JPH0445779B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention simultaneously measures the temperature and moisture content of coal deposited in an indoor or outdoor coal storage yard (hereinafter also referred to as deposited coal or coal pile). It relates to a sensor for detection (hereinafter also referred to as a composite sensor).

[Conventional technology]

For example, in coal-fired power plants that use coal, coal is sometimes left in a pile for a long time in an indoor or outdoor coal storage area. It is known that as time passes, the temperature gradually increases and the moisture content decreases, potentially leading to spontaneous combustion. The conditions for this ignition generally depend on temperature and moisture; for example, the moisture adhering to the coal surface (adhered moisture) is less than 1%, or the adhering moisture and the moisture contained in the coal pores (inherent moisture) are less than 1%. The total moisture content (expressed as the sum of moisture) is 5% or less, and the temperature is 80 to 90℃.
It has been clarified that if the temperature exceeds that level, it will ignite, and that the part of the coal pile that is 2 to 3 meters deep from the surface tends to reach the highest temperature and is the part that is most likely to catch fire. Therefore, it is necessary to insert sensors at multiple locations in the coal pile in advance, or use an infrared camera to detect locations where there is a risk of spontaneous ignition, and then insert sensors at the appropriate locations each time. Temperature and moisture content must be detected, and if danger is detected, it is necessary to prevent spontaneous combustion by excavating, compacting, or spraying water using a bulldozer or the like.

Therefore, the applicant has applied for a composite sensor that can simultaneously measure moisture and temperature at the same location in a coal pile (see Japanese Patent Laid-Open No. 144651/1983).
This system has a temperature sensor inside a protective tube that can be inserted into and removed from the coal pile, and a moisture sensor that is formed by filling plaster between an electrode formed on the surface of this sensor and another electrode. This allows for simultaneous measurement of temperature and moisture content.

[Problem that the invention seeks to solve]

However, such a composite sensor has a problem in that the moisture detection characteristics in particular vary considerably depending on the brand (type) of coal and the size (particle size) of the particles.

Therefore, it is an object of the present invention to provide a composite sensor for accumulated coal whose moisture detection characteristics are not particularly affected by the brand or particle size of the coal.

[Means for solving problems]

Coal glass particles are mixed into the gypsum of the composite sensor for deposited coal at a predetermined ratio.

[Effect]

Through a number of experiments, we have confirmed that when quartz glass particles are mixed into gypsum, the moisture detection characteristics are almost uniquely determined regardless of the brand of coal or particle size, and by utilizing this we aim to solve the above problem. In addition,
Figure 8 shows the results of an experiment in which the relationship between the water content W (%) and the detection resistance R (KΩ) was determined by changing the brand of coal and the particle size. As is clear from the figure, it can be considered that although there are some variations, they lie approximately on one line X. In other words, the detection resistance R (KΩ)
As a result of experiments, it has been clarified that the relationship between and moisture content W (%) is as follows: LogR=A+BLogW (1). Here, A and B are constants determined by the electrode structure of the sensor, etc.

〔Example〕

FIG. 1 is a sectional view showing the internal structure of a composite sensor according to the present invention, FIG. 1A is a sectional view taken along line A-A' in FIG. 1, and FIG. 2 is an external view of the composite sensor.

The composite sensor 1 according to the present invention, as shown in FIG. Ru. As mentioned above, the coal pile 2 tends to reach the highest temperature at a depth of 2 to 3 m from its surface, so the total length of the composite sensor 1 is also selected to be about 2 to 3 m, and its tip 11 is located at a depth of 2 to 3 m from the surface of the coal pile 2. It is formed into a conical shape, for example, to facilitate insertion into the interior, while a handle 12 is provided at the other end to facilitate insertion and removal. Note that this handle 12 also serves as a stopper to prevent the sensor 1 from sinking into the coal pile. The protective tube 10 is made of a stainless steel pipe, and a plurality of openings 17 for absorbing and dehydrating water are formed at predetermined positions near the tip thereof.

As shown in Fig. 1, the interior of the sensor includes a tip 11, electrodes 13, 13', a main body 15, and a joint 1.
The main body portion 15, the tip portion 11, and the joint portion 16 are each connected by a screw portion 18. Electrodes 13, 1 are provided in the hollow part of the main body 15.
3', and the space between them is filled with a moisture absorbing/desorbing material C, which is made of, for example, plaster mixed with quartz glass particles (see the shaded area). Main body part 15
Since a plurality of openings 17 are provided around the coal for absorption and dehydration of moisture in the coal, the water absorption/desorption material C comes into contact with the outside through these openings 17. When inserted into the pile, moisture inside the pile permeates through the water absorbing/extracting material C and maintains a moisture equilibrium state, thereby detecting moisture while also detecting temperature using the thermocouple 13A. If this sensor is removed from the coal pile and left in the atmosphere, the moisture in the gypsum will evaporate and the sensor will be restored to a usable condition. Further, 19 is an insulating part, which is provided to electrically insulate the electrodes 13, 13' from the protective tube 10, the main body part 15, and the joint part 16. Further, the electrode 13 is formed by, for example, plating the surface of a temperature sensor consisting of a sheathed thermocouple 13A with gold, thereby configuring a composite sensor having both a temperature sensor and a moisture sensor.
Furthermore, since the composite sensor configured in this way is used under harsh conditions such as being inserted into a coal pile, it is designed to be watertight and airtight, although it is not particularly shown. There is.

