JPS5818589B2 - Koushiyougekishiki Kansou Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes an air cap having a plate having a large number of air jet holes and a high pressure chamber, and sends high pressure hot air from the high pressure chamber to generate a jet through the jet holes, This invention relates to an air impact drying device in which the air impact drying device is caused to collide with a strip-like object to dry the strip, and the air flow after the impact is discharged to a discharge area behind a nozzle hole plate.

This type of drying device is, for example,
It is publicly known as described in Publication No. 4.

Air shock drying is particularly suitable for drying lightweight papers such as tissue paper and for drying coated papers.

These applications require a high heat transfer coefficient due to the limited drying length and the need for high speed operation.

One means of increasing the heat transfer coefficient is to increase the number of impact jets.

However, published literature indicates that increasing the open area by more than a factor of two does not further increase the heat transfer coefficient.

The reason was believed to be due to interference between adjacent impact jets.

That is, it was thought that as the open area increases, that is, the ejection holes become closer, and the impact jets become closer together, the adjacent jets interfere with each other and the heat transfer coefficient decreases.

However, recently published experimental data indicate that this reduction in heat transfer coefficient is due to cross-flow interference of the consumed air, rather than due to mutual interference between adjacent jets.

The jet after the impact must proceed to the outlet, but for this purpose the spent air, ie the spent steam, must reach the outlet after crossing the adjacent jet.

In other words, the impact jet stream injected from the jet hole at a high speed advances toward the discharge port at a relatively high speed.

At this time, cross-flow interference occurs because the jets cross adjacent jets and proceed to the outlet, and the adjacent impulsive jets do not hit the surface of the strip at right angles, but are bent at an angle.

If the impact jet deviates from a line perpendicular to the surface of the heated strip in this way, the heat transfer efficiency will be reduced.

Therefore, it is an object of the present invention to extremely reduce cross-flow interference of impact jets in an air-impact drying device, thereby eliminating the reduction in heat transfer efficiency caused by cross-flow interference.

To achieve the above object, the air impact drying device of the present invention has at least one air cap having a width corresponding to the convergence of the strip to be dried, each air camp having at least one air cap. a perforated plate, a hollow support device for supporting the perforated plate relatively close to the strip, and a hollow support device connected to the support device to blow high-pressure air through the jet holes of the perforated plate so as to impact the strip. and a high-pressure chamber configured to deliver the water, and the supporting device has a bright portion between the perforated plate and the high-pressure chamber, the cross-sectional area of which is smaller than that of the perforated plate, and the bright portion immediately connects to the bell-shaped bottom part that widens toward the front, and the perforated plate is supported on the bottom of this bell-shaped bottom part, and the high pressure chamber is located behind the perforated plate supported by the bell-shaped bottom part. The area between the bottom part, the bell-shaped bottom part of the perforated plate supporting device adjacent to each other, and the light part is such that the area between the light part near the bottom of the high pressure chamber is equal to forming a discharge area that is larger than the area between the perforated plates supported on the bottom, said discharge area being arranged around the entire periphery of each perforated plate, and after impacting the strip into this discharge area; The feature is that the airflow is advanced.

As described above, according to the present invention, the area between adjacent bright portions closer to the bottom of the high pressure chamber is equal to Perforated plate (
, a large number of ejection holes are formed in this perforated plate to form a discharge area wider than the area between the holes), so that the discharge area behind each plate serves as a discharge area with a large area, This large area allows the flow of impulsive air to flow at relatively low velocities and without excessive pressure drop, and the evacuation area is arranged with its inlet around the entire periphery of each perforated plate. Since no orifices in the perforated plate are separated by an excessive distance from the discharge area, cross-flow interference between adjacent orifices can be minimized.

DESCRIPTION OF THE PREFERRED EMBODIMENTS To illustrate the invention in detail, FIG. 1 shows an air impact drying apparatus suitable for drying lightweight webs such as tissue paper.

This drying device is equipped with a large-diameter steam-heated Yankee dryer drum 10, and a conveyor belt 11 that is hung around rollers 12.
A lightweight strip, such as tissue paper, is fed onto this drum 10 by.

As shown in FIG. 1, the tissue paper strip travels around most of the periphery of the drum 10, is removed from the drum 10 by a scraping blade 13, and is wound onto a take-up roll 14.

