TWI525298B - Air liquefaction separation method and device - Google Patents

Description

Air liquefaction separation method and device

The present invention relates to an air liquefaction separation method and apparatus, and more particularly to a method for utilizing a medium pressure column and a low pressure column to cryogenically separate compressed, purified, and cooled raw material air, and at least extracting liquid oxygen as Air liquefaction separation method and device for products.

When manufacturing oxygen, nitrogen and argon in the industry, it is usually a so-called deep-cooling air liquefaction separation device which uses air as a raw material and separates it by a compound rectifying column composed of a medium pressure column and a low pressure column. Made for manufacturing. In the cryogenic air liquefaction separation apparatus, about 5% of the product can be produced into liquid oxygen, liquid nitrogen, and liquid argon. However, when making more liquid products, a liquefaction procedure must be added.

The liquefaction procedure is such that the raw material air, nitrogen gas, or the like is compressed, circulated, and adiabatically expanded to obtain a cold required for the procedure. Various techniques have been disclosed for each program (for example, refer to Patent Document 1).

In the above liquefaction procedure, the circulating fluid is supplied to the distillation column in a partially liquefied state to extract a heat-balanced liquid product. In order to compress a circulating fluid in an air circulation liquefaction process for forming a circulating fluid, a portion of the high-pressure raw material air is compressed as compared with a nitrogen circulating liquefaction procedure in which a low-pressure and/or medium-pressure nitrogen gas is compressed to form a circulating fluid. The power consumption is less, so it is basically a program with advantages.

However, when the amount of liquid in the product, especially liquid nitrogen, is large, if the air circulation liquefaction procedure is performed, the liquefaction rate of the raw material air supplied to the intermediate pressure tower will increase, so the distillation conditions of the intermediate pressure tower will be lowered, thereby becoming Hard to deal with. On the other hand, the nitrogen circulation liquefaction process is a process of supplying liquid nitrogen equivalent to a liquid product to the intermediate pressure column, and even when the product liquid amount is large, the distillation conditions of the intermediate pressure column are not lowered. That is, when the product volume is small, the air circulation liquefaction process with less power consumption has an advantage, and when the product liquid amount is large, only the nitrogen circulation liquefaction program can cope with it.

Further, a procedure for applying an air circulation program to a single rectification column program is known (for example, refer to Patent Documents 2, 3, and 4). In the above-mentioned procedures, a part of the raw material air which is the same as the operating pressure of the single rectification column is circulated and heated to normal temperature, and then introduced into the raw material air compressor, and compressed together with the raw material air introduced from the outside. Loop the program. These materials do not contain water vapor or carbon dioxide in the circulating raw material air, but the circulating air also becomes a procedure for circulating the pretreatment device, so there is a waste of excessively large size of the pretreatment adsorption device.

Further, a procedure for applying an air circulation liquefaction program to a duplex distillation column program is also known (for example, refer to Patent Documents 5 and 6). For example, the raw material air is purified by a compressor to 460 kPa (gauge pressure, hereinafter referred to as kPaG), and then introduced into a circulating air compressor together with a part of the circulating air treated by the expansion turbine, and is pressurized to a necessary pressure. . The circulating air is cooled to a predetermined temperature by a heat exchanger and introduced into the expansion turbine to produce the cold required for the apparatus. A portion of the circulating air treated by the expansion turbine is introduced to the intermediate pressure tower, and the remainder is introduced to the recycle compressor together with the raw material air. In this procedure, the operating pressure of the intermediate pressure column is approximately 480 kPaG, which is the same as the operating pressure of the expansion turbine and the operating pressure of the pretreatment unit.

Further, there is also known an air liquefaction separation apparatus for extracting an oxygen product, which is capable of changing the ratio of the extracted liquid oxygen amount (for example, refer to Patent Documents 7 and 8), for example, introducing a fluid from an intermediate pressure tower into a pretreatment apparatus. After that, it flows and is boosted together with the raw material air. Further, it is also known that a compressor is used to compress a fluid from an intermediate pressure column together with raw material air to an operating pressure higher than that of the intermediate pressure column (for example, see Patent Document 9). However, in this procedure, the circulating fluid is also processed in the cooling device, the pretreatment adsorption device, and thus many processing capabilities are required in such devices.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 3213846

[Patent Document 2] Japanese Patent Publication No. Sho 56-034787

[Patent Document 3] Japanese Patent Publication No. Sho 60-044584

[Patent Document 4] Japanese Patent Publication No. Sho 54-095552

[Patent Document 5] Japanese Patent Laid-Open No. Hei 06-159929

[Patent Document 6] Japanese Patent Laid-Open No. Hei 06-159930

[Patent Document 7] Japanese Patent Laid-Open No. Hei 10-054657

[Patent Document 8] Japanese Patent Laid-Open No. Hei 10-054658

[Patent Document 9] Japanese Patent Laid-Open No. 06-300435

As described above, various proposals have been made as a liquefaction program, and the air circulation liquefaction procedure is mainly aimed at improving the efficiency of the procedure, but it is not sufficient in terms of improving the price of the apparatus.

Accordingly, it is an object of the present invention to provide an air liquefaction separation method and apparatus for reducing the cost of a device in an air circulation liquefaction process in which at least liquid oxygen is extracted as a product.

