WO2019075500A1

WO2019075500A1 - Apparatus and method for drying bulk material

Info

Publication number: WO2019075500A1
Application number: PCT/AT2018/060247
Authority: WO
Inventors: Kurt MÜHLBÖCK
Original assignee: Mühlböck Holztrocknungsanlagen Gmbh
Priority date: 2017-10-19
Filing date: 2018-10-18
Publication date: 2019-04-25
Also published as: AT520600A1; DE112018003241A5; AT520600B1

Abstract

The invention relates to an apparatus and to a method for drying bulk material, wherein the apparatus has a pre-drying region (1) and an after-drying region (2) and at least one conveying apparatus passing through the pre-drying region (1) and the after-drying region (2) for the bulk material, wherein an air stream (3) for bulk material drying in the at least one after-drying region (2) comprises recirculating air (5) that is recirculated, wherein the apparatus has at least one suction/intake opening (26, 27) connecting the surroundings of the apparatus at least to the after-drying region (2), at least one controllable valve (32) for opening and closing the at least one suction/intake opening (26, 27) and/or at least one fluid energy machine (28) for taking in air through the suction/intake opening (26, 27) at least from the after-drying region (2) and for taking in fresh air (31) through the at least one suction/intake opening (26, 27) at least into the after-drying region (22), in particular at least one pump and/or at least one blower.

Description

Apparatus and method for drying bulk material

The invention relates to a device for drying bulk material, wherein the device has a predrying area and a post-drying area and at least one den

Pre-drying region and the post-drying area passing through conveying device for the bulk material, wherein an air flow for bulk solids drying in the at least one post-drying area comprises a circulating circulating air. Furthermore, the invention relates to a method for drying bulk material, in which the bulk material is passed successively through at least one predrying area and at least one after-drying area, wherein an air stream for drying the bulk material in the at least one after-drying area comprises a recirculating circulating air, from which circulating air branched first partial air flow and passed through at least a first heat exchanger, wherein an air flow for drying the bulk material is at least partially formed from a fresh air sucked and heated via this heat exchanger, wherein the first diverted partial air flow after the passage through the at least one first heat exchanger and caused by condensation in the heat exchanger reduction of the moisture contained in this partial air flow back into the circulating air is returned.

An apparatus and a method of the above type have become known from AT 515 466 B1. The invention has for its object to further develop the known solution to allow an active exchange of air between the post-drying area and the environment in order to respond to changes in process parameters such as humidity, air pressure, temperature, etc. or actively influence this to be able to. The above object is achieved with a device of the type mentioned in the present invention that they at least one, an environment of the device at least with the after-drying area connecting from suction / suction, at least one switchable valve for opening and closing the at least one suction / suction and / or at least one fluid energy machine for sucking air through the suction / suction at least from the after-drying area and / or for sucking fresh air through the suction / suction at least in the after-drying area, in particular at least one pump and / or at least one fan ,

The device according to the invention makes it possible to introduce ambient air directly and specifically into the after-drying area or to let air out of the after-drying area directly and selectively into the environment. By means of this solution, it is also possible to always maintain a defined process conditions, in particular a defined internal pressure, in the after-drying region or in the device. In addition, the solution according to the invention makes it possible to prevent the formation of an underpressure or overpressure in the after-drying region in relation to the predrying region and to prevent an unwanted exchange of air between these two regions. A good drying of the bulk material can be achieved in that the device has at least one heating coil, via which the recirculating air circulated in the after-drying region is heated.

High energy efficiency with low emissions can be achieved by having at least one first heat exchanger, through which one from the recirculation air of the

Downstream diverted partial air flow is guided, wherein at least a portion of the air flow is formed to dry the bulk material in the at least one predrying from sucked and heated fresh air via the heat exchanger. According to an advantageous embodiment, provision may be made for fresh air sucked in via the suction / suction opening at least into the after-drying area or for air drawn off via the suction / suction opening at least from the after-drying area via at least one second heat exchanger. This variant of the invention is also distinguished by high energy efficiency and high efficiency.

Particularly preferably, the after-drying region is open to the predrying region in a conveying direction of the bulk material. For the detection of process parameters, it can be provided that at least one sensor for detecting an air pressure and / or at least one sensor for detecting an air humidity and / or at least one sensor for detecting an air temperature and / or in the predrying area are used in the after-drying area and / or in the predrying area. or a moisture content of the bulk material is arranged.

