CN117871591A - Fluid phase balance measuring device and method suitable for different volatility characteristics - Google Patents
Fluid phase balance measuring device and method suitable for different volatility characteristics Download PDFInfo
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- 239000012530 fluid Substances 0.000 title claims abstract description 78
- 238000000034 method Methods 0.000 title claims abstract description 24
- 239000012071 phase Substances 0.000 claims abstract description 48
- 238000005259 measurement Methods 0.000 claims abstract description 27
- 238000002347 injection Methods 0.000 claims abstract description 18
- 239000007924 injection Substances 0.000 claims abstract description 18
- 239000007788 liquid Substances 0.000 claims abstract description 14
- 239000007791 liquid phase Substances 0.000 claims abstract description 13
- 230000001105 regulatory effect Effects 0.000 claims abstract description 12
- 230000000087 stabilizing effect Effects 0.000 claims abstract description 12
- 238000007789 sealing Methods 0.000 claims description 25
- 239000000203 mixture Substances 0.000 claims description 22
- 230000000007 visual effect Effects 0.000 claims description 15
- 239000002904 solvent Substances 0.000 claims description 13
- 239000011259 mixed solution Substances 0.000 claims description 3
- 238000005303 weighing Methods 0.000 claims description 2
- 238000002474 experimental method Methods 0.000 description 6
- 239000000243 solution Substances 0.000 description 6
- 238000001308 synthesis method Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 238000009825 accumulation Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 238000013329 compounding Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G—PHYSICS
- 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
- G01N25/02—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering
- G01N25/12—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering of critical point; of other phase change
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Abstract
The invention relates to a fluid phase balance measuring device and a method suitable for different volatility characteristics, wherein the device comprises: the gas sample bottle, the gas cavity, the balance kettle, the gas buffer cavity and the pressure stabilizing gas bottle are sequentially communicated through the pipeline, and the gas cavity, the balance kettle and the gas buffer cavity are all arranged in a constant temperature tank with circulating fan blades; the vacuum pump is communicated with a pipeline between the gas sample bottle and the gas cavity through a pipeline; the injection pump is respectively communicated with the balance kettle and the gas buffer cavity through pipelines; and the data acquisition system is respectively connected with the gas cavity and the balance kettle and is used for measuring and collecting data of the gas cavity and the balance kettle. The balance kettle is internally provided with the piston, so that the pressure can be regulated, the volume can be changed, the calibration of the volume of the balance kettle in the measurement process is avoided, and the density of the nonvolatile liquid is not required to be known; the piston is arranged in the gas buffer cavity, so that the pressure stability in bubble point measurement can be realized, and the measurement error caused by incompressibility of liquid phase is avoided.
Description
Technical Field
The invention relates to a fluid phase balance measuring device and method suitable for different volatility characteristics, and belongs to the technical field of fluid thermophysical property measurement.
Background
The phase balance property of the mixed fluid is a basic parameter for researching a non-azeotropic fluid system, and has important significance in the fields of refrigeration, petroleum, chemical industry, aerospace and the like. Experimental measurement is the most reliable way to obtain such property data, wherein the composition ratio of a known mixed system is divided into an analysis method and a synthesis method according to whether the known mixed system is required, and the former is obtained by a certain analysis means without the known mixed system ratio; the latter requires known compounding ratios of the mixed systems and based thereon measurement of the phase equilibrium point. Both methods have many applications under different experimental requirements.
The isovolumetric saturation method is a typical sampling-free analysis method, is mainly used for measuring the solubility (phase balance) of gas in a non-volatile solvent, and has the advantages of simple experimental system, easy operation and the like. However, there are two significant drawbacks to the current isovolumetric saturation measurement systems: firstly, the volumes of a gas cavity and a mixing cavity need to be calibrated, and excessive volume calibration is easy to cause error accumulation, so that the measurement accuracy is reduced; secondly, the density data of the known liquid phase solvent under the experimental temperature and pressure are needed, which clearly increases the experimental cost and reduces the application range of the experimental system.
