Heat pump freeze drying system

A vacuum drying system for vacuum drying a material, said material comprising a substance to be removed to effect vacuum drying of said material, which system substantially eliminates need to supply heat from an external heat source for vacuum drying said material;

• said system comprising in combination:
• a. a drying chamber wherein is maintained a subatmospheric pressure to effect vacuum drying of said material;
• b. a means for passing the said material through said drying chamber for vacuum drying thereof during said passage;
• c. an evacuation means for continuously removing vapor from said drying chamber as it is generated in said chamber in the vacuum drying of said material, said evacuation means comprising an absorber through which a liquid absorbent medium is continuously passed, said absorbent medium being at a sufficiently low temperature to provide in said absorber a vapor pressure lower than in said chamber whereby to cause the vapor to pass from said drying chamber to said absorber where it is absorbed in said absorbent medium;
• an evaporator in which absorbed substance is continuously evaporated from the absorbent medium passing therethrough from said absorber at a rate similar to that at which said vapor is absorbed in said absorbent medium in said absorber, by heat exchange with condensing first refrigerant;
• a condenser in which vapor from said evaporator is condensed by heat exchange with evaporating first refrigerant;
• a first heat pump means adapted to compress at least a portion of first refrigerant vapor from said condenser, pass first refrigerant vapor so compressed to said evaporator and pass condensed first refrigerant from said evaporator through an expansion valve to said condenser, said first heat pump means including a cooling means for removing excess heat from said first refrigerant to maintain heat balance in said evaporator and in said condenser;
• a chiller in which the absorbent medium from said evaporator is cooled to restore the absorbent medium to the proper temperature for said absorber for passage to said absorber, by heat exchange with evaporating second refrigerant;
• a means for maintaining the absorbent medium in circulation between said absorber, evaporator, and chiller;
• and a means to purge the noncondensible gases from the system;
• d. a second heat pump means adapted to compress at least a portion of second refrigerant vapor from said chiller, pass the second refrigerant vapor so compressed to a heat exchange means for supplying heat to effect vacuum drying of said material in said drying chamber and pass condensed second refrigerant from said heat exchange means through an expansion valve to said chiller, said second heat pump means including a cooling means for removing excess heat from said second refrigerant to maintain heat balance in said heat exchange means and in said chiller.

A vacuum drying system for vacuum drying of a material, said material comprising a substance to be removed to effect vacuum drying of said material, which system substantially eliminates need to supply heat from an external heat source for vacuum drying said material;

• said system comprising in combination:
• a. a drying chamber wherein is maintained a subatmospheric pressure, the vapor pressure in the drying chamber being maintained above the triple point pressure of substance to be removed to effect vacuum drying of said material:
• b. a means for passing the said material through said drying chamber for vacuum drying thereof during said passage;
• c. an evacuation means for continuously removing vapor from said drying chamber as it is generated in said chamber in the vacuum drying of said material, said evacuation means comprising an absorber through which liquid of said vapor is continuously passed, said liquid being at a sufficiently low temperature to provide in said absorber a vapor pressure substantially lower than in said drying chamber but yet above the said triple point pressure whereby to cause vapor to pass from said drying chamber to said absorber where it is condensed in said liquid;
• a chiller adapted to cool the said liquid from said absorber to a proper temperature for said absorber for passage to said absorber, by heat exchange with evaporating second refrigerant;
• a means to maintain the said liquid in circulation between said absorber and chiller;
• and a means to purge the noncondensible gases from the system;
• d. a second heat pump means adapted to compress at least a portion of second refrigerant vapor from said chiller, pass so compressed second refrigerant vapor to a heat exchange means for supplying heat to effect vacuum drying of said material in said drying chamber and pass condensed second refrigerant from said heat exchange means through an expansion valve to said chiller, said second heat pump means including a cooling means for removing excess heat from said second refrigerant to maintain heat balance in said heat exchange means and in said chiller;
• e. and a means for continuously removing liquid at a rate corresponding to that at which said vapor is condensed in said absorber to prevent the accumulation of said liquid in said absorber.

An evacuation system substantially eliminating the need to supply heat from an external heat source for continuously removing vapor from a vacuum drying chamber maintained at a pressure above the triple point of the substance of the vapor as said vapor is generated in said chamber in the vacuum drying of a material, said system comprising an absorber through which liquid of said vapor is continuously passed;

• said liquid being at a sufficiently low temperature to provide in said absorber a pressure substantially lower than in said chamber but yet above the said triple point pressure whereby to cause vapor to rapidly pass from said chamber to said absorber where it is condensed in said liquid, a chiller adapted to cool heated liquid from the absorber to the desired temperature for said absorber by heat exchange with evaporating refrigerant for passage to said absorber and a heat pump means adapted to compress at least a portion of low pressure refrigerant vapor from said chiller and pass so compressed refrigerant vapor to a heat exchange means for heating the material in said chamber and passing condensed liquid refrigerant from said heat exchange means through an expansion valve to said chiller;
• said heat pump means including a cooling means for removing excess heat from said refrigerant to maintain a heat balance between said chiller and said chamber, and a means for continuously removing said liquid at a rate corresponding to that at which the said liquid is formed by condensing vapor in said absorber in order to maintain a steady state condition.

An evacuation system substantially eliminating the need to supply heat from an external heat source for continuously removing vapor from a vacuum drying chamber as it is generated in said chamber in the vacuum drying of a material, said system comprising an absorber through which a liquid absorbent medium is continuously passed, said absorbent medium being at a suficiently low temperature to provide in said absorber a vapor pressure substantially lower than in said chamber whereby to cause vapor to rapidly pass from said chamber to said absorber where it is absorbed in said absorbent medium, an evaporator in which liquid is continuously evaporated from the absorbent medium passing therethrough from said absorber at a rate similar to that at which said vapor is absorbed in said absorbent medium in said absorber, by heat exchange with condensing first refrigerant, a condenser in which vapor from said evaporator is condensed by heat exchange with evaporating first refrigerant, first heat pump means adapted to compress at least a portion of first refrigerant vapor from said condenser, pass first refrigerant vapor so compressed to said evaporator and pass condensed first refrigerant from said evaporator through an expansion valve to said condenser, said first heat pump means including cooling means for removing excess heat from said first refrigerant to maintain a heat balance between the evaporator and condenser, and a chiller adapted to cool heated absorbent medium from said evaporator to restore the absorbent medium to the desired temperature for said absorber for passage to said absorber.