US3721527A

US3721527A - Method for sterilizing bulk materials

Info

Publication number: US3721527A
Application number: US00116539A
Authority: US
Inventors: T Ernst; F Lodige; J Lucke; W Lodige
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-10-10
Filing date: 1971-02-18
Publication date: 1973-03-20
Anticipated expiration: 1990-03-20
Also published as: GB1243823A; FR1600886A

Abstract

A method and apparatus for sterilizing bulk materials. In the method, sterilization is achieved by means of steam or hot gas. Batches of the material are centrifuged in a closed chamber with simultaneous addition of sterilizing medium. Immediately thereafter, the sterilizing medium is separated out from the material at a sub-atmospheric pressure with centrifuging of the material. The apparatus comprises a pressure-tight container with a builtin centrifuge mechanism. A closed conveyor device is connected to the inlet and outlet of the container, for the supply and discharge of material being handled.

Description

United States Patent Lodige et al. 1 1March 20, 1973 [5 METHOD FOR STERILIZING BULK 1,915,242 6/1933 Rlbelro ..99 215 x MATERIALS 2,086,338 7/ 1937 Sodergreen 2,656,988 10 1953 Smith 1 Inventors! Wilhelm g Frill g Josef 2,958,570 11/1960 Fessler Lucke, all of Paderbom, Germany; 3,069,734 12/1962 Leuthner Theodor Ernst, Wettingen, Switz 3,088,179 5/1963 Leuthner ]and 3,102,781 9/1963 Hoskins et a1.

. 3,164,181 1/1965 Kunz [731 Assignees: Wilhelm Lodige; Fritz Lodige; Josef 3,548,737 12/1970 Evans ..99/216 x STERILE Lucke; by said Theodor Ernst, Paderborn, Germany Filed: Feb. 18, 1971 Appl. No.: 116,539

Related US. Application Data Continuation-in-part of Ser. No. 760,803, Sept. 19, 1968, abandoned.

Foreign Application Priority Data Oct. 10, 1967 Germany ..P 16 42 087.4

US. Cl. ..21/56, 21/2, 21/58,

21/93, 21/94, 21/96, 21/98, 99/216 Int. Cl. ..A61l 13/00, A611 1/00 Field of Search ..21/56, 93, 2, 91, 92, 9598,

References Cited UNITED STATES PATENTS 8/1932 Anges ..21/91 ux AIR STEAM STERILE AIR Primary Examiner-Barry S. Richman Attorney-Oberlin, Maky, Donnelly & Renner 5 7] ABSTRACT The apparatus comprises a pressure-tight container with a built-in centrifuge mechanism. A closed conveyor device is connected to the inlet and outlet of the container, for the supply and discharge of material being handled.

6 Claims, 2 Drawing Figures VACUUM i l STEAM STEAM PATENTEUmzmm 3,72 1,527

SHEET 1 BF 2 VACU U M LIJ i 1 LLl 2 5 INXENTORS a WILHELMHLODIGE, *J, FRITZ LQDIGE,

JOSEF LUCKE ERNST THEODOR STERILE AIR STEAM 1* VACUUM STEAM FIG. 2

. IINVENTORS WILHELM LO'DIGE, FRITZ LGDIGE, JOSEF LUCKE ERNST THEODOR METHOD FOR STERILIZING BULK MATERIALS CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of our earlier application, Ser. No. 760,803, filed Sept. 19, 1968 and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a method of sterilizing materials by means-of steam, or by means of hot gas. More especially bulk materials such as chips, fibers, powders, foods, feeding stuffs, etc., can be sterilized. The invention is further concerned with apparatus for sterilizing such materials.

In the chemical and pharmaceutical industry, as well as in the foodstuffs industry, it is often necessary for pulverous or granulated products which are to be processed to be satisfactorily sterile. Steam sterilization is for example suitable for sterilizing such materials.

