JPH08119603A - Production of carbon monoxide and hydrogen simultaneously from gaseous mixture - Google Patents

Abstract

PURPOSE: To produce high-purity carbon monoxide and hydrogen from a gaseous mixture without need for a large power at the time of forcing a gas necessary to purge an adsorption tower into the tower under pressure. CONSTITUTION: A gaseous mixture contg. carbon monoxide and hydrogen is introduced into an adsorption tower while maintaining a working pressure selected to control the partial pressure of carbon 2 monoxide to 1-5kg/cm<2> A in the adsorption stage. The gas in the adsorption tower is discharged under atmospheric pressure after the adsorption stage, and the pressure in the tower is lowered close to atmospheric pressure in the discharge stage. The adsorption tower is further evacuated by a vacuum pump to desorb the carbon monoxide adsorbed on an adsorbent in the desorption stage. The hydrogen obtained in the adsorption stage is forced into the adsorption tower under pressure after the desorption stage to increase the pressure in the tower above the pressure necessary to the succeeding adsorption stage in the pressure increasing stage.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a pressure fluctuation adsorption method (PS
According to A), it relates to a method for co-producing carbon monoxide and hydrogen from a mixed gas containing carbon monoxide, hydrogen and a small amount of carbon dioxide, methane and nitrogen.

[0002]

2. Description of the Related Art As a gas separation technique for separating and recovering a target gas such as hydrogen and carbon monoxide from a mixed gas containing carbon monoxide, hydrogen and a small amount of carbon dioxide, methane, nitrogen, etc. A gas separation method by a variable adsorption method is known. This is a gas separation method in which a specific gas is selectively adsorbed under a high pressure and the adsorbed gas is desorbed under a low pressure, and the productivity is suitable for treating a large amount of gas. Although it is a high method, the product hydrogen obtained in the adsorption process and the product carbon monoxide obtained in the desorption process are mixed with unadsorbed gas other than the target component and residual unadsorbed gas in the tower It is difficult to raise the purity of the product gas above the limit. Therefore, for the former, the selectivity of the adsorbent and the operating conditions are important, and for the latter, the displacement purging step of the adsorption tower is important. As a technique for highly purifying such a product gas, for example, in Japanese Patent Laid-Open No. 63-62522, a gas mixture consisting of a primary component / a secondary component is used to remove a primary component in an adsorption process and a desorption process in a desorption process. In order to separate the two-component product gas of the secondary component, an adsorbent having a gas selectivity of 20 or more is used, and a separation method by a process consisting of adsorption-displacement purge-decompression-desorption-pressurization is described. .

[0003]

However, in the method for separating a two-component gas described in JP-A-63-62522, the displacement purging step is performed under a high pressure which is almost the same as the adsorption pressure in the adsorption step. Since the replacement purge gas is increased, the replacement purge amount increases due to the increase in the adsorption amount of the secondary component gas, and the replacement purge gas needs to be compressed, which requires a large amount of power. Further, when applied to a mixed gas of two or more components, there is a drawback that a gas other than the target component is necessarily mixed with any of the gases unless the adsorbent accumulates other than the primary component / secondary component, and the purity is lowered. . The present invention has been made in view of the above circumstances, and does not require a large power for injecting the gas required for the displacement purge of the adsorption tower into the adsorption tower, and yet has a high purity and a carbon monoxide content higher than that of the mixed gas. And a method of co-producing hydrogen.

