CN112162003B - Device and method for measuring width of micro-scale flow system crystal metastable region - Google Patents
Device and method for measuring width of micro-scale flow system crystal metastable region Download PDFInfo
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- CN112162003B CN112162003B CN202010859307.2A CN202010859307A CN112162003B CN 112162003 B CN112162003 B CN 112162003B CN 202010859307 A CN202010859307 A CN 202010859307A CN 112162003 B CN112162003 B CN 112162003B
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- 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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- 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
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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
- G01N25/14—Investigating or analyzing materials by the use of thermal means by using distillation, extraction, sublimation, condensation, freezing, or crystallisation
- G01N25/145—Accessories, e.g. cooling devices
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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
- G01N2021/8411—Application to online plant, process monitoring
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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
- G01N2021/8477—Investigating crystals, e.g. liquid crystals
Abstract
The device for measuring the width of the crystal metastable zone of the micro-scale flow system comprises a temperature control system, a microscope, a camera, a computer and an injection pump, wherein the temperature control system consists of a constant-temperature circulating water bath, a first heat-preservation jacket, a second heat-preservation jacket and a temperature sensor. The invention relates to a method for measuring the width of a micro-scale flow system crystallization metastable zone, which comprises the steps of injecting a solution to be measured, which has the temperature of an initial test temperature and reaches a saturated state at the initial test temperature, into a micro-channel at a constant flow rate by using the measuring device through an injection pump, shooting the liquid to be measured in the micro-channel in real time by using a camera in combination with the amplification effect of a microscope on the micro-channel, capturing the crystal-out state of the fluid to obtain the crystal-out point temperature, and calculating the difference between the initial test temperature and the crystal-out point temperature, wherein the difference is the width of the micro-scale flow system crystallization metastable zone of the solution to be measured. The device and the method provide quantitative data analysis support for the research of the micro-channel-crystallization coupling technology.
Description
Technical Field
The invention belongs to the field of crystal data determination, and particularly relates to a device and a method for determining the width of a metastable zone of micro-scale flow system crystals.
Background
In chemical and pharmaceutical industries, crystallization is used as an effective separation and refining technology and widely applied to preparation and purification of fine chemicals and biological products. In order to obtain crystal products with required quality indexes, industrial crystallization is generally operated in a crystallization metastable zone. The metastable zone is a region (range) between a solubility curve of a solution system, i.e., the mass of a solute dissolved when a solid substance is saturated in 100g of a solvent at a certain temperature, and a supersolubility, i.e., the limit solubility of the solute when the solution is supersaturated at a certain temperature and crystal nuclei are to be spontaneously generated. The metastable zone width is the difference between the temperature at which the solution system reaches saturation and the temperature at the point of crystallization. The crystallization operation is first to determine the metastable zone width of the crystallization system.
The micro-channel has the advantages of high transmission rate, good operation performance and the like due to the micronization of the characteristic dimension,Controllable, high efficiency and the like.With the rapid development of the micro chemical technology and the deep knowledge of the flow mass transfer process of the micro channel,microchannel and crystallization process coupling The operation is carried out as follows. The operation utilizes a microFeatures of the channelPrecise control of the solution in the microchannelUnder micro-mixing to make the concentration of the solution uniform and strictly atMetastableAnd (c) to obtain a high quality crystalline product.To realizeThe precise regulation and control of the micro-channel-crystallization coupling process must determine the width of the crystallization metastable zone in the micro-scale flow system. The accurate measurement of the metastable zone has important significance for the research of the micro-channel-crystal coupling technology. However, to date, there has been no report on the determination of the width of the metastable region of crystallization under different flow conditions in microchannels.
