CN104614201A - Method for measuring raw CO gas content of coal seam - Google Patents

Abstract

The invention discloses a method for measuring the primary CO gas content of a coal seam. The method comprises: obtaining a coal sample by a wet drilling sampling method, and putting the coal sample into a whole-process integrated airtight sample tank whose airtightness has been checked; After entering the coal sample, use the airtight sample tank and use the atmospheric pressure natural desorption and degassing method to obtain the downhole CO desorption amount; then use the atmospheric pressure nitrogen desorption method to measure the CO desorption amount of the coal sample in the airtight sample tank before and after pulverization ; Use the air pressure change principle to correct the measured CO desorption amount in the well and the CO desorption amount before and after the coal sample is crushed, and then determine the CO loss during the measurement process through the exposure time of the coal sample; The sum of CO desorption and CO loss is taken as the original CO gas content of the coal seam. By adopting the measuring method disclosed in the invention, the original CO gas content of the coal seam can be accurately measured.

Description

Determination method of primary CO gas content in coal seam

technical field

The invention relates to the technical field of mines, in particular to a method for measuring the content of primary CO gas in coal seams.

Background technique

In the prediction and prediction of coal spontaneous combustion, the indirect method is mainly used, and the state of coal spontaneous combustion is determined by collecting gas samples and analyzing them and comparing them with the measured index gases. CO (carbon monoxide) gas is a commonly used and effective indicator gas because of its high concentration, high sensitivity, and low generation temperature. However, field practice has shown that coal spontaneous combustion is not the only source of underground CO gas, and some coal seams will also absorb a certain amount of CO gas. Therefore, during the mining process of some mines, it is very likely that coal does not spontaneously ignite and CO gas exceeds the limit, which affects the judgment of coal spontaneous combustion state and the normal production work of the mine. Produce paralysis, cause greater hidden danger to mine fire prevention and control work.

In the research and on-site analysis of mine fire prevention and control, it was generally believed that the generation of CO gas in coal seams was caused by the natural combustion of coal seams, thus ignoring the reasons such as the desorption and release of adsorbed CO gas in coal seams, which posed a great threat to the safety of coal mines. . At present, there is no specific method for the determination of primary CO gas in coal seams. Some tentative testing methods have high uncertainty, low repeatability, and poor effect. Determination.

Contents of the invention

The purpose of the present invention is to provide a method for measuring the original CO gas content of the coal seam, which can accurately measure the original CO gas content of the coal seam.

The purpose of the present invention is achieved through the following technical solutions:

A method for measuring coal seam primary CO gas content, the method comprising:

The coal sample is obtained by the wet drilling sampling method, and the coal sample is put into a whole-process integrated airtight sample tank that has been checked for airtightness;

After loading the coal sample, use the airtight sample tank downhole and use the normal pressure natural desorption degassing method to obtain the downhole CO desorption amount;

Then use the atmospheric pressure nitrogen desorption method to measure the CO desorption amount before and after the pulverization of the coal sample in the airtight sample tank;

Using the air pressure change principle to correct the measured CO desorption amount in the well and the CO desorption amount before and after the coal sample is pulverized, and then determine the CO loss during the measurement process through the exposure time of the coal sample;

The sum of the corrected downhole CO desorption amount, the CO desorption amount before and after coal sample pulverization, and the CO loss amount was taken as the original CO gas content of the coal seam.

Further, the described adopting the wet drilling sampling method to obtain the coal sample, and putting the coal sample into the whole-process integrated airtight sample tank whose airtightness has been checked includes:

Take coal samples in the drill holes in the perforable layer of Shimen or rock roadway, and inject water continuously during the drilling process of the drill pipe;

In the newly exposed coal roadway, use a coal core extractor or other fixed-point sampling device to collect coal samples at fixed points, and put them into a fully integrated airtight sample tank that has been checked for airtightness; wherein, the particle size of the coal sample does not exceed the airtight sample tank 1/2 of the aperture.

Further, after the coal sample is loaded, using the airtight sample tank downhole and using the atmospheric pressure natural desorption degassing method to obtain the downhole CO desorption amount includes:

Connect the CO desorption rate measuring instrument to the airtight sample tank by using the drainage gas collection method, and continuously inject nitrogen gas at a preset flow rate through the vent port for a certain period of time, and collect the gas;

Natural absorption and desorption of the collected gas: record the reading of the measuring tube and the measurement time at regular intervals, and observe continuously until the predetermined time or the desorption amount is less than the predetermined value; obtain the desorption amount of downhole CO according to the reading of the measuring tube.

