JPS6245469B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an improvement in a firing furnace for firing tile substrates and the like.

[Conventional technology and problems] Conventionally, as a firing furnace, the conveyance rollers in the firing furnace can be easily and quickly maintained, inspected, and replaced.
There are kilns related to Japanese Patent Application Nos. 59-5098 and 59-5099. That is, the firing furnace 1 is shown in FIGS. 1 and 2.
As shown in the figure, the lower half furnace body 3 of the furnace body 4 is formed by integrally constructing the furnace bottom portion 3b and the lower half portions 3c of the left and right furnace side walls with refractory bricks, etc., and both the left and right sides of the lower half furnace body 3 On the outside, a conveying means 2 consisting of an endless chain or the like moves along the lower half of the furnace side wall 3c at approximately the same height as the upper end of the lower half of the furnace side wall 3c.
1, 21, and both ends are removably attached to the conveying means 21, 21 at regular intervals, and the conveying means 21,
21 is made of a heat-resistant material, which is guided in the longitudinal direction of the lower half furnace 3 directly above the lower half furnace 3, and the length dimension between both ends of the lower half furnace 3 is Conveying means 6, 6 longer than the width dimension (see Figure 2)
and a conveying gap (hereinafter referred to as "conveying means passage A'") having a height dimension that does not impede the conveying of the conveying means 6, 6...
) is provided between the upper end surfaces of the lower half portions 3c, 3c of the furnace side walls, and is suspended from above.
The upper half furnace body 2 of the furnace body 4 is constructed by integrally constructing a furnace ceiling portion 2b and upper half portions 2c of left and right furnace side walls, 2c, using refractory bricks or the like.

By the way, the furnace body 4 is designed to keep the static pressure in the furnace 4a several mmAq lower than the outside pressure so that outside air does not flow into the furnace 4a.
It has been made to a high degree. Therefore, in the firing furnace 1, the hot air inside the furnace 4a may leak out from the conveying means passage A' formed in the furnace body 4, and the temperature distribution inside the furnace 4a becomes uneven, and the temperature distribution in the furnace 4a becomes uneven. Inconveniences such as abnormal heating of the transmission means 21, 21, etc., have occurred.

[Object of the present invention] In order to solve the above-mentioned disadvantages, the present invention aims to provide a firing furnace in which a conveying means passage formed in the furnace body has a sealing function to prevent hot air from leaking inside the furnace. .

[Structure of the Invention] The gist of the first invention is to provide a lower half furnace body of a furnace body formed by integrally forming a furnace bottom portion and lower half portions of left and right furnace side walls with refractory bricks, etc.; On both outsides, there is a conveying means such as an endless chain that moves along the lower half of the furnace side wall at approximately the same height as the upper end of the lower half of the furnace side wall; is made of a heat-resistant material and is removably attached, and is guided in the longitudinal direction of the lower half furnace directly above the lower half furnace as the conveying means moves.
A conveyance means whose length dimension between both ends is longer than the width dimension of the lower half furnace body, and a conveyance gap having a height dimension that does not impede the conveyance of the conveyance means between the upper end surface of the lower half of the furnace side wall. suspended from above, between the
In a firing furnace consisting of an upper half of a furnace body formed by integrally forming a furnace ceiling and upper halves of left and right furnace side walls of refractory bricks, the upper end surface of the lower half of the furnace side walls or facing this. The lower end surface of the upper half of the furnace side wall is provided with a suction port of an intake passage formed inside the furnace wall and communicating with a suction device provided outside the furnace.

The gist of the second invention is to provide a lower half furnace body in which a furnace bottom portion and lower half portions of left and right furnace side walls are integrally constructed of refractory bricks, etc., and a furnace side wall on both left and right outer sides of the lower half furnace body. A conveying means consisting of an endless chain or the like that moves along the lower half of the furnace side wall at a position approximately at the same height as the upper end of the lower half, and both ends of the conveying means are removably attached to the conveying means at regular intervals. , made of a heat-resistant material, which is guided in the longitudinal direction of the lower half-furnace body directly above the lower half-furnace body as the conveying means moves;
A conveyance means whose length dimension between both ends is longer than the width dimension of the lower half furnace body, and a conveyance gap having a height dimension that does not impede the conveyance of the conveyance means between the upper end surface of the lower half of the furnace side wall. suspended from above, between the
In a firing furnace consisting of an upper half of a furnace body formed by integrally forming a furnace ceiling and upper halves of left and right furnace side walls of refractory bricks, the upper end surface of the lower half of the furnace side walls or facing this. A suction port of a suction passage formed inside the furnace wall and communicating with a suction device provided outside the furnace is opened in one of the lower end surfaces of the lower half of the furnace side wall. On the end face, a discharge port of a hot air passage formed inside the furnace wall and having one end opened in the furnace is opened at a position such that the hot air discharged from the discharge port is directed toward the suction port. be.

