Powder sterilization method and device

Abstract

A powder sterilization method for sterilizing powder, in particular an active pharmaceutical ingredient in powder form or food in powder form, using fluid vapor, in particular steam. According to the invention, the fluid vapor is applied to the powder in an evacuated treatment chamber (3), in particular it is applied to the powder during its free fall along a drop section (7), in particular in countercurrent.

Claims

1. A powder sterilization method for sterilizing powder using fluid vapor, the fluid vapor being applied to the powder in an evacuated treatment chamber (3), the fluid vapor being applied to the powder during a free fall of the powder along a drop section (7), wherein evacuation means for providing a negative pressure in the treatment chamber (3) are operated in a permanent and continuous manner to provide a negative pressure in the treatment chamber, a suction pressure thus being permanently applied and the application of the fluid vapor causing the pressure to rise during the free fall after the powder has been supplied, and the evacuation means continuing to apply suction to the treatment chamber (3) during said fluid vapor application.

2. The method according to claim 1, wherein the fluid vapor condenses on a powder surface and the powder is dried by evaporating condensate from the powder surface, during the free fall, before discharging the powder from the treatment chamber (3).

3. The method according to claim 1 wherein the powder to be sterilized is supplied to the treatment chamber (3) when the treatment chamber (3) is at a first negative pressure level (Ppre), between 0.1 mbar and 300 mbar, and the fluid vapor is applied to said powder during the free fall along the drop section (7), and wherein the pressure in the treatment chamber (3) rises to a second pressure level (Pmax) above 0.5 bar, and wherein the pressure level is reduced for drying the powder before the powder is discharged from the treatment chamber (3), while the powder is still falling freely along the drop section (7), to a third negative pressure value (Ppost).

4. The method according to claim 1, wherein powder to be sterilized is supplied to the treatment chamber (3) via an inlet negative pressure lock (8), and wherein sterilized powder is discharged from the treatment chamber (3) via an outlet negative pressure lock (9), after the free fall along the drop section (7) and after the application of fluid vapor carried out during the free fall.

5. The method according to claim 4, wherein powder to be sterilized is supplied to the treatment chamber (3) solely during, or solely after, or during and after the discharging of sterilized powder.

6. The method according to claim 1, wherein the fluid vapor enters the treatment chamber (3) at an increased pressure compared to the pressure level in the treatment chamber (3) at the time the fluid vapor application starts.

7. The method according to claim 1, wherein the fluid vapor enters the treatment chamber (3) at an angle between a main jetting direction of the fluid vapor and vertical (V) between 1° and 60°.

8. The method according to claim 1, wherein the fluid vapor enters the treatment chamber (3) at several points spaced apart along the drop section (7) and/or at several points spaced apart in the circumferential direction.

9. The method according to claim 1, wherein the fluid vapor enters the treatment chamber (3) via at least one ring nozzle assembly (12, 13) extending in the circumferential direction along the drop section (7).

10. The method according to claim 1, wherein the fluid vapor is saturated or superheated when it enters the treatment chamber (3).

11. The method according to claim 1, wherein the treatment chamber (3) is heated to a temperature from a range between 150° C. and 400° C. by means of a wall heating device.

12. The method according to claim 1, wherein the powder is dispersed and/or separated and/or swirled and/or loosened, above and/or in an initial area of the drop section (7), in order to improve powder cloud formation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, features and details of the invention can be derived from the following description of preferred exemplary embodiments and from the drawings.

(2) In the following,

(3) FIG. 1 is a highly schematized view of a sterilization device realized according to the idea of the invention for performing a method according to the invention,

(4) FIG. 2 is a diagram showing the absolute pressure in a treatment chamber of the sterilization device over time, i.e., during a sterilization and drying process,

(5) FIG. 3 is an alternative embodiment of a sterilization device realized according to the idea of the invention and comprising a treatment chamber which has an annular contour in a cross-sectional view and into which vapor for sterilizing the powder during the free fall can be supplied or is supplied from the radial inside and from the radial outside,

(6) FIG. 4 is an alternative embodiment of a system which has four sterilization devices which are operated in parallel and to which powder to be sterilized can be supplied in portions and in a volume-metered manner via the negative pressure lock,

(7) FIG. 5a is a system comprising four sterilization devices realized according to the idea of the invention which are connected to a common packaging device on the outlet side and into which, by analogy with the sterilization device according to FIG. 3 and FIG. 4, powder portions to be sterilized are not supplied via an impeller lock, but via volumetric volume metering devices based on negative pressure, and

(8) FIG. 5b is a vacuum-based volume metering device as a vacuum lock which is used in the system shown in FIG. 5a and FIG. 4.