According to an advantageous development, the at least one sensor for detecting the air pressure and / or the at least one sensor for detecting the air humidity and / or the at least one sensor for detecting the air temperature and / or the at least one sensor for detecting the moisture content of the bulk material with a be connected to the at least one fluid energy machine and / or the at least one valve connected control. In order to produce an optimal process conditions, the controller may be adapted to the at least one fluid energy machine and / or the at least one valve in response to at least one sensor for detecting the air pressure and / or the at least one sensor for detecting the humidity and / or the at least one sensor for detecting the air temperature and / or the at least one sensor for detecting the moisture content of the bulk material produced and actuated to the control signals to operate.

In a particularly favorable variant of the invention, which makes it possible to set a defined pressure both in the predrying area and in the after-drying area, provision may be made for the suction / suction opening to be arranged at least partially in a transition area between the predrying area and the after-drying area is.

The drying process can be further improved in that at least one ventilation device for generating an air flow in the predrying region and at least one ventilation device for generating a recirculating air flow in the after-drying section Is provided area, wherein the device in addition to the suction from intake / additional additional an exhaust outlet for ejecting air from the predrying in the environment. According to an advantageous variant of the invention, provision may be made for the fresh air sucked in via the at least one suction / suction opening and / or the at least one second partial airflow to be conveyed via at least one filter of the suction / suction opening and / or via at least one of the suction / suction openings. / Inlet opening upstream or downstream filter is performed. It is advantageous in this embodiment of the invention that fresh air drawn in via the suction / suction opening flows into the post-drying area with relatively low turbulence due to the flow resistance of the filter, while emissions, in particular particle emissions, can be reduced when exhaust air is expelled from the post-drying area. The abovementioned object can also be achieved with a method of the type mentioned in the introduction by diverting at least one second partial air flow from the circulating air, which is discharged into the environment, or by drawing in fresh air from the environment and at least supplying the circulated air becomes. To increase the efficiency of the second partial air flow can be performed by at least one second heat exchanger.

For heating of the air used for predrying fresh air can be sucked and passed through the at least one second heat exchanger and heated.

According to an advantageous embodiment of the invention, it can be provided that the at least one first and the at least one second heat exchanger form a heat exchanger. The sucked and heated fresh air can be at least partially supplied to the pre-drying area and / or the post-drying area. Advantageously, the circulating air can be guided and heated via at least one heating register.

At least one controllable fluid energy machine and / or at least one switchable valve may be provided for generating the at least one second partial airflow or for aspirating the fresh air, wherein at least one valve opens and closes a suction / suction opening connecting at least the afterdrying area with the surroundings wherein a controller connected to the at least one fluid energy machine and / or the at least one valve is provided, wherein the controller actuates the fluid energy machine and / or the valve for generating the second partial air flow or for drawing in fresh air.

In addition, at least one process parameter, such as air humidity, moisture content of the bulk material, temperature and air pressure, can be detected by means of at least one sensor in the after-drying region and / or in the predrying region.

According to a preferred variant of the invention, the controller can actuate the at least one fluid energy machine and / or the at least one valve as a function of at least one signal generated by the at least one sensor.

In addition, the fresh air sucked in via the at least one suction / suction opening and / or the at least one second partial air stream can be guided via at least one filter of the suction / suction opening and / or via at least one filter upstream or downstream of the suction / suction opening.

For a better understanding of the invention, this will be explained in more detail with reference to the following figures.

In each case, in a highly simplified, schematic representation:

Fig. 1 is a block diagram of an embodiment of the inventive method for drying bulk material, in particular of wood bulk material; 2 shows a schematic longitudinal section through a heat exchanger for heat recovery or dewatering of air streams.

Fig. 3 sections of a device for drying bulk material in a schematic longitudinal section.

