EP2658693A1

EP2658693A1 - Method and device for wetting particle material, in particular fibers and/or chips, with a fluid

Info

Publication number: EP2658693A1
Application number: EP11807698.3A
Authority: EP
Inventors: Gernot Von Haas
Original assignee: Dieffenbacher GmbH Maschinen und Anlagenbau
Current assignee: Dieffenbacher GmbH Maschinen und Anlagenbau
Priority date: 2010-12-29
Filing date: 2011-12-28
Publication date: 2013-11-06
Also published as: CN103269836A; WO2012089774A1; DE102010064339A1

Abstract

The invention relates to a method and device for wetting particle material (1), in particular fibers and/or chips, with a fluid (8), in particular in the course of producing material plates, wherein the particle material (1) is introduced into a fall duct (4) by means of a metering device (2) and the particle material (1) forms a particle material curtain (5) in the fall duct (4), wherein the depth (t) of the particle material curtain (5) can be set and a fluid is applied to the particle material curtain by means of at least one row of nozzles (6) arranged in the fall duct (4). According to the invention for the method, the moisture and/or the presence of fluid drops outside of the particle material curtain (5) is monitored in the fall duct (4). A device suitable therefor is characterized in that at least one viewing window or one detector (8) for determining the moisture and/or for detecting the presence of fluid drops in the fall duct (4) is arranged in the fall duct (4) in order to monitor the moisture and/or the presence of fluid drops outside the particle material curtain (5).

Description

Method and device for wetting spreading material, in particular fibers and / or chips, with a fluid

The invention relates to a method for wetting spreading material, in particular fibers and / or chips, with a fluid, in particular in the course of the production of material plates according to the preamble of claim 1 and a device according to the preamble of claim 12.

The production of material plates from chips and / or chips

(Chipboard, OSB, ...), fibers (MDF, LDF, HDF, ...) or others

Free-flowing materials are now automated processes and have been used in many countries for many years. As is known, the compression of processed chips or fibers takes place either clock-bound or continuously. In addition to the many plant parts before and after the press, the gluing of the chips and / or fibers plays a role

outstanding role, since the quality of the grit mat created is an important factor in addition to the quality of the raw materials. In addition to these criteria, an optimal gluing but also has a high potential savings, since

Adhesive systems are very expensive and have a significant cost of a material plate.

Usually a urea-formaldehyde resin glue (also polycondensation glue or UF glue) or polymeric diphenylmethane diisocyanate (PMDI) or two-component glue. In the case of a two-component adhesive, the hardener (UF glue) or the foaming agent (usually polyol in the case of PMDI) is applied to the fibers / shavings by pressing as quickly as possible before pressing. In addition, the fibers to be glued or the chips are named as spreading material, since the fibers or the chips are generally scattered on a forming belt to a spreading material mat and then pressed.

For the large-scale production of wood-based panels, continuous presses are used. In these presses, as described in DE 39 13 991 C2, the pressing force by hydraulic

Actuators on the press and heating plates and continue on steel belts, which are supported by a rolling element carpet (rolling rods) arranged circumferentially, transferred to the grit. Such presses usually process glued spreading material, which has been formed in spreading machines to a flat grit mat on a continuously moving forming belt.

To form the grit mat is usually discharged from a metering grit and sprinkled with arranged in a scattering head rollers controlled on a forming belt to form a grit mat. It can also find a wind scattering use. Usually this is the grit already glued before the metering device. However, it may be necessary in the use of two-component adhesive liquors, between the spreader and the dosing still additives, especially hardener or foaming agent to spray on the grit. It is also conceivable to wet the surface of the material to be spread with water, paints or other additives in order to influence the production process of the material plates. In the prior art, there are a variety of Beleimvorrichtungen or wetting devices for grit in the course of the production of

Based panels. The problem with all these devices is that the wetting with fluid can be tested for accuracy later in the manufacturing process, usually this is by fracture tests of

Material plates out whether too inaccurate or too little fluid has been applied to the grit. Most often even too much fluid is applied to ensure wetting. Unfortunately, this leads to a significant and unnecessary additional consumption of the fluid and thus in the

Also related to caking within the devices, since dust connects to the fluid or form coagulations, which are reflected on the walls of the devices.

