CN112082898B - Automatic determination system and determination method for adsorption constant of coal sample - Google Patents
Automatic determination system and determination method for adsorption constant of coal sample Download PDFInfo
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- 238000001179 sorption measurement Methods 0.000 title claims abstract description 173
- 239000003245 coal Substances 0.000 title claims abstract description 48
- 238000000034 method Methods 0.000 title claims abstract description 43
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 260
- 238000003795 desorption Methods 0.000 claims abstract description 21
- 238000004364 calculation method Methods 0.000 claims abstract description 5
- 238000007789 sealing Methods 0.000 claims description 19
- 238000002474 experimental method Methods 0.000 claims description 10
- 238000011049 filling Methods 0.000 claims description 10
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- 238000007872 degassing Methods 0.000 claims description 9
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- 239000007788 liquid Substances 0.000 claims description 6
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- 230000006641 stabilisation Effects 0.000 claims description 3
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- 238000005259 measurement Methods 0.000 abstract description 20
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- 238000005273 aeration Methods 0.000 description 3
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- 238000004458 analytical method Methods 0.000 description 2
- 238000009530 blood pressure measurement Methods 0.000 description 2
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
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Abstract
The invention relates to an automatic measuring system and an automatic measuring method for the adsorption constant of a coal sample, and belongs to the field of desorption equipment of coal. The system comprises a measuring unit, a control unit and a signal connection unit, wherein the measuring unit comprises an adsorption tank, a temperature control device, a vacuum device and a gas charging device, the adsorption tank is arranged in the temperature control device and is respectively communicated with the vacuum device and the gas charging device, and the control unit is connected with the measuring unit through signals; the measuring unit further comprises an open water tank and a sealed water tank, and a first pipeline and a second pipeline are arranged between the sealed water tank and the open water tank; the method comprises the steps of low-pressure adsorption measurement, high-pressure adsorption measurement and adsorption constant calculation. The invention has high reliability, can automatically operate, effectively shortens the test time and improves the measurement efficiency. The test process is recorded completely, and the measurement result is reliable. Each process step is automatically monitored and controlled, unmanned operation is realized, human error is avoided, and the measurement result is more reliable.
Description
Technical Field
The invention belongs to the field of desorption equipment of coal, and relates to an automatic measurement system and an automatic measurement method for an adsorption constant of a coal sample.
Background
The adsorption constant of coal is a key technical parameter for calculating the mine gas content. The measurement precision and accuracy of the method are directly related to coal seam gas extraction design, mine ventilation design and normal ventilation gas management of a production mine.
At present, the domestic gas adsorption constant measurement generally adopts a high-pressure isothermal capacity method, and the method for measuring the adsorption constant comprises 6 process steps of sample preparation canning, degassing, low-pressure adsorption, aeration, high-pressure desorption and calculation of adsorption constant a and adsorption constant b. The existing high-pressure isothermal capacity method adsorption measuring device has the problems that the automation degree is low, the test time is long, the test personnel are required to be on duty for a long time, the manual operation is complicated, the professional requirement on the operator is high, whether the coal sample adsorption is balanced or not is required to be judged through experience by the test personnel, and the experience error and the reading error are easy to be introduced in the manual reading in the test process.
Disclosure of Invention
In view of the above, the present invention aims to provide an automatic measurement system and a measurement method for the adsorption constant of a coal sample, which can automatically desorb the coal sample and calculate the adsorption constant of the coal sample, and which is stable and reliable, and reduces the labor intensity of workers.
In order to achieve the above purpose, the present invention provides the following technical solutions: the automatic measurement system for the adsorption constant of the coal sample comprises a measurement unit, wherein the measurement unit comprises an adsorption tank, a temperature control device, a vacuum device and a gas charging device, the adsorption tank is arranged in the temperature control device and is respectively communicated with the vacuum device and the gas charging device, and the automatic measurement system further comprises a control unit which is in signal connection with the measurement unit; the measuring unit further comprises an open water tank and a sealed water tank, a first pipeline and a second pipeline are arranged between the sealed water tank and the open water tank, the first pipeline is a double-pass pipeline, the sealed water tank is communicated with the open water tank through the first pipeline to form a communicating vessel, the second pipeline is a single-pass pipeline, the sealed water tank is unidirectionally communicated with the open water tank through the second pipeline, and stop valves are respectively arranged on the first pipeline and the second pipeline; the gas filling device is characterized in that a liquid level switch is arranged in the sealed water tank, a pressure sensor is arranged in the adsorption tank, a weight detector is arranged on the open water tank, the sealed water tank is respectively communicated with the adsorption tank and the gas filling device, and a water filling port and an air outlet are further arranged on the sealed water tank.