Is often used for judgmentThe methods for crystal nucleation and metastable zone determination mainly include visual method, laser method, etc. However, because the characteristic size of the microchannel is small, the number of the first crystal nuclei is very small, and interference factors such as small fluctuation of the interface and the like cause that when the first crystal nuclei appear, the visual detection method with the detection precision generally more than 10 μm is difficult to respond to the appearance of the crystal nuclei in time, and the light intensity mutation signal corresponding to the laser method is difficult to detect and determine. Chinese patent CN 201210132413.6 provides a method for measuring solution concentration by on-line monitoring, which utilizes a relation curve corresponding to temperature, conductivity and solution concentration, determines the crystallization temperature of a system according to a conductivity mutation point in the cooling process of the solution system, and determines a supersolubility curve of a solute in a solvent, thereby determining a metastable zone of the system. However, in this method the conductivity measuring deviceThe probe is oversized compared with the micro-channel and cannot extend into the micro-channel to enter Line contact measurementTherefore, the metastable zone of the micro-scale flow system cannot be measured.
Therefore, the metastable zone measuring method in the prior art can not solve the problem of measuring the width of the metastable zone of the flow system crystal under the microscale. Therefore, there is a need to develop an apparatus and method for determining the width of the metastable region of a crystal suitable for use in microscale flow systems.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a device and a method for measuring the width of a micro-scale flow system crystallization metastable zone so as to realize accurate measurement of the width of the micro-scale flow system crystallization metastable zone.
The invention relates to a device for measuring the width of a micro-scale flow system crystallization metastable zone, which comprises:
the temperature control system is used for controlling the temperature of the solution to be measured when the solution flows through the microchannel observation section; the temperature control system consists of a constant-temperature circulating water bath, a first heat-preservation jacket, a second heat-preservation jacket and a temperature sensor, wherein the first heat-preservation jacket and the second heat-preservation jacket are sleeved on the microchannel at intervals, the intervals form a microchannel observation section, a water outlet of the constant-temperature circulating water bath is respectively connected with water inlets of the first heat-preservation jacket and the second heat-preservation jacket through pipe fittings, a water inlet of the constant-temperature circulating water bath is respectively connected with water outlets of the first heat-preservation jacket and the second heat-preservation jacket through pipe fittings, and the temperature sensor is arranged on the pipe fitting close to the microchannel observation section so as to monitor the temperature of the solution to be detected when the solution flows through the microchannel observation section;
the microscope is used for placing and fixing the microchannel and observing the state of the solution to be detected flowing through the microchannel observation section;
the camera is combined with an ocular lens of the microscope and is used for shooting the state of the solution to be measured when the solution flows through the microchannel observation section;
the computer is connected with the signal output end of the camera and used for converting the image signal from the camera into an image and storing the image;
and the injection pump is used for conveying the solution to be detected into the micro-channel.
In order to ensure that the solution to be measured flows stably in the observation section of the microchannel, in the device for measuring the width of the crystal metastable zone of the microscale flow system, the length of the first heat-preserving jacket is at least 3/4 of the length of the microchannel, the first heat-preserving jacket is sleeved on the section of the liquid inlet end of the microchannel, the second heat-preserving jacket is sleeved on the section of the liquid outlet end of the microchannel, and the distance between the first heat-preserving jacket and the second heat-preserving jacket is convenient for the microscope objective to adjust the focal length for determination.