The liquid to be sprayed and applied, referred to below as fluid, onto the spreading material may include, inter alia, adhesives such as MDI, LPF, UF, MUF, acrylate and / or additives such as hardeners, accelerators, buffers for UF glues,

Fire retardants, dyes, insecticides, (tempered) water, emulsion, or mixtures thereof. The object of the invention is to provide a method and an apparatus with which it is possible to manually or automatically check the wetting of grit with a sprayed through nozzles fluid and thus also controllable and at the same time the emergence of

Caking in the device to reduce or avoid altogether.

Further, it should be possible the method or device itself in the context of different types of production and thus changeable

Quantity throughput of material to be spread quickly and easily. The solution to the method is that for wetting the grit is introduced by means of a metering device in a chute and the grit in the chute forms a grit curtain, the grit curtain is adjustable in depth and by means of at least one row arranged in the chute nozzles with a Fluid is applied, the solution is in particular that in the chute, the humidity and / or the presence of fluid droplets outside of the

Grit curtain is checked.

The solution for the device is that at least one viewing window or a detector for detecting the moisture and / or for detecting the presence of fluid droplets in the chute is arranged in the chute for checking the humidity and / or the presence of fluid droplets outside the grit curtain. Advantageously, in the proposed system for applying fluids, the penetration behavior of the fluid in the grit curtain is checked and regulated accordingly by means of a suitable control device. In particular, single-fluid nozzles should be used for this purpose

Unlike two-component nozzles, only one substance (in this case the fluid) is sputtered and does not require atomization and / or conveying (compressed air). In the case of the most frequently used single-substance nozzles, atomization takes place at the nozzle outlet in such a way that the predominantly used solutions, emulsions or dispersions disintegrate into uniform droplets with a narrow distribution.

Due to the advantageous use of the one-fluid nozzles

- No further sputtering and / or subsidies needed, it accounts for the provision and cleaning costs including plant and

Maintenance costs for this agent;

- no means unnecessary in the production process entered into the fiber curtain to be glued; This minimizes air turbulence and material shifts within the spreading material curtain;

- facilitates the control and regulation, because only one component

(Glue or additives) on a controllable and controllable

High-pressure system must be supplied; Regelstörungen- and

Variations within a complex control system

(Two-fluid nozzles) are avoided. The production of a grit curtain is preferably carried out by dosing a predetermined amount of grit (fibers / chips) by means of a belt scale (dosing bunker) and a device for dissolution of the material to be spread (spiked or opening rollers), wherein the device for dissolution and separation of the material to be spread, the grit preferably directly into a Downfall passes. At the entrance of the chute can be arranged to adjust the thickness of the grit curtain vanes over the width thereof. The result is preferably a width of the grit curtain of 0.2 to 120 m and a depth of the grit curtain of 10 to 300 mm.

In the chute arranged sheets, respectively the walls, become

preferably cooled, since the freshly glued or provided with additives grit could adhere to the warm sheets, since the grit generally has a residual heat from the drying. Before and after

The production process is carried out by sheets which have already been spread with a release agent or equivalent emulsion

sprayed.

Preferably, the nozzle bars are arranged movably and can be moved to a maintenance position for manual or automated cleaning of the nozzles. Preference is given to atomizing pressure nozzles

(Flat jet nozzles or fan nozzles) arranged. In particular, a flat jet nozzle should be used which has the smallest droplet size allows. The atomization should preferably be carried out at a pressure of 50 to 200 bar.

The scattered material charged with the fluid is either (preferably) introduced via the chute into a spreader, sprinkled into a spreader mat and then pressed in a timely manner (before the glue hardens). Alternatively, the grit still has a moving belt and

Intermediate bunkers be stored or in another

mechanical gluing in a drum with rotating conveying tools (mechanical mixer) glued and / or treated, in the course of which again follows a scattering and compression.

Preference is given to using single-substance nozzles which are subjected to a pressure of 20-200 bar and which inject the fluid as fine liquid droplets into the falling spreading material curtain. The pressure setting should be carried out so that the momentum of the liquid droplets is sufficient to enter the grit curtain, but not so large that the liquid droplets on the other side emerge from the grit curtain again. This circumstance can be checked in a simple manner by means of detectors or even manually by an operator via a viewing window. There are also detectors that enter through the viewing window

Determine precipitation behavior on the viewing window automatically. Thus it is possible, the pollution of the walls a formation of thick drops of fluid, which can lead to agglomeration of particles and fibers to avoid. The nozzles and / or the nozzle bars are regulated according to the desired value of the necessary fluid throughput kg / h. Depending on the required flow rate, a plurality of nozzle bars can be arranged on one or both sides of the grit curtain and preferably be controlled individually. Also, the nozzles can be inside a

Nozzle bar, which is arranged transversely to the direction of fall, may be controllable in groups, for example, to be able to set a different number of nozzles across the width when setting respectively the regulation of the amount of fluid. It would be conceivable to arrange over a width of two m as a minimum four nozzles, which could be supported by a necessary increase in the amount of glue from three other nozzles.

