JPS61129020A - Separation of oxygen and nitrogen from gaseous mixture - Google Patents

Abstract

PURPOSE:To reduce power consumption and the amount of an absorbent, by pacing two or more of adsorbing towers with Na-A type zeolite containing divalent or more Fe and selectively adsorbing O2 at room temp. or less by said zeolite while producing O2 by pressure swing. CONSTITUTION:Air compressed by a compressor 2 enters a dehumidification and CO2-removal tower 4 from an inlet side line 1 and subsequently enters an adsorbing tower 8. The adsorbing tower 8 is packed with Na-A type zeolite 9 containing divalent or more Fe and O2 is adsorbed with said zeolite 9 while N2 is taken out through a product tank 13. an adsorbing tower 8' is evacuated to 0.08-0.5 ata by a vacuum pump 18 and O2 adsorbed by the adsorbent 9' is released and the adsorbent 9' is regenerated within a short time. When the adsorbent 9 of the adsorbing tower 8 is saturated, the flow passage of inlet air is changed over to perform adsorption in the adsorbing tower 8'.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides 02 ``It is less than a mixed gas whose main component is 2.

This relates to a method of separating M snow.

[Conventional technology]

The adsorption separation method of 0 and N from the air using 03 adsorbent has the advantage that the equipment is simple and requires almost no maintenance and is almost unmanned, so the production volume of N and N is 10 to 100.
In recent years, the use of small and medium-sized N gases of the order of 0 Mm''-H2/h has been increasing as production equipment, and replacement is progressing for cases in which liquid nitrogen produced in cryogenic separation equipment is transported and used. O = As an adsorbent, activated carbon-based molecular sieve carbon 4A is the most commonly used adsorbent.

To give an overview of typical equipment, the equipment consists of an air compressor and two or more towers. It consists of an adsorption tower and, in some cases, an air pump. In this device, when compressed air is sent to one tower, O2 in the air is adsorbed by the O3 adsorbent packed therein, and the remaining high pressure N flows out to the rear of the adsorption tower and is recovered. On the other hand, in other towers, the adsorbed 0
2 is released under reduced pressure conditions (sometimes a method of flowing a part of the product N in a countercurrent or strongly removing 02 with a vacuum pump is also used) to regenerate it. Repeat this alternately and continue o! , N, are separated. Typical 03 adsorbents packed in the above adsorption tower are Pelg (carbon molecular sieve '5', which is estimated to have a window diameter of approximately 4A and was put into practical use by Ufforschung);
This method selectively adsorbs O2 from a mixed gas of Ox and Nt 2 components by taking advantage of the fact that the adsorption rate of O2 is faster than that of N.

[Problem that the invention seeks to solve]

It was mentioned above that the 02r NZ separation device using this adsorption is advantageous in the small and medium-sized area, but in order to produce N of INm'',
9% N requires 0.45 KWh, and 99.9% N requires α65 KWh, and the power consumption is large compared to [145 K'Wh of N produced by large-capacity cryogenic separation method.

Also 0. Under the above operating conditions, N of lNm3
25-30% of zero-enriched air is recovered from the desorption side at a rate of 55-4 Nm''.

In addition, there is little merit of scale for increasing equipment capacity, and 1
It is said that it cannot compete with the cryogenic separation method in the region of 000 Nm''-N/h or more.

Therefore, various methods of improving these drawbacks can be considered, but when describing the method of improvement in relation to the present invention, the following obstacles usually appear.

First, in order to reduce power consumption, it is possible to lower the blowing pressure and perform the adsorption operation at a low pressure, but since the amount of O1 adsorption decreases approximately in proportion to the pressure, the capacity of the device increases significantly. Next, in order to increase the amount of N-rich production (03-enriched air), it is possible to shorten the cycle time, but there is a limit because it increases the consumption of valves, adsorbents, and rotating machinery.

Therefore, the present inventors conducted intensive research and experiments on a high-performance separation method for o = l Nt under low temperature and low pressure adsorption conditions that improved the above-mentioned drawbacks. It was found that Ha-A W zeolite increases the 08 adsorption amount and the 01 selectivity under low temperature and low pressure adsorption conditions.
The present invention was completed based on the discovery that compared to regeneration (vacuum depressurization), it is possible to significantly reduce power consumption without increasing the number of adsorption towers.

[Means for solving problems]

That is, the present invention provides N containing at least divalent or higher iron.
a - At least two adsorption towers are filled with A-type zeolite, and a mixed gas containing oxygen and nitrogen as main components is allowed to flow into the adsorption tower at a pressure above atmospheric pressure and below 3 ata to mix the mixture. selectively adsorbing oxygen contained in the gas and flowing out high-purity nitrogen or nitrogen-enriched gas from the outlet of the adsorption tower;
On the other hand, the adsorption tower that adsorbed oxygen was heated to Q of 0.08 ata or more,
This paper proposes a method for separating oxygen and nitrogen from a mixed gas under low temperature and low pressure conditions, which is characterized by producing 02-enriched air by reducing the pressure to 5ata or less and regenerating it.

