery of the shell is achieved in that the separation and / or baffles preferably abut each at its the screw conveyor longitudinal edge by means of sliding seals on the outer circumference of the shell of the screw conveyor.

In order to obtain the gas-tightness over a longer period of operation or not exactly round jacket, the sliding seals are expedient in the radial direction of the screw conveyor adjustable or adjustable. The adjustment or readjustment may e.g. if necessary by manual intervention, e.g. via adjusting screws, done or run automatically and steadily, e.g. by means of an acting on the sliding seals in the direction of the jacket and this applying against the jacket biasing force, which can be generated for example by one or more springs.

To simplify the construction and to reduce the parts expense for the dryer is provided that in each case one longitudinal edge of the channel and the adjacent longitudinal edge of a guide and a partition wall and the other longitudinal edge of the channel and the adjacent longitudinal edge of the other guide and partition are arranged directly adjacent to each other or connected to each other and are each provided with a common sliding seal.

It is further proposed for the dryer according to the invention that the housing has at least one closed in the drying operation, releasable for cleaning and maintenance opening, that the screw conveyor is interchangeable and that through the at least one opening, the screw conveyor can be removed and installed. In this embodiment, necessary cleaning and warehousing be carried out without problems. The interchangeability of the screw conveyor allows a simple and time-saving adaptation of the dryer to different drying tasks, in particular different drying goods that require different augers. If the jacket is connected to the screw conveyor, this can be replaced together with the screw conveyor in one operation. Thus, it is possible to provide for a dryer different screw conveyors or different units of screw conveyor and jacket, which are then installed according to the respective drying task in the housing.

Preferably, the opening is closable by a removable or adjustable top or side hood of the housing. With this configuration, the opening can be opened and closed quickly and easily. At the same time the opening is easily accessible.

Further, the invention provides that the at least one gas inlet is associated with a gas conditioning or upstream. By means of the gas conditioning device, the gas can be optimized in its properties for the respective intended drying purpose, in particular brought to a certain temperature and / or humidity.

As already mentioned above, the casing surrounding the conveyor screw is designed such that it is impermeable to the material to be dried. Nevertheless, however, particularly fine, dust-like particles which are contained in the drying material or which form in the dryer during drying can pass through the jacket. To discharge this dust from the dryer into the environment it is expedient to avoid or arrange a dust filter at least one gas outlet. In addition or as an alternative to the drying function, the device according to the invention can also be used here specifically or only for the dedusting of a pourable material.

Preferably, it is further provided that the at least one gas inlet is a pressure fan upstream or upstream and / or that the at least one gas outlet is a suction fan or downstream. With the blower or blowers, the gas is conveyed through the dryer. When using a pressure blower, a particularly high gas throughput is possible. In the arrangement of a suction fan on the side of the gas outlet is ensured that in the interior of the housing relative to the ambient pressure during operation, a negative pressure prevails. This ensures that gas and any dust inside it can not escape into the environment, protecting the environment from potentially harmful effects of the drying gas or dust from the dryer.

For drying, the material to be dried must be introduced into the auger from the outside. Thus, if this is annoying, ambient air does not get in this way in the interior of the screw conveyor and the housing or vice versa gas and / or dust does not escape, preferably a first end of the screw conveyor is assigned to the environment substantially gas-tight sealed input device. If the pressure conditions are such that no relevant gas exchange takes place, or a certain gas exchange is not disturbing, the screw conveyor can also be designed simply open at its input. The feed device preferably comprises an adjustable in its capacity vibratory conveyor or adjustable in their performance input screw as metering. Thus, a precisely metered feeding of drying material to be dried in the screw conveyor is possible. Depending on requirements, the delivery rate of the input device can be changed, for example, if the type of drying material to be dried or its drying properties change.

A concrete further development in this respect provides that the feed-in device comprises a delivery pipe concentric with the feed screw in its first end, and that the first end of the feed screw is closed by an elastic annular disk sealingly surrounding the feed pipe. In this way, the material to be dried can get into the screw without gas from the auger to the outside or ambient air can get into the auger in disturbing extent.