The visual synthesis method is a typical fluid phase balance test method requiring known composition ratios of a mixed system, is suitable for the measurement of volatile fluid in the system, has the characteristics of simple principle and strong applicability, and becomes one of the most widely applied phase balance measurement means. However, the method has high proficiency in the operation of the experimenter, especially in the measurement of bubble point pressure, because the liquid phase is incompressible, very small volume change can also cause very large pressure change, so that the experimenter is required to judge the gas-liquid phase change point very accurately, the operation difficulty and error of the experiment are increased, and the measured bubble point pressure can be far beyond the actual value.
Disclosure of Invention
Aiming at the technical problems, the invention designs a fluid phase balance measuring device and a fluid phase balance measuring method which comprise a variable volume balance kettle and a double gas cavity and are suitable for different volatility characteristics by combining an equal volume saturation method and a visual synthesis method.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a fluid phase balance measurement device adapted for use with different volatility characteristics, comprising:
the gas sample bottle, the gas cavity, the balance kettle, the gas buffer cavity and the pressure stabilizing gas bottle are sequentially communicated through the pipeline, and the gas cavity, the balance kettle and the gas buffer cavity are all arranged in a constant temperature tank with circulating fan blades;
the vacuum pump is communicated with a pipeline between the gas sample bottle and the gas cavity through a pipeline;
the injection pump is respectively communicated with the balance kettle and the gas buffer cavity through pipelines;
and the data acquisition system is respectively connected with the gas cavity and the balance kettle and is used for measuring and collecting data of the gas cavity and the balance kettle.
The fluid phase balance measuring device preferably comprises a balance kettle, an upper flange end cover and a lower flange end cover, wherein the upper flange end cover and the lower flange end cover are positioned at the upper end and the lower end of the visual mixing cavity, a movable sealing piston, a hand-operated push rod and an electromagnetic rotor are arranged in the visual mixing cavity, one end of the hand-operated push rod is connected with the movable sealing piston, the other end of the hand-operated push rod penetrates through a fluid lower inlet and outlet on the lower flange end cover and is positioned outside the visual mixing cavity, and an electromagnetic coil is arranged outside the visual mixing cavity.
The fluid phase balance measuring device is characterized in that a first pressure transmitter and a first thermometer are arranged on the gas cavity, a second pressure transmitter and a second thermometer are arranged on the balance kettle, and the first pressure transmitter, the first thermometer, the second pressure transmitter and the second thermometer are all connected with the data acquisition system.
Preferably, the data acquisition system comprises an electronic computer and a digital multimeter, wherein the electronic computer and the digital multimeter are connected, and the digital multimeter is respectively connected with the first pressure transmitter, the first thermometer, the second pressure transmitter and the second thermometer.
In the fluid phase balance measuring device, preferably, a gas buffer cavity is arranged in the gas buffer cavity and is provided with a movable sealing piston, and a pipeline connecting the gas buffer cavity and the pressure stabilizing gas cylinder is provided with a second pressure reducing valve.
In the fluid phase balance measuring device, preferably, a first valve is arranged on a pipeline connected between the vacuum pump and the gas sample bottle and a gas cavity, a first pressure reducing valve, a second valve and a third valve are arranged on a pipeline connected between the gas sample bottle and the gas cavity, a fourth valve is arranged on a pipeline connected between the gas cavity and the balance kettle, and a fifth valve is arranged on a pipeline connected between the balance kettle and the injection pump.
In the fluid phase balance measuring device, preferably, a sixth valve is arranged on a pipeline connected with the gas buffer cavity of the balance kettle, a seventh valve is arranged on a pipeline connected with the injection pump of the gas buffer cavity, and an eighth valve is arranged on a pipeline connected with the pressure stabilizing gas cylinder of the gas buffer cavity.
