Efficient volumetric high-pressure adsorption isotherm device and process thereof

Abstract

The invention discloses a device and a process for measuring the maximum gas adsorption / desorption capacity of a powder solid sample (particularly coal / shale) by a volumetric method. The method is characterized in that adsorption / desorption isotherm measurement can be carried out on a group of four samples at the same time, and four independent channels are manufactured through a single gas injection point. As natural adsorbent samples may come from different burial depths, the apparatus can simultaneously perform adsorption / desorption measurements on four samples through a partitioned water bath system at different temperatures corresponding to the depths of the four samples. In addition, the device can measure the gas adsorption capacity at very high pressures up to 40 MPa (replicating reservoir depths up to 4000 m). In addition, the sample appliance can also resist a pressure of 6000 Psi. The device is also capable of treating toxic, reactive and highly flammable gases. Another unique feature of the invention is that the high temperature accuracy is 0.1 DEG C. The device can be applied to gas storage capacity and recoverable reserve estimation of CBM, shale gas and CO2 geological storage projects.

Description

Technical Field

[0001] The present invention relates to an efficient volumetric high pressure adsorption isotherm [Al] device. In particular, the present invention relates to a device capable of measuring the adsorption capacity up to a maximum pressure of 40 MPa (corresponding to a burial depth of 4000 m). More specifically, the present invention relates to a device for measuring the maximum gas adsorption capacity of solid samples (particularly coal / shale) by a volumetric method. Background Art

[0002] Reference may be made to patent US2,692,497, which discloses and claims a system, a device for acquiring data, comprising a vacuum sealed chamber with a gas channel, a gravimetric analysis device in the solid chamber supporting the solid, and a device for maintaining a portion of the chamber supporting the solid at a substantially constant temperature. The inventors claim a new, automated, adsorption isotherm device that can simply, quickly, and accurately measure the adsorption capacity of porous solid samples. The invention also claims the measurement of the volume of gas adsorbed in a short period of time. The patent only discloses a process for adsorption isotherms of finely divided and porous solids, including the adsorption-desorption branches of the isotherms, and does not show any temperature changes. In the invention, the isotherms are measured over several minutes, so equilibrium is not maintained. In addition, the invention does not mention any pressure range over which the device can operate.

[0003] Reference may be made to patent US2,960,870, which discloses and claims a system for measuring surface area by the BET adsorption isotherm method, which has more efficient measurement, larger surface coverage area and low cost compared to the original device. Another object of the invention is to provide a method and device for measuring surface area using a flowing gas mixture flow. Another object of the invention is to provide a device for surface area determination, which has a much lower cost than the BET method and its modifications by the standards bureau, does not require a vacuum device, and is suitable for manufacture and sale as a standard part of a laboratory device. The patent only discloses a method for measuring surface area by using nitrogen as the adsorbent. The invention also claims that for monolayer adsorption, at a pressure of 1 atm and 25°C, 1m 3 N 2 Can cover almost about 2.84m 2 Therefore, the invention is limited to a specific adsorbate gas, namely an inert gas N 2 , and different adsorbates will be different. In addition, the invention is not suitable for high pressure adsorption isotherms.

[0004] Reference may be made to patent US 3,555,912, which discloses and claims a system for an apparatus for measuring the surface area of ​​solid materials, particularly solid materials in particulate form. The invention provides a technique for adsorbing an adsorbate from a mixture of a flowing carrier gas and an adsorbate, and after separating a powdered sample pool from the predetermined mixture, the concentration change in the gas stream is determined by determining the concentration of the adsorbate whose concentration difference the inventor has measured. The patent only discloses a method for determining the concentration change at different pressures, but does not take into account the temperature effect under pressure changes, because the concentration change with increasing temperature can have a significant negative impact, and the isotherm curve will deviate at different temperatures. In addition, in the invention, the authors made an apparatus with a single sample pool; there is no arrangement of multiple samples in a single experiment, and there is no liquid bath to maintain the temperature. The invention does not provide for maintaining different temperatures in a single experiment to heat or cool the reactor.

