JPH0780232A - Starting method of pressure swing adsorption facilities - Google Patents

Abstract

PURPOSE:To obtain a means for restarting a vacuum pump smoothly after the storage of an operation and thereby simplify facilities by connecting directly the raw material line of an adsorption tower with an internal condition other than decompressed to a decompression line and starting the tower in a stage before the start of an operation when restarting a number of the adsorption towers after the stoppage of their operation. CONSTITUTION:In adsorption towers 1A to 1C filled with an adsorbent for adsorbing a specific component gas, the cycles each consisting of an adsorption step for adsorbing each specific gas component using the adsorbent, a decompression step for releasing the specific gas component adsorbed by a decompression line, and further, a pressure boosting step for restoring the pressure of the adsorption tower after decompression by the introduction of a pressure boosting gas, are combined alternately for each adsorption tower. In this pressure swing adsorption method, an adsorption tower is started by connecting directly the raw material line of the adsorption tower with an internal condition other than decompressed in a stage before the start of an operation by connecting the raw material line of that adsorption tower directly to the decompression line, when stopping the operation of adsorption towers 1A to 1C and restarting the operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a pressure swing adsorption method for concentrating and recovering a specific component in a mixed gas by changing the pressure of an adsorbent such as recovery of oxygen or nitrogen in air.
In particular, the present invention relates to a restart method after the operation is stopped in the pressure swing adsorption method.

[0002]

2. Description of the Related Art The pressure swing adsorption method (Press)
The recovery itself of the specific gas component by ure Swing Adsorption) is widely known as described in JP-B-63-58614 and JP-A-3-229611.

Taking, for example, the separation and recovery of oxygen from the air, an air is introduced into the adsorption tower by using a pressure swing adsorption apparatus in which a plurality of adsorption towers filled with zeolite as a nitrogen absorbent are arranged. Adsorption step of adsorbing nitrogen to the adsorbent, depressurizing step of depressurizing and adsorbing the adsorbed nitrogen with a vacuum pump, etc., and pressurizing step for introducing adsorbent gas to restore adsorbent adsorption capacity after depressurization The adsorption cycle is alternately combined for each adsorption tower to perform continuous operation.

In the middle of such a process, there are cases where the operation of the pressure swing adsorption device is stopped due to a power failure or equipment maintenance failure. In that case, if the operation is stopped for a long time, air gradually enters the adsorption tower in the depressurization step, and nitrogen gas or the like is released in the adsorption tower in the adsorption step or the pressurization step, and all the adsorption towers are released. Becomes almost atmospheric pressure. Therefore, when the apparatus is restarted in such a state, particularly when the vacuum pump is started, the startup itself of the vacuum pump can be relatively smoothly performed regardless of which adsorption tower is connected.

However, when the operation stop time is relatively short due to a power failure or the like, the adsorption tower that was in the depressurization step is still kept in the depressurized state. It becomes a load condition and it is difficult to start smoothly.

As a countermeasure against this, for example, in the pressure swing adsorption device shown in FIG. 4, three adsorption towers 1A, 1B and 1C are used.
And a suction gas pipe 3 for sucking the gas components adsorbed in the adsorption towers 1A, 1B, 1C by a vacuum pump 2.
A recycle valve 4 for starting the vacuum pump without a load or a suction valve 5 for introducing air is arranged midway.
Further, the on-off valves 6A, 6B, 6 are provided in the respective pipelines.
C, 7A, 7B, 7C, 8A, 8B, 8C are provided,
These valves 4A, 4B, 4C, 5A, 5B, 5C, 8
By the operation operation of A, 8B and 8C, three adsorption towers 1
A specific gas recovery operation is performed by A, 1B, and 1C.

In this device, the restarting after the operation is stopped is as shown by ● in the figure, the open / close valves 6A, 6B, 6
C, 7A, 7B, 7C, 8A, 8B, 8C are closed,
As shown by, only the suction valve 6 or the recycle valve 4 of the decompression line is opened.

