WO2017163792A1 - Method for manufacturing concentrated target gas - Google Patents

Abstract

A method is disclosed for manufacturing a product gas that is a target gas that was concentrated from a mixed gas containing the target gas and an unnecessary gas by the pressure swing adsorption method. This method includes: a step 1 to supply a mixed gas to an adsorption tower (10A) and discharge gas from an adsorption tower (10B), and to have both adsorption towers communicate with each other; a step 2 to discharge gas from the adsorption tower (10A) and supply the mixed gas to the adsorption tower (10B), and to have both adsorption towers communicate with each other; a step 3 to discharge gas from the adsorption tower 10A and supply the mixed gas to the adsorption tower 10B, and to recover a product gas from the adsorption tower 10B; a step 4 to supply the mixed gas to the adsorption tower 10B and discharge gas from the adsorption tower 10A, and to have both adsorption towers communicate with each other; a step 5 to discharge gas from the adsorption tower 10B and supply the mixed gas to the adsorption tower 10A, and to have both adsorption towers communicate with each other; and a step 6 to discharge gas from the adsorption tower 10B and supply the mixed gas to the adsorption tower 10A, and to recover the product gas from the adsorption tower 10A.

Description

Method for producing concentrated target gas

The present invention relates to a method for producing a product gas in which a target gas is concentrated by a pressure fluctuation adsorption method from a mixed gas containing a target gas and an unnecessary gas.

A pressure fluctuation adsorption method (PSA method) is known as a method of separating and recovering oxygen as a target gas from a mixed gas containing oxygen (target gas) such as air and nitrogen (unnecessary gas). Concentrated oxygen gas (product gas) obtained by the PSA method is used in fields that consume large amounts of oxygen such as electric furnace steelmaking, nonferrous metal refining, garbage incineration, papermaking, oxygen aeration in water treatment facilities, ozone generators, etc. Besides being used, small ones are also used for home medical care.

As a technique for concentrating and recovering oxygen by the PSA method, a plurality of (for example, 2 to 4) adsorption towers are used, for example, a cycle including adsorption, depressurization, desorption, and pressurization is repeated in each adsorption tower to concentrate oxygen. What was devised so that gas can be obtained with a high recovery rate is known. The gas mixture is supplied to the adsorption tower by a blower during the adsorption and pressurization operations, and the inside of the adsorption tower is decompressed by a vacuum pump during the depressurization and desorption operations. Among the PSA methods carried out using a plurality of adsorption towers, when two adsorption towers are used, there are various power unit consumption (power consumption related to gas separation operation per unit oxygen generation amount), apparatus manufacturing costs, etc. Improvements have been attempted, and a method of efficiently using a blower and a vacuum pump has been proposed from the viewpoint of reducing power consumption.

Specifically, in a system in which a mixed gas is continuously supplied by the two-column PSA method and suction and exhaust are performed continuously using a vacuum pump, adsorption is performed using concentrated oxygen gas as a product. A system for cleaning the adsorbent (see, for example, Patent Document 1) and a system for cleaning the adsorbent using the residual concentrated oxygen gas in the adsorption tower (for example, see Example 3 of Patent Document 2) are known.

Generally, the PSA gas separation device is not supposed to be unusable in a few years, and it is assumed that it will be used for a long period of 10 years or longer. For this reason, both the reduction of the power consumption rate and the reduction of the device manufacturing cost are useful, but the reduction of the power consumption rate is particularly strongly desired. In the technique disclosed in Patent Document 1, the mixed gas is always supplied and the vacuum pump is continuously operated to try to reduce the power consumption, but because the product is cleaned using the concentrated oxygen gas as the product, There was a problem that the concentrated oxygen gas was wasted and the oxygen recovery rate was reduced.

Further, in the technique of Example 3 of Patent Document 2, the mixed gas is always supplied and the vacuum pump is continuously operated to perform cleaning using the residual concentrated oxygen gas in the adsorption tower. However, when the vacuum pump air volume and the blower air volume are the same, there is a problem that the concentrated oxygen gas generation amount is smaller than that of Example 1 in which the cleaning is not performed and the concentrated oxygen gas cannot be obtained efficiently. .

As a cause of the problem that the concentrated oxygen gas cannot be efficiently generated as described above, the oxygen concentration is low when the residual concentrated oxygen gas is supplied into the adsorption tower by constantly supplying the mixed gas and continuously using the vacuum pump. Since the mixed gas and the residual concentrated oxygen gas are mixed, it is conceivable that the oxygen concentration of the cleaning gas is lowered and the regeneration effect of the adsorbent by cleaning is reduced.

In addition, the system of Patent Document 2 in which a mixed gas is always charged and a vacuum pump is continuously used to perform cleaning with residual concentrated oxygen gas in the adsorption tower is provided with a blower attached to the adsorption tower having a high pressure. Since the mixed gas is supplied and used, the blower is loaded and considered to be undesirable from the viewpoint of reducing the power consumption rate.

JP 11-179133 A Japanese Patent Laid-Open No. 2-119915

The present invention has been conceived under such circumstances, and in producing a product gas in which a target gas is concentrated by a PSA method from a mixed gas containing a target gas and an unnecessary gas, the target gas is recovered. The main object is to provide a method suitable for reducing the power consumption while suppressing the decrease in efficiency.

