Apparatus and method for supplying moisture to a material web

Abstract

A method and device for regulating and / or controlling at least one dampening device having a valve, suitable for dampening a material web (8), in particular a paper material web, a cardboard material web or a fibrous material web, wherein the dampening device is capable of carrying out a cleaning cycle (12), and the valve is configured as a proportional valve, which pulses by a set target value (11) and, by timing control, causes deviations from the set target value (11) so that positive and / or negative deviations with respect to the target value occur.

Description

Technical Field

[0001] The present invention relates to a method for adjusting and / or controlling at least one humidifying device having at least one electromagnetic generator, a return force generator, a valve body, a control unit, and a spraying nozzle, which is suitable for humidifying a material web, particularly a paper material web, a cardboard material web, or a fiber material web.

[0002] Furthermore, the present invention relates to the use of a humidifying device for humidifying a paper web, a cardboard web, a tissue web, or other material webs as required in a manufacturing machine and / or a processing machine for a paper web, a cardboard web, a tissue web, or other material webs, and a humidifying device.

[0003] Humidifying the material web is performed to adjust a predetermined final dry weight or to change quality characteristics such as shape stability ("curl"). The material web may be humidified particularly by a plurality of humidifying devices to compensate for local moisture differences, and these humidifying devices are arranged dispersedly over the width of the material web, and moisture uniformity can be achieved over the width of the paper web. Regarding the adjustment of moisture over the width of the material web, terms such as "profiling" or "lateral profiling" are also used in documents such as German Patent Application Publication No. 102007025611.

[0004] Furthermore, based on the prior art, a humidifying device is known from German Patent Application Publication No. 4233992.

[0005] In this case, humidifying is performed via a nozzle that brings a spraying medium such as water or a water / steam mixture to the paper web. In this case, the water may contain various qualities, such as fresh water, condensed water, transparently filtered water, or relatively high-quality treated water. Since dirt, solids, or fibers may also flow into the nozzle and the valve body via the spraying medium, in this case, the problem of ensuring uniform operation and accurate adjustment of the humidifying device often occurs.

[0006] Therefore, in the prior art, particular attention has been paid to the control valve and spray nozzle. European Patent No. 1088594 describes the adjustment of the spray volume via a pulsating valve. In this case, the pulsating valve is binary controlled via pulsation, that is, it operates only in open and closed states. This means that the spray volume is adjusted by pulsation over the temporally continuous open and closed states of the valve. The pulsation is then compensated by a damping member, thus maintaining a uniform volumetric flow rate of the spray medium.

[0007] The advantage of a pulsating valve is that its movement forces the valve body against the stopper, which can typically be achieved with high speed and great force. This makes valve seizure, especially due to deposits or fouling, extremely rare. Furthermore, pulsating valves are usually operated regularly and quickly.

[0008] A drawback of pulsating valves, also known as timing-controlled valves, is the additional effort required to compensate for the resulting fluctuations in spray volume. This can be done by using damping members connected downstream, or by using multiple valves arranged in parallel or series, thereby achieving a compensated volumetric flow.

[0009] Proportional valves have not been used for material web humidification in conventional technology, due to their tendency to adhere due to deposits or fouling, especially when the amount of spray for web humidification is small and the operating pattern is constant. Furthermore, conventional proportional valves often cannot guarantee the rapid adjustment of the required humidification amount. If the adjustment is slow, there is a risk of incorrect moisture content values ​​occurring locally on the material web, which may not be compensated for in time and could cause quality problems in the web.

[0010] The objective of this invention is to reduce the aforementioned drawbacks by combining the advantages of a proportional valve with the advantages of a rapid pulsating valve in order to precisely adjust the amount of sprayed moisture supplied to the material web.

[0011] This problem is solved according to the present invention by a method corresponding to the independent claim and by the use of an apparatus or apparatus corresponding to the subordinate claim. Another advantageous embodiment of the present invention is described in the subordinate claim.