The second aspect of the present invention provides a method for measuring the phase balance of a non-volatile fluid and a gas with unknown composition ratios by using the fluid phase balance measuring device, comprising the following steps:
step 1): closing a sixth valve, a seventh valve and an eighth valve, opening a first valve, a second valve, a third valve, a fourth valve and a fifth valve, and vacuumizing a system pipeline by using a vacuum pump;
step 2): closing the first valve, the second valve and the third valve, injecting the solvent from the fluid upper inlet and outlet of the balance kettle by using an injection pump, then closing the fourth valve and the fifth valve, and weighing the fluid massm 2 ；
Step 3): opening the first valve, the second valve and the third valve, adjusting the first pressure reducing valve, and injecting the gas in the gas sample bottle into the gas cavity to enable the pressure to be slightly higher than the target pressure; then the second valve is closed to record the temperature in the gas cavityT 0 And pressurep 0 ；
Step 4): opening the fourth valve again, and adjusting the movable sealing piston to move downwards so that part of gas enters the balance kettle; then closing the fourth valve, and adjusting the movable sealing piston to move upwards to ensure that the pressure in the balance kettle is greater than the pressure in the gas cavity, so that the gas phase and the liquid phase are fully mixed;
step 5): opening the fourth valve again, regulating the movable sealing piston to move upwards to completely discharge the gas phase part into the balance kettle, and then recording the temperature in the gas cavity at the moment respectivelyT 1 Pressure and forcep 1 And balancing the temperature in the kettleT 2 Pressure and forcep 2 ；
Step 6): according to the temperature measured in step 3) and step 5)T 0 、T 1 And pressurep 0 、p 1 Calculating by using a state equation to obtain the front and rear gas densitiesρ 0 Andρ 1 and obtaining the front and back gas mole amount by the volume of the gas cavityn 0 Andn 1 the gas amount absorbed by the solvent is%n 0 －n 1 )；
According to the mass of the liquid solvent injected in the step 2)m 2 Calculating to obtain the liquid molar quantityn 2 At the temperature ofT 2 And pressurep 2 Solubility of gas underx=(n 0 －n 1 )/n 2 。
The third aspect of the present invention provides a method for measuring the phase balance of a volatile fluid with a known composition ratio by using the fluid phase balance measuring device, comprising the following steps:
step 1): the second pressure transmitter is moved to be arranged between the balance kettle and the sixth valve; closing the third valve and the eighth valve, opening the first valve, the second valve, the fourth valve, the fifth valve, the sixth valve and the seventh valve, and vacuumizing a system pipeline by using a vacuum pump;
step 2): closing the first valve and the vacuum pump, opening the eighth valve, adjusting the second pressure reducing valve, and filling gas into the gas buffer cavity from the pressure stabilizing gas cylinder; subsequently closing the eighth valve;
step 3): closing the second valve, the fourth valve and the fifth valve, injecting the proportioned mixed solution from the fluid lower inlet and outlet of the balance kettle by using an injection pump, then closing the sixth valve and the seventh valve, and adjusting the movable sealing piston to move upwards to ensure that the fluid is in a gas-liquid two-phase state; or closing the fourth valve, adjusting the first pressure reducing valve, injecting the proportioned mixed gas into the balance kettle from the gas sample bottle, and then closing the second valve, the fifth valve, the sixth valve and the seventh valve;
step 4): adjusting the movable sealing piston to move downwards to liquefy the fluid, and opening a sixth valve when the fluid is liquefied; the movable sealing piston is then moved further downwards until the mixed fluid is completely liquefied, and the mixture is left to stand, and the second pressure transmitter is countedp b I.e., the bubble point pressure of the mixed fluid at the known composition and the temperature indicated by the second thermometer;
step 5): closing the sixth valve, regulating the movable sealing piston to move upwards until the mixed fluid is completely vaporized, standing, and indicating the number of the second pressure transmitterp d I.e. the dew point pressure of the mixed fluid at the known composition and temperature indicated by the second thermometer.
Due to the adoption of the technical scheme, the invention has the following advantages:
1. the balance kettle is arranged between the two gas cavities, and can effectively realize the determination of the phase balance of fluids with different volatility characteristics through the valve switching pipeline.
2. The balance kettle is internally provided with the piston, so that the pressure can be regulated, the volume can be changed, the calibration of the volume of the balance kettle in the measurement process is avoided, and the density of the nonvolatile liquid is not required to be known; the piston is arranged in the gas buffer cavity, so that the pressure stability in bubble point measurement can be realized, and the measurement error caused by incompressibility of liquid phase is avoided.
