JPS60155521A - Process for purifying carbon monoxide from mixed gas containing carbon monoxide using adsorption process - Google Patents

Abstract

PURPOSE:To recover high-purity CO stably from feed gas, by measuring the concentrations of CO2 and N2 in the feed gas, controlling the amount of waste gas in the adsorption process or the amount of purge gas used in the purge process according to the concentrations, and carrying out the concentration and separation of CO. CONSTITUTION:An adsorbent capable of selectively adsorbing CO2 is packed in the adsorption columns A and B, and the column A is evacuated after purging. The pressure in the column A is raised to the adsorption pressure, and the feed gas is passed through the column A. After the adsorption process for a prescribed period, the pressure in the column A is released to atmospheric pressure or thereabout to effect the desorption of CO2 adsorbed to the adsorbent. The waste gas sent from the second-stage treatment apparatus is introduced into the column A under reduced pressure to purge the adsorbed CO2, and the column A is transferred to the next step after the completion of the purging process. The above operations are repeated alternately in the columns A and B to effect the continuous adsorption and removal of CO2 with the adsorbent. Separately, the product gas free from CO2 and ejected from the top of the columns A, B in the first-stage treatment is introduced into the second-stage treatment apparatus to remove H2 and N2, and is recovered as the highly concentrated CO gas.

Description

Detailed Description of the Invention The present invention uses a pressure fluctuation adsorption separation method (PSA method) to
The present invention relates to a method for stably obtaining high-purity carbon monoxide from a raw material gas containing at least carbon monoxide, carbon dioxide, and nitrogen, such as exhaust gas from a converter or blast furnace. Exhaust gas generated from smelting vessels in steel plants contains a relatively large amount of CO gas.

The composition of converter exhaust gas and blast furnace exhaust gas is within the range shown below.

If high-purity CO gas can be recovered at low cost from these exhaust gases, it could be used as a raw material for synthetic chemicals or as a suction gas into the molten metal in the scouring vessel. When considering CO gas as a raw material for synthetic chemicals, it is essential to remove oxidizing gases that would damage the reaction vessel, as synthesis reactions are usually carried out under high temperature and high pressure conditions. It is necessary to reduce it as much as possible. Furthermore, in order to increase the reaction efficiency, it is desirable to remove as much N2 as possible, which normally does not participate in the reaction. On the other hand, the gas suction operation into the scouring vessel is widely used to improve the efficiency of scouring molten metal, but it is expensive due to the risk of increasing the concentration of impure gas components (nitrogen, hydrogen, etc.) in the molten metal. Typically, Ar gas is used. If high-purity CO gas can be recovered at low cost from converter gas and blast furnace gas generated in steel plants, it is almost possible to use it as a suction gas in place of Ar. At this time, N2 in high purity CO gas. , N2
The concentration is preferably low to prevent increases in nitrogen and hydrogen concentrations in the molten iron, and the CO2 concentration is preferably low to prevent oxidation damage to carbon-based refractories, which are commonly used as refractory linings for smelting containers, or to prevent oxygen concentration in the molten iron. A low value is desirable from the viewpoint of preventing rise in temperature.

Conventionally, the process of recovering high-purity melon CO gas using the above-mentioned exhaust gas as a raw material has been to collect N2゜N2, C by a cryogenic separation method.
Method for dividing O2 or liquid preparation method, Coso
A method for selectively absorbing CO into a solution and recovering it, such as for RB, has been considered. However, the former requires low temperature and high pressure, and the latter requires high temperature and high pressure, and both have the disadvantage 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.

Previously, the present applicant proposed a pressure fluctuation adsorption separation method (P
An application was filed for an invention related to the SA method.