As a result, the vacuum pump immediately after starting can be smoothly started in a state where air is supplied without being directly connected to the adsorption tower in a depressurized state, and after the vacuum pump reaches a steady state. A predetermined depressurization step is performed by connecting to the required adsorption tower.

[0009]

As described above, in the conventional starting method having no suction valve or recycle valve, it is difficult to smoothly start the vacuum pump after the operation is stopped.
In addition, in the structure shown in FIG. 4, a suction valve and a recycle valve are newly required in the conventional equipment, and such a device causes problems such as breakdown and maintenance.

It is an object of the present invention to provide a smooth restarting means for a vacuum pump after an operation stop without providing equipment such as a suction valve and a recycle valve, and to simplify such equipment.

[0011]

In order to achieve the above object, the present invention is directed to adsorbing a plurality of adsorption towers filled with an adsorbent for adsorbing a specific component gas onto the adsorbent. A cycle consisting of a step, a depressurization step of releasing the adsorbed specific component gas through the depressurization line, and a pressurization step of introducing a pressurization gas to restore the pressure of the adsorption tower after depressurization are alternately performed for each adsorption tower. In the combined pressure swing adsorption method, when the operation of the plurality of adsorption towers is stopped and then restarted, the inside of the adsorption tower is directly connected to the raw material line of the adsorption tower other than the depressurized state before the start of the operation. The feature is that it is activated.

[0012]

[Advantages] In the adsorption tower whose inside of the adsorption tower is in a depressurized state before the start of operation, regardless of the length of the operation stop time,
The inside is at atmospheric pressure or higher, so that even when this adsorption tower is connected to the decompression line, the vacuum pump provided in the decompression line does not become overloaded at the time of restarting and is smooth. It becomes possible to start.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an outline of a conventional pressure swing adsorption tower equipment equipped with three adsorption towers in order to apply the present invention to separation and recovery of oxygen from air. The components corresponding to the conventional example shown in FIG. 4 are designated by the same reference numerals.

In this embodiment, the recycle valve and the suction valve provided in the decompression line are omitted in the pressure swing adsorption tower equipment shown in the conventional example. Further, 9 in the figure is an opening / closing valve 8A to 8A for taking out a high concentration of oxygen as a product after recovering nitrogen in the adsorption step.
Product gas introduction pipe provided with C, 10 are adsorption towers 1A to 1
After the depressurization process of C is completed, the valves 11A, 11B, 11
A pressure-increasing pipe for increasing the pressure of the recovered oxygen via C is shown.

FIG. 2 shows a combination of operating cycles of the adsorption device shown in FIG.

Referring to FIGS. 1 and 2, in the adsorption tower 1A, the valve 6A of the raw material gas supply pipe is opened to introduce the raw material gas into the adsorption tower 1A to adsorb the specific gas to the adsorbent. A step (b) and a decompression step (c) of closing the valve 6A of the raw material gas supply line, opening the suction gas line valve 7A, and operating the vacuum pump 2 to absorb the adsorbed gas.
The valve 11A is opened and a part of recovered oxygen is introduced into the adsorption tower 1A to increase the pressure inside the tower (a).

While the adsorption tower 1A is in the adsorption step (a), the adsorption towers 1B and 1C are in the pressurization step (c) and the depressurization step (b), and while the adsorption tower 1A is in the depressurization step (b). The adsorption towers 1B and 1C are in the adsorption step (a) and the pressurization step (c), and while the adsorption tower 1A is in the pressurization step (a), the adsorption towers 1B and 1C are in the depressurization step (b) and the adsorption step (a). ), Each cycle is set so that continuous operation of the entire system is possible.

Next, a method of stopping and starting this equipment will be described.

First, referring to FIG. 2, the stopping method is as shown in FIG. 2 at time T ₁ , that is, the pressure raising step (a) of the adsorption tower 1A.
When the stop signal of the facility was the point of the facility T ₄
Continue normal operation until and stop the operation at T ₄ .
In this case, the adsorption tower 1A is stopped at the stage of completion of the pressure increasing step (next adsorption step), the adsorption tower 1B is completed at the pressure reducing step (next pressure increasing step), and the adsorption tower 1C is completed at the stage of adsorption step completion (next pressure reducing step). Similarly, when a stop signal is input at T ₂ , it is T ₅ , and when a stop signal is input at T ₃ , it is T.
_The equipment will be shut down at ₆ .

