Liquid co2-co2 hydrate phase transition kinetics measurement experimental device, method and calculation method

Abstract

The application discloses a liquid CO2-CO2 hydrate phase change kinetics determination experimental device, an experimental method and a calculation method. The experimental device comprises a liquid injection constant pressure part, a reactor, a temperature control part, a CO2 gas source and a data acquisition and recording part. The liquid injection constant pressure part is communicated with the reactor, is used for injecting a hydrate reaction solution into the reactor in a liquid injection stage, and maintains the reactor and the liquid injection constant pressure part at the same constant pressure in a reaction stage. The CO2 gas source is communicated with the reactor, and is used for introducing CO2 into the reactor. The temperature control part is used for controlling the temperature of the reactor. The data acquisition and recording part is used for acquiring and recording parameters of a CO2 hydrate generation process in the reactor. The application can realize evaluation and research on a kinetic process of CO2 hydrate generated by liquid CO2, and provides theoretical support for implementation of a hydrate method CO2 capture and storage technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of gas hydrate, CO2 geological storage, low-carbon clean environmental protection technology, in particular to a liquid CO2-CO2 hydrate phase change kinetics determination experimental device, experimental method and calculation method. BACKGROUND

[0002] With the progress of industrialization and rapid population growth, CO2 emissions are increasing year by year. Global warming, climate change, and ecological destruction caused by the emission of greenhouse gases such as CO2 have attracted widespread attention. In order to achieve the goal of global carbon peak and carbon neutralization, it is necessary to develop potential CO2 treatment technologies. Carbon capture, utilization and storage (CCUS) technology is considered as a large-scale greenhouse gas emission reduction technology, and is considered as an indispensable key technology path to achieve global carbon neutralization.

[0003] Hydrate method CO2 capture and storage technology has obvious advantages due to its large gas storage capacity, environmental friendliness and stable and safe long-term storage capacity. CO2 hydrate refers to a cage-like structure composed of water molecules through hydrogen bonds, and CO2 fills the cage through van der Waals force. Under suitable temperature and pressure conditions, one volume of CO2 hydrate can store about 160-180 volumes (standard conditions) of CO2 gas, so CO2 hydrate has a large gas storage capacity. In addition, since CO2 hydrate is composed of water and CO2 molecules, the hydrate method CO2 capture and storage technology has obvious economic advantages and environmental friendliness. CO2 hydrate can exist stably for a long time under relatively mild temperature and pressure conditions (low temperature and high pressure), and is a CO2 storage medium with great potential. For example, CO2 is stored in the form of hydrate in seabed sediments, and the high pressure and low temperature natural environment in the seabed environment makes CO2 hydrate exist stably for a long time.

[0004] Currently, the key problem in the actual generation of CO2 hydrate is that CO2 has a relatively mild liquefaction condition compared with methane and nitrogen, and liquid CO2 can also be converted into CO2 hydrate. Therefore, under the temperature and pressure conditions of many practical application backgrounds, CO2 exists in the form of liquid, for example, in the hydrate method CO2 seabed storage technology at a water depth of more than 1000 meters, the pressure of CO2 hydrate generation is as high as 10 MPa or more, and the ambient temperature is about 3-10℃, under which CO2 can exist in the form of liquid. In addition, under the application background of CO2 capture at a high working pressure, CO2 can also exist in the form of liquid. However, the existing CO2 hydrate generation kinetics evaluation and quantitative research on CO2 capture and storage by the hydrate method are mostly suitable for the process of gaseous CO2 converting into CO2 hydrate. The inability to conveniently and quickly evaluate the kinetics (generation rate, etc.) of the process of liquid CO2 generating CO2 hydrate and quantitatively calculate the CO2 consumption is the biggest factor restricting the research and application of the phase change process.

[0005] It should be noted that the information disclosed in the above background section is only for understanding the background of the present application, and therefore can include information that does not constitute the prior art known to those of ordinary skill in the art. SUMMARY

[0006] In order to make up for the shortcomings of the above prior art, the present application provides a liquid CO2-CO2 hydrate phase change kinetics determination experimental device, experimental method and calculation method.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0008] In a first aspect, a liquid CO2-CO2 hydrate phase change kinetics determination experimental device is provided, comprising a liquid injection constant pressure part, a reactor, a temperature control part, a CO2 gas source and a data acquisition and recording part, wherein: the liquid injection constant pressure part is in communication with the reactor, and is used to inject a hydrate reaction solution into the reactor during the liquid injection stage, and continuously inject the hydrate reaction solution into the reactor at a predetermined constant pressure during the reaction stage; the CO2 gas source is in communication with the reactor, and is used to introduce CO2 into the reactor; the temperature control part is used to control the temperature of the reactor; and the data acquisition and recording part is used to acquire and record the parameters of the CO2 hydrate generation process in the reactor.

