CN112113881A - Density measuring method and density measuring device for adsorptive methane in coal - Google Patents

Abstract

The disclosure relates to a density measurement method and a density measurement device for adsorptive methane in coal, wherein the density measurement method for adsorptive methane in coal comprises the following steps: obtaining volume V of sample coal_c(ii) a Obtaining pore volume in the sample coal

Placing the sample coal in a closed measurement space; obtaining a volume V of the measurement space₁(ii) a Introducing a predetermined amount of methane into the measurement space; measuring the pressure P of the measuring space after the sample coal adsorbs methane₁(ii) a By the formula

Calculating the density rho of the adsorptive methane in the sample coal_eg(ii) a Wherein N is introduced into the measurement spaceA predetermined amount of molecular weight of methane; n is a radical of_AIs an Avogastron constant, R is a gas constant; t is the thermodynamic temperature; and c is the equivalent curvature of the surface of the sample coal after methane adsorption. Through the technical scheme, the density of the adsorptive methane in the coal can be directly calculated, the operation is simple and convenient, and the result is accurate and reliable.

Description

Density measurement method and density measurement device of adsorbed methane in coal

technical field

The present disclosure relates to the field of energy exploration equipment, in particular, to a density measurement method and a density measurement device of adsorbed methane in coal.

Background technique

Geophysical exploration refers to the detection of geological conditions such as stratigraphic lithology and geological structure by studying and observing changes in various geophysical fields. Because the different rock media that make up the crust often have differences in density, elasticity, electrical conductivity, magnetism, radioactivity, and thermal conductivity, these differences will cause local changes in the corresponding geophysical fields. By measuring the distribution and variation characteristics of these physical fields, combined with the known geological data for analysis and research, the purpose of inferring geological properties can be achieved.

At present, AVO technology is commonly used for oil and gas detection. There are two key problems in AVO technology. One is the difference in wave impedance between the reservoir and the surrounding rock, and the difference between the coal seam and the surrounding rock is obvious, and it is easy to obtain high-quality reflected waves from the coal seam. There are differences in the elastic parameters of rocks when there is fluid, and the elastic parameters of rocks with different fluids can be calculated by fluid replacement. The bulk modulus of gas is a function of density. When the coal seam is dominated by adsorbed gas, the key point of detection is to accurately obtain the density of adsorbed methane. In the related art, the density of adsorbed methane in coal has always been estimated by indirect methods, which brings large errors to the exploration of coalbed methane.

SUMMARY OF THE INVENTION

The purpose of the present disclosure is to provide a method for measuring the density of adsorbed methane in coal, which can solve the problem of inaccurate results of the current method for measuring the density of adsorbed methane in coal, and the exploration of coalbed methane. bring about large errors.

Another object of the present disclosure is to provide a device for measuring the density of adsorbed methane in coal, so as to solve the problem that the current measurement of the density of adsorbed methane in coal is complicated in operation, inaccurate in results, and brings large errors to the exploration of coalbed methane. The problem.

In order to achieve the above object, the present disclosure provides a method for measuring the density of adsorbed methane in coal, comprising the following steps:

Obtain the volume V _c of the sample coal;

Obtain the pore volume in the sample coal

placing the sample coal in a closed measurement space;

obtain the volume V ₁ of the measurement space;

Passing a predetermined amount of methane into the measurement space;

After the sample coal adsorbs methane, measuring the pressure P ₁ of the measurement space;

计算所述样品煤中吸附性甲烷的密度ρ_eg；by formula

Calculate the density ρ _eg of adsorbed methane in the sample coal;

Among them, N is the number of molecules of the predetermined amount of methane passing into the measurement space; N _A is the Avogadro constant, R is the gas constant; T is the thermodynamic temperature; Efficient curvature.

Optionally, the step of feeding a predetermined amount of methane into the measurement space includes:

Passing methane into a reference space and measuring the pressure P2 of the reference space _;

obtaining the volume V ₂ of the reference space;

Connecting the reference space and the measurement space, so that the methane introduced into the reference space is distributed to the reference space and the measurement space;

计算所述样品煤中吸附性甲烷的密度。by formula

The density of adsorbed methane in the sample coal is calculated.

Optionally, the step of passing methane into the reference space and measuring the pressure P of the reference space includes _:

Passing methane of volume _V0 at standard atmospheric pressure completely into the reference space,

计算所述样品煤中吸附性甲烷的密度，by formula

Calculate the density of adsorbed methane in the sample coal,

Among them, V _s is the gas volume of 1 mol of methane in the standard state.

