CN111044555A - Experimental method for capturing full-period form of gas hydrate crystal - Google Patents
Experimental method for capturing full-period form of gas hydrate crystal Download PDFInfo
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- CN111044555A CN111044555A CN201911346342.8A CN201911346342A CN111044555A CN 111044555 A CN111044555 A CN 111044555A CN 201911346342 A CN201911346342 A CN 201911346342A CN 111044555 A CN111044555 A CN 111044555A
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/14—Investigating or analyzing materials by the use of thermal means by using distillation, extraction, sublimation, condensation, freezing, or crystallisation
- G01N25/147—Investigating or analyzing materials by the use of thermal means by using distillation, extraction, sublimation, condensation, freezing, or crystallisation by cristallisation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
Abstract
The invention belongs to the technical field of gas hydrate generation experiments, and provides an experimental method for capturing a full-period form of a gas hydrate crystal. The system adopted by the method comprises a jacket type visual reaction kettle, image acquisition equipment, a backlight source, a heating and refrigerating circulator, an air injection pump, a data acquisition system and a computer. The method utilizes the memory effect of secondary generation of the hydrate, shortens the induction time and realizes the capture of the crystal form of the hydrate under different working conditions below a phase equilibrium point. The method is not limited by the problem that the hydrate is difficult to generate or cannot be generated under the working condition close to the phase equilibrium point, and the problem of long induction time is solved in time, so that crystal form capture under more working condition ranges is obtained, the hydrate crystallization process is convenient to control, and morphological basis is provided for hydrate research.
Description
Technical Field
The invention relates to the technical field of gas hydrate generation experiments, in particular to a visual experimental method for capturing the full-period morphology of a gas hydrate crystal based on a visual reaction kettle.
Background
The gas hydrate is an ice-shaped crystalline compound, a cage with different shapes is formed by water molecules through hydrogen bonds as a host, and gas molecules (such as hydrogen, methane and carbon dioxide) with different sizes and shapes are used as guest molecules to reside in the cage. The gas hydrate has the characteristics of high gas storage capacity, convenience in storage and transportation, economy, safety and the like, so the gas hydrate has important application prospects in industrial practice, and is widely researched in the fields of natural gas storage and transportation, gas separation process, carbon dioxide capture and sealing, seawater desalination, hydrate cold storage and the like.
At present, the research on gas hydrate mainly aims at the kinetics and thermodynamics in the generation and decomposition processes, and the research on the morphology of hydrate is still very limited. The research on the crystal form and the form change of the gas hydrate has important significance in understanding the hydrate generation mechanism and guiding the industrial application of the hydrate, for example, in the transportation, dehydration and storage processes of the gas hydrate, the size of the hydrate crystal is increased, the pressure loss in the transportation process of the hydrate can be reduced, the safety and the reliability of a transportation system are further increased, and the dehydration efficiency of the hydrate can be effectively improved. In the process of carbon dioxide sequestration at the seabed, the form change of the hydrate directly influences the permeability and mechanical properties of a hydrate layer, and the volume expansion caused by the dissociation of the hydrate in the pores of the sediment can cause the pressure to increase, thereby reducing the driving force of the dissociation and maintaining the stability of the reservoir, so that the crystal form of the hydrate needs to be known to evaluate the possibility of underground storage.
There are a large number of scholars observing the formation process of the hydrate under macroscopic conditions, but there are limitations: firstly, macroscopic observation cannot capture the form and size of a hydrate crystal; secondly, the generation of the gas hydrate needs harsher low-temperature and high-pressure conditions and longer induction time, and the growth condition of the hydrate crystal is difficult to capture or even cannot be captured under the working condition that the gas hydrate is closer to the phase equilibrium point of the hydrate.
Disclosure of Invention
Aiming at the defects, the invention provides an experimental method for capturing the full-period form of the gas hydrate crystal, and the method can capture the growth shape and size of the hydrate crystal from a microscopic angle under wider working conditions so as to be convenient for controlling the crystallization process of the hydrate and provide a morphological basis for the research of the hydrate.
