JPH0372007B2 - - Google Patents

Description

[Detailed description of the invention]

Object of the present invention The present invention relates to a method for adsorbing and separating CO from CO-containing gases, and in particular from multicomponent gases containing CO and N ₂ produced in steel plants, autothermal partial oxidation methods, air-blown coal gasification plants, etc. This paper relates to a CO adsorption separation method. Overview of conventional technology and its drawbacks Autothermal partial oxidation method using off-gas from steel plants, natural gas, liquefied petroleum gas, and naphtha as raw materials and air as a combustion improver, and air-blown coal gasification plants use CO, N ₂ , H ₂ Generates gas whose main components are O, _H2, etc. Selective enrichment of CO from this gas mixture is CO
It is extremely meaningful and important because it has various uses. One use of CO is as a raw material for methanol synthesis from a mixed gas of CO and H ₂ . For other uses, CO can be regarded as an H ₂ source since it generates H ₂ through a shift reaction in the coexistence of H ₂ O gas. Another possible use is as a raw material for a carbonylation method in which acetic acid is produced by reacting CO with methanol. Particularly in recent years, prospects for the practical application of gasoline synthesis using methanol as a raw material are opening up, and this is important in that sense as well. Conventionally, CO is separated using copper aluminum chloride (CuAlCl ₄ ).
The liquid phase absorption method using a toluene solution is said to have the best performance. In this method, the absorption reaction of CO as shown in equation (1) causes equimolar absorption with copper aluminum chloride. CuAlCl ₄ +COCuAlCl ₄・CO (1) Usually, CO is absorbed into the above absorption liquid through the absorption reaction of equation (1) above at around room temperature, and the CO that has been absorbed is released and recovered at a high temperature of 100°C or higher. be. In this method, the CO absorption capacity increases as the pressure increases, so a slightly higher pressure of several ata may be used to reduce the initial cost. or,
With this method, there is almost no CO and accompanying gas, so
The concentration of CO gas obtained is extremely high, around 99%.
And the recovery rate is also high. In addition to this method, there are CO concentration methods such as copper liquid cleaning method and cryogenic separation method, but the liquid phase absorption method mentioned above has become mainstream because it is superior in terms of equipment cost, power cost, and CO concentration obtained. It is becoming. However, due to toluene solution of aluminum copper chloride
The biggest drawback in the CO absorption and separation method is that H ₂ O, H ₂ S, SO _2, etc. that get mixed in due to incorrect operation etc.
CuAlCl ₄ reacts to form CuCl, HCl, CuAlCl ₆
It decomposes into (OH), etc., causing depletion of aluminum copper chloride, and the recovered CO is accompanied by HCl, significantly reducing the quality of the product. The next drawback is that olefin and acetylene react with CuAlCl ₄ to form a precipitate, and this reaction is irreversible, so make-up of CuAlCl ₄ is required. Also, since toluene is used as a solvent, off-gas and
Since toluene accompanies all CO recovery (stripper) units, a toluene recovery unit that uses activated carbon as an adsorbent and uses water vapor as regeneration gas is required, and of course, toluene make-up is also required. There is a drawback. In terms of power costs, this method has the advantage of being able to operate the absorption process at near atmospheric pressure and consumes little electricity; of water vapor is required, and the amount of heat to generate this water vapor is equivalent to 2 to 3 times the above power consumption in terms of electricity.
This is equivalent to double the power consumption, which is not economical as the power consumption is large. Purpose of the present invention The present invention is a method of selectively adsorbing only CO from a mixed gas mainly containing CO, _N2 , etc. at relatively low pressure (above atmospheric pressure) and recovering it under reduced pressure conditions of 0.5 ata or less. The purpose of the present invention is to provide a CO recovery method that uses an extremely simple process, requires little chemical make-up, and is easy to maintain and operate. New features of the present invention The present invention uses Na-A type zeolite or Na-A type zeolite impregnated with divalent or trivalent Fe and heat-treating it as an adsorbent. It is new to use. Judging from separation examples from two-component systems of N ₂ and O ₂ , these adsorbents have adsorption window diameters of 3.8 to 3.8.
Estimated to be 4.0Å. The Na-A type zeolite referred to herein refers to the following. Chemical formula Mk/n・(AlO ₂ )k・SiO ₂ (where M is an exchangeable metal ion, n is its valence, and K is
In aluminosilicate, which is expressed by the ratio AlO ₂ /SiO ₂ ), it usually has water of crystallization, and when heated and degassed, the water of crystallization is released without changing the crystal structure and gas adsorption ability appears. M is Na ion,
A zeolite with K=1 and n=1 is called Na-A type zeolite. Note that the Na-X type zeolite mentioned later refers to M as Na-X type zeolite.
ion, K=0.67-0.83, n=1. This adsorbent is packed into at least two or more adsorption towers, and the temperature of the adsorption tower is set at -30°C or higher and 25°C or lower (room temperature), and one to two gases containing CO and _N2 are packed into each tower.
5 ata to adsorb CO, and in another column, the previously adsorbed CO is reduced to 0.05 ata to 0.5 ata to become _N2.
Another novel feature is the ability to recover CO at a high concentration while suppressing the co-adsorption of CO. Furthermore, a portion of the recovered CO flows down into the adsorption tower immediately after the adsorption process is completed in the same gas flow direction as the adsorption process to scavenge the remaining N ₂ in the tower and improve the concentration of CO recovered during reduced pressure regeneration. You can also do so. That is, the present invention is an A-type zeolite obtained by mixing a binder with Na-A-type zeolite and heat-treating the mixture after molding, and a Na-A-type zeolite (including one in which up to 18 mol% of Na is substituted with K) is impregnated with Fe ions. A-type zeolite and Na-A-type zeolite are produced by mixing a binder, molding, and heat treatment.
Impregnated with ions and substituted with K up to 18 mol% of Na.
At least two types of A-type zeolite selected from the group consisting of A-type zeolite formed by mixing a binder, molding, and heat treatment are filled as a CO absorbent.
A mixed gas mainly containing CO, _N2 , etc. is introduced into an adsorption tower above the tower, and CO adsorption is performed under operating conditions of an adsorption pressure of 1 to 5 ata and an adsorption temperature of room temperature to -30°C, followed by a desorption pressure of 0.05 to -30°C. This invention relates to a CO adsorption separation method characterized by CO desorption under operating conditions of 0.5ata. Field of application of the present invention The present invention can be advantageously applied to the _H2 manufacturing industry, methanol industry, acetic acid industry, synthetic gasoline industry (C1 chemical industry), and can also be used to improve the calorific value of boiler fuel such as off gas and process gas. You can make it useful. Description of Specific Examples of the Present Invention Hereinafter, specific embodiments of the present invention will be described with reference to FIG. In FIG. 1, reference numeral 1 indicates a CO, H ₂ synthesis gas production apparatus using propane as a raw material and a partial oxidation method using oxygen-enriched air as a combustion improver. The CO,
Table 1 shows an example of the gas composition in the H ₂ synthesis gas production apparatus 1.