After passing through the conveyor line, the drying material then dried must be removed from the conveyor screw and the housing. So that if necessary even in this way false air can not get into the housing or gas and / or dust to the outside, a second end of the screw conveyor is assigned to the environment a substantially gas-tight sealed Gutausgabeeinrichtung expediently. Alternatively, for this second end of the screw, a simple open design can be provided, if this causes no disturbing effects.

A preferred possibility for gas-tight design of Gutausgabeeinrichtung is that this with a lock, in particular a rotary valve, is formed.

In order to store the screw conveyor on the one hand safely and on the other hand with low friction, it is provided that the screw conveyor has a central axis projecting on one or both sides of the end face or one or two axle stubs projecting only on the front side for screw mounting.

If the auger has a continuous axis, then this is preferably a closed shaft with an outer diameter which is small in relation to the outer diameter of the screw conveyor, so as not to hinder the desired formation of the fluidized bed of the material to be dried in the auger by the shaft or disturb.

If the screw conveyor has an axis projecting only on one side or only a stub axle protruding on the front side, or if the conveyor screw is particularly long, the auger is expediently additionally mounted in the channel and / or on bearing rollers. The bearing rollers are then suitably arranged on the end remote from the projecting axle or the projecting axle stub and / or between the ends of the conveyor worm, preferably in a closed mantle end region or mantle intermediate region of the auger. The other end of the screw conveyor is then conveniently mounted by means of the axle or stub axle.

To rotate the screw conveyor, it is provided that it can be driven in rotation by means of at least one drive motor via a gearwheel or friction wheel or belt or chain drive. In this way, the screw conveyor can be reliably rotated, with a Speed setting of the motor, the speed of the screw conveyor is set to appropriate values and thus the capacity of the screw conveyor and the throughput of the dryer are set in a desired manner. With a suitable transmission ratio, a relatively low drive power for the rotation of the conveyor screw and for the conveyance of the drying material in the screw is sufficient, which contributes to a low energy consumption of the dryer.

In order to carry out more complicated drying operations with the dryer according to the invention, proposes an embodiment that seen in the conveying direction of the material to be dried, the housing is divided into a plurality of gas-side housing sections separated, each case a separate gas flow is feasible. This can be done in the different housing areas different treatments of the material to be dried, wherein the gas flows, e.g. by their temperature, their speed or their composition. In the simplest case, the gas streams are air streams, wherein the air can be advantageously removed from the environment and discharged into the environment after the drying process, preferably after passing through the dust filter. Alternatively, a circulation of a gas is conceivable, for example of nitrogen. When running with a gas circulation, it is expedient to integrate a drying step for the gas in this circuit.

A preferred embodiment provides that viewed in the conveying direction of the material to be dried at least a first housing portion forms a drying zone, which is traversed by a warm drying gas flow, and that at least a second housing portion forms a cooling zone, which can be flowed through by a cool gas stream. In this way, the drying material can be dried in the at least one first housing region, wherein the drying material is necessarily heated when using the warm drying gas stream. In the second housing area, the material to be dried can be cooled again in order to avoid damage caused by an excessively high temperature of the material to be dried. This also makes it possible, for example, to pack the drying material immediately after drying and after the subsequent cooling without the risk of harmful condensation forming.

Furthermore, it is preferably provided for the dryer according to the invention that the screw conveyor is arranged horizontally. In this orientation results in a reliable and uniform delivery of the material to be dried by the screw conveyor, the screw conveyor at the same time ensures a favorable forced mixing and circulation of the material to be dried. Disturbances in the Trocknungsgutförderung, as may occur, for example, in known vertical driers with gravity conveyance of the material to be dried, are avoided here safe.

Alternatively, there is the possibility that the screw conveyor is arranged inclined to the horizontal, wherein preferably the angle to the horizontal is at most 45 °. Even in a limited inclined arrangement is still a reliable and uniform promotion of the material to be dried guaranteed by the screw conveyor. In the inclined arrangement, the good dispensing device is expediently higher than the goods receiving device, which, for example, the forwarding of the drying material to weiterverar- preparing facilities or the immediate packaging of the material to be dried easier.