In order to achieve the above object, a first aspect of the present invention is an air liquefaction separation method which utilizes a medium pressure column and a low pressure column to perform low temperature distillation of compressed, purified, and cooled raw material air to extract at least liquid oxygen as a product. And comprising the steps of: a raw material air compression step of boosting the total amount of the raw material air to a first set pressure higher than the operating pressure of the intermediate pressure tower to form a pressurized raw material air; and an adsorption purification step from the boosting step The raw material air adsorbs to remove impurities to form pressurized purified air; the circulating air combining step causes the pressurized purified air to merge with the pressurized return air described later to form circulating air; and the cooling step divides the circulating air into two The first split air is cooled to a first set temperature to form an intermediate pressure tower introduction air, and the second split air is cooled to a second set temperature higher than the first set temperature to form an expansion air; and the expansion step is performed by The expansion air is adiabatically expanded to a second set pressure lower than the first set pressure to form a low temperature air; and the introduction step is performed to lower the temperature One part of the gas is introduced into the above-mentioned intermediate pressure tower; a temperature increasing step is performed to restore the remaining portion of the low temperature air to form a return air; a cyclic compression step is performed to pressurize the return air to form the boosted return air; and another introduction step Introducing the above-mentioned intermediate pressure tower into the above-mentioned intermediate pressure tower.

Further, the second configuration of the present invention is an air liquefaction separation method in which at least liquid oxygen is extracted as a product by subjecting a compressed, purified, and cooled raw material air to low temperature distillation by using an intermediate pressure column and a low pressure column. The method comprises the following steps: a raw material air compression step of boosting the total amount of the raw material air to a first set pressure higher than the operating pressure of the intermediate pressure tower to form a pressurized raw material air; and an adsorption purification step for adsorbing air from the pressurized raw material Removing impurities to form pressurized purified air; circulating air mixing step, combining the pressurized purified air with the boosted return air described later to form circulating air; and cooling step to divide the circulating air into three The split air is cooled to the first set temperature, and the intermediate pressure tower is introduced to introduce air, and the second split air is cooled to a second set temperature higher than the first set temperature to form cold expansion air, thereby further cooling the third split air. The air for thermal expansion is formed at a third set temperature higher than the second set temperature; and the first expansion step is performed by using the air for cold expansion. Expanding to a second set pressure lower than the first set pressure to form a first low temperature air; and a second expansion step of adiabatically expanding the thermal expansion air to the second set pressure to form a first higher temperature a second low temperature air having a set temperature; an introduction step of introducing a portion of the first low temperature air into the intermediate pressure column; and a temperature increasing step of recovering a temperature between the remaining portion of the first low temperature air and the second low temperature air to form return air; a cyclic compression step of increasing the reflux air to form the boosted return air; and another introducing step of introducing the intermediate pressure column introduction air into the intermediate pressure column.

Further, in the first configuration or the second configuration, the circulating air pressure increasing step of raising the circulating air to be higher than the first set pressure is included.

Further, the third aspect of the present invention is an air liquefaction separation apparatus which performs low-temperature distillation of compressed, purified, and cooled raw material air by using an intermediate pressure tower and a low pressure column, and at least extracts liquid oxygen as a product. And the apparatus comprises: a raw material air compressor that boosts the total amount of the raw material air to a first set pressure higher than the operating pressure of the intermediate pressure tower to form a pressurized raw material air; and an adsorption device from which the raw material is pressurized The air adsorbs to remove impurities to form a boosted purified air; the circulating air merged pipe combines the boosted purified air with the boosted return air described later to form circulating air; the main heat exchanger, which makes the circulating air Dividing into two first split air, cooling to a first set temperature to form an intermediate pressure tower introduction air, and cooling the second split air to a second set temperature higher than the first set temperature to form expansion air; expansion turbine And aerating the expansion air to a second set pressure lower than the first set pressure to form a low temperature air; and piping, the part of the low temperature air Introduced to the intermediate pressure column; a circulation compressor that pressurizes the return air obtained by recovering the remaining portion of the low temperature air by the main heat exchanger to form the boosted return air; and another pipe The intermediate pressure column introduction air is introduced into the above intermediate pressure column.

Further, the fourth aspect of the present invention is an air liquefaction separation apparatus which uses at least an intermediate pressure tower and a low pressure column to perform low-temperature distillation of compressed, purified, and cooled raw material air to extract at least liquid oxygen as a product, and The separating apparatus includes: a raw material air compressor that boosts a total amount of raw material air to a first set pressure higher than an operating pressure of the intermediate pressure tower to form a pressurized raw material air; and an adsorption device from which the raw material is pressurized The air adsorbs to remove impurities to form a boosted purified air; the circulating air merged pipe combines the boosted purified air with the boosted return air described later to form circulating air; the main heat exchanger, which makes the circulating air Dividing into three first split air, cooling to a first set temperature to form an intermediate pressure tower introduction air, and cooling the second split air to a second set temperature higher than the first set temperature to form a cold expansion air, and further Cooling the third split air to a third set temperature higher than the second set temperature to form air for thermal expansion, and a cold expansion turbine for emptying the cold expansion Adiabatic expansion to a second set pressure lower than the first set pressure to form a first low temperature air; and a thermal expansion turbine that adiabatically expands the thermal expansion air to the second set pressure to form a second low temperature air; And introducing a part of the first low temperature air to the intermediate pressure tower; and a circulation compressor that restores a temperature between the remaining portion of the first low temperature air and the second low temperature air by using the main heat exchanger The return air is boosted to form the boosted return air; and another pipe is introduced to introduce the intermediate pressure tower into the intermediate pressure column.