〔Example〕

In order to demonstrate the effectiveness of the present invention, an air separation device shown in FIG.
-01 with 02 adsorbent of type A zeolite. An attempt was made to separate the N-goose.

This 02 adsorbent was prepared as follows.

First, 'l'@C1@ or Fe04 a IM concentration aqueous solution was added to a Ha-A type zeolite slurry solution exhibiting a pH of 9 to 11 so that CL was 1 to 1 vt% in terms of iron element based on the weight of Ha-A type zeolite. and precipitate on the surface of the adsorbent. At this time, if the pH of the mother liquor becomes 6 or less, exchange of Fe and Na ions will occur and O1 selectivity will be lost, so this must be avoided. Thereafter, filtration and water washing are performed, kaolin and silica sol are mixed as a binder, and after formation, the Ha-A type zeolite exhibits 02 selectivity by firing at a high temperature of 650° C. or higher. Note that by adding K at the same time as Fe, O1 selectivity can be obtained even during heat treatment at a lower temperature.

In the present invention, within the above preparation range, IFe is Q,
5 vt% (as IFe) added, temperature 720
The sample was baked at ℃ for 2 hours.

The details of the implementation will be explained below based on FIG.

1.05 to 5 at compressor 2 through inlet side line 1
The air pressurized to a is dehumidified and dehumidified from the flow path 3.:02 tower 4
The air enters the air and becomes extremely clean pressurized air.

The valve 5 installed downstream of the flow path 3' is open, and clean pressurized air enters the adsorption tower 8 through the flow path 6 and the open bell 7. The pressurized air that has entered the adsorption tower 8 is O1 adsorbent 9 where 02 is adsorbed and removed, and as it goes to the rear, it becomes N2.
concentration increases. After this, the pressurized air is supplied to the valve 10 in the open state.
．． 11.12 and valve 11. The product Nt is recovered as product N through the tank 13 inserted between the two.

On the other hand, the adsorption tower 8' has a valve 10' in a closed state, a valve 1 in an open state, and a vacuum pump 1 connected through a flow path 17.
Therefore, the adsorption tower 8' is under negative pressure and the O adsorbed on the 08 adsorbent 9' in the adsorption tower 8' is removed.
l is easily removed from KMI and 0. The adsorbent 9' is regenerated in a short time.

The 02 adsorbent 9 of the adsorption tower 8 is saturated, while the 02 adsorbent 9 of the adsorption tower 8' is saturated.
2 adsorbent 9' to 0. When the inlet air is removed and regeneration is completed, the inlet air flow path 6 is switched to 6', and the methods described so far are carried out alternately, so that the products Ml and Q and the enriched air can be continuously recovered.

A heat exchanger 19 is installed between the clean pressurized air line 3' at the inlet and the gas line 17 whose main component is separable gas. ′
A heat exchanger 22 also allows heat exchange between the two. Furthermore, since a compression type refrigerator 20 is installed in the flow path 5', the adsorption towers 8 and 8' are extremely efficiently cooled and set to a low temperature condition. In addition, when switching the adsorption tower, it is necessary not only to simply switch from flow path 6 to 6' (or vice versa), but also to prevent inlet air from blowing through due to pressure increase immediately after switching, and to prevent air from remaining behind the adsorption tower. In order to minimize the release of N and pressurized air from the front to the outside of the system, first, close the valve 10.
, 10' are fully opened and all other valves are fully closed, and a portion of the residual N at the rear of the adsorption tower 8 immediately after adsorption is transferred to the adsorption tower 8' immediately after regeneration. At this time, the pressure of the adsorption tower 8 is set to P.

(ata), and the pressure of the adsorption tower 8' is Pl (ata), the pressure after pressure equalization is approximately -p, +Fl (ata)
becomes. After this, about pn ” '+ (6t a '
), the adsorption tower 8' opens the pulps 10' and 11 to produce product N! The tank 13 and the adsorption tower are pressure-equalized and the adsorption tower 8
' is further filled with high pressure N. Pressure p when equalizing pressure with product N and tank 13.

(ata) is the dead volume of the adsorption towers 8, 8' (the volume of the space not occupied by the adsorbent in the adsorption tower).7. (t'),
Product N, the capacity of the tank is V (t), and the pressure of the product Ni tank 15 before pressure equalization is P. (ata), the pressure equalization pressure Pz (ata) is approximately equal, and is simply calculated from PH(ata) when switching columns to P(1(
Compared to rapid pressure increase to (ata), the above operation reduces P,
(ata), P0+P1(ata), p, (ata
), Po(ata'.