Optionally, after the step of feeding a predetermined amount of methane into the measurement space, let it stand for 3-10 minutes, and then measure the pressure P ₁ of the measurement space.

According to a second aspect of the present disclosure, there is also provided a density measurement device for adsorbed methane in coal, comprising:

The measuring chamber tank, which is constructed as a closed structure, is used to accommodate the sample coal;

an air source in communication with the measurement chamber tank; and

a pressure sensor, connected to the measuring chamber tank through a pipeline, for detecting the pressure in the measuring chamber tank;

计算所述样品煤中吸附性甲烷的密度；to be able to pass the formula

calculating the density of adsorbed methane in the sample coal;

为样品煤中的孔隙体积；V₁为所述测量室罐体(2)的体积；P₁为在样品煤吸附甲烷后所述测量室罐体(2)的压强；N为通入所述测量室罐体(2)的预定量的甲烷的分子个数；N_A为阿伏伽德罗常数，R为气体常数；T为热力学温度；c为样品煤吸附甲烷后的表面的等效曲率。Wherein, V _c is the volume of sample coal;

is the pore volume in the sample coal; V ₁ is the volume of the measurement chamber tank (2); P ₁ is the pressure of the measurement chamber tank (2) after the sample coal adsorbs methane; The number of molecules of the predetermined amount of methane in the measuring chamber tank (2); N _A is the Avogadro constant, R is the gas constant; T is the thermodynamic temperature; c is the equivalent curvature of the surface of the sample coal after adsorbing methane .

Optionally, also include:

a reference chamber tank, configured as a closed structure, connected between the gas source and the measurement chamber tank, and in selective communication with the measurement chamber tank,

The pressure sensor is communicated with the reference chamber tank through the pipeline;

计算所述样品煤中吸附性甲烷的密度；to be able to pass the formula

calculating the density of adsorbed methane in the sample coal;

Wherein, V ₀ is the volume of methane passed into the reference chamber tank under standard atmospheric pressure; V _s is the gas volume of 1 mol in the standard state; V ₂ is the volume of the reference chamber tank.

Optionally, a three-way ball valve is provided between the reference chamber tank body and the measurement chamber tank body, one port of the three-way ball valve is communicated with the atmosphere, and the other two ports are respectively connected with the reference chamber tank body and all the other ports. The measuring chamber tank is connected.

Optionally, the openings of the reference chamber tank body and the measurement chamber tank body are provided with sealing covers, and the ends of the reference chamber tank body and the measurement chamber tank body away from the opening are both provided with a sealing cover. The ejector rod is used to press the reference chamber tank body and the measurement chamber tank body against the sealing cover to form a closed space.

Optionally, it also includes a display connected to the pressure sensor for receiving and displaying the detection data of the pressure sensor.

Optionally, a pressure reducing valve is provided on one end of the pipeline at the gas source, and an unloading valve is provided on the pipeline at the outlet end of the pressure reducing valve.

放置样品煤的测量空间的体积V₁以及测量空间通入预定量的甲烷，在样品煤吸附甲烷后测量空间的压强P₁等各个参数，再通过公式

计算煤中吸附性甲烷的密度，该方法能够直接计算出煤中吸附性甲烷密度，结果准确可靠。Through the above technical solutions, the volume V _c of the sample coal and the pore volume in the sample coal are obtained

The volume V ₁ of the measurement space where the sample coal is placed and a predetermined amount of methane is fed into the measurement space, after the sample coal adsorbs methane, the pressure P ₁ and other parameters of the space are measured, and then through the formula

To calculate the density of adsorbed methane in coal, this method can directly calculate the density of adsorbed methane in coal, and the result is accurate and reliable.

Other features and advantages of the present disclosure will be described in detail in the detailed description that follows.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present disclosure, and constitute a part of the specification, and together with the following detailed description, are used to explain the present disclosure, but not to limit the present disclosure. In the attached image:

FIG. 1 is a flowchart of a method for measuring the density of adsorbed methane in coal provided by an exemplary embodiment of the present disclosure;

FIG. 2 is a structural diagram of a density measurement device for adsorbed methane in coal provided by an exemplary embodiment of the present disclosure.

Description of reference numerals

1 Reference chamber tank 2 Measurement chamber tank

3 Pressure sensor 4 Air supply

5 Line 6 3-Way Ball Valve

7 Paperless recorder 8 Seal cover

9 Ejector 10 Seal

11 Pressure reducing valve 12 Unloading valve

13 Stand

Detailed ways

The specific embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, but not to limit the present disclosure.

