JPS5982924A - Method for increasing production of gas - Google Patents

Abstract

PURPOSE:To maintain the adsorbent bed in an adsorption column at an adsorption temp. in the stage of process shutdown by utilizing the heat of evaporation when liquefied oxygen or liquefied nitrogen evaporates as the cold energy for maintaining the molecular sieve adsorbent bed at a low temp. CONSTITUTION: The raw air supplied from a pipe 1 is compressed by a compressor 2, and after the air is removed of heat generated by compression by cooling water or the like in a cooler 3, the air flows in a pipe 4 a valve 5a a pipe 6a, and is cooled to about -145 deg.C by a heat exchanger 7a. Impurities such as moisture and carbon dioxide are condensed and removed by a heat exchange part 19a and the clean low-temp. air is derived from the heat exchanger. Such air is introduced through a valve 8a and a pipe 9 into a heat exchanger 10. Liquid nitrogen is supplied from a storage tank 25 through a pipe 26 and a valve 27 into the heat exchanging part 28 in the heat exchanger 10. The raw air introduced therein from a pipe 9 is subjected to a heat exchange with the liquid nitrogen and is cooled to about -170 deg.C. The cooled air is introduced through a pipe 11 and a valve 12a into an adsorption column 13a.

Description

[Detailed Description of the Invention] The present invention relates to a method for increasing the production of oxygen gas or nitrogen gas for the purpose of vaporizing liquefied oxygen or nitrogen gas (in contrast, efficiently utilizing energy that was conventionally wasted). .

Conventionally, gases such as oxygen and nitrogen are purified by liquefying the air and separating it into their respective components. It is widely used in gaseous form by vaporizing it.

Recently, the cost of various types of energy has been rising extremely sharply, especially since the 16th century of petroleum, and this is putting pressure on the management of general industries. Since it is used for various purposes, there is a strong demand for productivity improvement from all aspects of society.

In response to such social demands, this invention supplies oxygen and nitrogen at low cost, and responds to changes in demand for so-called separated wastes such as oxygen, nitrogen, or argon separated from air. Expanding the range of oxygen and nitrogen-containing gases generated in fields such as metallurgy, chemistry, and fermentation, as well as utilizing discarded cold energy when vaporizing liquefied waste. (Thus - increase the production of oxygen gas and nitrogen scum) In one step, the amount of oxygen and nitrogen mixed gas Hq When liquefied oxygen or liquefied nitrogen is vaporized and used as oxygen gas or nitrogen gas, a gas containing oxygen and nitrogen obtained from another raw material source, which is the second raw material, is used to vaporize the first raw material. The flowing latent heat of vaporization and sensible heat are fed into a molecular sieve adsorbent bed kept at a low temperature of -18C to -140C by a cryogenic system. The nitrogen adsorbed in the second raw material is allowed to flow out as a non-absorbed component, thereby separating the oxygen and nitrogen contained in the second raw material. By desorbing and recovering the oxygen, these secondary
The present invention provides a method for increasing gas production, characterized in that oxygen scum and nitrogen gas separated from a raw material are used together with oxygen gas or nitrogen gas vaporized from a first raw material, respectively.

Conventionally, a method for adsorbing and separating an oxygen-nitrogen-containing gas such as air (hereinafter referred to as raw material gas) into its components is to adsorb nitrogen using a molecular sieve adsorbent such as natural or synthetic zeolite at room temperature and separate it from oxygen. It was a common method. However, in this separation method at room temperature, the amount of gas adsorbed per unit of adsorbent is small, and generally nitrogen, which is larger in amount than oxygen in the air, which is the raw material gas, is selectively adsorbed, so the adsorption separation effect is poor. As the amount of adsorbent required per unit of product gas increases, the actual scale of the equipment and the power consumption for compressing the raw material gas also increase. To remove impurities (natural or synthetic zeolite adsorbents have selective adsorption properties for moisture and carbon dioxide over oxygen and nitrogen, so if they remove moisture and carbon dioxide, they cannot adsorb oxygen and nitrogen. ] had the disadvantage of requiring an adsorption pretreatment device.