Because the pressure is increased slowly, it prevents air from blowing through during the pressure increase, and also allows residual nitrogen and high-pressure air from the desorption process to escape from the system.
Measures can be taken to minimize the release of It goes without saying that the above operation is not effective in reducing the concentration of the product in an operation where the main purpose is to recover zero-enriched air in the desorption process.

Air separation was carried out using the air separation apparatus shown in FIG. 1 using the above operating method. The operating specifications of the device are shown in Table 1.

Table 1 Adsorption device specifications Under the operating conditions shown in Table 1, 0% N2 was separated from air.

The results are summarized in Figure 2 and below.

From Figure 2 below, Na containing at least divalent iron
- Pressure swing type odor from air using A-type zeolite adsorbent (hereinafter referred to as Na-A-Fe).

The main improvements over the conventional carbon molecular sieve 4 A te for air separation by room temperature and high pressure adsorption will be explained.

Figure 2 is a graph showing the relationship between adsorption pressure and power consumption. In Figure 2, the horizontal axis is the adsorption pressure P6ata, and the vertical axis is the consumption required to produce M in INm'/h. Electric power (
KW). Fe(ffI) as an adsorbent Q, 5
Using Ha-A containing wt911+, temperature -50
°C, desorption pressure pl: == o, 1 ata, outlet N
2 concentration was set to 99.9%, and the adsorption tower pressure was set to 1.05%.
The power consumption was investigated when changing to ~4.5ataK.

As can be seen from Fig. 2, the power consumption is significantly reduced as the pressure decreases, and at an adsorption pressure of 5 ata or less, the carbon molecular sieve of 4 ml is a65KWh/Nm'-
For N2 (99.9% N2), we have discovered the extremely useful fact that nitrogen and zero-enriched air can be separated from air with a much smaller power unit. This is because any conventional air separation method using an O1 adsorbent that has been put into practical use does not utilize O adsorption in the low-pressure, low-temperature region.
Moreover, it can be said to be a completely new fact since it has not been described in any conventional literature.

Next, the adsorption pressure PQ, which is the region where the above effectiveness holds true, is
= 1.2 ata, outlet N2 concentration 99.9%
, the operating conditions were set to -30°C, and the desorption pressure P was set to C.
The power consumption was measured by changing L1 to α5 ata, and the results are shown in FIG. FIG. 3 is a graph showing the relationship between desorption pressure and power consumption. In FIG. 3, the horizontal axis shows the desorption pressure PI (ata), and the vertical axis shows the power unit when manufacturing 1 mm'/h (N). N in carbon molecular sieve, production power consumption is α65 KWh / Nm3-It (99
,9% 11. , ), it is considered that the desorption pressure range α1 to α3 ata, which shows a low unit consumption, is effective.

Next, an attempt was made to perform adsorption separation under cooling conditions in the adsorption tower in the range from room temperature to -305°C. This is because the adsorption amount and 0° selectivity generally increase by setting the temperature to low temperature conditions, so the breakthrough zone during adsorption is reduced, which can be expected to reduce the size of the device and improve separation efficiency. It is. Other operating conditions are adsorption pressure 1.2 ata, regeneration pressure (L 1 ata
, @Product The N2 concentration was set to 999 degrees, and the temperature was gradually lowered from room temperature to a low temperature to N21 Nm3. / h The power consumption rate during manufacturing was determined. FIG. 4 is a graph showing the relationship between operating temperature and power consumption rate. In FIG. 4, the horizontal axis shows temperature, and the vertical axis shows power consumption.

As can be seen from Figure 4, the power consumption rate continues to decrease as the temperature decreases.The power consumption rate of the 02 adsorbent of the present invention in the temperature range up to 60°C was investigated, and it was found that No particular problems occurred. Furthermore, small-scale tests predict that it will not lose its effectiveness even at temperatures as low as -100°C.

However, at a temperature below -70°C, the power consumption required for cooling is approximately four times that of 150°C and twice that of -60°C, and the equipment cost becomes relatively high, which is not preferred in practice.

FIG. 5 is a graph showing the relationship between temperature and 01 concentration in the adsorption tower outlet N2, in which the horizontal axis shows the temperature and the vertical axis shows the 02 concentration in the adsorption bath outlet N2. The operating conditions are adsorption pressure R
) = 1.2 ata, desorption pressure pl=0, 1 a
ta, cylinder speed σ = α451, / sec,
Adsorption separation was carried out by varying the temperature from 4CI'C to -110QC.