[0004]

A method according to the above-mentioned object.
The method of co-producing carbon monoxide and hydrogen from the described mixed gas is a method of adsorbing carbon monoxide in a mixed gas containing carbon monoxide and hydrogen under high pressure on an adsorbent to produce hydrogen which is a difficult-to-adsorb component. In the method of co-producing carbon monoxide and hydrogen from a mixed gas in a pressure swing adsorption method in which the adsorbed carbon monoxide is desorbed under a low pressure to obtain the product carbon monoxide, the carbon monoxide is selected. The mixed gas is introduced into an adsorption tower filled with an adsorbent that adsorbs the carbon monoxide while maintaining a selected operation pressure at which the partial pressure of carbon monoxide is 1 to 5 kg / cm ² A, and the carbon monoxide is introduced. Is adsorbed on the adsorbent to recover hydrogen discharged from the adsorption tower, and after the adsorption step, the gas in the adsorption tower is released under atmospheric pressure to reduce the internal pressure of the adsorption tower. Before the pressure release process to reduce the pressure to near atmospheric pressure, The desorption step of further decompressing the adsorption tower to below atmospheric pressure by a vacuum pump to desorb carbon monoxide adsorbed on the adsorbent, and the hydrogen obtained in the adsorption step after the desorption step is completed in the adsorption tower. And a pressure increasing step of increasing the internal pressure of the adsorption tower to near the adsorption pressure required for the next adsorption step.

A method for co-producing carbon monoxide and hydrogen from a mixed gas according to claim 2 is the method for co-producing carbon monoxide and hydrogen from a mixed gas according to claim 1, wherein the depressurizing step and the desorption are performed. During this step, part of carbon monoxide recovered in the desorption step is fed into the adsorption tower in the forward direction of the gas flow in the adsorption step to release the impurity component gas in the adsorption tower. It is configured to have a displacement purging step for cleaning the inside of the adsorption tower.

[0006]

In the method for co-producing carbon monoxide and hydrogen from the mixed gas according to claim 1, the adsorption pressure in the adsorption step is
Depending on the partial pressure of carbon monoxide, which is the adsorbing component, 1 to 5 kg /
Since a mixed gas containing carbon monoxide and hydrogen, which is selected from the range of cm ² A and maintains this operating pressure, is introduced into the adsorption tower as a raw material gas to adsorb the carbon monoxide on the adsorbent, The adsorption efficiency of carbon monoxide and the product hydrogen purity can be improved. Here, the carbon monoxide partial pressure is (adsorption operation pressure) × (carbon monoxide concentration in the raw material gas),
It is a value displayed in absolute pressure (kg / cm ² A). FIG. 3 shows the experimental results obtained by actually changing the adsorbed carbon monoxide partial pressure to obtain the carbon monoxide recovery rate in the adsorption step and the concentration change of carbon monoxide contained in the product hydrogen. By setting the adsorbed carbon monoxide partial pressure to 1 kg / cm ² A or more, the recovery rate of carbon monoxide in the adsorption process is significantly increased, and further, the concentration of carbon monoxide contained in the product hydrogen is reduced. You can see that The carbon monoxide recovery rate and the carbon monoxide concentration on the vertical axis are the carbon monoxide recovery rate in the adsorption process and the carbon monoxide concentration in the product hydrogen obtained when the adsorbed carbon monoxide partial pressure was 1 kg / cm ² A. The carbon concentration value was displayed as 1.0.

The partial pressure of adsorbed carbon monoxide is 5 kg / cm ^2.
Co-production is sufficiently possible even if the temperature exceeds A, but the operating pressure is high, and for the safety of the equipment, the structure must be of high strength, leading to an increase in equipment costs. The partial pressure of adsorbed carbon monoxide is 5 kg / cm ² because the recovery rate of carbon monoxide is hardly improved.
It is desirable to set A as the upper limit. Furthermore, after the adsorption step, the gas in the adsorption tower is released under atmospheric pressure, and the internal pressure of the adsorption tower is reduced to near atmospheric pressure, so that gases other than the target component remaining in the adsorption tower, It can be released without the need for power. In addition, after desorption and recovery of carbon monoxide, the hydrogen obtained in the adsorption step is pressed into the adsorption tower to increase the internal pressure of the adsorption tower to the adsorption pressure required for the next adsorption step. , The hydrogen concentration in the adsorption tower becomes high,
Stable quality can be maintained without reducing the purity of hydrogen recovered in the subsequent adsorption step.

