Method and system for collaboratively determining non-steady-state diffusion coefficient under normal pressure based on RC model and coal particle gas desorption experiment

Abstract

The present application relates to the field of gas measurement technology, and provides a method and system for collaboratively determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and the coal particle gas desorption experiment. In this method, the electric desorption simulation model constructed based on the adsorption desorption simulation circuit and the coal particle gas desorption non-steady-state diffusion model under normal pressure conditions determined by the traditional coal particle gas desorption experiment are simplified into exponential forms respectively, and the corresponding relationship between the non-steady-state diffusion coefficient of the coal particle gas and the desorption resistance in the adsorption desorption simulation circuit is determined; according to the determined piecewise function of the desorption resistance changing with the desorption time, based on the corresponding relationship between the non-steady-state diffusion coefficient of the coal particle gas and the desorption resistance, a piecewise expression of the non-steady-state diffusion coefficient of the coal particle gas is constructed, which effectively solves the problem that the accuracy of the traditional coal particle gas desorption non-steady-state diffusion coefficient measurement is insufficient, and the coal particle gas diffusion adsorption based on the constant constant diffusion coefficient cannot accurately describe the desorption process of the coal particle gas.

Description

Technical Field

[0001] The present application relates to the field of gas measurement technology, and in particular to a method and system for collaboratively determining a non-steady-state diffusion coefficient under normal pressure based on an RC model and a coal particle gas desorption experiment. Background Art

[0002] The gas diffusion coefficient is an important parameter for studying gas flow, which reflects the diffusion capacity of gas in porous media. In the coal industry, the study of gas diffusion coefficient is particularly important, which is directly related to the determination of coal particle gas desorption and the effectiveness test of its emission, thus affecting the safe production of coal mines.

[0003] At present, the experimental equipment for traditional coal particle gas desorption experiment is as follows: Figure 1 As shown in the figure, the system is mainly composed of high-pressure methane cylinders, reference tanks, coal sample tanks, and desorption gas collection devices. Taking the variable pressure desorption experiment as an example, the gas is first rushed into the reference tank from the gas cylinder at a constant pressure. After the pressure stabilizes, the gas is injected from the reference tank into the coal sample tank. The coal particles in the coal sample tank adsorb the gas in an isochoric environment, and the gas pressure in the tank decreases accordingly; after the adsorption equilibrium is reached, the gas in the coal sample tank is released into the desorption device of a specified volume, providing a desorption environment of a specified gas pressure for the coal particles, so that the coal particles desorb the gas under this pressure, and the gas pressure in the system increases with desorption. Summary of the invention

[0004] The purpose of this application is to provide a method and system for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and coal particle gas desorption experiment, so as to solve or alleviate the problems existing in the above-mentioned prior art.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] The present application provides a method for collaboratively determining a non-steady-state diffusion coefficient under normal pressure based on an RC model and a coal particle gas desorption experiment, comprising: step S101, simplifying an electric desorption simulation model constructed based on an adsorption-desorption simulation circuit and a coal particle gas desorption non-steady-state diffusion model under normal pressure conditions determined by a traditional coal particle gas desorption experiment into exponential forms, respectively, to determine a corresponding relationship between the non-steady-state diffusion coefficient of coal particle gas and a desorption resistor in the adsorption-desorption simulation circuit;

[0007] Step S102, determining a piecewise function of the desorption resistance varying with the desorption time;

[0008] Step S103: Based on the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance and according to the piecewise function of the desorption resistance, a piecewise expression of the coal particle gas non-steady-state diffusion coefficient is constructed.

[0009] Preferably, in step S101, the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance in the adsorption-desorption simulation circuit is:

[0010]

[0011] In the formula, With the desorption time The changing non-steady-state diffusion coefficient of coal particle gas, With the desorption time Variation of the desorption resistance, is the radius of coal particles in the conventional coal particle gas desorption experiment, is the capacitance value of the particle capacitance in the adsorption-desorption simulation circuit.

[0012] Preferably, in step S102, the piecewise function of the desorption resistance varying with the desorption time is:

[0013]

[0014] In the formula, With the desorption time Variation of the desorption resistance, The first desorption time The corresponding desorption resistance, The second desorption time The corresponding desorption resistance, All are constant terms.

[0015] Preferably, the first desorption time is determined based on the slope of the gas pressure versus time curve obtained from the coal particle gas desorption experiment. and the second desorption time .

[0016] Preferably, based on simulations of different resistance values, the first desorption time is determined. Corresponding desorption resistance , and the second desorption time Corresponding desorption resistance .

[0017] Preferably, the pressure change curve with desorption time in the conventional coal particle gas desorption experiment is matched with multiple voltage change curves with desorption time obtained by simulating different resistance values ​​to determine the first desorption time. and the second desorption time The constant term between the desorption resistance and the desorption time .

