JP2873473B2 - Air liquefaction separation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air liquefaction / separation method, and more particularly to an air liquefaction / separation method capable of constantly and efficiently producing a constant amount of product gas.

[Conventional technology]

For example, in the steelmaking industry or the like that uses a large amount of oxygen, a large air liquefaction / separation device is installed to supply oxygen. In such an industrial facility, the amount and cost of electric power greatly fluctuate depending on the time zone, the day of the week, and the like. For example, the amount of electric power used increases during the daytime, and the amount used at night decreases significantly. On the other hand, in order to reduce the difference in power consumption between day and night as described above, a power company discounts nighttime power rates and stimulates nighttime power demand. Therefore, in the air liquefaction / separation apparatus as well, it is desirable to be able to increase or decrease the power consumption by switching the operation state in consideration of the balance of the power consumption of the entire factory and the power rate.

[Problems to be solved by the invention]

However, in a general air liquefaction / separation device, although the amount of power consumption can be increased or decreased by reducing the processing amount of the raw material air compressor and switching between normal operation and reduced amount operation, the production amount of the product also changes depending on the operation state. Therefore, it cannot be applied to products that need to produce a certain amount of products. In addition, since most of the power consumption of the air liquefaction / separation apparatus is consumed by the raw material air compressor, little effect can be expected even if the power consumption is increased or decreased in other parts.

The present invention has been made in view of the above points, and an object of the present invention is to provide an air liquefaction / separation method capable of producing a fixed amount of a product and increasing or decreasing the power consumption.

[Means for solving the problem]

In order to achieve the above-mentioned object, the air liquefaction / separation method of the present invention first compresses raw material air as a first configuration,
In the air liquefaction separation method of purifying, cooling and liquefying and collecting oxygen gas as a product, the capacity of the raw material air compressor is set to be large with respect to the oxygen gas production amount, and the raw material air compressor is substantially Operating at the maximum processing capacity, storing oxygen produced in excess of the required oxygen gas amount as liquefied oxygen, and increasing the operation mode in which the refrigeration required for storing the liquefied oxygen is covered by introducing liquefied nitrogen; The air compressor is operated in a reduced amount, and liquefied oxygen stored in the increased operation mode is introduced in accordance with the oxygen gas amount that is insufficient for the required product oxygen gas amount. It is characterized by alternately performing a reduction operation mode for storing liquefied nitrogen.

Further, the present invention provides, as a second configuration, an air liquefaction separation method of compressing, purifying, cooling, liquefying and separating oxygen gas and nitrogen gas as products, and In addition to setting the capacity of the raw material air compressor to be large, the raw material air compressor is operated at approximately the maximum processing capacity, and oxygen and nitrogen produced in excess of the required amount are stored as liquefied gas, and the liquefied gas is stored. Operation mode in which the refrigeration required for the storage of refrigeration is covered by the introduction of liquefied air,
The raw material air compressor is operated in a reduced amount, and liquefied oxygen and liquefied nitrogen stored in the increased operation mode are introduced in accordance with the oxygen gas amount and the nitrogen gas amount that are insufficient for the required product oxygen gas amount and product nitrogen gas amount. The operation is alternately performed with a reduced-volume operation mode in which liquefied air equivalent to the cold, which becomes excessive due to the introduction of liquefied oxygen and liquefied nitrogen, is stored.

Further, according to the present invention, as a third configuration, the first or second embodiment is provided.
Is characterized in that a plurality of raw material air compressors are arranged, and an appropriate number of raw material air compressors are operated according to the increasing operation mode and the decreasing operation mode.

(Operation)

According to the present invention, the amount of oxygen gas produced can be kept substantially constant by introducing liquefied oxygen while reducing the power consumption of the raw material air compressor in the reduction operation mode. Also, by storing excess oxygen as liquefied oxygen in the increasing operation mode, liquefied oxygen required in the decreasing operation mode can be easily obtained.

Therefore, the power consumption can be increased or decreased while the amount of oxygen gas produced as a product is always kept substantially constant.

Also, as in the second configuration, by storing and introducing liquefied nitrogen in the same manner as liquefied oxygen, the amount of product nitrogen gas produced can always be kept substantially constant.

Further, as in the third configuration, by providing a plurality of raw material air compressors, it is possible to increase the difference between the supply amount of raw air and the power cost between the increased operation mode and the reduced operation mode.

〔Example〕

Hereinafter, the present invention will be described in more detail based on embodiments shown in the drawings.

