JPH0149643B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for separating and recovering high-purity CO from a mixed gas containing carbon monoxide (CO) by a pressure swing method using a specific adsorbent. Conventional technology As a typical gas whose main component is CO,
Examples include converter gas obtained from a converter in a steel mill, blast furnace gas obtained from a blast furnace, electric furnace gas obtained from an electric furnace, and generator gas obtained by gasifying coke. Most of these gases are normally used as fuel, but some of these gases contain around 70 vol% or more of CO, so the CO contained in these gases is If it can be obtained in high purity, it can be used as a raw material for the synthesis of formic acid, acetic acid, etc., and for the reduction of organic compounds, and is very useful in the chemical industry. Conventionally, cryogenic separation methods, copper ammonia methods, and COSORB methods are known as methods for separating and recovering CO from a gas whose main component is CO, but these methods require high equipment costs and electricity,
There is a problem in that the cost of thermal energy such as steam is high, and although it is suitable for separating and recovering large volumes of CO, it is not necessarily suitable for separating and recovering medium or small volumes of CO. Furthermore, the CO obtained by separation by these methods contains gas components such as oxygen and carbon dioxide that are a hindrance to organic synthesis reactions, so they have the disadvantage that they cannot be used as they are for organic synthesis. Incidentally, a pressure swing method is known as a method for selectively separating a specific gas from a medium or small volume of source gas. The pressure swing method is one of the methods for selectively separating a specific gas from a mixed gas.It adsorbs the adsorbent onto an adsorbent at high pressure, and then lowers the pressure of the adsorption system to release the adsorbent into the adsorbent. This is a method of desorbing adsorbed substances and separating adsorbed substances and non-adsorbed substances. Conventionally, such a pressure swing method uses a mordenite-based zeolite as an adsorbent (Japanese Patent Laid-Open No. 59-22625) , Japanese Patent Publication No. 1983
-49818 Publication), a method using copper halide () or copper halide and aluminum halide () supported on activated carbon or polystyrene particles as an adsorbent (Japanese Unexamined Patent Publication No. 58-49436, 58−
104009, JP-A-58-124516, JP-A-58-156517, etc.) have been proposed. Problems to be Solved by the Invention However, the method using mordenite-based zeolite as an adsorbent utilizes physical adsorption/desorption phenomena, and because the amount of CO adsorption is relatively small, the pressure swing is switched frequently. This is disadvantageous in terms of operation and valve life; CO ₂ must be removed before adsorption operation; and nitrogen (N ₂ )
The purity is low because of the adsorption of N2, and when cleaning the inside of the tower using product CO gas to remove the adsorbed _N2 , the amount of cleaning is large, resulting in a low recovery rate of product CO. There was a problem. In addition, the method using a carrier on which copper halide () or copper halide and aluminum halide () are supported is a method that uses carbon dioxide (CO ₂ ) or N ₂
This method is considered to be more effective than the method using mordenite-based zeolite as an adsorbent in that CO can be separated and recovered even in systems where CO coexists.
A system in which this method can be applied on an industrial scale has not yet been achieved. The present invention is an investigation into a method for separating and recovering high-purity CO from a mixed gas containing CO as a main component using a pressure swing method, and it is an industrially efficient method for producing high-purity CO suitable for organic synthesis. The purpose of this is to provide a method for obtaining the desired information. Means for Solving the Problems The present invention provides a method for separating and recovering high-purity carbon monoxide from a mixed gas containing carbon monoxide by a pressure swing method using a plurality of adsorption towers filled with adsorbents. As an agent, a carbon monoxide selective adsorption solid adsorbent in which copper halide () or copper halide and aluminum halide () are supported on a carrier that does not have a molecular sieving action is used; The operation is carried out in each adsorption tower by: (1) flowing the raw material gas into the adsorption tower to adsorb carbon monoxide gas; and determining whether the concentration of carbon monoxide in the exhaust gas is equal to the concentration of carbon monoxide gas in the raw