JPH01159017A - Psa switchover valve system - Google Patents

Abstract

PURPOSE:To simplify a valve system of PSA gas purifier, by providing a three or more way valve which, by switching action, can be connected with only one of a raw gas supply pipe, a washed gas supply pipe and a deodorized gas pull-out pipe connected to an inlet of an absorbing tower. CONSTITUTION:The raw gas is sent from a pipe 7 to an absorbing tower 6A through a four-way valve 21 and the exhaust gas resulting from the adsorption of a target gas is delivered to a pipe 19 through a four-way valve 20. In the subsequent washing process, the target gas is sent from a blower 11 to the adsorbing tower 6A through pipes 13 and 10 and the four-way valve 21 to force the off-gas out of the tower and said gas is sent from a pipe 20 to a pipe 7 through the four-way valve 21. In a detaching process, the pressure of the adsorbing tower 6A is reduced by a vacuum pump 15 and the detached gas is sent from the four-way valve 21 to a gas holder 12. In a pressure raising process, the washed exhaust gas is sent from an adsorbing tower 6C to the adsorbing tower 6A through pipes 7 and 9 and the four-way valve 21 for a rise in the pressure. The use of such four-way valve prevents the inclusion in a product gas of the other gases in the event of valve malfunctions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a gas switching system for a gas separation and purification device using the PSA method.

[Conventional technology]

The pressure fluctuation adsorption separation method, so-called PSA method, is a separation method in which only the target gas component is adsorbed on a special adsorbent under pressure, and then the gas component is extracted by reducing the pressure.

In this process, pressurized raw material gas is first fed into an adsorption tower filled with adsorbent to adsorb target gas components, and the remaining adsorbed exhaust gas (off-gas) is discharged outside the tower. Finish the adsorption process. Next, in order to remove components other than the target gas components and increase the purity of the target gas components, high-purity target gas is sent into the tower for cleaning, and the cleaning gas is sent to the next adsorption tower where it is The contained target gas is adsorbed and recovered. Subsequently, the pressure inside the column is reduced to release the target gas component from the adsorption layer, thereby completing the desorption process. This is a method in which the raw material gas and cleaning gas from other adsorption towers are fed into the adsorption tower where the desorption process has been completed to raise the pressure, and when the pressure increase process is completed, the process moves to the adsorption process and the above steps are repeated. The pressure increasing step may be included as the first half of the adsorption step and may be divided into three steps.

In the equipment used in this method, three to four adsorption towers 6 are usually used as shown in Figures 1 and 2, and each tower performs a different process, and each process is sequentially carried out in the next tower. A cyclical system is used. That is, first, a raw material gas is sent to the adsorption tower 6A to perform an adsorption process, and during that time, a cleaning gas is sent to the adsorption tower 6B to perform a cleaning process. The adsorption tower 6C is in the desorption process and is being sucked in by the vacuum pump 15, and the adsorption tower 6D is in the pressure increasing process and a mixed gas of raw material gas and cleaning exhaust gas from the adsorption tower B is sent to increase the pressure. When each step in all the columns is completed, each column enters the next step, with column 6A carrying out a washing process, column 6B carrying out a desorption process, column 6C carrying out a pressurization process, and column 6D carrying out an adsorption process.

When these steps of all the columns are completed, each enters the next step, and when the steps of one cycle are completed, the next cycle starts and these steps are repeated one after another.

Conventionally, in gas separation and purification equipment using this method, in order to switch the gas flow, the arrangement of valves is as shown in Figure 2: 6 adsorption columns - 3 at the bottom and 2 at the top per column. Two-way valves such as ball valves or butterfly valves 1.2.3.4
．． 5 in combination, and gas flow paths were switched by opening and closing the respective valves around these adsorption towers.

The flow of gas in the adsorption process was such that the raw material gas sequentially entered each adsorption tower 6 from the raw gas header pipe 7 via valve 1, and the off-gas from the adsorption tower 6 was sent to the off-gas header pipe 19 through valve 4. .

In this adsorption process, the valves around the adsorption tower were opened and closed as follows.