As a sensor for determining a fluid mist emerging from the spreading material curtain, at least one measuring device for droplets or moisture is arranged at least on one side, preferably opposite, and at least in the direction of fall at the same height or below the nozzles. In the case of opto-electronic monitoring (LED photodiode system), a droplet sensor is arranged on transparent glass or plastic.

Alternatively, a capacitive droplet sensor (conductivity)

be arranged. Preferably, however, the content of the moisture in the chute outside the grit curtain can be determined. Through a Increased moisture and / or droplet formation, preferably free fluid, the spreading material is not properly wetted.

A faulty wetting can have several causes. For example, at a relatively low depth of the grit curtain, but high

Material throughput per unit time of the entry of the fluid in the grit curtain reduced or prevented. Immediately below the nozzles there is an increase in moisture or droplet formation, which can be automated with a corresponding device or manually controlled via a transparent inspection window or inspection port. Remedy can bring in this case an increase in the pressure at the nozzle or an increase in the depth of the grit curtain. But if the increase in moisture or droplet formation on the opposite side of the nozzles of the grit curtain determined, the pressure in the nozzle is too strong and would have to be reduced. In order to compensate for a decreasing amount of throughput of the fluid per unit time, more nozzles or nozzle rows are connected in necessary number. Alternatively, the depth of the grit curtain can also be increased here. The measurement for a faulty wetting is generally on

Droplet formation and / or moisture is described. Droplets of the fluid do not necessarily lead to an increase in humidity when the fluid used has a relatively low water content, for example Hardener or foaming agent. In wetting devices, which usually drive always the same throughput of grit per unit time, it is not absolutely necessary to perform a full automation. It is sufficient a window to control the moisture or a

To arrange droplet formation at a suitable location of the chute and to inspect the window at the beginning of production or when changing the batch (grit and / or fluid) and adjust the operating pressure / nozzle number / depth of the grit curtain once and readjust at regular intervals. In the case of highly complex overall systems with daily or even hourly changes in the material throughput per time unit, of course, an automated setting is desired. The detectors (including the viewing window) are depending on the spray angle (this can also opposite angle to

Fall direction, so be directed upward) preferably on the

arranged opposite side of the nozzles. A person skilled in the art can calculate the transit time and the passageway of the fluid or follow experiments and will arrange the detector (s) in the chute in the appropriate height in order to obtain an optimum result

Monitoring for moisture or droplet formation within the

To get a chute. If there is a large amount of dust or particles forming on the spreading material, regular cleaning of the detectors / inspection window may be necessary. This can for example be done by an endless circulating or reversing film, which is arranged in the chute in front of the detector / the viewing window and during the circulation or a reversing run is cleaned continuously or at regular intervals. Of course, this film must be opto-electronic

Droplet measuring devices are included in the angle of refraction to detect the droplets. The droplet formation or the moisture can of course also be checked contactlessly by means of radiographic devices.

Due to the teaching of the invention is now an optimized

Maximum pressurization of the spreading material curtain automatable and adjustable. For this purpose, the pressure in the nozzles is increased until a moisture increase or droplet formation can be detected on the opposite side of the grit curtain. According to general control engineering experience, the pressure is subsequently slightly reduced again, and thus optimal loading of the material to be spread within the grit curtain with a fluid is realized.

It should be noted that the teaching of the invention is not limited to im

Cross-section rectangular grit curtains is limited, but

for example, can also be applied mutatis mutandis in circular grit curtains. Also, the device can stand alone

Find application or be used to carry out the process. Further advantageous measures and embodiments of the subject matter of the invention will become apparent from the dependent claims and the following description with the drawing. Show it:

Figure 1 is a schematic side view of an apparatus for wetting of grit, in particular of fibers and / or chips, with a fluid in the course of the production of material plates by means of a press not shown in the production direction, wherein the device for wetting the material to be spread with fluid with a

Spreader for grit mats and a metering device is operatively connected and connects as a chute these two parts of the plant,

Figure 2 shows another embodiment of an apparatus for wetting of grit in a two-stage design, wherein in a first

