Test device and method for inverting the gas permeability coefficients of two zones of municipal solid waste

Abstract

The present invention discloses a test device and method for inverting the gas permeability coefficients of two zones of municipal solid waste, including a sample cylinder, a gas supply system, a loading system, and a data acquisition system. The sample cylinder is used to fill the municipal solid waste sample. The tests for the gas permeability, porosity, and effective gas diffusion coefficient of the municipal solid waste sample are all carried out in the sample cylinder. The gas supply system is used to provide gas for the tests of the gas permeability, porosity, and gas diffusion coefficient of the municipal solid waste sample. The loading system is used to apply pressure to the municipal solid waste sample. The data acquisition system is used to monitor in real time the data of the gas inflow and outflow rates, pressure, temperature, and gas concentration changing with time. This test device and method solve the problem that the existing test methods cannot accurately predict the gas permeability coefficient of the landfill gas of municipal solid waste.

Description

Technical Field

[0001] The present invention relates to the field of environmental geotechnical engineering, and particularly relates to an experimental device and method for inverting the gas permeability coefficients of two zones of municipal solid waste. Background Art

[0002] At present, sanitary landfill has become the main method for treating municipal solid waste due to advantages such as simple operation, large daily treatment capacity, and low consumption cost. The operating mode of a sanitary landfill is layered landfill, and after reaching the service life, it is closed. Under the action of microorganisms, landfill gases such as methane and carbon dioxide are generated inside the municipal solid waste.

[0003] In order to accelerate the repair and reuse speed of landfills, aerobic remediation technology is often adopted, injecting air into the landfill. This technology can quickly make the municipal solid waste inside the landfill reach degradation stabilization, and the migration characteristics of gases are of great significance for the evaluation and prediction of aerobic ventilation. Gases migrate under the action of pressure difference and concentration difference, and the permeability of municipal solid waste, the spatial distribution of pore structure, and the effective diffusion coefficient have important effects on gas migration.

[0004] Since the pore structure inside municipal solid waste has strong heterogeneity, and the permeability characteristics are closely related to the pore structure characteristics, therefore, the permeability characteristics of municipal solid waste also have strong non-uniformity. There is a significant preferential permeability effect in municipal solid waste. Part of the fluid will flow out through the large pore area first, that is, the fracture area, under the action of a fixed pressure difference, and the other part of the fluid will then flow out through the small pore area, that is, the pore area. The main reason for this phenomenon is the large difference in permeability between the two areas. Currently, the simulation and prediction of gas migration in landfills mainly adopt a single permeability model, which usually assumes a constant intrinsic permeability and cannot simulate the preferential permeability process of gases.

[0005] Traditional gas permeability tests measure the stable flow value at the outlet under the pressure difference at the inlet and outlet of the municipal solid waste sample, and then obtain the intrinsic permeability through formula conversion, which also cannot reflect the difference in gas two-zone permeability ability in municipal solid waste. Therefore, using a gas two-zone permeability model and inverting the gas permeability coefficients of two zones of municipal solid waste is of great significance for the prediction and evaluation of gas migration in the aerobic ventilation project of landfills. Summary of the Invention

[0006] The present invention provides an experimental device and method for inverting the gas permeability coefficients of two zones of municipal solid waste to overcome the problem that the existing experimental methods cannot accurately predict the gas permeability coefficient of municipal solid waste landfills.

[0007] To achieve the above object, the technical solution of the present invention is:

[0008] An experimental device for inverting the gas permeability coefficients in two zones of municipal solid waste, comprising a sample cylinder, a gas supply system, a loading system and a data acquisition system; the sample cylinder is used for filling the municipal solid waste sample to provide a test environment for the measurement of the gas permeability, porosity and effective gas diffusion coefficient of the municipal solid waste sample; the gas supply system is used for providing the test gas required for the measurement of the gas permeability, porosity and gas diffusion coefficient of the municipal solid waste sample; the loading system is used for pressurizing the municipal solid waste sample; and the data acquisition system is used for real-time monitoring of the data of the gas inflow and outflow rates, pressures, temperatures and gas concentrations at the preset monitoring point positions varying with time, and each of the monitoring points is respectively arranged on the sample cylinder and the gas supply system according to the test requirements.

[0009] Further, the sample cylinder includes a heating and insulation layer, a cylinder body and an inversion layer. The heating and insulation layer is fixedly wound around the outside of the cylinder body. The cylinder body is fixed on the base. The inversion layer is arranged inside the cylinder body to promote uniform gas flow. The inversion layer includes a bottom inversion layer and a top inversion layer. One end of a water delivery pipe penetrates through the bottom of the cylinder body and the base below the bottom inversion layer. The other end of the water delivery pipe is connected to a leachate recovery tank for collecting the leachate discharged from the municipal solid waste sample. A water delivery valve is arranged on the water delivery pipe, and the water delivery valve is in a closed state and is only opened when it is detected that there is leachate deposition. A plurality of temperature sensors are arranged on one side of the cylinder body, and gas pressure sensors are symmetrically arranged on the other side of the cylinder body relative to the temperature sensors.

[0010] Further, the loading system includes a loading plate, a press frame, a cylinder and a force transmission rod. The press frame is installed outside the sample cylinder and fixed on the base. The cylinder is vertically fixed on the top of the press frame. One end of the force transmission rod is installed on the loading plate. The loading plate is installed on the top inversion layer. The other end of the force transmission rod penetrates through the top of the press frame and communicates with the bottom of the cylinder, and the axis of the force transmission rod coincides with the axis of the cylinder body. The cylinder can drive the loading plate to reciprocate in the cylinder body through the force transmission rod, and pressurize the municipal solid waste sample in the sample cylinder by pushing the loading plate. A displacement sensor is also arranged on the loading plate for monitoring the descending or ascending height of the loading plate.

[0011] Further, the gas supply system includes a gas supply device, an inlet gas mass flowmeter, a gas storage tank for storing test gases required for testing the gas permeability, porosity, and effective gas diffusion coefficient of municipal solid waste samples, an outlet gas mass flowmeter of the cylinder body, and a six-way valve. The gas supply device is connected to one end of the inlet gas mass flowmeter through a first gas pipeline. A gas filter is provided between the gas supply device and the inlet gas mass flowmeter to filter impurities in the gas. The other end of the inlet gas mass flowmeter is connected to the first valve port of the six-way valve through a first gas pipeline. An inlet gas collection port is provided between the inlet gas mass flowmeter and the six-way valve. The second valve port of the six-way valve is connected to the inlet of the gas storage tank through a second gas pipeline. The outlet of the gas storage tank is connected to the outlet gas mass flowmeter through a second gas pipeline. A gas storage tank outlet valve is provided on the second gas pipeline between the gas storage tank and the outlet gas mass flowmeter. The fourth valve port of the six-way valve is connected to the bottom inverted drainage layer through a third gas pipeline penetrating the base and the base of the sample cylinder. A sample cylinder inlet valve is provided on the third gas pipeline. An inlet pressure sensor is installed at the sixth valve port of the six-way valve. The cylinder body gas mass flowmeter penetrates the loading plate through a fourth gas pipeline and abuts against the top inverted drainage layer to monitor the gas flow rate at the outlet. A sample cylinder outlet valve is provided on the fourth gas pipeline between the cylinder body gas mass flowmeter and the sample cylinder. An outlet pressure sensor and an outlet gas collection port are provided on both sides of the sample cylinder outlet valve. The outlet pressure sensor is installed between the sample cylinder outlet valve and the cylinder body outlet gas mass flowmeter. The outlet gas collection port is provided between the sample cylinder outlet valve and the sample cylinder.