Further, in the method for co-producing carbon monoxide and hydrogen from the mixed gas according to the second aspect, the carbon monoxide having high purity recovered in the desorption step between the pressure release step and the desorption step is produced. By advancing into the adsorption tower in the forward direction of the gas flow in the adsorption step, the impurity component gas in the adsorption tower is released to clean the inside of the adsorption tower, so the purity of carbon monoxide recovered in the subsequent desorption step. Can be increased. Here, when carbon monoxide is fed in the opposite direction to the gas flow in the adsorption step, it is mixed with the impure gas component remaining in the upper part of the adsorption tower, so that the purity of carbon monoxide recovered in the desorption step is increased. Will fall.

[0009]

Embodiments of the present invention will now be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIG. 1 is an explanatory diagram showing an operation flow and a distribution state of gas in an adsorption tower in an apparatus to which a method of co-producing carbon monoxide and hydrogen from a mixed gas according to an embodiment of the present invention is applied, and FIG. FIG. 3 is an overall schematic explanatory view of the same apparatus, and FIG. 3 is a diagram showing a relationship between a carbon monoxide recovery rate and a carbon monoxide concentration in product hydrogen and an adsorbed carbon monoxide partial pressure in an adsorption step.

First, an apparatus to which the method for co-producing carbon monoxide and hydrogen from a mixed gas according to an embodiment of the present invention shown in FIG. 2 is applied will be described. An adsorbent for adsorbing carbon monoxide is filled inside the adsorption towers A, B, C, and D. The adsorption towers A, B, C, and D have an inner diameter of 25 mm and a height of 3700 mm, and as an adsorbent for carbon monoxide, JP-B-60-49022 (Patent 1326552).
The adsorbent containing aluminum halide supported on activated carbon as shown in Japanese Patent No. 4) is filled with 1.8 liters / tower. Here, as the carrier of aluminum halide,
Graphite can be used in addition to activated carbon, silica, activated alumina carrying a copper compound, zeolite being ion-exchanged with copper ions, inorganic compound carrier carrying copper chloride or aluminum halide, etc. It can be used.

Pipe pipes 12 and 12a are installed above and below the adsorption towers A, B, C and D, and automatic opening / closing valves A1 to A7 and B1 for communicating or closing the inside of the pipe pipes 12 are installed. ~ B7, C1 ~ C7, D1 ~ D
7 are provided. By opening / closing these automatic opening / closing valves, the adsorption towers A, B, C, D are moved to the mixed gas supply unit 15, the product carbon monoxide supply unit 16, the product hydrogen supply unit 17, and the off-gas supply unit 18 as required. It is configured to be able to communicate as appropriate. Further, a vacuum pump 10 and a buffer tank 13 are arranged in a path of a pipe pipe 12 connected to each adsorption tower A, B, C, D and a product carbon monoxide supply section 16, and each adsorption tower A, B, C is provided. , D is connected to the pipe pipe 12a and a compressor 11 for recycling the purge purge off gas containing carbon monoxide, which is used when purging the adsorption towers A, B, C and D, to the raw material. A buffer tank 14 for storage is provided. It should be noted that necessary instrumentation devices are omitted in the drawing.

Next, the operation of a series of steps for recovering carbon monoxide and hydrogen from the mixed gas using the above-mentioned apparatus is as shown in the time cycle of Table 1, for each of the adsorption towers A ...
D is the upper and lower automatic opening / closing valves An to Dn (only one of the valves provided in the adsorption tower of the target process is opened, n = 1 to 1).
Each step is cyclically repeated according to 7). Here, the method according to claim 2 will be described focusing on the operation of the adsorption tower A. Here, the concentrations of carbon monoxide, hydrogen, carbon dioxide, and methane in the mixed gas used as the raw materials are each 5
It is 0.20%, 45.93%, 3.52%, 0.35%. A state in which the lower pipe of the adsorption tower A communicates with the mixed gas supply unit 15 and the upper pipe communicates with the product hydrogen supply unit 17 independently at the time when the adsorption process of the target gas, carbon monoxide, is performed in the adsorption tower A. Then, the automatic opening / closing valves A1 and A5 are opened and the mixed gas is introduced into the adsorption tower A.

