JP2007187374A - Continuous calcination furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous calcination furnace capable of promptly discharging harmful gas generated from a baked article outside the furnace even in a high temperature range, and not requiring a lot of space or incidental equipment outside the furnace. <P>SOLUTION: A large number of gas injection nozzles 4 are disposed in the inner side wall of a furnace chamber 1 into which the baked articles W stacked in a multistage are transferred in a level between the baked articles W. The inside of an inner wall outside each the gas injection nozzle 4 is buried with a gas preheating chamber 5 provided with a heater 9 along a flow passage of injection gas preferably configured by a double porcelain tube. A gas such as nitrogen supplied from the outside is heated to an in-furnace temperature during passage through the gas preheating chamber 5 and is injected into the furnace chamber 1, and the harmful gas generated from the baked article W is discharged outside the furnace from a discharge port 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a continuous firing furnace provided with a gas injection nozzle for quickly removing harmful gas generated from a product to be fired during firing.

  Conventionally, continuous firing furnaces such as tunnel furnaces and base plate pusher furnaces have been widely used for firing electronic parts and various ceramic products. The product to be fired is heated and fired according to a predetermined heat curve while being transferred inside the furnace chamber.

  However, some types of products to be fired generate harmful gases during firing. In a certain ceramic firing step, oxygen gas is generated with a sintering reaction in a temperature range of 1000 to 1100 ° C. In many ceramic firings, a binder gas is generated in a low temperature range of about 300 ° C. If these gases are retained in the furnace as they are, they will adversely affect the firing quality, so it is desirable to discharge them out of the furnace as quickly as possible.

  Therefore, in many ceramic firing furnaces, a structure is adopted in which the binder gas is sucked from the inside of the furnace chamber by a circulation fan, and the same amount of atmospheric gas is injected to discharge the binder gas. However, such a structure using a circulation fan can be used only in a low temperature range, and since it is difficult to use a metal material in a high temperature range of 1000 ° C. or higher, a circulation structure cannot be used. Patent Document 1 discloses a system for circulating a furnace atmosphere containing a binder gas at around 500 ° C. outside the furnace, but it is difficult to use in a high temperature range of 1000 ° C. or higher.

Therefore, in order to discharge harmful gas from the furnace in a high temperature range of 1000 ° C. or higher, a hot air furnace must be provided outside the furnace, and hot air is driven into the furnace to replace it with the gas in the furnace. However, in this method, a hot air furnace must be installed outside the furnace, and the hot air must be guided through a duct. Therefore, there is a problem that the equipment configuration becomes complicated and an extra space is required. Moreover, in order to eliminate the temperature difference formed by buoyancy in the furnace chamber, it is necessary to drive hot air into the furnace at a considerably high speed, which may not be possible with this method.
JP-A-6-94369

  The present invention solves the above-mentioned conventional problems, and can quickly discharge harmful gas generated from the product to be fired to the outside of the furnace even in a high temperature range of 1000 ° C. or more. It was made in order to provide a continuous firing furnace that does not require additional equipment.

  The continuous firing furnace of the present invention made to solve the above-mentioned problems has a number of gas injection nozzles arranged on the inner wall of the furnace chamber to which the product to be fired is transferred, and the furnace wall outside each gas injection nozzle. A gas preheating chamber provided with a heater along the flow path of the implantation gas is embedded inside. It is preferable that the gas preheating chamber has a structure composed of a double porcelain tube that forms the flow path for the driving gas and a coiled heater disposed inside the chamber. It is preferable to have a structure in which a header pipe for distributing gas evenly in the flow path of the implantation gas is provided.

  The continuous firing furnace according to the present invention has a gas injection nozzle in which a gas preheating chamber provided with a heater is embedded in the furnace wall along the flow path of the injection gas, and the preheated injection gas is disposed on the inner wall of the furnace chamber Directly into the furnace chamber. For this reason, even in a high temperature range of 1000 ° C. or higher, harmful gas generated from the product to be fired can be quickly discharged out of the furnace. In addition, since the gas preheating chamber is embedded inside the furnace wall, no extra space is required, and a gas preheating chamber is provided for each gas injection nozzle, so each gas injection nozzle can be used even when the amount of gas is reduced. The gas can be injected evenly and the gas temperature can be made uniform. Further, the implanted gas has an effect of cooling the furnace wall, and heat exchange is performed inside the furnace wall, so that heat loss can be reduced.

  FIG. 1 is a sectional view showing an embodiment in which the present invention is applied to a base plate pusher furnace. Reference numeral 1 denotes a furnace chamber, and the products to be fired W are intermittently transferred in a direction perpendicular to the paper surface by well-known transfer means (not shown) in a state where they are stacked in multiple stages on the base plate 2. A large number of gas injection nozzles 4 are arranged on the left and right inner walls 3 in the temperature range where harmful gas is generated from the article to be fired W. In this embodiment, the article to be fired W is an electronic component, and the gas injection nozzle 4 is disposed in a high temperature region of 1000 ° C. or higher.

  FIG. 1 shows three gas injection nozzles 4 on each side. However, in this embodiment, since the products to be fired W are stacked in 9 stages, the furnace length as shown in FIG. 2 is set so that the gas injection nozzle 4 can inject gas into the intermediate height position of the products to be fired W in each stage. Eight pieces on each side are arranged slightly shifted in the direction. In this embodiment, the implantation gas is nitrogen gas. However, depending on the type of the article to be fired W and the atmosphere in the furnace, air or any other gas can be used.

