JPS5914600B2 - Sealed hood for paper machine drying section - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a closed hood for the drying section of a paper machine.

Conventionally, the drying section of a paper machine, which dissipates a large amount of thermal energy into the outside air, is surrounded by a closed hood, and dry air is introduced from the bottom of the closed hood to reduce the high temperature and high humidity containing water vapor dissipated from the drying section of the paper machine. Ventilation in which the air is sucked outside by an exhaust fan through an exhaust chamber provided at the top of the airtight hood, the thermal energy of the air sucked by the exhaust fan is recovered by a heat exchanger, and the heat-recovered air is exhausted. Closed hoods for paper machine drying sections are widely used.

In recent years, many airtight hoods have been developed that have various improvements over the conventional airtight hoods as described above. The paper machine dryer is equipped with an air intake section on the inside wall of the airtight hood, and an exhaust means for sucking and exhausting a part of the air inside the airtight hood from the air intake section using an exhaust fan. This is a sealed hood for the drying section of the paper machine, and the steam/drainage inlet/output equipment for the drying cylinder of the drying section of the paper machine can also be provided outside the side wall of the sealed hood.

Furthermore, the airtight hood disclosed in Japanese Patent Publication No. 44-23886 neutralizes and cancels the flow of air from the steam/drain inlet/output side to the opposite side of the steam/drain inlet/output side to the paper machine drying section. The device is added to the conventional ventilation means.

However, the exhaust means disclosed in Japanese Utility Model Publication No. 55-35360 further strengthens the ventilation of the pocket formed by the drying cylinder, canvas, paper web, and canvas roll in the drying section of the paper machine, thereby increasing the drying capacity. In order to prevent the forced airflow caused as a result of enhanced ventilation from reflecting off the inner wall of the sealed hood and causing turbulence, suction devices are installed on both sides of the pocket to quickly remove the air flowing out from the pocket. This is a means of suctioning and discharging the high temperature air to the outside, so even if heat is recovered using a heat exchanger, dry air equivalent to the amount of discharged air is added to the closed hood. Since the thermal energy must be introduced, the loss of thermal energy becomes even greater.

Furthermore, if the steam/drain inlet/output equipment is provided outside the side wall of the closed hood, the thermal energy released from the steam/drain inlet/outlet equipment and the thermal energy of the supplied air will be dissipated into the outside air.

Furthermore, in order to make the paper web moisture content distribution in the direction perpendicular to the paper web transport direction (hereinafter referred to as the widthwise moisture profile) uniform, the amount of suction air of each suction device installed on both sides of the pocket section must be adjusted. It is necessary to adjust the balance in a well-balanced manner, etc.
Not only did the device become complicated, but the operation became complicated, and there were many practical drawbacks.

On the other hand, the device disclosed in the above-mentioned Japanese Patent Publication No. 44-23886 is a device for controlling the situation where the edge of the paper web on the side of the steam/drain inlet/output equipment is overdried and the moisture profile in the width direction becomes uneven. However, in order to neutralize the ventilation in the pocket and remove the water vapor that forms and stagnates in the pocket, it is necessary to install a hot air jet nozzle as disclosed in Japanese Patent Publication No. 34-10254. As a result, turbulence is caused in the pocket portion, which causes flutter of the sheet in thin paper making, resulting in paper breakage and wrinkles.

Therefore, there were many problems such as the necessity to provide a suction device as disclosed in Japanese Patent Publication No. 44-23886.

Therefore, in order to eliminate the drawbacks of the conventional hermetic hoods mentioned above, the present inventor conducted a detailed investigation into the state of airflow in the airtight hood for the drying section of a paper machine, and based on the research data, repeatedly conducted various field tests and conducted research. As a result of repeated trial production, we developed a sealed hood for the drying section of a paper machine machine equipped with a device that has high drying capacity, extremely low thermal energy loss, and is extremely easy to adjust, allowing us to manufacture paper with a uniform moisture profile in the width direction. It was extremely successful.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a closed hood for a drying section of a paper machine according to the present invention will be explained in detail based on examples with reference to the drawings.

FIG. 1 is a longitudinal cross-sectional view of one embodiment of a sealed hood for a drying section of a paper machine according to the present invention, FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1, and FIG. A vertical cross-sectional view of another embodiment of the airtight hood for the department, FIG. 4 is taken along the line B-B in FIG.
FIG.

