EP4105585B1 - Freeze-drying method and apparatus - Google Patents
Freeze-drying method and apparatus Download PDFInfo
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- EP4105585B1 EP4105585B1 EP21180228.5A EP21180228A EP4105585B1 EP 4105585 B1 EP4105585 B1 EP 4105585B1 EP 21180228 A EP21180228 A EP 21180228A EP 4105585 B1 EP4105585 B1 EP 4105585B1
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- pressure
- temperature
- thermostatting
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- specified
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- 238000000034 method Methods 0.000 title claims description 34
- 238000004108 freeze drying Methods 0.000 title claims description 28
- 238000005092 sublimation method Methods 0.000 claims description 38
- 230000008022 sublimation Effects 0.000 claims description 32
- 238000000859 sublimation Methods 0.000 claims description 31
- 239000000126 substance Substances 0.000 claims description 18
- 239000000945 filler Substances 0.000 claims description 11
- 239000007789 gas Substances 0.000 claims description 11
- 238000005086 pumping Methods 0.000 claims description 9
- 229920006395 saturated elastomer Polymers 0.000 claims description 7
- 238000007710 freezing Methods 0.000 claims description 6
- 230000008014 freezing Effects 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 238000005057 refrigeration Methods 0.000 claims description 6
- 230000007704 transition Effects 0.000 claims description 6
- 238000012546 transfer Methods 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 4
- 238000004590 computer program Methods 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims description 2
- 238000007789 sealing Methods 0.000 claims description 2
- 230000008569 process Effects 0.000 description 17
- 239000012071 phase Substances 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000007787 long-term memory Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 230000007420 reactivation Effects 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 238000000935 solvent evaporation Methods 0.000 description 1
- 208000011117 substance-related disease Diseases 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
Images
Classifications
-
- 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
-
- 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
Definitions
- the invention relates to devices and methods for freeze-drying.
- Freeze-drying refers to the removal of moisture from frozen materials, such as food, medicine, and others, by sublimation of ice. Freeze-drying is based on the ability of ice to evaporate under certain conditions, bypassing the liquid phase. In industrial conditions, the drying process is carried out in a vacuum at a pressure of the vapor-gas medium below the pressure corresponding to the triple point of the substance phase transformation.
- Freeze-drying has several advantages over traditional preservation methods: there is no need for refrigeration since dry food can be stored for a long time at positive temperatures; the sales system of such goods is simplified and the time of their sale is increased; in addition, the taste of the product remains virtually unchanged.
- a known method and device for freeze-drying includes reducing the pressure to the first vacuum pressure, as a result of which the control system automatically activates the heater. Further, the method includes increasing the pressure to the second value of a vacuum pressure exceeding the value of the first pressure, where, as a result of reaching the value of the second pressure, the control system automatically turns off the heater. The result is a decrease in pressure, reactivation of the heater, sublimation of water, and an increase in pressure, which leads to the next turn-off of the pressure-activated heater.
- Another freeze-drying method involves lowering the temperature in the chamber of the device to -45.5 °F or below using a refrigeration system with a one-stage vacuum pump and sublimation under reduced pressure in the chamber of the device.
- the freeze dryer includes a chamber, a vacuum pump, a heater, and a control system programmed with instructions in effect to cycle through the pressure-activated heater.
- the main disadvantage of the known solution is the occasional shutdown of the heating elements, which leads to a decrease in the supply of thermal energy to the sublimated product, that is, the intensity of sublimation decreases. This mode of operation of the device leads to an increase in the time of its operation until the desired result is achieved, thereby reducing its performance.
- a known method for monitoring and controlling the process of lyophilization of a solution of a frozen product using a wireless sensor network includes arranging one or more wireless pressure sensors configured to fit into a lyophilization vial tray located in a lyophilization chamber having a plurality of product vials, wherein the wireless pressure sensors are distributed between the lyophilized product vials, thereby providing spatial pressure measurement, collection information on the spatial pressure from the specified wireless pressure sensors, calculation of the sublimation rate of the solution, and regulate the pressure and/or temperature in the lyophilization chamber so that the calculated sublimation rate remains within the specified ranges of parameters.
- the known process of the device operating modes control is based on the solvent evaporation rate control, and the process control is designed in such a way that the sublimation process should be the real sublimation process, and not a vacuum drying process (drying at low pressure and possibly at low temperature, but not lower than pressure and temperature of the triple point of the phase transformation of the substance).
- the Navier-Stokes equation is used as a tool for determining the control actions on the sublimation process and some parameters in the sublimation chamber required to solve this equation are measured by the abovementioned sensors.
