JP6431828B2 - Air liquefaction separation method and apparatus - Google Patents

Description

  The present invention relates to an air liquefaction separation method and apparatus, and more particularly to an air liquefaction separation method and apparatus for producing oxygen gas having a medium pressure.

  As an air liquefaction separation process for collecting oxygen gas having a medium pressure, for example, 270 to 500 kPa (absolute pressure, the same applies hereinafter) as a product, various processes have been proposed. A combination of four towers including a pressure tower, two low-pressure towers, and one mixing tower is known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 9-79744 (FIG. 7)

  The process described in Patent Document 1 can lower the raw material air pressure as compared with the conventional three-column process in which three columns of one medium-pressure column and two low-pressure columns are combined. Can be reduced. However, although the raw material air pressure can be reduced, there is a problem that an air blower for boosting a part of the raw material air is required, resulting in an increase in apparatus cost. In addition, when no air blower is used, the oxygen gas generation pressure is approximately 200 kPa, so an oxygen compressor is required to obtain a medium pressure oxygen gas. Invite. In other words, various conventional processes require additional compressors in addition to the minimum compressors such as raw air compressors and turbine blowers, increasing initial costs, increasing maintenance costs, and increasing the installation area. There was a disadvantage of causing.

  Therefore, an object of the present invention is to provide an air liquefaction separation method and apparatus capable of efficiently producing medium pressure oxygen gas.

  In order to achieve the above object, the air liquefaction separation method of the present invention is compressed, purified and cooled in the air liquefaction separation method of collecting at least oxygen gas as a product by distilling the compressed, purified and cooled raw material air. A first distillation step for separating the first raw material air into a first nitrogen gas component and a first oxygen-enriched liquid component by distilling, and depressurizing the first oxygen-enriched liquid component separated in the first distillation step A second distillation step of separating the second nitrogen gas component and the second oxygen-enriched liquid component by distillation, and a second oxygen-enriched liquid component separated in the second distillation step by distilling the second oxygen-enriched liquid component. A third distillation step that separates into one oxygen gas component and a third oxygen-enriched liquid component, and a second raw material that is compressed, refined, and cooled by pressurizing the third oxygen-enriched liquid component separated in the third distillation step Secondary oxygen by distilling with air A fourth distillation step for separating the first nitrogen gas component and the fourth oxygen-enriched liquid component, and the first nitrogen gas component and the second oxygen-enriched liquid component are indirectly heat exchanged to condense the first nitrogen gas component. At the same time, a first indirect heat exchange step for evaporating the second oxygen-enriched liquid component, and a third raw material air by indirectly heat-exchanging the compressed, purified and cooled third source air and the third oxygen-enriched liquid component. Product oxygen gas after using the second oxygen gas component separated in the second indirect heat exchange step for condensing the third oxygen-enriched liquid component and evaporating the third oxygen-enriched liquid component and the fourth distillation step as a cooling source for each raw material air And a product collecting step of collecting as a feature.

  Furthermore, the air liquefaction separation method of the present invention is characterized in that the oxygen concentration of the product oxygen gas is 36 to 98 vol%, preferably 70 to 98 vol%, and the pressure of the product oxygen gas is 270 to 500 kPa. In addition, when the product oxygen gas has an oxygen concentration Z [vol%], the pressure P [kPa] is 270 ≦ P ≦ 4 × Z + 125.

  The air liquefaction separation apparatus of the present invention distills compressed, purified, and cooled raw material air in an air liquefaction separation apparatus that collects at least oxygen gas as a product by distilling the compressed, purified, and cooled raw material air. Thus, in the air liquefaction separation apparatus that collects at least oxygen gas as a product, the first raw material air that has been compressed, purified, and cooled is distilled into a first nitrogen gas component and a first oxygen-enriched liquid component. A first distillation column and a second distillation column separated into a second nitrogen gas component and a second oxygen-enriched liquid component by depressurizing and then distilling the first oxygen-enriched liquid component separated in the first distillation column A third distillation column that separates the second oxygen-enriched liquid component separated in the second distillation column into a first oxygen gas component and a third oxygen-enriched liquid component by distilling, and the third distillation step 3rd separated by A fourth distillation column that separates the oxygen-enriched liquid component into a second oxygen gas component and a fourth oxygen-enriched liquid component by pressurizing and distilling the compressed, refined, and cooled second raw material air; A main condenser for condensing the first nitrogen gas component by condensing the nitrogen gas component and the second oxygen-enriched liquid component indirectly, and at the same time evaporating the second oxygen-enriched liquid component, and compression, purification, and cooling The third raw material air and the third oxygen-enriched liquid component are indirectly heat-exchanged to condense the third raw material air, and at the same time the third oxygen-enriched liquid component is evaporated and separated by the fourth distillation column. And a product collection path for collecting product oxygen gas after using the second oxygen gas component as a cooling source for each raw material air.