Further, the desorption amount of CO desorption measured before and after pulverization of the coal sample in the airtight sample tank by using the atmospheric pressure nitrogen desorption method includes:

Before and after the pulverization of the coal sample, under the control of the mass flow meter, the degassing method is realized by nitrogen filling and desorption under the control of the mass flowmeter, and then the gas is collected by the drainage and gas collection method and the gas sample is collected until the CO gas in the gas cannot be detected by the chromatograph , so as to obtain the amount of CO desorption before and after pulverization of the coal sample.

Further, the determination of CO loss during the measurement process through the coal sample exposure time includes:

According to the coal sample exposure time combined with Determine the amount of CO lost during the measurement process using the method or the power index method.

It can be seen from the above-mentioned technical solution provided by the present invention that, in the coal sample collection process, the wet borehole sampling with continuous water injection during the drilling process can be used to reduce the direct contact between coal and air and the loss of contained gas during the sampling process; and, In the measurement process, the whole integrated airtight sample tank is used, that is, the same airtight sample tank is used in the process of downhole sampling degassing, atmospheric pressure nitrogen desorption before and after coal sample crushing, so as to reduce the amount of coal samples and air. Oxygen is in contact with each other to reduce the possibility of errors and mistakes; in addition, the desorption and degassing of coal samples adopts the method of nitrogen filling and desorption under normal pressure, which can effectively prevent the outside air from entering the sealed sample tank. The use of nitrogen further ensures The coal sample will not be oxidized, and on the other hand, it is also conducive to the desorption of gas in the coal sample.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings on the premise of not paying creative work.

Fig. 1 is a flow chart of a method for measuring the primary CO gas content of a coal seam provided by an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example

Fig. 1 is a flow chart of a method for measuring the primary CO gas content of a coal seam provided by an embodiment of the present invention. As shown in Figure 1, the method mainly includes the following steps:

Step 11. The coal sample is obtained by the wet drilling sampling method, and the coal sample is put into the whole-process integrated airtight sample tank whose airtightness has been checked.

In the embodiment of the present invention, coal samples are collected by drilling in the perforable layer of Shimen or rock roadway, and water is injected continuously during the drilling process of the drill pipe; coal core extractors or other fixed-point sampling devices are used in newly exposed coal roadways Collect coal samples at fixed points and put them into a fully integrated airtight sample tank that has been checked for airtightness; among them, the particle size of the coal sample does not exceed 1/2 of the aperture of the airtight sample tank.

Step 12. After loading the coal sample, use the airtight sample tank downhole and use the atmospheric pressure natural desorption and degassing method to obtain the downhole CO desorption amount.

In the embodiment of the present invention, the CO desorption rate measuring instrument is connected to the airtight sample tank by the drainage gas collection method, and the nitrogen gas is continuously injected into the air port for a certain period of time at a preset flow rate, and the gas is collected; the collected gas is collected. Natural desorption: Record the reading of the measuring tube and the measurement time at regular intervals, and observe continuously until the predetermined time or the desorption amount is less than the predetermined value; obtain the desorption amount of downhole CO according to the reading of the measuring tube.

Step 13, using the atmospheric pressure nitrogen desorption method to measure the CO desorption amount before and after pulverization of the coal sample in the airtight sample tank.

In the embodiment of the present invention, before and after the pulverization of the coal sample, under the control of the mass flow meter, the degassing method is realized by nitrogen filling and desorption under the control of the mass flow meter, and then the gas is collected by the drainage and gas collection method and the gas sample is collected until it cannot be detected by the chromatograph. CO gas is contained in the gas, so as to obtain the CO desorption amount before and after the pulverization of the coal sample.

Step 14: Correct the measured downhole CO desorption amount and the CO desorption amount before and after coal sample pulverization by using the air pressure change principle, and then determine the CO loss amount during the measurement process according to the exposure time of the coal sample.

In the embodiment of the present invention, according to the coal sample exposure time combined with Determine the amount of CO lost during the measurement process using the method or the power index method.

Step 15: The sum of the corrected downhole CO desorption amount, the CO desorption amount before and after coal sample pulverization, and the CO loss amount is taken as the primary CO gas content of the coal seam.

In addition, the amount of non-desorbable CO at normal pressure can also be considered, that is, the sum of the amount of downhole CO desorption, the amount of CO desorption before and after coal sample crushing, the amount of CO loss, and the amount of non-desorbable CO under normal pressure can be taken as the original CO gas content of the coal seam.

