JPH07166B2 - CO adsorption separation method - Google Patents

Description

The present invention relates to a method of adsorbing and separating CO from a CO-containing gas,
In particular, the present invention relates to a CO adsorption separation method from a multi-component gas containing CO, N ₂ generated in a steelmaking plant, an autothermal partial oxidation method, an air-blown coal gasification plant, or the like.

[Conventional technology]

Auto-thermal partial oxidation method using off-gas, natural gas, liquefied petroleum gas, naphtha as raw material and air as a combustion improver in steel plant, CO, N ₂ , CO ₂ in air-blown coal gasification plant,
Generates gas containing H ₂ O and H ₂ as its main components.

The selective enrichment of CO from this mixed gas is extremely significant and important as CO has various uses. One use of CO is as a raw material for methanol synthesis from a mixed gas of CO and H ₂ . Another application is to use CO as a raw material for H ₂ because it produces H ₂ by a shift reaction in the coexistence of H ₂ O gas. Further, as another application, it can be considered as a raw material for a carbonylation method in which methanol CO is reacted to produce acetic acid. In particular, in recent years, prospects for the practical application of gasoline synthesis using methanol as a raw material are being opened, and this is also important.

It has been said that the liquid phase absorption method using a toluene solution of aluminum copper chloride (CuAlCl ₄ ) has the best performance for CO separation. In this method, CO absorption reaction as shown in equation (1) causes equimolar absorption with aluminum chloride copper.

CuAlCl ₄ + COCuAlCl ₄ · CO (1) Normally, CO is absorbed by the absorption liquid by the absorption reaction of the above formula (1) at around room temperature, and once absorbed at a high temperature of 100 ° C or higher.
This is a method of removing O and collecting it. C in this way
Since the absorption capacity of O increases as the pressure increases, a slightly high pressure of several atas may be adopted to reduce the initial cost. Further, in this method, since there is almost no gas accompanying CO, the concentration of CO gas obtained is as high as about 99% and the recovery rate is also high.

In addition to this method, there is a copper solution washing method, a CO concentration method for a cryogenic separation tower, but the liquid phase absorption method is mainstream because it is superior in equipment cost, power cost, and CO concentration obtained. It is becoming.

[Problems to be solved by the invention]

However, the biggest drawback of the method for absorption and separation of CO with toluene solution of aluminum copper chloride is that CuAlCl ₄ reacts with H ₂ O, H ₂ S, SO ₂ etc. H
It is to decompose into Cl, CuAlCl ₆ (OH), etc. to cause wear of aluminum chloride copper, and also HCl to accompany the recovered CO to significantly reduce the quality of the product.

The next drawback is that olefin and acetylene are CuAl.
It is to react with Cl ₄ to form a precipitate, and this reaction is irreversible, and thus it is necessary to make up CuAlCl ₄ . Also, since toluene is used as a solvent, toluene is associated with both off-gas and CO recovery (stripper) units, so a toluene recovery unit that uses activated carbon as an adsorbent and regenerates steam is required. That is, of course, there is a drawback that a make-up of toluene is required.

This method has the advantage that the absorption process can be operated near atmospheric pressure in terms of power cost and consumes less power, but it is a steam for regeneration of the toluene recovery unit and a steam as a heat source for recovery of the CO recovery unit. Is necessary, and the amount of heat for generating this steam is equivalent to 2 to 3 times the above-mentioned power consumption in terms of electric power, and after all the power consumption is large and not economical.

[Object of the Invention]

The present invention is extremely simple by selectively adsorbing only CO from a mixed gas mainly containing CO, N ₂ etc. at a relatively low pressure (above atmospheric pressure) and recovering it under a reduced pressure condition of 0.5ata or less. This process aims to provide a CO recovery method that requires almost no make-up of chemicals and is easy to maintain.

[Means for Solving Problems] The present invention has a chemical formula of Ca ₄₃ (AlO ₂ ) ₈₆ as a selective CO adsorbent.
It is a novel use of Ca-X type zeolite represented by (SiO ₂ ) ₁₀₈ as an adsorbent.

This adsorbent is packed in at least two or more adsorption towers, and the temperature of the adsorption tower is set between -30 ° C and 25 ° C (room temperature) and below in one tower.
A gas containing CO and N ₂ is passed through at 1 to 5 ata to adsorb CO, and in the other tower, the CO adsorbed before is depressurized at 0.05 to 0.5 ata while suppressing co-adsorption of N _2. Recovery of CO at high concentration is also a new point.

Furthermore, it is possible to improve the concentration of CO recovered during decompression regeneration by flowing recovered CO into the adsorption tower immediately after the adsorption process in the same gas flow direction as in the adsorption process to scavenge N ₂ remaining in the tower. This is a preferred embodiment.

