JP5307055B2 - Nitrogen and oxygen production method and nitrogen and oxygen production apparatus. - Google Patents

Description

  The present invention relates to a method for producing nitrogen and oxygen and an apparatus for producing nitrogen and oxygen, and more particularly, to a cryogenic air separation method and a cryogenic air separation device, which produce a small amount of medium-pressure oxygen together with nitrogen gas. The present invention relates to a method and an apparatus.

  In the semiconductor industry, a small amount of high-purity oxygen gas is often required simultaneously with a large amount of high-purity nitrogen gas. As a method for producing high-purity nitrogen and oxygen, a method of cryogenic separation of air is common, and many processes for producing high-purity nitrogen gas and a small amount of high-purity oxygen gas at the same time are disclosed. .

  Basically, a new rectification column is added to the single rectification nitrogen production system, which mainly produces high-purity nitrogen gas, and liquefied air or oxygen at the bottom of the single rectification column of the single rectification nitrogen production system is added. Many processes for introducing a rich fluid into an additional rectification column to produce a small amount of oxygen gas have been disclosed. For example, Patent Literature 1 discloses a process for producing high-purity oxygen from the auxiliary tower bottom by introducing the oxygen-enriched fluid at the bottom of the single fractionator and the fluid from the condenser into the auxiliary tower as a raw fluid. .

  Patent Documents 2 to 6 disclose that an oxygen-enriched fluid is extracted as a raw material fluid from a shelf several stages above the bottom of a single rectifying column and introduced into an auxiliary tower. By adopting such a process, it is possible to reduce the amount of high boiling point components such as hydrocarbons contained in the raw air into the product oxygen gas / liquid.

  Patent Document 7 discloses a process in which an oxygen-enriched fluid at the bottom of a single rectification column is introduced into a top condenser, a liquid fluid is extracted therefrom, and introduced into an auxiliary tower as a raw material gas.

Japanese Patent No. 3203181 Japanese Patent No. 3719832 JP-A-10-122740 JP-A-9-303957 Japanese Patent Laid-Open No. 9-264667 JP-A-9-184681 JP 2004-020158 A Japanese Patent No. 3545629 JP 2006-284075 A JP 2005-274008 A

However, in the single rectification column nitrogen production apparatus disclosed in Patent Documents 1 to 6, the yield of product nitrogen is about 40%. As a result, the liquefied air at the bottom of the tower, that is, the oxygen concentration in the raw material gas for producing a small amount of oxygen is about 35% at maximum (= 21 / (100-40)).
Therefore, in order to produce 99.5% product oxygen using a fluid containing about 35% oxygen as a raw material, an additional rectification column having a predetermined number of stages is required.

  In the process described in Patent Document 7, the fluid supplied to the oxygen tower as the source gas has a higher oxygen composition than the oxygen-enriched fluid at the bottom of the tower. Only increase.

  On the other hand, Patent Document 8 discloses a process for producing a small amount of product oxygen by adding an oxygen tower to a two-column nitrogen production apparatus. However, the apparatus described in Patent Document 8 is a nitrogen production apparatus in which raw air is supplied to each rectification column. That is, the oxygen composition of the raw material air for producing product oxygen is not greatly improved from the above-described single rectified nitrogen production apparatus.

  In addition, the heating source of the evaporator at the lower part of the oxygen tower is rectified by the second rectifying column as the oxygen-enriched fluid from the first rectifying column. In other words, since this oxygen-enriched fluid does not participate in the production of nitrogen in the second rectification column, the product nitrogen yield decreases in the entire apparatus of the second rectification column as the product oxygen is produced. Yes.

  Patent Document 9 discloses a high-purity oxygen production apparatus process using an additional rectification tower and an oxygen tower in a single rectification tower nitrogen production apparatus. This is because the liquefied air at the bottom of the single rectification column is introduced into the top of the additional rectification column, the waste gas of the air composition from the top of the rectification column is withdrawn, the pressure is increased at room temperature, and then introduced into the oxygen tower to supply product oxygen. It is a manufacturing process. In this invention, since the discharge pressure of the booster can be set freely, it is possible to produce product oxygen at an arbitrary pressure, and the compressor has the advantage of being able to adopt an air compressor. However, “the oxygen composition is 21%. This is oxygen production from “pseudo-air” and requires a new compressor and an additional rectification column with a predetermined number of stages.

  Patent Document 10 discloses a high-purity oxygen production apparatus process using an upper column in a single rectification column nitrogen production apparatus. In the present invention, the oxygen-enriched fluid at the bottom of the single rectification column is divided, one is used for production of product oxygen, and the other is used for generating cold after being vaporized in a condenser. Therefore, regardless of the operating pressure of the expansion turbine, it is possible to reduce the operating pressure of the upper tower and improve the separation efficiency. However, the oxygen concentration in the raw material fluid used for oxygen production is 35%, and a relatively large number of stages must be installed in the upper column.