A method for producing a target gas according to an embodiment of the present invention includes a first adsorption tower and a second adsorption packed with an adsorbent that selectively adsorbs the unnecessary gas from a mixed gas containing the target gas and the unnecessary gas. The above-described problems are solved in producing a product gas in which the above target gas is concentrated by a pressure fluctuation adsorption method performed using a tower. In the method, the mixed gas is supplied to the first adsorption tower in a state where the first adsorption tower and the second adsorption tower are in communication with each other, while the gas in the tower is supplied from the second adsorption tower. In a state where the first adsorption tower and the second adsorption tower are in communication with each other, the gas in the tower is exhausted from the first adsorption tower, while the second adsorption is performed. The step of supplying the mixed gas to the tower, and exhausting the gas in the tower from the first adsorption tower in a state where the first adsorption tower and the second adsorption tower are not communicated, Supplying the mixed gas to the second adsorption tower and recovering the product gas from the second adsorption tower in at least a part of the time; the first adsorption tower and the second adsorption tower; In the state where the two are connected, the mixed gas is supplied to the second adsorption tower, while the first adsorption tower In step 4 for exhausting the gas in the tower, and in the state where the first adsorption tower and the second adsorption tower are in communication, the gas in the tower is exhausted from the second adsorption tower, In step 5 for supplying the mixed gas to the first adsorption tower, and in a state where the first adsorption tower and the second adsorption tower are not communicated with each other, the gas in the tower is exhausted from the second adsorption tower. On the other hand, a cycle including step 6 of supplying the mixed gas to the first adsorption tower and recovering the product gas from the first adsorption tower in at least a part of time is repeated.

Preferably, at least a part of the supply of the mixed gas to the first adsorption tower and the second adsorption tower is performed using a turbo blower.

Preferably, in each of the steps 1 and 4, the pressure drop in the adsorption tower on the mixed gas introduction side at the start and end of the step is caused by the adsorption through the steps 1 to 6. It is in the range of -5 to 25%, in particular 0 to 15%, of the pressure difference between the highest and lowest pressures in the column.

Preferably, the time ratio occupied by each step of step 1 and step 4 with respect to the time of one cycle according to steps 1 to 6 is 2 to 18%, particularly 6 to 14%.

Preferably, at the end of each step of step 2 and step 5, the pressure difference between the first adsorption tower and the second adsorption tower is within 5 kPa.

Preferably, the product gas derived from the adsorption tower in each of the steps 3 and 6 is temporarily stored in a storage tank.

Preferably, in each of the steps 3 and 6, the adsorbing tower into which the mixed gas is introduced and the storage tank are communicated with each other in addition to the introduction of the mixed gas. And the operation of increasing the pressure by sending the product gas in the storage tank to the adsorption tower.

Preferably, in each of the steps 3 and 6, the introduction of the mixed gas is not performed at the initial stage of the steps without connecting the adsorption tower into which the mixed gas is introduced and the storage tank. Includes an operation for boosting the adsorption tower.

Preferably, the optimum duration for performing Step 3 and Step 6 is calculated according to the temperature of the mixed gas, and the duration of each step of Step 3 and Step 6 is updated.

Preferably, the target gas is oxygen and the unnecessary gas is nitrogen.

Preferably, the discharge pressure of the turbo blower is set higher than atmospheric pressure.

According to the method for producing a product gas of the present invention, even when a mixed gas is always charged and a vacuum pump is continuously used, cleaning using the residual concentration target gas (gas containing a lot of product gas) in the adsorption tower is performed. In addition, even when the mixed gas is supplied to a relatively high pressure during the cleaning, the power consumption can be reduced.

Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a schematic block diagram of the product gas manufacturing apparatus for implement | achieving the manufacturing method of the product gas which concerns on embodiment of this invention. It is a gas flow chart corresponding to each step of a manufacturing method of product gas concerning an embodiment of the present invention. It is a gas flow chart corresponding to each step of a manufacturing method of product gas concerning other embodiments of the present invention. It is a gas flow chart corresponding to each step of a manufacturing method of product gas concerning a comparative example of the present invention. It is a gas flow chart corresponding to each step of a manufacturing method of product gas concerning other comparative examples of the present invention.

Hereinafter, as a preferred embodiment of the present invention, a method for producing concentrated oxygen gas (product oxygen gas) from a mixed gas containing oxygen as a target gas and nitrogen as an unnecessary gas will be specifically described with reference to the drawings. To do.

FIG. 1 shows a schematic configuration of a product gas production apparatus X1 that can be used to execute a method for producing concentrated oxygen gas according to an embodiment of the present invention.

The product gas production apparatus X1 includes two adsorption towers 10A and 10B, a turbo blower 21, a vacuum pump 22, a storage tank 23, and pipes 31 to 37. The product gas production apparatus X1 is configured to be capable of concentrating and separating oxygen from a mixed gas (usually air) containing oxygen and nitrogen using a pressure fluctuation adsorption method (PSA method).

