JPH0611469A - Water content measuring method - Google Patents

Abstract

PURPOSE:To preclude drop of the electrolytic amperage in continuous measuring and enable measurement of the water content accurately by inverting the polarities of the impression voltage, and preventing production of an oxide film and electrodeposition of various substances on the electrodes. CONSTITUTION:A water content measuring device 6 is installed so that the tip 5 of its sensing part is positioned against the stream of a sludge cake 11 after water removal which flows in a piping 14 at a constant speed. In this water content measuring device 6, a plurality of positive electrodes 1 and a plurality of negative electrodes 2 are laid alternately, covered with epoxy resin, etc., in their part other than tips 5, and secured by a resin insulation part 3. The spacing between the positive and negative electrodes 1, 2 is made below 0.5mm, preferably between 0.1-0.3mm, in view of lessening the influence of the change in the electroconductivity of the object to be inspected, and a DC voltage over 2.5V is impressed with polarities inverted at certain intervals. This reduces the surface which has been anode oxidated to cause removal of the oxides, and the electrolytic amperage can be measured in the condition that a new electrode surface having good reactivity is held at all times to ensure that the water content is measured with high precision.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring water content, and more particularly, it is suitable for measuring water content in a flowing sample such as dehydrated sludge cake having a high water content with high accuracy and continuously. Concerning the law.

[0002]

2. Description of the Related Art In recent years, micro comb electrodes and the like have been developed as a measuring instrument using a pair of finely spaced electrodes, and these are used for detection and quantification of substances and water that reversibly carry out electrode reactions. The applicant of the present invention, in Japanese Patent Laid-Open No. 3-180747, is capable of continuously and highly accurately measuring the amount of water in a sample having a large water content with a simple device.
We proposed a method for measuring moisture by applying a DC voltage of 5 V or more to the electrodes.

However, in the above-mentioned water content measuring method, 2.
Since a constant DC voltage of 5 V or more is continuously applied, there is a problem that the electrolytic current value decreases due to generation of an oxide film on the anode and electrodeposition of various substances on the electrode with the lapse of measurement time. there were. Photoelectron spectroscopy of the electrode surface confirmed the formation of an oxide film on the anode and confirmed that iron adhered to the cathode.

In addition, when the flow rate of the sample is slow or in the non-solvent type sample such as dehydrated sludge cake, the diffusion of water is not performed smoothly, resulting in unsteady diffusion, and the electrolytic current decreases with the passage of time to stabilize. There was a problem that the measured values could not be obtained.

[0005]

The object of the present invention is to solve the above-mentioned problems of the prior art and to measure the water content in a flowing sample continuously and with high accuracy while preventing the measured value from decreasing over time. It is to provide a moisture measurement method that can be performed.

[0006]

According to the present invention, there is provided at least a pair of an anode and a cathode having a distance of 0.5 mm or less, and a resin insulating portion which fixes the anode and the cathode and exposes only a tip portion. After immersing the exposed electrode surface of the detector having a sample in a flowing sample, and applying a DC voltage of 2.5 V or more to the electrode to measure the water content in the sample, the polarity of the DC voltage is kept constant for a certain period of time. The present invention relates to a method for measuring water content, which is applied by reversing every time.

[0007]

[Effect] Even when a stable metal such as platinum (Pt) is used as an electrode, when a direct current voltage higher than the electrolysis voltage of water is continuously applied for a long period of time, the anode surface is oxidized to increase the resistance. Although the current decreases, in the present invention,
Since the polarity of the voltage ((+) and (-)) is inverted and applied at regular intervals, the electrode that was the anode next becomes the cathode, and the anodized surface is reduced to remove the oxide. A new electrode surface having good electrode reactivity similar to that at the beginning of electrolysis can always be retained.

Further, when measuring a non-solvent type sample such as a dehydrated sludge cake, even if the sample is in a fluid state, moisture does not diffuse smoothly, so that the unsteady diffusivity becomes strong and the electrolytic current is Although it decreases with the passage of time, in the present invention, the polarity of the voltage applied to the electrode can be reversed to always keep the electrode surface in the same state as in the initial stage of electrolysis, so that the decay tendency of the electrolytic current is always the same. Therefore, if the electrolysis current is measured each time the polarity of the applied voltage is reversed, an electrolysis current value that does not decrease over time can be obtained. In addition, since the sample on the electrode surface is not updated in the measurement of the sample that does not flow, the electrolytic current value obtained even when the measurement is performed by the method of the present invention gradually decreases.