  Against this background, there has been a demand for a method for producing oxygen using a rectification column having a relatively small number of stages or a short packing height in a method for producing nitrogen and oxygen. The fact was not.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a method for producing nitrogen and oxygen from air by a cryogenic separation method, and the first nitrogen gas fluid is obtained by distillation of compressed, purified and cooled raw material air A first separation step of separating the first nitrogen-enriched liquefied fluid, the first nitrogen gas fluid and the first oxygen-enriched liquefied fluid after decompression are indirectly heat-exchanged, and the first nitrogen gas fluid is A first indirect heat exchange step of condensing and liquefying to obtain first liquefied nitrogen and evaporating and gasifying the first oxygen enriched liquefied fluid to obtain a first oxygen enriched gas fluid; and the first oxygen enriched gas fluid. A second separation step in which a part of the second oxygen-enriched liquefied fluid is separated into a second nitrogen gas fluid and a second oxygen-enriched liquefied fluid; A third separation step for rectifying and separating into two oxygen-enriched gas fluid and high purity oxygen liquefied fluid; The second nitrogen gas fluid and a part of the high purity oxygen liquefied fluid are indirectly heat-exchanged to condense and liquefy the second nitrogen gas fluid to obtain second liquefied nitrogen, and a part of the high purity oxygen liquefied fluid A second indirect heat exchange step for evaporating gas to obtain a high purity oxygen gas fluid, a first product recovery step for deriving a part of the first nitrogen gas fluid as a first product nitrogen gas after heat recovery, 2 A second product recovery step for deriving a part of the nitrogen gas fluid as a second product nitrogen gas after heat recovery, and a liquid acid compression step for pressurizing a part of the high purity oxygen liquefied fluid in a liquid state to form liquid oxygen And a third product recovery step of deriving the pressurized liquid oxygen as product oxygen gas after heat recovery, and a method for producing nitrogen and oxygen.

  According to a second aspect of the present invention, the second oxygen-enriched liquefied fluid that performs the second separation step in the second rectification column and is subjected to low-temperature distillation in the third separation step is a column of the second rectification column. 2. The method for producing nitrogen and oxygen according to claim 1, wherein the method is derived from a position above the bottom.

  According to a third aspect of the present invention, the first oxygen-enriched liquefied fluid that is subjected to the first separation step in the first rectification column and is subjected to low-temperature distillation in the second separation step is the tower of the first rectification column. 2. The method for producing nitrogen and oxygen according to claim 1, wherein the method is derived from a position above the bottom.

  The invention according to claim 4 includes a cold generation step of generating a cold by introducing a part of the first oxygen-enriched gas fluid into the expansion turbine. 2. A method for producing nitrogen and oxygen according to item 1.

  The invention according to claim 5 includes a cold generation step of generating a cold by introducing a part of the raw material air into the expansion turbine, and producing nitrogen and oxygen according to claim 1 or claim 2 Is the method.

  The invention according to claim 6 is an apparatus for producing nitrogen and oxygen from raw material air by a cryogenic separation method, wherein the raw material air that has been compressed, purified, and cooled is subjected to low-temperature distillation to obtain a first nitrogen gas fluid at the top of the tower. Indirect heat exchange is performed between the first rectifying column for rectifying and separating the first oxygen-enriched liquefied fluid at the bottom of the column, and the first oxygen-enriched liquefied fluid depressurized by the pressure reducing valve. A first condenser for condensing and liquefying the first nitrogen gas fluid to obtain first liquefied nitrogen, and evaporating and gasifying the first oxygen enriched liquefied fluid to obtain a first oxygen enriched gas fluid; A second rectifying column for subjecting a part of the oxygen-enriched gas fluid to low-temperature distillation to perform rectification separation into a second nitrogen gas fluid at the top of the column and a second oxygen-enriched liquefied fluid at the bottom of the column; The second oxygen-enriched liquefied fluid is subjected to low-temperature distillation to obtain a second oxygen-enriched gas fluid at the top of the column and high pure oxygen at the bottom of the column. A third rectifying column that rectifies and separates into a liquefied fluid; and a part of the second nitrogen gas fluid and the high pure oxygen liquefied fluid is indirectly heat-exchanged to condense and liquefy the second nitrogen gas fluid. A second condenser for obtaining two-liquefied nitrogen and evaporating and gasifying a part of the high-purity oxygen liquefied fluid to obtain a high-purity oxygen gas fluid, an expansion turbine for generating the cold necessary for the apparatus, and the high-purity nitrogen A pump that pressurizes a part of the oxygen liquefied fluid in a liquid state to form liquid oxygen, a first product recovery line that extracts a part of the first nitrogen gas as a first product nitrogen gas after heat recovery, and the first 2) A second product recovery line for deriving a part of the nitrogen gas as a second product nitrogen gas after heat recovery; and a third product recovery for deriving the pressurized high-purity oxygen liquid fluid as product oxygen gas after heat recovery And an apparatus for producing nitrogen and oxygen, characterized by comprising:

