JPH03287020A - Method and device for liquid level detection - Google Patents

Abstract

PURPOSE:To improve the detection accuracy of a liquid level by dipping a couple of electrodes for level detection in a conductive molten body and measuring the resistance between those electrodes. CONSTITUTION:The couple of electrodes 1 for level detection are dipped in the conductive molten body G. A resistance measuring means 2 measures the resistance Ra between those electrode measuring means 2 measures the resistance Ra between those electrodes 1. Resistance information (including voltage and current information corresponding to resistance in addition to the resistance) obtained by the means 2 is converted by a liquid level determining means 3 into liquid level information. Consequently, the liquid level of even the conductive molten body in a sealed container like a vacuum degassing furnace can be detected with extreme accuracy.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a liquid level detection method and device for detecting the liquid level of a conductive melt such as molten glass or molten metal, and in particular, to The present invention relates to an effective liquid level detection method for detecting the liquid level of a conductive melt in a closed container such as a defoaming furnace, and improvements to the device.

[Conventional technology]

Generally, a vacuum degassing furnace for molten glass (for example,
No. 4205), in order to obtain homogeneous glass and to keep the flow rate of glass constant, which affects the weight of the product, it is necessary to operate while keeping the liquid level of the introduced molten glass constant. .

Under such demands, the usual method is to install a liquid level gauge to monitor the liquid level and control the amount of molten glass introduced based on the signal from this liquid level gauge. It will be done.

In this case, the liquid level gauge is equipped with a detection circuit that takes advantage of the fact that molten glass is a conductor, opens when the glass liquid level and the level sensor conductor are not in contact, and closes when they make contact. It is possible to employ a device in which the liquid level is detected by opening and closing a detection circuit (Japanese Patent Publication No. 57-59216).

[Problem to be solved by the invention]

By the way, in the above-mentioned vacuum degassing furnace, a phenomenon occurs in which ions are generated along with bubbles during the degassing process, and the ions fill the vacuum housing.

In this case, if the liquid level gauge described above is adopted, even if the level sensor conductor does not contact the glass liquid surface, the glass liquid surface and the level sensor conductor will be connected to each other through the ions in the vacuum housing. There is a risk that the detection circuit will be closed due to a short circuit, resulting in erroneous detection of the liquid level.

In addition, as another example of a liquid level gauge, there is a device that guides light or ultrasonic waves to the liquid level.
A method that detects the liquid level based on the reflection information is conceivable, but light and ultrasonic waves are diffusely reflected due to fluctuations in the liquid level and the presence of bubbles on the liquid surface. The problem remains that the liquid level is easily detected incorrectly.

This invention was made based on the above points of view, and it is possible to extremely accurately detect the liquid level of conductive melt in a closed container such as a vacuum degassing furnace. The present invention provides a method and device for detecting a liquid level.

[Means to solve the problem]

That is, in the liquid level detection method according to the first method invention, when detecting the liquid level of a conductive melt, a pair of level detection electrodes is immersed in the conductive melt, and a distance between the level detection electrodes is The resistance of the tank is measured, and the liquid level is detected based on this resistance change.

This type of method invention is effective when the temperature conditions and composition conditions of the conductive melt to be detected are uniquely determined in advance, and the level detection electrode is immersed in the conductive melt to be detected. The dimensions may be selected as appropriate depending on the liquid level range to be detected, or at least the correspondence between the resistance value between the level detection electrodes and the liquid level may be specified in advance and the corresponding relationship determined. It is necessary to determine the liquid level based on the relationship.

In addition, when detecting the conductivity of a vacuum degassing furnace or the liquid level of a conductive melt such as glass, it is said that the effect of resistance changes due to ions filling the vacuum defoaming furnace is reduced. From this point of view, it is preferable to insulate the area other than the detection part of the level detection electrode, and in order to maintain insulation more reliably, it is particularly preferable to insulate it with an insulating stepped double tube.

The method invention described above includes a pair of level detection electrodes 1 immersed in a conductive melt G, and a resistance Ra between the level detection electrodes 1, as shown in FIG.
a resistance measuring means 2 that measures the resistance, and a liquid level that converts the resistance information measured by the resistance measuring means 2 (including the resistance itself, as well as voltage and current information corresponding to the resistance) into liquid level information. The present invention is embodied in a device invention comprising determining means 3.