Each of the adsorption towers 10A and 10B has gas passages 11 and 12 at both ends, and is filled with a filler for selectively adsorbing nitrogen contained in the mixed gas between the gas passages 11 and 12. Yes. Examples of the adsorbent include LiX-type zeolite, CaA-type zeolite, and CaX-type zeolite, and these may be used alone or in combination.

The turbo blower 21 is for sending the mixed gas to the adsorption towers 10A and 10B. The vacuum pump 22 is for depressurizing the inside of the adsorption towers 10A and 10B. For example, a roots type is used as the vacuum pump 22. The storage tank 23 is an empty container for temporarily storing gas (product oxygen gas described later) derived from the adsorption towers 10A and 10B.

The pipe 31 has a main line 31 'having a mixed gas introduction end E1, and branch lines 31A and 31B each connected to the gas passage 11 side of the adsorption towers 10A and 10B. A turbo blower 21 and an automatic valve 31c are provided in the main line 31 '. The branch lines 31A and 31B are provided with automatic valves 31a and 31b that can switch between an open state and a closed state. Although details will be described later, in the present embodiment, a thermometer 40 is attached to the main line 31 ′ of the pipe 31.

The pipe 32 has a main line 32 ′ having a gas discharge end E <b> 2 and branch lines 32 </ b> A and 32 </ b> B each connected to the gas passage 11 side of the adsorption towers 10 </ b> A and 10 </ b> B. A vacuum pump 22 is provided in the main line 32 '. The branch lines 32A and 32B are provided with automatic valves 32a and 32b capable of switching between an open state and a closed state.

The pipe 33 has a main line 33 ′ having a storage tank connection end E <b> 3 and branch lines 33 </ b> A and 33 </ b> B each connected to the gas passage 12 side of the adsorption towers 10 </ b> A and 10 </ b> B. The branch lines 33A and 33B are provided with automatic valves 33a and 33b capable of switching between an open state and a closed state.

The pipe 34 is connected to the branch lines 33A and 33B of the pipe 33 in a bridge shape. Thereby, the gas passage ports 12 of the adsorption towers 10 </ b> A and 10 </ b> B communicate with each other via the pipe 34. The pipe 34 is provided with an automatic valve 34a capable of switching between an open state and a closed state, and a flow rate adjusting valve 34b (flow rate adjusting means).

The piping 35 has one end connected to the storage tank 23 and the other end has a product gas extraction end E4. Thereby, the product oxygen gas temporarily stored in the storage tank 23 is taken out via the pipe 35.

The pipe 36 is connected to the main line 31 ′ of the pipe 31 at both ends. More specifically, one end of the pipe 36 is connected to the main line 31 ′ upstream of the suction port of the turbo blower 21, and the other end is connected to the main line 31 ′ downstream of the discharge port of the turbo blower 21. The pipe 36 functions as a bypass line for bypassing the mixed gas introduced into the main line 31 ′ without passing through the turbo blower 21 and supplying the mixed gas to the adsorption towers 10 </ b> A and 10 </ b> B.

The pipe 37 has one end connected in a branched manner to the main line 31 ′ of the pipe 31 and the other end open to the atmosphere. Specifically, one end of the pipe 37 is connected to the main line 31 ′ between the discharge port side of the turbo blower 21 and the downstream connection end to the main line 31 ′ in the bypass pipe 36. The pipe 37 is provided with a flow rate adjustment valve 37a. Further, the automatic valve 31c provided in the main line 31 'is between the connection end of the pipe 37 to the main line 31' and the downstream side connection end to the main line 31 'in the pipe 36.

Using the product gas production apparatus X1 having the above configuration, the product gas production method according to the embodiment of the present invention can be executed. When the product gas production apparatus X1 is in operation, the automatic valve 31a, 31b, 31c, 32a, 32b, 33a, 33b, 34a, 36a, and the flow rate control valve 34b are appropriately switched, and a desired gas flow state in the apparatus. And one cycle consisting of the following steps 1 to 6 can be repeated. FIG. 2 schematically shows a gas flow state in the product gas production apparatus X1 in steps 1 to 6. Although details will be described later, step 3 includes sub-step 3-1 and sub-step 3-2, and step 6 includes sub-step 6-1 and sub-step 6-2.

In step 1, the automatic valves 31a, 32b, 34a and the flow rate adjusting valve 34b are opened, and a gas flow state as shown in FIG. 2A is achieved. In the adsorption tower 10 </ b> A, the mixed gas is supplied from the gas passage port 11 through the pipe 31. Since the adsorption tower 10A has been previously adsorbed (AS) (see sub-step 6-2 shown in FIG. 2 (h)), it is in a relatively high pressure state at the start of step 1 and is in the tower. In this case, gas containing a large amount of product oxygen gas remains. Note that the maximum pressure inside the adsorption tower 10A in the sub-step 6-2 for performing adsorption is, for example, 5 to 40 kPaG (gauge pressure: the same applies hereinafter), and preferably 10 to 30 kPaG.

