CA1143581A - Process and apparatus for cryogenic treatment of materials - Google Patents
Process and apparatus for cryogenic treatment of materialsInfo
- Publication number
- CA1143581A CA1143581A CA000387611A CA387611A CA1143581A CA 1143581 A CA1143581 A CA 1143581A CA 000387611 A CA000387611 A CA 000387611A CA 387611 A CA387611 A CA 387611A CA 1143581 A CA1143581 A CA 1143581A
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- Prior art keywords
- container
- temperature
- liquid
- liquid gas
- gas
- Prior art date
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D3/00—Devices using other cold materials; Devices using cold-storage bodies
- F25D3/10—Devices using other cold materials; Devices using cold-storage bodies using liquefied gases, e.g. liquid air
Abstract
ABSTRACT OF THE DISCLOSURE
A method and apparatus are disclosed for cryogenic treatment of materials, Liquefied gases are used for cooling instead of refrigeration units, thus avoiding maintenance of such units, and there are not the same constraints on chamber size as occurs with refrigeration units. The process comprises inserting a predetermined quantity of a liquid gas into an enclosed insulated container to vaporize, reduce the moisture content, and purge air; recirculating the vaporized gas within the container to maintain a substantially uniform temperature therein; cooling the container at a predetermined rate, and maintaining the container at a minimum temperature for a predetermined period of time; and heating the recirculat-ing vaporized gas to raise the temperature at a predetermined rate. The apparatus comprises an enclosed, insulated container having a sealed lid in the top thereof, open evaporator for liquid gas within the container, recirculating fan and duct means for maintaining substantially uniform temperature within the container, a primary cooling coil for liquid gas within the container, main cooling coils for liquid gas within the container, and heating means within the duct means.
A method and apparatus are disclosed for cryogenic treatment of materials, Liquefied gases are used for cooling instead of refrigeration units, thus avoiding maintenance of such units, and there are not the same constraints on chamber size as occurs with refrigeration units. The process comprises inserting a predetermined quantity of a liquid gas into an enclosed insulated container to vaporize, reduce the moisture content, and purge air; recirculating the vaporized gas within the container to maintain a substantially uniform temperature therein; cooling the container at a predetermined rate, and maintaining the container at a minimum temperature for a predetermined period of time; and heating the recirculat-ing vaporized gas to raise the temperature at a predetermined rate. The apparatus comprises an enclosed, insulated container having a sealed lid in the top thereof, open evaporator for liquid gas within the container, recirculating fan and duct means for maintaining substantially uniform temperature within the container, a primary cooling coil for liquid gas within the container, main cooling coils for liquid gas within the container, and heating means within the duct means.
Description
35~1 The present invention relates to a method and apparatus for controlled cooling and subsequent warming in a cryogenic treatmerlt of materials. More specifically, the invention relates to treating materials cryogenically, such materials include tool steels, copper alloy welding wheels and electrodes, leather and selected organic and inorganic materials to improve the performance of these materials.
It is known that dry cryogenic treatment of metals and selected organic materials improves the properties of these materials. In particular, tool steels appear to have a lon6er life after a cryogenic treatment. Such treatment is commercially used today, generally using air liquefiers which utilize compressor related refrigeration equipment. This equlp-ment has proven satisfactory, but there are several limitations in the use of compressor refrigeration equipment. One critical problem iB wear and tear which results in high maintenance costs. There are also severe constraints on the size of the cooling chamber that can be serviced by a refri~eration unit employing compressor equipment.
It has been found that cryogenic treatin~ of tool steels and other materials where temperatuIes drop as low as -196C, the temperature of liquid nitrogen, roqulre the~ tem-perature to be lowered slowly otherwise warping or other damage occurs to the material being treated. ~or most common tool steels a cooling rate of 0.5C per minute from ambient down to the minimum temperature has proven satisfactory. Warming rates of 0.25C per minute have proven satisfactory up to -20C; from there the warming rate is not critical unless the items are large.