  Furthermore, in the air liquefaction separation apparatus of the present invention, the oxygen concentration of the product oxygen gas is 36 to 98 vol%, preferably 70 to 98 vol%, the pressure of the product oxygen gas is 270 to 500 kPa, When the product oxygen gas has an oxygen concentration Z [vol%], the pressure P [kPa] is 270 ≦ P ≦ 4 × Z + 125.

  According to the present invention, when producing low-purity oxygen gas at a medium pressure, for example, a pressure of 270 to 500 kPa, the product oxygen gas is efficiently produced without adding an oxygen compressor or an air blower. can do.

It is a systematic diagram which shows one example of an air liquefaction separation apparatus for enforcing the air liquefaction separation method of this invention.

  FIG. 1 is a system diagram showing an embodiment of the air liquefaction separation apparatus of the present invention. The air liquefaction separation apparatus shown in the present embodiment is for carrying out an air liquefaction separation method for collecting at least oxygen gas as a product by distilling compressed, refined, and cooled raw material air. A first distillation column 11 for performing the step, a second distillation column 12 for performing the second distillation step, a third distillation column 13 for performing the third distillation step, a fourth distillation column 14 for performing the fourth distillation step, The main condenser 15 provided at the lower part of the second distillation column 12, the sub-condenser 16 provided at the lower part of the third distillation column 13, and the liquefied oxygen derived from the lower part of the third distillation column 13 are converted into the fourth distillation column. 14 is provided with a liquefied oxygen pump 17 for delivery to the vehicle 14.

  Most of the raw material air that has been compressed to a preset pressure by the air compressor 21, removed heat of compression by the aftercooler 21 a, and then removed impurities such as moisture and carbon dioxide by the purifier 22 is mostly in the path 23. And is introduced into the main heat exchanger 24 and cooled to a preset low temperature state by a return gas such as product oxygen gas.

  The raw material air that has been compressed to a predetermined pressure, purified and then cooled to a predetermined temperature is divided into three systems of a first raw material air, a second raw material air, and a third raw material air. Then, it is introduced into the lower part of the first distillation column 11 as a rising gas. The first distillation column 11 is subjected to a first distillation step at a pressure corresponding to the pressure of the first raw material air (hereinafter referred to as an intermediate pressure), and a first nitrogen gas component (intermediate pressure) is placed above the first distillation column 11. Nitrogen gas) is concentrated and separated, and the first oxygen-enriched liquid component is concentrated and separated in the lower part of the first distillation column 11. The first nitrogen gas component at the upper part of the first distillation column is introduced into the main condenser 15 through the path 26 and condensed, and the entire amount becomes liquefied nitrogen, and a part of the first nitrogen gas component is shunted into the path 27 to be the upper part of the first distillation column 11. Is introduced as a descending liquid.

  The remainder of the liquefied nitrogen is diverted to the path 28, cooled by the first supercooler 29, depressurized to near atmospheric pressure (hereinafter referred to as “low pressure”) by the first pressure reducing valve 30, and then the second distillation column 12 It is introduced into the upper part as a descending liquid. In addition, the first oxygen-enriched liquid component is extracted from the bottom of the column to the path 31 and cooled by the first supercooler 29, and then depressurized by the second pressure reducing valve 32 to become a low pressure. 12 is introduced as a descending liquid into the middle stage. Furthermore, after a part of the descending liquid component flowing down the middle stage of the first distillation column 11 is extracted to the path 33 and cooled by the first supercooler 29, the pressure is reduced by the third pressure reducing valve 34 to become a low pressure, It is introduced into the upper middle part of the second distillation column 12 as a descending liquid.