By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with the same reference numerals or the same component designations, wherein the disclosures contained in the entire description can be applied mutatis mutandis to the same parts with the same reference numerals or component names. Also, the location information chosen in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and these position information in a change in position mutatis mutandis to transfer to the new location. In Fig. 1, a method and apparatus for drying bulk material, in particular of wood in bulk form, shown schematically as a block diagram. The bulk material to be dried is first passed through at least one pre-drying area 1, and subsequently through at least one after-drying area 2. In the predrying zone 2, fresh air is sucked in at a first point of the predrying zone and, after passing through and / or overflowing the bulk material with the fresh air at a second location of the predrying zone 2, is again discharged as exhaust air to the environment. In the after-drying area 2, the air used for drying is at least partially guided as circulating air. Of course, a plurality of pre-drying or after-drying regions 1, 2 can be arranged directly one after the other, depending on requirements and plant size or desired drying capacity and drying capacity. In principle, this opens up the possibility of setting in each of these drying areas 1, 2 a drying climate which is favorable for the course of the process, essentially independently of one another.

The actual drying process for the bulk material in each region 1, 2 takes place by means of an air flow 3, which is passed through the respective drying region 1, 2. Therefor are the drying areas 1, 2 associated with ventilation devices 4, which among other things pass the respective air stream 3 through the corresponding area 1, 2. The device 1 can be structured in the vertical direction in three main planes. In a middle level (area) the bulk material is guided. Under a conveying plane of the bulk material, several compartments may be formed in the predrying area 1 and in the after-drying area in a lower level (area). Compartments may also be present in an upper level (area) above the conveying level of the bulk material. In the middle level, in which the bulk material is transported, preferably no structural separation between the pre-drying area 1 and the after-drying area 2 is provided. Preferably, an air stream in the predrying area is separated from an air stream in the post-drying area 2. Conveniently, there is essentially no exchange of air between the predrying area 1 and the after-drying area 2.

The device has one or more suction / suction openings 26, 27, which connects the after-drying area 2 with an environment of the device. It should be noted at this point that the term "connect" does not mean that the after-drying region at the location of the suction / suction opening is directly open into the environment, but that the suction / suction opening also has a pipe It is also possible for air ducts or shafts etc., which ultimately lead into the environment, to be connected to one another via the suction / suction opening 26, 27

After-drying area 2 discharged into the environment or supplied as fresh air 31 the after-drying area 2. To open and close the suction / suction ports 26, 27, one or more switchable valves 32 may be provided. Opening and closing the suction / suction opening in the present context means that an exchange of air between the after-drying area 2 and the environment is not possible ("closing") or an air exchange between the after-drying area 2 and the environment is possible (opening).

The valve 32 may be, for example, a switchable shut-off valve. Alternatively or in addition to the use of the valve 32, a fluid energy machine 28 may be provided. By means of the fluid energy machine 28, air through the suction / suction ports 26, 27 from sucked off the after-drying area 2 or fresh air 31 are sucked into this area. The fluid energy machine 28 can be, for example, a pump and / or at least one blower. In the exemplary embodiment shown in FIG. 1, each of the drying regions 1, 2 has a corresponding ventilation device 4, wherein it would also be conceivable to associate a common ventilation device 4 with a plurality of drying regions 1, 2. To improve a targeted or controlled adjustment of the respective climate in the drying areas 1, 2, however, it is advantageous to associate each drying area 1, 2 with at least one separate ventilation device 4.

An air flow 3 through an after-drying region 2 is in this case formed in part from a circulating air 5 guided via the ventilation device 4 in an air duct around the respective region 2. A partial flow of these guided around the after-drying zone 2 circulating air 5 is diverted as a partial air flow 6 and fed to a heat exchanger 7. In addition, as is clearly apparent from Fig. 1, the pre-drying region 1 fresh air 8 sucked through the heat exchanger 7, wherein the partial air flow 6 and the fresh air stream 8 are separated from each other by the heat exchanger 7. On the one hand, this allows the use of the heat energy contained in the partial air flow 6, on the other hand, a dehydration or a reduction of the water content of the partial air flow 6 takes place in the heat exchanger 7.