[0012] In the method for solving this problem according to the present invention, the humidification device is capable of performing a cleaning cycle, the valve is configured as a proportional valve, the proportional valve pulsates by a set target value, and at this time, a deviation from the set target value is generated by timing control such that a positive deviation and / or negative deviation occurs from the set target value.

[0013] In this case, the temporary pulsation during the cleaning cycle has the advantageous effect of detaching deposits and dirt that may adhere to the valve body or spray nozzle, thereby avoiding clogging of the spray nozzle. In this case, the spray nozzle may be formed as a spray opening. Furthermore, the spray nozzle or spray opening may include a ceramic insert to further minimize wear and / or fouling.

[0014] Advantageously, at least one humidification device suitable for humidifying material webs, particularly paper material webs, cardboard material webs, or fiber material webs, comprises a valve equipped with at least one electromagnetic force generator and a return force generator, a valve body, a control unit, and a spray nozzle or spray opening, wherein the valve is a proportional valve and has an adjustment range that can be adjusted to a target value in at least 25 steps, preferably at least 100 steps.

[0015] In this case, a proportional valve differs from a pulsating valve in that it may allow for multiple different target values ​​within the range between the closed and open states of the valve body. In contrast, a pulsating valve only allows for two states: open and closed. In this case, the target value relates to a specified variable volumetric flow rate that can pass through the valve when partially open. Since the valve opening amount and the flow rate or volumetric flow rate are directly dependent values, it is not important whether the target value is specified as a valve position or a spray rate.

[0016] Here, the desired target value can be adjusted by changing the force that can be applied to the valve body by the electromagnetic force generator.

[0017] In this case, the control unit for the humidifier can receive settings or signals to change the valve position, for example, as electrical signals from a higher-level control device, process regulator, or adjustment device, or as direct user manual input. The control unit can then change the current or voltage to the electromagnetic force generator in accordance with the settings, thereby adjusting the desired target value. To achieve rapid adjustment, the control unit operates at a high operating frequency in which it can process and modify the signals. This is typically done at an operating frequency above 100 Hz, preferably above 1 kHz, and especially above 1 MHz.

[0018] The humidification device described in the claim is further advantageous if the proportional valve has a valve body, and the valve body travels a distance of less than 5 mm, preferably less than 2 mm, from closed to open.

[0019] In this case, the aforementioned distance is the adjustment section over which the valve body can advance, and the volumetric flow rate through the valve can be changed in proportion to the adjustment section. In this case, a short adjustment section is advantageous because it only requires advancing a short distance between different target values. Therefore, a short distance allows for a correspondingly rapid valve response. In laboratory tests, the valve was tested at distances of less than 2 mm, and even less than 1 mm. The important point here is that, in order to enable precise adjustment of the spray volume, a high degree of decomposition of intermediate steps remains possible.

[0020] More preferably, in the humidification device according to one of the claims, one or more electromagnetic force generators are suitable for completely opening or closing a proportional valve from each target value in less than 0.3 seconds, preferably less than 0.1 seconds.

[0021] The rapid response of the proportional valve allows for uniform humidification of the material web. This is because even if a temporary change in the spraying rate is only compensated for as a relatively small difference here, it can still be compensated for later on the paper.

[0022] More advantageously, in the humidification device according to one of the claims, the electromagnetic force generator is suitable for adjusting the proportional valve to each target value in less than 0.3 seconds, preferably less than 0.1 seconds.

[0023] To ensure that localized differences in humidity can be quickly compensated for changes in production conditions, it is crucial that the humidity supply unit can respond rapidly. In this case, appropriate humidity adjustment based on the measured final humidity, along with the rapid response of the valve, can contribute to improving paper quality and humidity.

[0024] More advantageously, the humidifier is the humidifier described in any one of the prior claims, in which case the proportional valve is immediately followed by a nozzle or spray opening, and no other functional member is used, in particular, for pulsation damping.

[0025] One advantageous configuration of the present invention is that it is possible to eliminate the expensive and prone-to-failure pulsation attenuators used downstream of pulsating valves or timing-controlled valves in the prior art.

