JPS60155520A - Process for purifying carbon monoxide from mixed gas containing carbon monoxide gas by adsorption process - Google Patents

Abstract

PURPOSE:To obtain high-purity CO from a feed gas containing CO and N2, economically with simple process, by purging the product gas immediately after the adsorption process without using the evacuation and pressure-releasing process, and recovering the product gas. CONSTITUTION:The adsorption columns A and B containing adsorbent are evacuated to a prescribed vacuum, and the column A is pressurized by introducing feed gas composed of CO and N2. The mixed gas is passed continuously through the column A keeping the pressure in the column A, and when the purity of the outlet gas of the column becomes nearly equal to that of the inlet gas, the valves 1 and 3 are closed. The high-purity CO 11 obtained as the product is compressed 14 to a prescribed pressure and introduced into the column A through the opened valve 7, and the gas exhausted from the top of the column is recovered in the column B. After passing a specific amount of purge gas, the product gas is recovered from the column A. The cycle is repeated alternately in the columns A and B. The product gas recovered in the tank 11 is a high- purity CO composed of e.g. 99.2% CO and 0.8% N2.

Description

Detailed Description of the Invention The present invention provides a method for obtaining high-purity carbon monoxide from exhaust gas from a converter or blast furnace, or a raw material gas containing at least carbon monoxide and nitrogen, by a pressure fluctuation adsorption separation method (PSA method). Regarding.

The exhaust gas generated from the refining vessel in the vA ironworks contains a relatively large amount of CO gas. The composition of converter exhaust gas and blast furnace exhaust gas is within ti112Il as shown below.

COC02N2 82 Converter exhaust gas 60-87% 3-20% 3-20% 1-1
0% blast furnace exhaust gas 20-30% 20-30% 40-60
%1 to 10% If high-purity Co gas can be recovered at low cost from these exhaust gases, it can be used as a synthetic chemical raw material or as a gas to be blown into the molten metal in the R1#R container. When considering this Co gas as a raw material for synthetic chemicals, it is essential to remove oxidizing gases that can damage the reaction vessel, as the synthesis reaction is usually carried out under high temperature and high pressure conditions. It is necessary to reduce it as much as possible. In addition, in order to increase reaction efficiency, N, which does not normally participate in the reaction, is
It is desirable to remove 2 as much as possible. On the other hand, gas injection into a refining vessel for the purpose of improving the efficiency of refining molten metal is widely practiced, but from the viewpoint of not wanting to increase the concentration of impure gas components ('112, N2, etc.) in the molten metal. If high-purity Co gas can be recovered at a low cost from converter gas and blast furnace gas, which are generated in large quantities in steel plants, where expensive Ar gas is typically used, it is possible to replace it with Ar. be. At this time, high purity Co gas N2111
The temperature is desirably low from the viewpoint of preventing an increase in the nitrogen concentration of molten iron, and the CO29 temperature is also desirably low from the viewpoint of preventing oxidation of yAfFA in carbon-based refractories 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 Coso
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. Furthermore, in the cryogenic separation method, it is difficult to completely separate N2 and CO because the boiling points of N2 and CO are close to each other.

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

The above-mentioned adsorption separation using the adsorption method (PSA method) of exhaust gas is well known, and was developed in Japanese Patent Publication No. 38-239 for the purpose of recovering gas components that are difficult to adsorb to adsorbents (hereinafter referred to as difficult-to-adsorb components).
No. 28, No. 43-15045, etc. have been filed. In addition, there has been a long-standing method of separating easily adsorbable components with high purity by adsorbing gas components that are easily adsorbed onto an adsorbent (hereinafter referred to as "adsorbing components"), and then separating and recovering the gas components by adsorbing them onto an adsorbent. Examples include specific examples using ethylene as an easily adsorbed component and applications to nitrogen separation.

Conventional methods for recovering easily adsorbable components in a gas mixture by adsorbing them onto an adsorbent include operations of conventional methods. By repeating the adsorption pressurization process - reflux process - + B2B2 start in sequence, it is possible to extract a gas rich in easily adsorbable components to the adsorbent.

However, using conventional methods, it is difficult to remove nitrogen from a mixed gas containing carbon monoxide and nitrogen, gas components that tend to co-adsorb, such as the exhaust gas in this case, and collect and purify it as highly concentrated carbon monoxide.