In order to carry out drying operations accurately and reproducibly, it is further provided that one or more temperature and / or humidity sensors are arranged in the gas feed region and / or in the gas discharge region, with which a gas temperature and / or moisture can be detected in the drying operation, and the blower (s) and / or the gas conditioning device (s) and / or a desired amount of drying material and / or the screw conveyor rotational speed can be controlled or regulated in accordance with measured values detected by the sensor (s). For the control or regulation, a programmable electronic control unit is expediently used, which adjusts the aforementioned parameters of the drying appropriately according to the measurement signals supplied by the sensors and changed if necessary and controls the process and the result of the drying process and if necessary also documented.

Except for drying purposes, the dryer according to the invention can also be used as a device for other tasks in the treatment of bulk materials by means of a gaseous medium, for example, when a bulk material is to be intensively and as completely as possible brought into contact with a gas. Conversely, the treatment of a gas by contact with a pourable material is conceivable in the device.

Furthermore, the subject matter of the application is a method for operating a dryer for pourable material to be dried, wherein the material to be dried passes through a conveying path with at least one rotatable conveying screw in which a gas flows through the material to be dried, and in which the conveying path forming at least one rotatable screw conveyor is surrounded over its entire circumference with a gas-permeable and well-impermeable jacket.

In order to solve the second part of the problem related to the method, a method for operating a dryer is proposed, which is characterized

- That during operation of the dryer the pourable material to be dried is fed to the conveyor screw in an amount such that it only partially fills the cross-section of the conveyor screw inside the casing,

- That the gas is introduced in a lower region of the screw conveyor through the shell in the interior of the screw conveyor, that forms a fluidized bed in the drying material and

- That the gas is discharged after passing through the drying material forming the fluidized bed in an upper region of the screw conveyor through the jacket.

With the above-mentioned method, a dryer of the type described above with high efficiency and low energy consumption can be operated without loss of material to be dried and with gentle treatment of the material to be dried. The high efficiency is in particular caused by the fluidized bed in the material to be dried, so that the drying process is particularly efficient, despite or just because of the only partial filling of the cross section of the screw conveyor with material to be dried.

A preferred embodiment of the method provides that during operation of the dryer, the bulk material to be dried is fed to the conveyor screw in an amount such that it only increases the cross section of the conveyor screw 30 to 60%, preferably to 40 to 50%, fills. This ensures in any case sure that the formation of the desired fluidized bed in the drying material can be done without hindrance.

Embodiments of a dryer according to the invention are explained below with reference to a drawing. The figures of the drawing show:

1 shows a dryer in a schematic side view, partly in longitudinal section,

Figure 2 shows the dryer of Figure 1 in a cross section through a first portion of the dryer and

FIG. 3 shows the dryer in a partial cross section through its end region;

4 shows the dryer in a second embodiment in a cross section through a first section of the dryer, with closed housing, and

Figure 5 shows the dryer of Figure 4 in the same representation, now with the housing open.

As the figure 1 of the drawing shows, the dryer 1 shown there has a horizontally extending screw conveyor 2, which is surrounded at its periphery by a jacket 20. The screw conveyor 2 has a central, in relation to the outer diameter of the screw conveyor thin axis 23, with which the screw conveyor 2 including the attached thereto shell 20 is rotatably mounted in a substantially closed housing 3. The jacket 20 is designed so that it is permeable to gas, but impermeable to a Trocknungsgut. On the left in FIG. 1, a left, first end region 21 of the screw conveyor 2 projects slightly beyond the front end of the housing 3. At this first end region 21 of the screw conveyor 2 drying material to be dried is fed continuously and metered into the conveyor screw 2 via a feed input device 4.