[0026] In this case, the functional component is, for example, a pulsation attenuator, which provides pressure compensation using an elastomer, a spring member, or a compressible gas. In this case, conduits and (manual) shut-off valves used in maintenance work, for example, are not functional components in the sense of the present invention.

[0027] More advantageously, in the humidification device according to any one of the claims, the return force generator provided in the proportional valve may include a mechanical spring member and a magnetic force generator or an electromagnetic force generator or an air pressure generator.

[0028] In this case, the spring member may be any kind of mechanical spring, such as a metal spring, a spring disk, or an elastomer, or a similar material capable of applying a spring force due to its material properties, etc.

[0029] Even more advantageous is a method of adjusting and / or controlling at least one humidifying device according to any one of the preceding claims, which humidifies a material web, particularly a paper material web, a cardboard material web or a fiber material web, wherein the humidifying device can perform a cleaning cycle, and in the cleaning cycle, the proportional valve pulsates by only a set target value, and at this time, a deviation from the set target value is caused by timing control so that a positive deviation and / or a negative deviation occurs. In this case, the deviation is preferably at least of a similar length, preferably of equal length.

[0030] The purpose of this method is to keep the amount of the spraying medium constant at the target value as much as possible over time average. In this case, the pulsation means a temporary movement of the valve body in the adjustment section, and this temporary movement deviates from the target value first in the positive direction and then in the negative direction, or first in the negative direction and then in the positive direction.

[0031] If the target value is a fully or sufficiently open valve (~100%), the cleaning cycle can be carried out only by a partial temporary closing, and in this case, a temporary slight decrease in the amount of the spraying medium over this time cannot be avoided, but this is also part of the present invention.

[0032] This also applies when it is desirable that the valve position is fully closed (~0%). In this case as well, the cleaning cycle can be carried out only by a temporary opening of the valve, and as a result, a temporary slight increase in the amount of the spraying medium will occur. Therefore, in both of these cases (when closed or when open), the pulsation means a temporary deviation only in one direction from the target value.

[0033] More advantageously, in the method described in the claim, the humidifier has a proportional valve that can be rapidly and at least partially opened or closed so as to pulsate by a set target value, the deviation from the set target value lasting less than 0.3 seconds, preferably less than 0.1 seconds, and the pulsation can be repeated.

[0034] More advantageously, in the method according to the claim, which uses at least two, preferably four or more, humidifiers, the pulsating humidifier in the washing cycle is positioned next to at least one other humidifier capable of performing pulsation in the reverse direction.

[0035] In this configuration, the humidifier has multiple spray nozzles arranged across the width of the paper web, thereby compensating for differences in humidification across the width of the paper web. In this case, the cleaning cycle is not performed simultaneously in all humidifiers, but only in each individual humidifier, and adjacent nozzles may pulsate in opposite directions. Each spray nozzle delivers moisture to the material web by conical spray, and the conical spray generally involves crossing between adjacent nozzles, thereby enabling uniform humidification. In this way, temporary differences in the humidification of the material web can be effectively compensated by adjacent nozzles.

[0036] More advantageously, in a method using at least two, preferably four or more, humidification devices as described in any one of the claims, the reverse pulsation may have only half the amplitude or duration of the deviation from the set target value.

[0037] In this way, the cleaning cycle can be performed in individual nozzles among a plurality of nozzles arranged across the web width. The purpose of the reverse pulsation of each adjacent humidifier with half the amplitude is, in this case as well, uniform humidification of the material web. In other words, compensation of the humidifiers in the cleaning cycle can be achieved by each adjacent humidifier.

[0038] A more advantageous approach is to divert the flushing cycle and / or pulsation in only one direction from the target value, thereby allowing the flushing cycle (12) and / or pulsation to be initiated whether the valve is fully closed or fully open.

[0039] Even when the humidifier valve is closed, it is necessary to temporarily open the humidifier in order to perform the cleaning cycle and / or pulsation. In this case, fluctuation around the target value is not possible, and only pulsation toward the open state is expected. Similarly, even with a fully open valve, only pulsation toward at least a partially closed state may occur.