That is, in the prior invention (see Japanese Patent Application No. 58-110616), when CO is recovered by the PSA method from a mixed gas containing at least CO, CO2, and N2, CO2 is collected from '' in the first stage adsorption operation. By adsorbing and removing J:N2 in the second stage adsorption operation, high purity
Although a method for recovering O gas as a product gas has been shown, the method for operating a system based on this method under optimal conditions has not been sufficiently elucidated. In other words, the composition of the converter exhaust gas, which is the raw material gas for this system, is constantly changing, and high-purity CO
N2, which should be removed from the converter gas when recovering the gas,
The content of impure gas components such as CO2 is fluctuating. The most economical method to operate this system while maintaining the purity of the high-purity CO gas recovered under this pre-promotion above a certain level has not yet been determined. As a result of extensive research into this point, the present inventors have finally discovered the optimal method of operating this system.

The present invention provides a method for condensing carbon monoxide in a raw material gas containing at least carbon monoxide, carbon dioxide, and nitrogen by a two-stage adsorption operation. The method uses two or more adsorption towers containing an adsorbing material that selectively adsorbs carbon dioxide, and the method is a pressure fluctuation type in which at least an adsorption step and a desorption step including a purge operation are repeated in each adsorption tower. (b) The second stage adsorption operation consists of removing carbon dioxide from the raw material gas by adsorption separation. (hereinafter referred to as the first stage product gas) using two or more adsorption columns filled with adsorbent materials that are selective for carbon monoxide in the first stage product gas; Adsorption process of the adsorption tower (II) Purge of the adsorption tower (nl) Consists of repeating at least three steps consisting of desorption and recovery of product gas, and the waste gas discharged from the adsorption process of the second stage treatment is processed in the first stage. (C) measuring at least the carbon dioxide and nitrogen gas concentrations in the raw material gas, or measuring at least the carbon dioxide and nitrogen gas concentrations in the product gas; Based on the results, the following three methods (I) Control the exhaust capacity horn of the decompression exhaust equipment used in the purge process of the first stage treatment (II) Control the amount of waste gas in the second stage treatment and adsorption process ( If) By performing at least one operation of controlling the amount of purge gas used in the second stage treatment and purge step, -
The present invention relates to a method characterized by concentrating and separating carbon oxide.

The present invention will be explained in detail below.

The present invention provides at least carbon monoxide in the first step.
The process of removing carbon dioxide from a raw material gas containing carbon dioxide and nitrogen using a pressure fluctuation adsorption separation method is a normal PSA process.
The method may be carried out by repeating adsorption, depressurization, purging with product gas and pressurization with product gas, or other methods including at least an adsorption step and a desorption step including a purge operation. A preferred method for removing carbon dioxide from the raw material gas is as follows.

The method uses two or more adsorption towers filled with an adsorption material that is selective to carbon dioxide, and the method includes (I) a pressurization step of pressurizing the adsorption tower with the first stage product gas;
Pressurize at 0.2 to 3.0 KQ/ciG:J (I[) Adsorption to flow the raw material gas into an adsorption tower to mainly adsorb carbon dioxide, and recover the first stage product gas from which carbon dioxide has been removed. Step (In>) Next, a depressurization step (IV) in which the adsorption tower is depressurized to near atmospheric pressure. Next, an evacuation step (IV) in which the adsorption tower is evacuated by a decompression exhaust device (preferably, the discarding is performed at 300 T orr to 3
0 Torr) and (V) 2nd stage production < I) consists of a purge process in which the waste gas from the process is introduced into the adsorption tower after the exhaust process and is exhausted by a decompression exhaust equipment, and the adsorption is periodically performed. This method consists of repeating the above operation by changing the gas flow between the columns.

