JPH0142730B2 - - Google Patents

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to the use of low-boiling gases such as helium, hydrogen, neon, and argon that liquefy at an ultra-low temperature of −200°C or less under normal pressure. In cryogenic liquefaction refrigeration equipment used as a medium, impurity gas contained in low-boiling gas can be removed from the equipment, and purification of the low-boiling gas and regeneration of the equipment after removal of impurity gas can be efficiently performed. Regarding equipment.

(Prior Art) FIG. 7 is an example of a conventional technology of a cryogenic liquefaction refrigeration apparatus using helium gas as a low boiling point gas.

Oil injection type screw compressors are widely used in liquefaction refrigeration systems that use helium gas.

The helium gas pressurized by the screw compressor 1 is cooled by sequentially passing through a gas cooler 2, an oil separator 3, and an adsorber 4, and after oil is separated and impurity gas is removed, a discharge pipe 5, Next, high pressure gas pipe 1
After passing through 5, you will enter cold box 6. The inside of the cold box 6 is maintained at a high vacuum, and convection prevents heat from entering from the outside to the low-temperature equipment inside. There are six heat exchangers 7 in the cold box 6.
1 to 12 are installed, sequentially serving as the first to sixth heat exchangers. Liquid nitrogen flows into the first heat exchanger 7 through an inlet 13, exchanges heat with helium gas, and then flows out through an outlet 14. The high-pressure helium gas flowing through the high-pressure gas pipe 15 is cooled by this liquid nitrogen and the return gas flowing through the low-pressure gas pipe 16 to the screw compressor 1, and reaches almost the temperature of liquid nitrogen at the outlet of the first heat exchanger 7. cooled down. A part of the helium gas that has left the second heat exchanger 8 flows through the bypass pipe 17 and flows into the first-stage expander 18 where it performs expansion work and becomes low-pressure, low-temperature helium gas, which is then transferred to the low-pressure gas pipe 16. The high-pressure gas flows into the third heat exchanger 9 and exchanges heat with the remaining high-pressure gas flowing through the high-pressure gas pipe 15 to cool it. Also the fourth
A part of the high-pressure gas leaving the heat exchanger 10 flows through the bypass pipe 19 and enters the second-stage expander 20, where it performs expansion work and becomes low-pressure, low-temperature helium gas.
The heat exchanger 11 exchanges heat with the remaining high pressure gas to cool it. The high-pressure gas that has been further cooled in the sixth heat exchanger 12 enters the Joel-Thomson valve 21, where it undergoes isenthalpic expansion, a portion of which liquefies, and accumulates in the liquid distillation vessel 22. This liquid is used for the appropriate loading 23.

The helium gas that has not been liquefied returns to the sixth heat exchanger 12 in the state of saturated vapor, merges with the outlet gas of the expander 20, flows through the low pressure gas pipe 16, and is sequentially combined with the high pressure gas flowing through the high pressure gas pipe 15. After exchanging heat within the heat exchanger, it returns to the screw compressor 1 via the suction pipe 24.

As described above, the high-pressure gas and the low-pressure gas exchange heat in countercurrent flow, and the cold heat necessary to liquefy the high-pressure gas is transferred to the liquid nitrogen in the first heat exchanger 7 and the first and second expanders 18. ,20.

In the case of helium gas, it liquefies at 1 atm 4.2〓.
When operating at such extremely low temperatures, the device must be sufficiently thermally insulated from the outside. For this reason, the inside of the cold box 6 is maintained in an ultra-vacuum state of 10 ^-3 to ^{10 -6} mmHg or less to prevent heat transfer from the outside (normal temperature area) due to air convection. In addition, there is a temperature difference of about 300℃ between the inside and outside of the cold box 6, and there is a large amount of heat intrusion due to radiation, so in order to prevent this, all parts such as heat exchangers, piping, valves, expanders, etc. It is wrapped in several layers of radiant insulation material such as aluminum foil.

One of the most important technologies when manufacturing cold boxes is the vacuum insulation technology mentioned above. This vacuum insulation requires advanced technology and know-how, and construction can take anywhere from several weeks to several months. For this reason, once a cold box is finished, it is usually never opened. This is because it requires considerable cost and time to restore the original state after opening.