The heat exchanger 7 is preferably formed by a so-called cross-flow heat exchanger 9, in which the partial air flow 6 and the fresh air stream 8 at the respective inlet sides 11, 12 enter the heat exchanger 7, and at least predominantly at a right angle to each other through the heat exchanger, as this From Fig. 2 it can be seen. In Fig. 2 is a schematic longitudinal section through such a heat exchanger 7 is shown, wherein the same reference numerals as in the preceding Fig. 1 are used for the same parts. In order to avoid unnecessary repetition, reference is made to the description in the preceding FIG. It is noted at this point that the structural design of a heat exchanger 7 shown in FIG. 2 represents only one embodiment variant of the same. Alternatively, of course, other embodiments of the heat exchanger 7 deviating more or less from the embodiment shown in FIG. 2 are applicable. As shown in FIG. 1, the fresh air 8 preheated by energy transfer from the partial air stream 6 to the fresh air stream 8 in the heat exchanger 7 is used for predrying the bulk material 15 in the predrying zone 1.

The suctioned through the suction / suction ports 26, 27 air may be passed through a further heat exchanger 30.

The air flow 3 through the after-drying region 2 has the circulating air 5 guided around the after-drying region 2 and the partial air stream 6 diverted from the circulating air 5 and subsequently passed through the heat exchanger 7, which partial air stream 6 after the passage through the heat exchanger or after the moisture has been reduced in the heat exchanger 7 thus the circulating air flow 5 is supplied to the whole again. Before entering the after-drying area 2, it is necessary to heat this air stream 3. Therefore, the air stream 3 is guided before entering the post-drying area 2 via a heating coil 10, which can be fed with thermal energy.

As shown in FIG. 1, the air flow 3 through the predrying area 1 is formed by fresh air 8, which is sucked in via the ventilation device 4 and thereby passed through the at least one area. Before flowing through the predrying region 1, the fresh air 8 is passed through the heat exchanger 7 and thereby heated by means of the partial air flow 6. Depending on the availability of unused waste heat from peripheral installations, for example production plants, and / or to achieve a lower return temperature from the heating register 10 of the after-drying area 2, the heating register 10 can also be used before the predrying area 1. As a result, the drying performance of the at least one predrying region 1 can be increased. Therefore, in the embodiment shown in Fig. 1 for the predrying 1 also heating register 10 - shown by dashed lines - provided, which are arranged with respect to the flow direction of the fresh air 8 to the heat exchanger 7 and before the predrying 1. However, under favorable process conditions, and due to the use of the heat and condensation energy contained in the partial air flow 6, it is usually not necessary to further heat the fresh air 8 for the predrying area 1 by means of a heating register 10, or it may be possible entirely to such heating registers 10 be waived. As a source of energy for heating the heater 10 is basically any known energy source in question. It is particularly advantageous if a waste heat arising in the course of an externally running process, for example a power generation process, can be used for this purpose.

The process described describes a particularly energy-efficient process is achieved, in which for heating the fresh air 8 in the heat exchanger 7 - in addition to the temperature difference between fresh air stream 8 and partial air flow 6 - the inherent contained in the partial air flow 6 condensation energy is used, ie in the heat exchanger 7 as large as possible Amount of water is separated from the partial air flow 6 before the partial air flow 6 is returned to the recirculating air stream 5 again. Advantageously, this also reduces the absolute humidity of the partial air flow 6 at the same time before the partial air flow 6 is again supplied to the circulating air flow 5 in its entirety. The condensate water separated from the partial air flow 6 within the heat exchanger 7 can be discharged from the heat exchanger 7 in a known manner.

At least the flow velocities of the two air streams 6, 8 are matched to one another by the heat exchanger 7 such that at least partial sections of a surface 13 of the heat exchanger 7 facing the partial air flow 6, see FIG. 2, have a temperature which is below the dew point temperature of the partial air flow 6 ,

It may be useful to divert at least 10% of the circulating air 5 of the after-drying section 2 as a partial air flow 6, and pass through the heat exchanger 7. After the partial dehydration in the heat exchanger 7, the partial air flow 6 can be supplied to the circulating air stream 5 again.

Preferably, based on the one after-drying region 2, a total of leaving air quantity - between 10% and 90% of the circulating air 5 is diverted as a partial air stream 6.

It may be useful, for example, for the fresh air quantity supplied to the heat exchanger 7 to be selected such that it corresponds at least to twice the amount of the partial air flow 6 fed to the heat exchanger 7. Preferably, the amount of fresh air supplied to the heat exchanger 7 is selected or set such that it corresponds to 2 times to 20 times the amount of the partial air flow 6 fed to the heat exchanger 7.

