Method and apparatus for contact refrigeration in cryogenic solid belt freezer

Abstract

Methods and apparatus for contact freezing a food product. A conveyor belt or other support may have an active region that supports materials on an outer surface. Liquid cryogen may be provided in bulk contact with an inner surface of the active region via splashing, agitation, pumping, gravity feed, and the like.

1 . A material cooling system comprising:
 a conveyor belt having an inner surface and an outer surface, the conveyor belt having an active region in which the outer surface faces generally upwardly and is configured to support a material for cooling, and a return region in which the outer surface faces generally downwardly; and   a cryogen supply system arranged to provide a liquid cryogen in direct, bulk liquid contact with only the inner surface of the conveyor belt in at least part of the active region.   
     
     
         2 . The device of  claim 1 , further comprising a plenum constructed and arranged to contain the liquid cryogen. 
     
     
         3 . The device of  claim 2 , wherein the cryogen supply system further comprises a pump arranged to move liquid cryogen from a container to the inner surface of the conveyor belt in the active region. 
     
     
         4 . The device of  claim 3 , wherein the plenum is located below the inner surface of the conveyor belt in the active region, the plenum being constructed and arranged to receive a liquid cryogen from the pump. 
     
     
         5 . The device of  claim 4 , wherein the cryogen supply system further comprises a plate having a plurality of grooves, the plate arranged to direct a flow of liquid cryogen from the grooves toward the inner surface of the conveyor belt in the active region. 
     
     
         6 . The device of  claim 1 , further comprising a gap arranged to vent a gas between the cryogen supply system and the inner surface of the conveyor belt in the active region. 
     
     
         7 . The device of  claim 3 , further comprising a cryogen return constructed and arranged to guide liquid cryogen from the inner surface of the belt in the active region into the container. 
     
     
         8 . The device of  claim 2 , wherein the cryogen supply system further comprises at least one mechanical agitator in the plenum. 
     
     
         9 . The device of  claim 2 , wherein the cryogen supply system further comprises a mechanical wave generator constructed and arranged to create at least one wave on a surface of the liquid cryogen in the plenum. 
     
     
         10 . The device of  claim 1 , wherein the cryogen supply system is arranged to create a plurality of discrete contact regions where the liquid cryogen is in bulk liquid contact with at least a portion of the inner surface. 
     
     
         11 . The device of  claim 1 , wherein the cryogen supply system is arranged to move the liquid cryogen upwardly toward the inner surface such that the liquid cryogen makes direct bulk liquid contact with at least a portion of the inner surface. 
     
     
         12 . The device of  claim 11 , wherein the liquid cryogen is at nearly zero velocity during contact with at least a portion of the inner surface. 
     
     
         13 . The device of  claim 1 , wherein the belt includes a solid belt and a rod belt, wherein the rod belt lies below the solid belt in the active region and above the solid belt in the return region. 
     
     
         14 . The device of  claim 1 , further comprising providing liquid cryogen to the outer surface of the conveyor belt in at least part of the active region. 
     
     
         15 . A method for cooling a material, comprising:
 providing a solid conveyor belt having a top surface that faces generally upwardly and a bottom surface that faces generally downwardly, wherein the top surface is configured to hold the materials to be cooled; and   providing liquid cryogen in direct, bulk liquid contact with only the bottom surface of the solid conveyor belt by moving a liquid cryogen from a plenum to the bottom surface.   
     
     
         16 . The method of  claim 15 , wherein the step of providing liquid cryogen includes causing the liquid cryogen to contact the bottom surface in bulk liquid form at a plurality of discrete regions. 
     
     
         17 . The method of  claim 15 , wherein the step of providing liquid cryogen includes directing the liquid cryogen upwardly in bulk liquid form for contact with the bottom surface of the solid conveyor belt. 
     
     
         18 . The method of  claim 15 , wherein the step of providing liquid cryogen includes generating a wave on a surface of the liquid cryogen in the plenum.