Abstract: A cryogenic freezer with cryogenic vapor control is disclosed. The cryogenic freezer is characterized in that the vapor control system is adapted to control the speed of the transition fan which moves some of the cryogen from a first cryogenic freezer to a second freezer in response to differences between the temperature of the process room, operating temperature of the cryogenic freezer; and a temperature of the exhaust. By adjusting the transition fan speed in response to such temperature differences the vapor control system operates to limit the flow of air from the process room into the freezer and also limits cryogen vapor flow from the freezer to the process room.

Abstract: Hybrid cryo-mechanical apparatus is provided to collect condensable vapors from an incoming gas flow. The gas flow is refrigerated in a series of upstream mechanical refrigeration stages, and fed to an indirect contact heat exchanger suitable for operation with a cryogen refrigerant. Temperature of the cryogen leaving the heat exchanger is monitored, and is used to operate a control valve which throttles the heat exchanger output.