JP3219612B2 - Method for co-producing carbon monoxide and hydrogen from mixed gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 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 small amounts 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 pressure separation technique has been developed. A gas separation method using a variable adsorption method is known. This is a gas separation method in which a specific gas is selectively adsorbed to an adsorbent under high pressure, and the adsorbed gas is desorbed under low pressure. This method is expensive, but the product hydrogen obtained in the adsorption process and the product carbon monoxide obtained in the desorption process are mixed with non-adsorbed gas other than the target component and mixed with non-adsorbed gas remaining in the column. It is difficult to increase the purity of the product gas to be used more than 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 purifying such a product gas with high purity, for example, Japanese Patent Application Laid-Open No. 63-62222 discloses a technique in which a primary component / secondary component gas mixture is converted into a primary component in an adsorption step and a desorption step in a desorption step. In order to separate a two-component product gas of a secondary component, a separation method is described using an adsorbent having a gas selectivity of 20 or more, and comprising a step of adsorption-substitution purge-decompression-desorption-pressurization. .

[0003]

However, in the method for separating a two-component gas described in JP-A-63-62522, the displacement purge step is performed under a high pressure which is almost the same as the adsorption pressure in the adsorption step. Since the process is performed, the displacement purge amount is increased due to an increase in the amount of adsorption of the secondary component gas, and it is necessary to compress the displacement purge gas. Therefore, a large power is required. Further, when applied to a mixed gas of two or more components, there is a disadvantage that a gas other than the target component is always mixed into any one and the purity is reduced unless a component other than the primary component / secondary component is accumulated in the adsorbent. .

The present invention has been made in view of such circumstances, and does not require a large power when pressurizing a gas necessary for purging the adsorption tower into the adsorption tower. An object is to provide a method for co-producing carbon monoxide and hydrogen.

[0005]

According to the present invention, there is provided a semiconductor device comprising:
The method of co-producing carbon monoxide and hydrogen from the mixed gas described in the paragraph is that carbon monoxide in a mixed gas containing carbon monoxide and hydrogen is adsorbed to an adsorbent under high pressure to produce hydrogen that is a hardly adsorbable component. In the method of co-producing carbon monoxide and hydrogen from the mixed gas in the pressure swing adsorption method to obtain the product carbon monoxide by desorbing the adsorbed carbon monoxide under low pressure and selecting carbon monoxide The mixed gas is introduced into an adsorption tower filled with an adsorbent to be adsorbed while maintaining the selected operating pressure at which the partial pressure of carbon monoxide is 1 to 5 kg / cm ² A. Is adsorbed on an adsorbent to recover the 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 relief process to reduce the pressure to near atmospheric pressure The adsorption tower is further depressurized to a pressure equal to or lower than the atmospheric pressure by a vacuum pump, and a desorption step of desorbing the carbon monoxide adsorbed on the adsorbent, and after the desorption step is completed, the hydrogen obtained in the adsorption step is subjected to the adsorption tower. And pressurizing the internal pressure of the adsorption tower to near the adsorption pressure required for the next adsorption step, and between the pressure release step and the desorption step, A part of the carbon monoxide to be recovered is fed into the adsorption tower in the forward direction with respect to the gas flow in the adsorption step, thereby releasing the impurity component gas in the adsorption tower and washing the inside of the adsorption tower. It has a purging step.

[0006]

In the method for simultaneously producing carbon monoxide and hydrogen from a mixed gas according to claim 1, the adsorption pressure in the adsorption step is:
Depending on the partial pressure of carbon monoxide, which is an adsorption component, 1 to 5 kg /
selected from the range of cm ² A, a mixed gas containing carbon monoxide and hydrogen while maintaining the operating pressure is introduced into the adsorption column as a raw material gas, so is adsorbed onto the adsorbent of the carbon monoxide, The carbon monoxide adsorption efficiency and the product hydrogen purity can be increased. Here, the carbon monoxide partial pressure is (adsorption operation pressure) × (carbon monoxide concentration in the raw material gas),
It is a value expressed in absolute pressure (kg / cm ² A). FIG. 3 shows experimental results obtained by actually changing the adsorbed carbon monoxide partial pressure to obtain the recovery rate of carbon monoxide in the adsorption step and the change in the concentration of carbon monoxide contained in the product hydrogen. By increasing the partial pressure of adsorbed carbon monoxide to 1 kg / cm ² A or more, the recovery rate of carbon monoxide in the adsorption step is greatly increased, and the concentration of carbon monoxide contained in the product hydrogen is reduced. You can see that it can be done. The vertical axis represents the recovery rate of carbon monoxide and the concentration of carbon monoxide. The recovery rate of carbon monoxide in the adsorption step obtained when the partial pressure of adsorbed carbon monoxide is 1 kg / cm ² A, and the monoxide concentration in product hydrogen The value of the carbon concentration was indicated as 1.0.

