JPS6161611A - Separation of oxygen and nitrogen from gaseous mixture - Google Patents

Abstract

PURPOSE:To enhance the recovery rate of product O2 by using an adsorption tower packed with Na faujasite, adsorbing N2 at low temps. and pressure, and connecting the outflow passages of both adsorption towers at the end of adsorption and regeneration in a pressure swing method. CONSTITUTION:Air is compressed by a compressor 2 to 1.05-3ata, and sent into an adsorption tower 8 through a tower 4 for removing humidity and CO2, and N2 is adsorbed and removed to recover product O2 from a tank 13. Na faujasite is used as the adsorbent, and the adsorption tower is sent under low- temp. condition. Meanwhile, the pressure of an adsortion tower 8' is reduced by a vacuum pump 16 through a flow passage 15, and regeneration is carried out. The adsorption tower 8 at the end of adsorption and the adsorption tower 8' at the end of regeneration are connected for at least 6sec by opening valves 10 and 10' send O2 remaining in the adsorption tower 8 to the adsorption tower 8'. Consequently, the recovery rate of product O2 is enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention selectively adsorbs lx t'' from a mixed gas such as air whose main component is QM e NM:Os * using an adsorbent. 0 from a mixed gas whose main component is nitrogen
This invention relates to a method for improving the pressure equalization process when separating snow e''M.

[Conventional technology]

M! The adsorption separation method for snow from air using an adsorbent has the advantage that the equipment is small and simple, and requires almost no maintenance as it can be operated unmanned.
In recent years, the number of uses for small and medium-sized devices on the order of d-1000 Hm'' -Os/h has increased, and alternatives to cases in which liquid acid produced in cryogenic separation devices is transported and used are progressing.

To give an overview of a typical device, the device includes an air compressor and two or more N columns.

It consists of an adsorption tower and, in some cases, a vacuum pump. In this device, when compressed air is sent to one tower, the N2 adsorbent packed in the air absorbs N2! is removed by adsorption, and the remaining high pressure is 0! flows out to the rear of the adsorption tower and is recovered. On the other hand, in other towers, the adsorbed Nz is released under reduced pressure conditions (sometimes a part of the product is flowed in a countercurrent, or a method of powerfully removing Nst with a vacuum pump is also used) for regeneration. Turn this alternately and continue to 02°R.
Separate x. N, which was filled in the above adsorption tower,
A typical adsorbent is Union Car (Ma-A type zeolite Q60-70% commercialized by Ido Co., Ltd.).
Oa is an exchanger, O,, Nt from a binary mixed gas
It adsorbs st-selectively, and the co-adsorption of 0x2 under air conditions is estimated to be less than 10% of N2 adsorption.

As mentioned above, this adsorption-based O, N, separation device is advantageous in the small and medium-sized areas,
The power consumption is large compared to α4.5Kwh of 0, which is produced by large-capacity cryogenic separation method. In addition, there is little merit of scale for increasing equipment capacity,
It is said that it cannot compete with the cryogenic separation method in the region of 1000 Nm"-ox/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 suction operation at low pressure.
Since the amount of adsorption decreases almost in proportion to the pressure, the capacity of the device increases significantly. next.

In order to increase the amount of adsorption, it is possible to perform the adsorption operation under low temperature conditions, but in this case, N! Although the amount of adsorption increases, the rate of adsorption and desorption decreases significantly, so the product concentration at the same column length is even lower than at room temperature. Furthermore, as the temperature decreases, the amount of N and 02 co-deposited during adsorption increases, so the power consumption rate gradually increases.

Therefore, the inventors of the present invention have developed a low-temperature solution that improves the above drawbacks.

In the process of intensive research and experimentation on a high-performance separation method for 7kO,.1g under low-pressure adsorption conditions, we discovered that mineral-based sodium faudiasite, represented by Na-I type zeolite, can adsorb N2 under low-temperature, low-pressure adsorption conditions. N within a practical range as the number of staff increases.

It was discovered that the adsorption rate could be maintained and the decrease in N adsorption selectivity was small, and an invention based on this was already proposed in Japanese Patent Application No. 58-54626. In at least two adsorption towers filled with a typical mineral-based sodium faujasite, a gas mixture containing oxygen and nitrogen as main components is introduced into the adsorption towers at a pressure above atmospheric pressure and below 3 ata at a temperature below room temperature. The nitrogen contained in the mixed gas is selectively adsorbed, and high-purity oxygen or oxygen-enriched gas flows out from the outlet of the adsorption tower, while the adsorption tower that has adsorbed nitrogen is
The present invention relates to a method for separating oxygen and nitrogen from a mixed gas under low temperature and low pressure conditions, which is characterized in that the pressure is reduced to below .