On the other hand, since the screw compressor 1 of this device is an oil injection type, a large amount of lubricating oil is injected into the compressor, and an oil separator 3 is required to separate this oil from high pressure gas. Of course, this equipment liquefies at extremely low temperatures below -200°C, so if fine oil enters the system, it will condense and solidify on the walls of the heat exchanger, causing damage in the worst case. This will block the passage of the heat exchanger, making the device inoperable. Therefore, the intrusion of oil into the cold box is extremely discouraged, and measures are taken to prevent the emergency situation of blockage of the heat exchanger due to high viscosity oil. In order to prevent the above-mentioned emergency situation, four or five stages of oil separators 3 are installed, and an adsorber 4 containing an adsorbent such as activated carbon or molecular sieves is installed at the final stage.

In addition to the above-mentioned oil, gaseous impurities such as air, water vapor, methane, and ethane also result in the same disadvantageous conditions as oil, so the absorber 4 is designed to absorb not only oil but also these impurities. It is also configured to trap gas.

As mentioned above, in the prior art shown in FIG. 7, although an oil separator and an adsorber are provided, the adsorbent in the adsorber 4 is at room temperature.
Since only a few types of adsorbents such as activated carbon and molecular sieves can be filled as adsorbents, trace amounts of impure gas cannot be sufficiently adsorbed. This is because adsorption capacity is insufficient at room temperature, and when there are many types of impure gases, only specific gases depending on the type of adsorbent can be adsorbed.

As an improvement over such conventional technology, a device as shown in FIG. 8 can be considered. This device has a first adsorber 4, a second adsorber 31 in a purifier 30, and a third adsorber 32 in a cold box 6.
This device is different from the device shown in FIG. 7 in that the first heat exchanger 7 is provided on the high-pressure gas outlet side. According to the purifier 30 of this device, an evaporator 33 of a refrigeration cycle is installed in the adsorber 31. The refrigeration cycle is composed of a compressor 34, a condenser 35, an expansion valve 36, and the evaporator 33 mentioned above. According to a normal fluorocarbon refrigerator, the adsorbent in the adsorber 31 is cooled to about -40°C, thereby improving the adsorption capacity of the adsorbent. 37 is a coolant passage. Further, high-pressure gas that is close to the inlet temperature of the liquid nitrogen flowing into the first heat exchanger 7 flows into the third adsorber 32 . Portions with the same reference numerals as in FIG. 7 have the same functions, so their explanation will be omitted.

According to the experience of the prior art, the impurity gases in cryogenic liquefaction refrigeration systems using helium gas include (a) oil vapor in the compressor (hydrocarbon compounds such as methane, ethane, and propane), and (b) Possible causes include air and moisture remaining in the device, (c) foreign gases generated from structures (plastic, O-rings, gaskets, magnets), and (d) air and moisture entering from the outside.

These impure gases come in many varieties, including hydrocarbons, carbon dioxide, carbon monoxide, water, oxygen, nitrogen, and neon, and they are extremely trace amounts of less than 1 ppm. For this reason, even if the types of fillers in the adsorber 31 of the purifier 30 are increased and the temperature is cooled to about -40°C, most of the trace gases will not be captured here but will enter the cold box 6. become. The impure gas that has entered the cold box 6 is deposited on the heat exchanger walls and piping at temperatures corresponding to the respective partial pressures, and the performance of the cold box 6 decreases due to long-term continuous operation. Eventually, it becomes impossible to drive.

Since the impure gas that cannot be captured by the first heat exchanger 7 also adheres to the second and third heat exchangers 8 and 9, the third adsorber 32 is also attached to the outlet of the first heat exchanger 7. must be installed.