- the parameters required are the temperature of the gases, and precisely the gradient of the gas's temperature, which is flowing away and carry out the sublimated substance, and the pressure of the gases, in the places where the corresponding gas pressure and temperature sensors are installed.
- the main disadvantage of the known solution is the use of the gas temperature gradient to control the sublimation process, which only indirectly characterizes the temperature of the sublimated product, and since the solutions of substances in the sublimated products have a complex composition and the intensity of their evaporation depends not only on the temperature and pressure of the gases inside the chamber but also on the fractional the composition of the evaporated substances and their differences even for one type of sublimation products.
- the evaporation rate of the products depends on the fractional composition of the product, and over time the evaporation rate changes, since the lighter fractions volatilize easily; an example of a solution of alcohol in water - first alcohol begins to evaporate intensively, and only then, as the temperature rises, water begins to evaporate, or another example - oil rectification. Failure to take these circumstances into account leads to distortion of control actions, which reduces the quality of the sublimated product and reduces the productivity of units.
- the invention aims to eliminate the disadvantages of prior art.
- This goal is achieved by the proposed method and device for freeze-drying, according to which, to control the process of sublimation of the substance, temperature T, pressure P, and the Clausius-Clapeyron equation are used as control parameters and to determine the values of control actions. Controlling influences on the sublimation process is determined by their ratio. The temperature was selected as the main parameter and the pressure was selected as the correcting control parameter. More specifically, the objective is achieved due to the technical features indicated in the independent claims.
- the proposed device and method for freeze-drying and the control of the sublimation process of a substance use temperature T , pressure P , and the Clausius- Clapeyron equation to determine the values of control actions as control parameters. Controlling influences on the sublimation process is determined by their ratio. As the main parameter, the temperature was selected as a more inertial process, and as the correcting control parameter, the pressure was selected as a faster process.
- the proposed device ( Fig. 1 ) contains:
- Shelf temperature sensors 8, desublimating surface temperature sensor 7, pressure sensor 10 are connected to the control computer 11 with the possibility of transmitting a signal representing the data received by sensors 7, 8, 10.
- Vacuum pump 9, refrigeration unit 4, shelf heaters 3 are connected with a control computer 11 with the possibility of receiving and transmitting a signal to control the said elements of the device.
- control computer 11 is connected to computer-readable hardware that storing a computer program containing machine-executable instructions (or the control computer 11 itself contains these machine-executable instructions), the execution of which causes the processor to control the freeze-drying device according to steps (iii) - (vi) of the freeze-drying method described below.
- the freeze-drying process according to this invention comprises (Fig. 2 and 3):
- the sublimation process is carried out in several levels of thermostatting j from 1 to n T , and at each of the levels of thermostatting, several cycles i from 1 to n Tc of pressure change inside the vacuum chamber - desublimator (1) are performed.
- the current parameters of the sublimation process i.e., temperature T c and pressure p c inside the vacuum desublimator chamber, is checked for each level and cycle of the sublimation process and compare with the parameter T j and p j .
- the cycle of operation of the sublimation device vacuum pump (9) means the repeated process of pumping out the vapor-air mixture by the vacuum pump (9), from the limiting value pressure p j , to the lower value of the pressure p j-1 , and then its subsequent growth to the value p j due to the sublimation process.
- Transition to another thermostatting lavel is possible both by a change in the magnitude of the pressure increase over the given time, when it does not reach the given level, i.e., p j , or when current number n c of sublimation cycle reaching the limiting value of the repetitive operating cycles number n Tc of the vacuum pump, i.e., n c ⁇ n Tc .
- the filler substance Since the initial pressure in the chamber p 0 is lower than the saturated vapor pressure at the temperature of the first thermostatting level p 1 , that is, p 0 ⁇ p 1 , according to the specified sublimation parameters, the filler substance begins to sublimate from the product, and since the temperature of the desublimating surface 6 T D is below the temperature of the first level of thermostatting T 1 , and at the same time the initial pressure in the chamber p 0 is higher than the saturated vapor pressure P D corresponding to the temperature of the desublimating surface 6 T D according to the given parameters of the sublimation mode, then the filler substance is desublimated on the desublimating surface 6 as follows as T D ⁇ T 0 ⁇ T 1 .
- the control computer 11 turns on the vacuum pump 9 and reduces the pressure in the vacuum chamber-desublimator 1 to the initial level p 0 . The process is carried out until one of two events occurs:
- the next thermostatting level is carried out.