In the drawing, 1 is the main body of a sealed hood surrounded by a ceiling wall 10, side walls 11, 11' and end walls 12, 12', 13 is a floor provided at the bottom of the main body 1, and 14 is a ventilation means. An air introduction section 140 that is buried in the floor 13 and includes an underground duct 141 and an introduction port 142 that blows dry air from the underground duct 141 toward the lower part 130 inside the main body 1; Air intake port 142' in the upper part 100
A collection/exhaust area 1 that collects air containing more water vapor and exhausts it to the outside through an exhaust port 141' opened in the ceiling wall 10.
It consists of 40'.

2 is a drying section of the paper machine, in which a paper web 21 and an upper canvas 2 are
The upper drying cylinder group 23 and the upper canvas roll group 230 on which the paper web 21 and the lower canvas roll 22' are hung, and the lower drying cylinder group 23' and the lower canvas roll group 2 on which the paper web 21 and the lower canvas 22' are hung.
30', a gear transmission mechanism 231 that rotates the upper drying cylinder group 23, and a steam/transmission mechanism 231 that supplies superheated steam to the upper drying cylinder group 23 and discharges condensate from the upper drying cylinder group 23.
A gear transmission mechanism 231' that rotates the drain inlet/output equipment 232, the lower drying cylinder group 23', and another steam/transmission mechanism that supplies superheated steam to the lower drying cylinder group 23' and discharges condensate from the lower drying cylinder group 23'. Pocket section 24 formed by drain outlet equipment 232', upper and lower drying tube groups 23, 23', upper and lower canvas 22, 22', paper web 21, and upper and lower canvas roll groups 230°230' and,
A frame 25 that supports the upper and lower drying tube groups 23 and 23' and the upper and lower canvas roll groups 230 and 230'.
and 25'.

3 is an inlet 31 on the side wall 11 of the main body 1 on the steam/drain inlet/outlet side.
In addition, the lower part 130 of the paper machine drying section 2 and the steam of the main body 1
There is an outlet 3 on one or more of the side walls 11 on the opposite side to the drain inlet/outlet side.
3° 33' is a return air means for sucking and refluxing a part of the water vapor-containing air stagnant in the pocket part 24 of the drying part 2 of the paper machine using the blower 34, which is opened at 3° and 33'. a duct 32 that guides air containing water vapor to the outlets 33, 33' via a blower 34;
2, and a valve 35 for adjusting the amount of recirculation air.

Since the airtight hood for the drying section of a paper machine according to the present invention has the above-described structure, the upper and lower drying sections are hung with the upper and lower canvases 22 and 22' for continuously transporting the paper web 21 containing moisture. The paper machine drying section 2 in which the cylinder groups 23, 23' and the upper and lower canvas roll groups 230, 230' are arranged has a ceiling wall 10, side walls 11, 11', and an end wall 12.
.

In this paper machine drying section 2, gear transmission mechanisms 231, 2
Upper and lower drying cylinder groups 23, 23 are rotated by a drive device such as an electric motor (not shown) via 31'.
' is heated by introducing superheated steam into each drying cylinder through steam/drain inlet/output equipment 232, 232' attached to each shaft end, and the upper and lower canvases 22, 2 are heated.
The paper web 21 which is held between the outer peripheral surfaces of the upper and lower drying cylinder groups 23 and 23' is heated.

Most of the water that evaporates from the paper web 21 becomes water vapor and emanates into the airtight hood, and the remainder of the water is taken into the upper and lower canvases 22, 22', after which hot air is blown out from the surrounding surface. upper and lower canvas roll group 23
0,230' and the surfaces of the canvases 22, 22', such as through a hot air blowing duct (not shown), which turns into water vapor and diffuses it into the closed hood.

In this way, the airtight hood is filled with water vapor, but the air containing water vapor in the airtight hood is sucked out by an exhaust fan (not shown) or the like through the exhaust port 141' opened in the ceiling wall 10. The thermal energy held by the air is recovered by a heat exchanger (not shown), etc., and the moisture contained in the sucked air is condensed and recovered as hot water, and the thermal energy and moisture are recovered. The collected air is exhausted to the atmosphere.

On the other hand, inside the closed hood, high-temperature dry air heated by an air heater (not shown) or the like passes through an underground duct 141 of an air introduction section 140 buried in the floor 13 and reaches the lower part 130 of the main body 1 of the closed hood. It is introduced through the introduction port 142 that is open toward the.