The present invention provides a process and an apparatus utilizing a liquefied gas such as nitrogen, helium or hydrogen, thus avoiding the problems of refrigeration units 114~581 with compressors Such a system can be designed to handle larger loads than is presently possible with compressor refrigeration systems. The use of liquefied gases also allows colder temperatures than is now commercially possible with compressor equipment presently in service. The present invention also provides a system which can cool at the desired cooling rate and is supplied with a circulating system inside the cooling container so that the environment within the con-tainer remains at a substantially uniform temperature throughout.
The present invention provides a process for cryogenlc treatment of materials within an enclosed insulated container, comprising the steps of inserting a predetermined quantity of a liquid gas into the container to vaporize, reduce the moisture content within the container, and purge the container of air;
recirculating the vaporized gas within the container to maintaln a substantially uniform temperature within the container;
cooling the container at a predetermined rate, and maintaining the container at a minimum temperature for a predetermined period of time; and heating the recirculatlng vaporized gas to raise the temperature within thc container at a determined rate.
In prei'erred embodlments, the pressuri~.ed llquid ~as is nitrogen, hydrogen, or helium, cooling rate i8 0.5C per minute, and the warmin~ rate is 0.25C per minute.
In another embodiment, a process is provided for cryogenic treatment of materials within an enclosed insulated container having a primary cooling coil and main cooling coils therein, comprising the steps of inserting a predetermined quantity of a liquid gas into the container to vaporize, reduce the moisture content within the container, and purge the con-tainer of air; recirculating the vaporized ~as withln the con-tainer to maintain a substantially uniform temperature within the container; circulating a controlled flow of liqu~d gas throu~l~
,~~ 2 _ 1~35:' the primary cooling coil so the temperature in the container : drops at a predetermined rate to a predetermined temperature;
closing off liquid gas circulating through the primary cooling coil, and :
_ 2A -~3~8~
circulating liquid gas through the main cooling coils untll the temperature in the container drops to a minimum, and contlnuing circulation through the main cooling coils for a predetermined period of time; closing o~f liquid gas circulating through the main cooling coils; and heating the recirculating vaporized gas to raise the temperature within the container at a predeter-mined rate.
In a further embodiment, wherein nitrogen is the vap-orized liquid gas, the process includes the additional steps of purging the primary cooling coil with helium after shutting off the nitrogen, circulating liquid helium in the primary cooling coil, inserting a predetermined quantity of liquid helium into the container to vaporize, prevent the accumulation of liquid nitrogen and liquid oxygen in the container, and purge the container of other vaporized gases.
The present invention also provides an apparatus for cryogenic treatment o~ materials, comprising an enclosed insulated container having sealed doors, open evaporator for liquid gas wlthin the container, recirculatin~ ~an and duct means for main-taining substantially uni~orm temperaturc wlthin the contniner, a primary cooling coil for liquid 6as within the contnincr, main cooling coil~ i'or llquid ~as within the contniner, and heating means within the duct means.
The term "liquid ~as" used throu~hout the specificntlon includes all types o~ gases that are lique~ied and remain in n liquid state at low temperatures. Nitrogen becomes a liquid nt around -190C, hydrogen around -252C and helium around -2~8~C.
In all cases these temperatures represent normal atmospheric pressure conditions.