The steam sterilization of pourable goods has hitherto been carried out in so-called steam autoclaves, saturated steam being supplied to the material to be treated, the material being introduced into a chamber capable of being closed in gastight manner. Sterilization then proceeds automatically in accordance with a preselected time program, but can also be manually controlled. The charging and emptying of the autoclave, and also the commencement of the program, is in this case effected manually by the operating personnel. As a consequence, this known process is only suitable for dealing with very small quantities of material, the handling of larger quantities being precluded because of the necessary manual work with numerous separate operations of this method. The charging and emptying of the autoclave could only be carried out mechanically at heavy expense. In addition, a disadvantage is that the autoclave has to be set up in a sterile room if it is desired to prevent the sterilized materials coming into contact with non-sterile surroundings when the autoclave is emptied. Furthermore, the

sterilization time, depending on the thickness of the bed in the autoclave in which the material to be treated, is long, because the sterilizing medium,such as saturated steam or hot gas, must completely and sufficiently penetrate through the entire material before sterilization is completed. Nevertheless, with usual sterilization times, it is never certain that the sterilizing medium acts for a sufficiently long time on all parts of the material to be sterilized and thus for the treated batch to have become sterile throughout. Finally, it is also impossible by the known methods to undertake a homogenous conditioning of the sterilized material as regards its temperature and its moisture within a prescribed timetable. A uniform conditioning is however of great importance, particularly with foodstuffs and chemically active substances and also with litter or bedding for test animals in research laboratories.

An object of the invention is to overcome the aforementioned disadvantages connected with the known sterilization using saturated steam and to provide the possibility of being able to carry out the entire sterilizing operation in a fully automatic manner within an apparatus to be sealed off in sterile form from the exterior and with a shortest possible treatment time. It is also possible, after the sterilization, to add to the material other already sterile substances which do not withstand the high treatment temperatures of steam sterilization.

According to the invention, there is provided a method of sterilizing bulk materials by means of steam or hot gas, wherein the material is sterilized batchwise in a closed chamber with centrifuging and with simultaneous addition of sterilizing medium, and, immediately thereafter, the sterilizing medium is separatedout from the material at a sub-atmospheric pressure with centrifuging of the bulk material. As a consequence, it becomes possible for the charging and emptying of the sterilizing apparatus to be effected automatically without the assistance of manual labor. The sterilizing apparatus can without hesitation be set up in a non-sterile room, since the emptying of the apparatus and of the carrying away of the sterilized material can be effected in a closed system. Due to the fact that the material to be sterilized is loosened, advantageously by the known centrifuging and whirling method, during the sterilizing operation, the sterilizing medium can very quickly and uniformly come into contact with all parts of the material, whereby a good sterilizing effect is produced with minimum sterilization times. The same also applies as regards the removal of the sterilizing medium from the sterilized material after the sterilizing operation has been completed.

In order to accelerate the sterilization, which is carried out. batchwise, the material to be sterilized can be preheated, before starting sterilization, by means of relatively small quantities of the sterilizing medium, for example, while the material is introduced into the sterilization vessel. This medium serving for preheating purposes is then removed from the sterilizing vessel before starting the sterilizing operation proper or is even also used for the subsequent sterilization, so that the demand for sterilizing medium becomes correspondingly smaller.

If the material is sterilized with saturated steam, then drying of the material under the action of a vacuum has to be carried out after the sterilizing operation in accordance with a further development of the invention, the liquid which is still adhering to the material or to the particles thereof being substantially removed. When sterilizing with hot gas, the gas is likewise extracted by means of a vacuum after completing the sterilization. Drying is unnecessary in this case, since the hot gas has not supplied any liquid or moisture to the material.

However, if a drying operation is necessary, then in addition external heat can be supplied to the material while drying. It is at the same time possible to condition the material while drying, so that it contains a prescribed moisture content at a specific temperature. Following the drying operation, the sterilized material can in addition be ventilated with sterile air and then stored in a sterile container.

This method can be carried out in all stages while maintaining a prescribed timing program and in a minimum period of time and produces superior results.

For carrying out the method as proposed, an apparatus is provided which comprises a container which can be closed in pressure-tight manner and which is specially adapted for sterilization operations which container has a built-in centrifuging mechanism, while a closed transport device for supplying and discharging the material being treated is connected to the inlet and outlet, respectively, of said container. The sterilizing operation and the drying operation, but at least sterilization and a preliminary drying, can be affected in one and the same container. It is also possible for the sterilization with the preliminary drying, and the drying proper, to take place successfully in separate containers.

[n the accompanying drawing,

FIG. 1 is a side elevational view of an apparatus of the invention; and,

FIG. 2 is a transverse sectional view taken on line 2 2 of FIG. 1.