material gas. (2) After the adsorption process is completed, the adsorption tower is connected to the adsorption tower that has completed vacuum deaeration, and the pressure in the former adsorption tower is increased. (3) A part of the product gas is introduced cocurrently into the depressurized adsorption tower to reduce the pressure inside the tower. A cleaning process to clean residual impurity gas, and a process to use the gas discharged at this time to boost pressure in other columns (4) Vacuum depressurization to remove carbon monoxide gas adsorbed by the adsorbent. (5) Connecting the adsorption tower that has completed product recovery with the adsorption tower that has completed the adsorption process, and pressurizing the former adsorption tower to parallel flow. Pressurization () step, (6) Pressurization () step in which the pressure is increased in parallel flow using the washed exhaust gas from other adsorption towers, (7) Pressure raising () step in which the pressure is increased by the exhaust gas near the end of the adsorption process from other adsorption towers, in sequence. A method for separating and recovering high-purity carbon monoxide from a mixed gas containing carbon monoxide, which is characterized by repeated steps. By using a solid adsorbent and performing the pressure swing process according to a specific process, the above-mentioned conventional problems have been completely solved. In particular, the exhaust gas near the end of the adsorption process is used to boost the pressure of other columns, making it less likely that the pressure balance of the entire process will be disrupted, and the recovery rate is high because the exhaust gas is used without being discarded. One of the features of the present invention is that the exhaust gas pressure can be used effectively. As the mixed gas containing CO that can be applied to the method of the present invention, for example, converter gas generated from a converter in a steel mill is used. Converter gas usually contains CO as its main component, as well as oxygen (O ₂ ), methane and other hydrocarbons, water, and small amounts of hydrogen sulfide (H ₂ S).
Contains ammonia (NH ₃ ), etc. In addition to converter gas, blast furnace gas, electric furnace gas, generator gas, etc. can also be used as raw material gas. As the CO selective adsorption solid adsorbent, copper halide (2) or aluminum halide (2) supported on a carrier having no molecular sieving action is used. Examples of copper halides include copper chloride (), copper fluoride (), copper bromide (), and copper () compounds treated with reducing gases are also used. Aluminum halides () include aluminum chloride,
Examples include aluminum fluoride and aluminum bromide. Activated carbon and polystyrene particles are preferably used as the carrier, but inorganic carriers such as silica and/or alumina can also be used. However, porous materials having a molecular sieving action such as zeolite are not suitable for the purpose of the present invention. The adsorption phenomenon caused by the CO selective adsorption solid adsorbent mentioned above is mainly caused by copper halide () supported on a carrier or aluminum halide (aluminum halide) supported on the carrier.
It is based on a reversible chemical reaction between N ₂ and CO 2 (chemical reaction with N 2 and CO ₂ does not occur), and secondary physical adsorption onto the pore surface of the carrier and desorption from there. It is based on separation. In other words, basically, the chemical reaction is CO + copper halide () CO / copper halide (), that is, CO and copper halide ()
This method takes advantage of the fact that the complex formation reaction and dissociation reaction with the molecule proceed reversibly by changing the reaction pressure. By performing the following adsorption cycle using the above CO selective adsorption solid adsorbent, high purity can be obtained.
CO could be separated and recovered extremely efficiently. In addition, in the present invention, prior to the CO separation and recovery process by pressure swing as detailed below,
Adsorption and removal step of impurities such as sulfur compounds and _NH3 , which may poison the CO selective adsorption solid adsorbent or shorten its lifespan;
It is particularly preferred to provide a moisture removal step and an O ₂ removal step. However, it is not enough to provide a CO ₂ removal process or a N ₂ removal process. Adsorption cycle Figure 1 shows a diagram of a device that continuously separates and recovers CO from a mixed gas containing CO using four adsorption towers, where A, B, C, and D are the adsorption towers,
1A...5A, 1B...5B, 1C...5C, 1D...5
D and 6 are both valves, E is a vacuum pump, and F is a product CO tank. An example of an adsorption cycle is shown in Table 1 below.

