JPH06159952A - Batch type baking furnace - Google Patents

Abstract

PURPOSE:To efficiently purge gas contained in a fibrous insulating material of a furnace by a method wherein a cavity is provided between a casing and the insulating material and an atmospheric gas feed port is opened up to the cavity. CONSTITUTION:When the furnace temperature reaches a heat-treatment temperature, heat-treatment is carried out at this temperature while an atmospheric gas is fed at a specified flow rate for a specified period of time. After that, an on-off valve 7 of an exhaust pipe 8 is opened when the furnace temperature rises further, and an atmospheric gas having a low oxygen concentration is fed into the furnace from an air supply device. However, the supply gas pressure is increased for a specified period of time to purge oxygen contained in a fibrous insulating material 2. After that, the on-off valve 7 is closed and heat- treatment takes place after the gas supply pressure is regulated so that the differential pressure returns to the initial level again. Hereafter, heat treatment is similarly carried out under pre-programed conditions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a batch type firing furnace in which a fibrous heat insulating material is placed inside a casing and an atmosphere gas having a predetermined composition is supplied to perform firing.

[0002]

2. Description of the Related Art Conventionally, for example, when firing electronic ceramics such as Mn.Zn-based ferrite or fine ceramics in a batch-type firing furnace such as an elevating furnace or a truck furnace, the atmosphere is changed according to the firing temperature. Baking is performed by changing the gas from an oxidizing atmosphere to a non-oxidizing atmosphere.

Such switching of the oxygen concentration in the atmosphere gas can be achieved relatively easily by simply changing the composition of the supply gas in the case of the conventional batch-type firing furnace using a brick heat insulating material. In the case of a batch-type firing furnace that uses a fiber-based heat insulating material, the atmospheric gas is stored in the fiber-based heat insulating material, so even if the concentration of the supply gas is changed, the oxygen gas stored in the fiber-based heat insulating material is changed. However, there is a problem that the responsiveness is poor due to the gradual bleeding, especially when the oxygen concentration is set to a very low value of 1000 ppm or less, it takes a long time to reach the predetermined oxygen concentration. It was

FIG. 2 is a cross-sectional view schematically showing such a conventional cylindrical lifting type batch furnace, in which a fiber type heat insulating material 2 is arranged inside a casing 1 having a lower opening and a lower opening portion. Is configured so that a similar fibrous heat insulating material 2 is placed on the upper surface thereof, and a hearth trolley 5 holding a hearth plate 4 is fitted thereto via a pillar 3.

Gas inlets G are opened in the upper, side and lower parts of the furnace body, and a heater 6 is inserted through the upper part of the furnace body in the furnace. An exhaust pipe 8 having an opening / closing valve 7 is opened in the upper part. Reference numeral 9 is a terminal box, and 10 is a product to be fired.

In such a conventional batch type firing furnace, in order to avoid the above-mentioned problems, the operator empirically adjusts the supply amount to match the oxygen concentration of the atmosphere with the atmospheric temperature. In such a method, there is a problem that not only the adjustment takes time, but also the concentration distribution of the atmospheric gas is generated and the temperature in the vicinity of the article to be fired 10 and the oxygen partial pressure do not match and the yield of the fired article is reduced.

[0007]

As described above, in the conventional batch type firing furnace, the atmosphere is adjusted by the experience of the operator, so not only the adjustment takes time, but also the oxygen concentration distribution of the atmosphere gas is generated. There has been a problem that the yield of the fired product is lowered because the oxygen concentration does not match the temperature near the fired product.

The present invention has been made to solve such a conventional problem. When changing the composition of the atmosphere in the furnace, it is possible to quickly purge the atmospheric gas of the composition before the change, which is held in the fiber type heat insulating material. This makes it possible to match the temperature in the vicinity of the product to be fired with the composition of the atmospheric gas in a short time, thereby significantly reducing the firing lead time and providing a batch-type firing furnace in which the yield of fired products is improved. The purpose is to

[0009]

A batch type firing furnace of the present invention is a firing furnace in which a fiber type heat insulating material is arranged inside a casing and an atmosphere gas having a predetermined composition is introduced into the casing for firing. In the furnace, a space is provided between the casing and the fiber-based heat insulating material, an atmosphere gas supply port is opened in the space, and the atmosphere gas is passed from the space through the fiber-based heat insulating material. It is characterized in that it is configured to supply to.