In addition, the liquid level detection method according to the second method invention devised to further improve the detection accuracy of the liquid level is as follows:
When detecting the liquid level of a conductive melt, a pair of level detection electrodes is immersed in the conductive melt, the resistance between the level detection electrodes is measured, and the temperature of the conductive melt is determined from the resistance. After removing and correcting the resistance change between the level detection electrodes due to the change and composition change, the liquid level is detected based on the corrected resistance change between the level detection electrodes.

This type of method invention is effective when the temperature and composition conditions of the conductive melt to be detected change.
Regarding correction processing of the resistance between the level detection electrodes, for example, correction conditions are determined in advance for each change in the temperature conditions and composition conditions of the conductive melt to be detected, and the level detection electrodes are adjusted in accordance with each correction condition. Something that corrects the resistance between
As a concrete implementation example system, for example, by inputting the temperature conditions and composition conditions of the conductive melt to be detected into a microcomputer, etc., an electric correction resistor (simulated dummy An example of this method is to create a resistance (resistance) and correct the resistance between the level detection electrodes based on this. ] etc., but if there are relatively many variations in the temperature conditions and composition conditions of the conductive melt to be detected, the temperature conditions and composition conditions of the conductive melt to be detected may be modified as appropriate. It is preferable to adopt an apparatus configuration that allows changes in to be naturally canceled.

From this point of view, an apparatus invention embodying the above-mentioned method invention is, for example, as shown in FIG. 1(b).
A pair of level detection electrodes 1 immersed in the conductive melt G, and a pair of level detection electrodes 1 immersed in the conductive melt G to correct resistance changes between the level detection electrodes 1 due to temperature changes and composition changes of the conductive melt G. the correction electrode 4, and the level detection electrode l.
and a correction resistance measuring means that measures the resistances Ra and Rb between the correction electrode 4 and obtains a correction resistance Ra from which resistance changes due to temperature changes and composition changes of the conductive melt G are removed from both resistances Ra and Rb. 5 and the correction resistance R1 information measured by this correction resistance measuring means 5 (in addition to the resistance itself,
(including voltage and current information corresponding to the resistance) into liquid level information.

In such a device invention, the pair of correction electrodes 4
As long as it can be obtained as a semi-fixed material whose inter-electrode resistance does not affect changes in the liquid level, it may be selected as appropriate. In this case, specific ways to make the interelectrode resistance semi-fixed include, for example, making the electrode detection part spherical or cylindrical and setting its outward beak to be large, or A pair of rod-shaped electrodes may be inserted from the side wall of the storage case, etc., as appropriate.

In addition, in the case of detecting the liquid level of a conductive melt such as conductive molten glass in a vacuum degassing furnace, the correction electrode 4 is also insulated except for the detection part of the correction electrode 4. In order to maintain insulation properties more reliably, it is particularly preferable to cover the tube with an insulating stepped double tube.

Furthermore, as shown in FIG. 1(a) or FIG. 1(b), regarding the detection data of the liquid level detection device according to the present invention, the conductive melt is It is used as appropriate to control the supply amount of G and the temperature of the conductive melt G, but from the perspective of further improving the accuracy of monitoring the liquid level, it is important to detect the liquid level. It is preferable to add a display means 7 that allows data to be read directly.

[Effect]

According to the first liquid level detection method and device, when the liquid level of the conductive melt G changes, the resistance R between the pair of level detection electrodes 1 immersed in the conductive melt G
a changes in a predetermined relationship.

Therefore, if the state of change in the resistance Ra is accurately grasped, the level of the conductive melt G can be uniquely detected.

Further, according to the second liquid level detection method and device, when the liquid level of the conductive melt G changes, the gap between the pair of level detection electrodes 1 immersed in the conductive melt G changes. The resistance Ra changes according to a predetermined relationship, and the value of the resistance Ra includes a resistance change Rb due to changes in the temperature conditions and composition conditions of the conductive melt G.

Therefore, by removing and correcting the resistance change Rb from the resistance Ra, a correction resistance R1 between the level detection electrodes 1 that is not affected by changes in the temperature conditions and composition conditions of the conductive melt G can be obtained.