  The invention according to claim 7 is characterized in that a pipe for leading the second oxygen-enriched liquefied fluid introduced into the third rectifying column is connected to a position above the bottom of the second rectifying column. The apparatus for producing nitrogen and oxygen according to claim 6.

  According to an eighth aspect of the present invention, a conduit for leading out the first oxygen-enriched liquefied fluid introduced into the first condenser is connected to a position above the bottom of the first rectification column. The apparatus for producing nitrogen and oxygen according to claim 6.

  As a result of using the method for producing nitrogen and oxygen by the cryogenic air separation method of the present invention, oxygen can be produced using a rectification tower having a relatively small number of stages or a short packing height.

FIG. 1 is a system diagram of an air separation device according to a first embodiment of the present invention. FIG. 2 is a system diagram of an air separation device according to the second embodiment of the present invention. FIG. 3 is a system diagram of an air separation device according to the third embodiment of the present invention. FIG. 4 is a system diagram of an air separation device according to the fourth embodiment of the present invention. FIG. 5 is a system diagram of an air separation device shown as a comparative example. FIG. 6 is a graph showing the fluid temperature in the main heat exchanger.

  Hereinafter, a nitrogen and oxygen production method and a nitrogen and oxygen production apparatus according to embodiments to which the present invention is applied will be described with reference to the drawings.

[First Embodiment]
A nitrogen and oxygen production apparatus 1 according to a first embodiment to which the present invention is applied includes a first rectifying column 2, a second rectifying column 3, and a third rectifying column 4 as shown in FIG. The first condenser 5, the second condenser 6, the expansion turbine 7, the pump 8, the first product recovery line 9, the second product recovery line 10, and the third product recovery line 11. It has the composition which has. A method for producing nitrogen and oxygen by a cryogenic separation method using the production apparatus 1 is as follows.

  First, the raw material air sucked from the atmosphere through the filter 21 is pressurized to a predetermined pressure by the raw material air compressor 22, removed from the compression heat by the after cooler 23, and then introduced into the purifier 24. In the purifier 24, impurities such as water vapor and carbon dioxide contained in the raw material air are removed.

The raw material air from which impurities have been removed is introduced into the main heat exchanger 25 in the cold insulation outer tub and cooled to a predetermined temperature (for example, near the liquefaction point).
The cooled raw material air is introduced into the lower part of the first fractionator 2 via the raw material air introduction pipe 26. A rectification stage (shelf), a regular packing material, an irregular packing material, or the like is provided in the first rectifying column 2 and the second and third rectifying columns 3 and 4 described later. Yes.

  In the first rectifying column 2, the raw air is distilled at a low temperature and separated into a first nitrogen gas fluid at the top of the column and a first oxygen-enriched liquefied fluid at the bottom of the column (first separation step). That is, when the raw material air introduced into the first rectification column rises in the first rectification column, it is countercurrently contacted with the first liquefied nitrogen, which is a reflux liquid described later, so that the low-boiling component The composition increases. Moreover, when the 1st liquefied nitrogen which is a recirculation | reflux liquid descend | falls the inside of a 1st rectification tower, the composition of a high boiling point component increases by making countercurrent contact with the raw material air which is a rising gas.

  As a result, the first nitrogen gas fluid having a higher nitrogen concentration than the raw air and a lower oxygen concentration is purified at the top of the first fractionator 2 and the lower nitrogen concentration is lower than the raw air at the bottom of the tower. A first oxygen-enriched liquefied fluid having a high oxygen concentration is generated.

  A part of the first nitrogen gas fluid extracted from the top of the first rectifying column 2 to the pipe 27 is branched to the pipe 28 to perform indirect heat exchange with the raw air in the main heat exchanger 25. And is led out as first product nitrogen gas from the first product recovery line 9 (first product recovery step).

The remaining portion of the first nitrogen gas fluid extracted from the top of the first rectifying column 2 to the pipe 27 is branched into the pipe 29 and introduced into the first condenser 5.
Further, the first oxygen-enriched liquefied fluid purified at the bottom of the first rectifying column 2 is led out from the pipe line 30, and partly branches to the pipe line 41, and is adjusted to a predetermined pressure by the pressure reducing valve 42. After being depressurized, it is introduced into the first condenser 5. Further, the remaining portion branches to the pipe line 43, is decompressed to a predetermined pressure by the decompression valve 44, and is then introduced into the second rectifying column 3 as cold.

