초록

A material to be frozen is fed to an immersion bath having a recirculating flow of liquid nitrogen thereinside and at least partially frozen material is withdrawn from the bath downstream of where it is fed.

대표청구항 ▼

1. A method of freezing a product in a recirculating liquid nitrogen immersion bath contained within a container, wherein the container comprises: first, second, third and fourth walls extending upwardly from a floor, the first and third walls defining upstream and downstream ends of the container,

1. A method of freezing a product in a recirculating liquid nitrogen immersion bath contained within a container, wherein the container comprises: first, second, third and fourth walls extending upwardly from a floor, the first and third walls defining upstream and downstream ends of the container, respectively, the container having a height, width, and length;a horizontal baffle secured between the second and fourth walls, the baffle having upstream and downstream ends and upper and lower surfaces extending therebetween, the baffle having a length shorter than a length of the container and being disposed within the container at a position that leaves a gap between the upstream baffle and container ends, a gap between the downstream baffle and container ends, and a gap between the baffle lower surface and the container floor, a space defined by said first, second, third, and fourth walls and said floor being filled with a bath of liquid nitrogen to a level within the space to define a surface of the bath, the baffle being completely submerged below the surface of the bath;a pump that is completely submerged below the surface of the bath, said method comprising the steps of:maintaining a recirculating flow of the liquid nitrogen entirely within the bath using the pump, the flow following a flow path, in order, along the surface from the upstream end to the downstream end;along a bottom portion of the space in between the floor and baffle from the downstream end to the upstream end; andback along the surface, all vertical portions of the return section totally enclosing the flow of liquid nitrogen;feeding a material to be frozen to the horizontal treating section at a feed point;allowing at least a portion of the fed material to be frozen by the liquid nitrogen of the bath; andwithdrawing the at least partially frozen material from the horizontal treating section downstream of the feed point. 2. The method of claim 1, wherein: the material to be frozen is a liquid or semi-solid; andthe liquid or semi-solid material is fed to the horizontal treating section by allowing the liquid or semi-solid material to drip into or be injected into the horizontal treating section. 3. The method of claim 1, wherein the at least partially frozen material is withdrawn from the horizontal treating section with a porous discharge conveyor belt extending partially into the liquid nitrogen. 4. The method of claim 1, wherein a residence time within the liquid nitrogen of the material to be frozen is controlled by controlling a velocity of the liquid nitrogen flow via the pump. 5. The method of claim 1, wherein a residence time within the liquid nitrogen of the material to be frozen is controlled by controlling a speed of the discharge belt. 6. The method of claim 1, wherein a depth of the liquid nitrogen in the horizontal treating section is greater than a major dimension of the material to be frozen. 7. The method of claim 1, wherein a flow rate of the liquid nitrogen is increased when the rate at which the material to be frozen is fed to the horizontal treating section is increased. 8. The method of claim 1, wherein a flow rate of the liquid nitrogen is decreased when the rate at which the material to be frozen is fed to the horizontal treating section is decreased. 9. The method of claim 1, wherein the material to be frozen is a food item. 10. An immersion bath for recirculating a flow of liquid nitrogen, comprising: a container having first, second, third and fourth walls extending upwardly from a floor, the first and third walls defining upstream and downstream ends of the container, respectively, the container having a height, width, and length, the first, second, third, and fourth walls and the floor defining a space for being filled with the liquid nitrogen bath; a horizontal baffle secured to the second and fourth walls, the baffle having upstream and downstream ends and upper and lower surfaces extending therebetween, the baffle having a length shorter than a length of the container and being disposed within the container at a position that leaves a gap between the upstream baffle end and the upstream container end, a gap between the downstream baffle end and the downstream container end, and a gap between the baffle lower surface and the container floor, the container and space being adapted and configured to be filled with the bath of liquid nitrogen above the horizontal baffle to define a surface of the bath; and a pump disposed within the space under a level of the lower surface of the baffle, completely submerged within the below a surface of the liquid nitrogen bath, and being operationally associated with the container and baffle, the pump and the container being adapted to induce the recirculating flow of liquid nitrogen entirely within the bath, in order, over a top surface of the baffle in a first direction, through the gap between the downstream baffle end and the downstream container end, in between the floor and the lower surface of the baffle in a second direction opposite that of the first, and through the gap between the upstream baffle end and the upstream container end. 11. The immersion bath of claim 10, further comprising a material feeder operationally associated with the container and being adapted to feed liquid, semi-solid, or solid material to be frozen into the flow of liquid nitrogen at a feed point above the baffle upper surface. 12. The immersion bath of claim 11, wherein the material feeder is a drip tray. 13. The immersion bath of claim 11, wherein the material feeder is an injector. 14. The immersion bath of claim 10, further comprising a porous discharge conveyor belt operationally associated with the container extending downwardly into the gap between the downstream container and baffle ends to a point below and adjacent the baffle downstream end.