RU2513465C1 - Method for efficient detection of coal bed moisture - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: invention relates to mining and may be used to increase efficiency of moistening of edge areas in coal beds to control sudden release of coal and gas by efficient and reliable detection of coal bed moisture during moistening. In the method, using a pneumatic drill, they drill a well in the side of a developing entry, they determine speed of drilling to moistening and after moistening of the coal bed, and moisture growth is determined based on the results of comparison of measurements of drilling speed and results of preliminary laboratory tests.

EFFECT: increased efficiency and increased safety in determination of coal moisture in a coal bed under mine conditions during moistening of edge zones of impact- and release-dangerous coal beds.

3 dwg

Description

The invention relates to mining and can be used to increase the reliability and effectiveness of monitoring the process of moistening the edge zones of coal seams, used to prevent rockburst and sudden emissions of coal and gas.

One of the main parameters in assessing the effectiveness of pre-wetting coal seams is the moisture content of coal.

A known method for determining the moisture content of coal by the gravimetric method. For this, coal samples in the form of cores are drilled from a coal seam for which moisture is required to be determined. Then the samples are placed in waterproof containers and delivered to the laboratory, where further research is carried out. In laboratory conditions, the weight of the samples is determined by weighing before drying and after drying to constant weight at a temperature of 105 ± 2 ° C [GOST 5180-84 (2005): Soils. Laboratory methods for determining physical characteristics]. Calculation of humidity of coal samples is carried out according to the formula

, $$W=\frac{m-m_0}{{\mathrm{<figure-callout\; id="0"\; label="m"\; filenames="00000005.png"\; state="\{\{state\}\}">m</figure-callout>}}_0}\times \mathrm{one\; hundred}\%$$

,

where W is the moisture content of the sample,%;

m, m ₀ - the mass of the sample before drying and after drying to a constant weight, respectively, kg

In the process of moistening the coal seam in certain places, coal is also sampled by drilling and delivered to the laboratory to determine moisture.

The disadvantage of this method is the low efficiency in determining moisture, because it requires special laboratory conditions and appropriate equipment.

Closer in essence is a method for determining the moisture content of coal in a coal seam by electrometric measurements. To do this, in the preparatory development in the zone of preliminary moistening of the coal mass, samples are taken for preliminary laboratory studies by drilling cores from the coal seam [Impact and outburst hazard assessment of the moist zones of coal seams / VV Dyrdin [et al.]; under the editorship of P.V. Egorova; KuzGTU, Zap.-Sib. Department of the Russian Academy of Natural Sciences. Kemerovo: Kuzbassvuzizdat, 2000, 134 s]. In laboratory conditions, the cores investigate and establish the functional relationship between the resistivity of coal and its moisture content in the form

W = f (ρ),

where ρ is the resistivity of coal.

 Then, in the preparatory development in the zone of preliminary wetting of the coal seam, control wells are drilled. Special electrodes are installed in the wells, which are then connected to a special electric measuring device used for these purposes, an intrinsically safe ohmmeter (voltmeter). In the process of humidification, the specific resistance of coal is measured, and the moisture value is determined by the functional dependence W = f (ρ), obtained previously in laboratory conditions.

The disadvantage of this method is the use of special intrinsically safe equipment. In some cases, the use of electrometric equipment when conducting preparatory workings on coal seams prone to sudden emissions of coal and gas is prohibited, which leads to the need to use other methods for determining the moisture of the coal seam.

The technical result of the invention is to increase the efficiency and safety when determining the moisture content of coal in a coal seam in a mine environment while moistening the edge zones of impact and outburst coal seams.

The specified technical result is achieved by the fact that the method for quickly determining the moisture of a coal seam includes preliminary laboratory tests on coal samples drilled from the coal seam to be moistened, drilling control wells in the edge of the coal mass, according to the invention, the moisture of the coal seam is determined by the drilling speed of the control well, using a nomogram or function

W = f (C),

where W is the moisture content of coal samples,%;

C - drilling speed, m / s;

previously obtained according to the results of laboratory studies.