  In the first condenser 5, indirect heat exchange between the first nitrogen gas fluid and the first oxygen-enriched liquefied fluid is performed, and the first nitrogen gas fluid is condensed and liquefied to become first liquefied nitrogen. The enriched liquefied fluid is evaporated and gasified to become the first oxygen enriched gas fluid (first indirect heat exchange step). Then, the first liquefied nitrogen is introduced into the first rectifying column 2 from the pipe 45 and becomes a reflux liquid.

  Most of the first oxygen-enriched gas fluid led out from the first condenser 5 to the pipe 46 is branched into the pipe 47 and introduced into the lower part of the second rectification column 3. In the second rectifying column 3, the first oxygen-enriched gas fluid is subjected to low-temperature distillation and separated into a second nitrogen gas fluid at the top of the column and a second oxygen-enriched liquefied fluid at the bottom (second separation step). ). That is, the first oxygen-enriched gas fluid introduced into the second rectification column 3 makes a countercurrent contact with second liquefied nitrogen, which is a reflux liquid described later, when rising in the second rectification column 3. This increases the composition of the low boiling point component. In addition, the second liquefied nitrogen as the reflux liquid is counter-contacted with the first oxygen-enriched gas fluid as the rising gas when descending the second rectifying column 3, so that the composition of the high boiling point component is obtained. Will increase.

  As a result, a second nitrogen gas fluid having a higher nitrogen concentration and a lower oxygen concentration than the first oxygen-enriched gas fluid is generated at the top of the second rectifying column 3, and the first oxygen is generated at the bottom of the column. A second oxygen-enriched liquefied fluid having a lower nitrogen concentration and a higher oxygen concentration than the enriched gas fluid is generated.

  The remainder of the first oxygen-enriched gas fluid is branched into the pipe 48 and introduced into the expansion turbine 7 via the main heat exchanger 25 and used for generating the cold necessary for the apparatus (cold generation step). Then, the first oxygen-enriched gas fluid is used for regeneration of the purifier 24 together with the high-purity oxygen gas fluid that is led out via the pipe 68 described later after passing through the expansion turbine 7.

  Part of the second nitrogen gas fluid extracted from the top of the second rectifying column 3 to the pipe 49 is branched into the pipe 50 and introduced into the main heat exchanger 25 to indirectly exchange heat with the raw air. The temperature is raised by performing the above, and it is led out as the second product nitrogen gas from the second product recovery conduit 10 (second product recovery step).

  Note that the second product nitrogen gas fluid can be supplied to the supply destination with the derived pressure as it is, but when joining and supplying the first product nitrogen gas fluid, the pressure is increased by the nitrogen compressor 61, After cooling with the aftercooler 62, the first product nitrogen gas may be merged and supplied to the supply destination as product nitrogen gas from the product supply line 63.

The remaining portion of the second nitrogen gas fluid extracted from the top of the second rectifying column 3 to the pipe 49 is branched into the pipe 64 and introduced into the second condenser 6. In the second condenser 6, indirect heat exchange is performed between the second nitrogen gas fluid and a high-purity oxygen liquefied fluid described later, and the second nitrogen gas fluid is condensed and liquefied to become second liquefied nitrogen. A part of the fluid is evaporated and turned into a high purity oxygen gas fluid (second indirect heat exchange step).
Then, the second liquefied nitrogen is extracted from the pipe 65 and introduced into the top of the second rectifying column 3 as a reflux liquid.

  The second oxygen-enriched liquefied fluid generated at the bottom of the second rectifying column 3 is led out from the pipe 66 and depressurized to a predetermined pressure by the pressure reducing valve 67, and then the third rectifying column 4 as a reflux liquid. It is introduced at the top of the tower. The third rectification column 4 is a rectification column having a second condenser 6 at the bottom of the column. In the third rectification column 4, the second oxygen-enriched liquefied fluid is distilled at a low temperature, and high purity oxygen at the top of the column is obtained. Separated into a gasification fluid and a high purity oxygen liquefied fluid at the bottom of the column (third separation step).

  That is, the second oxygen-enriched liquefied fluid introduced as the reflux liquid has a countercurrent contact with the high-purity oxygen gas fluid evaporated and gasified by the second condenser 6 when descending the third rectifying column 4. By doing so, the composition of the low boiling point component increases. The high purity oxygen gas fluid evaporated and gasified by the second condenser 6 is in countercurrent contact with the second oxygen-enriched liquefied fluid that is the reflux liquid when rising in the third fractionator 4. Thus, the composition of the high boiling point component increases.

