AU2020103877A4 - A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL - Google Patents
A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL Download PDFInfo
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- 238000009792 diffusion process Methods 0.000 title claims abstract description 115
- 239000007789 gas Substances 0.000 claims abstract description 81
- 238000012360 testing method Methods 0.000 claims abstract description 44
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 19
- 239000001301 oxygen Substances 0.000 claims abstract description 19
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 19
- 230000008859 change Effects 0.000 claims abstract description 13
- 239000002689 soil Substances 0.000 claims abstract description 12
- 239000004575 stone Substances 0.000 claims abstract description 11
- 230000001681 protective effect Effects 0.000 claims abstract description 8
- 239000004927 clay Substances 0.000 claims abstract description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 13
- 229910052757 nitrogen Inorganic materials 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 7
- 230000005540 biological transmission Effects 0.000 claims description 6
- 238000005259 measurement Methods 0.000 claims description 5
- 238000009423 ventilation Methods 0.000 claims description 2
- 230000004888 barrier function Effects 0.000 abstract description 6
- 230000005012 migration Effects 0.000 abstract description 2
- 238000013508 migration Methods 0.000 abstract description 2
- 238000002474 experimental method Methods 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 3
- 239000012855 volatile organic compound Substances 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 238000012937 correction Methods 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- 125000005575 polycyclic aromatic hydrocarbon group Chemical group 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 239000008186 active pharmaceutical agent Substances 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 235000014113 dietary fatty acids Nutrition 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 229930195729 fatty acid Natural products 0.000 description 1
- 239000000194 fatty acid Substances 0.000 description 1
- 150000004665 fatty acids Chemical class 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000005210 holographic interferometry Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000012417 linear regression Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- -1 n-alkanes Chemical class 0.000 description 1
- 239000002957 persistent organic pollutant Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 150000007519 polyprotic acids Polymers 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
- G01N2013/003—Diffusion; diffusivity between liquids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N2015/0007—Investigating dispersion of gas
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- Chemical & Material Sciences (AREA)
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- General Health & Medical Sciences (AREA)
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Abstract
This invention discloses a device to determine gas diffusion coefficient under different
contacts between geomembrane/geosynthetic clay liner (GM/GCL) and compacted clay liner
(CCL). The device consists of a diffusion coefficient testing instrument and a pressurized
protective shell. The said testing instrument is assembled in a closed pressurized protective
shell; it is comprised of a pressure cap, porous stones, a geomembrane, seal rings, air holes, a
honeycomb perforated plate, a porous bearing plate, prestressing nuts, breather valves, an air
inlet, an air outlet, an oxygen sensor, a gas diffusion chamber and a vent groove; the pressurized
protective shell is comprised of a pressure servo system, a pressure head and a vertical sliding
support. This invention can, on the one hand, adjust the load applied to GM/GCL and upper
end of soil mass independently and conveniently, thus change the gap between soil and
GM/GCL, so as to change the different contact degree between the two; and, on the other hand,
acquire the gas migration under different contact conditions between GM/GCL and soil mass
indirectly by testing the gas diffusion coefficient, so as to quantitatively evaluate their contact
form and barrier efficiency.
(7) (2)(3
~(3)
(4)
(5)
(17()
F(1 ) (3
(9 (8) 4)
Figure 1
(7)
Figure 2
Description
(7) (2)(3 ~(3) (4) (5)
(17()
F(1 ) (3 (9 (8) 4)
Figure 1
(7)
Figure 2
A device to determine gas diffusion coefficient under different contacts between
GM/GCL and CCL
[01] This invention relates to the field of gas diffusion coefficient determination, in particular, it discloses a device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL.
[02] With the rapid development of industry, the types of pollution sources are increasing, especially in chemical industry areas, highly industrialized areas and their surrounding environment. The pollution modes and ecological damage types are becoming increasingly complex, the environmental pollution load is gradually increasing, and environmental pollution accidents occur from time to time. Statistical results show that volatile and semi-volatile organic compounds (VOCs/SVOCs) include hundreds of compounds such as n-alkanes, branched-chain fatty acids, n-alkanols, aliphatic dibasic acids, aromatic polybasic acids, polycyclic aromatic hydrocarbons (PAHs), isoparaffins, and triketones, which are the main pollutants in high industrialized areas and their surrounding environment soils in China. Organic pollutants tend to accumulate in high concentration in soil for a long time, which is easy to form high concentration release in a short time, polluting the surrounding atmospheric environment, causing a large number of toxic and harmful substances to deposit in human bodies and damaging human health.