The purpose of the first stage treatment of the present invention is to adsorb and remove carbon dioxide, and since the adsorption capacity of carbon dioxide to the adsorbent is large, there are few difficulties in the adsorption step of recovering the product gas from which carbon dioxide has been adsorbed and removed. However, on the contrary, if the adsorption tower is depressurized,
Then, in the exhausting process, it is difficult to desorb the carbon dioxide adsorbed on the adsorbent and discharge it to the outside of the adsorption tower smoothly. That is, a situation is likely to occur in which carbon dioxide desorbed from the adsorbent is re-adsorbed and cannot be easily discharged outside the adsorption tower. The method of introducing purge gas as a carrier gas to help discharge the desorbed carbon dioxide to the outside of the adsorption tower is also adopted in the normal PSA method, but in the method of the present invention, the introduction of purge gas is The feature lies in the fact that the purge gas volume is increased by performing the process under the reduced pressure exhaust line f1, and in the normal PSA method, the product gas is used as the purge gas, and as a result, the product gas recovery rate is forced to decrease. In the present invention,
Taking advantage of the characteristics of the two-stage adsorption method, there is also no rationality for using the unnecessary waste gas discharged from the adsorption process of the second stage treatment, which will be described later, as a purge gas. As a result, carbon dioxide can be smoothly removed from the adsorbent, and as a result, carbon dioxide can be adsorbed and removed in the next adsorption step without any problems. After a detailed study of the relationship between carbon dioxide adsorption and removal efficiency, the relationship shown in Figure 1 was found, and the present inventors believe that this can serve as an operational guideline for smoothly adsorbing and removing carbon dioxide. This has been confirmed. 1st
The figure shows 1 unit per adsorbent unit type M filled in the adsorption tower.
It shows a relationship in which the amount of carbon dioxide that can be adsorbed in the adsorption step of the cycle increases with the purge gas volume in the purge step. That is, we have discovered a relationship in which as the purge gas volume increases, the desorption efficiency of carbon dioxide from the adsorbent increases, and therefore the number of adsorption sites that can adsorb carbon dioxide in the next adsorption step increases.

Therefore, by determining the purge gas volume corresponding to the carbon dioxide to be completely adsorbed from the measured values of the raw material gas flow rate and the carbon dioxide gas concentration in the raw material gas according to FIG. 1, stable carbon dioxide adsorption and removal becomes possible.

The purge gas volume may be controlled by controlling the amount of gas introduced from the second stage treatment, but may also be controlled by controlling the exhaust capacity of the decompression exhaust equipment.

That is, it is possible to increase the gas volume by increasing the exhaust capacity saw. Reducing the power required for the decompression exhaust equipment is an important point required for the operation of this system, and is shown in Figure 1.
The method of controlling this power to the necessary minimum based on the relationship between the two can be said to be an extremely important technology.

The second stage adsorption operation of the present invention is performed using an adsorbent material that has selectivity to carbon monoxide in the first stage product gas discharged from the first stage adsorption process, such as natural zeolite or modified zeolite. Or, the preferred method is to use two or more adsorption towers filled with synthetic zeolite etc. Flow the gas into an adsorption tower,
Easily adsorbed components in the gas at the outlet of the adsorption tower (-carbon oxide)
Continue to flow with the product gas in the first stage section until the concentration of the easily adsorbed component in the gas reaches the concentration of the easily adsorbed component in the gas at the adsorption tower inlet, or for an appropriate amount or time after reaching the concentration, or the concentrations of both become equal. Adsorption (1) step in which the product gas in the first stage is allowed to flow until just before the point to allow the adsorbent to adsorb easily adsorbable components.

The gas discharged from the adsorption tower in this step is
It is used as a purge gas in the purge step of 12i<v>.

(I[[) After the suction step (1), the process of reducing the pressure of the adsorption tower to an arbitrary pressure between the adsorption pressure and atmospheric pressure, (IV) After the completion of the depressurization process, the adsorption tower and exhaust desorption are completed. A depressurization and depressurization process in which two adsorption towers are connected, the former gas is introduced from the former adsorption tower to the latter adsorption tower, and the pressure of the former adsorption tower is reduced to atmospheric pressure or near atmospheric pressure. At this time, the pressures of both adsorption towers may be approximately equalized. Alternatively, a method may be adopted in which the gas released when lowering the pressure in the former adsorption tower is released outside the system and is not introduced into the latter adsorption tower.

