JPH01316417A - Device for controlling dew point in atmospheric furnace - Google Patents

Abstract

PURPOSE:To precisely and freely control dew point in a furnace by arranging supplying devices for dry gas and wet gas, and a means for controlling the feeding volume for dry gas and wet gas based on difference between the setting dew point and the actual dew point in a ceramic sintering furnace. CONSTITUTION:In a hausing 11 of the heating furnace 1 for using to the ceramic sintering, etc., Mo-made electric resistant body 12 is inserted and electricity is conducted from the electric source 13 and heated to sinter the ceramic part in the furnace. In this case, the gas pressure in the furnace is held to 0.1 atm and the dew point is held to -40 deg.C. To this purpose, one end 21 of a dew point meter 2 is inserted in the furnace and the electric output 22 from the outer end is inputted to a control device 5 and compared with the setting dew point, and by controlling a flow meter 3 for the dry gas 6 or a flow meter 8 for the wet gas 7 having the gas supplying rate adjusting means 31, 41, the dry gas 6 or the wet gas 7 is supplied in the hausing 11 of the furnace from supplying hole 14 and adjusted so that the atmospheric gas in the hausing 11 becomes the setting dew point, to improve the product yield for the ceramic sintered material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for controlling the dew point (saturated water vapor pressure temperature) in an atmospheric furnace.

[Prior art] For firing ceramics, brightening stainless steel, firing sintered metals, etc., the atmosphere must be an inert gas such as argon or helium, ammonia decomposition gas, a reducing gas such as hydrogen, or a non-containing gas such as nitrogen. A continuous furnace containing oxidizing gas is used. Conventionally, in order to adjust the dew point inside the atmosphere furnace, drying gas with a low dew point is supplied into the furnace, and the workpieces entering the furnace are preheated to prevent dew condensation from forming on the workpieces inside the furnace. Various methods have been proposed to prevent product quality from deteriorating. In these conventional technologies, the main focus was on controlling the temperature inside the furnace in order to improve the quality of the product being processed, and the dew point adjustment was only concerned with preventing dew condensation on the processed material inside the furnace. .

[Problems to be Solved by the Invention] However, the inventor believes that for processing objects to be processed in an atmosphere furnace, especially for sintering ceramics, it is necessary to accurately and freely control the dew point in the furnace to achieve uniform yield. It was found that the dew point inside the furnace is influenced to a large extent by the humidity and temperature of the outside air.

An object of the present invention is to provide a dew point control device for an atmospheric furnace that can precisely and freely control the dew point inside the furnace.

1. Means for Solving the Problems] In order to achieve the above object, the present invention provides a drying gas supply means for supplying drying gas into an atmospheric furnace, a means for regulating the supply amount of the drying gas, and the atmospheric furnace. a humid gas supply means for supplying humid gas at a predetermined dew point into the atmosphere furnace; a means for adjusting the supply amount of the humid gas; a dew point meter for detecting the dew point in the atmospheric furnace; and a dew point setting means in the atmospheric furnace. , a control means that receives outputs from the dew point meter and the dew point setting means and operates the dry gas supply amount adjustment means and the wet gas supply amount adjustment stage f=, the control means is configured to control the dew point meter. If there is a difference between the dew point in the atmospheric furnace detected by the dew point and the humidity set by the dew point setting means, the dry gas supply amount adjusting means or the moist gas supply amount adjusting means is controlled so as to eliminate the difference. The configuration was adopted.

[Actions and Effects of the Invention] The dew point control device for an atmospheric furnace of the present invention produces the following actions and effects.

■The atmosphere furnace has supply flow rates of dry gas with a low dew point and wet gas with a high dew point, and each of these adjustment means is controlled by a control means so as to eliminate the difference between the preset dew point and the measured dew point meter. is controlled by. Therefore, the dew point in the atmosphere furnace can be precisely and freely controlled with a simple configuration. Furthermore, it is easy to constantly maintain the dew point at a certain set value below 0° C., which was difficult with the prior art.

