JPH02237677A - Far infrared-ray heating furnace - Google Patents

Abstract

PURPOSE:To obtain a far infrared-ray heating furnace which is capable of freely setting the temp. distribution in the furnace and inexpensive in energy cost by coating the heat release surface of a heat release pipe with the far infrared-ray radiant material and connecting a boiler to this heat release pipe via a control valve and providing an exhaust fan to the furnace wall. CONSTITUTION:Both a steam control unit 6 for controlling steam supplied to the steam heaters 3, 4, 5 and a control board 7 are provided to a furnace body 1 and an exhaust fan 8 is provided to a ceiling part. The steam control unit 6 is connected to a steam boiler via a steam pipeline 9. The steam heaters 3, 4, 5 are equipped with both a pair of header pipes 3a, 4a, 5a elongated to the lengthwise direction of the furnace body 1 and the heat release pipes 3b, 4b, 5b provided to the width direction or the height direction so as to be bridge thereto. The surfaces of the heat release pipes 3b, 4b, 5b are coated by the far infrared-ray radiant material.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a furnace for heating a member to be heated with far infrared rays, and in particular, a furnace whose heat radiation surface is coated with a far infrared radiating material as a far infrared radiation source. This invention relates to a far-infrared heating furnace using a steam heater.

[Prior Art] Because far-infrared rays have a long wavelength, they have a large penetrating power into, for example, paints whose main component is plastic or resin, and are efficiently absorbed by the paints. For this reason, a coating drying apparatus has been proposed that includes a plurality of far-infrared panel heaters arranged in a planar manner at least in the vertical direction and facing the workpieces to be coated that are conveyed in a line by a conveying device. In this way, the far infrared rays emitted from the far infrared panel heater are absorbed by the paint, and the inside of it is appropriately heated, so even if the heater is at a relatively low temperature, the parts to be coated can be quickly dried and high quality can be achieved. can get. Also,
Far-infrared rays are absorbed by the paint without waste, resulting in high energy efficiency.

By the way, in the drying device described above, far infrared rays emitted from far infrared panel heaters arranged at least in the vertical direction are projected onto the member to be coated, thereby exclusively heating the member to be coated. If the same electric energy or the like is supplied to each of the type heaters, the temperature at the upper part of the heated member becomes higher than that at the lower part due to the influence of convection, etc., which causes an inconvenience that the temperature distribution becomes non-uniform.

Therefore, in a coating drying apparatus having a plurality of far-infrared panel heaters arranged in a planar manner at least in the vertical direction and facing the member to be coated that is conveyed in a line by a conveyance device, (a) the plurality of far-infrared panels (b) an upper output control device that controls the output of the far-infrared panel heater located at the upper part of the plurality of far-infrared panel heaters; and (b) an output of the far-infrared panel heater located at the lower part of the plurality of far-infrared panel heaters. A lower output control device was proposed (Japanese Unexamined Patent Publication No. 104681/1981).

In this way, the parts to be painted. Of the plurality of far-infrared panel heaters facing each other and arranged in a plane at least in the vertical direction, the output of the upper one is controlled by the upper output control device, and the output of the lower one is controlled by the lower output control device. Therefore, by setting or controlling the output of the far-infrared panel heater located at the upper and lower parts according to the heating state of the upper and lower parts of the member to be coated,
The temperature distribution of the object to be coated in the drying region can be suitably improved.

[Problems to be Solved by the Invention] The far-infrared heater mainly used in the device proposed in JP-A-63-104681 was an electric panel type, and the energy cost was high. Although it is stated on page 3 of the same publication that the energy may be steam, there is no description of a specific steam control mechanism.

The present invention provides a far-infrared heating furnace in which the temperature distribution within the furnace can be freely set and the energy cost is low.

[Means for Solving the Problems] Claim (1) of the present invention is a heating furnace for heating a member to be heated, wherein a plurality of independently controlled heaters are installed in the heating furnace. In far-infrared heating furnaces installed at different locations, the heaters are steam-type heaters whose heat-radiating surfaces of heat-radiating pipes are coated with far-infrared radiating material, and the heat-radiating vibes are equipped with heat-radiating pipes that are coated with far-infrared radiating materials. The boiler is connected via a control valve that controls the steam flow rate accordingly, and the furnace wall is equipped with an exhaust fan. Claim (2) is the same as claim (!) except that the pressure reducing device for reducing the pressure inside the furnace is omitted.