The flow velocities, and thus the respective amounts of air, which are passed through the heat exchanger 7 in a certain time interval, can be selected in a conventional manner depending on pipe cross sections, pipe lengths, etc. mainly by the air conveying performance of the ventilation devices 4 be set.

It may be expedient if, for adjusting the flow velocity of the guided through the heat exchanger 7 partial air flow 6 in addition to the ventilation devices 4 of the drying areas 1, 2 at least one additional exhaust fan 14 is provided.

The efficiency of the process management with regard to the best possible use of the latent heat energy contained in the partial air flow 6 can be further increased if the ventilation devices 4, 14 for controlling the temperature conditions and flow rates between the fresh air stream 8 and the partial air flow 6 are speed controlled by the heat exchanger 7. This ensures that the air delivery rates of the existing ventilation devices 4, 14, and thus in particular the flow rates of the air streams in the entire system, for example, depending on measured at different points temperature values can be set so that the best possible use of in the partial air flow 6 inherently contained heat energy is possible.

Furthermore, a second partial air flow 29 is branched off from the circulating air 5 of the after-drying region 2, which is discharged via the suction / suction opening 26, 27 into the environment. Alternatively, for discharging air via the suction / suction from 26, 27, fresh air 31 can be sucked from the environment and the circulating air 5 supply. In this way, for example, in the after-drying area 2 and the pre-drying area 1 approximately equal pressure conditions prevail, so there is no unwanted mixing of air from the pre-drying area 1 and the post-drying area 2. The second partial air flow 29 can be passed through the heat exchanger 30. In the predrying 2 sucked fresh air 5 can also be through this second heat exchanger

30 are guided and heated. Furthermore, in particular when two suction / suction openings 26, 27 and two fluid energy machines 28 are used, fresh air 31 sucked into the after-drying area 2 via the suction / suction opening 26 can pass through the heat exchanger 30, and that through the suction / suction opening 27 aspirated partial air flow 29 is flowed through, guided and heated. The heat exchanger 7 and the heat exchanger 30 may also form a single common heat exchanger, wherein the partial air flow 29 can be coupled out, for example, after flowing through the common heat exchanger from the partial air flow 6 and discharged to the environment. Aspirated and heated fresh air 31 can thus be partially supplied to the predrying area 1 and / or the post-drying area 2.

In addition, the fresh air 31 sucked in via the suction / suction opening 26, 27 and / or the second partial air stream 29 can be filtered. For this purpose, the suction / suction opening 26, 27 have a filter. Additionally or alternatively, the suction / suction 26, 27 and one or more filters upstream and / or downstream, over which the fresh air

31 and / or the partial air flow 29 are performed.

In the after-drying region 2, one or more sensors 34, 35 for detecting an air pressure, a humidity, air temperature or a moisture content of the

Be arranged bulk material. Such sensors may alternatively or additionally also be present in the predrying region 1. The sensor or sensors 34, 35 may be connected to a controller 33, which in turn is connected to the fluid energy machine 28 and / or the valve 32. The control may be, for example, a suitably programmed micro or signal processor. The controller 33 is configured to supply the fluid energy machine 28 and / or the at least one valve 32 in response to the pressure generated by the sensor (s) 34, 35 and to the controller 33 transmitted signals to operate. The controller 33 can control the supply of air as well as the air discharge into and out of the after-drying area 2 as a function of the sensor signals. Thus, for example, in the event that a negative pressure with respect to the predrying area 1 is measured in the after-drying area 2, fresh air can be sucked into the after-drying area 2 via the fluid machine 28. For the reverse case, for example, air can be discharged from the after-drying area 2 into the environment. Pressure differences between the after-drying region 2 and the environment can be compensated, for example, only by opening and closing the valve 32. Also, the temperature and humidity in the after-drying area 2 can be selectively changed by supplying fresh air or by venting exhaust air from the after-drying area 2.