On the other hand, in the adsorption tower 10B, desorption (DS) is performed first (see sub-step 6-2 shown in FIG. 2 (h)), and the gas in the tower is continuously passed through the gas passage port 11 by the vacuum pump 22. It is led out of the tower as off-gas. The off-gas is discharged out of the system via the branch line 32B and the main trunk line 32 '. Note that the minimum pressure inside the adsorption tower 10B in the sub-step 6-2 for performing desorption is, for example, −80 to −45 kPaG, and preferably −75 to −55 kPaG.

In Step 1, the gas passage ports 12 of the adsorption towers 10A and 10B communicate with each other via the pipe 34. The internal pressure of the adsorption tower 10A at the start of Step 1 is substantially the same as the maximum pressure in Sub-Step 6-2 where the adsorption was performed previously. After the start of step 1, the adsorption tower 10A depressurizes while releasing the residual concentrated oxygen gas (gas containing a large amount of product oxygen gas) from the gas passage port 12, while the adsorption tower 10B releases from the adsorption tower 10A. The residual concentrated oxygen gas thus introduced is introduced from the gas passage port 12, and pressure increase / cleaning (PR / RS) having a cleaning effect is performed.

In Step 1, the internal pressure of the adsorption tower 10A is controlled, for example, by appropriately adjusting the flow rate adjustment valve 34b or by adjusting the duration of Step 1. The internal pressure of the adsorption tower 10A is lower at the end of step 1 than at the start (pressure reduction: DP), substantially the same as the start (pressure keep: PK), or higher than at the start. (Pressure: PR) can occur. The internal pressure of the adsorption tower 10A at the end of step 1 is, for example, 5 to 40 kPaG. The change in pressure in the adsorption tower 10A on the mixed gas introduction side from the start to the end of step 1 is, for example, a ratio of −5 to 25% with respect to the pressure difference between the maximum pressure and the minimum pressure in the adsorption tower 10A. Preferably, it is 0 to 15%. At the end of step 1, the internal pressure of the adsorption tower 10A is higher than the internal pressure of the adsorption tower 10B. The above step 1 is continued for 4 seconds, for example.

The storage tank 23 is filled with product oxygen gas (concentrated oxygen gas). The product oxygen gas derived from the adsorption tower 10B in sub-step 3-1 to be described later is sent to the storage tank 23, and the product oxygen gas derived from the adsorption tower 10A in sub-step 6-1 to be described later is stored in the storage tank 23. Is sent out. The product oxygen gas in the storage tank 23 is taken out through the pipe 35 and used after the flow rate is adjusted. In all steps 1 to 6 including step 1, product oxygen gas is continuously acquired from the storage tank 23 at a constant flow rate.

In step 2, the automatic valves 31b, 32a, 34a and the flow rate adjusting valve 34b are opened, and the gas flow state as shown in FIG. 2B is achieved. In the adsorption tower 10A, the inside of the tower is depressurized by the vacuum pump 22 and nitrogen is desorbed from the adsorbent (decompression / desorption: DP / DS), and the gas in the tower is led out of the tower as an off-gas through the gas passage port 11. The The off-gas is discharged out of the system through the branch line 32A and the main line 32 '. On the other hand, in the adsorption tower 10 </ b> B, the mixed gas is supplied from the gas passage port 11 via the pipe 31.

In Step 2, the gas passages 12 and 12 of the adsorption towers 10A and 10B are communicated with each other through the pipe 34, following Step 1. At the start of step 2, the adsorption tower 10A is in a relatively high pressure state as compared to the adsorption tower 10B.

After the start of Step 2, in the adsorption tower 10A, the concentrated oxygen gas remaining in the vicinity of the gas passage port 12 is decompressed while being released from the gas passage port 12. On the other hand, in the adsorption tower 10B, the residual concentrated oxygen gas released from the adsorption tower 10A is introduced from the gas passage 12 following step 1, and pressure increase / recovery (PR / RC) is performed.

In Step 2, the opening degree of the flow rate adjusting valve 34b is adjusted so that the pressure difference between the adsorption tower 10A and the adsorption tower 10B is within a predetermined range. At the end of step 2, the internal pressure of the adsorption tower 10A and the internal pressure of the adsorption tower 10B are approximate or the same pressure. For example, the pressure difference between the adsorption tower 10A and the adsorption tower 10B at the end of step 2 is within 5 kPaG. At the end of step 2, the internal pressure of the adsorption tower 10B is lower than the internal pressure of the storage tank 23. The above step 2 is continued for 4 seconds, for example.

In the present embodiment, step 3 includes sub-step 3-1 that continues from the start of step 3 (immediately after the end of step 2) to the elapse of a predetermined time, and sub-step 3-2 that is performed after sub-step 3-1. Including.

In sub-step 3-1, the automatic valves 31b, 32a and 33b are opened, and the gas flow state as shown in FIG. 2 (c) is achieved. In the adsorption tower 10A, following the step 2, the inside of the tower is decompressed by the vacuum pump 22 and nitrogen is desorbed (DS) from the adsorbent, and the gas in the tower is led out of the tower as an off-gas through the gas passage port 11. The off-gas is discharged out of the system. On the other hand, in the adsorption tower 10 </ b> B, the mixed gas is supplied from the gas passage port 11 through the pipe 31 following Step 2.