[0005] Reference may be made to US Pat. No. 3,732,736, which discloses and claims a system for measuring the adsorption of porous or fragmented solid surfaces, which gives The key information of the pore size and the specific surface area of ​​the solid at low temperature is the dynamic volumetric adsorption method. The dynamic volumetric adsorption method can be used to experiment with very small amounts of sample, less than one gram. This is also useful because the equal mass of adsorbate from the constant volume chamber is separated from the sample holding chamber by a valve, which is opened at each stage so that the pressure in the two chambers reaches equilibrium and is closed before the next stage. This patent only discloses a method for measuring the adsorption of solid and powder samples only at low pressure. The BET isotherm only satisfies this type of adsorption isotherm, and Freundlich and Langmuir cannot be satisfied well. Therefore, the invention is not universal enough. Moreover, there is currently no arrangement for measuring high temperature and high pressure reservoir samples.

[0006] Reference may be made to US Pat. No. 3,771,367, which discloses and claims a system, an apparatus and technique for exposing the surface to flowing adsorbates and carrier gases, and a method for constructing a desorption isotherm for testing the powder, and a scanning hysteresis region for the curve and the adsorption curve limiting its reverse range. The patent only discloses the study of the desorption / adsorption process of pure nitrogen and nitrogen-inert gas mixtures. In the invention, the inventors first introduced pure nitrogen or adsorbates, and then introduced a mixture of pure nitrogen and helium. They did not calculate the total void volume of micropores, mesopores or macropores present in the adsorbent. Therefore, it is not appropriate to perform volumetric measurements in this process.

[0007] Reference may be made to patent application US2009 / 0025403 and patent US 5,109,716, which disclose and claim a system for an adsorption heat pump using a specific adsorbent and the use of the specific adsorbent as an adsorbent for an adsorption heat pump. The invention provides an adsorption heat pump, in which, due to the use of an adsorbent having a large difference in the amount of water adsorbed during adsorption / desorption and being regenerated at a low temperature, water vapor can be effectively adsorbed and desorbed using a heat source at a lower temperature than before. The system only discloses the adsorption process of water vapor in the adsorbent. However, it does not describe in detail any adsorption process on a solid sample; the adsorbent and other adsorbates have a large difference in the amount of water vapor adsorbed. In addition, it only measures the adsorption isotherm in a very low pressure range, but the isotherm curve is mainly offset in the high pressure range.

[0008] Reference may be made to patent US 5,239,482, which discloses and claims a system for continuously measuring the adsorption-desorption isotherm of a gas from a solid sample. This patent discloses only the nitrogen adsorption process at low pressure, but the sorption pattern is different for different gases. The sorption behavior changes at high pressure, and it is not possible to mention data at small intervals, which can be achieved by the data acquisition system in the device of my invention. Sorption tests at different temperatures are not possible here because the invention maintains a constant temperature of the liquid nitrogen bath.

[0009] Reference may be made to US Pat. No. 5,342,580, which discloses methods of adsorption and desorption, wherein a system is disclosed and claimed, a device for measuring the amount of gas adsorbed or desorbed from a solid. Here, the properties of non-catalytic solids are predicted by gas adsorption capacity by nitrogen injection at 77°K. The reactivity of the gas at different pressures and the types of products formed by physical and chemical adsorption or desorption of the gas are determined by a volumetric method. The patent discloses methods of adsorption and desorption, but its efficiency is very low above 1 atm atmospheric pressure. The maximum time range of reservoir pressure is higher than atmospheric pressure. Therefore, it is impossible to measure adsorption capacity at high pressure with only 0.1% full-scale efficiency. In addition, the capacity of its sample container apparatus is 1500psi, however, its inventors have made a 6000psi sample container, that is, the container apparatus of the invention can withstand more than four times the pressure.

[0010] Reference may be made to US Pat. No. 5,360,743, which discloses and claims a system for measuring the adsorption and desorption gas analysis of a material. By adopting the apparatus and method disclosed therein, a non-adsorbing gas (e.g., helium) is used to determine the void volume. The patent only discloses the process of adsorption and desorption gas analysis of solid materials, and it involves a single sample cell, whereas the present invention involves four sample cells at the same time, which can measure four different samples under four different conditions.

[0011] Reference may be made to US Pat. No. 5,591,897, which discloses and claims a system for measuring the gas absorption and / or desorption characteristics of a substance having a gas absorbing property. The device comprises a sample container for containing an adsorbent, a gas until a predetermined pressure is reached, and a gas supply source for supplying the gas to a gas storage. The patent discloses only a method for a single component sample cell system, which cannot infer the effect of temperature of the same sample maintained at different temperatures in separate water baths.