[Description of Embodiments] The present invention will be described below based on embodiments shown in the drawings. In addition, in this description, "front" means the left side of FIGS. 1, 6, and 7,
"Rear" refers to the right side of these figures. Also “right”
refers to the right side of FIGS. 2, 3, 5, and 8, and "left" refers to the left side of these figures.

First, the main improvements of the present invention will be explained. As shown in FIGS. 3 and 4 in the most detail, the firing furnace of the present invention has a lower end surface 2a of the upper half part 2c of the furnace side wall on both sides of the upper half furnace body 2, and a lower end surface 2a of the lower half furnace body 3. The upper end surfaces 3a of the lower half portions 3c of the furnace side walls on both sides are brought as close as possible to each other, so that there is no large gap above and below both ends of the conveying means 6, which consists of conveying rollers that move within the conveying means passage A'. At the same time, a suction port 7 is opened in one of these opposing end surfaces 2a and 3a (2a in the illustrated embodiment), and a hot air discharge port 8 is opened in the other end surface (3a in the illustrated embodiment). It has been done. Of course, the hot air outlet 8 is opened at a position such that the hot air discharged from the outlet 8 is directed toward the suction port 7. In the illustrated embodiment, the suction port 7 has a groove 9 extending longitudinally in the lower end surface 2a of the upper half of the furnace side wall 2c, and the suction pipes 10, 10 are arranged on the groove surface of the groove 9. It is constructed by opening the lower ends 10a, 10a... at appropriate pitches. The intake pipes 10, 10...
are connected to the collecting pipe 15 at their upper ends 10b, 10b, . . . (see FIG. 3). Further, the collecting pipe 15 is connected to a suction port of a suction device (not shown) provided outside the furnace body 4, such as a turbo fan. Note that the groove 9 is provided for so-called rectification in order to equalize the suction negative pressure on the lower end surface 2a of the upper half of the furnace side wall 2c, but the arrangement pitch of the intake pipes 10, 10... When reducing the size of the intake pipe 10, without providing the concave groove 9,
10..., the lower ends 10a, 10a... of the lower end surface 2a...
An opening may be made directly at the top (see FIG. 8).

The hot air outlet 8 is an opening at the upper end of a hot air passage 11 which is provided in the shape of a slit that extends in the front and back direction toward the upper end surface 3a of the lower half portion 3c of the furnace side wall, facing the groove 9 on the suction side. be. A compressed air supply pipe 12 lies at the bottom of the hot air passage 11,
From the compressed air supply pipe 12, the hot air passage 11
Nozzles 14, 14, . . . project inward at appropriate pitches. On the other hand, the other end 13b of the in-furnace gas suction passage 13, which has one end 13a opened in the inside of the furnace 4a, is opened in the vicinity of the nozzle opening 14a of each nozzle 14 in the hot air passage 11. When high-speed air is discharged from each nozzle port 14a, the high-temperature gas in the furnace 4a is sucked and mixed from the furnace gas suction passage 13 due to its dynamic pressure suction action, and the mixed gas has a high temperature (for example, 400
℃), the slit-shaped hot air passage 11
The liquid is discharged from the discharge port 8 toward the suction port 7.
The high temperature air flow discharged from the hot air passage 11 is passed through a conveying means passage directly above the slit-shaped hot air passage 11.
An air curtain is formed that partitions A′ inside the furnace. Note that the slit-shaped hot air passage 11 diffuses the high temperature air in the front and rear directions within the hot air passage 11, thereby transferring the discharged high temperature air to the hot air passage 11.
This was provided to form a long air film extending from the upper end in the front and back direction. If the projection pitch of the nozzles 14, 14... and the formation pitch of the furnace gas suction passages 13, 13... are made smaller,
The slit-shaped hot air passage 11 is not necessarily required. That is, although not shown in the drawings, instead of the slit-shaped hot air passage 11, a columnar hot air discharge passage whose upper end is opened on the upper end surface 3a of the lower half of the furnace side wall 3c is bored in the lower half of the furnace side wall 3c. In addition, the nozzle port 14a and the other end 13b of the furnace gas suction passage 13 may be configured to face near the bottom of the hot air discharge passage.

