JPH0573449B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] _The present invention uses a N _{2 adsorbent that selectively adsorbs N 2 from} a mixed gas mainly composed of O ₂ and N ₂ such as air _. O ₂ from the mixed gas as a component,
This paper relates to a method for improving the adsorption process in N ₂ separation. [Prior art] The adsorption separation method of O ₂ and N ₂ from air using an N ₂ adsorbent has the advantage that the equipment is small and simple and requires almost no operation, so the amount of O ₂ produced can be reduced. Ten
In recent years, the use of small and medium-sized devices with a capacity of about 3000 Nm ³ −O ₂ /h has been increasing, and replacement of cases in which liquid acid produced in cryogenic separation devices is transported and used is progressing. To give an overview of a typical device, the device consists of an air compressor, two or more N ₂ adsorption towers, and in some cases a vacuum pump. In this device, when compressed air is sent to one tower, the N ₂ in the air is adsorbed and removed by the N ₂ adsorbent filled, and the remaining high-pressure O ₂ flows out to the rear of the adsorption tower and is recovered. On the other hand, in other towers, the adsorbed N ₂ is released under reduced pressure conditions (sometimes a part of the product O ₂ is flowed in a countercurrent, or a vacuum pump is used to powerfully remove N ₂ ) for regeneration. This is repeated alternately to continuously separate O ₂ and N ₂ . The typical N ₂ adsorbent packed in the adsorption tower mentioned above was put into practical use by Union Carbide.
It is a 60-70% Ca exchanger of Na-A type zeolite, and selectively adsorbs N ₂ from a binary gas mixture of O ₂ and N ₂ , and co-adsorption of O ₂ under air conditions is Estimated to be less than 10% of _N2 adsorption. This adsorption-based O ₂ and N ₂ separation device is advantageous for small and medium-sized areas, as mentioned above, but it is not suitable for producing 1Nm ³ of O ₂ .
It requires 0.75 to 1Kwh, which is higher than the 0.45Kwh of O ₂ produced by large-capacity cryogenic separation.
Furthermore, it is said that there is little merit of scale for increasing the capacity of the equipment, and that it cannot compete with the cryogenic separation method in the region of 3000 Nm ³ -O ₂ /h or more. Therefore, various methods of improving these drawbacks can be considered, but when describing the improvement methods 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 low pressure, but since the amount of N ₂ adsorbed 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, although the amount of _N2 adsorption increases, the adsorption/desorption rate will decrease significantly, so On the contrary, the product O ₂ concentration will be lower than at room temperature. Also, as the temperature decreases
Since the amount of O ₂ co-adsorbed during N ₂ adsorption increases, the power consumption rate gradually increases. Therefore, the present inventor has developed a low-temperature solution that improves the above-mentioned drawbacks.
In the process of conducting intensive research and experiments on a high-performance separation method for O ₂ and N ₂ under low-pressure adsorption conditions, we discovered that Na-X
Sodium phaausiasite, a mineral represented by type zeolite, increases the amount of N ₂ adsorption under low temperature and low pressure adsorption conditions, and can maintain the N ₂ adsorption rate within a practical range, and is highly selective for N ₂ adsorption. We have already proposed an invention based on this in Japanese Patent Application No. 58-54626. In a two-column adsorption tower, at a temperature below room temperature, a gas mixture containing oxygen and nitrogen as main components is allowed to flow into the adsorption tower at a pressure above atmospheric pressure and below 3ata to selectively adsorb nitrogen contained in the gas mixture. , under low-temperature, low-pressure conditions, characterized in that high-purity oxygen or oxygen-enriched gas flows out from the outlet