CN114184005B - Drying device and method capable of judging primary and secondary drying critical points in freeze-drying process - Google Patents
Drying device and method capable of judging primary and secondary drying critical points in freeze-drying process Download PDFInfo
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- CN114184005B CN114184005B CN202111331012.9A CN202111331012A CN114184005B CN 114184005 B CN114184005 B CN 114184005B CN 202111331012 A CN202111331012 A CN 202111331012A CN 114184005 B CN114184005 B CN 114184005B
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- 238000005485 electric heating Methods 0.000 claims abstract description 22
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- 238000009777 vacuum freeze-drying Methods 0.000 claims description 12
- 230000006835 compression Effects 0.000 claims description 10
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B5/00—Drying solid materials or objects by processes not involving the application of heat
- F26B5/04—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum
- F26B5/06—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum the process involving freezing
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B23/00—Heating arrangements
- F26B23/04—Heating arrangements using electric heating
- F26B23/06—Heating arrangements using electric heating resistance heating
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
- F26B25/22—Controlling the drying process in dependence on liquid content of solid materials or objects
- F26B25/225—Controlling the drying process in dependence on liquid content of solid materials or objects by repeated or continuous weighing of the material or a sample thereof
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- Engineering & Computer Science (AREA)
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- General Engineering & Computer Science (AREA)
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Abstract
The invention relates to a drying device capable of judging primary and secondary drying critical points in a freeze-drying process, wherein a freezing system comprises a refrigerator, a compressor and a refrigerating coil pipe which are arranged in a machine case, a freezing bin is arranged in the machine case, and the refrigerating coil pipe is wound on the lower part of the outer wall of the freezing bin; the vacuum system comprises a vacuum pump, a vacuum regulating valve and a vacuum gauge, wherein the vacuum pump is connected to the freeze-drying bin through a vacuum pipeline, and the vacuum regulating valve and the vacuum gauge are arranged on the vacuum pipeline; the heating system is positioned in the freeze-drying bin and comprises an electric heating plate and a defrosting electric heating plate; the measuring system comprises a bracket, a baffle, an S-shaped pulling and pressing sensor, a first temperature sensor, a second temperature sensor, a wireless transmission antenna and a control unit, wherein the bracket, the baffle, the S-shaped pulling and pressing sensor, the first temperature sensor and the second temperature sensor are arranged in the freeze-drying bin. The drying device and the method can detect the drying state of the material in real time, accurately judge the boundary point and the end point of the primary drying stage and the secondary drying stage, effectively improve the drying efficiency and improve the product quality.
Description
Technical Field
The invention belongs to the technical field of vacuum freeze drying, and particularly relates to a device and a method capable of judging primary and secondary drying critical points in a freeze drying process, which are particularly suitable for freeze drying related experiments for scientifically researching thermosensitive materials such as medicines, foods and the like.
Background
It is well known that lyophilization is divided into three stages as shown in figure 2. A pre-freezing stage, a primary drying stage (sublimation drying stage), and a secondary drying stage (analytical drying stage), in which: freezing the aqueous material below the freezing point to convert the moisture in the material to ice. The free water of the material is removed during the primary drying process, and the remaining bound water is removed during the secondary drying process. A drying method for removing ice by converting the ice into water vapor in a high vacuum environment during the whole drying process. However, the two stages of primary drying and secondary drying in the vacuum freeze-drying process are the main stages of energy consumption, accounting for about 87% of the entire process. Excessive drying in the drying process can cause unnecessary energy waste, and the drying is finished in advance, so that the product quality is reduced, and the product requirement cannot be met. Therefore, the method is important to judging the primary drying end point and the secondary drying end point of the freeze drying process, not only can reduce ineffective drying, but also can improve the drying rate and reduce energy waste. At present, the types of freeze-drying machines on the market are different, and a series of problems that whether the drying state of materials is finished or not is completely based on experience and the like cannot be accurately judged exist.
Many researchers at home and abroad have focused on developing new methods of detecting the demarcation point of the freeze-drying stage for twenty years, however the extreme conditions (low temperature, high vacuum, sterility) involved in the freeze-drying process make this task extremely challenging. Nonetheless, many of the related methods and apparatus are available for review and purchase. However, they cannot automatically monitor when the water in the material is sublimated, which is the core purpose and technology of the present patent.