In the embodiment shown in FIGS. 3 and 4, a suction port 7 is opened in the lower end surface 2a of the upper half portion 2c of the furnace side wall, and a hot air discharge port 8 is provided in the upper end surface 3a of the lower half portion 3c of the furnace side wall. The suction port 7 is opened at the upper end surface 3a of the lower half 3c of the furnace side wall, and the hot air is opened at the lower end surface 2a of the upper half 3c of the furnace side wall, although it is not shown in the drawing without limiting this in any way. Of course, a structure in which the discharge port 8 is open is also possible.

Further, in each of the left and right conveying means passages A', two or more sets of air curtain generating structures each consisting of a combination of the suction port 7 and the hot air discharge port 8 are arranged in parallel at appropriate intervals in the left and right direction. Of course, this is also possible.

FIG. 8 shows suction ports 10a, 1 which are the lower ends of suction pipes 10, 10... on the lower end surface 2a of the upper half of the furnace side wall 2c.
This is an example in which the openings 0a... are opened at appropriate pitches along the front-rear direction. The opening position of the suction port 10a is preferably located closer to the outside of the furnace than the center of the lower end surface 2a. This is because, as the distance between the suction port 10a and the inside of the furnace 4a is increased, the passage resistance of the hot air inside the furnace passing through the conveying means passage A' toward the outside of the furnace increases, and the suction of the hot air inside the furnace increases. This is because the amount can be reduced and the temperature difference between the main body 6'b of the conveying means 6' and the arm 6'a thereof can be prevented from increasing. Furthermore, suction port 1
Since reducing the distance between 0a and the outside of the furnace means that a larger amount of outside air will be sucked in from the suction port 10a, the seal plates 34, 34, . This helps to further cool down and prevent overheating. Although not shown, the other ends of the suction tubes 10, 10, .

Note that the suction ports 10 of the suction tubes 10, 10...
a, 10a... are not directly opened on the lower end surface 2a of the upper half portion 2c of the furnace side wall.
Similar to the embodiment shown in the figure, suction ports 10a and 10 are provided in the groove 9 formed on the lower end surface 2a along the front-rear direction.
a... may be opened. Furthermore, the suction port 10
The location of the opening a is not limited to the lower end surface 2a, and it is of course possible to open the upper end surface 3a of the lower half 3c of the furnace side wall, or to open both end surfaces 2a and 3a.

Next, the structure of the remaining parts of the firing furnace according to the present invention, excluding the seal structure, will be explained based on FIGS. 3, 4, and 8. The structure of the remaining parts of the kiln except for the seal structure is the same as that of the conventional kiln shown in FIGS. 1 and 2. That is, the furnace body 4 is divided into several sections along the front-rear direction, which is the direction in which the objects to be fired are conveyed, and each section consists of an upper half furnace body 2 and a lower half furnace body 3, and both furnace bodies 2, 3. The conveyance means path A' along the front and back direction (see Figure 3)
It is configured to hold the . As shown in FIG. 3, the lower half furnace body 3 has a strongly framed frame 1.
8 is placed on the lower cross beam 18a. On the other hand,
The upper half furnace body 2 is suspended 19 at its center from the upper cross beam 18b of the frame 18 in a height-adjustable manner, and at both sides is connected to each bracket 18c of the frame 18 in a height-adjustable manner. .

Conveying mechanisms 5, 5 are disposed on both left and right outer sides of the furnace body 4 along the front-rear direction. Each of the transmission mechanisms 5 includes left and right transmission means 21, 21 each comprising an endless chain that moves along the lower half of the furnace side wall 3c at approximately the same height as the upper end surface 3a of the lower half of the furnace side wall 3c. , inverted chain sprockets 22, 22, . . . shown in FIG. 1, and a pair of upper and lower chain guide rails 23, 23 attached to the frame 18.
and a chain drive motor 24, and is configured to drive the left and right transmission means 21, 21 synchronously. In addition, if the transmission means 21, 21 consisting of the endless chain become unstable during driving, the braking characteristics of the left and right reversible sprockets 22, 22 arranged on the loading side D of the firing furnace, although not shown, are adjusted. By braking with the drive motor or brake that has the drive motor, the chain stretched between the carry-in side D and the carry-out side E is given an appropriate back tension and tensioned, and the endless chain is smoothly driven. so that The conveying means 21 is constructed by stretching one endless chain on both the right and left outsides of the furnace body 4, but is not limited to this in any way. For example, the preheating zone along the front and back direction,
Of course, it is also possible to divide it into a firing zone, a cooling zone, etc., and to construct one or more endless chains in each section.

