JPS6116722B2 - - Google Patents

Description

[Detailed description of the invention]

In particular, the present invention adsorbs nitrogen from the air under pressure in an adsorption tower, then depressurizes the adsorption tower and discharges nitrogen to regenerate the adsorption tower, while continuously separating only oxygen, which is a non-adsorbed substance. The present invention relates to a method and apparatus for concentrating oxygen. In general, such oxygen concentration methods are based on a method called pressure fluctuation adsorption separation method, which performs the above operations using two or three or four adsorption towers for pressurized adsorption and reduced pressure adsorption. The switching is performed alternately, and the switching time is between several tens of seconds and several tens of minutes. The switching operation is generally performed by using a timer to operate a solenoid valve installed in the piping connecting each adsorption tower. Therefore, adsorption and desorption operations are repeated in multiple adsorption towers in a short period of time as described above, and therefore, during the switching period, that is, from adsorption to desorption, and from desorption to adsorption, it takes several seconds to reach a stable state. pressure fluctuates. This pressure fluctuation results in a temporary fluctuation in the flow rate of oxygen taken out, which significantly decreases compared to steady operation. One possible way to overcome this drawback is to provide an oxygen storage tank before sending the oxygen taken out from the adsorption tower to the feed end. However, in order to suppress flow rate fluctuations due to valve switching, a storage tank with a considerably larger volume than the adsorption tower body is required, which is extremely uneconomical. Therefore,
It is desired to suppress fluctuations in oxygen flow rate by other methods. SUMMARY OF THE INVENTION An object of the present invention is to provide an oxygen concentrating method and an oxygen concentrating device that suppress fluctuations in oxygen flow rate when switching valves and allow stable oxygen extraction. In order to achieve this objective, the oxygen concentration method of the present invention uses a plurality of adsorption towers filled with an adsorbent that adsorbs nitrogen, and uses a pressure fluctuation method that includes pressurized adsorption operation and reduced pressure desorption operation as basic operations. In the oxygen concentration method for separating and recovering oxygen-rich gas from the air, the buffer tank is a multi-stage buffer tank, and when switching between adsorption and desorption, the gas remaining in the first stage buffer tank of the multi-stage buffer tank is returned to the adsorption tower and transferred to the second stage buffer tank. It is characterized by the fact that the gas that remains is taken out. Furthermore, the oxygen concentrator according to the present invention has a multi-stage buffer tank installed at the adsorption tower outlet as a means for eliminating fluctuations in the oxygen flow rate from the adsorption tower outlet when switching between adsorption and desorption. The feature is that a switching means such as a valve is provided between the two. The present invention will be further described below with reference to embodiments shown in the accompanying drawings. FIG. 1 is a system diagram showing an embodiment of an oxygen concentrator according to the present invention. In FIG. 1, reference numerals 1,
2 is a nitrogen adsorption tower, and air supplied through an air feed pipe 21 is compressed by a compressor 3. The air compressed by the compressor 3 is passed through the water droplet separator 4
is dehumidified. The dehumidified air is passed through pipe 22 and valve 1.
1, and further sent to adsorption towers 1 and 2 via valve 12. The oxygen coming out of the adsorption towers 1 and 2 is passed through valves 15 and 16.
The buffer tank of this embodiment has a two-stage buffer tank structure including a front-stage buffer tank 5 and a rear-stage buffer tank 6, and a valve 17 is provided between the buffer tanks 5 and 6 as a switching means. Therefore, the oxygen that has passed through the valves 15 and 16 is taken out by the extraction pipe 23 via the front stage buffer tank 5, the valve 17 and the rear stage buffer tank 6. Next, the operation of this embodiment will be explained. First, an adsorption process is carried out in adsorption tower 1, and adsorption tower 2
Perform the desorption process. In this case, valve 11,1
4, 15 and 17 are open, and valves 12, 13 and 16 are closed. By this valve operation, the air sent from the inlet pipe 21 is transferred to the compressor 3, the water droplet separator 4, and the pipe 2.
2. It passes through the valve 11 and is supplied to the adsorption tower 1. Nitrogen is adsorbed by the adsorption tower 1, and oxygen is sent to the valve 15, the front stage buffer tank 5, the valve 17, and the rear stage buffer tank 6. On the other hand, the adsorption tower 2 discharges the nitrogen adsorbed in the previous step through the valve 14 and the discharge pipe 24 while returning the pressure to the atmosphere. The above is the first cycle, and the next step is entered as the second cycle. That is, in the adsorption tower 2 after the desorption process,
First, open the valve 16 and close the valves 12 and 14 to return the concentrated oxygen remaining in the upstream buffer tank 5 to the adsorption tower 2, and equalize the pressure between the adsorption tower 2 and the upstream buffer tank 5 (pressure equalization step). ). In this case, the valve 17 located between the front stage buffer tank 5 and the rear stage buffer tank 6 is kept closed. Thereby, the oxygen remaining in the rear stage buffer tank 6 can be sent out to the extraction pipe 23, and product oxygen can be continuously extracted even when switching between adsorption and desorption. On the other hand, in the adsorption tower 1 that has completed the adsorption step, the valve 13 is opened, the valves 11 and 15 are closed, and the pressure is reduced from the pressurized state to the atmosphere for desorption and regeneration. Next, in the third cycle, the valves 12 and 16 are opened on the adsorption tower 2 side, the valve 14 is closed, and air is supplied to the adsorption tower 2 to enter the adsorption step. Oxygen concentrated in the adsorption step enters the pre-stage buffer tank 5 via the valve 16. The valve 17 is operated by the front stage buffer tank 5.
When the oxygen remains in the tank, it is opened and oxygen is sent to the rear buffer tank 6, and then the oxygen is taken out to the extraction pipe 2.
Send to 3. On the other hand, on the adsorption tower 1 side, which is the desorption step, the valve 13 is open and the valves 11 and 15 are closed, which is the same valve operating state as in the second cycle. In the fourth cycle, the pressure is equalized, and the adsorption tower 1, which has completed the desorption step, equalizes the pressure with the front stage buffer tank 5, and the adsorption tower 2, which has completed the adsorption step, exhausts the adsorbed nitrogen. One cycle is formed by the first to fourth cycles. As an example of the above operating method, actual measurements were conducted using the specifications and operating conditions of the oxygen concentrator shown in Table 1.

