GB1575070A - Apparatus for the heat treatment of particulate solid material - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO APPARATUS FOR THE HEAT TREATMENT OF PARTICULATE SOLID MATERIAL (71) We, THE A.P.V. COMPANY LIMITED, a British Company of, Manor Royal, Crawley, Sussex do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to apparatus for the heat treatment of particulate solid materials and is an improvement in or modification of the invention forming the subjectmatter of our patent No. 1 445 941, hereinafter referred to as the main patent.

The main patent describes and claims apparatus for preparing sterilized particulate solid material, comprising a sterilizing vessel mounted on hollow trunnions for rotation about a generally horizontal axis and shaped so as to provide a tumbling action on the solid material therein as it rotates, a fluid inlet leading via one of the hollow trunnions, a discharge valve at a point remote from the axis of rotation leading in to a solids discharge duct passing out via one of the hollow trunnions, and a supply line for cleaning and sterilizing fluids passing via one of the hollow trunnions, whereby the discharge duct may be cleaned and sterilized in preparation for discharge while the vessel is rotating.

In a copending Application No. 53759/ 77 (Serial No. 1 575 069) in the name of Societe Des Produits Nestle S.A., and filed simultaneously herewith, there is described and claimed a batch process for the sterilization of particulate solid materials, in which a batch of particulate solid material to be sterilized is introduced into a rotary vessel shaped so that rotation of the vessel imparts a tumbling action to the solid material; the solid material is heated in the vessel while rotating the same to subject the material to a tumbling action; a lubricant liquid is injected under pressure into the vessel at a temperature in excess of the temperature of the heated solids; the lubricant liquid and solid material are held at a sterilization temperature while maintaining the tumbling action; and the sterilized solid material is withdrawn from the vessel.

In a preferred form of the invention in the copending application, the lubricant liquid is injected from a sterile heating circuit and withdrawn from the vessel and returned to the sterile heating circuit.

In accordance with the present invention, apparatus as claimed in the main patent is associated with a sterile heating circuit for the supply of hot, pressurised lubricating liquid to the vessels via the fluid inlet.

The invention will be further described with reference to the accompanying drawing, which is a circuit diagram showing the principal features of a preferred form of apparatus for putting the invention into effect.

A tumbling vessel is shown at 1, and it may be assumed that this vessel is substantially the same as that described in the main patent. This vessel has hollow trunnions as indicated at 2 and 3, mounted on bearing blocks 4 on support platforms 5.

The vessel has a feed and access aperture 6 and a solids discharge duct 7 which feeds out through the trunnion 2. The trunnion 3 carries lines leading to an inlet nozzle 8 and a withdrawal and venting pipe 9 carrying a bell mouth or other filter 29. The nozzle 8 may be used for injection of steam along a line 8a from a line 11 via a valve 12, or alternatively for the introduction of hot lubricant liquid from a line 13 via a valve 14. It may also be used for the provision of sterile air via a sterilizing filter 17a, line 17 and valve 18 or for streile sauce or liquids through pipe 30 and valve 31.

The pipe 9 leads to line 9a for withdrawal of gases or liquids to a vent or drain line 15 via a valve 16. Line 9a also serves for the withdrawal of lubricant from vessel 1 to vessel 22 via a valve 21 and pipe 19. For this purpose of withdrawing liquid the pipe 9 is moved to the position shown dotted in the drawing and indicated by reference number 9b with the filter 29 near the bottom of the vessel.

Other details of the description of the vessel 1 and its associated equipment can be found in the specification of the main patent, the contents of which are imported by reference.

A pressure vessel 22 contains the lubricant which may be heated by circulation via pump 23, a valve 23a and heat exchanger 24, then returning to the pressure vessel via pipe 19. The heat exchanger may be either an indirect heat exchanger or a steam injector may provide direct heat exchange. This constitutes a heating loop which can remain sterile if required. A sterilizing vent filter is shown at 27 on the vessel 22. A drain or outlet line 25 is shown controlled by a valve 26' which is opened when it is desired to empty the vessel 22.

The vessel 22 also includes an upper level limit probe which controls the valves 21 and 16 so that when liquid is being returned via line 9a the vessel 22 is only filled to a level and excess liquid is directed to drain via line 15.

In operation, a charge of particulate material is introduced via the aperture 6 into the vessel 1, and with this charge there may, if required, by introduced a minimum amount of lubricant liquid, which may be water, oil or liquid from the vessel 22. The lubricant may be introduced via aperture 6 or via the inlet nozzle 8. The charge is heated by injection of steam through the inlet nozzle 8 while tumbling the charge of material by rotating the vessel 1, and this rotation may be either continuous or nter- mittent. As the solid material approaches sterilizing temperature, it becomes more subject to damage from the tumbling action and it becomes necessary to introduce the sterilizing liquid from the vessel 22 and this is achieved by opening the valve 14 and closing valve 23a so that the hot sterilizing liquid is injected under pressure via the nozzle 8. Air and steam displaced from the vessel leave via the pipe 9. Air to replace the liquid lost from the vessel 22 passes in through the sterilizing filter 27 so that sterility within the liquid circuit is maintained.