In the cleaning process, target gas enters the adsorption tower 6 from the purge gas blower 11 via valve 2, and the cleaning exhaust gas that has cleaned the tower is sent to the next adsorption tower 6 via valve 5. In this cleaning process, the valves were opened and closed as follows.

In the desorption process, the adsorbed target gas component was separated from the adsorption layer by the reduced pressure from the vacuum pump 15, and was sent to the gas holder 12 from the vacuum pump 15 via the valve 3. In this desorption process, the valves were opened and closed as follows.

After the desorption process is finished, the adsorption tower 6A moves to the pressure increase process,
The raw material gas that has passed through the valve 1 and the cleaning gas from the adsorption tower 6C during the cleaning process are mixed and flowed into the adsorption tower 6A, where the pressure is increased.

On the other hand, the generated off-gas was sent to the off-gas header 19 via the valve 4. The opening and closing states of the valves during this pressure increasing process were as follows.

After the pressure increasing step, the adsorption tower 6A moves to the adsorption step and one cycle is completed, and each time the adsorption tower 6A moves, the gas flow is switched by repeating the opening and closing operations of the valves around each adsorption tower. was.

[Problem that the invention seeks to solve]

In such a device, it is necessary to accurately operate a large number of valves at predetermined times, and this operation is not easy. For example, in the apparatus shown in FIG. 2, it is necessary to operate more than 20 valves accurately each time each process is changed over, and it is difficult to do this manually. Therefore, in -g, the valves are opened and closed by automatic operation, but even in this case, it is difficult to maintain and manage the large number of valves that are opened and closed many times to ensure that they all operate without failure. . If one of the valves malfunctions or the timing of its operation is incorrect, this will have a significant impact on gas purification, and in many cases will lead to the product gas being rejected. I had no choice but to restart it. These require a lot of labor and increase the cost of the product, so it is desirable to develop a system in which all valves always operate accurately and even if there is a malfunction, off-gas will not enter the product gas line. was.

[Means for solving problems]

This invention was made to achieve the above object, and by using a multi-way valve, the total number of valves can be significantly reduced, and by using a multi-way valve that is connected to only one pipe, this invention can be achieved. The purpose has been achieved.

That is, the present invention consists of a plurality of adsorption towers, each of which has a raw material gas supply pipe, a cleaning gas supply pipe, and a desorption gas withdrawal pipe connected to its inlet, and an adsorbed exhaust gas discharge pipe connected to its outlet. has been done.

In a device that separates and purifies target gas using the PSA method,
P characterized in that the inlet is provided with a four-way or more multi-way valve that switches between the source gas supply pipe, the cleaning gas supply pipe, and the desorption gas withdrawal pipe and connects to only one of them.
This relates to the SA switching valve system.

The number of adsorption towers is usually 4 or a multiple thereof, but it may be 3 or 5 or more.

On the other hand, in the PSA method, at least two adsorption towers are required because the washed exhaust gas is used in another tower in the pressure increasing step.

A raw material gas supply pipe, a cleaning gas supply pipe, and a desorption gas drawing pipe are connected to the inlet of each adsorption tower.

The raw material gas depends on the type of target gas, for example - converter gas to separate and obtain carbon oxide gas, combustion waste gas from a boiler etc., or hot air from a blast furnace to separate and obtain carbon dioxide from methanol decomposition gas, etc. COG gas and the like are used to separate and obtain furnace gas and hydrogen gas.

The cleaning gas is used to pass the raw material gas remaining in the tower after the adsorption step through an adsorption layer to replace the inside of the tower with the target gas, and usually a part of the desorption gas is used as the cleaning gas.

The desorbed gas may be used as it is or further purified if necessary to become a product gas.

Since the specific gravity of the target gas is generally light, the inlet of the adsorption tower is usually provided at the bottom.

On the other hand, an adsorption exhaust gas exhaust pipe is connected to the outlet of each adsorption tower. Adsorbed exhaust gas is normally treated to make it non-polluting if necessary and then released into the atmosphere, but if useful gas still remains, it may be sent to a recovery process. In addition, a cleaning exhaust gas exhaust pipe is separately connected to the outlet of each adsorption tower, and the other end of this cleaning exhaust gas exhaust pipe is connected so that the cleaning exhaust gas can be introduced into the inlet of another adsorption tower in the pressure increasing process. It is desirable to recover the target gas inside by adsorbing it to the adsorption layer of this tower.