If impure gas adheres to the first heat exchanger 7 and causes a problem in operation, the device is stopped and warmed up to room temperature, and the heat exchanger 7 and adsorber 3 are heated up to room temperature.
2 must be regenerated. Furthermore, if the third adsorber 32 becomes unusable due to long-term use, the cold box 6 must be opened and replaced. However, since the inside of cold box 6 is kept at an ultra-vacuum of 10 ^-3 cmHg or less, once it is exposed to the atmosphere, it requires a great deal of manpower and time to return the interior to the original ultra-vacuum.
Further, if the adsorber 32 is connected to the cold box 6 by a replaceable flange, the reliability of the box will be significantly reduced in maintaining ultra-vacuum. Furthermore, if the adsorber inlet/outlet piping is welded,
This time it will be extremely difficult to replace.

(Problems to be Solved by the Invention) The prior art has various problems as described above. The object of the present invention is to obtain a purification and regeneration device that eliminates the above-mentioned problems.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above-mentioned problems, the low boiling point gas purification and regeneration device in the cryogenic liquefaction refrigeration system of the present invention has the following configuration. A purifier is constructed by providing two or more sets each consisting of a heat exchanger and an adsorber connected to the outlet of the heat exchanger, separately from the cold box in which the heat exchanger group below the second heat exchanger is accommodated. be placed in a box.
Connect these sets to the compressor side and cold box side using gas pipes. The gas pipes are provided with switching valves that can be switched so that when one set operates as a refining side, the other set operates as a regeneration side.

Second invention In addition to the configuration of the first invention, an external fluid supply pipe for heating or cooling the heat exchanger is provided to connect the first heat exchanger of each set and the refrigeration cycle.

In the present invention, the "first heat exchanger" refers to a device in which heat exchange is performed between three fluids, high-pressure gas, low-pressure gas, and an external coolant for cooling, during liquefaction refrigeration operation of the liquefaction refrigeration system, and the heat exchanger exits the heat exchanger. refers to a heat exchanger that is cooled until the temperature of the high pressure gas at is approximately equal to the inlet temperature of the external coolant to the heat exchanger.

(Function) A first heat exchanger and an adsorber are housed in a purifier box separately from a cold box in which a group of heat exchangers below the second heat exchanger are housed, and this adsorber is connected to the first heat exchanger. Since the heat exchanger is connected to the outlet side of the heat exchanger, it is extremely easy to clean the heat exchanger and replace the adsorber regardless of the cold box which is maintained at a high vacuum.

By providing two or more sets of the first heat exchanger and the adsorber, this set can be switched between the purification side and the regeneration side, allowing continuous operation without stopping the apparatus.

There are two or more sets of the first heat exchanger and adsorber, and an external fluid supply pipe for heating or cooling the heat exchanger is provided to connect the first heat exchanger and the refrigeration cycle. Both can be operated in parallel, and impure gas can be sufficiently captured in the adsorber to prevent impurity gas from entering the cold box.

(Embodiment) FIG. 1 is a flow sheet diagram of an embodiment of the present invention, in which the purifier 30 in the prior art in FIG. 8 is replaced with a purifier box 40, and the cold box 6 in FIG. The set of the first heat exchanger 7 and the third adsorber 32 that were in the interior is accommodated, and two sets of this set, namely 7a and
Two sets, 2a and 7b and 32b, are installed in parallel for gas flow between the compressor side and the cold box side. The discharge pipe 5 from the compressor is connected to the high pressure gas pipe 15 in the cold box 6 by branching gas pipes 41 and 42, while the low pressure gas pipe 16 is connected to the suction pipe 24 to the compressor.
They are connected by branching gas pipes 43 and 44. 5
1 to 58 are switching valves for switching gas flow paths. Further, the fluid that exchanges heat with the first heat exchanger 7a flows in from the external fluid supply pipe 45. Similarly, the fluid that exchanges heat with the first heat exchanger 7b is the external fluid supply pipe 4.
It flows in from 7.

A cooling fluid flows through the heat exchanger during purification, and a heating fluid flows during regeneration. In the code,
The parts that are the same as those in FIG. 8 are the same parts and have the same functions, so their explanation will be omitted.

The adsorbers 32a, 32b are the second adsorbers following the first adsorber 4, and the first heat exchangers 7a,
7b respectively connected to the high pressure gas outlet side. Next, the operation will be explained with reference to FIG. It is now assumed that the first heat exchanger 7b on the left side of the figure is in operation for liquefaction refrigeration, and the first heat exchanger 7a on the right side is in operation for regeneration.