Optionally, the device further comprises a water inlet pump, the water inlet pump is connected with a water injection port of the sealed water tank, stop valves are respectively arranged between the sealed water tank and the water inlet pump and between the sealed water tank and the air charging device, an atmosphere valve is further arranged on an exhaust port of the sealed water tank, and the sealed water tank is communicated with the atmosphere through the atmosphere valve.
Optionally, the adsorption tank is communicated with the sealed water tank through an adsorption pipeline, and the atmospheric valve is arranged on the adsorption pipeline.
Optionally, the temperature control device is a constant-temperature water bath, and the adsorption tank is arranged in the constant-temperature water bath.
Optionally, the control unit is a PLC control system.
An automatic determination method for the adsorption constant of a coal sample provides the automatic determination system for the adsorption constant of the coal sample, which comprises the following steps: low-pressure adsorption measurement, high-pressure adsorption measurement and adsorption constant calculation;
the "low pressure adsorption assay" comprises the following sub-steps: vacuumizing, namely filling the coal sample into an adsorption tank, and then degassing the adsorption tank until the inside of the adsorption tank is vacuumized; cleaning the sealed water tank, and injecting water into the sealed water tankDischarging all air in the sealed water tank until the sealed water tank is full; the water tank is inflated, gas is filled into the sealed water tank filled with water, a first pipeline is opened, and water in the sealed water tank enters the open water tank through the first pipeline until the air pressure in the sealed water tank is greater than the air pressure in the open water tank; opening an atmosphere communication valve, releasing partial gas by the closed water tank, refluxing water in the open water tank to the sealed water tank through a first pipeline, closing the atmosphere communication valve after the control unit monitors that the weight of the water in the open water tank is stable, and recording that the weight of the water in the open water tank is W 0 The method comprises the steps of carrying out a first treatment on the surface of the The method comprises the steps of low-pressure adsorption, communicating a sealed water tank with an adsorption tank, adsorbing gas in the sealed water tank by a degassed coal sample, gradually refluxing the sealed water tank by water in an open water tank through a first pipeline, monitoring that the weight of the water in the open water tank is stable again by a control unit, sealing the adsorption tank, and recording the weight of the water in the open water tank through a weight detector; repeating the above steps until the air pressure in the adsorption tank is equal to the atmospheric pressure, and the atmospheric pressure is P 0 The weight of the water in each open water tank after water stabilization is W respectively 1 To W n ；
The "high pressure adsorption assay" comprises the following sub-steps: high-pressure air filling is carried out, and gas is filled into the adsorption tank until the air pressure in the adsorption tank reaches the calibrated pressure; high-pressure adsorption is carried out, the adsorption tank is kept stand in a constant-temperature state, so that the coal sample in the adsorption tank fully adsorbs gas until the pressure value in the adsorption tank is less than or equal to 0.005Mpa within 30 minutes, the high-pressure adsorption is balanced, and the pressure in the adsorption tank is the initial pressure Pm; step-by-step desorption, after balancing high-pressure adsorption, injecting water into the sealed water tank until the sealed water tank is filled, closing the first pipeline, opening the second pipeline, and opening the open water tank, wherein the initial weight of the open water tank is M 0 The method comprises the steps of carrying out a first treatment on the surface of the Will calibrate the pressure P m The adsorption tank is sequentially desorbed to balance under each pressure measuring point, and the measured pressure in the adsorption tank after each desorption balance is recorded as P respectively m-1 To P 1 The weight added by the open water tank after each desorption balance is recorded as M in turn m To M 2 The pressure in the adsorption tank is reduced to P 1 After that, the adsorption tank is communicated with the sealed water tank, so that the gas in the adsorption tank is fully discharged into the sealed water tank, and the air pressure in the adsorption tank and the atmospheric pressure P are ensured 0 Balance, the weight M added by the water tank 1 。
Alternatively, the initial pressure is 6MPa and the number of pressure measuring points is 6.