[Table] The synthesis gas in the CO, H ₂ synthesis gas production apparatus 1 is pressurized by the compressor 3 through the flow path 2. The pressurized synthesis gas passes through channel 4 to valve 5 . At this time, the valves 5 and 6 are open, and the synthesis gas flows through the adsorption tower 8. In the adsorption towers 8 and 8', the inlet half is filled with activated alumina, and the rear half is filled with Na-X type zeolite. Therefore, water is adsorbed at the front of the tower 8, and CO ₂ is adsorbed at the rear. On the other hand, once adsorbed
H ₂ O and CO ₂ are in the state of the adsorption tower 8', that is, in the vacuum desorption process, and the valve 7' is open;
6' is closed. Channel 9 leading to valves 7, 7'
communicates with the vacuum pump 10 on the other side. The maximum pressure in the adsorption tower 8' reaches 0.05ata, and H ₂ O, CO ₂
Remove and play. The adsorption towers 8, 8' are switched alternately every 2 to 10 minutes to continuously dehumidify and remove _CO2 . The dehumidified and CO _2- removed synthesis gas is passed through the flow path 11,
The gas passes through the surge tank 12 to a heat exchanger 13 and a refrigerator 14, where the gas temperature is cooled to an arbitrary temperature from room temperature to -60°C, and then reaches a valve 15. Valves 15 and 16 are in an open state. Table 2 shows the gas composition of the flowing synthesis gas in the channel 11.