[0012] Further, the data acquisition system includes a gas analyzer, a data acquisition instrument, and a data terminal. The gas analyzer is respectively connected to the inlet gas collection port and the outlet gas collection port for monitoring the gas concentration at the inlet gas collection port and the outlet gas collection port. The data acquisition instrument is respectively electrically connected to the inlet pressure sensor, the inlet gas mass flowmeter, the gas analyzer, the outlet pressure sensor, the cylinder body gas mass flowmeter, the temperature sensor, the displacement sensor, and the gas pressure sensor for collecting gas flow rate, pressure, temperature, and displacement values. The data terminal is electrically connected to the data acquisition instrument.

[0013] Further, a plurality of through holes are provided in both the bottom inverted drainage layer and the top inverted drainage layer for uniformly discharging gas or liquid inside the municipal solid waste sample.

[0014] A test method for inverting the two-region gas permeability coefficient of municipal solid waste includes:

[0015] Step S1: Collect a sample of municipal solid waste and load it into the cylinder.

[0016] Step S2: Conduct gas permeability tests, porosity tests, and diffusion coefficient tests on the municipal solid waste sample respectively to obtain the permeability, porosity, and effective diffusion coefficient of the municipal solid waste sample.

[0017] Step S3: Obtain the gas breakthrough curve for the municipal solid waste sample through a pressure reduction test.

[0018] Step S4: Substitute the three sets of data obtained from the gas permeability test of the municipal solid waste sample, the porosity test of the municipal solid waste sample, and the effective gas diffusion coefficient test of the municipal solid waste sample into the inversion calculation of the dual-zone permeability model in the numerical analysis software to obtain the gas breakthrough curve under the simulation results and the dual-zone gas permeability coefficient of the municipal solid waste.

[0019] Further, in step S2, when conducting the gas permeability test on the municipal solid waste sample to obtain the permeability, porosity, and effective diffusion coefficient of the municipal solid waste sample, specifically:

[0020] Step S2.1: Control the sample cylinder to a constant temperature environment through the heating and insulation layer and the temperature sensor; open the inlet valve of the sample cylinder, the first, fourth, and sixth ports of the six-way valve, and close the second, fifth, and third ports. Send the gas from the gas supply device through the six-way valve and the third gas pipeline to the inlet at the bottom of the cylinder cavity, and set the inlet pressure to the first preset pressure. The inlet pressure value is monitored by the inlet end pressure sensor, and the gas in the cylinder cavity flows out through the cylinder gas mass flowmeter on the fourth gas pipeline; when the flow of the cylinder gas mass flowmeter is stable, record the outlet flow value by the data acquisition instrument, and the outlet pressure sensor measures the outlet pressure value. Based on the permeability calculation formula, obtain the permeability of the municipal solid waste sample. The permeability calculation formula is:

[0021]

[0022] k is the gas permeability, with the unit of m 2 ; Q is the gas flow rate, with the unit of m 3 / s; P in is the inlet end pressure, with the unit of Pa; P out is the outlet end pressure, with the unit of Pa; L is the length of the municipal solid waste sample, with the unit of m; μ is the gas dynamic viscosity, Pa·s; A is the cross-sectional area of the municipal solid waste sample, with the unit of m 2 .

[0023] Step 2.2: Regulate the sample cylinder to a constant temperature environment through the heating and insulation layer and the temperature sensor; close the outlet valve and the inlet valve of the sample cylinder, close the third, fourth, fifth valve ports of the six-way valve and the outlet valve of the gas storage tank, open the first, second and sixth valve ports of the six-way valve, and inject gas into the gas storage tank by using the gas supply device; observe the gas injection pressure value through the inlet end pressure sensor, and when the gas injection pressure reaches the second preset pressure, close the first valve port of the six-way valve, keep the pressure in the gas storage tank stable and record its pressure value; open the fourth valve port of the six-way valve and the inlet valve of the sample cylinder to inject gas into the sample cylinder, and after the air pressure is stable, record the pressure value through the gas pressure sensor, and obtain the porosity of the municipal solid waste sample according to Boyle's law and the porosity calculation formula. Boyle's law is:

[0024] p1v1 = p2v2

[0025] where p1 is the pressure value of the gas storage tank, in Pa; v1 is the volume of the gas storage tank, in m 3 ; p2 is the value when the pressure in the sample cylinder reaches stability, in Pa; v2 is the sum of the volume of the gas storage tank and the pore volume of the municipal solid waste after the pressure is stable, in m 3 ;

[0026] The porosity calculation formula is:

[0027]

[0028] where n is the porosity, v0 is the total volume of the municipal solid waste sample, in m 3 .

[0029] Step S2.3: The sample tube is regulated to a constant temperature environment through the heating and insulation layer and the temperature sensor, the outlet valve of the sample tube, the air inlet valve of the sample tube and the first valve port, the sixth valve port and the fourth valve port of the six-way valve are opened, and the second valve port, the third valve port and the fifth valve port of the six-way valve are closed. The gas supply device uses a mixed gas of methane and carbon dioxide in equal proportions, and the gas of the gas supply device is transported to the bottom of the cylinder cavity of the sample tube through the six-way valve for flushing. A first flushing flow value is preset, and the air intake flow value is determined by the The gas mass flowmeter at the air inlet end is used for monitoring. During the flushing process, gas is collected through the gas collection port at the air inlet end and the gas collection port at the air outlet end at given time values, and the gas concentration is tested by the gas analyzer. When the gas concentration at the gas collection port at the air outlet end is stable, the gas supply device, the first valve port and the fourth valve port of the six-way valve are closed, and the outlet gas flow value is monitored by the gas mass flowmeter at the air outlet end of the cylinder. When the outlet gas flow value is zero, the sample cylinder outlet valve is closed; the first valve port, the sixth valve port, the second valve port of the six-way valve and the outlet of the gas storage tank are opened. The third valve port, the fourth valve port and the fifth valve port of the six-way valve are closed. The gas provided by the gas supply device is air. The gas of the gas supply device is transported to the gas inlet of the gas storage tank through the six-way valve to flush the gas storage tank. The preset flushing time and the preset second flushing flow value are monitored by the gas mass flowmeter at the inlet end. After the flushing time is reached, the gas supply device, the first valve port and the second valve port of the six-way valve are closed. When the flow value of the gas outlet end of the gas storage tank is zero, the valve at the gas outlet of the gas storage tank is closed. The flow value of the gas outlet end of the gas storage tank is monitored by the outlet gas mass flowmeter. At the same time, the second valve port, the fourth valve port and the valve of the sample tube outlet are opened. The gas flow value of the gas outlet end is monitored by the gas mass flowmeter at the gas outlet end. The gas at the gas outlet end is sampled from the gas collection port at the gas outlet end. The preset interval sampling time is set. The gas concentration at the gas outlet end is monitored by the gas analyzer. After the gas concentration at the gas outlet end is stable, the effective diffusion coefficient of the municipal solid waste sample is obtained according to the gas diffusion formula. The calculation formula of the effective diffusion coefficient of the gas is:

[0030]

[0031] D=0.78D1+0.21D2

[0032] J i is the gas diffusion flux, in mol / (m 2 ·s); i=1,2 represents nitrogen and oxygen respectively; C is the gas molar concentration, unit mol / m 3 ; D is the effective diffusion coefficient of air, D1 and D2 are the effective diffusion coefficients of nitrogen and oxygen respectively, the unit is m 2 / s; z is the height, the unit is m.

[0033] Further, in step S3, a gas penetration curve is obtained for the municipal solid waste sample through a pressure reduction test, specifically as follows:

[0034] Step S3.1: Adjust the sample cylinder to a constant temperature environment through the heating and insulation layer and the temperature sensor. Close the outlet valve of the sample cylinder, the inlet valve of the sample cylinder, the fourth valve port, the third valve port, the fifth valve port of the six-way valve, and the outlet of the gas storage tank. Open the first valve port, the sixth valve port, and the second valve port of the six-way valve, and inject gas into the gas storage tank using the gas supply device;

[0035] Step S3.2: Observe the gas injection pressure value through the inlet end pressure sensor. After the gas injection pressure reaches the third preset pressure value, close the first valve port of the six-way valve to fill the gas storage tank with gas;

[0036] Step S3.3: Open the outlet valve of the sample cylinder, the inlet valve of the sample cylinder, and the fourth valve port of the six-way valve to allow gas to pass through the municipal solid waste sample in the sample cylinder. Record the gas flow rate at the outlet end of the sample cylinder and the data values of the gas pressure drop process in the gas storage tank respectively through the cylinder gas mass flowmeter and the inlet end pressure sensor, and further obtain the gas penetration curve and the pressure drop curve from these data values.