[0012] Reference may be made to patent US 6,595,036, which discloses a process for measuring desorbed gas at atmospheric pressure and temperature. Both the reference cell and the sample cell are immersed in a cryogenic fluid temperature bath, the initial dead volume of the reference cell, and the initial gas pressure of the reference cell measured at the time point when the initial dead volume of the reference cell is measured. The initial dead volume of the sample cell measured initially is then corrected based on the change in the dead volume of the sample cell to calculate the amount of gas adsorbed on the solid sample. The patent does not include a temperature control unit and only measures desorbed gas at normal atmospheric temperature and pressure. The system simply collects coal cores from the well site and then periodically measures the volume of gas released within the experimental setup within the atmospheric pressure and temperature range. Therefore, these methods are not accurate for measuring total gas desorption in coal core samples under reservoir conditions.

[0013] The present invention relates to a device and method for measuring the amount of gas adsorbed on a solid material.

[0014] A typical adsorption isotherm measures the volume of a gas adsorbed into a solid at a constant temperature. Experimental data also validate some numerical expressions. Low-pressure adsorption isotherms are analyzed to measure the surface area and pore volume of powder samples. The diffusivity of a gas in a solid can also be measured with the aid of this experiment.

[0015] The amount of gas adsorbed on a solid sample with increasing pressure and constant temperature provides an isotherm. The amount of gas injected into the sample cell is measured by volumetric measurement. The pressure increases and stabilizes at the equilibrium pressure. When adsorption occurs on a sample, the equilibrium pressure is greater than the adsorption pressure. The amount of gas adsorbed and the corresponding pressure in the sample cell are the data points of the adsorption isotherm. However, some gases have a significant effect after the equilibrium pressure is reached or exceeded, which is called excess adsorption.

[0016] The invention relates to adsorption studies aiming at the measurement of adsorbed volume at a specific pressure, with a particular focus on the adsorption of gases on solid materials, mainly coal / shale. This measurement allows the characterization of many solids, based on their gas adsorption capacity, surface area measurement and pore volume. For example, coal has an adsorption capacity due to its dual porosity. By injecting different gases, adsorption isotherms allow the determination of the adsorption capacity of different coal samples. The amount of gas adsorbed is very important for the calculation of pore volume and surface area. Apart from this, it is one of the important parameters in the characterization of coalbed methane reservoirs.

[0017] Purpose of the Invention

[0018] The main object of the present invention is to provide a device for measuring the amount of gas adsorbed on a solid coal / shale sample.

[0019] Another object of the present invention is to provide a method for measuring the amount of gas adsorbed on a solid coal / shale sample.

[0020] It is a further object of the present invention to provide an adsorption isotherm setup with an integrated digital temperature control unit for measuring the adsorbed gas.

[0021] Yet another object of the present invention is to develop an adsorption isotherm setup for measuring the adsorbed gas capacity at very high pressures up to 40 MPa (replicating reservoir depths up to 4000 m).

[0022] Yet another object of the present invention is to introduce a water bath at the bottom of the adsorption isotherm setup so that the reference / reference cell is completely immersed in water.

[0023] Yet another object of the present invention is to add a heater in the water bath to maintain a uniform temperature of the coal / shale sample pool, and to add four independent water chambers in a single water bath to maintain four different temperatures simultaneously.

[0024] Yet another object of the present invention is to conduct adsorption isotherm experiments of four samples simultaneously, wherein four independent channels are made through a single gas injection point. Summary of the invention

[0025] Therefore, the present invention provides a high-efficiency volumetric high-pressure adsorption isotherm device [ Figure 1 ], including in a water bath [ Figure 1 , B] in the adsorption isotherm device main body [ Figure 1 , A];

[0026] The main body of the adsorption isotherm device [ Figure 1 , A] also includes:

[0027] a) Stainless steel reference cell[ Figure 1 , A11-a] and sample pool [ Figure 1 , A11-b], calibrated in the pressure range of 0 to 6000 psi;

[0028] b) Digital temperature display unit [ Figure 1 , A14-a] and thermocouples [ Figure 1 , A14-b];

[0029] c) Seamless pipe Figure 1 , A1];

[0030] d) Two-stage diaphragm pressure gauge (0–40MPa)[ Figure 1 , A2];

[0031] e) Quick Connect Body [ Figure 1 , A3];

[0032] f) Quick-connect rod Figure 1 , A4];

[0033] g) Check valve Figure 1 , A5];

[0034] h)NPT male thread connector[ Figure 1 , A6];