FIG. 3 shows a further embodiment of the method for bulk material drying, which is possibly independent of itself, wherein the same reference numerals or component designations are again used for the same parts as in the preceding figures. To avoid unnecessary repetition, reference is made to the detailed description in the preceding figures. In Fig. 3 is a detail of a schematic longitudinal section through a device for

Bulk or wood drying shown. In the exemplary embodiment shown, the bulk material 15 to be dried is first conveyed by means of a conveyor belt 16 of a belt conveyor 17 through at least one pre-drying area 1 and subsequently through at least one after-drying area 2. As can be seen from FIG. 3, the conveyor belt 16 forms an at least approximately horizontal conveying plane for the bulk material 15.

The dosage of the applied to the conveyor belt 16 amount of bulk material 15 per unit time can be done in different ways. Thus, for example, a supply of the bulk material 15 by controlled irrigation of the activated conveyor belt 16 with bulk material 15 via a funnel-shaped task evorrichtung 18 conceivable, as indicated in Fig. 3. Alternatively or in combination, an active application of the bulk material 15 via a motor-driven application device, for example in the form of a screw or double screw is possible. It may be expedient to carry out such an application in a quantity-controllable manner, since, irrespective of the shape and type of the bulk material 15, a quantity of water contained in the bulk material 15 to be dried may vary with respect to a unit mass or a unit weight of the bulk material 15. As can be seen from the exemplary embodiment shown in FIG. 3, the bulk material height 19 on the conveyor belt 16 can be increased or decreased as a function of the initial water content of the bulk material 15 and / or depending on the available, external amount of thermal energy , Furthermore, it is expedient to adjust the bulk material height 19 to the type of bulk material 15 to be dried. In particular, the piece or grain size of the bulk material 15 is crucial for this. For a smaller piece or grain size of the bulk material 15, such as sawdust, the bulk material height 19 can be reduced expediently, and for a larger piece or grain size, for example for wood chips or the like, the bulk material height 19 can be raised.

In order to at least largely compensate for variations in the moisture content of the bulk material 15 in the continuous process, it may also be expedient to increase or decrease the conveying speed of the bulk material 15 or the transport speed of the conveyor belt 16 as a function of the initial water content of the bulk material 15.

As an alternative or in combination, the flow velocities of the partial air flow 6 or of the fresh air flow 8 separated from the circulating air 5 can also be increased or decreased, for example, in order to achieve, for example, higher drying rates per unit time, depending on the initial water content of the bulk material 15.

In order generally to achieve higher drying rates per unit time in the drying areas 1, 2, especially for wood in bulk form, it is expedient to guide the air stream 3 guided through the respective area 1, 2 at least for the most part through the conveyor belt 16.

For this purpose, the conveyor belt 16 shown in Fig. 4 16, for example, sieve-like, fine mesh or other measures at least partially air permeable.

As a result, for the respective air flow in the drying area 1, 2 predefined and specifically prepared airways directly through the conveyor belt 16 and therefore also by the bulk material 15 available. In this context, it is further expedient if the width of the conveyor belt approximately corresponds to the width of a drying region 1, 2, since the drying air 3 is thereby forced, as it were, to flow through the conveyor belt, and thus the bulk material 15.

In the exemplary embodiment shown in FIG. 3, both the fresh air stream 8 for the predrying region 1 and the circulating air 5 and the partial air stream 6 for the after-drying region 2 are sucked in each case by ventilation devices 4 and as drying air streams 3 through the respective regions 1, 2 or. passed through the conveyor belt 16 and bulk material 15. The respective pipes or air ducts for the exhaust air 25, which is discharged after passing through the predrying 1 to the ambient air - see Fig. 1 - and for the circulating air 5 to the post-drying area 2 are located on the side facing away from the viewer side of FIG. 3 Schüttguttrock- shown, and are not shown in Fig. 3. The discharged to the environment exhaust air 25 comes exclusively from the predrying area 1 and is highly saturated, and has a temperature of less than 25 ° C.

In particular, to increase the drying performance or increase the drying quality, it may also be useful to provide a distribution device 20, with which the bulk material 15 is distributed over the entire width of the conveyor belt 16 as evenly as possible. Such a distribution device 20 can be realized for example by a limited pivoting distribution screw. Depending on the nature of the bulk material 15 to be dried, in particular as a function of its degree of soiling or as a function of the fines contained therein, at least one belt blow-off device 21 can be provided. Thus, the surface 22 of the conveyor belt 16 after passing through a discharge or discharge device 23 for the dried bulk material 15 of any adhering to the conveyor belt 16, solid or liquid residues of the bulk material 15 can be freed. For this purpose, one or more nozzles, possibly arranged at different angles to the surfaces 22 of the conveyor belt 16, through which nozzles, for example compressed air is blown by means of a compressor in the direction of the surfaces 22 of the conveyor belt 16. Furthermore, it may be helpful and / or necessary to clean or wash the surfaces 22 of the conveyor belt 16 after passing through the discharge or discharge device 23 for the dried bulk material 15 by means of a washing device 24. In this case, water is sprayed or sprayed against a surface 22 of the conveyor belt 16 under pressure.