Patent CN 213335194U proposes a freeze dryer that medicine processing used, and the device includes freeze dryer body, heat dissipation grid, display screen, control button, axis of rotation, side maintenance window, circular recess, freeze drying storehouse, its characterized in that: simple structure, reasonable design, convenient use and good heat dissipation effect. But this patent fails to monitor the material condition.
Patent CN 207764670U proposes a temperature detection device of a freeze dryer and a temperature control system comprising the temperature detection device, and the temperature detection device comprises an infrared thermometer arranged on the outer side of a box body of the freeze dryer and an infrared-transmitting glass arranged on the box body of the freeze dryer. The provided temperature control system can perform real-time data transmission with the PLC controller, so that the automatic control of the temperature of the freeze dryer is realized. However, the method for measuring materials in the patent is not a contact measurement method, and the infrared measurement method has a large temperature difference.
Patent CN 210486286U proposes a novel freeze dryer, has solved the inconvenient problem of using of general freeze dryer, can be quick and effectual put the medicine bottle, has avoided the medicine bottle to appear damaged phenomenon in putting the in-process. Although the efficiency of putting medicine bottles is improved and the working efficiency of people is also improved, the patent can not shorten the freeze-drying time and can not judge the boundary point of primary drying and secondary drying.
Patent CN 203336903U provides an experimental freeze dryer integration equipment, conveniently realizes the centralized management of relevant instrument such as freeze dryer, improves the availability factor of laboratory freeze dryer, reduces the energy consumption when running, reduces the pollution of freeze dryer operation to the laboratory. But the device cannot judge the dry state of the material.
Therefore, how to determine the dryness of the material during the lyophilization process, define the boundary points between primary drying and secondary drying, shorten the drying time, and reduce the energy consumption is a problem to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process.
The invention also provides a drying method of the drying device based on the critical point of primary and secondary drying in the freeze-drying process, which not only can detect the drying state of the material in real time, but also can accurately judge the drying end point of the material, and can also measure the temperature of the material and the partition plate in real time, further judge and verify the accuracy of the boundary point of primary drying and secondary drying of the material according to the temperature change, and control the temperature of the product, thereby improving the quality of the product.
The invention aims at realizing the following technical scheme:
a drying device capable of judging critical points of primary and secondary drying in a freeze-drying process comprises a freezing system, a vacuum system, a heating system, a measuring system and a control system;
the refrigerating system comprises a refrigerator, a compressor and a refrigerating coil pipe which are arranged in the case, a refrigerating bin is arranged in the case, and the refrigerating coil pipe is wound on the lower part of the outer wall of the refrigerating bin;
the vacuum system comprises a vacuum pump, a vacuum regulating valve and a vacuum gauge, wherein the vacuum pump is connected to the freeze-drying bin through a vacuum pipeline, and the vacuum regulating valve and the vacuum gauge are arranged on the vacuum pipeline;
the heating system is positioned in the freeze-drying bin and comprises an electric heating plate and a defrosting electric heating plate;
the measuring system comprises a bracket, a baffle, an S-shaped pulling and pressing sensor, a first temperature sensor, a second temperature sensor, a wireless transmission antenna and a control unit, wherein the bracket, the baffle, the S-shaped pulling and pressing sensor, the first temperature sensor, the second temperature sensor, the wireless transmission antenna and the control unit are arranged in the freeze-drying bin;
the control system comprises a controller, a frequency converter, a power supply and a control panel, wherein the S-shaped pull-press sensor, the first temperature sensor, the second temperature sensor and the third temperature sensor are connected to a wireless transmission antenna through data lines, and the wireless transmission antenna is in remote communication connection with the controller.
And the outside of the case and the outside of the refrigerating coil are wrapped by adopting heat insulation materials, so that the load of the refrigerating machine is reduced.
And moreover, a vacuum gauge arranged on the vacuum pipe collects pressure signals and transmits the pressure signals to the controller, and the pressure is regulated through a vacuum regulating valve.
And moreover, the S-shaped tension and compression sensor is wrapped by a heat insulation material, so that the influence of temperature change on the sensor precision is avoided.
