JP2011027318A - Method and device for liquefying and separating air - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for liquefying and separating air, reducing the price of a device used when fluid products are collected. <P>SOLUTION: The method for liquefying and separating air has: a raw material air compressing process of making total amount of material air become compressed raw material air having a first set pressure higher than operating pressure of an intermediate pressure tower; an adsorbing and purifying process of removing impurities from the compressed raw material air to obtain compressed purified air; a circulation air merging process of merging the compressed purified air with compressed returned air to obtain circulation air; a cooling process of cooling a first divided flow air formed by dividing a flow of the circulation air into two to first set temperature to obtain intermediate tower introduction air and cooling a second divided flow air to second set temperature higher than the first set temperature to obtain expansion air; an expansion process of adiabatically expanding the expansion air to second set pressure lower than the first set pressure to obtain low-temperature air; a process of introducing part of the low-temperature air to the intermediate pressure tower; a temperature increasing process of returning the temperature of the remaining low-temperature air to obtain returned air; a circulating and compressing process of compressing the returned air to obtain the compressed returned air; and a process of introducing the intermediate tower introduction air to the intermediate pressure tower. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an air liquefaction separation method and apparatus, and more particularly, to an air liquefaction separation method for collecting at least liquid oxygen as a product by subjecting compressed, purified and cooled raw material air to cryogenic separation in an intermediate pressure tower and a low pressure tower. And an apparatus.

  When industrially producing oxygen, nitrogen and argon, the production is generally carried out by a so-called deep-cooling type air liquefaction separation apparatus which uses air as a raw material and separates it by a double rectification column comprising an intermediate pressure column and a low pressure column. is there. In this cryogenic air liquefaction separation apparatus, about 5% of the product can be produced as liquid oxygen, liquid nitrogen, or liquid argon. However, additional liquefaction processes are required to produce more liquid products.

  The liquefaction process is a process in which raw air, nitrogen gas, etc. are compressed, circulated, and adiabatic expansion to obtain the cooling required for the process, and many techniques have been disclosed for each process (for example, see Patent Document 1). .)

  In such a liquefaction process, the circulating fluid is partially liquefied and supplied to the distillation tower, and a liquid product that is thermally compatible is collected. Compared with the nitrogen circulation liquefaction process that compresses low-pressure and / or medium-pressure nitrogen gas into a circulating fluid, the air circulation liquefaction process that compresses a part of higher-pressure raw material air and uses it as a circulating fluid This is a fundamentally advantageous process that requires less power to compress the fluid.

  However, when the amount of product liquid, especially liquid nitrogen, is high, the air circulation liquefaction process increases the liquefaction rate of the raw material air supplied to the intermediate pressure tower, and the distillation conditions of the intermediate pressure tower decrease, making it difficult to cope with it. Become. On the other hand, in the nitrogen circulation liquefaction process, liquid nitrogen suitable for the liquid product is supplied to the intermediate pressure tower, and even when the amount of the product liquid is large, the distillation conditions of the intermediate pressure tower are not lowered. That is, when the amount of product liquid is relatively small, an air circulation liquefaction process with less power consumption is superior, but when the amount of product liquid is relatively large, only the nitrogen circulation liquefaction process can be handled.

  In addition, a process using an air circulation process for a single rectification column process is known (see, for example, Patent Documents 2, 3, and 4). In both cases, a part of the raw air equivalent to the operating pressure of the single rectifying column is circulated, the temperature is raised to room temperature, introduced into the raw air compressor, and compressed with the raw air introduced from outside to circulate the process. I try to let them. In these processes, the raw material air that circulates does not contain water vapor or carbon dioxide, but the circulating air is also a process that circulates through the pretreatment device, so the pretreatment adsorption device becomes larger than necessary. There was a waste to be done.

  Furthermore, a process using an air circulation liquefaction process for the double rectification column process is also known (see, for example, Patent Documents 5 and 6). For example, the raw material air is pressurized to 460 kPa (gauge pressure, hereinafter referred to as kPaG) with a compressor and purified, and then introduced into the circulating air compressor together with a part of the circulating air processed by the expansion turbine. The pressure is increased to a suitable pressure. These circulating air is cooled to a predetermined temperature by a heat exchanger and then introduced into an expansion turbine to generate the necessary cooling for the apparatus. A part of the circulating air treated by the expansion turbine is introduced into the intermediate pressure tower, and the rest is introduced into the circulating compressor together with the raw air. In this process, the operation pressure of the intermediate pressure tower is about 480 kPaG, which is approximately the same as the expansion turbine discharge pressure and the pretreatment device operation pressure.

  There is also known an air liquefaction separation apparatus for collecting product oxygen, which can change the ratio of the amount of liquid oxygen to be collected (see, for example, Patent Documents 7 and 8). This fluid is introduced into the wake of the pretreatment facility and pressurized together with the raw material air. In addition, a process is also known in which a fluid from an intermediate pressure tower is compressed to a pressure higher than the operation pressure of the intermediate pressure tower with a raw material air using a compressor (see, for example, Patent Document 9). However, in this process, since the circulating fluid is also processed by the cooling device or the pretreatment adsorption device, a lot of processing capacity is required for these.