An embodiment of the method of the invention will be described below with reference to FIG. In Fig. 1, the air is pressurized to 1.05 to 3 ata by the compressor 2 through the inlet line 1.
The air enters the dehumidifying membrane CO and tower 4 from the flow path 3, and becomes extremely clean pressurized air. The valve 5 installed in the aureole of the flow path 5' is open and clean pressurized air enters the adsorption tower 8 through the flow path 6 and the open valve Z. The pressurized air that entered the adsorption tower 8 is N, and the adsorbent 9 is N! is adsorbed and removed and as it moves backward, the concentration of 01 increases. The pressurized air is then recovered as product O1 through the product 0° tank 13 inserted between the open valves 10, 11.12 and 11.12.

On the other hand, the adsorption tower 8' has a valve 14' in an open state and a flow path 15t.
- The pressure is reduced and drawn by the vacuum pump 16 connected through the adsorption tower 8', so that the N1 adsorbed on the adsorbent 9' in the adsorption tower 8' is easily released and the adsorbent 9' is regenerated in a short time. . Adsorption tower 8 ON! When the adsorbent 9 is saturated and the N2 in the adsorption tower 8' is removed from the adsorbent 9' and regeneration is completed, the flow path is switched to the inlet air flow path At-6',
If the methods described so far are carried out alternately, the product will be 0. can be collected continuously. In addition, clean pressurized air line 3 at the inlet
A heat exchanger 17 is used to exchange heat between the gas line 15 whose main component is separated N2, and a heat exchanger 19 is used between the product 0□ line 18 and the flow path 3'. It is replaceable. Furthermore, since a compression type refrigerator 20 is installed in the flow path 3', the adsorption towers 8 and 8' are cooled extremely efficiently and are set outside the prefecture at low temperatures. In addition, when switching the adsorption tower, it is not only necessary 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. 0 remaining behind the adsorption tower
! In order to minimize the release of pressurized air from the front to the outside of the system, first, the valves 10 and 10' are fully opened to ensure that there is no residual air remaining at the rear of the adsorption tower 8 immediately after adsorption. is partially transferred to the adsorption tower 8' immediately after regeneration. At this time, if the pressure in the adsorption tower 8 is iP@(ata) and the pressure in the adsorption tower 8' is t'Pt(ata), then the pressure after pressure equalization will be about 1 convex (, ta). After this, the construction EE (
In the adsorption tower 8', which has become the product 02, the pulps 10' and 11i are opened, and the pressure of the product 02 tank 13 and the adsorption tower is equalized, and the adsorption tower 8' is filled with even higher pressure O. Product 0 Pressure P when equalizing pressure with tank 13! (ata) is adsorption tower B,
8' dead volume (volume MR of space not occupied by adsorbent in the adsorption tower) is V, (Z), product 0! Tank capacity t
vt(t), and the product before pressure equalization, 0=approximately equal to the pressure t-oo (ata) of the tank 15, the equalization pressure Pl (ata) is approximately PK(ata)'ds at the time of conversion. RaPo (ata)
Compared to rapid pressure increase to Fi PI (a
ta), h Sat'-(ata), PI (ata), PI
Since the pressure is gradually increased to (ata), it prevents air from blowing through when increasing the pressure, and there is no residual air left in the desorption process! Measures can be taken to minimize the release of high-pressure air outside the system.

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 From air under the operating conditions in Table 1! +N! was separated.

However, the pressure swing type shown in FIG.
In the separation method, pressure equalization between adsorption towers 8 and 8' [related to this, an operation of 5 seconds or less, which is the inter-column pressure equalization time considered to be sufficient for fluid transfer between the columns (usually used)] So, effective 7k
(h) No improvement in recovery rate was found.

[While the invention is trying to solve; i month invention invention #: t%
The purpose of this invention is to eliminate the drawbacks of the method proposed in the above-mentioned Japanese Patent Application No. 58-54626, that is, to improve the recovery rate.

[Means for solving problems]

The present inventors, while proceeding with studies on improving the recovery rate, discovered that there is a significant relationship between the inter-column pressure equalization time and the 02 recovery rate.

That is, in the method shown in FIG.
On the contrary, by performing the process for at least 6 seconds or more, the product O1 recovery rate is improved from 35 degrees without pressure equalization to more than 55% at once, and with pressure equalization for about 15 seconds, the product O1 recovery rate is improved to 75% or more.
It was found that it reached as high as 2%.