[0018] Preferably, the segmented expression of the non-steady-state diffusion coefficient of coal particle gas is:

[0019]

[0020] In the formula, With the desorption time The changing non-steady-state diffusion coefficient of coal particle gas, is the radius of coal particles in the conventional coal particle gas desorption experiment, is the capacitance value of the particle capacitance in the adsorption-desorption simulation circuit, The first desorption time The corresponding desorption resistance, The second desorption time The corresponding desorption resistance, All are constant terms.

[0021] The embodiment of the present application also provides a system for determining a non-steady-state diffusion coefficient under normal pressure based on an RC model and a coal particle gas desorption experiment, comprising:

[0022] A matching unit is configured to simplify the electric desorption simulation model constructed based on the adsorption-desorption simulation circuit and the coal particle gas desorption non-steady-state diffusion model under normal pressure conditions determined by the traditional coal particle gas desorption experiment into exponential forms, so as to determine the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance in the adsorption-desorption simulation circuit;

[0023] a desorption resistance determination unit configured to determine a piecewise function of the desorption resistance varying with desorption time;

[0024] The diffusion coefficient determination unit is configured to construct a piecewise expression of the coal particle gas non-steady-state diffusion coefficient based on the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance and according to the piecewise function of the desorption resistance.

[0025] Beneficial effects:

[0026] In the method for collaboratively determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and the coal particle gas desorption experiment provided in the embodiment of the present application, the electric desorption simulation model constructed based on the adsorption desorption simulation circuit and the coal particle gas desorption non-steady-state diffusion model under normal pressure conditions determined by the traditional coal particle gas desorption experiment are simplified into exponential forms respectively to determine the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance in the adsorption desorption simulation circuit; then, according to the determined piecewise function of the desorption resistance changing with the desorption time, based on the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance, a piecewise expression of the coal particle gas non-steady-state diffusion coefficient is constructed. Thus, the RC electrical simulation is combined with the traditional coal particle gas desorption, which effectively solves the problem that the traditional coal particle gas desorption non-steady-state diffusion coefficient is insufficient in accuracy when measuring the coal particle gas desorption, and the coal particle gas diffusion adsorption based on the constant constant diffusion coefficient cannot accurately describe the coal particle gas desorption process, and the coal particle gas desorption non-steady-state diffusion coefficient under normal pressure conditions is efficiently and accurately obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. Among them:

[0028] Figure 1 It is a system schematic diagram of coal particle adsorption and desorption experiment in the prior art;

[0029] Figure 2 A schematic flow chart of a method for determining a non-steady-state diffusion coefficient under normal pressure based on an RC model and a coal particle gas desorption experiment according to some embodiments of the present application;

[0030] Figure 3 A circuit diagram of an adsorption-desorption simulation circuit provided according to some embodiments of the present application;

[0031] Figure 4 for Figure 3 A schematic diagram of a gas adsorption simulation circuit in the adsorption and desorption simulation circuit shown;

[0032] Figure 5 for Figure 3 A schematic diagram of a gas desorption simulation circuit in the adsorption and desorption simulation circuit shown;

[0033] Figure 6 A schematic diagram showing a comparison between a curve of a change in gas pressure versus desorption time in a conventional coal particle gas desorption experiment provided according to some embodiments of the present application and a plurality of curves of a change in voltage versus desorption time obtained by simulating different resistance values;

[0034] Figure 7A simulation schematic diagram of a linear resistor provided according to some embodiments of the present application;

[0035] Figure 8 A schematic diagram of changes in desorption resistance over time according to some embodiments of the present application;

[0036] Fig. 9 A schematic diagram of the structure of a system for collaboratively determining a non-steady-state diffusion coefficient under normal pressure based on an RC model and a coal particle gas desorption experiment according to some embodiments of the present application. DETAILED DESCRIPTION

[0037] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application and does not limit the present application. In fact, it will be clear to those skilled in the art that modifications and variations may be made in the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as a part of an embodiment may be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the embodiments of the present invention should belong to the scope of protection of the embodiments of the present invention.

[0038] In the experimental device of the traditional coal particle gas desorption experiment, the gas cylinder mainly provides constant pressure gas to the reference tank; the reference tank provides constant volume gas to the coal sample tank; the coal particles in the coal sample tank adsorb the gas provided by the reference tank to reduce the gas pressure in the reference tank; the coal particles in the coal sample tank desorb gas to the desorption gas collection device. The existing gas diffusion theory believes that in microscopic pores, the gas moves in the form of diffusion, and the Fick law plays a leading role. In the Fick diffusion process, the effective gas diffusion coefficient is defined as:

[0039]

[0040] In the formula, is the effective diffusion coefficient of gas in coal, is the tortuosity factor, is the effective surface porosity of coal, is the relative molecular mass of gas, is the absolute temperature, is the universal gas constant, is the mean free path of gas molecules (constant). Therefore, in the existing coal particle gas diffusion model, the tortuosity factor is considered to be , effective surface porosity of coal is constant, and thus, the effective diffusion coefficient of gas in coal It is considered to be a constant and will not change with time.