Further, in sub-step 3-1, the communication between the adsorption towers 10A and 10B is cut off, while the gas passage port 12 and the storage tank 23 of the adsorption tower 10B communicate with each other via the main line 33 'and the branch line 33B. Yes. At the start of sub-step 3-1, the adsorption tower 10B is in a relatively low pressure state as compared with the storage tank 23. Accordingly, after the start of sub-step 3-1, the product oxygen gas in the storage tank 23 is released to the main line 33 '. On the other hand, in the adsorption tower 10B, the product oxygen gas released from the storage tank 23 is introduced from the gas passage port 12, and pressure increase (PR) is performed. At the end of sub-step 3-1, the internal pressure of the adsorption tower 10B and the internal pressure of the storage tank 23 are substantially the same pressure. The sub-step 3-1 is continued for 2 seconds, for example.

In sub-step 3-2, the automatic valves 31b, 32a, and 33b are continuously opened, and the gas flow state as shown in FIG. 2D is achieved. In the adsorption tower 10A, following the sub-step 3-1, the inside of the tower is decompressed by the vacuum pump 22 and nitrogen is desorbed (DS) from the adsorbent, and the gas in the tower is led out of the tower as an off-gas through the gas passage port 11. Is done. The off-gas is discharged out of the system. On the other hand, in the adsorption tower 10B, the mixed gas is supplied from the gas passage port 11 through the pipe 31 following the sub-step 3-1. In the adsorption tower 10A that performs desorption, the internal pressure continues to decrease, and at the end of the sub-step 3-2, the inside of the adsorption tower 10A reaches the minimum pressure. The minimum pressure is, for example, −80 to −45 kPaG, and preferably −75 to −55 kPaG.

Further, in the sub-step 3-2, following the sub-step 3-1, the adsorption tower 10B and the storage tank 23 communicate with each other via the main line 33 ′ and the branch line 33B. At the start of sub-step 3-2, the adsorption tower 10B and the storage tank 23 have substantially the same pressure. After the start of sub-step 3-2, the mixed gas is supplied to the adsorption tower 10B to increase the internal pressure of the adsorption tower 10B, while the product oxygen gas is taken out from the storage tank 23 through the pipe 35. Thus, the internal pressure of the storage tank 23 decreases. For this reason, a gas flow is generated from the adsorption tower 10 </ b> B toward the storage tank 23. In the adsorption tower 10B, the internal pressure rises, and nitrogen contained in the mixed gas is adsorbed (AD) by the adsorbent. Then, product oxygen gas enriched with oxygen is led out from the gas passage port 12. The product oxygen gas is sent to the storage tank 23 via the branch line 33B and the main line 33 '. In sub-step 3-2, the internal pressure of the adsorption tower 10B continues to rise, and at the end of sub-step 3-2, the internal pressure of the adsorption tower 10B reaches the maximum pressure. The maximum pressure is, for example, 5 to 40 kPaG, and preferably 10 to 30 kPaG. The sub-step 3-2 is continued for 15 seconds, for example.

In subsequent steps 4 to 6, as shown in FIGS. 2E to 2H, the operation performed on the adsorption tower 10A in steps 1 to 3 is performed on the adsorption tower 10B, and the operation performed on the adsorption tower 10B is performed. It carries out for the adsorption tower 10A.

In step 4, the automatic valves 31b, 32a, 34a and the flow rate adjusting valve 34b are opened, and a gas flow state as shown in FIG. 2 (e) is achieved. In step 5, the automatic valves 31a, 32b, 34a and the flow rate adjusting valve 34b are opened, and the gas flow state as shown in FIG. 2 (f) is achieved. In sub-step 6-1, the automatic valves 31a, 32b, 33a are opened, and the gas flow state as shown in FIG. 2 (g) is achieved. In sub-step 6-2, the automatic valves 31a, 32b, and 33a are continuously opened, and the gas flow state as shown in FIG. 2 (h) is achieved. Although detailed explanation is omitted, in steps 4 and 5 and sub-steps 6-1 and 6-2, the adsorption tower 10B is in the same state as the adsorption tower 10A in steps 1 and 2 and sub-steps 3-1 and 3-2. The adsorption tower 10A is in the same state as the adsorption tower 10B in steps 1 and 2 and sub-steps 3-1 and 3-2.

Then, the product oxygen gas from which nitrogen is significantly removed from the mixed gas is continuously acquired by repeatedly performing the cycle including the above steps 1 to 6 in each of the adsorption towers 10A and 10B. Note that the time of one cycle (cycle time) in steps 1 to 6 is 50 seconds.

In the production of the product oxygen gas according to the present embodiment, the recovery rate of the product oxygen gas can be increased by reducing or eliminating the cleaning with the product oxygen gas in the storage tank 23. The mixed gas is supplied to the adsorption towers 10 </ b> A and 10 b using a turbo blower 21. The turbo blower 21 consumes less power when the discharge pressure is higher than atmospheric pressure. Therefore, by using the turbo blower 21 to supply the mixed gas, the mixed gas is supplied to a relatively high pressure state during cleaning using the residual concentrated oxygen gas in the adsorption towers 10A and 10B ( In addition to efficiently supplying the mixed gas, the power consumption can be reduced efficiently.