In the present disclosure, unless otherwise stated, the orientation words used, such as "upper, lower", may refer to the drawing direction shown in FIG. 1 . "Inside and outside" refers to the inside and outside of the corresponding part profile. Where the following description refers to the drawings, the same numerals in different drawings refer to the same or similar elements unless otherwise indicated.

再将样品煤置于封闭的测量空间，获取测量空间的体积V₁；进一步地，向测量空间通入预定量的甲烷，在样品煤吸附甲烷后，测量测量空间的压强P₁；获取通入测量空间的预定量的甲烷的分子个数N，可以将标准大气压下的甲烷通入一个容器中，通过克拉伯龙方程，根据容器的体积与压强可得到通入测量空间的预定量的甲烷的分子个数N；最后通过粒子显微镜测得样品煤吸附甲烷后表面的等效曲率c，关于样品煤吸附甲烷后表面的等效曲率c下面进行详细的说明：The present disclosure provides a method for measuring the density of adsorbed methane in coal, with specific reference to FIG. 2 , the method for measuring the density of adsorbed methane in coal includes the following steps: obtaining the volume V _c of the sample coal, and generally cutting the sample coal into regular shapes , such as a cylindrical shape, in order to calculate the volume V _c of the sample coal; then measure the porosity of the sample coal by a porosimeter, and multiply the volume of the sample coal by the porosity of the sample coal to obtain the pore volume in the sample coal

The sample coal is then placed in a closed measurement space, and the volume V ₁ of the measurement space is obtained; further, a predetermined amount of methane is introduced into the measurement space, and after the sample coal adsorbs methane, the pressure P ₁ of the measurement space is measured; The number of molecules N of the predetermined amount of methane in the measurement space can be passed into a container under standard atmospheric pressure. Through the Clapeyron equation, according to the volume and pressure of the container, the predetermined amount of methane passed into the measurement space can be obtained. The number of molecules is N; finally, the equivalent curvature c of the surface of the sample coal after adsorbing methane is measured by a particle microscope. The equivalent curvature c of the surface of the sample coal after adsorbing methane is described in detail below:

凸曲面为

凹曲面为

For convex and concave surfaces (the curvature body corresponds to the cross section), assuming that the coordinates of the particle P are (0, 0, -h) and (0, 0, h), the uniform coordinates of the particle are (0, 0, Z _p ), for For convex curves Zp ₌ -h, for concave curves Zp ₌ h. Define dimensionless coordinates~

The convex surface is

The concave surface is

Expression for surface body potential with external particles:

高斯曲率

以及主曲率

有以下关系：Dimensionless mean curvature

Gaussian curvature

and the principal curvature

There are the following relationships:

Substituting equation (2)(3) into equation (1), we get

Equation (4) is dimensionless and can be rewritten as:

其中

为粒子P与半有限平面相互作用的相互作用势。假设粒子之间的对势u(r)＝C/rn,其中r和C的距离是常数。对于半无限平面，假设其分子数密度为ρ，粒子与平面的距离为h，则

可以表示为：Equation (5) gives the expression of the potential between the surface and the external particles. When the surface becomes flat, where H=K=0, then there is

in

is the interaction potential of the particle P interacting with the semifinite plane. Suppose the pair potential between particles u(r)=C/rn, where the distance between r and C is constant. For a semi-infinite plane, assuming that its molecular number density is ρ, and the distance between the particle and the plane is h, then

It can be expressed as:

因此,

回到式(4)，取n＝6为范德瓦尔斯势，得到：Suppose one of the principal curvatures is 0, and the other principal curvature that is not 0 is

therefore,

Going back to formula (4), taking n=6 as the van der Waals potential, we get:

忽略式(7)中的二阶，它会得到：Note that in formula (7), the concave surface has

Ignoring the second order in equation (7), it gives:

是常数，对于引力势，

是负的。In formula (9),

is a constant, for the gravitational potential,

is negative.

In the vicinity of the material surface, the external particles will be affected by the driving force generated by the curvature, and the larger the curvature _˜c1 , the greater the attractive force. At the onset of adsorption, the methane molecules near the surface of the sample coal will move towards places where the surface curvature is large. When methane is gradually adsorbed in the place of large area, the place gradually becomes flat and the curvature gradually decreases, and finally an equipotential surface with the same surface curvature at any point is formed. The purpose of the derivation of the equipotential surface function is to clarify the state of methane adsorption in coal.