The Bandabblasungsvorrichtung 21 and / or washing device 24 shown in Fig. 3 is particularly useful when using the described air-permeable conveyor belt 16, since there is an increased probability that adhering to the conveyor belt 16 bulk or dirt residues affect the air permeability of the conveyor belt 16 gradually negative. When an air-permeable conveyor belt 16 is used, both at least one belt-blowing device 21 and at least one washing device 24 can be arranged, which can be directed to both surfaces 22 of the conveyor belt 16, as can be seen in FIG.

As can be seen from FIG. 3, the suction / suction opening 26 is connected only to the after-drying area 2. However, it can also be advantageous if the suction / suction chimney 28 is arranged between the predrying area 1 and the after-drying area 2. So it is in a transitional area between these two areas. Such an arrangement is particularly advantageous with regard to the production of a rapid pressure equalization between the two drying areas 1 and 2.

For the sake of order, it should finally be pointed out that, for a better understanding of the structure, elements have been shown partly out of scale and / or enlarged and / or reduced in size. REFERENCE NUMBERS

Predrying area fresh air

After-drying valve

Airflow control

Venti 1 ati on s p a tion 34 Sensor

Circulating air 35 sensor

Partial air flow

heat exchangers

fresh air

Cross-flow heat exchanger

heater

Entry side

entry page

surface

extractor fan

bulk

conveyor belt

Supporting regulations

Task precaution

depth of material

distribution device

Blowing instructions

surface

discharging device

Washing precaution

exhaust

From suction / suction opening

Suction / suction opening

Fluid energy machine

Partial air flow

heat exchangers

Claims

Patent claims

1. An apparatus for drying bulk material, wherein the apparatus has a predrying area (1) and an after-drying area (2) and at least one conveying device for the bulk material passing through the predrying area (1) and the after-drying area (2), wherein an air stream (3 ) for bulk material drying in the at least one after-drying area (2) comprises a recirculating circulating air (5), characterized in that it at least one, an environment of the device at least with the after-drying area (2) connecting suction / suction opening (26, 27) at least one switchable valve (32) for opening and closing the at least one suction / suction opening (26, 27) and / or at least one fluid energy machine (28) for sucking air through the suction / suction from (26, 27) at least from the after-drying area (2) and / or for sucking fresh air (31) through the at least one suction / suction opening (26, 27) at least into the night skirt area (2), in particular at least one pump and / or at least one fan.

2. Apparatus according to claim 1, characterized in that it comprises at least one heating coil (10) via which the recirculated circulating air (5) of the after-drying region (2) is heated.

3. Device according to claim 1 or 2, characterized in that it comprises at least a first heat exchanger (7) through which a from the circulating air (5) of the

At least part of the air flow (3) for drying the bulk material in the at least one pre-drying (1) from a via the heat exchanger (7) sucked and heated fresh air (8) is formed.

4. Device according to one of claims 1 to 3, characterized in that on the suction / suction (26, 27) at least in the after-drying area (2) sucked fresh air (31) or via the suction / suction at least off the

Night drying area (2) sucked air over at least one second heat exchanger (30) is guided.

5. Device according to one of claims 1 to 4, characterized in that the

Drying area (2) to the pre-drying area (1) viewed in a conveying direction of the bulk material is open.

6. Device according to one of claims 1 to 5, characterized in that in the after-drying region (2) and / or the predrying region (1) at least one sensor (34, 35) for detecting an air pressure and / or at least one sensor for detecting a Humidity and / or at least one sensor for detecting an air temperature and / or a moisture content of the bulk material is arranged.