[0040] More advantageously, in the method according to any one of the claims, the pulsation or cleaning cycle is preferably performed when a degraded material web is being produced or when the machine producing the material web is in a special operating condition.

[0041] The timing and frequency of the flushing cycle and pulsation required to avoid valve sticking can vary considerably, due to various influencing factors, such as: • Water quality, especially dissolved solids, undissolved solids, and impurities • Flow rate and nozzle geometry and valve geometry based on flow rate (relatively large valves and nozzles do not actually tend to stick as much). • Thermal changes in the humidifier and spray medium. However, this can lead to adhesion.

[0042] Accordingly, depending on the embodiment of the present invention, it may be necessary to move the valve body at a constant or near-constant rate by pulsation or a cleaning cycle, or in another embodiment, only a few times per day. In this embodiment, the pulsation or cleaning cycle can be performed, for example, during tearing, type change, while the cleaning is stopped, or when starting up after a stop. This is because, in this way, moisture differences do not reach the sellable material web.

[0043] A further advantage is the use of at least two humidifiers, in which case multiple humidifiers are arranged across the width of the material web, each suitable for providing different humidification to different zones. These devices are also known as nozzle humidifiers in the paper industry. The humidity of the lateral profile of the paper web can be adjusted via multiple humidifiers. In this case, generally 20 to 200 humidifiers can be arranged across the material web. This can achieve zone widths of 5 cm to 50 cm, with a zone width of 5 cm to 20 cm for each individual humidifier being particularly advantageous.

[0044] Based on the examples, another advantageous embodiment of the present invention will be described with reference to the drawings. The features described above are advantageously realized in the illustrated combinations, but may also be combined individually with each other. [Brief explanation of the drawing]

[0045] [Figure 1] This is a schematic cross-sectional view partially showing one possible embodiment of a humidifier for supplying moisture to a material web. [Figure 2] This figure shows a schematic characteristic curve illustrating the adjustment range for the spraying amount in the method described in the claims of the present invention. [Figure 3] This is a schematic diagram partially illustrating one possible embodiment of the method and apparatus of the present invention.

[0046] The following provides a detailed explanation of each figure.

[0047] Figure 1 shows a schematic diagram partially illustrating one possible embodiment of the humidifier 1. The humidifier 1 has a proportional valve 2 equipped with an electromagnetic force generator 3 and a return force generator 4, which move the valve body 10 within an adjustment range 9. The valve body is controlled or adjusted by a control unit 5 to target values. The adjusted volumetric flow of the spray medium is then sprayed onto the material web 8 by a spray nozzle 6 or spray opening 7. In this case, the spray nozzle has a nozzle shape with a tapered cross-section. The outflowing liquid is atomized into small droplets based on the high shear force at the spray opening 7, enabling uniform humidification of the material web 8.

[0048] Figure 2 shows a schematic characteristic curve illustrating the adjustment range for the spray amount in the method according to the claims of the present invention. This adjustment range is shown as a percentage of the valve opening amount or spray amount on the vertical axis. The horizontal axis relates to time [t]. The cleaning cycle 12 shows pulsating motion. The reverse pulsation 13 shows the inversely proportional opening amounts of adjacent valves as described in the claims of the present invention, and these opening amounts differ from the target value 11 by half the amplitude of the cleaning cycle 12 in this example. The target value 11 is shown in this example as 50% of the possible valve opening amount or spray amount.

[0049] Figure 3 shows a schematic plan view partially illustrating one possible embodiment of the method of the present invention. Illustrated are a plurality of spray nozzles 6, each with corresponding spray openings 7, arranged side-by-side across the width of a material web 8. The sprayed spray medium is schematically indicated by a dotted line. In this case, the central nozzle performs exactly one wash cycle 12, while two adjacent nozzles perform reverse pulsations 13. Thus, the material web 8 is humidified fairly evenly on average. When the wash cycle 12 and the reverse pulsations 13 are performed correspondingly and rapidly, the moisture content of the paper can be more easily and locally compensated for, and accordingly, the quality of humidification remains acceptable. In this figure, the material web 8 extends perpendicular to the figure along the Z-axis (not shown). In this case, the spray nozzles 6 are part of a humidification device 1, each including a proportional valve 2 (not shown). In the illustrated method, the wash cycle 12 is performed by one humidification device 1, in this case, each adjacent humidification device 1 performs reverse pulsations 13. [Explanation of Symbols]