In this embodiment, in each of the above steps 1 and 4, even if the pressure of the adsorption towers 10A and 10B on the mixed gas introduction side decreases from the start to the end of the step, the decrease The ratio is controlled to 25% or less, preferably 15% or less of the pressure difference between the maximum pressure and the minimum pressure in each adsorption tower. Thus, in the cleaning using the residual concentrated oxygen gas in the adsorption towers 10A and 10B, the decrease in the oxygen concentration of the cleaning gas is suppressed by suppressing the pressure change of the mixed gas supply side adsorption tower, and the adsorbent is efficiently regenerated. It can be performed.

In the present embodiment, the time ratio occupied by each step of Step 1 and Step 4 is, for example, 2 to 18% with respect to the time of one cycle (50 seconds) according to Steps 1 to 6, and preferably 6 ~ 14%. At the end of step 2 and step 5, the pressure difference between the 10A adsorption tower and the adsorption tower 10B is within 5 kPaG.

There is a method to reduce the load of the vacuum pump by increasing the minimum pressure in the adsorption tower to reduce the unit of electric power when obtaining the product oxygen gas, but with this method the pressure width of the adsorption and desorption (swing width) ) Decreases, the amount of nitrogen adsorbed decreases and the necessary adsorbent increases. Thus, the power intensity and the necessary amount of adsorbent are usually in a trade-off relationship. In contrast, the time ratio occupied by steps 1 and 4 is 2 to 18%, preferably 6 to 14% of the cycle time of steps 1 to 6, and at the end of steps 2 and 5, the adsorption tower Adjusting the opening of the flow rate control valve 34b so that the pressure difference between 10A and 10B is within 5 kPaG enables the product oxygen gas (concentrated oxygen gas) to be recovered efficiently, and the necessary adsorption while reducing the power consumption rate. The dosage can be reduced.

During the course of steps 1 to 6, the optimum duration for performing steps 3 and 6 is calculated according to the outside air temperature, and the duration of steps 3 and 6 is repeated in the process of repeating the manufacturing cycle. May be updated. When product oxygen gas (concentrated oxygen gas) is produced using air as a mixed gas mainly containing nitrogen and oxygen, the oxygen content per unit volume varies depending on the change in temperature. In addition, the nitrogen adsorption capacity of the adsorbent varies with changes in temperature. Therefore, in order to maintain the oxygen concentration of the product oxygen gas and the product flow rate at the set values, it is necessary to shorten the cycle time when the temperature rises and lengthen the cycle time when the temperature falls. In the present embodiment, a thermometer 40 (temperature measuring means) is provided in the main line 31 'of the pipe 31 for supplying the mixed gas to the adsorption towers 10A and 10B. Then, according to the temperature of the mixed gas measured by the thermometer 40, the optimum duration time for performing Step 3 and Step 6 is calculated, and the duration time of Step 3 and Step 6 is updated, The oxygen concentration and product flow rate can be automatically maintained at the set values.

Further, sub-step 3-1 in step 3 is to open the automatic valve 33b while the internal pressure of the storage tank 23 is higher than the internal pressure of the adsorption tower 10B, and to connect the adsorption tower 10B and the storage tank 23. Thus, the pressure in the adsorption tower 10B is increased with the oxygen-enriched gas in the storage tank 23 as a product. However, the sub-step 3-1 is omitted, and the automatic valve 33b is opened at the sub-step 3-2 to delay the timing for communicating the adsorption tower 10B and the storage tank 23, so that the adsorption is performed with the oxygen-enriched gas as the product. It is not necessary to boost the tower 10B. In this case, the preceding step 2 is continued until the internal pressure of the adsorption tower 10B becomes equal to the internal pressure of the storage tank 23, and then step 3 (sub-step 3-2) is performed. That is, sub-step 3-1 in step 3 may be omitted. Similarly, sub-step 6-1 in step 6 may be omitted.

In this embodiment, the discharge pressure of the turbo blower 21 is always higher than the atmospheric pressure. In supplying the mixed gas, when supplying the mixed gas to the adsorption towers 10 </ b> A and 10 </ b> B having a pressure lower than the atmospheric pressure, mixing is performed using the supply pressure of the mixed gas itself from the bypass pipe 36 bypassing the turbo blower 21. Gas can be supplied. Further, instead of the bypass pipe 36, a means for separately supplying a mixed gas using its own supply pressure may be employed. Thus, when supplying mixed gas using the supply pressure of mixed gas itself, the turbo blower 21 will be in an idle operation state. Here, in the turbo blower 21, since the power consumption becomes small when the discharge pressure is higher than the atmospheric pressure, the discharge pressure of the turbo blower 21 during the idling operation of the turbo blower 21 is effective for reducing the power consumption (atmospheric pressure). By adjusting to a higher discharge pressure, the power consumption can be reduced. The discharge pressure of the turbo blower 21 can be adjusted, for example, by closing the automatic valve 31c on the downstream side of the turbo blower 21 and adjusting the opening of the flow rate adjustment valve 37a provided in the pipe 37.