Drawings
FIG. 1 is a schematic diagram of a fluid phase balance measurement apparatus suitable for different volatility characteristics according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a balance kettle according to the embodiment of the present invention;
the figures are marked as follows:
1-gas sample bottle, 2-first pressure reducing valve, 3-thermostatic bath, 4-circulating fan blade, 5-first valve, 6-second valve, 7-third valve, 8-first pressure transmitter, 9-first thermometer, 10-gas cavity, 11-fourth valve, 12-fifth valve, 13-second pressure transmitter, 14-second thermometer, 15-metal bracket, 16-balance kettle, 17-sixth valve, 18-seventh valve, 19-gas buffer cavity, 20-eighth valve, 21-second pressure reducing valve, 22-syringe pump, 23-camera, 24-steady pressure gas cylinder, 25-vacuum pump, 26-electronic computer, 27-digital multimeter, 28-direct current power supply, 29-visual mixing cavity, 30-lower flange end cover, 31-upper flange end cover, 32-upper inlet and outlet, 33-lower inlet and outlet of fluid, 34-hand-operated push rod, 35-electromagnetic coil, 36-movable sealing piston, 37-electromagnetic rotor.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are intended to be within the scope of the present disclosure.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The terms "first," "second," "third," "fourth," and the like as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof, but does not exclude other elements or items. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.
For ease of description, spatially relative terms, such as "inner," "outer," "lower," "upper," and the like, may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.
The existing isovolumetric saturation method measuring system has two obvious defects: firstly, the volumes of a gas cavity and a mixing cavity need to be calibrated, and excessive volume calibration is easy to cause error accumulation, so that the measurement accuracy is reduced; secondly, the density data of the known liquid phase solvent under the experimental temperature and pressure are needed, which clearly increases the experimental cost and reduces the application range of the experimental system. The visual synthesis method is a typical fluid phase balance test method requiring known composition ratios of a mixed system, is suitable for the measurement of volatile fluid in the system, has the characteristics of simple principle and strong applicability, and becomes one of the most widely applied phase balance measurement means. However, the method has high proficiency in the operation of the experimenter, especially in the measurement of bubble point pressure, because the liquid phase is incompressible, very small volume change can also cause very large pressure change, so that the experimenter is required to judge the gas-liquid phase change point very accurately, the operation difficulty and error of the experiment are increased, and the measured bubble point pressure can be far beyond the actual value.
Therefore, in order to solve the problems and improve the application range of the experimental system, the invention combines an equal volume saturation method and a visual synthesis method, and designs a fluid phase balance measuring device and method which comprise a variable volume balance kettle and a double gas cavity and are applicable to different volatility characteristics.
As shown in fig. 1 and 2, the fluid phase balancing device suitable for different volatility characteristics provided by the present invention mainly includes: the gas sample bottle 1, the first pressure reducing valve 2, the constant temperature tank 3, the circulating fan blade 4, the first valve 5, the second valve 6, the third valve 7, the first pressure transmitter 8, the first thermometer 9, the gas cavity 10, the fourth valve 11, the fifth valve 12, the second pressure transmitter 13, the second thermometer 14, the metal bracket 15, the balance kettle 16, the sixth valve 17, the seventh valve 18, the gas buffer cavity 19, the eighth valve 20, the second pressure reducing valve 21, the injection pump 22, the camera 23, the pressure stabilizing gas bottle 24, the vacuum pump 25, the electronic computer 26, the digital multimeter 27 and the direct current power supply 28.
The gas sample bottle 1 is communicated with the gas cavity 10 and the balance kettle 16 through a first pressure reducing valve 2 and a stainless steel pipeline, and is used for injecting pure gas with certain pressure or mixed gas with known composition ratio. The gas buffer cavity 19 is internally provided with a movable sealing piston, is integrally arranged between the balance kettle 16 and the pressure stabilizing gas cylinder 24 and is used for injecting gas with pressure regulated by the second pressure reducing valve 21, so that the pressure in the balance kettle 16 is stable during bubble point measurement. The gas chamber 10, the balance kettle 16 and the gas buffer chamber 19 are all placed in the constant temperature tank 3 with the circulating fan blades 4 to ensure that the experimental temperature is maintained near the designated temperature. The injection pump 22 is connected with the balance kettle 16 through a three-way head and a stainless steel pipeline and is used for injecting pure liquid with certain pressure or mixed liquid with known composition ratio. The vacuum pump 25 is connected to the system piping via a three-way connection for evacuating the piping at the beginning of the experiment.
The digital multimeter 27 is respectively connected with the first thermometer 9 and the second thermometer 14, and the direct current power supply 28 is respectively connected with the first pressure transmitter 8 and the second pressure transmitter 13 and is used for supplying power and measuring temperature and pressure data in the gas cavity 10, the balance kettle 16 and the constant temperature tank 3. The electronic computer 26 is connected to a digital multimeter 27 for dynamically recording measured temperature and pressure values.