[Operation] According to the invention of claim (1), the heater output can be controlled by adjusting the opening degree of the control valve. This allows the input heating energy at each location in the furnace to be controlled as desired. In addition, the heat source is steam, and the energy cost is low. With the configuration as claimed in claim (2), heat loss associated with air heating is reduced. [Example] Hereinafter, an example will be described based on the drawings.

FIG. 1 is a partially cutaway perspective view of the embodiment apparatus, and shows a conveying device (not shown) for passing the heated member 2 into the furnace body 1.
is provided. A ceiling steam heater 3 is provided on the ceiling of the furnace body 1, and a side steam heater 4.5 is provided on the side wall. The furnace body 1 is provided with a steam control unit 6 and a control panel 7 for controlling the steam supplied to the steam heaters 3, 4, 5. Further, an exhaust fan 8 is provided on the ceiling of the furnace body 1 .

In addition, the steam control unit is connected to the steam pipe 9.
It is connected to a steam boiler (not shown) via.
Further, a sensor for measuring the temperature inside the furnace (ambient temperature and surface temperature of the member to be heated 2) is provided in the furnace body 1, and the output value of the sensor is inputted to the control panel 7. The control panel 7 is provided with a setting device for a heating program for the member to be heated 2 in the furnace.

The steam heaters 3, 4.5 each include a pair of header pipes 3a, 4a, 5a extending in the longitudinal direction of the furnace body 1,
A heat dissipating vibrator 3b arranged in the width direction or height direction of the furnace body so as to bridge the pair of header pipes. 4b, 5b, and the surfaces of the heat dissipation pipes 3b, 4b, 5b are coated with a far-infrared radiation material (note that the header pipes 3a,
A similar coating may be applied to 4a and 5a. ) In the heating device configured in this way, the member to be heated 2 is the furnace body 1.
The steam is sent sequentially in the longitudinal direction, and along the way it is sufficiently heated by far infrared rays emitted from the steam heaters 3, 4.5. In this case, the output of each steam heater 3, 4.5 can be controlled independently, and the radiant energy input to the side and top surfaces of the member to be heated 2 can be controlled for each surface. In addition, the temperature inside the furnace and the surface temperature of the heated member 2 at this time are detected by the sensor, and the steam control unit 6 is operated so that the detected temperature matches the temperature of the set program. 2 can be heated exactly according to the set program.

The gas etc. evaporated from the heated member 2 etc. due to this heating is
The exhaust fan 8 exhausts the gas out of the furnace.

In addition, when drying the paint on wooden furniture and floorboards using the above-mentioned example device, the drying time was 1% compared to the conventional hot air drying oven.
Drying took about 1/2 to 1/3 of the time. Also, unlike hot air drying ovens, hot air is not circulated inside the oven, so
The atmosphere inside the furnace is now clean and free of dust, and there is no chance of the paint surface getting dirty. Furthermore, since steam was used as the heat source, the energy cost was low.

In the above embodiment, the steam heater was provided separately on the ceiling and the side wall, but in the present invention, for example, the steam heater is provided separately on the inlet side and the outlet side of the furnace body 1. The division of the area is arbitrary.

In the present invention, a pressure reducing device may be attached to reduce the pressure inside the furnace, if necessary. The degree of pressure reduction is preferably 50 torr or less, particularly 20 to 30 torr. By reducing the pressure in this way, the heat loss associated with air heating is significantly reduced. In wood invention, there are no particular restrictions on the far-infrared emitting material, and various far-infrared emitting ceramics can be used. There is also no particular limit to the thickness of the coating layer, and it is generally determined as appropriate within the range of about 0.01 to 0.5 mm, taking into consideration the size, performance, required characteristics of the heater 1, strength of the coating layer, etc. Ru.

