CN110389126B - Visualization reaction system of hydrate formation and decomposition and evaluation method of memory effect - Google Patents
Visualization reaction system of hydrate formation and decomposition and evaluation method of memory effect Download PDFInfo
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- CN110389126B CN110389126B CN201910564897.3A CN201910564897A CN110389126B CN 110389126 B CN110389126 B CN 110389126B CN 201910564897 A CN201910564897 A CN 201910564897A CN 110389126 B CN110389126 B CN 110389126B
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G—PHYSICS
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- 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
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Abstract
本发明提出一种水合物生成分解可视化反应系统及记忆效应评价方法，所述可视化反应系统包括供给模块、主体模型、回压控制模块、控温模块、摄像监控模块和数据采集与控制模块，所述主体模型采用特殊的结构设计，通过可变容积的全可视反应釜的恒压模式，在不改变釜内气液组分的条件下，通过容积变化平衡温度变化对釜内压力的影响，并可通过丝杠精确控制全可视腔体的容积；在实验过程中，通过摄像头监控全可视化反应釜中的水合物成核时间，通过视频录得的成核时间，在恒温箱的温度变化曲线上找到水合物最终成核的温度，通过统计大量重复实验的结果，绘制水合物成核概率随成核过冷度的概率分布曲线以及其他相关曲线进行记忆效应的评价研究。
The present invention provides a visualization reaction system for hydrate formation and decomposition and a memory effect evaluation method. The visualization reaction system includes a supply module, a main model, a back pressure control module, a temperature control module, a camera monitoring module and a data acquisition and control module. The main body model adopts a special structural design. Through the constant pressure mode of the fully visible reaction kettle with variable volume, without changing the gas-liquid composition in the kettle, the effect of temperature changes on the pressure in the kettle is balanced by volume changes. The volume of the fully visible cavity can be precisely controlled by the lead screw; during the experiment, the hydrate nucleation time in the fully visible reaction kettle is monitored by the camera, the nucleation time recorded by the video, and the temperature change in the incubator The final nucleation temperature of the hydrate is found on the curve, and the probability distribution curve of the hydrate nucleation probability with the nucleation undercooling and other related curves are drawn to evaluate the memory effect by counting the results of a large number of repeated experiments.
Description
Technical Field
The invention belongs to the field of natural gas hydrate exploitation, and particularly relates to a linear temperature and pressure control visual reaction system for hydrate generation and decomposition and a memory effect evaluation method, wherein the system can quantitatively evaluate the influence of different potential influence factors on a hydrate secondary synthesis memory effect.
Background
The phenomenon that the induction time of the hydrate is obviously reduced during secondary generation is called memory effect, and the cause mechanism and the accurate prediction of the induction time of the secondary nucleation are key scientific problems in the fields of flow guarantee, deep sea carbon sequestration, hydrate resource development and the like.
Currently, the research on hydrate formation and decomposition is mainly focused on 3 aspects: firstly, hydrate is prevented from blocking pipelines and forming hydrate in oil gas transmission during mining, namely the hydrate formation inhibiting effect is achieved, and the induction period of hydrate generation is prolonged; secondly, the hydrate is stored and transported in a solid hydrate mode, namely, the generation rate of the hydrate is accelerated, and the induction period of the generation of the hydrate is shortened; thirdly, the research of the exploitation and carbon dioxide sequestration of natural gas hydrate relates to CH4Fast decomposition of hydrate and CO enhancement2Rate of hydrate formation, i.e. shortening of CO2Induction period of hydrate formation.
In addition, the memory effect plays a crucial role in the fields of environmental effect evaluation in the hydrate exploitation process, separation technology of mixed gas hydrate, petrochemical industry, biochemical pharmacy and the like. Therefore, the research on the memory effect cause mechanism of the hydrate in the actual environment and the exploration of the artificial intervention method in the induction period of the hydrate formation play a positive and important role in the exploitation, storage and transportation of the natural gas hydrate and the development of the environmental science.