[0035] i) Bulkhead male thread connector [ Figure 1 , A7];

[0036] j) Branch internal thread NPT tee [ Figure 1 , A8];

[0037] k) Two-way (on / off) ball valve (1 / 4 inch) [ Figure 1 , A9];

[0038] l) Strain gauge based pressure sensor[ Figure 1 , A10];

[0039] m) 0.5 μm pore size stainless steel particulate filter [ Figure 1 , A12];

[0040] n) Sample cylinder and spacer mounting bracket [ Figure 1 , A13];

[0041] In yet another embodiment of the present invention, the water bath [ Figure 1 , B] was divided into four parts for each channel so that experiments with four different samples at four different temperatures could be performed simultaneously.

[0042] In yet another embodiment of the invention, the device is used for determination of the adsorption capacity of a solid adsorbent and for measuring the desorption of a gas from a solid desorbent.

[0043] In yet another embodiment of the present invention, there is provided a process for determining the adsorption capacity of a solid adsorbent using an apparatus, comprising the following steps:

[0044] i. Moisture balance of pulverized coal sample (-72 mesh BSS) at 96-97% relative humidity to obtain equilibrium moisture coal sample;

[0045] ii. Provide a sample cell of known volume (150cc) maintained at reservoir temperature and with a continuous supply for gas injection and exhaust;

[0046] iii. placing the moisture balance coal sample obtained in step (i) into the sample cell of step (ii);

[0047] iv. Evacuate the air in the reference cell, sample cell and pipeline by using a vacuum pump;

[0048] v. Maintain the water bath temperature of the reference cell and the sample cell at the desired temperature for isotherm determination;

[0049] vi. Close the valves of the vacuum pump and sample cell, and open the valve of the reference cell;

[0050] vii. Inject an inert gas at a known pressure into the reference cell, then close the reference cell valve and allow the temperature to equilibrate with the water bath;

[0051] viii. Connect the reference cell and the sample cell for temperature balance;

[0052] ix. Open the valves of the sample cell, reference cell and vacuum line;

[0053] x. Evacuate the entire system to ensure that there is no air or any other gas;

[0054] xi. Close the valves of the vacuum pump and sample cell, and open the valve of the reference cell;

[0055] xii. introducing the adsorbate gas into the reference cell at different pressure steps;

[0056] xiii. Close the valve of the reference cell and equilibrate the temperature with a water bath for one hour;

[0057] xiv. Open the valve of the sample cell and allow the adsorbate gas to enter the sample cell;

[0058] xv. Record the temperature equilibrium and pressure drop in the sample cell;

[0059] xvi. Increase the pressure in the reference cell to the next pressure step by adjusting the regulator on the gas cylinder;

[0060] xvii. Repeating the above steps at an increased pressure up to 40 MPa as required;

[0061] xviii. After reducing the pressure of the sample cell in a stepwise manner during the desorption process, an equilibrium pressure is reached in each step.

[0062] In yet another embodiment of the present invention, the inert gas is selected from helium or argon.

[0063] In yet another embodiment of the present invention, the adsorbate gas is injected at different pressure steps for measuring the adsorption capacity in multiple steps during the adsorption measurement at consecutive time points.

[0064] In another embodiment of the present invention, there is provided a process for determining gas desorption from a solid desorbent using the apparatus as claimed in claim 1, comprising the following steps:

[0065] i. Provide a vacuum chamber / reference cell of known volume and maintain it at a predetermined reservoir temperature using an exhaust system;

[0066] ii. a previously degassed sample wherein the desorbent present has a gaseous state at equilibrium with the water bath temperature;

[0067] iii. Establish the equilibrium pressure of the gaseous desorbate as it exits the sample cell as a function of the adsorbate gas concentration;

[0068] iv. Correlate the amount of gaseous desorbed mass and the equilibrium pressure.

[0069] In yet another embodiment of the present invention, the gaseous adsorbate / desorbate is a physisorbate and the process is completely physisorption.

[0070] In yet another embodiment of the present invention, the water bath temperature is maintained throughout substantially the entire desorbate discharge.

[0071] In yet another embodiment of the present invention, the adsorbent / desorbent is selected from coal or shale.

[0072] In yet another embodiment of the present invention, the adsorbent / desorbent gas is selected from methane, carbon dioxide, nitrogen or any adsorbent / desorbent gas.