[0009] In a second aspect, an experimental method for determining the phase transition kinetics of liquid CO2-CO2 hydrate is provided, which adopts the experimental apparatus of the first aspect mentioned above and includes the following steps: (1) In the liquid injection stage, at a predetermined liquid injection temperature, a predetermined volume of hydrate reaction solution is injected into the reactor through the liquid injection constant pressure section; (2) CO2 is introduced into the reactor through a CO2 gas source until the remaining volume of the reactor is filled with liquid CO2; (3) In the reaction stage, the reactor is cooled from the predetermined liquid injection temperature to the predetermined reaction temperature through the temperature control section, and the hydrate reaction solution is continuously injected into the reactor at a predetermined constant pressure through the liquid injection constant pressure section; (4) When the cumulative water injection volume of the liquid injection constant pressure section no longer changes, it indicates that no more hydrate is generated, and the reaction ends.

[0010] Thirdly, a method for determining and calculating the phase transition kinetics of liquid CO2-CO2 hydrate is provided, including the following steps:

[0011] S1. Record the pressure, temperature, and cumulative water injection volume during the experiment at predetermined time intervals, and take the moment when CO2 hydrate begins to form as the initial time for calculation;

[0012] S2. Based on the initial temperature and pressure, calculate the initial density of liquid CO2 and the density ρ of the aqueous solution, respectively. w0 The solubility of CO2 in aqueous solution and the solubility of water in liquid CO2 are calculated. Based on the pressure and temperature at each subsequent moment from the initial moment, the density of liquid CO2 and the density of the aqueous solution ρ at the corresponding moments are also calculated. w The solubility of CO2 in aqueous solution and the solubility of water in liquid CO2;

[0013] S3. For the initial moment, based on the conservation of reactor volume and the conservation of the amount of water, and using the cumulative water injection volume, the density of the aqueous solution, and the solubility of water in liquid CO2 at the initial moment, calculate the volume V of liquid CO2 in the reactor at the initial moment. CO20 Volume V of the aqueous solution aq0 The amount of water in an aqueous solution The amount of water dissolved in liquid CO2 Since no hydrate has formed initially, the volume of CO2 hydrate, V, is... h0 The amount of water in the hydrate phase is 0. The value is 0, where the formulas for the conservation of reactor volume and the conservation of the amount of water are respectively:

[0014]

[0015]

[0016]

[0017] wherein, p0 is the density of water corresponding to the initial time of hydrate formation, V0 is the volume of the reactor, n0 is the amount of substance of water injected into the reactor at the initial time of hydrate formation, Q0 is the cumulative water injection amount injected into the reactor at the initial time of hydrate formation; w0 w0 wherein, n0 is the amount of substance of water injected into the reactor at the initial time of hydrate formation, Q0 is the cumulative water injection amount injected into the reactor at the initial time of hydrate formation;

[0018] S4, calculating the total amount of substance of CO2 in the reactor at the initial time according to the volume of liquid CO2, the volume of aqueous solution, the density of liquid CO2, the density of aqueous solution, and the solubility of CO2 in aqueous solution at the initial time calculated according to steps S2 and S3;

[0019] S5, for each time subsequent to the initial time, calculating the amount of substance of CO2 in the hydrate in the reactor at the corresponding time according to the volume conservation of the reactor, the amount of substance conservation of water, and the amount of substance conservation of CO2 in the process of CO2 hydrate reaction, using the total amount of substance of CO2 in the reactor at the initial time, and using the cumulative water injection amount, the density of liquid CO2, the density of aqueous solution, the solubility of CO2 in aqueous solution, and the solubility of water in liquid CO2 at the corresponding time of each time subsequent to the initial time; and calculating the amount of substance of CO2 dissolved in the aqueous solution according to the amount of substance conservation of CO2 in the reaction system and the amount of substance of CO2 remaining in liquid CO2 wherein, the formulae of the volume conservation of the reactor, the amount of substance conservation of water, and the amount of substance conservation of CO2 are respectively:

[0020]

[0021]

[0022]

[0023]

[0024] wherein, n0 is the amount of substance of water injected into the reactor at the initial time of hydrate formation, Q0 is the cumulative water injection amount injected into the reactor at the initial time of hydrate formation; w w wherein, n0 is the amount of substance of water injected into the reactor at the initial time of hydrate formation, Q0 is the cumulative water injection amount injected into the reactor at the initial time of hydrate formation;