In drawings which illustrate the embodiments of the invention, Fig, 1 is a schematic cross sectional elevation showin~
3~' one embodiment of a cryogenic treatment apparatus suitable for ;` the present invention, ~ ig. 2 is a graph showing the temperature against time for a typical cryogenic treatment, Referring now to Fig, 1, a container 10, preferably made from stainless steel, has an lnsulation space 11 surround-ing it and an outer insulation cover 12 to insulate the container 10, Insulated covers or lids (not shown) are provided on the top of the container for loading the container with the materials to be cryogenically treated, The openings are made in the top so that if the container 10 has to be opened with gas still inside, the gas will not spill out of the container, A dryer connection (not shown) is provided to the insulation space 11 so the moist air can be removed from this space, Moisture ln the insulation space can freeze and reduce the insulation properties o~ the unit, A primary cooling coil 13 is positioned in the con-tainer 10 at one side adjacent a blower inlet duct 14, The primary cooling coil 13 has a liquid inlet line 15 which is shown connected to the liquid nitro~en or liquid helium line ~upply, A vent line 16 with a valve therein, allows the evaporated gas to vent into the container 10, Main cooling coils 17 are positioned around the perlphery of the container 10, hcld in place pre~erably by an expanded metal shield 18, A liquid inlet line 19 from the nitrogen supply supplies liquld nitrogen to the main cooling coils 17 and a vent line 20 with a valve therein allows the evaporated nitrogen to vent into the con-tainer 10, An open evaporator 22 is located in the bottom of the 'l~ 30 container 10, The evaporator 22 may be a bucket or open con-tainer and has a liquid nitrogen feed line 23 from the nitrogen supply and a liquid helium feed line 24 from the helium supply.
~35~31 A vent line 25 from the inside of the container 10 is a purge outlet and has a pressure relief valve 26 to prevent pressure build up in the container 10, The nitrogen supply has a valve 27 on the liquid inlet line 19 for the main cooling coils 17, a valve 28 on the feed line 23 for the evaporator 22 and a valve 29 on the liquid inlet line 15 to the primary cooling coil 14.
The helium supply has a valve 30 on the feed line 24 to the evaporator 22 and a valve 31 on the liquid inlet line 15 to the primary cooling coil 14, All the valves are preferably globe valves and have restrictive orifices therein so the flow of liquid can be controlled to suit selected cooling rates, A
globe valve 32 with a restrictive orifice is located in the helium supply line to control the flow of helium to the container.
A blower 33 with an inlet duct 34 from the container 10 circulates the gases within the container, blowing them throu~h outlet duct 35 back into the container lO so that the gases in the container are continually circulated, thus the temperature in the container is maintained substantially uni~orm throughout, A heater element 36 is provided in the outlet duct 35 controlled by a temperature indicator controller (TIC) 37 which operates ~rom a thermocouple 38 within the container lO, Another thermocouple 39 controls the operation o~ n temperature indicator controller 40 which in turn operates a control valve 4]. in the liquid inlet llne 15 to primary coolin~
coil 14, A ~urther thermocouple 42 controls the operation of a temperature indicator controller 43 which in turn operates a control valve 44 in the liquid inlet line 19 to the main coolin~
coils 17.
A pressure gauge or manometer 45 is provided so the pressure inside the container is indicated. It is preferable that the pressure is always slightly higher than atmospheric to ensure that air does not enter the container, 358~L
An air line purge 46 is provided for use when it is required to warm up the container faster than normal. This purge takes outside air and circulates it through the container.
In operation, material to be treated is placed into the container 10 through a lid in the top and the container is closed. Valve 28 is opened and a liquid gas, preferably nitrogen, is fed through feed line 23 into the evaporator 22 This liquid gas evaporates at a temperature well below the freez-ing point of water, therefore, as it evaporates and cools the chamber, most of the moisture present in the container condenses and falls to the bottom of the container as ice. The boilin~
liquid in the evaporator 22 forces air out of the container 10 through the vent line 25 so that air is purged from the container 10 and the atmosphere within the container is primarily the vaporized gas from the evaporator 22. Valve 28 is left cracked open to ensure the container 10 remains pressurized which prevents air from entering the container.