In the batch-type firing furnace of the present invention, in order to automatically control the flow rate of the atmospheric gas, a differential pressure detecting device for measuring the differential pressure between the atmospheric gas in the void and the furnace, and the output of the differential pressure detecting device. It is desirable to provide a flow rate control device that controls the supply flow rate of the atmospheric gas by a signal. In this case, the relationship between the differential pressure and the ventilation resistance of the fiber-based heat insulating material and the optimum flow rate at this time are measured in the field in advance and input to the arithmetic unit.

Further, as another means for automatically controlling the flow rate of the atmospheric gas, a differential pressure detecting device for measuring the differential pressure of a specific component gas of the atmospheric gas, for example, oxygen, in the void and the furnace, and the differential pressure detection. A flow rate control device for controlling the supply flow rate of the atmospheric gas according to the output signal of the device may be provided. As the differential pressure detecting device for measuring the differential pressure of the component gas, for example, a device in which an oxygen concentration sensor for detecting the oxygen concentration is arranged at each position and the difference output of these sensors is used can be used.

When the flow rate is controlled by this method, the atmosphere in the furnace is directly controlled, so that more precise control can be performed.

[0013]

In the present invention, the composition of the atmospheric gas is changed when the temperature in the furnace reaches a predetermined temperature. At this time, however, the atmospheric gas passes through the fibrous heat insulating material and is supplied into the furnace. The atmospheric gas of the previous composition contained in the fiber heat insulating material is efficiently purged and is supplied from a wide surface of the fiber heat insulating material, so that the concentration distribution of the atmospheric gas occurs in the furnace. There is no.

Further, when the supply gas flow rate control device for increasing the supply amount of the ambient gas is provided at the time of switching the ambient gas, the gas retained in the fiber type heat insulating material is purged in a shorter time. In addition, the composition of the atmospheric gas can be precisely adjusted.

[0015]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows a cylindrical lifting type batch furnace according to an embodiment of the present invention, and the portions common to those in FIG. 2 are designated by the same reference numerals.

This batch furnace has a casing 1 open at the bottom.
The metal wire mesh 12 made of stainless steel is disposed inside the metal mesh 12 so that a space S is formed between the metal wire mesh 12 and the casing 1 via the stud bolt 11, and the fiber heat insulating material 2 is fixed on the metal wire mesh 12. . A stainless steel wire net 12 is arranged inside the terminal box 9 at the upper part, and the fiber-based heat insulating material 2 is fixed on the wire net 12. A hearth trolley 5 having a fiber-based heat insulating material 2 arranged inside is fitted into the lower open portion. This fiber-based heat insulating material 2 is also provided on the hearth trolley 5 through a stud bolt 11 to form a gap. It is fixed on a stainless steel wire mesh 12 arranged so that S is formed. Also,
A hearth plate 4 is held on the fiber-based heat insulating material 2 on the hearth trolley 5 via columns 3.

Further, a gas supply port G is opened in each of the upper, side and lower voids S of the furnace body,
Further, a heater 6 is inserted through the upper part of the furnace body in the furnace, and an exhaust pipe 8 having an opening / closing valve 7 is opened in the upper part of the furnace body.

In this embodiment, the pressure sensor 13 is arranged in each of the voids S in the upper, side and lower parts of the furnace body, and the pressure introducing pipe opening in the vicinity of the hearth plate 4 is also provided in the furnace. 14 is inserted, and a pressure sensor (not shown) is arranged at the base. The differential pressure oscillator 15 detects the differential pressure of the pressure sensor 13 of each void S and the differential pressure of the pressure sensor of the pressure introducing pipe 14, and outputs a differential pressure signal to the flow rate calculating device 16.
Output to. The flow rate calculation device 15 controls the air supply device (mass flow controller) 17 that supplies the atmosphere gas whose concentration is adjusted to each gas air supply port G, and also the exhaust pipe 8
Control the opening and closing of. Although not shown, a nitrogen gas cylinder and an oxygen gas cylinder are connected to the gas supply device 17 to adjust an atmospheric gas having a predetermined oxygen partial pressure, and the atmospheric gas is supplied to each gas supply port G. Further, when the temperature inside the furnace reaches a predetermined temperature set in advance by a temperature sensor (not shown), gases with different oxygen partial pressures are adjusted and supplied to each gas supply port G. It has become.

The batch type firing furnace of this embodiment is used as follows.

First, by a conventional method, the article to be fired 10, for example, Mn.Zn-based ferrite parts are arranged on a suitable holding plate in multiple stages on the hearth plate 4 and inserted from below the furnace body. Next, the open / close valve 7 of the exhaust stack 8 is opened, and the atmosphere gas having a high oxygen concentration (mixed gas of nitrogen gas and oxygen gas) is supplied from the air supply device 17 into the space S at a constant pressure. The atmospheric gas supplied to the void S passes through the inside of the fiber-based heat insulating material 2 to replace the air inside the furnace. However, since the fiber-based heat insulating material 2 has ventilation resistance, the pressure of the supplied atmospheric gas is , Is supplied into the furnace at a pressure higher than atmospheric pressure.