Therefore, when the inventors use air as a raw material gas and separate oxygen and nitrogen in a mixed state, the amount of oxygen is smaller than the amount of nitrogen. We investigated this method, focusing on the fact that the required amount of adsorbent is smaller. However,
In the case of the conventional pressure-fluctuating adsorption method at room temperature, 1e+1 method - Natural or synthetic zeolite adsorbents are used to selectively adsorb nitrogen, so one oxygen is adsorbed to reduce the amount of adsorbent. This is shown in Fuyl (January 1964), published on page 164.
The figure shows a synthetic zeolite with a diameter of 4λ.
At each temperature below ℃ (the single adsorption amount of oxygen and nitrogen is shown in this figure), from 0℃ to -100℃
Up to around 100°C, the amount of nitrogen adsorbed is larger than the amount of oxygen adsorbed, or the amount of nitrogen adsorption peaks at around 100°C, and then decreases rapidly at lower temperatures; ,: ゛ is low tAIX. 1. Niriichi especially -1
It has been shown that at low temperatures below 50° C., nitrogen is hardly adsorbed, but oxygen is adsorbed, and the amount of adsorbed gas is much larger than at room temperature.

Next, compare the amount of adsorbed gas per adsorbent position 111-1-2
゜ and the typical one used in the conventional room temperature method -1,; 5
X-synthetic zeolite selectively adsorbs mononitrogen - the amount of nitrogen adsorbed is approximately 0.78% by weight (weight ratio per adsorbent).On the other hand, 4λ synthetic zeolite C-ma selectively adsorbs nitrogen at a low temperature of -196°C. , selectively adsorbs oxygen, and this oxygen is approximately 24% by weight or more.
- It has an adsorption capacity of -. This result −′帛j+ITL! 2
The difference in service ability between low-temperature adsorption and low-temperature adsorption is about 30 times that of low-temperature adsorption.''
Second, it becomes very large. Taking advantage of this effect, which occurs at low temperatures], an adsorption operation is carried out especially at -1,50'C or lower to adsorb and desorb oxygen, which is the smaller component in the raw material gas, and allow nitrogen to flow out as a non-adsorbed component. It is thought that the amount of adsorbent required is very small.

As already mentioned, judging from Figure 3, the lower the temperature, the thicker the separation effect C between oxygen and nitrogen (- since it was expected that only oxygen could be adsorbed without much adsorption of nitrogen). However, the inventors discovered that oxygen in a mixed state at this low temperature,
As a result of extensive research on nitrogen, we unexpectedly came to a conclusion completely different from what was expected from the figures shown in the above-mentioned known documents, which provided us with a foothold to complete the present invention. The obtained results are illustrated in FIG. 4. This figure shows the amount of oxygen and nitrogen adsorbed using air as a raw material gas and the change in the amount of nitrogen product when the temperature was summerized using the single-power fluctuation adsorption method. However, the amount of oxygen adsorbed was around -110°C. The amount of adsorption decreases at temperatures both higher and lower than this peak. In addition, the amount of nitrogen adsorbed reaches its minimum at around -13 (,1'C), and the amount of adsorption increases whether it is higher or lower than this temperature. Therefore, we confirmed a result that is completely different from the conclusion that the adsorption effect increases as the temperature decreases, which was predicted from Fig. 3. The effective temperature range for separation is -80 to -
I came up with the idea that it would be better to control it to 140 degrees.

In this invention, as mentioned above, the adsorption operation temperature is -8
In order to set the temperature to 0 to 1.4 tJ 'C, it is necessary to cool the raw material gas to this temperature range before introducing it into the molecular sieve adsorbent bed. At this temperature, water and carbon dioxide freeze and solidify, so Since moisture, carbon dioxide, etc. in the raw material waste are condensed and removed, there is no need for pre-adsorption treatment to remove moisture and carbon dioxide.

This invention utilizes a molecular-decorated adsorbent bed as described below.
As cold energy to maintain the temperature at a low temperature of 0 to -140°C, the heat of vaporization when liquefied oxygen or liquefied nitrogen vaporizes (i.e. - cold energy such as latent heat of vaporization or sensible heat)
This idea was based on the idea of making use of materials that had previously been discarded and completely neglected.