[0025] S6, outputting the amount of substance of CO2 in each phase at the initial time and at each time subsequent to the initial time, respectively.​​ and

[0026] The present application has the following advantages: the liquid CO2-CO2 hydrate phase transition kinetics determination experimental device, experimental method and calculation method provided by the present application solve the quantitative analysis problem of liquid CO2 generating CO2 hydrate, can realize the evaluation and research of the kinetic process of liquid CO2 generating CO2 hydrate, and provide theoretical support for the implementation of the hydrate method CO2 capture and storage technology. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is the structure schematic diagram of the liquid CO2-CO2 hydrate phase transition kinetics determination experimental device in embodiment 1 of the present application;

[0028] Figure 2 is the flow chart of the liquid CO2-CO2 hydrate phase transition kinetics determination calculation method in embodiment 3 of the present application;

[0029] Figure 3 is the change curve of the amount of substance of CO2 in each phase with time calculated by the present application. DETAILED DESCRIPTION

[0030] The embodiments of the present application will be described in detail below. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope of the present application and its applications, and the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0031] The inventors found in the research that in the phase transition process of liquid CO2 generating CO2 hydrate, due to the existence of liquid CO2, the pressure parameter (such as pressure reduction) of the reaction system in the CO2 hydrate generation process cannot reflect the amount of CO2 consumption, therefore, the calculation of CO2 consumption and distribution in each phase when liquid CO2 generates CO2 hydrate is a difficult problem, and for this, the present application provides a liquid CO2-CO2 hydrate phase transition kinetics determination experimental device, experimental method and calculation method, so as to determine the consumption of CO2 in the reaction system and the distribution in each phase. Through the experimental device, experimental method and calculation method provided by the present application, the evaluation and research of the kinetic process of liquid CO2 generating CO2 hydrate can be realized, and theoretical support is provided for the implementation of the hydrate method CO2 capture and storage technology.

[0032] The embodiment of the present application provides a liquid CO2-CO2 hydrate phase transition kinetics determination experimental device, which comprises a liquid injection constant pressure part, a reactor (i.e. a reactor for hydrate reaction), a temperature control part, a CO2 gas source and a data acquisition and recording part, wherein: the liquid injection constant pressure part is communicated with the reactor, is used for injecting a hydrate reaction solution into the reactor in a liquid injection stage, and continuously injects the hydrate reaction solution into the reactor at a predetermined constant pressure in a reaction stage; the CO2 gas source is communicated with the reactor, and is used for introducing CO2 into the reactor; the temperature control part is used for controlling the temperature of the reactor; and the data acquisition and recording part is used for acquiring and recording parameters of a CO2 hydrate generation process in the reactor.

[0033] In a preferred embodiment, the liquid injection constant pressure part comprises a plunger pump and a piston container, and the temperature control part comprises a first circulating water bath box, a second circulating water bath box, a first water bath tank and a second water bath tank; wherein: the piston container is used for containing the hydrate reaction solution, is placed in the first water bath tank, is communicated with the reactor, and the first water bath tank is connected with the first circulating water bath box; the plunger pump is communicated with the piston container, is used for injecting the hydrate reaction solution in the piston container into the reactor in the liquid injection stage, and is used for continuously injecting the hydrate reaction solution into the reactor at a predetermined constant pressure in the reaction stage; the reactor is placed in the second water bath tank, and the second water bath tank is connected with the second circulating water bath box; and the temperature of the second water bath tank is always equal to the temperature of the first water bath tank.

[0034] In another preferred embodiment, the liquid injection constant pressure part comprises a plunger pump, and the temperature control part comprises a second circulating water bath box and a second water bath tank; wherein:

[0035] The plunger pump is used for containing the hydrate reaction solution, is communicated with the reactor, is used for injecting the hydrate reaction solution into the reactor in the liquid injection stage, and is used for continuously injecting the hydrate reaction solution into the reactor at a predetermined constant pressure in the reaction stage; and the reactor is placed in the second water bath tank, and the second water bath tank is connected with the second circulating water bath box.

[0036] In a preferred embodiment, the experimental device further comprises a magnetic stirrer, the second water bath tank is located on the magnetic stirrer, and the magnetic stirrer is used for stirring the solution in the reactor to make CO2 fully dissolved and accelerate the generation of CO2 hydrate.

[0037] In a preferred embodiment, the parameters of the CO2 hydrate formation process include the pressure in the reactor, the temperature in the reactor and the cumulative water injection volume of the plunger pump, the data acquisition and recording unit includes a data acquisition device, a temperature sensor and a pressure sensor; the temperature sensor and the pressure sensor are both installed on the reactor to detect the temperature and the pressure in the reactor in real time, respectively; the data acquisition device is connected with the temperature sensor, the pressure sensor and the plunger pump, respectively, to acquire the pressure, the temperature and the cumulative water injection volume, respectively.