For ease of understanding, the above steps of the embodiment of the present invention will be described in detail below in conjunction with a specific example.

1. Collection of coal samples

1) Preparation before sampling

(1) All sealed sample tanks used for sampling must be tested for air tightness before use; the air tightness test can be performed by injecting air into the sealed sample tank to a gauge pressure of 1.5 MPa or more, and then leave it for 12 hours after closing without pressure drop or It can be used only when it is put into water without bubbles.

(2) Before using the desorption instrument, fill the measuring tube with water, close the bottom plug and turn it upside down. It is qualified if the water level in the measuring tube does not drop for 10 minutes.

2) Collect coal samples

(1) Sampling drilling arrangement

At least two sampling boreholes shall be arranged at the same location, and the distance between sampling points shall not be less than 5m.

(2) Sampling method

Coal samples are collected by drilling in the penetrable layer of Shimen or rock roadway, and water is injected continuously during the drilling process of the drill pipe. In newly exposed coal roadways, coal core extractors (referred to as coal core pipes) or other fixed-point sampling should be preferred. The device collects coal samples at fixed points.

(3) Sampling depth

The sampling depth should exceed the influence range of the roadway at the drilling construction site, and meet the following requirements: when sampling at the mining face, the sampling depth should be determined according to the exposure time of the mining face, but should not be less than 12m; , the vertical distance from the coal seam shall depend on the lithology, but shall not be less than 5m.

(4) Sampling time

Sampling time refers to the actual time taken for the coal sample used for CO content determination from exposure to being sealed in a closed sample tank, which should not exceed 20s.

(5) Sampling requirements

When collecting coal samples, the following requirements should be met: use the wet method of drill pipe water injection to drill and sample until the coal samples are taken out; for columnar coal cores, take the complete part without gangue in the middle; For gangue and ground charred parts, only measure the coal samples with larger particle size, but also pay attention to the aperture size of the airtight sample tank, the maximum particle size of the coal sample should not exceed 1/2 of the aperture; do not wash the coal sample with water , keep it in a natural state and put it into a sealed tank, do not compact it, leave a gap of about 50mm at the tank mouth, put the metal block used when the coal sample is broken into the airtight sample tank before loading the sample, the weight of the airtight sample tank and the metal block is already Weigh (W1) before sampling.

(6) Sampling record

When sampling, the following relevant parameters should be collected and recorded in the sampling record table: sampling location - mine name, coal seam name, buried depth (ground elevation, coal seam floor elevation), sampling depth, drilling orientation, drilling inclination angle; sampling time - Sampling start time, sampling end time, coal sample canning end time; number - tank number, sample number.

2. Measurement method and steps

1) Measurement of downhole natural desorption of CO

(1) The amount of natural desorption of CO in the well is measured by the drainage and gas collection method. The CO desorption rate measuring instrument is connected to the airtight sample tank, and the nitrogen gas is continuously injected at a flow rate of 200ml/min for 4 minutes through the vent port, and the gas is collected (G1). Record its volume V ₁ , after which the natural desorption of the gas begins.

(2) Record the reading of the measuring tube and the measurement time at regular intervals, observe continuously (60-120) min or until the desorption volume is less than 2 cm ³ /min, collect the gas sample (G2), and record its volume V ₂ . Within 30 minutes before the start of the observation, read the data every 1 minute, and then read the data every (2-5) minutes; fill in the observation results in the measurement record form, and record the air temperature, water temperature and atmospheric pressure at the same time.

(3) After the measurement is finished, seal the sample tank and sink it into clear water, observe carefully for 10 minutes, if bubbles are found, the sample should be discarded and re-sampled for testing; if there is no air leakage, send it to the experiment The room continues to be fixed. The collected gas samples G1 and G2 are tested for CO concentration in the laboratory using a gas chromatograph, which are recorded as C ₁ and C ₂ respectively.

2) Determination of residual CO content

(1) Coal sample inspection and registration

After the coal sample is delivered to the laboratory, conduct a leak test according to the above method; if a leak is found, it is a waste sample, and the inspection result will be indicated in the report; check whether the coal sample delivery test sheet is consistent with the tank number, and whether the experimental data are complete ; After the inspection is correct, the registration number is unified, and the sealed sample tank is weighed (W2), and then the next step of measurement is carried out.