- the control computer 11 turns on the vacuum pump 9, which reduces the pressure in the vacuum desublimator 1 to the initial level p j-1 . The process is carried out until one of two events occurs:
- the condition is checked by the control computer 11, that the number of sublimation cycles n c is more or equal to the specified value n i,j for a given cycle of the sublimation process, that is, n c ⁇ n i,j :
- the temperature of the shelves 2 stabilizes, the current pressure p c begins to increase, tending to the value of p nT corresponding to the temperature T nT :
- p 2 p 1 exp ⁇ ⁇ H cy ⁇ , mol R ⁇ 1 T 1 ⁇ 1 T 2
- the filler substance desublimates on the desublimating surface 6, since T D ⁇ T nT . If the intensity of the sublimation process exceeds the intensity of the desublimation process, then the current pressure p c in the desublimator chamber 1 increases, and if, for a given duration t i,nT of the sublimation process, the current pressure p c in the desublimator chamber 1 reaches pressure p nT , then the control computer 11 of device turn on the vacuum pump 9 is turned on, which lowers the pressure in the desublimator chamber 1 to the initial level p nT-1 . The process is carried out until one of two events occurs:
- the desublimator chamber 1 is depressurized, the desublimator chamber 1 is unloaded, and the device is turned off.
Description
- The invention relates to devices and methods for freeze-drying.
- Freeze-drying refers to the removal of moisture from frozen materials, such as food, medicine, and others, by sublimation of ice. Freeze-drying is based on the ability of ice to evaporate under certain conditions, bypassing the liquid phase. In industrial conditions, the drying process is carried out in a vacuum at a pressure of the vapor-gas medium below the pressure corresponding to the triple point of the substance phase transformation.
- Freeze-drying has several advantages over traditional preservation methods: there is no need for refrigeration since dry food can be stored for a long time at positive temperatures; the sales system of such goods is simplified and the time of their sale is increased; in addition, the taste of the product remains virtually unchanged.
-
US 6971187 B1 andEP 2674712 A1 disclose different freeze-drying apparatuses. - A known method and device for freeze-drying (
US9459044 - A known method for monitoring and controlling the process of lyophilization of a solution of a frozen product using a wireless sensor network (
US2020340743 ). The method includes arranging one or more wireless pressure sensors configured to fit into a lyophilization vial tray located in a lyophilization chamber having a plurality of product vials, wherein the wireless pressure sensors are distributed between the lyophilized product vials, thereby providing spatial pressure measurement, collection information on the spatial pressure from the specified wireless pressure sensors, calculation of the sublimation rate of the solution, and regulate the pressure and/or temperature in the lyophilization chamber so that the calculated sublimation rate remains within the specified ranges of parameters. Thus, the known process of the device operating modes control is based on the solvent evaporation rate control, and the process control is designed in such a way that the sublimation process should be the real sublimation process, and not a vacuum drying process (drying at low pressure and possibly at low temperature, but not lower than pressure and temperature of the triple point of the phase transformation of the substance). This protects the base substance from degradation, which is very important, for example, for pharmaceutical and cosmetic substances. The Navier-Stokes equation is used as a tool for determining the control actions on the sublimation process and some parameters in the sublimation chamber required to solve this equation are measured by the abovementioned sensors. The parameters required are the temperature of the gases, and precisely the gradient of the gas's temperature, which is flowing away and carry out the sublimated substance, and the pressure of the gases, in the places where the corresponding gas pressure and temperature sensors are installed. The main disadvantage of the known solution is the use of the gas temperature gradient to control the sublimation process, which only indirectly characterizes the temperature of the sublimated product, and since the solutions of substances in the sublimated products have a complex composition and the intensity of their evaporation depends not only on the temperature and pressure of the gases inside the chamber but also on the fractional the composition of the evaporated substances and their differences even for one type of sublimation products. At the same temperature and pressure of the air-vapor medium inside the chamber, the evaporation rate of the products depends on the fractional composition of the product, and over time the evaporation rate changes, since the lighter fractions volatilize easily; an example of a solution of alcohol in water - first alcohol begins to evaporate intensively, and only then, as the temperature rises, water begins to evaporate, or another example - oil rectification. Failure to take these circumstances into account leads to distortion of control actions, which reduces the quality of the sublimated product and reduces the productivity of units. - The invention aims to eliminate the disadvantages of prior art. This goal is achieved by the proposed method and device for freeze-drying, according to which, to control the process of sublimation of the substance, temperature T, pressure P, and the Clausius-Clapeyron equation are used as control parameters and to determine the values of control actions. Controlling influences on the sublimation process is determined by their ratio. The temperature was selected as the main parameter and the pressure was selected as the correcting control parameter. More specifically, the objective is achieved due to the technical features indicated in the independent claims.