In this case, install a separate ladder pipe for the cleaning exhaust gas discharge pipe.
Although a branch pipe may be provided from this header pipe to the inlet of each adsorption tower, it is preferable to connect each discharge pipe to the raw material gas supply pipe and send the cleaning exhaust gas mixed with the raw material gas to the tower for the pressurization process. It's simple.

The outlet of each adsorption column is usually located at the top of the column.

In the system of the present invention, the raw material gas supply pipe, the cleaning gas supply pipe, and the desorption gas sluice pipe are switched to the inlet of each adsorption tower, and only one of them is connected.
The feature is that it has more than one multi-way valve. Therefore,
All of the three pipes are connected to this multi-way valve, and by switching the valve, only one of the pipes is connected to the adsorption tower. In addition, when a header pipe for the cleaning exhaust gas discharge pipe is provided separately, it is preferable that the multi-way valve is a five-way valve, and a branch pipe from this header pipe is also connected to this multi-way valve. In principle, the multi-way valves of each adsorption tower are operated simultaneously, but each tower may be operated separately at the end of the process.

On the other hand, when a cleaning exhaust gas exhaust pipe is provided at the outlet, it is preferable to provide a three-way or more multi-way valve for switching between the cleaning exhaust gas exhaust pipe and the adsorbed exhaust gas exhaust pipe.

In that case, the multi-way valve at the inlet and the multi-way valve at the outlet of each adsorption tower are linked. If the only pipe connected to the outlet is an adsorbed exhaust gas discharge pipe, a two-way switching valve may be installed.

[Effect]

In the valve system of the present invention, the multi-way valve at the inlet is used only for the raw material gas supply pipe in the adsorption process, only the cleaning gas supply pipe in the cleaning process, and only the desorption gas withdrawal pipe in the desorption process.
In the pressure increasing step, only the raw material gas supply pipe and other gas supply pipes used to raise the pressure of the adsorption tower are connected to the adsorption tower.

Therefore, the desorption gas drawing pipe will not be erroneously connected to another pipe even if there is any malfunction of the valve.

〔Example〕

FIG. 1 is a piping configuration diagram showing an embodiment of the PSA switching valve system according to the present invention. This switching valve system has a configuration in which one four-way valve 20 is provided at the top of the adsorption tower and one four-way valve 21 is provided at the bottom as switching valves for gas flowing in and out of each adsorption tower 6.

The flow path 22 of the bottom four-way valve 21 corresponds to a connection port with the adsorption tower 6, and is connected to the adsorption tower 6 through a pipe 8. Channel 23.24
．． 25 are valve 1, valve 2, and valve 3 in Fig. 2.
The flow path 23 corresponds to the raw material gas supply valve 1 and is connected to the raw material gas header pipe 7 via the raw material gas supply pipe 9. The flow path 24 corresponds to the cleaning gas supply valve 2 and is connected to the header pipe 13 from the purge gas blower 11 via the cleaning gas supply pipe 10.

The flow path 25 corresponds to the desorption gas extraction valve 3 and is connected to the header pipe 16 from the vacuum pump 15 via the desorption gas extraction pipe 14 .

The flow path 26 of the four-way valve 20 is connected to the adsorption tower 6 through a pipe 17, and is connected to the adsorption tower 6 through the pipe 17. The flow paths 27 and 28 correspond to the valves 4 and 5 in FIG. 2, and the flow path 27 corresponds to the off-gas take-off valve 4 and is connected to the off-gas header pipe 19 through the adsorption exhaust gas discharge pipe 18.

The flow path 28 corresponds to the cleaning gas take-off valve 5 and is connected to the ladder pipe 7 through a pipe 20 to the raw material gas.

