JPS6219882B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a gas adsorption separation method and an apparatus thereof, and relates to a pressure fluctuation adsorption method in which the operations of pressurized adsorption and reduced pressure desorption and regeneration are repeated, and an adsorption method that maintains the adsorption pressure during adsorption operation at a constant pressure and improves the adsorption efficiency. This invention relates to an adsorption device. Generally, in the pressure fluctuation adsorption method, a plurality of adsorption beds filled with an adsorbent that selectively adsorbs at least one component is provided, and a mixed gas is supplied under pressure to the adsorption beds to adsorb easily adsorbable components. There is an adsorption step in which difficult-to-adsorb components are collected, a depressurization step in which the gas in the bed is released after the adsorption step and the pressure is reduced to approximately atmospheric pressure, and the gas in the difficult-to-adsorb components is circulated through the bed to be adsorbed by the adsorption bed. The regeneration process, which consists of a scavenging process to desorb easily adsorbed components and regenerate the adsorbent, and a pressurization process to aerate the poorly adsorbed component gas to raise the pressure to the adsorption pressure, is normally carried out in the above-mentioned order. . In other words, in order to continuously collect product gas by adopting the pressure fluctuation method,
A plurality of adsorption beds are provided and each of these is switched to the above-mentioned process, and during the process operation, for example, the product gas derived from the adsorption bed in the adsorption process is used for the scavenging process of other columns, or Because it is used for the pressure raising process of other columns, the outlet flow rate of the adsorption bed in the adsorption process increases, the pressure in the adsorption bed in the adsorption process decreases, and the flow rate of the raw material gas flowing in the bed increases. Phenomena such as Figure 1 shows experimentally determined pressure changes within the adsorption bed during each of the above-mentioned steps. The process of increasing the pressure to the process pressure,
The Loch line is the adsorption process, the Hohe line is the decompression process, and the Hohe line is the decompression process.
The line D is the scavenging process. In this case, the adsorption step
Line H shows a tendency for pressure to increase over time, but when some of the gas for scavenging is supplied to other adsorption beds during regeneration (point C), the pressure decreases rapidly. The phenomenon continues until the supply of scavenging gas stops and the supply of gas for pressurization (point 2) ends. That is, the pressure within the adsorption bed generally increases gradually during the adsorption process, but when other adsorption beds are scavenged or gas is supplied for the pressure raising process, pressure fluctuations occur where the pressure drops rapidly. This pressure fluctuation, especially a rapid pressure drop phenomenon, not only causes the adsorption front in the adsorption bed under the adsorption process to rapidly extend toward the outlet side, but also causes the adsorbed components to be desorbed and mixed into the product gas, resulting in This causes inconveniences such as a decrease in gas purity. In addition, switching operations between multiple adsorption beds are normally performed by opening and closing the inflow valve provided on each adsorption bed at fixed intervals using a timer, etc. The raw material gas flows through the bed, supplying unnecessary raw material and causing the pressure inside the bed to become excessive. This also pushes the adsorption front in the adsorption bed toward the outlet side, resulting in the same disadvantages as described above, such as a decrease in product gas purity. Based on the above findings, the present invention has discovered that pressure fluctuations within the adsorption bed during the adsorption process are a major factor in reducing the yield in this type of adsorption method, and has solved this problem. The adsorption method and adsorption device of the present invention will be explained in detail below with reference to the drawings. FIG. 2 shows an embodiment of the adsorption apparatus according to the present invention, and for ease of understanding, shows an example of an apparatus provided with two adsorption beds. In the figure, A and B are adsorption beds filled with an adsorbent that selectively adsorbs at least one component in the mixed gas to be separated. For example, when extracting oxygen from air, nitrogen is selectively adsorbed. filled with adsorbents such as natural or synthetic zeolites. 1
is a compressor; 2 is a raw material tank; the raw material tank 2 is connected to the discharge port of the compressor 1 via a pipe 3; 4 is a main supply pipe that supplies raw materials from the raw material tank 2 to each adsorption bed, and 5A and 5B are branched from the main supply pipe 4 and have electromagnetic valves 6 at one end of each adsorption bed A and B, respectively.