The drying apparatus of FIG. 1 has a pair of air cap devices that are located very close to the surface of the advancing web and extend the entire width of the web.

High pressure hot air is supplied from a source of pressurized air (not shown) to an inlet manifold 15 which is connected to conduits 16 and 17 spaced along the arcuate perimeter of the air cap device. Air is pumped out to create a high-pressure chamber 18, from which air is fed to a plurality of bell-shaped plate supports 19.

The shape of these bell-shaped plate supports 19 is shown in detail in FIGS. 2 to 6.

As can be seen from these drawings, the bell-shaped plate support 19 is formed with a rounded entrance portion 20, a relatively small-diameter bright portion 21, and a bell-shaped bottom portion 22 with a flared tip. There is a perforated plate 23.

A set of small recesses 24 and tabs 25 are provided around the periphery to securely confine the plate 23 within the bottom of the bell-shaped bottom portion.

The perforated plate 23 has symmetrically arranged ejection holes 26, which form a square pattern, as shown in FIG.

As shown in FIG. 5, the inlet end of each orifice 26 has an inlet 2T shaped to minimize flow irregularities and turbulence.

The high temperature and high pressure air passing through the holes 26 of the perforated plate 23 flows at a rate of 6 per minute.
,100m (20,00oft) to 9,100m(
The band on the surface of the dryer drum 10 is impacted at a fairly high speed of the order of 30,000oB).

Typical speeds for lightweight paper strips are approximately 1,200 m/min (4,000 m/min).
000ft) to 1,988m (6,500ft).

After impacting the strip surface, the air is diverted from the periphery of each bell plate support 19 to the area between the relatively small diameter throat portions 21.

This area is the discharge area shown in FIGS. 1 and 2.

As shown in FIGS. 1 and 2, the discharge region 28 is in fluid communication with the discharge conduits 29, and each discharge conduit 2
9 has a rounded inlet portion 30 and an outwardly tapered body portion 31 to provide the exhaust air flow with as low a pressure drop as possible and with as little turbulence as possible. There is.

The discharged air enters the pressure chamber 32, from which it is removed by means of a discharge conduit 33.

Another air cap system shown in FIG. 1 is the same as that just described, and corresponding parts of this system are designated by the same reference numerals as previously described with the suffix "(, ajl).

In the above device, since the perforated plate 23 is supported by the bell-shaped acid portion 22 that widens toward the front, the area between the throat portions 21 of the perforated wave support device 19 is smaller than the area between adjacent perforated plates 23. The area is wider, which allows for a space behind each perforated plate.
A discharge area 28 is formed which is enlarged on the side closer to the bottom of the high pressure chamber 18 .

Therefore, the high-pressure hot shock air ejected from the nozzle 26 impinges on the strip to be dried and, after drying it, the spent air is released between the strip and the bell-shaped bottom, as shown by the arrow in FIG. The outer discharge area 2.
i and can flow through the enlarged discharge area 28 at a relatively low velocity and without significant pressure drop.

Furthermore, the widened discharge area 2β・□ is located at its entrance, that is,
The outlet of the jet after the impact is arranged around the entire periphery of the perforated plate 23, and each air outlet 26 of each perforated plate 23 is connected to the entrance of the hot area 28 (perforated). Since the plate 23 is arranged so as not to be separated by an excessively large distance from the outer periphery of the plate 23, it is possible to avoid cross-flow interference as described earlier, that is, to prevent the impact jet flow from being relatively fast. When proceeding toward the discharge port, it is possible to minimize and reduce the jet obstruction phenomenon that occurs due to the jet flowing across adjacent collapsing jets, thereby eliminating the reduction in heat transfer efficiency due to cross flow interference.

An alternative embodiment for high velocity air impact drying is shown in FIG.

In this embodiment, a plurality of generally square perforated plates 34 are each perforated in a square pattern and housed in a support having sloped side walls 35 secured to a relatively small diameter tube 36.

The ends of tube 36 are fixed to wall 37 and these ends have smoothly rounded lips 38.

An outer wall 39 is spaced outwardly from the inner wall 37 and defines a high pressure chamber 40 between these walls for directing high pressure heated air therefrom via a tube 36. It is introduced through the hole plate 34.