of the adsorption tower, while the adsorption tower adsorbing nitrogen is depressurized to 0.08 ata or more and 0.5 ata or less for regeneration. The present invention relates to a method for separating oxygen and nitrogen from a mixed gas. An embodiment of the above description will be explained below based on FIG. 2. In FIG. 2, air that has been pressurized to 1.05 to 3 ata by the compressor 2 through the inlet line 1 enters the dehumidifying and dehumidifying CO ₂ tower 4 through the flow path 3, 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 valve 7. The pressurized air that entered the adsorption tower 8 is N ₂ adsorbent 9
As N ₂ is adsorbed and removed, the O ₂ concentration increases as it moves toward the rear. The pressurized air is then recovered as product O ₂ through the open valves 10, 11, 12 and the product O ₂ tank 13 inserted between the valves 11, 12. On the other hand, the adsorption tower 8' is depressurized and drained by the vacuum pump 16 connected through the open valve 14' and the flow path 15, so that the N ₂ adsorbed by the adsorbent 9' in the adsorption tower 8' is removed. is easily separated and the adsorbent 9' is regenerated in a short time. The _N2 adsorbent 9 of the adsorption tower 8 is saturated, while the _N2 adsorbent 9' of the adsorption tower 8'
After the _N2 is removed and regeneration is completed, the inlet air flow path 6
By switching to 6' and performing the methods described so far alternately, product O ₂ can be continuously recovered. A heat exchanger 17 is installed between the clean pressurized air line 3' at the inlet and the gas line 15 whose main component is separated _N2 , and the product _O2 line 18 is connected to the flow path. 3', heat exchange is also possible with a heat exchanger 19. Furthermore, since a compression refrigerator 20 is installed in the flow path 3', the adsorption towers 8 and 8' are extremely efficiently cooled and set to a low-temperature condition. When switching the adsorption tower, it is important not only to simply switch from flow path 6 to 6' (or vice versa), but also to prevent the inlet air from blowing through due to pressure increase immediately after switching, and to In order to minimize the release of the O ₂ remaining at the rear and the pressurized air at the front out of the system, first, the valves 10 and 10' are fully opened to regenerate the O ₂ remaining at the rear of the adsorption tower 8 immediately after adsorption. A portion is transferred to the adsorption tower 8'. At this time, the pressure of adsorption tower 8 is set to Po
(ata) If the pressure of the adsorption tower 8' is P ₁ (ata), the pressure after pressure equalization will be approximately P ₀ +P ₁ /2 (ata). After this, the adsorption tower 8', which has reached approximately P ₀ + P ₁ /2 (ata), opens valves 10' and 11 to equalize the pressure of the product O ₂ tank 13 and the adsorption tower, and then increases the pressure of the adsorption tower 8' to an even higher pressure. Fill with _O2 . Pressure P ₂ (ata) when equalizing pressure with product O ₂ tank 13
is the dead volume of adsorption towers 8 and 8' (the volume of the space not occupied by adsorption in the adsorption tower), V ₁ (), and the product
Let the capacity of the O ₂ tank be V ₂ (), and the product O ₂ before pressure equalization
Assuming that the pressure in the tank 13 is approximately equal to P ₀ (ata), the equalized pressure P ₂ (ata) is approximately P ₂ P ₀ +P ₁ /2V ₁ +P ₀ V ₂ /V ₁ +V ₂ , which is simply the column From P ₁ (ata) when switching
Compared to _the rapid increase in pressure to _{P 0} (ata), _{the above} operation reduces _the
) Since the pressure is gradually increased, it is possible to prevent air from blowing through during pressure increase, and to minimize the release of residual O ₂ and high-pressure air from the system during the desorption process. Air separation was carried out using the air separation apparatus shown in FIG. 2 using the above operating method. The operating specifications of the device are shown in Table 1.