[Table] CO is adsorbed from the synthesis gas flowing through the CO adsorption tower 18, and N ₂ is co-adsorbed depending on the selectivity of the CO adsorbent. Adsorption of _H2 is negligible. In this example, the CO adsorption tower 18 was filled with the following five types for comparison. Fe()Cl ₃ is added to Na-A type zeolite (Molecular Sieves 4A powder manufactured by Union Carbide) slurry, and Fe() hydroxides such as Fe(OH) ₃ and FeO・OH are added to Na-A type zeolite. is precipitated with 1w% asFe on zeolite. After washing and filtering this with water, 30w% of kaolin is mixed as a binder, molded, and placed in the air.
Baked at 700℃ for 1 hour. According to another test regarding O ₂ adsorption and N ₂ co-adsorption from a two-component system of O ₂ and N ₂ , the window diameter is 3.9 to 3.95 Å, which is slightly smaller than that of Na-A. (Sample A) Fe was added to the same Na-A type zeolite slurry as above.
() Adding _Cl3 to Na-A type zeolite
Fe(OH) hydroxides such as Fe(OH) ₃ and FeO・OH are precipitated at 1w% asFe on zeolite, and Na−
5 mol% of Na in A-type zeolite is exchanged with K. After filtering and washing with water, 30w% of kaolin is mixed as a binder and molded at 700℃ in air.
Baked for 3 hours. Adsorption tests using a two-component system of O ₂ and N ₂ show that the window diameter is even smaller, ranging from 3.8 to 3.85 Å. (Sample B) The same Na-A zeolite as above was mixed with 30w% of kaolin as a binder, molded, and calcined in air at 650°C for 1 hour. The window diameter is about 4 Å. (Sample C) 66 mol% of Na in the same Na-A zeolite
was replaced with an equivalent amount of Ca, mixed with 30w% kaolin as a binder, and fired in air at 650℃ for 1 hour. The window diameter is 5 Å. (Sample D) The Na-A type zeolite mentioned above was completely replaced with K, and 30w% of kaolin was mixed and molded as a binder, and the mixture was calcined in air at 650°C for 1 hour. The window diameter is 3 Å. (Sample E) In the adsorption tower 18' where CO adsorption has been completed, valve 1
5', 16', and 17 are closed, and the valve 17' is open, and the CO installed in the adsorption tower 18' is discharged from the channel 21 under reduced pressure through the channel 19, the heat exchanger 13', and the vacuum pump 20. Collected at high concentration. By repeating this operation alternately every 1 to 5 minutes, high-concentration CO is continuously recovered. The heat exchanger 22 is installed to cool the product CO after the vacuum pump because the temperature rises to about 150°C. One-way adsorption tower 18, flow path 23 through valve 16
Gas with low CO concentration flows through. Note that the low CO gas in the flow path 23 contains H ₂ at a high concentration, so if N 2 is removed using an adsorbent with a large amount of N ₂ adsorption, such as Na-X zeolite or Ca-substituted Na-A zeolite, a high concentration of H ₂ can be obtained. _H2 is obtained. Furthermore, even if N ₂ is liquefied and removed by cryogenic separation, highly pure H ₂ can be obtained in the same way. Moreover, if the gas in the flow path 23 is used as fuel, heat can be recovered. In addition, from a heat balance perspective, the gas in the flow path 11, the flow path 19, and the flow path 23
Since the gas is subjected to gas-to-gas heat exchange in the heat exchangers 13, 13', 13'', the power consumption of the refrigerator 14 is extremely small. A valve was installed in the cold box 24 to perform adsorption operations at low temperatures. With the above equipment configuration and gas composition, CO recovery was attempted by performing the operations shown in Table 3.