On a two-dimensional plane, any curve is represented by a function f, and the curvature of any point on the curve is:

Then there are:

Let f'=P; then there is

Separate variables:

Integrate both sides:

Let P=tanu, then

So

so

sin(arctanP)+A ₂ =cx+A ₁ ; if A=A ₁ -A ₂

arctanP=arcsin(cx+A) (17)

so

Let Q=cx+A

so

样品煤中吸附性甲烷的体积

It can be seen from equation (23) that in the two-dimensional plane, the final shape of methane adsorption in the sample coal is a circle, and when extended to three-dimensional, methane is adsorbed in coal pores, and the final adsorption shape is a spherical shape. Therefore, the volume of free methane in the sample coal is

The volume of adsorbed methane in the sample coal

The volume of free methane in the measurement space is

The total molecular mass M of the incoming CH ₄ is:

After the sample coal adsorbs methane, the number n of free methane molecules in the measurement space is:

After the adsorption is completed, the mass M _eg of the adsorbed methane in the sample coal is:

计算样品煤中吸附性甲烷的密度ρ_eg；其中，N_A为阿伏伽德罗常数，R为气体常数；T为热力学温度。Finally, by formula

Calculate the density ρ _eg of the adsorbed methane in the sample coal; wherein, NA is the Avogadro constant, _R is the gas constant; T is the thermodynamic temperature.

It should be noted that the method for measuring the density of adsorbed methane in coal provided by the present disclosure does not limit the order of each step. For example, the volume V ₁ of the measurement space can be obtained first, and then the sample coal can be placed in the measurement space. All parameters are sufficient, and all belong to the protection scope of the present disclosure.

因此通过公式

计算样品煤中吸附性甲烷的密度。According to some embodiments, the step of introducing a predetermined amount of methane into the measurement space includes: introducing methane into the reference space and measuring the pressure P ₂ of the reference space; obtaining the volume V ₂ of the reference space; connecting the reference space with the measurement space, So that the methane entering the reference space is distributed to the reference space and the measurement space, so that the number of molecules of the predetermined amount of methane entering the measurement space can be accurately obtained:

So by formula

Calculate the density of adsorbed methane in the sample coal.

其中，V_s为标准状态下1mol的气体体积。因此，通过公式

计算样品煤中吸附性甲烷的密度。Specifically, the steps of passing methane into the reference space and measuring the pressure P ₂ of the reference space include: completely passing methane with a volume of V ₀ under standard atmospheric pressure into the reference space, and the gas pressure at this time is P ₂ , according to Boyle Law: V ₂ ·P ₂ =V ₀ ·P ₀ , where P ₀ is the standard atmospheric pressure, and the number N of molecules of CH ₄ introduced is:

Among them, V _s is the gas volume of 1 mol in the standard state. Therefore, by formula

Calculate the density of adsorbed methane in the sample coal.

Further, after the step of introducing a predetermined amount of methane into the measurement space, it needs to stand for 3-10 minutes until the methane adsorption is complete and the pressure in the measurement space is stable, and then the pressure P ₁ in the measurement space is measured.

可以计算出样品煤中吸附性甲烷的密度；其中，V_c为样品煤的体积；

为样品煤中的孔隙体积；V₁为测量室罐体2的体积；P₁为在样品煤吸附甲烷后测量室罐体2的压强；N为通入测量室罐体2的预定量的甲烷的分子个数；N_A为阿伏伽德罗常数，R为气体常数；T为热力学温度；c为样品煤吸附甲烷后的表面的等效曲率。另外，管线5可以为高压管线，以便于甲烷气体流入测量室罐体2。The present disclosure also provides a density measurement device for adsorbed methane in coal. Referring to FIG. 1 , the density measurement device for adsorbed methane in coal includes: a measurement chamber tank 2 , a gas source 4 and a pressure sensor 3 , wherein the measurement chamber The tank body 2 is constructed as a closed structure for accommodating the sample coal. The gas source 4 is communicated with the measurement chamber tank body 2. The gas source 4 can be a gas cylinder containing methane. The pressure sensor 3 and the measurement chamber tank body 2 pass through the pipeline 5. connection to detect the pressure in the measuring chamber tank 2, and then through the formula

The density of adsorbed methane in the sample coal can be calculated; where V _c is the volume of the sample coal;

is the pore volume in the sample coal; V ₁ is the volume of the measuring chamber tank 2; P ₁ is the pressure of the measuring chamber tank 2 after the sample coal adsorbs methane; N is the predetermined amount of methane that passes into the measuring chamber tank 2 NA is the Avogadro constant, _R is the gas constant; T is the thermodynamic temperature; c is the equivalent curvature of the surface of the sample coal after adsorbing methane. In addition, the pipeline 5 may be a high-pressure pipeline so that the methane gas flows into the measuring chamber tank 2 .

