DE2659546A1 - METHOD FOR PRODUCING FROZEN GRANULES - Google Patents

Description

2659545

Z ι "

BOEHRINGER MÄNNHEIM GMBH 21O7

Process for the production of frozen granules

It is known that food, e.g. fish, meat and vegetables, can be preserved by freezing. Drinks, e.g. fruit juices, Coffee, tea and soups can be converted into easily soluble granules, so-called by freezing and drying in the frozen state Instant powder. Even medicinal products that are applied as a solution, but not in a solvent are stable, have been stored as lyophilisates for a long time.

In order to avoid destruction of the structure of the solid food or separation of the solutions, it is necessary to freeze these products as quickly as possible. In particular for freezing solutions are in the past a greater number of techniques have been developed.

It is known to freeze the solvents in block form in cooling containers and to close the blocks by cold grinding crush. Another method is to apply the liquid to a cooled, rotating cylinder or a likewise Cooled conveyor belt is sprayed on, from which it is detached again after solidification by appropriate scrapers or scratches will. In a variant of this apparatus, the heat is not generated by cooling the base but by spraying it on of easily evaporating coolants (carbon dioxide, nitrous oxide and especially liquid nitrogen) withdrawn. Common to these procedures is; that by crushing or detachment of the frozen product grains of various sizes and shapes, and in particular a considerable one

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Part of the dust arises, which the further processing in the freeze-drying difficult. (Schormüller, Handbuch der Lebensraittelchemie, 1974, pages 262-266, Springer-Verlag). As possible are free-flowing, i.e. spherical, frozen granules furthermore desirable for the production of porous tablets according to DT-OS 22 46 013.5.

From DTOS 2140747 it is known that granules can be made more uniform Shape and size can be obtained if the solution to be frozen is introduced into a moving bath through appropriate nozzles from a boiling fluorocarbon (Freorr ^) as a coolant sprayed. The resulting granulate is normally discharged discontinuously, as the discharge is continuous requires a considerable outlay in terms of equipment. Anything frozen onto parts of the apparatus, especially the stirrer The product makes a quick product change difficult, which can only be achieved by completely emptying, heating and thorough cleaning of the Plant is possible.

The object was therefore to provide a continuous process for the production of uniform, frozen granules to find for freeze-drying, which allows a quick change of the products with the lowest possible expenditure on equipment.

According to the invention the object is achieved in that in a sufficiently cooled environment, a stream of an easily evaporating liquid coolant in contact with a stream brings the product liquid, causing the product to dissolve in a shock freezes into small, spherical particles. These balls can then easily be separated from the gaseous coolant are freeze-dried and further processed by methods known per se. The freeze-dried ones produced in this way Granules are surprisingly very uniform, Easily soluble and optimally due to their spherical shape

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process, while one actually unevenly shaped grains or snowflake-like products are very different Size distribution would have expected.

As a coolant, all of the product solution can evaporate at normal pressure below the freezing point, but not with the product reactive liquid substances are used. Examples are nitrous oxide, alkylene oxide, ammonia, carbon dioxide, low-boiling hydrocarbons such as butane and propane, fluorocarbons called as freon. Liquid nitrogen has proven to be particularly advantageous because it is inexpensive does not react with any of the product solutions, does not cause environmental pollution by the escaping gases and due to its low boiling point cools the products very quickly and deeply. For products that are insensitive to oxygen can be used in the same way as liquid air. ;

A suitable one for carrying out the method according to the invention The device is shown in FIG. The device ordered from a conical downwardly narrowing Cooling column (1), which in its upper part has a centrally arranged feed nozzle (2) for the coolant and one or several nozzles (3) for the product solution and at the lower end an opening (4) for discharging the frozen granulate or has to escape the evaporated coolant. The pillar (1) is preferably an insulated inner jacket (5) as well an inner lining (6) between which the evaporating Coolant as a cooling and insulating material via a valve (7) can flow off. For the supply of coolant and product solution further controllable valves (R) and (9) are provided. The amount of dos flowing off through the valve (7) for cooling the outer jacket serving gaseous coolant can through

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an additional pressure relief valve (10) can be regulated. That Coolant is supplied from the storage tank (12) via a line (11), the pressure in the storage tank increasing the delivery causes. The product solution is taken from the storage container (13), which is preferably also double-walled and is cooled by the coolant discharged via the valves (7) and (10) by means of the line (14), removed by means of the line (15) and pressed into the product nozzle (3) via the pump (16) and the valve (9). The product nozzle can advantageously be heated to prevent freezing. The ones falling out through the opening (4) due to gravity Frozen granules can be collected in a collecting container and fed discontinuously for freeze-drying will.

The granules that fall out are preferably transported continuously over the conveyor belt (17) through a continuous Freeze-drying apparatus (18) are conveyed and then arrive in the packaging or storage station (19). For protection The conveyor belt (17) is still against the outside temperature and humidity until it enters the freeze-drying system surrounded by a jacket (20), the interior of which is also cooled by the evaporated coolant. if not Liquid nitrogen or liquid air is used as a coolant, a device for collecting and Reliquefaction of the evaporated coolant can be provided.

Fig. 2 shows a plan view of an arrangement according to the invention of 6 product nozzles (3) with the supply line (15) and the coolant nozzle (2).