Further, the third or fourth configuration includes a circulating air compressor that boosts the circulating air to be higher than the first set pressure, and the circulating air booster is provided in an expansion turbine brake blower of the expansion turbine. (blower), and braking of the expansion turbine is performed by any one of a blower, a generator, and a hydraulic pump.

According to the present invention, the total amount of the raw material air previously pressurized to the pressure corresponding to the operating pressure of the intermediate pressure column is boosted to a first set pressure higher than the operating pressure of the intermediate pressure column, for example, the operation of the intermediate pressure column The pressure is at least about 1.5 times the pressure, and in this state, the water vapor, carbon dioxide and the like contained in the raw material air are adsorbed and removed, so that the adsorption device and its periphery can be compared with the conventional air liquefaction separation device. The piping is miniaturized. Further, since the partial pressure of the water vapor contained in the raw material air is relatively lowered, the necessary amount of the adsorbent for adsorbing and removing moisture can be reduced, and the energy required for the regeneration of the adsorbent can also be reduced. Therefore, it is possible to reduce the price of the device or the like with the same power consumption as conventionally.

In the air liquefaction separation apparatus shown in the first embodiment of Fig. 1, the medium pressure tower 11 and the low pressure column 12 are used to perform low temperature distillation of the compressed, purified, and cooled raw material air to extract liquid oxygen LO ₂ and liquid. Crude argon LAr and liquid nitrogen LN _{2 are} used as liquid products, and oxygen GO ₂ and nitrogen GN ₂ are extracted as gas products, and include raw material air compressor 13, adsorption device 14, circulation compressor 15, main heat exchanger 16, expansion The turbine 17, the main condenser 18, the crude argon column 19, the argon condenser 20, and the subcooler 21 are main components.

First, the total amount of the raw material air is introduced into the raw material air compression step of raising the raw material air by the raw air compressor 13 to a first set pressure higher than the operating pressure of the intermediate pressure column 11. The pressurized raw material air is cooled by the cooler 13a, and after the condensed water is separated by a drain separator 13b, it is introduced to the adsorption device 14 for performing the adsorption purification step. In the adsorption device 14, impurities such as water vapor or carbon dioxide contained in the raw material air are adsorbed to the adsorbent and removed, and the pressurized raw material air is purified to be pressurized purified air. The boosted purified air is cooled by the cooler 14a, and then ejected from the recirculation compressor 15 to the other confluent pipe, that is, the pressurized return air of the pipe 51b, through one pipe 51a constituting the circulating air joining pipe 51. Then, the circulating air joining step is performed to become the circulating air flowing in the pipe 51c.

The circulating air of the piping 51c is divided into two, which are the first divided air of the piping 52 and the second divided air of the piping 53, and then introduced into the main heat exchanger 16 for performing the cooling step. The first split air is cooled to the first set temperature by the main heat exchanger 16, and the cold end of the main heat exchanger 16 is led to the pipe 54 to be introduced into the intermediate pressure tower. The medium pressure tower introduces air to a pressure corresponding to the operating pressure of the intermediate pressure column 11 by the valve 31, and is introduced from the piping 55 to the lower portion of the intermediate pressure column 11 in a state of being mostly liquefied.

The second split air of the pipe 53 is cooled to a second set temperature higher than the first set temperature by a cooling step by the main heat exchanger 16, and before reaching the cold end of the main heat exchanger 16 The air is taken out to the pipe 56 to be expanded air, and is introduced into the expansion turbine 17 . The expansion air is a low-temperature air which is adiabatically expanded to a second set pressure lower than the first set pressure by the expansion turbine 17, and becomes a low-temperature air of the pipe 57. The low-temperature air is branched from the piping 57 to the piping 58 and the piping 59, and the low-temperature air branched into the piping 59 is introduced into the lower portion of the intermediate pressure tower 11 as a rising gas from the piping 60 via the valve 32.

The remaining portion of the low-temperature air branched into the pipe 58 is introduced into the cold end of the main heat exchanger 16 to perform a temperature rising step, and exchanges heat with the first split air and the second split air to cool each of the split air to The temperature is set to a predetermined temperature, and the temperature of the self returns to the vicinity of the normal temperature, thereby becoming the return air of the pipe 61. The return air is sucked into the circulation compressor 15 to perform a cyclic compression step, and is pressurized to a pressure corresponding to the pressurized purified air, and then discharged to the pipe 51b to merge with the pressurized purified air of the pipe 51a. The above-mentioned circulating air of the pipe 51c is obtained.

The raw material air introduced into the lower portion of the intermediate pressure column 11 from the piping 55 and the piping 60 is separated into the nitrogen-rich gas at the top of the intermediate pressure column by the distillation operation in the intermediate pressure column 11. And an oxygen-rich liquid at the bottom of the medium pressure column. The oxygen-rich liquid is extracted from the bottom of the intermediate pressure column to the piping 62, cooled by the subcooler 21, and then branched to the piping 63 and the piping 64. The oxygen-rich liquid of the piping 64 is depressurized to the low pressure tower via the valve 33. After the pressure corresponding to the operating pressure of 12, the piping 65 is introduced as a reflux liquid to the intermediate portion of the low pressure column 12.

Further, the oxygen-rich liquid flowing through the pipe 63 is depressurized by the valve 34, and then introduced into the argon condenser 20 provided in the upper portion of the crude argon column 19. The oxygen-rich gas vaporized by the argon condenser 20 is introduced into the intermediate portion of the low pressure column 12 through the pipe 66 as a rising gas. The oxygen-rich liquid and the oxygen-rich gas introduced into the low-pressure column 12 are concentrated in the bottom of the low-pressure column by distillation in the low-pressure column 12 to become low-pressure liquid oxygen. A part of the low-pressure liquid oxygen is taken out to the pipe 67, cooled by the subcooler 21, and extracted from the pipe 68 as a liquid oxygen product.