Downpipe by means of a metering a spill curtain for spraying with a first part of the fluid is formed and the chute, a mechanical mixer is connected downstream, in which the second part of the fluid is sprayed onto the grit, in which case a mechanical mixing of the grit is accompanied and

FIG. 3 shows a control and regulation scheme for loading the

Nozzles in nozzle bars of a chute with associated Detector and schematic representation of the operatively connected means for controlling the high-pressure device with a control device. Figure 1 shows a schematic side view of a system for forming a grit mat 25 from free-flowing material 1 on a forming belt 10 in the course of the production of material plates by means of a in

Production direction 23 arranged, but not shown press. The dosing device 2 is designed as a dosing bunker with a discharge device above the spreader 3. The metering device 2 has on the input side at least one side wall 22 and a

Backscatter rake 21 above a bottom belt 19 which sweeps back the grit 1 entering the dosing device 2 on the bottom belt 19 to a Schüttberg. During the discharge is by means of the

Bottom band 19 of Schüttberg from grit 1 controlled against a

Discharge device 20, here discharge rollers, proceed and it is thus achieved a uniform discharge of the material to be spread 1 in the chute 4.

At the same time, the spreading material 1 is dissolved and separated by the discharge device 20. This results in the chute a grit curtain 5, which is carried out by means of fixed walls or an adjustable guide device 7, preferably designed as adjustable flaps, in its depth t. The depth t corresponds to a one-sided application of fluid of the penetration depth of the fluid in the grit curtain 5. After the transition from Chute 4 in the scattering device 3 forms the grit 1 on the

Spreading rollers 24, which constitute a spreader carpet, one

Grit carpet 17 off. The grit 1 then falls in the direction of fall 1 1 on the forming belt 10 and forms a grit mat 25, which in

Production direction 23 for further processing up to the pressing in a press (not shown) is transported.

The nozzles 6 are preferably arranged over the width of the chute 4 in a nozzle bar 12, with 6 'and 12' respectively additional rows of nozzles / nozzle bars are shown. To determine increased humidity or moisture precipitation, respectively droplets, the nozzles 6 and the nozzle strips 12 detectors 8 are arranged in the direction of fall 1 1 of the material to be spread. Alternatively or additionally, a viewing window 18 may be provided for the detectors 8 or for the review of operating personnel. Also, a lockable lock for the operator would be conceivable to introduce, for example, a detector 8 or other conceivable means as sensors in the chute. It is obvious that the means for testing in the chute 4 but not in the grit curtain 5 itself should be arranged.

Depending on the degree of ventilation, turbulence and grit 1 used, it may be necessary to provide an exhaust 27 above the grit carpet 17 in the spreader 3. This suction can also be arranged as close as possible or even on the output side of the chute 4 itself in order to suck dust or fluid-cooled air in a controlled manner. FIG. 2 shows a further exemplary embodiment of a device for wetting spreading material 1 in a two-stage design. For this purpose, from a metering bunker 26 to an independent metering device 13 (both

together form a similar metering device 2 as shown in Figure 1 from) spreading material 1, which in a chute 4 a

Scattering curtain 5 forms, which is sprayed with a first part of the fluid. It is expressly understood that the grit curtain 5 does not necessarily have to have a rectangular shape, but can also be discharged for example from a tube with a central expansion device of the material to be spread. It then results

Hollow-cylindrical grit curtain 5, which can be sprayed, for example, from inside to outside and / or from outside to inside with fluid. The

Arrangement of the detectors 8 is carried out analogously. In the illustrated embodiment of Figure 2, the grit 1 then falls in a down the chute 4 mechanical mixer 14 with a mixer shaft 15 in which, for example, the second part of the fluid can be sprayed onto the grit 1 by means of mixer nozzles 16 or

Grit 1 is only mixed in addition. Preferably, however, 1/3 of the fluid in the chute 4 and 2/3 of the fluid, in particular a glue liquor for gluing the material to be spread, is applied to the grit 1 in the mixer 14. Of course, other combinations are possible, for example

Applying a hardener or foamer in the chute 4 and the glue in the Mixer 14 or vice versa. Again, however, an advantageous test for droplet formation or moisture is performed in the chute 4 by means of detectors 8. In this chute, the detectors are arranged in the direction of fall 1 1 below the nozzles 6, in which case the nozzles 6, 6 ', 6 ", 6"' are arranged alternately. In order to enable advantageous control or regulation, preferably two or more rows of nozzles are arranged, and preferably the effect of two nozzle strips 12, 12 ', 12 ", 12"' is checked with at least one detector 8. The detector 8 arranged at the bottom right in the chute can even be used in a double function since it can check the passage effect of the nozzles 6 ", 6"'and the entry effect of the nozzles 6, 6'. Also in the mixer 14, an exhaust 27 may be arranged to remove dust and / or fluidgeschwängerter air. For reasons of cost, the detector can also check only a small area over the width of the chute 4 and is, however, in this case moved at regular intervals over the entire width of the chute 4.