These are conduits connected via A and 6B. 7
A and 7B are conduits provided at the other end of each adsorption bed A and B to lead out the product gas, and these conduits 7A and 7
B is an overflow valve 8A, 8B that opens at a certain pressure or higher.
are connected to the main outlet pipe 9 through the respective pipes. 1
Reference numeral 0 designates a product gas tank, to which one end of the main outlet pipe 9 is connected, and a conduit 11 for supplying the product gas to a consumption location is provided. Further, the conduits 7A and 7B are provided with solenoid valves 12A and 12A, respectively, bypassing the overflow valves 8A and 8B, respectively.
Side channel pipes 13A, 13B with 12B are provided. 14A and 14B are purge conduits branched from conduits 5A and 5B between the adsorption beds A and B and the solenoid valves 6A and 6B, each of which is connected to the solenoid valve 1.
It is connected to the discharge main pipe 16 via 5A and 15B. A pressure regulator 17 keeps the pressure of the raw material tank 2 constant at a desired set pressure, and detects the pressure of the raw material tank 2 and sends a signal to the compressor 1 to drive or stop the compressor 1. As another example, a suction port of the compressor 1 and a pipe 3 communicating with the raw material tank from the discharge port of the compressor 1 are connected via a valve 18 to a pipe 19.
The raw material tank 2 is connected to the raw material tank 2 by connecting the raw material tank 2 with
The pressure may be maintained at a desired pressure. FIG. 3 is a schematic diagram of the structure of the overflow valves 8A and 8B in FIG. 104 is spring spring 1
05 to seal the introduction port 102. Reference numeral 106 denotes an adjustment screw for adjusting the pressing force of the spring spring, and is set so that it opens when the gas pressure introduced from the inlet 102 reaches a desired pressure, allowing gas to flow in. The adsorption apparatus of the present invention is constructed as described above, and its operation will be described below by exemplifying the case where air is used as a raw material, nitrogen in the air is adsorbed, and oxygen is collected as a product gas. Adsorption beds A and B are each filled with synthetic zeolite (Molecular Sieve 5A manufactured by Linde) that selectively adsorbs nitrogen.
The operating pressure of the overflow valves 8A and 8B is set to the optimum pressure depending on the product gas to be sampled, the adsorbent used therein, the compression power to the product gas yield, the number of beds to be switched, the process switching time, etc. In this embodiment, the pressure is set to 2.5 kg/cm ² G, for example. Also, the pressure of the raw material tank 2 for pressure buffering is controlled by overflow valves 8A and 8B.
The overflow valve is used to maintain the pressure in the bed at a constant pressure even when switching valves, so that a part of the product gas collected from the bed in the adsorption process is used for scavenging and pressurizing other beds. In relation to the working pressure of 8A, 8B, 0.2 to 1.2 from the working pressure of the overflow valves 8A, 8B.
Set the pressure higher by an arbitrary value between Kg/cm ² G. For example, in this embodiment, the operating pressure of the overflow valves 8A and 8B is 3.2Kg/cm ² G, which is 0.7Kg/cm ² G higher than the 2.5Kg/cm ² G.
The pressure regulator 17 is set to maintain the pressure in the raw material tank 2 at a pressure of . Also, adsorption beds A and B are one bed, for example, while adsorption bed A is in the adsorption process, the other adsorption bed B goes through a process of depressurization, scavenging, and pressure increase, and then adsorption bed B goes through the adsorption process, and the other adsorption bed A undergoes a process of depressurization, scavenging, and pressure increase,
Thereafter, the valves 6A, 6B, 12A, 12B,
The valves 15A and 15B are opened and closed. Each of the valves is operated by setting the process order by time setting means such as a timer. That is, this is displayed as follows. The valve that is still open is the second valve.