[0037] Further, in step S4, the dual-region gas permeability coefficients of the municipal solid waste represented by the inverse calculation of the dual-region permeability model are specifically as follows:

[0038] Step S4.1: Substitute the gas permeability test data of the municipal solid waste sample, the porosity test data of the municipal solid waste sample, and the effective gas diffusion coefficient test data of the municipal solid waste sample into the numerical analysis software to inversely calculate the dual-region gas permeability coefficients of the municipal solid waste represented by the dual-region permeability model. The dual-region gas permeability model is:

[0039]

[0040]

[0041]

[0042]

[0043] M is the average molar mass of the gas, with the unit of kg / mol; R is the gas constant, with the unit of Pa·m 3 / (mol·K); T is the thermodynamic temperature, with the unit of K; f and m respectively represent the fracture region and the pore region to be inversed; P is the pressure, with the unit of Pa; Pf is the pressure value of the fracture area to be inverted; P m is the pressure value of the pore area to be inverted; k f is the permeability of the fracture domain of municipal solid waste; k m is the permeability of the pore domain of municipal solid waste; ρ is the gas concentration, with the unit of kg / m 3 ; t is the time, with the unit of s; d is the diameter of the sample cylinder where the solid waste is located; z is the height, with the unit of m; D is the effective diffusion coefficient of air, with the unit of m 2 / s; Q f and Q m are the gas exchange amounts in the two zones, with the unit of kg / (m 3 ·s); β is the shape factor, which is taken as 10 according to the characteristics of municipal solid waste; α is the distance from the center of the fracture area to the fracture boundary, which is taken as 0.008 m according to the characteristics of municipal solid waste; r w is the empirical coefficient, which is taken as 0.4 according to the characteristics of municipal solid waste; k a is the permeability between the fracture area and the pore area, and the specific value is half of the permeability of the fracture area.

[0044] Step S4.2: According to the seepage characteristics of municipal solid waste, obtain the permeability result of the gas permeability test of the municipal solid waste sample. The permeability result of the gas permeability test of the municipal solid waste sample is the permeability k f of the fracture domain of municipal solid waste and the permeability k m of the pore domain of municipal solid waste, and k m is less than k f , that is, k f / k m is greater than 1. The ratio of k f / k m is given according to the permeability test result of the municipal solid waste sample. The ratio w f of the fracture domain in the total test area ranges from 0 < w f < 1, and the ratio of the pore domain in the total test area is 1 - w f ;

[0045] Preset the porosity sizes of the pore domain and the fracture domain according to the test result of the porosity test of the municipal solid waste sample. The test result of the porosity test of the municipal solid waste sample is the total porosity result of the municipal solid waste. Calculate the values of the pore domain and the fracture domain of the municipal solid waste sample according to the sum of the products of the porosities of different regions and their proportions being the total porosity;

[0046] Step S4.3: The permeability k f、The permeability k of the pore domain in the urban solid waste sample m 、Substitute the porosity values of the pore domain and the fracture domain of the urban solid waste sample and the air effective diffusion coefficient obtained from the air effective diffusion test of the urban solid waste sample into the numerical analysis software, and perform inversion calculation in combination with the sample size and the pressure reduction test data to obtain the gas penetration curve under the simulated data result.

[0047] Step S4.4: Compare the gas penetration curve under the simulated result with the gas penetration curve obtained through the pressure reduction test, and adjust the inversion data, that is, compare the test data obtained from the pressure reduction test with the simulated data, and then adjust the ratio of the fracture domain permeability to the porosity permeability and the proportion values of the pore domain and the fracture domain until the simulated data adopted is the same as the measured data result obtained from the pressure reduction test. Then, this data is considered the required final data result, and in this way, the optimal and most accurate two-region gas permeability coefficient of urban solid waste is obtained.

[0048] Advantages of the present invention:

[0049] The present invention provides an experimental device and method for inverting the two-region gas permeability coefficient of urban solid waste. Pressure sensors, temperature sensors, gas mass flow meters, and gas concentration analyzers are electrically connected to a data acquisition instrument, which can monitor the pressure, temperature, flow rate, and concentration changes of the gas flowing through the urban solid waste sample in real time at the data terminal, and can conveniently and accurately read the test data, with strong usability; the loading system of this device can directly compact the urban solid waste sample to the target height without excessive operations, greatly saving manpower and improving the test efficiency; the structure of this device is relatively simple and easy to operate, and it is applicable not only to urban solid waste but also to ordinary unsaturated soil, with wide applicability; the mathematical model selected for inversion in the present invention is a two-region gas permeability model, which can describe the preferential flow effect of gas in the urban solid waste medium, and can more accurately predict the gas flow and pressure distribution state in urban solid waste compared with the previous single-field models, thereby affecting the gas well collection volume and ventilation effect evaluation during the pumping process of landfills. Description of the drawings

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0051] Figure 1Schematic structural diagram of a test device for inverting the gas permeability coefficients of two zones of municipal solid waste according to the present invention;

[0052] Figure 2 Stereoscopic schematic diagram of a sample cylinder of a test device for inverting the gas permeability coefficients of two zones of municipal solid waste according to the present invention;

[0053] Figure 3 Cross-sectional schematic diagram of a sample cylinder of a test device for inverting the gas permeability coefficients of two zones of municipal solid waste according to the present invention;

[0054] Figure 4 Schematic structural diagram of an inverted drainage layer of a test device for inverting the gas permeability coefficients of two zones of municipal solid waste according to the present invention.

[0055] In the figure: 1, heating and heat preservation layer; 2, cylinder body; 3, gas pressure sensor; 4, base; 5, leachate recovery tank; 51, water delivery pipe; 6, inverted drainage layer; 7, temperature sensor; 8, loading plate; 9, displacement sensor; 10, press frame; 11, force transmission rod; 12, air cylinder; 13, outlet end pressure sensor; 14, gas mass flowmeter at the cylinder body outlet; 15, data acquisition instrument; 16, data terminal; 17, gas supply device; 18, gas filter; 19, gas mass flowmeter at the inlet end; 111, first gas pipeline; 222, second gas pipeline; 333, third gas pipeline; 444, fourth gas pipeline; 20, inlet end pressure sensor; 21, six-way valve; 211, first valve port; 212, second valve port; 213, third valve port; 214, fourth valve port; 215, fifth valve port; 216, sixth valve port; 22, gas storage tank; 23, gas analyzer; 24, gas collection port at the outlet end; 25, gas collection port at the inlet end; 26, valve for the gas outlet of the gas storage tank; 27, gas mass flowmeter at the outlet of the gas storage tank; 28, water delivery valve; 29, sample cylinder outlet valve; 30, sample cylinder inlet valve. Detailed implementation manners

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0057] This embodiment provides a test device for inverting the gas permeability coefficients of two zones of municipal solid waste, as shown in Figure 1As shown, it includes a sample cylinder, a gas supply system, a loading system, and a data acquisition system. The sample cylinder is used to fill the municipal solid waste sample to provide a test environment for the tests of the gas permeability, porosity, and effective gas diffusion coefficient of the municipal solid waste sample. The gas supply system is used to supply the test gases required for the tests of the gas permeability, porosity, and gas diffusion coefficient of the municipal solid waste sample. The loading system is used to perform a pressurization operation on the municipal solid waste sample. The data acquisition system is used to monitor in real time the data of the gas inflow and outflow rates, pressure, temperature, and gas concentration changing with time at the positions of each monitoring point preset. Each of the monitoring points is respectively arranged on the sample cylinder and the gas supply system according to the test requirements.

