JPH083438B2 - Interface detection method in the tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an interface in a tank, in particular, an interface such as a liquid surface or a foam surface in a tank which is highly ruffled and has a "foaming" state like a fermentation tank. .

Conventional technology In a fermenter, the liquid level in the tank is greatly rippling and foaming, and the "foam retention" state also changes as the culture changes over time, especially the cell concentration changes. Since the liquid surface of the liquid also fluctuates greatly, its detection control becomes a problem.

As a conventional liquid level detector, there are a differential pressure type, a displacement type, an electrode type, a capacitance type, an ultrasonic liquid level gauge, etc., but when used in a fermentation tank, the differential pressure type is the specific gravity of the liquid in the tank. Displacement type has a dead space and is structurally unsuitable for changes, electrode type and capacitance type often cause malfunction due to mist etc., ultrasonic level gauge has problems in pressure resistance and heat resistance, liquid level If the noise increases due to changes or the like, there are many malfunctions, and neither is satisfactory. Moreover, the bubble surface cannot be detected.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention It is an object of the present invention to provide a method for detecting an interface such as a liquid level or a bubble level in a tank, which solves the above-mentioned drawbacks of the conventional liquid level detector.

B. Configuration of the Invention Means for Solving the Problems The method for detecting the interface between a liquid phase and a foam phase and a foam phase and a gas phase in a tank according to the present invention is a method in which a liquid phase, a foam phase and a gas phase are present in a longitudinal direction. Irradiate light in the range of 400 nm to 800 nm into the tank from multiple external locations arranged through the sight glass provided on the side wall of the tank, measure the intensity of the reflected light of each phase, and the liquid phase, bubbles It consists of checking the intensities of the reflected light at wavelengths where there is a significant difference between the phase and the gas phase.

To explain this with reference to FIG. 1, light is emitted from a plurality of external locations (positions 3A to 3D) vertically arranged through the sight glass 2 provided on the side wall of the tank 1 into the tank, and the light receiving portion ( Each reflected light is received by the positions (3A to 3D).

The light irradiation may be performed by a light source provided separately from the light receiving unit, but as shown in an enlarged view in FIG. 2, the probe 3 (A having a structure in which the light emitting unit 31 and the light receiving unit 32 are integrated is used. ~
It is convenient to use D).

In such a probe 3, the light from the lamp 33 is sent to the light irradiation section 31 through the optical fiber 34 and is sent to the sight glass 2
The light is radiated to the inside of the tank through the through, and the reflected light from the liquid phase portion 11, the bubble phase portion 12 or the gas phase portion 13 inside the tank is captured by the light receiving portion 32, and is sent to the light irradiation analysis unit through the optical fiber 35.

The light irradiation analysis unit 5 measures and collates the intensity of the reflected light from the liquid phase portion, the foam phase portion, or the gas phase portion.

The intensity of the reflected light from the liquid phase, the bubble phase or the gas phase has a large difference from each other as described later, so these values are collated with each other, or the liquid phase, the foam phase or the By collating with the known measurement value such as the intensity value of the reflected light from the gas phase, a specific light receiving part receives the reflected light. It is easy to know whether or not it is in the gas phase.

As a reference when measuring the intensity of reflected light,
It may be appropriately selected depending on the properties of the substance to be measured.
For example, when a liquid with a relatively high reflectance is targeted, the reflectance from a white paper is set as 100% as a reference, or a liquid with a low reflectance such as when the target liquid is colored. In that case, the reflectance from the liquid may be used as a reference.

The angle of irradiating light into the tank may be appropriately selected depending on the properties of the substance to be measured. For example, when targeting a liquid with a relatively high reflectance,
It is appropriate that the angle is 20 to 80 degrees, preferably around 45 degrees. At a right angle (90 degrees), the reflected light from the sight glass is too strong and the difference in reflectance becomes unclear. At 20 degrees or less, the reflected light from the tank is too weak to make measurement difficult.

When a liquid having a low reflectance is targeted, the interface can be detected by the reflected light from the meniscus generated at the interface between the liquid phase and the gas phase by irradiating the sight glass surface at 90 degrees.

As shown in FIG. 1, the light receiving portions (32A, 32B, 32) built in the plurality of probes 3A, 3B, 3C, 3D arranged vertically.
The light received by C, 32D) is sent to the light irradiation analysis unit 5 via the multi-switch 4.

For example, the light received by the light receiving section 32A is liquid phase, 32B, 32C.
If the light received at is a bubble phase, and the light received at 32D is a gas phase, the liquid level is between 32A (where the reflected light is received, the same below) and 32B. The plane will be between 32C and 32D.

Note that FIG. 1 shows a state in which a probe having a light irradiation unit and a light receiving unit is fixedly installed at each of a plurality of external locations arranged in the vertical direction. It is also possible to irradiate the inside of the tank with light from a plurality of positions through the sight glass provided on the side wall of the tank, measure the intensity of the reflected light at each position, and collate it.

In this case, it may be possible to measure and collate only the intensity of reflected light at a plurality of positions specified in advance, but if the intensity of reflected light is continuously measured and collated as the probe moves, Since the intensity of the reflected light rapidly changes when reaching the interface, the position of the interface can be detected more clearly.

In FIG. 1, such information is displayed on the interface indicator 6. When the liquid surface or the bubble surface changes from a position within a predetermined range, for example, when the bubble surface becomes high and the light received by the light receiving unit 32D has a value corresponding to the foam phase, an instruction from the light irradiation analysis unit 5 is given. This opens the valve 71 of the defoamer tank 7,
An antifoaming agent can be introduced to keep the foam surface within a predetermined range.