The blower 33 is then started up to circulate the gas within the container and ensure that the temperature throu~h-out the container remains substantially unlform At tlle same time, liquid nitrogen is introduced to the liquid inlet line 15 to the primary cooling coil 14 The rate o~ flow o~ liquid nitrogen i8 set either by the valve 29 or by the control vnlve 41 on a control si~nal irom the temperature indicator controllor 40 When the container temperature drops to a predetermined amount, in one embodiment this amount i9 -188C, the tempernture is measured by the thermocouple 39 and the temperature indicator controller 40 shuts off the flow of liquid nitrogen to the primary cooling coil 14 and opens the control valve 44 in the liquid inlet line 19 to the main cooling coils 17, The rate of flow of liquid nitrogen to the main cooling coils 17 is set by either the valve 27 or the control valve 44 so that the tempera-1~3581 ture drops at a preset rate. This preset rate is approximately 0.5C per minute or may be slower. When the temperature reaches the minimum level, the thermocouple 42 records this and the pre~
set time period commences with the f low of liquid nitrogen continuing through the main cooling coils 17 until the end of the time period. The minimum level of temperature for liquid nitrogen is usually around -190C. The liquid nitrogen is then shut off, and the container commences to warm up, While this so-called "soaking" period is continuing, the fan 33 remains on and the gas within the container 10 circulates through ducts 34, 35. At the end of the soak perlod, the liquid nitrogen is shut off and the heater 36 in duct 35 is turned on and controlled by the temperature indicator controller 37, so that a small quantity of heat slowly warms up the contniner at a predetermined rate. This predetermined rate is preferably .25C per minute or less. When the temperature reaches -20 the warming rate is generally not critical, If colder temperatures than liquid nitro~en tempera-tures are desired, then helium may be added. When the tempern-ture has dropped to a minimum temperature using liquid nitrogen, usually not below -200C, the primary cooling coil 14 is first purged with gaseous helium, i'ollowed by liquid helium, The temperature o~ llquid helium is around 268C so the container 10 commences to cool down below the liquid nitrogen temperature, At the same time, a predetermined quantity of liquid helium ls fed into the evaporator 22 through helium feed line 24 and commences to boil within the container so that the hellum pur~es out the nitrogen and other gases in the container to prevent the accumulation of liquid nitrogen and liquid oxygen when the ., ~ 30 temperature in the container drops below the liquefying temperA-,, ture of those gases, By use of liquid helium in the primary cooling coil, the temperature within the container is dropped ~3581 considerably lower than the temperature obtained using liquid nitrogen, An example of a test run ior a container slmilar to that shown in Fig, 1 is illustrated in Fig, 2, In the case of liquid nitrogen, the cooling cycle took approximately 10 hours and the temperature drops to approximately -190C, The soak period was 22 hours and the warming period was 18 hours, This cycle is shown as an even cooling and heating rate. It will be apparent to those skilled in the art that this rate may vary somewhat in practice, A second helium cooling cycle is illustrated in Fig, 2 which dropped the temperature to -250C, It will be apparent that whereas liquid nitrogen and helium have been disclosed in the specification, liquid hydro~en mlght be used, or any stable gas that liquefies and is suitable for cooling, Various changes may be made to the present invention without departing i'rom the scope of the present invention which is limited only by the following claims, .,
It is known that dry cryogenic treatment of metals and selected organic materials improves the properties of these materials. In particular, tool steels appear to have a lon6er life after a cryogenic treatment. Such treatment is commercially used today, generally using air liquefiers which utilize compressor related refrigeration equipment. This equlp-ment has proven satisfactory, but there are several limitations in the use of compressor refrigeration equipment. One critical problem iB wear and tear which results in high maintenance costs. There are also severe constraints on the size of the cooling chamber that can be serviced by a refri~eration unit employing compressor equipment.
It has been found that cryogenic treatin~ of tool steels and other materials where temperatuIes drop as low as -196C, the temperature of liquid nitrogen, roqulre the~ tem-perature to be lowered slowly otherwise warping or other damage occurs to the material being treated. ~or most common tool steels a cooling rate of 0.5C per minute from ambient down to the minimum temperature has proven satisfactory. Warming rates of 0.25C per minute have proven satisfactory up to -20C; from there the warming rate is not critical unless the items are large.
The present invention provides a process and an apparatus utilizing a liquefied gas such as nitrogen, helium or hydrogen, thus avoiding the problems of refrigeration units 114~581 with compressors Such a system can be designed to handle larger loads than is presently possible with compressor refrigeration systems. The use of liquefied gases also allows colder temperatures than is now commercially possible with compressor equipment presently in service. The present invention also provides a system which can cool at the desired cooling rate and is supplied with a circulating system inside the cooling container so that the environment within the con-tainer remains at a substantially uniform temperature throughout.