The partial pressure of adsorbed carbon monoxide is 5 kg / cm.
It is possible to co-produce even where ² A is exceeded, but the operating pressure is high, and the structure must be high in strength for the safety of equipment, leading to an increase in equipment costs. The partial pressure of adsorbed carbon monoxide is 5 kg / cm due to little improvement in the product carbon monoxide recovery rate.
It is desirable that the upper limit be ² A. Further, after the end of 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. Can be released without the need for power. Further, after performing the desorption to recover carbon monoxide, the hydrogen obtained in the adsorption step is press-fitted into the adsorption tower, and the internal pressure of the adsorption tower is increased to the adsorption pressure required for the next adsorption step. In addition, the concentration of hydrogen in the adsorption tower is increased, and stable quality can be maintained without lowering the purity of hydrogen recovered in the subsequent adsorption step.

Then, between the pressure release step and the desorption step, the high-purity carbon monoxide recovered in the desorption step is fed into the adsorption tower in the forward direction with respect to the gas flow in the adsorption step. Is released to clean the interior of the adsorption tower, so that 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, the purity of the carbon monoxide recovered in the desorption step is reduced because it is mixed with the impure gas components remaining in the upper part of the adsorption tower. Will drop.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will now be described with reference to the accompanying drawings to provide an understanding of the present invention. 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 for simultaneously producing carbon monoxide and hydrogen from a mixed gas according to an embodiment of the present invention is applied, and FIG. FIG. 3 is a diagram schematically illustrating the entire apparatus, and FIG. 3 is a diagram illustrating the relationship between the recovery rate of carbon monoxide in the adsorption step, the concentration of carbon monoxide in the product hydrogen, and the partial pressure of adsorbed carbon monoxide.

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

[0011] Pipe pipes 12, 12a are mounted above and below the adsorption towers A, B, C, D, respectively, and automatic opening / closing valves A1 to A7, B1 for communicating or closing the inside of the respective pipe pipes 12 are provided. ~ B7, C1 ~ C7, D1 ~ D7
Is provided. By the opening and closing operation of these automatic opening and closing valves, each of the adsorption towers A, B, C, and D is connected 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 necessary. It is configured to be able to communicate appropriately. A vacuum pump 10 and a buffer tank 13 are arranged in a path of a pipe 12 connecting each of the adsorption towers A, B, C, D and the product carbon monoxide supply unit 16. , D are connected to a compressor 11 for recycling a purge purge off gas containing carbon monoxide used for purging the adsorption towers A, B, C, and D into raw materials. A buffer tank 14 for storage is provided. In the figure, necessary instrumentation devices are omitted.

Next, the operation of a series of steps for recovering carbon monoxide and hydrogen from the mixed gas using the above-mentioned apparatus is described in the time cycle of Table 1 in each of the adsorption towers A to A.
D denotes upper and lower automatic on-off valves An to Dn (open only one of the valves provided in the adsorption tower in the target process, n = 1 to
Each step is repeated cyclically according to 7). Here, a method focusing on the operation of the adsorption tower A will be described. Here, carbon monoxide, hydrogen,
The concentrations of carbon dioxide and methane are 50.20% and 4 respectively.
5.93%, 3.52% and 0.35%. Adsorption tower A
At the time when the adsorption step of carbon monoxide as the target gas is being performed in
5, the upper piping opens the automatic opening / closing valves A1 and A5 so as to communicate with the product hydrogen supply unit 17 independently, and introduces the mixed gas into the adsorption tower A.

As shown in FIG. 1A, the desorption step is terminated before the breakthrough front of carbon monoxide reaches the upper part of the adsorption tower and in a state where at least one component other than hydrogen does not break through. . The breakthrough front indicates the state of adsorption breakthrough of a 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 and the like,
Alternatively, when the gas component of the discharged gas is measured and the concentration of the hydrogen gas reaches a predetermined level, the automatic opening / closing valves A1 and A5 arranged above and below the adsorption tower are fully closed, and the adsorption step is ended (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 about 2.3 kg / cm ² A in terms of the partial pressure of adsorbed carbon monoxide.

