JPH0743319A - Method and device for measuring moisture content of coal - Google Patents

Abstract

PURPOSE:To provide a simple method and device for measuring moisture content of coal. CONSTITUTION:In principle, microwaves are propagated to coals 2 fed by a belt conveyor 3 to calculate their moisture values based on the changes in the microwaves. In such a measuring method for moisture content, a symmetrical pair of side skirts 7 and 7 are provided on the conveyor 3, and while the feeding width of the coals 2 is adjusted thereby, the layer thickness of the fed coals 2 is adjusted to be constant with a leveller 11, so that the same accuracy as that of conventional method using a radiation instrument can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring water content of coal.

[0002]

2. Description of the Related Art Generally, the water content of coal charged in a coke oven is very important information for the operation guideline and action of the coke oven. That is, the water content of coal not only greatly affects the heat balance of the coke oven operation, but also changes the bulk density of the coal charged in the coke oven and affects the coke quality. Therefore, in many cases, the moisture content of coal is measured before charging it into the coke oven.

As one of the conventional methods for continuously measuring the water content of coal, there is a water content measuring apparatus using a microwave as shown in FIG. As shown in the figure, the water content measuring apparatus 1 has a microwave transmitting antenna 1a attached at a predetermined angle below a belt conveyor 3 that conveys coal 2, and a microwave that transmits the coal 2 is attached above the belt conveyor 3. The wave receiving antenna 1b receives the signal, inputs it to the arithmetic unit 4, outputs the arithmetic result to the display unit 5, and records it.

Now, assuming that the bulk density of coal is Q (g / cm ³ ), and the layer thickness thereof is d (cm), the phase change of the microwave transmitted through the microwave receiving antenna 1b is φ (deg). ,
Degree of attenuation (ratio of received wave to transmitted wave) is D
Assuming (-), the relationship between the water content W (%) of the coal to be measured and φ, D is generally expressed by the following equation within the limited water content range.

W = {Aφ / (Qd)} + {BD / (Qd)} + C (1) where Q is the bulk density (g / cm ³ ), d Is the thickness of the raw material layer (cm), and A, B and C are constants determined by the properties of the microwave. Although it is difficult to directly obtain the above-mentioned bulk density Q directly, it is possible to combine the density and the radiation intensity by utilizing the property that radiation such as gamma rays is weakened when passing through a substance. Therefore, as shown in FIG. 3, the radiation measuring device 6 including the radiation source 6a and the radiation detector 6b arranged on the upper and lower portions of the belt conveyor 3 is used to measure the radiation transmitted through the coal 2 and attenuated. The intensity I (r; roentgen) is measured. The intensity I of the attenuated radiation changes based on the well-known Lambert's law shown by the following equation (2).

I = I ₀ exp (−η · Q · d) (2) where I ₀ is the intensity (r) of the non-attenuated radiation output from the radiation source 6 a, and η Is a constant determined by the nature of radiation. This equation (2) is transformed into the following equation (3), and Q · d = − (1 / η) · ln (I / I ₀ ) ………… (3) This equation (3) is transformed into (1 ) Combined with the formula
Equation (4) is obtained.

W = {A ′ · φ / ln (I / I ₀ )} + {B ′ · D / ln (I / I ₀ )} + C ... (4) Here, A ′ = − A · η and B ′ = B · η. this
By combining the radiation transmission measurement results with the measured values of φ and D for microwaves according to equation (4),
The water content value W will be obtained.

[0008]

However, the radiation measuring device 6 used in the above-mentioned microwave type moisture measuring device 1 is severely regulated because its radiation adversely affects the human body. When installing and installing it, there are obligations to notify the relevant central government agencies, and detailed rules are set regarding maintenance after installation. Therefore, there is a problem in that the use thereof requires a great deal of cost and manpower.

The present invention has been made in order to solve the problems of the prior art as described above, and has the accuracy of being practically usable without using a radiation measuring device for density correction of coal. An object of the present invention is to provide a method for measuring water content and an apparatus therefor.

[0010]

According to the present invention, a microwave is propagated to a coal conveyed by a belt conveyor, and a moisture value is obtained from the change of the microwave to obtain a moisture value. A method for measuring water content of coal, which comprises measuring water content in an adjusted state. Further, the present invention, by propagating this using microwave to coal conveyed by the belt conveyor, in a moisture measuring apparatus for obtaining the moisture value from the change, the width of the belt conveyor installed on the belt conveyor. A water content measuring device for coal, comprising: a pair of left and right side skirts that can be freely expanded and contracted in a given direction, and a leveling device that adjusts a layer thickness of coal to a constant level.