-
-
Fig. 1 is a schematic diagram of an embodiment of a freeze-drying device; - fig. 2 is a schematic diagram of one embodiment of a freeze-drying method;
- fig. 3 is a schematic diagram of another embodiment of the freeze-drying method.
- The proposed device and method for freeze-drying and the control of the sublimation process of a substance use temperature T, pressure P, and the Clausius- Clapeyron equation to determine the values of control actions as control parameters. Controlling influences on the sublimation process is determined by their ratio. As the main parameter, the temperature was selected as a more inertial process, and as the correcting control parameter, the pressure was selected as a faster process.
- The proposed device (
Fig. 1 ) contains: - a vacuum chamber-desublimator 1, in which one or
more shelves 2 are located, adapted to accommodate the product to be freeze-dried; the shelf orshelves 2 are equipped with one ormore heaters 3, adapted to heat theshelves 2 and maintain the predetermined temperature of theshelves 2; - a
refrigeration unit 4 connected to aheat exchanger 5, which is installed in such a way as to ensure heat transfer from thedesublimating surface 6 located in the vacuum chamber-desublimator 1; moreover, thedesublimating surface 6 can be represented as walls of the vacuum chamber-desublimator 1, or one or more plates connected to theheat exchanger 5 with the possibility of mutual heat transfer (for taking heat from thedesublimating surface 6 and cooling it); - at least one
temperature sensor 7 of thedesublimating surface 6, installed and configured to take temperature readings from thedesublimating surface 6; - one or
more temperature sensors 8 of theshelves 2, adapted to take temperature readings from theshelves 2 and, preferably, protected by housing to protect against the influence of the temperatures of other elements of the device; - at least one
vacuum pump 9, installed with the possibility of pumping out gases from the vacuum chamber-desublimator 1; - at least one
pressure sensor 10 was installed with the possibility of obtaining pressure readings in the vacuum chamber-desublimator 1. -
Shelf temperature sensors 8, desublimatingsurface temperature sensor 7,pressure sensor 10 are connected to thecontrol computer 11 with the possibility of transmitting a signal representing the data received bysensors Vacuum pump 9,refrigeration unit 4,shelf heaters 3 are connected with acontrol computer 11 with the possibility of receiving and transmitting a signal to control the said elements of the device. - Moreover, the
control computer 11 is connected to computer-readable hardware that storing a computer program containing machine-executable instructions (or thecontrol computer 11 itself contains these machine-executable instructions), the execution of which causes the processor to control the freeze-drying device according to steps (iii) - (vi) of the freeze-drying method described below. - The freeze-drying process according to this invention comprises (Fig. 2 and 3):
- determination of the product to be sublimated and selection of the appropriate operating mode of the device, that is, the determination of the program for the sublimation of the product filler, which contains data on the thermophysical properties of the product filler;
- according to the specified mode, information about the sublimation mode is loaded into the sublimation program from the long-term memory of the control computer 11: the pressure P0 of the triple point of the product's filler substance phase transformation, the temperature of its triple point of phase transformation T0, its heat capacity ΔH, as well as the temperatures of the thermostatting levels of the shelves Tj j = 1, ..., nT, and TD desublimating
surface 6, the temperature of the beginning TB = T0 , as well as the number of thermostatting levels nT ; - the implementation of the loading of the product on one or
more shelves 2 of the vacuum chamber-desublimator 1 (the product can be placed in trays, open cans, etc.); - the implementation of the sealing of the vacuum chamber-desublimator 1;
- freezing the
desublimating surface 6 to a temperature TD <T0; - carrying out freezing of the
shelves 2 to a temperature TB, so that TD <TB =T0 <T0; - the implementation of the evacuation of the vacuum chamber-desublimator 1 by pumping out the air-vapor medium to a pressure p0 , so that PD <p0 <P0, below the pressure p1 corresponding to the temperature T1 of the first level of thermostatting of the substance sublimation. Moreover, the values of the pressure parameters are determined by Clausius-Clapeyron equation according to the set temperature values and the initial data of the sublimation mode
- Moreover, the sublimation process is carried out in several levels of thermostatting j from 1 to nT, and at each of the levels of thermostatting, several cycles i from 1 to nTc of pressure change inside the vacuum chamber - desublimator (1) are performed. The current parameters of the sublimation process, i.e., temperature Tc and pressure pc inside the vacuum desublimator chamber, is checked for each level and cycle of the sublimation process and compare with the parameter Tj and pj. And further, the cycle of operation of the sublimation device vacuum pump (9) means the repeated process of pumping out the vapor-air mixture by the vacuum pump (9), from the limiting value pressure pj, to the lower value of the pressure pj-1, and then its subsequent growth to the value pj due to the sublimation process. The range of cycle pressure changes is determined by control computer (11) for each thermostatting level based on the thermostatting temperature of the
shelves 2 of the current Tj and the previous Tj-1 levels. For the first step, i.e., j = 1, the previous step is zero-step Tj-1 = T0, and, accordingly, pj-1 = p0. Transition to another thermostatting lavel is possible both by a change in the magnitude of the pressure increase over the given time, when it does not reach the given level, i.e., pj, or when current number nc of sublimation cycle reaching the limiting value of the repetitive operating cycles number nTc of the vacuum pump, i.e., nc ≥ nTc. - The pressure p0 and the temperature T0 of the lower-level and the temperature T1 of the first level of sublimation j = 1, of the first cycle i = 1 coincide with the parameters of the lower level of sublimation PB and TB, that is, TD < TB = T0 < T1 <T0 and PD < PB = p0 < p1 < P0.