(V) Next, a purge step in which the product gas is introduced into the depressurized adsorption tower to purge difficult-to-adsorb components. The step of introducing the gas discharged from the adsorption tower in this step into the adsorption tower that has completed the adsorption (II) step described later is optional.

(Vl) A recovery step in which the adsorption tower that has completed the purge step is evacuated to below atmospheric pressure, the easily adsorbed components adsorbed by the adsorbent are desorbed, and the gas is recovered as a product gas.

(■) The adsorption tower that has completed product gas recovery and the adsorption tower that has completed the absorption W (I) process are connected, and the depressurized and released gas from the latter adsorption tower is introduced into the former adsorption tower to easily absorb the adsorbent. Adsorption (I[) step to adsorb adsorbed components.

(■) Next, the suction @jh that has completed the adsorption (I) step and the adsorption tower that has completed the depressurization and release step are connected, and the gas discharged from the purge step of the latter adsorption tower is introduced into the former adsorption tower. ,
This method consists of an adsorption (Ill) step in which easily adsorbable components are adsorbed onto an adsorbent, and is characterized in that the above operation is repeated by periodically changing the flow of gas between adsorption towers. Note that steps (Vl) and (W) are determined according to the methods of steps (1) and (rV), respectively, and their implementation is arbitrary.

In the second stage treatment (I) of the present invention, the first stage 111!
This is the pressurization process of the adsorption tower that absorbs the product gas.

Since the gas to be recovered at this stage is a component that is easily adsorbed, high adsorption pressure is not required, and only 3KO/dGl! i! It is sufficient to use an adsorption pressure of about 100%, and a lower adsorption pressure may also be used.

Step (IF) is an adsorption (I) step, which is a step in which easily adsorbable components in the first stage product gas are adsorbed onto an adsorbent. The point at which the concentration of easily adsorbable components in the gas flowing into the adsorption tower outlet becomes equal to that in the gas flowing into the adsorption tower inlet means the end of adsorbent breakthrough. Since the adsorbent component is easily adsorbed, it is possible to recover a large amount of product gas per ton with a predetermined amount of adsorbent, or to collect product gas with good purity.
In order to achieve this, it is necessary to adsorb easily adsorbable components to the adsorption sites that remain in the adsorbent even after the completion of breakthrough or after the completion of breakthrough.
It requires flowing a stage product gas or flowing a first stage product gas for a period of time. Alternatively, there may be fewer problems in terms of product gas purity even if the adsorption is performed until a little before reaching the end of breakthrough.

Since it is important to determine the purity of the product gas that the adsorption (I) step is continued to any level before or after the adsorbent breakthrough, this point was studied in detail. The easily adsorbed component in the first stage product gas of the present invention is carbon monoxide, and the poorly adsorbed component is nitrogen. Before the breakthrough ends, nitrogen, which is a difficult-to-adsorb component, is also co-adsorbed on the adsorbent, and if the product gas is collected as is, the product purity will decrease by 1.
It's hard to play. However, the degree of co-adsorption of poorly adsorbed components depends on the composition of the first stage product gas, and when a gas with a small amount of poorly adsorbed components is introduced into the adsorption (I) process, the breakthrough ends. It is also possible to finish the suction step (1) beforehand. It is not desirable to continue the adsorption (I) step for an excessively long time even after the breakthrough has been completed, as this results in a large amount of easily adsorbable components being discarded.

Therefore, it is desired to control the adsorption (I) process in such a way that the purity of the product gas is maintained constant and the waste M of easily adsorbed components is kept to a minimum. Upon consideration, it would be desirable to have a fingernail that can determine at which level the adsorption (I) process should be completed before or after the breakthrough.

