JPS60155519A - Process for purifying carbon monoxide from mixed gas containing carbon monoxide using adsorption process - Google Patents

Abstract

PURPOSE:To recover high-purity CO from feed gas containing CO and N2, economically with simple process, by using a plurality of adsorption columns each containing an adsorbent having selectivity to CO, and discharging the gas rich in hardly adsorbable component which has hitherto been recovered with an adsorption column. CONSTITUTION:The adsorption columns A and B are packed with an adsorbent and evacuated 12 to a prescribed vacuum. The column A is supplied with a mixture of CO and N2 by opening the valve 1, and the pressure in the column is adjusted to a prescribed level. The valve 3 is opened, and the mixed gas is passed through the column for a period longer than the time necessary to get the CO purity of the outlet gas equal to that of the inlet gas of the column A by a prescribed time. The inlet valve 1 is closed, and the gas left in the space in the column A is discharged from the column and recovered 13. When the pressure in the column A approaches the atmospheric pressure, the product gas is pressed into the column A to expel the gas left in the space in the column A to the column B. After the completion of the purging process, the CO gas which is an easily adsorbable component adsorbed to the adsorbent is desorbed by evacuating the column A, and recovered 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for obtaining high-purity carbon monoxide from a raw material gas containing at least carbon monoxide and nitrogen, exhaust gas from a converter or blast furnace, etc., using a pressure fluctuation adsorption separation method (CPSA method). .

Exhaust gas generated from refining vessels in steel plants contains a relatively large amount of Co 2 gas. The composition of converter exhaust gas and blast furnace exhaust gas is within the range shown below.

COCO2N2N2 Converter exhaust gas 60-87% 6-20% 6-20%
1-10% blast furnace exhaust gas 20-60%20-60%40
~60% 1-10% If high-purity GO gas can be recovered at low cost from these exhaust gases, it could be used as a raw material for synthetic chemicals or as a gas to be blown into the molten metal in the smelting vessel. When considering gases, it is essential to remove oxidizing gases that can damage the reaction vessel, as synthesis reactions are usually carried out under high temperature and high pressure conditions, and it is necessary to reduce the GO2a degree as much as possible. be. Furthermore, in order to increase reaction efficiency, it is desirable to remove as much N2 as possible, which normally does not participate in the reaction. On the other hand, gas injection into the smelting vessel is widely carried out for the purpose of improving the efficiency of smelting molten metal. Usually, expensive Ar gas is used.

If high-purity Co 2 gas can be recovered at low cost from converter gas and blast furnace gas generated in large quantities in steel plants, it is possible to replace it with Ar 2 . At this time, the N2 concentration of the high-purity CO gas is kept low to prevent an increase in the nitrogen concentration of the molten iron.
T is desirable, and the CO2 concentration is also desirable to be low from the viewpoint of preventing oxidative damage to carbon-based refractories, which are commonly used as refractory linings for refining vessels.

Conventionally, the processes for recovering high-purity CO gas using the above-mentioned exhaust gas as raw materials include the cryogenic separation method, the liquid preparation method, and the Ca5O
Solution absorption methods such as the rb method are being considered. However, the former requires low temperature and high pressure, and the latter requires high temperature and high pressure, and both have the drawback that the equipment is complicated and expensive. In addition, in the cryogenic separation method, N2 and Go
It is also difficult to completely separate N2 and CO because their boiling points are close to each other.

In view of the above-mentioned current situation, the present inventors attempted to develop an adsorption method as a technique for recovering high-purity Go gas at low cost through a simpler process.

The above-mentioned adsorption separation using the adsorption method (PSA method) is well known, and was developed in Japanese Patent Publication No. 38-239 for the purpose of recovering gas components (hereinafter referred to as difficult-to-adsorb components) that cannot be adsorbed onto an adsorbent.
28.43-15045, etc. have been filed. or,
A method of separating easily adsorbed components with high purity by adsorbing gas components that are easily adsorbed onto an adsorbent (hereinafter referred to as easily adsorbed components) and separating and recovering them by desorption has also been practiced for a long time.

For example, there are specific examples of using ethylene as an easily adsorbable component and its application to nitrogen separation.The conventional method of recovering easily adsorbable components in a gas mixture by adsorbing them onto an adsorbent does not include the operations of ordinary methods. It is something. By sequentially repeating the adsorption pressurization process, the reflux process, and the desorption process, it is possible to take out the gas that has been refined into easily adsorbable components by the adsorbent.