[0041] However, in reality, due to the deformation of the medium structure during the desorption of coal gas, the gas diffusion channel will change accordingly (i.e., the tortuosity factor As the desorption time increases, the gas pressure gradient inside the coal pores decreases continuously. This process is a dynamic interaction between gas molecules and coal microscopic pores. The desorption of gas molecules causes the contraction of coal microscopic pores (i.e., the effective surface porosity of coal). The shrinkage of coal micropores negatively affects gas diffusion, which makes the gas desorption in coal particle gas adsorption and desorption have non-steady-state characteristics.

[0042] The volume of coal expands after it absorbs gas, and shrinks after it desorbs gas. Therefore, during the gas desorption process, some microscopic pores in the coal gradually shrink, causing the change of the gas diffusion coefficient. That is, during the gas desorption process, the effective diffusion coefficient of gas in coal is It is not constant, based on the constant diffusion coefficient Diffusion adsorption of coal particle gas cannot accurately describe the desorption process of coal particle gas.

[0043] Based on this, this application constructs an RC circuit that simulates the structure of coal particles based on the traditional coal particle gas desorption experiment, and in view of the similarities between coal particles and capacitors in their own structures, physical processes and physical laws during adsorption, desorption and charging and discharging, a method for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and the coal particle gas desorption experiment is proposed, so as to efficiently and accurately obtain the non-steady-state diffusion coefficient of gas desorption of coal particles under normal pressure conditions. Figures 2 to 8 As shown, the method for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and the coal particle gas desorption experiment includes:

[0044] Step S101, simplify the electric desorption simulation model constructed based on the adsorption-desorption simulation circuit and the coal particle gas desorption non-steady-state diffusion model under normal pressure conditions determined by the traditional coal particle gas desorption experiment into exponential forms respectively, so as to determine the corresponding relationship between the coal particle gas steady-state diffusion coefficient and the desorption resistance in the adsorption-desorption simulation circuit.

[0045] The structure of coal sample particles is highly similar when they adsorb and desorb gas and when they charge and discharge capacitors. First, both coal sample particles and capacitors adsorb microscopic particles. Coal sample particles adsorb and desorb gas molecules, and capacitors store and release charges. Second, coal sample particles adsorb gas molecules on the surface of the coal matrix. The larger the specific surface area of ​​the coal, the stronger the adsorption capacity. Capacitors store electrons on the surface of the capacitor plates. The larger the area of ​​the capacitor plates, the more electrons are stored. Third, the gas desorption airflow of coal sample particles and the capacitor discharge current are both formed by the detachment of particles from the material surface. The coal pore airflow is formed by the detachment of gas molecules from the surface of the coal matrix. The more desorbed molecules, the greater the gas flow. The capacitor discharge current is formed by the detachment of charges from the surface of the capacitor plates. The more charges released, the greater the current.

[0046] The physical processes of coal sample particles during gas adsorption and desorption and capacitor charging and discharging are highly similar. First, coal sample particle adsorption and desorption and capacitor charging and discharging both involve the process of particle monolayer adsorption and release on the solid surface. In coal sample particle adsorption and desorption, the particles are gas molecules and the solid is the coal matrix surface; in capacitor charging and discharging, the particles are electrons and the solid is the plate surface. Secondly, coal sample particle adsorption and desorption and capacitor charging and discharging both involve particle flow processes; in coal particle adsorption and desorption, gas molecules flow in the pores, and during adsorption, the molecules flow from the outside of the coal particles along the pore cracks to the pore surface, and during desorption, the molecules flow from the pore surface to the outside of the coal particles; in capacitor charging and discharging, electrons flow in the circuit, and during charging, electrons flow from the power supply through the circuit to the particle capacitor plate surface, and during discharging, electrons flow from the particle capacitor plate surface to the low-voltage component. Furthermore, coal sample particle adsorption and desorption and capacitor charging and discharging are both driven by gradient action. During the adsorption and desorption of coal sample particles, the adsorption environment is a high-pressure environment relative to the coal sample particles, and the desorption environment is a low-pressure environment relative to the coal sample particles; during capacitor charging and discharging, the charging power supply is a high-voltage environment relative to the particle capacitor, and the low-voltage component is a low-voltage environment relative to the particle capacitor.

[0047] Based on this, the adsorption and desorption experiment of coal particles can be simulated by the adsorption simulation circuit. Specifically, the adsorption and desorption simulation circuit includes: voltage source , adsorption capacitance , coal particle simulation circuit and desorption capacitor Among them, the voltage source Used to simulate the gas source in coal particle adsorption and desorption experiments, adsorption capacitance Through the first circuit switch With voltage source Electrical connection, coal particle simulation circuit through the second circuit switch With adsorption capacitance Electrical connection, desorption capacitor Through the third circuit switch It is electrically connected to the coal particle simulation circuit. In the coal particle simulation circuit, there are ( is a positive integer) parallel RC simulation circuits, each RC simulation circuit includes a particle capacitor and a particle resistor in series. That is, in the coal particle simulation circuit, there are Particle capacitors ,as well as Particle resistance .