And moreover, an acrylic outer cover is arranged at the upper part of the freeze-drying bin, and vacuum silicone grease is adopted at the top of the acrylic outer cover to be connected with a top cover in a sealing manner, so that the vacuum degree is ensured.
And the bottom of the freeze-drying bin is provided with a drain pipe, and water condensed around the refrigeration coil can be drained after drying is finished.
In addition, the control panel adopts a capacitive touch screen, and is provided with a usb and a data transmission port on the side surface, so that data and operation are convenient to process in the experiment.
A drying method based on a drying device capable of judging the critical point of primary and secondary drying in a freeze-drying process is characterized by comprising the following steps: the method comprises the following steps:
1) Freezing: the power switch is turned on, the refrigerator is turned on the control panel, the refrigerating system starts to refrigerate, the temperature is rapidly reduced, and when the refrigerating temperature is reduced to 40-60 ℃ below zero, the materials are placed on the partition plate for freezing;
2) Vacuum freeze-drying stage: after the materials are completely frozen, closing a drainage valve, sealing a top cover on an acrylic outer cover, ensuring the vacuum degree, opening a vacuum pump, setting a vacuum value, starting to vacuumize a freeze drying bin, and performing vacuum freeze drying operation;
3) Judging critical points of primary and secondary drying: along with the continuous vacuum freeze drying, the S-shaped tension and compression sensor can measure the mass change of the material in real time, and judge the drying state of the material according to the mass change, and the judging process is as follows:
s-type tension and compression sensor measures total mass G of material, when total mass G=G Fixing device +(G Fixing device X 10%) G, wherein G Fixing device For the absolute dry quality of the materials, the secondary drying can be judged to be started after the primary drying is finished, and the temperature of the materials approaches to the temperature of the partition plate after the primary drying is finished;
after the primary drying stage is finished, the temperature of a heating plate is increased to 30-45 ℃, and the secondary drying stage is finished to continue drying;
4) And (3) drying is finished: stopping drying, closing the vacuum pump to recover normal pressure of the freeze-drying bin, then closing the refrigerator, closing the electric heating plate, opening the water outlet, taking off the acrylic outer cover and the top cover when the pressure of the freeze-drying bin is changed to normal pressure, taking out materials, and ending drying.
The invention has the advantages and beneficial effects that:
1. the drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process can directly freeze materials in the freeze-drying bin, and the dried products are prepared through the vacuum freeze-drying process, the whole process is completed in the same equipment, the frozen materials are not required to be transferred, and the equipment integration degree is high.
2. According to the drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process, the first temperature sensor is in direct contact with the material in the primary drying and secondary drying stages, so that compared with infrared temperature measurement, the drying device is more accurate, the temperature control of the electric heating plate on the material is facilitated, and products with higher quality can be produced.
3. According to the drying device capable of judging the primary and secondary drying critical points in the freeze-drying process, the first temperature sensor and the second temperature sensor are extremely fine K-type thermocouples, the diameter is about 0.1mm, the material temperature can be measured while the material quality change is not influenced, and the influence of the self weight of the temperature sensor on the actual weight of a product is avoided. The data accuracy is improved.
4. According to the drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process, the S-shaped pulling and pressing sensor is arranged in the freeze-drying bin, the quality of materials is detected by the S-shaped pulling and pressing sensor, the heating temperature of the materials is regulated by the control panel, and the drying temperature is controlled within a reasonable range according to the actually measured material temperature, so that the drying time can be greatly shortened, the drying efficiency can be improved, and the drying device is very suitable for heat-sensitive materials such as medicines and foods.
5. According to the drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process, the S-shaped pulling and pressing sensor is a core component for judging the quality change of materials, and the periphery of the pulling and pressing sensor is provided with the thermal insulation protection layer, so that the influence of temperature change on the accuracy of the pulling and pressing sensor is prevented.
6. The drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process can accurately judge the boundary point of the primary drying stage and the secondary drying stage according to the mass change and the temperature change of materials in the vacuum freeze-drying process, can realize real-time automatic monitoring of the weight of the materials during sublimation in the drying process, can operate in a low-temperature, high-vacuum and sterile environment of equipment, can shorten the drying time, improve the product quality, provides theoretical guidance and technical support for freeze-drying mass production, and solves a great difficulty of freeze-drying.