(2) Atmospheric pressure nitrogen desorption

①Desorption system tightness inspection

Fill the measuring tube with water to a certain height and isolate the measuring tube from connecting with the outside world. After the liquid level is stable, if the liquid level in the measuring tube drops by less than ^2cm within 5 minutes, the gas path sealing is qualified.

②The airtight sample tank is connected to the desorption device

Connect the airtight sample tank to the atmospheric pressure nitrogen desorption device through a rubber hose.

③Measurement of nitrogen desorption CO amount before pulverization

a. Fill the desorption volumetric tube with water to a certain scale, read and record the initial reading of the liquid level of the volumetric tube, first open the nitrogen valve of the vent pipe, then slowly open the valve of the closed sample tank, read the gas production once at a certain time interval, analyze and collect Whether the gas volume is basically the same as the nitrogen gas volume, and if abnormalities are found, deal with them in time or scrap them.

b. When the measured desorption gas volume reaches 80% of the maximum range of the measuring tube, record the gas production volume, turn on the switch to discharge the gas, and collect the sample (G3) with the gas collection bag, and record the gas volume as CO concentration was measured using a gas chromatograph Repeat at intervals of one hour until the CO concentration in the gas is lower than 1ppm, and the volume and concentration of the gas collected each time are recorded as and … and so on.

c. Record the temperature of the desorption environment, atmospheric pressure, coal sample weight, test personnel, and the time when the coal sample is delivered to the laboratory and the ground desorption starts, and fill the test measurement data into the record sheet.

④Measurement of desorbing CO by pulverizing and filling with nitrogen

a. Leakage inspection: Carry out airtightness inspection in the same way as above.

b. Crush the coal sample: Load the airtight sample tank on the coal sample crusher, and continue to crush it at a specific vibration frequency for 3 hours.

c. Measuring the amount of crushed nitrogen-filled desorption CO: Connect the closed sample tank to the atmospheric pressure nitrogen-filled desorption device through a rubber tube; Slowly open the valve of the closed sample tank after the nitrogen valve of the trachea, read the gas production volume at a certain time interval, analyze whether the gas production volume is basically consistent with the nitrogen gas volume, and deal with any abnormality in time or scrap it; when the measured desorption gas volume reaches the maximum of the measuring tube When the range is 80%, record the gas production volume, turn on the transfer switch to discharge the gas, and collect the sample (G4) with the gas collection bag, and record the gas volume as CO concentration was measured using a gas chromatograph Repeat at intervals of one hour until the CO concentration in the gas is lower than 1ppm, and the volume and concentration of the gas collected each time are recorded as and … and so on.

d. After the measurement, take out the coal sample, use a precision balance to measure its weight (W3), and analyze the weight difference between the two weighings of the other closed sample tanks, which is roughly equal. If the difference does not exceed 1%, then W3 is considered to be the weight of the coal sample .

e. Record the temperature of the desorption environment, atmospheric pressure, coal sample weight, test personnel, and the time when the coal sample is delivered to the laboratory and the ground desorption starts, and fill the test measurement data into the record sheet.

The coal sample is qualified when 80% of the coal sample passes through a 60 mesh (0.25mm) sieve.

(3) Component analysis

The gas samples taken are sent to the laboratory in time, and the various components of the gas are analyzed using a gas chromatograph.

3. Data processing

1) Gas volume correction

(1) Correction principle

When desorbing with nitrogen at normal pressure, only the formula (1) is used to correct the gas volume in the measuring tube under the test environment.

(2) Conversion of natural desorption amount

According to formula (1), the reading of each measuring tube obtained in the desorption process is converted into the volume under the standard state:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 273.2</span>}}{\mathrm{<span\; class="notranslate">\; 101.3</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 273.2</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.00981</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula:

V _t ′——converted to the gas volume under the standard state, the unit is cubic centimeter (cm ³ );

V _t ——the volume of gas obtained during the desorption by filling nitrogen at normal pressure and the natural desorption volume, that is, V ₁ , V ₂ , as well as The unit is cubic centimeter (cm ³ );

p ₁ —atmospheric pressure, in kilopascals (kPa);

T _w - the water temperature in the measuring tube, in degrees Celsius (°C);

h _w - the height of the water column in the measuring tube, in millimeters (mm);

p ₂ —saturated vapor pressure of water at _Tw , in kilopascals (kPa).

Fill in the record sheet with each measuring tube reading converted one by one.