Figure 1 presents a schematic diagram of an installation for determining the drilling speed of a coal sample in laboratory conditions, where 1 is a drilling machine; 2 - coal sample; 3 - drill; 4 - dynamometer.

Figure 2 presents the obtained graphical dependence (trend line, nomogram) of coal moisture on the drilling speed W = f (C), obtained using the MS EXCEL program.

Figure 3 presents the location of the control points relative to the humidification well: 1 - moisturizing wells in the preparatory development; 2 - drilling points of control wells for measuring the drilling speed; 3 - the calculated zone of moistening the coal seam; 4 - pumping unit.

A method for quickly determining the moisture content of a coal seam is as follows.

With the help of a drill bit and a pneumatic drill, coal samples are drilled in the form of cores in the preparatory development from the coal seam, where it is planned to hydrate.

In laboratory conditions, studies of the obtained coal samples are carried out: the moisture content of the coal samples and the drilling speed are determined. Using a drilling machine, a relationship is established between the drilling speed and the moisture content of the coal samples.

The drilling speed is determined in this way (figure 1):

- set a sample of coal on a drilling machine;

- establish a constant load on the drill using a dynamometer;

- using a stopwatch measure the drilling time t, and using a caliper, the drilling depth h;

- the drilling speed is determined by the formula

C = h / t

where h is the drilling depth, m;

t is the drilling time, s.

The moisture content of coal samples is determined as follows:

- a coal sample is weighed on a laboratory balance to determine the mass m before drying;

- a coal sample is dried in an oven at a temperature of 105 ± 2 ° C to constant weight and again weighed;

- determine the moisture content of the coal sample by the formula

, $$W=\frac{m-m_0}{{\mathrm{<figure-callout\; id="0"\; label="m"\; filenames="00000005.png"\; state="\{\{state\}\}">m</figure-callout>}}_0}\times \mathrm{one\; hundred}\%$$

,

where W is the moisture content of the coal sample,%;

m, m ₀ - mass of coal sample before drying and after drying to

constant weight, respectively, kg.

Similarly, studies are carried out with other samples of coal at various humidity. According to the results of studies in the MS EXCEL program, a graphical dependence of the moisture content of coal samples on the drilling speed W = f (C) is built, for which the trend line and its functional dependence are obtained using the program tools (Fig. 2):

W = kC + b,

where k and b are the constants of the trend line.

In the mine conditions, after humidification at the control points of the coal seam according to the diagram in Fig. 3, a well with a diameter of 43 mm is drilled with a pneumatic drill into the depth of the coal mass to a depth of 3-4 m, while fixing: the drilling depth, the force produced during drilling and time drilling one meter of the length of the well, and according to the formula

C = h / t

where h is the drilling depth, m;

t is the drilling time, s,

calculate the drilling speed C.

Using the functional dependence or nomogram obtained in laboratory conditions, establish the moisture content of the coal seam at the control points. To do this, knowing the drilling speed C ₀ before moistening the coal seam at its natural moisture content W ₀ , determine the parameter b ₁ for mine conditions from the equation: W ₀ = k ₁ C ₀ + b ₁ . Moreover, k ₁ = k. We get: b ₁ = W ₀ -k ₁ C ₀ . Using the obtained function for mine conditions, the coal seam moisture is determined after wetting using the formula W = KC + b ₁ , where C is the drilling speed of the control well after wetting.

An example of the method for the rapid determination of the humidity of an outburst coal seam.

Samples of coal of the correct geometric shape are made, samples, for example, are drilled in the same way with respect to bedding from a coal seam (Severnaya mine, Verkhny seam, volatility yield - 28%, grade KZh), the ends are processed on a lathe or grinder and after processing the coal samples take the following geometric dimensions:

height H _arr = 56 · 10 ^-3 m;

diameter d _0бp = 43 · 10 ^-3 m.