[0038] In a preferred embodiment, the parameters of the CO2 hydrate formation process further include the reaction condition of CO2 hydrate in the reactor, the data acquisition and recording unit further includes a CCD camera for capturing the reaction condition in the reactor, and the data acquisition device is connected with the CCD camera to acquire the data detected thereby.

[0039] In a preferred embodiment, the temperature control unit is used to control the reactor at a predetermined water injection temperature (e.g. 15℃) in the water injection stage, and is used to cool the reactor from the predetermined water injection temperature to a predetermined reaction temperature (e.g. 2℃) in the reaction stage.

[0040] In a preferred embodiment, the predetermined constant pressure (e.g. 5.5MPa) is lower than the CO2 hydrate phase equilibrium pressure and higher than the CO2 liquefaction pressure at the predetermined water injection temperature; and the predetermined pressure is higher than the CO2 hydrate phase equilibrium pressure at the predetermined reaction temperature.

[0041] The application will be further described in the following specific examples.

[0042] Example 1

[0043] As Figure 1As shown, the liquid CO2-CO2 hydrate phase transition dynamics measurement experimental device includes a liquid injection constant pressure part, a reactor 6, a magnetic stirrer 8, a temperature control part, a CO2 gas source, and a data acquisition and recording part. The liquid injection constant pressure part includes a plunger pump 1 and a piston container 4, and the temperature control part includes a first circulating water bath box 2, a second circulating water bath box 3, a first water bath tank 5, and a second water bath tank 7. The piston container 4 is used to contain the hydrate reaction solution (in this case, the hydrate reaction solution is a 0.3wt% methionine solution), is placed in the first water bath tank 5, and is connected with the reactor 6, the first water bath tank 5 is connected with the first circulating water bath box 2; the plunger pump 1 is connected with the piston container 4, in the liquid injection stage, the hydrate reaction solution in the piston container 4 is injected into the reactor 6, and in the reaction stage, the hydrate reaction solution is continuously injected into the reactor 6 at a constant pressure (in this case, 5.5MPa); the reactor 6 is placed in the second water bath tank 7, the second water bath tank 7 is connected with the second circulating water bath box 2, the second water bath tank 7 is located on the magnetic stirrer 8, the magnetic stirrer 8 is used to stir the solution in the reactor 6 to make CO2 fully dissolved, and the temperature of the second water bath tank 7 is always equal to the temperature of the first water bath tank 5. The CO2 gas source is provided by a CO2 gas cylinder 10, which is connected with the reactor 6 and is used to introduce CO2 into the reactor 6, and the gaseous CO2 becomes liquid CO2 in the reactor 6 to carry out the hydrate reaction; the temperature control part is used to keep the temperature of the liquid injection constant pressure part and the reactor always the same, that is, the temperature of the second water bath tank 7 is always equal to the temperature of the first water bath tank 5, in this case, in the liquid injection stage, the temperature control part is used to keep the liquid injection constant pressure part and the reactor at 15℃, and in the reaction stage, the temperature control part is used to keep the liquid injection constant pressure part and the reactor at 2℃. The data acquisition and recording part is used to acquire and record the parameters of the CO2 hydrate generation process in the reactor, wherein the parameters include the pressure in the reactor, the temperature in the reactor, the cumulative water injection amount of the plunger pump (that is, the amount of hydrate reaction solution added, in volume), and the CO2 hydrate reaction condition in the reactor (such as hydrate morphology, hydrate growth state, hydrate nucleation and crystallization process, etc.), thereby the data acquisition and recording part includes a data acquisition device 11, a temperature sensor 12, a pressure sensor 13, and a CCD camera 9, the temperature sensor 12 and the pressure sensor 13 are both mounted on the reactor 6 to respectively detect the temperature and pressure in real time during the CO2 hydrate generation process; the second water bath tank 7 is transparent, the CCD camera 9 is located outside the second water bath tank 7 and is used to shoot the reaction condition in the reactor 6, and the data acquisition device is connected with the temperature sensor 12, the plunger pump 1, the pressure sensor 13, and the CCD camera 9 respectively to acquire the data detected by them.

