JPH0215660B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for removing foreign objects and liquids from permeable fabrics.

[Conventional technology]

In the pulp and paper industry, cleaning of papermaking felts, especially compaction felts, is important for efficient operation of papermaking machines. As the speed of paper machines increases over the years and the cost of production factors such as energy increases, it is important to find more efficient ways to clean, condition and remove water from felts used in the compaction process of paper machines. has become essential.

Currently, two methods are employed for cleaning felt. Both methods are used in conjunction with a water spray to loosen the material on the felt.
In the first method, the felt is passed over a stationary suction box, and the dirt and water loosened at that time are sucked out of the felt. In the second method, the felt is passed through a hoop or drawing press. In this case, the press or the wheel-containing roll may or may not have a suction box integrated therein.

In methods utilizing stationary suction boxes, the felt is indexed across the face of the box, and due to the resulting friction, a significant amount of energy is expended by the motor driving the felt; Extra energy is also consumed in providing the necessary vacuum. It is well known that the felt and suction box covers are subject to considerable wear. Methods using rings or drawing presses are more energy efficient because the press/suction rolls rotate. but,
The equipment required is more sophisticated and expensive, and the pressing action is known to reduce the effectiveness of the felt.

[Means for solving problems]

Accordingly, it is an object of the present invention to provide a method for removing foreign matter and moisture from permeable fabrics in a relatively effective and low energy consuming manner.

Another object of the invention is to provide a method and apparatus for felt water removal and conditioning systems in the pulp and paper industry.
This effectively removes foreign matter and moisture, improves the dryness of the paper as it leaves the press area of the paper machine, and reduces the energy required to dry the paper.

According to one aspect of the invention, there is provided a method for removing liquid from a permeable fabric, the method comprising: applying a narrow jet of a gaseous substance to a surface of the fabric; The method includes the step of impinging on a surface with sufficient force and velocity to create an area of low pressure on the surface, thereby causing liquid in the fabric to flow away in the direction of the area of low pressure. provided.

An apparatus for removing a liquid from a permeable fabric containing a liquid, the apparatus comprising: means for supporting the fabric in a desired position; a gas supply means; connected to the gas supply means; directing a narrow jet so that the gaseous material impinges on the surface to create a low pressure region on at least one side of the jet;
A device is also provided comprising injection and control means adapted to cause liquid within the fabric to flow in the direction of this low pressure area.

More particularly, the method and apparatus of the present invention are intended for use with fabrics containing liquid to remove at least a portion of the liquid from the fabric. There are many types of fabrics to which the present invention may be applied. Although the primary application is in the water removal and conditioning of felts used in papermaking, there are many other permeable fabrics that are suitable for removal of contained substances using the method and apparatus of the present invention. exist. Suffice it to say that the fabric is permeable and has a certain porosity that contains the liquid to be removed. Similarly, although the present invention is primarily utilized for removing liquids from liquid-containing fabrics,
It can also be suitably used for gas removal. A number of commercial possibilities are possible, including operations such as dry cleaning of fabrics.

The present invention directs a narrow jet of gas against the surface of a supported fabric and impinges the gas on the fabric surface with sufficient force and velocity to create a low-pressure area on the fabric, thereby creating a jet. At least one side of the stream acts to cause liquid/substance to flow out of the fabric. Here, "low pressure" refers to a pressure that is less than the pressure that exists inside the fabric.
Usually, the pressure inside this fabric is atmospheric pressure, and the "low pressure" is negative pressure. The phenomenon that occurs here is known as the "Bernoulli effect."

For maximum effectiveness in practicing the invention, the velocity of the jet of gaseous material should be adjusted to such an extent that the gas does not escape through the fabric to the other side. In order to operate the present invention efficiently,
Most of the gas should not penetrate the fabric and should remain on the side of the jet to produce the desired effect. Of course, the particular speed used in a particular case will depend on the porosity of the fabric, the loading of the fabric, gaseous material, and other known factors. Other factors that have a relationship include the distance between the gas injection nozzle and the fabric, the width of the nozzle, the velocity of the gaseous substance, the position of the part of the fabric surface affected by the gaseous substance, the relative velocity between the fabric and the jet stream, etc. be.

To obtain maximum efficiency of the present invention, especially when using highly porous fabrics, experiment with the optimum jet flow rate to prevent or at least minimize the amount of gas penetration through the fabric. It is necessary to seek This can be carried out using well-known monitoring devices, such as, for example, installing a gas movement sensor on the side of the fabric opposite to the side on which the jet acts. Usually, papermaking felt is very dense, and the leakage of air through the fabric is 80~
This is not a problem as long as air velocities in the 1600 ft/sec range are used. However, in the case of very porous fabrics, much lower speeds are required. Generally, in the present invention, air leakage of 10% or less is acceptable and will function satisfactorily.