The present invention provides a process for cryogenlc treatment of materials within an enclosed insulated container, comprising the steps of inserting a predetermined quantity of a liquid gas into the container to vaporize, reduce the moisture content within the container, and purge the container of air;
recirculating the vaporized gas within the container to maintaln a substantially uniform temperature within the container;
cooling the container at a predetermined rate, and maintaining the container at a minimum temperature for a predetermined period of time; and heating the recirculatlng vaporized gas to raise the temperature within thc container at a determined rate.
In prei'erred embodlments, the pressuri~.ed llquid ~as is nitrogen, hydrogen, or helium, cooling rate i8 0.5C per minute, and the warmin~ rate is 0.25C per minute.
In another embodiment, a process is provided for cryogenic treatment of materials within an enclosed insulated container having a primary cooling coil and main cooling coils therein, comprising the steps of inserting a predetermined quantity of a liquid gas into the container to vaporize, reduce the moisture content within the container, and purge the con-tainer of air; recirculating the vaporized ~as withln the con-tainer to maintain a substantially uniform temperature within the container; circulating a controlled flow of liqu~d gas throu~l~
,~~ 2 _ 1~35:' the primary cooling coil so the temperature in the container : drops at a predetermined rate to a predetermined temperature;
closing off liquid gas circulating through the primary cooling coil, and :
_ 2A -~3~8~
circulating liquid gas through the main cooling coils untll the temperature in the container drops to a minimum, and contlnuing circulation through the main cooling coils for a predetermined period of time; closing o~f liquid gas circulating through the main cooling coils; and heating the recirculating vaporized gas to raise the temperature within the container at a predeter-mined rate.
In a further embodiment, wherein nitrogen is the vap-orized liquid gas, the process includes the additional steps of purging the primary cooling coil with helium after shutting off the nitrogen, circulating liquid helium in the primary cooling coil, inserting a predetermined quantity of liquid helium into the container to vaporize, prevent the accumulation of liquid nitrogen and liquid oxygen in the container, and purge the container of other vaporized gases.
The present invention also provides an apparatus for cryogenic treatment o~ materials, comprising an enclosed insulated container having sealed doors, open evaporator for liquid gas wlthin the container, recirculatin~ ~an and duct means for main-taining substantially uni~orm temperaturc wlthin the contniner, a primary cooling coil for liquid 6as within the contnincr, main cooling coil~ i'or llquid ~as within the contniner, and heating means within the duct means.
The term "liquid ~as" used throu~hout the specificntlon includes all types o~ gases that are lique~ied and remain in n liquid state at low temperatures. Nitrogen becomes a liquid nt around -190C, hydrogen around -252C and helium around -2~8~C.
In all cases these temperatures represent normal atmospheric pressure conditions.
In drawings which illustrate the embodiments of the invention, Fig, 1 is a schematic cross sectional elevation showin~
3~' one embodiment of a cryogenic treatment apparatus suitable for ;` the present invention, ~ ig. 2 is a graph showing the temperature against time for a typical cryogenic treatment, Referring now to Fig, 1, a container 10, preferably made from stainless steel, has an lnsulation space 11 surround-ing it and an outer insulation cover 12 to insulate the container 10, Insulated covers or lids (not shown) are provided on the top of the container for loading the container with the materials to be cryogenically treated, The openings are made in the top so that if the container 10 has to be opened with gas still inside, the gas will not spill out of the container, A dryer connection (not shown) is provided to the insulation space 11 so the moist air can be removed from this space, Moisture ln the insulation space can freeze and reduce the insulation properties o~ the unit, A primary cooling coil 13 is positioned in the con-tainer 10 at one side adjacent a blower inlet duct 14, The primary cooling coil 13 has a liquid inlet line 15 which is shown connected to the liquid nitro~en or liquid helium line ~upply, A vent line 16 with a valve therein, allows the evaporated gas to vent into the container 10, Main cooling coils 17 are positioned around the perlphery of the container 10, hcld in place pre~erably by an expanded metal shield 18, A liquid inlet line 19 from the nitrogen supply supplies liquld nitrogen to the main cooling coils 17 and a vent line 20 with a valve therein allows the evaporated nitrogen to vent into the con-tainer 10, An open evaporator 22 is located in the bottom of the 'l~ 30 container 10, The evaporator 22 may be a bucket or open con-tainer and has a liquid nitrogen feed line 23 from the nitrogen supply and a liquid helium feed line 24 from the helium supply.