[03] For industrial organic pollution sites, the conventional practice is to excavate and transport contaminated soil in the site, and cover the excavated contaminated soil surface with a horizontal barrier system, including gas guiding layer, compacted clay layer (CCL), geomembrane (GM), geosynthetic clay liner (GCL), drainage blanket, topsoil layer, vegetation, etc. The horizontal barrier system plays an important role in the emission-reduction of landfill gas. Relevant research shows that diffusion is the main way of gas migration in landfill. Therefore, it is very important to prevent gas diffusion by overburden materials, and the measurement of related parameters is one of the links that cannot be ignored in scientific research and engineering application. In the horizontal barrier system for VOC prevention and control and the landfill cover system for landfill gas prevention and control, GM/GCL is always supported by CCL (Compacted Clay Layer) beneath in direct contact. Therefore, the contact degree between soil layer and geomembrane is also an important factor affecting gas emission. It is very positive for controlling gas leakage to make the contact degree as close to perfect as possible.
[04] For the experimental determination of gas diffusion coefficient, researchers have given different kinds of determination methods, such as laser holographic interferometry and gas chromatography, which indirectly derive molecular diffusion coefficient by detecting the change of gas concentration with excessive cost of related test methods.
[05] According to the characteristics of the present invention, it is found by searching patents in China that there have been methods or devices for directly measurement of the gas diffusion coefficient in China. For example, Chinese patent CN104865164B adopts the method of volatile liquid-air, of which the advantage lies in that it cannot only ensure automatic, smooth and slow injection of liquid into the diffusion tube, so as not to produce obvious convection disturbance in the gas space above the liquid, but also arrange the determination of several liquids at the same time, thus improving the testing efficiency. However, the operation of this device is cumbersome without guaranteed safety; Chinese patent CN108444869A discloses a device to determine gas diffusion coefficient in coal shale, which integrates all testing devices onto one experiment module, simplifying the experiment operation and reducing the influence of external factors in the experiment, but these devices are suitable only for materials science or soil science without considering the test of barrier performance parameters of materials under complex stress conditions.
[06] This invention researches gas diffusion under different contact conditions of GM/GCL, gives the thresholds of perfect contact, general contact and poor contact for reference in practical engineering.
[07] This invention discloses testing instrument and method to determine the gas diffusion coefficient of horizontal barrier system under different contact conditions between GM/GCL and CCL, solving the problem of not able to quantitatively calculate the contact degree between GM/GCL and CCL by existing devices and methods in China.
[08] To realize the above objective, the technical proposal adopted by this invention is as following:
[09] A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL, comprising testing instrument and pressurized protective shell; the said testing instrument comprises gas diffusion testing instrument and diffusion chamber; the said gad diffusion testing instrument is connected to the diffusion chamber via gas pipeline at the bottom end; the said gas diffusion testing instrument comprises pressure cap, porous stones, geomembrane, seal rings, air holes, honeycomb perforated plate, porous bearing plate, prestressing nuts, breather valves, air inlet, air outlet, oxygen sensor, gas diffusion chamber and vent groove set from bottom up; the said diffusion chamber is set with air inlet at one end and air outlet at the other; gas in the said diffusion chamber is vertically pressurized by the pressure servo system; the said diffusion chamber is set with oxygen sensor inside; the said tested material is geomembrane or geosynthetic clay liner.
[010] Furthermore, the said pressurizing device is just above the gas diffusion chamber. It is equipped with switch and safety valve, adopting hydraulic pressurization.
[011] Furthermore, the said pressure cap is set with air channel.
[012] Furthermore, the said permeable stones are porous stones.
[013] Furthermore, the said exhaust piston is round air permeating piston arranged in concentric ring.
[014] Furthermore, the said seal ring (6) is O-ring.
[015] Furthermore, the said gas diffusion testing instrument and diffusion chamber are connected via air holes, honeycomb perforated plate and porous bearing plate.
[016] Furthermore, the permeable plate of the said gas diffusion testing instrument is honeycomb porous permeable plate.