[0048] In the adsorption capacitor With voltage source The connected circuit is equipped with an adsorption resistor , through the adsorption resistance The adjustment of the resistance value can effectively adjust the adsorption capacitance At the same time, the voltage value of the adsorption capacitor The first electric meter is connected in parallel at both ends to realize the adsorption capacitance Real-time monitoring of the voltage at both ends. When closed, the adsorption resistor , the first voltmeter It can realize the simulation and adjustment of the pressure when the gas is filled into the reference tank in the traditional coal particle adsorption and desorption experiment.

[0049] Voltage Source , adsorption capacitance , coal particle simulation circuit to form a gas adsorption simulation circuit, and perform gas adsorption simulation in coal particle adsorption and desorption experiments. After charging is completed, disconnect the first circuit switch , close the second circuit switch , adsorption capacitance That is, it starts to discharge to the coal particle simulation circuit; ( is a positive integer) parallel RC simulation circuits, the particle capacitor in each RC simulation circuit begins to charge, so as to perform an equivalent simulation of the process of gas adsorption by the coal sample particles in the coal sample tank from the reference tank in the coal particle adsorption and desorption experiment. When the voltage balance is reached with the coal particle simulation circuit, the particle capacitance in the coal particle simulation circuit is fully charged, which is equivalent to the reference tank and the coal sample tank reaching pressure balance, and the gas adsorption of the coal sample particles in the coal particle adsorption and desorption experiment is completed. Here, it should be noted that by adjusting the resistance value of the particle resistor of each RC simulation circuit, the adsorption physical conditions such as the pore size of the coal sample particles can be simulated.

[0050] Coal particle simulation circuit and desorption capacitor A gas desorption simulation circuit is formed to simulate the gas desorption in the coal particle adsorption experiment. Specifically, after the particle capacitor in the coal particle simulation circuit is fully charged, the second circuit switch is disconnected. , close the third circuit switch , the particle capacitance in the coal particle simulation circuit is discharged, and the desorption capacitance The coal particle simulation circuit and the desorption capacitor are connected to realize the gas desorption simulation between the coal sample tank and the desorption gas collection device in the traditional gas adsorption and desorption experiment. When the voltage reaches equilibrium, the particle capacitance in the coal particle simulation circuit is discharged, and the desorption capacitance The charging is completed, which is equivalent to the pressure balance between the coal sample tank and the desorption gas collecting device in the traditional gas adsorption and desorption experiment, and the gas desorption is completed.

[0051] At the same time, the desorption capacitor A desorption resistor is also provided between the coal particle simulation circuit and the , by adjusting the desorption resistance The resistance value is used to realize the desorption capacitance The voltage value at both ends is regulated; at the same time, the desorption capacitor A second voltmeter is connected in parallel at both ends of , in order to achieve the desorption capacitance Real-time monitoring of the voltage at both ends. When closed, the desorption resistor is used , Second voltmeter It can realize the simulation adjustment of the effective space volume of the desorption gas collection device during desorption in the traditional coal particle adsorption and desorption experiment.

[0052] The electro-desorption simulation model is constructed based on the adsorption-desorption simulation circuit. The electro-desorption simulation model is:

[0053]

[0054] In the formula, The desorption time of coal particles in the adsorption and desorption experiment Variable gas desorption amount. Desorption capacitance Capacitance value; is standard atmospheric pressure, is the termination ambient temperature in the coal particle adsorption and desorption experiment, is the initial ambient temperature in the coal particle adsorption and desorption experiment; When simulating gas adsorption, the adsorption capacitor Balance voltage with coal particle simulation circuit; Desorption capacitance The initial voltage, ,and ; When simulating gas adsorption, the adsorption capacitor The time it takes to reach voltage balance with the coal particle simulation circuit, When simulating gas desorption, the desorption capacitor The time it takes to reach voltage equilibrium with the coal particle simulation circuit; for The total resistance value of the particle resistors; for The total capacitance value of the particle capacitors.

[0055] The electro-desorption simulation model is simplified as follows:

[0056]

[0057] In the formula, are all intermediate variables; the electrodesorption simulation model can be simplified as:

[0058] ………… (1)

[0059] In the traditional coal particle gas desorption experiment, the diffusion coefficient is considered during the differential pressure desorption process. The non-steady-state diffusion model of coal particle gas desorption that changes with desorption time is:

[0060]

[0061] In the formula, is the corresponding gas desorption amount at the end of the experiment, is the desorption time.

[0062] Define the transcendental equation:

[0063]

[0064] In the formula, is the solution of the transcendental equation, Take values ​​of time for the boundary and initial conditions of the transcendental equation.