FIG. 1 is an explanatory diagram of a moisture measuring method showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of a moisture measuring device used in FIG. 1, and FIG. 2 (a) is a moisture measuring device. 2B is a front view thereof, and FIG. 6C is a sectional view taken along line I-I of FIG. Figure 1
In, the moisture measuring instrument 6 is installed so that the tip portion (electrode surface) 5 of the detecting portion thereof faces the flow of the dehydrated sludge cake 11 flowing in the pipe 14 at a constant speed. Moisture analyzer 6
As shown in FIG. 2, a plurality of anodes 1 and cathodes 2 are alternately arranged, and a power source 20 and a recorder 21 are connected via lead wires.
Connected to. The parts other than the tip parts 5 of the anode 1 and the cathode 2 are covered with an epoxy resin or the like and fixed by a resin insulating part 3. The tip portion (electrode surface) 5 has a cylindrical curved surface, and the resin insulating portion 3 for fixing the electrode surface 5 has a spherical shape.

The distance between the anode 1 and the cathode 2 is set to 0.5 mm or less, preferably 0.1 to 0.3 mm in order to reduce the influence of the change in the conductivity of the sample. The electrode width of the cathode and / or the anode is preferably 0.2 mm or less in order to prevent oxygen gas or hydrogen gas generated during electrolysis from stagnating on the electrode surface and generating noise.

The polarity of the voltage applied to the anode 1 and the cathode 2 is reversed by the power supply 20. There is no particular limitation on the method of reversing the polarity of the applied voltage. For example, + 2.5V is applied even if the voltage of the same potential (for example, ± 2.5V) is switched at the same time (for example, every 30 seconds) and applied. Different voltages may be applied for different times, such as applying -4V for 40 seconds after applying for 1 minute. The electrolytic current value obtained by applying a voltage may be measured by measuring the electrolytic current at both electrodes each time the polarity is switched, but it can also be obtained by applying the same voltage to the (+) pole and the (-) pole. Since the generated electrolysis current values are different, it is sufficient to measure the electrolysis current obtained when a voltage of either polarity is applied.

[0012]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 Twenty disc-shaped Pt plates having a thickness of 0.1 mm and a diameter of 17 mm (10
Pair), a lead wire 4 connected to a power source 20 and a recorder 21 is connected alternately to form an anode 1 and a cathode 2.
The cathode 2 and the cathode 2 were arranged so that the distance between them was 0.2 mm, and the gap between the electrodes was filled with an epoxy resin to produce a cylindrical electrode. Then, only a part of the curved surface of the cylindrical electrode was exposed to form a spherical resin insulating portion 3 with an epoxy resin, and a moisture measuring instrument 6 was obtained. This moisture measuring device 6 is attached to a support 10, and the dehydrated sludge cake 11 having a water content of 80.1% by weight moves at a constant speed in a pipe 14 in which the electrode 10 of the moisture measuring device is dehydrated sludge. It was installed to face the flow of cake. Next, a DC voltage of 2.5 V is applied to the electrode 30
After a second, the (+) and (-) electrodes were switched and applied, and the water content of the dehydrated sludge cake was continuously measured for 1 hour. The obtained electrolytic current curve is shown in FIG. 3, but no decrease in the obtained electrolytic current value was observed even after continuous measurement for 1 hour.

Comparative Example 1 A water content of 80.1 was obtained in the same manner as in Example 1 except that a DC voltage of 2.5 V was continuously applied to the electrodes.
The water content of the weight% dehydrated sludge cake was continuously measured for 1 hour. The obtained electrolytic current curve is shown in FIG. 4, and a decrease in electrolytic current value was observed.

[0014]

According to the moisture measuring method of the present invention, the polarity of the applied voltage can be reversed to prevent the formation of an oxide film on the electrode and the electrodeposition of various substances on the electrode.
Even if the moisture content is continuously measured, the obtained electrolytic current value does not decrease, and the water content can be measured with high accuracy.

[Brief description of drawings]

FIG. 1 is an explanatory view of a water content measuring method showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a moisture measuring device used in FIG.

FIG. 3 is a diagram showing an electrolytic current curve obtained in Example 1.

FIG. 4 is a diagram showing an electrolytic current curve obtained in Comparative Example 1.

[Explanation of symbols]

1 ... Anode, 2 ... Cathode, 3 ... Resin insulation part, 4 ... Lead wire,
5 ... Tip (electrode surface), 6 ... Moisture measuring device, 10 ... Support, 11 ... Dewatered sludge cake, 12 ... Sludge particles, 13 ... Hair, 14 ... Piping, 20 ... Power supply, 21 ... Recorder.

Claims (1)

[Claims] 1. An exposed electrode surface of a detector having at least a pair of an anode and a cathode having a distance of 0.5 mm or less, and a resin insulating portion fixing the anode and the cathode and exposing only a tip portion. In order to measure the water content in the sample by applying a DC voltage of 2.5 V or more to the electrode after immersing the sample in a flowing sample, the polarity of the DC voltage should be reversed and applied at regular intervals. Moisture measurement method characterized by.