[017] A method to test the gas diffusion coefficient under different contacts between GM/GCL and CCL, characterized in that the steps are as following:
[018] (1) Place the said gas diffusion testing instrument within a level place without disturbance and direct sunlight; meanwhile, set a humidifier in the surrounding environment to ensure that the test environment is in constant temperature and humidity;
[019] (2) Check whether the instrument can function normally before the measurement;
[020] (3) Connect the air inlet of the diffusion chamber to nitrogen transmission device and adjust the pressure;
[021] (4) Installed the gas diffusion testing instrument used in the test according to the sequence shown, with the upper end connected to the pressure servo system and the tail end connected to the diffusion chamber; set the pressure value of the pressure servo system;
[022] (5) Open the air inlet of diffusion chamber and valve of gas pipeline to jointly turn down the air outlet valve, so as to connect the nitrogen with volume concentration of 100% to the diffusion chamber at a smaller air flow after ventilation at bigger flow for about 60s; the original air in the diffusion chamber is discharged from the air outlet until the oxygen content measured by the sensor is zero or close to the set threshold (concentration less than 3%); keep for 3-5s and then close the nitrogen inlet and outlet;
[023] (6) After closing the valves for air inlet and outlet, open the gas pipeline valve to start gas diffusion and timing; the oxygen sensor measures the change of oxygen concentration in the diffusion chamber along with time, and calculates the diffusion coefficient according to the gas transmission principle;
[024] (7) Change the pressure value or change the gap and adjust the contact manner between soil sample and geomembrane with pressure servo system again; repeat steps (3) - (6).
[025] Due to the adoption of the above technology, this invention possesses the following beneficial effects when compared with prior arts:
[026] (1) When compared with existing instruments and methods for measuring gas diffusion coefficient, this invention is simple to operate and convenient to calculate, and greatly reduces the cost compared to some similar instruments.
[027] (2) This invention quantitatively calculates the contact method between GM/GCL and CCL, skilfully converts it into gas diffusion coefficient; the contact mode is judged by cross reference between the two according to the calculated threshold.
[028] (3) With the help of the pressure servo system in the pressurized protective shell, this invention can accurately control the pressure, thus to change the contact mode between the GM/GCL and the sample structure, reduce the research difficulty of this experiment.
[029] Figure 1 is a structural schematic diagram for a testing instrument testing the gas diffusion under different contact conditions between geomembrane and geosynthetic clay liner;
[030] Figure 2 is a top view of the permeable plate;
[031] wherein: 1. pressure servo system, 2. pressure head, 3. pressure cap, 4. porous stone, 5. geomembrane, 6. seal ring, 7. air holes, 8. honeycomb perforated plate, 9. porous bearing plate, 10. prestressing nuts, 11. breather valve, 12. air inlet, 13. air outlet, 14. oxygen sensor, 15. gas diffusion chamber, 16. vent groove.
[032] The invention is further elaborated with reference to the drawings and specific embodiments below.
[033] A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL, comprising testing instrument and pressurized protective shell; the said testing device is assembled inside the closed pressurized protective shell; the said testing instrument comprises gas diffusion testing instrument and diffusion chamber 15; the said gad diffusion testing instrument is connected to the diffusion chamber 15 via gas pipeline at the bottom end; the said gas diffusion testing instrument comprises pressure cap 3, porous stones 4, GCL/GM 5, seal rings 6, air holes 7, honeycomb perforated plate 8, porous bearing plate 9, prestressing nuts 10 set from bottom up; the said diffusion chamber 15 is set with air inlet 12 at one end and air outlet 13 at the other; the said diffusion chamber 15 is set with oxygen sensor 14 inside.
[034] The said gas pipeline 12 and 13 are set with pipeline valves 11.
[035] The said pressure cap 3 is set with air holes 7. The pressure cap 3 is modified with consolidometer, top of which can be applied with different loads or concentrations to simulate different contact modes between GM/GCL and CCL.
[036] The said permeable stones 4 are porous stones.
[037] The said exhaust piston is round air permeating piston arranged in concentric ring.
[038] The said porous bearing plate 9 is honeycomb porous permeable plate with hole area accounting for more than 50%.
[039] The said tested material 5 is geomembrane.