[Table] * "Deaeration process" means "deaeration (product recovery)." Adsorption towers A, B, C, and D are filled with a CO selective adsorption solid adsorbent. The dehumidified, desulfurized compound and deammoniated converter gas is supplied to the adsorption tower A through the valve 1A at atmospheric pressure to 6 Kg/cm ² G, preferably 1 to 6 Kg/cm ²
The gas is supplied at a pressure of G, and the CO adsorption process is carried out. The adsorption pressure is 6Kg/cm ²
Near G, the reaction of CO + copper halide () → CO and copper halide () reaches a stoichiometric equilibrium point, so if the pressure is increased any further, impure gases (CO ₂ , N ₂ , etc.)
Only the physical adsorption of CO increases, making it difficult to obtain high purity CO. At this time, the valve 2A is open and unadsorbed gas is being discharged. Valve 3A, 4
A, 5A is closed. The outlet gas of the column A just before the end of the adsorption step is supplied to the column C through valves 6 and 3C, and is used to raise the pressure of the column C ( ), in preparation for the next adsorption step of the column C. In adsorption tower B, vacuum pump E operates valve 5.
A product recovery process is carried out to degas the CO gas adsorbed through B. The degree of vacuum at this time is
It is preferable to set it at 200 to 10 Torr, preferably 100 to 50 Torr. This is because the desorption of CO, that is, the dissociation reaction of CO・CuCl→CO+CuCl, proceeds rapidly below atmospheric pressure. Valves 1B, 2B, 3B, and 4B are closed at this time. In adsorption tower C, after product recovery is completed, the gas from the depressurization process in tower B is supplied to tower C through valve 3C and pressurized (), and the gas discharged from the cleaning process in tower D is also fed through valve 3C. It is supplied and boosted (). At this time, valves 1C and 2
C, 4C, and 5C are closed. Further, the outlet gas of the adsorption tower A just before the end of the adsorption step is supplied to the tower C through valves 6 and 3C, and is pressurized ( ), thereby preparing for the next adsorption step. After the adsorption process is completed, the adsorption tower D is depressurized to near atmospheric pressure, and this depressurized gas is passed through valve 3.
C is used for pressurization of column C (). Additionally, a portion of the product is supplied through valve 4D;
The residual impurity gas inside the column is discharged. The gas discharged at this time is also used to raise the pressure of column C through valve 3C. In the above pressure reduction step,
Physically adsorbed impurity gases such as N ₂ and CO ₂ are desorbed, and the desorption of impurity gases is promoted by the simultaneously desorbed CO gas, resulting in a significant reduction in the amount of product gas used in the cleaning process. . By sequentially repeating the above operations in each adsorption tower, highly pure CO gas can be continuously separated and recovered at a high recovery rate. Next, the present invention will be further explained by giving examples. Examples Example 1 Aluminum chloride () 39 m-mol, copper chloride () 39 m-mol and particulate polystyrene resin (Diaion HP-20 manufactured by Mitsubishi Kasei Corporation)
was placed in a 100 ml Erlenmeyer flask, 45 ml of carbon disulfide was added thereto, and the mixture was heated under reflux for about 6 hours while stirring using a magnetic stirrer in a dry N ₂ atmosphere. Then, the carbon disulfide was evaporated in dry _N2 and further under reduced pressure at a temperature of 50 °C and a pressure of 5 torr for about 12
After drying for several hours, a CO selective adsorption solid adsorbent was obtained. Using the four-column pressure swing device shown in Figure 1, the adsorption towers A, B, C, and D (all 34 m/mφ×
300 m/m) was filled with 150 c.c. of each of the CO selective adsorption solid adsorbents obtained above, and a mixed gas with a composition of CO: 70 vol% N ₂ : 14 vol% CO ₂ : 16 vol% was applied at 500 N-cc/min. 0~
The gas was introduced under a pressure of 5 Kg/cm ² G, and the gas introduction was stopped just before reaching the breakthrough point. Next, after reducing the pressure to atmospheric pressure in parallel flow, the inside of the tower was washed with product CO gas. Then, the product was degassed to 50 torr using a vacuum pump to obtain CO. Exit gas near breakthrough point,
Purge gas during pressure reduction and exhaust gas during cleaning were used to increase pressure in other columns. These operations were repeated for each column in sequence. The detailed adsorption cycle is shown in Table 1 above. The results are also shown in Table 2 below.