Therefore, in each stop state, the two adsorption towers excluding the adsorption tower which has completed the depressurization step are carried out in a state in which the adsorption pressure is slightly increased from atmospheric pressure, so that the state is substantially atmospheric pressure. Will stop at.

Next, referring to FIG. 3, a method of starting this equipment will be described.

For example, when restarting the equipment stopped at T ₅ , the next step is the decompression step in the adsorption tower 1
The raw material air introduction valve 6A and the vacuum exhaust valve 7A of A are opened. When the vacuum pump 2 is started in this state, the suction of the vacuum pump 2 is performed at atmospheric pressure, so that the vacuum pump 2 can be started in a no-load state. Vacuum pump 2 for equipment startup
You can do it as soon as is stable. In this state, the valve 6A is closed and the valves 6B, 8B, and 11C are opened, so that the adsorption tower 1A starts the depressurization step, the adsorption tower 1B starts the adsorption step, and the adsorption tower 1C starts the pressure increase step. enter.

When the operation is started from T ₄ and T ₆ , the same measures are taken as shown below.

That is, when the operation is started from T ₄ ,
The raw material air introduction valve 6 of the adsorption tower 1C whose next step is the depressurization step
C, the air exhaust valve 7C is opened. Also, when the operation is started from T ₆ , the next step is the adsorption tower 1B of the pressure reducing step.
The raw material air introduction valve 6B and the air exhaust valve 6C are opened.

By operating the valve as described above, the vacuum pump is prevented from being overloaded at the start of restarting, and smooth starting can be performed.

In the above embodiment, the case where three adsorption towers are provided has been described, but the present invention is not limited to this and can be applied to equipment having at least two adsorption towers. Further, in the present example, the raw material line and the decompression line of the adsorption tower after the adsorption step are connected and activated, but as another method, the raw material line and the decompression line of the adsorption tower after the pressurization step are finished. It may be directly connected and activated. Furthermore, the present invention can be applied to a pressure swing adsorption method in which the adsorption step of the next adsorption column is started in a step in which the adsorption capacity of the specific gas by the adsorbent in the specific adsorption column has a surplus capacity.

[0027]

As described above, according to the present invention, the vacuum pump provided in the decompression line does not become overloaded at the time of restarting the restart, and can be smoothly started. Is unnecessary,
Simplification of such equipment is achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of equipment for implementing the present invention.

FIG. 2 is a diagram showing an operation cycle of an adsorption tower.

FIG. 3 is a diagram showing an operation mode of the equipment shown in FIG.

FIG. 4 is a diagram showing a system of a conventional pressure swing adsorption device.

[Explanation of symbols]

 1A, 1B, 1C Adsorption tower 2 Vacuum pump 3 Suction gas pipe 4 Recycle valve 5 Intake valve 6A, 6B, 6C Open / close valve 7A, 7B, 7C Open / close valve 8A, 8B, 8C Open / close valve 9 Product gas introduction pipe 10 Boosting pipe 11A, 11B, 11C open / close valve 12 boost gas flow rate adjustment valve

Claims (1)

[Claims] 1. An adsorption step of adsorbing a specific gas component to each of a plurality of adsorption towers filled with an adsorbent that adsorbs a specific component gas, and a decompression step of releasing the adsorbed specific component gas through a decompression line. In addition, in a pressure swing adsorption method in which a cycle consisting of a pressurizing step of introducing a pressurizing gas and returning the pressure of the adsorption tower after depressurization is alternately combined for each adsorption tower, the operation of the plurality of adsorption towers is performed. Upon restarting after stopping, the starting method of the pressure swing adsorption facility is characterized in that the raw material line of the adsorption tower and the depressurization line other than the depressurized state are directly connected to the inside of the adsorption tower before starting the operation. .