The results of this study are shown in Figure 2. Figure 2 shows that the ratio of the concentration of poorly adsorbed components in the gas before and after the second stage treatment is
The relationship that changes depending on the amount of waste gas per unit weight of adsorbent per cycle in the adsorption (1) process is shown. When the concentration of the poorly adsorbed component in the first stage product gas increases, the absolute value of the concentration of the poorly adsorbed component in the product gas can be maintained constant by increasing the amount of waste gas. Therefore, while measuring the concentration of poorly adsorbed components in the first stage product gas, we determined from Figure 2 the minimum adsorption (I) process waste gas level necessary to maintain a constant product gas purity. This means that it is possible to operate to maximize recovery, and this is also an important technology.

In the step (Ill), after the adsorption step is completed, any pressure between the adsorption pressure and atmospheric pressure is preferably reduced to about atmospheric pressure. Discard the ingredients. This process (doesn't necessarily have to be done).

Step (IV) is to reduce the pressure inside the adsorption tower after the adsorption (I) step, and release the gas rich in difficult-to-adsorb components present in the gap between the adsorbent and the adsorbent to the outside of the adsorption tower. It is something to do. Either reduce the pressure of this adsorption tower to atmospheric pressure, or stop it at an appropriate pressure above atmospheric pressure, or use another adsorption tower that finishes product gas recovery below atmospheric pressure. The pressure may be lowered until the pressure is equalized. Note that it is optional to introduce reduced pressure gas into the adsorption tower after product gas recovery.

In step (V), the product gas is introduced into the adsorption tower under reduced pressure to purge the hardly adsorbable components still remaining in the voids of the adsorbent. In this case, the introduction pressure of the product gas is preferably lower than the adsorption pressure and higher than atmospheric pressure. Because it makes a big difference in purity,
Must be properly controlled. In other words, if the amount of purge gas is too small, the poorly adsorbed components in the adsorbent volume voids will not be sufficiently released to the outside of the adsorption tower, and the poorly adsorbed components will co-exist in the product gas that is subsequently recovered. Therefore, no improvement in product gas purity can be expected. However, if too much product gas is refluxed as purge gas, although the purity of the product gas is improved, there is the disadvantage that the amount of product gas that can be used as a product is reduced. Therefore, it is desired to establish a method for optimally controlling the amount of purge gas depending on the case and ensuring product gas purity and product gas amount. When this point was examined in detail, the relationship shown in FIG. 3 was obtained.

That is, the removal rate of poorly adsorbed components in the second stage treatment increases with the amount of purge gas used in the purge step. Therefore, if the concentration of the poorly adsorbed component in the first stage product gas subjected to the two-stage process is low, even if the purge operation has a low removal rate of the poorly adsorbed component, that is, the amount of purge gas is reduced,
It can be said from the relationship shown in FIG. 3 that a constant product gas purity can be ensured. Therefore, it is possible to actually measure the concentration of a difficult-to-adsorb component in the raw material gas to be subjected to the second stage treatment (a certain first stage product gas, or to predict it from the concentration in the raw material gas and the efficiency of carbon dioxide removal in the first stage treatment). Based on the estimated concentration of the poorly adsorbed component in the first stage product gas, the removal rate of the poorly adsorbed component is determined with reference to the required product gas purity, and the amount of purge gas required for this is determined and controlled. By adopting this method, it is possible to simultaneously ensure the purity of the product gas and the maximum amount of product gas recovered.

In addition, in this purge step, the gas discharged from the adsorption tower is the product gas plus gas rich in poorly adsorbed components in the adsorbent volume voids, and has a composition sufficiently rich in easily adsorbed components. It is preferable to introduce it into another adsorption tower that has completed the adsorption (I[) step, which is product gas recovery or vacuum gas recovery, to adsorb and recover easily adsorbable components, but it may also be disposed of outside the system. do not have.

In the step (Vl), the adsorption tower after the purge step is heated to 300 TOrr or less, preferably 300 to 3
The pressure is reduced to 0T orr, and the components adsorbed by the adsorbent are desorbed and recovered as a product gas.

Step ′ (■) is the adsorption tower and adsorption (1
) An adsorption (If) step in which the adsorption towers that have completed the process are connected, and the reduced pressure gas from the latter adsorption tower is introduced into the former adsorption tower to cause the adsorbent to adsorb easily adsorbable components.