In Figure 3 is a control and regulation scheme (without claim to completeness) for acting on the nozzles 6 in the nozzle bar 12 of a chute 4 with associated detector 8 and a schematic representation of the operatively connected means for controlling the

High-pressure device with a control device 9 shown. For carrying out the method for wetting of grit 1, in particular of fibers and / or chips, with a fluid 28, in particular in the course of Production of material plates, the grit 1 is to be introduced by means of a metering device 2 in a chute 4, the grit 1 in the chute 4 a rectangular in cross-section or hollow cylindrical (not shown) grit curtain 5 is formed. Of the

Chute 4 is not shown in Figure 3, wherein the width of the nozzle bars 12 is substantially the width b of the chute 4 respectively of the

Grit curtain 5 corresponds. To the grit curtain 5 in its depth t by means of at least one row over the width of the chute 4th

arranged nozzle 6 to be able to apply a fluid, the fluid 28 is passed through a filter 29 and then by means of a high pressure pump 30, the necessary pressure to the fluid 28 is generated. For measuring the flow per unit time are pressure gauge 31 and

Flow meter 32 is arranged. In the pressure direction to the nozzles 6, 6 ', 6 ", 6"' respectively the nozzle bars 12, 12 ', 12 ", 12"' are switching valves, which are preferably individually switchable by the control device 9. In order for the control device 9 to be able to set the optimum pressure and / or the optimum number of nozzle bars 12 and / or nozzles 6, the latter is provided with a moisture in the chute 4 and / or the presence of

Fluid droplets outside the grit curtain 5 examining detector 8 operatively connected. The pressure setting should be such that the pulse of the sprayed fluid 28, respectively, the liquid droplets is so large that this enters the grit curtain 5, but no longer exits on the other side. To check this manually (operator) or automated can, in the chute 4, the moisture by means of at least one window, by means of at least one device for determining the moisture and / or by means of at least one device for detecting the presence of fluid droplets outside the grit curtain 5 determine. For this purpose, viewing window 18 or detectors 8 are arranged as devices for determining the humidity and / or for determining the presence of fluid droplets, which are arranged substantially in the direction of fall 1 1 at the same height or after the nozzles 6. An automated control device 9 for controlling the nozzles 6, 6 'and / or the nozzle bars 12, 12' should be equipped with the means (valves, pressure gauge 31, flow meter 32, high pressure pump 30 ....) for controlling or regulating the nozzles 6 , 6 ', ... and / or the

Nozzle strips 12, 12 ', ... be operatively connected. It is possible to adjust the amount of fluid per unit of time over the number of nozzles 6 and / or the pressure at the nozzles 6 itself. The nozzle strips 12 and the nozzles 6 can preferably be controlled independently of each other, so that the fluid is atomized by means of pressure nozzles.

When using a mixer 14 following the chute 4, preferably one third of the fluid in the chute 4 and two thirds of the fluid are introduced into the grit 1 via mixer nozzles 16 in the mixer 14.

As can be seen from the synopsis of the figures, the nozzles 6 should be arranged transversely to the direction of fall 1 1 in the nozzle strips 12, not is shown that the nozzle bars 12 can be brought into a maintenance position. For example, in the case of a plurality of nozzle strips 12, the nozzle strips 12 can always be operated alternately in order to be able to clean a nozzle strip 12. It may also be necessary to use different nozzles 6 or nozzle bars 12 for different fluids. In order to be able to clean the chute 4 and / or the nozzles 6 directly before or after operation, cleaning liquid 33 can be sprayed through the nozzles 6 via a valve. The cleaning liquid 33 may also be an anti-adhesive agent for the fluid used to adhere the fluid or fluid / grit dust compounds to the walls or others

To reduce device parts.