Japanese Patent No. 3213846 Japanese Patent Publication No. 56-034787 Japanese Patent Publication No. 60-045484 Japanese Utility Model Publication No. 54-095552 Japanese Patent Laid-Open No. 06-159929 Japanese Patent Application Laid-Open No. 06-159930 JP 10-045657 A Japanese Patent Laid-Open No. 10-054658 Japanese Patent Application Laid-Open No. 06-300435

  As described above, many proposals have been made as a liquefaction process. The air circulation liquefaction process is mainly aimed at improving the efficiency of the process, but it is still not sufficient in terms of improving the device price.

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

  In order to achieve the above object, a first configuration of the present invention is an air liquefaction separation method in which at least liquid oxygen is collected as a product by low-temperature distillation of compressed, purified, and cooled raw material air in a medium-pressure tower and a low-pressure tower. A raw material air compression step in which the total amount of the raw material air is increased to a first set pressure higher than the operation pressure of the intermediate pressure tower to make the pressurized raw material air; An adsorbing purification step, a circulating air merging step in which the pressure-purified air and pressure-returning return air, which will be described later, are merged to circulate air, and the first diverted air that has been divided into two circulated air is cooled to the first set temperature. And a cooling step in which the second divided air is cooled to a second set temperature higher than the first set temperature to be expanded air, and the expansion air is lower than the first set pressure. 2 Adiabatic expansion to set pressure A step of expanding the low-temperature air into the intermediate pressure tower, a step of raising the temperature of the remaining portion of the low-temperature air to return air to return air, and the return air And a step of introducing the intermediate pressure tower introduction air into the intermediate pressure tower.

  The second configuration of the present invention is an air liquefaction separation method in which at least liquid oxygen is collected as a product by low-temperature distillation of compressed, purified and cooled raw material air in an intermediate pressure column and a low pressure column. A raw material air compression step in which the total amount is increased to a first set pressure higher than the operation pressure of the intermediate pressure tower to obtain pressurized raw material air; and an adsorption purification step in which impurities are removed by adsorption from the pressurized raw material air to obtain pressurized purified air. , A circulating air merging step for joining the pressure-purified air and pressure-returning return air, which will be described later, to form circulating air, and introducing the intermediate-pressure tower by cooling the first divided air that has been circulated into the circulating air to the first set temperature. Air, the second divided air is cooled to a second set temperature higher than the first set temperature to be cold expansion air, and the third divided air is cooled to a third set temperature higher than the second set temperature. For air expansion A first expansion step of adiabatic expansion of the cold expansion air to a second set pressure lower than the first set pressure, and a first low temperature air, and the second set pressure. A second expansion step of adiabatic expansion into the second low-temperature air having a temperature higher than the first set temperature, a step of introducing a part of the first low-temperature air into the intermediate pressure tower, and the first low temperature A temperature raising step of recovering the temperature of the remaining air and the second low-temperature air to obtain return air, a circulation compression step of raising the feedback air to obtain the boosted feedback air, and the intermediate pressure tower introduction air to And a step of introducing into the intermediate pressure tower.

  Further, in the first configuration or the second configuration, a circulating air pressurizing step for boosting the circulating air to a pressure higher than the first set pressure is provided.

  Further, the third configuration of the present invention is an air liquefaction separation apparatus that collects at least liquid oxygen as a product by low-temperature distillation of compressed, purified, and cooled raw material air in an intermediate pressure column and a low pressure column. A raw material air compressor that boosts the total amount to a first set pressure that is higher than the operating pressure of the intermediate pressure tower to obtain pressurized raw material air; an adsorption device that removes impurities from the pressurized raw material air to obtain pressurized purified air; A circulating air merging conduit that circulates the boosted purified air and boosted return air, which will be described later, and a first divided air that is divided into two by circulating the circulating air to the first set temperature and introduced into the intermediate pressure tower A main heat exchanger that is air and cools the second shunt air to a second set temperature higher than the first set temperature to form expansion air; and a second set pressure that is lower than the first set pressure. Adiabatic expansion into low temperature air A circulating turbine, a pipe for introducing a part of the low-temperature air into the intermediate pressure tower, and a return air whose temperature is recovered by the main heat exchanger for the rest of the low-temperature air to be pressurized and circulated as the boosted feedback air A compressor and a pipe for introducing the intermediate-pressure tower introduction air into the intermediate-pressure tower are provided.

  Furthermore, the fourth configuration of the present invention is an air liquefaction separation apparatus that collects at least liquid oxygen as a product by low-temperature distillation of compressed, purified, and cooled raw material air in an intermediate pressure column and a low pressure column. A raw material air compressor that boosts the total amount to a first set pressure that is higher than the operating pressure of the intermediate pressure tower to obtain pressurized raw material air; an adsorption device that removes impurities from the pressurized raw material air to obtain pressurized purified air; A circulating air merging conduit that circulates the pressurized purified air and boosted return air, which will be described later, and a first divided air that has been circulated into the circulating air for 3 minutes are cooled to a first set temperature and an intermediate pressure tower is introduced. Air, the second divided air is cooled to a second set temperature higher than the first set temperature to be cold expansion air, and the third divided air is cooled to a third set temperature higher than the second set temperature. Main heat for air for temperature expansion An air conditioner, a cold expansion turbine that adiabatically expands the cold expansion air to a second set pressure lower than the first set pressure, and makes the first low temperature air adiabatic, and the warm expansion air is insulated to the second set pressure The main expansion of the thermal expansion turbine to be expanded into the second low-temperature air, the piping for introducing a part of the first low-temperature air into the intermediate pressure tower, the remainder of the first low-temperature air and the second low-temperature air. It is characterized by comprising a circulating compressor that pressurizes the return air whose temperature has been recovered by a heat exchanger to form the boosted feedback air, and a pipe that introduces the intermediate pressure tower introduction air into the intermediate pressure tower. .