Further, when the liquid level changes from a position within a predetermined range and, for example, the light received at 32B indicates a liquid phase value, the control valve 82 is opened by an instruction from the light irradiation analysis unit 5, and the inside of the tank is opened. The liquid can be extracted and the liquid surface can be maintained at a position within a predetermined range.

When the light received by 32A indicates the value of the foam phase, the control valve 81 is opened by the instruction from the light irradiation analysis unit 5 and the liquid is supplied into the tank so that the liquid level is within a predetermined range. Can be kept at

In the measurement, the error due to the properties of the liquid to be measured,
For example, in a fermentation broth, in order to eliminate errors due to the color of the bacterium, metabolites, medium, etc., it is preferable to select the optimum wavelength of light for the properties of the liquid.

 Symbol 9 is an air dispersion pipe, and symbol 10 is an agitator.

[Example 1] In a bubble column with a vinyl chloride 30 draft tube,
Yeast culture solution (concentration about 44g-drycell /)
Was charged, and air was blown into the bubble column at a linear velocity of about 3 cm / sec to circulate the liquid, and the liquid surface was disturbed and became a foaming state.

Fix the probe as shown in Fig. 2 by tilting it upward by 45 degrees, and irradiate the inside of the tower through the sight glass installed on the side wall of the bubble tower to intensify the reflected light of the liquid, bubble, and air parts. The result of measuring the height is shown in FIG. Here, the horizontal axis represents the wavelength (nm) of light and the vertical axis represents the reflectance.

In addition, as a reference, a white paper has a reflectance of 100% and a space has a reflectance of 0%.

As is clear from FIG. 3, the reflectance (L) from the liquid phase
Is the highest, followed by the reflectance (F) from the foam phase, the lowest (G) from the gas phase, and there is a significant difference between them.

Therefore, by comparing the measured values at a plurality of locations with each other, or by collating with the known measured value, the specific location in the tower where the light receiving section receives the reflected light is the liquid phase or the foam phase. It is possible to easily discriminate between the gas phase and the gas phase.

[Example 2] A molasses medium having a low reflectance was used in place of the culture solution used in Example 1 (an example having a high reflectance from the culture solution).

In a bubble column with 30 draft tubes made of vinyl chloride,
Mixture of molasses medium and baker's yeast (Baker's yeast concentration about 5g-dr
ycell /), and in the same manner as in Example 1,
The intensity of the reflected light in the liquid, foam and air portions was measured.

The data thus obtained are shown in FIG. Here, the horizontal axis represents the wavelength (nm) of light and the vertical axis represents the reflectance. The foam with the highest reflectance was used as a reference. That is, the reflectance of bubbles was set to 100%.

As is clear from FIG. 4, when the molasses medium is used, there is a significant difference between the reflectances of the foam phase, the liquid phase and the gas phase in the wavelength range of about 700 to 800 nm.

As described above, in the present invention, even in the case of a liquid having a rich color such as molasses medium, by appropriately selecting the wavelength of the light used for the measurement, it is possible to make a remarkable difference between the reflected lights of the three phases. Since the difference is obtained, the place to be measured in the tank is the foam phase,
It is possible to easily detect whether it is a liquid phase or a gas phase.

C. Effects of the invention Rippling like a fermenter, in a state of "foaming",
It is possible to detect an interface such as a liquid surface or a bubble surface in the tank in which the specific gravity of the liquid also changes.

Since the interface is detected from the outside of the tank through the sight glass installed in the tank, dead space in the tank does not occur, and there is no risk of contamination of the culture fluid by the sensor.

The present invention can be carried out on an existing tank having a sight glass without any special modification.

[Brief description of drawings]

1 is an explanatory view showing an embodiment of the present invention, FIG. 2 is an enlarged view of a light receiving portion, FIG. 3 is a view showing test results in Example 1, and FIG. 4 is a test result in Example 2. FIG. 1 ... Tank, 11 ... Liquid phase, 12 ... Bubble phase, 13 ... Gas phase, 2 ...
… Sight glass, 3 (A to D) …… Probe, 31 …… Light emitting part, 32 …… Light receiving part, 33 …… Lamp, 34,35 …… Optical fiber, 4 …… Multi switch, 5 …… Light Irradiation analysis unit, 6 ... Interface indicator, 7 ... Defoamer tank, 71 ...
Valve, 81, 82 ... Valve, 9 ... Air dispersion pipe, 10 ... Stirrer L ... Reflectance from liquid phase, F ... Reflectance from foam phase, G
...... Reflectance from gas phase

Continuation of the front page (56) References JP 59-10348 (JP, A) Shinsaku Takenaka, "Photoelectronic control and its applications" Showa August 20, 40, Nikkan Kogyo Shimbun, P. P, 45-46

Claims (1)

[Claims] 1. In a tank in which a liquid phase, a foam phase and a gas phase are present, light in the range of 400 nm to 800 nm is introduced into the tank from a plurality of external locations arranged in the vertical direction through sight glass provided on the side wall of the tank. And measuring the intensity of the reflected light of each phase to check the intensity of the reflected light at the wavelength where there is a significant difference between the liquid phase, the bubble phase, and the gas phase. A method for detecting an interface between a liquid phase and a foam phase and a foam phase and a gas phase.