■Since the dew point inside the atmospheric furnace can be controlled to the set dew point, it is less affected by the humidity and temperature outside the furnace.

[Embodiment 1] Next, the present invention will be explained based on a first embodiment shown in FIGS. 1 and 5.

The atmospheric furnace dew point control device HN of the present invention includes a dew point meter 2 with an electric output 22 mounted at a predetermined position inside the furnace body 1.
, a flow meter 3.4, a control means 5, a dry gas supply means 6, and a wet gas supply means 7.

In this embodiment, the furnace body 1 is a semi-sealed batch type furnace, which is formed of a stainless steel housing 11, has an electric resistor 12 made of molybdenum disposed therein, is energized by an energizing means 13, and is energized at 1000 m Heating is performed to around 0.degree. C., and atmospheric gas is passed through the atmosphere supply port 14. Here, the furnace body 1. The gas pressure inside the mouthpiece is 0.1 atm and the dew point is maintained at -40°C (dew point setting means).

The dew point meter 2 has one end 21 connected to the furnace body 1 in order to measure the dew point.
The electrical output 22 is taken out from the other end and input to the control means 5. Also, this dew point meter 2 is -70℃
It has a measurement range of ~60°C.

The flow meter 3.4 has an accuracy of 0.1 m'/hr and is equipped with mass flow control means 31.41 for each gas. A dry gas supply means 6 and a wet gas supply means 7 are connected to one end of the flowmeter 3.4, respectively. The other end of the flow rate d3.4 is connected to the atmosphere supply port 14 in the furnace body 1 after being connected.

The control means 5 controls the electrical output 22 from the other end of the dew point meter 2.
Based on this, mass flow control of the flowmeter 3.4 is performed by PID control, and the flow rates of dry gas and wet gas are controlled. The dry gas supply means 6 is a high-pressure hydrogen gas cylinder filled with hydrogen gas having a dew point of 165° C. and a purity of 99.99% or more.

The moist gas supply means 7 is a high-pressure hydrogen gas cylinder filled with hydrogen gas having a dew point of 35° C. by humidifying hydrogen gas with a purity of 99.99% or more.

The atmospheric furnace dew point control device ff1N of the present invention controls the dew point of the furnace in the following manner.

(2) While heating the electric resistor 12 of the furnace body 1 with the current supply means 13, the drying gas supply means 6 introduces 1 m'/hr to maintain the temperature at 1000°C, and stabilize the dew point at -44°C.

(2) Operate the wet gas supply means 7, flow meter 4, and control means 5 to perform PID control.

In this example, the dew point stabilized at -40°C 7 minutes after starting PID control, and the change in dew point for the next 23 minutes was ±2.
Can be kept within ℃. (For comparison, if the above-mentioned step (2) is not carried out and only the drying gas is continued to flow, the dew point continues to fall and reaches -48°C after 30 minutes, as shown by the broken line in Figure 4.) The two examples are shown in Figures 1 and 6.
This will be explained with figures.

This configuration is the same as the first embodiment.

In this embodiment, the dew point of the furnace is controlled by the following method.

(2) Maintain the inside of the furnace at 1150°C, operate only the drying gas supply means 6 for 24 hours, and bring the dew point to around -54°C.

■ Operate the wet gas supply means 7, flow meter 4, and control means 5 to perform PID control. Here, the total supply amount of dry gas and wet gas is 1 m3/hr, and the temperature inside the furnace is 1000°C.
to hold.

In this embodiment, the dew point stabilizes at -40°C 7 minutes after starting PID control.

Next, a third embodiment of the present invention is shown in FIGS. 1, 7, and 8.
This will be explained with figures.

This configuration is the same as the first embodiment.

In this embodiment, the dew point of the furnace is controlled by the following method.

As shown in Figure 8, the temperature of the furnace was raised to 800℃.
PID control is performed from the moment the furnace temperature reaches 10
Hold at 00°C.