In addition, there are 0 products! The recovery rate R is the O! Kei GA, O, [u
l/h] and 02 p Gp in product 0 wealth, -
It is the ratio of [ut/h], and is calculated by equation (1).

“A, O.

Therefore, the present invention provides at least two adsorption towers filled with the mineral name sodium faujasite represented by Ma-X K, at a temperature below room temperature, at atmospheric pressure. The nitrogen contained in the mixed gas is selectively adsorbed by the adsorption tower KR under 3 ata or less, and high-purity oxygen or oxygen-enriched gas is flowed out from the outlet of the adsorption tower, while the adsorption tower 1i adsorbing nitrogen is :(10
In a method for separating oxygen and nitrogen from a mixed gas at low temperature and pressure conditions of 1 degree Celsius, where the pressure is reduced to 8 ata or more [15 ata or less and regenerated, N
By connecting the adsorption tower and the flow path on the outlet side of the adsorption tower, the product oxygen remaining at the rear of the tower after the completion of adsorption is transferred to the N, adsorption tower after the regeneration is completed, and the product oxygen is recovered. The present invention provides a method for separating oxygen and nitrogen from a gas mixture with the mission of increasing the efficiency.

〔Example〕

The effects of the method of the present invention will be explained below using Examples.

EXAMPLE Using the apparatus shown in FIG. 1, which has already been described, with the pressure equalized between the adsorption tower 8 and the adsorption tower 8', the open state time of the pulp 1o and the pulp 10' was varied from 0 seconds to 15 seconds. The product at that time is 0. The changes in the recovery rate were investigated. The results are shown in FIG.

In FIG. 2, the horizontal axis represents the time during which the pulp 10 and the pulp 10' are in an open state (ie, the pressure equalization time), and the vertical axis represents the product 02 recovery rate R(1).

As is clear from Fig. 2, increasing the pressure equalization time significantly improves the product zero-volume recovery rate R(a).

The present invention addresses this trend with a product of 0.0. Collection yiR@) is
Product 0 when no pressure is equalized. Recovery rate from 35ch to 5
The effective range of the present invention is a pressure equalization time of 6 seconds or more, which is improved by 5% or more.

At this time, the improvement in the power consumption (power unit) required to manufacture 08 of 1 klrn' is shown in Figure 3.

In Figure 3, the horizontal axis is the pressure equalization time (seconds) as in Figure 2.
, and the vertical axis indicates the power consumption unit 0 (Kwh/Im''-01), respectively.

As is clear from Figure 3, the power consumption rate of 0 is the value when no pressure is equalized, Q, 75 (Kwh 71m”-
[lL55 (KWh
/Nl''-0!], and further improved to α351: Kwh/Nm'-0! after equalizing the pressure for 15 seconds.

〔Effect of the invention〕

As is clear from the above description and the results of the examples, the method of the present invention is an economically advantageous method that can improve the recovery rate of oxygen and reduce power consumption.

[Brief explanation of the drawing]

Fig. 1 is an illustration of an air separation device used to implement the method of the present invention, Fig. 2 is a graph showing the relationship between pressure equalization time and recovery rate of product or snow, and Fig. 3 is a graph showing the relationship between pressure equalization time and the recovery rate of products or snow. It is a graph showing the relationship with basic unit. Sub-Agents 1) Meifuku Agent Ryo Ogihara - Figure 1

Claims (1)

[Claims] At least two adsorption towers filled with the mineral name sodium faujasite, represented by Na-X, adsorb a gas mixture mainly consisting of oxygen and nitrogen at a pressure above atmospheric pressure and below 3 ata at a temperature below room temperature. The nitrogen contained in the mixed gas is selectively adsorbed into the column, and high-purity oxygen or oxygen-enriched gas is discharged from the outlet of the adsorption column, while the adsorption column that has adsorbed nitrogen is heated to a concentration of 0.08 ata or more. In a method for separating oxygen and nitrogen from a mixed gas under low temperature and low pressure conditions in which the pressure is reduced to 5 ata or less and regenerated, at least 6
N_2 adsorption tower after adsorption for more than seconds and N_2 after regeneration
A mixed gas characterized in that the recovery rate of product oxygen is improved by connecting the flow paths on the outlet side of the adsorption tower and transferring the product oxygen remaining at the rear of the tower after completion of adsorption to the N_2 adsorption tower after completion of regeneration. Method for separating oxygen and nitrogen from