[0065] Here, the series is transformed by Taylor's formula Expand it and you can know the series Converges very quickly, the first term of the series ( of (Right now )) can meet the accuracy requirement, so the diffusion coefficient can be The non-steady-state diffusion model of coal particle gas desorption that changes with desorption time is transformed into:

[0066]

[0067] In the formula,

[0068] ,

[0069] make:

[0070]

[0071] In the formula, are all intermediate variables; then the diffusion coefficient The non-steady-state diffusion model of coal particle gas desorption that changes with desorption time can be simplified as:

[0072] …………(2)

[0073] It can be seen that the simplified form of the electrolysis simulation model (Formula (1)) and the simplified form of the coal particle gas desorption non-steady-state diffusion model (Formula (2)) are both exponential function equations, both of which have a constant term, a base term and an exponential coefficient; in Formula (1) and Formula (2), the left side of the equal sign is the adsorption amount of coal particles, so there is an equivalent relationship between the exponential coefficients of Formula (1) and Formula (2):

[0074]

[0075] in,

[0076]

[0077] In the formula, is the radius of the coal particle, for n The total capacitance value of the particle capacitors.

[0078] Then we have:

[0079]

[0080] Diffusion coefficient With resistance ( The total resistance value of the individual particle resistors) shows an inverse proportional functional relationship.

[0081] In the RC electrical simulation model, the resistance value The resistance of coal particles to gas migration during coal particle gas desorption is characterized. The diffusion coefficient of desorption is represented by the desorption resistance, which is actually difficult to measure. The desorption process includes two parts: gas seepage diffusion in the pores and desorption on the surface of the coal matrix. Usually, the desorption process is instantaneous and resistance-free. Therefore, the desorption resistance is mainly the flow process of gas in the pores.

[0082] The migration of methane in different pores and cracks can be simplified as the flow of gas in pipes of different sizes. When the gas flows in a uniform straight pipe, the resistance mainly comes from the friction of the pipe wall on the gas, that is, the resistance along the way. The expression is as follows:

[0083]

[0084] In the formula, is the friction coefficient of the pipeline, is the pipe length, is the pipe diameter, is the flow velocity of the gas in the pipe.

[0085] Along the way resistance With flow speed Is positively correlated. For the migration of methane in coal, the high flow rate when the airflow initially rushes into the pores of the coal particles brings high resistance along the way. As the gas pressure inside and outside the coal particles tends to balance, the gas flow rate decreases significantly, and the friction resistance decreases accordingly. In the RC electrical simulation model, resistance represents the charging resistance, which corresponds to the friction resistance during adsorption; current represents the flow rate of electrons, which corresponds to the migration rate of gas in the pores. Based on this, the resistance value is expressed as a function of the square of the current, which decreases as the current decreases. From the charging process of the total capacitance to the sub-capacitance, it can be seen that the current The change conforms to the exponential function form, that is:

[0086]

[0087] In the formula, is the desorption time; are all constants.

[0088] Resistance value of the resistance along the way It is proportional to the square of the current, that is,

[0089]

[0090] in, are all intermediate variables. ; .

[0091] In addition, the structure of coal particles is complex, and there are a lot of bends and crosses between pores. The local resistance is difficult to quantify directly. The local resistance is simplified to a constant , then the resistance of the fixed pore resistance during the whole desorption process can be expressed as:

[0092]

[0093] During the adsorption and desorption process of coal particles, adsorption will cause the coal particles to expand, and desorption will cause the coal particles to shrink. When the coal particles expand due to adsorption, the pores of the coal particles may increase; when the coal particles shrink due to desorption, the pores of the coal particles may decrease. The expansion and contraction amplitude of coal particles is positively correlated with the adsorption amount and desorption amount. The pore contraction of coal particles will increase the resistance to methane migration in coal particles. Therefore, when considering the desorption resistance, the desorption deformation resistance of coal particles is also included. In other words, in the RC electrical simulation model, the resistance ( The total resistance value of the particle resistance) changes with the desorption time. Therefore, the corresponding relationship between the non-steady-state diffusion coefficient of coal particle gas and the desorption resistance in the adsorption and desorption simulation circuit is:

[0094]

[0095] In the formula, With the desorption time The changing non-steady-state diffusion coefficient of coal-particle gas, With the desorption time Variation of desorption resistance, is the radius of coal particles in the traditional coal particle gas desorption experiment, is the capacitance value of the particle capacitance in the adsorption-desorption simulation circuit, that is, The total capacitance value of the particle capacitors.

[0096] Step S102: determining a piecewise function of the variation of the desorption resistance with the desorption time.