The nitrogen-rich gas in the top of the intermediate pressure column is introduced into the main condenser 18 disposed at the bottom of the low-pressure column through the pipe 69, and is indirectly heat-exchanged with the low-pressure liquid oxygen to form a low-pressure liquid to form low-pressure oxygen. And it is liquefied to become liquid nitrogen. One part of the liquid nitrogen is returned to the upper portion of the intermediate pressure column 11 through the pipe 70 as a reflux liquid, and the remaining portion of the liquid nitrogen is cooled by the subcooler 21 through the pipe 71, and a part is branched to the pipe 72. Extracted as a liquid nitrogen product. Most of the liquid nitrogen is depressurized by the valve 35 to a pressure corresponding to the operating pressure of the low pressure column 12, and then introduced into the upper portion of the lower pressure column 12 through the pipe 73 as a reflux liquid.

Further, from the intermediate portion of the lower pressure column 12, an argon-rich gas fluid (feeding argon) is withdrawn to the pipe 74 and introduced to the lower portion of the crude argon column 19, by distillation operation in the crude argon column 19, in the crude argon At the top of the column, the crude argon gas concentrated under argon is separated, and the liquid having a reduced argon concentration is separated at the bottom of the crude argon column. The liquid having the reduced argon concentration is taken out from the bottom of the crude argon column to the pipe 75, and returned to the intermediate portion of the low pressure column 12 as a descending liquid.

The crude argon gas at the top of the crude argon column is introduced into the argon condenser 20 through the pipe 76, and is liquefied into liquid crude argon by heat exchange with the oxygen-rich liquid in the argon condenser 20. One portion of the liquid crude argon is extracted from the pipe 77 as a liquid crude argon product, and the remaining portion of the liquid crude argon is introduced into the upper portion of the crude argon column 19 through the pipe 78 as a reflux.

The low-pressure nitrogen gas concentrated at the top of the low-pressure column by the distillation operation in the low-pressure column 12 is taken out to the pipe 79 and introduced into the subcooler 21, and used as a cooling source for each of the liquids, and then introduced into the pipe 80 through the pipe 80. The cold end of the main heat exchanger 16. Further, a part of the low-pressure oxygen vaporized by the main condenser 18 is taken out to the pipe 81, and introduced to the cold end of the main heat exchanger 16, and the remaining majority of the low-pressure oxygen becomes the rising gas of the low-pressure column 12. Further, a part of the gas which rises in the low pressure column 12 is taken out as an exhaust gas WG from the upper portion of the low pressure column 12 to the pipe 82, becomes a cooling source of the subcooler 21, and is introduced to the cold end of the main heat exchanger 16.

The low-pressure nitrogen gas, the low-pressure oxygen gas and the exhaust gas are heat-exchanged with the respective split air introduced from the hot end of the main heat exchanger 16, and after the temperature is restored to the normal temperature by the temperature recovery, the low-pressure nitrogen gas is extracted from the pipe 83 as a nitrogen gas product. The low-pressure oxygen is extracted from the pipe 84 as an oxygen product, and the exhaust gas is taken out to the pipe 85, and used as a regeneration gas or the like of the adsorption device 14.

In the air liquefaction separation apparatus formed as described above, the first set pressure of the pressurized raw material air which is boosted by the raw material air compressor 13 by the raw material air compressor 13 is set to be higher than the operating pressure of the intermediate pressure column 11. pressure. Generally, the intermediate pressure column 11 in the double rectification column including the intermediate pressure column 11, the low pressure column 12, and the main condenser 18 has an operating pressure of about 500 kPaG, and the pressure of the low temperature air introduced from the piping 60 to the lower portion of the intermediate pressure column 11 In the same manner, the return air flowing through the pipe 61 is also about 500 kPaG to the same operating pressure as the intermediate pressure column 11, so that the compression ratio of the circulating compressor 15 that raises the circulating air is set to 1.5. ～1.8, the pressure of the pressurized raw material air equal to the discharge pressure of the recycle compressor 15, that is, the first set pressure is about 750 kPaG (500 kPaG x 1.5) to 900 kPaG (500 kPaG x 1.8).

Therefore, in the present embodiment, the operating pressure of the adsorption device 14 for removing impurities from the raw material air is about 1.5 times that of the conventional air liquefaction separation device, so that the adsorber body in the adsorption device 14 or The peripheral piping is miniaturized, thereby reducing the price of the device. That is, compared with the conventional adsorption device, the diameter of the adsorption tube of the adsorption device 14 can be reduced, so that the price of the adsorption tube material is lowered, and the amount of water vapor coexisting with the raw material air is reduced, thereby reducing adsorption removal. The amount of alumina gel required for water vapor can greatly reduce the equipment cost of the entire adsorption unit. Further, since the amount of water vapor contained in the raw material air is reduced, it is not necessary to cool the raw material air to a low temperature, and the cost required for the cooling equipment is also reduced.

In the description of the other embodiments of the present invention, the same components as those of the air liquefaction separation device shown in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Further, the configuration of the periphery of the intermediate pressure tower and the low pressure tower can be the same as that of the first embodiment, and the illustration and description of the portions are omitted.

