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CN-122015432-A - Circulation air-cooling freeze-drying method and system

CN122015432ACN 122015432 ACN122015432 ACN 122015432ACN-122015432-A

Abstract

The invention relates to the technical field of freeze drying, in particular to a circulating air-cooled freeze drying method and a circulating air-cooled freeze drying system, wherein the method comprises a freezing procedure, a vacuumizing sublimation drying procedure and a defrosting procedure, and the three procedures are sequentially carried out, namely, a refrigerating assembly and a circulating fan are started, and air flow is driven to forcedly circulate between a ventilating pipeline and a cold trap to finish material freezing; and after the completion, the refrigeration component and the vacuum component are closed, the circulating fan and the heating component are synchronously started, and closed circulating airflow is formed between the ventilating pipeline and the cold trap through heated hot airflow to defrost. The invention realizes forced circulation of air flow in the cold trap, improves heat exchange efficiency of the inner wall of the cold trap, realizes closed automatic defrosting, reduces defrosting energy consumption, and adapts to vacuum sealing and high-low temperature working environment requirements of the cold trap in system structure.

Inventors

  • CHEN HAOHONG
  • LIAO YINGXUE

Assignees

  • 广东利钜制冷有限公司

Dates

Publication Date
20260512
Application Date
20260226

Claims (10)