  In addition, in the third configuration or the fourth configuration, a circulating air compressor that boosts the circulating air to a pressure higher than the first set pressure is provided, and the circulating air booster includes the expansion It is an expansion turbine brake blower provided in the turbine, and the expansion turbine is braked 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 that has been conventionally increased to a pressure corresponding to the operation pressure of the intermediate pressure tower is set to a first set pressure higher than the operation pressure of the intermediate pressure tower, for example, the operation pressure of the intermediate pressure tower. On the other hand, the pressure is increased to at least about 1.5 times, and impurities such as water vapor and carbon dioxide contained in the raw material air are adsorbed and removed in that state. Thus, the adsorption device and the surrounding piping can be reduced in size. Further, since the partial pressure of water vapor contained in the raw air becomes relatively low, it is possible to reduce the necessary amount of adsorbent for adsorbing and removing moisture, and to reduce the energy required for regeneration of the adsorbent. Therefore, the device price and the like can be reduced with the same power consumption as in the conventional case.

1 is a system diagram of an air liquefaction separation apparatus showing a first embodiment of the present invention. It is a principal part systematic diagram of the air liquefaction separation apparatus which shows the 2nd form example of this invention. It is a principal part systematic diagram of the air liquefaction separation apparatus which shows the 3rd example of this invention. It is a principal part systematic diagram of the air liquefaction separation apparatus which shows the 4th example of this invention. It is a principal part systematic diagram of the air liquefaction separation apparatus which shows the 5th example of this invention. It is a principal part systematic diagram of the air liquefaction separation apparatus which shows the 6th form example of this invention.

The air liquefaction / separation apparatus shown in the first embodiment of FIG. 1 is obtained by subjecting raw material air that has been compressed, purified, and cooled to low temperature distillation in a medium pressure tower 11 and a low pressure tower 12, thereby producing liquid oxygen LO ₂ and liquid as liquid products. The crude argon LAr and the liquid nitrogen LN ₂ are collected, and the oxygen gas GO ₂ and the nitrogen gas GN ₂ are collected as gas products. As the main components, the raw material air compressor 13, the adsorption device 14, and the circulating compressor 15 are collected. , A main heat exchanger 16, an expansion turbine 17, a main condenser 18, a crude argon tower 19, an argon condenser 20, and a supercooler 21.

  First, the entire amount of the raw material air is introduced into the raw material air compression step in which the raw material air compressor 13 boosts the pressure to the first set pressure higher than the operation pressure of the intermediate pressure tower 11 to obtain the boosted raw material air. The pressurized raw material air is cooled by a cooler 13a, separated from condensed water by a drain separator 13b, and then introduced into an adsorption device 14 that performs an adsorption purification process. In the adsorption device 14, impurities such as water vapor and carbon dioxide contained in the raw material air are adsorbed and removed by the adsorbent, and the pressurized raw material air is purified to become pressurized purified air. The pressure-purified air is cooled by the cooler 14a, passes through one pipe 51a constituting the circulating air confluence pipe 51, and is discharged from the circulation compressor 15 to the pipe 51b that is the other confluence pipe. A circulating air merging step is performed by merging with the return air to become circulating air flowing through the pipe 51c.

  The circulating air in the pipe 51c is introduced into the main heat exchanger 16 that performs the cooling process after being divided into two parts, the first divided air in the pipe 52 and the second divided air in the pipe 53. The first diverted air is cooled to the first set temperature by the main heat exchanger 16, led out from the cold end of the main heat exchanger 16 to the pipe 54, and becomes intermediate pressure tower introduction air. This intermediate pressure tower introduction air is depressurized by the valve 31 to a pressure corresponding to the operation pressure of the intermediate pressure tower 11, and is mostly introduced into the lower part of the intermediate pressure tower 11 from the pipe 55 in a liquefied state.

  The second shunt air of the pipe 53 is cooled to the second set temperature higher than the first set temperature in the cooling process in the main heat exchanger 16 and is piped before reaching the cold end of the main heat exchanger 16. The air is extracted into the expansion air 56 and introduced into the expansion turbine 17. The expansion air is subjected to an expansion process in which the expansion turbine 17 adiabatically expands to a second set pressure lower than the first set pressure, and becomes low-temperature air in the pipe 57. This low-temperature air is divided into the pipe 58 and the pipe 59 from the pipe 57, and the low-temperature air divided into the pipe 59 is introduced as a rising gas from the pipe 60 to the lower part of the intermediate pressure tower 11 through the valve 32.

  The remaining portion of the low-temperature air that has been diverted to the pipe 58 is introduced into the cold end of the main heat exchanger 16 to perform a temperature raising step, and heat exchange is performed with the first and second diverted air to exchange each diverted air. While cooling to a predetermined temperature, the temperature itself recovers to near normal temperature and becomes return air of the pipe 61. The return air is sucked into the circulation compressor 15 and subjected to a circulation compression process. After the pressure is increased to a pressure corresponding to the pressurized purified air, the compressed air is discharged to the pipe 51b and joined to the pressurized purified air in the pipe 51a. Then, it becomes the circulating air of the pipe 51c.