LIST OF REFERENCE NUMBERS

1 . Grit 22. Sidewall of 2

2. Dosing device 23. Production direction

3. spreading device 24. scattering rollers

4. Chute 25. Grit mat

5. Grit curtain 26. Dosing bunker

6. Nozzles 27. Suction

7. Guide 28. Fluid

8. Detector 29. Filter

9. Control device 30. High-pressure pump

10. Form band 31. pressure gauge

1 1. Direction of fall 32. Flow meter

12. Nozzle strip 33. Cleaning liquid

13. Metering device

14. Mixer

15. mixer shaft b width of 5

16. Mixer nozzles t depth of 5

17. Scatter carpet on 24

18. View window

19th floor tape

20. Discharge

21. Evener combs

Claims

claims

Method for wetting spreading material (1), in particular fibers and / or shavings, with a fluid (8), in particular in the course of producing material plates,

wherein the grit (1) by means of a metering device (2) in a

Chute (4) is introduced and the grit (1) in the

Falling shaft (4) forms a grit curtain (5),

wherein the grit curtain (5) in its depth (t) is adjustable and by means of at least one row in the chute (4) arranged nozzles

(6) is subjected to a fluid,

characterized in that

in the chute (4) the humidity and / or the presence of

Fluid droplets outside the grit curtain (5) is checked.

A method according to claim 1, characterized in that in the chute (4) the moisture by means of at least one

View window, determined by means of at least one device for determining the humidity and / or by means of at least one device for detecting the presence of fluid droplets outside the grit curtain (5). Method according to claim 1 or 2,

characterized in that as a device for

Determining the humidity and / or to determine the presence of fluid droplet detectors (8) are used, which are arranged substantially in the direction of fall (11) at the same level or after the nozzles (6).

Method according to one or more of the preceding claims, characterized in that for controlling or regulating the nozzles (6, 6 ') and / or the nozzle bars (12, 12') a control device (9) is used, which is connected to the detectors (8 ) and the means for controlling or regulating the nozzles (6, 6 ', ...) and / or the nozzle bar (12, 12', ...) is operatively connected.

Method according to one or more of the preceding claims, characterized in that the amount of fluid per unit time on the number of nozzles (6) and / or the pressure at the nozzles (6) is adjusted. 6. The method according to one or more of the preceding claims, characterized in that the fluid means

Pressure nozzles is atomized.

7. The method according to one or more of the preceding claims, characterized in that the depth (t) of the

Grit curtain (5) is set to 10 mm to 300 mm.

8. The method according to one or more of the preceding claims, characterized in that the walls of the

Chute (4) are cooled.

9. The method according to one or more of the preceding claims, characterized in that as the fluid adhesive such as MDI, LPF, UF, MUF, acrylate and / or additives such as hardener,

Accelerators, buffers for UF sizes, fire retardants, dyes, insecticides, (tempered) water, emulsion or mixtures thereof.

10. The method according to one or more of the preceding claims, characterized in that the fluid is sprayed at a pressure of 50 to 200 bar at the nozzle (6).

11. The method according to one or more of the preceding claims, characterized in that when using a subsequent mixer (14) one third of the fluid in the chute (4) and two-thirds of the fluid is introduced into the grit (1) via mixer nozzles (16) in the mixer (14).

Apparatus for wetting spreading material (1), in particular fibers and / or shavings, with a fluid (8) in the course of the production of material plates, wherein the spreading material (1) by means of a

Dosing device (2) in a chute (4) is introduced and the grit (1) in the chute (4) forms a grit curtain (5), wherein the grit curtain (5) in its depth (t) is adjustable and by means of at least one row in the chute (4) arranged nozzles (6) is acted upon by a fluid,

characterized in that in the chute (4) for checking the humidity and / or the presence of fluid droplets outside the grit curtain (5) at least one viewing window or a detector (8) for determining the humidity and / or detecting the presence of fluid droplets in the chute (4) is arranged.

13. The apparatus according to claim 12, characterized in that as nozzles (6) single-substance nozzles, preferably flat jet nozzles, are arranged.

14. The apparatus of claim 12 or 13, characterized in that the nozzles (6) are arranged transversely to the direction of fall (11) in a nozzle bar (12).

Device according to one or more of the preceding

Device claims, characterized in that the nozzle bars (12) can be brought into a maintenance position.

16. Device according to one or more of the preceding

Device claims, characterized in that for the control or regulation of the nozzles (6, 6 ') and / or the

Nozzle bar (12, 12 ') a control device (9) is arranged, which with the detectors (8) and the means for controlling or

Regulation of the nozzles (6, 6 ', ...) and / or the nozzle bar (12, 12', ...) is operatively connected.