It should be noted that a number of patents are known for blowing air through felt to clean it. These are usually used in combination with centrifugal force to force the liquid away from the felt in the same direction. Examples of this include U.S. Pat.
There is No. 4270978 etc. The air pressure of these prior inventions is of the extent necessary to force the liquid (with or without the aid of centrifugal force) through the fabric to the other side. In the present invention, two gas pressures are used; one pressure is set by blowing a high-speed gas onto the fabric surface, and due to the Bernoulli effect, a low-pressure area is created immediately before and after the fabric surface that the high-speed jet collides with. It is that of a gas jet flow that is caused to occur. It is this area of low pressure that sucks liquid out of the fabric on the same side where the impact occurred. In this way, the liquid flow from the fabric flows in the opposite direction to that disclosed in the prior art mentioned above, and the liquid is sucked out of the fabric instead of being blown away.

The gas used is appropriately selected depending on the purpose. In many cases, and when felt conditioning is required, as is done in the paper industry, air is a suitable substance.

The gas injection nozzle can be of various shapes, and in fact, the nozzle may simply be a slit cut from a portion of a pipe. Multiple nozzles can also be employed to cover the entire width of the fabric. As previously mentioned, one simple example utilizes a single pipe with multiple slits or one long slit to cover the entire width of the felt. Gas may be supplied from one end or from the middle to minimize pressure drop.

In the pulp and paper industry, felt is sprayed with liquid to loosen foreign objects inside. Subsequently, gas is injected towards the felt to remove foreign matter and liquid contained therein. It has been found that by applying the present invention, foreign matter can be removed very efficiently and good performance of the felt can be maintained.

〔Example〕

The present invention will be explained in more detail based on preferred embodiments shown in the drawings.

FIG. 1 is a side view of an apparatus for applying the present invention to remove foreign matter and liquids from fabrics, and in particular for conditioning wet pressed felts in paper machines. There are numerous wet compaction devices throughout the system. FIG. 1 illustrates a small portion of the overall system showing where the invention is applied. Preferably, the descending section of the felt running path is chosen because it is convenient for collecting and draining the water extracted by the device. However, a horizontal path may be convenient in some designs.

FIG. 1 shows a portion of a wet pressed felt run. A pair of felt guide rollers 1
0, 12 are provided, the rollers 10, 12 being pivotally mounted on suitable support members (not shown) and indicated by arrows 1.
It is rotating as shown at 4 and 16. A shower pipe 18 is provided and is connected to a source of water or a suitable liquid (not shown) for spraying the felt to loosen foreign blockages. Reference numeral 20 indicates a perforated air injection nozzle or blowpipe, which will be described later. A tray 22 is provided to capture water extracted from the felt and blown away by the air jet. The wet compressed felt 24 is attached to the guide rollers 10, 12.
through which it travels in the direction indicated by arrow 26.

FIG. 2 is a detailed view of the nozzle 20. Nozzle 2
0 is a part of the pipe, in which a narrow slit 28 is provided. The length of the slit is approximately equal to the width of the felt, and the width of the slit is determined by several factors described below. A connection 30 is provided which communicates with a gas supply source. Depending on the length and diameter of the pipe, direct the air from both ends (also from the midpoint) to minimize pressure drop and avoid uneven air injection.
It is preferable to feed it into the pipe from the source. Alternatively or in conjunction with this, the pipe may be tapered. If desired, a series of circular clamps 32 may be provided to adjust the local width of the air holes and maintain a uniform longitudinal velocity distribution of the air jet as it passes through the slit 28. (This adjustment is made by a small set screw 34 whose tip rests against the outside wall of the pipe).

Figure 3 shows possible parameters. The relationship between these parameters and the pressure (negative pressure) generated on the fabric surface with which the jet impinges is shown in FIGS. 4 and 5. FIG. 4 shows the relationship between the distance D and the air pressure state of the fabric surface with which the jet collides. FIG. 5 shows the relationship between distance L and air pressure (or negative pressure) at points along this distance.

As can be seen from Figures 3, 4, and 5, W is the width of the slit, the velocity of the jet stream blown out from it is J, and its energy source is the air pressure P in the pipe nozzle. slit (or jet outlet)
The distance from the fabric is represented by D, and the distance from the slit to the part of the fabric surface affected by the jet flow is L.
, and the pressure (or negative pressure) in this area was measured while the fabric was moving at a relative speed S to the jet stream.