[0050] 1. Humidification device 2. Proportional valve 3. Electromagnetic force generator 4. Return force generator 5. Control Unit 6. Spray nozzle 7. Spray opening 8 Materials Web 9. Adjustment range 10 Valve body 11 Target Values 12 wash cycles 13. Pulsation in the opposite direction

Claims

1. A method for adjusting and / or controlling at least one humidifier (1) suitable for humidifying a material web (8), particularly a paper material web, a cardboard material web, or a fiber material web, the humidifier (1) having at least one electromagnetic force generator (3) and a return force generator (4) in a valve (2), a valve body (10), a control unit (5), and a spray nozzle (6), The method is characterized in that the humidifying device (1) can perform a cleaning cycle (12), the valve (2) is configured as a proportional valve (2), the proportional valve (2) pulsates by a set target value (11), and at this time, a deviation from the set target value (11) is generated by timing control such that a positive deviation and / or negative deviation occurs relative to the target value (11).

2. The method according to claim 1, wherein the proportional valve (2) is opened and / or closed quickly, at least partially, so as to pulsate by a set target value (11), wherein the deviation from the set target value lasts for less than 0.3 seconds, and the pulsation can be repeated.

3. The method according to claim 1 or 2, wherein for the method, at least two or more humidifiers (1) are controlled and / or regulated, and a humidifier (1) that pulsates in the washing cycle (12) is located next to at least one other humidifier (1) that performs pulsation in the opposite direction (13).

4. The method according to claim 3, wherein the reverse pulsation (13) has only half the amplitude of the deviation with respect to the set target value (11) or only half the duration of the deviation with respect to the set target value (11).

5. The method according to any one of claims 1 to 4, comprising performing the cleaning cycle (12) and / or the pulsation.

6. The method according to any one of claims 1 to 5, wherein the cleaning cycle (12) and / or the pulsation is diverted in only one direction from the target value (11), thereby enabling the cleaning cycle (12) and / or the pulsation to be initiated even when the valve (2) is completely closed or completely open.

7. A humidifying device (1) suitable for humidifying a material web (8), comprising a valve (2) equipped with at least one electromagnetic force generator (3) and a return force generator (4), a valve body (10), a control unit (5), and a spray nozzle (6) or spray opening (7), wherein the valve (2) is a proportional valve and has an adjustment range (9) that can be adjusted to a target value (11) in at least 16 steps, in the humidifying device (1), The humidifying device (1) is characterized in that it is suitable for performing the cleaning cycle (12) and / or pulsation described in any one of claims 1 to 6 via the control unit (5).

8. The proportional valve (2) has the valve body (10), the valve body moves a distance of less than 5 mm from closed to open, according to claim 7, humidifier (1).

9. The humidifier (1) according to claim 7 or 8, wherein one or more of the electromagnetic force generators (3) are suitable for completely opening or closing the proportional valve (2) from each target value (11) in a time of less than 0.3 seconds.

10. The humidifier (1) according to any one of claims 7 to 9, wherein the electromagnetic force generator (3) is suitable for adjusting the proportional valve (2) to each target value (11) in a time of less than 0.3 seconds.

11. The humidifier (1) according to any one of claims 7 to 10, wherein the nozzle (6) or the spray opening (7) is immediately followed by the proportional valve (2), and no other functional member is used, in particular, for pulsation damping.

12. The humidifier (1) according to any one of claims 7 to 11, wherein the return force generator provided in the proportional valve may have a mechanical spring member and a magnetic force generator or an electromagnetic force generator or an air pressure generator.

13. In the method according to any one of claims 1 to 6, in the use of at least two humidifiers (1) according to any one of claims 7 to 12, The use is characterized in that a plurality of the humidifying devices (1) are arranged over the width of the material web (8) in a manner suitable for supplying different humidification to different zones.

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