  The raw material air introduced into the lower part of the intermediate pressure tower 11 from the pipe 55 and the pipe 60 is subjected to distillation operation in the intermediate pressure tower 11 so that the medium pressure nitrogen-enriched gas at the top of the intermediate pressure tower and the oxygen enrichment at the bottom of the intermediate pressure tower. Separated from the chemical solution. The oxygen-enriched liquid is extracted from the bottom of the intermediate pressure tower to the pipe 62 and cooled by the supercooler 21, and then is divided into the pipe 63 and the pipe 64. The oxygen-enriched liquid in the pipe 64 is After being reduced to a pressure corresponding to the operating pressure of the low-pressure column 12, it is introduced as a reflux liquid into the intermediate portion of the low-pressure column 12 through the pipe 65.

  Further, the oxygen-enriched liquid flowing through the pipe 63 is decompressed by the valve 34 and then introduced into the argon condenser 20 provided at the upper part of the crude argon column 19. The oxygen-enriched gas vaporized in the argon condenser 20 is introduced as an ascending gas into the intermediate portion of the low-pressure column 12 through the pipe 66. The oxygen content in the oxygen-enriched liquid and oxygen-enriched gas introduced into the low-pressure column 12 is concentrated at the bottom of the low-pressure column by distillation operation in the low-pressure column 12 to become low-pressure liquid oxygen. A part of this low-pressure liquid oxygen is extracted to the pipe 67 and cooled by the supercooler 21 and then collected from the pipe 68 as product liquid oxygen.

  The medium-pressure nitrogen-enriched gas at the top of the intermediate-pressure tower is introduced into the main condenser 18 disposed at the bottom of the low-pressure tower through the pipe 69, and indirectly heat exchanges with the low-pressure liquid oxygen to vaporize the low-pressure liquid oxygen. As a result, the gas is liquefied into liquid nitrogen. The liquid nitrogen is partially returned to the upper portion of the intermediate pressure tower 11 through the pipe 70 as a reflux liquid, and the remainder of the liquid nitrogen is cooled by the supercooler 21 through the pipe 71 and then partially. The product is diverted to the pipe 72 and collected as product liquid nitrogen. Most of the liquid nitrogen is reduced to a pressure corresponding to the operating pressure of the low-pressure column 12 by the valve 35 and then introduced into the upper portion of the low-pressure column 12 through the pipe 73 as a reflux liquid.

  Further, a gas fluid rich in argon (feed argon) is extracted from the intermediate portion of the low-pressure column 12 into the pipe 74 and introduced into the lower portion of the crude argon column 19. A crude argon gas enriched with argon is separated at the top of the column, and a liquid having a reduced argon concentration is separated at the bottom of the crude argon column. The liquid having a reduced argon concentration is extracted from the bottom of the crude argon tower to the pipe 75 and returned to the intermediate part of the low-pressure tower 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 by heat exchange with the oxygen-enriched liquid in the argon condenser 20 to become liquid crude argon. A part of the liquid crude argon is collected from the pipe 77 as the liquid crude argon of the product, and the remaining liquid crude argon is introduced as a reflux liquid through the pipe 78 into the upper portion of the crude argon tower 19.

  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 extracted into the pipe 79 and introduced into the supercooler 21 and used as a cooling source for the liquids. And then introduced into the cold end of the main heat exchanger 16. A part of the low-pressure oxygen gas vaporized in the main condenser 18 is extracted into the pipe 81 and introduced into the cold end of the main heat exchanger 16, and most of the remaining low-pressure oxygen gas is supplied to the low-pressure column 12. Ascending gas. Further, a part of the gas rising in the low-pressure column 12 is extracted from the upper part of the low-pressure column 12 to the pipe 82 as waste gas WG and becomes a cooling source for the supercooler 21, and then the main heat exchanger 16 introduced at the cold end.

  These low-pressure nitrogen gas, low-pressure oxygen gas and waste gas exchange heat with each of the diverted air introduced from the warm end of the main heat exchanger 16, recover the temperature, raise the temperature to room temperature, and then low-pressure nitrogen gas Is collected from the pipe 83 as product nitrogen gas, the low-pressure oxygen gas is collected from the pipe 84 as product oxygen gas, and the waste gas is extracted into the pipe 85 and then used as a regeneration gas for the adsorption device 14.

  In the air liquefaction separation apparatus formed as described above, the first set pressure of the pressurized feed air obtained by boosting the feed air with the feed air compressor 13 is set to a pressure higher than the operation pressure of the intermediate pressure tower 11. Generally, the operation pressure of the intermediate pressure column 11 in the double rectification column having the intermediate pressure column 11, the low pressure column 12 and the main condenser 18 is about 500 kPaG, and is introduced into the lower part of the intermediate pressure column 11 from the pipe 60. The pressure of the low-temperature air is about the same, and the return air flowing through the pipe 61 is about 500 kPaG, which is about the same as the operation pressure of the intermediate pressure tower 11, so that the compression ratio of the circulating compressor 15 for boosting the circulating air is 1 .5 to 1.8, the pressure of the pressurized raw material air having a pressure equal to the discharge pressure of the circulating compressor 15, that is, the first set pressure is about 750 kPaG (500 kPaG × 1.5) to 900 kPaG (500 kPaG × 1. 8).