Step (■) connects the adsorption tower that has completed the adsorption (If) process and the adsorption tower that has completed the depressurization and release process, and introduces the gas discharged from the purge process of the latter adsorption tower into the former adsorption tower. death,
This is an adsorption (I [[-) step] in which easily adsorbable components are adsorbed onto the adsorbent. This step (■) is optional.

Hereinafter, a detailed explanation of the present invention will be given based on a method of first removing carbon dioxide in converter exhaust gas, then removing nitrogen and hydrogen, and separating and recovering carbon monoxide, which is a typical example of the present invention. However, the method of the present invention is not limited to these specific examples.

FIG. 4 is a flow sheet of a system for continuously separating and recovering carbon monoxide from converter exhaust gas by an adsorption cycle, and FIG. 5 is a flow sheet showing the concept of the control system of the system of FIG. In FIG. 5, G and H represent the first and second stage processing devices, respectively.

First, the suction operation will be explained based on FIG.

Adsorption towers A and B house adsorbents that selectively absorb carbon dioxide. Adsorption tower A has completed the purge process, valves 1 to 6 are closed, and the adsorption tower pressure is 300To.
The pressure is reduced to below rr, preferably to 30 Torr.

On the other hand, adsorption tower B has completed the adsorption process and is ready for the depressurization process.
All valves 7 to 12 are in an idle state, and only valve 9 is in an open state. Taking this state as a reference and focusing on the adsorption tower A, an example of the adsorption cycle is as follows. First, valve 6 is turned on to introduce the first stage product gas into adsorption tower A.

The pressure of adsorption tower A is 0.01~”k(1/ci G
, preferred L/ <&;t O,2Jl ~1.0kll
When the adsorption pressure of l/cIIG is reached, valve 6 is closed and valve 1.2 is opened to adsorb the raw material gas to maintain the adsorption pressure f? Flow to 31A. After completion of the adsorption process for a certain amount of raw material gas for a certain period of time, valves 1 and 2 are closed, and then valve 3 is turned on to reduce the internal pressure of the adsorption tower to near atmospheric pressure. When the pressure in adsorption tower A reaches near atmospheric pressure, valve 3 is closed, then valve 4 is opened, and vacuum pump 40 is used to perform reduced pressure iJI gas to desorb carbon dioxide adsorbed on the adsorbent. . Evacuation is performed until the exhaust pressure at this time becomes 300 Torr or less, preferably 30 Torr, and then a purge step is performed in which the valve 5 is opened and the waste gas from the second stage treatment device is introduced under reduced pressure. When the purge process is completed, valves 4 and 5 are closed. The next step is to go back to the beginning and listen to valve 6.

By sequentially repeating the above operations in each of the adsorption towers A and B, carbon dioxide is continuously adsorbed onto the adsorbent and removed. In the first stage treatment, the first stage product gas from which carbon dioxide has been removed flowing out from the tops of adsorption towers A and B is introduced into the second stage treatment equipment, where hydrogen and nitrogen are removed and the product gas is highly concentrated. It is recovered as concentrated carbon monoxide gas. Adsorption towers C, l)', E, and F house adsorbents that selectively adsorb easily adsorbable components (-carbon oxide). Adsorption towers C and Dk,! The adsorption process will be explained below. This is based on the situation where adsorption tower C is in the absorption@(I) process and adsorption tower C is in the product gas recovery process. At this time,
Valve 18.17 becomes a leap and the first stage 111! i Product gas is flowing into the adsorption tower C, while the valve 27 is open to desorb and desorb easily adsorbed components adsorbed on the adsorbent in the adsorption tower.
It is recovered as product gas. The adsorption pressure of the adsorption tower C is naturally determined by the pressure of the first stage product gas, but is 0.01 to 3.0k (1/crtr G %
Preferably, 2 to 1.0 kg/air G is appropriate. On the other hand, in the process of recovering product gas from the adsorption tower, it is desirable to maintain the adsorption tower pressure at 300 Torr or less, preferably at 30 Torr.