[0073] In another embodiment of the present invention, the adsorption isotherm device body [ Figure 1 , A] consists of SS304 custom panels with supporting frame.

[0074] In yet another embodiment of the present invention, a vacuum pump is introduced to ensure that the entire system is free of air / any gas before injecting the adsorbate.

[0075] In yet another embodiment of the present invention, an inert gas such as helium / argon is injected before the adsorbate gas is injected to calculate the void volume within the sample cell containing the adsorbent.

[0076] In yet another embodiment of the present invention, four independent channels were fabricated, through which adsorption isotherm experiments of four samples could be performed simultaneously from a single injection point.

[0077] In yet another embodiment of the present invention, the water bath is divided into four sections for each channel so that experiments with four different samples at four different temperatures can be performed simultaneously.

[0078] In yet another embodiment of the present invention, the digital temperature display unit is installed with a thermocouple to maintain a constant temperature with an accuracy of ±0.1°C throughout the experiment.

[0079] In yet another embodiment of the present invention, the desorbent gas is discharged at different pressure steps so that the desorption isotherm is constructed in multiple steps at consecutive time points. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 Schematic diagram of a high pressure adsorption isotherm [AI] apparatus with an integrated digital temperature control unit, wherein [A] is the adsorption isotherm apparatus body, which consists of different parts, namely, the following parts: seamless pipe [A1]; two-stage diaphragm sensing pressure gauge (0–40 MPa) [A2]; quick connect body (1 / 4 inch) [A3]; quick connect rod (1 / 4 inch) [A4]; SS poppet check valve (6000 psi) [A5]; NPT male connector [A6]; bulkhead male connector [A7]; Connector [A7]; branch female NPT tee [A8]; two-way (on-off) ball valve (1 / 4 inch) [A9]; strain gauge based pressure sensor (range 0–40 MPa) [A10]; stainless steel reference cell calibrated at 6000 psi [A11-a] and sample cell [A11-b]; 0.5 μm pore size stainless steel type particulate filter [A12]; mounting bracket for sample cylinder and baffle [A13]; digital temperature display unit [A14-a] and thermocouple [A14-b];

[0081] And [B] is a water bath.

[0082] Figure 2 Indicates AI-CH 4 Construction of methane adsorption / desorption isotherms for the / 01 sample.

[0083] Figure 3 Indicates AI-CO 2 Construction of carbon dioxide adsorption / desorption isotherms for / 02 samples.

[0084] Figure 4 Represents the mixed gas adsorption / desorption isotherm construction of AI-Mix / 03 sample. DETAILED DESCRIPTION

[0085] In order to advantageously use solid materials such as powdered materials, adsorbents, and membranes, it is important to obtain information about the specific surface area and pore size distribution of such solid materials. In order to obtain such information, it is necessary to prepare an adsorption isotherm by measuring the gas adsorption on the solid material while maintaining the solid material at a constant temperature.

[0086] For example, a volumetric gas adsorption measuring device is used to measure gas adsorption on a solid material. The volumetric gas adsorption measuring device comprises: a solid material having a known geometric volume (V) and maintained at a predetermined temperature (T). s ), a sample cell containing a solid sample A and connected to the manifold through a valve, and a constant temperature bath containing a cryogenic coolant such as liquid nitrogen. A gas inlet / outlet pipeline is connected to the manifold through a valve, and a sample retaining portion of the sample cell is immersed in the cryogenic coolant contained in the constant temperature bath to maintain the solid sample A at a cryogenic temperature.

[0087] When using a volumetric gas adsorption measurement device, first evacuate the manifold and sample cell with the valve open. Then, with the valve closed, gas is introduced into the manifold and the valve is closed. At this point in time, the gas pressure (Pi) and the amount of gas adsorbed on the solid sample A are measured.

[0088] The present invention discloses an adsorption isotherm experimental setup for measuring the amount of adsorbed gas on a solid sample. A process for estimating the adsorbed gas of a coal / shale sample present in the sample is also provided.

[0089] The invention also provides an adsorption isotherm setup with an integrated digital temperature control unit for measuring the adsorbed gas.

[0090] The experimental setup also included a water bath at the bottom of the adsorption isotherm setup to allow for complete immersion of the reference / reference cell and to maintain a uniform temperature of the sample cell. The water bath consisted of 4 different chambers for maintaining 4 different temperatures. The dimensions of each chamber were 18″×18′×24″. The inner wall of the bath was made of heavy gauge stainless steel plate while the outer wall was made of stainless steel plate with thick glass insulation and ceramic blanket between the two walls to minimize heat loss.