7. The device according to claim 6, characterized in that the at least one sensor (34, 35) for detecting the air pressure and / or the at least one sensor for detecting the humidity and / or the at least one sensor for detecting the air temperature and / or at least one sensor for detecting the moisture content of the bulk material is connected to a controller (33) connected to the at least one fluid energy machine (28) and / or the at least one valve (32).

8. The device according to claim 7, characterized in that the controller (33) is adapted to the at least one fluid energy machine (28) and / or the at least one valve (32) in response to the at least one sensor (34, 35). for detecting the air pressure and / or the at least one sensor for detecting the humidity and / or the at least one sensor for detecting the air temperature and / or the at least one sensor for detecting the moisture content of the bulk material generated and to the controller (33) transmitted signals actuate.

9. Device according to one of claims 1 to 8, characterized in that the suction / suction opening (26, 27) at least partially into a transition region between the pre-drying area (1) and the after-drying area (2) opens.

10. Device according to one of claims 1 to 9, characterized in that at least one ventilation device (4) for generating an air flow in the pre-drying area (1) and at least one ventilation device (4) for generating a recirculating air flow in the after-drying area (2) is provided , the device next to the suction / suction opening (26, 27) additionally has an exhaust air outlet for discharging air from the predrying area (1) into the environment.

11. The device according to one of claims 1 to 10, characterized in that the suction / suction (26, 27) has at least one filter or that the device has at least one filter, which of the at least one suction / suction (26, 27 ) is upstream or downstream.

12. A method for drying bulk material, in which the bulk material is passed successively through at least one pre-drying area (1) and at least one after-drying area (2), wherein an air stream (3) for drying the bulk material in the at least one after-drying area (2) in the Circulation-guided circulating air (5) comprises, from which circulating air a first partial air flow (6) is diverted and passed through at least one first heat exchanger (7), wherein an air flow (3) for drying the bulk material at least partially from one via this heat exchanger (7) sucked and heated fresh air is formed, wherein the first branched partial air flow (6) after the passage through the at least one first heat exchanger and a condensation in the heat exchanger (7) caused reduction in this partial air flow (6) moisture is returned to the recirculation , characterized in that at least from the circulating air (5) at least e is diverted into the second partial air flow (29), which is discharged into the environment, or that from the environment fresh air (31) is sucked in and at least the circulating air (5) is supplied.

13. The method according to claim 12, characterized in that the second partial air flow (29) through at least one second heat exchanger (30) is guided.

14. The method according to claim 13, characterized in that fresh air (31) is sucked and passed through the at least one second heat exchanger (30) and heated.

15. The method according to claim 13 or 14, characterized in that the at least one first heat exchanger (7) and the at least one second heat exchanger (30) form a heat exchanger.

16. The method according to any one of claims 12 to 15, characterized in that the sucked and heated fresh air (31) is at least partially fed to the predrying area (1) and / or the post-drying area (2).

17. The method according to any one of claims 12 to 16, characterized in that the

Circulating air (5) via at least one heating coil (10) is guided and heated.

18. The method according to any one of claims 12 to 17, characterized in that for generating the at least one second partial air flow (29) or for sucking the fresh air (31) at least one controllable fluid energy machine (28) and / or at least one switchable valve (32 ), wherein at least one valve (32) opens and closes a suction / suction opening (26, 27) connecting at least the after-drying area (2) with the environment, one with the at least one fluid energy machine (28) and / or or the at least one valve (32) connected control (33) is provided, wherein the controller (33) the fluid energy machine (28) and / or the valve (32) for generating the second partial air flow (29) or for the intake of fresh air (31) pressed.

19. The method according to claim 18, characterized in that in the after-drying area (2) and / or in the predrying area (1) at least one process parameter, such as humidity, moisture content of the bulk material, temperature and air pressure, by means of at least one sensor (34, 35) is detected.

20. The method according to claim 19, characterized in that the controller (33) the at least one fluid energy machine (28) and / or the at least one valve (32) in response to at least one signal generated by the at least one sensor (34, 35) actuated.

21. The method according to any one of claims 12 to 20, characterized in that via the at least one suction / suction from (26, 27) sucked fresh air (31) and / or at least a second partial air flow (29) via at least one filter the suction / suction opening (26, 27) and / or via at least one of the suction / suction opening (26, 27) upstream or downstream filter is performed.