Adsorption (I) in which carbon oxide is adsorbed by the adsorbent by flowing a certain amount of gas into the adsorption tower C for a certain period of time or a certain amount The recovery process is completed.Next, the valve 19 in the connecting pipe between adsorption towers C and D is opened to reduce the internal pressure of adsorption tower C to near atmospheric pressure.The gas released at this time is introduced into the adsorption tower. (adsorption<II) step). Adsorption tower C (7) When the internal pressure of the tower approaches atmospheric pressure, the valve 20 is opened to introduce the product gas from the product gas tank 42 into the adsorption tower CC, thereby expelling the difficult-to-adsorb component gas present in the gaps between the adsorbents. Perform a purge step. At this time, the gas flowing out from the top of adsorption tower C is controlled by valve 1.
9 into the adsorption column, and easily adsorbed components are adsorbed by the adsorbent (adsorption step (■)).

When the purge process is completed, valves 19, 20 are closed and valves 21 and 22 are opened. With this operation, the adsorption tower C moves to the product gas recovery process under reduced pressure using the decompression exhaust equipment 41, while the adsorption tower C moves to the adsorption (II) process,
Following the adsorption (I[) step, a pressurization step using the first stage product gas begins. When the pressure inside the column of adsorption [0] reaches a predetermined suction pressure in the pressurization step, the valve 23 is closed. The adsorption tower is opened and the adsorption tower moves to the suction 5t (I) step.The above operations are the steps until the adsorption towers C and D return to the standard situation, although their roles have changed.This operation is repeated in sequence. As a result, it is difficult to separate and purify carbon oxide gas, which is an easily adsorbed component, by continuously adsorbing it on the adsorbent.
, F are also made by repeating the same process as C and D.

Next, based on FIG. 5, the optimal operating method of this system will be described. The concentration of carbon dioxide and nitrogen in the raw material gas is measured using an analyzer 45.
1st stage 111! The i-product gas is continuously measured by an analyzer 46, and the product gas is continuously measured by an analyzer 47. Gas chromatography, infrared absorption meter, etc. can be used as the analyzer. These analytical signals are transmitted by the flowmeter (
(not shown) is transmitted to the computer 44 together with the signal. Control to most efficiently remove carbon dioxide in the first stage treatment (carry out as follows.Based on the carbon dioxide 111 signal of the analyzer 45 and the raw material gas flow rate signal, the amount of carbon dioxide to be adsorbed is determined by a computer. 44 and determine the required purge gas volume from the relationship shown in Figure 1. Next, the amount of second stage waste gas that can be used for purging is determined based on the flow rate signal, and the required purge gas volume and 1- , decompression exhaust equipment 40
Calculate the exhaust capacity of If the decompression exhaust device 40 is a variable voltage/frequency electric motor, for example, it is extremely easy to control the transmission of computer signals that match the required exhaust capacity, and it is also possible to install a plurality of decompression exhaust devices in series or in series. Alternatively, a system may also be used that supports starting and stopping individual equipment as needed. Through these operations, even when the carbon dioxide concentration in the raw material gas becomes high, it is possible to remove carbon dioxide by increasing the exhaust capacity. On the other hand, when the degree of biliquefied carbon in the raw material gas decreases, by measuring the decrease in exhaust capacity, it becomes possible to reduce the operating power cost of the system.