[0097] In the coal particle gas desorption process of the traditional coal particle gas desorption experiment, from the analysis of the microscopic process of gas desorption, in the early stage of desorption, the gas gushing out from the coal particles is mainly free gas in large pores and cracks, and the gushing speed is fast and relatively stable. Only a small part of the adsorbed gas begins to desorb, and the deformation of the coal pore structure is small, so the diffusion coefficient is relatively stable. In the middle stage of desorption, the gas desorbed by the coal particles is mainly the gas adsorbed on the pore surface. The large amount of desorption of adsorbed gas causes the rapid deformation of the coal pore structure, so the diffusion coefficient of coal decreases rapidly at this stage. In the late stage of desorption, most of the gas adsorbed in the coal has been desorbed, and the remaining gas slowly desorbs outside the coal particles. The lower desorption rate brings a smaller degree of desorption deformation, so the diffusion coefficient of coal remains basically stable at this stage. That is to say, in the process of coal particle desorption, the initial stage of desorption is the rapid desorption stage, and the corresponding diffusion coefficient is relatively stable and is expressed as a constant; in the middle stage of desorption, that is, the desorption stage, the diffusion coefficient decreases rapidly and is expressed as an exponential function; in the late stage of desorption, that is, the slow desorption stage, the diffusion coefficient remains basically unchanged and is expressed as a constant. Here, the piecewise function of the desorption resistance changing with the desorption time is defined as:

[0098]

[0099] In the formula, With the desorption time Variation of the desorption resistance, The first desorption time The corresponding desorption resistance, The second desorption time The corresponding desorption resistance, All are constant terms.

[0100] In the RC simulation model, the resistance value represents the resistance of coal particles to gas migration during the actual coal particle gas desorption process. Since the desorption resistance changes with time and cannot be directly measured, in this application, the change of desorption resistance is determined by simulating different resistance values, that is, the desorption resistance With desorption time Specifically, first, based on the slope of the gas pressure versus time curve obtained from the coal particle gas desorption experiment, the first desorption time is determined. (i.e. the desorption time corresponding to the initial stage of desorption in the desorption process) and the second desorption time (i.e. the desorption time corresponding to the final stage of desorption in the desorption process).

[0101] In this application, the curve of gas pressure changing with desorption time is obtained through the traditional coal particle gas desorption adsorption experiment. It can be seen that the change curve is a monotonically increasing convex curve, which conforms to the change law that the desorption of coal gas is fast at first and then slow. Recorded as a The two-dimensional point set composed of data points is recorded as:

[0102]

[0103] During the experiment, the same intervals were used. Sampling is performed, therefore, the change curve Can be recorded as:

[0104]

[0105] The curve of gas pressure changing with desorption time In , the slope of the curve is defined as:

[0106]

[0107] Then we have:

[0108]

[0109] In this application, the gas pressure variation curve with desorption time is determined When the slope change threshold is equal to 0.95, the corresponding desorption time is the first desorption time and the second desorption time. The desorption time corresponding to the time is the first desorption time. The desorption time corresponding to the time is the second desorption time. In a period less than or equal to the first desorption time, , at the desorption time During a period greater than or equal to the second desorption time, .

[0110] After determining the first desorption time , Second desorption time After that, the first desorption time is determined by simulating different resistance values. Corresponding desorption resistance and the second desorption time Corresponding desorption resistance Here, by selecting resistors of different magnitudes for simulation, the time-varying range of the particle resistance is determined, and then at the first desorption time , Second desorption time The segmented amount is reduced at two time nodes to complete further simulation. Then, the time-varying range of the resistance value is determined by comparing the mean square error of multiple curves of voltage change with desorption time obtained by simulating the resistance value with the change curve of gas pressure change with desorption time in the traditional coal particle gas desorption experiment.

[0111] In a specific example, first, a random number is selected As the resistance value of the simulated resistor, the resistance values ​​are The resistance simulation is carried out to obtain two corresponding curves of voltage change versus desorption time, making the resistance values The simulation curve of the resistor is located on both sides of the curve of the change in gas pressure versus desorption time in the traditional coal particle gas desorption experiment. Otherwise, a random number is reselected as the resistance value of the simulation resistor for resistance simulation until the two obtained curves of the change in voltage versus desorption time are located on both sides of the curve of the change in gas pressure versus desorption time in the traditional coal particle gas desorption experiment. The resistance values ​​(random numbers) corresponding to the two curves of the change in voltage versus desorption time are used as the time-varying range of the desorption resistor.

[0112] Then, pick a random number , and construct a random number As the first item, with a random number is the last term, and the common ratio is a random number The geometric sequence is denoted as ,in, ; and respectively in the geometric sequence ( is a positive integer) element is used as the simulated resistor to perform resistance simulation, and the Resistance simulation curve.

[0113] Furthermore, by comparing the pressure change curve with desorption time in the traditional coal particle gas desorption experiment (experimental value) with the multiple voltage change curves with desorption time obtained by simulation with different resistance values, we can find out the difference between the pressure change curve with desorption time and the desorption time curve. Among the resistance simulation curves, the two simulation curves that are closest to the upper and lower sides of the curve of the change of gas pressure with desorption time in the traditional coal particle gas desorption experiment are selected, and the corresponding resistance values ​​are determined as the first desorption time. Corresponding desorption resistance and the second desorption time Corresponding desorption resistance .