Therefore, if the state of change of the correction resistance R1 is accurately grasped, the liquid level of the conductive melt G will be almost unaffected by changes in the temperature conditions and composition conditions of the conductive melt G. Uniquely detected.

[Embodiments] Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

◎Example 1 1. Overview of liquid level detection system Figure 2 shows the application of this invention to a vacuum degassing furnace for degassing molten glass G.

In the figure, a vacuum degassing furnace 10 has a vacuum housing 11 made of stainless steel that is vacuum-suctioned by a vacuum pump (not shown), and a vacuum degassing tank 1 is housed in the vacuum housing Il.
2 is arranged.

A riser pipe 13 made of platinum is connected to the bottom side of the vacuum degassing tank I2, and a downcomer pipe 14 made of platinum is also connected to the other side of the vacuum degassing tank, The lower ends of the rising pipe 13 and the descending pipe 14 are immersed in molten glass in a pre-processing storage tank and a post-processing storage tank (not shown). In addition, the above-mentioned vacuum degassing tank 12
are separately arranged into three tanks 12a, 12b, and 12c which are sequentially connected in order to prevent generated bubbles from following and moving.

In this embodiment, the third tank 12 of the vacuum degassing tank 12
A liquid level sensor 20 is disposed at a location corresponding to c, and a signal from this liquid level sensor 20 is processed by a liquid level detection system 30.

(2) Liquid Level Sensor FIGS. 3 and 4 show details of the liquid level sensor 20.

In this embodiment, as shown in FIG. 3, the liquid level sensor 20 includes a pair of rod-shaped electrodes 21 made of platinum wire, for example, on a sensor substrate 23 (see FIG. 2) disposed outside the vacuum housing 11. .22 are attached with caps spaced apart from each other by a predetermined distance, and the tips of the electrodes 21 and 22 are exposed in the vacuum housing 11 and immersed in the molten glass G by a predetermined distance.

In particular, in this embodiment, one electrode 22 is arranged to protrude downward from the other electrode 21 by ΔE (about 5 degrees in this embodiment). This is intended to be used as an on/off level meter for the liquid level when one electrode 22 is in contact with the molten glass G and the other electrode 21 is out of contact with the molten glass G. The purpose is to check whether it cannot be used as a level meter at two times (at the time when the contact between the electrode 21 and the molten glass G is lost, and when the contact between the electrode 22 and the molten glass G is lost). It is.

In this embodiment, the electrodes 21 and 22 are
As shown in FIG. 4, the detection part 24 on the tip side is covered with an insulating tube 25, and is inserted and fixed into a mounting hole 26 in the earthen wall of the vacuum housing 11 through this insulating tube 25. There is. The insulating tube 25 has a double tube structure consisting of an inner tube 25a and an outer tube 25b made of porcelain, for example, and the end of the outer tube 25b on the detection part 24 side is connected to the inner tube 25a.
A stepped portion 25c is located above the side end of the detection portion 24 and is formed between the inner tube 25a and the outer tube 25b. This stepped portion 25c serves to effectively prevent volatilized ions attached to the circumferential surface of the outer tube 25b from entering the electrode 21.22 portion and causing a short circuit, thereby making the insulation effect more reliable. I'm making it a thing.

(2) Liquid Level Detection System FIG. 5 is a block diagram showing a specific example of the liquid level detection system 30.

In the figure, reference numeral 31 is a resistance measuring device for measuring the resistance Ra between the electrodes 21 and 22 of the liquid level sensor 20, and 32 is resistance information from the resistance measuring device 31 (specifically, output as voltage information). ) amplifier to adjust the level,
33 is a regulator for adjusting the amplification factor of the amplifier 32;
4 is a divider that divides the preset fixed resistance information Rc (input to the Z terminal) by the resistance information Ra from the amplifier 32 (input to the X terminal); 35 is a divider for dividing the output information from the divider 34 into an effective area 36 is a regulator for setting the effective area m of the limiter 35; 37 and 38 are regulators and amplifiers for setting reference scale information for the liquid level; 39 40 is a display meter that digitally displays the liquid level information from the adder 39. 41 is an adder that adds the liquid level information from the limiter 35 and the reference scale information. 41 is a display meter that digitally displays the liquid level information from the adder 39. Convert to D
The A converter 42 is a Venn recorder that displays time fluctuations of analog data from the DA converter 41.