[Table] Actual measurements were carried out using the following three operations in order to compare the effect of suppressing fluctuations in the flow rate of the extracted gas according to the present invention, and the results are shown in FIGS. 2 to 4. Each figure shows the change over time in the oxygen extraction flow rate. FIG. 2 shows the fluctuation state of the oxygen flow rate taken out from the valve 15 or 16 in the system of the embodiment shown in FIG. 1 according to the present invention without installing the latter two buffer tanks 5 and 6. The axis is the elapsed operation time, and the vertical axis is the oxygen extraction flow rate. The adsorption/desorption switching time was set to 30 seconds, and the steady state oxygen extraction flow rate was
When set to 100, the flow rate at the time of switching between adsorption and desorption decreased to about 50% of the steady state, and it took 22 seconds to return to the steady flow state after switching. Figure 3 shows the buffer tanks 5 and 6 of the 2nd front stage.
The oxygen flow rate is fluctuating when the valve 17 is always open and the adsorption/desorption switching time is 30 seconds. Similarly to the above, when the steady flow rate was set to 100, the oxygen flow rate at the time of switching to adsorption/desorption decreased to about 70% of the steady state, and it took 15 seconds to return to the steady flow state after switching. FIG. 4 shows the results obtained when two stages of buffer tanks 5 and 6 are provided, in accordance with the embodiment of the present invention shown in FIG. 1, and the valve 17 is opened and closed when the pressure is equalized. It is something. The adsorption time was 30 seconds, and a pressure equalization time of 10 seconds was introduced within this 30 seconds.
The optimal condition for suppressing flow rate fluctuations is to close the valve 17 for a total of 15 seconds, 10 seconds under pressure equalization and 5 seconds after the adsorption step, and then open it. In addition, as a result of considering that the volume of the buffer tank is as small as possible and has a large flow rate fluctuation suppressing effect, it was found that it is preferable that the first stage buffer tank 5 is the same as the adsorption tower volume, and the second stage buffer tank 6 is twice the adsorption tower volume. . In other words, if it is larger than twice, there will be a delay in transmission of the flow rate, and there will be a delay in the time it takes to return to a constant flow, and there will be uneconomical effects due to the increase in size, while if it is smaller than twice, the effect of suppressing flow fluctuations will be However, if the amount is doubled, a harmonious effect without any of these drawbacks can be obtained. As a result of measurement under the above conditions, when the steady state of oxygen flow rate is taken as 100, the flow rate fluctuation is within 98%.
Moreover, it took about 7 seconds to return to a steady flow rate.
At this time, the oxygen extraction amount is 60N/h, and the oxygen concentration is 90
% achieved. Although it is conceivable that the required capacity of the buffer tank would increase with an increase in the oxygen extraction flow rate, even when the extraction flow rate was increased from 60 to 10 N/h, the flow rate fluctuations could be sufficiently suppressed. Further, if the oxygen extraction flow rate is 100 N/h or more, the oxygen concentration effect is not good and it is out of the practical range. In the above case, in Figures 2, 3 and 4,