  As a result, a high-purity oxygen-enriched gas fluid having a lower oxygen concentration than the second oxygen-enriched liquefied fluid is generated at the top of the third fractionator 4 and the second oxygen-enriched gas is produced at the bottom of the tower. A highly pure oxygen-enriched liquefied fluid having a higher oxygen concentration than the liquefied fluid is produced.

  The high-purity oxygen gas fluid generated at the top of the third rectifying column 4 is extracted to the main line 68 from the line 69 together with the first oxygen-enriched gas fluid extracted from the line 68 and decompressed by the expansion turbine 7. After being introduced into the exchanger 25 and heated to room temperature, it is used to regenerate the purifier 24.

  The high purity oxygen liquefied fluid at the bottom of the third rectifying column 4 is extracted from the pipe 70 and introduced into the liquid acid pump 8. In the liquid acid pump 8, the high-purity oxygen liquefied fluid is pressurized to a predetermined pressure and becomes medium-pressure liquid oxygen (liquid acid compression step). Thereafter, the medium-pressure liquid oxygen is heated to room temperature in the main heat exchanger 25, becomes medium-pressure product oxygen gas, and is led out from the product recovery pipe 11 through the pipe 12 (third product recovery step). ). In this embodiment, since raw material oxygen is used as a heat source for vaporizing medium pressure liquid oxygen, it is not necessary to prepare a new heat source for vaporizing medium pressure liquid oxygen.

  In the method for producing nitrogen and oxygen according to the present embodiment, the oxygen concentration contained in the second oxygen-enriched liquefied fluid of the raw material introduced into the third rectifying column 4 that produces product oxygen is higher than the conventional one. ing. That is, as a result of passing through both the first separation step and the second separation step, a third separation step for generating product oxygen is performed using the second oxygen-enriched liquefied fluid having a high oxygen concentration as a raw material. . As a result, it is possible to use a rectifying column having a relatively small number of stages or a short packing height as compared with the prior art.

  In addition, since the operating pressure of the third rectifying column 4 can be lowered as compared with the conventional case, the relative volatility between the component compositions is increased, and the separation efficiency is improved. That is, the second oxygen-enriched liquefied fluid introduced as a raw material into the third rectifying column 4 is a fluid depressurized by the pressure reducing valve 42 and the pressure reducing valve 67 as compared with the raw material air introduced into the first rectifying column 2. The operating pressure of the third rectifying column 4 is designed to be inevitably small. In other words, the operating pressure of the third rectifying column 4 is set so that the high-purity oxygen gas fluid led out from the top of the third rectifying column 4 is a pressure at which the purifier 25 can be regenerated. The raw material air may be compressed by the raw material air compressor 22 so as to be set and increased by two steps accordingly. As described above, the operating pressure of the third rectifying column 4 can be reduced as compared with the conventional one, and the separation efficiency is thereby improved. Therefore, the third rectifying column 4 has a relatively small number of stages or a packing height. It is possible to use a short rectification column.

  Further, when the product oxygen is derived from the third rectifying column 4, the liquid high purity oxygen liquefied fluid is extracted and introduced into the liquid acid pump 8. Therefore, compared with the case where the gas phase high pure oxygen gas fluid is extracted, As a result, the fluid having a higher oxygen concentration can be extracted. Thereby, the number of stages of the third fractionator 4 can be reduced, or the packing height can be shortened.

In addition, since the first oxygen-enriched gas fluid is introduced into the expansion turbine 7 that generates the cold necessary for the production apparatus, the operating pressure of the third rectifying column 4 can be lowered as compared with the conventional case. it can. That is, the fluid introduced into the expansion turbine 7 to generate cold needs to have a pressure higher than a certain level, but conventionally, the fluid derived from the third rectifying column 4 has been introduced into the expansion turbine 7. The operating pressure of the third rectifying column 4 was inevitably set to a certain level. On the other hand, in this embodiment, since the first oxygen-enriched gas fluid derived independently of the third rectifying column 4 is introduced into the expansion turbine 7, the operating pressure of the third rectifying column 4 is limited. I was not able to take it. Thereby, since the operating pressure can be lowered, the separation efficiency is improved, and a rectification column having a relatively small number of stages or a short packing height can be used as the third rectification column 4.
In this embodiment, since raw material oxygen is used as a heat source for vaporizing medium pressure liquid oxygen, it is not necessary to prepare a new heat source for vaporizing medium pressure liquid oxygen.

[Second Embodiment]
Next, a nitrogen and oxygen production apparatus and a nitrogen and oxygen production method according to a second embodiment to which the present invention is applied will be described. In addition, this embodiment is a modification of 1st Embodiment, and abbreviate | omits description about the same part.