The completed device has on the order of 24 to 36 plates, leaving a discharge area 41 in the center of the array of plates.

An exhaust conduit 42 having a tapered end 43 communicates with the exhaust area 41 for removing exhaust air therefrom.

In this embodiment, the perforated plate 34 has a square shape, and the bell-shaped part at the bottom of the device that supports it is formed into a pyramid-shaped piece that protrudes laterally as it goes inward due to four inclined side walls 35. It differs from the embodiment described with reference to FIGS. 1 to 6 only in the way it is formed, but its functions and effects are the same.

In the embodiments described above, the exhaust air is directed towards the back of the perforated plate into a single widened exhaust area around the entire periphery of the plate with the perforated air vents and into the exhaust stream. It will be appreciated that creating a relatively punched area with a relatively low evacuation velocity, without a moderate pressure drop, and with very little cross-flow interference of the impinging airflow.

Various types of high pressure chamber devices can be constructed using the advantages of this invention.

For example, air discharged into a discharge zone behind each perforated plate can be directed to a vertical discharge zone located between adjacent high pressure chambers.

In this case, the exhaust air coming from the adjacent high pressure chambers is combined in this exhaust area and removed therefrom.

In the practice of the present invention, the total area of the orifices in the plate is no more than about 3% of the area of the plate, and the diameter of the holes is approximately 1/15 in. ) to about 1
It has been found that it is desirable to have a range of up to 9.0'l (3/4 inch).

Further, the ratio of the distance from the surface of the strip to the hole to the diameter of the hole is correlated so that when the open area is large, the distance to diameter ratio becomes small.

It has been experimentally determined that for best results the ratio of the distance of the pores from the strip surface to the pore diameter should follow the following table.

To ensure uniform heat transfer across the strip, it is preferred that the holes be arranged symmetrically in the plate, with each hole being equidistant from adjacent holes.

It is therefore recommended to arrange the holes in a square or equilateral triangular pattern.

Preferably, the perforated plate is approximately square.

In order to bring the hole located in the center of the plate closer to the peripheral discharge area surrounding the plate, the length of a side of the square plate should not be greater than about 1.8 times the diameter of the hole divided by the open area. That is a good idea.

As a special case, the diameter is 3.1758 (1/8 in)
For a plate with holes with an open area of 0.0276 (2,76%), the maximum length of one side of the square plate is approximately 20.7 cm (8.7 cm).
, 15in).

[Brief explanation of drawings]

1 is a schematic diagram showing the air cap device of the present invention in combination with a large diameter Yankee dryer drum; FIG. 2 is a vertical cross-sectional view of a portion of the perforated plate bell-shaped support device; FIG. Figure 4 is a partial cross-sectional view of a perforated plate of the type used in the structure shown in Figures 2 and 3. , FIG. 5 is a partial enlarged cross-sectional view taken along line v-■ in FIG. 4, and FIG. 6 is a partially enlarged cross-sectional view taken along line VI-
FIG. 7 is a schematic, partially cutaway view of another air cap structure constructed in accordance with the present invention. In the drawing, 18 is a high pressure chamber, 19 is a bell-shaped plate support, and 2
1 is a small diameter throat portion, 23 is a perforated plate, and 28 is an enlarged discharge area.

Claims (1)

[Claims] 1 at least one air cap having a width corresponding to the width of the strip to be dried, each air cap having at least one perforated plate and with said perforated plate relatively close to the strip; and a high pressure chamber connected to the support device and configured to send out high pressure air through the jet hole of the perforated plate so as to impact the strip, The device has a throat portion having a smaller cross-sectional area than the perforated plate between the perforated plate and the high pressure chamber; The bottom of the high pressure chamber is supported on the bottom of this bell-shaped bottom part, and the bottom part of the high pressure chamber behind the perforated plate supported by the bell-shaped bottom part, and the bell-shaped end of the perforated plate supporting device adjacent to each other are widened. The bottom part and the throat part define a discharge area in which the area between the throat parts closer to the bottom of the high pressure chamber is larger than the area between the perforated plates supported at the bottom of the flared bell-shaped bottom part. A device for drying moving webs, wherein the evacuation area is arranged around the entire periphery of each perforated plate, and the evacuation area is arranged to advance the airflow after impacting the web.