  1. 1. The circulating air-cooling freeze-drying method is characterized by being applied to a circulating air freeze-drying system and comprising a freezing process, a vacuumizing sublimation drying process and a defrosting process, wherein the three processes are sequentially carried out; The freezing procedure comprises the steps of starting a refrigeration assembly (2) to cool a cold trap (13), synchronously starting a circulating fan (31), driving air flow between a ventilation pipeline (32) and the cold trap (13) through the circulating fan (31) to form circulating air flow, and sweeping the circulating air flow against the inner wall of the cold trap (13) and performing heat exchange with a dried object in the cold trap (13); The vacuumizing sublimation drying process comprises the steps of keeping a refrigeration assembly (2) to work continuously, stopping a circulating fan (31) from working, starting a vacuum assembly to vacuumize the inside of a cold trap (13) to a preset vacuum degree, sublimating ice frozen in a dried object, and forming a frost layer on the inner wall of the cold trap (13) by water vapor generated by sublimation; After the vacuumizing sublimation drying process is finished, the refrigerating assembly (2) and the vacuum assembly are closed, the circulating fan (31) and the heating assembly (4) are started synchronously, the heating assembly (4) heats air flow in the ventilating duct (32), the heated hot air flow is driven by the circulating fan (31) to form closed circulating air flow between the ventilating duct (32) and the cold trap (13), the hot air flow blows a frost layer on the inner wall of the cold trap (13) against the inner wall of the cold trap (13), the temperature of the inner wall of the cold trap (13) is detected by the detecting assembly (5), and when the detected temperature value reaches a preset value, the heating assembly (4) and the circulating fan (31) are closed.
  2. 2. The circulating air-cooled freeze-drying method according to claim 1, wherein in the defrosting process, the temperature value of the air flow in the ventilation pipeline (32) heated by the heating component (4) is 60-80 ℃.
  3. 3. The method for circulating air-cooled freeze drying according to claim 1, wherein during the operation of the circulating fan (31), heat generated by the motor (311) of the circulating fan (31) is discharged to the external environment through the heat radiation assembly (6).
  4. 4. A circulating air-cooled freeze-drying system for implementing the circulating air-cooled freeze-drying method according to any one of claims 1-3, which is characterized by comprising a freeze-drying main body (1), a refrigerating assembly (2), a circulating air assembly (3), a heating assembly (4), a detecting assembly (5), a heat radiating assembly (6), a vacuum assembly and a control assembly (7); A cold trap (13) is formed in the freeze-drying main body (1), and an air inlet (111) and an air return opening (121) are respectively formed at two ends of the cold trap (13); the refrigeration component (2) is matched with the outer wall of the cold trap (13) and is used for providing cold energy for the cold trap (13); The circulating air assembly (3) comprises a circulating fan (31), a ventilation pipeline (32) and a sealing shell (33), the circulating fan (31) comprises a motor (311) and an impeller (312), the impeller (312) is arranged in the ventilation pipeline (32), the motor (311) is arranged in the sealing shell (33), a through hole (321) is formed in the ventilation pipeline (32), the sealing shell (33) is covered outside the through hole (321) of the ventilation pipeline (32), an output shaft (313) of the motor (311) penetrates through the through hole (321) and is in transmission connection with the impeller (312), and two ends of the ventilation pipeline (32) are respectively communicated with an air inlet (111) and an air return opening (121) of the cold trap (13); the heating component (4) is arranged in the ventilation pipeline (32) and is used for heating air flow in the ventilation pipeline (32); The detection assembly (5) comprises a first temperature sensor (51), a second temperature sensor (52) and a third temperature sensor (53), wherein the first temperature sensor (51) is arranged at the heating assembly (4), the second temperature sensor (52) is arranged at the cold trap (13), and the third temperature sensor (53) is arranged at the motor (311); the heat dissipation assembly (6) is arranged outside the sealing shell (33) and is used for discharging heat generated by the operation of the motor (311); The vacuum assembly is communicated with the cold trap and is used for vacuumizing the cold trap, the vacuum assembly comprises a vacuum pump, a vacuum pipeline and a vacuum valve, the vacuum pump is communicated with the cold trap (13) through the vacuum pipeline, and the vacuum valve is arranged on the vacuum pipeline; The control assembly (7) is electrically connected with the refrigerating assembly (2), the circulating fan (31), the heating assembly (4), the detection assembly (5) and the heat dissipation assembly (6) respectively, and the control assembly (7) is used for controlling the working state of each assembly.
  5. 5. Circulating air freeze drying system according to claim 4, characterized in that the freeze-drying body (1) is formed by two oppositely arranged counter walls (11) and a connecting wall (12) connecting the two counter walls (11), two counter walls (11) and the connecting wall (12) form the cold trap (13), wherein one of the counter walls (11) is connected with the freeze-drying body (1) in an openable and closable manner; The opposite wall (11) fixedly connected with the freeze-drying main body (1) is radially provided with a plurality of air inlets (111) around the center, the outer wall of the opposite wall (11) is provided with an air inlet ring pipe (112) around the plurality of air inlets (111), the plurality of air inlets (111) are communicated with the air inlet ring pipe (112), and the air inlet ring pipe (112) is communicated with the ventilating duct (32); The wall surface of the connecting wall (12) is provided with a plurality of air return openings (121) around the axial direction of the cold trap (13), the outer wall of the connecting wall (12) is provided with an air return ring pipe (122) around a plurality of the air return openings (121), a plurality of the air return openings (121) are communicated with the air return ring pipe (122), and the air return ring pipe (122) is communicated with the ventilating duct (32).
  6. 6. The circulating air freeze drying system according to claim 4, wherein the refrigeration assembly (2) comprises a refrigeration compressor (21), a condenser (22), a drying filter (23), an electromagnetic valve (24), a thermal expansion valve (25) and an evaporator coil (26) which are sequentially connected in a pipeline manner, and the evaporator coil (26) is spirally wound and attached to the outer wall of the freeze-drying main body (1).
  7. 7. The circulating air freeze drying system according to claim 4, wherein the circulating fan (31) is a vortex centrifugal fan, a heat insulation plate (34) is arranged between the sealing shell (33) and a ventilation pipeline (32) where the impeller (312) is located, the heat insulation plate (34) is provided with a mounting hole (341), the mounting hole (341) and the through hole (321) are correspondingly arranged, an output shaft (313) of the motor (311) sequentially penetrates through the mounting hole (341) and the through hole (321) and is in transmission connection with the impeller (312), the output shaft (313) of the motor (311) is in small clearance fit with the mounting hole (341) and the through hole (321), and the distance of the small clearance is 0.1-0.2mm.
  8. 8. Circulated-air freeze-drying system according to claim 4, characterized in that the heating assembly (4) is a tubular electric heater.
  9. 9. The circulating air freeze drying system according to claim 6, wherein the heat radiation assembly (6) comprises a heat pipe evaporator (61), a heat pipe condenser (62) and a communicating pipe (63), the heat pipe condenser (62) is located above the heat pipe evaporator (61), the heat pipe evaporator (61) is spirally wound and attached to the motor (311), and two ends of the communicating pipe (63) are respectively communicated with the heat pipe evaporator (61) and the heat pipe condenser (62) for circulating a working medium between the heat pipe evaporator (61) and the heat pipe condenser (62).
  10. 10. The circulating air freeze drying system of claim 4, wherein the control assembly (7) comprises a program controller (71) and a relay (72), and the program controller (71) is electrically connected with the refrigeration assembly (2), the circulating fan (31), the heating assembly (4), the detection assembly (5) and the heat dissipation assembly (6) through the relay (72).