However, using conventional methods, it is difficult to remove VX from a mixed gas containing carbon monocarbon and nitrogen, gas components that are easy to co-adsorb, such as the exhaust gas in this case, and recover and refine it as highly concentrated carbon monoxide.

The applicant previously proposed that a small amount (both N2 and CO or N2, C
N2 is extracted from a mixed gas consisting of O2 and CO by the PSA method.
filed an application for a method to remove the
7-159211). This prior application 1977-159
When carbon monoxide is concentrated from the mixed gas in No. 211,
Nitrogen removal was insufficient and the concentration of carbon monoxide could not be increased sufficiently. As a result of various studies, we found that it is easier to purify, separate and concentrate high-concentration carbon dioxide by disposing of the gas containing a relatively large amount of difficult-to-adsorb components during the depressurization process, which was conventionally collected in other adsorption towers. It turns out that it can be done economically.

The present invention relates to a method for recovering high-purity carbon oxide gas by removing nitrogen from a raw material gas containing carbon oxide gas and aqueous gas by a pressure fluctuation type adsorption separation method. Using two or more adsorption towers containing adsorbents having selectivity 7al- to Continue to flow the raw material gas for an appropriate amount of gas or time until or after reaching the point where the easily adsorbed component at the adsorption tower outlet reaches the easily adsorbed component at the adsorption tower inlet, or until the concentration of both becomes equal. Adsorption (I+ step) in which the raw material gas is passed for a short while to cause the adsorbent to adsorb easily adsorbable components.

(iii) Adsorption (depressurization step (1v) to reduce the pressure of the adsorption tower after the completion of step 11) Product gas is introduced into the depressurized adsorption tower to purge the difficult-to-adsorb components. a-ji step, (V) purge step (vl) A recovery process in which the adsorption tower after the product gas recovery is evacuated to below atmospheric pressure to desorb easily adsorbed components adsorbed by the adsorbent and product gas is recovered; It consists of an adsorption Cl11 step in which the adsorption tower after the process is connected and the purge gas from the latter adsorption tower is introduced into the former adsorption tower, and the above operation is repeated by periodically changing the flow between the adsorption towers. Regarding the characterized method.

Step (1) of the present invention is a 0-pressure step of the adsorption tower in which a raw material gas is introduced into the adsorption tower. In the present invention, since the gas to be recovered is an easily adsorbed component, high adsorption pressure is not necessary (,
An adsorption pressure of about 6 kg/crA-G is sufficient, and a lower adsorption pressure may be used.

Step (11) of the present invention is an adsorption (1) step. The point at which the concentration of easily adsorbed components (such as Go) at the outlet of the adsorption tower becomes equal to the concentration of easily adsorbed components at the inlet of the adsorption tower means the end of breakthrough of the adsorbent. The component to be recovered is an easily adsorbed component, and in order to recover a sufficiently large amount of product gas under a predetermined amount of adsorbent, it must remain in the adsorbent at the end of breakthrough or even after the end of breakthrough. It is necessary to adsorb easily adsorbable components to adsorbent zyte, and it is necessary to flow a constant amount of raw material gas or to flow raw material gas for a certain period of time even after breakthrough ends.Or until shortly before reaching the end of breakthrough. Even if only adsorption is performed, it may not be a problem from the viewpoint of product gas purity.

Step (11) is carried out to reduce the pressure inside the adsorption tower after the adsorption step and to dispose of the difficult-to-adsorb components in the gap between the adsorbent and the adsorbent outside the adsorption tower. In this case, adsorption pressure (cage pressure) It is preferred to discard the gas until the pressure is reduced to between 1 and 4 degrees.

In the step (IVI), the product gas is introduced into the adsorption tower under reduced pressure to purge the poorly adsorbed component (N2) remaining in the adsorption tower.In this case, the introduction pressure of the product gas is lower (or higher) than the adsorption pressure. It is desirable that the pressure be higher than the atmospheric pressure, and in this case there is no need to use a pump or the like, and purging can be carried out by connecting the product gas tank and the adsorption tower.

In step (v), the adsorption tower after the ξ-di step is evacuated using a vacuum evacuation device such as a vacuum pump, floor, or ejector.
00 Torr or less, preferably 300 to 30'rorr
The pressure is reduced to 100%, and the components (Co gas, etc.) adsorbed on the adsorbent are desorbed and recovered as product gas.