[Table] Example 2 After dissolving 100 mmol of copper chloride () and 30 c.c. of hydrochloric acid (3N) in a 100 ml Erlenmeyer flask,
Add activated carbon (manufactured by Kuraray Chemical Co., Ltd.) to this.
It was impregnated with 30 c.c. of 4GSA ₂ ) and allowed to stand for about 1 hour.
Thereafter, moisture was evaporated at about 100°C in a dry N ₂ atmosphere, and heat treatment was further performed at about 180°C to obtain a CO selective adsorption solid adsorbent. Using the CO selective adsorption solid adsorbent obtained above,
The same operation as in Example 1 was performed. The results are shown in Table 3.

[Table] Example 3 A CO selective adsorption solid adsorbent was obtained in the same manner as in Example 1, except that particulate polystyrene resin (Diaion HP-50 manufactured by Mitsubishi Kasei Corporation) was used as a carrier. Using this adsorbent, the same operation as in Example 1 was performed. Note that the adsorption pressure was set at 2 Kg/cm ² G. The results are shown in Table 4. Comparative Example 1 Using the adsorbent obtained in Example 3, in the steps shown in Table 1, the "pressurization ()" step of pressurizing other columns using the outlet gas just before the end of the adsorption step was canceled, and the pressure was increased until the adsorption step. The same operation as in Example 3 was carried out, except that the step () was replaced by pressurization () using the raw material gas. The results are shown in Table 4.

【table】

[Table] As shown in Table 4, by using the outlet gas near the end of the adsorption process to boost pressure in other columns, it is possible to obtain highly pure CO and also ensure an extremely high CO recovery rate. Effects of the Invention The present invention uses a carbon monoxide selective adsorption solid adsorbent in which copper halide () or copper halide and aluminum halide () are supported on a carrier that does not have a molecular sieving action. In
High purity CO can be obtained regardless of the CO concentration, and the pressure swing process is performed as described above using a plurality of adsorption towers filled with such solid adsorbents. The outlet gas near the end of the adsorption process is used to boost pressure in other columns, making it difficult to disturb the pressure balance of the entire process, and the exhaust gas and its pressure are efficiently used, and the exhaust gas during depressurization and cleaning exhaust gas is also efficiently used,
An extremely high CO recovery rate can be ensured. Therefore, by carrying out the method of the present invention,
Highly purified CO can be separated and recovered from converter gas and other CO-containing gases on an industrial scale, and is of great significance in the chemical industry.

[Brief explanation of drawings]

FIG. 1 shows a diagram of an apparatus for separating and recovering CO using four adsorption towers. A, B, C, D...Adsorption tower, 1A...5A, 1B
...5B, 1C...5C, 1D...5D, 6...Valve, E...Vacuum pump, F...Product CO tank.

Claims (1)

[Claims] 1. In separating and recovering high-purity carbon monoxide from a mixed gas containing carbon monoxide by a pressure swing method using a plurality of adsorption towers filled with adsorbents, copper halide is used as the adsorbent. () or aluminum halide () supported on a carrier that does not have a molecular sieving action. (1) In the step of flowing the raw material gas into an adsorption tower to adsorb carbon monoxide gas, and shortly before the concentration of carbon monoxide in the exhaust gas becomes equal to the concentration of carbon monoxide gas in the raw material gas, (2) After the adsorption process is completed, the adsorption tower is connected to the adsorption tower that has undergone vacuum deaeration, and the pressure in the former adsorption tower is brought to a level close to atmospheric pressure in parallel flow. A depressurization step to reduce the pressure, and a corresponding step to increase the pressure of the latter adsorption tower (3) A cleaning step in which a part of the product gas is introduced in parallel flow into the depressurized adsorption tower to clean any impurity gas remaining inside the tower. (4) A step in which the gas discharged at this time is used to raise the pressure of another column (4) The pressure is reduced to vacuum, and the carbon monoxide gas adsorbed on the adsorbent is degassed from the adsorbent in a countercurrent manner. , a product recovery process for recovering product gas; (5) a pressurization () process for connecting the adsorption tower where product recovery has been completed and the adsorption tower where the adsorption process has been completed to raise the pressure of the former adsorption tower to parallel flow; (6) ) step of pressurization () in which the pressure is increased in parallel flow with the cleaning exhaust gas from other adsorption towers; and (7) step () in which the pressure is increased by the exhaust gas near the end of the adsorption step of other adsorption towers, which are sequentially repeated. A method for separating and recovering high-purity carbon monoxide from a mixed gas containing carbon monoxide. 2. The method according to claim 1, wherein a raw material gas from which impurities such as sulfur compounds and ammonia, moisture, and oxygen have been removed is used as the raw material gas to be fed to the adsorption tower.