JPS634825A - Method for separating and recovering carbon monoxide - Google Patents

Abstract

PURPOSE:To efficiently carry out purging by using only the raw gaseous mixture in the pressure increasing stage, compressing and heating the gaseous product by adiabatic compression in the purging stage, and supplying the gaseous product to an adsorption tower. CONSTITUTION:A gaseous mixture contg. CO, CO2, and N2 is introduced into the tower D wherein the desorption and recovery stage is finished, and compressed to the atmospheric pressure. The mixture then enters into the adsorption stage, adsorption is continued until the breakthrough of N2 and CO2 occurs, the outlet gas from a tower C after being purged is introduced into the tower D to carry out preliminary purging, then the outlet of the tower D is closed, and the tower D is pressurized by the gas after purging. The gaseous product is then compressed and heated by the adiabatic compression at that time, and introduced into the tower D to carry out purging. The pressure is then turned off to the atmospheric pressure, and the adsorbed CO is desorbed and recovered through a vacuum pump. The cycle is repeated, and the towers A-D are successively used.

Description

Detailed Description of the Invention (Industrial Application Method) The present invention uses a carbon monoxide selective adsorbent to separate carbon monoxide from a mixed gas by a pressure swing adsorption method (hereinafter abbreviated as PSA method). Regarding the method of collection.

(Prior art and its problems) Recently, in order to effectively utilize carbon monoxide contained in converter gas, electric furnace gas, blast furnace gas, etc., a method of separating carbon monoxide from these gases using PSA has been developed. , has been extensively studied.

For example, Japanese Patent Laid-Open No. 59-22625 proposes a method of concentrating carbon monoxide from converter gas or the like by PSA using a general zeolite adsorbent. However, the adsorbent used in this method adsorbs more carbon dioxide, which coexists with carbon monoxide, than carbon monoxide. For this reason, this method requires a pre-treatment device such as CO2-PSA to remove carbon dioxide in the first stage, making the process complicated.
The disadvantage is that the equipment cost is high. In addition, with this method, if you try to improve the carbon monoxide concentration, barge farming will increase and the recovery rate will decrease significantly, and Go-PS
In A, since a general zeolite adsorbent is used, the co-adsorption of nitrogen becomes large, making it difficult to reduce the nitrogen concentration sufficiently.

Also, JP-A-61-21906 and JP-A-61-265
No. 06 discloses a method for separating carbon monoxide in a PSA using an adsorbent that selectively adsorbs carbon monoxide. Here other gaseous components, such as nitrogen, coexist with carbon monoxide as adsorbents.

Using a device that selectively adsorbs carbon monoxide with respect to carbon dioxide, hydrogen, and oxygen, the raw material mixed gas containing these components is passed through one adsorption tower, and goes through the steps of pressurization and adsorption.
A method is disclosed in which carbon monoxide is recovered by a vacuum desorption process after the co-current depressurization process is performed by connecting it with another column that has completed the vacuum desorption process. , a method of adding a product pressurization process and a depressurization exhaust process is shown. However, according to the example described in this publication, the raw material mixed gas concentration is C090.0%, N
29.2% and CO20.8%, the product gas concentration is CO96.2%, N22.7%, and CO21.10%, and the product purity has not improved much. Much less C
The O21 degree is higher than that of the raw material mixed gas. Therefore, it can be said that gas purging is insufficient in this method.

Furthermore, Japanese Patent Publication No. 54-3822 describes a method of purging with product gas under the same pressure as during adsorption before desorption, in order to separate easily adsorbable components from a mixed gas with high purity. . In addition, in Japanese Patent Publication No. 54-3823, in order to continuously separate and recover poorly adsorbed components and easily adsorbed components from a mixed gas with high purity, a pressure raising process using tail gas is carried out before the mixed gas is supplied, and a desorption process is carried out before the desorption process. A method of purging with product gas under the same pressure as during adsorption is described.

However, purging with product gas does not necessarily have to be carried out at the same pressure as during adsorption, and although increasing the pressure with tail gas seems to be useful for improving the recovery rate, in reality it is not necessary to perform purge with the same pressure as during adsorption, and although it seems that increasing the pressure with tail gas is useful for improving the recovery rate, in reality, it is not necessary to perform purge with the same pressure as during adsorption. The disadvantage is that the increased amount of adsorption makes purging operations more difficult.