A coating layer of such a far-infrared emitting material can be formed by applying the far-infrared emitting material to the surface of a substrate such as a steel circular tube by brush coating or spray coating, and then heating and drying or sintering it. It can be easily formed by thermal spraying a radiation material. Note that the steam heaters 3.4.5 shown in the figures are examples, and the present invention is not limited to what is shown in the figures.

For example, by changing the connection form between the header pipe and the heat dissipation pipe, the heater is not limited to the planar shape shown, but can be made into various shapes.

The cross section of the header is not limited to circular, but may be rectangular or half-moon shaped, and the heat dissipation tube is not limited to circular pipes, but may also be so-called square pipes with a rectangular cross section. Alternatively, a finned tube may be used.
When using a square vibrator, the heat dissipation surface is approximately flat,
This has the advantage of increasing heat dissipation efficiency. In addition, in the case of a finned tube, the heat dissipation area increases by the area of the fins, increasing heat dissipation efficiency. FIG. 2 is a front view of the steam heater 20 according to a preferred example, and FIG. 3 is a sectional view taken along the line III--II in FIG. 2.

This steam heater 20 has a heat radiation pipe 23 installed between a pair of header pipes 21 and 22. This heat sink 2
3 has small diameter portions 23a at both ends, and a large diameter portion 23b in the shape of a body with an expanded diameter at the center. In this steam heater 20, the space between the large diameter portions 23b is narrowed (for example, 5 mm or less, particularly about 2 to 3 mm), and the heat radiation area of the steam heater as a whole is increased.

In FIG. 3, the small diameter portion 23a and the large diameter portion 23b are provided coaxially, but in the present invention, as shown in FIG.
The inner surface of a and the inner surface of the large diameter portion 23b may form a continuous surface 23A. When the continuous surface 23A is formed in this way, condensed water and the like in the heat dissipation pipe 23 are transferred to the header pipe 21.
The effect is that it becomes easier to flow toward the direction 22. Fourth
The steam heater shown in the figure is particularly suitable for being arranged to heat the bottom surface of the object to be heated, but it is clear that it may also be arranged to heat the top or side surfaces of the object to be heated. be. Note that the steam heater having the configuration shown in FIG. 3 is suitable when it is disposed so as to heat the top or side surface of the object to be heated.

In the steam heater 20 shown in Figs. 2 to 4, when the small diameter portion 23a is welded to the header pipe 21.22, the welding length (bead length) is short and the circumference of the small diameter portion 23a is Since there is a space, welding can be easily performed.

In the present invention, the coating layer of the far-infrared emitting material includes:
It is preferable to use a material formed by the following method because it can be easily cured by heating and drying at a relatively low temperature and can be firmly attached to a metal substrate. That is, far infrared emitting ceramic powder 2
0-90% by weight, primary aluminum phosphate powder 5-20
100 parts by weight of a powder raw material containing 5 to 75 parts by weight of aggregate with an average particle diameter of 50 to 800 μm, a liquid raw material consisting of water glass and/or alumina sol, and optionally a diluent. , are mixed and kneaded so that the solid content in the liquid raw material is 5 to 25 parts by weight based on 100 parts by weight of the powder raw material to form a paste or slurry, which is then poured into a heat dissipation pipe such as a steel pipe. This is a method in which it is applied to the surface of a substrate and dried and cured at temperatures ranging from room temperature to 300°C or less. Below, a method for forming a coating layer of such a far-infrared emitting material will be explained. In addition, in the following, % represents weight % unless otherwise specified.

First, far infrared emitting ceramic powder 20-90%, preferably 40-75%, monobasic aluminum phosphate powder 5%
~20%, preferably 10-20%, and aggregate 5-75
%, preferably 5 to 50%, is mixed in advance and used as a powder raw material. Next, water glass, alumina sol, or a mixed solution of alkali silicate and alumina sol, further adding a diluent as necessary, is prepared as a liquid raw material, and the liquid raw material is added to the powder raw material. The solid content in the liquid raw material is 5 to 25 liters per 100 parts by weight! Add in parts to form a paste or slurry of desired viscosity.