The apparatus comprises a cylindrical container 1, in which the sterilization and also the preliminary drying of the material to be treated is carried out. Mounted longitudinally of the container is a shaft 2 which is driven by a motor 3, preferably at different speeds which can be selected as desired. The shaft carried centrifuge mechanism to be described hereinbelow for thoroughly loosening and whirling the material in the container 1 for sterilization and preliminary drying purposes.

The container 1 has a filling mechanism 4 which can be closed in pressure-tight manner, and an inlet pipe 5 of said mechanism has fitted herein a bucket wheel lock chamber 6, which is to prevent the high treatment temperatures obtaining in the container from being transferred into the supply device, whereby a fire could easily be caused therein. A pipe conduit can be connected to the inlet side of the said bucket wheel lock chamber 6, said pipe providing a connection to a storage vessel for the material being handled.

Arranged on the top of the container 1 is a dome 7, into which opens a vacuum pipe 8 which can be closed off. A closable expansion pipe 9 is also connected to the dome 7.

Opening into the front end of the container 1 is a pipe 10 for the admission of sterile air, when a shut-off valve 11 provided in this pipe is opened. A pipe 12 for the supply of the sterilizing medium, such as saturated steam or hot gas, also opens into the container 1.

The complete container 1 is provided with an insulating jacket 13, which is arranged in the region of the cylindrical container wall at a distance 14 around the container 1. By this means, a double jacket for the supply of a heating medium is formed. This double jacket is provided with inlet unions 15 for steam or the like and an outlet union 16 for condensate, etc., and

contains guide plates (not shown) for guiding the heating medium. It is obviously also possible for a liquid heating medium to flow in the reverse direction through the double jacket.

Arranged on that end wall of the container 1 which is opposite to the inlet end is a closure plug 17 which, when closed, maintains the pressure in the container. The closure plug 17 is opened and closed by an electric motor 18. This closure plug or flap 17 opens into a discharge housing 19, on the top of which is arranged an inspection or cleaning flap 20 which can also serve as a suction union for the medium used for making the apparatus sterile, which medium is as far as possible discharged through the pipe 9.

The container 1 is supported on a similarly constructed cylindrical drying container 21. A centrifuge mechanism to be described is driven by a shaft 22 which is in turn driven by a motor 23 mounted exteriorly of the container. An inlet union 24 of the container 21 is connected to the outlet housing 19 of the container l. The container 21 likewise has a double jacket 29 with a lower inlet union 30 and an upper outlet union 31 for a heating medium, such as hot water. The lower container 21 is likewise provided with an outlet housing 32, which encloses a closure flap or valve 33, which can be opened and closed by an electric motor 34. Suitable inlet and discharge lines are provided.

The container 1 is supported by means of

feet

25 and 26 on the container 21, and the latter in its turn can be supported by

feet

27 and 28 on any suitable support.

Referring to the means for centrifuging the material in the container 1, a plurality of axially spaced, radially extending arms 37 are fixed to the shaft 2 and carry at the ends thereof mixing tools 35 shaped generally in the form of a plow-share. The tools 35 at the opposed ends of the container are transversely truncated to contact the end walls of the container. It will be noted that each tool 35 is offset from the axially adjacent tools, as can also be seen in FIG. 2. Each tool 35 has a flat, wallengaging, outer edge which functions to scrape and loosen the material from the walls of the container and to throw the material, due to the shape of the tools, on either side of the tool, thereby enhancing the mixing operation.

It will also be noted that tools 35 are axially offset from each other thereby serving to facilitate movement of the material from the feed to the discharge end of the container. The speed of the motor 3 is such that the material by centrifugal force is thrown radially outwardly toward the container walls for scraping action by the tools 35. The material is thereby continuously whirled in the container to enhance the sterilization process.

The container 21 likewise is provided with radial arms 38 at the ends of which are mounted blade-like mixing tools 36. These tools scrape the walls of the container 21 thereby whirling the material radially inwardly. The centrifugal force due to the speed of rotation of the shaft 22 in turn causes the material to be thrown radially outwardly, with the overall effect being to create intensive whirling action of the material thereby to enhance the drying operation. Truncated mixing tools 39 similar to the endmost tools 35 in the container 1 are provided in the container 21 to prevent material from being lodged in the corners of the container. In addition the mixing tools 36 are pitched relative to the axis of the shaft 22 to facilitate movement of the material in the container toward the discharge end.