The invention is realized by the following technical scheme:
an experimental method for capturing a full-period form of a gas hydrate crystal is based on an experimental system, wherein the experimental system comprises a jacket type visible reaction kettle, image acquisition equipment, a backlight source, a heating and refrigerating circulator, an air injection pump, a data acquisition system and a computer; the jacket type visible reaction kettle body is connected with an air injection pump and an injection pump, and the jacket is connected with the heating and refrigerating circulator and used for controlling the temperature in the reaction process; one end of the temperature and pressure acquisition equipment is connected with the interface of the reaction kettle body, and the other end of the temperature and pressure acquisition equipment is connected with the data acquisition system; the upper water inlet and the lower water inlet of the water bath jacket of the reaction kettle body are connected with the heating and refrigerating circulator to control the temperature in the reaction process, and glycol solution is used as circulating liquid; one end of the gas injection pump is connected with the gas cylinder, the other end of the gas injection pump is connected with the reaction kettle and is used for injecting gas according to a fixed pressure, and meanwhile, the gas temperature in the gas injection pump is controlled by utilizing the heating and refrigerating circulator; one end of the liquid injection pump is connected in the liquid, and the other end of the liquid injection pump is connected with the reaction kettle body and is used for quantitatively injecting liquid; the image acquisition equipment and the data acquisition system are connected with the computer and are used for acquiring images and dynamic temperature and pressure data in the reaction kettle;
the method comprises the following steps:
firstly, connecting a pipeline and detecting leakage; assembling the reaction kettle body; a liquid outlet at the lower end of the kettle body is blocked by a plug; the connection of a feeding pipeline and temperature and pressure acquisition equipment at the upper end of a reaction kettle body in the reaction system is completed, a liquid injection pump is connected with the kettle body, a gas injection pump is connected with pipelines between the kettle body and a gas cylinder, and valves are connected among the liquid injection pump and the kettle body, so that the connection of a water bath jacket outer pipe with a heating and refrigerating circulator is completed. And carrying out pipeline leakage detection after connection is finished.
Secondly, reaction liquid is added, and system air is discharged; opening a liquid inlet valve, quantitatively injecting reaction liquid from a liquid inlet interface at the upper end of the reaction kettle body through a liquid injection pump, and closing the liquid inlet valve; filling a gas injection pump with gas for reaction; adjusting the pressure of a gas injection pump, and opening a gas inlet valve to inject gas into the kettle body; closing the air inlet valve and opening the air outlet valve to exhaust air; repeating the three groups of air inlet and exhaust processes to replace the original air in the kettle body.
Thirdly, injecting reaction gas with specified pressure into the reaction kettle; adjusting the heating and refrigerating circulator to control the temperature of the gas in the reaction kettle and in the gas injection pump to be consistent; adjusting the pressure of a gas injection pump to the pressure required by the reaction; and opening the air inlet valve, injecting gas into the kettle body through a gas injection pump at constant pressure until the pressure is stable, and closing the air inlet valve.
Step four, cooling and finishing the generation of a hydrate for the first time: adjusting a heating and refrigerating circulator to cool the reaction kettle to below zero so as to quickly realize the primary generation of the hydrate and simultaneously form ice;
fifthly, heating and decomposing: adjusting a heating and refrigerating circulator to heat the reaction kettle to a temperature 1-2 ℃ higher than the phase equilibrium point; after visually confirming the dissociation of all hydrate crystals, shaking the reaction kettle to ensure that the gas in the liquid phase is saturated and uniform; the temperature is reduced to the temperature corresponding to the phase equilibrium point; opening an air inlet valve to adjust the pressure in the kettle to the pressure required by the reaction;
and sixthly, cooling, finishing the generation of the hydrate for the second time, and capturing the crystal form of the hydrate: adjusting the heating and refrigerating circulator to continuously cool the reaction kettle to the required temperature; and adjusting the position of the image acquisition equipment and the backlight source, and capturing the hydrate crystal form in real time.
The invention has the beneficial effects that:
(1) the jacket type visible reaction kettle adopted by the invention is convenient for regulating and controlling the temperature in the experimental process, the experimental operation is simple, and the crystal growth process in the kettle can be clearly observed.
(2) The memory effect of secondary generation of the hydrate is utilized, the induction time is shortened, and the crystal form capture of the hydrate under different working conditions below a phase equilibrium point is realized. The method is not limited by the problem that hydrate is difficult to generate or does not generate under the working condition close to a phase equilibrium point and the problem of long induction time, so that crystal form capture under more working condition ranges can be obtained.
Drawings
FIG. 1 is a schematic structural view of a jacketed visual reaction kettle.
FIG. 2 is a diagram of an experimental system.
In the figure: 1 a temperature sensor; 2 a pressure sensor; 3, a liquid injection pump; 4, a data acquisition system; 5, a gas cylinder; 6, an air injection pump; 7 heating the refrigeration circulator; 8, a backlight source; 9 jacket type visible reaction kettle; 10 an image acquisition device; 11 computer.
Fig. 3 is a crystal morphology image captured by the embodiment.
Detailed Description
The following detailed description of the invention refers to the accompanying drawings.
Example the trapping of gas hydrate crystals was accomplished at 3MPa, 16 ℃ with a solution of carbon dioxide + thermodynamic additives in 3 mol% tetrahydrofuran. The corresponding phase equilibrium temperature of carbon dioxide at 3MPa at this concentration of additive was obtained by literature investigation to be 17 ℃. The specific implementation comprises the following steps:
(1) and assembling and connecting the experimental system, and completing pipeline leakage detection.
(2) Preparing 3.0 mol% tetrahydrofuran solution, opening a liquid inlet valve, injecting 3.5 ml of the tetrahydrofuran solution with the mol% concentration from a liquid inlet port at the upper end of the reaction kettle body through an injection pump until the liquid level reaches the center of the reaction kettle, and closing the liquid inlet valve; filling a gas injection pump with gas for reaction; adjusting the pressure of a gas injection pump to 0.2MPa, and opening a gas inlet valve to inject gas into the kettle body; closing the air inlet valve and opening the air outlet valve to exhaust air; repeating the three groups of air inlet and exhaust processes to replace the original air in the kettle body.
(3) Adjusting a heating and refrigerating circulator to control the temperature of gas in the reaction kettle and in a gas injection pump to be 19 ℃; adjusting the pressure of the gas injection pump to 3 MPa; and opening an air inlet valve, injecting gas into the kettle body to 3MPa through a gas injection pump at constant pressure, and closing the air inlet valve after the stability.
(4) And regulating the heating and refrigerating circulator to cool the reaction kettle to-3 ℃ so as to quickly realize the one-time generation of the hydrate and simultaneously form ice.
(5) Adjusting a heating and refrigerating circulator to heat the reaction kettle to 19 ℃; after visually confirming the dissociation of all hydrate crystals, shaking the reaction kettle to ensure that the gas in the liquid phase is saturated and uniform; the temperature is reduced to 17 ℃ of phase equilibrium temperature; and opening an air inlet valve to adjust the pressure in the kettle to 3 MPa.
(6) Adjusting the heating and refrigerating circulator to cool the reaction kettle to 16 ℃ for the second generation of hydrate; and adjusting the position of a CCD (charge coupled device) of the image acquisition equipment and a backlight source, and capturing the hydrate crystal form in real time.
The above description is only one embodiment of the present invention, and any modification, equivalent replacement, and improvement made within the principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. An experimental method for capturing a gas hydrate crystal full-period form is characterized in that the method is based on an experimental system, and the experimental system comprises a jacketed visual reaction kettle (9), an image acquisition device (10), a backlight source (8), a heating and refrigerating circulator (7), a gas injection pump (6), a liquid injection pump (3), a data acquisition system (4) and a computer (11); the jacket type visible reaction kettle body is connected with an air injection pump (6) and an liquid injection pump (3), and the jacket is connected with the heating and refrigerating circulator and used for controlling the temperature in the reaction process; one end of the temperature and pressure acquisition equipment is connected with the interface of the reaction kettle body, and the other end of the temperature and pressure acquisition equipment is connected with the data acquisition system; the image acquisition equipment (10) and the data acquisition system (4) are connected with the computer (11) and are used for acquiring images and dynamic temperature and pressure data in the reaction kettle;
the method comprises the following steps:
firstly, connecting a pipeline and detecting leakage;
secondly, reaction liquid is added, and system air is discharged;
thirdly, injecting reaction gas with specified pressure into the reaction kettle;
step four, cooling and finishing the generation of a hydrate for the first time: adjusting a heating and refrigerating circulator (7) to cool the reaction kettle to below zero so as to quickly realize the one-time generation of the hydrate and simultaneously form ice;
fifthly, heating and decomposing: adjusting a heating and refrigerating circulator (7) to heat the reaction kettle to 1-2 ℃ higher than the phase equilibrium point; after visually confirming the dissociation of all hydrate crystals, shaking the reaction kettle to ensure that the gas in the liquid phase is saturated and uniform; the temperature is reduced to the temperature corresponding to the phase equilibrium point; opening an air inlet valve to adjust the pressure in the kettle to the pressure required by the reaction;
and sixthly, cooling, finishing the generation of the hydrate for the second time, and capturing the crystal form of the hydrate: adjusting the heating and refrigerating circulator (7) to continuously cool the reaction kettle to the required temperature; and adjusting the position of the image acquisition equipment (10) and the backlight source (8) to capture the hydrate crystal form in real time.
2. An experimental method for capturing a gas hydrate crystal full-period morphology according to claim 1, characterized in that the adopted experimental system jacket type visible reaction kettle body is provided with interfaces which are all set as quick connectors and are convenient to disassemble, the four interfaces are respectively a temperature measuring interface, a pressure measuring interface, a liquid discharging interface and a feeding interface, the feeding interface respectively completes the functions of liquid inlet, gas inlet and gas outlet through a connecting cross joint, and a valve is arranged to realize switching.
3. The experimental method for capturing the full-period morphology of the gas hydrate crystals as claimed in claim 1, wherein sapphire window glass at two ends of the jacketed visual reaction kettle (9) is sealed and fixed with the cylinder body through a front flange and a rear flange by O-shaped sealing rings.
4. An experimental method for capturing a full-period morphology of a gas hydrate crystal according to claim 1, characterized in that the first to third steps are as follows:
step one, connecting pipelines and detecting leakage: assembling the reaction kettle body; a liquid outlet at the lower end of the kettle body is blocked by a plug; connecting a feeding pipeline and temperature and pressure acquisition equipment at the upper end of a reaction kettle body in the reaction system, connecting a liquid injection pump with the kettle body, connecting a gas injection pump with pipelines between the kettle body and a gas cylinder, and connecting valves therein, and completing the connection of an outer pipe of a water bath jacket with a heating and refrigerating circulator; performing pipeline leakage detection after connection is finished;
secondly, reaction liquid is added, and system air is discharged: opening a liquid inlet valve, quantitatively injecting reaction liquid from a liquid inlet interface at the upper end of the reaction kettle body through a liquid injection pump, and closing the liquid inlet valve; filling a gas injection pump with gas for reaction; adjusting the pressure of a gas injection pump, and opening a gas inlet valve to inject gas into the kettle body; closing the air inlet valve and opening the air outlet valve to exhaust air; repeating the three groups of air inlet and exhaust processes to replace the original air in the kettle body;
thirdly, injecting reaction gas with specified pressure into the reaction kettle: adjusting the heating and refrigerating circulator to control the temperature of the gas in the reaction kettle and in the gas injection pump to be consistent; adjusting the pressure of a gas injection pump to the pressure required by the reaction; and opening the air inlet valve, injecting gas into the kettle body through a gas injection pump at constant pressure until the pressure is stable, and closing the air inlet valve.
5. An experimental method for capturing the full periodic morphology of gas hydrate crystals as claimed in claim 1, characterized in that ethylene glycol solution is used as the circulating liquid.
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| CN114019115A (en) * | 2022-01-06 | 2022-02-08 | 清华大学深圳国际研究生院 | Reaction system and method for rapidly screening hydrate inhibitor |
| CN115650230A (en) * | 2022-11-03 | 2023-01-31 | 清华大学深圳国际研究生院 | CO (carbon monoxide) 2 Method for promoting hydrate formation and CO 2 Method for calculating sealing quantity |
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