In the method of this invention, a gas containing oxygen and nitrogen, which is a second raw material, is fed into a molecular sieve adsorbent bed maintained at -80 to -140°C [7] to remove oxygen in the raw material from the adsorbent. The second raw material is adsorbed by an adsorbent on the bed and the nitrogen in the raw material flows out as a non-adsorbent I component to separate the oxygen and nitrogen contained in the first and second raw materials. Any mixed gas containing oxygen and nitrogen can be used, but the separation efficiency is particularly high for raw material gases such as air, which have a higher nitrogen content than air. Therefore, it is preferable to use a gas rich in nitrogen gas.

On the other hand, as the first raw material, either liquefied oxygen or liquefied nitrogen can be used, and if necessary, both can be switched in the same equipment, but when switching at all, the purity can be improved by mixing the two. Since a reduced gas is generated, it is naturally necessary to have a control system that can meet the purity requirements of the application or the customer. The method of this invention utilizes the cold energy possessed by liquefied oxygen or liquefied nitrogen, which is the first raw material (2) separates oxygen and nitrogen from the second raw material as well.
These are used in combination, and the product gas obtained from the first raw material and the product gas obtained from the second raw material may be used alone or in combination, but The product gas obtained from the first raw material and the product gas obtained from the second raw material naturally differ in purity, so depending on the final use, they may be used semi-exclusively or as a mixture. Naturally, it is necessary to use the mixing ratio of the tobacco as appropriate. The method of the invention can optionally be carried out in one stage or in multiple stages depending on the requirements for high purity of the product.

As mentioned above, the apparatus for carrying out the method of this invention does not require a pretreatment apparatus for removing moisture and carbon dioxide gas, and the separation efficiency is high when using the second raw material rich in nitrogen. The device is relatively small, the compressor can be small, the gas is passed through a bed of molecular sieve adsorbent, and it uses cold energy that was previously discarded. Although it requires a large amount of cooling energy, it is easy to operate.

The method of this invention (in which the low-temperature liquid oxygen and nitrogen used as the first raw materials each have a storage temperature of -18
At extremely low temperatures of 3°C and -196°C, it has enough temperature and cold energy to cool the raw material gas of this invention - by implementing this low-temperature adsorption separation method, the disadvantages of the conventional normal temperature method can be overcome. At the same time, it is easy to obtain base/fi by using low-temperature 7F silicide gas, which is the same as the gas to be obtained as a product, as a refrigerant. In order to prevent the temperature of the adsorbent bed from rising to 2M degrees, the temperature of the adsorbent bed is increased by passing heat through a heat exchange pipe installed in or around the adsorbent bed. This method eliminates the need to lower the adsorbent bed to a low temperature when starting the device, which is a disadvantage of low-temperature adsorption methods, and keeps the device at a normal γS low temperature (it is also possible to .

Using the same low-temperature liquefied gas as this product, i.e., liquid nitrogen in the case of nitrogen, which is a non-adsorbed component, and liquid oxygen, in the case of oxygen, which is an adsorbed component, is used as a refrigerant in the process as described above. In addition to the effect of suppressing the temperature rise of the adsorbent bed by having a cold source even when it is stopped, the adsorbed and separated gas unit has limited uses due to its purity, but is mixed with the evaporated gas of the liquefied gas, which is a refrigerant. This has the effect of increasing purity and widening the range of uses. In other words, when mononitrogen is produced as a product by low-temperature adsorption, the product nitrogen from the adsorption tower is generally 1
This 99.0~999. with one refrigerant with a purity of % by volume.

The low temperature liquefied nitrogen contained in the fl is 99.999% by volume. Further, when oxygen is used as a product, the adsorption product oxygen is 90 to 97% by volume, and the refrigerant liquefied oxygen is 996% by volume, and when these are mixed, the adsorption product gas purity is doubled.

First, as a first embodiment of the present invention, the outline of an apparatus for producing nitrogen gas from air using two adsorption towers will be explained with reference to FIG.

In the figure, -1 is an introduction pipe for air as a raw material,
A compressor 2 - a cooler 3 are sequentially connected to this pipe 1, and a pipe 4 connected to the outlet of the cooler 3 is branched into two, and a valve 5a
, 51) - connected to two heat exchangers 7a, 7b via pipes 5a, 51).