The apparatus described operates in the following manner. The material to be sterilized is introduced in measured quantities into the container 1 from a storage silo, by means of conveyor devices. While the container 1 is being filled, a measured quantity of sterilizing medium is introduced for heating the material and the excess quantity of this heating medium is withdrawn from the container.

After the completion of the filling operation, the sterilization container is closed in pressure-tight manner, whereupon saturated steam is introduced into the container for sterilization purposes. The centrifuge mechanism provided in the container runs while the container is being charged and while the sterilizing medium is being introduced. In this way, there is obtained through the mixing tools 35 an intensive whirling and permeation of the material with the sterilizing medium, so that the sterilizing operation is completed after a short time, for example, after 3 minutes. The centrifuge mechanism is then stopped and the sterilizing medium is released and collected in a suitable installation.

By means of a vacuum pipe 8, the sterilizing container l is now evacuated, in order to dry the material. The centrifuge mechanism starts to run again at a certain reduced pressure, so that all the particles of the material participate uniformly in the drying operation, and thus an effective and uniform drying is produced. The heat necessary for this purpose is supplied by steam, which flows through the double jacket 14. The material is thereafter ventilated with sterile air and the fully treated material, after opening the emptying valve 17, is emptied into a sterile container, from whence it can be further transported and further processed.

If the method is carried out in two stages, the sterilized material is delivered to the container 21 through the unions 19 and 24, and the drying operation proper and the ventilation with sterile air are effected in the second container 21.

The evacuation provided during the drying operation can be so controlled that the centrifuge mechanism is only set in motion when a certain vacuum (e.g. 30 mm. Hg.) is reached, so that none of the material being treated passes by suction effect into the vacuum apparatus.

Although the method and apparatus described are primarily for the purpose of sterilizing bulk materials, it will be apparent to those skilled in the art that the apparatus could be used for other purposes, for example, as a polymerization reactor, or wherever intimate mixing is the desired objective.

We claim:

l. A method of sterilizing bulk materials by means of steam or hot gas in a stationary container defining a closed chamber, comprising the steps of:

a. introducing said sterilizing medium and said material into said chamber,

b. subjecting said material to centrifugal force so as to throw the material radially outwardly towards the walls of said chamber,

. simultaneously scraping said material from said walls and whirling said material radially inwardly thereby to create an intensive whirling action of said material in said chamber to enhance the sterilization operation,

(I. evacuating said sterilizing medium from said chamber in the absence of centrifugal force on said material, and

e. again subjecting said material to centrifugal force at a predetermined, sub-atmospheric pressure while simultaneously scraping said material from the walls of said chamber and whirling said material radially inwardly thereby to facilitate drying of the sterilized material.

2. The method of claim 1 further including the step of preheating said material in said chamber by introducing relatively small quantities of said sterilizing medium into said chamber before the main sterilizing operation.

3. The method of claim 1 further including the step of ventilating the rnaterial, following the drying operatron, with sterile air, and storing sai sterilized ma erial in a sterile container.

4. The method of claim 1 wherein said sterilizing operation is carried out in a first container and said drying operation in a second container, and further including the step of transferring said sterilized material from said first container to said second container while maintaining the pressure existing in said first and second container.

5. The method of claim 1 further including the step of applying heat to the exterior walls of said closed chamber during the drying operation.

6. The method of claim 5 further including the step of controlling the application of centrifugal force during the drying operation so that centrifugal force is applied to said material only when a predetermined subatmospheric pressure has been reached.

Claims

2. The method of claim 1 further including the step of preheating said material in said chamber by introducing relatively small quantities of said sterilizing medium into said chamber before the main sterilizing operation.
3. The method of claim 1 further including the step of ventilating the material, following the drying operation, with sterile air, and storing said sterilized material in a sterile container.
4. The method of claim 1 wherein said sterilizing operation is carried out in a first container and said drying operation in a second container, and further including the step of transferring said sterilized material from said first container to said second container while maintaining the pressure existing in said first and second container.
5. The method of claim 1 further including the step of applying heat to the exterior walls of said closed chamber during the drying operation.
6. The method of claim 5 further including the step of controlling the application of centrifugal force during the drying operation so that centrifugal force is applied to said material only when a predetermined sub-atmospheric pressure has been reached.