The invention discloses a method for measuring the width of a metastable zone of micro-scale flow system crystal, which uses the measuring device and comprises the following steps:
(1) fixing the micro-channel sleeved with the first heat-insulating jacket and the second heat-insulating jacket on an objective table of a microscope, aligning a microscope objective with a micro-channel observation section, starting a camera combined with an eyepiece of the microscope, observing the interior of the micro-channel, shooting a focal plane area in the micro-channel, and starting a computer to receive an image signal;
(2) starting a constant-temperature circulating water bath, setting the temperature of circulating water as an initial test temperature, filling the first heat-preservation jacket and the second heat-preservation jacket with circulating water, measuring the temperature close to the microchannel observation section in real time through a temperature sensor, and controlling the microchannel observation section to be at the initial test temperature;
(3) starting an injection pump, injecting a solution to be detected, the temperature of which is an initial test temperature and reaches a saturated state at the initial test temperature, into a micro-channel at a constant flow rate through the injection pump, taking an image as a background image after the solution to be detected flows stably, then reducing the circulating water temperature by 1 ℃, keeping the flow rate of the solution to be detected unchanged, observing the fluid state in the micro-channel in real time for at least 2min, shooting the image and comparing the image with the background image, when no crystal is precipitated under the condition, reducing the circulating water temperature by 1 ℃ and keeping the flow rate of the solution to be detected unchanged, observing the fluid state in the micro-channel for at least 2min and shooting the image in real time, operating in the above way until crystals appear in an observation visual field, marking the temperature of the crystals appearing in the observation visual field as Tn, the temperature of the crystal-out point of the solution to be detected between Tn-Tn +1 ℃, then increasing the circulating water temperature to Tn +1 ℃, cooling the circulating water from Tn +1 ℃ by taking the highest precision of the temperature control system as a cooling gradient, keeping the flow of the solution to be measured unchanged during each cooling, observing the fluid state in the microchannel for at least 2min in real time, and shooting an image, wherein the corresponding temperature is the crystal outlet point temperature when crystals appear in the visual field again;
(4) and calculating the difference between the initial test temperature and the crystal outlet point temperature, wherein the difference is the width of the crystal metastable zone when the tested solution flows in a microscale mode.
After the steps are finished, injecting a good solvent of the crystallization system with the temperature higher than the initial measurement temperature into the microchannel by using an injection pump, cleaning the inner surface of the microchannel for not less than 10min, and then introducing hot air to sweep the inner surface of the microchannel for 10min so as to keep the inner surface of the microchannel clean and dry.
According to the method, when the solubility curve of a tested solution system is the prior art, the tested solution can be directly prepared according to the solubility curve and the initial testing temperature can be determined. When the tested solution system is a new solution system, a solubility curve of the solution system is constructed, the tested solution is prepared according to the solubility curve, and the initial testing temperature is determined.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention provides a device and a method for measuring the width of a micro-scale flow system crystallization metastable zone for the first time, which aims to explore and develop micro-channel-crystallizationThe coupling technique providesQuantitative data analysis support。
(2) The response of the method to the crystal nucleus formation is realized by comparing the front image and the rear image, the amplification effect of a microscope on the microchannel is combined, the camera is adopted to carry out real-time amplification, slow-down and continuous shooting on the liquid to be detected in the microchannel, and the crystal nucleus formation state of the liquid can be successfully captured, so that the crystal nucleus formation is accurately judged, and the precision of measuring the width of the metastable zone is ensured.
(3) Because the micro-channel has small volume and the consumption of raw materials is small, the method is suitable for measuring the width of the metastable zone of the expensive solution system crystal, and effectively reducesHigh priceSolutions ofSystem ofCost of metastable zone determination.
(4) The method of the invention has the advantages of easy change of the operating conditions and simple process control, thereby being used for measuring the width of the metastable zone of the crystallization of various solution systems.
(5) The device is easy to construct, simple to operate and convenient to clean, so that the method is favorable for popularization and application.
Drawings
FIG. 1 is a schematic structural diagram of a device for measuring the width of a metastable region of micro-scale flow system crystal according to the present invention and a schematic installation diagram of a micro-channel during testing; in the figure, 1-temperature sensor, 2-injection pump, 3-computer, 4-microscope, 5-camera, 6-microchannel, 7-1-first heat-preserving jacket, 7-2-second heat-preserving jacket, 8-constant temperature water inlet, 9-constant temperature water outlet, 10-constant temperature circulating water bath, and 11-liquid receiving container.
FIG. 2 is a graph showing the test results obtained in example 2, wherein (a) is a background picture and (b) is a picture of precipitated crystals.
Detailed Description
The following describes the apparatus and method for measuring the width of metastable zone of micro-scale flow system crystallization by embodiments and with reference to the drawings.