(Technical problem to be solved by the invention) The present invention can separate and recover carbon monoxide with high purity and high recovery rate from a mixed gas containing carbon monoxide, carbon dioxide, nitrogen, etc. The purpose of the present invention is to provide a method for separating and recovering carbon monoxide.

(Means for Solving Technical Problems) This invention involves passing a mixed gas containing carbon monoxide as one of the main components and containing at least carbon dioxide and/or nitrogen through a column containing a carbon monoxide selective absorbent. In a method for separating and recovering carbon monoxide in which carbon monoxide is selectively adsorbed and then recovered, a pressurization step of supplying the above-mentioned mixed gas to a tower where desorption and recovery of carbon monoxide has been completed and increasing the pressure to at least atmospheric pressure. and an adsorption step in which a mixed gas at a pressure higher than atmospheric pressure is passed through the tower where the pressure increasing step has been completed until at least the component with the highest amount of adsorption next to carbon monoxide begins to break through, and into the tower where the adsorption step has been completed. A preliminary purge process in which the outlet gas of the purge process is supplied while depressurizing to purge carbon monoxide and other adsorbed components other than the component with the second highest adsorption rate after carbon monoxide, and a column where the preliminary purge process has been completed. A post-purging gas recovery step in which the outlet end of the gas is closed to recover the outlet gas from the purge step, and the product gas after the 1q arrival is pressurized to a pressure higher than the adsorption pressure in the adsorption step, and the temperature is raised by the adiabatic compression heat. This is supplied to the inlet end of the tower where the post-purging gas recovery process has been completed, and at the same time the outlet end is opened to purge the adsorbed components that have the second largest adsorption amount after carbon monoxide, and the tower is depressurized after the purge process is completed. This is a carbon monoxide separation and recovery method in which a desorption and recovery step of recovering concentrated carbon monoxide is sequentially repeated.

(Detailed Description of the Invention) In order to separate and recover easily adsorbable components (here, carbon monoxide) with high purity from a mixed gas containing carbon monoxide, carbon dioxide, nitrogen, etc., in one stage PSA, the coexisting mixed gas must be It is essential to use an adsorbent that adsorbs carbon monoxide the most among the components, and it is also necessary to replace and adsorb other components that co-adsorb (carbon dioxide, nitrogen, etc.) with reflux of the product gas (carbon monoxide). In other words, the most important point is how efficiently the purge operation can be performed.

The present inventors have already disclosed a method for producing such an adsorbent and excellent adsorption performance in Japanese Patent Application Laid-Open No. 17413/1983. That is, this adsorbent contains Ni, Mn, Rh, on zeolite with a silica/alumina ratio of 10 or less.
, Cu(1), A(J, and mixtures thereof), and the method for manufacturing this adsorbent is to zeolite in the first step by ion exchange method. This is a method in which the metal is supported by an impregnation method in the second step.As a result of further studies on the breakthrough and purge characteristics of these carbon monoxide selective adsorbents, the inventors have found that the purge process can be carried out efficiently. We have found that the following two points are important for this purpose.

1) Raise the purge temperature.

2) Increase the amount of purge gas.

That is, the higher the temperature at which displacement adsorption is performed, the more the selective adsorption ability of carbon monoxide of this adsorbent increases, and the mass transfer rate increases, so that purging can be performed quickly. Furthermore, when the purge pressure is increased, the amount of carbon monoxide removed increases, so the amount of purge can be increased without changing the amount of carbon monoxide recovered. Furthermore, it was found that by increasing the pressure of the purge gas, a synergistic effect could be obtained in that the temperature of the purge gas could be increased by the heat of adiabatic compression.

The inventors have completed the present invention as a process that can efficiently reflect these characteristics in the PSA system and improve the purity and recovery rate of carbon monoxide.

Table 1 and FIG. 1 show one example of the method of the present invention. here 4
Using the adsorption towers A to D, each process of pressurization, @contamination, preliminary purge, post-purging gas recovery purge, and desorption/recovery is set up in a cycle of 8 steps. By using at least four adsorption towers, supply of the raw material mixed gas,
Supply of purge gas and recovery of product gas can be operated continuously. Here, in order to explain the process in an easy-to-understand manner, only basic operations are shown, but the present invention is not limited thereto. In addition, converter gas (
0080%, CO2 10%, N29%, N21%).

First, let's focus on Tower D and explain it.