[Problem that the invention seeks to solve]

The present invention aims to solve the problem of reducing the power unit consumption in the above method. [Means for Solving the Problems] While investigating ways to reduce the power unit consumption in the above method, the present inventors discovered that the power consumption could be reduced by manipulating the method by which inlet air flows into the adsorption tower during the adsorption process. We found a remarkable way to reduce unit consumption. That is, the present invention provides at least two adsorption towers filled with sodium phaujasite, a mineral represented by Na-X, at a temperature below room temperature.
A gas mixture containing oxygen and nitrogen as main components is flowed into an adsorption tower at a pressure higher than atmospheric pressure and lower than 3ata to selectively adsorb nitrogen contained in the gas mixture, and high-purity oxygen or oxygen-enriched gas is produced from the outlet of the adsorption tower. In a method for separating oxygen and nitrogen from a mixed gas under low temperature and low pressure conditions, the adsorption tower that has adsorbed nitrogen is depressurized to 0.08 ata or more and 0.5 ata or less for regeneration.
During the adsorption process, the mixed gas is allowed to naturally flow into the adsorption tower up to atmospheric pressure, and then is heated to 3ata above atmospheric pressure by a compressor.
A method for separating oxygen and nitrogen from a mixed gas is provided, which is characterized by reducing the power consumption during oxygen production by introducing the oxygen and nitrogen under pressure. In the method of the present invention, inlet air is first allowed to naturally flow up to atmospheric pressure into the adsorption tower which is under reduced pressure at the beginning of the adsorption process, and then a compressor is used to raise the atmospheric pressure to 3 atm.
By dividing the operation into two steps: pressurized inflow below, the power cost for the compressor required to flow the mixed gas into the adsorption tower can be reduced compared to conventional O ₂ production methods. 93% _O2
When manufacturing, we were able to reduce the power consumption by approximately 12.5% compared to the conventional method. The apparatus for carrying out the method of the present invention is the apparatus shown in FIG. 1, but only needs to be provided with an air inlet and a flow path upstream of the dehumidification/removal CO ₂ tower 4 to bring the pressure to atmospheric pressure. Details are explained in the examples below. [Examples] Example 1 Using the air separation device shown in Fig. 2, O ₂ and N ₂ were removed from the air using a sodium phaujasite N ₂ adsorbent such as Na-X, according to the method of the present invention. Tried to separate. In Figure 2, the same symbols as in Figure 1 refer to the same parts, and the device in Figure 2 further includes an inlet air filter 21, a flow path 22, a valve 23, and dehumidification/CO A flow path 22' leading to _{the two} towers is provided. Atmospheric pressure inlet air passes through filter 21 and flow path 2
2. The air enters the dehumidifying and dehumidifying CO ₂ tower 4 through the open valve 23 and flow path 22', and becomes extremely clean air.
The valve 5 installed downstream of the flow path 3' is open, and clean air is naturally sucked to atmospheric pressure through the flow path 6 and the open valve 7 into the adsorption tower 8, which is previously in a reduced pressure state. . Approximately 4320Nm ³ /h at this time
of air enters the adsorption tower 8. After that, the valve 23 is closed, and the atmospheric pressure inlet air is passed through the inlet side line 1 to the compressor 2 at 1.2 ata.
The air pressurized _to
The air enters the air and becomes extremely clean pressurized air. Channel 3'
Valve 5 installed in the wake of is open,
Clean pressurized air flows through the flow path 6 and the open valve 7,
It enters the adsorption tower 8 through. Approximately 6560Nm ³ /h at this time
of air enters the adsorption tower 8. The pressurized air that has entered the adsorption tower 8 has N ₂ adsorbed and removed by the N ₂ adsorbent 9, and the O ₂ concentration increases as it moves toward the rear. After this, the pressurized air is transferred to the open valves 10, 11, 12 and the product O ₂ tank 13 inserted between the valves 11, 12.
The product O ₂ with an O ₂ concentration of 93% is approximately 1600Nm ³ /h.
It will be collected. On the other hand, in the regeneration step, the same operations as in the regeneration step of the conventional method are performed. Air separation was performed using the above operating method. The operating specifications of the device are shown in Table 2.

【table】

[Table] O ₂ and N ₂ were separated from air under the operating conditions shown in Table 2. Table 3 summarizes the comparison of experimental results between the conventional example shown in FIG. 2 and Table 1 and the embodiment of the present invention shown in FIG. 1 and Table 2.

〔Effect of the invention〕

As explained in detail above, the present invention proposes a method for improving the adsorption process in the separation of oxygen and nitrogen from a mixed gas, which requires less power consumption than conventional methods and is very useful industrially. It is something.

[Brief explanation of the drawing]

FIG. 1 is an illustration of an air separation apparatus used to carry out the method of the present invention, and FIG. 2 is an illustration of an air separation apparatus used to carry out the conventional method.

Claims (1)

[Claims] 1 In at least two adsorption towers filled with the mineral name sodium phaujasite represented by Na-X, a mixed gas containing oxygen and nitrogen as main components is heated 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 by flowing into an adsorption tower, and high-purity oxygen or oxygen-enriched gas is discharged from the outlet of the adsorption tower, while the adsorption tower that has adsorbed nitrogen is heated to a temperature of 0.08 ata or more to 0.5 ata. In the following method for separating oxygen and nitrogen from a gas mixture under low temperature and low pressure conditions where the gas is depressurized and regenerated, the gas mixture is allowed to flow naturally into an adsorption tower up to atmospheric pressure during the adsorption process, and then is compressed into a compressor. A method for separating oxygen and nitrogen from a mixed gas, characterized by reducing power consumption during oxygen production by pressurizing the inflow at a pressure above atmospheric pressure and below 3ata.