Example 1
In this example, the microchannel 6 is a quartz glass tube having an inner diameter of 0.9mm, an outer diameter of 1.5mm, and a length of 23 cm. The device for measuring the width of the metastable zone of the micro-scale flow system crystal is shown in figure 1 and comprises a temperature control system, a microscope 4, a camera 5, a computer 3 and a syringe pump 2. The temperature control system comprises a constant temperature circulating water bath 10, a first heat preservation jacket 7-1, a second heat preservation jacket 7-2 and a temperature sensor 1, wherein the length of the first heat preservation jacket 7-1 is 17.5cm, the first heat preservation jacket is sleeved on the section of the liquid inlet end of the micro-channel, the second heat preservation jacket 7-2 is sleeved on the section of the liquid outlet end of the micro-channel, the distance between the first heat preservation jacket and the second heat preservation jacket is 1cm, the distance forms a micro-channel observation section, the water outlet of the constant temperature circulating water bath 10 is respectively connected with the water inlets 8 of the first heat preservation jacket 7-1 and the second heat preservation jacket 7-2 through pipe fittings, the water inlet of the constant temperature circulating water bath 10 is respectively connected with the water outlets 9 of the first heat preservation jacket 7-1 and the second heat preservation jacket 7-2 through pipe fittings, the temperature sensor 1 is arranged on the pipe fittings close to the micro-channel observation section, so as to monitor the temperature of the solution to be measured when the solution flows through the observation section of the micro-channel; the microscope 4 is used for placing and fixing the microchannel 6 and observing the state of the solution to be detected flowing through the microchannel observation section; the camera 5 is combined with an ocular lens of the microscope and is used for shooting the state of the solution to be detected when the solution flows through the microchannel observation section; the computer 3 is connected with the signal output end of the camera and is used for converting the image signal from the camera into an image and storing the image; the syringe pump 2 is used to deliver the solution to be tested into the microchannel.
In this embodiment, the microscope 4 is a common optical microscope, the camera 5 has a continuous shooting function, the model is Canon EOS1300D, the computer 3 is a PC, the syringe pump 2 is a micro syringe pump, the model is LEAD flash TYD01, the temperature sensor 1 is a platinum resistance temperature sensor, the model of the platinum resistance is UHR-102, the model of the digital display Thermometer is RTD Thermometer CENTER 375, the model of the constant temperature circulating water bath 10 is juebo vivo RT4, and the first heat-preserving jacket 7-1 and the second heat-preserving jacket 7-2 are made of quartz glass.
Example 2
In this example, the width of the metastable zone was measured at a microscale flow of an aqueous solution of potassium dihydrogen phosphate which reached saturation at 40 ℃ using the apparatus described in example 1.
According to the existing potassium dihydrogen phosphate solubility curve, 33.5g of potassium dihydrogen phosphate crystals (analytically pure) are dissolved in 100g of deionized water to form a potassium dihydrogen phosphate aqueous solution which is saturated at 40 ℃ and is kept at a constant temperature of 40 ℃ for later use.