Optionally, the volume of the gas adsorbed at low pressure is:wherein i is the number of times of "low pressure adsorption", ρ Water and its preparation method Is the density of water.
Optionally, in the step desorption step of the high pressure adsorption determination step, the volume increase of the gas adsorbed by the gas at the pressure measurement point is DeltaV i The volume of gas adsorbed under the pressure measuring point is V j ，V j ＝△V j +V j-1 ，△V j ＝M j /ρ Water and its preparation method The method comprises the steps of carrying out a first treatment on the surface of the j is the number of desorption steps, and j is more than or equal to 1 and less than or equal to m;
through the gas adsorption volume V of the coal sample 0 To V m Calculating to obtain adsorption quantity Q 0 To Q m ；
Performing curve fitting on P/Q and P according to Langmuir equation Q= abP/(1+bP) to obtain adsorption isothermal curves, and obtaining slope 1/a and intercept 1/ab to obtain adsorption constants a and b, wherein Q= (Q) 0 ……Q m )，P＝(P 0 ……P m )。
Optionally, the method further comprises the following steps: and (3) accurately judging, and calculating a correlation coefficient r value of the adsorption isothermal curve, wherein if r is more than or equal to 0.99, the experiment is qualified, and if r is less than 0.99, the experiment is wrong, and the experiment needs to be carried out again.
The invention has the beneficial effects that: the high PLC control system is adopted, the reliability is high, the 24-hour automatic operation can be realized, the test time is effectively shortened, and the measurement efficiency is improved. The sensor has high sensitivity and precision, higher data acquisition precision, more accurate control, more complete test process record and more reliable measurement result. The process steps are automatically monitored and controlled, the conditions are automatically switched, the water temperature in the constant-temperature water area is automatically adjusted and maintained, the adsorption balance is automatically judged, the whole test process is high in automation degree, and one-key starting, unmanned or unattended operation is realized. Unmanned operation is avoided, human error is avoided, and the measurement result is more reliable.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and other advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the specification.
Drawings
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in the following preferred detail with reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram of a system for automatically measuring the adsorption constant of a coal sample.
Reference numerals: the gas cylinder 1, the three-way valve 2, the atmosphere valve 3, the vacuum pump unit 4, the adsorption tank 5, the pressure sensor 6, the temperature sensor 7, the liquid level sensor 8, the constant-temperature water bath 9, the water inlet pump 10, the first pipeline 11, the second pipeline 12, the open water bath 13, the platform scale 14 and the sealed water tank 15.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the illustrations provided in the following embodiments merely illustrate the basic idea of the present invention by way of illustration, and the following embodiments and features in the embodiments may be combined with each other without conflict.
Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to limit the invention; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, it should be understood that, if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc., that indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but not for indicating or suggesting that the referred device or element must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and should not be construed as limiting the present invention, and that the specific meaning of the above terms may be understood by those of ordinary skill in the art according to the specific circumstances.
Referring to fig. 1, an automatic measurement system for the adsorption constant of a coal sample includes a measurement unit, wherein the measurement unit includes an adsorption tank 5, a temperature control device, a vacuum device, and a gas charging device. In this embodiment, the temperature control device is a constant temperature water bath 9, and the adsorption tank 5 is disposed in the constant temperature water bath 9. The adsorption tank 5 is respectively communicated with the vacuum device and the gas charging device, and further comprises a control unit, wherein the control unit is a PLC control system, and the control unit is in signal connection with the measuring unit.
The measuring unit further comprises an open water tank 13 and a sealed water tank 15, a first pipeline 11 and a second pipeline 12 are arranged between the sealed water tank 15 and the open water tank 13, the first pipeline 11 is a double-way pipeline, the sealed water tank is communicated with the open water tank 13 through the first pipeline 11 to form a communicating vessel, the second pipeline 12 is a single-way pipeline, the sealed water tank is unidirectionally communicated with the open water tank 13 through the second pipeline 12, and stop valves are respectively arranged on the first pipeline 11 and the second pipeline 12.