- Since the initial pressure in the chamber p0 is lower than the saturated vapor pressure at the temperature of the first thermostatting level p1, that is, p0 < p1, according to the specified sublimation parameters, the filler substance begins to sublimate from the product, and since the temperature of the desublimating surface 6 TD is below the temperature of the first level of thermostatting T1, and at the same time the initial pressure in the chamber p0 is higher than the saturated vapor pressure PD corresponding to the temperature of the desublimating surface 6 TD according to the given parameters of the sublimation mode, then the filler substance is desublimated on the
desublimating surface 6 as follows as TD < T0 <T1. - If the intensity of the sublimation process exceeds the intensity of the desublimation process, then the current pressure pc in the chamber rises, and if, for a given duration t1,1 of the sublimation process, the pressure in the vacuum chamber-desublimator 1 reaches a pressure corresponding to the temperature of thermostatting, that is, pc = p1, then the
control computer 11 turns on thevacuum pump 9 and reduces the pressure in the vacuum chamber-desublimator 1 to the initial level p0. The process is carried out until one of two events occurs: - either the current number of sublimation cycles nc do not less than the specified value for this first stage, the first cycle of the sublimation process nc ≥ n1,1,
- either for a given time t1,1, the pressure in chamber pc will not be able to reach the value of p1 .
- The condition is checked that the current number nc of sublimation cycles do not exceeded the specified value for the given, first stage, the first cycle of the sublimation process nc ≤ n1,1:
- if the condition nc ≤ n1,1 is not met, then the
control computer 11 transmits the sublimation device to the next level of thermostatting, which is set by the temperature T2 ofshelves 2 of the vacuum chamber-desublimator 1. - if the condition nc < n1,1 is satisfied, then the transition to checking the condition pc < p1.
- The fulfillment of the condition is checked that for a given time t1,1 the pressure pc in the vacuum chamber-desublimator 1 did not reach the value p1, that is, pc < p1:
- if the condition pc < p1 is not met, then the
control computer 11 turns on thepump 9 and lowers the pressure inside the vacuum chamber-desublimator 1 to the value p0, and the process is repeated; - if the condition pc < p1 is fulfilled, then the
control computer 11 transmits the device to the next level of thermostatting, which is set by the temperature T2 of theshelves 2 of the vacuum chamber-desublimator 1. - Then, the next thermostatting level is carried out. For this, with the help of
heaters 3, theshelves 2 with the product are heated, followed by their thermostatting Tj = const, and then the current pressure pc of the sublimation process is measured by thepressure sensor 10, and thecontrol computer 11 checks its compliance to the parameters of the i-th cycle of the j-th level of the sublimation process. That is, compliance of the current pressure value pc to the limit value of the i-th cycle of sublimation of the j-th level of thermostatting, i.e., with pj. -
- However, the filler substance desublimates on the
desublimating surface 6, since TD < Tc ≤ Tj for all i=1,...,nTc and j=1,...,nT , decreasing the rate of current pressure pc growth. But if the intensity of the sublimation process exceeds the intensity of the desublimation process, then the pressure in the vacuum chamber-desublimator 1 increases, and if, for a given duration ti,j of the sublimation process, the current pressure pc in the vacuum chamber-desublimator 1 reaches or exceeds the pressure pj, that is, pc ≥ p,j, then thecontrol computer 11 turns on thevacuum pump 9, which reduces the pressure in the vacuum desublimator 1 to the initial level pj-1. The process is carried out until one of two events occurs: - the current number of sublimation cycles nc has reached or exceeded the specified amount ni,j of the cycle number of this level of the sublimation process nc ≥ ni,j;
- for a given time ti,j, the current pressure pc in the chamber do not reach the specified value of pressure pj, that is, pc<pj.