That is, the present invention mainly contains CO, N _{2 and the} like in at least two or more adsorption columns filled with a Ca-X type zeolite represented by the chemical formula Ca ₄₃ (AlO ₂ ) ₈₆ (SiO ₂ ) ₁₀₈ as a CO absorbent. It is characterized in that a mixed gas is introduced, CO is adsorbed under operating conditions of adsorption pressure of 1 to 5ata and adsorption temperature of room temperature to -30 ° C, and then CO is desorbed under operating conditions of desorption pressure of 0.05 to 0.5ata. The present invention relates to a CO adsorption separation method.

[Application field of the present invention]

INDUSTRIAL APPLICABILITY The present invention can be advantageously applied to the H ₂ manufacturing industry, methanol industry, acetic acid industry, synthetic gasoline industry (C1 chemical industry), and can also be used to improve the heat generation amount of boiler fuel such as off gas and process gas. .

Example 1 Hereinafter, a first example of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 1 is a CO, H ₂ synthesis gas production apparatus by a partial oxidation method using propane as a raw material and oxygen-enriched air as a combustion improver. Table 1 shows an example of the gas composition in the CO, H ₂ synthesis gas production apparatus 1.

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 reaches the valve 5 through the flow path 4. 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 8a, activated alumina is filled in the inlet half and activated carbon is filled in the rear. Therefore, water is adsorbed in the front of the adsorption tower 8 and CO ₂ is adsorbed in the rear of the adsorption tower 8. On the other hand, the once adsorbed H ₂ O, CO ₂ is in the state of the adsorption tower 8a, that is, in the desorption process under reduced pressure, and the valve 7a is open and the valves 7 and 6a are closed.
The flow path 9 communicating with the valves 7 and 7a communicates with the vacuum pump 10 on the other side. The adsorption tower 8a reaches a maximum pressure of 0.05ata,
₂ O and CO ₂ are removed and regenerated. The adsorption towers 8 and 8a are alternately switched for about 2 to 10 minutes to continuously dehumidify and remove CO ₂ .

The dehumidified and CO ₂ removed synthesis gas is in the flow path 11 and surge tank 1.
Through 2 the heat exchanger 13 and the refrigerator 14 are reached, and the gas temperature is cooled to an arbitrary temperature below room temperature up to -60 ° C and reaches the valve 15. The valves 15 and 16 are open. Table 2 shows the gas composition of the flowing synthesis gas in the flow path 11.

CO is adsorbed from the synthesis gas flowing through the CO adsorption tower 18, and
Depending on the selectivity of the adsorbent, N ₂ is co-adsorbed, but in this case H ₂ adsorption is negligible.

In the adsorption tower 18a for which CO adsorption has ended, the valves 15a, 16a, 17 are closed, the valve 17a is open, the flow path 19, the heat exchanger 13a,
The CO adsorbed by the adsorption tower 18a through the vacuum pump 20 is recovered from the flow path 21 to a high concentration under reduced pressure. This operation 1
High-concentration CO is continuously recovered by repeating every 5 minutes.

The heat exchanger 22 has a product CO temperature of 150 ° C behind the vacuum pump.
It is installed for cooling because it rises to some extent.

A gas having a low CO concentration flows through the flow path 23 through the one-way adsorption tower 18 and the valve 16.

Since low CO gas passage 23 containing H ₂ at a high concentration, N ₂ with a large adsorbent such as N ₂ adsorption Ca substituted Na-A type zeolite
Is removed, a high concentration of H ₂ is obtained. High-purity H ₂ can also be obtained by liquefying and removing it by the cryogenic separation method. If the gas in the flow path 23 is used as fuel, heat can be recovered. In terms of heat balance, the gas in channel 11 and channel 19, channel
Since the gas of 23 is subjected to gas-gas heat exchange in the heat exchangers 13, 13a, 13b, the power consumption of the refrigerator 14 is extremely low.

In the present invention, the adsorption towers 18 and 18a and the pipes and valves around them are installed in the cold box 24 to perform adsorption operation at low temperature.

Perform the operation shown in Table 3 with the above equipment configuration and gas composition.
I tried to recover.

The CO recovery results under the above operating conditions are shown.

Fig. 2 shows the performance of each adsorbent at the time of CO recovery at an adsorption temperature of 0 ° C and a desorption pressure of 0.1ata, with the abscissa indicating the adsorption pressure and the ordinate indicating the CO concentration.

Fig. 3 shows the adsorption pressure of 1.2ata and the adsorption temperature of 0 ℃ for each adsorbent.
The CO recovery performance is shown by selecting the desorption pressure on the horizontal axis and the CO concentration on the vertical axis.