As shown in FIG. 1 (a), the desorption process is terminated before the breakthrough front of carbon monoxide reaches the upper part of the adsorption tower and at least one component other than hydrogen is not broken through. . The breakthrough front refers to the state of adsorption breakthrough of the specific component gas in the adsorption tower, and when the breakthrough front reaches the upper part of the adsorption tower, the concentration of the specific component in the discharged gas rapidly increases. Then, when the passage of the breakthrough front moving in the adsorption tower reaches a predetermined time predicted by experiments, etc.,
Alternatively, when the gas component of the discharge gas is measured and the concentration of hydrogen gas reaches a predetermined level, the automatic opening / closing valves A1 and A5 arranged above and below the adsorption tower are fully closed to end the adsorption step (FIG. 1 (a )). The internal pressure of the adsorption tower A in this step is a pressure higher than the atmospheric pressure by +3.5 kg / cm ^2, which is approximately 2.3 kg / cm ² A when converted to the adsorption carbon monoxide partial pressure.

Thereafter, the upper automatic opening / closing valve A7 is opened to release the gas in the adsorption tower A as off-gas until the atmospheric pressure is reduced to about atmospheric pressure. However, if necessary, the automatic opening / closing valve A7 is closed and A4 is opened. It can also be stored in the buffer tank 14. Impurity gas containing a large amount of components other than carbon monoxide and hydrogen is efficiently removed by such a pressure release step (FIG. 1 (b)). Then, at a predetermined time or when the internal pressure of the adsorption tower reaches a predetermined pressure, the automatic opening / closing valve A7 or A4 is fully closed, and the pressure release step is ended.

Then, from the lower part of the adsorption tower A, that is, in the forward direction of the gas flow in the adsorption step, the high concentration carbon monoxide stored in the buffer tank 13 is adsorbed by opening the automatic opening / closing valves A3 and A4. Impurity gas in the adsorption tower A is pushed out from the lower part to the upper part by feeding into the tower A,
The inside of the adsorption tower A was washed (Fig. 1 (c)). In this displacement purging step, the high concentration of carbon monoxide fed in uses the gas obtained in the desorption step according to the required product carbon monoxide purity, but in this example, it was obtained in the desorption step. About 50% of the gas is supplied to the adsorption tower A, and when the predetermined time is reached, the automatic opening / closing valves A3 and A4 are closed and this step is completed.

Next, the automatic on-off valve A2 at the bottom of the adsorption tower A is opened, and the pressure inside the adsorption tower A is reduced by the vacuum pump 10 until the adsorption pressure becomes 50 Torr, and the carbon monoxide adsorbed by the adsorbent is removed. It was desorbed (Fig. 1 (d)). During this period, the carbon monoxide is supplied through the buffer tank 13 as a gas used in the product carbon monoxide supply unit 16 and the substitution purge process. Then, when the predetermined time was reached, the automatic opening / closing valve A2 was closed to complete the desorption process.

In the pressurizing step, the high-purity hydrogen obtained in the adsorbing step is supplied to the automatic opening / closing valve A6 from the upper part of the adsorption tower A, which has completed the desorption step as described above, or from the lower part if necessary. It is opened and fed (Fig. 1 (e)), and the internal pressure of the adsorption tower A is raised to about 3.5 kg / cm ² G (the pressure difference from the atmospheric pressure) for a predetermined time or in a predetermined adsorption tower. When the pressure is reached, the automatic opening / closing valve A6 is closed to end this process, and the adsorption tower A moves to the next desorption process.