A liquid level switch and a water inlet pump 10 are arranged in the sealed water tank 15, and the water inlet pump 10 is connected with a water injection port of the sealed water tank 15. The adsorption tank 5 is internally provided with a pressure sensor 6, and the open water tank 13 is provided with a weight detector, which in this embodiment is a platform balance 14. The weight detector sealing water tank 15 is respectively communicated with the adsorption tank 5 and the gas charging device, and the sealing water tank 15 is also provided with a water filling port and an air outlet.
Stop valves are respectively arranged between the sealing water tank 15 and the water inlet pump 10 and between the sealing water tank 15 and the air charging device of the adsorption tank 5, an atmosphere valve 3 is further arranged on the exhaust port of the sealing water tank 15, and the sealing water tank 15 is communicated with the atmosphere through the atmosphere valve 3. The adsorption tank 5 and the sealing water tank 15 are communicated through an adsorption pipeline, and the air valve 3 is arranged on the adsorption pipeline.
The actual adsorption parameter measurement comprises the following steps:
1. preparation of experiments
(1) Sample preparation: collecting fresh coal samples of crushed coal beds, screening coal samples with the diameter of 0.2-0.25 mm for adsorption test coal samples, screening coal samples with the diameter of less than 0.15mm for industrial analysis, selecting lump coal with the diameter of more than 35mm as a apparent density measurement coal sample, and respectively measuring moisture (Mad), ash (Aad), volatile matters (Vdaf) and the like of the rest coal samples. Weighing about 50g of coal sample to 0.0001g accurately, placing the weighed coal sample into a vacuum drying oven, setting the temperature of the vacuum drying oven to be 80-85 ℃, starting a vacuum pump to start degassing, and when the vacuum degree in the drying oven is kept below-0.07 MPa, drying the coal sample at a constant temperature for about 6 hours, taking out, and immediately placing into a dryer for cooling and preserving.
(2) And (3) canning: and loading the dried and cooled coal sample into an adsorption tank 5, and measuring the seam height by using a vernier caliper.
(3) And (3) air tightness checking: filling high-pressure gas with pressure greater than 4MPa into the adsorption tank 5, placing the adsorption tank in water, and checking that no bubbles exist at the joint positions, the high-pressure valve ports and the screw positions.
(4) The adsorption tank 5 is connected with a test system as shown in fig. 1, a power supply is connected, a PLC control system is started, coal sample measurement parameters, basic information and industrial analysis results are input, and preparation work before the test is completed.
(5) The air tightness is good when the adsorption tank 5 is inflated and pressurized to 4MPa and the adsorption tank 5 is closed for 5 minutes without reducing the pressure. The good tightness flag triggers the start of the degassing step.
2. Low pressure adsorption assay
(1) And a degassing step, namely closing a stop valve between the adsorption tank 5 and the sealing water tank 15, and vacuumizing the adsorption tank 5. The method comprises the following specific steps: the control unit starts a water inlet pump 10 connected with the constant-temperature water bath 9, and cold water is injected into the constant-temperature water bath 9 until the water is full. The constant temperature water bath 9 is internally provided with a temperature sensor 7, the temperature sensor 7 transmits signals to a control unit, and the control unit controls the constant temperature water bath 9 to heat and keep the constant temperature of 60 ℃. The liquid level sensor 8 in the constant-temperature water bath 9 transmits a water level signal to the control unit, and the control unit controls the water inlet pump 10 of the constant-temperature water bath 9 to automatically supplement water if the water level of the water vapor is reduced in the constant-temperature process. The control unit starts the vacuum pump unit 4 to degas the coal sample tank. The pressure sensor 6 in the adsorption tank 5 transmits the pressure in the adsorption tank 5 to the control unit, and if the pressure in the auxiliary tank is lower than 4Pa, the degassing is continued for 4 hours, and the degassing is completed.
(2) After the degassing is completed, the closed water tank is cleaned, and water is injected into the sealed water tank 15 until the sealed water tank 15 is filled. The method comprises the following specific steps: the control unit controls the temperature in the constant temperature water bath 9 to be 30 ℃ and keeps the temperature. The control unit controls the atmosphere valve 3 to be opened, and water is injected into the sealed water tank 15 through the water inlet pump 10 on the sealed water tank 15, and air in the sealed water tank is discharged by the atmosphere valve 3. The liquid level sensor 8 in the sealed water tank 15 detects that the sealed water tank 15 is full, then transmits a signal to the control unit, stops water injection, and closes the atmosphere valve 3.