Thereafter, the upper automatic opening / closing valve A7 is opened, and the gas in the adsorption tower A is released as an off-gas until the pressure almost drops to the atmospheric pressure. If necessary, the automatic opening / closing valve A7 is closed and A4 is opened. It can also be stored in the buffer tank 14. By such a pressure release step, an impure gas containing a large amount of components other than carbon monoxide and hydrogen is efficiently removed (FIG. 1B). Then, when the internal pressure of the adsorption tower reaches a predetermined time or a predetermined pressure, the automatic on-off valve A7 or A4 is fully closed, and the pressure release step is completed.

Then, the high-concentration carbon monoxide stored in the buffer tank 13 is adsorbed from the lower portion of the adsorption tower A, that is, in the forward direction of the gas flow in the adsorption step, by opening the automatic on-off valves A3 and A4. The impure 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 replacement purge step, the amount of high concentration carbon monoxide to be sent is used according to the required product carbon monoxide purity using the gas obtained in the desorption step, but in this example, the gas obtained in the desorption step is used. About 50% of the gas is supplied to the adsorption tower A, and when a predetermined time has been reached, the automatic opening / closing valves A3 and A4 are closed to terminate the present process.

Next, the automatic opening / closing valve A2 at the lower portion 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 detached (FIG. 1 (d)). During this time, the carbon monoxide is supplied via the buffer tank 13 as a gas used in the product carbon monoxide supply unit 16 and the replacement purge step. Then, when a 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 on-off valve A6 from above or, if necessary, from the lower part of the adsorbing tower A after the desorption step is completed. It is opened and fed (FIG. 1 (e)), and the internal pressure of the adsorption tower A is increased to about 3.5 kg / cm ² G (differential pressure from the atmospheric pressure) for a predetermined time or in the predetermined adsorption tower. When the pressure reaches the pressure, the automatic opening / closing valve A6 is closed to end this step, and the adsorption tower A shifts to the next desorption step.

The above operations are sequentially performed on the adsorption towers A to D cyclically according to the time cycles shown in Tables 1 and 2. In Tables 1 and 2, the blanks of the automatic on-off valves A1 to D7 indicate that the valves are in the closed state.
Column D indicates adsorption columns A to D, respectively. In addition, the same operation can be performed by a process in which the operation process for performing the replacement purge process is omitted. As an example, a time cycle in three adsorption towers is shown in Table 3.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

As a result of the separation of the mixed gas as described above, the components of hydrogen, carbon monoxide, carbon dioxide, and methane contained in the product hydrogen are 96.16%, 3.33%,
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 the mixed gas, product hydrogen, and product carbon monoxide are 314.75, 107.09, and 141.5, respectively.
It was 1 Nl / Hr. Note that the adsorption and desorption times in this example were each 300 seconds.

As a comparative example, the purging of the adsorption tower A with the product carbon monoxide was performed under a high pressure of 3.5 kg / cm ² G, and the amount of gas used for the purging purge was changed to 2. Except for using 7 times, as a result of performing the separation of the mixed gas under the same conditions as in the above example, each component of hydrogen, carbon monoxide, carbon dioxide, and methane contained in the product hydrogen was:
94.09%, 5.42%, 0.01% and 0.48%, and hydrogen, carbon monoxide contained in the product carbon monoxide,
Each component of carbon dioxide and methane is 4.28%, 88.9
They were 3%, 6.56% and 0.23%. In the comparative example, the purity of hydrogen and carbon monoxide was lower than in the example, and power was required for injection of carbon monoxide in the displacement purge step. It has risen 50%.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and all changes and the like without departing from the gist are within the scope of the present invention. For example, in the above embodiment, an apparatus in which the number of adsorption towers is four has been described. However, the present invention is applicable without being limited to the number of adsorption towers. And the compressor 11 and the buffer tank 14 may be omitted, or a blower or a fan may be installed between the buffer tank 13 and the automatic opening / closing valves A3 to D3.