As shown in FIG. 2, the present embodiment is different from the first embodiment in that the cold necessary for the manufacturing apparatus 80 is generated by using raw material air.
That is, a part of the raw material air is branched and extracted from the middle of the main heat exchanger 25 to the pipe 81, introduced into the expansion turbine 7, and introduced into the second rectification tower 3 as cold through the pipe 82. Has been.

Also in this embodiment, the same effect as that of the first embodiment can be obtained, and the number of stages of the third rectifying column 4 can be reduced or the packing height can be shortened.
Moreover, since the raw material air unrelated to the third rectifying column 4 is used as the fluid introduced into the expansion turbine 7, the operating pressure of the third rectifying column 4 is not limited. As a result, the operating pressure can be lowered, the separation efficiency can be improved, and a rectifying column having a relatively small number of stages or a short packing height can be used as the third rectifying column 4.

[Third Embodiment]
Next, a nitrogen and oxygen production apparatus and a nitrogen and oxygen production method according to a third embodiment to which the present invention is applied will be described. Note that this embodiment is also a modification of the first embodiment, and description of similar parts is omitted.

  As shown in FIG. 3, in the manufacturing apparatus 90 of the present embodiment, the fluid introduced into the second rectifying column 3 is different from the first embodiment. That is, the column bottom liquid extracted from the column bottom of the first rectifying column 2 is led out from the conduit 91 and introduced into the first condenser 5b through the pressure reducing valve 92 to perform indirect heat exchange. After being vaporized, it is introduced into the expansion turbine 7 and used for regeneration of the purifier through the pipe 69. Then, the first oxygen-enriched liquefied fluid led out from the position above the bottom of the first rectifying column 2 via the conduit 93 is introduced into the second rectifying column 3. Specifically, a part of the first oxygen-enriched liquefied fluid led out from the pipe 93 is branched to the pipe 94, compressed to a predetermined pressure by the pressure reducing valve 95, and vaporized by the first condenser 5a. Later, it is introduced into the second rectification tower 3 via a pipe 96. The remainder of the first oxygen-enriched liquefied fluid led out from the pipe 93 is branched into the pipe 97, compressed to a predetermined pressure by the pressure reducing valve 98, and then introduced directly into the second rectifying column 4 as cold. The

Also in this embodiment, the same effect as that of the first embodiment can be obtained, and the number of stages of the third rectifying column 4 can be reduced or the packing height can be shortened.
In addition, since the second separation step and subsequent steps are performed using the first oxygen-enriched liquefied fluid derived from the position above the bottom of the first fractionator 2 as a raw material, the oxygen concentration of product oxygen is improved. That is, the raw air also contains high-boiling components such as trace amounts of hydrocarbons, but these high-boiling components are concentrated at the bottom of the first rectifying column in the first separation step. Therefore, the first oxygen-enriched liquefied fluid derived not from the tower bottom but from a position above the tower bottom contains almost no high-boiling component, and as a result, suppresses impurities contained in the product oxygen. be able to.

[Fourth Embodiment]
Next, a nitrogen and oxygen production apparatus and a nitrogen and oxygen production method according to a fourth embodiment to which the present invention is applied will be described. Note that this embodiment is also a modification of the first embodiment, and description of similar parts is omitted.

  As shown in FIG. 4, in the manufacturing apparatus 100 of the present embodiment, the fluid introduced into the third rectifying column 4 is different from that of the first embodiment. That is, the bottom liquid extracted from the bottom of the second fractionator 3 to the pipe 101 is introduced into the pressure reducing valve 102 and compressed to a predetermined pressure, and then indirectly heat exchanged by the second condenser 6b. And is vaporized and used for regeneration of the purifier 24 through the pipe 103. Then, the second oxygen-enriched liquefied fluid led out from the position above the bottom of the second rectifying column 3 via the pipe line 105 is compressed to a predetermined pressure by the pressure reducing valve 106, and then the third refined liquid. It is introduced into the distillation column 4.

  The second nitrogen gas fluid extracted from the top of the second rectification tower 3 to the pipe 49 and branched to the pipe 64 is introduced into the second condenser 6a. In the second condenser 6a, indirect heat exchange between the second nitrogen gas fluid and the high purity oxygen liquefied fluid is performed.

Also in this embodiment, the same effect as that of the first embodiment can be obtained, and the number of stages of the third rectifying column 4 can be reduced or the packing height can be shortened.
In addition, since the third separation step is performed using the second oxygen-enriched liquefied fluid derived from the position above the bottom of the second rectification column 3 as a raw material, the product oxygen is the same as in the third embodiment. Improves oxygen concentration. That is, the raw air contains a high-boiling component. In the second separation step, the high-boiling component is concentrated on the bottom of the second rectifying column 3 and is not above the bottom but above the bottom. The second oxygen-enriched liquefied fluid derived from the position of FIG. Thereby, impurities contained in product oxygen can be suppressed.