In this example, the dew point reaches the set value of -40°C 9 minutes after the start of control, and the change over the next 20 minutes is ±2.
It was within ℃.

Next, a fourth embodiment of the present invention will be described based on FIGS. 2 and 9.

The dew point control device G for an atmospheric furnace of the present invention includes a dew point meter 2 with an electric output 22 mounted at a predetermined position inside the furnace body 1.
, solenoid valves 3A, 4A, control means 5, dry gas supply means 6, and wet gas supply means 7.

The solenoid valves 3A and 4A are electromagnetic valves that are opened and closed by energization.

The control means 5A receives the electric output from the dew point meter 2, performs PID control, and outputs 0N to the solenoid valves 3A and 4A.
10FF control signal is output.

In this example, the temperature of the furnace is raised, and from the time when the temperature inside the furnace reaches 800°C, the ON1 is used to alternately flow dry gas and wet gas.
0 F F control is performed, and the temperature inside the furnace is maintained at 1000°C.

10 minutes after the start of control, the set value of -40℃ is reached,
After that, all changes during the next 20 minutes were within 0°C±3°C. Since solenoid valves 3A and 4A are used, the batch type furnace has a lower cost I compared to the first to third embodiments.
・Can be done cheaply.

Next, a fifth embodiment of the present invention will be described based on FIGS. 3 and 10.

The dew point control device l (for an atmospheric furnace of the present invention) includes a dew point meter 2 with an electric output 22 mounted at a predetermined position inside the furnace body 1, a control means 5, a dry gas supply means 6, and a moist gas It consists of a supply means 7 and a three-way valve 8.

The three-way valve 8 is electromagnetic and its opening degree is adjusted by the control means 5.

In this embodiment, the dew point of the furnace is controlled by the following method.

When the furnace temperature reaches 800℃, P
ID control is performed to maintain the furnace temperature at 1000°C.

Six minutes after the start of control, the set value of -40°C was reached, and the change over the next 24 minutes was within 13°C.

In addition, in the first to fifth embodiments, when the weather is clear, the temperature is 2.
The cleaning was carried out under the environmental conditions of 5° C. and 55% humidity (at the end of cleaning).

Next, a sixth embodiment of the present invention will be described based on FIG. 4.

The dew point control device for an atmospheric furnace of the present invention includes a dew point meter 2 with an electric output 22 mounted at a predetermined position inside the furnace main body IA, flowmeters 3B and 4B, a control means 5, and a dry gas supply. It consists of a means 6, a humid gas supply means 7, and a carrier gas supply means 9.

The furnace body IA is a continuous atmosphere furnace and includes a heating section 10, a cooling section 25, and a driving section 35.

The heating section 10 has an electric resistor 12 arranged in a coil shape inside a pine full case 11A made of stainless steel, a mesh belt 15 is wrapped around the inside, an atmosphere supply port 14 is provided on the upper center surface, and an inlet 16 of the heating section 10 is provided. , and the outlet 17 are formed with carrier gas supply ports 18 and 19, respectively. Note that the pressure inside the furnace is atmospheric pressure, and the target value of the dew point is set at -35°C.

The cooling section 25 cools the heating section outlet 17 by supplying cooling water from an inlet [ ] 26 and an outlet 27 .

The driving unit 35 drives the mesh belt 15 made of stainless steel and having a total length of 301 mm by means of a belt driving device 38 and a belt driving drum 36, 37 at a speed of 10 cm per second.

The dry gas supply means 6 and the wet gas supply means 7 supply gas at a total rate of 10 m'/hr (using a flow meter with an accuracy of 0.5 m'/hr).

Flowmeters 3B and 4B have an accuracy of 0.5 m'/hr,
The meter is equipped with mass flow control means 31, 41 for each gas. A dry gas supply means 6 and a wet gas supply means 7 are connected to one ends of the flowmeters 3B and 4B, respectively. The other ends of the flowmeters 3B and 4B communicate with the atmosphere supply port 14 of the connected after-furnace main body IA.