[0058] In a specific embodiment, as Figures 2 to 3 shown, the sample cylinder includes a heating and insulation layer 1, a cylinder body 2, and an inversion layer 6. The heating and insulation layer 1 is fixedly surrounded outside the cylinder body 2 in a soft package manner to play a role in heating and insulating the municipal solid waste sample in the sample cylinder. The cylinder body 2 has a specification of an inner diameter of 300 mm, a height of 800 mm, and a wall thickness of 10 mm. The material is selected as 316L stainless steel, which has the characteristics of corrosion resistance and rust prevention. The cylinder body 2 is fixed on a base 4. The base 4 is used to fix the sample cylinder and take out the municipal solid waste sample. The inversion layer 6 is arranged inside the cylinder body 2 to promote uniform gas flow. The inversion layer 6 includes a bottom inversion layer and a top inversion layer. One end of a water delivery pipe 51 penetrates through the bottom of the cylinder body 2 and the base 4 below the bottom inversion layer. The bottom of the cylinder body 2 is fixed to the base 4 by bolts. The bottom inversion layer is fitted and installed with the bottom of the cylinder body 2. As Figure 4 shown, the inversion layer 6 is provided with a number of small through holes for uniformly discharging the gas and liquid inside the municipal solid waste sample. The other end of the water delivery pipe 51 is connected to a leachate recovery tank 5. The leachate recovery tank 5 is used to collect the leachate discharged from the municipal solid waste sample. A water delivery valve 28 is arranged on the water delivery pipe 51. The water delivery valve 28 is in a closed state and is only opened when leachate deposition is detected. A number of temperature sensors 7 are arranged on one side of the cylinder body 2. Gas pressure sensors 3 are symmetrically arranged on the other side of the cylinder body 2 relative to the temperature sensors 7, including two temperature sensors 7 and two gas pressure sensors 3. One of the temperature sensors 7 and the corresponding gas pressure sensor 3 are arranged at a position 25 cm away from the base on the cylinder body. The other temperature sensor 7 and the corresponding other gas pressure sensor 3 are arranged at a position 45 cm away from the base on the cylinder body. And the range of the temperature sensor 7 is 0 - 200 °C.

[0059] In a specific embodiment, the loading system includes a loading plate 8, a press frame 10, a cylinder 12, and a force transmission rod 11. The press frame 10 is installed outside the specimen cylinder and fixed to the base 4 by welding to increase the stability of the cylinder 12. The cylinder 12 is vertically fixed at the top of the press frame 10 and drives the force transmission rod 11 to move vertically upward or downward under the action of high-pressure gas. One end of the force transmission rod 11 is installed on the loading plate 8, and the loading plate 8 is installed on the top inverted layer. The other end of the force transmission rod 11 penetrates through the top of the press frame 10 and communicates with the bottom of the cylinder 12, and the axis of the force transmission rod 11 coincides with the axis of the cylinder 2. The cylinder 12 can drive the loading plate 8 to reciprocate in the cylinder 2 through the force transmission rod 11, thereby pushing the loading plate 8 to pressurize the municipal solid waste specimen in the specimen cylinder. A displacement sensor 9 is also provided on the loading plate 8 to monitor the descending or ascending height of the loading plate 8.

[0060] In a specific embodiment, the gas supply system includes a gas supply device 17, an inlet gas mass flowmeter 19, a gas storage tank 22 for storing test gases required for testing the gas permeability, porosity, and effective gas diffusion coefficient of municipal solid waste samples, a cylinder outlet gas mass flowmeter 14, and a six-way valve 21. The gas supply device 17 is connected to one end of the inlet gas mass flowmeter 19 through a first gas pipeline 111. A pressure gauge is provided on the gas supply device 17 to detect the gas pressure. A gas filter 18 is provided between the gas supply device 17 and the inlet gas mass flowmeter 19 to filter impurities in the gas. The other end of the inlet gas mass flowmeter 19 is connected to the first valve port 211 of the six-way valve 21 through the first gas pipeline 111 to supply the required test gases. An inlet gas collection port 25 is provided between the inlet gas mass flowmeter 19 and the first valve port 211 of the six-way valve 21. The second valve port 212 of the six-way valve 21 is connected to the inlet of the gas storage tank 22 through a second gas pipeline 222 for storing test gases in the testing of the gas permeability, porosity, and effective gas diffusion coefficient of municipal solid waste samples. The outlet of the gas storage tank 22 is connected to the outlet gas mass flowmeter 27 through the second gas pipeline 222. A gas storage tank outlet valve 26 is provided on the second gas pipeline 222 between the gas storage tank 22 and the outlet gas mass flowmeter 27. The fourth valve port 214 of the six-way valve 21 is connected to the bottom inverted drainage layer through a third gas pipeline 333 passing through the base 4 and the sample cylinder base to supply test gases to the sample cylinder. A sample cylinder inlet valve 30 is provided on the third gas pipeline 333 to control the opening or closing of the sample cylinder inlet. An inlet pressure sensor 20 is installed at the sixth valve port 216 of the six-way valve 21 to monitor the gas pressure in the space connected to the six-way valve 21. The cylinder gas mass flowmeter 14 passes through a fourth gas pipeline 444 through the loading plate 8 and abuts against the top inverted drainage layer to monitor the gas flow rate at the outlet. A sample cylinder outlet valve 29 is provided on the fourth gas pipeline 444 between the cylinder gas mass flowmeter 14 and the sample cylinder. An outlet pressure sensor 13 and an outlet gas collection port 24 are provided on both sides of the sample cylinder outlet valve 29 to control the opening or closing of the sample cylinder outlet. The outlet pressure sensor 13 is installed between the sample cylinder outlet valve 29 and the cylinder outlet gas mass flowmeter 14 to detect the outlet pressure. The outlet gas collection port 24 is provided between the sample cylinder outlet valve 29 and the sample cylinder. The cylinder outlet gas mass flowmeter 14 is used to monitor the gas flow rate at the outlet.

[0061] In a specific embodiment, the data acquisition system includes a gas analyzer 23, a data collector 15, and a data terminal 16. The gas analyzer 23 is respectively connected to the gas collection port 25 at the intake end and the gas collection port 13 at the outlet end for monitoring the gas concentration at the gas collection port 25 at the intake end and the gas collection port 13 at the outlet end. The data collector 15 is respectively electrically connected to the intake end pressure sensor 20, the intake end gas mass flowmeter 19, the gas analyzer 23, the outlet end pressure sensor 13, the cylinder gas mass flowmeter 14, the temperature sensor 7, the displacement sensor 9, and the gas pressure sensor 3 for collecting gas flow, pressure, temperature, and displacement values. The measuring ranges of the intake end pressure sensor 20 and the outlet end pressure sensor 13 are 0 - 2 MPa, and the models of the gas mass flowmeters are all 10L. The data terminal 16 is electrically connected to the data collector 15 for feeding back the collected data to the data terminal 16 and saving it.

[0062] A test method for inverting the gas permeability coefficients in two zones of municipal solid waste, comprising:

[0063] Step S1: Collect a municipal solid waste sample and load it into the cylinder, specifically:

[0064] Collect a municipal solid waste sample from a landfill, cut the municipal solid waste sample, and the maximum size of the cut municipal solid waste sample is less than one-fourth of the inner diameter of the cylinder 2;

[0065] Load the cut municipal solid waste sample into the cylinder 2 in layers. The cylinder 12 drives the loading plate 8 to reciprocate in the cylinder 2 through the force transmission rod 11, thereby extruding the municipal solid waste sample; monitor the municipal solid waste sample to reach a preset target height through the displacement sensor 9.