[0044] Example 2

[0045] A liquid CO2-CO2 hydrate phase transition dynamics measurement experimental method, which adopts the experimental device described above, includes the following steps:

[0046] (1) In the injection stage, a predetermined volume of hydrate reaction solution is injected into the reactor through the injection constant pressure part at a predetermined injection temperature;

[0047] (2) CO2 is introduced into the reactor through the CO2 gas source until the remaining volume of the reactor is filled with liquid CO2;

[0048] (3) In the reaction stage, the reactor is cooled from the predetermined injection temperature to a predetermined reaction temperature through the temperature control part, and the injection constant pressure part continuously injects hydrate reaction solution into the reactor at a predetermined constant pressure; wherein the injection constant pressure part is constant at a predetermined constant pressure, but the pressure of the reactor fluctuates above and below this constant pressure as CO2 hydrate is generated.

[0049] (4) When the cumulative water injection amount of the injection constant pressure part no longer changes, it indicates that no more hydrate is generated, and the reaction is ended.

[0050] Based on the above Figure 1 The experimental device shown, in a preferred embodiment, the liquid CO2-CO2 hydrate phase transition kinetics determination experimental method includes the following steps:

[0051] 1. Clean and dry the reactor 6 and seal it, put it into the second water bath 7, clean and dry the piston container 4, then fill it with hydrate reaction solution (in this case, 0.3wt% methionine solution), and then put the piston container 4 into the first water bath 5;

[0052] 2. Turn on the data acquisition device 11 and the CCD camera 9, record the temperature, pressure, cumulative water injection amount and reaction in the reactor (such as hydrate morphology, hydrate growth state, hydrate nucleation and crystallization process) during the hydrate formation process. The data acquisition device 11 can set a certain time interval for data acquisition according to experimental needs, in this case, data is collected every five seconds;

[0053] 3. Adjust the first circulating water bath 2 and the second circulating water bath 3 to keep the temperature of the first water bath 5 and the second water bath 7 consistent, in this case, both are stabilized at 15℃;

[0054] 4. When the temperature in the reactor 6 is stabilized at 15℃, make the piston container 4 communicate with the reactor 6, turn on the plunger pump 1, and make the hydrate reaction solution in the piston container 4 inject into the reactor 6 until the specified amount (the amount of hydrate reaction solution added (also referred to as water injection amount in this paper, in volume) can be determined according to experimental conditions, which is less than the volume of the reactor 6), in this case, the volume of the reactor 6 is 100.0mL, and 60.0mL of hydrate reaction solution is injected, thus the injection stage is ended;

[0055] 5. After the liquid injection is completed, connect reactor 6 to CO2 cylinder 10 and introduce CO2 through the high-pressure cylinder (CO2 cylinder 10) until the remaining volume (i.e. 40.0 mL) in reactor 6 is completely filled with liquid CO2. After the liquid CO2 is filled, disconnect CO2 cylinder 10 from reactor 6.

[0056] 6. Adjust the plunger pump 1 to the predetermined pressure, which is 5.5 MPa in this example, and then connect the piston container 4 to the reactor 6;

[0057] 7. Turn on the magnetic stirrer 8 to stir the solution in reactor 6 to fully dissolve CO2. When the water injection rate of plunger pump 1 is stable, the dissolution of CO2 is considered to be complete.

[0058] 8. By adjusting the temperature settings of the first circulating water bath 2 and the second circulating water bath 3, the reactor 6 and the piston container 4 are simultaneously cooled to the hydrate formation temperature, which is 2℃ in this example.

[0059] 9. When the cumulative water injection volume of plunger pump 1 no longer changes, it indicates that the volume of each phase in the reactor no longer changes, that is, no more hydrates are formed, and the reaction ends.

[0060] Example 3

[0061] In the kinetic evaluation of the formation of CO2 hydrate from liquid CO2, since pressure parameters cannot reflect the amount of CO2 in the hydrate formation system, this invention proposes to accurately calculate the amount of CO2 in the reaction system by using the injection volume under constant pressure conditions and based on the basic method of volume conservation.

[0062] like Figure 2 As shown, a method for determining and calculating the phase transition kinetics of liquid CO2-CO2 hydrate includes the following steps:

[0063] S1. Record the pressure, temperature, and cumulative water injection volume during the experiment at predetermined time intervals, and take the moment when CO2 hydrate begins to form as the initial time for calculation;

[0064] S2. Based on the initial temperature and pressure, calculate the initial density of liquid CO2 and the density ρ of the aqueous solution, respectively. w0 The solubility of CO2 in aqueous solution and the solubility of water in liquid CO2 are calculated. Based on the pressure and temperature at each subsequent moment from the initial moment, the density of liquid CO2 and the density of the aqueous solution ρ at the corresponding moments are also calculated. w The solubility of CO2 in aqueous solution and the solubility of water in liquid CO2;