[0114] Since the curve of the change of gas pressure with desorption time in the traditional coal particle gas desorption experiment is The resistance simulation curves overlap to different degrees in different time periods. Therefore, the pressure change curve with desorption time in the traditional coal particle gas desorption experiment is matched with the multiple voltage change curves with desorption time obtained by simulating different resistance values, and the variance of the two is calculated to ensure the matching degree of the pressure change curve with desorption time in the traditional coal particle gas desorption experiment and the resistance simulation curve. The second desorption time The simulation curves of each segment matching are combined and fitted according to the exponential function model to determine the first desorption time. and the second desorption time The constant term of the desorption resistance changing with the desorption time .

[0115] Step S103: Based on the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance and according to the piecewise function of the desorption resistance, a piecewise expression of the coal particle gas non-steady-state diffusion coefficient is constructed.

[0116] The corresponding relationship between the non-steady-state diffusion coefficient of coal gas and the desorption resistance in the adsorption-desorption simulation circuit:

[0117]

[0118] And the piecewise function of the desorption resistance changing with the desorption time is:

[0119]

[0120] It can be seen that the segmented expression of the non-steady-state diffusion coefficient of coal particle gas is:

[0121]

[0122] In the formula, With the desorption time The changing non-steady-state diffusion coefficient of coal-particle gas, is the radius of coal particles in the traditional coal particle gas desorption experiment, is the capacitance value of the particle capacitance in the adsorption-desorption simulation circuit, The first desorption time The corresponding desorption resistance, The second desorption time The corresponding desorption resistance, All are constant terms.

[0123] The method for determining the non-steady-state diffusion coefficient of gas desorption in the present application effectively overcomes the problem that traditional conventional simulation uses a fixed diffusion coefficient to calculate the pressure of the desorption process, and cannot accurately describe the desorption process of coal particle gas when the desorption amount changes. By combining RC electrical simulation with traditional coal particle gas desorption, a non-steady-state desorption simulation model is used to use non-steady-state resistance to characterize the non-steady-state diffusion coefficient in the desorption process, which is closer to the actual physical process of desorption, effectively solving the lack of accuracy in measuring the non-steady-state diffusion coefficient of traditional coal particle gas desorption, and accurately obtaining the non-steady-state diffusion coefficient of gas desorption of coal particles under normal pressure conditions.

[0124] like Fig. 9 As shown, the embodiment of the present application also provides a system for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and the coal particle gas desorption experiment, the system comprising:

[0125] The matching unit 901 is configured to simplify the electric desorption simulation model constructed based on the adsorption-desorption simulation circuit and the coal particle gas desorption non-steady-state diffusion model under normal pressure conditions determined by the traditional coal particle gas desorption experiment into exponential forms, so as to determine the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance in the adsorption-desorption simulation circuit;

[0126] a desorption resistance determination unit 902, configured to determine a piecewise function of a desorption resistance varying with a desorption time;

[0127] The diffusion coefficient determination unit 903 is configured to construct a piecewise expression of the non-steady-state diffusion coefficient of the coal particle gas based on the corresponding relationship between the non-steady-state diffusion coefficient of the coal particle gas and the desorption resistance and according to the piecewise function of the desorption resistance.

[0128] The system provided in the embodiment of the present application for collaboratively determining the non-steady-state diffusion coefficient at normal pressure based on the RC model and the coal particle gas desorption experiment can implement the steps and processes of the method for collaboratively determining the non-steady-state diffusion coefficient at normal pressure based on the RC model and the coal particle gas desorption experiment in any of the above-mentioned embodiments, and achieve the same technical effects, which will not be repeated here one by one.

[0129] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0130] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0131] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0132] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0133] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0134] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and coal particle gas desorption experiment, characterized in that: include: Step S101, simplifying the electric desorption simulation model constructed based on the adsorption-desorption simulation circuit and the coal particle gas desorption non-steady-state diffusion model under normal pressure conditions determined by the traditional coal particle gas desorption experiment into exponential forms, so as to determine the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance in the adsorption-desorption simulation circuit; wherein the electric desorption simulation model is: In the formula, is the gas desorption amount in the coal particle adsorption and desorption experiment; is the capacitance value of the desorption capacitor in the adsorption-desorption simulation circuit; is standard atmospheric pressure, is the termination ambient temperature in the coal particle adsorption and desorption experiment, is the initial ambient temperature in the coal particle adsorption and desorption experiment; It is the equilibrium voltage between the adsorption capacitor and the coal particle simulation circuit during the gas adsorption simulation in the adsorption-desorption simulation circuit; is the initial voltage of the desorption capacitor, ,and ; is the time it takes for the adsorption capacitor and the coal particle simulation circuit to reach voltage balance during the gas adsorption simulation. The time length for the desorption capacitor and the coal particle simulation circuit to reach voltage balance during the gas desorption simulation; For the adsorption-desorption simulation circuit The total resistance value of the particle resistors; for The total capacitance of the particle capacitors; Step S102, determining a piecewise function of the desorption resistance varying with the desorption time; Step S103: Based on the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance, and according to the piecewise function of the desorption resistance, a piecewise expression of the coal particle gas non-steady-state diffusion coefficient is constructed; wherein the piecewise expression of the coal particle gas non-steady-state diffusion coefficient is: In the formula, With the desorption time The changing non-steady-state diffusion coefficient of coal particle gas, is the radius of coal particles in the conventional coal particle gas desorption experiment, is the capacitance value of the particle capacitance in the adsorption-desorption simulation circuit, The first desorption time The corresponding desorption resistance, The second desorption time The corresponding desorption resistance, All are constant terms.