Indicated by reference numerals in the figure.

【table】

[Table] In each process, valves other than those listed above are closed during that process. By operating the valves as described above, the first step in the table above, that is, the adsorption bed A is the adsorption step, while the adsorption bed B is under reduced pressure.
Part 2 regarding the case of operation in the scavenging-pressure boosting process.
This will be explained based on the diagram. The raw air is dehumidified and carbon dioxide is removed in advance by a dehumidifier and a decarbonization tower (not shown), and then taken in from the suction port of the compressor 1, compressed to approximately 3 kg/cm ² G by the compressor 1, and then passed through the pipe 3. and introduced into the raw material tank 2. The pressure in the raw material tank 2 is maintained at a desired pressure, for example 3.2 kg/cm ² G, by a pressure regulator 17. That is, the pressure regulator 17 detects the pressure in the raw material tank 2, and the detected pressure is set to a preset pressure, for example, 3.2.
If the pressure is below Kg/cm ² G, a signal is sent to the compressor 1 to keep it moving, and if the pressure exceeds a preset pressure, for example 3.2 Kg/cm ² G, the drive of the compressor 1 is stopped. A signal is sent to stop or open the valve 18, and the pressure in the raw material tank 2 is constantly maintained at a desired pressure, for example, 3.2 kg/cm ² G. The raw material air stored in the raw material tank 2 in this state is transferred from the raw material supply main pipe 4 to the branch pipe 5.
A, Adsorption bed A in adsorption process via solenoid valve 6A
is supplied to Nitrogen in the air is selectively adsorbed in the bed A, and oxygen component gas, which is a difficult to adsorb component, is led out through the pipe 7A. The flow then flows to the overflow valve 8A, which has a spring spring 105 so as to open when a predetermined pressure is reached as described above.
For example, if the pressure is adjusted to open the valve at a pressure of 2.5 kg/cm ² G, the pressure of the product oxygen component gas flowing from the pipe 7 to the overflow valve 8A will be 2.5 kg/cm 2 G.
When the pressure is less than cm ² G, the valve does not open, but when the pressure reaches 2.5 kg/cm ² G, the valve opens, flows through the overflow valve 8A, flows into the main outlet pipe 9, is supplied to the product tank 10, and is stored. Then, it is supplied from the pipe 11 to the place of consumption. Meanwhile, during this time, adsorption bed B undergoes each step of depressurization, scavenging, and pressure increase, but the pressure inside bed B is maintained in the pressurized state from the previous step. is led out to the main discharge pipe 16 via the pipe 14B and the valve 15B, and further discharged to the outside air. At this time, the oxygen component gas, which is a component that is difficult to adsorb, and a part of the nitrogen component, which is an easily adsorbable component, that is adsorbed on the adsorbent, which stays in the space in the bed B, is desorbed and discharged (depressurization step). Then, when the pressure inside the bed B is reduced to a pressure close to atmospheric pressure, the valve 12B is opened, and a part of the product oxygen component gas extracted from the adsorption bed A in the adsorption step and flowing through the main outlet pipe 9 is released. tube 13B,
The material is introduced into the adsorption bed B through the valve 12B in a countercurrent direction to the flow of the raw material in the adsorption step, and is discharged to the atmosphere through the pipe 14B, the valve 15B, and the main discharge pipe 16. At this time, nitrogen, which is an easily adsorbed component adsorbed on the adsorbent in the adsorption bed B, is desorbed and scavenged by the flow of oxygen gas, which is a poorly adsorbed component, and the adsorbent in the adsorption bed B is regenerated (scavenging step). Subsequently, after a certain period of time, the valve 15B is closed, and a part of the product oxygen component gas flowing through the main outlet pipe 9 flows into the adsorption bed B through the pipe 13.