  Therefore, in this embodiment, the operating pressure of the adsorption device 14 that removes impurities from the raw air is about 1.5 times that in the case of a conventional ordinary air liquefaction separation device. It is possible to reduce the size of the main body and the surrounding piping, and to reduce the device price. That is, compared with the conventional adsorption apparatus, the diameter of the adsorption cylinder of the adsorption apparatus 14 can be reduced, so that the price of the adsorption cylinder material is reduced and the amount of water vapor entrained in the raw material air is reduced. Since the amount of alumina gel necessary for the adsorption device can be reduced, the equipment cost of the entire adsorption device can be greatly reduced. Further, since the amount of water vapor contained in the raw air is reduced, it is not necessary to cool the raw air to a low temperature, and the cost required for the cooling equipment can be reduced.

  In the description of other embodiments of the present invention described below, the same components as those of the air liquefaction separation apparatus shown in the first embodiment are denoted by the same reference numerals and detailed description thereof is omitted. . Further, since the configuration around the intermediate pressure tower and the low pressure tower can adopt the same configuration as that of the first embodiment, the illustration and description of these portions are omitted.

  In the air liquefaction separation apparatus shown in the second embodiment of FIG. 2, the circulating compressor 15 is a multistage compressor having a first compression stage 15a and a second compression stage 15b, and the boosted feedback air discharged from the first compression stage 15a. And the pressurized purified air are combined to form a circulating air, and the circulating air is further pressurized to a high-pressure circulating air by performing a circulating air pressurizing step in the second compression stage 15b of the circulating compressor 15, and then the expansion turbine. By performing the second circulating air pressurizing step with 17 brake blowers 22, the pressure is further increased to a high pressure.

  That is, the pressure-purified air obtained by refining the raw material air whose total amount has been increased to the first set pressure by the raw material air compressor 13 by the adsorption device 14 passes through the pipe 51a of the circulating air merging pipe line 51 and passes through the first compression stage 15a. The pressurized feedback air of the pipe 51b discharged and cooled by the aftercooler merges with the pipe 51c, and is pressurized to a pressure higher than the first set pressure by the second compression stage 15b to become high-pressure circulating air.

  A part of the high-pressure circulating air discharged from the circulation compressor 15 is divided into the pipe 52 and, as described above, is introduced into the main heat exchanger 16 and cooled to the first set temperature. Then, it is introduced into the lower part of the intermediate pressure tower 11 in a state where most of the liquid is liquefied through the pipe 55.

  The remainder of the high-pressure circulating air that has been diverted to the pipe 53 is introduced into the brake blower 22 of the expansion turbine 17 and further boosted to a high pressure, and then introduced into the main heat exchanger 16 via the pipe 86. It is cooled to a high second set temperature and extracted to the piping 56 before reaching the cold end of the main heat exchanger 16 to become expansion air, which is introduced into the expansion turbine 17. The expansion air is adiabatically expanded to a second set pressure that is lower than the first set pressure in the expansion turbine 17 and becomes low-temperature air in the pipe 57. A part of this low-temperature air is diverted to the pipe 59 and introduced into the lower part of the intermediate pressure tower through the valve 32 and the pipe 60, and the rest of the low-temperature air is diverted to the pipe 58 and the cold end of the main heat exchanger 16. Then, the temperature is recovered to return air to the pipe 61, which is sucked into the first compression stage 15a of the circulating compressor 15 and circulated.

  In this way, by increasing the pressure of the circulating air in the circulating air pressurizing step to obtain a higher-pressure circulating air, the expansion rate in the expansion turbine 17 can be increased, and the amount of cold generated can be increased.

  The air liquefaction separation apparatus shown in the third embodiment of FIG. 3 is a cold expansion that adiabatically expands the expansion air (cold expansion air) having the relatively low temperature as the expansion turbine that performs the expansion process. A turbine 17a and a thermal expansion turbine 17b that adiabatically expands expansion air (temperature expansion air) having a third set temperature that is relatively higher than the second set temperature are provided, and braking of both the expansion turbines 17a and 17b is provided. For this purpose, a cold expansion turbine braking blower 22a and a warm expansion turbine braking blower 22b are provided.

  Similarly to the second embodiment, the circulated air that has been pressurized by the second compression stage 15b of the circulating compressor 15 and has become high pressure after the pressurized purified air and the pressurized return air have joined together is combined with the first shunt air in the pipe 52. The second diverted air divided into the second diverted air in the pipe 53 and further divided into the pipe 53 is further pressurized by the cold expansion turbine brake blower 22a, and introduced into the main heat exchanger 16 from the pipe 86 to be set in the second setting. In the state cooled to the temperature, it is extracted into the pipe 56 and becomes cold expansion air. The cold expansion air is converted into the first low-temperature air near the first set temperature by performing the first expansion step in the cold expansion turbine 17a and adiabatically expanding to the second set pressure.

  A part of the first low-temperature air is diverted from the pipe 57 to the pipe 59, introduced into the lower portion of the intermediate pressure tower 11 via the valve 32 and the pipe 60, and the remaining first low-temperature air diverted to the pipe 58 is main heat. When the temperature is recovered by being introduced into the cold end of the exchanger 16, it becomes the return air of the pipe 61 and is sucked into the first compression stage 15 a of the circulating compressor 15 and circulated in the same manner as described above.