  Into the second distillation column 12, liquefied nitrogen from the path 28, the first oxygen-enriched liquid component from the path 31, the descending liquid component from the path 33, and the like are introduced, and the second distillation step is performed at a low pressure. The second nitrogen gas component (low-pressure nitrogen gas) is concentrated and separated at the upper part of the second distillation column 12, and the second oxygen-enriched liquid component is concentrated and separated at the lower part of the second distillation column 12. The second nitrogen gas component in the upper part of the second distillation column is extracted to the path 35, and the temperature rises as a cooling source for cooling the raw air and the like in the first supercooler 29 and the main heat exchanger 24, and the path 36 Is recovered as low-pressure nitrogen gas.

  In addition, the second oxygen-enriched liquid component at the lower part of the second distillation column performs indirect heat exchange with the first nitrogen gas component in the main condenser 15 to condense the first nitrogen gas component, and to enrich the second oxygen-rich component. A part of the chemical liquid component evaporates and becomes the rising gas of the second distillation column 12. The remainder of the second oxygen-enriched liquid component flows down the path 37 and is introduced as a descending liquid into the upper part of the third distillation column 13.

  In the third distillation column 13, by performing a third distillation step at a low pressure on the second oxygen-enriched liquid component, the first oxygen gas component is concentrated and separated on the upper portion of the third distillation column 13, and the third distillation is performed. The third oxygen-enriched liquid component (high purity liquefied oxygen) is concentrated and separated at the bottom of the column 13. The first oxygen gas component in the upper part of the third distillation column is introduced as a rising gas into the lower part of the second distillation column 12 via the path 38.

  The sub-condenser 16 provided at the lower part of the third distillation column 13 is supplied with the third raw material air that has been diverted to the path 39, and performs indirect heat exchange with the third oxygen-enriched liquid component at the lower part of the third distillation column. And the third raw material air is condensed to form liquefied air of medium pressure, and is introduced as a descending liquid into the lower middle stage of the first distillation column 11 through the path 40, and a part of the third oxygen-enriched liquid component is It evaporates and becomes the rising gas of the third distillation column 13. The remaining portion of the third oxygen-enriched liquid component is withdrawn into the passage 41, is pressurized to a preset pressure by the liquefied oxygen pump 17, passes through the second subcooler 42, and enters the upper portion of the fourth distillation column 14. Introduced as descending liquid.

  In the lower part of the fourth distillation column 14, the second raw material air divided into the path 43 is introduced as an ascending gas, and the fourth distillation at a medium pressure is performed by the descending liquid composed of the remainder of the third oxygen-enriched liquid component. The second oxygen gas component having a preset purity (oxygen concentration) and pressure is concentrated and separated in the upper part of the fourth distillation column 14, and the fourth oxygen enriched liquid is formed in the lower part of the fourth distillation column 14. The components are concentrated and separated.

  The fourth oxygen-enriched liquid component at the lower part of the fourth distillation column is withdrawn into the path 44 and cooled by the second supercooler 42, and the pressure is reduced by the fourth pressure reducing valve 45 to become a low pressure. It is introduced into the lower part of the middle stage as a descending liquid. Further, a part of the descending liquid component is extracted from the middle stage of the fourth distillation column 14 to the path 46, cooled by the second supercooler 42, and then depressurized by the fifth pressure reducing valve 47. Depending on the composition of the components, it is introduced from the lower part of the second distillation column 12 to the upper part of the third distillation column 13.

  Then, the second oxygen gas component in the upper part of the fourth distillation column is extracted to the path 48 and becomes a cooling source for the raw air in the main heat exchanger 24, and is heated to room temperature to be converted into product oxygen gas from the product sampling path 49. Collected. This product oxygen gas has a pressure and an oxygen concentration according to the operating conditions of the fourth distillation step in the fourth distillation column 14. For example, the pressure is 270 to 500 kPa according to the pressure of the second raw material air. The oxygen concentration is the amount of introduction of the second raw material air that becomes the rising gas and the amount of introduction of the third oxygen-enriched liquid component that becomes the descending liquid, the number of theoretical plates of the fourth distillation column 14, the path By appropriately setting the amount of the descending liquid component extracted to 46, the oxygen concentration can be in the range of 36 to 98%, and preferably in the range of 70 to 98%.

