JPS5935242B2 - freeze dryer shelf - Google Patents

Description

[Detailed description of the invention] This invention relates to a shelf for a shelf-type freeze dryer.

In a shelf-type freeze dryer, the number of shelves for storing materials to be dried is usually installed in the drying chamber, and the number of shelves is determined according to the capacity of the freeze dryer.

However, the structure of the shelf allows for pre-cooling to freeze the material to be dried before freeze-drying and heating for efficient drying during freeze-drying. The temperature of the upper and lower surfaces of the shelf and each column can be made uniform by circulating a medium (triclene, etc.) and installing a cooler using refrigerant expansion or a heater using an electric heater inside the shelf, or by combining the above methods. It is configured as follows.

Therefore, the temperature conditions given to the dried material are usually approximately the same as the temperature of the upper surface of the shelf in which the dried material is stored and the temperature of the lower surface of the upper shelf facing each other across a space.

Freeze-drying of pharmaceutical products is usually done in solutions (sometimes suspensions) in ampoules or vials.

), pre-frozen, and freeze-dried.

In this pre-freezing, the solution is frozen by cooling the shelf containing the material to be dried.

The solution is then supercooled to a very low temperature.

The moment supercooling breaks, the entire solution solidifies rapidly.

This rapid solidification causes the solute and solvent in the solution to be distributed in an extremely fine state, and when drying progresses during the subsequent freeze-drying period and the evaporation surface descends to the lower layer, the existing The drying layer has an extremely porous structure, and if there is an obstacle when water vapor is evaporated, the permeation rate will be slowed down, which will cause a delay in the freeze-drying rate.

In addition, such rapid solidification often results in a mextable crystal structure, which may cause melting during the heating process during freeze-drying, impeding drying and further impairing commercial value.

In addition, during the freeze-drying period, the conventional shelf structure switches the shelf from cooling to heating, and heat is supplied mainly from the top surface of the shelf where the material to be dried is stored, from the bottom of the material to the evaporation surface through the undried frozen layer is supplied to

In this case, it is not preferable that the temperature of the portion closest to the shelf contact portion of the dried material also exceeds the eutectic point.

The shelf temperature is controlled low to ensure safety, and heat is not efficiently supplied to the evaporation surface.

Furthermore, the application of freeze-drying is often seen in food products and pharmaceutical products, and can be said to be an extremely effective method from the viewpoints of maintaining product stability, restorability during regeneration, and convenience.

However, in order to take advantage of these characteristics, and because of the constraint of drying at low temperatures, freeze-drying has the drawback of requiring an extremely long time.

This invention attempts to eliminate these conventional drawbacks by configuring the shelves into upper and lower shelves, each of which can independently control the temperature. During pre-freezing, the top surface temperature of the shelf containing the material to be dried remains unchanged. Control the temperature to a low temperature to enable freezing,
On the other hand, the temperature of the lower surface of the upper shelf, which faces each other across the space, can be independently controlled to maintain a high temperature within a range that does not impair the quality of the material to be dried.

In this way, the solution filled in the ampoule or vial will have a temperature gradient of low temperature at the bottom and high temperature at the top, and the portion and degree of supercooling will be alleviated.

Therefore, even if the solidification occurs due to supercooling or rupture, it will not reach the entire surface, but only in a portion, and thereafter, the solidification will gradually be completed toward the upper layer.

This gradual solidification promotes the growth of large ice crystals,
It progresses upward in a shelf-like manner.

Therefore, the porous structure of the already dried layer is relaxed, water vapor permeability is increased, and the decrease in drying rate is alleviated.

In addition, during pre-freezing, even if the entire substance appears to solidify, the average temperature of the material to be dried is high, so the proportion of solids is small, and the remaining liquid solidifies slowly, which increases the drying rate for the same reason. Become.

To explain the diagram, FIG. 1 is an explanatory diagram of conventional shelf-type freeze drying, in which shelves 2 are arranged in several stages inside a drying chamber 1, and a heat exchanger 6 and a circulation pump 1 are connected to each other via piping 3 outside the chamber. is connected to.

The interior of the refrigerator is vacuumed during drying.

(Since this is a well-known means, it is not shown in the figure.