B. The pressure inside the bed is increased through the valve 12B until the adsorption pressure reaches 2.5 kg/cm ² G (pressure increasing step). Next, the valves are opened and closed so that adsorption bed A and adsorption bed B are operated in the second process indicated above, that is, adsorption bed A is operated in each step of depressurization, scavenging, and pressure increase, and adsorption bed B is operated in the adsorption process. Thereafter, each adsorption bed is valved to alternately perform an adsorption step and a depressurization-scavenging-pressurization step. During this time, the raw material tank 2 is closed to the overflow valve 8 as described above.
Working pressure of A and 8B 2.5Kg/cm ² 0.2 to 1.2Kg/cm ² from G
Any pressure value between G, for example 0.2 in this example
It is controlled by the pressure regulator 17 so that the pressure is always maintained at 3.2Kg/cm ² G, which is higher by Kg/cm ² G.
By installing overflow valves 8A and 8B and setting their operating pressures, part of the product oxygen from one adsorption bed in the adsorption process is scavenged from the other adsorption bed, and the adsorption pressure in the adsorption bed in the pressure increase process is varied. It is possible to maintain a constant pressure without overloading, enable extremely stable operation, and collect product gas with stable purity without fluctuations. Furthermore, there are advantages such as improved yield and reduced power consumption, and increased operating efficiency of the apparatus. Next, using the device of the present invention, the raw material tank pressure is 0.2 to 1.2 Kg/cm ² G lower than the overflow valve operating pressure, as described above, by determining the relationship between the overflow valve operating pressure and the raw material tank set pressure.
Performance when operated with a high setting (Example 1, Example 2) and the relationship between the overflow valve operating pressure and the raw material tank set pressure using the device of the present invention at raw material tank pressures other than the above values. The performance when operated (Example 3) and the performance when operated with a conventional device without an overflow valve and raw material tank (Example 4) are compared and displayed. The adsorbent used in each example was Molecule Sieve 5A manufactured by Linde, packing amount 25 kg/bed, number of adsorption beds used: 2, adsorption process 90 seconds, depressurization process 20 seconds,
The raw material is air in the scavenging process for 50 seconds and the pressure increasing process for 20 seconds.
Oxygen gas was collected as a product.

[Table] Using the device of the present invention as described above, the relationship between the overflow valve operating pressure and the raw material tank set pressure is calculated as follows: Raw material tank set pressure (Kg/cm ² G) = Overflow valve operating pressure (Kg/cm ²
G) In Examples 1 and 2 where the pressure was set to +0.2 to 1.2 (Kg/cm ² G), not only did the oxygen yield reach 55 to 59%, but also the adsorption process pressure was kept constant and extremely stable as described above. Driven to the state. On the other hand, in Example 3 where the device of the present invention is used, but the relationship between the overflow valve operating pressure and the raw material tank set pressure is set to a value outside of the above relationship, the raw material tank set pressure is lower than the overflow valve operating pressure.
Although the setting was 1.4 Kg/cm ² G higher, the flow rate of the product oxygen was lower than the flow rate of the raw material in Example 2, and despite the low oxygen purity, the yield remained at 50%. This is thought to be because the pressure in the raw material tank is high and the pressure within the adsorption bed fluctuates somewhat as the overflow valve operates during the adsorption process. Furthermore, in the conventional apparatus of Example 4, no overflow valve or raw material tank for buffering pressure fluctuations was installed, so the pressure inside the adsorption bed during the adsorption process was kept at a constant pressure of 3.3 Kg/cm ² G Despite efforts to maintain the temperature, pressure fluctuations occurred and the system was extremely unstable, resulting in a yield of only 48% of the product oxygen. In addition, in the device of the present invention, when the set pressure of the raw material tank was set higher than the overflow valve operating pressure by a value of 0.2 kg/cm ² G or less, the overflow valve did not operate satisfactorily and good operation could not be maintained. . In the above example, two adsorption beds were used and the operation was performed by switching the adsorption-depressurization-scavenging-pressure raising process, but the present invention is not limited to this, and the present invention is not limited to this. It goes without saying that it can be used as appropriate when using an adsorption bed, and the same effects can be achieved, and the adsorption and separation gas components are also limited to the separation of oxygen and nitrogen from the raw air as exemplified in the above examples. However, if the adsorbent is appropriately selected and used depending on the desired separated component gas,