  On the other hand, the fourth raw material air that has been compressed to a predetermined pressure and purified and then diverted from the passage 23 to the passage 50 before the introduction of the main heat exchanger is further compressed by the turbine blower 51 to become high-pressure raw material air, and the aftercooler 51a Then, after the compression heat is removed, the main heat exchanger 24 cools the compression heat to an intermediate temperature and then introduces it into the expansion turbine 52. The high pressure raw material air is isentropically expanded (adiabatic expansion) in the expansion turbine 52 to generate cold corresponding to the heat loss of the apparatus to become low pressure and low temperature, and through the path 53 to the lower middle part of the second distillation column 12. Introduced as rising gas.

  Depending on the operating conditions, a part of the liquefied nitrogen flowing through the path 28 can be extracted into the path 54 and collected as product liquefied nitrogen. Further, the whole or a part of the medium-pressure liquefied air flowing through the path 40 can be introduced as a descending liquid into the second distillation column 12 after the pressure reduction.

  Thus, in the air liquefaction separation apparatus shown in this embodiment, in the sub-condenser 16 disposed at the lower part of the third distillation column 13, the third oxygen-enriched liquid component that is high-purity liquefied oxygen and the first from the path 39 are used. In order to ensure the temperature difference between the fluids for heat exchange with the three raw material air, the saturation temperature of the third raw material air must be higher than the saturation temperature of the third oxygen-enriched liquid component at the bottom of the third distillation column 13. Don't be. Since the saturation temperature of the third oxygen-enriched liquid component in the lower part of the third distillation column varies depending on the oxygen concentration, the pressure of the third raw material air varies depending on the oxygen concentration of the third oxygen-enriched liquid component. The third oxygen-enriched liquid component at the lower part of the third distillation column is introduced into the upper part of the fourth distillation column 14 after being pressurized by the liquefied oxygen pump 17, and product oxygen gas is collected from the upper part of the fourth distillation column 14. Therefore, the oxygen concentration of the third oxygen-enriched liquid component at the bottom of the third distillation column 13 is governed by the oxygen concentration required for the product oxygen gas.

Therefore, in the air liquefaction separation apparatus as shown in the present embodiment, the range satisfying the following expression in the relationship between the product oxygen gas pressure P [kPa] and the product oxygen gas oxygen concentration Z [vol% O ₂ ]. Thus, more effective results can be obtained.
270 ≦ P ≦ 4 × Z + 125

Here, using the air liquefaction separation apparatus shown in this embodiment, the flow rate is 300 Nm ³ / H (Nm ³ is a volume converted to a standard state of 0 ° C. and 1 atm), the oxygen concentration is 80 vol% or more, and the pressure is Table 1 shows the flow rate, pressure, and oxygen concentration of the main path when collecting the product oxygen gas of 360 kPa. It is possible to reduce the power cost by about 5% compared to the case where product oxygen gas is collected under the same conditions in the conventional three-column process combining one medium-pressure column and two low-pressure columns. .

  In addition, the extraction position, introduction position, and flow rate of each component can be appropriately set in an optimal state according to the oxygen concentration and pressure of the product oxygen gas.

DESCRIPTION OF SYMBOLS 11 ... 1st distillation column, 12 ... 2nd distillation column, 13 ... 3rd distillation column, 14 ... 4th distillation column, 15 ... Main condenser, 16 ... Subcondenser, 17 ... Liquid oxygen pump, 21 ... Air compression Machine, 21a ... after cooler, 22 ... purifier, 23 ... path, 24 ... main heat exchanger, 25 ... path, 26 ... path, 27 ... path, 28 ... path, 29 ... first subcooler, 30 ... first 1 pressure reducing valve, 31 ... path, 32 ... second pressure reducing valve, 33 ... path, 34 ... third pressure reducing valve, 35 ... path, 36 ... path, 37 ... path, 38 ... path, 39 ... path, 40 ... path, 41 ... path, 42 ... second subcooler, 43 ... path, 44 ... path, 45 ... fourth pressure reducing valve, 46 ... path, 47 ... fifth pressure reducing valve, 48 ... path, 49 ... product collection path, 50 ... Route 51: Turbine blower 51a ... After cooler 52 ... Expansion turbine 53 ... Route 54 ... Route