  As mentioned above, although this invention was demonstrated based on embodiment, it cannot be overemphasized that this invention can be variously changed in the range which is not limited to the said embodiment and does not deviate from the summary. For example, the fourth embodiment and the second embodiment may be combined.

EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not restrict | limited to the following Example at all.
As Example 1, a simulation for producing product nitrogen gas and product oxygen gas was performed using the nitrogen and oxygen production apparatus shown in FIG. Table 1 shows the flow rate, pressure, and oxygen composition of each pipe line when the product nitrogen flow rate is 100.
Further, as Example 2, a simulation for producing product nitrogen gas and product oxygen gas was performed using the nitrogen and oxygen production apparatus shown in FIG. Table 2 shows the flow rate, pressure, and oxygen composition of each pipe line when the product nitrogen flow rate is 100.

FIG. 6 shows the fluid temperature in the main heat exchanger. In the figure, the temperature at a location where there is no temperature change, that is, a location horizontal to the horizontal axis is the dew point of the air where the raw material air is liquefied and the boiling point of oxygen where the pressurized liquid oxygen is vaporized.
In Example 1 or Example 2, since the flow rate of the product oxygen to be produced is small relative to the raw material air flow rate, the latent heat for vaporizing the pressurized liquid oxygen is small, so the product oxygen pressure is 8.4 bar. In the case of (G), heat exchange is established even when the raw air is at a relatively low pressure (9.3 bar (G)). At this time, the dew point of the raw material air is lower than the boiling point of the pressurized liquid oxygen.

  On the other hand, in the normal nitrogen / oxygen production apparatus in which the product oxygen produced from Example 1 or Example 2 increases, the amount of heat exchanged in the main heat exchanger increases, so a line representing the temperature of the raw air and the pressurized liquid oxygen is displayed. It is necessary to set the pressure so that it does not intersect. The pressure of the raw material air at this time is about 20 bar, which requires a pressure twice or more that of Example 1 or Example 2.

  As shown in Tables 1 and 2 above, the oxygen composition of the pipe 66 is 0.54 (54%) and 0.52 (52%), and is introduced into the third rectification column that produces product oxygen. It can be seen that the oxygen concentration contained in the second oxygen-enriched liquefied fluid of the starting material is high. Further, the pressure in the pipe 68 is 0.4 bar (G), and it is recognized that the operating pressure of the third rectifying column is low.

Next, the power consumption of Example 1 will be described in comparison with a comparative example. In the comparative example, a simulation for producing product nitrogen gas was performed using the nitrogen production apparatus shown in FIG. Since the nitrogen / oxygen production apparatus in Example 1 is an apparatus that produces a small amount of oxygen, the comparative example is a separate liquid oxygen storage tank (not shown) in the production apparatus 110 that simply produces product nitrogen gas. ) To send a small amount of oxygen. The production apparatus 110 is not provided with a rectification tower for producing product oxygen gas, and the second oxygen-enriched liquefied fluid led out from the bottom of the second rectification tower 3 is supplied to the second condenser 111. Indirect heat exchange and evaporative gasification are used to regenerate the purifier 24.
It shows in Table 3 about the power consumption of an Example and a comparative example. In the comparative example, in addition to the power of the nitrogen gas production apparatus 110, it is assumed that oxygen is sent from a separate liquid storage tank, and power for production of the oxygen is taken into account.

  As shown in Table 3 above, in the example, it is recognized that the power consumption per product (oxygen / nitrogen) decreases compared to the comparative example.

DESCRIPTION OF SYMBOLS 1,80,90,100 ... Manufacturing apparatus, 2 ... 1st rectification tower, 3 ... 2nd rectification tower, 4 ... 3rd rectification tower, 5, 5a, 5b ... 1st condenser, 6, 6a, 6b ... 2nd condenser, 7 ... Expansion turbine, 8 ... Pump, 9 ... 1st product recovery line, 10 ... 2nd product recovery Pipe 11, third product recovery pipe 21, filter 22, raw material air compressor 23, after cooler 24, purifier 25, main heat exchange vessel

Claims (8)

