JP2835848B2 - Operation control method of pressure fluctuation adsorption separation device - Google Patents

Description

The present invention relates to a method for controlling the operation of a pressure fluctuation adsorption / separation apparatus, and more specifically, to an operation control method in which a specific component in a mixed gas is adsorbed to an adsorbent. The present invention relates to a method for efficiently and stably operating a pressure fluctuation adsorption / separation apparatus having a cleaning step of introducing a cleaning gas of the same type as a specific component and discharging a gas other than the specific component in an adsorption tower.

[Conventional technology]

2. Description of the Related Art Conventionally, a pressure fluctuation adsorption separation apparatus has been known as a means for purifying a gas by separating a specific component in a mixed gas. Generally, this pressure fluctuation adsorption separation apparatus is performed using an adsorption tower filled with an adsorbent for adsorbing a specific component in a mixed gas. A plurality of adsorption towers are connected in parallel, and for example, each of them is adsorbed and washed. By switching to the respective steps of desorption and desorption sequentially, the strongly adsorbable specific components in the mixed gas are adsorbed and separated and recovered.

FIG. 3 shows an example of a three-column type pressure fluctuation adsorption / separation apparatus for recovering strongly adsorptive components by adsorbing and separating a mixed gas using three such adsorption towers in parallel.

In the pressure fluctuation adsorption separation apparatus 10, for example, when high-purity nitrogen is obtained as a product by using air as a raw material mixed gas, a synthetic zeolite is used as an adsorbent in each of the adsorption columns 11a, 11b, 11b.
Then, the above adsorption, washing and desorption steps are sequentially switched for each of the adsorption towers 11a, 11b and 11c to separate nitrogen in the air. The first column 11a is an adsorption step, the second column 11b is a washing step,
The case where the column 11c is in the desorption step will be described. First, the first column 11a in the adsorption step is a predetermined column supplied through the raw air valve 12 from a pretreatment step (not shown) for removing moisture and carbon dioxide. Raw material air A at a pressure is introduced from an inlet valve 13a on the inlet side of the adsorption tower associated with the first column 11a, and nitrogen, which is a strongly adsorbed component in the raw air, is adsorbed by the synthetic zeolite in the column and other oxygen Concentrate weakly adsorbed components such as at the outlet.

At this time, in the second column 11b in the cleaning step, the cleaning valve 14b on the inlet side of the adsorption tower is opened, and the high-purity nitrogen recovered in the recovery tank 15 is used as the cleaning gas F by the blower 16 at a predetermined pressure. And the weakly adsorbed component is discharged as exhaust gas W from an outlet valve 17b on the outlet side of the adsorption tower via an exhaust valve 18.

Then, the third column 11c in the desorption step opens the recovery valve 19c on the outlet side of the adsorption tower, sucks and exhausts the interior of the adsorption tower 11c by the vacuum pump 20, and uses the nitrogen adsorbed on the synthetic zeolite as the recovery gas G as a recovery tank G Collect at 15.

Part of the nitrogen recovered in the recovery tank 15 in this way is led out of the valve 21 as product high-purity nitrogen PN, and the remainder is used as the cleaning gas F used in the cleaning step.

Hereinafter, by sequentially opening and closing the respective valves in a predetermined order, each of the adsorption towers 11a, 11b, and 11c is switched to the above-described adsorption, washing, and desorption steps, and the high-purity nitrogen product is collected. During the above process, each valve other than those described above is in a closed state.
In addition, about each valve other than the above-mentioned description, the code | symbol a, b, and c attached to the corresponding adsorption tower is attached | subjected to the code | symbol of each valve, and the detailed description is abbreviate | omitted.

[Problems to be solved by the invention]

In the pressure fluctuation adsorption / separation apparatus configured as described above, in order to stably and efficiently obtain a product gas of a predetermined purity, a sufficient and sufficient amount of product gas is required as a cleaning gas for discharging and cleaning weakly adsorbed components. It is necessary to use a gas, but if the amount of the cleaning gas is small, a product gas having a predetermined purity cannot be obtained. Therefore, the cleaning gas is usually introduced with a certain margin. Conversely, if the cleaning gas is increased more than necessary, the purity of the product will improve, but the amount of product gas collected will decrease,
The basic unit deteriorates. Furthermore, with the fluctuation of the adsorption temperature due to the fluctuation of the outside temperature, the required amount of cleaning gas changes,
Conventionally, the amount of the cleaning gas has been set with allowance for this. Therefore, depending on the outside air temperature, a considerable amount of product gas is actually wasted as cleaning gas.