Step 1 shows a pressure increase step. The D column in this step has completed the desorption and recovery step and is in a vacuum state, and the raw material mixed gas is introduced from the inlet end of the D column using a blower. The end point of this process is when the boring pressure reaches about atmospheric pressure to the feed pressure. The reason why the raw material mixed gas is directly blown in this process and the tail gas (described later) is not supplied is that the tail gas has a lower carbon monoxide concentration than the raw material mixed gas, so if the pressure is increased with this tail gas, the This is because it becomes difficult to purge the adsorbed components.

Step 2, column D, represents the adsorption step. In this step, the outlet end is opened and the raw material mixed gas is passed through at mR. It is sufficient for the pressure of the raw material mixed gas to be raised by feeding, and may be 0 to 0.5 Ky/cdG. This process allows hydrogen to be absorbed with low adsorption capacity.

Enzymes are easily breakthroughs. The end point of this process is at least until nitrogen has broken through and carbon dioxide has begun to break through. This point is the end point of step 2. Note that if adsorption continues even after carbon dioxide breakthrough ends, the recovery rate of carbon monoxide will decrease. The reason for lowering the adsorption pressure is to minimize the co-adsorption of components other than carbon monoxide. Another advantage is that a booster is not required to supply the raw material mixed gas, and only a blower is required.

Step 3, Column D, represents a preliminary purge step.

In this step, the purged outlet gas from the C tower outlet is introduced from the inlet end. Since breakthrough has not been completed on the bath outlet side after the adsorption process is completed, the tail gas with a high concentration of nitrogen and carbon dioxide is exhausted by opening the bath outlet end. This step is carried out at least up to the point at which displacement desorption of the co-adsorbed carbon dioxide begins, ie, the point at which purge begins. Note that it is not preferable to continue this step beyond the carbon dioxide purge starting point because the recovery rate of carbon monoxide will decrease.

Step 4, Column D, represents a post-purging gas recovery step. Here, the outlet end is closed and the purged gas at the outlet of the C column is recovered and pressurized. Since the carbon monoxide concentration in the column is high even in the gas after purging, this step improves the recovery rate. Additionally, the nitrogen and carbon dioxide adsorption zones move to the outlet end, facilitating the next purge step.

Step 5, Column D, represents a purge step. In this step, pressurized product gas (gas mainly composed of desorbed and recovered carbon monoxide) is introduced from the tower inlet via a booster.

The purged gas from the outlet end enters the inlet end of the A column. The purge gas pressure is at least higher than the adsorption pressure <5Kt/
ct! G or less, preferably higher than the adsorption pressure <2Kg1c
dG or less, and set arbitrarily according to the purity of the product gas. The purge gas is heated by the heat of adiabatic compression accompanying pressure increase, improving purge efficiency.

Column D in step 6 shows a purge step with pressurized product gas similar to step 5. In this step, since the outlet end of bath A is closed, purging is performed while the pressure inside column D is increased. The purity of the product gas used in this purge step (step 5.6) improves as the amount increases, but if the amount is too large, the throughput decreases, so it is preferably 80% or less of the product gas obtained in the desorption and recovery step. is preferably 60% or less.

Step 7 shows the column just after the purge step is completed. Here, the pressure in the purge step is released to atmospheric pressure or a pressure near atmospheric pressure. Furthermore, when the pressure reaches atmospheric pressure or near atmospheric pressure, it is depressurized and desorbed via an air pump.

In step 8, desorption is then performed under reduced pressure via a vacuum pump. Since the carbon monoxide adsorption capacity of the adsorbent is high below atmospheric pressure, the degree of vacuum here is preferably as low as possible, and at least 1
It is 50 Torr or less, preferably 100 Torr or less.

In the illustrated example, four columns A to D are provided, each of which sequentially performs steps 1 to 8 described above. In the 8 towers, steps 1 to 8 are shifted as shown in Table 1 so that carbon monoxide can be separated and recovered continuously. The connections of the eight columns in each step are as shown in FIG. The structure for continuously operating eight towers is shown in Figure 2, and the equipment shown is controlled by a computer.

The code 1 indicates a feed of 11 m, and the raw material mixed gas F is sent to the towers A to D.
It will be sent sequentially to Also, the vacuum pump 2 sequentially reduces the pressure in the columns A to D. Pressurization n3 sequentially sends a part of the product gas R in the gas holder 4 to columns AD.