First, FIGS. 1 to 3 show a first embodiment of the present invention. FIG. 1 is a system diagram of a main portion of an air liquefaction / separation apparatus to which the present invention is applied, and FIG. Explanatory diagram, 3rd
The figure is an explanatory diagram of the reduction operation mode.

The air liquefaction / separation apparatus 1 compresses the raw material air A to a predetermined pressure with a raw material air compressor (hereinafter, simply referred to as a compressor) 2,
After purifying by removing impurities such as water and carbon dioxide in the raw material air by the purifying device 3, the heat exchanger 4 heat-exchanges with oxygen gas, nitrogen gas, exhaust gas and the like, which will be described later, and cools to near the liquefaction point. Then, the mixture is introduced into the bottom of the lower tower 6 of the double rectification column 5 and liquefied rectification separation is performed in the double rectification column 5 to separate nitrogen and oxygen in the raw material air.

The raw material air A is separated into an oxygen-enriched liquefied air (hereinafter, referred to as liquefied air) LA at the bottom of the lower tower 6 and a nitrogen gas GN at the upper part by a rectification operation in the lower tower 6. Liquefied air LA
Is discharged from the bottom of the lower tower 6 and is provided with a pressure reducing valve (not shown).
And then introduced into the middle stage of the upper tower 7. A part of the nitrogen gas in the upper part of the lower tower 6 is led out of the tower as nitrogen gas GN, and the remaining part is condensed and liquefied by the condensing evaporator 8 to form liquefied nitrogen.
LN. A part of the liquefied nitrogen LN becomes a reflux liquid in the lower tower, and the remainder is led out from the lower tower 6, and after reducing the pressure, is introduced as a reflux liquid into the top of the upper tower 7.

In the upper tower 7, rectification is performed with the liquefied air LA and liquefied nitrogen LN, so that nitrogen gas is separated at the upper part of the upper tower and liquefied oxygen is separated at the bottom of the upper tower. The liquefied oxygen at the bottom of the upper tower is vaporized and vaporized in the condensing evaporator 8 to become oxygen gas, a part of which is led out as product oxygen gas PO, and the remainder becomes rising gas of the upper tower 7. Nitrogen gas at the upper part of the upper tower is led out from the top of the tower as product nitrogen gas PN, and exhaust gas W is discharged from the middle part of the upper tower. The various gases derived from the double rectification column 5 are supplied to a demand destination as a product after the raw material air A is cooled by the heat exchanger 4 or are used for regeneration of the purification device 3 and the like.

In order to carry out the present invention, the compressor 2 includes:
A compressor having a larger capacity than that required to produce the required amount of product oxygen gas PO is used, and the double rectification column 5 stores liquefied nitrogen LN derived from the upper portion of the lower column. A nitrogen storage tank 9 and a liquefied oxygen storage tank 10 for extracting and storing liquefied oxygen LO at the bottom of the upper tower are provided.

The liquefied nitrogen storage tank 9 and the liquefied oxygen storage tank 10 store liquefied nitrogen LN and liquefied oxygen LO according to the operation mode, respectively.
Alternatively, it is introduced into the double rectification column 5, and is connected by a storage and introduction conduit equipped with a valve, a pump and the like as necessary. In addition, both storage tanks 9 and 10 need to have a capacity to receive a maximum liquid product supply amount per unit time described later for at least 12 hours continuously.

In the air liquefaction / separation apparatus 1 configured as described above,
For example, when collecting 65 parts of product oxygen gas PO, the usual required amount of raw material air is about 330 parts. Therefore, in practicing the present invention, a compressor having a larger processing capacity, for example, a compressor capable of compressing 400 parts of the raw air A to a predetermined pressure is used as the compressor 2. The capacity of the compressor 2 at this time is preferably determined by the balance between the maximum operation mode and the reduction operation mode, and the average of the product oxygen gas PO obtained in both modes is the required product oxygen gas amount. Should be set.

When the maximum operation mode is performed in the air liquefaction / separation apparatus 1, the compressor 2 is operated at its maximum capacity and 400 parts of the raw material air A is introduced into the double rectification 5 or the like. Thereby, the double rectification column 5
Can provide 80 parts of oxygen.
Part of oxygen gas is derived as product oxygen gas PO, and 15 parts is derived as liquefied oxygen LO.
Store in 10. At this time, the refrigeration that is insufficient for deriving oxygen in a liquid state is to maintain the refrigeration balance in the apparatus by introducing 16 parts of liquefied nitrogen LN in the liquefied nitrogen storage tank 9 into the double rectification column 5 and replenishing it. Can be.