At this time, the differential pressure oscillator 15 detects the internal pressure of the furnace and the internal pressure of the void S and outputs a differential pressure signal to the flow rate calculating device 16.
Then, the flow rate calculation device 16 supplies a control signal to the air supply device 16 so as to obtain a predetermined pressure difference, and adjusts the supply gas amount so as to maintain a constant flow rate. When the temperature reaches a constant heat treatment temperature, the heat treatment is performed while the atmospheric gas is supplied at this temperature for a predetermined time at a constant flow rate. After that, the furnace temperature is further increased, the on-off valve 7 of the exhaust stack 8 is opened, and the atmosphere gas having a low oxygen concentration is supplied from the air supply device 17 into the furnace. In order to purge the retained oxygen, the gas supply pressure is raised for a certain period of time.
After that, the on-off valve 7 is closed, the gas supply pressure is adjusted again to the original differential pressure, and the heat treatment is performed. Thereafter, the heat treatment is similarly performed under the pre-programmed conditions.

By the way, according to this embodiment, when the oxygen concentration of the atmosphere gas was reduced from 10.000 ppm to 100 ppm, the purge time could be reduced to 1/5 of the conventional time.

In the above embodiment, a differential pressure detecting device for measuring the differential pressure between the void S and the atmospheric gas in the furnace is provided, and the supply flow rate of the atmospheric gas is controlled by the output signal of this differential pressure detecting device. Although an example of doing so has been described, the present invention is not limited to this, and for example, by providing a differential pressure detection device that measures the differential pressure between the void S and a specific component gas of the atmospheric gas in the furnace, such as oxygen, The supply flow rate of the atmospheric gas may be controlled by the output signal of the pressure detection device.

In this case, since the oxygen concentration can be directly controlled, the atmosphere can be controlled with higher accuracy, so that the yield of the fired product can be further improved and the firing lead time can be greatly shortened.

[0026]

By using the batch type firing furnace as described in detail above, the following excellent effects can be obtained.

The gas held in the furnace body heat insulating material can be efficiently purged.

It is possible to make the concentration distribution of the atmosphere in the furnace uniform.

The atmosphere adjustment time can be shortened.

Further, as shown in the embodiment, a differential pressure detecting device for measuring the differential pressure between the void S and the atmosphere gas in the furnace, and a differential pressure for measuring the differential pressure between a specific component gas such as oxygen. When a detection device is provided, the operation is very easy and automation is possible, and the amount of atmospheric gas used can be reduced. The atmosphere reproducibility and accuracy are remarkably improved without being affected by the furnace volume and the thickness of the heat insulating layer.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a cylindrical lifting batch furnace of the present invention.

FIG. 2 is a cross-sectional view schematically showing a conventional cylindrical lifting type batch furnace.

[Explanation of symbols]

1 ... Casing, 2 ... Fiber insulation, 3 ... Strut,
4 ... hearth plate, 5 ... hearth truck, 6 ... heater, 7 ...
On-off valve, 8 ... Exhaust pipe, 9 ... Terminal box, 10 ... Product to be fired, 11 ... Stud bolt, 12 ... Wire mesh, 13 ...
... pressure sensor, 14 ... pressure introduction pipe, 15 ... differential pressure oscillator, 16 ... flow rate calculation device, 17 ... air supply device, S
…… Void area, G …… Gas inlet.

Claims (3)

[Claims] 1. A firing furnace in which a fibrous heat insulating material is disposed inside a casing and an atmosphere gas having a predetermined composition is introduced into the interior of the casing to perform firing, and between the casing and the fibrous heat insulating material. It is characterized in that a void is provided, an atmospheric gas supply port is opened in the void, and the atmospheric gas is passed through the fiber insulating material from the void and supplied into the furnace. Batch type firing furnace. 2. A differential pressure detecting device for measuring a differential pressure between the atmosphere gas in the void and the furnace, and a flow rate control device for controlling a supply flow rate of the atmospheric gas by an output signal of the differential pressure detecting device. The batch type firing furnace according to claim 1, wherein 3. A differential pressure detecting device for measuring a differential pressure of a specific component gas of the atmospheric gas in the void and the furnace, and a flow rate control for controlling a supply flow rate of the atmospheric gas by an output signal of the differential pressure detecting device. The batch-type firing furnace according to claim 1, further comprising a device.