The goods input device 4 comprises, for example, an adjustable or adjustable vibratory conveyor, which introduces the feed material, which is initially poured into the input device 4, into the conveyor screw 2 via a conveyor tube 40. The front end of the screw conveyor 2 and the shell 20 is closed by an elastic annular disc 41 with a central opening for the delivery tube 40 here. With the delivery pipe 40, the annular disk 41 forms a simple, but here sufficient rotary seal. The lying outside of the housing 3 short auger and Mantelendbereich 21 is performed well and gas tight at its periphery. For rotatable mounting of the screw conveyor 2, two bearing rollers 27 are arranged in the lower region of the jacket 20 below this end region 21 of the jacket 20, on which the jacket 20 rests. A holding-down roller 27 'arranged above the end region 21 of the jacket 20 ensures that during operation of the dryer 1 the conveying screw 2 retains its intended position and can not escape upwards.

By rotating the screw conveyor 2 by means of a drive motor 24 arranged at the other, in FIG. 1, right end region 22, the material to be dried is forcibly conveyed through the dryer 1 in the conveying direction 25. To dry the material to be dried, a gas, for example air, is used, which is guided through here three gas inlets 30 into the interior of the housing 3. Inside the housing 3, the gas flows through one or more Gaszuführbereiche 31 are each guided so that they flow through the screw conveyor 2 with the drying material therein substantially in cross-flow, wherein moisture contained in the Trocknungsgut is entrained by the gas stream. The gas streams are then removed via at least one, here two gas discharge 33 and two gas outlets 34 from the dryer 1. The gas outlets 34 may be one or more dust filter upstream or downstream.

To promote the gas flows serve one or more fans, which are not shown in the drawing figure. The blowers are e.g. designed as a pressure fan and the gas inlets 30 connected upstream or assigned. Alternatively, they are designed as a suction fan and the gas outlets 34 assigned or downstream, to generate a negative pressure in the interior of the housing 3 relative to the environment. This vacuum avoids a discharge of Staubgut from the interior of the housing 3 in the environment. It is also possible to use both types of blowers.

In the example of the dryer 1 shown in FIG. 1, the housing 3 has three housing areas, namely two first housing areas 3.1 and 3.1 'and a second housing area 3.2. The first two housing sections 3.1. and 3.1 'are used to dry the material to be dried with a heated gas, such as warm air, while the second housing section 3.2 serves here for cooling the previously heated during drying drying material. For this purpose, by the second housing portion 3.2 a cool gas stream, eg. B. a cooled air flow, out. The dried and re-cooled drying material then leaves in the second, in Figure 1 right end portion 22 of the screw conveyor 2 the dryer 1 via a there arranged Gutausgabeeinrichtung 5. At its protruding from the housing 3 end of the screw conveyor 2 is closed, eg by the jacket 20 here gas-tight is designed to prevent escape of gas in this way. In the Gutausgabeeinrichtung 5, for example, a lock, such as rotary valve, integrated to avoid a gas or air passage through the Gutausgabeeinrichtung 5. By means of an output funnel 50, the dried material to be dried falls down out of the good dispensing device 5 and can for example be filled directly into transport or storage containers or fed to a further conveyor line for any further processing required.

In the drying operation, the housing 3 of the dryer 1 is closed in order to ensure the desired gas flows. For maintenance and repair purposes, the housing 3 can be opened by a top-side hood 35 is pivoted or completely removed here. Through the then open top of the housing 3, the interior of the housing 3 is accessible.

In addition, in the open state of the housing 3, the screw conveyor 2 including its shell 20 can be replaced quickly and easily. In this way, the dryer 1 can be equipped with different screw conveyors 2 and different jackets 20 in order to adapt the dryer 1 to different drying tasks, in particular different dry goods. Furthermore, the dryer 1 is suitably associated with a not specifically shown in the drawing control and / or regulating device with which the operation of the dryer 1 is monitored and controlled, in particular by moisture and temperatures recorded gas temperatures, gas volumes and / or gas velocities regulated and the Conveying the donation device 4, the screw conveyor 2 and the Gutausgabeeinrichtung 5 are regulated as needed.

FIG. 2 shows the dryer 1 in cross-section through the first housing region 3.1. In the center of the housing 3 is the screw conveyor 2 with the surrounding, rotating together with the screw 2 mantle 20. Inside the screw conveyor 2 and the shell 20, the Trocknungsgut 6 is shown here occupying only a less than half of the cross section Space occupied in the screw conveyor 2. By the rotation of the mounted on the axis 23 screw conveyor 2 and the associated shell 20, the pourable conveyed 6 is taken in the conveying direction of the screw conveyor 2, resulting in the transport of the material to be dried 6 through the dryer 1.