A method for producing nitrogen and oxygen from air by a cryogenic separation method,
A first separation step of separating the compressed, purified and cooled raw material air into a first nitrogen gas fluid and a first oxygen-enriched liquefied fluid by distillation;
Indirect heat exchange is performed between the first nitrogen gas fluid and the first oxygen-enriched liquefied fluid after decompression to condense and liquefy the first nitrogen gas fluid to obtain first liquefied nitrogen, and the first oxygen-enriched fluid A first indirect heat exchange step of evaporating and gasifying the liquefied fluid to obtain a first oxygen-enriched gas fluid;
A second separation step of cryogenic distillation of a portion of the first oxygen-enriched gas fluid to separate it into a second nitrogen gas fluid and a second oxygen-enriched liquefied fluid;
A third separation step of low-temperature distillation of the second oxygen-enriched liquefied fluid after decompression to rectify and separate into a second oxygen-enriched gas fluid and a high-purity oxygen liquefied fluid;
A portion of the second nitrogen gas fluid and the high purity oxygen liquefied fluid are indirectly heat exchanged to condense and liquefy the second nitrogen gas fluid to obtain second liquefied nitrogen, and a portion of the high purity oxygen liquefied fluid A second indirect heat exchange step for obtaining a high purity oxygen gas fluid by evaporating the gas;
A first product recovery step of deriving a part of the first nitrogen gas fluid as first product nitrogen gas after heat recovery;
A second product recovery step of deriving a part of the second nitrogen gas fluid as second product nitrogen gas after heat recovery;
A liquid acid compression step in which a portion of the high purity oxygen liquefied fluid is pressurized in a liquid state to form liquid oxygen;
A third product recovery step of deriving the pressurized liquid oxygen as product oxygen gas after heat recovery;
A process for producing nitrogen and oxygen. Performing the second separation step in a second rectification column;
The second oxygen-enriched liquefied fluid that is subjected to low-temperature distillation in the third separation step is derived from a position above the bottom of the second rectification column. A method for producing nitrogen and oxygen. Carrying out the first separation step in a first rectification column;
The first oxygen-enriched liquefied fluid that is subjected to low-temperature distillation in the second separation step is derived from a position above the bottom of the first rectifying column. A method for producing nitrogen and oxygen.   The nitrogen and oxygen according to any one of claims 1 to 3, further comprising a cold generating step of generating a cold by introducing a part of the first oxygen-enriched gas fluid into an expansion turbine. Manufacturing method.   The method for producing nitrogen and oxygen according to claim 1 or 2, further comprising a cold generation step of generating a cold by introducing a part of the raw material air into an expansion turbine. An apparatus for producing nitrogen and oxygen from raw air by a cryogenic separation method,
A first rectifying column for subjecting the compressed, purified and cooled raw material air to low temperature distillation to rectify and separate into a first nitrogen gas fluid at the top of the column and a first oxygen-enriched liquefied fluid at the bottom of the column;
Indirect heat exchange is performed between the first nitrogen gas fluid and the first oxygen-enriched liquefied fluid decompressed by a pressure reducing valve to condense and liquefy the first nitrogen gas fluid to obtain first liquefied nitrogen, and the first A first condenser for evaporating and gasifying the oxygen enriched liquefied fluid to obtain a first oxygen enriched gas fluid;
A second rectifying column for subjecting a part of the first oxygen-enriched gas fluid to low-temperature distillation to rectify and separate into a second nitrogen gas fluid at the top of the column and a second oxygen-enriched liquefied fluid at the bottom of the column;
A third rectifying column for subjecting the second oxygen-enriched liquefied fluid after decompression to low-temperature distillation to rectify and separate into a second oxygen-enriched gas fluid at the top of the column and a high-purity oxygen liquefied fluid at the bottom of the column;
The second nitrogen gas fluid and a part of the high pure oxygen liquefied fluid are indirectly heat exchanged to condense and liquefy the second nitrogen gas fluid to obtain second liquefied nitrogen, and one of the high pure oxygen liquefied fluids. A second condenser for evaporating the gas to obtain a high purity oxygen gas fluid;
An expansion turbine that generates the cold necessary for the device;
A pump that pressurizes a portion of the high purity oxygen liquefied fluid in a liquid state to form liquid oxygen;
A first product recovery line for deriving a part of the first nitrogen gas as a first product nitrogen gas after heat recovery;
A second product recovery line for deriving a part of the second nitrogen gas as a second product nitrogen gas after heat recovery;
A third product recovery line for deriving the pressurized high pure oxygen liquid fluid as product oxygen gas after heat recovery;
An apparatus for producing nitrogen and oxygen, comprising:   The pipe line for leading out the second oxygen-enriched liquefied fluid introduced into the third rectifying column is connected to a position above the bottom of the second rectifying column. 6. The apparatus for producing nitrogen and oxygen according to 6.   The pipe line for leading out the first oxygen-enriched liquefied fluid introduced into the first condenser is connected to a position above the bottom of the first rectification tower. 2. The apparatus for producing nitrogen and oxygen according to 1.

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