[0066] Step S2: Conduct gas permeability tests, porosity tests, and diffusion coefficient tests on the municipal solid waste sample respectively to obtain the permeability, porosity, and effective diffusion coefficient of the municipal solid waste sample;

[0067] Step S3: Obtain a gas breakthrough curve for the municipal solid waste sample through a pressure reduction test;

[0068] Step S4: Substitute the three groups of data obtained from the gas permeability test of the municipal solid waste sample, the porosity test of the municipal solid waste sample, and the effective gas diffusion coefficient test of the municipal solid waste sample into the inversion calculation two-zone permeability model in numerical analysis software to obtain the gas breakthrough curve and the gas permeability coefficients in two zones of the municipal solid waste under the simulation results.

[0069] In a specific embodiment, in step S2, the gas permeability of the municipal solid waste sample is tested to obtain the permeability, porosity, and effective diffusion coefficient of the municipal solid waste sample, specifically as follows:

[0070] Step S2.1: The sample cylinder is regulated to a constant temperature environment through the heating and insulation layer 1 and the temperature sensor 7; the inlet valve 30 of the sample cylinder, the first valve port 211, the fourth valve port 214, and the sixth valve port 216 of the six-way valve are opened, and the second valve port 212, the fifth valve port 215, and the third valve port 213 are closed. The gas from the gas supply device 17 is transported to the inlet at the bottom of the cylinder cavity through the six-way valve 21 and the third gas pipeline 333. A first preset pressure value of 3 kPa is given, and the inlet pressure value is monitored by the inlet end pressure sensor 20. The gas in the cylinder cavity flows out through the cylinder gas mass flowmeter 14 on the fourth gas pipeline 444;

[0071] When the gas flow of the outlet cylinder gas mass flowmeter 14 is stable, the data acquisition instrument 15 records the outlet gas flow value, and the outlet pressure sensor 13 tests the outlet pressure value. Based on the permeability calculation formula, the permeability of the municipal solid waste sample is obtained. The permeability calculation formula is:

[0072]

[0073] k is the gas permeability, with the unit of m 2 ; Q is the gas flow, with the unit of m 3 / s; P in is the inlet end pressure, with the unit of Pa; P out is the outlet end pressure, with the unit of Pa; L is the length of the municipal solid waste sample, with the unit of m; μ is the gas kinetic viscosity, Pa·s; A is the cross-sectional area of the municipal solid waste sample, with the unit of m 2 .

[0074] Step 2.2: The sample cylinder is regulated to a constant temperature environment through the heating and insulation layer 1 and the temperature sensor 7; the outlet valve 29 of the sample cylinder and the inlet valve 30 of the sample cylinder are closed, the third valve port 213, the fourth valve port 214, the fifth valve port 215 of the six-way valve 21, and the outlet valve 26 of the gas storage tank are closed, the first valve port 211, the second valve port 212, and the sixth valve port 216 of the six-way valve are opened, and the gas supply device 17 is used to inject gas into the gas storage tank 22;

[0075] The injection pressure value is observed through the intake end pressure sensor 20. After the injection pressure reaches the second preset pressure value of 0.06 MPa, the first valve port 211 of the six-way valve is closed to keep the pressure in the gas storage tank 22 stable and record its pressure value; the fourth valve port 214 of the six-way valve and the specimen cylinder outlet valve 29 are opened to inject gas into the specimen cylinder. After the air pressure is stable, the pressure value is recorded through the gas pressure sensor 3. The porosity of the municipal solid waste specimen is obtained according to Boyle's law and the porosity calculation formula. Boyle's law is:

[0076] p1v1 = p2v2

[0077] where p1 is the pressure value of the gas storage tank, in Pa; v1 is the volume of the gas storage tank, in m 3 ; p2 is the value when the pressure in the specimen cylinder reaches stability, in Pa; v2 is the sum of the volume of the gas storage tank and the pore volume of the municipal solid waste after the pressure stabilizes, in m 3 ;

[0078] The porosity calculation formula is:

[0079]

[0080] where n is the porosity, v0 is the total volume of the municipal solid waste specimen, in m 3 .

[0081] Step S2.3: The specimen cylinder is regulated to a constant temperature environment through the heating and insulation layer 1 and the temperature sensor 7. The specimen cylinder outlet valve 29, the specimen cylinder inlet valve 30, the first valve port 211, the sixth valve port 216, and the fourth valve port 214 of the six-way valve are opened, and the second valve port 212, the third valve port 213, and the fifth valve port 215 of the six-way valve are closed. The gas supply device 17 uses a mixed gas of methane and carbon dioxide in equal proportions. The gas from the gas supply device 17 is transported to the bottom of the cylinder cavity of the specimen cylinder through the six-way valve 21 for flushing. A first flushing flow rate value of 10 L / min is given, and the intake flow rate value is monitored by the intake end gas mass flowmeter 19. During the flushing process, every given time value of 5 minutes, gas is collected through the intake end gas collection port 25 and the outlet end gas collection port 24, and the gas concentration is tested by the gas analyzer 23; when the gas concentration at the outlet end gas collection port 24 is stable, the gas supply device 17, the first valve port 211 of the six-way valve, and the fourth valve port 214 are closed. The outlet flow rate value is monitored by the cylinder outlet end gas mass flowmeter 14. When the outlet flow rate value is zero, the specimen cylinder outlet valve 29 is closed;

[0082] Open the first valve port 211, the sixth valve port 216, the second valve port 212 of the six-way valve, and the gas outlet of the gas storage tank 22. Close the third valve port 213, the fourth valve port 214, and the fifth valve port 215 of the six-way valve. The gas provided by the gas supply device 17 is air. Transport the gas from the gas supply device 17 to the gas storage tank 22 inlet through the six-way valve for flushing the gas storage tank. Preset a given flushing time and a given second flushing flow rate value. The given flushing time is 30 minutes, and the second flushing flow rate value is 10 L / min. The inlet flow rate value is monitored by the inlet gas mass flowmeter 19;

[0083] After reaching the flushing duration, close the gas supply device 17, the first valve port 211, and the second valve port 212 of the six-way valve. When the flow rate value at the gas outlet end of the gas storage tank 22 is zero, close the gas outlet valve 26 of the gas storage tank 22. The flow rate value at the gas outlet end of the gas storage tank 22 is monitored by the outlet gas mass flowmeter 27; At the same time, open the second valve port 212, the fourth valve port 214 of the six-way valve, and the valve 29 at the sample cylinder gas outlet. The gas flow rate value at the gas outlet end is monitored by the gas mass flowmeter 14 at the gas outlet end. The gas at the gas outlet end is sampled from the gas collection port 24 at the gas outlet end. Preset a given interval sampling time of 1 minute. The gas concentration at the gas outlet end is monitored by the gas analyzer 23. After the gas concentration at the gas outlet end is stable, obtain the effective diffusion coefficient of the municipal solid waste sample according to the gas diffusion formula. The calculation formula for the gas effective diffusion coefficient is:

[0084]

[0085] D = 0.78D1 + 0.21D2

[0086] J i is the gas diffusion flux, with the unit of mol / (m 2 ·s); i = 1, 2 represent nitrogen and oxygen respectively; C is the gas molar concentration, with the unit of mol / m 3 ; D is the air effective diffusion coefficient, D1 and D2 are the effective diffusion coefficients of nitrogen and oxygen respectively, with the unit of m 2 / s; z is the height, with the unit of m.