Different valves are arranged in the system for controlling the fluid passage, wherein the first valve 5 is connected with the vacuum pump 25, the second valve 6 is connected with the gas sample bottle 1 through the first pressure reducing valve 2, the third valve 7 is connected with the gas cavity 10, the fourth valve 11 is connected with the balance kettle 16, the fifth valve 12 is connected with the injection pump 22, the sixth valve 17 is arranged between the balance kettle 16 and the gas buffer cavity 19, the seventh valve 18 is arranged between the gas buffer cavity 19 and the injection pump 22, and the eighth valve 20 is connected with the pressure stabilizing gas bottle 24 through the second pressure reducing valve 21.
Referring to fig. 2, the balance tank 16 mainly includes: the visual mixing cavity 29, a lower flange end cover 30, an upper flange end cover 31, a fluid upper inlet and outlet 32, a fluid lower inlet and outlet 33, a hand-operated push rod 34, an electromagnetic coil 35, a movable sealing piston 36 and an electromagnetic rotor 37. Wherein the visual mixing chamber 29 is placed between the upper and lower flange end caps as the core unit for the measurement. The fluid upper inlet and outlet 32 and the fluid lower inlet and outlet 33 are respectively positioned in the upper flange end cover and the lower flange end cover and are used for injecting and discharging fluid to be tested. A movable sealing piston 36 is connected to the hand-operated push rod 34 to effect up and down adjustment of the position for changing the pressure in the balance tank 16 and for exhausting undissolved gas. The electromagnetic rotor 37 is controlled by the external electromagnetic coil 35 to realize rotation in the mixing chamber 29 so as to accelerate the mixing of the solutions uniformly.
The using method of the device for measuring the balance (solubility) of the nonvolatile fluid with the gas phase with unknown composition ratio comprises the following steps:
1) Pulling the piston 36 to the lower end, opening the third valve 7, the fourth valve 11, the fifth valve 12, the sixth valve 17 and the seventh valve 18, and closing the first valve 5, the second valve 6 and the eighth valve 20, injecting pure water into the system line using the syringe pump 22, and closing the fifth valve 12 and the seventh valve 18 when the balance tank 16 is filled with liquid. After 1 hour of holding, if the system pressure change was less than 1kPa, the system was considered to have good sealability.
2) The experiment pipeline is purged with gas, and pure water is discharged. The piston 36 is pushed to the upper end, the sixth valve 17, the seventh valve 18 and the eighth valve 20 are closed, the first valve 5, the second valve 6, the third valve 7, the fourth valve 11 and the fifth valve 12 are opened, and the system pipeline is vacuumized by using the vacuum pump 25.
3) The first valve 5, the second valve 6 and the third valve 7 are closed, a certain amount of pure solvent is injected from the fluid upper inlet 32 of the balance tank 16 using the injection pump 22, and then the fourth valve 11 and the fifth valve 12 are closed. The balance kettle 16 is taken down, and the mass thereof is weighed on a balancem 21 And then reinstalled back into the system. Molar amount of liquid phase solvent injected
（1）
Wherein, in the formula,m 20 to balance the net mass of the tank before any fluid is injected,M L is the molar mass of the solvent.
4) The first valve 5, the second valve 6 and the third valve 7 are opened, the first pressure reducing valve 2 is adjusted, and the gas in the gas sample bottle 1 is injected into the gas cavity 10, so that the pressure is slightly higher than the experimental target pressure. The second valve 6 is then closed, after about 20 minutes, and the indication of the first thermometer 9 and the first pressure transmitter 8 is recorded as the temperature in the gas chamber 10T 0 And pressurep 0 Further, the density of the gas at the moment can be obtained according to the state equationρ 0 The molar amount thereofn 0 The method comprises the following steps:
（2）
in the method, in the process of the invention,m 0 for the total mass of gas at this point,M G in order to be a molar mass of the gas,V 1 is the volume of the gas chamber.