[0091] A mechanical stirrer is connected to the water bath connected to a motor, which stirs the liquid in the water bath to maintain uniform temperature throughout the chamber. A heater is provided for heating the water. A sensor is located in the water of each water bath for controlling the temperature. Each sensor is equipped with a separate digital display for displaying the temperature of the 4 separate chambers.

[0092] An additional data acquisition system is also provided to collect frequent data in cases where volume changes are small.

[0093] The present invention provides a one-end completely leak-proof sample / reference cell that is calibrated at a massive pressure of 6000 psi.

[0094] A roller mill can also be provided for comminuting the sample as feed to the sample chamber according to different standard rules.

[0095] The moisture balance coal sample is placed in the sample cell. The vacuum pump is used to evacuate the air from the sample cell and the reference cell. Since the reference cell and the sample cell are kept in a water bath, the water bath should be at the required temperature for isotherm determination. First, the valves of the vacuum pump and the sample cell are closed and the valve of the reference cell is opened. Helium is introduced into the reference cell at a known pressure as it is considered to be a non-adsorbing gas and it has the smallest molecular diameter. Now, the valve of the reference cell is closed and allowed to equilibrate with the water bath temperature for one hour. To determine the void volume, the reference cell is connected to the sample cell to allow helium to enter the sample cell and allow the sample cell to reach pressure and temperature equilibrium. The pressure drop is recorded to determine the dead volume. After determining the dead volume, the valves of the reference cell, sample cell and vacuum line are opened. Now, the entire system is evacuated. Then the valves of the vacuum pump and the sample cell are closed and the valve of the reference cell is opened. The adsorbate gas is introduced into the sample cell at a known pressure. The valve of the reference cell is closed and allowed to equilibrate with the water bath temperature for one hour. Now, the valve to the sample cell is opened and the adsorbate gas is slowly introduced into the sample cell. The sample is left for at least one hour to obtain pressure and temperature equilibrium in the sample cell. The pressure drop is measured and the volume adsorbed is calculated. A graph of the partial pressure or concentration versus the volume of gas adsorbed by the solid is plotted, which represents the adsorption isotherm.

[0096] The device of the present invention provides an accurate measurement of the adsorption capacity of any gaseous sorbent on a solid sorbent. More precisely, it measures the maximum adsorption capacity on a solid coal / shale sample. In addition, the present invention is unique because the four water chambers are completely isolated from each other and each water chamber is connected to a single independent channel. Thus, the device is capable of conducting experiments on four different samples under four different conditions. The instrument is capable of measuring negligible adsorption / desorption at high pressure using a high-precision pressure sensor. The adsorption includes the following steps: pouring a known volume of solid sample into the sample vessel and simultaneously evacuating the existing air or gas from the sample vessel and the pipeline; injecting a non-adsorbate gas, especially helium, to measure the void volume; re-evacuating the system; injecting the adsorbate gas at different pressure steps at a predetermined reservoir temperature to measure the adsorbate gas volume. Similarly, the desorption step includes measuring the volume of gas desorbed at a constant temperature by exhausting the gas from the sample vessel at different pressure steps.

[0097] The invention is special in that it can withstand a maximum pressure of 40MPa, corresponding to a burial depth of 4000m. In addition, the sample apparatus is also able to withstand a pressure of 6000Psi. The device is also capable of handling toxic, reactive and highly flammable gases. Another unique feature of the invention is the high temperature accuracy of 0.1°C.

[0098] After reaching the equilibrium pressure, the gas is gradually injected or exhausted from the sample device containing a known volume of solid adsorbent. The present invention also makes it possible to avoid contamination in the adsorbate, because the whole system is connected to a vacuum pump, which can evacuate the previously accumulated gas in the system.

[0099] The present invention also measures a desorption isotherm as an alternative to the canister desorption test and establishes the equilibrium pressure of the desorbate as a function of time as it exits the sample vessel.