~35~31 A vent line 25 from the inside of the container 10 is a purge outlet and has a pressure relief valve 26 to prevent pressure build up in the container 10, The nitrogen supply has a valve 27 on the liquid inlet line 19 for the main cooling coils 17, a valve 28 on the feed line 23 for the evaporator 22 and a valve 29 on the liquid inlet line 15 to the primary cooling coil 14.
The helium supply has a valve 30 on the feed line 24 to the evaporator 22 and a valve 31 on the liquid inlet line 15 to the primary cooling coil 14, All the valves are preferably globe valves and have restrictive orifices therein so the flow of liquid can be controlled to suit selected cooling rates, A
globe valve 32 with a restrictive orifice is located in the helium supply line to control the flow of helium to the container.
A blower 33 with an inlet duct 34 from the container 10 circulates the gases within the container, blowing them throu~h outlet duct 35 back into the container lO so that the gases in the container are continually circulated, thus the temperature in the container is maintained substantially uni~orm throughout, A heater element 36 is provided in the outlet duct 35 controlled by a temperature indicator controller (TIC) 37 which operates ~rom a thermocouple 38 within the container lO, Another thermocouple 39 controls the operation o~ n temperature indicator controller 40 which in turn operates a control valve 4]. in the liquid inlet llne 15 to primary coolin~
coil 14, A ~urther thermocouple 42 controls the operation of a temperature indicator controller 43 which in turn operates a control valve 44 in the liquid inlet line 19 to the main coolin~
coils 17.
A pressure gauge or manometer 45 is provided so the pressure inside the container is indicated. It is preferable that the pressure is always slightly higher than atmospheric to ensure that air does not enter the container, 358~L
An air line purge 46 is provided for use when it is required to warm up the container faster than normal. This purge takes outside air and circulates it through the container.
In operation, material to be treated is placed into the container 10 through a lid in the top and the container is closed. Valve 28 is opened and a liquid gas, preferably nitrogen, is fed through feed line 23 into the evaporator 22 This liquid gas evaporates at a temperature well below the freez-ing point of water, therefore, as it evaporates and cools the chamber, most of the moisture present in the container condenses and falls to the bottom of the container as ice. The boilin~
liquid in the evaporator 22 forces air out of the container 10 through the vent line 25 so that air is purged from the container 10 and the atmosphere within the container is primarily the vaporized gas from the evaporator 22. Valve 28 is left cracked open to ensure the container 10 remains pressurized which prevents air from entering the container.