  A gas preheating chamber 5 is provided corresponding to each gas injection nozzle 4. Each gas preheating chamber 5 is embedded in the furnace wall outside the gas injection nozzle 4, and the gas injection nozzle 4 and the gas preheating chamber 5 communicate with each other. As shown in FIGS. 3 and 4, the gas preheating chamber 5 is provided with a double outer ceramic tube 7 and an inner ceramic tube 8 inside a hole formed in the furnace wall 6 to provide a flow path for the gas to be implanted. While being formed, a coiled heater 9 is provided so as to surround the outer periphery of the inner porcelain tube 8. That is, the inner porcelain tube 8 has a function as a support for the coiled heater 9.

As shown in FIG. 1, a header pipe 10 is provided outside the furnace wall 6 to distribute the gas evenly to the flow paths of the implanted gas, and the implanted gas is placed in the gas preheating chamber 5 in the outer porcelain. While passing through the flow path formed by the tube 7 and the inner porcelain tube 8, it is rapidly preheated by the heater 9 and driven into the furnace chamber 1 from the gas injection nozzle 4. The preheating temperature is preferably 1000 ° C. or more, which is equal to the furnace temperature. The speed is preferably about 1 to 10 m / second, and the amount of implanted gas is 4 to 5 m ³ / hr in this embodiment.

  The heater 9 preferably has a resistance value that does not change with temperature and changes with time, and therefore does not change the amount of heat generation. In this embodiment, a Fe—Cr—Al metal heater was used. The heater 9 used here has a shape in which two parallel coils are connected at an end portion as shown in FIG. 5, and an electrode 11 is arranged at the center of each coil. Therefore, as shown in FIG. 2, two gas injection nozzles 4 are paired, and each coil is arranged in the gas preheating chamber 5 of each gas injection nozzle 4.

  The continuous firing furnace of the present invention configured as described above stacks the products to be fired W on the base plate 2 and performs heat firing along a predetermined temperature curve while intermittently transporting the inside of the furnace chamber 1. Is what you do. Preheated nitrogen gas is multi-staged from a large number of gas injection nozzles 4 arranged on the left and right inner walls 3 at a position where the article to be fired W reaches a reaction temperature (for example, 1100 ° C.) and harmful gas is generated. The air is blown into the gaps between the stacked products to be fired W at a high speed, and the generated gas is discharged from the exhaust port 12 at the bottom of the ceiling to the outside of the furnace. For this reason, the fall of the calcination quality by the gas generated from the to-be-fired goods W can be prevented.

  The gas injected from each gas injection nozzle 4 is a gas embedded in the furnace wall and heated to a temperature substantially equal to the furnace temperature by the gas preheating chamber 5. That is, the gas distributed from the header pipe 10 provided outside the furnace wall 6 passes through the flow paths inside the outer porcelain pipe 7 and the inner porcelain pipe 8 that are doubly arranged inside the gas preheating chamber 5. In the meantime, it is rapidly preheated by the heater 9 and driven into the furnace chamber 1 from the gas injection nozzle 4. Because of such a structure, harmful gas generated from the product to be fired can be quickly discharged out of the furnace even in a high temperature range of 1000 ° C. or higher.

  In the present invention, the gas preheating chamber 5 is embedded in the furnace wall. For this reason, an extra space and ancillary equipment are not required outside, and the gas preheating chamber 5 can be accommodated inside the furnace wall having a thickness required for a normal furnace body. Further, since the gas preheating chamber 5 is provided for each gas injection nozzle 4, even when the amount of gas is reduced, the gas can be injected uniformly from each gas injection nozzle 4, and the gas temperature can be made uniform. it can. Further, since the implantation gas has an effect of cooling the furnace wall by heat exchange, the temperature rise on the outer surface of the furnace wall is suppressed, and heat loss can be reduced. Needless to say, the present invention is not limited to a base plate pusher furnace, and can be applied to various types of continuous furnaces.

It is sectional drawing which shows embodiment of this invention. It is a side view which shows arrangement | positioning of a gas implantation nozzle. It is sectional drawing of a gas preheating chamber. It is sectional drawing of the other direction of a gas preheating chamber. It is an external view which shows the shape of a heater.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Furnace room 2 Base plate 3 Inner side wall 4 Gas injection nozzle 5 Gas preheating chamber 6 Furnace wall 7 Outer porcelain tube 8 Inner porcelain tube 9 Heater 10 Header pipe 11 Electrode 12 Exhaust port

Claims (3)

  A number of gas injection nozzles are arranged on the inner wall of the furnace chamber to which the product to be fired is transferred, and a heater is provided in the furnace wall outside the gas injection nozzles along the flow path of the injection gas. A continuous firing furnace characterized in that the chamber is embedded.   2. The continuous firing furnace according to claim 1, wherein the gas preheating chamber is composed of a double porcelain tube constituting a flow path for the implantation gas, and a coil-shaped heater disposed therein. 2. The continuous firing furnace according to claim 1, wherein a header pipe is provided outside the furnace wall for evenly distributing the gas to the flow paths of each implantation gas.

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