The carrier gas supply means 9 supplies nitrogen gas having a dew point of 170 DEG C. to the carrier gas supply ports 18 and 19 at a rate of 12 m'/hr.

In this embodiment, the dew point of the furnace is controlled by the following method.

■Keep the temperature inside the furnace at 1150℃ and mesh belt 15
The inside of the furnace is cleaned for four days using the drying gas supply means 6 and the carrier gas supply means 9 without turning the switch, and then the temperature inside the furnace is lowered to 1050°C and the dew point is lower than the set value (
In this example, the temperature is -45°C.

(2) While maintaining the furnace temperature at 1050° C., the wet gas supply means 7, flowmeters 3B and 4B, and control means 5 are operated to perform PID control.

In this example, the conditions of clear skies, temperature of 22°C, and humidity of 58% (
20 minutes after the start of control, the set value of -35°C was reached, and the change over the next 10 hours was within ±3°C.

Next, a seventh embodiment of the present invention will be described with reference to FIG.

This configuration and furnace dew point control are the same as in the sixth embodiment.

In this example, the conditions of rainy weather, temperature of 20°C, and humidity of 89% (
At the end of cleaning), the initial dew point was -39℃, but 15 minutes after the start of control, it returned to the set value of -35℃.
was reached, and the change over the subsequent 10 hours was within ±3°C.

The present invention includes the following embodiments in addition to the above embodiments.

a. In the first to fourth embodiments, the dry gas is always allowed to flow, and the wet gas flow (by opening and opening of the valve)
(including control by N10FF).

b. The atmospheric gases to be circulated may include carbon oxide (CO), carbon dioxide (CO2), ammonia (NHl), oxygen (02), argon (Ar), depending on the desired heat treatment application.
, various chlorinated gases, etc. may be used as appropriate.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of the first to third embodiments of a dew point control device for an atmospheric furnace according to the present invention. FIG. 2 shows a schematic configuration diagram of a fourth embodiment of the dew point control device for an atmospheric furnace of the present invention. FIG. 3 shows a schematic configuration diagram of a fifth embodiment of the dew point control device for an atmospheric furnace of the present invention. FIG. 4 shows a schematic diagram of the sixth and seventh embodiments of the dew point control device for an atmospheric furnace of the present invention. FIG. 5 is a graph showing the dew point control state of the first embodiment. FIG. 6 is a graph showing the dew point control state of the second embodiment. FIG. 7 is a graph showing the dew point control state of the third embodiment. FIG. 8 is a graph showing the temperature inside the furnace and the passage of time in the third embodiment. FIG. 9 is a graph showing the dew point control state of the fourth embodiment. FIG. 10 is a graph showing the dew point control state of the fifth embodiment. In the diagram: N, G, N, L... Dew point control device for atmospheric furnace
1... Furnace body (atmosphere furnace) 2... Dew point meter 5...
- Control means 6...Dry gas supply means 7...Moist gas supply means 22...Electric output (output from the dew point meter) 31.41...Mass flow control means (supply amount adjustment means)

Claims (1)

[Claims] 1) a dry gas supply means for supplying dry gas into the atmospheric furnace; a means for adjusting the supply amount of the dry gas; a moist gas supply means for supplying moist gas at a predetermined dew point into the atmospheric furnace;
A supply amount adjusting means for the moist gas, a dew point meter for detecting the dew point in the atmospheric furnace, a dew point setting means in the atmospheric furnace, and outputs from the dew point meter and the dew point setting means are input, and the drying A control means for operating a gas supply amount adjustment means and a humid gas supply amount adjustment means, the control means being configured to adjust the dew point in the atmospheric furnace detected by the dew point meter and the humidity set by the dew point setting means. A dew point control device for an atmospheric furnace that controls the dry gas supply amount adjusting means or the wet gas supply amount adjusting means so as to eliminate the difference when there is a difference.