It has proven advantageous to keep the product solution at a temperature just above the freezing point of the solution to the nozzles, as this makes the best use of the coolant. By varying the nozzle size of the nozzles (2) and (3) and the pressure with which the coolant and product solution are supplied, the size of the granules can be varied within wide limits. For economic reasons, the amount of liquid coolant supplied will be set so high that it is just sufficient.

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is enough to freeze the solution and the heat losses to cover the surroundings Depending on the concentration of the solution, the preferred liquid nitrogen is also used a consumption of 2-3 kg per kg of solution can be expected.

Of course, a large number of variations of the devices described are conceivable with which the inventive Process is also feasible, so of course the columns can be cylindrical or double-conical be shaped, instead of a simple coolant and product supply, several such nozzles can be present Instead of being continuously fed into a freeze-drying process, products can be collected and closed in a storage tank can be used at a later date.

Practically all materials can be used to build the device that are still at the temperature of the liquid coolant Have sufficient stability and toughness / stainless steel, copper, polyethylene or the like are examples called.

By spraying through two different nozzles at the same time, it is possible to spray incompatible components and so already a randomly mixed granulate to obtain. If desired, a different nozzle size or a different spray pressure can also be used get different grain size of the respective granules.

The method according to the invention is explained in more detail in the following example.

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example

1. Forming the frozen granules

A cooling column (1) according to FIG. 1 was used for the experiment, which have a height of 200 cm, a diameter of 80 cm and an outlet opening (4) with a width of 20 cm. The cylindrical part of the column had a length of 60 cm, the conical part had an angle of inclination of 30 °. Lines, valves and storage vessels corresponded of Fig. 1, instead of the continuous freeze-drying system shown a cooled storage vessel was placed under the outlet opening (4).

1 kg of sucrose was distilled in 10 1. Dissolved in water. These 10% solution was in a thermostatically controlled storage container . (13) and kept there at approx. + 1 ° C. Of the The freezing point of the solution was - 0.5 C. Liquid became liquid from a second storage container (12) (LN2) via an insulated copper line (11) and a control valve (0) fed to the LNp nozzle (2). This nozzle had a Inner diameter of 8 mm. The reaction space (1) was .solange pre-cooled until at the discharge opening (4) in the outflowing Nitrogen gas stream reaches a temperature of about - 50 ° C was.

The sucrose solution was then injected into the liquid nitrogen stream by means of the pump (IG) at an injection pressure of 1.5 bar via a polyethylene line (15), a control valve (9) and 6 product nozzles (3). The 6 nozzles were arranged in a circle at a cone angle of 60 ° around the LN ^ jet and had an internal diameter of approx. 0.15 mm. The distance between the exit point (lev, LNp from the LN ^ '^ üso and the Mi schpuiikt "with the Löijunq l .-' j was 12 5 mm, the AL ¹ Ki and product d" ise / Mi ru-h punk t 30 mm. Home contact with dom LNo-otrnhl

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The sucrose solution suddenly froze into small spheres, while most of the LN2 evaporated. This gaseous, cold nitrogen was used to cool the reaction space (1) and the storage container (13).

The frozen spheres fell down in the reaction space (1), were discharged through the opening (4) and collected in a deep-cold Dewar vessel. Their grain boundary range was between 0.16 and 1.0 mm spherical diameter, the Gaussian distribution having its maximum Lei 0.63 mm with 85 % mass fraction. Over 99 % of the granules were spherical in shape. It poured very well and did not stick together. In a chilled container it can be kept practically indefinitely. The consumption of LN2 was 2.5 kg / kg of solution (including precooling of the reaction space and losses).

2. Freeze-drying the frozen granules

The frozen spheres collected in the Dewar flask were poured onto pre-cooled metal sheets (−50 ° C.) of a lyophilization system and batch freeze-dried under the following conditions:

a) 13 hours at 0.2 mbar and 25 ° C,

b) 5 hours at 1.333 10 ^-3 mbar and 25 ° C.

After lyophilization, the grain boundary distribution and spherical shape of the granulate have not changed compared to the frozen state. Its density was calculated to be about 116 kg / m. The residual water content was 1.6 %. The product showed a homogeneous, white color. The granulate retained its shape when poured over and sieved. It can be easily rubbed between your fingers. The electrostatic charge is low. The balls hardly stick to each other and

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not at all on the walls of the bottles in which they are kept. The pourability is very good. That The flow behavior of the granulate is similar to that of a liquid. To the starting concentration of the single sucrose solution restore, 100 g of granules in 1 1 of dist. Given water. Without the liquid mechanically was moved, the solution time was 32 seconds.

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Claims (1)

Paten-tans ρ rüche I1.1 Device for the continuous production of granules consisting of a cooling column, feed devices for coolant flows and product liquid flows in the center the upper part and a discharge opening for the granulate at the lower end of the cooling column and outlets for gaseous coolant. 2 '. Device according to claim 1, characterized in that the product discharge opening via a conveyor belt with a continuous freeze-drying system is connected. 3. A method for the production of frozen granules, characterized in that the product solution in one from top to bottom moving stream of an easily evaporable, liquid coolant is entered and the after frozen granules remaining after the evaporation of the coolant is removed. 4. The method according to claim 3, characterized in that the size and solids content of the granules by the concentration, the viscosity and the injection pressure of the product solution as well as the nozzle diameter varies. 5. The method according to claim 3 and 4, characterized in that liquid nitrogen is used as a coolant. 809828/0085 ORIGINAL INSPECTED ^