According to the production of the product oxygen gas of this embodiment, even when the mixed gas is always supplied and the vacuum pump 22 is continuously used, the cleaning using the residual concentrated oxygen gas in the adsorption towers 10A and 10B is effectively performed. Can be done. Further, by limiting the pressure drop in the adsorption tower (the adsorption tower 10A in Step 1 and the adsorption tower 10B in Step 4) on the mixed gas supply side during cleaning, the reduction in the oxygen concentration of the cleaning gas is suppressed and efficiently performed. The adsorbent can be regenerated. This is preferable for recovering the product oxygen gas at a high concentration and a high recovery rate.

FIG. 3 shows another example of a product gas manufacturing method configured to repeat one cycle consisting of steps 1 to 6 in which a part of the steps is different from the case described above with reference to FIG.

In the cycle consisting of steps 1 to 6 shown in FIG. 3, the configuration of sub-step 3-1 and sub-step 6-1 is different from the case shown in FIG. Since the configuration of steps 1, 2, 3, 2, 4, 5, and 6-2 other than sub-steps 3-1 and 6-1 is substantially the same as that shown in FIG. To do.

In the embodiment shown in FIG. 3, in the sub-step 3-1, the automatic valves 31b and 32a are opened, and the gas flow state as shown in FIG. In the adsorption tower 10A, following the step 2, the inside of the tower is decompressed by the vacuum pump 22 and nitrogen is desorbed from the adsorbent, and the gas in the tower is led out of the tower as an off-gas through the gas passage port 11. The off-gas is discharged out of the system. On the other hand, in the adsorption tower 10 </ b> B, the mixed gas is supplied from the gas passage port 11 through the pipe 31 following Step 2. In the present embodiment, in sub-step 3-1, the communication between the adsorption towers 10A and 10B is cut off, and the communication between the gas passage 12 of the adsorption tower 10B and the storage tank 23 is also cut off (automatically). The valve 33b is closed). Therefore, in the adsorption tower 10B, the pressure is increased only by supplying the mixed gas, and the pressure is not increased by the product oxygen gas. At the end of sub-step 3-1, the internal pressure of the adsorption tower 10B is substantially the same as the internal pressure of the storage tank 23 or higher than the internal pressure of the storage tank 23. This sub-step 3-1 is continued for 4 seconds, for example.

In sub-step 3-2, the automatic valves 31b, 32a and 33b are opened, and the gas flow state as shown in FIG. 3D is achieved. In the adsorption tower 10A, following the sub-step 3-1, the inside of the tower is decompressed by the vacuum pump 22 and nitrogen is desorbed from the adsorbent, and the gas in the tower is led out of the tower as an off-gas through the gas passage port 11. The off-gas is discharged out of the system. On the other hand, in the adsorption tower 10B, the mixed gas is supplied from the gas passage port 11 through the pipe 31 following the sub-step 3-1. In the adsorption tower 10A that performs desorption, the internal pressure continues to decrease, and at the end of sub-step 3-2, the inside of the adsorption tower 10A reaches the minimum pressure. The minimum pressure is, for example, −80 to −45 kPaG, and preferably −75 to −55 kPaG.

Further, in the sub-step 3-2, unlike the sub-step 3-1, the adsorption tower 10B and the storage tank 23 communicate with each other via the main line 33 ′ and the branch line 33B. At the start of sub-step 3-2, the internal pressure of the adsorption tower 10B is substantially the same as the internal pressure of the storage tank 23 or higher than the internal pressure of the storage tank 23. After the start of sub-step 3-2, the mixed gas is supplied to the adsorption tower 10B to increase the internal pressure of the adsorption tower 10B, while the product oxygen gas is taken out from the storage tank 23 through the pipe 35. Thus, the internal pressure of the storage tank 23 decreases. For this reason, a gas flow is generated from the adsorption tower 10 </ b> B toward the storage tank 23. In the adsorption tower 10B, the internal pressure rises and nitrogen contained in the mixed gas is adsorbed by the adsorbent. Then, product oxygen gas enriched with oxygen is led out from the gas passage port 12. The product oxygen gas is sent to the storage tank 23 via the branch line 33B and the main line 33 '. In sub-step 3-2, the internal pressure of the adsorption tower 10B continues to rise, and at the end of sub-step 3-2, the internal pressure of the adsorption tower 10B reaches the maximum pressure. The maximum pressure is, for example, 5 to 40 kPaG, and preferably 10 to 30 kPaG. The substep 3-2 is continued for 13 seconds, for example.

In subsequent steps 4 to 6, as shown in FIGS. 3E to 3H, the operation performed on the adsorption tower 10A in steps 1 to 3 is performed on the adsorption tower 10B, and the operation performed on the adsorption tower 10B is performed. It carries out for the adsorption tower 10A.

Then, the product oxygen gas from which nitrogen is significantly removed from the mixed gas is continuously acquired by repeatedly performing the cycle including the above steps 1 to 6 in each of the adsorption towers 10A and 10B. Note that the time of one cycle (cycle time) in steps 1 to 6 is 50 seconds.

Also in the production of the product oxygen gas of the present embodiment shown in FIG. 3, the same effects as in the case of the above-described embodiment shown in FIG. 2 can be obtained.