The blower 33 is then started up to circulate the gas within the container and ensure that the temperature throu~h-out the container remains substantially unlform At tlle same time, liquid nitrogen is introduced to the liquid inlet line 15 to the primary cooling coil 14 The rate o~ flow o~ liquid nitrogen i8 set either by the valve 29 or by the control vnlve 41 on a control si~nal irom the temperature indicator controllor 40 When the container temperature drops to a predetermined amount, in one embodiment this amount i9 -188C, the tempernture is measured by the thermocouple 39 and the temperature indicator controller 40 shuts off the flow of liquid nitrogen to the primary cooling coil 14 and opens the control valve 44 in the liquid inlet line 19 to the main cooling coils 17, The rate of flow of liquid nitrogen to the main cooling coils 17 is set by either the valve 27 or the control valve 44 so that the tempera-1~3581 ture drops at a preset rate. This preset rate is approximately 0.5C per minute or may be slower. When the temperature reaches the minimum level, the thermocouple 42 records this and the pre~
set time period commences with the f low of liquid nitrogen continuing through the main cooling coils 17 until the end of the time period. The minimum level of temperature for liquid nitrogen is usually around -190C. The liquid nitrogen is then shut off, and the container commences to warm up, While this so-called "soaking" period is continuing, the fan 33 remains on and the gas within the container 10 circulates through ducts 34, 35. At the end of the soak perlod, the liquid nitrogen is shut off and the heater 36 in duct 35 is turned on and controlled by the temperature indicator controller 37, so that a small quantity of heat slowly warms up the contniner at a predetermined rate. This predetermined rate is preferably .25C per minute or less. When the temperature reaches -20 the warming rate is generally not critical, If colder temperatures than liquid nitro~en tempera-tures are desired, then helium may be added. When the tempern-ture has dropped to a minimum temperature using liquid nitrogen, usually not below -200C, the primary cooling coil 14 is first purged with gaseous helium, i'ollowed by liquid helium, The temperature o~ llquid helium is around 268C so the container 10 commences to cool down below the liquid nitrogen temperature, At the same time, a predetermined quantity of liquid helium ls fed into the evaporator 22 through helium feed line 24 and commences to boil within the container so that the hellum pur~es out the nitrogen and other gases in the container to prevent the accumulation of liquid nitrogen and liquid oxygen when the ., ~ 30 temperature in the container drops below the liquefying temperA-,, ture of those gases, By use of liquid helium in the primary cooling coil, the temperature within the container is dropped ~3581 considerably lower than the temperature obtained using liquid nitrogen, An example of a test run ior a container slmilar to that shown in Fig, 1 is illustrated in Fig, 2, In the case of liquid nitrogen, the cooling cycle took approximately 10 hours and the temperature drops to approximately -190C, The soak period was 22 hours and the warming period was 18 hours, This cycle is shown as an even cooling and heating rate. It will be apparent to those skilled in the art that this rate may vary somewhat in practice, A second helium cooling cycle is illustrated in Fig, 2 which dropped the temperature to -250C, It will be apparent that whereas liquid nitrogen and helium have been disclosed in the specification, liquid hydro~en mlght be used, or any stable gas that liquefies and is suitable for cooling, Various changes may be made to the present invention without departing i'rom the scope of the present invention which is limited only by the following claims, .,
Claims (15)
1 A process for cryogenic treatment of materials within an enclosed insulated container, comprising the steps of inserting a predetermined quantity of a liquid gas into the container to vaporize, reduce the moisture content within the container, and purge the container of air;
recirculating the vaporized gas within the container to maintain a substantially uniform temperature within the con-tainer;
cooling the container at a predetermined rate, and maintaining the container at a °minimum temperature for a pre-determined period of time; and heating the recirculating vaporized gas to raise the temperature within the container at a predetermined rate.
recirculating the vaporized gas within the container to maintain a substantially uniform temperature within the con-tainer;
cooling the container at a predetermined rate, and maintaining the container at a °minimum temperature for a pre-determined period of time; and heating the recirculating vaporized gas to raise the temperature within the container at a predetermined rate.
2. The process according to claim 1 wherein the con-tainer is cooled at the rate of about 0.5°C per minute.
3 The process according to claim 1 wherein the con-tainer is heated at a rate of about 0.25°C per minute.
4. The process according to claim 1 wherein the liquid gas is nitrogen.
5. The process according to claim 1 wherein the liquid gas is hydrogen.
6. The process according to claim 1 wherein the liquid gas is helium.
7 The process according to claim 4 wherein the min-imum temperature is at least about -190°C.
8. The process according to claim 4 wherein the con-tainer is cooled at a rate of about 0.5°C per minute to a minimum temperature of at least about -190°C.