[0011]

[Operation] The structure of the present invention will be described below.
As shown in FIG. 1, a pair of left and right side skirts 7, 7 are arranged near the coal dropping position from the upstream side belt conveyor 3a on the belt conveyor 3 so as to sandwich the moisture measuring device 1, and the side skirt drive devices are arranged respectively. It is possible to expand and contract in the width direction of the belt conveyor 3 by 8, 8. The side skirt drive devices 8 and 8 are controlled based on a signal from the coal feed amount control device 10 via the side skirt control device 9. Further, a leveling device 11 for adjusting the layer thickness of the coal 2 is provided at a predetermined height by the holding members 12 and 12 on the top of the side skirts 7 and 7 at the substantially central portion.

Now, the layer thickness of coal 2 is L (m
When the lower surface height of the leveling device 11 is set to be m), the side skirt 7 has a predetermined bulk density with respect to the transport amount W _COAL (t / h) of the coal 2. The distance W _SS (mm) between the distances 7 and 7 is calculated by the following equation (5). W _SS = {(W _COAL / K) -S _BC } / L (5) Here, K is a constant determined by the belt speed and the coal density, and S _BC is on the belt conveyor 3 shown in FIG. Is the area of the bottom of the coal cross section.

Since the layer thickness of the coal after being applied with the leveling device 11 is determined by the equation (5), it is not necessary to measure the layer thickness. Therefore, since the density of coal can be made constant in this way, the moisture measurement relational expression of the above equation (1) can be simply expressed as the following equation (6). W = (A ″ · φ / d) + (B ″ · D / d) + C (6) Here, the constants A ″ and B ″ are A ″ = A / Q and B ″, respectively.
= B / Q.

As a result, the water content W can be measured with substantially the same accuracy as the conventional method using the radiation transmission measurement result, by only measuring the phase change φ and the attenuation degree D of the microwave with the water content measuring device 1. Is possible.

[0015]

EXAMPLE The method of the present invention was applied to a belt conveyor on the outlet side of a coal dryer for feeding coal to a coke oven. The specifications of this belt conveyor are: belt width; 1050mm, belt speed;
210m / min, maximum transfer capacity; 600t / h, actual coal feed rate;
400t / h (same as maximum processing capacity of coal dryer). The layer thickness L was 110 mm, and the side skirt 7 width control period was 1 minute. The material of the side skirt 7 was made of stainless steel (SUS 304), a hydraulic cylinder was used as the side skirt drive device 8, and the moisture measurement period was set to 1 minute in accordance with the width control period of the side skirt 7. The measurement results by the method of the present invention are shown in Table 1. For comparison,
The measurement results by the conventional method are also shown in the same table. In addition, after adjusting the particle size with a pulverizer before the coal dryer, the water content was controlled with the coal dryer so that the target value was 6.5%. Further, for calibration of the microwave type moisture measuring device 1, measurement by an absolute drying method was performed once per day.

[0016]

[Table 1]

As is clear from Table 1, according to the method of the present invention, the difference between the absolute drying method and the conventional method is the same as that of the conventional method, even though the variation in the particle size of coal is large. It was confirmed that accuracy was obtained.

[0018]

As described above, according to the present invention,
Since the density of coal is controlled to be constant by always keeping the layer thickness on the belt conveyor constant according to the amount of coal to be conveyed, it is not necessary to use a radiation meter unlike the conventional method, This makes it possible to reduce the introduction cost of the moisture measuring device and also reduce the maintenance load.

[Brief description of drawings]

1A and 1B are plan views showing an embodiment of the present invention, and FIG.
FIG.

FIG. 2 is a sectional view taken along the line BB of FIG.

FIG. 3 is a schematic diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1 Moisture Measuring Device 2 Coal 3 Belt Conveyor 4 Computing Device 5 Display Device 7 Side Skirt 8 Side Skirt Drive Device 9 Side Skirt Control Device 10 Coal Feeding Volume Control Device 11 Leveling Device 12 Holding Member

Claims (2)

[Claims] 1. A water content measuring method in which a microwave is propagated to a coal conveyed by a belt conveyor to obtain a water content value from the change, in which the water content is measured while the layer thickness of the coal being conveyed is adjusted to be constant. A method for measuring the moisture content of coal, characterized in that 2. A water content measuring device, wherein microwave is propagated to coal conveyed by a belt conveyor by using microwaves, and a water content value is obtained from the change of the microwave, which is installed on the belt conveyor and the width direction of the belt conveyor. A moisture measuring device for coal, comprising: a pair of left and right side skirts that can be freely expanded and contracted, and a leveling device that constantly adjusts the layer thickness of coal.