The pipes connected to the outlets of the bithermal exchangers 7a and 7b are valve 8
a.81], it becomes a re-chilled pipe 9 and is connected to a heat exchanger 10. Pipe 11 connected to the outlet of this heat exchanger 10
is 2 trees (branched into valve 12a).

121] and then connected to two adsorption towers 13a, 131). This adsorption q i 3 a , l 3 b has a bed of molecular sieve adsorbent such as synthetic zeolite, and a pipe 15 is connected to the pipe 15 through a valve 141, 141). The pipe 16 is branched into two branches and has a valve 1.
71.171), and are connected to the heat exchange parts 19a and 19b of the heat exchangers 7a and 7b through pipes 181 and 1813, and the output [-1 of both heat exchange parts 19a and 1913 is the pipe 2
Connected by 0.

+iiJ There is another heat exchange section η in the heat exchangers 7a and 7b.
a1221) - each heat exchange section 22a, 22+)
The inlet 1' is connected to a pipe having valves 21a and 21b (the pipes 18a and 1B+), respectively, and the outlet r] is connected to one product outlet pipe 24 via valves 23a and 231]. There is.

25 is a liquefied gas storage tank, which in this example contains liquid nitrogen. A pipe 26 connected to this tank 25 branches into two, one pipe is connected to the inlet of the heat exchange section 28 of the heat exchanger 10 through a valve 27, and the outlet is connected to the heat exchange section 28 of the heat exchanger 10 through a valve 29. 15 and 16. The other pipe is connected to valve 4.
3, and is connected to a single outlet pipe 45 via a heat exchange pipe 44 in each adsorption tower 13a, 13b.

31 is a valve 30a for each adsorption tower 13a, 13b.

301] - This pipe 31 is branched into two parts and connected to each heat exchanger 7a, 71) via valves 32a and 32b.
3a, 33b, and this heat exchange section 331.3
The pipes 34a, 341) respectively connected to the outlets of 31) are connected to a single pipe 35, to which pipes 36 and 42 are connected.

Pipe 36 (this includes a discharge valve 37 leading to the atmosphere and a vacuum pump 39)
A valve 38 communicating with the inlet of the vacuum pump 39 is provided, and an exhaust pipe 40 is connected to the exhaust port of the vacuum pump 39. Further, the pipe 42 is branched into two pipes 5a, 411) via valves 41a, 411).
5b.

Next, an example of a method for separating nitrogen gas using the apparatus described in "2" will be explained.

Valve 5b, 813, 12b, 14b, 17b, 2
1a, 23L], 30a, 32b, 41a,
When the compressor 2 is operated with the valves 38 and 43 closed and all other valves open, the raw air supplied from the pipe 1 is compressed to approximately 3 kg/c/cm and is cooled by the cooler 3. After the heat of compression is removed by water or the like, the pipe 4 → valve 5a → pipe 6a is cooled to about -145°C by the heat exchanger 7a, and impurities such as water and carbon dioxide are condensed and removed by the heat exchanger 19a. The purified low/111F air and γX are drawn out and introduced into heat exchanger No. 10 via valves 8a'i+i'9. The heat exchange section 28 in the heat exchanger 10 (here
Liquid nitrogen is supplied from Hjji 25 through pipe 26 and valve 27, and the raw material air from pipe 9 exchanges heat with this liquid nitrogen and is cooled to about -170°C.
Adsorption tower 13a+? via valve 12a? :,,M people are seen. On the other hand, the liquid nitrogen supplied to the heat exchange section 28ζ is evaporated and gasified by heat exchange with the raw material air, and mixed with adsorbed and separated nitrogen, which will be described later, through the valve 29.

The adsorption towers 13a, 131) are each filled with a molecular sieve adsorbent such as synthetic zeolite that selectively adsorbs oxygen at low temperatures, and periodically adsorbs oxygen at predetermined time intervals. "1" and regeneration are repeated alternately. Now, the adsorption tower 13a absorbs li, lI-
131) is the regenerator t, so the feed air C is drawn out from the heat exchanger 10, and the adsorbent that is introduced into the adsorption tower 13a through the pipe 11 and valve 12a as described above and filled in the tower. Then, oxygen is selectively adsorbed and nitrogen is led out as a non-adsorbed component via the valve 14a.