[0065] S3, for the initial moment, according to the reactor volume conservation, the water mass conservation, and by using the initial moment cumulative water injection, the water solution density, the water solubility in liquid CO2, the volume of liquid CO2 in the reactor at the initial moment is calculated The volume of water solution V aq0 The water mass in the water solution The water mass dissolved in liquid CO2 Since the hydrate is not generated at the initial moment, the CO2 hydrate volume V h0 The water mass in the hydrate phase is 0 , wherein the reactor volume conservation formula and the water mass conservation formula are respectively:

[0066]

[0067]

[0068]

[0069] Wherein, ρ w0 is the water density corresponding to the initial moment of hydrate generation, V0 is the reactor volume, n w0 is the water mass injected into the reactor at the initial moment of hydrate generation, Q0 is the cumulative water injection into the reactor at the initial moment of hydrate generation;

[0070] S4, according to the volume of liquid CO2 at the initial moment calculated in step S3, the volume of water solution, and according to the liquid CO2 density at the initial moment calculated in step S2, the water solution density, the CO2 solubility in the water solution, the total mass of CO2 in the reactor at the initial moment is calculated

[0071] S5, for each time after the initial moment, according to the reactor volume conservation, the water mass conservation, and the CO2 mass conservation in the CO2 hydrate reaction process, by using the total mass of CO2 in the reactor at the initial moment, and by using the cumulative water injection at the corresponding moment, the liquid CO2 density, the water solution density, the CO2 solubility in the water solution, and the water solubility in liquid CO2 at each time after the initial moment, the CO2 mass in the hydrate at the corresponding moment in the reactor is calculated And according to the CO2 mass conservation in the reaction system, the CO2 dissolved in the water solution is calculated And the remaining CO2 mass of liquid CO2 Wherein, the reactor volume conservation formula, the water mass conservation formula, and the CO2 mass conservation formula are respectively:

[0072]

[0073]

[0074]

[0075]

[0076] wherein, n w is the amount of substance of water injected into the reactor at the respective time of each of the subsequent times of the initial time, Q is the cumulative amount of water injected into the reactor at the respective time of each of the subsequent times of the initial time, p w is the density of the corresponding aqueous solution at the respective time of each of the subsequent times of the initial time;

[0077] S6, outputting the amount of substance of CO2 in each phase at the initial time and at each of the subsequent times respectively and

[0078] In the present application, the aqueous solution mainly comprises water and also a small amount of additives, such as kinetic promoters like methionine, and since the content of the additives is very small (for example, the amount of additives added is ≤ 5wt%), it can be considered that the effect of the additives on the density of the aqueous solution and the solubility of CO2 in the aqueous solution can be ignored, and thus the effect of the additives on the density of the aqueous solution and the solubility of CO2 in the aqueous solution is reasonably simplified in the above calculation process, i.e. it is considered that the volume of water is equal to the volume of the aqueous solution, the density of the aqueous solution is equal to the density of water, and the solubility of CO2 in the aqueous solution is equal to the solubility in water. Therefore, in the present application, "water", "aqueous solution" and "hydrate reaction solution" are not specially distinguished and refer to the same concept in the present application.

[0079] In a specific example, the calculation process is as follows:

[0080] At the initial time of the reaction, 60 mL of a 0.3wt% methionine solution was injected into the reactor at 288.15K by means of a plunger pump.

[0081] 1. At the initial time of the hydrate generation, the temperature in the reaction system was 275.23K, the pressure was 5.5MPa, and the cumulative amount of water injected was 71.85 mL.

[0082] 2. The calculated density of liquid CO2, the density of the aqueous solution, the solubility of CO2 in the aqueous solution, and the solubility of water in liquid CO2 at the initial time were 0.92 g / cm 3 , 1.00 g / cm 30.033 mol / mol, 0.001 mol / mol.

[0083] 3、The volume of liquid CO2, the volume of aqueous solution and the volume of hydrate in the reactor at the initial moment are calculated as 28.16 mL, 71.84 mL and 0 mL respectively.

[0084] 4、The amount of substance of CO2 in each phase (i.e. the amount of substance of CO2 in hydrate, the amount of substance of CO2 dissolved in aqueous solution and the amount of substance of CO2 remaining in liquid CO2) and the amount of substance of water in aqueous solution at the initial moment are calculated, specifically, the amount of substance of water in aqueous solution, the amount of substance of CO2 in liquid CO2 and the amount of substance of CO2 in dissolved phase at the initial moment are 3.99 mol, 0.59 mol and 0.14 mol respectively, and no hydrate is generated at the initial moment, so the amount of substance of CO2 in hydrate phase is 0, and the total amount of substance of CO2 at the initial moment is 0.73 mol.