(3) After the water tank is inflated and the sealed water tank 15 is filled, the control unit controls the three-way valve 2 to enable the first pipeline 11 to be communicated with the sealed water tank 15, the control unit controls the gas cylinder 1 communicated with the sealed water tank 15 to charge gas into the sealed water tank 15, and water in the sealed water tank 15 enters the open water tank 13 through the first pipeline 11 until the air pressure in the sealed water tank 15 is greater than the air pressure in the open water tank. The control unit is provided with an atmospheric pressure sensor 6 for detecting the atmospheric pressure, the air pressure in the open water tank being equal to the atmospheric pressure.
After the air pressure in the sealed water tank 15 is greater than the air pressure in the open water tank, the control unit controls the atmospheric valve 3 to open, water in the open water tank flows back to the sealed water tank 15 through the first pipeline 11, and the air pressure in the sealed water tank 15 gradually and greatly increasesThe air pressure is equal until the weight of the water in the open water tank is stable, and the air pressure in the closed water tank is equal to the atmospheric pressure after the weight detector reads for 2 minutes. The control unit records the weight W of the stabilized water in the open water tank through the weight detector 0 。
(4) After the water weight in the open water tank is stable through low-pressure adsorption, the control unit controls the atmospheric valve 3 to be closed, and enables the sealed water tank 15 to be communicated with the adsorption tank 5, the water in the open water tank enters the sealed water tank 15 until the water weight in the open water tank is stable again, and the reading of the weight detector is stable after 2 minutes. The control unit records the weight of the water after the water in the open water tank is stabilized again through the weight detector;
repeating the above-mentioned "water tank aeration" and "low-pressure adsorption" for n times until the air pressure in the adsorption tank 5 is identical to the atmospheric pressure, and the atmospheric pressure is P 0 The weight of the water in each open water tank after water stabilization is W respectively 1 To W n 。
3. High pressure adsorption assay
(1) The control unit controls the gas cylinder 1 connected with the adsorption tank 5 to charge gas into the adsorption tank 5 until the gas pressure in the adsorption tank 5 reaches the calibration pressure, which is 6MPa in this embodiment.
(2) High pressure desorption, high pressure aeration, standing for 8 hr, and if the variation of gas pressure in the adsorption tank 5 is less than or equal to 0.005Mpa within 30 min, the desorption is balanced, and the pressure in the adsorption tank 5 is the initial pressure P m 。
(3) After the desorption balance of the high-pressure desorption, water is injected into the sealing water tank 15 until the sealing water tank 15 is filled up, and the temperature in the constant-temperature water bath 9 is kept at 30 ℃. The control unit controls the three-way valve 2 to close the first pipeline 11 and open the second pipeline 12, so that the water sealing tank is communicated with the open water tank through the second pipeline 12. The second pipeline 12 is a one-way pipeline, water in the sealed water tank 15 can enter the open water tank from the second pipeline 12, and water in the open water tank cannot enter the sealed water tank 15 through the second pipeline 12. The initial weight of the open water tank is M 0 The method comprises the steps of carrying out a first treatment on the surface of the Will initiate pressure P m Is evenly divided into m pressure measuring points, each pressure measuring pointThe actual pressure after point desorption balance is P in turn m To P 1 In this embodiment, the number of pressure measurement points is 6. Specifically, the control unit controls the connection between the adsorption tank 5 and the sealed water tank 15, so that the pressure in the adsorption tank 5 is reduced to the next pressure measuring point, and the control unit controls the closing between the adsorption tank 5 and the sealed water tank 15, and if the weight of the open water tank 13 is measured to be unchanged within 2min, the adsorption is balanced. After adsorption equilibrium, the measured pressure in the adsorption tank 5 is P m-1 The added weight of the open water tank is M m . Repeating the above steps until the pressure in the adsorption tank 5 is reduced to the last pressure measuring point, and after adsorption equilibrium, the measured pressure in the adsorption tank 5 is P 1 The added weight of the open water tank is M 2 . After the adsorption tank 5 is in desorption balance at the last pressure measuring point, the control unit controls the adsorption tank 5 to be communicated with the sealing water tank 15, so that the gas in the adsorption tank 5 is fully discharged into the sealing water tank, and the pressure in the adsorption tank 5 and the atmospheric pressure P 0 Balance, the added weight of the open water tank is M 1 。
4. Calculating an adsorption constant;
the volume of the gas adsorbed at low pressure is as follows:wherein i is the adsorption times, i is more than or equal to 1 and less than or equal to n, ρ Water and its preparation method Is the density of water.