As can be seen from FIG. 5, in the 02 adsorbent of the present invention, the 01 concentration in N2 at the outlet of the adsorption tower decreases significantly as the temperature decreases in the low temperature range.

What has been described above is mainly related to power cost + 02 purity, but next we will discuss items related to initial equipment cost. At adsorption pressure Po == 1.2 at&, desorption pressure P1 = 0.1 ata, output product N,
The amount of product M2 collected was adjusted so that the concentration of 08 in
The amount of adsorbent required to collect Hz (02 concentration 0.1%) of Mm”/h was evaluated and the results are shown in Figure 6. Figure 6 shows the amount of adsorbent and This is a graph showing the relationship between the following: In the figure, the horizontal axis is temperature, and the vertical axis is the adsorbent weight required to produce the above-mentioned INm'N per hour.

As can be seen from Figure 6, the carbon molecular sieve is
When producing islands of INm per hour under the adsorption conditions of , atm, the amount of adsorbent required is 25 yu', but under these adsorption conditions, even if the pressure drops to around atmospheric pressure, the temperature remains at -50°C. As described in detail above, according to the present invention, at least 251 kg
Ha-A type zeolite containing more than the iron content is used, the adsorption process pressure is 5 ata or less, and the desorption process force is 0.1
~ (If pressure swing type adsorption separation of a mixed gas, such as air, is carried out under a pressure region of L 5 ata and using a temperature range below room temperature, the power required to produce N of INm" per hour conventionally can be reduced. Unit is cryogenic separation method [145~α65
KWh The current adsorption separation, which requires more than l 65 KWh, has been reduced to around α25 KWh,
In addition, the amount of adsorbent used can be maintained at the same level as the current adsorbent method.

The above description has mainly been about N2 production using the zero adsorbent, but next we will explain about KO and enriched air production.

In this case, in the present invention, since air can be blown at near atmospheric pressure, the power consumption rate does not increase even if the O snow adsorption tower is accompanied by M from the rear of the O snow adsorption tower. Rather, it is preferable to increase the 03 concentration in the snow at the outlet N and increase the 03 partial pressure of the 03 adsorption tower to increase the recovered 03 concentration.

The inventors used the apparatus shown in FIG. 1, and the inlet air amount was 10
Mt/switching time, exit N snow 0. The concentration was increased to 5%, and 4 ML of O-enriched air with an O-O concentration of about 65% was collected from the desorption side regeneration line under the conditions of a temperature of -50°C, an adsorption pressure of 1.1 ata, and a regeneration pressure of 11 ata.

In addition, the recovery was 0. If a portion of the nitrogen is passed through the tower immediately after adsorption in the same direction as the air flow to purge the residual N, the O
s concentration increased. Calculating the power unit based on the material balance under these conditions, the power consumption is calculated as (L
27 KWh/Nm'-02, extremely effective (cryogenic method is a, 45 KWh/MW"-0,) o
This can be a method for producing 8-enriched air.

As explained in detail above, the present invention proposes a method for separating oxygen and nitrogen from a mixed gas that requires less power consumption and less adsorbent than conventional adsorbent methods, and is very useful industrially. It is.

[Brief explanation of the drawing]

Figure 1 is an illustration of an air separation device used to carry out the separation method of the present invention, Figure 2 is a graph showing the relationship between adsorption pressure and power consumption, and Figure 3 is a graph showing the relationship between adsorption pressure and power consumption. Figure 4 is a graph showing the relationship between temperature and power unit, Figure 5 is a graph showing the relationship between temperature and O concentration at the adsorption tower outlet N1, and Figure 6 is a graph showing the relationship between temperature and power consumption. temperature and 11m
3- is a graph showing the relationship with the adsorbent required to produce Nl/h. 2...Compressor, 4...Dehumidification/Dehumidification CO, tower, 8...Adsorption tower, 13...Product 02 tank, 18...Vacuum pump, 2゜...Compression refrigerator recovery Agents 1) Akifuku Agent Ryo Hagihara - Figure 2 Figure 3 Desorption pressure Pt Cata) Figure 5 Temperature (0C) Temperature [°C]

Claims (1)

[Claims] At least two adsorption towers are filled with Na-A zeolite containing at least divalent iron, and at a temperature below room temperature,
Mixed gas containing oxygen and nitrogen as main components at atmospheric pressure or higher 3a
ta or less to selectively adsorb oxygen contained in the mixed gas, and high-purity nitrogen or nitrogen-enriched gas flows out from the outlet of the adsorption tower, while the adsorption tower that has adsorbed oxygen is heated to 0. 1. A method for separating oxygen and nitrogen from a mixed gas under low temperature and low pressure conditions, characterized by recovering oxygen-enriched air by reducing the pressure to 0.08 ata or more and 0.5 ata or less.