For this reason, for example, in the method described in JP-A-59-73029, the composition of the gas derived from the adsorption tower is detected during the cleaning step to control the timing of terminating the cleaning step, thereby reducing the cleaning gas. I was

However, this method requires an expensive gas analyzer, a valve control interface, and the like, and has a disadvantage of increasing equipment costs. In particular, a small apparatus has a high cost increase rate, which is a serious problem. In addition, in order to minimize the time delay of analysis, it is necessary to place the gas analyzer as close to the adsorption tower as possible. Sufficient consideration was needed for the arrangement of the tower and the arrangement of the analyzer, and it was difficult to apply it to actual equipment.

In Japanese Patent Application Laid-Open No. 62-97622, an analyzer for detecting the concentration of a specific component is provided to analyze the concentration of the specific component in the cleaning gas and the cleaning waste gas. A method for terminating the cleaning step when it is within the range is proposed. However, this method also has the same disadvantages as described above, and requires a complicated apparatus for sampling two fluids.

Therefore, the present invention is to control the amount of cleaning gas used with a simple configuration to reduce the amount of product gas used for cleaning, improve product collection efficiency, and stably obtain a product of a predetermined purity. It is an object of the present invention to provide a method for controlling the operation of a pressure fluctuation adsorption / separation apparatus which can be performed.

[Means for solving the problem]

In order to achieve the above object, the operation control method of the pressure fluctuation adsorption / separation apparatus of the present invention includes introducing a mixed gas into an adsorption tower filled with an adsorbent that adsorbs a specific component in the mixed gas, thereby converting the specific component. An adsorption step of adsorbing to the adsorbent, a cleaning step of introducing a gas of the same type as the specific component into the adsorption tower as a gas for cleaning, and discharging a gas other than the specific component in the tower to the outside of the tower; Each step of the desorption step of exhausting the column and recovering the specific component adsorbed on the adsorbent is sequentially switched to perform the adsorption separation of the specific component in the mixed gas and the specific component obtained in the desorption step. In controlling the operation of the pressure fluctuation adsorption / separation device that collects the gas in the recovery tank and uses a part of the gas as the gas used in the cleaning process, and collects the remaining product gas, the gas is recovered from the adsorption tower in the desorption process. To the tank The amount of collected gas is constantly detected, and during the period in which the amount of collected gas is detected to be large, the amount of cleaning gas is controlled to increase in accordance with the amount of collected gas, and the period in which the amount of collected gas is detected to be small Is characterized in that the amount of the cleaning gas is controlled to decrease in accordance with the reduced amount of the recovered gas, and the amount of the cleaning gas used in the cleaning step is increased or decreased in accordance with the increase or decrease in the amount of the recovered gas.

[Action]

As described above, by constantly detecting the amount of gas recovered from the adsorption tower in the desorption step to the recovery tank, it is possible to constantly read the change in the amount of mixed gas introduced into the raw material and the change in the amount of recovered gas due to changes in the outside air temperature. Based on this, it is possible to supply the necessary and sufficient cleaning gas by controlling the amount of the cleaning gas to increase or decrease according to the increase or decrease of the amount of the recovered gas.

〔Example〕

Hereinafter, the present invention will be described in more detail based on one embodiment in which the present invention is applied to the pressure fluctuation adsorption separation apparatus for collecting high-purity nitrogen shown in FIG. In the following description, the same elements as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

According to the present invention, as shown in FIG. 1, a detector 30 for detecting the amount of the recovered gas G is provided in the recovery tank 15 and a return path is provided to the blower 16 for pumping the cleaning gas F.
A flow control mechanism 33 including a flow control valve 31 and a flow control valve 32 is provided, and the flow control mechanism 33 is operated based on the detection value of the detector 30 to control the flow rate of the cleaning gas F.

As described above, the nitrogen gas adsorbed by the adsorbent in the third adsorption tower 11c in the desorption step is recovered from the recovery valve 19c to the recovery tank 15 via the vacuum pump 20, and this recovered gas G Varies with the change in the temperature inside the adsorption tower due to the change in the outside air temperature. In the case where high-purity nitrogen is collected by the above operation, the supply amount of the raw material gas and the amount of the desorbed gas (recovered gas) decrease as the outside temperature increases, and these amounts increase when the outside temperature decreases. .