Claims (10)

  In an air liquefaction separation method in which at least oxygen gas is collected as a product by distilling compressed, purified, and cooled raw material air, the first nitrogen gas component and the second component are obtained by distilling the compressed, purified, and cooled first raw material air. A first distillation step that separates into one oxygen-enriched liquid component, and a second nitrogen gas component and a second oxygen-enriched product by distilling after depressurizing the first oxygen-enriched liquid component separated in the first distillation step. A second distillation step that separates into the chemical liquid component and a second oxygen enriched liquid component separated in the second distillation step to separate the first oxygen gas component and the third oxygen enriched liquid component by distillation. The second oxygen gas component and the fourth oxygen enrichment are obtained by increasing the pressure of the third distillation step and the third oxygen-enriched liquid component separated in the third distillation step and distilling with the compressed, refined and cooled second raw material air. 4th distillation process separated into chemical liquid components A first indirect heat exchange step in which the first nitrogen gas component and the second oxygen-enriched liquid component are indirectly heat exchanged to condense the first nitrogen gas component and at the same time evaporate the second oxygen-enriched liquid component; The second indirect heat that condenses the third raw material air at the same time as the third raw material air is condensed by indirect heat exchange between the compressed, purified and cooled third raw material air and the third oxygen enriched liquid component. An air liquefaction separation method comprising: an exchange step; and a product collection step of collecting the second oxygen gas component separated in the fourth distillation step as product oxygen gas after using the second oxygen gas component as a cooling source for each raw material air.   The air liquefaction separation method according to claim 1, wherein the product oxygen gas has an oxygen concentration of 36 to 98 vol%.   The air liquefaction separation method according to claim 1, wherein the product oxygen gas has an oxygen concentration of 70 to 98 vol%.   The air liquefaction separation method according to any one of claims 1 to 3, wherein the product oxygen gas has a pressure of 270 to 500 kPa.   4. The air according to claim 1, wherein the product oxygen gas has a pressure P [kPa] of 270 ≦ P ≦ 4 × Z + 125 when the oxygen concentration is Z [vol%]. 5. Liquefaction separation method.   In an air liquefaction separation apparatus that collects at least oxygen gas as a product by distilling compressed, refined, and cooled raw material air, the first nitrogen gas component and the first component are obtained by distilling the compressed, purified, and cooled first raw material air. A first distillation column that separates into one oxygen-enriched liquid component; and a second nitrogen gas component and a second oxygen-enriched product by distillation after depressurizing the first oxygen-enriched liquid component separated in the first distillation column. A second distillation column that is separated into a liquid component and a second oxygen-enriched liquid component that is separated in the second distillation column, thereby separating the first oxygen gas component and the third oxygen-enriched liquid component. The second oxygen gas component and the fourth oxygen enrichment are obtained by pressurizing the third distillation column and the third oxygen-enriched liquid component separated in the third distillation step, and distilling with the compressed, refined and cooled second raw material air. A fourth distillation column that separates into a chemical liquid component; A main condenser that condenses the first nitrogen gas component by indirect heat exchange between the elementary gas component and the second oxygen-enriched liquid component, and at the same time evaporates the second oxygen-enriched liquid component, and compression, purification, and cooling A sub-condenser that indirectly heat exchanges the third raw material air and the third oxygen-enriched liquid component to condense the third raw material air and simultaneously evaporate the third oxygen-enriched liquid component; and the fourth distillation column An air liquefaction separation apparatus comprising: a product collection path for collecting product oxygen gas after using the separated second oxygen gas component as a cooling source for each raw material air.   The air liquefaction separation apparatus according to claim 6, wherein the product oxygen gas has an oxygen concentration of 36 to 98 vol%.   The air liquefaction separation apparatus according to claim 6, wherein the product oxygen gas has an oxygen concentration of 70 to 98 vol%.   The air liquefaction separation apparatus according to any one of claims 6 to 8, wherein the product oxygen gas has a pressure of 270 to 500 kPa. 9. The air according to claim 6, wherein the product oxygen gas has a pressure P [kPa] of 270 ≦ P ≦ 4 × Z + 125 when the oxygen concentration is Z [vol%]. Liquefaction separation device .

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