Right below in Figure 2, a gas inlet 30 can be seen, through which a gas, for. B. heated air, in a Gaszuführbereich 31 in the interior of the housing 3 can be introduced. The gas channel 31 leads, according to the position of the material to be dried 6 in a lower cross-sectional part of the screw conveyor 2, to the in Fig. 2 downwardly facing the peripheral region of the screw conveyor 2 and the shell 20th

In this lower region of the screw conveyor 2 and the jacket 20 is directly on the outer periphery of the shell 20, a gas guide element in the form of a perforated groove 26th arranged. This groove 26 consists of a plate or foil made of metal or plastic with formed therein, arranged in a regular narrow grid openings. In addition to a gas guide, the channel 26 can also be used to support a storage of the screw conveyor 2, in which case the screw conveyor 2 with its jacket 20 slidably lies in the channel 26.

The perforated channel 26 allows a passage of the gas flow from the gas supply 31 through the holes in the channel 26 and through the jacket 20 into the interior of the screw conveyor 2 and in this way through the Trocknungsgut 6 through in such a way that in the Trocknungsgut 6 forms a fluidized bed. In this case, inside the screw conveyor 2 and the jacket 20, there is sufficient space for the drying material 6 swirling up in the fluidized bed and partially lifting off from the inner surface of the jacket 20 because this only partially fills the cross-section of the screw 2.

The flowing gas advantageously ensures a good contact of the channel 26 on the outer circumference of the shell 20 of the screw conveyor 2, whereby gap spaces between the channel 26 and the outer periphery of the shell 20, which could interfere with the gas flow are avoided.

Inside the housing 3, the gas supply area 31 is delimited by separation and guide walls 32. Shell-side edges of the separation and baffles 32 lie with the interposition of sliding seals 36 and 36 'on the outer circumference of the shell 20 in order to guide the gas flow as completely as possible through the Trocknungsgut 6. In the sliding seals 36 and 36 'end here also the two longitudinal edges of the perforated channel 26th After flowing through the drying material 6 forming the fluidized bed in the feed screw 2, the gas flow flows upwards through the casing 20 into the gas discharge region 33 and even further upwards through the gas outlet 34.

The upper portion of the screw conveyor 2 is covered by the hood 35, which forms a pivotable or removable part of the housing 3.

As indicated in FIG. 2, the temperature and / or the humidity of the gas in the gas supply region 31 can be measured via sensors 37, 37 'before flowing through the material to be dried 6 and in the gas discharge region 33 after passing through the material to be dried and the control not specifically shown - And / or control device to be supplied.

Figure 3 shows the right in Figure 1 end portion 22 of the screw conveyor 2 with the arranged there Good output device 5. In the upper part of Figure 3 seen in the conveying direction rear end of the screw conveyor 2 with the central axis 23 is visible. Through a frontally open area of the screw conveyor 2, the dried material to be dried enters the discharge hopper 50 and falls through it by gravity downward, for example in a transport or storage container or on another conveyor line.

Figure 4 shows the dryer 1 in a modified embodiment in cross-section through a first portion of the housing 3. In the center of the housing 3, the screw conveyor 2 with this surrounding, together with the screw 2 rotatable jacket 20. Inside the screw conveyor 2 and the shell 20 is the Trocknungsgut 6, which occupies only a less than half of the cross-section occupying space in the screw conveyor 2. By rotating the axis 23 having screw conveyor 2 and the associated shell 20, the flowable conveyed 6 is taken in the conveying direction of the screw conveyor 2, whereby a transport of the material to be dried 6 is effected by the dryer 1.