[0085] 5、For each time point after the initial moment, the corresponding data of each group at the time point are calculated. and Taking the 1000th group of data, i.e. 5000 seconds after the initial moment of CO2 hydrate generation, as an example, the pressure P is 5.58 MPa and the temperature T is 275.23 K, and the calculation is performed to obtain 0.41 mol, 0.06 mol, 0.26 mol.

[0086] 6、The amount of substance of CO2 in each phase is output respectively and

[0087] The amount of substance of CO2 in each phase in the above examples obtained according to the calculation method of Example 3 is shown in Table 1. Figure 3 Table 1

[0088] Through the above calculation process, the process of liquid CO2 generating CO2 hydrate can be accurately and conveniently quantitatively analyzed, the kinetic process of CO2 hydrate and the consumption of CO2 can be accurately evaluated, and theoretical support is provided for subsequent hydrate method CO2 capture and storage technology. The application can be applied in the fields of hydrate-based CO2 seabed storage, hydrate-based CO2 capture, gas hydrate storage and transportation, CO2 hydrate refrigeration technology, hydrate method fruit juice concentration and the like.

[0089] Other modifications:

[0090] 1. As a variation of Example 1, the piston container 4 and its corresponding first water bath 5 and first circulating water bath 2 in the experimental apparatus can be removed, and the plunger pump 1 can be directly connected to the reactor.

[0091] 2. When Figure 1 The apparatus shown is used for CO2 hydrate reaction kinetics experiments in porous media. Porous media such as sand, clay, and glass microspheres can be pre-loaded into the reactor to generate CO2 hydrates in porous media.

[0092] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. An experimental method for determining the phase transition kinetics of liquid CO2-CO2 hydrate, characterized in that, The phase transition kinetics of liquid CO2-CO2 hydrate was measured using an experimental apparatus, which includes a liquid injection constant pressure section, a reactor, a temperature control section, a CO2 gas source, and a data acquisition and recording section. The constant pressure injection section is connected to the reactor and is used to inject the hydrate reaction solution into the reactor during the injection stage and to continuously inject the hydrate reaction solution into the reactor at a predetermined constant pressure during the reaction stage. The CO2 gas source is connected to the reactor and is used to introduce CO2 into the reactor. The temperature control unit is used to control the temperature of the reactor; The data acquisition and recording unit is used to acquire and record parameters of the CO2 hydrate formation process in the reactor; The experimental method for determining the phase transition kinetics of liquid CO2-CO2 hydrate includes the following steps: (1) During the injection stage, at a predetermined injection temperature, a predetermined volume of hydrate reaction solution is injected into the reactor through the injection constant pressure section; (2) CO2 is introduced into the reactor through a CO2 gas source until the remaining volume of the reactor is filled with liquid CO2; (3) During the reaction stage, the temperature control unit cools the reactor from the predetermined injection temperature to the predetermined reaction temperature, and the constant pressure injection unit continuously injects the hydrate reaction solution into the reactor at a predetermined constant pressure. (4) When the cumulative water volume of the constant pressure injection section no longer changes, it indicates that no more hydrates are generated, and the reaction ends.

2. The experimental method for determining the phase transition kinetics of liquid CO2-CO2 hydrate as described in claim 1, characterized in that: The constant pressure injection unit includes a plunger pump and a piston container, and the temperature control unit includes a first circulating water bath, a second circulating water bath, a first water bath tank, and a second water bath tank; wherein: The piston container is used to hold the hydrate reaction solution, is placed in the first water bath, and is connected to the reactor. The first water bath is connected to the first circulating water bath. The plunger pump is connected to the piston container and is used to inject the hydrate reaction solution from the piston container into the reactor during the injection phase. During the reaction phase, the hydrate reaction solution is continuously injected into the reactor at a predetermined constant pressure. The reactor is placed in the second water bath, which is connected to the second circulating water bath tank. The temperature of the second water bath is always equal to the temperature of the first water bath.

3. The experimental method for determining the phase transition kinetics of liquid CO2-CO2 hydrate as described in claim 1, characterized in that: The constant pressure injection unit includes a plunger pump, and the temperature control unit includes a second circulating water bath and a second water bath tank; wherein: The plunger pump is used to dispense the hydrate reaction solution and is connected to the reactor; The plunger pump is used to inject the hydrate reaction solution into the reactor during the injection phase, and to continuously inject the hydrate reaction solution into the reactor at a predetermined constant pressure during the reaction phase. The reactor is placed in the second water bath, which is connected to the second circulating water bath tank.