  On the other hand, the first divided air divided into the pipe 52 is further pressurized by the hot expansion turbine braking blower 22b and introduced into the main heat exchanger 16 from the pipe 87, and reaches a third set temperature higher than the second set temperature. After being cooled, a part of the air is diverted as third diverted air, and is extracted to the pipe 88 to become hot expansion air. The warm expansion air undergoes a second expansion step in the thermal expansion turbine 17b and adiabatically expands to the second set pressure, whereby a second temperature higher than the first set temperature and lower than the third set temperature. It becomes low-temperature air, is introduced into the main heat exchanger 16 from the pipe 89 at a position corresponding to the temperature of the second low-temperature air, merges with the first low-temperature air during temperature recovery, is led to the pipe 61, and becomes return air, It circulates in the circulation compressor 15. The remaining portion of the first diverted air is cooled to the first set temperature by the main heat exchanger 16, and is introduced into the intermediate pressure tower 11 through the pipe 54, the valve 31, and the pipe 55.

  Thus, by dividing the expansion step into two steps of warm and cool, adiabatic expansion by the expansion turbine can be efficiently performed, and the raw air introduced into the intermediate pressure tower 11 can be effectively cooled. it can.

  The air liquefaction separation apparatus shown in the fourth embodiment of FIG. 4 is a multistage compressor having the first compression stage 15a, the second compression stage 15b, and the third compression stage 15c. It is a thing. The circulating air whose pressure has been increased in the second compression stage 15b of the circulating compressor 15 is divided into the first divided air in the pipe 52 and the second divided air in the pipe 53, as described above, and the first divided air is subjected to thermal expansion. The pressure is further increased by the turbine braking blower 22b and introduced into the main heat exchanger 16 from the pipe 87, and a part of the pressure is diverted to the pipe 88 as the third diverted air at the third set temperature to form the temperature expansion air. It is introduced into the turbine 17b. By adiabatic expansion to the second set pressure in the thermal expansion turbine 17b, the second low-temperature air is obtained as described above. After being introduced into the main heat exchanger 16 from the pipe 89 and recovered in temperature, it is circulated to the circulation compressor 15 through the pipe 61. To do.

  On the other hand, the second shunt air in the pipe 53 is further pressurized to a high pressure by the third compression stage 15c and the cold expansion turbine braking blower 22a, and then introduced into the main heat exchanger 16 through the pipe 86, and at the second set temperature. The air is drawn into the pipe 56 to be cold expansion air, and is adiabatically expanded to the second set pressure by the cold expansion turbine 17a, thereby becoming the first low-temperature air near the first set temperature. A part of the first low-temperature air in the pipe 57 is introduced from the pipe 59 through the valve 32 and the pipe 60 to the lower portion of the intermediate pressure tower 11, and the remaining first low-temperature air is introduced into the main heat exchanger 16 from the pipe 58. Then, it merges with the second low-temperature air, recovers the temperature, becomes the return air of the pipe 61, is sucked into the circulation compressor 15 and circulates.

  In the air liquefaction separation apparatus shown in the fifth embodiment of FIG. 5, a generator 23 is installed instead of the cold expansion turbine braking blower 22a in the fourth embodiment, and the generator 23 brakes the cold expansion turbine 17a. In addition, the second shunt air that has been shunted to the pipe 53 and increased in pressure by the third compression stage 15c of the circulating compressor 15 is introduced into the main heat exchanger 16 from the pipe 90 at the same pressure. Thus, motor braking and oil braking other than blower braking can be employed for braking the expansion turbine.

  The air liquefaction separation apparatus shown in the sixth embodiment of FIG. 6 is boosted to a first set pressure higher than the operating pressure of the intermediate pressure tower 11 by the raw air compressor 13 and purified by the adsorption device 14. And the boosted feedback air that has been boosted by the circulating compressor 15 and further boosted by the cold expansion turbine braking blower 22a and the warm expansion turbine braking blower 22b.

  That is, the pressure-purified air led out from the adsorption device 14 to the pipe 91 is divided into the pipe 92 and the pipe 93 that constitute the circulating air merge pipe. On the other hand, the boosted feedback air obtained by boosting the feedback air of the pipe 61 by the circulating compressor 15 is divided into a pipe 94 directed to the cold expansion turbine brake blower 22a and a pipe 95 directed to the warm expansion turbine brake blower 22b.

  The boosted feedback air that has been shunted to the pipe 94 and further pressurized by the cold expansion turbine braking blower 22a joins the pressurized purified air from the pipe 92 through the pipe 96 that constitutes the circulating air merging pipe, and passes through the pipe 97. Then, it is introduced into the main heat exchanger 16, cooled to the second set temperature, extracted into the pipe 56, and introduced into the cold expansion turbine 17a as the cold expansion air.

  The boosted feedback air that is shunted to the pipe 95 and further pressurized by the thermal expansion turbine braking blower 22b joins the pressure-purified air from the pipe 93 through the pipe 98 that constitutes the circulating air merging pipe. And is introduced into the main heat exchanger 16 and is partially extracted to the pipe 88 when it is cooled to the third set temperature, and is introduced into the thermal expansion turbine 17b as air for thermal expansion. After being cooled to the set temperature, the air is introduced into the intermediate pressure tower 11 as the intermediate pressure tower introduction air of the pipe 54.