- The condition is checked by the
control computer 11, that the number of sublimation cycles nc is more or equal to the specified value ni,j for a given cycle of the sublimation process, that is, nc ≥ ni,j : - if the condition nc ≥ ni,j the condition is not met, then the
control computer 11 of the device turns on theheaters 3 of theshelves 2 and goes to the next thermostatting level, which is set by the temperature Tj+1 of theshelves 2 of the device. - if the condition nc ≥ ni,j is satisfied, then the transition to checking the condition pc < pj is carried out.
- The fulfillment of the condition is checked that for a current time ti,j the current pressure pc in the chamber has not reached the value pj. i.e., pc < pj
- if the condition pc < pj is not met, then the
control computer 11 turns on thevacuum pump 9 and lowers the pressure inside the desublimator chamber 1 to the value pj-1, and the process is repeated; - if the condition pc < pj is satisfied, then the device turns on the
heaters 3 of theshelves 2 and goes to the next level of thermostatting, which is set by the temperature Tj+1 of theshelves 2 of the device. - The parameters of the upper level of the last thermostatting level, i.e., j = nT , of the last cycle i = nTc coincide with the parameters of the upper level of the sublimation process, that is, T0 ≥ TnT = const and pc ≤ pnT ≤ P0.
-
- In this case, the filler substance desublimates on the
desublimating surface 6, since TD < TnT. If the intensity of the sublimation process exceeds the intensity of the desublimation process, then the current pressure pc in the desublimator chamber 1 increases, and if, for a given duration ti,nT of the sublimation process, the current pressure pc in the desublimator chamber 1 reaches pressure pnT, then thecontrol computer 11 of device turn on thevacuum pump 9 is turned on, which lowers the pressure in the desublimator chamber 1 to the initial level pnT-1. The process is carried out until one of two events occurs: - the current number of sublimation cycles nc reach or exceed the specified value of the cycle number of the thermostatting level nc ≥ nnT, or
- for a current time tc, the current pressure pc in the desublimator chamber 1 does not reach its limitation value, i.e., pc < pnT.
- The fulfillment of the condition is checked that the current number of sublimation cycles nc lower the specified value for the given thermostatting level nc < nnT.
- if the condition nc < nnT is not met, then the device switches its mode of operation to the completion of the sublimation process, that is, bringing the pressure inside the desublimator chamber 1 to the ambient pressure and the temperature of the
shelves 2 to the set value, and gives a signal about the end of the sublimation cycle. - if the condition nc < nnT is satisfied, then the transition to the verification of the condition pc ≤ pnT is made.
- The fulfillment of the condition is checked that for a current time tc,nT the current pressure pc in the chamber lower than the value pnT , that is, pc < pnT.
- if the condition pc < pnT is not met, then the
control computer 11 turns on thevacuum pump 9 and lowers the pressure inside the desublimator chamber 1 to the value of pnT-1, and the process is repeated. - if the condition pc < pnT is satisfied, then the
control computer 11 switches the mode of its operation to complete the sublimation process, that is, to bring the pressure inside the desublimator chamber 1 to the ambient pressure and the temperature of theshelves 2 till a predetermined value and gives a signal about the end of the goods sublimation. - Next, the desublimator chamber 1 is depressurized, the desublimator chamber 1 is unloaded, and the device is turned off.