The liquid in the vessel 22 is maintained at a temperature somewhat above the sterilizing temperature of the solid charge, so that it continuous to heat the . solid charge by supplementing the steam. The heating process is terminated when the sterilizing temperature has been held for a sufficient time, as judged by an F0 meter which integrates the sterilization temperature with time and automatically controls the apparatus to finish the sterilization step at a preset value, e.g. 20 minutes at 250"F (or equivalent sterilization value). Thesolids, condensate and lubricant are then cooled by circulating cold water in the jacket 28 of vessel 1. The cooled sterile liquid component is recovered by pressure transfer through line 9 valve 21 and line 19 into the vessel 22 with the pipe 9 in the 9b position. Any excess liquor beyond that required to fill the vessel 22 is directed by transfer via valve 16 and line 15. When the liquid is accumulated in vessel 22 it may be reheated by circulation through the heating loop, i.e. through pump 23 and heat exchanger 24. This heating may be a comparatively slow process as there is likely to be some delay before there is a further demand for hot liquid.

It will be appreciated that a hot liquid circuit such as illustrated may be used to service more than one vessel 1, provided they are all operating the same process.

The charge in the vessel 1 is then further treated e.g. by introduction of a cold sterile sauce via line 30 and valve 31, and the finally treated charge is removed via the line 7 and the trunnion 2. This discharge line formed by these will of course have been sterilized during the course of the treatment so that sterility is maintained.

WHAT WE CLAIM IS: 1. Apparatus as claimed in any of the claims 1 to 12 of the main patent (British Specification No. 1 445 941), having associated therewith a sterile heating circuit for the supply of hot, pressurised lubricating liquid to the vessel via the fluid inlet.

2. Apparatus as claimed in claim l, in which the heating circuit includes means for injecting steam in the circulating liquid: 3. Apparatus as claimed in claim 1 or above, as dependent on claim 6 of the main patent, in which the vent and fluid discharge pipe is also connected to the heating circuit for discharging liquid thereto.

4. Apparatus for the heat treatment of particulate solid material substantially as hereinbefore described with reference tO: the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. withdrawal of lubricant from vessel 1 to vessel 22 via a valve 21 and pipe 19. For this purpose of withdrawing liquid the pipe 9 is moved to the position shown dotted in the drawing and indicated by reference number 9b with the filter 29 near the bottom of the vessel. Other details of the description of the vessel 1 and its associated equipment can be found in the specification of the main patent, the contents of which are imported by reference. A pressure vessel 22 contains the lubricant which may be heated by circulation via pump 23, a valve 23a and heat exchanger 24, then returning to the pressure vessel via pipe 19. The heat exchanger may be either an indirect heat exchanger or a steam injector may provide direct heat exchange. This constitutes a heating loop which can remain sterile if required. A sterilizing vent filter is shown at 27 on the vessel 22. A drain or outlet line 25 is shown controlled by a valve 26' which is opened when it is desired to empty the vessel 22. The vessel 22 also includes an upper level limit probe which controls the valves 21 and 16 so that when liquid is being returned via line 9a the vessel 22 is only filled to a level and excess liquid is directed to drain via line 15. In operation, a charge of particulate material is introduced via the aperture 6 into the vessel 1, and with this charge there may, if required, by introduced a minimum amount of lubricant liquid, which may be water, oil or liquid from the vessel 22. The lubricant may be introduced via aperture 6 or via the inlet nozzle 8. The charge is heated by injection of steam through the inlet nozzle 8 while tumbling the charge of material by rotating the vessel 1, and this rotation may be either continuous or nter- mittent. As the solid material approaches sterilizing temperature, it becomes more subject to damage from the tumbling action and it becomes necessary to introduce the sterilizing liquid from the vessel 22 and this is achieved by opening the valve 14 and closing valve 23a so that the hot sterilizing liquid is injected under pressure via the nozzle 8. Air and steam displaced from the vessel leave via the pipe 9. Air to replace the liquid lost from the vessel 22 passes in through the sterilizing filter 27 so that sterility within the liquid circuit is maintained. The liquid in the vessel 22 is maintained at a temperature somewhat above the sterilizing temperature of the solid charge, so that it continuous to heat the . solid charge by supplementing the steam. The heating process is terminated when the sterilizing temperature has been held for a sufficient time, as judged by an F0 meter which integrates the sterilization temperature with time and automatically controls the apparatus to finish the sterilization step at a preset value, e.g. 20 minutes at 250"F (or equivalent sterilization value). Thesolids, condensate and lubricant are then cooled by circulating cold water in the jacket 28 of vessel 1. The cooled sterile liquid component is recovered by pressure transfer through line 9 valve 21 and line 19 into the vessel 22 with the pipe 9 in the 9b position. Any excess liquor beyond that required to fill the vessel 22 is directed by transfer via valve 16 and line 15. When the liquid is accumulated in vessel 22 it may be reheated by circulation through the heating loop, i.e. through pump 23 and heat exchanger 24. This heating may be a comparatively slow process as there is likely to be some delay before there is a further demand for hot liquid. It will be appreciated that a hot liquid circuit such as illustrated may be used to service more than one vessel 1, provided they are all operating the same process. The charge in the vessel 1 is then further treated e.g. by introduction of a cold sterile sauce via line 30 and valve 31, and the finally treated charge is removed via the line 7 and the trunnion 2. This discharge line formed by these will of course have been sterilized during the course of the treatment so that sterility is maintained. WHAT WE CLAIM IS:

1. Apparatus as claimed in any of the claims 1 to 12 of the main patent (British Specification No. 1 445 941), having associated therewith a sterile heating circuit for the supply of hot, pressurised lubricating liquid to the vessel via the fluid inlet.

2. Apparatus as claimed in claim l, in which the heating circuit includes means for injecting steam in the circulating liquid:

3. Apparatus as claimed in claim 1 or above, as dependent on claim 6 of the main patent, in which the vent and fluid discharge pipe is also connected to the heating circuit for discharging liquid thereto.

4. Apparatus for the heat treatment of particulate solid material substantially as hereinbefore described with reference tO: the accompanying drawing.