The measurement procedure of this example is as follows:
(1) fixing a micro-channel 6 sleeved with a first heat-insulating jacket 7-1 and a second heat-insulating jacket 7-2 on an objective table of a microscope 4, aligning a microscope objective with a micro-channel observation section, starting a camera 5 combined with an ocular lens of the microscope 4, observing the interior of the micro-channel, shooting a focal plane area in the micro-channel, and starting a computer 3 to receive an image signal;
(2) starting a constant-temperature circulating water bath 10, setting the temperature of circulating water to be 40 ℃, filling the first heat-preserving jacket 7-1 and the second heat-preserving jacket 7-2 with the circulating water, measuring the temperature close to the observation section of the microchannel in real time by using a temperature sensor 1, and controlling the observation section of the microchannel to be constantly at 40 ℃;
(3) starting an injection pump 2, injecting a potassium dihydrogen phosphate aqueous solution which has the temperature of 40 ℃ and reaches a saturated state at 40 ℃ into a microchannel 6 at the flow rate of 0.3ml/min through the injection pump, taking an image as a background image after the potassium dihydrogen phosphate aqueous solution flows stably (see (a) in figure 2), then reducing the circulating water temperature to 39 ℃, keeping the flow rate of the potassium dihydrogen phosphate aqueous solution unchanged, observing the fluid state in the microchannel for 2min in real time, and taking the image to compare with the background image, wherein no crystal appears in a visual field under the condition; then, reducing the temperature of the circulating water to 38 ℃, keeping the flow of the monopotassium phosphate water solution unchanged, observing the fluid state in the microchannel in real time for 2min, shooting an image, and showing that crystals appear in a visual field, wherein the temperature of a crystal-out point is 38-39 ℃; then, the temperature of circulating water is increased to 39 ℃, then the circulating water is cooled from 39 ℃ by taking the highest precision of a temperature control system of 0.1 ℃ as a cooling gradient, the flow of the monopotassium phosphate aqueous solution is kept at 0.3ml/min each time of cooling, the liquid state in the microchannel is observed for 2min in real time, images are shot, crystals appear in the visual field when the temperature of the circulating water is reduced to 38.1 ℃, the temperature of a crystal outlet point is 38.1 ℃, and the image (b) in the graph in the figure 2 is a crystal image shot in the microchannel with the inner diameter of 0.9mm by the monopotassium phosphate aqueous solution with the feeding flow of 0.3ml/min and the temperature of 38.1 ℃;
(4) and calculating the difference between the initial test temperature of 40 ℃ and the crystal forming point temperature of 38.1 ℃, wherein the difference of 1.9 ℃ is the width of the micro-scale flow system crystal metastable zone of the tested potassium dihydrogen phosphate aqueous solution.
Example 3
This example uses the apparatus described in example 1 to determine the width of the metastable zone of a flow system at micro-scale of an aqueous solution of potassium dihydrogen phosphate which reaches saturation at 40 ℃.
According to the existing potassium dihydrogen phosphate solubility curve, 33.5g of potassium dihydrogen phosphate crystals (analytically pure) are dissolved in 100g of deionized water to form a potassium dihydrogen phosphate aqueous solution which is saturated at 40 ℃ and is kept at a constant temperature of 40 ℃ for later use.
The measurement procedure of this example is as follows:
(1) fixing a micro-channel 6 sleeved with a first heat-insulating jacket 7-1 and a second heat-insulating jacket 7-2 on an objective table of a microscope 4, aligning a microscope objective with a micro-channel observation section, starting a camera 5 combined with an ocular lens of the microscope 4, observing the interior of the micro-channel, shooting a focal plane area in the micro-channel, and starting a computer 3 to receive an image signal;
(2) starting a constant-temperature circulating water bath 10, setting the temperature of circulating water to be 40 ℃, filling the first heat-preserving jacket 7-1 and the second heat-preserving jacket 7-2 with the circulating water, measuring the temperature close to the observation section of the microchannel in real time by using a temperature sensor 1, and controlling the observation section of the microchannel to be constantly at 40 ℃;
(3) starting an injection pump 2, injecting a potassium dihydrogen phosphate aqueous solution which has the temperature of 40 ℃ and reaches a saturated state at 40 ℃ into a microchannel 6 at the flow rate of 0.05ml/min through the injection pump, taking an image as a background image after the potassium dihydrogen phosphate aqueous solution flows stably, then reducing the circulating water temperature to 39 ℃, keeping the flow rate of the potassium dihydrogen phosphate aqueous solution unchanged, observing the fluid state in the microchannel for 2min in real time, and taking the image to compare with the background image, wherein no crystal appears in a visual field under the condition; then, reducing the temperature of the circulating water to 38 ℃, keeping the flow of the monopotassium phosphate water solution unchanged, observing the fluid state in the microchannel for 2min in real time, and shooting images, wherein crystals still do not appear in the visual field; then, reducing the temperature of the circulating water to 37 ℃, keeping the flow of the monopotassium phosphate water solution unchanged, observing the fluid state in the microchannel for 2min in real time, shooting an image, and showing that crystals appear in a visual field, wherein the temperature of a crystal-out point is 37-38 ℃; then, the temperature of circulating water is increased to 38 ℃, then the circulating water is cooled from 38 ℃ by taking the highest precision of a temperature control system as a cooling gradient, the flow of the potassium dihydrogen phosphate aqueous solution is kept at 0.05ml/min for each cooling, the liquid state in the microchannel is observed for 2min in real time, an image is shot, when the temperature of the circulating water is reduced to 37.7 ℃, crystals appear in a visual field, and the temperature of 37.7 ℃ is the temperature of a crystal forming point;
(4) and calculating the difference between the initial test temperature of 40 ℃ and the crystal-forming point temperature of 37.7 ℃, wherein the difference is 2.3 ℃ and is the width of the micro-scale flow system crystal metastable zone of the tested potassium dihydrogen phosphate aqueous solution.