The above operations are cyclically and sequentially performed for the adsorption towers A to D according to the time cycles shown in Tables 1 and 2. In Tables 1 and 2, the automatic open / close valves A1 to D7 indicated by blanks indicate that they are in the closed state.
Tower D displays adsorption towers A to D, respectively. According to the method of claim 1, the same operation may be performed by a step omitting the operation step for performing the displacement purging step,
As an example, Table 3 shows the time cycle in three adsorption towers.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

As a result of separating the mixed gas as described above, the respective components of hydrogen, carbon monoxide, carbon dioxide and methane contained in the product hydrogen are 96.16%, 3.33%,
It is 0.01% and 0.50%, and the components of hydrogen, carbon monoxide, carbon dioxide and methane contained in the product carbon monoxide are 0.32%, 99.64%, 0.03%, 0.01
%, And the gas amounts of mixed gas, product hydrogen, and product carbon monoxide are 314.75, 107.09, and 141.5, respectively.
It was 1 Nl / Hr. The adsorption and desorption times in this example were each 300 seconds.

As a comparative example, displacement purging of the adsorption tower A with product carbon monoxide was carried out under a high pressure of 3.5 kg / cm ² G, and the amount of gas used for the displacement purging was determined as in 2. As a result of separating the mixed gas under the same conditions as in the above-mentioned example except that it was used 7 times, each component of hydrogen, carbon monoxide, carbon dioxide, and methane contained in the product hydrogen was
94.09%, 5.42%, 0.01%, 0.48%, and hydrogen and carbon monoxide contained in the product carbon monoxide,
Each component of carbon dioxide and methane is 4.28%, 88.9
It was 3%, 6.56%, and 0.23%. In the comparative example, the purities of hydrogen and carbon monoxide are lower than those of the examples, and moreover, the power for the injection of carbon monoxide is required in the displacement purging step. It rose by 50%.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and all modifications and the like without departing from the scope of the invention are within the scope of the present invention. For example, in the above-mentioned embodiment, an apparatus in which the number of adsorption towers is 4 has been described, but the present invention can be applied without being limited to the number of adsorption towers, and the replacement purge off-gas can be used as an off gas without being recycled to the raw material. It is also possible to omit the compressor 11 and the buffer tank 14 or to install a blower or a fan between the buffer tank 13 and the automatic opening / closing valves A3 to D3.

[0025]

According to the method for co-producing carbon monoxide and hydrogen from a mixed gas according to claim 1, carbon monoxide and hydrogen are placed in an adsorption tower filled with an adsorbent which selectively adsorbs carbon monoxide. The mixed gas containing the carbon monoxide has a partial pressure of 1 to 5
an adsorption step of introducing while maintaining a selected operating pressure of kg / cm ² A to adsorb the carbon monoxide on an adsorbent and recovering hydrogen discharged from the adsorption tower; and the adsorption step. After the end of the step, the gas in the adsorption tower is released under atmospheric pressure, and a pressure releasing step of reducing the internal pressure of the adsorption tower to near atmospheric pressure, and further reducing the adsorption tower to below atmospheric pressure by a vacuum pump. A desorption step of desorbing carbon monoxide adsorbed on the adsorbent, and after completion of the desorption step, hydrogen obtained in the adsorption step is pressure-injected into the adsorption tower, and the internal pressure of the adsorption tower is changed to the next adsorption. Since it is configured to have a pressure raising step that raises the pressure to near the adsorption pressure required for the step, the hydrogen concentration in the adsorption tower becomes high, and the purity of hydrogen recovered in the subsequent adsorption step is stable without deteriorating. You can keep the quality that you did.

In the method for co-producing carbon monoxide and hydrogen from the mixed gas according to the second aspect, the carbon monoxide of high purity recovered in the previous step is adsorbed between the pressure release step and the desorption step. By feeding into the adsorption tower in the forward direction along with the gas flow of the process, the impurity component gas remaining in the adsorption tower is released to clean the inside of the adsorption tower, so that carbon monoxide recovered in the subsequent desorption step The purity can be further increased.