FIG. 2 shows a change in the amount of the collected gas G due to the change in the outside air temperature by a change in the pressure in the collection tank 15 having a constant volume. Recovery tank 15 when the temperature t ₁ which is the outside air temperature
The pressure of the inner rises with the start of the desorption step, returns to the original pressure gradually decreases after reaching a certain peak pressure P _1. The lower the outside temperature, the recovery tank 15 to the the recovery gas amount becomes lower temperatures t ₂ than the temperature t ₁ is increased
The pressure of the inner well, rises to high peak pressure P ₂ than the peak pressure P _1.

Therefore, when a collection tank 15 having a constant volume is used, a change in the amount of collected gas can be detected by providing a pressure sensor as the detector 30 in the collection tank 15. When a variable-capacity container such as a gas holder or a gas balloon is used as the collection tank 15, a position sensor is provided as the detector 30 to detect a change in the tank height of the container, and the like. Changes in volume can be detected.

Then, when the detector 30 is indicated that a small amount of stripping gas G, for example, when the detection value of the peak pressure P ₁ is the adsorption tower in the washing step by increasing the opening of the flow regulating valve 32 controlled so as to reduce the amount of cleaning gas F supplied to 11b, the detection value is controlled so as to increase the cleaning gas quantity by reducing the opening degree of the flow control valve 32 at the time of the peak pressure P _2.

Thereby, even if the outside air temperature fluctuates and the amount of the cleaning gas F necessary to obtain a predetermined product purity changes, an appropriate amount of the cleaning gas F can be supplied, and the product purity is reduced, It is possible to prevent a reduction in the product gas amount.

Here, the results of an experiment in which high-purity nitrogen is sampled by the three-column pressure fluctuation adsorption / separation apparatus 10 will be described.

Each adsorption tower was filled with zeolite 5A (manufactured by Tosoh Corporation), and the switching time of each of the adsorption, washing and desorption steps was 3 minutes. Then, the amount of the cleaning gas F was adjusted according to a conventional method so as to obtain nitrogen having a purity of 99.995% or more.

It is found, the amount of stripping gas G per step when the ambient temperature is 30 ° C. is 4 Nm ^3, which uses this inner 3 Nm ³ as a cleaning gas F, collecting 1 Nm ³ as a product high purity nitrogen PN Was completed. Then, when the outside temperature decreases to 23 ° C., the amount of the recovered gas G increases to 4.5 Nm ³ and the purity of the product becomes 9 Nm ^3.
It dropped to 9.99%.

At this time, the amount of the cleaning gas F required to obtain nitrogen having a purity of 99.995% was measured. As a result, it was 3.4 Nm ³ per process.

Therefore, when the outside temperature fluctuates from 30 ° C. to 23 ° C., in order to stably obtain a high-purity nitrogen PN having a purity of 99.995% or more with the conventional apparatus, it is necessary to reduce the purity when the outside temperature decreases at night or the like. To prevent this, it was necessary to always set the amount of cleaning gas to 3.4 Nm ³ . As a result, the day decreased to recover gas amount 4 Nm ³ / h to ambient temperature ascent of secondary, even when the cleaning gas required amount is reduced to 3 Nm ^3, to 3.4 nm ³ is used as a gas for cleaning, Although the purity of the product was improved, only 0.6 Nm ³ could be taken out as a product.

At this time, using a variable-volume gas balloon (3 m ³ ) as the collection tank 15 and observing the change in the tank height of the balloon due to the change in the amount of collected gas due to the outside air temperature,
The maximum tank height of the balloon at the recovered gas volume at 30 ° C is 12
It was 00 mm, and the maximum tank height of the balloon at the outside gas temperature of 23 ° C. was 1400 mm at the recovered gas volume.

Therefore, a photoelectric position sensor is installed as the detector 30 for detecting the tank height of the balloon, and the flow control valve of the flow control mechanism 33 formed as described above based on the detection value of the photoelectric position sensor. It was configured to adjust the opening of 32.