The switching valves 52, 54, 56, and 58 of the high-pressure gas pipe 42 and the low-pressure gas pipe 44 for the first heat exchanger 7b are all open, and cooling fluid flows into the external fluid supply pipe 47 to perform the first heat exchange. The container 7b is being cooled. By using a low-temperature fluorocarbon-based refrigerant, such as refrigerant R13B1, as the cooling fluid, the heat exchanger can be
It can be cooled to 80°C, and by using a binary refrigeration system using refrigerant R13 and refrigerant R22, it can be cooled to about -100°C. Furthermore, by using liquid nitrogen as a cooling fluid, it is possible to cool down to about -190°C. Therefore, in the purifier box 40 provided separately from the cold box 6, it is possible to cool the adsorbers 32a and 32b to nearly -100°C, which is much lower than -40°C in the prior art.

On the other hand, the high pressure gas pipe 4 for the first heat exchanger 7a
1 and the switching valves 51, 53, 55 of the low pressure gas pipe 43,
57 are all closed, and the external fluid supply pipe 4
5, heating fluid flows to heat the first heat exchanger 7a.

Immediately after switching the first heat exchanger 7a to regeneration, if liquid nitrogen is used as the external cooling fluid, the first heat exchanger 7a and adsorber 32a are -
The temperature is extremely low, around 190℃. Therefore, the impure gas adhering (condensing or solidifying) to the heat exchanger surface and the adsorber must be heated to a temperature higher than room temperature to desorb it. For this purpose, heating fluid is flowed as described above. At the same time, the on-off valve 62 of the bypass pipe 61 is opened, and the valves 66 and 67 are opened.
is opened, a purified gas pressurized at room temperature or above is supplied from the purified gas supply pipe 63, circulated through the system via the bypass pipe 61, and the purified gas supplied from the discharge pipe 64 is discharged to the outside of the system.

The emitted gas is either released into the atmosphere or sent to a separately installed purification and recovery equipment, where it is purified and recovered. The heating fluid flowing inside the external fluid supply pipe 45 is heated nitrogen, low-temperature fluorocarbon refrigerant, brine, etc.
Heat is supplied to heat a. Discharge pipe 6
When the temperature of the gas No. 4 reaches room temperature or higher, the valve 67 is closed and the valve 68 of the vacuum generating tube 65 is opened, and the gas and impure gas in the system are discharged by the vacuum pump.
The supply of pressurized purified gas and evacuation are alternately performed, and this operation is repeated until the impurity gas in the system is sufficiently removed.

After operating for a certain period of time, the first heat exchanger 7 on the left
When the refining capacity or liquefaction refrigeration capacity of b begins to decrease, open and close the switching valve to switch the first heat exchanger 7a on the right side, which has completed regeneration, to liquefaction refrigeration operation, and switch the first heat exchanger 7a on the left side to liquefaction refrigeration operation. switch 7b to regeneration operation.

FIG. 3 shows a case in which the first heat exchanger 7b on the left side is performing liquefaction freezing operation and the first heat exchanger 7a on the right side is performing regeneration operation, and the cooling fluid is supplied to the external fluid supply pipe 47. In order to flow the heating fluid into the supply pipe 45, the compressor 71 and the condenser 7
2. A refrigeration cycle consisting of an expansion valve 73 and an evaporator 74 is operated, and cold heat is indirectly conveyed to the pipe 47 by brine, while heat due to condensation is indirectly conveyed to the pipe 45. This is an example of energy saving. 75 is a cooling tower.

Also, FIG. 4 shows an embodiment designed to save energy in the same way as FIG.
The difference is that they each flow into 7.

Both FIG. 3 and FIG. 4 use R13B1 as a refrigerant in a compression refrigeration cycle, and show a part of a flow sheet of a heating and cooling system useful for energy saving. Therefore, the first one on the left
Also in the heat exchanger 7b, a bypass pipe 61, a purified gas supply pipe 63, a discharge pipe 64, a vacuum generation pipe 65,
Although valves 66, 67, and 68 are naturally provided, their illustration is omitted. In addition, the heat of evaporation and heat of condensation of the refrigeration cycle are transferred to the pipe 45,
The illustration of the pipe system to be provided to 47 is also omitted.