[0100] The present invention relates to a method and experimental setup for adsorption / desorption isotherm measurements of coal / shale samples by volumetric method, which is capable of constructing an adsorption, the present invention relates to a unique device in which four independent channels are made through which adsorption isotherm experiments of four samples can be carried out simultaneously from a single gas injection point. In a way, this is a unique experimental setup that can measure adsorption isotherms of four different samples at four different temperatures at a time. A water bath attached to the device is used to maintain the isotherm with a temperature accuracy of 0.1°C. The present invention is also capable of performing isotherm measurements of any gas, regardless of the gas composition, with a maximum pressure of up to 40MPa. Depending on the requirement of the pressure drop step during the desorption process, the gas in the system can be exhausted through a single exhaust point for four independent channels individually or simultaneously. Similarly, the vacuum process can be carried out separately for each independent channel without hampering the pressure conditions of other channels.

[0101] Example

[0102] The following examples are given by way of illustration and therefore should not be construed as limiting the scope of the present invention.

[0103] The maximum amount of gas that can be adsorbed onto the adsorbent at constant temperature as a function of pressure at equilibrium is called the adsorption isotherm. It represents the sorptive capacity or maximum amount of gas that can be stored in a particular coal / shale. The adsorption capacity varies between surface conditions and its reservoir conditions. Moisture content is an important parameter affecting the adsorption capacity. The equilibrium moisture is considered to be equivalent to the bed moisture. Therefore, in order to measure the actual adsorption capacity of coal / shale under reservoir conditions using the present invention, a crushed coal sample (-72 mesh BSS) was moisture balanced at 96-97% relative humidity before the experiment (values ​​given in the table). The adsorption isotherm determination experiment of the moisture balanced sample mainly includes two stages:

[0104] 1. Measurement of void space (void volume) in a sample.

[0105] 2. Determination of adsorption capacity.

[0106] In this experiment, adsorbate (pure methane or any adsorbate gas) is supplied to the adsorbent (coal sample) to adsorb gas molecules at reservoir temperature and pressure, and the adsorbed gas volume is calculated by the pressure drop in the pressure sensor.

[0107] In the present invention, the adsorption capacity has been measured with different adsorbents (coal / shale) and different adsorbate gases to achieve different purposes. Example 1 shows the adsorption of pure methane in coal, which determines the methane adsorption capacity of a specific coal / shale reservoir. Example 2 shows the adsorption of CO 2 Adsorption capacity, which helps predict CO in some coals 2 Storage capacity and CH 4 Recovery potential. Because coal bed methane (CBM) is not composed of pure methane, it contains a small amount of CO 2 , Example 3 consists of the mixed gas adsorption capacity of a specific coal to predict the actual adsorption capacity of a CBM reservoir. The adsorption capacity of the sample is expressed in Langmuir volume (VL). 4 , pure CO 2 The experimental results of mixed gases are listed in the following table.

[0108] Measuring the desorption isotherm is an indirect method for determining the gas storage capacity of a solid adsorbent. It represents the reverse process of adsorption and helps determine the critical desorption pressure and the maximum desorption capacity from a specific coal / shale sample. Desorption data is used to estimate the amount of gas that can be recovered from a given coal / shale formation and is used to optimize CBM / shale gas production. The hysteresis created between the adsorption and desorption isotherm curves describes the sorptive characteristics of the adsorbent. Desorption isotherm measurements are performed by venting the adsorbate gas from the sample cell after adsorption is complete and building up the equilibrium pressure in a stepwise manner to construct a desorption isotherm.

[0109] Example 1: Construction of high pressure methane adsorption / desorption isotherms

[0110]

[0111]

[0112] Example 2: Construction of high pressure carbon dioxide adsorption / desorption isotherms

[0113]

[0114] Example 3: Construction of mixed gas adsorption / desorption isotherms

[0115]

[0116] Advantages of the present invention

[0117] The main advantages of this device are:

[0118] 1. Adsorption isotherms can be carried out up to an adsorbate pressure of 40 MPa, corresponding to a burial depth of 4000 m.

[0119] 2. Claims a unique device where four independent channels are fabricated through which adsorption isotherm experiments of four samples can be carried out simultaneously from a single gas injection point.

[0120] 3. Four samples can be analyzed simultaneously under different PT conditions according to the coal seam depth where the samples were collected.

[0121] 4. This research has the potential to better understand CBM, enhanced coal bed methane (ECBM-CO 2 ) recovery and CO in suitable candidate geologies 2 Archive.

[0122] 5. Maintaining isothermal conditions by water bath is cheaper than nitrogen and air bath.