The adsorbed and separated nitrogen derived from the adsorption tower 13a is passed through the valve 14a.
- through pipe 15, it is mixed with the evaporated gas of the refrigerant liquid nitrogen mentioned above;
After being introduced into the heat exchange section 19H in the heat exchanger 19H of the heat exchanger 71 which is being regenerated, the air is introduced into the heat exchange section 191 in the heat exchanger 71 which is being regenerated through the pipe 20 and heated to approximately room temperature by exchanging heat with the feed air. The mixed nitrogen is cooled again by exchanging heat with impurities such as moisture and carbonic acid scum that were frozen in the previous cycle (tube 18I),
It enters the heat exchange section 22a in the heat exchanger 7a through the valve 211), exchanges heat with the raw material air again, reaches almost room temperature, and then passes through the valve 231-pipe 24 and is supplied to the required section as product nitrogen. be done.

From the adsorption tower 131 in the regenerator, the oxygen adsorbed in the previous cycle passes through the valve 30b, the pipe 31, and the valve 32a, and then enters the heat exchange section 33a in the heat exchanger 7a, where it enters the feed air and heat exchanger 7a. After being exchanged and heated, it is discharged to the atmosphere through the pipe 34a% 35.36 and the valve 37, and the pressure inside the adsorption tower 13b is reduced from the adsorption pressure to atmospheric pressure.

After the pressure inside the adsorption tower 131 is reduced to atmospheric pressure, either the valve 37 is closed or the valve 38 is suddenly opened, and the oxygen inside the adsorption tower 13b is released through the same process as the pressure release described above. It is sucked in by the vacuum pump 39 and discharged to the outside of the system through the exhaust pipe. At the same time, impurities such as moisture and carbon dioxide in the heat exchanger 7b, which has been heated and thawed by the aforementioned mixed nitrogen, are removed from the tube 6.
1) It is sucked in by the vacuum pump 39 through the valve 41b, the pipe 42, 36, and the valve 38, and is also discharged outside the system through the exhaust pipe 40.

-1- After continuing the above operation for a certain period of time, open the previously closed valves, close the open valves (valve 27.29.
43 remains the same) with adsorption tower 13b as the adsorption period.
Let's perform the same operation as described above using 3a as a regenerator.

In addition, when the process is stopped (in this case, the valve 27 is closed and the valve 43 is opened to supply liquid nitrogen from the stored 4% M25 to the pipe 26 and the valve 43.
The heat exchange pipes 441 in the adsorption towers 13a and i3b
This supply suppresses the rise in temperature of the thermal adhesive due to heat entering from the outside, and the evaporated and gasified nitrogen exits the system through the pipe 45.

As mentioned above, the greatest effect of the present invention can be achieved in factories that currently use low-temperature liquid oxygen-nitrogen. The object of the present invention is to utilize low-temperature cold energy, which was previously emitted without any use at all, in accordance with the content of the present invention.

To explain the effect in detail, the first example described in 2 is a case of the two-column switching type shown in the figure, and the adsorbent required to produce 8 ONm/hour of adsorbed and separated nitrogen is one column. Approximately 9 kg per serving, which is less than the conventional method. Conventional room temperature method (for nitrogen sludge production), natural, synthetic zeolite,
Although there are differences depending on the operating method, one adsorbent weighs 1,200 to 2,000 kg for roughly the same nitrogen production, and in the low temperature adsorption of this invention, the adsorbent JiiJil/6 to 1/ It has been significantly reduced to 11, and the effect is tremendous.

In addition, within the range of product nitrogen purity of 99 to 99.9%, 1 m3 of refrigerant liquid nitrogen to 1 adsorbed and separated nitrogen of 2 to 4 N+
Currently, liquid nitrogen is used by evaporating and gasifying it, but by utilizing the cold temperature, it is possible to increase the amount of nitrogen by 2 to 4 times.

FIG. 2 shows a second embodiment for producing oxygen scum from air, and most of the features are the same as the first embodiment, so only the differences will be explained.

