JPH0761904B2 - Cooling method for baked products - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for cooling a fired product in a firing furnace for ceramic products such as sanitary ware, roof tiles and tiles.

(Prior Art) When firing a fired product as described above in a firing furnace, it is possible to give a fairly rapid temperature change in the temperature raising process, but in the cooling process, it is necessary to pass the transformation point of the ceramics. Therefore, it was not possible to apply a rapid temperature change in order to prevent cooling cracks.

Therefore, conventionally, as shown in FIG. 3, as shown in FIG.
It cools at a relatively fast speed from 1200 ℃ to around 600 ℃, and a slow speed of 40 to 70 ℃ / H in the temperature range from around 600 ℃ to around 400 ℃ where cooling cracks are likely to occur. In general, the cooling method is that cooling is performed at 1, and then cooling is performed again at a relatively high speed. Therefore, for sanitary ware, for example, it takes about 6 hours to cool from 1200 ° C. to 100 ° C., and there is a problem that the firing furnace cannot be used effectively during this period.

(Problems to be Solved by the Invention) The present invention solves the conventional problems as described above, and burns sanitary ware, roof tiles, tiles and other fired products in a shorter time than conventional without causing cooling cracks. It has been completed to provide a method for cooling a fired product that can be cooled.

(Means for Solving the Problem) In order to solve the above problem, the present inventor has studied in detail the actual temperature change of the fired product at each position in the firing furnace.
As a result, when the conventional cooling rate limit of 70 ° C./H is exceeded, cracks start to occur depending on the position of the fired product in the firing furnace, but many fired products do not crack,
It was confirmed that the fired product with cracks was placed at the dead point of the circulating gas in the furnace and was locally cooled at a cooling rate far exceeding 70 ° C / H. Therefore, the present inventors have reached the present invention by thinking that if the temperature distribution in the firing furnace is made uniform, cooling cracks can be prevented even if a cooling rate of 70 ° C./H or more is applied.

The present invention thus completed maintains cooling air from the opposing wall surfaces of the firing furnace for firing ceramic products, and maintains the relationship that when the cooling air from one wall surface is strong, the cooling air from the other wall surface becomes weak. At the same time, the strength of the fired product is periodically increased and ejected in a certain direction toward the inside of the furnace, and the collision position of the cooling air from both sides is moved in the width direction of the furnace, while the baked product is almost constant from a temperature range of 1000 ° C or higher to near room temperature It is characterized by cooling at a cooling rate of.

Note that it is preferable to perform cooling while setting the ratio of the cooling airflow from one wall surface to the cooling airflow from the other wall surface at 1.5: 1 to 5: 1.

In order to make the temperature distribution in the furnace uniform, it is necessary to cause the cooling air to collide while moving the collision position at a predetermined time pitch within a range of 1/10 to 1/2 in the furnace width direction. As a result of testing by varying the cooling air flow from the wall surface, the temperature distribution in the firing furnace was close to uniform and cooling was 70 ° C / H or more if the air flow ratio was in the range of 1.5: 1 to 5: 1. It was found that cooling cracks do not occur even if a speed is applied.

In addition, it is preferable to perform cooling while gradually increasing the total amount of cooling air from the wall surfaces on both sides as the temperature of the fired product decreases.

Hereinafter, the present invention will be described in more detail with reference to the illustrated embodiments.

(Example) In FIG. 1, (1) is a firing furnace for firing ceramic products such as ceramics, and (2) and (2) are burners provided on the opposing wall surfaces. As shown in the figure, these burners (2) and (2) are supplied with a combustion gas and secondary air, and the firing product stored in the furnace is fired as in the conventional case. (3) and (3) are jets of cooling air provided coaxially with these burners (2) and (2), and jet the cooling air in a certain direction in the furnace.
When the cooling process is started, these jets (3),
Cooling air is supplied to (3) from a blower (not shown) through the cooling air supply pipes (4) and (4), and these cooling air supply pipes (4) and (4) are provided with flow rate control valves, respectively. (5) and (6) are provided, and the opening is electrically controlled so that when one is opened, the other is closed and the opening is periodically changed. As a result, the air volume of the cooling air from the jet outlets (3) and (3) denoted by A and B can be periodically changed as shown in FIG.