Fig. 4 shows the CO recovery performance of each adsorbent at an adsorption pressure of 1.2ata and a desorption pressure of 0.1ata, with the abscissa indicating the temperature during adsorption and the ordinate indicating the CO concentration.

As seen above, Ca-X type zeolite N from CO, N _2, etc.
It was shown that CO can be recovered with high CO selectivity while suppressing the adsorption of ₂ as much as possible. This is something that has not been known so far, and can be said to be a new CO adsorption and separation method.

The CO recovery rate in the method of the present invention largely depends on the CO concentration of the raw material, but is about 90% when the CO concentration of the raw material (after removal of CO ₂ and H ₂ O in the flow channel 11) is 50 vol%. .

The CO recovery rate is It is defined in.

In Fig. 3, the closer the regeneration pressure is to the absolute vacuum, the more CO
The concentration is rising. However, if it is less than 0.05ata, the power consumption of the vacuum pump increases and the capacity is limited, so it cannot be said to be industrially effective.

In Fig. 4, it can be seen that good CO adsorption performance is exhibited even at a low temperature of -30 ° C or lower. However, if the temperature is -30 ° C or higher, the refrigerator is composed of a single-stage refrigerant single-stage compressor. However, if the temperature is lower than -30 ° C, two or more kinds of refrigerants are required or two stages of compressors are required, which is a great facility problem and power consumption during freezing is significantly increased, which is not preferable.

[Embodiment 2] A second embodiment of the present invention will be described with reference to FIG. Fifth
In the figure, the same reference numerals as in FIG. 1 indicate the same parts as in FIG.

As shown in FIG. 5, C recovered from the adsorption tower 18a by the vacuum pump 20 under a reduced pressure condition through the flow path 19 and the heat exchanger 13a.
O is taken out to the flow path 21 through the heat exchanger 22. At this time, paying attention to the adsorption tower 18, the raw material CO gas flows into the front of the adsorption tower 18 and the N ₂ concentration increases toward the rear of the tower.

In the first example (FIG. 1), since CO was recovered from this state, N ₂ remaining in the void portion of the tower was accompanied and the CO concentration was lowered.

Therefore, here, the product CO is scavenged from the valves 27 and 15 which are in an open state through the flow path 26 and the heat exchanger 13c for a part of the gas in the product tank 25 immediately after the end of the adsorption step. By doing so, the residual N _{2 in} the void portion of the adsorption tower 18 is discharged to the outside of the system through the valve 16 in the open state, the flow path 23, and the heat exchanger 13b. At this time, since the CO concentration in the tower 18 increases, N _{2 in the} void portion is increased.
Not only is part of the co-adsorbed N ₂ removed.

In addition, the scavenging air of the void part due to the product CO was recovered as a product
About 10% of CO is sufficient.

In the present invention, the Ca-X type zeolite has an adsorption pressure of 1.2ata
Scavenging with product CO was performed at a regeneration pressure of 0.1ata and a tower temperature of 0 ° C, and in each case, a CO concentration of 99% or more could be obtained.

An example of the following valve operation is shown.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining the first embodiment of the present invention,
The figure is a graph showing the performance of the adsorbent during CO recovery at an adsorption temperature of 0 ° C and desorption pressure of 0.1ata, with the abscissa axis indicating the adsorption pressure and the ordinate axis indicating the CO concentration. Graph showing the CO recovery performance of the adsorbent of Fig. 4 with the desorption pressure on the horizontal axis and the CO concentration on the vertical axis. Fig. 4 shows the CO recovery performance of the adsorbent at adsorption pressure 1.2ata and desorption pressure 0.1ata. Absorption temperature on the horizontal axis and CO on the vertical axis
FIG. 5 is a flow chart for explaining the second embodiment of the present invention, in which the density is selected and shown.

Claims (2)

[Claims] 1. At least two or more adsorption columns filled with a Ca-X type zeolite represented by the chemical formula Ca ₄₃ (AlO ₂ ) ₈₆ (SiO ₂ ) ₁₀₈ as a CO absorbent mainly contain CO, N _{2 and the} like. Guide the mixed gas, adsorption pressure 1 ~ 5ata, adsorption temperature room temperature ~
After desorption of CO under operating conditions of -30 ° C, desorption pressure of 0.05
Characterized by desorption of CO under operating conditions of ~ 0.5ata
CO adsorption separation method. 2. The desorption operation is performed after scavenging the adsorption tower at the end of the adsorption with the recovered CO gas in a gas flow in the same direction as that at the adsorption, and then performing the desorption operation. Method.