In each embodiment, liquid oxygen LO ₂ , liquid crude argon LAr, and liquid nitrogen LN ₂ are collected as liquid products. However, the liquid liquefaction separation apparatus collects only liquid oxygen LO ₂ as the liquid product. Can be applied, and a combination of liquid oxygen LO ₂ and liquid crude argon LAr, liquid oxygen LO ₂ and liquid nitrogen LN ₂ is also possible. In addition, a compressor having four or more compression stages according to the suction pressure, the discharge pressure, and the processing amount can be used as the circulation compressor.

Then use the cryogenic air separation unit shown in the third embodiment, a specific example of a case where liquid oxygen 1500 Nm ³ / h, liquid nitrogen 1000 Nm ³ / h and liquid argon 50 Nm ³ / h taken . [Nm ³ / h] represents a flow rate per hour converted to 0 ° C. and 1 atmosphere.

First, the raw material air (8800 Nm ³ / h) is pressurized to about 850 kPaG by the raw material air compressor 13 and then introduced into the adsorption device 14 using activated alumina gel and zeolite, and is contained in the raw material air. Impurities such as water vapor and carbon dioxide are adsorbed and removed for purification. The purified raw material air (pressure-purified air) is introduced between the first compression stage 15a and the second compression stage 15b of the circulating compressor 15, and is supplied with pressure-returned return air (12800 Nm ³⁾ discharged from the first compression stage 15a. / H), the pressure is increased to 2700 kPaG in the second compression stage 15b, and becomes circulating air.

Part of the circulating air (first shunt air 7700 Nm ³ / h) is boosted to 4000 kPaG by the hot expansion turbine braking blower 22 b and then introduced into the main heat exchanger 16. Part of the first shunt air (third shunt air 4000 Nm ³ / h) is extracted from the main heat exchanger 16 when it is cooled to the third set temperature by the main heat exchanger 16, and is supplied to the thermal expansion turbine 17b. When introduced and adiabatically expanded to the second set pressure, second low-temperature air is obtained. The remaining part of the first diverted air (3700 Nm ³ / h) is cooled to the first set temperature by the main heat exchanger 16, reduced to the pressure corresponding to the intermediate pressure tower by the valve 31, and then passed through the pipe 55 to the intermediate pressure tower. 11 is introduced.

The remainder of the circulating air (second shunt air 13900 Nm ³ / h) is boosted to 4000 kPaG by the cold expansion turbine braking blower 22 a and introduced into the main heat exchanger 16, and is cooled to the second set temperature by the main heat exchanger 16. Then, it is introduced into the cold expansion turbine 17a and adiabatically expands to become the first low-temperature air. A part 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 recover the temperature by serving as a cooling source for the raw air (circulation air). Return air. The remainder (5100 Nm ³ / h) of the first low-temperature air is introduced into the lower part of the intermediate pressure tower 11 through the valve 32 and the pipe 60.

(3700Nm ³ / h from the pipe 55, 5100Nm ³ / h from the pipe 60) feed air introduced into the medium pressure column 11, the medium pressure column 11, be cryogenic distillation in the low pressure column 12 and crude argon column 19 Accordingly, liquid oxygen 1500 Nm ³ / h, liquid nitrogen 1000 Nm ³ / h, and liquid product liquid argon 50 Nm ³ / h, and the gas products of the oxygen gas, nitrogen gas, into a waste gas.

The flow rate, temperature, pressure, and oxygen composition of the gas and liquid flowing through the main piping are shown in Table 1, and the main specifications of the adsorption device comparing the adsorption device in the present example with the conventional adsorption device are shown in Table 2. . In Table 2, the amount of activated alumina or less is a relative value when the conventional apparatus is 100.

  DESCRIPTION OF SYMBOLS 11 ... Medium pressure tower, 12 ... Low pressure tower, 13 ... Raw material air compressor, 14 ... Adsorption apparatus, 15 ... Circulating compressor, 15a ... 1st compression stage, 15b ... 2nd compression stage, 15c ... 3rd compression stage, DESCRIPTION OF SYMBOLS 16 ... Main heat exchanger, 17 ... Expansion turbine, 17a ... Cold expansion turbine, 17b ... Warm expansion turbine, 18 ... Main condenser, 19 ... Coarse argon tower, 20 ... Argon condenser, 21 ... Subcooler, 22 ... Brake blower, 22a ... Cold expansion turbine brake blower, 22b ... Warm expansion turbine brake blower, 23 ... Generator, 51 ... Circulating air confluence line

Claims (8)