DETAILED DESCRIPTION

(9) In FIG. 1, a sterilization device 1 is shown. Sterilization device 1 comprises a vessel 2 which is made of stainless steel, for example, and which is elongated along the vertical and which limits an elongated treatment chamber 3 (reactor chamber). The realistic diameter length ratio cannot be derived from the schematic view—in fact, the diameter of treatment chamber 3 is considerably smaller than its length and height extension.

(10) Vessel 2 or treatment chamber 3 can be heated, for example to a temperature of 300° C., via heating means 4 comprising a wall heating device, which is realized as an oil heating device in the present case. The arrows in the left drawing portion illustrate the flow and return flow. Treatment chamber 3 can be evacuated, i.e., can reach a negative pressure level, by means of evacuation means 6 comprising a vacuum pump 5.

(11) Treatment chamber 3 comprises a drop section 7 which extends along vertical V and along which powder supplied via an inlet negative pressure lock 8, in an exemplary manner realized as an impeller lock, can fall freely downwards along vertical V inside evacuated treatment chamber 3 towards an outlet negative pressure lock 9 also realized as an impeller lock in an exemplary manner. Instead of an impeller lock, a preferably vacuum-based powder metering device is preferably used as inlet negative pressure lock 8 for metering powder portions to be sterilized one after the other.

(12) In the shown exemplary embodiment, facultative dispersing means 10 are disposed downstream of inlet negative pressure lock 8 in order to improve powder cloud formation or loosening of the supplied powder. In the shown exemplary embodiment, dispersing means 10 comprise a vibrating grid.

(13) Drop section 7 is divided into an upper fluid vapor application section in which fluid vapor can be applied to the free-falling powder, in particular in the form of a powder cloud. To this end, fluid vapor application means 11 (shown in a highly schematized and sectional manner) are provided. In the specific exemplary embodiment, said fluid vapor application means 11 comprise two ring nozzle assemblies 12, 13 which are spaced apart along vertical V and which are connected to a vapor generator via a corresponding vapor line for generating saturated vapor. A drying section is disposed below the fluid vapor application section, the powder to which the fluid vapor has been applied being dried or dryable in said drying section by the evaporation of the condensate formed on the powder surface by the fluid vapor application. This is achieved by a corresponding negative pressure atmosphere during the free fall through the drying section.

(14) When the sterilized and dried powder reaches the lower area, it is discharged from treatment chamber 3, which is at a negative pressure level, via outlet negative pressure lock 9.

(15) FIG. 1 shows that, in the present embodiment, the powder is supplied and treated in portions, in such a manner that a supplied powder portion to be sterilized is optionally loosened or dispersed by means of dispersing means 10 and then falls down along drop section 7 in evacuated treatment chamber 3 while fluid vapor, steam in the present case, is applied to the powder portion. The powder with the condensate which is condensed thereon continues to trickle down and is simultaneously dried. As will be explained on the basis of FIG. 2, the fluid vapor application causes the pressure level in vessel 2 to rise, starting from a first negative pressure level, to a second pressure level, for example to or even above a normal pressure (alternatively to a higher negative pressure level), evacuation means 6 ensuring that a sufficient negative pressure level is reached again at least during a period of time of the free fall along the drying section of the drop section in order to evaporate the condensate. A third negative pressure level is reached towards the end of the drying process at the latest.

(16) In FIG. 2, a possible pressure development in the treatment chamber during a combined sterilization and drying process for a respective powder portion is shown, i.e., plotted over time. Said process repeats over time for each new powder portion which is supplied into treatment chamber 3.

(17) It can be seen that a powder portion is supplied into the treatment chamber, is loosened, if required, and starts to fall along the drop section during a first period of time I during which a first negative pressure level at a pressure P.sub.pre of approximately 0.12 bar absolute is present in the present case. During the period of time II of 0.2 s in the present case, fluid vapor is applied to the powder during its free fall along the fluid vapor application section of the drop section, the pressure thus increasing to a second pressure level (in the present case a pressure P.sub.max of 1.3 bar absolute, for example). During the subsequent, longest period of time III, the powder falls along the longer drying section of the drop section, the pressure level being reduced during this continuing free fall, in the present case to a third negative pressure level (P.sub.post), i.e., a pressure of approximately 0.35 bar absolute, which is slightly higher, namely by pressure difference ΔP.sub.0, than the initial, first pressure level P.sub.pre. The dried powder is then discharged. Prior to a new supply of a next powder portion, the pressure level is preferably reduced from P.sub.post to P.sub.pre. If the vacuum pump and the length of the drop section are dimensioned in a corresponding manner, a third negative pressure level (P.sub.post) can preferably be reached during the free fall, said third negative pressure level being reduced to first pressure level P.sub.pre.

(18) Alternative exemplary embodiments realized according to the idea of the invention are explained below, differences compared to the aforementioned exemplary embodiments being primarily explained in order to avoid repetitions. Components of exemplary embodiments described below can be replaced by components of the aforementioned exemplary embodiments and vice versa.