In step (vl), the adsorption tower that has completed product gas recovery and the adsorption tower that has completed the pressure reduction process are connected, and the gas discharged in the purge process of the latter adsorption tower is introduced into the former adsorption tower to facilitate adsorption. Adsorb the components onto an adsorbent.

Adsorbents that can be used in the present invention include activated carbon and those based on natural, modified or synthetic zeolites.

The following is a typical example of the present invention, N2 in converter exhaust gas.
Although the present invention will be described in detail based on a method of removing 1 N2 and separating and recovering CO, the method of the present invention is not limited to these specific examples.

Figure 1 shows N2, a component that is difficult to adsorb, continuously extracted from the converter exhaust gas through an adsorption cycle. Removes N2 and removes CO, an easily adsorbed component.
Adsorption towers A and B, which are probably flow sheets for separating and concentrating the substances, contain adsorbents that selectively adsorb easily adsorbable components.

Exhaust adsorption towers A and B under reduced pressure using a vacuum pump, etc. to 300 To
rr or less, preferably in the range of 00 to 3 Q Torr, and the raw material gas is now fed into the adsorption tower A from a reduced pressure state to a pressure increasing step by opening the valve 1. At this time, pulp 2.
3. 4゜5, 6. '7. 8. ”9.10
are all closed.

Adsorption tower B is still maintained at reduced pressure in this step. After increasing the pressure in adsorption tower A, the adsorption pressure is 0.019/c.
a G to 6. Q kg/art G, preferably to 0.2! 9/crlG to 2.0 kg/cnt
The valve 6 is opened to maintain the adsorption pressure of G, and the acid adsorbed gas is collected in the gas holder 16. The internal pressure of the column is reduced to atmospheric pressure. When the pressure in adsorption column A reaches atmospheric pressure, close valve 6, then open valve 5 on the connection pipe to adsorption column B, and then open valve 7. Then, the product gas enters the process of purging the difficult-to-adsorb components in the voids during the adsorption period in the adsorption tower AK at atmospheric pressure or at a pressure slightly higher than atmospheric pressure (product gas tank pressure).In the purge process, the adsorption tower The gas discharged from A is recovered to adsorption tower B via valve 5. After the purge amount reaches a pre-calculated product gas amount or after a certain period of time, valve 5.7 is closed. Then, valve 9 is closed. In order to desorb the easily adsorbed components adsorbed on the open adsorbent, the vacuum exhaust device 12 is used to reduce the pressure to 30' O Torr, preferably 60 Torr.
The product gas, C0, is recovered by evacuation to a reduced pressure.

By sequentially repeating the above operation in each adsorption tower, it is possible to continuously separate CO gas, which is a component easily adsorbed onto the adsorbent.

Example 1 Based on the method of the present invention, a carbon mixed gas (GO=9
1.2% N2 = 8.8%) was attempted.

As mentioned above, the purification process is ``adsorption-depressurization (co-current)--
It was carried out based on the purification cycle of ξ-di (co-current)-vacuum evacuation (counter-current)-pressurization (co-current).

Activated zeolite (0.5kg, 1/8R let)
After evacuating the stainless steel adsorption tower filled with water and maintaining the vacuum at 6 Q Torr, the above mixed gas (
Co = 91.2% N2 = 8.8%) at a linear speed of 2c
The mixed gas was purified by introducing it from the bottom of the column using an mZ tank (required time for purification was approximately 6 minutes).In this case, the amount of purified carbon oxide gas was 4.67N7 for the amount of supplied gas of 13.15NA. , Co recovery rate is 39
%-carbon oxide purity was greater than 99%.