[040] A method to test the gas diffusion under different contacts between GM/GCL and CCL, in the following steps:
[041] Step 1: place the said gas diffusion testing instrument within a level place without disturbance and direct sunlight; meanwhile, set a humidifier in the surrounding environment to ensure that the test environment is in constant humidity;
[042] Step 2: check functions of the instrument before the measurement;
[043] Step 3: connect the air inlet 12 of the diffusion chamber 15 to nitrogen transmission device and keep the air outlet 11 valve open;
[044] Step 4: install the gas diffusion testing instrument according to the sequence shown in the Figure, with the upper end connected to the pressure servo system 1, the force transmission cap and the directional steel ball, and then connected to the dial indicator of the sensor; adjust the reading of the dial indicator, start the air compressor, set the pressure value with pressure device, power on the automatic loading controller, and then the data collector to make the loading system work;
[045] Step 5: open the air inlet 12 of diffusion chamber and gas pipeline valve 11, turn down the valve 11 of air outlet (13), so as to connect the nitrogen with volume concentration of 100% via the air inlet 12 to the diffusion chamber at a smaller air flow; the original air in the diffusion chamber is discharged from the air outlet 13 until the oxygen content measured by the sensor 14 is zero or close to the set threshold (concentration less than 3%); keep for 3-5s and then close the nitrogen inlet 12 and outlet 13;
[046] Step 6: after closing the valves for air inlet 12 and outlet 13, the gas diffusion timing will be conducted independently; the oxygen sensor 14 measures the change of oxygen concentration in the diffusion chamber 15 along with time, and calculates the diffusion coefficient according to the gas transmission principle;
[047] Step 7: change the pressure value (and thus the gap between tested material GM/GCL (5) and CCL (16)) with pressure servo system (1) again, adjust the contact manner; repeat steps 3-6.
[048] The following further explains the specific contents of pressure loading: install the pressure cap 3 and the directional steel ball, and then connected to the dial indicator of the sensor; adjust the reading of the dial indicator at about 8.0mm to acquire sufficient measuring range during the compression; start the air compressor to increase the pressure source output gradually from zero; power on the automatic loading controller, and then the data collector to make the loading system work;
[049] The following is the specific calculation process of gas diffusion coefficient:
[050] According to Fick's second law: dq AC
[051] dt h, (1)
[052] In equation (1): q is the gas amount entering the diffusion chamber in cm; t is the time required for diffusion in s; A is the diffusing surface area of the sample
structure in cm 2; hs is the height of sample structure in cm; D is the gas diffusion coefficient of the sample structure in cm2/s; AC is the difference between the02 concentrations at two ends of the sample structure in g/cm3
[053] Equation 2 calculates the rate of change of the volumeof 02diffusing into the diffusion chamber 8 with time:
dq d(AC)hA
[054] dt dt (2)
[055] In equation (2): he is the height of diffusion chamber in cm.
[056] By joining equations (1) and (2):
-DA AC, = d(AC,) hA
[057] hk d, (3)
[058] At the moment of t-0,02concentration in the diffusion chamber 8 is 0, and the 02 concentration in atmosphere connected with the diffusion chamber is Co; according to calculation, the02 concentration difference between the two ends of the sample structure is ACo = Co; after opening the valve, oxygen diffuses to the diffusion chamber 8 freely via the sample structure, increasing the02 concentration in the diffusion chamber 8; at the moment of t, the02concentration in the diffusion chamber 8 is f(t), and the02concentration in atmosphere maintains constant, being is Co; the02 concentration difference between the two ends of the sample structure at this moment is calculated as ACt= Co-f(t).
[059] With initial conditions t=0, ACt =ACo =Co, both sides of the equation integrate t at the same time:
AC D' ln(AC')=- "h t
[060] ACO hkh (4)
D St=K
[061] Make hshe , equation (4) is simplified into:
ln( AC')Kt
[062] ACO (5)
[063] Use the least square method for linear regression analysis, and draw the
In(AC, scatter plots of ACO and t, and the obtained slope is K.
[064] Introducing the correction coefficient K
D e 1 K.I - _
[065] D alh'he (6)
[066] Wherein, DS is the corrected diffusion coefficient, D is the diffusion
coefficient before correction, and a Iis the first solution bigger than 0 of equation
(ah)tan(ah)=h-D /Do he is the ratio between the directly determined soil mass gas diffusion coefficient and diffusion coefficient of the gas under same temperature
barometric pressure in free atmosphere. D is calculated from equation (6). D0 is temperature corrected according to the following equation:
Do(T2)= Do )(-)1
[067] T (7)
[068] Wherein DO(T) is the diffusion coefficient of oxygen diffusion from oxygen to nitrogen at 0 °C, which is 0.181 cm 2 /s. The above description of embodiment is to facilitate the understanding and application of this invention by ordinary technicians in the field of invention. The present invention is not limited to the embodiment listed in this paper. Any improvements and modifications made by technicians in relevant fields according to the principle of the present invention without departing from the scope of this invention should be within the protection scope of the present invention.