Conveying means 2 consisting of the endless chain
1 and 21, as shown in FIG. 5, a set of chucking means 26 and 27 mounted opposite each other is installed at an appropriate interval P (see FIG. 6; for example, P=
25 to 50 mm), a plurality of sets of conveying means holding mechanisms 25 are attached. Chatting means 2
6 and 27 respectively include support shafts 28 and 28' integrally formed with ring pin portions 28a and 28'a of the transmission means 21 consisting of an endless chain constituting the transmission mechanisms 5 and 5; bearing 2
Rotating tubes 30, 3 attached via 9, 29
0', and press holders 31, 31 screwed onto rotary cylinders 30, 30'. Further, in the right-hand chucking means 26, a planetary device 32 consisting of a chain sprocket is screwed onto a rotating cylinder portion 30.
Either or both of the pressers 31, 31' have presser heads 31a, 31'a made of an elastic body made of heat-resistant rubber, coil springs, etc. that can be expanded and contracted in the left-right direction, and made of a conveying roller to be described later. The transport means 6 is configured to be detachable.
Note that a cavity 31a' is formed inside the pressing head 31a as necessary, and the amount of elastic deformation is increased so that thermal expansion in the longitudinal direction of the conveying means 6 can be absorbed.

The conveying means 6, 6, which are cylindrical rollers that are detachably attached to the chucking means 26, 27 of each set of the conveying means holding mechanism 25, move as the conveying means 21, 21 consisting of the endless chain move. As mentioned above, the conveying means passage A' and the inside of the furnace 4
It is configured to move in a conveying means passage A extending in the longitudinal direction of a. Front and rear 2 adjacent to each other
Seal plates 34 are fitted near the side ends of the conveyance means 6, 6, which are book conveyance rollers, as necessary, to reduce the amount of outside air flowing into the furnace interior 4a, and to reduce the amount of outside air flowing into the furnace interior 4a. Inside the furnace 4a from A'
This prevents radiant heat from leaking out of the furnace. The seal plates 34, 34, . . . pass through a seal plate passage B (see FIG. 6) formed at the outer edge of the upper half furnace body 2 and the lower half furnace body 3, accompanying each conveying means 21. It is configured as follows.

The planetary device 32 attached to the rotary cylinder 30 of the chucking means 26 (see FIG. 5) consists of a chain sprocket, but is not limited to this, and may include an externally toothed spur gear or a friction wheel (not shown). Of course, it is also possible to construct it from an appropriate conductive device such as the like. Furthermore, the mounting position of the planetary device 32 is not limited to the chucking means 26, and although not shown, it can also be mounted on the transport means 6 (preferably near the supporting end thereof) consisting of transport rollers. .

As shown in FIGS. 1, 3, and 7, the solar device 38 applies a rotational reaction force to the planetary devices 32, 32, etc. in order to rotate the conveying means 6, 6, consisting of the conveying rollers. A second endless chain 39 is stretched so as to mesh with a chain sprocket which is a planetary device 32, and a frame 18 is stretched so as to guide the second endless chain 39.
A guide rail 40 (FIG. 5) attached to Drive source 4 consisting of a variable speed motor etc.
3 (see FIG. 1), and is adapted to rotate the conveying means 6, 6, . . . around its central axis at a desired rotational speed (for example, 0.5 to 2.0 m/min).

Note that the solar device 38 is similar to the planetary device 32.
When the planetary device 32 is an externally toothed spur gear, it is composed of a rack gear, and when the planetary device 32 is a friction wheel, it is composed of a band-shaped friction plate.

FIG. 8 shows yet another embodiment, and the major difference from the embodiment shown in FIG.
The arm portion 6'a of the conveying means 6' is removably fixed to the attachment 21'a, and the conveying means 6' is constructed so as not to rotate. The conveying means 6' has a main body 6'b made of a heat-resistant material and having a T-shaped vertical section or an I-shaped cross section.