The output from the temperature sensor 13A is connected to the lead wire L.
2 and L3 to a temperature detection circuit (not shown) to measure the temperature, while the output from the moisture sensor consisting of a pair of electrodes 13 and 13' is
It is applied to a moisture detection circuit via lead wires L0 and L1 to perform moisture measurement. FIG. 3 shows a specific example of the moisture detection circuit.

In the figure, 31 is a moisture sensor, 32 is an oscillator, 33 is a low-pass filter, 34A, 34B are diodes, 35 is a logarithmic amplifier (log amplifier),
36 is an output amplifier.

That is, the output of the moisture sensor 31 is transmitted to the oscillator 32.
modulated by an alternating current signal of a predetermined frequency from
4A and the other through a diode 34B, a logarithmic output of the sensor output is obtained in a logarithmic amplifier 35, and this is sent to an output amplifier 36.
It is taken out through. The reason why the logarithmic amplifier 35 is used here is that the relationship between the detection resistor and the moisture in the coal is expressed as a logarithmic relationship as shown in equation (1) above.

FIG. 4 is a sectional view showing another embodiment of the present invention;
FIG. 4A is a sectional view taken along line A-A'.

In this case, a conductive part 14 is provided in place of the electrode 13' shown in FIG. 1, while the protective tube 10 is used as a conductor.
The structure is simplified by arranging the water absorption/drainage material C between these to form a moisture sensor. Therefore, the lead wire L0 (not shown)
is connected to the protection tube 10, and by guiding this and the lead wire L1 to the moisture detection circuit shown in FIG. 3, moisture detection becomes possible in the same manner as in the case of FIG.

In the configuration shown in Figure 4, when only gypsum is used as the water absorbing and desorbing material, and when quartz glass particles are mixed into the gypsum,
The relationship between moisture and detection resistance is shown in FIG. 5, for example. Here, the points marked with "O" indicate the case where only gypsum is present, and the points indicated with the "△" mark indicate the case where quartz glass is mixed. As is clear from comparing the two, when quartz glass is mixed, the range of moisture change is larger for the same detection resistance range, so moisture detection can be performed with higher accuracy. Note that the mixing ratio of quartz glass particles is approximately 20% from the viewpoint of strength.

Similarly, if the moisture sensor output is observed over time when only gypsum is used as the water absorbing/desorbing material and when quartz glass is mixed into the gypsum, the result will be as shown in FIG. 6, for example. Here, the points marked with "O" indicate the case where quartz glass is mixed, and the points indicated with the "□" mark indicate the case where only gypsum is present. From these results, it can be seen that the time it takes for the moisture sensor output to stabilize, that is, the response time, is shorter when quartz glass is mixed.

Figure 7 shows the changes in moisture detection characteristics when the distance between the electrodes of the moisture sensor and the electrode structure are changed. 4 shows the case where the length (see FIG. 4, D3) of the electrode is changed without changing the diameter (see, FIG. 4, D2) of the electrode.

It goes without saying that even the case shown in FIG. 1 exhibits the characteristics as shown in FIGS. 5 and 6.

〔Effect of the invention〕

According to this invention, there is an advantage that moisture can be detected at high speed and with high precision simply by mixing quartz glass particles into gypsum without being concerned with the brand of coal or the particle size.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the internal structure of a composite sensor according to the present invention, FIG. 1A is a sectional view taken along line A-A' in FIG. 1, FIG. 2 is an external view of the composite sensor, and FIG.
The figure is a block diagram showing a specific example of a moisture detection circuit, FIG. 4 is a block diagram showing another embodiment of the present invention, and FIG.
Figure A is a cross-sectional view taken along line A-A' in Figure 4, Figure 5 is a graph for explaining the difference in moisture detection characteristics between gypsum alone and when quartz glass particles are mixed with gypsum, and Figure 6 The figure is a graph to explain the difference in moisture detection response characteristics between plaster only and when quartz glass particles are mixed in. Figure 7 shows moisture detection when the distance between the electrodes of the moisture sensor and the electrode structure are changed. FIG. 8, which is a graph for explaining changes in characteristics, is a graph showing the relationship between moisture content and detection resistance when the brand of coal and particle size are changed. Explanation of symbols, 1...Composite sensor, 2...Coal pile, 10...Protection tube, 11...Tip, 12...
Handle, 13, 13'... Electrode, 13A... Thermocouple (temperature sensor), 14... Conductive part, 15... Body part, 16... Joint part, 17... Opening, 1
8...Screw part, 19...Insulation part, 31...Moisture sensor, 32...Oscillator, 33...Low pass filter, 34A, 34B...Diode, 35...Logarithmic amplifier (log amplifier), 36...Output Amplifier,
C...Water absorption/desorption material, L0-L3...Lead wire.

Claims (1)

[Claims] 1. A protective tube of a predetermined length that has a plurality of openings in predetermined portions and can be freely inserted into and removed from the deposited coal is filled with gypsum, and the temperature at a predetermined position within the deposited coal is filled inside the protective tube. and a moisture sensor consisting of a pair of electrodes and detecting the moisture content from the inter-electrode resistance value due to moisture absorbed and dehydrated by the plaster through an opening formed in the protective tube. A composite sensor for deposited coal, characterized in that quartz glass particles are mixed in the gypsum at a predetermined ratio. 2. The composite sensor for deposited coal according to claim 1, wherein the protective tube is electrically conductive and is used as one electrode of the moisture sensor. 3. The composite sensor for deposited coal according to claim 1, wherein one of the pair of electrodes is formed on the surface of the temperature sensor.