5) The fourth valve 11 is opened again and the regulating piston 36 is moved downwards so that part of the gas enters the balancing tank 16. The fourth valve 11 is then closed and the piston 36 is adjusted to move upward to bring the pressure in the balance tank 16 to a pressure greater than the pressure in the gas chamber 10. And then, opening the electromagnetic rotor 37 to fully mix the gas phase and the liquid phase, and considering that the mixed system reaches the gas-liquid phase balance when the pressure change of the balance kettle within 20 minutes is less than 1 percent.
6) The fourth valve 11 is opened again and the slow adjusting piston 36 is moved upwards so that the gas phase part just completely exits the balancing tank 16 and re-enters the gas chamber 10. When the pressure change of the balance kettle in 20 minutes is less than 1%, the indication of the first thermometer 9 and the first pressure transmitter 8 at the moment are respectively recorded as the temperature in the gas cavity 10T 1 And pressurep 1 The second thermometer 14 and the second pressure transmitter 13 are registered as the temperature in the balance tank 16T 2 And pressurep 2 . The solubility (mole fraction) of the measured gas in the non-volatile solvent is:
（3）
in the formula deltanIn order to obtain a molar quantity of dissolved gas,n 1 means of solution andn 0 the same applies.
7) Closing the fourth valve 11, increasing the set temperature of the constant temperature tank 3, and repeating the step 6) after the temperature is stable to obtain the gas solubility under the new conditionx'。
To ensure accuracy and reproducibility of the experimental results, 3 measurements were made for each experimental point.
The using method of the device for measuring the phase balance of the volatile fluid with known composition ratio comprises the following steps:
1) The movable sealing piston 36 is pulled to the lower end, the third valve 7, the fourth valve 11, the fifth valve 12, the sixth valve 17 and the seventh valve 18 are opened, the first valve 5, the second valve 6 and the eighth valve 20 are closed, pure water is injected into the system pipeline by using the injection pump 22, and when the balance tank 16 is filled with liquid, the fifth valve 12 and the seventh valve 18 are closed. After 1 hour of holding, if the system pressure change was less than 1kPa, the system was considered to have good sealability.
2) The experiment pipeline is purged with gas, and pure water is discharged. Moving the second pressure transmitter 13 between the balance tank 16 and the sixth valve 17; closing the third valve 7 and the eighth valve 20, opening the first valve 5, the second valve 6, the fourth valve 11, the fifth valve 12, the sixth valve 17 and the seventh valve 18, and vacuumizing the system pipeline by using a vacuum pump 25;
3) The first valve 5 and the vacuum pump 25 are closed, the eighth valve 20 is opened, the second pressure reducing valve 21 is adjusted, gas with a certain pressure is filled into the gas buffer chamber 19 from the pressure stabilizing gas cylinder 24, and then the eighth valve 20 is closed. The injected gas pressure should be near and slightly lower than the estimated bubble point pressure, which may be gradually increased during the course of the experiment if the bubble point pressure is difficult to initially estimate.
4) For the mixed composition measurement of liquid under normal temperature difference, the second valve 6, the fourth valve 11 and the fifth valve 12 are closed, the mixed solution which is proportioned is injected from the fluid lower inlet and outlet 33 of the balance kettle 16 by using the injection pump 22, then the sixth valve 17 and the seventh valve 18 are closed, and the upward movement of the piston 36 is regulated, so that the fluid is ensured to be in a gas-liquid two-phase state; for the mixed composition measurement of the gas under normal temperature difference, the fourth valve 11 is closed, the first pressure reducing valve 2 is adjusted, the proportioned mixed gas is injected into the balance kettle 16 from the gas sample bottle 1, the piston 36 is kept at a higher position, and the piston can be ensured to completely liquefy the mixture before the piston moves to a lower limit position. The second valve 6, the fifth valve 12, the sixth valve 17 and the seventh valve 18 are then closed.
5) The regulating piston 36 moves downwards to liquefy the fluid and simultaneously opens the electromagnetic rotor to mix the fluid thoroughly and when it is near full liquefaction, the sixth valve 17 is opened. Subsequently, piston 36 is continued to be moved downward until the mixed fluid is completely liquefied, and when the balance tank pressure change is less than 1% within 20 minutes, an indication of the time at which the second pressure transducer 13 was recordedp b I.e., the bubble point pressure of the mixed fluid at the known composition and temperature indicated by the second thermometer 14.