When performing the reduction operation mode, the compressor 2 is set to 75%
A 300 parts feed air A is introduced into the double rectification column 5 by a reduction operation. As a result, 51 parts of oxygen are obtained from the double rectification column 5, and by introducing the liquefied oxygen LO in the liquefied oxygen storage tank 10 to the 15 parts double rectification column 5, 66 parts of the product oxygen gas PO is obtained. Can be produced. At this time, the excessive cooling for introducing the liquefied oxygen LO is performed by removing 16 parts of the liquefied nitrogen LN from the liquefied nitrogen storage tank 9.
, The cold balance in the apparatus can be maintained.

As described above, the increase operation mode and the decrease operation mode are set, and this operation is repeated alternately, for example, at night and day, so that the power consumption can be averaged and the power rate can be reduced. That is, by performing the increased operation mode during the night when the power consumption is reduced and the reduced operation mode during the day when the power consumption is increased, the power consumption during the night can be increased and the power consumption during the day can be reduced. Further, even if the compressor having a large processing capacity is operated at the maximum capacity, the nighttime power, which is cheaper than the daytime, is used, so that the power rate can be reduced even if the power consumption increases. Furthermore, by setting both operation modes to 12 hours each, liquefied oxygen LO and liquefied nitrogen
LN storage and introduction can be balanced.

Table 1 shows the amounts of gas and liquid in both operation modes at this time.

Further, in the apparatus of the first embodiment shown in FIGS. 2 and 3, the product oxygen gas sampling amount is set to the same condition as in the first embodiment, and the case where the increase / decrease amount of the raw material air is set to 100: 60. Table 1 also shows two examples. In recent years, the performance of the raw material air compressor has been improved, and it has become possible to supply up to 40% of the raw material with one compression unit, and the above-described operation is possible.

Further, it is possible to arrange a plurality of compressors as shown by the imaginary line in FIG. 2 and adjust the number of operating compressors in the increasing operation mode and the decreasing operation mode. In this case, the difference in the supply amount of the raw material air between the increase operation mode and the decrease operation mode can be increased as compared with the case of one compressor. Here, the case where two raw material air compressors are installed and two are operated during the increasing operation and one is operated during the decreasing operation is the third case.
An example is shown in Table 1.

In addition, various conditions such as the processing capacity of the compressor, the storage amount and introduction amount of the liquid, and the switching time between both operation modes are determined by the necessary amount and purity of the product oxygen gas, whether or not the liquid product and the product nitrogen gas are collected,
Various other factors such as the usage status of the power at the installation site, the power rate, the configuration of the air liquefaction separation device, for example, those with an independent purification device and heat exchanger and those with a reversible heat exchanger Optimal conditions can be set in consideration of this.

FIGS. 4 and 5 show a fourth embodiment of the present invention, in which liquefied air is stored and introduced in addition to the liquefied oxygen and liquefied nitrogen.

In the case of performing the increased operation mode in the present embodiment, as shown in FIG. 4, the compressor 2 is operated at the maximum capacity in the same manner as described above and the amount is larger than the amount necessary for collecting the product oxygen gas PO. The raw material air A is introduced into the double rectification column 5, and the excess oxygen and nitrogen generated are stored as liquefied oxygen LO and nitrogen nitride LN in the storage tanks 9 and 10, respectively. The supply is made up by introducing liquefied air LA from the storage tank 11 to the lower part of the lower tower. In the case of the reduction operation mode, as shown in FIG. 5, the compressor 2 is operated to reduce the amount of oxygen, and the insufficient oxygen in the product supply amount is supplemented by introducing liquefied oxygen LO from the liquefied oxygen storage tank 10, Liquefied nitrogen LN is also introduced from the liquefied nitrogen storage tank 9 into the double rectification column 5, and excess liquefied air LA corresponding to the cold, which becomes excessive due to the introduction of the liquefied gas, is stored in the liquefied air storage tank 11.
This liquefied air storage tank 11 also needs to have a capacity to receive the maximum liquid air supply amount per unit time for at least 12 hours, as described above.

Thus, by adding the liquefied air LA as a cold source, the production amount of the product nitrogen gas PN can be stabilized. That is, in the above-described first to third embodiments, the product nitrogen gas PN produced along with the storage or introduction of the liquefied nitrogen LN is used.
In this embodiment, the storage and introduction of the liquefied oxygen LO are performed in the same manner as in the previous embodiment, and also in the nitrogen, an amount equivalent to the product nitrogen gas which becomes excessive during the increase operation mode is liquefied nitrogen LN. As a product, and can be replenished by introducing liquefied nitrogen LN in the amount insufficient as a product in the reduction operation mode. Therefore, in this embodiment, the air liquefaction / separation apparatus which uses a plastic heat exchanger for the purification process of the raw air and requires a relatively large amount of exhausted nitrogen as a regeneration gas relative to the raw air amount. This is suitable when it is necessary to simultaneously supply a fixed amount of oxygen gas and nitrogen gas as products.