In the figure, numerals 5 to 8 indicate flow rate adjustment valves, and numerals 9 to 29 indicate switching valves. ■
indicates tail gas.

Note that the raw material mixed gas to which the present invention can be applied can contain any component as long as an adsorbent that adsorbs the largest amount of -m carbon is used under the conditions of temperature and pressure for 2 hours in the adsorption step and purge step. It's okay to stay.

However, this does not apply to impurities that reduce the carbon monoxide adsorption ability of the adsorbent. Such raw material mixed gas includes off-gas generated from converters, blast furnaces, N-air furnaces, etc., but is not limited thereto.

Further, the adsorbent used in the present invention may be any adsorbent as long as it selectively adsorbs carbon monoxide relative to other components.

In the present invention, at least four adsorption towers are required to continuously operate the supply of raw material mixed gas, supply of purge gas, and recovery of product gas.

Examples are shown below.

Example 1 A 1N solution of CuCJ12 was prepared and 100J11! Na-Y type zeolite (1.5 mφ) was placed in a round bottom flask.

5 tan L pellets (including 20% binder) 10g
Add 50ml of 1NCLICJ12 solution, attach a condenser to the round bottom flask, and heat to 100°C with a mantle heater.
The mixture was heated under reflux for 2 hours. After standing still, the supernatant was collected by decantation, and further added with INCtlCfz solution 5.
0d was added and refluxed in the same manner. A total of 5 reflux operations
The zeolite was thoroughly washed with pure water, dried at 110°C, and then calcined in an electric furnace at 550°C for 2 hours to prepare an adsorbent.

In addition, as a result of mixing the recovered supernatant liquid and measuring the ion exchange rate by determining the Nam released by luminescence analysis, it was found that 86
．． 5%, and the loading Cujfi per unit adsorbent is 8
．． It was 87wt%.

This Cu (n)-Y type zeolite (1.5 mφ, 5
Weigh 1 (l) of mtm h pellets, place them in a 100-sized eggplant-shaped flask, set in a rotary vacuum evaporator, and vacuum degas at 95°C or higher.

After degassing, the sample is cooled to room temperature while applying a vacuum.

- On the other hand, Cu C1,2.2H208,39 was dissolved in 14 times of water to make it 20m. This becomes a saturated solution of CuCJ12.

A capillary is attached to the leak cock of a rotary vacuum evaporator, and while the inside of the eggplant-shaped flask is maintained in a vacuum, the above solution is dropped 2 to 3 drops at a time to impregnate the adsorbent.

When the adsorbent leaks out evenly, stop dropping and return the inside of the flask to normal pressure. Further, the impregnated sample is transferred to a suction filter equipped with a wire mesh, the remaining solution is poured onto the sample, and after suction filtration for about 30 minutes, it is spread on a magnetic mouth and air-dried overnight. The air-dried sample was vacuum-dried at 110° C. for 3 hours in a vacuum dryer to obtain an adsorbent of the present invention. Supported Cuf of this adsorbent
It was 15.96 wt%.

Cu(n)Y-CUCLz obtained in this way,
CLI content 15wt%, 1.5#1IIIφ.

5ma L pellet with inner diameter of 50Mφ and height of 800an
1000g (dry) was filled into the adsorption tower, and the
% or higher purity Co gas at 250°C for 2 hours, about 1Nf
/min distribution, Cu Z 10 Cu ” kZiJ
It cost 1 yuan. While supplying FJ and CO gas, the temperature inside the column was lowered to 60° C. and maintained at approximately atmospheric pressure. The Co
The gas supply was stopped, a vacuum pump was connected, and the mixture was evacuated for 5 minutes. The pressure inside the column after 5 minutes was 80 Torr.

Standard gas (Go 80.0% by volume) assumed to be converter gas from the inlet end into the adsorption tower under reduced pressure.

CO210, 51 mountain%, H21,0 caecum%.

N28.5% by volume) was injected at 1.4Nf/1n, and 0.
After reaching 3KI/aiG, the outlet end was opened and a Co/CO2 gas analyzer using non-dispersive infrared absorption method was used to measure the Co,
CO2 concentration was measured continuously. When the outlet gas concentration almost matches the inlet gas concentration, the standard gas flow is stopped and the temperature reaches 99.9.
%up of Co gas, same < 1.4Ni/1n, 0
．． The outlet gas concentration was measured by flowing at 3 Ky/dG.