The air liquefaction separation apparatus shown in the second embodiment of Fig. 2 is formed by forming the circulation compressor 15 as a multi-stage compressor having the first compression stage 15a and the second compression stage 15b. The boosted return air ejected from the compression section 15a merges with the boosted purified air to form circulating air, and the circulating air boosting step is performed by the second compressed section 15b of the circulating compressor 15 to further boost the circulating air. After the high-pressure circulating air is formed, the second circulating air step-up step is performed by the brake blower 22 of the expansion turbine 17, and the circulating air is further pressurized to a high pressure.

In other words, the pressure-purifying purified air which has been purified by the raw material air compressor 13 to increase the total amount of the raw material air to the first set pressure by the adsorption device 14 is passed through the piping 51a of the circulating air joining pipe 51, and The boosted return air discharged from the first compressed section 15a and cooled by the after cooler is merged into the pipe 51c, and is boosted to a higher pressure than the first set pressure by the second compressed section 15b. air.

A part of the high-pressure circulating air discharged from the circulation compressor 15 is branched to the pipe 52, and is introduced into the main heat exchanger 16 in the same manner as described above, and is cooled to the first set temperature, and is passed through the pipe 54, the valve 31, The piping 55 is introduced to the lower portion of the intermediate pressure tower 11 in a state of being mostly liquefied.

The remaining portion of the high-pressure circulating air that has been branched into the pipe 53 is introduced into the brake blower 22 of the expansion turbine 17 to be further pressurized to a high pressure, and then introduced into the main heat exchanger 16 via the pipe 86 to be cooled to a temperature higher than the first set temperature. The second set temperature is extracted to the pipe 56 before reaching the cold end of the main heat exchanger 16, and is expanded air, and then introduced into the expansion turbine 17. The air for expansion is adiabatically expanded by the expansion turbine 17 to a second set pressure lower than the first set pressure, and becomes the low temperature air of the pipe 57. One part of the low-temperature air is branched to the piping 59, and introduced to the lower portion of the intermediate pressure tower via the valve 32 and the piping 60. The remaining portion of the low-temperature air is branched to the piping 58 and introduced to the cold end of the main heat exchanger 16, and is subjected to temperature recovery. The return air which becomes the piping 61 is then sucked into the 1st compression stage 15a of the circulation compressor 15, and it circulates.

As described above, by the circulating air pressure increasing step, the circulating air is pressurized to form a higher-pressure circulating air, whereby the expansion ratio in the expansion turbine 17 can be increased, and the amount of cold generation can be increased.

In the air liquefaction separation apparatus shown in the third aspect of the present invention, the cold expansion turbine 17a for adiabatically expanding the expansion air (cold expansion air) having the second set temperature at a relatively low temperature is provided, and the temperature is relatively The thermal expansion turbine 17b that adiabatically expands the expansion air (the air for thermal expansion) at the third set temperature higher than the second set temperature, and serves as an expansion turbine that performs the expansion step; and is provided with a cold expansion turbine brake blower 22a and a thermal expansion turbine brake, respectively. The blower 22b is used as a brake for the two expansion turbines 17a, 17b.

In the same manner as in the second embodiment, the boosted purified air is combined with the boosted return air, and then pressurized by the second compression stage 15b of the recycle compressor 15 to be a high-pressure circulating air, which is branched into a pipe 52. The second split air of the first split air and the pipe 53 and the second split air branched to the pipe 53 are further pressurized by the cold expansion turbine brake blower 22a, and introduced into the main heat exchanger 16 from the pipe 86, and In the state of being cooled to the second set temperature, the pipe 56 is taken out to be the air for cold expansion. The cold expansion air is adiabatically expanded to the second set pressure by the first expansion step by the cold expansion turbine 17a, and becomes the first low temperature air in the vicinity of the first set temperature.

One of the first low-temperature air is branched from the piping 57 to the piping 59, and introduced into the lower portion of the intermediate pressure tower 11 via the valve 32 and the piping 60, and the first low-temperature air branched to the remaining portion of the piping 58 is introduced to the main heat exchange. The temperature is restored by the cold end of the device 16, and the return air of the pipe 61 is sucked into the first compression stage 15a of the circulation compressor 15, and is circulated in the same manner as described above.

On the other hand, the first split air branched to the pipe 52 is further pressurized by the thermal expansion turbine brake blower 22b, introduced into the main heat exchanger 16 from the pipe 87, and cooled to a third set temperature higher than the second set temperature. Thereafter, a part of the air is branched as the third split air, and is taken out to the pipe 88 to become air for thermal expansion. The thermal expansion air is subjected to the second expansion step by the thermal expansion turbine 17b, and is adiabatically expanded to the second set pressure, thereby becoming the second low temperature air that is higher than the first set temperature and lower than the third set temperature. The piping 89 from the position corresponding to the temperature of the second low-temperature air is introduced into the main heat exchanger 16, merges with the first low-temperature air during temperature recovery, and is led to the piping 61 to be return air, and then in the circulation compressor 15 In the loop. The remaining portion of the first split air is cooled to the first set temperature by the main heat exchanger 16, and introduced into the intermediate pressure tower 11 via the pipe 54, the valve 31, and the pipe 55.

As described above, by dividing the expansion step into two steps of heat and cold, the adiabatic expansion by the expansion turbine can be efficiently performed, and the raw material air introduced into the intermediate pressure column 11 can be efficiently cooled.