Right below in Figure 4, a gas inlet 30 can be seen, through which a gas, for. B. heated air, in a Gaszuführbereich 31 in the interior of the housing 3 can be introduced. The gas channel 31 leads, according to the position of the material to be dried 6 in a lower cross-sectional part of the screw conveyor 2, to the in Fig. 2 downwardly facing the peripheral region of the screw conveyor 2 and the shell 20th

In this lower region of the screw conveyor 2 and the jacket 20, a gas guide element in the form of a perforated channel 26 is arranged directly on the outer circumference of the jacket 20. This groove 26 consists of a plate or foil made of metal or plastic with formed therein, arranged in a regular narrow grid openings. Apart from the gas guide, the channel 26 can also serve to support the auger 2, wherein the auger 2 with its jacket 20 slidably lies in the channel 26.

The perforated channel 26 allows a passage of the gas flow from the gas supply 31 through the holes in the channel 26 and through the gas-permeable jacket 20 into the interior of the screw conveyor 2 and in this way through the Trocknungsgut 6 therethrough in such a way that in Drying material 6 forms a fluidized bed. In this case, inside the conveyor 2 and the jacket 20 sufficient space for the aufströmbelnde in the fluidized bed and partially contrasting with the inner surface of the shell 20 drying material 6, because this only partially fills the cross section of the screw 2.

Inside the housing 3, the gas supply area 31 is delimited by separation and guide walls 32. Shell-side edges of the separation and baffles 32 lie with the interposition of sliding seals 36 and 36 'on the outer circumference of the shell 20 in order to guide the gas flow as completely as possible through the Trocknungsgut 6. In the sliding seals 36 and 36 'terminate here also the two longitudinal edges of the perforated channel 26. To avoid undesirable side flows of the gas, the arrangement of the holes in the groove 26 may be made so that holes are present only where inside the jacket 20 drying material 6 is located, while in the two upper edge regions of the channel 26 near the walls 32 then no holes are provided.

After flowing through the drying material 6 forming the fluidized bed in the feed screw 2, the gas flow flows upwards through the casing 20 into the gas discharge region 33 and then further to the side into the gas outlet 34 arranged laterally.

The upper portion of the screw conveyor 2 is covered by a hood 35, which forms a pivotable upper part of the housing 3 here.

In Figure 5 of the drawing, the hood 35 is shown in an open position pivoted by about 90 °. For pivoting the hood 35, it only needs to be separated from a gas discharge line connected to the gas outlet 34. In the open position of the hood 35 is the Conveying screw 2 with its jacket 20 upwards and can, if necessary after disassembly of drive or coupling elements, are removed from the housing at the top without the separation and guide walls 32 and their seals 36, 36 'being removed. or dismantled. As a result, the screw conveyor 2 can be exchanged with the casing 20 quickly and easily, eg during wear or for adaptation of the dryer 1 to different drying goods 6 to be treated.

Claims

Claims:

1. dryer (1) for pourable drying material (6), with one of the drying material (6) to be traversed conveyor line with at least one rotatable conveyor screw (2), in which the Trocknungsgut (6) can be traversed by a gas, wherein the conveying path forming at least one rotatable conveyor screw (2) is surrounded over its entire circumference by a gas-permeable and impermeable jacket (20), characterized

- That during operation of the dryer (1) the pourable Trocknungsgut (6) only partially fills the cross section of the screw conveyor (2) within the jacket (20),

- That the gas in a lower portion of the screw conveyor (2) through the jacket (20) into the interior of the screw conveyor (2) to form a fluidized bed in the drying material (6) can be introduced and

- That the gas after the flow through the fluidized bed forming material to be dried (6) in an upper region of the screw conveyor (2) through the jacket (20) through can be discharged.

2. Dryer according to claim 1, characterized in that it is a continuous dryer with a continuously running screw conveyor (2).

3. Dryer according to claim 1, characterized in that it is a batch dryer with a current during a filling and emptying of the dryer (1) conveyor screw (2), wherein during a drying nens of the material to be dried (6), the conveyor screw (2) is stationary or rotates back and forth.

4. Dryer according to one of the preceding claims, characterized in that the jacket (20) attached to the screw conveyor (2) and is rotatable with this.

5. Dryer according to one of the preceding claims, characterized in that the jacket (20) consists of a latticed or perforated material or a fabric or mesh material, wherein the material is metal or plastic.