The applicant has previously disclosed that at least N2 and CO or N2,
N is extracted from a mixed gas consisting of CO2 and CO by the PSA method.
An application was filed for a method for removing 2 (Patent application 1982
-159211). Prior application 15921/1986
In method No. 1, in order to increase the N2 removal rate,
After the adsorption process is completed, in addition to the depressurization/release process in which gas rich in difficult-to-adsorb components (N2, etc.) that are present in the voids in the adsorption tower without being adsorbed by the adsorbent is discharged to the outside of the adsorption tower, an even more difficult-to-adsorb process is performed. This method employs a purge process in which a product gas with a small amount of components is introduced to purge the components that are difficult to adsorb, and the process is complicated.

As a result of various studies, we found that even if we use a simple process of omitting the depressurization/pressure release process, performing product gas purification immediately following the adsorption process, and then recovering the product gas, we could achieve purity comparable to the method of the previous application. It was found that carbon oxide gas can be purified and separated.

The present invention provides a method for removing nitrogen from a raw material gas containing at least carbon monoxide gas and nitrogen gas by a pressure fluctuation adsorption separation method and recovering high purity carbon oxide gas. Using two or more adsorption towers containing @n agents having properties, the method is (I) pressurizing the adsorption towers with raw material gas, and (II)
Roughly feed the raw material gas into the adsorption tower until the concentration of easily adsorbed components (carbon oxide, etc.) at the outlet of the adsorption tower reaches the concentration of easily adsorbed components at the inlet of the adsorption tower, or after reaching the concentration of the easily adsorbed components (carbon oxide, etc.) Adsorption (I) step (III) in which the easily adsorbable components are adsorbed by the adsorbent by continuing to flow the raw material gas for a while, or by flowing the raw material gas until just before the point where the concentrations of both become equal. Product gas is introduced into the adsorption tower to purge difficult-to-adsorb components (nitrogen, etc.).
Purge step (IV) After the purge step, the adsorption tower is reduced to atmospheric pressure or nearly atmospheric pressure, and then evacuated to below atmospheric pressure to desorb the easily adsorbed components adsorbed on the adsorbent and release the product gas. and (V) the adsorption tower and other adsorption units after product gas recovery (I).
The present invention relates to a method characterized in that the adsorption towers that have completed the process are connected, the purge gas discharged in the purge process of the latter adsorption tower is connected, and the above operation is repeated by periodically changing the flow between the adsorption towers.

Step (I) 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, high adsorption pressure is not necessary, and Oka/
0112 ・It is fine if it is 0 or more, but generally 1 kg/c
An adsorption pressure of u+2 .G@degrees is sufficient, and a lower adsorption pressure may be used. The process of the present invention (I [> is adsorption (I> step). The point where the concentration of easily adsorbed components (such as CO) at the outlet of the adsorption tower becomes equal to the concentration of easily adsorbed components at the inlet of the adsorption tower means that This refers to the breakthrough point of the agent.The components to be recovered are easily adsorbed components, and in order to recover a sufficient amount of product gas with a predetermined amount of adsorbent, it is necessary to In addition, it is necessary to adsorb easily adsorbable components to adsorption sites remaining in the adsorbent, and even after breakthrough, it is necessary to not flow a certain amount of raw gas Φ or to flow raw material gas for a certain period of time. In some cases, it may be acceptable from the viewpoint of product gas purity to perform adsorption until just before the end of the process.

In the step <fir), the product gas is introduced into the adsorption tower that has completed the adsorption step (1), and the difficult-to-adsorb components (
N2, etc.). In this case, the introduction pressure of the product gas needs to be higher than the adsorption pressure, and the back pressure of the decompression exhaust equipment used in the product gas recovery process in step (IV) is not sufficient, so the product gas must be introduced with increased pressure. There is a must-drink. However, it is unlikely that the product gas will be used as a synthetic chemical raw material at the back pressure of the vacuum evacuation unit 11, and a pressure boosting system for that purpose will always be installed in the product gas system. With partial use, there is usually no need for an extra special boost system.

A relationship was found between the product gas m used in the purge process and the purity of the product gas recovered afterwards, which is not shown in Figure 1.As long as difficult-to-adsorb components are removed at a high level, conventional depressurization and depressurization processes Tl1a shows that it is possible to achieve the same product gas purity by using slightly more product gas than in a method that performs purge, and by operating based on this relationship, process simplification can be achieved.