9. The process according to claim 4 wherein the con-tainer is heated at a rate of 0.25°C per minute to -20°C.
10. A process for cryogenic treatment of materials within an enclosed insulated container having a primary cooling coil and main cooling coils therein, comprising the steps of inserting a predetermined quantity of a liquid gas into the container to vaporize, reduce the moisture content within the container, and purge the container of air;
recirculating the vaporized gas within the container to maintain a substantially uniform temperature within the con-tainer;
circulating a controlled flow of liquid gas through the primary cooling coil so the temperature in the container drops at a predetermined rate to a predetermine temperature;
closing off liquid gas circulating through the primary cooling coil and circulating liquid gas through the main cooling coils until the temperature in the container drops to a minimum, and continuing circulation through the main cooling coils for a predetermined period of time;
closing off liquid gas circulating through the main cooling coils; and heating the recirculating vaporized gas to raise the temperature within the container at a predetermined rate.
recirculating the vaporized gas within the container to maintain a substantially uniform temperature within the con-tainer;
circulating a controlled flow of liquid gas through the primary cooling coil so the temperature in the container drops at a predetermined rate to a predetermine temperature;
closing off liquid gas circulating through the primary cooling coil and circulating liquid gas through the main cooling coils until the temperature in the container drops to a minimum, and continuing circulation through the main cooling coils for a predetermined period of time;
closing off liquid gas circulating through the main cooling coils; and heating the recirculating vaporized gas to raise the temperature within the container at a predetermined rate.
11. The process according to claim 10 wherein the liquid gas is nitrogen, and the predetermined temperature of the container after circulating liquid nitrogen through the primary coil is approximately -188°C.
12. The process according to claim 1 or claim 10 wherein the pressure within the container after being purged of air is above atmospheric.
13. The process according to claim 11 including the additional steps of purging the primary cooling coil with helium after shutting off the liquid nitrogen, circulating liquid helium in the primary cooling coil, inserting a predetermined quantity of liquid helium into the container to vaporize, prevent the accumulation of liquid nitrogen and liquid oxygen in the con-tainer, and purge the container of other vaporized gases.
14, An apparatus for cryogenic treatment of materials comprising:
an enclosed, insulated container having a sealed lid in the top thereof, open evaporator for liquid gas within the container, recirculating fan and duct means for maintaining sub-stantially uniform temperature within the container, a primary cooling coils for liquid gas within the container, main cooling coils for liquid gas within the container, and heating means within the duct means.
an enclosed, insulated container having a sealed lid in the top thereof, open evaporator for liquid gas within the container, recirculating fan and duct means for maintaining sub-stantially uniform temperature within the container, a primary cooling coils for liquid gas within the container, main cooling coils for liquid gas within the container, and heating means within the duct means.
15, The apparatus according to claim 14 including at least one temperature indicator controller within the container to control the operation of the primary cooling coil and the main cooling coils.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000387611A CA1143581A (en) | 1981-10-08 | 1981-10-08 | Process and apparatus for cryogenic treatment of materials |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000387611A CA1143581A (en) | 1981-10-08 | 1981-10-08 | Process and apparatus for cryogenic treatment of materials |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1143581A true CA1143581A (en) | 1983-03-29 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000387611A Expired CA1143581A (en) | 1981-10-08 | 1981-10-08 | Process and apparatus for cryogenic treatment of materials |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1143581A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1987003472A1 (en) * | 1985-12-07 | 1987-06-18 | Bernd Blaudszun | Process for producing a conditioned atmosphere for cryo-treatment of rheumatic patients |
-
1981
- 1981-10-08 CA CA000387611A patent/CA1143581A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1987003472A1 (en) * | 1985-12-07 | 1987-06-18 | Bernd Blaudszun | Process for producing a conditioned atmosphere for cryo-treatment of rheumatic patients |
| EP0226107A1 (en) * | 1985-12-07 | 1987-06-24 | Nusec Anlagenbau GmbH | Method of producing a working atmosphere for treating at cryogenic temperatures persons suffering from rheumatism, and a complete body treatment system for carrying out the method |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |