JPH09310973A - Web heating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cause a surface temperature of a steam type far infra-red ray heater to be uniform, eliminate a variation in temperature and perform a uniform heating of a web. SOLUTION: A web 13 is applied to transporting rollers 15 and transported in a vertical direction between steam type far infra-red ray heaters 20 within a heating furnace 10. Steam is supplied from a steam pipe 21 to each of the infra-red ray heaters 20, and the web 13 being transported is heated with radiation of far infra-red ray attained from its surface and convection flow of atmosphere. Steam drain generated under condensation of steam within each of steam type far infra-red ray heaters 20 is sucked by an ejector type pump 25 connected to a drain pipe 22 and the drain is forcedly discharged outside from inside part of each of the steam type far infra-red ray heaters.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a web heating method, and more particularly to a web heating method for heating a web with far infrared rays from a steam type far infrared heater whose surface is coated with a far infrared emitting material. .

[0002]

2. Description of the Related Art In addition to passing steam through the heater body,
A steam-type far-infrared heater is known in which the surface of the heater body is covered with a far-infrared radiation material to irradiate far-infrared rays to a heating target efficiently (for example, the actual Kaihei 2-
34915). Further, the web is continuously conveyed into a furnace provided with a far-infrared heater and heated while the web passes through the furnace so that the web or the coating solution applied to the web is heated and dried. A known web heating method is known.

By the way, when a heating object such as a web or a coating solution is heated using a steam type far infrared heater, the object to be heated is heated by the far infrared rays emitted from the heater body. Due to the convection of air in the furnace equipped with, the temperature of the upper part of the heating target becomes higher than that of the lower part, and the temperature distribution of the heating target becomes uneven. In order to improve this inconvenience, the air in the furnace equipped with a steam type far infrared heater is circulated, and the flow rate of steam supplied to the steam type far infrared heater is controlled to control the temperature distribution of the heating object. A far-infrared heating furnace improved to uniformly heat an object to be heated is known (Actual Kaihei 3-48).
696, JP-A-2-237677).

[0004]

However, even if the object to be heated is heated by the steam type far infrared heater as described above, the object to be heated cannot be heated sufficiently uniformly. This is because the steam drain generated as the steam supplied as a heat source condenses in the heater body is not sufficiently discharged to the outside of the heater body and stays inside the heater body, and the upper and lower parts of the heater body This is because there is a difference in surface temperature between and, and the irradiation amount of far infrared rays between the upper part and the lower part of the heater body is different. Especially, since the steam drain is accumulated in the lower part of the heater body, the temperature is extremely lowered and the object to be heated cannot be heated sufficiently. Moreover, when the conventional steam trap is used, This is caused by the problem that the surface temperature of the heater body fluctuates greatly with time because it is discharged intermittently, and it is difficult to control the surface temperature to a predetermined temperature.

The present invention has been made in order to solve the above-mentioned problems, and the surface temperature of a steam type far infrared heater can be made uniform to uniformly heat a web as a heating object or a coating liquid. It is intended to provide a heating method.

[0006]

In order to achieve the above object, according to the invention of claim 1, when a continuously traveling web is heated by a steam type far infrared heater, the inside of the steam type far infrared heater is The drain of steam generated in the above is sucked by a pump and forcedly discharged to the outside of the steam type far infrared heater. According to the second aspect of the invention, the pump for sucking the drain is an ejector type pump.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a heating device using a steam type far infrared heater embodying the present invention. Heating furnace 10
A transport inlet 11 and a transport outlet 12 are provided in the.
The web 13 as a heating object is fed into the heating furnace 10 from the transfer inlet 11, is hung on a large number of transfer rollers 15 arranged at predetermined intervals in the heating furnace 10 and is formed in the heating furnace 10. It is transported while reciprocating along the vertical transport path. The web 13 is obtained by applying the coating liquid on the surface of a support, and the coating liquid is dried on the support 13 by passing through the heating furnace 10 to form a layer. Of course, it may be used for purposes other than drying the coating liquid to form a layer.

A steam type far-infrared heater (hereinafter referred to as a far-infrared heater) 20 for heating the web 13 is provided between the conveyance path of the web 13 and the conveyance path in the heating furnace 10.
Are arranged respectively. The far-infrared heater 20 has a width (length in a direction orthogonal to the transport direction of the web 13) larger than the width of the web 13 and is arranged so as to face the web 13.

Each far-infrared heater 20 is connected to a steam pipe 21 inside the heating furnace 10 from a steam boiler (not shown) outside the heating furnace 10 and is connected to an upper portion of the heating furnace 10 to supply steam serving as a heat source. To be done. Infrared heater 2
As 0, a tubular shape or a panel shape provided with a gap is used, and the surface thereof is covered with a far infrared radiation material such as ceramics. Inside the infrared heater 20, high-pressure steam from the steam pipe 21 is supplied to the infrared heater 20.
Of the infrared heater 20 to raise the temperature of the tubular or panel-shaped wall surface of the infrared heater 20 from above to below, and the radiant heat transfer by far infrared rays radiated from the surface of the infrared heater 20 and the air in the heating furnace 10 and the like. The web 13 being transported is heated by convective heat transfer in the atmosphere.

The infrared heater 20 is made of a metal having a high thermal conductivity, such as steel or stainless steel, which is used as a heater body in a tubular or panel shape. As the far-infrared radiation material, alumina silica, titania, zirconia, carbon, etc. are mixed, and the mixture is prepared into a slurry form. Then, by coating this on the surface of the heater main body by a spray method or the like and drying and curing it, a coating layer of the far infrared radiation material can be formed on the surface of the heater main body.

The steam passing through the inside of the far infrared heater 20 is condensed by heat exchange with the wall surface of the heater body, becomes a steam drain inside the far infrared heater 20, and flows below the far infrared heater 20. Far infrared heater 20
A drain pipe 22 is connected to a lower portion of the far-infrared heater 20, and a steam drain generated inside each far-infrared heater 20 is sucked into the end portion of the drain pipe 22 and forcedly discharged to the outside of each far-infrared heater 20. A pump 25 is connected to the pump. A well-known ejector type pump is used as the pump 25. It is possible to use a pump other than the ejector pump, but since the steam drain is at a high temperature, it is preferable to use an ejector pump that does not introduce the steam drain into the pump suction portion and the discharge portion.

The pump 25 sucks the steam drain generated inside each far infrared heater 20 and forcibly discharges the steam drain inside each far infrared heater 20 to the outside of each far infrared heater 20. Due to
The steam drain is prevented from staying inside each far infrared heater 20. As a result, each far infrared heater 2
The flow of steam is prevented from being obstructed by the steam drain staying inside 0, and is evenly spread inside each far infrared heater 20, and the surface temperature of each far infrared heater 20 is made uniform.

The steam drain sucked by the pump 25 is stored in a tank 26, sent from the tank 26 to the boiler again, and is supplied to each far infrared heater 20 as steam.

In order to control the surface temperature of each far-infrared heater 20, a measuring means for measuring the surface temperature of each far-infrared heater 20 is provided, and each far-infrared heater 20 is provided based on the measurement result of this measuring means. A controller for controlling the steam flow rate supplied to each far-infrared heater 20 via the flow rate control valve is provided, and heating is performed in order to keep the temperature of the furnace wall of the heating furnace 10 and the transfer roller 15 below a predetermined temperature. Although an air conditioner for sending conditioned air is provided in the furnace 10, these are omitted in FIG. 1 in order not to complicate the drawing.

As a method of controlling the surface temperature of each far infrared heater 20, each far infrared heater 20 is based on the difference between the set temperature set in the far infrared heater 20 and the measured temperature from the measuring means. The PID control method for controlling the steam flow rate supplied to the. Further, as a measuring means for measuring the surface temperature of the far infrared heater 20,
A non-contact method using an infrared radiation thermometer or a contact method using a thermocouple is used.

The operation of the heating device having the above structure will be briefly described below. Far infrared heater 20
Steam from the steam boiler is in the steam piping 21
And the steam is passed through the inside of each far-infrared heater 20, the temperature of the wall surface becomes high, and the far-infrared rays are radiated from the surface of each infrared heater 20 as well as inside the heating furnace 10. The atmosphere becomes convective. Further, the surface temperature of each infrared heater 20 is constantly measured by the measuring means, and the controller adjusts each flow rate control valve based on the measurement result to control the steam flow rate supplied to each infrared heater 20. As a result, the surface temperature of each infrared heater 20 is maintained at the set temperature.

The web 13 is transferred into the heating furnace 10 in such a state through the transfer inlet 11. Web 13
By being hung on each of the transport rollers 15, it is continuously transported between the far-infrared heaters 20 in the vertical direction, and is transported toward the transport outlet 12.

In this way, the web 13 is heated by the heating furnace 10.
While being transported inside, the web 13 is heated by convection of the far infrared rays and the atmosphere in the heating furnace 10 by irradiation from each far infrared heater 20. By this heating, the coating liquid applied on the support of the web 13 is dried, and the web 13 in the dried state of the coating liquid is sent out from the carrying outlet 12 of the heating furnace 10.

On the other hand, the steam passed through each far-infrared heater 20 condenses inside each far-infrared heater 20 to become a steam drain by exchanging heat with its wall surface. By suctioning the pump 25 in the operating state, each far infrared heater 20
It is quickly discharged from the inside to the drain pipe 22 connected to the lower part. The steam drain discharged to the drain pipe 22 is further
By being sent to the tank 26 through the steam drain, the steam drain does not stay inside each far infrared heater 20, and the steam flow is not obstructed by the steam drain. As a result, steam is evenly distributed inside each far-infrared heater 20, the surface temperature of each far-infrared heater 20 becomes uniform, the web 13 is uniformly heated, and the coating liquid is evenly dried.