Next, the transport operation of the firing furnace according to the present invention will be explained. As shown in FIG. 1, the conveyance means 6 on the input side D,
6... (see Figure 3) The object to be fired (not shown), such as a tile base, placed on the top is conveyed and guided by conveying means 6, 6... that move while rotating, and the heated interior 4a of the furnace is guided. It is baked while passing through and is carried out to the carrying-out side E. When glaze or the like adheres to the surfaces of the conveying means 6, 6, etc., and the object to be fired cannot be conveyed smoothly, the conveying means 21, 21, which consists of an endless chain, etc., are conveyed to the carry-in side D or the carry-out side E. The means 6, 6... are moved intermittently at a speed that does not have a thermal effect, and the conveying means 6 that has come out of the furnace due to the intermittent movement of the conveying means 21 is replaced with a new one while the conveying means 21 is stopped. do.

In the embodiment shown in FIG. 8, the objects to be fired (not shown) such as tile bases placed on the conveying means 6', 6'... passing through the carry-in side are transported by the moving conveying means 6', 6'. ..., and is fired while passing through the heated furnace 4a and then transported out of the furnace. When glaze or the like adheres to the support surfaces of the conveying means 6', 6', etc. and the objects to be fired cannot be conveyed smoothly, the conveying means 21' consisting of an endless chain of the conveying mechanism 5' is moved to the loading side. D or discharge side E, the conveying means 6' is intermittently moved at a low speed that does not cause sudden thermal changes. Next, the conveying means 6' that has come out of the furnace due to the intermittent movement of the conveying means 21' is replaced with a new one while the conveying means 21' is stopped.

[Function] Next, the function regarding the seal structure of the firing furnace according to the present invention will be explained. As shown in FIGS. 3 and 4, a suction port 7 is opened in the lower end surface 2a of the upper half portion 2c of the furnace side wall, and a hot air discharge port 8 is opened in the upper end surface 3a of the lower half portion 3c of the furnace side wall. In the case, when high-speed air is ejected from each nozzle port 14a, 14a..., the high-temperature gas in the furnace 4a is sucked and mixed from the furnace gas suction passage 13 due to its dynamic pressure suction action, and the mixed gas has a high temperature (e.g. 400℃) from the outlet 8 of the slit-shaped hot air passage 11 to the suction port 7.
Discharge towards. The high-temperature mixed gas diffuses in the longitudinal direction while passing through the slit-shaped hot air passage 11, and forms an air film with a substantially uniform wind speed in the longitudinal direction from the upper end opening of the hot air passage 11. and discharges it toward the suction port 7. When the air film discharged from the hot air discharge port 8 passes upward through the conveyance means passage A', it forms an air curtain between the adjacent conveyance means 6 and 6, and creates a uniform negative force in the front and rear direction. It is sucked into the suction port 7 which is in a pressure state. Note that a part of the mixed gas that collided with the lower surface of the conveying means 6 was
The flow direction is attempted to be changed to the left and right direction along the conveying means 6, but the adjacent conveying means 6, 6
Dynamic pressure suction effect of the air curtain between and suction port 7
It is forcibly guided to the suction port 7 without changing direction due to the negative pressure suction action. The hot air inside the furnace 4a is prevented from leaking out of the furnace by the presence of the acre tent. Further, the conveyance means 6 is not affected by heat at all because the air curtain is at a high temperature. Furthermore, the amount of suction from the suction port 7 is large and the conveyance means passage is
When the inside of A' is in a negative pressure state, outside air is guided to the suction port 7, thereby preventing the seal plates 34, 34, . . . from being heated.

As shown in FIG. 8, in the case of a structure in which suction ports 10a, 10a, . Since the inside of A' is in a negative pressure state, the hot air inside the furnace 4a and the outside air are sucked into the suction port 10.
a, 10a..., so inside the furnace 4a
The hot air does not leak out of the furnace. Furthermore, the seal plates 34, 34, . . . are cooled by the outside air drawn into the suction port 10'a.

[Effects of the Invention] As detailed above, in the firing furnace according to the present invention, the hot air inside the furnace does not leak out through the conveying means passage, so the temperature distribution inside the furnace can be maintained uniformly. In addition, it has an excellent effect of maintaining smooth operation of the conveying means without damaging the conveying means disposed on both sides of the furnace body.