[Table] Shows the CO recovery results under the above operating conditions. Figure 2 shows the adsorption temperature at 0℃ and desorption pressure at 0.1ata.
The performance of each adsorbent during CO recovery is plotted with adsorption pressure on the horizontal axis,
The vertical axis shows CO concentration. In order to understand the data for each sample in the figure, the actual measurement points are marked ◎ for sample A, ○ for sample B, △ for sample C, and □ for sample D. Note that sample E (K-A) did not show any adsorption ability and was therefore deleted from the diagram. Figure 3 shows the CO recovery performance of each adsorbent at an adsorption pressure of 1.2 ata and an adsorption temperature of 0°C, with the horizontal axis representing the desorption pressure and the vertical axis representing the CO concentration. The symbols in the figure are the same as in FIG. Figure 4 shows the CO recovery performance of each adsorbent at an adsorption pressure of 1.2 ata and a desorption pressure of 0.1 ata, with the temperature at adsorption plotted on the vertical axis.
The vertical axis shows CO concentration. The symbols in the figure are the same as in FIG. As can be seen from the above, Na-A type zeolite (Document C) or A type zeolite with a slightly smaller window diameter (Samples A and B) suppresses the adsorption of _N2 from CO, _N2, etc. as much as possible while reducing high CO2. It was shown that it can be recovered with selectivity. This has not been previously known and provides a new method for adsorption and separation of CO. Regarding K substitution, only Material C is listed, but almost the same results as Material C were obtained when Na was substituted up to 18 mol%. In addition, although there is no reference to K substitution for Na in Na-A type zeolite before Fe impregnation, K substitution is the same before and after Fe impregnation, and after first replacing up to 18 mol% of Na with K, Almost the same results as Material C were obtained for the material impregnated with Fe. Note that the CO recovery rate in the method of the present invention depends on the raw material.
Although it depends largely on the CO concentration, it is around 90% when the raw material CO concentration (after removing CO ₂ and H ₂ O in the flow path 11) is 50 vol%. Note that the CO recovery rate is defined as: CO recovery rate = amount of CO recovered per unit time in the product CO flow path 21 / amount of CO flowing in per unit time in the inlet flow path 11 x 100%. In Figure 3, the recovered CO concentration increases as the regeneration pressure approaches absolute vacuum. But 0.05ata
Below this, the power consumption of the vacuum pump increases and the capacity is limited, so it cannot be said to be industrially effective. In Figure 4, it shows good performance even at low temperatures below -30℃.
It can be seen that it shows CO adsorption performance. However, if it is above -30℃, the unitary refrigerant
The refrigerator consists of stage compressors. However, −30℃
Below this, it becomes difficult to use equipment because two or more types of refrigerants are required and two stages of compressors are required. Furthermore, the power consumption during refrigeration also increases significantly. Another embodiment of the invention is shown in FIG. In FIG. 5, the same reference numerals as in FIG. 1 indicate the same parts as in FIG. As shown in FIG. 5, the flow path 19 and the heat exchanger 13'
The CO recovered from the adsorption tower 18' by the vacuum pump 20 under reduced pressure conditions is taken out to the flow path 21 through the heat exchanger 22. At this time, focusing on the adsorption tower 18, the raw material CO gas flows into the front of the adsorption tower 18, and as it goes to the rear of the tower,
_N2 concentration is rising. In the embodiment (Fig. 1), CO
Since the CO was recovered, the N ₂ remaining in the guide section of the tower accompanied the CO and lowered the concentration of CO. Therefore, immediately after the adsorption process is completed, a part of the gas in the product tank 25 is passed through the flow path 26 and the heat exchanger 13, and the product CO is scavenged from the valves 27 and 15 which are in an open state. For this reason, the residual N ₂ in the void part of the adsorption tower 18 is released to the outside of the system through the open valve 16, the flow path 23, and the heat exchanger 13''.
Not only N ₂ but also part of the co-adsorbed N ₂ is removed. Note that approximately 10% of the CO recovered as a product is sufficient for scavenging the void area with product CO. In the present invention, for samples A, B, and C, the adsorption pressure
Scavenging with product CO was carried out at a regeneration pressure of 1.2 ata, 0.1 ata, and a tower temperature of 0°C, and CO with a concentration of over 99% could be obtained in both cases. An example of valve operation is shown below.

[Table] Other specific embodiments of the present invention are shown below. In the same flow sheet as Figure 5, Table-4
A part of the steelworks converter gas having the gas composition shown in was branched and separated and concentrated at 940Nm ³ /h. The separation conditions and results are shown in Table 5.

【table】

【table】

【table】 [Brief explanation of drawings]

Figure 1 is a flowchart explaining one embodiment of the present invention, and Figure 2 is a flowchart for explaining an embodiment of the present invention.
Graph showing the performance of various adsorbents during CO recovery, with adsorption pressure on the horizontal axis and CO concentration on the vertical axis, Part 3
The figure shows the CO recovery performance of various adsorbents at an adsorption temperature of 0°C, with the horizontal axis representing the desorption pressure and the vertical axis representing the CO concentration. Figure 4 shows the adsorption pressure at 1.2ata and the desorption pressure.
A graph showing the CO recovery performance of various adsorbents at 0.1 ata, with the temperature during adsorption on the horizontal axis and the CO concentration on the vertical axis. Figure 5 is a flowchart explaining another embodiment of the present invention. .

Claims (1)

[Claims] 1. A-type zeolite, Na-A, which is obtained by mixing Na-A type zeolite with a binder and heat-treating the mixture after molding.
Type A zeolite (including those in which up to 18 mol% of Na is substituted with K) is impregnated with Fe ions, mixed with a binder, molded, and heat treated to produce Type A zeolite, and Na-A type zeolite impregnated with Fe ions. A-type zeolite selected from the group consisting of A-type zeolite obtained by substituting K up to 18 mol% of Na, mixing with a binder, molding, and heat-treating the A-type zeolite is
A mixed gas mainly containing CO, _N2 , etc. is introduced into at least two or more adsorption towers packed as absorbents, at an adsorption pressure of 1 to 5 ata and an adsorption temperature of room temperature to -30 mA.
After CO adsorption at operating conditions of °C, the desorption pressure
A CO adsorption separation method characterized by desorbing CO under operating conditions of 0.05 to 0.5 ata. 2. The method according to claim 1, wherein the adsorption column is scavenged with the recovered CO gas at the end of adsorption with a gas flow in the same direction as during adsorption, and then the desorption operation is performed.