) Place an ampoule or vial 4 on the shelf 2 to contain the material to be dried.

The heat exchanger 6 is associated with heating means 8 or a refrigerator 9.

In the preliminary freezing stage, the medium is cooled by the refrigerator 9 via the heat exchanger 6, and the medium is circulated by the circulation pump 1 to cool and freeze the ampoule 4.

Then, the heating means heats the medium through a heat exchanger,
Vacuum drying is promoted while heating the ampoule 4 moderately from below.

In the figure, 5 indicates the evaporation surface. In this conventional device, since the material rapidly solidifies from supercooling, it becomes porous and when water vapor is released, the permeation rate becomes slow and the freeze-drying speed is delayed.

Furthermore, during vacuum drying, the ampoule is heated from below, but due to restrictions on the eutectic point of the material to be dried, if the shelf v temperature is raised too much in order to speed up drying, it may cause melting during the heating process, causing problems with drying.

This invention attempts to eliminate these drawbacks and is the second
The figure shows an explanatory diagram of the shelf of the present invention.

The shelf 20 according to the invention is an upper shelf 2'l (!:, upper shelf 2
It is divided into 2.

The upper shelf 21 is connected to a heat exchanger 25 and a circulation pump 26 by a pipe 24, and the upper shelf 22 is connected to a heat exchanger 28 and a circulation pump 29 by a pipe 2γ.

During pre-freezing, the heat exchanger 25 uses a refrigerator to cool the medium to -40°C to -50°C, and the circulation pump 26 cools the medium to the shelf 2.
0 to the upper shelf 21, and the ampoule is cooled from below.

At the same time, in the heat exchanger 28, the medium is heated by the heating means and the heated medium is sent to the upper shelf 22 of the shelf 20 by the circulation pump 29, and as shown in the figure, the medium is sent to the upper shelf 22 of the shelf 20, which is one level above the shelf on which the ampoule 4 is placed. Heat is radiated above the ampoule from the upper shelf 22' of the ampoule, and an appropriate temperature gradient is formed in the ampoule by cooling from below and radiation from above. After that, the solidification is gradually completed toward the upper layer, and because the solidification is slow, large crystals are formed and become horizontally shelf-like, increasing water vapor permeability and reducing the decrease in drying rate.

In the figure, 30 and 32 are heaters connected to heat exchangers 25 and 28, respectively, and 31 and 33 are refrigerators.

Next, in the vacuum drying stage, heat exchangers 25 and 28 independently control the heating of the medium.

At this time, if the temperature of the medium going from the heat exchanger 25 to the upper shelf 21 is 12, and the temperature of the medium going from the heat exchanger 28 to the upper shelf 22 is tlJ, the condition 11>12 is always maintained.

Even during pre-freezing, the upper shelf is cooled and the upper shelf is heated, so it goes without saying that 11:>12, and the condition of 11>t2 is maintained in any case. It is.

Invention 1 has the above-described structure, in which the temperature of the upper surface of the shelf on which the items to be dried are placed is set to the conventional temperature condition, while the lower surface of the shelf one step above facing each other across the space is independently temperature controlled. Therefore, by maintaining an appropriate high temperature and supplying heat to the evaporation surface using radiant heat, heat can be supplied safely and effectively, and freeze-drying can be completed in a short time.

In addition, the upper shelf in the present invention uses a medium circulation system instead of
A similar effect can be obtained by a direct heating method such as a hot plate.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional device, and FIG. 2 is a detailed explanatory diagram of the present invention. Explanation of symbols: 1...Drying cabinet, 2...Shelf, 3...Piping, 4...Ampoule, 5.
...Evaporation surface, 6...Heat exchanger, γ...
...Circulation pump, 8...Heating means, 9...
...Freezer, 20...Shelf, 21...
Upper shelf, 22... Upper shelf, 24,2γ...
... Piping, 25, 28... Heat exchanger, 26,
29...Circulation pump, 30°32...
Heating means, 31, 33... bent refrigerator.

Claims (1)

[Claims] 1. A shelf for a freeze dryer, characterized in that the shelf in the drying chamber has a combination structure of upper and lower layers, which can independently control the temperature of the upper and lower layers.