JPH0362996B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] The present invention relates to a method and apparatus for rapidly cooling ceramic products containing quartz in a cooling zone of a roller hearth kiln, and its purpose is to rapidly cool ceramic products containing quartz after firing. In particular, cooling time can be shortened by rapidly cooling sanitary ware to a specific temperature.

[Prior Art] Conventionally, various inventions have been made for the purpose of shortening the total firing time in roller hearth kilns, but most of them relate to the pre-heating zone and the firing zone, and the cooling zone. There are very few inventions related to this.

This can be achieved by simply improving the heating technology in the preheating zone and firing zone, but when it comes to cooling zones, when the product to be fired is sanitary ware, the heating time can be reduced by 30% or more. In order to obtain good quality sanitary ware containing quartz, the transformation temperature of quartz (573℃) is required.
The surrounding area must be cooled slowly, and as a result, as is clear from Figure 4, the cooling time becomes longer.
As a result, the total firing time became longer.

[Structure of the invention] The present invention has been made in view of the above circumstances, and
The gist of this is to shorten the cooling time by rapidly cooling high-temperature ceramic products, especially sanitary ware, after firing in the cooling zone to around the transformation temperature of quartz (10 to 100 degrees Celsius higher than the transformation temperature). Embodiments will be described below with reference to the accompanying drawings.

In FIGS. 1 and 2, the roller hearth kiln A of the present invention has a preheating zone P, a firing zone F, and a cooling zone C formed sequentially from the inlet to the exit. The sum of the lengths is approximately equal to the length of the cooling zone C.

A plurality of rollers 1 are arranged at predetermined intervals in each of the preheating zone P, the firing zone F, and the cooling zone C, and both ends of the rollers 1 protrude outside the furnace and are each equipped with a bearing 2. Supported. Each roller 1 is driven and rotated by a drive device (not shown), thereby causing the article to be fired placed on the refractory transfer plate 3, such as a ceramic product such as a plate, a ceramic tableware such as a bowl, or a sanitary ware. sanitary ware 4 is transferred at a low speed from the inlet to the outlet of the roller hearth kiln A.

Further, above the furnace in the first half of the cooling zone C, a plurality of ceramic heat transfer tubes 5 having both good thermal conductivity and heat resistance are arranged at predetermined intervals in the width direction of the furnace. As shown in FIG. 3, this heat exchanger tube 5 has a large number of minute ventilation holes 9 bored all around its circumference, and both ends thereof protrude outside the furnace. This ceramic is alumina, cordierite, β-spodium, silicon carbide, silicon nitride, beryllium,
Ceramics with thermal conductivity, heat resistance, and low thermal expansion are used, such as aluminum nitride and partially stabilized zirconia sintered bodies. Usually, a slurry consisting of these ceramic raw material powders, clay, and additives is cast into a porous plaster mold and molded, but it is also possible to extrude and mold clay with a moisture content of 30 to 35%. The molded product is green-finished, dried, and fired to obtain the heat exchanger tube 5. One end of each heat transfer tube 5 whose both ends protrude outside the furnace is connected to a blowing duct 6, and the other end is connected to an exhaust duct 7. A blower 8 is connected to one end of the blowing duct 6 for blowing air, which is a cooling medium, into each of the heat transfer tubes 5 .

Then, when the roller 1 drive device (not shown) is driven to rotate each roller 1, the ceramic product or sanitary ware 4 to be fired is preheated in the preheating zone P and then in the firing zone F. It is fired and transferred to cooling zone C. Here, a plurality of heat transfer tubes 5 are arranged in the furnace width direction above the inside of the furnace in approximately the front half of the cooling zone C, and when air at about room temperature is sent into the heat transfer tubes 5 by the blower 8, the inside of the furnace is The heat of the gas above is conductively transferred to the flowing air through the tube wall of the heat transfer tube 5, and air at about room temperature flows out from the micro vents 9 of the heat transfer tube 5 into the high-temperature furnace. The heated air lowers the temperature inside the furnace and at the same time creates forced convection in the gas inside the furnace. Due to this action, as shown in FIG. 4, in almost the first half of the cooling zone C, the ceramic product or sanitary ware 4 that has been heated to a high temperature is rapidly cooled to a temperature 10 to 100 degrees Celsius higher than the transformation temperature of quartz. Then, it is slowly cooled in a slow cooling area,
Thereafter, it is transferred to the latter half of cooling zone C, where it is rapidly cooled again.