Next, a method for efficiently separating difficult-to-adsorb components, particularly nitrogen from carbon monoxide, in the second stage treatment will be explained. The analyzer 46 measures the nitrogen concentration in the first stage product gas (analyzer 4
Based on the nitrogen concentration in the raw material gas according to 5, the concentration estimated by calculation 1144 may be used) and the removal rate of difficult-to-adsorb components determined from the predetermined product gas purity, and from the relationship in FIG. 2 or 3, the required Calculate the operation to determine the amount of waste gas in the adsorption (I) process or the product gas m used in the purge process vA
Do it at 44. Based on this, the opening degree of the flow m regulating valve 14 for regulating the waste gas m@ of the adsorption (I) step or the opening degree of the flow m regulating valve 43 for regulating the amount of purge gas is controlled. By performing one or both of the above operations at the same time, the nitrogen removal rate can be improved by increasing the opening degree of the flow control valve 14 and/or 43 even when the nitrogen concentration in the raw material gas is high. By doing so, the product gas purity can be kept constant, and conversely, when the nitrogen concentration in the raw material gas is low, the product gas recovery rate and recovery amount of this system can be improved by reducing the waste gas amount and purge gas amount. It is possible to achieve an improvement in

Although the above explanation shows an example of feedforward control based on the raw material gas concentration signal, a feedback control system based on the product gas concentration signal of the analyzer 41 based on the relationships shown in FIGS. 1 to 3 is equally effective. .

In addition, activated carbon, activated alumina, synthetic or natural (including modified ones) zeolite, etc. are suitable as the adsorbent used in the adsorption tower for the first and second stage treatments.

Examples Examples will be described to provide a detailed explanation of the present invention. Figure 6 shows N2 in the raw material gas and product gas when product gas is recovered using converter exhaust gas as raw material by a system having the functions shown in the flow sheets of Figures 4 and 5.
This is the result of keeping CO2 constant at 11 degrees. Example (I)
The dynamic control system shown in Fig. 5 is used to set the capacity of the first stage decompression exhaust equipment appropriate for the initial raw material gas composition, and to adjust the adsorption process waste gas amount and purge of the second stage treatment. This is the result of continuous operation with the process purge gas amount set. Although product gas recovery with the required 99% CO purity has almost been achieved, depending on the raw material gas composition, the purity may deteriorate to about 98% CO.

On the other hand, in Example (II), the fifth
This is the result of performing control according to the control loop shown in the figure, and product gas containing 99% CO is stably recovered.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the purge gas volume and CO2 absorption @ Figures 2 and 3 are graphs showing the relationship between the amount of waste gas in the adsorption (I) process and the removal rate of difficult-to-adsorb components. FIG. 4 is a flow sheet of a preferred apparatus for carrying out the present invention; FIG. 5 is a flow sheet for the operating system of the present invention; and FIG. 6 is a flow sheet of a preferred apparatus for carrying out the present invention;
@It is a graph showing the measured results. Patent applicant: Kawasaki Steel Corporation Osaka Sanso Kogyo Co., Ltd. (4 others)

Claims (1)

[Claims] In a method for concentrating and separating carbon monoxide in a raw material gas containing at least carbon monoxide, carbon dioxide, and nitrogen by a two-stage adsorption operation, (a) the first stage adsorption operation comprises: Two or more adsorption towers containing an adsorbing material that has a selective adsorption method for carbon dioxide in the raw material gas are used, and the method uses a pressure reduction process in which at least an adsorption step and a desorption step including a purge operation are repeated in each adsorption tower. (b) the second stage adsorption operation consists of removing carbon dioxide from the feed gas by variable adsorption separation; The method uses two or more adsorption towers filled with adsorbent materials that are selective for carbon monoxide in the first stage product gas (1) Adsorption process of the old tower (IF) Purging of the adsorption tower (III) Consists of repeating at least three steps consisting of recovery of the product gas, and the waste gas discharged from the adsorption process of the second stage treatment is (C) Measuring at least the carbon dioxide and nitrogen gas concentrations in the raw material gas, or measuring at least the carbon dioxide and nitrogen gas concentrations in the product gas. And based on the results,
The following three methods (I) Control the exhaust capacity of the decompression exhaust equipment used in the purge process of the first stage treatment (IF> Control the amount of waste gas in the adsorption process of the second stage treatment (III) Second stage treatment By performing at least one operation of controlling the amount of purge gas used in the purge process of -
- A method characterized by concentrating and separating carbon oxide.