2. The method for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and coal particle gas desorption experiment according to claim 1 is characterized in that: In step S101, the corresponding relationship between the non-steady-state diffusion coefficient of coal particle gas and the desorption resistance in the adsorption and desorption simulation circuit is: In the formula, With the desorption time The changing non-steady-state diffusion coefficient of coal particle gas, With the desorption time Variation of the desorption resistance, is the radius of coal particles in the conventional coal particle gas desorption experiment, is the capacitance value of the particle capacitance in the adsorption-desorption simulation circuit.

3. The method for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and coal particle gas desorption experiment according to claim 1 is characterized in that: In step S102, the piecewise function of the desorption resistance changing with the desorption time is: In the formula, With the desorption time Variation of the desorption resistance, The first desorption time The corresponding desorption resistance, The second desorption time The corresponding desorption resistance, All are constant terms.

4. The method for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and coal particle gas desorption experiment according to claim 3 is characterized in that: The first desorption time is determined based on the slope of the gas pressure versus time curve obtained from the coal particle gas desorption experiment. and the second desorption time .

5. The method for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and coal particle gas desorption experiment according to claim 3 is characterized in that: Based on simulations with different resistance values, determine the first desorption time Corresponding desorption resistance , and the second desorption time Corresponding desorption resistance .

6. The method for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and coal particle gas desorption experiment according to claim 3 is characterized in that: The curve of the change of gas pressure with desorption time in the conventional coal particle gas desorption experiment is matched in sections with multiple curves of the change of voltage with desorption time obtained by simulating different resistance values ​​to determine the first desorption time. and the second desorption time The constant term between the desorption resistance and the desorption time .

7. A system for determining the non-steady-state diffusion coefficient under normal pressure based on the RC model and coal particle gas desorption experiment, characterized in that: include: The matching unit is configured to simplify the electric desorption simulation model constructed based on the adsorption-desorption simulation circuit and the coal particle gas desorption non-steady-state diffusion model under normal pressure conditions determined by the traditional coal particle gas desorption experiment into exponential forms, so as to determine the corresponding relationship between the coal particle gas non-steady-state diffusion coefficient and the desorption resistance in the adsorption-desorption simulation circuit; wherein the electric desorption simulation model is: In the formula, in the formula, is the gas desorption amount in the coal particle adsorption and desorption experiment; is the capacitance value of the desorption capacitor in the adsorption-desorption simulation circuit; is standard atmospheric pressure, is the termination ambient temperature in the coal particle adsorption and desorption experiment, is the initial ambient temperature in the coal particle adsorption and desorption experiment; It is the equilibrium voltage between the adsorption capacitor and the coal particle simulation circuit during the gas adsorption simulation in the adsorption-desorption simulation circuit; is the initial voltage of the desorption capacitor, ,and ; is the time it takes for the adsorption capacitor and the coal particle simulation circuit to reach voltage balance during the gas adsorption simulation. The time length for the desorption capacitor and the coal particle simulation circuit to reach voltage balance during the gas desorption simulation; For the adsorption-desorption simulation circuit The total resistance value of the particle resistors; for The total capacitance of the particle capacitors; a desorption resistance determination unit configured to determine a piecewise function of the desorption resistance varying with desorption time; The diffusion coefficient determination unit is configured to construct a piecewise expression of the non-steady-state diffusion coefficient of the coal particle gas based on the corresponding relationship between the non-steady-state diffusion coefficient of the coal particle gas and the desorption resistance according to the piecewise function of the desorption resistance; wherein the piecewise expression of the non-steady-state diffusion coefficient of the coal particle gas is: In the formula, With the desorption time The changing non-steady-state diffusion coefficient of coal particle gas, is the radius of coal particles in the conventional coal particle gas desorption experiment, is the capacitance value of the particle capacitance in the adsorption-desorption simulation circuit, The first desorption time The corresponding desorption resistance, The second desorption time The corresponding desorption resistance, All are constant terms.

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