Description

Circulation air-cooling freeze-drying method and system Technical Field The invention relates to the technical field of freeze drying, in particular to a circulating air-cooling freeze drying method and system. Background The vacuum freeze-drying technology is widely applied to the fields of foods, medicines, biological products and the like by virtue of the advantage that the dried material forms and nutrient components are well reserved, and a vacuum freeze dryer is an important application device of the technology. The cooler of the vacuum freeze dryer and the cold trap dryer are integrally arranged to form a cold trap, the cold trap has two core functions, firstly, the object to be dried is cooled from normal temperature to a set low temperature below the eutectic point temperature to finish freezing of the material, secondly, the frozen ice in the material is sublimated under the vacuumizing condition to realize sublimation drying, thirdly, the drying process is ensured to be continuously carried out through water vapor generated by low-temperature condensation and sublimation. In the cooling and freezing process of the object to be dried, heat transfer is realized by sequentially transferring cold energy to the outer wall surface of the cold trap by the low-temperature evaporator coil on the outer wall of the cold trap, transferring the cold energy to the inner wall surface of the cold trap by the outer wall surface of the cold trap in a heat conduction mode, transferring the cold energy to air in the trap by the inner wall surface of the cold trap in a heat release mode, and transferring the cold energy to the object to be dried by the air in the trap in the heat release mode. The existing vacuum freeze dryer has a plurality of technical problems in practical application, and is specifically as follows: (1) The heat transfer efficiency is low, the freezing effect is poor, the inner wall surface of the cold trap is in a natural convection heat transfer mode, and the analysis is carried out from a heat transfer chemical formula Air convection heat transfer coefficientOnly about 8W/m 2. K, corresponding thermal resistance 1 +.=0.125 M.K/W, which is far greater than the thermal conduction resistance of the cold trap wall surfaceThe whole heat transfer coefficient is smaller, the heat transfer capacity is limited, the refrigeration efficiency of the refrigerator cannot be fully exerted, the cooling speed of the frozen article is slow, the freezing time is greatly increased, and the quality of the article after drying is further affected; (2) The frost melting mode has obvious defects that after freeze drying is finished, the inner wall surface of a cold trap can be fully covered with a frost layer with a certain thickness, if a refrigerator system is adopted to reversely run for hot air frost melting, the frost layer can be melted from the contact surface with the wall surface, and then the whole peeling wall surface falls down, so that frost blocks can not be melted quickly, melted frost water can be cooled again to ice easily, and a water outlet of the cold trap is blocked; (3) The realization difficulty of forced convection heat exchange is high, the optimal measure for improving the natural convection air heat exchange capacity of the inner wall surface of the cold trap is to change the natural convection heat exchange into forced convection heat exchange, but the inner space of the cold trap is limited, the strict requirement of vacuumizing and sealing exists, meanwhile, the cold trap is in an extreme working environment with alternating high temperature and low temperature, and a fan is not arranged in the cold trap to realize the forced convection heat exchange. Disclosure of Invention The invention aims to provide a circulating air-cooling freeze-drying method, which realizes forced circulation of air flow in a cold trap, improves heat exchange efficiency of the inner wall of the cold trap, realizes closed automatic defrosting, reduces defrosting energy consumption, and adapts to vacuum sealing and high-low temperature working environment requirements of the cold trap in a system structure. Another object of the present invention is to provide a circulating air-cooled freeze drying system, which implements a circulating air-cooled freeze drying method as described above. To achieve the purpose, the invention adopts the following technical scheme: a circulating air cooling freeze-drying method is applied to a circulating air freeze-drying system and comprises a freezing process, a vacuumizing sublimation drying process and a defrosting process, wherein the three processes are sequentially carried out; The freezing process comprises the steps of starting a refrigeration assembly to cool a cold trap, synchronously starting a circulating fan, and driving air flow between a ventilation pipeline and the cold trap by the circulating fan to form circulating air flow, wherein the circulating air flow is bl