[069] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms, in keeping with the broad principles and the spirit of the invention described herein.
[070] The present invention and the described embodiments specifically include the best method known to the applicant of performing the invention. The present invention and the described preferred embodiments specifically include at least one feature that is industrially applicable
Claims (9)
1. A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL, characterized in that: it comprises testing instrument and pressurized protective shell; the said testing instrument comprises gas diffusion testing instrument and diffusion chamber; the said gad diffusion testing instrument is connected to the diffusion chamber via gas pipeline at the bottom end; the said gas diffusion testing instrument comprises pressure head (2), pressure cap (3), porous stones (4), geomembrane/geosynthetic clay liner (GM/GCL) (5), seal rings (6), air holes (7), honeycomb perforated plate (8), porous bearing plate (9), prestressing nuts (10), breather valves (11), air inlet (12), air outlet (13), oxygen sensor (14), gas diffusion chamber (15), CCL (16) and cutting ring set from bottom up; the said diffusion chamber is set with air inlet (12) at one end and air outlet (13) at the other; gas in the said diffusion chamber is vertically pressurized by pressure servo system (1); the said diffusion chamber is set with oxygen sensor (14) inside; the said tested material is geomembrane (5).
2. A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL of claim 1, characterized in that: the said pressurizing device is just above the gas diffusion chamber (15). It is equipped with switch and safety valve, adopting hydraulic pressurization.
3. A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL of claim 1, characterized in that: the said pressure cap is set with air channel.
4. A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL of claim 1, characterized in that: the said permeable stones are porous stones.
5. A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL of claim 4, characterized in that: the said exhaust piston is round air permeating piston arranged in concentric ring.
6. A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL of claim 1, characterized in that: the said seal ring (6) is O-ring.
7. A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL of claim 1, characterized in that: the said gas diffusion testing instrument and diffusion chamber are connected via air holes (7), honeycomb perforated plate (8) and porous bearing plate (9).
8. A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL of claim 1, characterized in that: the permeable plate of the said gas diffusion testing instrument is honeycomb porous permeable plate with hole area accounting for more than 50%.
9. The method to test the gas diffusion coefficient under different contacts between GM/GCL and CCL with the gas diffusion testing instrument of any of the claim 1-6, characterized in that the steps are as following:
(1) Place the said gas diffusion testing instrument within a level place without disturbance and direct sunlight; meanwhile, set a humidifier in the surrounding environment to ensure that the test environment is in constant temperature and humidity;
(2) Check whether the instrument can function normally before the measurement;
(3) Connect the air inlet (12) of the diffusion chamber to nitrogen transmission device and adjust the pressure;
(4) Installed the gas diffusion testing instrument used in the test according to the sequence shown, with the upper end connected to the pressure servo system (1) and the tail end connected to the diffusion chamber; set the pressure value of the pressure servo system (1);
(5) Open the air inlet (12) of diffusion chamber and valve of gas pipeline to jointly turn down the air outlet valve (13), so as to connect the nitrogen with volume concentration of 100% to the diffusion chamber at a smaller air flow after ventilation at bigger flow for about 60s; the original air in the diffusion chamber is discharged from the air outlet (13) until the oxygen content measured by the sensor is zero or close to the set threshold (concentration less than 3%); keep for 3-5s and then close the nitrogen inlet (12) and outlet (13);
(6) Close the valves for air inlet (12) and outlet (13); open the gas pipeline valve to start gas diffusion and timing; the oxygen sensor (14) transfers and records the change of oxygen concentration in the diffusion chamber along with time at real time, and calculates the diffusion coefficient according to the gas diffusion mechanism;
(7) Change the pressure value or change the gap and adjust the contact manner between soil sample and geomembrane (5) with pressure servo system (1) again; repeat steps (3) - (6).
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| AU2020103877A AU2020103877A4 (en) | 2020-12-03 | 2020-12-03 | A device to determine gas diffusion coefficient under different contacts between GM/GCL and CCL |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115979899A (en) * | 2022-11-23 | 2023-04-18 | 北京大学 | Device and method for testing effective diffusion coefficient of helium in helium-containing natural gas |
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2020
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115979899A (en) * | 2022-11-23 | 2023-04-18 | 北京大学 | Device and method for testing effective diffusion coefficient of helium in helium-containing natural gas |
| US11841304B1 (en) | 2022-11-23 | 2023-12-12 | Peking University | Device and method for testing effective diffusion coefficient of helium in helium-bearing natural gas |
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