Through the above technical solution, each parameter in the formula can be directly and accurately measured. The density measuring device provided by the present disclosure has simple structure, convenient operation, accurate measurement results, and can directly calculate the density of adsorbed methane in coal.

计算样品煤中吸附性甲烷的密度，其中，V₀为通入参考室罐体1的甲烷在标准大气压下的体积；V_s为标准状态下1mol甲烷的气体体积；V₂为参考室罐体1的体积。In an exemplary embodiment of the present disclosure, the device for measuring the density of adsorbed methane in coal further comprises: a reference chamber tank 1, which is configured as a closed structure, connected between the gas source 4 and the measurement chamber tank 2, and connected with the gas source 4 and the measurement chamber tank 2. The measuring chamber tank 2 is selectively connected, and the pressure sensor 3 is communicated with the reference chamber tank 1 through a pipeline 5 . When starting the measurement, first pass a predetermined amount of methane into the reference chamber tank 1, obtain the volume and pressure of the reference chamber tank 1, and obtain the volume of the predetermined amount of methane and the standard atmospheric pressure according to Boyle's law, and then obtain the flow rate. The number of methane molecules in the reference chamber tank 1; then turn on the pipeline 5 between the reference chamber tank 1 and the measurement chamber tank 2, so that the methane is distributed to the reference chamber tank 1 and the measurement chamber tank 2, through the pressure The sensor 3 obtains the pressure of the measuring chamber tank 2 after methane adsorption, and then passes the formula

Calculate the density of adsorbed methane in the sample coal, where V ₀ is the volume of methane passing into the reference chamber tank 1 under standard atmospheric pressure; V _s is the gas volume of 1 mol of methane in the standard state; V ₂ is the reference chamber tank 1 volume.

Referring to Figure 1, a three-way ball valve 6 may be provided between the reference chamber tank 1 and the measurement chamber tank 2. One port of the three-way ball valve 6 is connected to the atmosphere, and the other two ports are respectively connected to the reference chamber tank 1 and the measurement chamber tank. Body 2 is connected. Through the three-way ball valve 6, the methane in the reference chamber tank 1 can be passed into the measurement chamber tank 2, and the methane gas after the measurement can be discharged out of the reference chamber tank 1 and the measurement chamber tank 2, so as to repeat the test and increase the Accuracy.

In order to make the reference chamber tank 1 and the measurement chamber tank 2 form a closed structure respectively, a sealing cover 8 is provided at the opening of the reference chamber tank 1 and the measurement chamber tank 2. The reference chamber tank 1 and the measurement chamber tank One end of 2 away from the opening is provided with a push rod 9, and the push rod 9 can be a high-strength push rod, so that the reference chamber tank body 1 and the measurement chamber tank body 2 are pressed against the sealing cover 8 to form a closed space. In addition, sealing rings are respectively provided between the sealing cover 8 and the reference chamber body 1 and between the sealing cover 8 and the measurement chamber body 2, so that the reference chamber body 1 and the measurement chamber body 2 are more tightly sealed. Further, both the reference chamber tank body 1 and the measurement chamber tank body 2 are arranged on the bracket 13 .

According to some embodiments, the device for measuring the density of adsorbed methane in coal further includes a display 7 connected to the pressure sensor 3 for receiving and displaying the detection data of the pressure sensor 3 , so that the measuring personnel can intuitively record the experimental data through the display 7 .

Further, referring to FIG. 1 , a pressure reducing valve 12 is arranged on the end of the pipeline 5 located at the gas source 4 , and an unloading valve 12 is arranged at the outlet end of the pressure reducing valve 11 on the pipeline 5 . The pressure reducing valve 11 and the unloading valve 12 can ensure the safety of the density measuring device under high pressure.

The preferred embodiments of the present disclosure have been described above in detail with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details of the above-mentioned embodiments. Various simple modifications can be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure. These simple modifications all fall within the protection scope of the present disclosure.

In addition, it should be noted that the various specific technical features described in the above-mentioned specific embodiments can be combined in any suitable manner unless they are inconsistent. In order to avoid unnecessary repetition, the present disclosure provides The combination method will not be specified otherwise.