In this way, an upward air current is generated in the airtight hood from the lower part 130 toward the upper part 100, and the water vapor emitted from the paper web 21 and the upper and lower canvases 22, 22' rises on the upward air current. , the collection and drainage affected area 14 in the upper part of the main body 1
The air is collected into the air collection chamber formed directly under the ceiling wall 10 of the main body 1 through the air collection port 142' at 0', and is exhausted to the outside through the exhaust port 141' as described above.

Note that even when the forced air supply from the lower part is small, a draft effect occurs due to the exhaust from the upper part and due to the difference in specific gravity since the lower air is dry, and the exhaust from the exhaust port 141' increases. As a result, the side wall of the hood exhibits a condition similar to a chimney phenomenon.

However, as described above, an upward air current is generated in the sealed hood, and the paper web 21 and the upper and lower canvases 22,
22', the upper and lower drying cylinder groups 23, 23' and the upper and lower canvases 22, 22'
and paper roll 21 and upper and lower canvas roll groups 230 and 23
The pocket part 24 is formed by the pocket part 24 formed by 0'.
This is blocked by the group of drying cylinders forming the drying cylinders, and almost no upward airflow occurs.

Therefore, not only the drying efficiency of the drying section 2 of the paper machine becomes low, but also the hot air flow emanating from the steam/drain inlet/output equipment 232, 232' attached to the side ends of the upper and lower drying cylinder groups 23° and 23'. The end portion of the filter paper web 21 that is continuously conveyed by the steam/drainage equipment 232, 232' side becomes over-dried, and the moisture profile in the width direction becomes non-uniform.

Therefore, the steam-containing air in the sealed hood is sucked by the blower 34 through the inlet 31 opened on the side of the steam/drain inlet/output equipment 232° 232', and the air is sucked through the duct 32 to the steam/drain inlet/output equipment located at the bottom of the drying section 2 of the paper machine. 232, 232'
Exit 33 each opened to one or more of the opposite sides of the side
, 33', the suction air is returned to the closed hood.

In this way, the water vapor-containing air stagnated in the pocket portion 24 flows to the steam/drain outlet equipment 232, 232' side and is sucked in from the inlet 31, and also the steam/drain inlet/output equipment 232,
The hot air flow emanating from 232' also flows to the inlet 31 side and is sucked in.

On the other hand, the air returned from the outlet 33 to the lower part 130 inside the hermetic hood joins the high-temperature dry air flow introduced from the inlet 142, is diffused within the dry air flow, and is caused to rise inside the hermetic hood. Also, a part of the air that is returned to the closed hood from the outlet 33' which is opened on the side opposite to the steam/drain inlet/output side flows almost horizontally through the pocket part 24 of the drying section 2 and returns to the inlet. 31, and the other part of the air joins the rising airflow inside the closed hood and is exhausted to the outside.

Note that the duct 32 of the return air means 3 is provided with a valve 35 for adjusting the amount of air recirculated in the duct 32, or a rotation speed control device that increases or decreases the rotation speed of an electric motor (not shown) that drives the blower 34. (not shown) is preferably provided.

Further, it is preferable that a wire mesh or the like be provided at the entrance 31 to prevent pieces of paper from being sucked into the duct 32.

Further, the number of return air means 3 provided in the closed hood depends on the size of the drying section 2, etc., but one to several return air means 3 is sufficient.

In this way, a vertical upward airflow by the ventilation means 14 and a horizontal return airflow by the return air means 3 are generated in the airtight hood, and air flows vertically and horizontally within the drying section 2. is no longer retained, and therefore the drying efficiency of the drying section 2 is improved.

In addition, the air flowing in and around the drying section 2 has almost the same temperature and humidity, especially the steam drain inlet/output equipment 232, 23.
Since the hot air current emanating from the paper web 2' no longer flows toward the end of the paper web 21, the steam/drain inlet/output side end of the paper web 21 does not become overly dry, and the widthwise moisture profile becomes uniform.

Furthermore, the thermal energy dissipated from the steam/drain inlet/output equipment 232, 232' is not only not discharged to the outside, but also caused by the upward airflow by the ventilation means 14 and/or the return air means 3.
The drying section 2
The drying capacity is further increased.