Step (IV) is to reduce the pressure of the adsorption tower that has completed the purge step to atmospheric pressure or nearly atmospheric pressure, and then use a vacuum exhaust device such as a pneumatic pump, blower, ejector, etc. to reduce the pressure to below atmospheric pressure, preferably 300 Torr. A product gas recovery process in which components (such as Co) desorbed from the adsorbent during this process are recovered. At this time, the gas released from the adsorption tower at the beginning of the pressure reduction step may be diffused without being recovered. In this case, although the product gas recovery rate is slightly lowered, the purity of the product gas can be improved.

In step (V), a gas enriched with difficult-to-adsorb components and having a relatively high purity of easily adsorbable components is introduced into another adsorption tower that has finished product gas recovery, with respect to the product gas discharged in the purge step. This is an adsorption (I) step in which easily adsorbable components are adsorbed.

Adsorbents that can be used in the present invention include activated carbon, natural, modified or synthetic zeolites. 'Remove N2 from the converter exhaust gas, which is necessary in the following representative examples of the present invention,
Although the present invention will be described in detail based on a method for separating and recovering CO, the method of the present invention is not limited to these specific examples.

Figure 2 shows that N2, a component that is difficult to adsorb, is continuously removed from the converter exhaust gas through an adsorption cycle, and CO, an easily adsorbable component, is removed by 1 part.
111 [This is a flow sheet that shrinks 111.

Adsorption towers A and B house adsorbents that selectively adsorb easily adsorbable components. The adsorption towers A and B are evacuated using a vacuum pump or the like to a pressure of 300 Torr or less, preferably 300 to 30 Torr.
The raw material gas is now fed into the adsorption tower A from a reduced pressure state to a pressure increasing step by turning on valve 1. At this time, valves 2.3, 4, 5°6, 7.8.9.10.15.
The suction column B, in which all 16 are open, still maintains a reduced pressure state in this step. After increasing the pressure, adsorption term 8 changes from adsorption pressure kg/cm2-G to 3.0k (J/CIl+2-
Q, preferably 0.2+<g, 'am2- G to 2.
After adjusting the opening degree of the valve 3 to maintain the adsorption pressure of Oh/cm2-G, the raw material gas is introduced, and the gas rich in wax adsorption components is collected in the gas boulder 13. After a certain period of time or after the end of the rx deposition (I) process of a constant raw material gas m, close the raw material supply valve 1 and outlet valve 3, and then check the valve 7 to adsorb the product gas at the flow rate set by the flow m control valve 17. (I) Enters the step of purging the difficult-to-adsorb components present in the voids of the adsorbent by introducing it at a pressure higher than the pressure of the step.At this time, open the valve 5 at the same time or with a slight delay, and from the purge step. The discharged gas is collected in the adsorption tower B. Reference numeral 14 is a booster that increases the pressure of the product gas.After the purge process has been carried out for a preset time or after a predetermined amount of purge gas is supplied, valve 7. 5 is closed.Next, the valves 9 and 15 are opened to reduce the pressure in the adsorption tower A to atmospheric pressure, and the gas released during this time (including easily adsorbed components that are desorbed) is collected into the product gas tank 11, and further When the pressure in the adsorption tower A reaches atmospheric pressure, close the valve 15, close the valve 1G connected to the decompression exhaust equipment 12, and perform depressurization and exhaust to 300 Torr or less, preferably 30 Torr, to release a product gas rich in 00 minutes. By repeating the above operation sequentially 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, carbon monoxide mixed gas ( CO=9
0%, N2=10%) was attempted. As described above, the purification process was a cycle of "adsorption-purge-depressurization/exhaust-pressurization". The flow of the purification device is shown in FIG. Adsorption tower Δ.

B contains 0.51<g of modified mordenite zeolite activated at 350°C, and
Evacuate to Torr. Next, the -carbon oxide mixed gas is introduced into the adsorption tower A by listening to the valve 1, and the pressure of the adsorption tower A is set to 1. Okg/cn+2 ・G additional pressure is applied. Subsequently, valve 3 was opened, and the adsorption tower pressure was increased to 1.0 kO/c.
Flow the mixed gas continuously while maintaining m2 ・G. Valves 1 and 3 are closed when the purity of the gas at the outlet of the adsorption tower becomes approximately the same as the purity of the gas at the inlet.

Then, high purity CO gas (CO=
99.2%, N2 = o, g%) was pressurized to 2 kg/cm2 ・G using a pressurizing l1114, and introduced into the adsorption tower A by opening valve 7, and at this time, it was discharged from the top of the tower. The gas is recovered to the adsorption tower B by opening the valve 5. After flowing a predetermined purge gas, the valve 7.5 is closed, and the product gas is recovered from the adsorption tower A through the steps of (valve 9, 15) → (valve 15 closed, valve 16). Switching of valves 15 and 16 is done when the adsorption tower pressure is 0.0.
To 5! 17cm2 ・G, and exhaust is 40To
I went to rr.