[0087] In a specific embodiment, in step S3, the gas penetration curve of the municipal solid waste sample is obtained through a pressure reduction test, specifically as follows:

[0088] Step S3.1: Regulate the sample cylinder to a constant temperature environment through the heating and insulation layer 1 and the temperature sensor 7; close the sample cylinder outlet valve 29, the sample cylinder inlet valve 30, the fourth valve port 214, the third valve port 213, the fifth valve port 215 of the six-way valve 21, and the outlet of the gas storage tank 22, and open the first valve port 211, the sixth valve port 216, and the second valve port 212 of the six-way valve, and inject gas into the gas storage tank 22 by using the gas supply device 17;

[0089] Step S3.2: Observe the gas injection pressure value through the inlet end pressure sensor 20. After the gas injection pressure reaches the third preset pressure value of 0.06 MPa, close the first valve port 211 of the six-way valve to fill the gas storage tank 22 with gas;

[0090] Step S3.3: Open the sample cylinder outlet valve 29, the sample cylinder inlet valve 30, and the fourth valve port 214 of the six-way valve to allow the gas to pass through the municipal solid waste sample in the sample cylinder, and record the gas flow rate at the outlet end of the sample cylinder and the data values of the gas pressure drop process in the gas storage tank 22 through the cylinder gas mass flowmeter 14 and the inlet end pressure sensor 20 respectively, and further obtain the gas penetration curve and the pressure drop curve from these data values.

[0091] In a specific embodiment, in step S4, the inversion calculation of the dual-zone gas permeability coefficient of the municipal solid waste represented by the dual-zone permeability model is specifically as follows:

[0092] Step S4.1: Substitute the test data of the gas permeability of the municipal solid waste sample, the test data of the porosity of the municipal solid waste sample, and the test data of the effective gas diffusion coefficient of the municipal solid waste sample into the numerical analysis software COMSOL Multiphysics to inversely calculate the dual-zone gas permeability coefficient of the municipal solid waste represented by the dual-zone permeability model. The dual-zone gas permeability model is:

[0093]

[0094]

[0095]

[0096]

[0097] M is the average molar mass of the gas, with the unit of kg / mol; R is the gas constant, with the unit of Pa·m 3 / (mol·K); T is the thermodynamic temperature, with the unit of K; f and m respectively represent the fracture region and the pore region to be inverted; P is the pressure, with the unit of Pa; Pf is the pressure value of the fracture area to be inverted; P m is the pressure value of the pore area to be inverted; k f is the permeability of the fracture domain of municipal solid waste; k m is the permeability of the pore domain of municipal solid waste; ρ is the gas concentration, with the unit of kg / m 3 ; t is the time, with the unit of s; d is the diameter of the sample cylinder where the solid waste is located; z is the height, with the unit of m; D is the effective diffusion coefficient of air, with the unit of m 2 / s; Q f and Q m are the gas exchange amounts in the double regions, with the unit of kg / (m 3 ·s); β is the shape factor, which is taken as 10 according to the characteristics of municipal solid waste; α is the distance from the center of the fracture area to the fracture boundary, which is taken as 0.008 m according to the characteristics of municipal solid waste; r w is the empirical coefficient, which is taken as 0.4 according to the characteristics of municipal solid waste; k a is the permeability between the fracture area and the pore area, and the specific value is half of the permeability of the fracture area.

[0098] Step S4.2: According to the seepage characteristics of municipal solid waste, obtain the permeability result of the gas permeability test of the municipal solid waste sample. The permeability result of the gas permeability test of the municipal solid waste sample is the permeability k f of the fracture domain of municipal solid waste, the permeability k m of the pore domain of municipal solid waste, and k m is less than k f , that is, k f / k m is greater than 1. The ratio of k f / k m is given according to the permeability test result of the municipal solid waste sample. The ratio w f of the fracture domain in the total test area ranges from 0 < w f < 1, and the ratio of the pore domain in the total test area is 1 - w f ;

[0099] Preset the porosity sizes of the pore domain and the fracture domain according to the test result of the porosity test of the municipal solid waste sample. The test result of the porosity test of the municipal solid waste sample is the total porosity result of the municipal solid waste. Calculate the double-region value of the municipal solid waste sample according to the sum of the products of the porosities in different regions and their proportions. The double-region value is the value of the pore domain and the fracture domain of the municipal solid waste sample;

[0100] Step S4.3: The permeability kf , the permeability k of the pore domain in the urban solid waste sample m , substitute the porosity values of the pore domain and the fracture domain of the urban solid waste sample and the air effective diffusion coefficient obtained from the air effective diffusion test of the urban solid waste sample into the numerical analysis software COMSOL Multiphysics, and perform inverse calculation in combination with the sample size and the pressure reduction test data to obtain the gas penetration curve under the simulated data result

[0101] Step S4.4: Compare the gas penetration curve under the simulation result with the gas penetration curve obtained through the pressure reduction test, and adjust the inverse data, that is, compare the test data obtained from the pressure reduction test with the simulated data, and then adjust the ratio of the fracture domain permeability to the porosity permeability and the proportion values of the pore domain and the fracture domain until the simulated data used is the same as the measured data result obtained from the pressure reduction test. Then, it is considered that this data is the required final data result, and in this way, the optimal and most accurate two-region gas permeability coefficient of urban solid waste is obtained.

[0102] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A test method for an experimental device for inverting the gas permeability coefficients of two zones of municipal solid waste, characterized in that, Specifically, it includes the following steps: Step S1: Collect a sample of municipal solid waste and load it into the sample cylinder of the test device for inverting the two-zone gas permeability coefficient of municipal solid waste; And the test device for inverting the two-zone gas permeability coefficient of municipal solid waste includes a sample cylinder, a gas supply system, a loading system, and a data acquisition system; the sample cylinder is used to load the municipal solid waste sample to provide a test environment for the permeability test of the gas in the municipal solid waste sample, porosity, and effective gas diffusion coefficient test. The gas supply system is used to provide the required test gas for the permeability, porosity, and gas diffusion coefficient tests of the gas in the municipal solid waste sample. The loading system is used to pressurize the municipal solid waste sample. The data acquisition system is used to monitor in real time the data of the gas inflow and outflow rate, pressure, temperature, and gas concentration changing with time at the positions of each monitoring point preset. Each monitoring point is respectively set on the sample cylinder and the gas supply system according to the test requirements; Step S2: Conduct gas permeability test, porosity test, and diffusion coefficient test on the municipal solid waste sample respectively to obtain the permeability, porosity, and effective diffusion coefficient of the municipal solid waste sample; Step S3: Obtain the gas breakthrough curve for the municipal solid waste sample through a pressure reduction test; Step S4: Substitute the three groups of data obtained from the gas permeability test of the municipal solid waste sample, the porosity test of the municipal solid waste sample, and the effective gas diffusion coefficient test of the municipal solid waste sample into the inversion calculation two-zone permeability model in the numerical analysis software to obtain the gas breakthrough curve and the two-zone gas permeability coefficient of the municipal solid waste under the simulation result. Specifically: Step S4.1: Substitute the gas permeability test data of the municipal solid waste sample, the porosity test data of the municipal solid waste sample, and the effective gas diffusion coefficient test data of the municipal solid waste sample into the two-zone gas permeability coefficient of the municipal solid waste represented by the inversion calculation two-zone permeability model in the numerical analysis software. The two-zone gas permeability model is: $M$ is the average molar mass of the gas, with the unit of kg / mol; $R$ is the gas constant, with the unit of Pa·m 3 / (mol·K); $T$ is the thermodynamic temperature, with the unit of K; $f$, $m$ respectively represent the fracture region and pore region to be inverted; $n$ is the porosity, $P$ is the pressure, with the unit of Pa; $P$ f is the pressure value of the fracture region to be inverted; $P$ m is the pressure value of the pore region to be inverted; $k$ f is the permeability of the fracture domain of municipal solid waste; $k$ m is the permeability of the pore domain of municipal solid waste; $\rho$ is the gas concentration, with the unit of kg / m 3 ; $t$ is the time, with the unit of s; $d$ is the diameter of the specimen cylinder where the solid waste is located; $z$ is the height; $D$ is the effective diffusion coefficient of air, with the unit of m 2 / s; $Q$ f and $Q$ m are the gas exchange amounts in the two regions, with the unit of kg / (m 3 ·s); $\beta$ is the shape factor, which is taken as 10 according to the characteristics of municipal solid waste; $\alpha$ is the distance from the center of the fracture region to the fracture boundary, which is taken as 0.008 m according to the characteristics of municipal solid waste; $r$ w is the empirical coefficient, which is taken as 0.4 according to the characteristics of municipal solid waste; $k$ a is the permeability between the fracture region and the pore region, and the specific value is half of the permeability of the fracture region; $\mu$ is the dynamic viscosity coefficient of the gas; Step S4.2: According to the seepage characteristics of municipal solid waste, obtain the permeability results of the gas permeability test of the municipal solid waste specimen. The permeability results of the gas permeability test of the municipal solid waste specimen are the fracture domain permeability k f of the municipal solid waste and the pore domain permeability k m of the municipal solid waste. And k m is less than k f , that is, k f / k m is greater than 1. The ratio of k f / k m is given according to the permeability test results of the municipal solid waste specimen. The ratio w f of the fracture domain in the total test area ranges from 0 < w f < 1, and the ratio of the pore domain in the total test area is 1 - w f ; Preset the porosity sizes of the pore domain and the fracture domain according to the test results of the porosity test of the municipal solid waste sample. The test results of the porosity test of the municipal solid waste sample are the total porosity results of the municipal solid waste. Calculate the values of the pore domain and the fracture domain of the municipal solid waste sample according to the sum of the products of the porosity of different regions and their proportions being the total porosity; Step S4.3: Substitute the calculated fracture domain permeability k of the municipal solid waste sample f , the permeability k of the pore domain in the municipal solid waste sample m , the porosity values of the pore domain and fracture domain of the municipal solid waste sample, and the air effective diffusion coefficient obtained from the air effective diffusion test of the municipal solid waste sample into the numerical analysis software COMSOL Multiphysics, and perform inversion calculations in combination with the sample size and the pressure reduction test data to obtain the gas penetration curve under the simulated data results; Step S4.4: Compare the gas breakthrough curve under the simulation data result with the gas breakthrough curve obtained through the pressure reduction test, and adjust the inversion data, that is, compare the test data and the simulation data obtained through the pressure reduction test, and then adjust the ratio of the fracture domain permeability to the pore domain permeability and the proportion values of the pore domain and the fracture domain until the simulation data used is the same as the measured data result obtained through the pressure reduction test. Then the simulation data is the required final data result, and in this way, the optimal and most accurate two-zone gas permeability coefficient of the municipal solid waste can be obtained.