When separating and purifying gas using such a device, in the adsorption process performed in the column 6A, the raw gas header pipe 7
The raw material gas from the pipe 9 enters the adsorption tower 6A via the flow path 23 and 22 of the four-way valve 21, and the adsorbed exhaust gas with the target gas adsorbed by the adsorption layer enters the flow path of the four-way valve 20. 26 , the gas is sent to the off-gas header pipe 19 via the flow path 27 and the piping 18 . During this time, a washing process is carried out in the column 6B, a desorption process is carried out in the column 6C, and a pressure increasing process is carried out in the column 6D. After the adsorption process, the adsorption tower 6A moves to a cleaning process.

In the cleaning process, the target gas passes from the purge gas blower 11 through the piping 13 and piping 10, and then through the flow path 2 of the four-way valve 21.
4 into the adsorption tower 6A via the flow path 22, and pushes out the off-gas in the tower. The cleaning exhaust gas flows through the flow path 26 of the four-way valve 20.
The raw material gas is sent to the header pipe 7 via the flow path 28 and the pipe 20 . Meanwhile, in tower 6B, a desorption process is carried out in tower 6B.
A pressure increasing step is carried out in C and an adsorption step is carried out in column 6D. After the washing step, the adsorption tower 6A moves to a desorption step.

In the desorption step, the adsorption tower 6A is sucked in by the vacuum pump 15 and is reduced in pressure. The desorbed gas (target gas) desorbed from the adsorption layer by the reduced pressure is sent from the flow path 22 of the four-way valve 21 via the flow path 25 to the piping 14 and piping 16 to the gas holder 12 from the vacuum pump 15. can be stored in At this time, the flow path of the four-way valve 20 is in the blind position and is in a closed state. During this time, a pressure raising process is being carried out in the column 6B, and a washing process is being carried out in the adsorption process 6D in the column 6C. After the desorption step, the adsorption tower 6A moves to a pressure increasing step.

In the pressure increasing process, this mixed gas passes through the pipe 9 from the ladder pipe 7 to the raw material gas into which the cleaning exhaust gas discharged from the intake group 6C in the cleaning process is flowing, and from the flow path 23 of the four-way valve 21 to the flow path 22. It enters the adsorption tower 6A via , and the pressure inside the tower is increased. During this time, the four-way valve 20 is closed.

Separation and purification of the target gas is performed continuously with the above steps as one cycle.

〔Effect of the invention〕

In the valve system of the present invention, by introducing a multi-way valve at the inlet of the adsorption tower, the feedstock gas can be supplied even if any valve malfunctions in the desorption process, except for malfunctions in which the valve on the outlet side opens. None of the pipes, the adsorption exhaust gas discharge pipe and the cleaning exhaust gas discharge pipe are connected to the desorption gas withdrawal pipe, so that these gases do not mix with the product gas. In addition, since a multi-way valve is used as the switching valve, the number of switching valves is small, and the installation space for the valve is small.
Since the system can be simplified, equipment maintenance costs can be reduced.

The control system is also simpler, so troubles are less likely to occur.
A highly reliable device can be obtained at low cost. Furthermore, since one cycle of the operating process can be handled by one rotation of the switching valve, the life of the valve can be extended.

[Brief explanation of the drawing]

FIG. 1 is a piping configuration diagram of a PSA switching valve system according to an embodiment of the present invention. FIG. 2 is a piping configuration diagram of a conventional PSA switching pulp system.

Claims (2)

[Claims] (1) Consisting of multiple adsorption towers, the inlet of each adsorption tower is connected to a raw material gas supply pipe, cleaning gas supply pipe, and desorption gas withdrawal pipe, and the outlet is connected to an adsorbed exhaust gas discharge pipe. , in an apparatus for separating and purifying target gas by the PSA method, a three-way or more multi-way valve that switches between the source gas supply pipe, the cleaning gas supply pipe, and the desorption gas withdrawal pipe and connects only one of them to the inlet. A PSA switching valve system characterized by the provision of (2) A cleaning exhaust gas discharge pipe connected to the raw material gas supply pipe is connected to the outlet, and a three-way or more multi-way valve is provided for switching between the cleaning exhaust gas discharge pipe and the adsorption exhaust gas discharge pipe. PSA switching valve system as described in item 1