The paste or slurry thus prepared is applied to the surface of a heat dissipation pipe or the like by brush coating or spray coating, and then dried and cured at a low temperature of room temperature to 300° C. or less.

In this case, the far-infrared emitting ceramic powder may be any commonly used ceramic powder, and is not particularly limited, but examples thereof include powders of zirconia, alumina, titania, and other transition metal oxide ceramics. Among these, those containing 50% by weight or more of transition metal oxides are preferred. The particle size of this far-infrared emitting ceramic powder is smaller than the particle size of the aggregate, and is preferably as fine as possible.

As the primary aluminum phosphate powder, aluminum tripolyphosphate powder is preferred. Examples of the aggregate include coarse particles of ceramics such as chamotte, sintered alumina, and sintered zirconia, and inorganic aggregates such as natural minerals such as silica sand and sintered clay, and the average particle size thereof is preferably 50 to 800 μm. , 200-600pm.

As the water glass, there are various types of commercially available soda water glass, potash water glass, etc., and the type suitable for the purpose is appropriately selected and used. Further, alumina sol is preferably used when it is desired to suppress the efflorescence phenomenon of alkali silicates.

Examples of diluents include colloidal silica, water, and alcohol. In addition, in order to adjust the viscosity of the raw material paste or slurry during the manufacturing process, or to improve the water resistance of the obtained far-infrared emitting material, fillers such as kaolin, clay, and talc having a layered structure may be added as necessary. It can also be blended into raw materials.

By using monophosphoric acid aluminum salt, water glass, alumina sol, etc. in this way, a coating layer can be formed by heating and drying at a relatively low temperature of room temperature to 300° C. or less. In addition, the monobasic aluminum phosphate has the effect of increasing water resistance, suppressing efflorescence, and bringing the coefficient of thermal expansion of the material closer to that of the metal.

The adhesion of the coating layer formed in this way to the heat sink substrate is extremely strong. Moreover, by adding aggregate, the outer surface of the coating layer formed becomes rough, making it possible to increase its surface area. Furthermore, by adding aggregate, it is possible to prevent cracks, chips, and shedding of the coating layer. In addition to the above-mentioned advantages of steam heaters, steam heaters manufactured using far-infrared emitting ceramics in this way are durable because the heat sink is coated with thermally and chemically stable ceramics. Excellent in sex.

■ Heating and drying time is shortened, improving productivity.

■ Existing steam heaters can be easily covered.

It has effects such as powder drying, printing surface drying, gypsum board, etc.
It can be widely used in various heating and drying processes such as drying plywood, drying painted surfaces, drying cloth, and drying web materials.

[Effects of the Invention] As described above, the far-infrared heating furnace of claims (1) and (2) of the present invention provides the following various effects.

■ Temperature distribution can be set freely, improving the quality of the heated product.

■ Heating with a steam heater keeps the product temperature low and prevents overheating. Also, the ambient temperature can be kept low. ■ No fan is required to circulate hot air. (however,
In the present invention, this hot air circulation fan may be used in combination. ) ■ Various sources can be used as a steam source.

For example, process steam, steam from a boiler using waste wood as fuel, etc. can be used.

According to claim (2), heat loss is reduced and heating efficiency is improved.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment. FIG. 2 is a front view of the steam heater 20, and FIGS. 3 and 4 are sectional views of the steam heater. 1... Furnace body, 3, 4, 5. 20... Steam heater, 8... Exhaust fan. Agent Patent Attorney Tsuyoshi Shigeno

Claims (2)

[Claims] (1) A far-infrared heating furnace for heating a member to be heated, in which a plurality of independently controlled heaters are installed at different locations; This is a steam heater in which the heat radiation surface of a heat radiation pipe is coated with a far-infrared radiation material, and the heat radiation pipe includes:
A far-infrared heating furnace characterized in that a boiler is connected to the boiler via a control valve that controls the steam flow rate according to the temperature inside the furnace and the set temperature, and an exhaust fan is provided on the furnace wall. (2) The far-infrared heating furnace according to claim (1), further comprising a pressure reducing device for reducing the pressure inside the heating furnace.