In addition, the various embodiments of the present disclosure can also be arbitrarily combined, as long as they do not violate the spirit of the present disclosure, they should also be regarded as the contents disclosed in the present disclosure.

Claims (10)

1. A density measurement method of adsorptive methane in coal comprises the following steps:

obtaining volume V of sample coal_c；

Obtaining pore volume in the sample coal

Placing the sample coal in a closed measurement space;

obtaining a volume V of the measurement space₁；

Introducing a predetermined amount of methane into the measurement space;

measuring the pressure P of the measuring space after the sample coal adsorbs methane₁；

By the formula

Calculating the density rho of the adsorptive methane in the sample coal_eg；

Wherein N is the number of molecules of a predetermined amount of methane introduced into the measurement space; n is a radical of_AIs an Avogastron constant, R is a gas constant; t is the thermodynamic temperature; and c is the equivalent curvature of the surface of the sample coal after methane adsorption.

2. The density measurement method according to claim 1,

the step of introducing a predetermined amount of methane into the measurement space comprises:

introducing methane into a reference space and measuring the pressure P of said reference space₂；

Obtaining a volume V of the reference space₂；

Communicating the reference space with the measurement space such that methane passing into the reference space is distributed to the reference space and the measurement space;

by the formula

Calculating the density of the adsorptive methane in the sample coal.

3. A density measurement method according to claim 2, wherein said passing methane into a reference space and measuring the pressure P of said reference space₂Comprises the following steps:

will have a volume V at standard atmospheric pressure₀Is completely passed into said reference space,

by the formula

Calculating the density of the adsorptive methane in the sample coal,

wherein, V_sThe gas volume is 1mol methane in the standard state.

4. The density measurement method according to claim 1, wherein the step of introducing a predetermined amount of methane into the measurement space is followed by standing for 3 to 10 minutes, and the pressure P of the measurement space is measured₁。

5. A density measuring device of adsorptive methane in coal is characterized by comprising:

a measuring chamber tank (2) configured as a closed structure for containing sample coal;

the gas source (4) is communicated with the measuring chamber tank body (2); and

the pressure sensor (3) is connected with the measuring chamber tank body (2) through a pipeline (5) and is used for detecting the pressure in the measuring chamber tank body (2);

to be able to pass through

Calculating the density of adsorptive methane in the sample coal;

wherein, V_cIs the volume of the sample coal;

pore volume in the sample coal; v₁The volume of the measuring chamber tank body (2); p₁The pressure of the measuring chamber tank body (2) is the pressure after the sample coal adsorbs methane; n is the number of molecules of the predetermined amount of methane introduced into the measuring chamber tank body (2); n is a radical of_AIs an Avogastron constant, R is a gas constant; t is the thermodynamic temperature; and c is the equivalent curvature of the surface of the sample coal after adsorbing methane.

6. The density measurement device of claim 5, further comprising:

a reference chamber tank (1) configured as a closed structure, connected between the gas source (4) and the measurement chamber tank (2), and in selective communication with the measurement chamber tank (2),

the pressure sensor (3) is communicated with the reference chamber tank body (1) through the pipeline (5);

to be able to pass through

Calculating the density of adsorptive methane in the sample coal;

wherein, V₀Is the volume of methane introduced into the reference chamber tank (1) at standard atmospheric pressure; v_sIs a gas volume of 1mol in a standard state; v₂Is the volume of the reference chamber tank body (1).

7. Density measuring device according to claim 6, characterised in that a three-way ball valve (6) is provided between the reference chamber tank (1) and the measurement chamber tank (2), one port of the three-way ball valve (6) being in communication with the atmosphere and the other two ports being in communication with the reference chamber tank (1) and the measurement chamber tank (2), respectively.

8. The density measuring device according to claim 6, wherein the opening of the reference chamber tank (1) and the opening of the measuring chamber tank (2) are both provided with a sealing cover (8), and the ends of the reference chamber tank (1) and the measuring chamber tank (2) far away from the opening are both provided with a push rod (9) so that the reference chamber tank (1) and the measuring chamber tank (2) are pressed on the sealing covers (8) to form a closed space.

9. The density measuring device according to claim 5, further comprising a display (7) connected to the pressure sensor (3) for receiving and displaying the detection data of the pressure sensor (3).

10. Density measuring device according to claim 5, characterised in that the line (5) is provided with a pressure reducing valve (12) at the end of the gas source (4) and that the line (5) is provided with an unloading valve (12) at the outlet end of the pressure reducing valve (11).

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