6) The sixth valve 17 is closed, the regulating piston 36 is moved upwards until the mixed fluid is completely vaporized, and when the pressure change of the balance kettle in 20 minutes is less than 1%, the indication of the second pressure transmitter 13 is recorded at the momentp d I.e. the dew point pressure of the mixed fluid at the known composition and temperature indicated by the second thermometer 14.
7) Raising the set temperature of the constant temperature tank 3, and repeating the step 5) and the step 6) after the temperature is stabilized to obtain the bubble point pressure under the new temperature conditionp b ' and dew point pressurep d '。
To ensure accuracy and reproducibility of the experimental results, 3 measurements were made for each experimental point.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. A fluid phase balance measurement device adapted for use with different volatility characteristics, comprising:
the gas sample bottle (1), the gas cavity (10), the balance kettle (16), the gas buffer cavity (19) and the pressure stabilizing gas bottle (24) are sequentially communicated through pipelines, and the gas cavity (10), the balance kettle (16) and the gas buffer cavity (19) are all arranged in the constant temperature tank (3) with the circulating fan blade (4);
a vacuum pump (25) which is communicated with the pipeline between the gas sample bottle (1) and the gas cavity (10) through the pipeline;
the injection pump (22) is respectively communicated with the balance kettle (16) and the gas buffer cavity (19) through pipelines;
and the data acquisition system is respectively connected with the gas cavity (10) and the balance kettle (16) and is used for measuring and collecting data of the gas cavity and the balance kettle.
2. The fluid phase balance measuring device according to claim 1, wherein the balance kettle (16) comprises a visual mixing cavity (29), an upper flange end cover (31) and a lower flange end cover (30) which are positioned at the upper end and the lower end of the visual mixing cavity (29), a movable sealing piston (36), a hand-operated push rod (34) and an electromagnetic rotor (37) are arranged in the visual mixing cavity (29), one end of the hand-operated push rod (34) is connected with the movable sealing piston (36), a fluid lower inlet and outlet (33) of which the other end penetrates through the lower flange end cover (30) is positioned outside the visual mixing cavity (29), and an electromagnetic coil (35) is arranged outside the visual mixing cavity (29).
3. The fluid phase balance measuring device according to claim 2, characterized in that a first pressure transmitter (8) and a first thermometer (9) are arranged on the gas chamber (10), a second pressure transmitter (13) and a second thermometer (14) are arranged on the balance kettle (16), and the first pressure transmitter (8), the first thermometer (9), the second pressure transmitter (13) and the second thermometer (14) are all connected with the data acquisition system.
4. A fluid phase balance measuring device according to claim 3, characterized in that the data acquisition system comprises an electronic computer (26) and a digital multimeter (27), the electronic computer (26) and the digital multimeter (27) being connected, respectively, to the first pressure transmitter (8), the first thermometer (9), the second pressure transmitter (13) and the second thermometer (14).
5. The fluid phase balance measuring device according to claim 4, wherein a gas buffer chamber movable sealing piston is arranged in the gas buffer chamber (19), and a second pressure reducing valve (21) is arranged on a pipeline connecting the gas buffer chamber (19) and the pressure stabilizing gas cylinder (24).
6. The fluid phase balance measuring device according to claim 5, wherein a first valve (5) is arranged on a pipeline connected between the vacuum pump (25) and the gas sample bottle (1) and the gas chamber (10), a first pressure reducing valve (2), a second valve (6) and a third valve (7) are arranged on a pipeline connected between the gas sample bottle (1) and the gas chamber (10), a fourth valve (11) is arranged on a pipeline connected between the gas chamber (10) and the balance kettle (16), and a fifth valve (12) is arranged on a pipeline connected between the balance kettle (16) and the injection pump (22).
7. The fluid phase balance measuring device according to claim 6, wherein a sixth valve (17) is arranged on a pipeline connecting the balance kettle (16) and the gas buffer cavity (19), a seventh valve (18) is arranged on a pipeline connecting the gas buffer cavity (19) and the injection pump (22), and an eighth valve (20) is arranged on a pipeline connecting the gas buffer cavity (19) and the steady-pressure gas cylinder (24).