6. Dryer according to one of the preceding claims, characterized in that at least in a peripheral region of the screw conveyor (2), in which the gas enters the screw conveyor (2), parallel to the jacket (20) of the screw conveyor (2) on the coat

(20) form adapted, non-rotating gas guide element in the form of a perforated groove (26) is arranged.

7. Dryer according to claim 6, characterized in that the channel (26) is provided with spaced-apart in a regular grid holes for the in the screw conveyor (2) guided gas.

8. Dryer according to claim 6 or 7, characterized in that the channel (26) is flexible.

9. Dryer according to one of claims 6 to 8, characterized in that the channel (26) is formed of a plate or sheet of plastic or of a metal sheet.

10. Dryer according to one of claims 6 to 9, characterized in that the channel (26) as a whole in the circumferential direction of the screw conveyor (2) is rotatable and fixable in desired positions.

11. Dryer according to one of claims 6 to 10, characterized in that the channel (26) is adjustable in its circumferential direction in the circumferential direction of the screw conveyor (2) seen extension and fixed in different directions in the circumferential direction.

12. Dryer according to claim 4 or 5 and one of claims 6 to 11, characterized in that the perforated groove (26) at their in the circumferential direction of the screw conveyor (2) spaced from each other longitudinal edges by means of sliding seals (36, 36 ') on the outer circumference of the jacket (20) of the screw conveyor (2) is applied.

13. Dryer according to one of the preceding claims, characterized in that the screw conveyor (2) with the jacket (20) in a substantially gas-tight housing (3) with at least one gas inlet

(30) and at least one gas outlet (34) is arranged and in that the housing (3) is divided in its interior in a gas inlet (31) connected to the gas inlet (30) and a gas discharge area (33) connected to the gas outlet (34) wherein the gas feed area (31) and the gas discharge area

(33) are fluidly interconnected only by the screw conveyor (2).

14. Dryer according to claim 13, characterized in that the gas supply region (31) and the gas discharge rich (33) radially outside the screw conveyor (2) by two oppositely arranged in the housing separation and / or baffles (32, 32 ') are separated from each other.

15. Dryer according to claim 14, characterized in that the separating and / or guide walls (32, 32 ') seen in the circumferential direction of the screw conveyor (2) are jointly and / or individually adjustable and fixable in selected positions.

16. Dryer according to claim 4 or 5 and claim 14 or 15, characterized in that the separating and / or guide walls (32, 32 ') respectively at its screw conveyor (2) facing the longitudinal edge by means of sliding seals (36, 36') on Outer circumference of the jacket (20) abut the screw conveyor (2).

17. Dryer according to claims 12 or 16, characterized in that the sliding seals (36, 36 ') in the radial direction of the screw conveyor (2) are adjustable or adjustable.

18. Dryer according to claim 12 and claim 16 or 17, characterized in that in each case one longitudinal edge of the channel (26) and the adjacent longitudinal edge of a guide and partition (32) and the other longitudinal edge of the channel (26) and the adjacent longitudinal edge of the other guide and partition wall (32 ') are arranged directly adjacent to each other or connected to each other and each with a common sliding seal (36, 36') are provided.

19. Dryer according to one of claims 13 to 18, characterized in that the housing (3) at least one closed in the drying operation, releasable for cleaning and maintenance opening has that the screw conveyor (2) is interchangeable and that through the at least one opening, the screw conveyor (2) can be removed and installed.

20. Dryer according to claim 19, characterized in that the opening by a removable or adjustable top or side hood (35) of the housing (3) is closable.

21. Dryer according to one of claims 13 to 20, characterized in that the at least one gas inlet

(30) a gas conditioning device is assigned or upstream.

22. Dryer according to one of claims 13 to 11, characterized in that the at least one gas outlet

(34) is a dust filter upstream or downstream.

23. Dryer according to one of claims 13 to 22, characterized in that the at least one gas inlet

(30) a pressure fan is upstream or upstream and / or that the at least one gas outlet (34) is a suction fan or downstream.

24. Dryer according to one of the preceding claims, characterized in that a first end (21) of the screw conveyor (2) is associated with an environment substantially gas-tight sealed feed-in device (4).