The relationships shown in FIG. 4 are not absolute values. This is because these values depend on the velocity J of the jet (and to some extent on the shape of the jet) and also on the position of the fabric surface being tested, i.e. the portion of the fabric surface being tested from the center of the slit. This is because it changes depending on the distance L to. However, it is clear that for a given speed J, there is a certain distance D at which the negative pressure has a maximum value V, and at this point maximum efficiency is obtained. Generally, the value of distance D for optimal negative pressure V changes only slightly as J changes. It is not necessary to position and maintain the jet outlet at this specific value D, and the jet flow only needs to exist in the vicinity of this value, so the felt may move a little. If the pressure and negative pressure are balanced, the felt will automatically occupy this particular distance. The value D for optimum negative pressure is typically on the order of 2 mm or less. At this particular value D for the maximum value V, the applicant has found that as L changes, V also changes. In fact, as shown in FIG. 3, if the jet is perpendicular to the fabric surface, a pressure zone will be created at and directly above the jet. Negative pressure areas are then formed on both sides, the intensity of which decreases evenly as the value of L increases. This is shown in FIG. The magnitude of the negative pressure peak is approximately half of the pressure peak,
The pressure peak gradually approaches the pressure P inside the pipe. When L is approximately 2.5 mm, a negative pressure peak occurs.
It has been found that in some cases it is preferable to have the jets act at right angles to the fabric, while in other cases it is preferable to have the jets act at various angles to the fabric. For example, if the fabric is moving at a relatively high speed across the jet, it may be desirable to tilt the jet slightly toward the incoming felt (i.e., tilt it so that it faces the travel of the felt). It has been found. This increases the suction effect.

Generally, as the value of J increases, the value of V also increases. And since V is more sensitive to the value of J than to the amount of air, it is economical to form the jet with a small amount of air and utilize the narrow slit of the nozzle to obtain the high speeds needed for optimal V. It is advantageous.
Slits having a width of 0.015 inches or less have been found effective for papermaking felts.
There are several practical relationships between fabric velocity S and jet velocity S, of which only the cases where S is significant are significant. That is, although the negative pressure near the fabric surface is independent of fabric velocity, if the fabric is moving very rapidly, the negative pressure will affect the fabric and reduce the amount of water that has entered the voids inside the fabric. It is clear that the time for extraction is too short. The relationship between the air pressures P and J in the pipe is of course fixed and is influenced only by the velocity coefficient (which varies depending on the type of orifice and other operating conditions).
As is clear from the foregoing discussion, the values assigned to the above-mentioned parameters should be selected based on the conditions of use and economics of the invention. As previously mentioned, the fabric or felt will automatically assume a position at the desired distance from the jet stream. However, in order to prevent large flapping vibrations of the felt, guide rollers 10 (FIG. 1), which are not used in conventional felt running, would prevent this problem. If necessary, more guide rollers may be added under certain conditions.

Another important factor that affects the efficiency of the invention is the area/surface/volume at which the air jet bounces off the fabric and begins to flow parallel to it. For example, a jet stream ejected from a nozzle embedded in a flat surface on which a fabric runs can be visualized. It has been found that such devices are generally unsatisfactory depending on the width of the flat surface. This is in part because, during escape, the gas-liquid mixture extracted from the fabric must pass through a thin space defined by the fabric and the flat surface of the nozzle. the height of which is essentially constant at 2 mm). A curved surface is highly preferred since the gas (air) is pulled away from the fabric and moved along the curved surface. The optimal shape of this surface will vary depending on variables such as jet velocity and volume. From a manufacturing standpoint, a circular curvature is most preferred as it allows the use of regular pipe. For the same reason, small diameter pipe nozzles are preferred over large diameter ones. It is therefore preferable to supply gas into the pipe from as many points as necessary in order to minimize the diameter and minimize the pressure drop of the gas flowing through the pipe. At the other end, a nozzle with elongated orifice sides vertical and straight, ie perpendicular to the fabric, can be utilized.
The design of the intermediate section is such that the sides are straight and inclined at an angle to the surface of the fabric.