Furthermore, Fig. 5 shows an embodiment in which liquid nitrogen is supplied to the external fluid supply pipes 45 and 47, where (a) shows the liquefaction freezing operation in progress, (b) shows the regeneration operation in progress, and 80 shows the liquid nitrogen being heated. It is a heater.

Further, FIG. 6 shows an embodiment in which two external fluid supply pipes are used, and liquid nitrogen is supplied to the supply pipe 47a, and brine is supplied to the supply pipe 47b. According to this embodiment, liquefaction freezing can be performed with a reduced amount of liquid nitrogen used or without using it at all. In this case, although the liquefaction rate (refrigeration capacity) is slightly lower than when liquid nitrogen is used, there is an advantage that liquid nitrogen does not need to be used.

〔Effect of the invention〕

According to the present invention, it becomes easy to clean the heat exchanger and replace the adsorber. In the conventional cold box, if oil enters the cold box due to an operational error or the like, it is very difficult to clean it. That is, it was necessary to open the cold box, take out the internal structure and wash it with a solvent, or cut a portion of the piping. Furthermore, after cleaning, it took several weeks to restore the inside of the cold box to an ultra-vacuum state. In other words, in the prior art, cleaning the first heat exchanger and replacing the adsorber required an enormous amount of cost and time.

On the other hand, according to the present invention, since the purifier box is provided separately from the cold box and houses the first heat exchanger and the adsorber, it is extremely easy to clean the heat exchanger and replace the adsorber. . That is, since the first heat exchanger and adsorber are housed in the purifier box, insulation at low temperatures down to -190°C is much simpler than in a cold box, and even when vacuum insulation is used, the temperature is 10 ^-1 mmHg. A vacuum of about 10 ^-3 is sufficient, as in the case of a cold box.
There is no need to maintain an ultra-vacuum below 10 ^-6 mmHg,
It is also possible to simply perform ordinary heat insulation construction using heat insulating materials without using a vacuum chamber. Additionally, purifier boxes are much smaller than cold boxes, and can be designed with cleaning and replacement considerations in mind. Furthermore, cleaning of the first heat exchanger, replacement of the adsorbent, etc. can be performed extremely easily and in a short time.

By installing two or more sets consisting of the first heat exchanger and adsorber in parallel, unless an unexpected accident occurs, the above-mentioned sets can be switched to liquefaction freezing and regeneration. No opening is required.

Further, according to the present invention, most of the impure gases in the low boiling point gas entering the purifier box are first collected by condensing and solidifying on the wall surface of the first heat exchanger. This impure gas on the heat exchanger surface can be easily removed by simply bringing it to room temperature. Therefore, regeneration can be easily performed without stopping liquefaction freezing.

According to the present invention, the first heat exchanger and the adsorber connected to its outlet are provided separately from the cold box, and the temperature is much lower than -40°C in the adsorber in the conventional purifier. Since the temperature of the adsorber can be lowered to the same temperature as the above, the adsorption performance is significantly improved. Even trace amounts of impure gas that were not captured by the first heat exchanger are almost completely adsorbed by this adsorber. Even if impurity gas that is not collected here does enter the cold box, it will be in an extremely small amount and only 1 to 2
This amount is just enough to allow the vehicle to be operated without any problems during regular inspections once a year. In contrast, in the conventional technology, if impure gas enters the cold box and the performance of the first heat exchanger deteriorates, it is necessary to stop the liquefaction refrigeration operation itself and warm up the cold box.

According to the present invention, the number of adsorbers can be reduced. The adsorber contains particles such as activated carbon and molecular sieves. If care is taken to prevent these fine particles from circulating within the system, the adsorbent and filter will cause a pressure loss in the high pressure line, reducing the capacity of the liquefaction refrigeration system. Therefore, the fewer the number of adsorbers, the better, but according to the present invention, the adsorbers in the cold box in the prior art can be omitted.