  In an air liquefaction separation method in which at least liquid oxygen is collected as a product by low-temperature distillation of compressed, purified, and cooled raw material air in a medium-pressure tower and a low-pressure tower, the total amount of raw material air is higher than the operating pressure of the medium-pressure tower A raw material air compression step for increasing the pressure to the first set pressure to obtain pressurized raw material air; an adsorption purification step for adsorbing and removing impurities from the pressurized raw material air to obtain pressurized purified air; Circulated air merging step that circulates the circulated air into the circulated air, the first diverted air that is divided into two circulated air is cooled to the first set temperature to be the intermediate pressure tower introduction air, and the second diverted air is the first divergence air. A cooling step of cooling to a second set temperature higher than a set temperature to obtain expansion air, and an expansion step of adiabatic expansion of the expansion air to a second set pressure lower than the first set pressure The A step of introducing a part of the hot air into the intermediate pressure tower, a temperature raising step of recovering the temperature of the remaining part of the low-temperature air to obtain the return air, and a circulating compression to pressurize the return air to obtain the boosted return air. An air liquefaction separation method comprising: a step; and a step of introducing the medium-pressure tower introduction air into the medium-pressure tower.   In an air liquefaction separation method in which at least liquid oxygen is collected as a product by low-temperature distillation of compressed, purified, and cooled raw material air in a medium-pressure tower and a low-pressure tower, the total amount of raw material air is higher than the operating pressure of the medium-pressure tower A raw material air compression step for increasing the pressure to the first set pressure to obtain pressurized raw material air; an adsorption purification step for adsorbing and removing impurities from the pressurized raw material air to obtain pressurized purified air; Circulated air merging step to circulate the circulated air to form a circulated air, the first diverted air obtained by circulating the circulated air for 3 minutes is cooled to the first set temperature to be the intermediate pressure tower introduction air, and the second diverted air is the first divergence air. A cooling step of cooling to a second set temperature higher than the set temperature to form cold expansion air, and further cooling the third shunt air to a third set temperature higher than the second set temperature to make the temperature expansion air; Air for cold expansion A first expansion step in which the first low-temperature air is adiabatically expanded to a second set pressure lower than the first set pressure; and the first setting is performed by adiabatically expanding the warm expansion air to the second set pressure. A second expansion step for forming a second low-temperature air having a temperature higher than the temperature; a step of introducing a part of the first low-temperature air into the intermediate pressure tower; the remainder of the first low-temperature air; and the second low-temperature air. A temperature raising step for recovering the temperature of the return air to obtain the return air, a circulation compression step for raising the pressure of the return air to obtain the boosted return air, and a step for introducing the intermediate pressure tower introduction air into the intermediate pressure tower. An air liquefaction separation method.   3. The air liquefaction separation method according to claim 1, further comprising a circulating air boosting step of boosting the circulating air to a pressure higher than the first set pressure.   In an air liquefaction separation apparatus that collects at least liquid oxygen as a product by low-temperature distillation of compressed, purified, and cooled raw material air in a medium-pressure tower and a low-pressure tower, the total amount of raw material air is higher than the operating pressure of the medium-pressure tower A raw material air compressor that pressurizes to a first set pressure to obtain pressurized raw material air, an adsorption device that adsorbs and removes impurities from the pressurized raw material air to obtain pressurized purified air, the pressurized purified air, and boosted feedback air to be described later And the first divided air obtained by dividing the circulating air into two parts are cooled to the first set temperature to be the intermediate pressure tower introduction air, and the second divided air is used as the first divided air. A main heat exchanger that cools to a second set temperature that is higher than the set temperature to obtain expansion air, and an expansion turbine that adiabatically expands the expansion air to a second set pressure that is lower than the first set pressure to produce low-temperature air. And the low-temperature air A pipe for introducing a part into the intermediate pressure tower, a circulating compressor for increasing the pressure of the return air whose temperature is recovered by the main heat exchanger, and introducing the intermediate pressure tower into the pressure return feedback air An air liquefaction separation apparatus comprising: a pipe for introducing air into the intermediate pressure tower.   In an air liquefaction separation apparatus that collects at least liquid oxygen as a product by low-temperature distillation of compressed, purified, and cooled raw material air in an intermediate pressure column and a low pressure column, the total amount of raw material air is higher than the operating pressure of the intermediate pressure column A raw material air compressor that pressurizes to a first set pressure to obtain pressurized raw material air, an adsorption device that adsorbs and removes impurities from the pressurized raw material air to obtain pressurized purified air, the pressurized purified air, and boosted feedback air to be described later Circulated air merging pipes that circulate the circulated air, and the first diverted air obtained by circulating the circulated air into three parts are cooled to the first set temperature to be the intermediate pressure tower introduction air, and the second diverted air is used as the first diverted air. The main heat exchanger is cooled to a second set temperature higher than the set temperature to be cold expansion air, and the third shunt air is cooled to a third set temperature higher than the second set temperature to be the temperature expansion air. And the cooling expansion air A cold expansion turbine that adiabatically expands to a second set pressure that is lower than the first set pressure to form a first low-temperature air, and a thermal expansion that adiabatically expands the hot expansion air to the second set pressure to form a second low-temperature air A return air obtained by recovering the temperature of the turbine, a pipe for introducing a part of the first low-temperature air into the intermediate pressure tower, and the remaining portion of the first low-temperature air and the second low-temperature air by the main heat exchanger. An air liquefaction / separation apparatus comprising: a circulating compressor that pressurizes and supplies the boosted feedback air; and a pipe that introduces the intermediate-pressure tower introduction air into the intermediate-pressure tower.   6. The air liquefaction separation apparatus according to claim 4, further comprising a circulating air compressor that boosts the circulating air to a pressure higher than the first set pressure.   The air liquefaction separation apparatus according to claim 6, wherein the circulating air booster is an expansion turbine braking blower provided in the expansion turbine.   The air liquefaction separation apparatus according to any one of claims 4 to 6, wherein braking of the expansion turbine is performed by any one of a blower, a generator, and a hydraulic pump.

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