Details of this embodiment are as follows. In the flow shown in Fig. 1, 0.5 kg of modified mordenite-based zeolite activated at 350°C is stored in adsorption towers A and B, respectively, and evacuated to 6 (] T'orr by vacuum pump 12.-
Carbon oxide mixed gas (Go = 91.2% N2 = 8.8
%) valve (1) was opened, the adsorption tower (Al was introduced into the tower, and the pressure inside the tower was set to 1.0 kl?/dG. Furthermore, as part of the adsorption process, the adsorption tower outlet valve 6 was opened, and the adsorption tower outlet gas From the time when the CO line purity becomes the same as the CO purity of the inlet gas, y is 2NA? When the extra mixed gas was flowed, the feed gas supply was controlled so that the adsorption column pressure was 1.0 kg/cr4.Next, , the adsorption tower inlet valve 1 is closed, and the void gas accumulated in the voids (between the adsorbents) of the adsorption tower A is disposed of outside the tower and collected in the waste gas tank 16. When the internal pressure of the A tower is close to atmospheric pressure < (0.02kg10+ !G) Become Valve 6
Close the valve (7) installed between the product gas tank and tower A, and open the adsorption tower outlet valve (5) to transport the product gas (-carbon oxide) from the product gas tank at the pressure of the product gas tank to the adsorption tower (n). Next, a purge step is started in which the gas remaining in the gaps between the adsorbents without being adsorbed by the adsorbents is expelled to the adsorption tower CB+ at atmospheric pressure.

When this purge process is completed, valves (5) and (7) are closed, and at the same time the adsorption tower inlet side (lower part) and the vacuum pump (12
Open the valve (9) installed in the pipe connecting the
The gas was desorbed from the adsorption tower (8) while being evacuated from atmospheric pressure to 6 Q Torr, and collected in the product tank.

Example 2 Below, in order to explain the present invention more specifically, CO2
Converter exhaust gas (C02=88%, C03=0.
2%, N2-76%, N2=4.2%). N2
Remove and Go minute 1tl#:#reduce the ivy example.

In the flow shown in Fig. 1, 0.5 kg of synthetic zeolite (MS-5A) activated at 650°C is stored in adsorption towers A and B, respectively, and evacuated to 60 Torr with vacuum pump α2. 11 is opened to introduce the converter flue gas, which has already been dehumidified and removed Co2, into the adsorption tower A, and the pressure inside the tower is increased to 1.5k.
g/cF! In addition, as an adsorption step, the adsorption tower outlet valve 6 is opened, and the raw material gas is continued to flow until the adsorption tower outlet gas purity becomes y the same as the inlet gas purity.This removal tower pressure is 1. The raw material gas supply was controlled to maintain 5 kg/cr/lGt.When the CO line purity of the gas at the outlet of the adsorption tower and the CO line purity of the gas at the inlet, the inlet valve 1
The adsorption tower (A) is closed and the void gas accumulated in the Al voids (between the adsorbents) is disposed of outside the tower.
/CdCx ), the pulp 6 is closed and the pulp 7 and adsorption tower outlet valve 5 installed between the product gas cylinder 11 and the A tower are opened to allow the product gas (CO
) is introduced into the adsorption tower (Al) at the pressure of the product gas tank, and the remaining gas that has not been adsorbed by the adsorbent is forced into the adsorption tower (Bl) into the voids between the adsorbents at atmospheric pressure. When the process is completed, pulps 5 and 7 are closed, and at the same time, pulp 9, which connects the adsorption tower inlet side (lower part) and Makabe Honzo 12, is opened, and Go and Co2 gases, which are easily adsorbed components adsorbed by the adsorbent, are removed. was desorbed while evacuating the adsorption tower A from atmospheric pressure to 60 TOrr and collected in the product gas tank 11.

At this time, the amount of gas collected in the product gas tank 11 is 5.
At 55 Nl, the gas concentration was 991% GO.

At this time, the converter exhaust gas supply amount was 15.5 Nl, the purge gas amount was 0.69 Nl, and the recovery rate of CO that could be used as a product was 41%.

The embodiments of the present invention are as follows.

The present invention provides a method for purifying and separating carbon monoxide gas of high purity from a mixed gas containing at least carbon monoxide gas and nitrogen gas by a pressure fluctuation type adsorption separation method. Using two or more adsorption towers containing an adsorbent having the following properties, the adsorption tower is pressurized with a raw material gas, the raw material gas is then flowed through the adsorption tower to cause the adsorbent to adsorb easily adsorbed components, and then the inside of the adsorption tower is The pressure is reduced and the gas released during this time is not introduced into another adsorption tower, and then the product gas is introduced into the adsorption tower to purge the poorly adsorbed components in the adsorbent volume voids in the adsorption tower. At the same time, the purge gas discharged from the adsorption tower is introduced into another adsorption tower that has completed product gas recovery and is adsorbed onto easily adsorbable components and adsorbents, and then the adsorption tower that has completed purging is evacuated to below atmospheric pressure. Purification of high-purity carbon oxide gas characterized by periodically changing the gas flow between the adsorption towers and repeating the operation of recovering gas rich in easily adsorbable components discharged from the adsorption tower as a product gas. Regarding separation method.

