FREEZE-DRYING METHOD AND APPARATUS FOR THE SAME

• US 20130326899A1
• Filed: 11/29/2012
• Published: 12/12/2013
• Est. Priority Date: 11/30/2011
• Status: Active Grant

• Current Assignee: Futami Seika Co., Ltd., Sanwa Engineering Co., Ltd.
• Original Assignee: Shunichi Yagi
• Inventors: YAGI, Shunichi
• Granted Patent: US 9,046,303 B2
• Time in Patent Office: Days
• US Class Current: 34/266
• CPC Class Codes: F26B 3/30 from infrared-emitting elements by radiation emanating from passages containing heated fluids other than combustion gases F26B23/10
• CPC Class Codes: F26B 5/06 the process involving freezing

Abstract

A freeze-drying method by a far infrared heater including the steps of: mounting the frozen objects to be dried prior to heating in the containers in which an absorption power of the radiant heat from the far infrared heater and a thermal conductivity are high, respectively; mounting the said objects which are contained in the containers into the reduced pressure tank under an atmospheric pressure; heating the containers by the radiant heat from the far infrared heater disposed in the reduced pressure tank; and sublimating the frozen water contents of the objects in a reduced pressure state where sublimation of the objects occurs in the reduced pressure tank.

Claims

1. A heating method to objects to be dried in freeze-drying by a far infrared heater, including a step of mounting frozen objects to be dried or unfrozen objects to be dried in containers having a high absorption power of radiant heat from the far infrared heater and having a suitable thermal conductivity, or mounting the objects to be dried in containers with lids which keep atmosphere in a reduced pressure tank;

a step of mounting the frozen objects to be dried or the unfrozen objects to be dried which are mounted in the containers, into the reduced pressure tank under an atmospheric pressure; and

a step of sublimating the objects to be dried in a reduced pressure state where the sublimation of the objects to be dried takes place in the reduced pressure tank through heating and heat conduction to the containers or the containers with the lids by the radiant heat of the far infrared heater disposed in the reduced pressure tank.

2. The method according to claim 1 is characterized in that the containers or the containers with the lids used in the method in claim 1 having a high absorption power of the radiant heat to the containers by the far infrared heater and a suitable thermal conductivity form films coating of black or a color close to the black on outer surfaces of the containers made of a metal, or the outer surfaces of the containers made of the metal and lid surfaces of the containers made of the metal respectively, and conduct heat to the objects to be dried from both sides of each of the containers and each of the lids.

3. The method according to claim 1 characterized in that the objects to be dried which are mounted in the containers or the containers with the lids having the high absorption power of the radiant heat from the far infrared heater and having the suitable thermal conductivity are frozen outside the reduced pressure tank before the objects to be dried are mounted into the reduced pressure tank, or the objects to be dried in an unfrozen state are mounted into the reduced pressure tank, pressure reduction is advanced, and the objects to be dried are frozen by evaporation latent heat of evaporation of water contents of the objects to be dried themselves.

4. The method according to claim 1, characterized in that prior to the heating of the objects to be dried which are mounted in the containers or the containers with the lids having the high absorption power of the radiant heat from the far infrared heater and having the suitable thermal conductivity in the reduced pressure tank, pressure reduction is advanced to a pressure which is not more than a pressure under which a boiling point of water becomes zero degree or lower, to freeze the surfaces of the objects to be dried by evaporation latent heat and sublimation latent heat generated by evaporation of water contents and sublimation of ices which occur in the objects to be dried, and then center of the objects to be dried are also frozen by heat conduction from the containers or the containers with the lids.

5. The method according to claim 1, characterized in that as processing prior to the mounting of the objects to be dried in the containers, the objects to be dried are subjected to a pre-treatment such as cutting, slicing or grinding so that the surfaces of the objects to be dried noticeably come in contact with the inner surfaces of the containers including the lids.

6. A freeze-drying apparatus is characterized in that the said freeze-drying apparatus includes a reduced pressure tank in which a far infrared heater is disposed along a sidewall, or the sidewall and a ceiling;

a container carrier which conveys a plurality of containers to contain mounted objects to be dried into the reduced pressure tank, and supports the containers in a drying step;

the containers having a high absorption power of radiant heat and mounted via a space in multistage of the container carrier;

the frozen objects to be dried which are contained in the containers;

a tray support member of the container carrier in which the respective containers containing the frozen objects to be dried are vertically arranged via the space on multistage so that the containers are evenly irradiated with heat radiated from the far infrared heater and in which the containers mounted on the respective stages are tilted at the same angle or at such angles that the containers are evenly irradiated with the radiated heat; and

inside the reduced pressure tank, a control section including a heating temperature detecting section and a pressure detecting section is arranged in order to sublimate the objects to be dried in the reduced pressure state where the sublimation of the objects to be dried occurs in the reduced pressure tank; and

outside the reduced pressure tank, a heating temperature control section of the far infrared heater to the containers and a pressure control section which controls the pressure inside the tank are arranged.

7. The freeze-drying apparatus according to claim 6 is characterized in that respective outer surfaces of the containers which are made of a metal and in which the objects to be dried are mounted or respective outer surfaces of containers with drop lids as the containers with the lids which keep atmosphere in the reduced pressure tank are baking-finished with a fluoric resin or a silicon resin in black or a color close to the black.

8. The freeze-drying apparatus according to claim 6 is characterized in that a metal material of the metal containers in which the objects to be dried are mounted and the lids for the containers is an aluminum plate or a stainless steel plate.

9. The freeze-drying apparatus according to claim 6, characterized in that shelves forming the plurality of stages on which sets of the metal containers to contain the mounted objects to be dried and the lids for the containers are mounted are made of stainless steel, the shelves of the stages are arranged via a space of 80 mm or more, and each of the stages includes a frame which is provided with a gradient of 10 degrees or more and which supports the containers containing the mounted objects to be dried.

10. The freeze-drying apparatus according to claim 6, characterized in that inside the reduced pressure tank, the far infrared heater is disposed along the sidewall, or the sidewall and the ceiling, a temperature detector finished in the same black or the same color close to the black as a color of each of the metal containers to contain the mounted objects to be dried is disposed in a portion corresponding to a distance between the far infrared heater and the vicinity of the center of each of the containers to contain the mounted objects to be dried, and means for detecting a heating temperature by the far infrared heater to the outer surface of each of the containers containing the mounted objects to be dried is disposed;

further, inside the reduced pressure tank, a pressure detecting means including a pressure sensor is disposed in order to detect a pressure value in the tank; and

outside the reduced pressure tank, a temperature controller of the far infrared heater, a pressure gauge, a pressure regulating valve, a pressure controller, a return pressure valve and a vacuum pump are arranged, connecting to one another via a metal pipe or a resin pipe.