In the step of step desorption in the step of high-pressure adsorption determination, the volume of gas adsorbed at the corresponding pressure measuring point is V j The volume increment of the gas adsorption gas under the corresponding pressure measuring point is delta V j ，V j ＝△V j +V j-1 ，△V j ＝M j /ρ Water and its preparation method The method comprises the steps of carrying out a first treatment on the surface of the j is the number of stepwise desorption, and m to 1 in turn.
Obtain V 0 To V m Then, the adsorption quantity Q is obtained through calculation of the adsorption volume of the coal sample gas 0 To Q m Curve fitting is performed on P/Q and P according to Langmuir equation Q= abP/(1+bP) to obtain adsorption isothermal curves, and slope 1/a and intercept 1/ab are obtained to obtain adsorption constants a, b, wherein Q= (Q) 0 ……Q m )，P＝(P 0 ……P m )。
5. And (3) accurately judging, and calculating a correlation coefficient r value of the adsorption isothermal curve, wherein if r is more than or equal to 0.99, the experiment is qualified, and if r is less than 0.99, the experiment is wrong, and the experiment needs to be carried out again.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the claims of the present invention.
Claims (7)
1. The automatic determination method of the adsorption constant of the coal sample is based on an automatic determination system of the adsorption constant of the coal sample, and comprises a determination unit, wherein the determination unit comprises an adsorption tank, a temperature control device, a vacuum device and a gas charging device, the adsorption tank is arranged in the temperature control device and is respectively communicated with the vacuum device and the gas charging device, and the automatic determination method further comprises a control unit, and the control unit is in signal connection with the determination unit;
the measuring unit further comprises an open water tank and a sealing water tank, a first pipeline and a second pipeline are arranged between the sealing water tank and the open water tank, the first pipeline is a double-pass pipeline, the sealing water tank is communicated with the open water tank through the first pipeline to form a communicating vessel, the second pipeline is a single-pass pipeline, the sealing water tank is communicated with the open water tank through the second pipeline in a one-way manner, and stop valves are respectively arranged on the first pipeline and the second pipeline;
a liquid level switch is arranged in the sealed water tank, a pressure sensor is arranged in the adsorption tank, a weight detector is arranged on the open water tank, the sealed water tank is respectively communicated with the adsorption tank and the gas charging device, and a water filling port and an air outlet are also arranged on the sealed water tank;
the method is characterized by comprising the following steps of:
low-pressure adsorption measurement, high-pressure adsorption measurement and adsorption constant calculation;
the "low pressure adsorption assay" comprises the following sub-steps:
vacuumizing, namely filling the coal sample into an adsorption tank, and then degassing the adsorption tank until the inside of the adsorption tank is vacuumized;
cleaning the closed water tank, injecting water into the closed water tank until the closed water tank is filled, and discharging all air in the closed water tank;
the water tank is inflated, gas is filled into the sealed water tank filled with water, a first pipeline is opened, and water in the sealed water tank enters the open water tank through the first pipeline until the air pressure in the sealed water tank is greater than the air pressure in the open water tank;
opening an atmosphere communication valve, releasing partial gas by the closed water tank, refluxing water in the open water tank to the sealed water tank through a first pipeline, closing the atmosphere communication valve after the control unit monitors that the weight of the water in the open water tank is stable, and recording that the weight of the water in the open water tank is W 0 ；
The method comprises the steps of low-pressure adsorption, communicating a sealed water tank with an adsorption tank, adsorbing gas in the sealed water tank by a degassed coal sample, gradually refluxing the sealed water tank by water in an open water tank through a first pipeline, monitoring that the weight of the water in the open water tank is stable again by a control unit, sealing the adsorption tank, and recording the weight of the water in the open water tank through a weight detector;
repeating the above steps until the air pressure in the adsorption tank is equal to the atmospheric pressure, and the atmospheric pressure is P 0 The weight of the water in each open water tank after water stabilization is W respectively 1 To W n ；