2) Calculation of loss amount

(1) Calculation of coal sample desorption time

① Exposure time (t ₀ ) is the time taken from coal sample exposure to the end of canning, calculated according to formula (2):

t ₀ =t ₂ -t ₁ (2)

In the formula:

t ₀ ——exposure time, in minutes (min);

t ₁ ——Coal core (crumbs) start time, hour: minute: second;

t ₂ ——the time when filling the tank (downhole desorption measurement starts), hour: minute: second.

② The desorption time of the coal sample is the sum of the desorption observation time t after the exposure time t ₀ after filling the tank, which is recorded as t ₀ +t.

(2) Calculation of lost gas volume

The amount of CO loss can be calculated by selecting the following two methods or other effective methods verified by experiments according to the measured rules.

① Law

This method is based on V and It is determined in a linear relationship, that is:

In the formula:

V——accumulative desorption volume within t time, unit is cubic centimeter (cm ³ );

V _loss '——the loss amount within the exposure time t ₀ , the unit is cubic centimeter (cm ³ );

K - undetermined constant.

Before calculating the V _loss ' value, first use As the abscissa, draw a graph with V as the ordinate, roughly determine the measuring points in a linear relationship from the graph, and then calculate the V _loss ' value according to the coordinate values of these points by the least square method or graphing method.

②Power function method

Convert the measured (t, V _t ) data into desorption velocity data ( q _i ), and fill in the record form, then for ( q _i ) Fit q ₀ and n according to formula (4).

q _t ＝q ₀ ·(1+t) ^-n (4)

In the formula:

q _t ——gas desorption rate at time t, unit is cubic centimeter per minute (cm ³ /min);

q ₀ ——the desorption speed at t ₀ , the unit is cubic centimeter per minute (cm ³ /min);

t——desorption time, in minutes (min);

n——Desorption speed attenuation coefficient, 0<n<1.

The loss of coal sample gas is calculated according to formula (6).

In the formula:

V _loss' —the loss of coal sample within the exposure time t ₀ , the unit is cubic centimeter (cm ³ );

t ₀ ——coal sample exposure time, unit is minute (min).

3) Calculation of CO content in coal seam

(1) Calculation of CO content in coal samples at each stage

Downhole CO desorption X ₁ , CO loss X ₂ , CO desorption X ₃ before pulverization and CO desorption X ₄ after pulverization are calculated according to formulas (6)-(9):

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

In the formula:

X _i - the amount of CO in coal samples at each stage (i=1, 2, 3, 4), in cubic centimeters per gram (cm ³ /g);

m—mass of coal sample (divided into air-dried base and dry ash-free base), in grams (g);

V ₁ ', V ₂ ', ——respectively the volume of gas at each stage after calibration in formula (1), in cubic centimeter (cm ³ );

_V'loss —the loss amount of coal sample within the exposure time t ₀ , the unit is cubic centimeter (cm ³ );

C _loss - the concentration of CO in the loss gas, which is approximately considered to be equal to the CO concentration of the downhole desorbed gas, that is, C _loss = C ₂ ;

C ₁ , C ₂ , ——CO gas concentration at each stage (j=1, 2, 3...n), the unit is ppm (10 ^-6 ).

In addition, the amount of non-desorbable CO at normal pressure can also be considered. The amount of non-desorbable CO at normal pressure can be calculated according to formula (10) or the adsorption capacity at normal pressure measured by MT/T 752 method. quantity.

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 0.1</span>}\mathrm{<span\; class="notranslate">\; ab</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 0.1</span>}\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; ad</span>}}}{\mathrm{<span\; class="notranslate">\; 100</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 0.31</span>}{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; ad</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

In the formula:

X _b ——the amount of non-desorbable CO in coal under standard atmospheric pressure, in cubic centimeters per gram (cm ³ /g);

a—CO adsorption constant of coal, the limit adsorption capacity of coal at the test temperature, the unit is cubic centimeter per gram (cm ³ /g);

b—CO adsorption constant of coal, unit is per megapascal (MPa ^-1 );

A ^ad - ash content of coal, %;

M ^ad — moisture content of coal, %;

π—the porosity of coal, in cubic centimeter per cubic centimeter (cm ³ /cm ³ );

γ—the bulk density (false specific gravity) of coal, in grams per cubic centimeter (g/cm ³ ).