The above cycle was repeated alternately in adsorption towers A and B. The raw material gas supplied per cycle of this process is 15.2
N y and C O recovered in the product gas tank 11
= 99.2%, high purity CO gas with N2 = 0.8% was more than 9.8N. However, since 3.7 N of the 9.8 N of product gas was used in the purge process, the apparent amount of product gas recovered was 6. INi, CO recovery rate is 44
．． It became 2%.

Example 2 In order to explain the present invention more specifically, a converter exhaust jj
(G O = 82.6%, CO2 = 5.7%, N
2=7.2%, 1-12=4.5%) was dehumidified and purified using the apparatus shown in FIG. 2. Adsorbent is 350
Synthetic zeolite activated at °C, MS-5A O,
5 kg/adsorption tower. Further, the exhaust pressure was increased to 85 Torr. In the refining process, the raw material gas supply amount per cycle was 17.4Nl, and the CO recovered in the product gas tank was 92
．． 8%, C02=6.4%, N2=0.8%, the product gas amount is 10. INl, the amount of product gas used in the purge process is 2.8Nl, and the apparent amount of product gas recovered is 8.2Nl.
The NCCO recovery rate was 52.9%. In this case,
CO2 is also an easily adsorbed component and is recovered in the product gas. High purity CO gas can be obtained by separately removing CO2.

Embodiments of the invention are as follows.

The present invention provides a method for purifying and separating carbon monoxide gas of high purity from a raw material containing at least carbon monoxide gas and nitrogen gas by pressure fluctuation type adsorption separation method, which has selectivity to carbon monoxide in the raw material gas. 2 containing adsorbent
Using two or more adsorption towers, the adsorption tower is pressurized with raw material gas, then the raw material gas is passed through the adsorption tower to cause the adsorbent to adsorb easily adsorbed components, and then the adsorption pressure of the adsorption tower or higher pressure is increased. Initially, an amount of product gas corresponding to the concentration of the poorly adsorbed component in the raw material gas and/or the desired product gas is introduced to reduce the amount of the poorly adsorbed component in the adsorbent volume void in the adsorption tower. - The adsorption tower is periodically depressurized to approximately atmospheric pressure, and then the gas rich in easily adsorbable components discharged from the adsorption tower is recovered as a product gas while the adsorption tower is depressurized to approximately atmospheric pressure and then evacuated to below atmospheric pressure. A method for purifying and separating carbon monoxide gas, which is characterized by repeating the process by changing the flow of gas between columns.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the amount of purge gas and the concentration of poorly adsorbed components in the product gas. In Figure 1, the “apparent amount of product gas recovered” is the “amount of gas recovered by reduced pressure exhaust” and the “no ξ
- the amount of gas. FIG. 2 is a flow sheet of a preferred apparatus for carrying out the invention. Patent applicant: Kawasaki Steel Corporation Osaka Sanso Kogyo Co., Ltd. (4 others) Figure 1

Claims (1)

[Scope of Claims] In 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, an adsorption agent having selective adsorption properties for carbon monoxide in the raw material gas Using two or more adsorption towers containing the agent, the method is (I) pressurizing the adsorption tower with a raw material gas,
(If) The raw material gas is further passed through the adsorption tower until the concentration of easily adsorbed components at the outlet of the adsorption tower reaches the concentration of easily adsorbed components at the inlet of the adsorption tower, or after that, the raw material gas is supplied for an appropriate gas period or time. The adsorption process (I [[
) Purge step (IV) in which product gas is introduced into the adsorption tower to purge difficult-to-adsorb components as soon as the suction @ (■) step is completed. After the purge step, the adsorption tower is reduced to atmospheric pressure or almost atmospheric pressure, and then A recovery process in which the gas is evacuated to a pressure below atmospheric pressure to desorb easily adsorbed components adsorbed on the adsorbent and recovered as a product gas, and (V) the adsorption column after product gas recovery and other adsorption (I).
The process consists of an adsorption (I) process in which the adsorption towers that have completed the process are connected and the purge gas discharged in the purge process of the latter adsorption tower is introduced into the former adsorption tower, and the flow between the adsorption towers is periodically changed. A method characterized by repeating the above operations.