Examples 2 and 3 show that: for the same solution to be tested, the width of the micro-scale flow system crystallization metastable zone increases as the flow rate decreases.
Example 4
This example uses the apparatus described in example 1 to determine the width of the metastable zone of a flow system at micro-scale of an aqueous solution of potassium dihydrogen phosphate which reaches saturation at 50 ℃.
According to the existing potassium dihydrogen phosphate solubility curve, 40.7g of potassium dihydrogen phosphate crystals (analytically pure) are dissolved in 100g of deionized water to form a potassium dihydrogen phosphate aqueous solution which is saturated at 50 ℃ and is kept at a constant temperature of 50 ℃ for later use.
The measurement procedure of this example is as follows:
(1) fixing a micro-channel 6 sleeved with a first heat-insulating jacket 7-1 and a second heat-insulating jacket 7-2 on an objective table of a microscope 4, aligning a microscope objective with a micro-channel observation section, starting a camera 5 combined with an ocular lens of the microscope 4, observing the interior of the micro-channel, shooting a focal plane area in the micro-channel, and starting a computer 3 to receive an image signal;
(2) starting a constant-temperature circulating water bath 10, setting the temperature of circulating water to be 50 ℃, filling the first heat-preservation jacket 7-1 and the second heat-preservation jacket 7-2 with the circulating water, measuring the temperature close to the observation section of the microchannel in real time through a temperature sensor 1, and controlling the observation section of the microchannel to be constantly at 50 ℃;
(3) starting an injection pump 2, injecting a potassium dihydrogen phosphate aqueous solution which is at 50 ℃ and reaches a saturated state at 50 ℃ into a micro-channel 6 at a flow rate of 0.1ml/min through the injection pump, taking an image as a background image after the potassium dihydrogen phosphate aqueous solution flows stably, then reducing the circulating water temperature to 49 ℃, keeping the flow rate of the potassium dihydrogen phosphate aqueous solution unchanged, observing the fluid state in the micro-channel in real time for 2min, and taking the image to compare with the background image, wherein crystals appear in a visual field under the condition, and the temperature of a crystal point is indicated to be 49-50 ℃; then, the temperature of circulating water is increased to 50 ℃, then the circulating water is cooled from 50 ℃ by taking the highest precision of a temperature control system as a cooling gradient, the flow of the potassium dihydrogen phosphate aqueous solution is kept at 0.1ml/min for each cooling, the liquid state in the microchannel is observed for 2min in real time, an image is shot, crystals appear in a visual field when the temperature of the circulating water is reduced to 49.2 ℃, and the temperature of a crystal-forming point is 49.2 ℃;
(4) and calculating the difference between the initial test temperature of 50 ℃ and the crystal forming point temperature of 49.2 ℃, wherein the difference of 0.8 ℃ is the width of the micro-scale flow system crystal metastable zone of the tested potassium dihydrogen phosphate aqueous solution.