In the air liquefaction separation apparatus shown in the fourth embodiment of the present invention, the circulation compressor 15 in the third embodiment is a section including the first compression stage 15a, the second compression stage 15b, and the third compression stage 15c. Compressor. In the same manner as described above, the circulating air pressurized by the second compression section 15b of the circulation compressor 15 is branched into the first split air of the pipe 52 and the second split air of the pipe 53, and the first split air is thermally expanded. After the turbine brake blower 22b is further pressurized, it is introduced into the main heat exchanger 16 from the pipe 87, and a part of the third divided air is branched into the pipe 88 at the third set temperature, and is introduced into the thermal expansion turbine 17b as the air for thermal expansion. . By the thermal expansion turbine 17b, the second set air is adiabatically expanded to the second set pressure, and is introduced into the main heat exchanger 16 from the pipe 89 to recover the temperature, and then the compressor 15 is placed in the circulation compressor 15 via the pipe 61. Loop in.

On the other hand, the second split air of the pipe 53 is further pressurized to a high pressure by the third compression stage 15c and the cold expansion turbine brake blower 22a, and then introduced into the main heat exchanger 16 via the pipe 86, and is described above. 2, the temperature is extracted to the pipe 56 to be the cold expansion air, and the cold expansion turbine 17a is adiabatically expanded to the second set pressure, thereby becoming the first low temperature air in the vicinity of the first set temperature. A part of the first low-temperature air of the piping 57 is introduced from the piping 59 to the lower portion of the intermediate pressure tower 11 via the valve 32 and the piping 60, and the remaining first low-temperature air is introduced from the piping 58 to the main heat exchanger 16, and The second low-temperature air merges as a return air of the pipe 61 after the temperature is recovered, and is then sucked into the circulation compressor 15 to be circulated.

In the air liquefaction separation apparatus shown in the fifth aspect of the present invention, the generator 23 is provided in place of the cold expansion turbine brake blower 22a in the fourth embodiment, and the cold expansion turbine 17a is braked by the generator 23, and The second split air that is boosted by the third compression section 15c of the circulation compressor 15 is branched to the piping 53, and is introduced into the main heat exchanger 16 from the piping 90 while maintaining such pressure. Thus, as the brake of the expansion turbine, motor brake or hydraulic brake other than the blower brake can be employed.

The air liquefaction separation apparatus shown in the sixth embodiment of Fig. 6 is formed by raising the pressure to a first set pressure higher than the operating pressure of the intermediate pressure column 11 by the raw material air compressor 13, and The boosted purified air purified by the adsorption device 14 is combined with the boosted return air pressurized by the circulating compressor 15 and further pressurized by the cold expansion turbine brake blower 22a and the thermal expansion turbine brake blower 22b.

That is, the pressurized purified air which is taken out from the adsorption device 14 to the pipe 91 is branched to the piping 92 and the piping 93 which constitute the circulating air joining pipe. On the other hand, the step-up return air that boosts the return air of the pipe 61 by the circulation compressor 15 is branched into a pipe 94 that faces the cold expansion turbine brake blower 22a, and a pipe 95 that faces the thermal expansion turbine brake blower 22b.

The step-up return air which is further pressurized by the cold expansion turbine brake blower 22a is branched into the piping 94, and is merged with the pressurized purified air from the piping 92 through the piping 96 for constituting the circulating air joining duct, and passed through the piping 97. The main heat exchanger 16 is introduced into the main heat exchanger 16 and is cooled to the second set temperature, and then extracted into the pipe 56 to be introduced into the cold expansion turbine 17a.

The step-up return air which is further pressurized by the thermal expansion turbine brake blower 22b is branched into the piping 95, and is connected to the pressurized purified air from the piping 93 through the piping 98 for constituting the circulating air joining duct, and is passed through the piping 99. The main heat exchanger 16 is introduced into the main heat exchanger 16, and a part thereof is drawn to the pipe 88 at the stage of cooling to the third set temperature, and is introduced into the thermal expansion turbine 17b as air for thermal expansion, and the remaining portion is cooled to the first set temperature to become a pipe. The intermediate pressure tower 54 is introduced into the intermediate pressure column 11 by introducing air.

Further, in each of the examples, the series of liquid oxygen LO ₂ , liquid crude argon LAr and liquid nitrogen LN _{2 are taken} as liquid products, but can also be applied to air liquefaction which only extracts liquid oxygen LO ₂ as a liquid product. The separation device can also be applied to extract a combination of liquid oxygen LO ₂ and liquid crude argon LAr, liquid oxygen LO ₂ and liquid nitrogen LN ₂ . Further, as the circulation compressor, a compressor having a compression stage of four or more stages can be used depending on the suction pressure, the discharge pressure, and the throughput.

Next, a specific example in which liquid 1500 Nm ³ /h, liquid nitrogen 1000 Nm ³ /h, and liquid argon 50 Nm ³ /h are extracted using the air liquefaction separation apparatus shown in the third embodiment will be described. Further, [Nm ³ /h] is an hourly flow rate obtained by conversion at 0 ° C and 1 atm.

First, the total amount of raw material air (8800 Nm ³ /h) is pressurized to about 850 kPaG by the raw material air compressor 13, and then introduced into an adsorption device 14 using activated alumina gel and zeolite. The water vapor or carbon dioxide contained in the raw material air is adsorbed and removed and purified. The purified raw material air (boosted purified air) is introduced between the first compression section 15a and the second compression section 15b of the recycle compressor 15 and the boosted return air (12800 Nm) ejected from the first compression section 15a. ³ / h) merges and is boosted to 2700 kPaG by the second compression section 15b to become circulating air.