The data on the display meter 40 is used as liquid level information.
It is used to control the flow rate and temperature of molten glass G.

(2) Operation of the liquid level detection device First, the operation of the liquid level detection device according to this embodiment will be theoretically analyzed.

Now, in FIG. 3, the radius of the rod-shaped electrodes 21 and 22 is r,
If the distance between the electrodes 21 and 22 is d, the effective insertion depth of the electrodes 21 and 22 (not including the dimension Δl where only the electrode 22 is immersed) is h, and the specific resistance of the molten glass G is ρ, then the electrodes 21 and 22 The resistance Ra between Ra
= (ρ/πh)・ln[(d-r)/r]−
It is expressed as (1).

Here, if we list each condition used in this example, for example, r = 4 lucid = 40 mm ρ = 8 Ωc, m (molten glass temperature = 1350 ° C), Ra = 5.60/ It becomes h-(1').

A Ra-h characteristic graph created based on this (1゛) is shown in FIG.

According to FIG. 6, it is understood that as the effective insertion depth h increases, Ra decreases inversely.

Therefore, in this embodiment, the fixed resistance information Re set in advance by the multiplier 35 is divided by the detected resistance information Ra, and a linear characteristic is established between this division data and the effective insertion depth h. I try to have it. Therefore, liquid level information proportional to the division data is output within the area set by the limiter 36, and predetermined liquid level information is displayed on the display meter 40.

When the display data of the display meter 40 and the measured data at this time were compared, it was confirmed that the two substantially matched.

If a characteristic curve as shown in Fig. 6 is created in advance based on actual measurements and a converter corresponding to this characteristic curve is constructed, this converter can calculate the liquid level from the resistance information Ra. It is possible to transform the information immediately.

◎Embodiment 2 ■Characteristics of the liquid level detection system In this embodiment, as shown in FIG. We are prepared.

The basic structure of the liquid level correction sensor 50 consists of a pair of electrodes 51 and 52 which are insulated in substantially the same way as the liquid level sensor 20, and are immersed in the molten glass G. Unlike the above, the correction resistance Rb between the electrodes 51 and 52 does not change as the liquid level changes. Specifically, the one electrode 51
The detection section 53 (the part that can be immersed in the molten glass G) is rod-shaped, whereas the other electrode 52 includes a cylindrical detection section 54 with a large surface area surrounding the detection section 53 of the electrode 51.

In addition, in this example as well, for the same reason as in Example 1,
The electrodes of each pair of electrodes of the liquid level sensor 20 and the liquid level correction sensor 50 are arranged to protrude slightly downward by Δl from one or the other of the electrodes.

■Liquid level detection system The liquid level detection system used in this example is shown in the eighth section.
As shown in the figure.

In the figure, reference numeral 61 is a resistance measuring device for measuring the resistance Ra between the electrodes 21 and 22 of the liquid level sensor 20, and 62 is a resistance measuring device for measuring the resistance Ra between the electrodes 51 and 22 of the liquid level correction sensor 50.
63 is an amplifier for adjusting the level of resistance information (specifically output as voltage information) from the resistance measuring device 61;
4 is a regulator for adjusting the amplification factor of the amplifier 63; 65;
66 is an amplifier for adjusting the level of resistance information (specifically output as voltage information) from the correction resistance measuring device 62;
is a regulator for adjusting the amplification factor of the amplifier 65, and 67 is a divider that divides the resistance information Rb from the amplifier 65 (input to the Z terminal) by the resistance information Ra from the amplifier 63 (input to the X terminal). , 68 is a limiter that converts the output information from the divider 67 into liquid level information within the effective area m, 69 is an adjuster for setting the effective area m of the limiter 68, 7
0 and 71 are regulators and amplifiers for setting reference scale information of the liquid level; 72 is an adder for adding the liquid level information from the limiter 68 and the reference scale information;
73 is a display meter that digitally displays the liquid level information from the adder 72, 74 is a DA converter that converts the digital data of the display meter 73 into analog data, and 75 is a time variation of the analog data from the DA Sicon-Tough 4. This is a pen recorder that displays .