In the application for conditioning wet pressed felts shown in FIG.
After the was properly set and the air jet and water spray were applied, the following was observed. The shower of water penetrates the felt to loosen foreign matter contained therein and saturate the felt surface with water, while the air jet stream sucks a significant amount of water (and foreign matter) out of the felt, followed by a blowing step. The second suction action begins (see Figure 5). As a result of this,
Water (and foreign matter) in the form of a heavy spray flies off the felt surface and is collected in tray 22 and carried away. This rapid and sudden negative pressure, as well as the blowing and suction action of the air jet splitting into two streams (in the case of conventional vacuum suction boxes, there is only a single suction action), cause the felt to The surface becomes more absorbent, making it easier to remove water from the paper during the wetting process. For example, the fluff on the surface of the felt did not lie flat, but tended to stand up. One of the advantages of this device is that less energy is required to perform this cleaning and conditioning action. For example, 100
A standard 10 inch Hg negative pressure suction is used to condition inch wide felt.
When running at 2000cfm, approximately 100 horsepower is required,
Using the nozzle of the present invention, the same effect can be achieved with less energy consumption. Moreover, since the felt rests on the air cushion, little energy is required to move the felt through the suction zone. However, in conventional suction boxes, passing through the felt creates a lot of friction and requires a lot of energy. Furthermore, since it does not come into contact with a solid surface, there is almost no chance that the sticky substance will be smeared onto the felt surface or penetrate into the inside of the felt, reducing its absorption performance.

FIG. 2 shows the structure of the nozzle, in which the pipe is provided with a longitudinal slit. In the case of long pipes this is a difficult task, and since the slit vibrates and acts like a whistle, a construction as shown in cross-section in FIG. 6 is preferred. A slit 38 of approximate dimensions is provided in the cross section of the pipe 36, the width of which is several times the width of the final orifice and has at least the same length. This area of the nozzle serves as a support for two strips 40 attached to the outer surface of the nozzle, which define an injection orifice. The strip may be made of any suitable material, such as high-density polyethylene, stainless steel, etc., which can form a uniform and neat orifice and which can withstand any corrosive substances drawn from the felt through the orifice. Steel etc. are preferred. These orifice strips are pre-shaped to match the curvature of the pipe and have sufficient flexibility to accommodate this. These are attached to the pipe 36 by screws 44. The strip can be adjusted using the holes for the screws. When the orifice is long, it is necessary to stabilize the width of the injection hole, and tension rods 46 may be used to provide mechanical reinforcement at appropriate intervals in the longitudinal direction of the pipe. Screw thread and nut (gasket)
48 are provided at both ends to adjust the tension (and orifice profile). Various known techniques are used to support the entire nozzle and to keep it straight. One method is to include a spray/mist collection device, as described below. If the slit is non-uniform, the nozzle may be configured to reciprocate transversely below the felt. It has been found that in the case of high velocity jet streams, the water separated from the felt becomes a very fine mist which penetrates into the working area, which is undesirable in some applications. Figure 7 shows a device for collecting this mist and spray,
It also provides a means for supporting and adjusting the pipe to maintain a constant height over its length. Of course, this is important in the case of long pipes, which tend to sag if supported only at both ends. Independent longitudinal support means are possible in some cases, but it is generally desirable to use one with robust cross-sectional characteristics.

In FIG. 7, 36 indicates a nozzle (see FIG. 6 for details), and 52 is a trough-like container for holding the mist and spray that have passed through the working area. Retention brackets 54 are provided at appropriate intervals along the length of container 52 to provide rigidity to container 52. Rod 56 is threaded into bracket 54, and the other end of rod 56 is attached to bracket 58 by a pair of nuts to provide added strength and support for nozzle 36. A small diameter rod or pipe 62 is installed over which the fabric runs. The top surface of rod 62 is substantially level with the top surface of nozzle 36. Other sealing members may be used to prevent the fabric from contacting sharp edges. The trough-like container may be sealed at both ends by known techniques and configured to receive some pressure or negative pressure, depending on the circumstances.
As previously mentioned, if the nozzle 36 is long enough to cause a severe pressure drop, a smaller diameter nozzle 36 is preferable, so the lower part of the trough-like vessel is connected to the nozzle 36.
It can be used for large-diameter gas supply pipes that supply a desired gas to the air. To avoid too much mist escaping past the various sealing areas, the mist in the gutter is continuously removed by an inexpensive fan ejector, and any liquid that collects at the bottom of the gutter is removed. Ejected through appropriate playing cards. In practice, after expelling the mist, the gas (air) is recirculated to the nozzle through a blower to maintain the pressure within the nozzle at a predetermined value. Next, an example of a wet felt for paper manufacturing will be described.