[0020]

EXAMPLE Next, an example in which the temperature distribution of the far infrared heater according to the present invention, the time variation of the temperature, and the temperature variation of the web were measured will be described. In this embodiment, as shown in FIG. 2, the far infrared heater 20 has a heater body of one unit.
A tubular horizontal pipe 20b is provided between a pair of tubular vertical pipes 20a.
Used was manufactured by Noritake Co., Ltd. The heater body of the far infrared heater 20 (vertical pipe 2
0a, horizontal pipe 20b) is made of steel, and the surface thereof is coated with a ceramic mainly containing cordierite as a far-infrared radiation material. Also, vertical piping 2
The outer diameter of the pipe 0a is 60.5 mm, and the outer diameter of the horizontal pipe 20b is 34.0 mm.

The far infrared heater 20 is a vertical pipe 20.
The steam from the steam pipe 21 is supplied from the upper part of "a", and this steam spreads to each horizontal pipe 20b. Then, the steam drain generated inside the far infrared heater 20 is made to flow out to the discharge pipe 20c through each vertical pipe 20a. This discharge pipe 20
c is connected to the drain pipe 22. The far-infrared heater 20 is arranged such that the vertical pipe 20a is in the direction along the transport direction of the web 13 and the horizontal pipe 20b is in the width direction of the web 13.

As the flow rate control valve for controlling the steam flow rate supplied to each infrared heater 20, K-4-30 manufactured by Yamatake Honeywell was used. In addition, the far infrared heater 20
Surface temperature is measured by KEYENCE radiation thermometer (type: IT
2-50) and based on this measurement result,
Yamatake Honeywell controller (model: SDC300
0), the steam flow rate was controlled by the PID control method. As the PID constant of the controller, P = 4
0, I = 100, and D = 20. Further, the primary pressure of steam was 3.5 Kg / cm ² .

As the web 13 to be heated,
A resin coated paper of polyethylene having a thickness of 220 μm, one surface of which was coated with a ceratin layer having a thickness of 0.3 μm and the other surface of which was coated with an alumina sol layer, was used.

Further, the far infrared heater 20 is set at a temperature of 120 ° C., the web 13 is conveyed at a speed of 200 m / min,
As a method for discharging steam drain when the web is heated under the condition that conditioned air (temperature at the time of blowing: 30 ° C., linear velocity in the furnace: 0.5 m) is introduced into the heating furnace 10,
As the pump 25, an ejector type pump C manufactured by TLV Co., Ltd.
A forced discharge method for forcibly discharging steam drain as in the present invention using PV-1 and one steam trap (manufactured by TLV, type: J5N-8) for each far infrared heater 20 as a comparative example. We measured the temperature distribution of the far-infrared heater, the temperature variation over time, and the temperature variation of the web for the trapping method in which each was installed to discharge steam drain. The measurement results are shown in Table 1 below.

The heater temperature distribution in each of the methods in Table 1 is the temperature difference between the upper and lower surfaces of the far infrared heater 20, and the temporal change of the heater temperature is the variation value of the upper surface of the far infrared heater 20. Is shown.

[0026]

[Table 1]

As can be seen from Table 1 above, when the steam trap is used, there is a large difference in the surface temperature between the upper and lower parts of the far infrared heater 20, and the operation of the trap causes the far infrared heater 20 to move. Surface temperature is 1
It shows a large fluctuation of 35 to 80 ° C., and it can be seen that the temperature of the web 13 also changes relatively large. On the other hand, when the steam drain is forcibly discharged from the inside of the far infrared heater 20 by the pump 25, there is a difference in the surface temperature between the upper and lower parts of the far infrared heater 20, but the difference is extremely small. . Further, it is also understood that since the steam drain is constantly discharged, the fluctuation of the surface temperature of the far infrared heater 20 is extremely small. further,
In this way, since the surface temperature of the far-infrared heater 20 is extremely small, it can be seen that the temperature of the web 13 hardly changes. Thus, according to the present invention, it can be seen that the web 13 can be heated uniformly.

[0028]

As described above, according to the web heating method of the present invention, when the continuously conveyed web is heated by the steam type far infrared heater, it is condensed inside the steam type far infrared heater by the pump. The steam drain is sucked and forcibly discharged to the outside of the steam type far infrared heater, so the steam drain is quickly discharged from the inside of the steam type far infrared heater. There is almost no difference in temperature between the upper part and the lower part of the surface and the temporal temperature fluctuation can be extremely reduced, whereby the web can be heated uniformly.

[Brief description of drawings]

FIG. 1 is a schematic view showing an outline of a heating furnace in which the present invention is carried out.

FIG. 2 is a plan view showing a steam far-infrared heater used in Examples.

[Explanation of symbols]

 10 heating furnace 13 web 20 steam type far infrared heater 22 drain pipe 25 pump 26 tank

Claims (2)

[Claims] 1. A web heating method for heating a continuously conveyed web by a steam far-infrared heater, wherein a steam drain generated inside the steam far-infrared heater is sucked by a pump to forcibly A method for heating a web, comprising discharging the steam far infrared heater to the outside. 2. The web heating method according to claim 1, wherein the pump is an ejector type pump.