In this embodiment as well, the data on the display meter 73 is used as liquid level information to control the flow rate and temperature of the molten glass G.

(2) Operation of the liquid level detection device First, the operation of the liquid level detection device according to this embodiment will be theoretically analyzed.

Now, in FIG. 7, the radius of the rod-shaped electrode 2122 is rl,
The distance between the electrodes 21 and 22 is d, the effective insertion depth of the electrodes 21 and 22 is hl, the radius of the rod-shaped electrode 51 is r7, the diameter of the cylindrical detection part 54 of the electrode 52 is D, and the effective depth of the cylindrical detection part 54 is The immersion dimension is (-constant), and the specific resistance of the molten glass G is ρ.
Then, the resistance Ra between the electrodes 21 and 22 and the electrode 51
．． The correction resistance Rb between 52 and 52 is theoretically Ra = (ρ/yh,) ・1n1(d-r+)/
r+1− (2) Rb = (ρr'2πh2) ・l
It is expressed as n(1(D/2>-rtl/'ra] (3).

Kokote, from equations 2 (2) and (3) above, when Rb is divided by Ra, Rb'Ra = k -h, -(
4) = becomes constant.

According to this equation (4), the Rb/Ra information is proportional to the electrode insertion depth hl of the liquid level sensor 20, and the molten glass G
This means that it is given as a physical quantity unrelated to the specific resistance ρ based on the temperature and substrate composition.

Therefore, even if the temperature or base composition of the molten glass G changes, the Rb, /Ra information will not be affected.
It changes only in proportion to the electrode insertion depth hl of the liquid level sensor 20.

In this embodiment, if the correction resistance Rb is 10Ω (constant), the (Rb/Ra)-h characteristic graph is created as shown in FIG.

According to FIG. 9, it is understood that the above (Rb/Ra)-h characteristic graph has a linear characteristic k.

Based on such (Rb/Ra) h based on the characteristic graph, an appropriate range in the linear region is selected as the effective region m of the limiter 68, and a proportional characteristic corresponding to the linear region k is set in the limiter 68. If you do this,
Predetermined liquid level information will be displayed on the display meter 73.

When the display data of the display meter 73 and the measured data at this time were compared, it was confirmed that the two substantially matched.

(2) Modified example of the device In this modified example, the liquid level correction sensor 50 is modified, and as shown in FIG. It is equipped with spherical detection sections 83 and 84.

In this modification, the distance between the electrodes is a1, the radius of the spherical detector is Rb', and the resistance between the electrodes of the spherical detector is Rb'.

If the immersion dimension of the electrodes other than the spherical detection part is Δh, the interelectrode resistance of the Δh part is ΔR1, and the specific resistance of the molten glass G is ρ, then Rb'= (ρ/2π) [(1/b)-1/( a-b
)] −(5)ΔR= (o/yr△h)j+
n[(a-b)/b] - (6), and the combined resistance Rb between both electrodes is Rb = (Rb'X△R)/(Rb'+△R) =
RbV [(Rb'/ΔR)+l)...(7) Here, since Rb"(ΔR, Rb'/ΔR→0
and Rbζ Rb'...(7°)
become.

That is, it is understood that the combined resistance Rb between both electrodes is kept substantially constant without being affected by changes in Δh.

Looking at a specific numerical example, Rb' = 10Ω and ΔR is 1
Assuming that the resistance changes from 00Ω to 120Ω, if ΔR is 100Ω, the combined resistance Rb is Rb=(Ioo
XIO)/(100+1O)=9.10Ω, and if △R is ]20Ω, Rb= (120X10)/(120+IO)#9,
It is 23Ω.

Therefore, the change δ is: δ = (9,23-9,10)/9.10 0.015
(1.5%), and it is confirmed that it hardly changes.

〔Effect of the invention〕

As explained above, according to the liquid level detection method and device according to claims 1 to 5, the difference between the resistance change between the level detection electrodes immersed in the conductive melt and the liquid level change is Since we focused on regularity and detected the liquid level, even if volatilized ions are generated in a closed space such as a vacuum degassing furnace, there is no contact or non-contact state between the conductive melt and the level detection sensor. As with the method of detecting the liquid level based on Even when changing the surface level, there is no need to move and set the level detection electrode each time, and it can be used in a stationary state, making it suitable even in closed spaces such as vacuum degassing furnaces. This can be handled very easily.