Furthermore, the degree of rapid cooling described above can be freely varied by changing the number of ceramic heat exchanger tubes 5 disposed, the amount of air flowing out from the minute ventilation holes 9, or the amount of air flowing inside the heat exchanger tubes 5. I can do it. Note that the air that passes through the heat exchanger tube 5 and is discharged from the exhaust duct 7 is heated to a temperature of 100 to 500°C due to heat exchange within the furnace.
Since the air is heated to a certain degree, it can be used as combustion air for burners to save energy.

[Effects of the Invention] The present invention provides a plurality of Lamic heat exchanger tubes having good thermal conductivity, heat resistance, and low thermal expansion, which are arranged above the inside of the cooling zone of a roller hearth kiln.
In addition, since micro ventilation holes were drilled around the entire circumference of the heat exchanger tube, air at about room temperature was allowed to flow through the heat exchanger tube, allowing the heat inside the furnace to be conductively transferred to the air through the ceramic heat exchanger tube. At the same time, air at about room temperature flows out into the high-temperature furnace from micro vents drilled around the entire circumference of the heat transfer tube, and this outflowing air lowers the temperature inside the furnace and at the same time creates forced convection in the gas inside the furnace. By producing this, ceramic products fired at high temperatures, especially sanitary ware containing quartz, can be rapidly cooled, so compared to conventional roller hearth kilns, the cooling time can be shortened, resulting in rapid firing. becomes possible.

Furthermore, according to the present invention, it is possible to quickly cool the ceramic product or sanitary ware containing quartz to be fired to around the transformation temperature of quartz, and then slowly cool it around the transformation temperature of quartz, so that the cooling time can be reduced. At the same time, high quality ceramic products or sanitary ware can be fired.

[Brief explanation of drawings]

Figure 1 shows a roller hearth kiln A according to the present invention.
2 is a partially sectional plan view of
The enlarged X-ray sectional view and FIG. 3 are perspective views of the heat exchanger tube. FIG. 4 is a graph showing the relationship between the firing temperature and firing time of the ceramic product or sanitary ware 4 that is the product to be fired, where curve A relates to the conventional roller hearth kiln, and curve B relates to the conventional roller hearth kiln. This relates to a roller hearth kiln. 5...Ceramic heat transfer tube, 6...Blowing duct, 7...Discharge duct, 8...Blower, 9...Minute ventilation hole, A...Roller hearth kiln, P...
Preparation zone, F...firing zone, C...cooling zone.

Claims (1)

[Scope of Claims] 1. A plurality of ceramic blocks having both good thermal conductivity and heat resistance, and having a large number of micro ventilation holes perforated along the entire circumference, are provided above the cooling zone of the roller hearth kiln. A manufactured heat transfer tube is installed, air at about room temperature flows through the heat transfer tube, and a portion of the air flows into the furnace through micro vents, thereby creating forced convection in the gas in the furnace. A method for rapidly cooling a ceramic product in a cooling zone of a roller hearth kiln, characterized in that the heat inside the ceramic product is transferred through the heat transfer tube to the remaining air flowing in the heat transfer tube to cool the ceramic product. 2. Claim 1, wherein the ceramic is an alumina, cordierite, β-spodium, silicon carbide, silicon nitride, beryllia, aluminum nitride, or partially stabilized zirconia sintered body. A method for rapidly cooling ceramic products in the cooling zone of a roller hearth kiln. 3. In the cooling zone of the roller hearth kiln according to claim 1, wherein the ceramic is obtained by casting or extruding a mixture of ceramic powder, water, and additives, drying and firing. Method for rapidly cooling ceramic products. 4. A method for rapidly cooling ceramic products in a cooling zone of a roller hearth kiln according to claims 1 to 3, wherein the ceramic is sanitary porcelain. 5. A plurality of ceramic heat transfer tubes with good thermal conductivity and heat resistance are arranged in the width direction of the furnace above the furnace in almost the front half of the cooling zone of the roller hearth kiln, and both ends of the tubes are connected to the furnace. Each heat exchanger tube is made to protrude outward, one end of each heat exchanger tube is connected to an inlet duct, the other end is connected to an exhaust duct, a blower is connected to the inlet duct, and the heat exchanger tube is connected to the entire circumference of the heat exchanger tube. A rapid cooling device for ceramic products in the cooling zone of a roller hearth kiln configured to have a large number of minute ventilation holes.