(19) In FIG. 3, a sterilization device 1 is shown in which treatment chamber 3 is annular, in the present case circular, in a cross-sectional view. Vessel 2 comprises a radially outer wall 14 which limits vessel 2 on the radial outside by analogy with the aforementioned exemplary embodiments. In a central area, vessel 2 comprises or includes a (in the present case circular-cylindrical) center section 15 which has an inner vessel wall 16 which limits treatment chamber 3 on the radial inside. It can be seen that fluid vapor application means 11, in an exemplary manner in the form of ring nozzle assemblies, are disposed on the radial outside, i.e., both in the area of outer wall 14 and on the radial inside, i.e., in the area of inner wall 16 of center section 15, in order to be able to supply fluid vapor both from the radial outside and from the radial inside, in particular diagonally upwards into treatment chamber 3 in order to ensure uniform mixing with the powder to be sterilized during the free fall. In the present case, center section 15 extends up to an upper edge of the vessel; alternatively, treatment chamber 3 can be free in its center area in an upper area.

(20) In the present case, inlet negative pressure lock 8 is realized as a vacuum-operated volume metering device instead of an impeller lock. To this end, inlet negative pressure lock 8 comprises a metering chamber 17 to which negative pressure is applicable via a negative pressure line 18 in order to be able to suck powder from a powder reservoir 20 (powder reservoir vessel) via a supply line 19. Metering chamber 17 is closed on the outlet side via closing means 21. After filling metering chamber 17, in particular sterile compressed air is applied to metering chamber 17 via a compressed gas line 22 and metering chamber 17 is opened towards vessel 2 or treatment chamber 3 by displacing closing means 21 in a corresponding manner and the metered powder volume is supplied into treatment chamber 3 which, in an exemplary manner only, has an annular contour. To avoid confusion, facultative dispersing means are not illustrated. After falling through the drop section, the powder which has been sterilized by applying vapor and which has been dried during the free fall arrives at an outlet negative pressure lock 9 which leads to a packaging device 23 which is located directly downstream and by means of which the powder can be packed into final packaging 24, which is realized as pouches in the present case, by gravity.

(21) The exemplary embodiment according to FIG. 4 is a system 25 having several sterilization devices 1. Respective elongated vessels 2 each having an integrated drop section 7 and nozzle assemblies for injecting vapor are shown. In a lower area, each sterilization device 1 has an individual packaging device 23.

(22) Supports 26 which support respective vessels 2 and respective inlet negative pressure locks 8 can be seen, one inlet negative pressure lock 8 being shown in isolation on the right in the drawing layer. Inlet negative pressure lock 8, which is shown in principle in FIG. 3, is realized as a vacuum-based metering device by means of which powder can be sucked from a powder reservoir 20, which is a common powder reservoir 20 in the example at hand, via a supply line 19 and supplied in portions to the respective vessel in a volumetrically metered manner, preferably by applying negative pressure and/or by means of a discharge plunger, after opening the closing means of the metering chamber.

(23) The exemplary embodiment according to FIGS. 5a and 5b essentially corresponds to the exemplary embodiment according to FIG. 4 but differs from the exemplary embodiment according to FIG. 4 in that individual sterilization devices 1 or their vessels 2 are connected to one another on the outlet side via pipelines 27 leading to a common packaging device 23 or, alternatively, to a common reservoir. In the exemplary embodiment according to FIG. 5a, the inlet negative pressure locks are also realized as volume metering devices which suck powder from a powder reservoir 20 via supply lines 19 and which supply said powder to respective treatment chamber 3 by means of a plunger and/or by applying compressed gas after opening metering chamber closing means.

(24) Reference sign 28 shows preferably superheated vapor being supplied into a vapor distribution system by means of which vapor can be supplied to the outlet openings, in particular the ring nozzle assemblies, which are disposed in treatment chamber 3. Reference sign 29 is assigned to a heating means flow, in the present case an oil flow for the heating of the outer wall.

REFERENCE SIGNS

(25) 1 sterilization device 2 vessel 3 treatment chamber 4 heating means 5 vacuum pump 6 evacuation means 7 drop section 8 inlet negative pressure lock 9 outlet negative pressure lock 10 dispersing means 11 fluid vapor application means 12 ring nozzle assembly 13 ring nozzle assembly 14 outer vessel wall 15 center section 16 inner vessel wall 17 metering chamber 18 negative pressure line 19 supply line 20 powder reservoir 21 closing means 22 compressed air line 23 packaging device 24 final packaging 25 system 26 support 27 pipelines 28 arrow (vapor supply) 29 arrow (heating means flow) V vertical P.sub.pre negative pressure level while powder is being supplied (first negative pressure level P.sub.max pressure level immediately after fluid vapor application (second negative pressure level) P.sub.post negative pressure level at the end of the drying process (third negative pressure level)