[Brief explanation of the drawing]

Fig. 1 is a partially omitted cross-sectional view showing the main parts of a conventional firing furnace, Fig. 2 is an enlarged sectional view cut along the line -, and Fig. 3 is a half-cut enlarged cross-sectional view showing an embodiment of the firing furnace according to the present invention. Figure 4 is a cutaway perspective view showing the main parts of the seal structure, Figure 5 is an enlarged sectional view with the middle omitted showing the mounting state of the conveying means, and Figure 6 is the same as above.
FIG. 7 is an enlarged side view showing the solar device with the intermediate portion omitted, and FIG. 8 is an enlarged sectional view of a main part of another embodiment of the firing furnace according to the present invention. 2...Upper furnace wall, 2a...Lower end surface, 3...Lower furnace wall, 3a...Upper end surface, 4...Furnace body, 6...Transporting means, 7
...Suction port, 8...Hot air discharge port, 9...Concave groove, 11...
Hot air passage, 13...Furnace gas suction passage, 14...Compressed air discharge nozzle, A'...Transportation means passage.

Claims (1)

[Scope of Claims] 1. A lower half furnace body formed by integrally forming a furnace bottom and lower halves of left and right furnace side walls with refractory bricks, and lower halves of furnace side walls on both left and right outer sides of the lower half furnace body. a conveying means consisting of an endless chain that moves along the lower half of the furnace side wall at a position approximately at the same height as the upper end of the furnace; The length between both ends of the heat-resistant material is guided directly above the lower furnace half in the longitudinal direction of the lower furnace half as the guiding means moves. A conveyance gap having a height dimension that does not impede the conveyance of the conveyance means is provided between the conveyance means longer than the conveyance means and the upper end surface of the lower half of the furnace side wall,
In a firing furnace consisting of an upper half of a furnace body, which is hung from above and is made of refractory bricks or the like and integrally constitutes the furnace ceiling and the upper halves of left and right furnace side walls, the lower half of the furnace side walls is A suction port of an intake passage formed inside the furnace wall and communicating with a suction device provided outside the furnace is opened at the upper end surface or the lower end surface of the upper half of the furnace side wall opposite thereto. A firing furnace. 2. The suction port is opened in a groove recessed along the longitudinal direction of the furnace body on the upper end surface of the lower half of the furnace side wall or the lower end surface of the upper half of the furnace side wall opposite thereto. A firing furnace according to claim 1. 3 The lower half of a furnace body, which is made of refractory bricks or the like, integrally comprising the furnace bottom and the lower halves of the left and right furnace side walls, and the upper ends of the lower halves of the furnace side walls on both the left and right outer sides of the lower half furnace body. a conveying means consisting of an endless chain that moves at the same height position along the lower half of the furnace side wall;
A heat-resistant heat-resistant material whose both ends are removably attached to the conveying means at regular intervals, and which is conveyed directly above the lower half furnace body in the longitudinal direction of the lower half furnace body as the conveying means moves. The lower half of the furnace side wall is provided with a conveyance means made of a flexible material, the length dimension between both ends of which is longer than the width dimension of the lower half furnace body, and a conveyance gap with a height dimension that does not impede the conveyance of the conveyance means. so that it is provided between the upper end surface of the
In a firing furnace consisting of an upper half of a furnace body, which is hung from above and is made of refractory bricks or the like and integrally constitutes the furnace ceiling and the upper halves of left and right furnace side walls, the lower half of the furnace side walls is A suction port of a suction passage formed inside the furnace wall and communicating with a suction device provided outside the furnace is opened on either the upper end surface or the lower end surface of the upper half of the furnace side wall opposing thereto. At the same time, the other end face is located such that a discharge port of a hot air passage formed inside the furnace wall and having one end opened in the furnace directs the hot air discharged from the discharge port toward the suction port. A firing furnace characterized by having an opening. 4. The suction port is opened in a groove recessed along the longitudinal direction of the furnace body on the upper end surface of the lower half of the furnace side wall or the lower end surface of the upper half of the furnace side wall opposite thereto. A firing furnace according to claim 3. 5 A compressed air discharge nozzle port is opened near the other end of the hot air passage having the discharge port formed at one end, and an in-furnace gas suction port communicating with the inside of the furnace is opened near the nozzle port. A firing furnace according to claim 3 or 4.