2. The test method of a test device for the dual-zone gas permeability coefficient of inverted municipal solid waste according to claim 1, characterized in that The sample cylinder includes a heating and heat preservation layer (1), a cylinder body (2), and an inversion layer (6). The heating and heat preservation layer (1) is fixedly wound around the outside of the cylinder body (2). The cylinder body (2) is fixed on the base (4). The inversion layer (6) is arranged inside the cylinder body (2) to promote uniform gas flow. The inversion layer (6) includes a bottom inversion layer and a top inversion layer. One end of a water delivery pipe (51) penetrates through the bottom of the cylinder body (2) and the base (4) below the bottom inversion layer. The other end of the water delivery pipe (51) is connected to a leachate recovery tank (5) for collecting the leachate discharged from the municipal solid waste sample. A water delivery valve (28) is arranged on the water delivery pipe (51). The water delivery valve (28) is in a closed state and is only opened when it is detected that there is leachate deposition. A plurality of temperature sensors (7) are arranged on one side of the cylinder body (2). The gas pressure sensor (3) is symmetrically arranged on the other side of the cylinder body (2) relative to the temperature sensors (7).

3. The test method of an inversion test device for the gas permeability coefficient of two zones of municipal solid waste according to claim 2, characterized in that, The loading system includes a loading plate (8), a press frame (10), a cylinder (12), and a force transmission rod (11). The press frame (10) is installed outside the sample cylinder and fixed on the base (4). The cylinder (12) is vertically fixed on the top of the press frame (10). One end of the force transmission rod (11) is installed on the loading plate (8). The loading plate (8) is installed on the top inversion layer. The other end of the force transmission rod (11) penetrates through the top of the press frame (10) and communicates with the bottom of the cylinder (12). And the axis of the force transmission rod (11) coincides with the axis of the cylinder body (2). The cylinder (12) can drive the loading plate (8) to reciprocate in the cylinder body (2) through the force transmission rod (11), and pressurize the municipal solid waste sample in the sample cylinder by pushing the loading plate (8). A displacement sensor (9) is also arranged on the loading plate (8) for monitoring the lifting height of the loading plate (8).

4. The test method of a test device for the double-zone gas permeability coefficient of inverted municipal solid waste according to claim 3, characterized in that, The gas supply system includes a gas supply device (17), an inlet gas mass flowmeter (19), a gas storage tank (22) for storing test gases required for testing the gas permeability, porosity, and effective gas diffusion coefficient of municipal solid waste samples, a cylinder outlet gas mass flowmeter (14), and a six-way valve (21). The gas supply device (17) is connected to one end of the inlet gas mass flowmeter (19) through a first gas pipeline (111). A gas filter (18) is provided between the gas supply device (17) and the inlet gas mass flowmeter (19) to filter impurities in the gas. The other end of the inlet gas mass flowmeter (19) is connected to the first valve port (211) of the six-way valve (21) through the first gas pipeline (111). An inlet gas collection port (25) is provided between the inlet gas mass flowmeter (19) and the six-way valve (21). The second valve port (212) of the six-way valve (21) is connected to the inlet of the gas storage tank (22) through a second gas pipeline (222). The outlet of the gas storage tank (22) is connected to the outlet gas mass flowmeter (27) through the second gas pipeline (222). A gas storage tank outlet valve (26) is provided on the second gas pipeline (222) between the gas storage tank (22) and the outlet gas mass flowmeter (27). The fourth valve port (214) of the six-way valve (21) penetrates through the base (4) and the sample cylinder base through a third gas pipeline (333) and is connected to the bottom inverted drainage layer. A sample cylinder inlet valve (30) is provided on the third gas pipeline (333). An inlet pressure sensor (20) is installed at the sixth valve port (216) of the six-way valve (21). The cylinder outlet gas mass flowmeter (14) penetrates through the loading plate (8) through a fourth gas pipeline (444) and abuts against the top inverted drainage layer to monitor the gas flow rate at the outlet. A sample cylinder outlet valve (29) is provided on the fourth gas pipeline (444) between the cylinder outlet gas mass flowmeter (14) and the sample cylinder. An outlet pressure sensor (13) and an outlet gas collection port (24) are provided on both sides of the sample cylinder outlet valve (29). The outlet pressure sensor (13) is installed between the sample cylinder outlet valve (29) and the cylinder outlet gas mass flowmeter (14). The outlet gas collection port (24) is provided between the sample cylinder outlet valve (29) and the sample cylinder.

5. The test method of an inversion test device for the gas permeability coefficient of two zones of municipal solid waste according to claim 4, characterized in that, The data acquisition system includes a gas analyzer (23), a data acquisition instrument (15), and a data terminal (16). The gas analyzer (23) is respectively connected to the gas collection port (25) at the intake end and the gas collection port (24) at the outlet end, and is used for monitoring the gas concentration at the gas collection port (25) at the intake end and the gas collection port (24) at the outlet end. The data acquisition instrument (15) is respectively electrically connected to the intake end pressure sensor (20), the intake end gas mass flowmeter (19), the gas analyzer (23), the outlet end pressure sensor (13), the gas mass flowmeter (14) at the outlet of the cylinder body, the temperature sensor (7), the displacement sensor (9), and the gas pressure sensor (3), and is used for collecting the values of gas flow, pressure, temperature, and displacement. The data terminal (16) is electrically connected to the data acquisition instrument (15).

6. The test method of a test device for the dual-zone gas permeability coefficient of invert municipal solid waste according to claim 4, characterized in that A plurality of through holes are provided in both the bottom inverted layer and the top inverted layer for uniformly discharging the gas or liquid inside the urban solid waste sample.