[0025]

According to the method for simultaneously producing carbon monoxide and hydrogen from a mixed gas according to the first aspect, carbon monoxide and hydrogen are supplied to an adsorption tower packed with an adsorbent for selectively adsorbing carbon monoxide. The mixed gas to be contained has a partial pressure of carbon monoxide of 1 to 5
an adsorption step of introducing while maintaining the selected operating pressure of kg / cm ² A to adsorb the carbon monoxide to the adsorbent and recovering hydrogen discharged from the adsorption tower; After the end of, the gas in the adsorption tower is released under atmospheric pressure, a pressure release step of reducing the internal pressure of the adsorption tower to near atmospheric pressure, and further reducing the pressure of the adsorption tower to below atmospheric pressure by a vacuum pump. After the completion of the desorption step of desorbing the carbon monoxide adsorbed on the adsorbent and the desorption step, the hydrogen obtained in the adsorption step is injected into the adsorption tower, and the internal pressure of the adsorption tower is adjusted to the next adsorption level. It is configured to have a pressure boosting step to raise the pressure to near the adsorption pressure required for the process, so that the hydrogen concentration in the adsorption tower increases, and it is stable without reducing the purity of hydrogen recovered in the subsequent adsorption step Quality can be maintained. Then, between the pressure release step and the desorption step, the high-purity carbon monoxide recovered in the previous step is fed into the adsorption tower in a forward direction with the gas flow in the adsorption step, thereby removing impurities remaining in the adsorption tower. Since the inside of the adsorption tower is washed by releasing the component gas, the purity of carbon monoxide recovered in the subsequent desorption step can be further increased.

[Brief description of the 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 simultaneously 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 view of the apparatus.

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

[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 open / close valve, A4: Automatic open / close valve, A5: Automatic open / close valve, A6: Automatic open / close valve, A7: Automatic open / close valve, B:
Adsorption tower, B1: automatic open / close valve, B2: automatic open / close valve, B3:
Automatic open / close valve, B4: Automatic open / close valve, B5: Automatic open / close valve, B
6: Automatic open / close valve, B7: Automatic open / close valve, C: Adsorption tower, C
1: Automatic open / close valve, C2: Automatic open / close valve, C3: Automatic open / close valve, C4: Automatic open / close valve, C5: Automatic open / close valve, C6: Automatic open / close valve, D: Adsorption tower, D1: Automatic Open / close valve, D2: Automatic open / close valve, D3: Automatic open / close valve, D4: Automatic open / close valve, D5: Automatic open / close valve, D6: Automatic open / close valve, D
7: Automatic open / close valve

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiya Higuchi 46-59 Ohara Nakahara, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Machinery & Plant Business Department (72) Inventor Yuzuru Kato Tobata-ku, Kitakyushu-shi, Fukuoka Ohara Nakahara 46-59 Nippon Steel Corporation Machinery & Plant Division (56) References JP-A-49-56893 (JP, A) JP-A-49-41292 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C01B 3/56 B01D 53/04 C01B 31/18

Claims (1)

(57) [Claims] 1. A method for adsorbing carbon monoxide in a mixed gas containing carbon monoxide and hydrogen onto an adsorbent under high pressure to discharge hydrogen, which is a component that is hardly adsorbed, as a product, and removing the adsorbed carbon monoxide. In a method in which carbon monoxide and hydrogen are co-produced from a mixed gas in a pressure swing adsorption method that is desorbed under low pressure and obtained as product carbon monoxide, an adsorption tower filled with an adsorbent that selectively adsorbs carbon monoxide is used. The mixed gas has a partial pressure of carbon monoxide of 1 to 5 kg / cm.
^An adsorption step of introducing while maintaining the selected operating pressure of ² A, adsorbing the carbon monoxide on an adsorbent, and recovering hydrogen discharged from the adsorption tower; and A pressure release step of releasing the gas in the adsorption tower to atmospheric pressure and reducing the internal pressure of the adsorption tower to near atmospheric pressure; A desorption step of desorbing the carbon monoxide adsorbed on the agent, and after completion of the desorption step, pressurize the hydrogen obtained in the adsorption step into the adsorption tower and use the internal pressure of the adsorption tower for the next adsorption step. A pressure increasing step to increase the pressure to near the adsorption pressure, and furthermore, between the pressure release step and the desorption step, a part of the carbon monoxide recovered in the desorption step is combined with the gas flow of the adsorption step. Impurities in the adsorption tower are sent by feeding the adsorption tower in the forward direction. A method for co-producing carbon monoxide and hydrogen from a mixed gas, the method comprising a purging step of discharging a substance component gas to wash the inside of the adsorption tower.