The "high pressure adsorption assay" comprises the following sub-steps:
high-pressure air filling is carried out, and gas is filled into the adsorption tank until the air pressure in the adsorption tank reaches the calibrated pressure;
high-pressure adsorption is carried out, the adsorption tank is kept stand in a constant-temperature state, so that the coal sample in the adsorption tank fully adsorbs gas until the pressure value in the adsorption tank is less than or equal to 0.005Mpa within 30 minutes, the high-pressure adsorption is balanced, and the pressure in the adsorption tank is the initial pressure Pm;
fractional desorption "After the high-pressure adsorption is balanced, water is injected into the sealed water tank until the sealed water tank is filled, the first pipeline is closed, the second pipeline is opened, and the initial weight of the open water tank is M 0 The method comprises the steps of carrying out a first treatment on the surface of the Will calibrate the pressure P m The adsorption tank is sequentially desorbed to balance under each pressure measuring point, and the measured pressure in the adsorption tank after each desorption balance is recorded as P respectively m-1 To P 1 The weight added by the open water tank after each desorption balance is recorded as M in turn m To M 2 The pressure in the adsorption tank is reduced to P 1 After that, the adsorption tank is communicated with the sealed water tank, so that the gas in the adsorption tank is fully discharged into the sealed water tank, and the air pressure in the adsorption tank and the atmospheric pressure P are ensured 0 Balance, the weight M added by the water tank 1 ；
The volume of the gas adsorbed at low pressure is as follows:wherein i is the number of times of "low pressure adsorption", ρ Water and its preparation method Is the density of water;
in the step desorption step of the high-pressure adsorption determination step, the volume increment delta V of the gas adsorbed by the gas under the pressure measuring point i The volume of gas adsorbed under the pressure measuring point is V j ，V j ＝△V j +V j-1 ，△V j ＝M j /ρ Water and its preparation method The method comprises the steps of carrying out a first treatment on the surface of the j is the number of desorption steps, and j is more than or equal to 1 and less than or equal to m;
through the gas adsorption volume V of the coal sample 0 To V m Calculating to obtain adsorption quantity Q 0 To Q m ，
Performing curve fitting on P/Q and P according to Langmuir equation Q= abP/(1+bP) to obtain adsorption isothermal curves, and obtaining slope 1/a and intercept 1/ab to obtain adsorption constants a and b, wherein Q= (Q) 0 ……Q m )，P＝(P 0 ……P m )。
2. The automatic determination method of the adsorption constant of the coal sample according to claim 1, wherein the method comprises the following steps: the initial pressure is 6MPa, and the number of pressure measuring points is 6.
3. The automatic determination method of the adsorption constant of the coal sample according to claim 1, further comprising the steps of: and (3) accurately judging, and calculating a correlation coefficient r value of the adsorption isothermal curve, wherein if r is more than or equal to 0.99, the experiment is qualified, and if r is less than 0.99, the experiment is wrong, and the experiment needs to be carried out again.
4. The automatic determination method of the adsorption constant of the coal sample according to claim 1, wherein the method comprises the following steps: still include the intake pump, the intake pump with sealed water tank's water injection mouth is connected, sealed water tank with the intake pump the adsorption tank be provided with the stop valve respectively between the aerating device, still be provided with the atmospheric valve on sealed water tank's the gas vent, sealed water tank passes through atmospheric valve and atmosphere intercommunication.
5. The automatic determination method of the adsorption constant of the coal sample according to claim 4, wherein the method comprises the following steps: the adsorption tank is communicated with the sealed water tank through an adsorption pipeline, and the atmosphere valve is arranged on the adsorption pipeline.
6. The automatic determination method of the adsorption constant of the coal sample according to claim 1, wherein the method comprises the following steps: the temperature control device is a constant-temperature water bath, and the adsorption tank is arranged in the constant-temperature water bath.
7. The automatic determination method of the adsorption constant of the coal sample according to claim 1, wherein the method comprises the following steps: the control unit is a PLC control system.
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