7. The test method of an inversion test device for the gas permeability coefficient of two zones of municipal solid waste according to claim 5, characterized in that In step S2, a gas permeability test is performed on the urban solid waste sample to obtain the permeability, porosity, and effective diffusion coefficient of the urban solid waste sample. Specifically: Step S2.1: Regulate the sample cylinder to a constant temperature environment through the heating and insulation layer (1) and the temperature sensor (7); open the sample cylinder inlet valve (30), the first valve port (211), the fourth valve port (214), and the sixth valve port (216) of the six-way valve (21), and close the second valve port (212), the fifth valve port (215), and the third valve port (213). Deliver the gas from the gas supply device (17) to the inlet at the bottom of the cylinder cavity through the six-way valve (21) and the third gas pipeline (333), and set the inlet pressure to the first preset pressure. The inlet pressure value is monitored by the intake end pressure sensor (20). The gas in the cylinder cavity flows out through the gas mass flowmeter (14) at the outlet of the cylinder body on the fourth gas pipeline (444); when the gas flow of the gas mass flowmeter (14) at the outlet of the cylinder body is stable, the data acquisition instrument (15) records the outlet end flow value, and the outlet end pressure sensor (13) measures the outlet pressure value. Based on the permeability calculation formula, the permeability of the urban solid waste sample is obtained. The permeability calculation formula is: k is the gas permeability with the unit of m 2 ; Q is the gas flow rate with the unit of m 3 / s; P in is the inlet pressure with the unit of Pa; P out is the outlet pressure with the unit of Pa; L is the length of the municipal solid waste sample with the unit of m; μ is the gas dynamic viscosity, Pa·s; A is the cross-sectional area of the municipal solid waste specimen with the unit of m 2 ; Step 2.2: Regulate the sample cylinder to a constant temperature environment by heating the thermal insulation layer (1) and the temperature sensor (7); close the sample cylinder outlet valve (29) and the sample cylinder inlet valve (30), close the third valve port (213), the fourth valve port (214), the fifth valve port (215) of the six-way valve and the gas storage tank outlet valve (26), open the first valve port (211), the second valve port (212) and the sixth valve port (216) of the six-way valve, and inject gas into the gas storage tank (22) by using the gas supply device (17); observe the gas injection pressure value through the inlet end pressure sensor (20), and when the gas injection pressure reaches the second preset pressure, close the first valve port (211) of the six-way valve, keep the pressure in the gas storage tank (22) stable and record its pressure value; open the fourth valve port (214) of the six-way valve and the sample cylinder inlet valve (30) to inject gas into the sample cylinder, and after the gas pressure is stable, record the pressure value through the gas pressure sensor (3), and obtain the porosity of the municipal solid waste sample according to Boyle's law and the porosity calculation formula. Boyle's law is: p1v1 = p2v2 Among them, p1 is the pressure value of the gas storage tank, with the unit of Pa; v1 is the volume of the gas storage tank, with the unit of m 3 ; p2 is the value after the pressure in the sample cylinder reaches stability, with the unit of Pa; v2 is the sum of the volume of the gas storage tank and the pore volume of municipal solid waste after the pressure stabilizes, with the unit of m 3 ; The porosity calculation formula is: where n is the porosity, v0 is the total volume of the municipal solid waste sample, with the unit of m 3 ; Step S2.3: The sample tube is regulated to a constant temperature environment by heating the insulation layer (1) and the temperature sensor (7), the sample tube outlet valve (29), the sample tube inlet valve (30) and the first valve port (211), the sixth valve port (216) and the fourth valve port (214) of the six-way valve are opened, and the second valve port (212), the third valve port (213) and the fifth valve port (215) of the six-way valve are closed. The gas supply device (17) uses a mixed gas of methane and carbon dioxide in equal proportions, and the gas of the gas supply device (17) is delivered to the bottom of the cylinder cavity of the sample tube through the six-way valve (21) for flushing. A first flushing flow value is preset, and the intake air is The flow value is monitored by a gas mass flow meter (19) at the gas inlet end. During the flushing process, gas is collected through a gas collection port (25) at the gas inlet end and a gas collection port (24) at the gas outlet end at given time intervals, and the gas concentration is tested by a gas analyzer (23). When the gas concentration at the gas collection port (24) at the gas outlet end is stable, the gas supply device (17), the first valve port (211) and the fourth valve port (214) of the six-way valve are closed, and the gas outlet flow value is monitored by a gas mass flow meter (14) at the outlet of the cylinder body. When the gas outlet flow value is zero, the sample cylinder outlet valve (29) is closed. The first valve port (211), the sixth valve port (216) and the second valve port (212) of the six-way valve are closed. , the gas outlet of the gas storage tank (22) is opened, the third valve port (213), the fourth valve port (214) and the fifth valve port (215) of the six-way valve are closed, the gas provided by the gas supply device (17) is air, the gas of the gas supply device (17) is delivered to the gas inlet of the gas storage tank (22) through the six-way valve to flush the gas storage tank, a preset flushing time and a preset second flushing flow value, and the gas inlet flow value is monitored by the gas mass flow meter (19) at the gas inlet end; after the flushing time is reached, the gas supply device (17), the first valve port (211) and the second valve port (212) of the six-way valve are closed, and the gas storage tank (22) is closed when the flow value at the gas outlet end is zero. The gas outlet valve (26) of the storage tank is closed, and the gas outlet flow value of the gas storage tank (22) is monitored by the outlet gas mass flow meter (27); at the same time, the second valve port (212), the fourth valve port (214) of the six-way valve, and the valve (29) of the sample tube outlet are opened, and the gas flow value of the gas outlet is monitored by the cylinder outlet gas mass flow meter (14), and the gas at the gas outlet is sampled by the gas collection port (24) at the gas outlet, and a given interval sampling time is preset. The gas concentration at the gas outlet is monitored by the gas analyzer (23), and after the gas concentration at the gas outlet is stable, the effective diffusion coefficient of the urban solid waste sample is obtained according to the gas diffusion formula. The calculation formula of the gas effective diffusion coefficient is: D=0.78D1+0.21D2 J i is the gas diffusion flux, with the unit of mol / (m 2 ·s); i = 1, 2 represent nitrogen and oxygen respectively; C is the gas molar concentration, with the unit of mol / m 3 ; D is the effective diffusion coefficient of air, and D1, D2 are the effective diffusion coefficients of nitrogen and oxygen respectively, with the unit of m 2 / s; z is the height, with the unit of m.

8. The test method of a test device for the dual-zone gas permeability coefficient of inverted municipal solid waste according to claim 7, characterized in that In step S3, a gas breakthrough curve is obtained by performing a pressure reduction test on the municipal solid waste sample, specifically: Step S3.1: Regulate the sample cylinder to a constant temperature environment by heating the thermal insulation layer (1) and the temperature sensor (7). Close the sample cylinder outlet valve (29), the sample cylinder inlet valve (30), the fourth valve port (214), the third valve port (213), the fifth valve port (215) of the six-way valve, and the outlet of the gas storage tank (22). Open the first valve port (211), the sixth valve port (216), and the second valve port (212) of the six-way valve, and inject gas into the gas storage tank (22) using the gas supply device (17). Step S3.2: Observe the gas injection pressure value through the inlet end pressure sensor (20). After the gas injection pressure reaches the third preset pressure value, close the first valve port (211) of the six-way valve to fill the gas storage tank (22) with gas. Step S3.3: Open the sample cylinder outlet valve (29), the sample cylinder inlet valve (30), and the fourth valve port (214) of the six-way valve to allow the gas to pass through the municipal solid waste sample in the sample cylinder. Record the gas flow rate at the outlet end of the sample cylinder and the data values of the gas pressure drop process in the gas storage tank (22) respectively through the cylinder outlet gas mass flowmeter (14) and the inlet end pressure sensor (20). Further obtain the gas penetration curve and the pressure drop curve from these data values.

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