4. The experimental method for determining the phase transition kinetics of liquid CO2-CO2 hydrate as described in claim 2 or 3, characterized in that: The experimental apparatus also includes a magnetic stirrer, with the second water bath located on the magnetic stirrer. The magnetic stirrer is used to stir the solution in the reactor to fully dissolve CO2 and accelerate the formation of CO2 hydrates.

5. The experimental method for determining the phase transition kinetics of liquid CO2-CO2 hydrate as described in claim 2 or 3, characterized in that: The parameters of the CO2 hydrate formation process include the pressure inside the reactor, the temperature inside the reactor, and the cumulative water injection volume of the plunger pump. The data acquisition and recording unit includes a data acquisition device, a temperature sensor, and a pressure sensor. The temperature sensor and the pressure sensor are both mounted on the reactor to detect the temperature and pressure inside the reactor in real time, respectively. The data acquisition device is connected to the temperature sensor, the pressure sensor, and the plunger pump, respectively, to collect the pressure, the temperature, and the cumulative water injection volume.

6. The experimental method for determining the phase transition kinetics of liquid CO2-CO2 hydrate as described in claim 5, characterized in that: The parameters of the CO2 hydrate formation process also include the CO2 hydrate reaction in the reactor. The data acquisition and recording unit also includes a CCD camera, which is used to capture the reaction in the reactor. The data acquisition device is connected to the CCD camera to acquire the data it detects.

7. The experimental method for determining the phase transition kinetics of liquid CO2-CO2 hydrate as described in claim 1, characterized in that: During the liquid injection phase, the temperature control unit is used to control the predetermined liquid injection temperature of the reactor. During the reaction phase, the temperature control unit is used to cool the reactor from the predetermined liquid injection temperature to the predetermined reaction temperature.

8. A method for calculating the phase transition kinetics of liquid CO2-CO2 hydrate according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Record the pressure, temperature, and cumulative water injection volume during the experiment at predetermined time intervals, and take the moment when CO2 hydrate begins to form as the initial time for calculation; S2. Based on the initial temperature and pressure, calculate the initial density of liquid CO2 and the density ρ of the aqueous solution, respectively. w0 The solubility of CO2 in aqueous solution and the solubility of water in liquid CO2 are calculated. Based on the pressure and temperature at each subsequent moment from the initial moment, the density of liquid CO2 and the density of the aqueous solution ρ at the corresponding moments are also calculated. w The solubility of CO2 in aqueous solution and the solubility of water in liquid CO2; S3. For the initial moment, based on the conservation of reactor volume and the conservation of the amount of water, and using the cumulative water injection volume, the density of the aqueous solution, and the solubility of water in liquid CO2 at the initial moment, calculate the volume of liquid CO2 in the reactor at the initial moment. Volume V of the aqueous solution aq0 The amount of water in an aqueous solution The amount of water dissolved in liquid CO2 Since no hydrate has formed initially, the volume of CO2 hydrate, V, is... h0 The amount of water in the hydrate phase is 0. The value is 0, where the formulas for the conservation of reactor volume and the conservation of the amount of water are respectively: Where, ρ w0 Let V0 be the density of water at the initial moment of hydrate formation, and n be the reactor volume. w0 Q0 represents the amount of water injected into the reactor at the initial moment of hydrate formation, and Q0 represents the cumulative amount of water injected into the reactor at the initial moment of hydrate formation. S4. Based on the initial volume of liquid CO2 and aqueous solution calculated in step S3, and the initial density of liquid CO2, density of aqueous solution, and solubility of CO2 in aqueous solution calculated in step S2, calculate the total amount of CO2 in the reactor at the initial moment. S5. For each subsequent moment after the initial moment, based on the conservation of reactor volume, water quantity, and CO2 quantity during the CO2 hydrate reaction, the total amount of CO2 in the reactor at the initial moment, along with the cumulative water injection volume, liquid CO2 density, aqueous solution density, CO2 solubility in aqueous solution, and water solubility in liquid CO2 at the corresponding moments after the initial moment, can be used to calculate the amount of CO2 in the hydrate in the reactor at the corresponding moment. Based on the conservation of the amount of CO2 in the reaction system, the amount of CO2 dissolved in the aqueous solution was calculated. The amount of substance of the remaining CO2 and liquid CO2 The formulas for the conservation of reactor volume, the conservation of the amount of water, and the conservation of the amount of CO2 are as follows: Where, n w Let ρ be the amount of water injected into the reactor at each subsequent time point after the initial time point, and Q be the cumulative amount of water injected into the reactor at each subsequent time point after the initial time point. w This represents the density of the aqueous solution at each subsequent time point after the initial time. S6. Output the amount of CO2 in each phase at the initial time and at each subsequent time. and

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