One part of the circulating air (the first divided air 7700 Nm ³ /h) is boosted to 4000 kPaG by the thermal expansion turbine brake blower 22b, and then introduced into the main heat exchanger 16. One of the first split air (third split air 4000 Nm ³ /h) is at a stage where the main heat exchanger 16 is cooled to the third set temperature, and the main heat exchanger 16 is taken out and introduced into the thermal expansion turbine 17b. The adiabatic expansion expands to the second set pressure, thereby becoming the second low temperature air. The remaining portion of the first split air (3700 Nm ³ /h) is cooled to the first set temperature by the main heat exchanger 16, and is depressurized to a pressure corresponding to the intermediate pressure tower via the valve 31, and then introduced into the medium through the pipe 55. Press tower 11.

The remaining portion of the circulating air (second split air 13900 Nm ³ /h) is boosted to 4000 kPaG by the cold expansion turbine brake blower 22a and introduced into the main heat exchanger 16, and cooled to the second heat exchanger 16 After the temperature is set, it is introduced into the cold expansion turbine 17a to perform adiabatic expansion, thereby becoming the first low temperature air. One of the first low-temperature air (8800 Nm ³ /h) is introduced into the main heat exchanger 16 and merges with the second low-temperature air to become a cooling source of the raw material air (circulating air), thereby being restored by temperature. Return air. The remaining portion of the first low temperature air (5100 Nm ³ /h) is introduced into the lower portion of the intermediate pressure column 11 through the valve 32 and the pipe 60.

The raw material air (3700 Nm ³ /h from the piping 55 and 5100 Nm ³ /h from the piping 60) introduced into the intermediate pressure tower 11 is performed by using the intermediate pressure tower 11, the low pressure column 12, and the crude argon column 19. Low-temperature distillation, which becomes liquid product of liquid oxygen 1500 Nm ³ /h, liquid nitrogen 1000 Nm ³ /h, liquid argon 50 Nm ³ /h, oxygen gas, nitrogen gas product and exhaust gas.

The flow rate, temperature, pressure, and oxygen composition of the gas liquid flowing in the main piping are shown in Table 1, and the main specifications of the adsorption apparatus which compares the adsorption apparatus of this embodiment with the adsorption apparatus of the prior art are shown in the table. 2. In addition, the amount of activated alumina in Table 2 below is a relative value when the conventional apparatus is set to 100.

11. . . Medium voltage tower

12. . . Low pressure tower

13. . . Raw air compressor

13a, 14a. . . Cooler

13b. . . Water remover

14. . . Adsorption device

15. . . Circulating compressor

15a. . . First compression section

15b. . . Second compression section

15c. . . Third compression section

16. . . Main heat exchanger

17. . . Expansion turbine

17a. . . Cold expansion turbine

17b. . . Thermal expansion turbine

18. . . Main condenser

19. . . Crude argon column

20. . . Argon condenser

twenty one. . . Subcooler

twenty two. . . Brake blower

22a. . . Cold expansion turbine brake blower

22b. . . Thermal expansion turbine brake blower

twenty three. . . generator

31~35. . . valve

51. . . Circulating air joining pipe

51a～51c, 52～99. . . Piping

Fig. 1 is a system diagram showing an air liquefaction separation apparatus according to a first embodiment of the present invention.

Fig. 2 is a system diagram showing the main part of an air liquefaction separation apparatus according to a second embodiment of the present invention.

Fig. 3 is a system diagram showing main parts of an air liquefaction separation apparatus according to a third embodiment of the present invention.

Fig. 4 is a system diagram showing the main part of an air liquefaction separation apparatus according to a fourth embodiment of the present invention.

Fig. 5 is a system diagram showing the main part of an air liquefaction separation apparatus according to a fifth embodiment of the present invention.

Fig. 6 is a system diagram showing the main part of an air liquefaction separation apparatus according to a sixth embodiment of the present invention.

11. . . Medium voltage tower

12. . . Low pressure tower

13. . . Raw air compressor

13a, 14a. . . Cooler

13b. . . Water remover

14. . . Adsorption device

15. . . Circulating compressor

16. . . Main heat exchanger

17. . . Expansion turbine

18. . . Main condenser

19. . . Crude argon column

20. . . Argon condenser

twenty one. . . Subcooler

31~35. . . valve

51. . . Circulating air joining pipe

51a～51c, 52～85. . . Piping

Claims (10)