The nozzle was the same as shown in Figure 2, approximately 16 inches long. Air pressure was maintained at 15 psig, which corresponds to a jet velocity J of approximately 1000 fps. The width W of the orifice slit is
It was 0.010 inch (see Figure 3). D is 2mm
(0.079 inch).

The present invention was applied to a conventional papermaking wet felt after it had been subjected to the action of a conditioner (with a static suction box) installed in modern newsprint machines. By measuring the moisture content of the felt before and after passing over the orifice slit of the present invention,
It was found that 10-20 g of water was removed per m ² . It was clear that the water removal efficiency of the present invention was greater than that of the prior art, since no attempt had been made to optimize its effect. Furthermore, the cleanliness of the felt was improved and the drying condition of the paper was also improved. As a result of this test, samples of water extracted from the felt were tested for solids content and the nature of the extracted material. With these tests,
The solids content was 0.65% and was found to be mainly wood chips and sulfurized pulp fragments and traces of felt fuzz. The cleaning efficiency of the present invention was therefore found to be greater than that of the prior art.

From the above explanation, it can be said that in the present invention, the jet flow, or at least a large part thereof, does not penetrate the fabric and escape to the opposite side. Therefore, in order to maintain the porosity of the fabric, the velocity of the jet flow should be adjusted to
It may be decelerated to such an extent that it has sufficient energy to create the desired negative pressure/suction effect without penetrating the fabric. According to another embodiment of the invention:
It involves a combination of linear blowing action on one side of the fabric and the invention on the other side. That is, a controlled low pressure is used on one side of the fabric while simultaneously impinging the jet on the side of the fabric directly opposite to the jet of the present invention and penetrating the fabric to reduce the force of the two jets (and By controlling the position), one jet stream (opposite to the one creating the low pressure) forces the liquid to the other side, where the low pressure effect causes extraction of the liquid and this It turns it into a spray/mist. Similarly, if the fabric is fairly thick, the jet stream of the present invention can also be used to create a low pressure effect on both sides of the fabric at the same time. Other combinations utilizing the present invention within themselves or as part of a continuous process are also possible.

Since the present invention has high water removal/cleaning efficiency, the device does not need to be operated continuously. Therefore, in the case of a nozzle that spans the entire width of the felt,
It may be performed intermittently or in appropriate cycles. In the case of a short nozzle, this can be moved back and forth across the width of the felt at a suitable speed/cycle inside the collection chamber, or the slit itself can be the entire width and the short region of the jet itself can be moved along the felt. You may move it. The use of a single long slit weakens the pipe (nozzle), so multiple slits (i.e., with reinforcement spaces between the slits) are used to allow sufficient oscillation of the pipe in the transverse direction. , so that the jet stream also covers the fabric in the non-perforated nozzle area. In addition to dewatering/cleaning wet felt fabrics on paper machines,
The present invention can also be used to clean wire fabrics utilized in paper making machines, thereby replacing high pressure swinging needles and fan shears. It can also be used to clean wire fabrics for rope twisting machines and dryer felts. It will be understood that the embodiments described above are merely illustrative, and modifications may be made without departing from the spirit and scope of the invention.

[Brief explanation of drawings]

Fig. 1 is a side view of the water removal device of the present invention, Fig. 2 is a side view of the nozzle, Fig. 3 is a detailed sectional view of a part of the water removal device of Fig. 1, and Fig. 4 shows the fabric and the nozzle. FIG. 5 is a graph showing the relationship between the distance of the fabric and the pressure on the surface of the fabric, FIG. 5 is a graph showing the relationship between the pressure within a specific area of the fabric and its effect, FIG.
The figure is a side view of a device for supporting a nozzle and collecting moisture removed from a fabric. DESCRIPTION OF SYMBOLS 10, 12... Guide roller, 18... Shower pipe, 20... Nozzle, 22... Tray, 24... Felt, 28... Slit.

Claims (1)

[Claims] 1. A method for removing liquid from a permeable fabric, the fabric being supported, a gas jet being blown onto the surface of the fabric, and the jet flowing across the fabric surface without penetrating the fabric. , so that a low-pressure area is formed on the surface of the fabric on the side where the jet is blown, thereby sucking out the liquid contained in the fabric towards this low-pressure area. Characteristic fabric cleaning method. 2. The method according to item 1, characterized in that the fabric is supported in front of the jet stream so that it can run freely in the area of action of the jet stream. 3. The method of claim 1, wherein the fabric is in the form of a double-sided flat sheet. 4. The method according to claim 3, wherein the jet stream acts on both sides of the fabric.