The fluctuation of oxygen flow rate was compared with the steady flow rate based on the base of the fluctuation, but in order to make a more accurate comparison, it was examined using the integrated flow rate. The range of flow fluctuations in each figure from Fig. 2 to Fig. 4 is indicated by diagonal lines, but when comparing the areas of Fig. 2, if the shaded area in Fig. 2 is 100, Fig. 3 is 60, and the area of the present invention is 60. If a two-stage buffer tank is installed, the effect will be 12, which is 8 times more effective than the cumulative flow rate. Furthermore, before moving from the desorption process to the adsorption process, by equalizing the pressure between the adsorption tower and the pre-stage buffer tank, the adsorption tower is filled with oxygen gas, thereby maintaining high concentration oxygen gas in a stable state. There are effects that can be taken out. It should be noted that the respective times for adsorption, pressure equalization, and valve operation located between the front stage and rear stage buffer tanks in the examples are determined by the size of the adsorption tower, and are not particularly limited. The multi-stage buffer tank in the present invention may be constructed by providing a partition within a single-tower buffer tank, and FIG. 5 shows one embodiment thereof. That is, in this embodiment, a partition is provided at an intermediate position of the single-column buffer tank 7 by a switching means such as a damper 8, and the inside of the buffer tank 7 is divided into a front-stage buffer tank 7A and a rear-stage buffer tank 7B to form a multi-stage buffer tank, and the adsorption process Now, open the damper 8, and when the pressure equalization process begins, the damper 8
close. Through this operation, the oxygen that had entered the lower part of the buffer tank 7 during the pressure equalization process is returned to the adsorption tower where the desorption process has been completed, and the pressure is equalized. on the other hand,
The oxygen remaining in the upper part of the buffer tank 7 is
The oxygen is sent out from the oxygen take-off pipe 23. This allows product oxygen to be extracted continuously even when switching between adsorption and desorption. As explained above, by optimally operating the opening and closing of the switching means located in the middle of the two-stage buffer tank according to the present invention at the time of switching between adsorption and desorption, changes in the extraction oxygen position can be suppressed, and high concentration oxygen can be stabilized. It can be taken out in the same state.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the oxygen concentrator according to the present invention; FIGS. 2, 3, and 4 are diagrams comparing and explaining the fluctuation states of the oxygen extraction flow rate;
The figure is a system diagram showing another embodiment of the present invention. 1, 2...Adsorption tower, 3...Compressor, 5...Previous stage buffer tank, 6...Rear stage buffer tank, 7
... Buffer tank, 7A... Front stage buffer tank, 7B... Rear stage buffer tank, 8... Damper, 17... Valve.

Claims (1)

[Scope of Claims] 1. An adsorption step in which air sent from a compressor is guided to an adsorption tower filled with a nitrogen adsorbent, and nitrogen is processed and adsorbed from the air onto the adsorbent, and the pressure in the buffer tank and the adsorption tower is equalized. In an oxygen concentration method that sequentially repeats a pressurizing process and a desorption process in which the adsorption tower is depressurized to remove nitrogen and the adsorbent is desorbed, the buffer tank is a multi-stage buffer tank, and when switching between adsorption and desorption, the multi-stage buffer tank is An oxygen concentration method characterized by returning the gas remaining in the first stage buffer tank to the adsorption tower and taking out the gas remaining in the second stage buffer tank. 2 Consists of a compressor that compresses air, an adsorption tower that receives air from the compressor and adsorbs nitrogen from the air using a nitrogen adsorbent, and a buffer tank that is installed after the adsorption tower. An oxygen concentrator characterized in that the buffer tank is composed of a multi-stage buffer tank, and a switching means is provided between a front-stage buffer tank and a rear-stage buffer tank of the multi-stage buffer tank.