Claims (5)
- A freeze-drying device containing a vacuum chamber-desublimator (1), in which one or more shelves (2) are located, adapted to accommodate the product to be freeze-dried; wherein the shelf or shelves (2) are equipped with one or more heaters (3) adapted to heat the shelves (2) and maintain a predetermined temperature of the shelves (2); wherein the freeze-drying device further comprises a refrigeration unit (4) connected to a heat exchanger (5), which is installed in such a way as to provide heat transfer to the desublimating surface (6) located in the vacuum desublimator chamber (1); wherein the desublimating surface (6) is connected to the heat exchanger (5) with the possibility of providing mutual heat transfer for cooling the desublimating surface (6); wherein the freeze-drying device further comprises at least one temperature sensor (7) of the desublimating surface (6) is installed and configured to take temperature readings from the desublimating surface (6); wherein the freeze-drying device further comprises one or more temperature sensors (8) of the shelves (2) adapted to take temperature readings from the shelves (2) and, preferably, protected by a housing to protect against the influence of the temperature of other elements of the device; wherein the freeze-drying device further comprises at least one vacuum pump (9) installed with the possibility of pumping out gases from the vacuum desublimator chamber (1); wherein the freeze-drying device further comprises at least one pressure sensor (10) installed with the possibility of obtaining pressure readings in the vacuum desublimator chamber (1); wherein the freeze-drying device further comprises a control computer (11), connected to the sensors (7, 8 and 10) for receiving a signal from these sensors, and also connected to the vacuum pump (9), the refrigeration unit (4) and the shelf heaters (3) for receiving and transmitting a signal for providing control of the mentioned elements of the device; wherein the control computer (11) contains computer-executable instructions or the control computer (11) is connected to a computer-readable hardware storing a computer program containing computer-executable instructions, the execution of which causes the control computer (11) to perform the following steps:(iii) freezing the desublimating surface (6) to a temperature TD< T0;(iv) freezing one or more shelves (2) to a temperature of the sublimation process beginning TB, so that TD<TB≤T0;characterised in that said execution further causes the control computer to perform the following steps:(v) evacuation of the desublimator chamber (1) by evacuating the air-vapor medium with a help of vacuum pump (9) to the pressure of the onset of sublimation PB so that PD < PB < P0, moreover, the pressure P0 and PD determined for the given values of T0 and TD according to the Clausius-Clapeyron equationwhere:p2 is the saturated vapor pressure of the filler substance at temperature T2, for the all-possible values of T2 (for example T2 = TB, T2 = TD or others; in this case pB = p2, pD = p2 or other will be determinates in accordance of equation result);p1 - the pressure of saturated vapors of the filler substance at temperature T1, for the beginning of the sublimation process p1 = P0;ΔHsubl,mol - molar latent heat of the phase transition taking place at temperature T, where T=(T1+ T2)/2;T1 - temperature of the previous thermostatting mode, for the beginning of the sublimation process T1 = T0;T2 is the temperature of the subsequent thermostatting mode, for the beginning of the sublimation process T1 = TB ;R = 8.314- J·K-1 ·mol-1 - universal gas constant;(vi) to determine the pressure pj according to the Clausius-Clapeyron equation, thermostatting temperature Tj of the shelves (2) is used, and then pj is used to comparing it with the current pressure pc in the vacuum desublimator chamber (1) that is measured by the pressure sensor (10) for the current time;(a) if the current pressure is equal to or more than the preset pressure - the pressure is lowering by a vacuum pump (9) to a predetermined level; if less than the preset one -(b) determining the cycle time of the pressure increase from the initial value, after pumping out the vapor-air mixture by the vacuum pump (9), to the calculated pressure value of the sublimation process, calculated based on the thermostatting temperature Tj-1 the shelves (2); if the current cycle time is less than the specified one - return to the step (vi), if equal to or greater than the specified one -(c) determining the number of cycles; if the number of cycles is less than the specified one - go to step (e), if equal or more -(d) determining the current pressure; if the current pressure is not less than the preset one - return to step (v), if less than the preset one -(e) determining the number of thermostatting levels; if the number of thermostatting levels is less than the specified one, heating the shelves (2) by heaters (3) to the next thermostatting level, determining the upper-pressure limit of the next thermostatting level according to the Clausius-Clapeyron equation; if the number of thermostatting levels is greater than or equal to the specified one, the device is shut down.
- The device according to claim 1, characterized in that steps (c) and (d) of said computer-executable instructions are combined into one step, which forces the processor to determine the number of cycles and the current pressure in the vacuum desublimator chamber (1); if the number of cycles not less than the specified one or the current pressure is lower than specified one - go to step (e); if the number of cycles is less than the specified one or the current pressure is not less than the specified one - transmit to the mentioned step (a) determining the current pressure; pumping down the pressure to the previous level; if the current pressure is lower than the preset one, transmit the sublimation process to perform next thermostating level: heating of the device shelves (2) to the next level of temperature, determination of the upper-pressure limit corresponding to this temperature using Clausius-Clapeyron equation, and transmit the sublimation process to the step (vi), if it is not less than the preset one, the pressure is lowered by the vacuum pump (9) to the preset level and returns to step (vi) if it is lower than the preset one, go to step (e).
- The device according to any one of claims 1-2, characterized in that the desublimating surface (6) is made in the form of the walls of the vacuum desublimator chamber (1) or in the form of one or more plates connected to the heat exchanger (5) with the possibility of providing mutual heat transfer.