[Brief description of drawings]

FIG. 1 is an operation flow diagram and an explanatory diagram showing a distribution state of gas in an adsorption tower in an apparatus to which a method for co-producing carbon monoxide and hydrogen from a mixed gas according to an embodiment of the present invention is applied.

FIG. 2 is an overall schematic explanatory diagram of the device.

FIG. 3 is a diagram showing a relationship between a recovery rate of carbon monoxide and a carbon monoxide concentration in product hydrogen and an adsorbed carbon monoxide partial pressure in an adsorption step.

[Explanation of symbols]

 10 vacuum pump 11 compressor 12 pipe piping 12a pipe piping 13 buffer tank 14 buffer tank 15 mixed gas supply section 16 product carbon monoxide supply section 17 product hydrogen supply section 18 off-gas supply section A adsorption tower A1 automatic open / close valve A2 automatic open / close valve A3 automatic opening / closing valve A4 automatic opening / closing valve A5 automatic opening / closing valve A6 automatic opening / closing valve A7 automatic opening / closing valve B adsorption tower B1 automatic opening / closing valve B2 automatic opening / closing valve B3 automatic opening / closing valve B4 automatic opening / closing valve B5 automatic opening / closing valve B6 automatic opening / closing valve B7 automatic opening / closing Valve C Adsorption tower C1 Automatic opening / closing valve C2 Automatic opening / closing valve C3 Automatic opening / closing valve C4 Automatic opening / closing valve C5 Automatic opening / closing valve C6 Automatic opening / closing valve C7 Automatic opening / closing valve D Adsorption tower D1 Automatic opening / closing valve D2 Automatic opening / closing valve D3 Automatic opening / closing valve D4 Automatic opening / closing Valve D5 automatic opening / closing valve D6 automatic opening / closing valve D7 automatic opening / closing valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Kato 46-59 Nakahara, Tobata-ku, Kitakyushu, Fukuoka Prefecture 46-59 Nippon Steel Corporation Machinery & Plant Division

Claims (2)

[Claims] 1. Carbon monoxide in a mixed gas containing carbon monoxide and hydrogen is adsorbed on an adsorbent under high pressure, and hydrogen, which is a difficult-to-adsorb component, is discharged as a product, and the adsorbed carbon monoxide is removed. In the method of co-producing carbon monoxide and hydrogen from a mixed gas in the pressure swing adsorption method, which is desorbed under low pressure to obtain the product carbon monoxide, in an adsorption tower packed with an adsorbent that selectively adsorbs carbon monoxide. The mixed gas has a partial pressure of carbon monoxide of 1 to 5 kg / cm.
Was introduced while maintaining the chosen operating pressure becomes ² A, the carbon monoxide adsorbed on the adsorbent, the adsorption step for the recovery of hydrogen to be discharged from the adsorption tower after completion of the adsorption step A pressure release step of releasing the gas in the adsorption tower under atmospheric pressure to reduce the internal pressure of the adsorption tower to near atmospheric pressure, and further reducing the pressure of the adsorption tower below atmospheric pressure by a vacuum pump, A desorption step of desorbing carbon monoxide adsorbed on the agent, and after the desorption step is completed, the hydrogen obtained in the adsorption step is pressed into the adsorption tower, and the internal pressure of the adsorption tower is required for the next adsorption step. And a step of increasing the pressure up to near the adsorption pressure, the method for co-producing carbon monoxide and hydrogen from a mixed gas. 2. Between the pressure release step and the desorption step,
Part of the carbon monoxide recovered in the desorption step is fed into the adsorption tower in the forward direction of the gas flow in the adsorption step to release the impurity component gas in the adsorption tower to release the gas in the adsorption tower. The method for co-producing carbon monoxide and hydrogen from a mixed gas according to claim 1, which comprises a displacement purging step of performing cleaning.