10 coal samples are made. Then, in the laboratory, several coal samples are humidified, so that all coal samples have different humidity from 0% to 6%. On the drilling machine, holes are drilled with a diameter of d = 8.0 mm to a depth of h = 3 cm of the sample, while the constant applied force during drilling is fixed with a dynamometer, and the drilling time / with a stopwatch (Fig. 1).

The drilling speed is determined by the formula

C = h / t = 3 / 0.75 = 4 cm / min,

where h is the drilling depth, m;

t is the drilling time, s.

The applied force must be such that the pressure generated on the drill during drilling in laboratory conditions and in the shaft is the same:

, $$\sigma =\frac{P}{S}=\frac{P}{\frac{\mathrm{one}}{\mathrm{four}}\mathrm{<figure-callout\; id="2"\; label="\pi \; d"\; filenames="00000005.png"\; state="\{\{state\}\}">\pi \; </figure-callout>}{d}^{}{}^2}=\frac{13.84}{\frac{\mathrm{one}}{\mathrm{four}}\cdot 3.14\cdot {0.008}^2}=276000P\mathrm{but}$$

,

where P = 13.84 - the force exerted on the drill, N;

d is the diameter of the drill, m

The speed of rotation of the drill should be the same.

Then, for each sample of coal after drilling, determine its moisture content. For this, the coal sample is weighed, the mass is determined before drying m, the coal sample is dried in an oven at a temperature of 105 ± 2 ° C to constant mass m ₀ and again weighed, the sample moisture is determined by the formula

, $$W=\frac{m-m_0}{{\mathrm{<figure-callout\; id="0"\; label="m"\; filenames="00000005.png"\; state="\{\{state\}\}">m</figure-callout>}}_0}\times \mathrm{one\; hundred}\%$$

,

where W is the moisture content of the coal sample,%;

m, m ₀ is the mass of the coal sample before drying and after drying to a constant weight, respectively, kg.

Similarly, studies are carried out with other samples at different humidity.

In the MS EXCEL program, a graphical dependence of the moisture content of coal samples on the drilling speed W = f (C) is built, for which the trend line and its functional dependence are obtained using the program tools: W = kC + b or W = 1,0215С-3,2184 (Fig. 2), k and b are the constants of the trend line.

In the mine conditions, after humidification at the control points according to the diagram in Fig. 3, a pneumatic drill is used to drill wells with a diameter of 43 mm deep into the coal seam to a depth of 3-4 m, while fixing: the drilling depth, the force produced during drilling and the drilling time of one meter length of the well, and according to the formula

C = h / t

where h is the drilling depth, m;

t - drilling time, s, calculate the drilling speed.

Using the functional dependence or nomogram obtained using the MS EXCEL program based on the results of laboratory tests, the moisture of the coal seam is established at the control points. For this, knowing the drilling speed C ₀ = 4 cm / min of the well before moistening at the natural moisture content of the coal seam W ₀ = 1.5%, determine the parameter b ₁ for mine conditions from the equation: W ₀ = 1.0215C ₀ + b ₁ . Moreover, k ₁ = k. We get: b _l = W ₀ -1.0215C ₀ = 1.5-1.0215-4 = -2.586.

см/мин.After wetting the coal seam, the drilling speed of the control well is measured: $$C=\frac{96}{12}=8$$

cm / min

Using the obtained function for mine conditions, we determine the moisture of the coal seam after wetting: W = 1.0215С-2.586 = 1.0215 · 8-2.586 = 5.586%.

Thus, a technical result is achieved, which consists in increasing the efficiency of the results due to the lack of laboratory research on coal samples after wetting and increasing safety during preventive work, since electrometric equipment is not used in the preparatory development.

Claims (1)

A method for quickly determining the moisture of a coal seam, including preliminary laboratory tests on coal samples drilled from a coal seam to be moistened, drilling control wells in the edge of the coal mass, characterized in that the humidity of the coal seam is determined by the drilling speed of the control well using a nomogram or function
W = f (C),
where W is the moisture content of coal samples,%;
C - drilling speed, m / s,
previously obtained according to the results of laboratory studies.

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