8. A method of measuring the phase balance of a non-volatile fluid of unknown composition with a gas using the fluid phase balance measuring device of claim 7, comprising the steps of:
step 1): closing a sixth valve (17), a seventh valve (18) and an eighth valve (20), opening a first valve (5), a second valve (6), a third valve (7), a fourth valve (11) and a fifth valve (12), and vacuumizing a system pipeline by using a vacuum pump (25);
step 2): closing the first valve (5), the second valve (6) and the third valve (7), injecting the solvent from the fluid upper inlet (32) of the balance kettle (16) by using the injection pump (22), then closing the fourth valve (11) and the fifth valve (12), and weighing the fluid massm 2 ；
Step 3): opening a first valve (5), a second valve (6) and a third valve (7), adjusting the first pressure reducing valve (2), and injecting gas in the gas sample bottle (1) into a gas cavity (10) to enable the pressure to be slightly higher than the target pressure; subsequently, the second valve (6) is closed, and the temperature in the gas chamber (10) is recordedT 0 And pressurep 0 ；
Step 4): the fourth valve (11) is opened again, and the movable sealing piston (36) is regulated to move downwards, so that part of gas enters the balance kettle (16); then the fourth valve (11) is closed, and the movable sealing piston (36) is adjusted to move upwards, so that the pressure in the balance kettle (16) is higher than the pressure in the gas cavity (10), and the gas phase and the liquid phase are fully mixed;
step 5): the fourth valve (11) is opened again, the movable sealing piston (36) is regulated to move upwards, the gas phase part is completely discharged into the balance kettle (16), and the temperature in the gas cavity (10) at the moment is recorded respectivelyT 1 Pressure and forcep 1 And the temperature in the balance kettle (16)T 2 Pressure and forcep 2 ；
Step 6): according to the temperature measured in step 3) and step 5)T 0 、T 1 And pressurep 0 、p 1 Calculating by using a state equation to obtain the front and rear gas densitiesρ 0 Andρ 1 and the front and rear gas molar quantity is obtained by the volume of the gas cavity (10)n 0 Andn 1 the gas amount absorbed by the solvent is%n 0 －n 1 )；
According to the mass of the liquid solvent injected in the step 2)m 2 Calculating to obtain the liquid molar quantityn 2 At the temperature ofT 2 And pressurep 2 Solubility of gas underx=(n 0 －n 1 )/n 2 。
9. A method of measuring the phase balance of a volatile fluid of known composition using the fluid phase balance measuring device of claim 7, comprising the steps of:
step 1): the second pressure transmitter (13) is moved to be arranged between the balance kettle (16) and the sixth valve (17); closing the third valve (7) and the eighth valve (20), opening the first valve (5), the second valve (6), the fourth valve (11), the fifth valve (12), the sixth valve (17) and the seventh valve (18), and vacuumizing a system pipeline by using a vacuum pump (25);
step 2): closing the first valve (5) and the vacuum pump (25), opening the eighth valve (20), adjusting the second pressure reducing valve (21), and filling gas into the gas buffer cavity (19) from the pressure stabilizing gas cylinder (24); subsequently closing the eighth valve (20);
step 3): closing the second valve (6), the fourth valve (11) and the fifth valve (12), injecting the proportioned mixed solution from the fluid lower inlet and outlet (33) of the balance kettle (16) by using an injection pump (22), then closing the sixth valve (17) and the seventh valve (18), and adjusting the movable sealing piston (36) to move upwards to ensure that the fluid is in a gas-liquid two-phase state; or closing the fourth valve (11), adjusting the first pressure reducing valve (2), injecting the proportioned mixed gas into the balance kettle (16) from the gas sample bottle (1), and then closing the second valve (6), the fifth valve (12), the sixth valve (17) and the seventh valve (18);
step 4): adjusting the movable sealing piston (36) to move downwards to liquefy the fluid, and opening a sixth valve (17) when liquefying; subsequently, the movable sealing piston (36) is moved downwards until the mixed fluid is completely liquefied, and the pressure sensor is kept still, and the indication of the second pressure transmitter (13) is displayedp b I.e., the bubble point pressure of the mixed fluid at a temperature indicated by the known composition and the second thermometer (14);
step 5): closing the sixth valve (17), regulating the upward movement of the movable sealing piston (36) until the mixed fluid is completely vaporized, standing, and indicating the number of the second pressure transmitter (13)p d I.e. the dew point pressure of the mixed fluid at a temperature indicated by the known composition and the second thermometer (14).
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