In order to carry out the present invention with the firing furnace (1) configured as described above, first, as shown in FIG. 3, a burner (2),
After heating the inside of the furnace to, for example, 1200 ° C. by (2) and baking, the cooling air is kept constant from the cooling air jet ports (3) and (3) provided on the opposite wall surfaces of the baking furnace (1). Ejects periodically in the direction. As mentioned above, each jet (3),
The strength of the cooling air from (3) is periodically blown into the furnace while maintaining the relationship that when the cooling air from one wall surface side is strong, the cooling air from the other wall surface side becomes weaker. Therefore, as shown by the arrow in FIG. 1, the collision position of the cooling air constantly approaches one wall surface side or approaches the other wall surface side and constantly changes. For this reason, the cooling air is distributed almost uniformly over the entire inside of the firing furnace (1), and dead points of the circulating flow of the cooling air are extremely unlikely to occur.

Thus, in the present invention, as shown by the broken line in FIG. 3, the fired product is cooled from the temperature range of 1000 ° C. or higher to around room temperature at a substantially constant cooling rate. In Figure 3, the cooling rate is
Since it cools from 1100 ℃ to 100 ℃ in 4 hours, the average temperature is 275 ℃ / H, which means that the fired product will be cooled much more rapidly than before. Since the fired product is also uniformly cooled, cooling cracks do not occur.

In order to ensure uniform cooling, it is desired that the ratio of the cooling airflow from one wall surface to the cooling airflow from the other wall surface be 1.5: 1 to 5: 1. When the maximum ratio of the air volume is smaller than this, there are portions where uniform cooling cannot be obtained, and when the above rapid cooling is performed, cracks may occur. Further, in order to make the cooling rate almost constant, it is necessary to perform cooling while gradually increasing the total air volume of the cooling air from the wall surfaces on both sides as the temperature of the fired product decreases as shown by the two-dot chain line in FIG. is necessary. This is because the temperature difference between the fired product and the cooling air gradually decreases as the cooling progresses,
This is because heat transfer becomes difficult.

In the above embodiment, the firing furnace (1) is a single furnace, and the cooling air jet ports (3) and (3) are provided coaxially with the burners (2) and (2), but the firing furnace (1) is It may be a tunnel furnace, and the jet outlets (3) and (3) may be provided at positions different from those of the burners (2) and (2) as long as they are on opposite wall surfaces of the firing furnace (1). Of course.

(Effects of the Invention) As described above, according to the present invention, sanitary ware, roof tiles,
Ceramic products such as tiles can be cooled from a temperature range of 1000 ° C or higher to near room temperature at a substantially constant cooling rate without causing cooling cracks, so the cooling process can be performed in a much shorter time than before. It can be completed and effective utilization of the firing furnace can be achieved. Therefore, the present invention has an extremely large contribution to industrial development as a method for cooling a fired product that solves the conventional problems.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention, FIG. 2 is a graph showing a state of temporal change in cooling air volume, and FIG. 3 is a graph showing temperature change and cooling air volume change in a cooling process. . (1): firing furnace, (3): jet of cooling air

Claims (3)

[Claims] 1. The strength of a cooling furnace for firing ceramic products is periodically increased and decreased while maintaining the relationship that cooling air from opposite wall surfaces of a firing furnace is weak when cooling air from one wall surface is strong. Attached to the furnace and ejected in a certain direction toward the inside of the furnace, moving the collision position of the cooling air from both sides in the width direction of the furnace and cooling the fired product from the temperature range of 1000 ° C or more to near room temperature at a substantially constant cooling rate A method for cooling a fired product, comprising: 2. The cooling of the fired product according to claim 1, wherein the cooling is performed while setting the ratio of the cooling airflow from one wall surface to the cooling airflow from the other wall surface at 1.5: 1 to 5: 1. Method. 3. The method for cooling a fired product according to claim 1, wherein the cooling is performed while gradually increasing the total amount of cooling air from the wall surfaces on both sides as the temperature of the fired product decreases.