An air liquefaction separation method comprises the following steps: using a medium pressure column and a low pressure column to perform low temperature distillation on the compressed, purified and cooled raw material air, and at least extracting liquid oxygen as a product, the air liquefaction separation method comprises the following steps: a raw material air compression step of boosting the total amount of the raw material air to a first set pressure higher than the operating pressure of the intermediate pressure column to form a pressurized raw material air; and an adsorption purification step of adsorbing and removing impurities from the pressurized raw material air, And forming a step-up purified air; the circulating air combining step, the pressurized purified air is merged with the boosted return air described later to form circulating air; and the cooling step is performed to divide the circulating air into two first split air cooling When the first set temperature is reached, the intermediate pressure tower is introduced to introduce air, and the second split air is cooled to a second set temperature higher than the first set temperature to form expansion air; and the expansion step adiabatically expands the expansion air to a second set pressure lower than the first set pressure to form a low temperature air; and an introduction step to guide a part of the low temperature air To the above medium pressure column; a temperature increasing step of recovering the remaining portion of the low temperature air to form a return air; a cyclic compression step of boosting the return air to form the boosted return air; and another introducing step, wherein The pressure column introduction air is depressurized to a pressure corresponding to the operating pressure of the above-mentioned intermediate pressure column, and is introduced into the above intermediate pressure column. An air liquefaction separation method is characterized in that the air liquefaction separation method comprises the following steps by using a medium pressure column and a low pressure column to perform low temperature distillation on the compressed, purified and cooled raw material air, and at least extracting liquid oxygen as a product; a raw material air compression step of boosting the total amount of the raw material air to a first set pressure higher than the operating pressure of the intermediate pressure column to form a pressurized raw material air; and an adsorption purification step of adsorbing and removing air from the pressurized raw material Impurity, forming a pressurized purified air; a circulating air combining step, combining the pressurized purified air with a pressurized return air described later to form a circulating air; and a cooling step to divide the circulating air into a first split of three The air is cooled to the first set temperature to form an intermediate pressure tower introduction air, and the second split air is cooled to a second set temperature higher than the first set temperature to form a cold expansion air, and further the third split air is cooled to a high temperature. Forming a thermal expansion air at a third set temperature of the second set temperature; the first expansion step is formed by adiabatically expanding the cold expansion air to a second set pressure lower than the first set pressure 1 low temperature air; the second expansion step is performed by adiabatically expanding the thermal expansion air to the second set pressure to form a second higher than the first set temperature a step of introducing a portion of the first low temperature air into the intermediate pressure column; and a temperature increasing step of recovering a temperature of the remaining portion of the first low temperature air and the second low temperature air to form a return air; The reflux air is pressurized to form the boosted return air; and another introduction step is performed to reduce the pressure of the intermediate pressure column introduction air to a pressure corresponding to the operating pressure of the intermediate pressure column and introduce the pressure into the intermediate pressure column. The air liquefaction separation method according to claim 1 or 2, further comprising a step of increasing the circulating air to a circulating air pressure increasing step higher than the first set pressure. An air liquefaction separation device for performing low-temperature distillation of compressed, purified, and cooled raw material air by using an intermediate pressure tower and a low pressure column, and extracting at least liquid oxygen as a product, the air liquefaction separation device comprising: raw material air a compressor that boosts a total amount of raw material air to a first set pressure higher than an operating pressure of the intermediate pressure column to form a pressurized raw material air; and an adsorption device that adsorbs impurities from the pressurized raw material air to form an impurity Pressurizing purified air; a circulating air merge conduit that combines the boosted purified air with a boosted return air described later to form circulating air; and a main heat exchanger that divides the circulating air into a first split The air is cooled to the first set temperature, and the intermediate pressure tower is introduced to introduce air, and the second split air is cooled to a second set temperature higher than the first set temperature to form expansion air; and the expansion turbine is configured to expand the air. Adiabatically expanding to a second set pressure lower than the first set pressure to form a low temperature air; piping for introducing a portion of the low temperature air to the upper portion a medium pressure tower; a circulation compressor that pressurizes return air that recovers a temperature of a remaining portion of the low temperature air by the main heat exchanger to form the boosted return air; and another piping that uses the medium pressure tower The introduction air is depressurized by a valve to a pressure corresponding to the operating pressure of the above-mentioned intermediate pressure column, and is introduced into the above-mentioned intermediate pressure column. An air liquefaction separation device for performing low-temperature distillation of compressed, purified, and cooled raw material air by using an intermediate pressure tower and a low pressure column, and extracting at least liquid oxygen as a product, the air liquefaction separation device comprising: raw material air a compressor that boosts the total amount of raw air to be higher than the intermediate pressure tower a first set pressure of the operating pressure to form a boosted feed air; an adsorption device that adsorbs impurities from the pressurized feed air to form a boosted purified air; and a circulating air combined conduit that causes the pressurized purified air to be described later The boosted return air merges to form circulating air; the main heat exchanger cools the first split air that divides the circulating air into three to a first set temperature, and forms an intermediate pressure tower to introduce air to make the second The split air is cooled to a second set temperature higher than the first set temperature to form a cold expansion air, and the third split air is cooled to a third set temperature higher than the second set temperature to form a heat expansion air; An expansion turbine that adiabatically expands the cold expansion air to a second set pressure lower than the first set pressure to form a first low temperature air, and a thermal expansion turbine that adiabatically expands the thermal expansion air to the second set pressure a second low temperature air; a pipe for introducing one of the first low temperature air to the intermediate pressure column; and a circulation compressor The heat exchanger boosts the remaining portion of the first low temperature air and the return air of the second low temperature air recovery temperature to form the boosted return air; and another pipe that introduces the intermediate pressure tower into the air The pressure is reduced by a valve to a pressure corresponding to the operating pressure of the above-mentioned intermediate pressure column, and introduced into the above-mentioned intermediate pressure column. An air liquefaction separation apparatus according to claim 4 or 5, further comprising a circulating air compressor that boosts said circulating air to a temperature higher than said first set pressure. Such as the air liquefaction separation device of claim 6 of the patent scope, wherein The circulating air booster is provided in an expansion turbine brake blower of the above expansion turbine. The air liquefaction separation device according to claim 4, wherein the brake of the expansion turbine is performed by any one of a blower, a generator, and a hydraulic pump. The air liquefaction separation device according to claim 6, wherein the expansion turbine is braked by any one of a blower, a generator, and a hydraulic pump. The air liquefaction separation device according to claim 7, wherein the expansion turbine is braked by any one of a blower, a generator, and a hydraulic pump.