- A freeze-drying method comprising the following steps:(i) loading the product onto one or more shelves (2) of the vacuum desublimator (1);(ii) sealing the vacuum desublimator chamber (1);(iii) freezing the desublimating surface (6) to a temperature TD< T0;(iv) freezing one or more shelves (2) to a temperature of the sublimation process beginning TB , so that TD<TB≤T0;characterised in that the method further comprises the following steps:(v) evacuation of the desublimator chamber (1) by pumping out the air-vapor medium with a vacuum pump (9) to the pressure of the onset of sublimation PB so that PD < PB < P0, moreover, the pressure PB and PD is determined for the given values of TB and TD according to the Clausius-Clapeyron equationwhere:p2 is the saturated vapor pressure of the filler substance at temperature T2, for the all-possible values of T2 (for example T2 = TB, T2 = TD or others; in this case pB = p2, PD = p2 or other will be determinates in accordance of equation result);p1 - the pressure of saturated vapors of the filler substance at temperature T1, for the beginning of the sublimation process p1 = P0;ΔHsubl,mol - molar latent heat of the phase transition taking place at temperature T, where T=(T1+ T2)/2;T1 - temperature of the previous thermostatting mode, for the beginning of the sublimation process T1 = T0;T2 is the temperature of the subsequent thermostatting mode, for the beginning of the sublimation process T1 = TB ;R = 8.314- J·K-1 ·mol -1 - universal gas constant;(vi) thermostatting temperature Tj of the shelves (2) is used to determine the pressure pj according to the Clausius-Clapeyron equation; pj is used to compare it with the current pressure pc in the vacuum desublimator chamber (1) that is measured by the pressure sensor (10) for the current time;(a) if the current pressure is greater than or equal to the preset pressure - pumping down the pressure to the previous level, if less than the preset one -(b) determining the cycle time of the pressure increase from the initial value, after pumping out the vapor-air mixture by a vacuum pump (9), to the calculated pressure value of the sublimation process, calculated based on the thermostatting temperature of the shelves (2); if the current cycle time is less than the specified one - return to the step (vi), if equal to or greater than the specified one -(c) determining the number of cycles; if the number of cycles not less than the specified one - go to step (e), if equal or more -(d) determining the current pressure; if the current pressure not less than the preset one - the pressure is lowered by a vacuum pump (9) to a predetermined level and return to step (vi), if less than the preset one -(e) determination of the number of thermostatting levels; if the number of thermostatting levels is less than the specified one, heating the shelves (2) by heaters (3) to the next thermostatting level, determining the upper-pressure limit of the next thermostatting level according to the Clausius-Clapeyron equation; if the number of thermostatting levels is greater than or equal to the specified one, the device is shut down.
- The method according to claim 4, characterized in that steps (c) and (d), i.e., determination of the number of cycles and determining the current pressure are combined into one step, which determines the number of cycles and the current pressure in the vacuum desublimator chamber (1); if the number of cycles not less than the specified number or the current pressure lower than the specified one - go to step (e), if the number of cycles less than specified one or the current pressure not less than the specified one - lowering the pressure in the vacuum chamber-decublimator (1) to the lower preset level and return to step (vi); (j) determining the current pressure; if the current pressure is equal to or more than a given one - the pressure the pressure is lowered by a vacuum pump (9) to a predetermined level and return to step (vi), if less than a given one - go to step (e).
Priority Applications (2)
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EP21180228.5A EP4105585B1 (en) | 2021-06-18 | 2021-06-18 | Freeze-drying method and apparatus |
PCT/EP2022/066230 WO2022263471A1 (en) | 2021-06-18 | 2022-06-14 | Freeze-drying method and device for its implementation |
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EP21180228.5A EP4105585B1 (en) | 2021-06-18 | 2021-06-18 | Freeze-drying method and apparatus |
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EP4105585B1 true EP4105585B1 (en) | 2023-10-11 |
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US4547977A (en) * | 1984-05-21 | 1985-10-22 | The Virtis Company, Inc. | Freeze dryer with improved temperature control |
US6971187B1 (en) * | 2002-07-18 | 2005-12-06 | University Of Connecticut | Automated process control using manometric temperature measurement |
BR112013002936B1 (en) * | 2010-08-06 | 2020-09-29 | Hospira Australia Pty Ltd | PREPARATION METHOD UNDERSTANDING A PLASTER OF BOTTLES |
ES2814824T3 (en) * | 2011-02-08 | 2021-03-29 | Kyowa Vacuum Eng | Calculation method and calculation device for sublimation interface temperature, bottom temperature and sublimation rate of material to be dried in freeze drying device |
US9459044B1 (en) | 2013-03-15 | 2016-10-04 | Harvest Right, LLC | Freeze drying methods and apparatuses |
US11243029B2 (en) | 2019-04-26 | 2022-02-08 | Purdue Research Foundation | Process monitoring and control for lyophilization using a wireless sensor network |
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- 2021-06-18 EP EP21180228.5A patent/EP4105585B1/en active Active
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