25. Dryer according to claim 24, characterized in that the goods input device (4) adjustable in its delivery vibratory conveyor or comprises an adjustable in their performance input screw as a metering device.

26. A drier according to claim 24 or 25, characterized in that the feed input device (4) concentrically to the feed screw (2) in the first end (21) opening conveyor tube (40) and that the first end (21) of the screw conveyor (2 ) is closed by a resilient annular disc (41) sealingly surrounding the delivery pipe (40).

27. Dryer according to one of the preceding claims, characterized in that a second end (22) of the screw conveyor (2) is associated with an environment substantially gas-tight sealed Gutausgabeeinrichtung (5).

28. Dryer according to claim 27, characterized in that the good output device (5) with a lock, in particular a rotary valve is formed.

29. Dryer according to one of the preceding claims, characterized in that the screw conveyor (2) has a central, one or both sides frontally projecting axis (23) or one or two only frontally projecting stub axle for screw storage.

30. Dryer according to claim 29, characterized in that the screw conveyor is additionally mounted in the channel (26) and / or on bearing rollers (27).

31. Dryer according to claim 29 or 30, characterized in that the axis (23) is a closed WeI- Ie with an outer diameter which is small in relation to the outer diameter of the screw conveyor (2).

32. Dryer according to one of the preceding claims, characterized in that the screw conveyor (2) by means of at least one drive motor (24) via a gear or Reibrad- or belt or chain drive is driven in rotation.

33. Dryer according to one of claims 13 to 32, characterized in that in the conveying direction (25) of the drying material (6) seen the housing (3) is divided into a plurality of gas side separate housing portions (3.1, 3.1 ', 3.2), wherein each

Housing area (3.1, 3.1 ', 3.2) a separate gas flow is feasible.

34. Dryer according to claim 33, characterized in that in the conveying direction (25) of the material to be dried (6) at least a first housing portion (3.1, 3.1 ') forms a drying zone, which can be traversed by a warm drying gas flow, and that at least a second housing portion (3.2) forms a cooling zone, which is traversed by a cool gas stream.

35. Dryer according to one of claims 1 to 34, characterized in that the conveyor screw (2) is arranged horizontally.

36. Dryer according to one of claims 1 to 34, characterized in that the conveyor screw (2) is arranged inclined to the horizontal, wherein vorzugswei- the angle to the horizontal is at most 45 °.

37. Dryer according to claim 21 and / or 23, characterized in that in the Gaszuführbereich (31) and / or in Gasabführbereich (33) one or more temperature and / or humidity sensors (37, 37 ') are arranged with which in the drying operation a gas temperature and / or humidity is / are detectable, and in that the blower (s) and / or the gas conditioning device (s) and / or a dry goods input quantity and / or the screw conveyor rotational speed are controlled by the sensor (s) (37, 37 ') measured values controllable or controllable is / are.

38. A method for operating a dryer (1) for pourable Trocknungsgut (6) according to one of claims 1 to 37, wherein the Trocknungsgut (6) passes through a conveyor line with at least one rotatable conveyor screw (2), in which the Trocknungsgut (6) a gas is flowed through, and wherein the conveying path forming at least one rotatable screw conveyor (2) is surrounded over its entire circumference with a gas-permeable and well-impermeable jacket (20), characterized

- That during operation of the dryer (1) the pourable material to be dried (6) of the screw conveyor (2) is supplied in an amount that it only partially fills the cross section of the screw conveyor (2) in the interior of the jacket (20),

- That the gas in a lower region of the screw conveyor (2) is introduced through the jacket (20) in the interior of the screw conveyor (2), that in the drying material (6) forms a fluidized bed and

- That the gas is discharged after flowing through the fluidized bed forming material to be dried (6) in an upper region of the screw conveyor (2) through the jacket (20).

39. The method according to claim 38, characterized in that during operation of the dryer (1) the pourable material to be dried (6) of the screw conveyor (2) is supplied in an amount such that it reduces the cross section of the conveyor screw (2) by only 30 to 60%. , preferably to 40 to 50%, fills.