In FIG. 2, the output of the heat exchanger 28 of the heat exchanger 10 [-
A pipe 46 is connected to 1, and this pipe is branched into 2 wooden blocks, and heat exchange parts 48a, 4 are further provided in each heat exchanger 7a, 71].
8b via valves 47a, 471). Also, the outlets of both heat exchange parts 48a, 4B+) are pipes 49a, 4B+).
9b to the valve 50, and this valve 50 is connected to the oxygen extraction pipe 51, and the discharge [ ] of the vacuum pump 39 and the valve 3
7 is connected to the extraction pipe 51.

The process of this embodiment differs in that the storage tank 25 is filled with liquid oxygen, and the adsorption tower 13a is
) is the regeneration period, the liquid oxygen supplied from the storage tank to the heat exchanger section 2B in the heat exchanger 10 through the valve 27 is evaporated and gasified by heat exchange with the raw material air, and the pipe 46-valve 47a
It is introduced into the heat exchanger 48a in the heat exchanger 7a through the pipe 49a-valve 50, and is further heated by exchanging heat with the raw material air.
It is mixed with adsorbed and separated oxygen through the pipe 51 and supplied as product oxygen. When the adsorption tower 13a is used for the regeneration period and the adsorption tower 131 is used for the adsorption amount, oxygen from the pipe 46 flows from the valve 471) to the heat exchanger 481) to the valve 50. Meanwhile, nitrogen gas is exhausted via pipe 24.

This invention Lt It goes without saying that, as in each of the above embodiments, the same adsorption efficiency and IW efficiency can be obtained by adsorbing more oxygen, which is the smaller component in an oxygen-nitrogen-containing gas such as air, at a low temperature. However, the same low-temperature liquid gas as the product gas is used as a refrigerant to obtain a low temperature, that is, low-temperature liquid nitrogen is used when nitrogen is the product, and low-temperature liquid oxygen is used when oxygen is the product. By mixing these refrigerants gasified by heat exchange with the product gas,
It has the advantage of being able to use refrigerant effectively. Also - low temperature to cool the raw material gas that is inevitably required during the process +
Use i1-. Impurities such as water and carbon dioxide can be condensed and removed by the process, and the liquefied gas that is always available during the process can be used as a cooling source to keep the adsorbent bed in the adsorption tower at the absorption temperature when the process is stopped. This eliminates the need to cool the adsorbent bed during startup, which was a problem with low-temperature adsorption.
It also has the effect of significantly shortening the startup time by 5.

[Brief explanation of drawings]

Figures 1 and 2 are system diagrams showing each embodiment of the present invention, Figure 3 is a diagram showing the relationship between temperature and adsorption amount for nitrogen and oxygen, respectively, and Figure 4 is the temperature for the coexistence of nitrogen and oxygen. and adsorption are diagrams showing temperature and product nitrogen amount. 2...Compressor, 3...Cooler, 7a, 7b...Heat exchanger-10...Heat exchanger, 13a, 13')...
Adsorption tower-25...Liquefied gas storage tank, 39...Vacuum pump. Special d'1 applicant Inutama Sanso Co., Ltd. II7+ ie pass jillF)
1-1 Ke -Figure 3Figure 11 u8<+ 140- +c+o 6(1-2(1-Temperature °C

Claims (1)

[Claims] When the first raw material, liquid oxygen or liquid nitrogen, is vaporized and used as monooxygen or nitrogen gas, the second raw material, a gas containing oxygen and nitrogen obtained from another raw material source, is used as the first raw material. Vaporization of raw materials (-80 to -14 tJ due to the cooling energy of evaporation heat and sensible heat)
The first raw material is fed into a molecular sieve adsorbent bed kept at a low temperature, and the oxygen contained in the second raw material is adsorbed by the adsorbent of this adsorbent bed, and the nitrogen contained in the second raw material is used as a non-adsorbed component. From this, the oxygen and nitrogen contained in the second raw material are separated (-1) The oxygen adsorbed by this adsorbent is desorbed and recovered (thereby, the oxygen scum and nitrogen separated from these second raw materials are A method for increasing gas production characterized by using nitrogen gas together with oxygen gas or nitrogen gas, respectively, which are vaporized from a first raw material.