Further, according to the present invention, it is possible to provide two or more sets consisting of the first heat exchanger and the adsorber, and to operate these sets simultaneously on the liquefaction refrigeration side and the regeneration side by switching operation of the switching valve. Therefore, the purpose of energy saving can also be achieved by operating a separate refrigeration cycle and using the endotherm due to the heat of evaporation and the heat of condensation obtained at the same time for cooling and heating on the liquefaction refrigeration side and the regeneration side. Can be done.

[Brief explanation of drawings]

FIG. 1 is a flow sheet diagram of the embodiment of the present invention, FIG. 2 is a detailed explanatory diagram of a part of the embodiment, and FIGS. 3 and 4 are the first heat exchanger of the purifier box of the embodiment. Flow sheet diagrams of different embodiments of the refrigeration cycle for heating and cooling the first heat exchanger, FIGS. 7 and 8 are simple flow sheet diagrams of the prior art. 6... Cold box, 7a, 7b... 1st
Heat exchanger, 41-44... Gas pipe, 45, 47...
...External fluid supply pipe, 51-58...Switching valve.

Claims (1)

[Claims] 1. A set consisting of a first heat exchanger and an adsorber connected to the outlet of the heat exchanger is separated from a cold box in which a group of heat exchangers below the second heat exchanger are housed. Two or more sets are provided and housed in the purifier box, and these sets are connected to the compressor side and the cold box side through gas pipes, and when one set is on the refining side, the other set is on the regeneration side. 1. An apparatus for purifying and regenerating low boiling point gas in a cryogenic liquefaction refrigeration system, characterized in that the gas pipe is provided with a switching valve that can be switched in the following manner. 2. Two or more sets consisting of a first heat exchanger and an adsorber connected to the outlet of the heat exchanger are provided separately from a cold box in which a group of heat exchangers below the second heat exchanger is housed. These sets are housed in a purifier box, and these sets are connected to the compressor side and the cold box side through gas pipes, and can be switched so that when one set is on the refining side, the other set is on the regeneration side. A cryogenic liquefier characterized in that a switching valve is provided in the gas pipe, and an external fluid supply pipe for heating or cooling the heat exchanger is further provided to connect the first heat exchanger of each set and the refrigeration cycle. Purification and regeneration equipment for low boiling point gas in refrigeration equipment. 3. Each set of gas pipes is provided with two high-pressure and low-pressure sides, one of which is connected to a purified gas supply pipe and the other to a discharge pipe via a switching valve,
A vacuum generation pipe was further connected to the discharge pipe via a switching valve, and the high-pressure side gas pipe and the low-pressure side gas pipe were connected to each other by a bypass pipe having an on-off valve, and the purified gas was supplied from the purified gas supply pipe. Purified gas is
The switching valve and the on-off valve are switched so that the gas flows through the high-pressure side and low-pressure side gas pipes via the bypass pipe, flows out from the discharge pipe, and then creates a vacuum in the system by the vacuum generating pipe. A low boiling point gas purification and regeneration device in a cryogenic liquefaction refrigeration system according to claim 2, characterized in that the device is configured as follows. 4. According to claim 2, any one of liquid nitrogen, low-temperature fluorocarbon refrigerant, or brine can flow through the external fluid supply pipe that heats and cools the first heat exchanger. A purification and regeneration device for low boiling point gas in cryogenic liquefaction refrigeration equipment. 5. Claim 2 or 4, characterized in that the adsorber connected to the low boiling point gas outlet on the high pressure side of the first heat exchanger can be cooled to a temperature lower than -80°C. Purification and regeneration equipment for low boiling point gas in cryogenic liquefaction refrigeration equipment. 6 Of the set consisting of the first heat exchanger and adsorber,
so that when one set of external fluid supply pipes is on the evaporation side, the other set of external fluid supply pipes is on the condensation side;
The low boiling point gas purification and regeneration device in a cryogenic liquefaction refrigeration system according to claim 2 or 4, wherein a refrigeration cycle is connected to the fluid supply pipe.