At present, the research on the memory effect of the hydrate is mainly focused on the induction time of generating the hydrate twice or more by the same object (gas), the research on the memory effect among different object (gas) hydrates is less, and the corresponding research on the memory effect of multi-type object molecules does not relate to a large amount of complex gas components. In addition, due to the strong randomness of hydrate nucleation, even under the same experimental conditions, the induction time is greatly different, which brings great random errors to the general experimental research of hydrate formation memory effect. Statistically, this random error can be reduced by a large number of repeated experiments. However, since the driving force for hydrate nucleation is small under the condition of low supercooling degree, the required induction time is extremely long, and a large number of induction experiments under the general low nucleation driving force are not feasible.
Therefore, in view of the above problems, it is desirable to provide a method for forcibly inducing hydrate nucleation in an experimental sample by performing continuous linear cooling or linear pressurization.
Disclosure of Invention
The invention provides a hydrate formation decomposition visualization reaction system and a memory effect evaluation method for overcoming the defects in the prior art, and provides a method capable of quantitatively evaluating a hydrate secondary formation memory effect under different experimental conditions based on the hydrate formation decomposition visualization system, so that a basis is provided for flow guarantee and pipeline anti-blocking design in the hydrate exploitation process.
The invention is realized by adopting the following technical scheme: a hydrate generation decomposition visualization reaction system comprises a supply module, a main body model, a back pressure control module, a temperature control module, a camera monitoring module and a data acquisition and control module;
the supply module and the back pressure control module are connected with the main body model, and the supply module is used for providing gas components and liquid components required by hydrate synthesis; the main model and the camera monitoring module are arranged in the temperature control module, the main model is a hydrate generation place, and the camera monitoring module comprises a camera and a data processing system thereof and is used for monitoring the hydrate reaction condition in the main model; the temperature control module realizes linear temperature control of the main body model to control the synthesis and decomposition of the hydrate; the back pressure control module is used for protecting the main body model and avoiding the pressure from exceeding a safety value; the data acquisition and control module realizes pressure acquisition and pressure control in the main model in the experimental process and realizes temperature control of the thermostat;
the main body model comprises an upper flange, a lower flange and a full-visible reaction kettle arranged between the upper flange and the lower flange, wherein the upper flange and the lower flange are connected through a pull rod and are fastened and tightened through fastening bolts; the lower end of the lower flange is connected with a righting cylinder, a plunger capable of moving up and down is further installed in the full-visual reaction kettle, the plunger is located in the righting cylinder, the lower portion of the plunger is connected with a ball screw and a ball screw bottom support, the ball screw is matched with a screw nut arranged on the outer side of the ball screw through a gear, a plane bearing is installed on the lower end face of the screw nut, the plane bearing is installed in a concave groove of the ball screw bottom support, and the screw nut is connected with a servo motor through a turbine speed reducer;
drive worm gear reducer through servo motor and rotate, turbine reducer drives the lead screw nut rotatory, lead screw nut through with ball between the gear interlock promote ball up-and-down motion, in addition, rectangular spacing groove has been seted up along its length direction at rightting section of thick bamboo side, rectangular spacing inslot portion installs perpendicular to ball and the guide arm of rightting rather than linking to each other, the guide arm of righting is along rectangular spacing groove up-and-down motion under the exogenic action, combine the rotary motion of rectangular spacing groove restriction ball.
Furthermore, the whole full-visual reaction kettle is installed on a turning support through a bearing seat, a rotating shaft connected with the righting barrel is arranged on the bearing seat, the rotating shaft is connected with an output shaft of a turning motor, and the full-visual reaction kettle rotates within +/-90 degrees in a vertical plane through the turning motor.
Further, supply with the module and include high-pressure gas cylinder, gaseous booster pump, air compressor machine and gas storage tank, high-pressure gas cylinder is connected to the entry end of main part model through gaseous booster pump, and main part model's entry end and exit end are provided with entry pressure gauge and export pressure gauge respectively, and gas storage tank sets up on the connecting line, and still is provided with gaseous relief pressure valve and gas flowmeter between gas storage tank and main part model, and gas flowmeter's low reaches still is provided with the check valve.
Furthermore, the full-visible reaction kettle adopts a full-visible design of sapphire materials, and all phase states are visible under the working pressure.
The invention also provides a memory effect evaluation method based on the hydrate formation decomposition visualization reaction system, which comprises the following steps:
step 1, experimental condition preparation:
adjusting the plunger of the main body model to the lowest position to fill the plunger with test liquid, then injecting gas with determined components into the main body model, discharging a certain amount of water, continuously injecting gas and pressurizing to a set pressure value, and keeping back pressure tracking in the gas injection process to prevent the model from being damaged;
the gas cylinder is opened, gas is pressurized through a booster pump, and the gas injection process is completed in two steps: in the initial stage of gas injection, injecting gas components at a small speed, collecting and measuring the volume of discharged liquid from a bottom outlet valve by using a measuring cylinder, and subtracting the volume of the liquid discharged by gas injection at the stage from the total volume of the main model to obtain the actual volume of the liquid in the model; in the later stage of gas injection, gas injection is continuously performed at a high speed, and the gas injection amount is calculated according to the liquid injection amount and the gas-liquid ratio required by the experiment;
(1) the method comprises the following steps of carrying out linear cooling under the constant pressure condition until the hydrate is generated:
setting corresponding pressure according to the experiment requirement, and controlling the pressure in the full-visible reaction kettle to enter a constant pressure mode; opening a constant temperature box for cooling, setting a cooling rate according to experiment needs, simultaneously opening a camera to start timing and video recording, and monitoring a reaction process in the main body model in real time;
(2) monitoring and recording the nucleation time, and obtaining the nucleation temperature according to the nucleation time, wherein the method specifically comprises the following steps:
when the generation phenomenon of the hydrate at the gas-liquid interface is monitored, stopping cooling, switching the constant temperature box to a rapid heating mode for decomposition experiment, and setting a target decomposition temperature according to an actual experiment scheme;
after the temperature rises to a target value, keeping for a specific time according to the requirement of an experimental scheme, cooling again to induce hydrate synthesis, and resetting the camera to restart timing and recording while cooling again;
(3) and (3) repeating the step (2) until required experimental data are obtained, and performing data processing research to realize quantitative evaluation of the influence degree of each factor on the memory effect.
Further, the step 2 can also be implemented in the following manner: linear pressurization is carried out under the constant temperature condition until the hydrate is generated, nucleation pressure is recorded, the nucleation pressure is reduced and the nucleation pressure is kept for a certain time during decomposition, then a nucleation probability curve is drawn based on experimental data, and quantitative evaluation and analysis are realized on the memory effect.
Further, step 2 is followed by step 3, the effect of inhibitor or promoter factors on memory effects:
and (3) replacing the injection liquid in the step (1) with a hydrate generation inhibitor or accelerator solution with a specific concentration, carrying out experimental study by changing the concentration of the inhibitor or accelerator solution to explore the existence of the inhibitor or accelerator and the influence of the concentration on the memory effect, and evaluating the influence on the memory effect based on experimental data.
Compared with the prior art, the invention has the advantages and positive effects that:
the visual hydrate reaction system provided by the scheme is ingenious in structural design, the induction time of the hydrate can be effectively shortened by combining a specific evaluation method, a large number of repeated experiments can be realized in a short time, in the experiment process, the nucleation time of the hydrate in the full visual reaction kettle can be monitored by the camera, the final nucleation temperature of the hydrate is found on the temperature change curve of the constant temperature box through the video recorded nucleation time, and the probability distribution curve of the nucleation probability of the hydrate along with the nucleation supercooling degree and other related curves are drawn to evaluate and research the memory effect through the statistical experiment result.
Drawings
Fig. 1 is a schematic view of a visual hydrate reaction system according to an embodiment of the present invention;
FIG. 2 is a schematic view of the overall structure of a fully-visible reaction vessel of the main body model in the embodiment of the invention;
FIG. 3 is a schematic diagram of the overall structure of the main body model according to the embodiment of the present invention;
FIG. 4 is a schematic flow chart of a hydrate formation decomposition memory effect evaluation method according to an embodiment of the present invention.
Detailed Description
In order that the above objects and advantages of the present invention may be more clearly understood, a detailed description of the embodiments of the present invention will be made below with reference to the accompanying drawings:
embodiment 1, a hydrate formation decomposition visualization reaction system, as shown in fig. 1, includes a supply module 1, a main body model 2, a back pressure control module 3, a temperature control module 4, a camera monitoring module, and a data acquisition and control module; the main body model 2 and the camera monitoring module are arranged in a temperature control module 4 (high and low temperature thermostat), the main body model 2 is a hydrate generation place, the camera monitoring module comprises a camera and a data processing system thereof, the camera is arranged in the thermostat 4 to monitor the reaction condition in the main body model, and the camera monitoring module can be fixed in the thermostat through magnet adsorption so as to flexibly adjust the position; the temperature control module 4 carries out linear temperature control on the main body model 2 to control the synthesis and decomposition of the hydrate; the supply module 1 and the back pressure control module 3 are both connected with the main body model 2, the supply module 1 is used for providing gas components and liquid components required by hydrate synthesis, and the back pressure control module 3 comprises a back pressure pump 3-2 and a back pressure valve 3-1 and is used for protecting the main body model and avoiding the pressure from exceeding a safety value; the data acquisition and control module is used for controlling and acquiring gas injection and liquid injection amount, pressure, temperature and other temperature data in the experimental process and carrying out data preprocessing, and a hardware part mainly comprises a pressure gauge, a flow meter, a temperature meter and the like at an inlet and an outlet of a main body model, so that the pressure acquisition and the control of the pressure in the main body model can be realized, and the temperature control of the constant temperature box can be realized.
In the embodiment, the supply module comprises high-pressure gas cylinders (a methane gas cylinder 1-1, a carbon dioxide gas cylinder 1-2 and the like), a gas booster pump 1-3, an air compressor 1-4, an injection pump 1-9 and a gas storage tank 1-5, wherein the methane gas cylinder 1-1 and the carbon dioxide gas cylinder 1-2 are connected to the inlet end of the main model 2 through the gas booster pump 1-3, the inlet end and the outlet end of the main model 2 are respectively provided with an inlet pressure gauge 2-1 and an outlet pressure gauge 2-2, the gas storage tank 1-5 is arranged on a connecting pipeline, a gas pressure reducing valve 1-6 and a gas flow meter 1-7 are also arranged between the gas storage tank 1-5 and the main model, the downstream of the gas flow meter 1-7 is also provided with a one-way valve 1-8, through the design of the imported one-way flowmeter, the gas-liquid ratio correlation research can be conveniently carried out in a matching manner, the opening degree of the flowmeter can be controlled through software, so that the gas injection speed can be accurately controlled, and the gas injection quantity can be measured and recorded.
Referring to fig. 2 and 3, the main body model 2 includes an upper flange 21, a lower flange 22 and a full-visible reaction vessel 210 disposed between the upper flange 21 and the lower flange 22, the upper flange 21 and the lower flange 22 are connected by a tie rod 9 and are fastened tightly by fastening bolts 5, and a sealing member 6 is further disposed between the upper flange 21 and the full-visible reaction vessel 210 and between the lower flange 22 and the full-visible reaction vessel 21 to ensure the internal pressure sealing of the full-visible reaction vessel; an upper inlet and an upper outlet 23 and a lower inlet and an lower outlet 24 are respectively arranged on the upper flange 21 and the lower flange 22, the lower end of the lower flange 22 is connected with a righting cylinder 26, a plunger 25 is also arranged in the full-visual reaction kettle 210, and the plunger 25 is positioned in the righting cylinder 26; in order to control the volume of the full-visual reaction kettle 210 by the plunger 25, particularly, the lower part of the plunger 25 is connected with a ball screw 27 and a ball screw bottom support 10, the side surface of the righting cylinder 26 is provided with a rectangular limiting groove along the length direction, a righting guide rod 28 connected with the ball screw 27 is arranged in the rectangular limiting groove, the ball screw 27 is matched with a screw nut 29 arranged on the outer side of the ball screw 27 through a gear, the lower end surface of the screw nut 29 is provided with a plane bearing 7, the plane bearing 7 is arranged in a concave groove of the ball screw bottom support 10, the ball screw 27 is connected with a turbine speed reducer 8, and the turbine speed reducer 8 is connected with a servo motor.
The concrete motion mode of the connection is as follows: the servo motor drives the worm speed reducer 8 to rotate, the worm speed reducer 8 drives the lead screw nut 29 to rotate, and the lead screw nut 29 pushes the ball screw 27 to move up and down through meshing with a gear between the ball screw 27. To ensure the up-and-down movement of the ball screw, the rotation of the ball screw 27 must be prevented, so that the centering guide 28 moves up and down in the rectangular limiting groove by fixedly connecting the centering guide 28 with the ball screw 27, and the rotation of the ball screw 27 is limited by the rectangular limiting groove, that is, the screw nut 29 rotates to drive the ball screw 27 to move up and down, and the centering guide 28 and the ball screw 27 move up and down together and are limited by the rectangular limiting groove.
When high pressure conditions exist in the full-visual reaction kettle, downward acting force is generated on the plunger 25, the ball screw 27 is forced to move downwards, and due to the fact that the ball screw 27 is meshed with the screw nut 29 through threads, the screw nut 29 bears the downward acting force, so that the screw nut 29 is directly contacted with the groove of the ball screw bottom support 10, and great sliding friction is generated. To solve this problem, in this embodiment, a flat bearing 7 is provided between the spindle nut 29 and the recess of the ball screw shoe 10, which, when the spindle nut 29 is rotated, drives the lower flat bearing 7 into a simultaneous rotational movement, so that sliding friction between the spindle nut 29 and the ball screw shoe 10 is prevented.
In order to change the contact surface of gas and water in the full-visual reaction kettle under the condition of constant pressure, as shown in fig. 3, the full-visual reaction kettle is integrally installed on a turnover support 20 through a bearing seat 202, the turnover of the full-visual reaction kettle is realized through a turnover motor 201, namely, the rotation of +/-90 degrees is realized in a vertical plane, and the influence of the contact surface on the synthesis process of the hydrate and the memory effect is verified in an auxiliary way through the turnover of the full-visual reaction kettle.
In this embodiment, the fully-visible reaction kettle is designed to be fully visible from the german imported sapphire material, all phases are visible under the working pressure, and the rest contact fluid portions are made of 316L stainless steel. To coordinate the reaction pressure related studies. The pressure and the piston position in the full-visual reaction kettle are monitored through computer software, the speed reducer is controlled through the software to rotate so as to control the movement of the plunger, constant pressure in the kettle can be maintained under the condition that gas-liquid components in the kettle are not changed, a hydrate generation and decomposition experiment is carried out under the accurate constant pressure condition, and the influence of temperature change of the constant temperature box is avoided.
The visual reaction system provided by the embodiment can perform related research on the constant pressure condition by balancing the influence of temperature change on the pressure in the kettle through volume change under the condition of not changing gas-liquid components in the kettle through the constant pressure mode of the full visual reaction kettle with variable volume; meanwhile, the change rule of the hydrate memory effect under the conditions of constant temperature and constant pressure is considered, the volume of the full-visible cavity is accurately controlled through the lead screw, and the defect that the memory effect is presumed only through the pressure and temperature change is overcome.
(1) the research of the secondary synthesis memory effect generally indicates that the induction time of the nucleation of the hydrate represents the difficulty of the nucleation of the hydrate, and the research indicates that the induction time is determined by the nucleation driving force, and the determining factors of the nucleation driving force comprise temperature, pressure, gas fugacity and the like. Therefore, the change of the driving force required by secondary nucleation of the hydrate, namely the change of the difficulty degree of nucleation of the hydrate can be evaluated through indexes such as the temperature and the pressure of the final nucleation of the hydrate, and the related research on the memory effect is carried out.
(2) Because the randomness of hydrate nucleation is strong, even under the same experimental conditions, the induction time has great difference, which brings great random error to the general experimental research of hydrate formation memory effect. Statistically, this random error can be reduced by a large number of repeated experiments; however, since the driving force for nucleation of hydrates is small under the condition of low supercooling degree, the required induction time is extremely long, and the experiment of carrying out a large amount of induction synthesis and decomposition under the general low nucleation driving force is not feasible. Therefore, the continuous linear cooling or linear pressurization can be carried out on the experimental sample to forcibly induce the nucleation of the hydrate. Under the linear temperature-decreasing pressurization condition, the temperature (pressure) of the incubator is decreased (increased) at a constant rate along with the increase of time, and the nucleation driving force of the hydrate is gradually increased until the nucleation is forced. The method can effectively shorten the induction time of the hydrate, realize a large number of repeated experiments in a short time, and provide data support for quantitative evaluation of the memory effect.
As shown in fig. 4, the method for evaluating a hydrate formation decomposition memory effect described in this embodiment specifically includes the following steps:
step 1, experimental condition preparation:
1.1, retracting the plunger inside the main body model to the lowest position, opening the outlet valve at the top of the model, injecting distilled water into the main body model through the liquid injection pump to ensure that the main body model is filled with liquid, exhausting air in the model, and then closing the liquid injection pump and the outlet valve at the top;
1.2 open the gas cylinder to carry out the pressure boost through the booster pump to gas:
1.3 opening a bottom outlet valve of the main model, controlling the opening of a one-way gas flowmeter through software, injecting gas components at a low speed, collecting and measuring the volume of discharged liquid from the bottom outlet valve by using a measuring cylinder, and subtracting the volume of the liquid discharged by gas injection at the stage from the total volume of the main model to obtain the actual volume of the liquid in the model; the actual liquid injection amount is determined according to the experiment requirement, and the bottom outlet valve is closed immediately after the liquid injection amount reaches the experiment requirement value.
And 1.4, changing the opening of the one-way gas flowmeter to continuously inject gas at a high speed, wherein the gas injection amount is calculated according to the liquid injection amount and the gas-liquid ratio required by the experiment.
1.5 applying back pressure to protect the main body model at the back pressure module, wherein the back pressure value is determined according to the experiment requirement, and the back pressure value is generally higher than the pressure of the main body model required by the experiment.
It should be noted that, in step 1.3, since the heat conduction requires a certain time, the injection amount in the subject model should be as small as possible without affecting the experiment and observation in order to reduce the temperature difference between the oven and the inside of the main model as much as possible.
2.1 setting corresponding pressure according to the experiment requirement, and controlling the pressure in the full-visible reaction kettle to enter a constant pressure mode;
2.2, opening the thermostat for cooling, setting a cooling rate according to experimental needs, and considering that the heat conduction between the environment of the thermostat and the internal environment of the main model needs a certain time, generally keeping the cooling rate at a smaller value;
2.3 when the step 2.2 is started, opening a camera to start timing and video recording, and monitoring the reaction process in the main body model in real time;
2.4 in the step 2.3, when the generation phenomenon of the hydrate at the gas-liquid interface is monitored, stopping cooling, switching the constant temperature box to a rapid heating mode for decomposition experiment, and setting the target decomposition temperature according to the actual experiment scheme;
2.5 in step 2.4, after the temperature rises to the target value, keeping for a certain time according to the experimental scheme, and then cooling again to induce hydrate synthesis again, wherein the cooling rate is the same as that in step 2.2;
2.6 in step 2.5, resetting the camera to restart timing and recording while cooling is started again;
2.7 repeating the steps 2.4-2.6 until enough experimental data are obtained, and carrying out data processing research to realize quantitative evaluation of the influence degree of each factor on the memory effect.
In this embodiment, since the hydrate nucleation occurs at the gas-liquid interface first, the monitoring range of the camera in this step only needs to be controlled at the gas-liquid interface; in addition, if the final nucleation pressure is used as an index to evaluate the change of the driving force required by the secondary nucleation of the hydrate, the influence of the decomposition pressure on the memory effect is studied. The temperature is changed into the yield, the pressure is changed into a variable, the temperature is constant in the experimental process through the thermostat, and linear pressurization is realized through the piston.
It must be pointed out that during the above experiments, if the driving force required for the nucleation of hydrates is high, the final nucleation temperature used is probably lower than 0 ℃, and in order to avoid the phenomenon of hydrate nucleation from being confused by the freezing of the liquid in the reaction vessel at a temperature lower than 0 ℃, the conditions for generating hydrates corresponding to the gas components used for carrying out the experiments should be as easy as possible.
In step 1.1, the injection liquid is changed to a solution of hydrate formation inhibitor or accelerator at a certain concentration, and experimental studies can be carried out by changing the concentration of the solution. The rest experiment steps are the same as 1.1-2.7, the influence of the existence and the concentration of the inhibitor or the accelerator on the memory effect is researched, and the influence is evaluated through a large number of repeated experiments.
By the full-visual hydrate reaction system and the method capable of linearly controlling temperature and pressure, the hydrate growth and decomposition processes under different conditions are observed in a full-visual manner, the hydrate synthesis distribution state under different conditions is observed, the generation of the hydrate in the reaction kettle is induced in a short time, a large number of hydrate generation and decomposition experiments are completed, and corresponding experimental data are obtained; based on a large amount of experimental data, quantitative evaluation is carried out on the influence degree of each potential influence factor on the secondary synthesis memory effect of the hydrate.
The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention in other forms, and any person skilled in the art may apply the above modifications or changes to the equivalent embodiments with equivalent changes, without departing from the technical spirit of the present invention, and any simple modification, equivalent change and change made to the above embodiments according to the technical spirit of the present invention still belong to the protection scope of the technical spirit of the present invention.
Claims (5)
1. The memory effect evaluation method of the hydrate generation decomposition visualization reaction system comprises a supply module, a main body model, a back pressure control module, a temperature control module, a camera monitoring module and a data acquisition and control module; the supply module and the back pressure control module are connected with the main body model, and the supply module comprises a high-pressure gas cylinder, a gas booster pump, an air compressor and a gas storage tank and is used for providing gas components and liquid components required by hydrate synthesis; the main model and the camera monitoring module are arranged in the temperature control module, the main model is a hydrate generation place, and the camera monitoring module comprises a camera and a data processing system thereof and is used for monitoring the hydrate reaction condition in the main model; the temperature control module realizes linear temperature control of the main body model to control the synthesis and decomposition of the hydrate; the back pressure control module is used for protecting the main body model and avoiding the pressure from exceeding a safety value; the data acquisition and control module realizes pressure acquisition and pressure control in the main model in the experimental process and realizes temperature control of the thermostat;
the main body model comprises an upper flange, a lower flange and a full-visible reaction kettle arranged between the upper flange and the lower flange, wherein the upper flange and the lower flange are connected through a pull rod and are fastened and tightened through fastening bolts; the lower end of the lower flange is connected with a righting cylinder, a plunger which moves up and down is further installed in the full-visual reaction kettle and is positioned in the righting cylinder, the lower portion of the plunger is connected with a ball screw and a ball screw bottom support, the ball screw is matched with a screw nut arranged on the outer side of the ball screw through a gear, a plane bearing is installed on the lower end face of the screw nut and is installed in a concave groove of the ball screw bottom support, and the screw nut is connected with a servo motor through a turbine speed reducer;
the worm gear speed reducer is driven to rotate through the servo motor, the worm gear speed reducer drives the screw nut to rotate, the screw nut pushes the ball screw to move up and down through meshing with a gear between the screw nut and the ball screw, in addition, a rectangular limiting groove is formed in the side surface of the centering cylinder along the length direction of the centering cylinder, a centering guide rod which is perpendicular to the ball screw and connected with the ball screw is installed in the rectangular limiting groove, the centering guide rod moves up and down along the rectangular limiting groove under the action of external force, and the rotating motion of the ball screw is limited by combining the rectangular limiting groove;
the memory effect evaluation method is characterized by comprising the following steps of:
step 1, experimental condition preparation:
(1) adjusting the plunger of the main body model to the lowest position to fill the plunger with test liquid, then injecting gas with determined components into the main body model, discharging a certain amount of water, continuously injecting gas and pressurizing to a set pressure value, and keeping back pressure tracking in the gas injection process to prevent the model from being damaged;
(2) opening a high-pressure gas cylinder, and pressurizing gas by a booster pump, wherein the gas injection process is completed by two steps:
in the initial stage of gas injection, injecting gas components at a small speed, collecting and measuring the volume of discharged liquid from a bottom outlet valve by using a measuring cylinder, and subtracting the volume of the liquid discharged by gas injection at the stage from the total volume of the main model to obtain the actual volume of the liquid in the model; in the later stage of gas injection, gas injection is continuously performed at a high speed, and the gas injection amount is calculated according to the liquid injection amount and the gas-liquid ratio required by the experiment;
step 2, hydrate secondary synthesis memory effect experiment:
(1) the method comprises the following steps of carrying out linear cooling under the constant pressure condition until the hydrate is generated:
setting corresponding pressure according to the experiment requirement, and controlling the pressure in the visual reaction kettle to enter a constant pressure mode; opening a constant temperature box for cooling, setting a cooling rate according to experiment needs, simultaneously opening a camera monitoring module to start timing and video recording, and monitoring a reaction process in the main body model in real time;
(2) monitoring and recording the nucleation time, and obtaining the nucleation temperature according to the nucleation time, wherein the method specifically comprises the following steps:
when the generation phenomenon of the hydrate at the gas-liquid interface is monitored, stopping cooling, switching the constant temperature box to a rapid heating mode for decomposition experiment, and setting a target decomposition temperature according to an actual experiment scheme;
after the temperature rises to a target value, keeping for a specific time according to the requirement of an experimental scheme, cooling again at the same cooling rate to induce hydrate synthesis, and resetting the camera to restart timing and recording while cooling again;
(3) repeating the step (2) until required experimental data are obtained, carrying out data processing research, and realizing quantitative evaluation of the influence degree of each factor on the memory effect, wherein the method specifically comprises the following steps: the nucleation time of the hydrate in the full-visualization reaction kettle is monitored through the camera, the final nucleation temperature of the hydrate is found on the temperature change curve of the constant temperature box through the nucleation time recorded through the video, and the probability distribution curve of the nucleation probability of the hydrate along with the nucleation supercooling degree and other related curves are drawn to evaluate and study the memory effect through the result of a statistical experiment.
2. The method for evaluating the memory effect of the visual reaction system for hydrate formation decomposition according to claim 1, wherein: said step 2 is followed by a step 3, the effect of inhibitor or promoter factors on memory effects:
and (3) replacing the injection liquid in the step (1) with a hydrate generation inhibitor or accelerator solution with a specific concentration, carrying out experimental study by changing the concentration of the inhibitor or accelerator solution to explore the existence of the inhibitor or accelerator and the influence of the concentration on the memory effect, and evaluating the influence on the memory effect based on experimental data.
3. The method for evaluating the memory effect of the visual reaction system for hydrate formation decomposition according to claim 2, wherein: the whole full-visual reaction kettle is installed on a turning support through a bearing seat, a rotating shaft connected with a righting cylinder is arranged on the bearing seat, the rotating shaft is connected with an output shaft of a turning motor, and the full-visual reaction kettle rotates within +/-90 degrees in a vertical plane through the turning motor.
4. The method for evaluating the memory effect of the visual reaction system for hydrate formation decomposition according to claim 2, wherein: the high-pressure gas cylinder is connected to the inlet end of the main body model through the gas booster pump, the inlet end and the outlet end of the main body model are respectively provided with an inlet pressure gauge and an outlet pressure gauge, the gas storage tank is arranged on a connecting pipeline, a gas pressure reducing valve and a gas flowmeter are further arranged between the gas storage tank and the main body model, and a check valve is further arranged on the downstream of the gas flowmeter.
5. The method for evaluating the memory effect of the visual reaction system for hydrate formation decomposition according to claim 2, wherein: the full-visual reaction kettle adopts a full-visual design of sapphire materials, and all phases are visible under the working pressure.
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