Claims (2)
1. A device for measuring the width of a metastable zone of micro-scale flow system crystallization is characterized by comprising:
the temperature control system is used for controlling the temperature of the solution to be measured when the solution flows through the microchannel observation section; the temperature control system consists of a constant temperature circulating water bath (10), a first heat preservation jacket (7-1), a second heat preservation jacket (7-2) and a temperature sensor (1), the first heat preservation jacket and the second heat preservation jacket are sleeved on the micro-channel (6) at intervals, the interval forms a microchannel observation section, a water outlet of a constant-temperature circulating water bath (10) is respectively connected with a water inlet (8) of a first heat-preservation jacket (7-1) and a water inlet (8) of a second heat-preservation jacket (7-2) through a pipe fitting, a water inlet of the constant-temperature circulating water bath (10) is respectively connected with a water outlet (9) of the first heat-preservation jacket (7-1) and a water outlet (9) of the second heat-preservation jacket (7-2) through a pipe fitting, and a temperature sensor (1) is arranged on the pipe fitting close to the microchannel observation section so as to monitor the temperature of a solution to be detected when the solution flows through the microchannel observation section;
a microscope (4) for placing and fixing the microchannel and observing the state of the solution to be measured flowing through the observation section of the microchannel;
the camera (5) is combined with an ocular lens of the microscope and is used for shooting the state of the solution to be measured when the solution flows through the microchannel observation section;
the computer (3) is connected with the signal output end of the camera and used for converting the image signal from the camera into an image and storing the image;
a syringe pump (2) for delivering the solution to be tested into the microchannel;
the micro-channel (6) is a quartz glass tube;
the length of the first heat-insulating jacket (7-1) is at least 3/4 of the length of the microchannel, the first heat-insulating jacket is sleeved on the section of the liquid inlet end of the microchannel, the second heat-insulating jacket (7-2) is sleeved on the section of the liquid outlet end of the microchannel, and the distance between the first heat-insulating jacket and the second heat-insulating jacket is convenient for the microscope objective to adjust the focal length for determining.
2. A method for measuring the width of a metastable zone of micro-scale flow system crystallization, which is characterized by using the device of claim 1 and comprising the following steps:
(1) fixing the micro-channel sleeved with the first heat-insulating jacket and the second heat-insulating jacket on an objective table of a microscope, aligning a microscope objective with a micro-channel observation section, starting a camera combined with an eyepiece of the microscope, observing the interior of the micro-channel, shooting a focal plane area in the micro-channel, and starting a computer to receive an image signal;
(2) starting a constant-temperature circulating water bath, setting the temperature of circulating water as an initial test temperature, filling the first heat-preservation jacket and the second heat-preservation jacket with the circulating water, measuring the temperature close to the microchannel observation section in real time through a temperature sensor, and controlling the microchannel observation section to be constantly at the initial test temperature;
(3) starting an injection pump, injecting a solution to be detected, the temperature of which is an initial test temperature and reaches a saturated state at the initial test temperature, into a micro-channel at a constant flow rate through the injection pump, taking an image as a background image after the solution to be detected flows stably, then reducing the temperature of circulating water by 1 ℃, keeping the flow rate of the solution to be detected unchanged, observing the fluid state in the micro-channel in real time for at least 2min, comparing the image with the background image, when no crystal is precipitated under the condition, reducing the temperature of the circulating water by 1 ℃ and keeping the flow rate of the solution to be detected unchanged, observing the fluid state in the micro-channel for at least 2min and taking the image in real time, operating in the above way until crystals appear in an observation visual field, marking the temperature of the crystals appearing in the observation visual field as Tn, the temperature of the crystal-out point of the solution to be detected between Tn-Tn +1 ℃, then increasing the temperature of the circulating water to Tn +1 ℃, cooling the circulating water from Tn +1 ℃ by taking the highest precision of the temperature control system as a cooling gradient, keeping the flow of the solution to be measured unchanged during each cooling, observing the fluid state in the microchannel for at least 2min in real time, and shooting an image, wherein the corresponding temperature is the crystal outlet point temperature when crystals appear in the visual field again;
(4) and calculating the difference between the initial test temperature and the crystal forming point temperature, wherein the difference is the width of the micro-scale flow system crystal metastable zone of the tested solution.
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| CN112162003B true CN112162003B (en) | 2022-03-29 |
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