Claims

1. An efficient volumetric high-pressure adsorption isotherm device [ FIG. 1 ], comprising an adsorption isotherm device body [ FIG. 1 , A] in a water bath [ FIG. 1 , B]; The adsorption isotherm device body [Figure 1, A] also includes: a) a stainless steel reference cell [Fig. 1, A11-a] and a sample cell [Fig. 1, A11-b], calibrated over a pressure range of 0 to 6000 psi; b) digital temperature display unit [Figure 1, A14-a] and thermocouple [Figure 1, A14-b]; c) Seamless pipe [Figure 1, A1]; d) Two-stage diaphragm sensing pressure gauge (0–40 MPa) [Figure 1, A2]; e) Quick connection body [Figure 1, A3]; f) Quick-connect rod [Figure 1, A4]; g) Check valve [Figure 1, A5]; h) NPT male thread connector [Figure 1, A6]; i) Bulkhead male threaded connector [Figure 1, A7]; j) Branch internal thread NPT tee [Figure 1, A8]; k) Two-way (on-off) ball valve (1 / 4 inch) [Figure 1, A9]; l) Strain gauge based pressure sensor [Figure 1, A10]; m) Stainless steel type particulate filter with pore size of 0.5 μm [Figure 1, A12]; n) Mounting bracket for sample cylinder and partition [Figure 1, A13].

2. An apparatus as claimed in claim 1, wherein the water bath [Fig. 1, B] is divided into four parts for each channel so that experiments with four different samples can be carried out simultaneously at four different temperatures.

3. The device as claimed in claim 1, wherein the device is used for determining the adsorption capacity of a solid adsorbent and for measuring the desorption of a gas from a solid desorbent.

4. A process for determining the adsorption / desorption capacity of a solid adsorbent using the apparatus as claimed in claim 1, comprising the following steps: i. Moisture balance of pulverized coal sample (-72 mesh BSS) at 96-97% relative humidity to obtain equilibrium moisture coal sample; ii. Provide a sample cell of known volume (150cc) maintained at reservoir temperature and with a continuous supply for gas injection and exhaust; iii. placing the moisture balance coal sample obtained in step (i) into the sample cell of step (ii); iv. Evacuate the air in the reference cell, sample cell and pipeline by using a vacuum pump; v. Maintain the water bath temperature of the reference cell and the sample cell at the desired temperature for isotherm determination; vi. Close the valves of the vacuum pump and sample cell, and open the valve of the reference cell; vii. Inject an inert gas at a known pressure into the reference cell, then close the reference cell valve and allow the temperature to equilibrate with the water bath; viii. Connect the reference cell and the sample cell for pressure balance; ix. Open the valves of the sample cell, reference cell and vacuum line; x. Evacuate the entire system to ensure that there is no air or any other gas; xi. Close the valves of the vacuum pump and sample cell, and open the valve of the reference cell; xii. introducing the adsorbate gas into the reference cell at different pressure steps; xiii. Close the valve of the reference cell and equilibrate the temperature with a water bath for one hour; xiv. Open the valve of the sample cell and allow the adsorbent gas to enter the sample cell; xv. Record the temperature equilibrium and pressure drop in the sample cell; xvi. Increase the pressure in the reference cell to the next pressure step by adjusting the regulator on the gas cylinder; xvii. Repeating the above steps at an increased pressure up to 40 MPa as required; xviii. After reducing the pressure of the sample cell in a stepwise manner during the desorption process, an equilibrium pressure is reached in each step.

5. The process of claim 1, wherein the inert gas is selected from helium or argon.

6. A process for determining gas desorption from a solid desorbent using the apparatus of claim 1, comprising the steps of: i. Provide a vacuum chamber / reference cell of known volume and maintain it at a predetermined reservoir temperature using an exhaust system; ii. a previously degassed sample wherein the desorbent present has a gaseous state at equilibrium with the water bath temperature; iii. Establish the equilibrium pressure of the gaseous desorbate as it exits the sample cell as a function of the adsorbate gas concentration; iv. Correlate the amount of gaseous desorbed mass and the equilibrium pressure.

7. A process as claimed in claims 4 and 6, wherein the gaseous adsorbate / desorbate is a physisorbate and the process is entirely physisorption.

8. The process of claim 1 wherein the water bath temperature is maintained during substantially the entire adsorption / desorption process.

9. The process as claimed in claims 4 and 6, wherein the adsorbent / desorbent is selected from coal or shale.

10. The process as claimed in claims 4 and 6, wherein the adsorbate / desorbate gas is selected from methane, carbon dioxide, nitrogen or any adsorbate / desorbate gas.

Images