Furthermore, according to the liquid level detection method according to claim 3, since the resistance change between the level detection electrodes due to the temperature and composition change of the conductive melt is canceled, the temperature and composition of the conductive melt are canceled. The liquid level can be detected accurately at all times without considering changes in composition.

In particular, according to the liquid level detection device according to claim 4, the liquid level detection method according to claim 3 can be implemented by simply adding a correction electrode to the level detection electrode and performing simple arithmetic processing. Therefore, the liquid level can be accurately detected at all times without considering changes in the temperature and composition of the conductive melt, while simplifying the device configuration.

Furthermore, according to the liquid level detection device according to the fifth aspect of the present invention, the liquid level can be visually observed, so that the accuracy of monitoring the liquid level can be further improved.

[Brief explanation of drawings]

1(a) and (b) are explanatory diagrams showing the configuration of a liquid level detection device according to the present invention, FIG. 2 is an explanatory diagram showing an outline of a liquid level detection system according to Embodiment 1, and FIG. is an explanatory diagram showing a schematic configuration of a liquid level sensor, FIG. 4 is an explanatory diagram showing an example of an electrode configuration of a liquid level sensor, FIG. 5 is a block diagram showing a specific example of a liquid level detection system, and FIG. is a graph showing the relationship between the inter-electrode resistance of the liquid level sensor and the electrode insertion depth, FIG. 7 is an explanatory diagram showing an overview of the liquid level detection system according to the second embodiment, and FIG. A block diagram showing a specific example of the liquid level detection system, Fig. 9 is a graph showing the relationship between the inter-electrode resistance correction value of the liquid level sensor and the electrode insertion depth, and Fig. 10 is a modification of the liquid level correction sensor. It is an explanatory diagram showing an example. [Explanation of symbols] G... Conductive melt Ra... Resistance between electrodes for level detection Rb... Resistance between electrodes for correction L... Electrode for level detection 2... Resistance measuring means 3... -Liquid level determining means 4...Correction electrode 5...Correction resistance measuring means 6...Liquid level detection means 7...Display means

Claims (1)

[Claims] 1) When detecting the liquid level of the conductive melt (G), a pair of level detection electrodes (1) are immersed in the conductive melt (G), and the level detection electrodes (1) are immersed in the conductive melt (G). (1) Resistance between (Ra)
A liquid level detection method characterized in that the liquid level is detected based on changes. 2) a pair of level detection electrodes (1) immersed in the conductive melt (G); and a resistance measuring means (2) for measuring the resistance (Ra) between the level detection electrodes (1); A liquid level detection device characterized by comprising: liquid level determining means (3) for converting resistance information measured by the resistance measuring means (2) into liquid level information. 3) When detecting the liquid level of the conductive melt (G), a pair of level detection electrodes (1) are immersed in the conductive melt (G), and the resistance between the level detection electrodes (1) is (Ra)
After removing and correcting the resistance change between the level detection electrodes (1) due to temperature changes and composition changes of the conductive melt (G), the correction resistance (Ra) between the level detection electrodes (1) is corrected.
') A liquid level detection method characterized in that the liquid level is detected based on changes. 4) A pair of level detection electrodes (1) immersed in the conductive melt (G); and a pair of level detection electrodes (1) immersed in the conductive melt (G).
The above level detection electrode (
Measure the resistance (Ra, Rb) between the pair of correction electrodes (4) that corrects the resistance change between the electrodes (1) and the level detection electrode (1) and the correction electrode (4). Ra, Rb
), the corrected resistance measuring means (5) calculates the corrected resistance (Ra') from which the resistance change due to the temperature change and composition change of the conductive melt (G) is removed; Liquid level determination means (6) that converts the measured correction resistance information into liquid level information.
) A liquid level detection device characterized by comprising: 5) The device according to claim 2 or 4, further comprising display means (7) on which liquid level information from the liquid level determination means (3, 6) is displayed in a direct readable manner. Characteristic liquid level detection device.