Of course, the present invention can be applied to the separation of any component gas. As described above, the present invention provides an overflow valve on the outlet side of the adsorption bed and a pressure buffer raw material tank on the inlet side, and adjusts the set pressure of the raw material tank pressure by 0.2 to 1.2 Kg/1 to the operating pressure of the overflow valve. In a pressure fluctuation adsorption method in which two or more adsorption beds are provided and operated by sequentially switching between an adsorption process, a depressurization process, a scavenging process, and a pressure increase process, by increasing the pressure by an arbitrary amount between cm ² G, The adsorption pressure in the adsorption step can always be kept constant and stable. Therefore, the extension of the adsorption front of the substance adsorbed by the adsorbent in the adsorption bed is stabilized, and the purity of the collected product gas is not only kept constant, but also the purity can be easily improved and the yield can be improved. You can improve your performance. Furthermore, the operation is stable, and the equipment can be operated with an appropriate amount and minimum compression power without supplying more raw material than necessary or performing more compression than necessary, which improves the operational efficiency of the equipment. This brings about many advantages, such as making it possible to greatly improve the performance.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the fluctuation of the pressure inside the adsorption bed during the adsorption process in the conventional method, Fig. 2 is a system diagram showing an embodiment of the present invention, and Fig. 3 is an implementation of the overflow valve used in the present invention. It is a sectional view showing an aspect. 1 is a compressor, 2 is a raw material tank, 3 and 19 are pipes,
4 is the main supply pipe, 5A, 5B, 7A, 7B, 11 is the conduit, 6A, 6B, 12A, 12B, 15A, 1
5B is a solenoid valve, 8A, 8B are overflow valves, 9 is a main outlet pipe, 10 is a product gas tank, 13A, 13B are side pipes, 14A, 14B are purge pipes, 16 is a main discharge pipe, 17 is a pressure regulator, 18 1 is a valve, 101 is a valve box, 102 is a gas inlet, 103 is a gas outlet, 104 is a valve, 105 is a spring spring, 1
06 is an adjustment screw.

Claims (1)

[Scope of Claims] 1. At least two adsorption beds are provided, each bed is operated according to the order of pressurized adsorption, depressurization, scavenging, and pressurization, and each of the at least two adsorption beds is In a method of separating gases using a pressure fluctuation adsorption method, in which one adsorption bed is used for the pressurized adsorption process, while the other adsorption beds are operated in the depressurization, scavenging, and pressurization processes by switching each adsorption bed. , a pressure buffer raw material tank is provided on the inlet side to the adsorption bed, and an overflow valve is provided on the outlet side, and the pressure of the raw material tank is increased to an arbitrary value between 0.2 and 1.2 Kg/cm ² G than the overflow valve operating pressure. A gas adsorption/separation method characterized by supplying raw material gas to an adsorption bed under control such that the pressure is maintained at a high level, thereby stabilizing the pressure inside the bed during the adsorption process. 2 At least two adsorption beds filled with an adsorbent that selectively adsorbs one component of the mixed gas are provided, and one end of each adsorption bed is connected to a main material supply pipe connected in sequence to a compressor and a pressure buffer material tank, respectively. It is connected to a branch pipe provided with a valve that branches and opens and closes according to the process order, and also branches from between each adsorption bed and each opening and closing valve, and is connected to the main discharge pipe through the valve that opens and closes. The other end of each adsorption bed is connected to the main outlet pipe via an overflow valve that opens at a desired set pressure, and is provided with an opening/closing valve that bypasses the overflow valve. A pressure regulator is provided for controlling the raw material tank to a set pressure higher than the opening operating pressure of the overflow valve by an arbitrary value between 0.2 and 1.2 Kg/cm ² G. Gas adsorption separation equipment.