7. According to the drying device capable of judging the primary and secondary drying critical points in the freeze-drying process, different vacuum degrees can be set by adjusting the vacuum valve, corresponding vacuum values are set according to the requirements of different products on the vacuum degrees, variable controllability is achieved, and scientific research is convenient.
8. According to the drying device capable of judging the primary and secondary drying critical points in the freeze-drying process, the technology of the Internet of things is introduced, and the antenna is arranged at the top end of the freeze dryer and used for remote data transmission, so that experimental data are remotely collected, the processing is convenient, and the time is saved.
9. According to the drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process, the refrigerating coil and the pipeline are wrapped by the heat insulation material, so that the temperature in the circulating pipeline can be maintained in a low-temperature state, the temperature in the freeze-drying bin is ensured to be constant, and the materials are ensured not to be melted in the freeze-drying process. Further ensuring the product quality.
10. According to the drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process, after freeze-drying is finished, water vapor condensed near the cold trap can be quickly melted into water through a defrosting function, and then the water vapor is discharged through the drain pipe, so that equipment cleaning is more convenient and quicker.
11. The drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process can only put materials into the case in the whole drying process, reduces interference of human factors and improves the accuracy of equipment data.
12. The drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process has the characteristics of simple structure, convenient operation and high integration degree, can help scientific researchers to better study the mechanism of the freeze-drying process, and aims to provide technical support for process optimization of freeze-drying products.
13. The invention is a drying device and a drying method capable of judging the critical point of primary and secondary drying in the freeze-drying process, can detect the drying state of materials in real time, accurately judge the boundary point and the end point of the primary drying stage and the secondary drying stage, can effectively improve the drying efficiency and the product quality, and has important significance for the production of high-added-value foods, medicines and biological products.
Drawings
FIG. 1 is a schematic diagram of an experimental freeze dryer of the present invention;
FIG. 2 is a schematic diagram of a freeze-drying process;
FIG. 3 is a graph showing the mass change of a material using the drying apparatus of the present invention;
FIG. 4 is a graph showing the temperature change of the material and the separator using the drying apparatus of the present invention.
Drawings
The device comprises a 1-top cover, a 2-acrylic housing, a 3-S type pulling and pressing sensor, a 4-bracket, a 5-data wire, a 6-partition board, a 7-first temperature sensor, an 8-second temperature sensor, a 9-electric heating plate, a 10-defrosting electric heating plate, an 11-refrigeration coil pipe, a 12-compressor, a 13-drain pipe, a 14-valve, a 15-wireless transmission antenna, a 16-machine box, a 17-control panel, an 18-refrigerator, a 19-vacuum regulating valve, a 20-vacuum pump, a 21-vacuum gauge, a 22-third temperature sensor and a 23-cold trap.
Detailed Description
The invention is further illustrated by the following examples, which are intended to be illustrative only and not limiting in any way.
A drying device capable of judging critical points of primary and secondary drying in a freeze-drying process comprises a freezing system, a vacuum system, a heating system, a measuring system and a control system.
The refrigerating system comprises a refrigerator 18, a compressor 12 and a refrigerating coil 11 which are arranged in the case, wherein the refrigerator, the compressor and the refrigerating coil are in circulation communication, the refrigerating coil is arranged at the periphery of the bottom of a freeze-drying bin in the case and used for refrigerating the freeze-drying bin, and a cold trap 22 is formed at the lower part of the freeze-drying bin;
the vacuum system comprises a vacuum pump 20, a vacuum regulating valve 19 and a vacuum gauge 21, wherein the vacuum pump is connected to a freeze-drying bin in the case through a vacuum pipeline, the vacuum pipeline is provided with the vacuum regulating valve and the vacuum gauge, and the vacuum system provides negative pressure for the freeze-drying bin.
The heating system is located inside the freeze-drying bin and comprises an electric heating plate 9 and a defrosting electric heating plate 10, wherein the electric heating plate is located at the lower part of the partition plate in the freeze-drying bin, and the defrosting electric heating plate is located at the inner wall of the lower part of the freeze-drying bin.
The measuring system comprises a bracket 4, a baffle 6, an S-shaped pulling and pressing sensor 3, a first temperature sensor 7, a second temperature sensor 8, a wireless transmission antenna 15 and a control unit, wherein the bracket is arranged in a freeze-drying bin, the baffle is hoisted at the lower part of the bracket through the S-shaped pulling and pressing sensor, the bracket is fixedly arranged with the freeze-drying bin, the electric heating plate is arranged at the bottom of the baffle, the S-shaped pulling and pressing sensor measures the quality of the baffle, the electric heating plate and the upper material thereof in real time, and the baffle, the electric heating plate and the electric heating plate are fixed in quality and are connected with the S-shaped pulling and pressing sensor 3, so before drying, the S-shaped pulling and pressing sensor 3 is required to return to zero through a control panel 17, and the S-shaped pulling and pressing sensor 3 only measures the quality of the material and the tray. And secondly, determining the quality of a tray for containing materials, and correcting the data displayed by the S-shaped tension and compression sensor 3 in real time through the control panel 17, namely subtracting the quality of the tray, so that the sensor only measures and displays the real-time change of the quality of the materials. The first temperature sensor measures the material temperature and the second temperature sensor measures the diaphragm temperature and also includes a third temperature sensor 22 that measures the temperature within the refrigeration coil. An acrylic outer cover 2 is arranged on the upper portion of the freeze-drying bin, and vacuum silicone grease is adopted at the top of the acrylic outer cover to be in sealing connection with a top cover 1, so that the vacuum degree is ensured. The bottom of the freeze-drying bin is provided with a drain pipe 13, a drain valve 14 is arranged on the drain pipe, and water condensed in the freeze-drying bin at the position of the refrigeration coil can be drained after the drying is finished.
The control system comprises a controller, a frequency converter, a power supply and a control panel 17, wherein the S-shaped pulling and pressing sensor, the first temperature sensor, the second temperature sensor and the third temperature sensor are connected to a wireless transmission antenna through a data line 5, and the wireless transmission antenna is in remote communication connection with the controller.
The outside of the case 16 and the outside of the refrigerating coil are both wrapped by adopting heat insulation materials, so that the load of the refrigerating machine is reduced. The S-shaped tension and compression sensor is wrapped by a heat insulation material, so that the influence of temperature change on the accuracy of the sensor is avoided. The vacuum gauge 21 arranged on the vacuum pipe collects pressure signals and transmits the pressure signals to the controller, and the pressure is regulated through the vacuum regulating valve.
The control panel adopts a capacitive touch screen, and is provided with a usb and a data transmission port on the side surface, so that data and operation are convenient to process during experiments.
A drying method of a drying device capable of judging critical points of primary and secondary drying in a freeze-drying process comprises the following steps:
1) Freezing: closing the valve 14, turning on a power switch, turning on a refrigerator on a control panel, starting the compressor to work after the refrigerator runs for 2min, starting refrigerating the refrigerating system, quickly reducing the temperature, starting reducing the temperature in a cold trap, freezing materials when the temperature displayed by a third temperature sensor on the control panel reaches about-50 ℃, taking off a top cover of a freeze-drying bin and an acrylic outer cover, placing a tray containing the materials on a partition plate, inserting a first temperature sensor into the materials, measuring the change temperature of the materials in real time, and ending the freezing stage after the materials are completely frozen.
2) And (3) a freeze drying stage: sealing a top cover on an acrylic outer cover, smearing the vacuum silicone grease on the joint of the top cover of a freeze-drying bin and the acrylic outer cover, so as to ensure the air tightness, opening a vacuum pump, setting a vacuum value, starting vacuumizing the freeze-drying bin, performing freeze-drying operation, observing the change condition of the vacuum value in real time through a vacuum gauge, when the pressure reaches 10Pa and remains unchanged, indicating that the air tightness is good, regulating a vacuum regulating valve 19 according to experimental requirements, enabling the vacuum regulating valve to reach a required vacuum value, starting at the freeze-drying stage, and collecting water vapor which is risen and escaped in the material in the freeze-drying process after condensation by the inner wall of a cold trap 23 of the freeze-drying bin.
3) Judging critical points of primary and secondary drying: along with the continuous freeze drying, the S-shaped tension and compression sensor can measure the mass change of the material in real time, and can judge the drying state of the material according to the mass change, and the judging process is as follows:
s-type tension and compression sensor measures total mass G of material, when total mass G=G Fixing device +(G Fixing device X 10%) G, wherein G Fixing device The absolute dry quality of the material can be judged that the primary drying is finished, the secondary drying is started, and the temperature of the material approaches after the primary drying is finishedSeparator temperature.
In actual operation, it is necessary to ensure that the mass of each batch of material is the same, and measure the absolute dry mass G of the material before drying Fixing device The moisture removal condition is monitored in real time by displaying the numerical value through a weight sensor in the freeze drying process, and the material quality in the primary drying stage is reduced fast as shown in fig. 3, which indicates that the moisture sublimation speed is fast. The weight at this time is the absolute dry mass G Fixing device 。
As can be seen from fig. 4, the material temperature gradually approaches the same temperature as the separator at a certain point in time in the later stage of freeze-drying, and the point in time when the temperatures are the same is identical to the point in time when the boundary point between the primary and secondary drying stages is determined by weight. In actual operation, the accuracy of judging the demarcation point can be further verified according to the temperature of the material and the temperature of the partition plate, namely, when the temperature of the material is the same as the temperature of the partition plate, the end of the primary drying stage can be judged.
The freeze drying is divided into two stages in the drying stage, namely a primary drying stage and a secondary drying stage, free water in the material is removed in the sublimation stage, and bound water adhered in the pore structure of the material is required to be removed in the secondary drying stage, wherein the water content of the material is usually lower than 10% of the solid, namely when the total mass of the material reaches the solid G Fixing device +(G Fixing device X 10%) time (wherein G Fixing device The absolute dry quality of the material), the end of the primary drying and the start of the secondary drying can be judged. Therefore, the principle of material change in the freeze drying process can be utilized, and the demarcation point can be judged by the value of the real-time change of the material weight, and the device and the method are based on the principle.
As shown in fig. 2, it can be seen from the graph that the mass of the material decreases more rapidly when the material is in the primary drying stage, and the mass of the material is maintained in a more constant state after the primary drying is completed. In the analysis stage, the mass of the material is very slow to decrease, and the residual water in the material is bound water in the stage, and the water is adsorbed on the inner wall of the pore structure of the material and the polar groups through weak molecular forces such as hydrogen bonds. If this part of the water is to be removed, the intermolecular forces need to be overcome, i.e. more energy is required. The temperature of the partition plate can be raised through the heating plate 9, so that the residual moisture in the material is volatilized. In the sublimation stage, the device can measure the temperature of the material and the partition board 6, and the temperature curve data shows that the temperature of the material is approximately the same as the temperature of the partition board 6 in 600 minutes, at the moment, the free water in the material sublimates completely, and only a small part of bound water is contained in the material, so that the temperature change is not obvious, and the fact that the primary drying and secondary drying demarcation point is defined through the material quality change is further verified to be accurate.
After the primary drying stage is finished, the temperature of a heating plate is increased to 30-45 ℃ to finish the drying in the secondary drying stage; the method comprises the following steps: the first temperature sensor is used for measuring the real-time temperature inside the material, and the second temperature sensor is used for measuring the temperature of the partition plate; the value of the S-shaped pulling and pressing sensor connected with the control panel 17 gradually decreases along with the volatilization of the moisture in the material; when the primary drying is completed, the temperature of the heating plate 9 can be raised to 40 ℃ until the drying is completed, because the bound water attached to the inside of the material needs higher heat to be removed. The control panel records data per second throughout the drying period and transmits it in real time via the antenna.
4) And (3) drying is finished: stopping drying, closing the vacuum pump to recover normal pressure of the freeze-drying bin, then closing the refrigerator, closing the electric heating plate, opening the water outlet, taking off the acrylic outer cover and the top cover when the pressure of the freeze-drying bin is changed to normal pressure, taking out materials, and ending drying. The defrost electric heating plate 10 is opened and the condensate valve 14 is opened.
The device completes the whole material freezing and vacuum freeze drying process in the freeze-drying bin, low-temperature liquid is not needed in the freezing process, the frozen liquid is prevented from being contacted with the material, the frozen material is not needed to be transferred to be directly dried in the freeze-drying bin, and the risk of pollution to the material is completely avoided. The closed operation of the system further improves the sterility of the freeze-drying process, does not pollute the environment, and reduces the production energy consumption and the processing cost. The drying process is carried out in a high vacuum environment, the heating temperature is controllable, and the method is also suitable for freeze drying of other heat-sensitive materials.
The method is a detailed explanation of the method and principle for judging the primary drying and secondary drying stages. In the actual operation, the materials can be heated in the primary drying stage and the secondary drying stage, the heating temperature is ensured not to exceed the common melting point temperature of the materials in the primary drying stage, if the heat provided by the heating plate is larger than the heat required by the sublimation of the water content of the materials, the internal temperature of the materials can be increased, when the temperature exceeds the common melting point temperature of the materials, the internal tissues collapse and collapse to influence the appearance quality of the materials, and therefore, when the temperature of the heating plate is set, different settings can be carried out according to the physical characteristics of different materials. In the secondary drying stage, the residual water in the material is bound water, and the water is adsorbed on the inner wall of the pore structure of the material and the polar groups through weak molecular forces such as hydrogen bonds. If this part of the water is to be removed, the intermolecular forces need to be overcome, i.e. more heat is required.
After the demarcation point is determined by the method, the temperature of the heating plate can be increased after the primary drying stage is finished, and the temperature is generally set to be 30-45 ℃. The purpose of heating at this stage is to shorten the drying time at the secondary drying stage, thereby improving the overall drying efficiency, saving energy and reducing energy consumption. The aim of accurately judging the boundary point between primary drying and secondary drying is to improve heat quantity of materials in accurate time, shorten drying time and further improve product quality.
The device completes the whole material freezing and vacuum freeze drying process in the freeze-drying bin, low-temperature liquid is not needed in the freezing process, the frozen liquid is prevented from being contacted with the material, the frozen material is not needed to be transferred to be directly dried in the freeze-drying bin, and the risk of pollution to the material is completely avoided. The closed operation of the system further improves the sterility of the freeze-drying process, does not pollute the environment, and reduces the production energy consumption and the processing cost. The drying process is carried out in a high vacuum environment, the heating temperature is controllable, and the method is also suitable for freeze drying of other heat-sensitive materials.
Although the embodiments of the present invention and the accompanying drawings have been disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and thus the scope of the invention is not limited to the embodiments and the disclosure of the drawings.
Claims (7)
1. A drying method based on a drying device capable of judging the critical point of primary and secondary drying in a freeze-drying process is characterized by comprising the following steps:
the drying device capable of judging the critical point of primary and secondary drying in the freeze-drying process comprises a freezing system, a vacuum system, a heating system, a measuring system and a control system;
the refrigerating system comprises a refrigerator, a compressor and a refrigerating coil which are arranged in the case, a freeze-drying bin is arranged in the case, and the refrigerating coil is wound on the lower part of the outer wall of the freeze-drying bin;
the vacuum system comprises a vacuum pump, a vacuum regulating valve and a vacuum gauge, wherein the vacuum pump is connected to the freeze-drying bin through a vacuum pipeline, and the vacuum regulating valve and the vacuum gauge are arranged on the vacuum pipeline;
the heating system is positioned in the freeze-drying bin and comprises an electric heating plate and a defrosting electric heating plate;
the measuring system comprises a bracket, a baffle, an S-shaped pulling and pressing sensor, a first temperature sensor, a second temperature sensor, a wireless transmission antenna and a control unit, wherein the bracket, the baffle, the S-shaped pulling and pressing sensor, the first temperature sensor, the second temperature sensor, the wireless transmission antenna and the control unit are arranged in the freeze-drying bin;
the control system comprises a controller, a frequency converter, a power supply and a control panel, wherein the S-shaped pull-press sensor, the first temperature sensor, the second temperature sensor and the third temperature sensor are connected to a wireless transmission antenna through data lines, and the wireless transmission antenna is in remote communication connection with the controller;
the drying method comprises the following steps:
1) Freezing: the power switch is turned on, the refrigerator is turned on the control panel, the refrigerating system starts to refrigerate, the temperature is rapidly reduced, and after the refrigerating temperature is reduced to 40-60 ℃ below zero, the materials are placed on the partition plate for freezing;
2) Vacuum freeze-drying stage: after the materials are completely frozen, closing a drainage valve, sealing a top cover on an acrylic outer cover, ensuring the vacuum degree, opening a vacuum pump, setting a vacuum value, starting to vacuumize a freeze drying bin, and performing vacuum freeze drying operation;
3) Judging critical points of primary and secondary drying: along with the continuous vacuum freeze drying, the S-shaped tension and compression sensor can measure the mass change of the material in real time, and judge the drying state of the material according to the mass change, and the judging process is as follows:
s-type tension and compression sensor measures total mass G of material, when total mass G=G Fixing device +（G Fixing device X 10%) G, wherein G Fixing device For the absolute dry quality of the materials, the secondary drying can be judged to be started after the primary drying is finished, and the temperature of the materials approaches to the temperature of the partition plate after the primary drying is finished;
the accuracy of judging the demarcation point is further verified according to the temperature of the material and the temperature of the partition plate, namely, when the temperature of the material is the same as the temperature of the partition plate, the end of the primary drying stage can be judged;
after the primary drying stage is finished, the temperature of the electric heating plate is increased to 30-45 ℃, and the secondary drying stage is finished to continue drying;
4) And (3) drying is finished: stopping drying, closing the vacuum pump to recover normal pressure of the freeze-drying bin, then closing the refrigerator, closing the electric heating plate, opening the water outlet, taking off the acrylic outer cover and the top cover when the pressure of the freeze-drying bin is changed to normal pressure, taking out materials, and ending drying.
2. The drying method of claim 1, wherein the drying device is capable of determining the critical point of primary and secondary drying in the freeze-drying process, and is characterized by comprising the following steps: the outside of the case and the outside of the refrigerating coil are both wrapped by adopting heat insulation materials, so that the load of the refrigerating machine is reduced.
3. The drying method of claim 1, wherein the drying device is capable of determining the critical point of primary and secondary drying in the freeze-drying process, and is characterized by comprising the following steps: and a vacuum gauge arranged on the vacuum pipeline collects pressure signals and transmits the pressure signals to the controller, and the pressure is regulated through a vacuum regulating valve.
4. The drying method of claim 1, wherein the drying device is capable of determining the critical point of primary and secondary drying in the freeze-drying process, and is characterized by comprising the following steps: the S-shaped tension and compression sensor is wrapped by a heat insulation material, so that the influence of temperature change on the accuracy of the sensor is avoided.
5. The drying method of claim 1, wherein the drying device is capable of determining the critical point of primary and secondary drying in the freeze-drying process, and is characterized by comprising the following steps: and an acrylic outer cover is arranged on the upper part of the freeze-drying bin, and vacuum silicone grease is adopted at the top of the acrylic outer cover to be connected with a top cover in a sealing way, so that the vacuum degree is ensured.
6. The drying method of claim 1, wherein the drying device is capable of determining the critical point of primary and secondary drying in the freeze-drying process, and is characterized by comprising the following steps: the bottom of the freeze-drying bin is provided with a drain pipe, and water condensed around the refrigeration coil can be drained after drying is finished.
7. The drying method of claim 1, wherein the drying device is capable of determining the critical point of primary and secondary drying in the freeze-drying process, and is characterized by comprising the following steps: the control panel adopts a capacitive touch screen, and is provided with a usb and a data transmission port on the side surface, so that data and operation are convenient to process during experiments.
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Application publication date: 20220315 Assignee: Ningbo Sanchuan Equipment Manufacturing Co.,Ltd. Assignor: TIANJIN University OF SCIENCE AND TECHNOLOGY Contract record no.: X2024980009885 Denomination of invention: Drying device and method for determining the critical points of primary and secondary drying in the freeze-drying process Granted publication date: 20230505 License type: Common License Record date: 20240717 |