In addition, instead of blowing a high-speed hot air stream directly onto the surface of the paper web 21 and the upper and lower canvases 22, 22', a relatively low-speed airflow is applied to the paper web 21 and the upper and lower canvases 22, 22'.
Since the entire front and back surfaces of the paper web 22' are evenly contacted, it is possible to produce a paper product with a uniform moisture content in the paper web 21 and the upper and lower canvases 22, 22'.

The above explanation has been made regarding an example in which steam and drain equipment for supplying superheated steam and discharging condensate are both located on the same side, but depending on the structure of the paper machine, the superheated steam supply side, that is, the superheated steam There is a paper machine in which the inlet side and the drain discharge side, that is, the drain outlet side, are divided into an operation side and a drive side of the paper machine, respectively.

In such a case, drying is not necessarily promoted only on one side, such as the superheated steam inlet side, and the other side, for example, the drain outlet side, may be excessively dried.

Therefore, it has been confirmed that in such a paper machine, it is effective to provide a suction port on the side wall portion where drying is accelerated or where drying is excessive.

Furthermore, even if the moisture profile in the width direction of the paper is symmetrical, considering the conditions such as the evaporation atmosphere mentioned above, the moisture profile tends to have a higher moisture content in the center of the paper web. Therefore, ventilation can be controlled arbitrarily and optimally by providing a large number of suction ports on both side walls along the moving direction of the paper web and controlling the amount of suction from each suction port using valves, dampers, etc. As a result, it is possible to obtain a uniform moisture profile in the width direction, and as a result, the drying gradient of the paper web can be controlled to a large extent, making it possible to effectively control the quality of paper products such as curl and surface strength. It becomes.

The airtight hood for the drying section of a paper machine according to the present invention as described in detail above can overcome the drawbacks of conventional airtight hoods without installing complicated equipment, has excellent thermal efficiency and paper web drying ability, and has excellent moisture content. Since it is possible to produce paper products with a uniform profile and stable quality, its industrial value is extremely high.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing one embodiment of a sealed hood for a drying section of a paper machine according to the present invention, FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1, and FIG. 3 is a paper machine according to the present invention. FIG. 4 is a longitudinal cross-sectional view showing another embodiment of the airtight hood for the drying section, and FIG. 4 is a cross-sectional view taken along the line BB in FIG. 3. Explanation of symbols: 1...Main body, 10...Ceiling wall, 100...Top of main body, 11, 11'.
...Side wall, 12, 12'...End wall,
13...floor, 130...lower part of main body,
14... Ventilation means, 140-... Air introduction section, 141... Underground duct, 142...
...Inlet, 140'... Collection and drainage affected area, 141'
...Exhaust port, 142'...Intake port, 2
... Paper machine drying section, 21 ... Paper roll, 2
2... Upper canvas, 22'... Lower canvas, 23-... Upper drying tube group, 230...
...Upper canvas roll group, 231...Gear transmission mechanism, 232...Steam/drain inlet/output equipment, 23'...Lower drying tube group, 230'...・・・
...Lower canvas roll group, 231'...Gear transmission mechanism, 232'...Steam/drain inlet/output equipment, 24...Pocket section, 25, 25'...・
...Frame, 3... Return air means, 31...
...Entrance, 32...Duct, 33...
Outlet, 34...Blower, 35...Valve.

Claims (1)

[Scope of Claims] 1. An airtight enclosure in which a ceiling wall, a side wall, and an end wall surround a drying section of a paper machine in which a group of drying tubes hung with canvas and a group of canvas rolls are arranged to continuously convey a web of paper. Ventilation means, which is a hood, which introduces dry air from the lower part and causes water vapor emitted from the drying section to accompany the upward flow of the dry air to form water vapor-containing air and exhaust it from the upper part;
An inlet is opened in the side wall on the side where the steam/drain is inlet or outlet from the drying cylinder, and an outlet is opened in one or more of the lower part of the drying section and the side wall opposite to the inlet or outlet side of the steam/drain, respectively. A paper machine drying section characterized by comprising a return air means for sucking a part of the water vapor-containing air with a blower and refluxing it so that the water vapor-containing air inside the paper machine drying section flows toward the above-mentioned inlet side. Closed hood for use. 2. The airtight hood for a drying section of a paper machine machine according to claim 1, wherein the duct extending from the inlet to the outlet of the return air means is provided with a valve for adjusting the amount of water vapor-containing air. 3. An airtight hood for a paper machine drying section according to claim 1, wherein the blower of the return air means is a blower driven by an electric motor provided with a rotation speed control device that increases or decreases the rotation speed.