(2) Calculation of CO content in coal seam

Calculate according to formula (11):

X＝X ₁ +X ₂ +X ₃ +X ₄ +X _b ..........(11)

In the formula:

X ₁ ——The amount of CO desorbed downhole of the coal sample, the unit is cubic centimeter per gram (cm ³ /g);

X ₂ —— CO loss amount of coal sample, unit is cubic centimeter per gram (cm ³ /g);

X ₃ —the amount of CO desorbed before the coal sample is pulverized, the unit is cubic centimeter short gram (cm ³ /g);

X ₄ ——The amount of CO desorbed after the coal sample is pulverized, the unit is cubic centimeter per gram (cm ³ /g);

X _b ——the amount of non-desorbable CO, in cubic centimeter per gram (cm ³ /g).

4) Calculation accuracy requirements

The above calculated values are processed according to the rounding off rules, and only four decimal places are retained. When the calculated value is less than four decimal places, only "trace amount" is stated in the measurement report.

In the embodiment of the present invention, during the coal sample collection process, the wet borehole sampling with continuous water injection during the drilling process is adopted, which can reduce the direct contact between coal and air and the loss of contained gas during the sampling process; Type airtight sample tank, that is, the same airtight sample tank is used in the process of downhole sampling degassing, atmospheric pressure nitrogen desorption before and after coal sample crushing, so that the coal sample can be reduced to avoid contact with oxygen in the air, reducing In addition, the desorption and degassing of coal samples adopts the method of atmospheric pressure nitrogen desorption, which can effectively prevent the outside air from entering the closed sample tank. The use of nitrogen further ensures that the coal samples will not be oxidized. , On the other hand, it is also beneficial to the desorption of gas in coal samples.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field can easily conceive of changes or changes within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (5)

1. a method for assaying coal seam primary CO gas content, is characterized in that, the method comprises: The coal sample is obtained by the wet drilling sampling method, and the coal sample is put into a whole-process integrated airtight sample tank that has been checked for airtightness; After loading the coal sample, use the airtight sample tank downhole and use the normal pressure natural desorption degassing method to obtain the downhole CO desorption amount; Then use the atmospheric pressure nitrogen desorption method to measure the CO desorption amount before and after the pulverization of the coal sample in the airtight sample tank; Using the air pressure change principle to correct the measured CO desorption amount in the well and the CO desorption amount before and after the coal sample is pulverized, and then determine the CO loss during the measurement process through the exposure time of the coal sample; The sum of the corrected downhole CO desorption amount, the CO desorption amount before and after coal sample crushing, and the CO loss amount was taken as the original CO gas content of the coal seam. 2. The method according to claim 1, wherein said adopting wet drilling sampling method to obtain the coal sample, and putting the coal sample into the airtightness-checked full-range integrated airtight sample tank comprises: Take coal samples in the drill holes in the penetrable layer of Shimen or rock roadway, and inject water continuously during the drilling process of the drill pipe; In the newly exposed coal roadway, use coal core extractor or other fixed-point sampling devices to collect coal samples at fixed points, and put them into the whole-process integrated airtight sample tank that has been checked for airtightness; wherein, the particle size of the coal sample does not exceed the airtight sample tank 1/2 of the aperture. 3. The method according to claim 1, characterized in that, after the coal sample is loaded, using the airtight sample tank downhole and using the normal pressure natural desorption degassing method to obtain the downhole CO desorption amount comprises: Using the drainage gas collection method, connect the CO desorption rate measuring instrument to the airtight sample tank, and continuously inject nitrogen gas at a preset flow rate through the vent port for a certain period of time, and collect the gas; Natural absorption and desorption of the collected gas: record the reading of the measuring tube and the measurement time at regular intervals, and observe continuously until the predetermined time or the desorption amount is less than the predetermined value; obtain the desorption amount of downhole CO according to the reading of the measuring tube. 4. method according to claim 1, is characterized in that, described utilizing atmospheric pressure nitrogen desorption method to measure the CO desorption amount before and after the pulverization of coal sample in airtight sample tank comprises: Before and after the pulverization of the coal sample, under the control of the mass flow meter, the degassing method is realized by nitrogen filling and desorption under normal pressure, and then the gas is collected by the drainage and gas collection method and the gas sample is collected until the CO gas in the gas cannot be detected by the chromatograph , so as to obtain the amount of CO desorption before and after pulverization of the coal sample. 5. The method according to claim 1, characterized in that, determining the amount of CO loss in the measurement process by coal sample exposure time comprises: According to the coal sample exposure time combined with Determine the amount of CO lost during the measurement process using the method or the power index method.