Breakthrough and purge measurements were similarly conducted with the inside of the tower set at 70°C. Figure 3 shows the results of purge measurements at 60°C and 70'C. It can be seen that the purge characteristics of H2 and N2 are almost the same, but for CO2, the width of the adsorption zone is smaller in the 70'C method, and the displacement adsorption of CO2 is easier at high temperatures.

Examples 2 to 7 Cu(II)Y-CUC produced by the method shown in Example 1
JL2. Ctl content 16W%, 1.5mφ.

Four adsorption towers each having an inner diameter of 50 mφ and a height of BOOm were each filled with 5 mL pellets (10,009 dry) and installed in the apparatus shown in FIG. 2. Pure hydrogen gas was passed through INf/win at 120°C for 2 hours to activate the adsorbent.
Cu ” ” wocLI ” was reduced.

After setting the temperature inside the tower to the specified operating temperature, dust is removed.

Dehumidified converter gas (Co) 78-82% by volume.

CO29-11% by volume, N27-10% by volume.

H20, 8-2% by volume, 020.05% by volume or less.

PS with the system shown in the method of the present invention
A was performed to separate CO.

Cycle time is 20 minutes for each step, 2 minutes for step 1,
Step 2 was 3 minutes. Each experiment was run over 20 cycles, with flow 1. After the temperature was stabilized, the flow layer and concentration at each part were measured. The results of Examples 2) to 7) are shown in Table 2.

Note that with the throughput of this experimental equipment, the temperature increase due to adiabatic compression of the purge gas was small and no effect was observed.
The results were good.

(Effect of the invention) According to this invention, no tail gas is used in the pressure increasing step,
All use a mixed raw material gas, and the product gas is pressurized and heated through adiabatic compression in the purge process, which increases the adsorbent's selective adsorption capacity for carbon monoxide and increases the mass transfer rate. Processes can be carried out efficiently.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining one side of the flow of each gas in the separation and recovery method of the present invention, Fig. 2 is a diagram showing a four-column PSA @ installation for implementing the separation and recovery method of the present invention, and Fig. 3 The figure shows CO purge gas flowing through the tower after adsorption and exiting CoI.
It is a figure which calculated|required the change of 2 degrees. 1... Blower, 2... Vacuum pump, 4... Boosting nada, 4... Gas holder, 5-8... Flow rate control valve, 9
~29...Switching valve, A-D...Adsorption group, F...Mixed raw material gas, P...Purge gas, ■...Tail gas, De...1112 destination gas. Step step 1 diagram

Claims (2)

[Claims] (1) A mixed gas containing carbon monoxide as one of the main components and at least carbon dioxide and/or nitrogen is passed through a column containing a carbon monoxide selective adsorbent to selectively adsorb carbon monoxide. In the separation and recovery method for carbon monoxide, which is desorbed after carbon monoxide has been desorbed, there is a pressurization step in which the above-mentioned mixed gas is supplied to the tower where desorption and recovery of carbon monoxide has been completed, and the pressure is increased to at least atmospheric pressure; The adsorption process involves flowing the mixed gas at the above pressure until at least the component with the highest amount of adsorption after carbon monoxide begins to break through, and the outlet gas from the purge process is supplied to the tower after the adsorption process while releasing the pressure. Then, there is a preliminary purge step in which carbon monoxide and other adsorbed components are purged except for the component with the second largest amount of adsorption after carbon monoxide, and the outlet end of the column after the preliminary purge step is closed and the outlet gas from the purge step is removed. The product gas after desorption and recovery is pressurized to a pressure higher than the adsorption pressure in the adsorption step, and the temperature is raised by the heat of adiabatic compression. There is a purge process in which the gas is supplied to the end and at the same time the outlet end is opened to purge the adsorbed components that have the second largest amount of adsorption after carbon monoxide, and a desorption recovery process in which the column is depressurized after the purge process is completed to recover concentrated carbon monoxide. A carbon monoxide separation and recovery method in which the steps are repeated in sequence. (2) The carbon monoxide selective adsorbent has a silica/alumina ratio of 1
0 or less zeolite, Ni, Mn, Rh, Cu(I)
2. The carbon monoxide separation and recovery method according to claim 1, wherein one or more metals selected from Ag, Ag, and mixtures thereof are supported.