The first step of the present invention is an adsorption tower pressurization step in which a raw material gas is introduced into the adsorption tower. In the present invention, since the gas to be recovered is an easily adsorbed component, a high adsorption pressure is not required, and 6 kg/
An adsorption pressure of approximately cIIL2G is sufficient, and an adsorption pressure lower than that may be sufficient.

The second step of the present invention is the adsorption (I) step. This step is preferably continued until around the breakthrough point of the adsorbent, at which the concentration of easily adsorbable components (such as CO) in the gas at the outlet of the adsorption tower becomes equal to that in the gas at the inlet of the adsorption tower. The components to be recovered are easily adsorbable components, and in order to recover a sufficient amount of product gas with a given amount of adsorbent, adsorption sites that remain on the adsorbent even after breakthrough or after breakthrough are necessary. It is necessary to adsorb easily adsorbable components to the reactor, and it is necessary to flow a constant amount of raw material gas or to flow raw material gas for a certain period of time even after the breakthrough is completed. Alternatively, there may be fewer problems in terms of product purity even if the adsorption is carried out until just before the breakthrough point is reached.

The third step of the present invention is to reduce the pressure inside the adsorption tower after the adsorption (I) step and to dispose of the gas rich in difficult-to-adsorb components in the gap between the adsorbent and the adsorbent to the outside of the adsorption tower. Let's do it.

In this case, the gas released during the pressure drop to (at least) 10 to 10 times the adsorption pressure in gauge pressure is discarded without being introduced into another adsorption tower.

In the fourth step of the present invention, the product gas is introduced into the adsorption tower under reduced pressure, and the gas rich in difficult-to-adsorb components (such as N2) remaining in the adsorption tower is purged. In this case, the introduction pressure of the product gas is preferably lower than the adsorption pressure and higher than atmospheric pressure, and in this case there is no need to use a pump, etc., and purging can be performed each time the product gas tank and adsorption tower are connected.

In the fifth step of the present invention, the adsorption tower after the purge step is heated to 500 Tovr or less, preferably 600 to 30 Tovr using a vacuum pump, blower, ejector, etc.
The pressure is reduced to Tovr, and easily adsorbed components adsorbed on the adsorbent are desorbed and recovered as a product gas.

The process accompanying the fourth step is to connect the adsorption tower after product gas recovery and the adsorption tower after the pressure reduction process, and introduce the gas discharged in the purge process of the latter adsorption tower into the former adsorption tower. The easily adsorbable component is then adsorbed onto the adsorbent.

Adsorbents that can be used in the present invention include activated carbon and those based on natural, modified or synthetic zeolites.

[Brief explanation of the drawing]

The figure is a flow sheet of a preferred apparatus for carrying out the invention. Patent applicant Kawasaki Steel Corporation Osaka Sanso Kogyo Co., Ltd.-1 (4 others)

Claims (1)

[Claims] A method for removing nitrogen gas from a raw material gas containing at least carbon monoxide gas and nitrogen gas by a pressure fluctuation adsorption separation method, which provides selectivity to carbon monoxide in the raw material gas. The method is as follows: (1) pressurizing the adsorption tower with a raw material gas;
(11) Furthermore, the raw material gas is passed through the adsorption tower until the concentration of the easily adsorbed component at the outlet of the adsorption tower reaches the concentration of the easily adsorbed component at the inlet of the adsorption tower, or for an appropriate amount of gas or time after reaching the concentration of the easily adsorbed component at the inlet of the adsorption tower. Adsorption (1) step in which the easily adsorbed components are adsorbed by the adsorbent by continuing to flow the raw material gas or by flowing the raw material gas until just before the point where the roughness of both becomes equal; (1v) Purge step to introduce the product gas into the reduced pressure adsorption tower to remove difficult-to-adsorb components; M After the purge step, the adsorption tower is evacuated to below atmospheric pressure and the adsorption A recovery step in which adsorbed easily adsorbable components are desorbed and product gas is recovered, and (vl) an adsorption tower in which product gas recovery has been completed is connected to an adsorption tower in which another pressure reduction step has been completed, and the latter adsorption tower is An adsorption (■) step in which the purge gas from the previous adsorption tower is introduced into the former adsorption tower.A method characterized by periodically changing the flow between the adsorption towers and repeating the above operation.