That is, the photoelectric position sensor is installed at a position with a tank height of 1200 mm, and when the tank height exceeds 1200 mm, the flow rate control valve is used.
Reduce the amount of cleaning gas F to 3.4 Nm ³ by squeezing 32, and the tank height is 1200 mm
In the following cases, the flow control valve 32 is opened to adjust the amount of the cleaning gas F.
3.0 Nm ³ .

As a result, even when the outside air temperature is high and the amount of the recovered gas G is small, it is possible to obtain 1 Nm ³ of product high-purity nitrogen PN per process, and even when the outside air temperature falls, 99.995% high-purity nitrogen PN can be obtained. 1Nm ³ could be obtained. That is, even when the outside air temperature fluctuates and the amount of the collected gas changes, it is possible to stably obtain a product having a predetermined purity.

The present invention can be applied to other than the production of high-purity nitrogen, and the configuration and operation of the optimal adsorption / separation apparatus are appropriately adjusted according to the composition of the mixed gas as the raw material, the type of the component to be separated, and the like. You can choose. Further, as the means for detecting the amount of the recovered gas and the means for controlling the flow rate of the cleaning gas, appropriate means can be used depending on the device configuration, the amount of gas, and the like. Further, in the above experiment, the amount of change of the cleaning gas is set to two stages, but it is also possible to change the amount in multiple stages or continuously.

〔The invention's effect〕

As described above, the operation control method of the pressure fluctuation adsorption / separation apparatus of the present invention constantly detects the amount of gas recovered from the adsorption tower in the desorption step to the recovery tank, and detects that the amount of recovered gas is large. During the period, control the cleaning gas amount to increase according to the increased recovered gas amount, and control the cleaning gas amount to decrease according to the reduced recovered gas amount during the period when it is detected that the recovered gas amount is small, Since the amount of the cleaning gas used in the cleaning step is increased or decreased in accordance with the increase or decrease in the amount of the collected gas, the optimum amount of the cleaning gas is always obtained by looking at the total amount of the cleaning gas in one cycle. The amount of the cleaning gas can be accurately controlled based on the amount of the mixed gas introduced into the raw material and the amount of the collected gas due to the change in the temperature. Therefore,
A product gas having a predetermined purity can be stably obtained, and the amount of gas used for cleaning can be reduced to improve the product yield.

[Brief description of the drawings]

FIG. 1 is a system diagram of a main part showing an embodiment of a pressure fluctuation adsorption / separation apparatus to which the present invention is applied, FIG. 2 is a diagram for explaining a change in the amount of recovered gas due to a change in outside air temperature, and FIG. It is a system diagram of an adsorption separation device. 10: Pressure fluctuation adsorption / separation device, 11a, 11b, 11c: Adsorption tower, 15: Recovery tank, 30: Detector, 32: Flow control valve, 33: Flow control mechanism, F: Cleaning gas , G ... Collected gas

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B01D 53/02-53/12

Claims (2)

(57) [Claims] 1. An adsorption step in which a mixed gas is introduced into an adsorption tower filled with an adsorbent for adsorbing a specific component in the mixed gas to adsorb the specific component on the adsorbent; A washing step of introducing a gas of the same type as a washing gas and discharging gases other than the specific components in the tower to the outside of the tower, and a desorption step of exhausting the inside of the adsorption tower and collecting the specific components adsorbed by the adsorbent While sequentially performing the adsorption and separation of the specific component in the mixed gas by sequentially switching the respective steps, the gas of the specific component obtained in the desorption step is collected in a recovery tank, and a part of the gas is used as the gas used in the cleaning step. In controlling the operation of the pressure fluctuation adsorption / separation apparatus that uses the remaining part as product gas, the amount of gas recovered from the adsorption tower in the desorption step to the recovery tank is constantly detected, and the amount of the recovered gas is detected as being large. Cleaning period The amount of recovered gas is controlled to increase according to the increased amount of recovered gas, and during the period when the amount of recovered gas is detected to be small, the amount of cleaning gas is controlled to decrease according to the reduced amount of recovered gas. An operation control method for a pressure fluctuation adsorption / separation apparatus, wherein the amount of a cleaning gas used in the cleaning step is increased or decreased according to the increase or decrease. 2. A recovery tank is provided with a detector for detecting the amount of recovered gas, and a flow control mechanism comprising a recirculation path and a flow control valve is provided at a blower for cleaning gas pressure feeding. 2. The method according to claim 1, wherein the flow control mechanism is operated based on the detected value to control the flow rate of the cleaning gas.