HKY-II type coalbed methane isothermal adsorption device

1、 Principle

This device uses the high-pressure volumetric method to determine the methane adsorption capacity in coal and rock.

A large number of micropores in coal have surface energy on their inner surfaces. When gas comes into contact with the inner surface, the molecular forces cause methane or other gas molecules to concentrate on the surface, known as adsorption. The concentration of gas molecules gradually increases, which is the adsorption process; Gas molecules return to a free state in the gas phase, and the number of gas molecules on the surface gradually decreases, which is a desorption process. When a certain number of gas molecules are maintained on the surface and the adsorption rate and desorption rate are equal, it is adsorption equilibrium.

2、 Measurement method

The high-pressure capacity method is used to determine the methane adsorption capacity of coal. The processed dry coal sample is loaded into an adsorption tank, vacuum degassed, and the remaining volume of the adsorption tank is measured. A certain volume of methane is filled or released into the adsorption tank to achieve equilibrium pressure inside the tank. Part of the gas is adsorbed, and part of the gas remains in a free state in the remaining volume. Given the volume of methane filled (released), deducting the free volume of the remaining volume is the adsorption volume. Repeat this measurement to obtain the equilibrium pressure and adsorption volume of each pressure segment, which are connected to form the adsorption isotherm. When the pressure is tested by injecting methane gas from low to high, the adsorption isotherm is obtained; On the contrary, when the pressure is tested by releasing methane gas from high to low, the desorption isotherm is obtained. The adsorption and desorption isotherms are reversible under high pressure, and measuring one of them is equivalent in practical applications.

3、 Measurement device

The experimental setup structure is shown in the figure.

The main components and specifications are as follows:

1. Gas booster pump

Used to pressurize methane and increase testing pressure. The booster pump has a pressure of 40MPa and a flow rate of 20L/h, and uses an explosion-proof motor. Use an electric contact pressure gauge to control the pump outlet pressure, and automatically stop the pump protection when the set pressure is reached.

2. Boosting tank

Piston type structure, using water to top gas method to pressurize methane into the storage tank, can be repeatedly pressurized. The pressurized tank has a capacity of 2000ml and a pressure of 60MPa.

3. Gas storage tank

Used for storing high-pressure methane gas, with a storage tank capacity of 2000ml and a pressure of 60MPa.

4. Methane gas high-pressure regulating valve

Model 44-1100, inlet pressure 10000PSI, outlet pressure 50-6000PSI adjustable.

5. Helium pressure regulating valve

The inlet pressure is 16MPa, and the outlet pressure is adjustable from 0-4MPa.

6. Pressure gauges for booster tanks and gas storage tanks

Range of 60MPa, accuracy level 1.5. Used for measuring the pressure of booster tanks and gas storage tanks.

7. Inflatable canister

The volume is about 210ml (based on the calibration value), and the pressure is 50MPa.

8. Adsorption tank

The volume is about 90ml (based on the calibration value), and the pressure is 50MPa.

9. Calibration Room

Used for calibrating the volume of inflatable cans, calibration method: Boyle's law.

10. Constant temperature bath

model: ZC-10, Temperature control range: room temperature -95 ℃, temperature control accuracy: ± 0.1 ℃.

11. Pressure measurement of inflatable tank and adsorption tank

Measure the pressure of the inflation tank and adsorption tank using a pressure transmitter with a range of 60MPa.

12. Vacuum unit

Adopting Roots vacuum pump unit, Roots pump model: ZJ-30， Rotary vane pump model: 2XZ-4C,

Vacuum gauge model: ZD-52T。

13. Balance scale

model: BSA224S, Range 220g, accuracy 0.1g.

14. Vacuum drying oven

model: ZK-2020， Temperature control range: 50-150 ℃, accuracy ± 1 ℃

15. Automatic Data Collection and Processing System

Composed of a computer, data acquisition board, and data acquisition and processing software.

4、 Security

The safe operation of the instrument involves the personal safety of the operator and the normal service life of the instrument. The manufacturer reminds the operator to pay attention to the following points:

*All types of instruments and computers must ensure correct power input and be equipped with automatic voltage stabilization protection devices.

*Ensure that all parts of the instrument have good grounding.

*The pressure of each part of the process manifold should not exceed the design pressure, especially not exceed the range of various detection instruments. Extra caution must be taken when using gas pressurization.

*The valve design of the instrument is manual operation. Please pre design the test process according to the test steps. Any valve operation error may lead to the failure of the entire test.

5、 Installation

All instruments have been installed and tested before leaving the factory. For the convenience of packaging and transportation, the instrument is divided into different parts for packaging. Please carefully refer to the flowchart during installation.

The installation work can also be jointly completed by the factory's technical personnel and the user, so that the user can further familiarize themselves with the instrument and facilitate daily maintenance in the future.