In addition, the amounts of gas and liquid in both operation modes of this embodiment are shown in Table 1 as in the first to third embodiments.

[Effects of the Invention] As described above, the air liquefaction separation method of the present invention includes:
While the capacity of the compressor is set to be large, the compressor is operated at approximately the maximum processing capacity to store oxygen gas as liquefied oxygen in an increasing operation mode. In this mode, the amount of power consumed can be increased or decreased while constantly producing the required amount of oxygen gas as a product. By operating the system and increasing the amount of power at night, the difference in power consumption between day and night can be reduced, and the overall power cost of the air liquefaction separation device can be reduced by effectively using low-cost nighttime power. Reduction can be achieved.

Also, by storing and introducing liquefied nitrogen in the same manner as liquefied oxygen and simultaneously introducing and storing an amount of liquefied air that compensates for this, the amount of product nitrogen gas produced can be kept substantially constant, and nitrogen gas can be maintained. Can be supplied stably.

Further, by providing a plurality of raw material air compressors, it is possible to increase the difference between the supply amount of raw air and the power cost between the maximum operation mode and the reduction operation mode, and the difference in electric power consumption is increased. It is.

[Brief description of the drawings]

FIGS. 1 to 3 show the first to third embodiments of the present invention. FIG. 1 is a system diagram showing an air liquefaction / separation apparatus to which the method of the present invention is applied, and FIG. FIG. 3 is an explanatory view of the increasing operation mode in the embodiment to the third embodiment, FIG. 3 is an explanatory view of the decreasing operation mode, and FIGS. 4 and 5 show a fourth embodiment of the present invention. Is an explanatory diagram of the increasing operation mode, and FIG. 5 is an explanatory diagram of the decreasing operation mode. 1 ... air liquefaction separation device 2 ... raw material air compressor 5 ...
... double rectification tower, 9 ... liquefied nitrogen storage tank, 10 ... liquefied oxygen storage tank, 11 ... liquefied air storage tank, A ... raw material air, LA ... liquefied air, LN ... liquefied nitrogen, LO ... liquefied oxygen , PN …… Product nitrogen gas, PO …… Product oxygen gas

Claims (3)

(57) [Claims] 1. An air liquefaction and separation method for compressing, purifying, cooling and liquefying raw air, and collecting oxygen gas as a product, wherein the capacity of the raw air compressor is increased with respect to the amount of oxygen gas produced. At the same time, the raw material air compressor is operated at substantially the maximum processing capacity, oxygen produced in excess of the required amount of oxygen gas is stored as liquefied oxygen, and refrigeration necessary for storing the liquefied oxygen is converted to liquefied nitrogen. And the liquefied oxygen stored in the increased operation mode is introduced according to the amount of oxygen gas that is insufficient for the required product oxygen gas amount, and the liquefaction is performed. An air liquefaction / separation method characterized by alternately performing a reduction operation mode for storing liquefied nitrogen equivalent to cold, which becomes excessive due to the introduction of oxygen. 2. An air liquefaction and separation method for compressing, purifying, cooling and liquefying raw air, and extracting oxygen gas and nitrogen gas as products, wherein the amount of oxygen gas produced by the raw air compressor is reduced. The capacity is set to be large, and the raw material air compressor is operated at approximately the maximum processing capacity, oxygen and nitrogen produced in excess of the required amount are stored as liquefied gas, and the refrigeration required for storing the liquefied gas is stored. Operating mode in which the supply of liquefied air is used to increase the amount of oxygen gas and the amount of nitrogen gas that are insufficient for the required product oxygen gas amount and product nitrogen gas amount by reducing the amount of the raw material air compressor. Introduce liquefied oxygen and liquefied nitrogen stored in mode,
An air liquefaction / separation method comprising alternately performing a reduction operation mode in which liquefied air corresponding to a cold amount which becomes excessive due to introduction of liquefied oxygen and liquefied nitrogen is stored. 3. The air liquefaction separation method according to claim 1, wherein a plurality of raw material air compressors are provided, and an appropriate number of raw material air compressors are operated according to the increasing operation mode and the decreasing operation mode. An air liquefaction separation method characterized by the above-mentioned.