In the present embodiment, the communication between the storage tank 23 and the adsorption towers 10B and 10A is interrupted in the sub-step 3-1 and the sub-step 6-1. As a result, the pressure in the adsorption towers 10B and 10A is increased only by supplying the mixed gas, and the pressure is not increased by the product oxygen gas. In sub-steps 3-1 and 6-1 in the present embodiment, the timing for switching to the next sub-steps 3-2 and 6-2 is 2 seconds later than in the case shown in FIG. (Sub-steps 3-1 and 6-1 shown in FIG. 2 take 2 seconds, whereas sub-steps 3-1 and 6-1 shown in FIG. 3 take 4 seconds), and the next sub-step 3-2 And the duration of 6-2 is shortened by 2 seconds.

The embodiment of the present invention has been described above, but the scope of the present invention is not limited to the above-described embodiment. For example, a cycle composed of a plurality of steps that is repeatedly performed in each of the adsorption towers 10A and 10B by the PSA method is not limited to the above embodiment.

In addition, the method for producing a product gas according to the present invention is not limited to the application to the oxygen PSA that concentrates and separates oxygen as in the above embodiment, but is applied to the gas separation by the PSA method using other gas components as target gases. May be.

Next, the usefulness of the present invention will be described with reference to examples and comparative examples.

[Example 1]
In this embodiment, the product gas production apparatus X1 shown in FIG. 1 is used as a mixed gas under the following conditions by the production method of product oxygen gas comprising the steps described with reference to FIG. Concentrated oxygen gas was obtained as product gas from air.

As the adsorption towers 10A and 10B, cylindrical ones having a capacity of about 2 L (2 dm ³ ) were used, and each of the adsorption towers 10A and 10B was filled with 1.2 kg of LiX type zeolite as an adsorbent. In the other examples and comparative examples described later, the same adsorption towers 10A and 10B and adsorbent used in this example were used.

The duration of each step is 4 seconds for Step 1, 4 seconds for Step 2, 2 seconds for Sub Step 3-1, 15 seconds for Sub Step 3-2, 4 seconds for Step 4, 4 seconds for Step 5, Step 6-1 was 2 seconds, sub-step 6-2 was 15 seconds, and the time cycle of one cycle consisting of steps 1 to 6 was 50 seconds. In sub-steps 3-2 and 6-2, the maximum pressure inside the adsorption towers 10B and 10A during the adsorption operation was set to 20 kPaG, and the minimum pressure inside the adsorption towers 10A and 10B during the desorption operation was set to -65 kPaG. At the end of steps 1 and 4, the flow rate adjustment valve 34b was adjusted so that the internal pressure of the adsorption towers 10A and 10B on the mixed gas supply side was 15 kPaG. At this time, the internal pressures of the adsorption towers 10A and 10B at the end of steps 2 and 5 were the same.

In this embodiment, the pressure drop in the adsorption towers 10A and 10B on the mixed gas introduction side at the start and end of steps 1 and 4 is the maximum pressure (20 kPaG) and the minimum pressure (−65 kPaG) of the adsorption towers 10A and 10B. ) And a pressure difference (85 kPa) with respect to 5.9).

In this example, when the average concentration of the product oxygen gas to be acquired is 93%, the mixed gas supply amount is 827 NL / h (N indicates a standard state, and the same applies hereinafter), and the product oxygen gas flow rate is 102 NL / h. h. Further, when oxygen acquired amount is assumed 1000 Nm ³ / h at a concentration of 100% conversion, required air volume of the vacuum pump 22 is 16372m ³ / h, required air volume of the turbo blower 21 became 8887Nm ³ / h.

Roots type vacuum pump (model number: TLIF-400WP) manufactured by Otsuchi Machine Industry Co., Ltd. (Kumage-gun, Yamaguchi, Japan, URL: https://www.taiko-kk.com/) as a vacuum pump 22 and a turbo blower 21 Using the performance curve of a turbo blower (model number: 12A112XY) manufactured by Niji Gi Co., Ltd. (Himeji, Hyogo, Japan, URL: http://www.kogi.co.jp/) The power intensity was calculated with the efficiency constant at 95% and the motor efficiency of the turbo blower 21 at constant 65%. In addition, when supplying mixed gas to an adsorption tower below atmospheric pressure, it is assumed that mixed gas is supplied from the bypass pipe 36 by bypassing the turbo blower 21, and the basic unit of electric power is calculated by setting the discharge pressure of the turbo blower 21 to 0 kPaG. did. As a result, the power consumption (per unit of power) per 1 Nm ^{3 of} oxygen was 0.286 kWh.

[Example 2]
In the present embodiment, the product gas production apparatus X1 shown in FIG. 1 is used as a mixed gas under the following conditions by the product oxygen gas production method including the steps described with reference to FIG. Concentrated oxygen gas was obtained as product gas from air.

In this embodiment, the duration of each step is 4 seconds for Step 1, 4 seconds for Step 2, 4 seconds for Sub Step 3-1, 13 seconds for Sub Step 3-2, 4 seconds for Step 4, and Step 5 Is 4 seconds, sub-step 6-1 is 4 seconds, sub-step 6-2 is 13 seconds, and the time cycle of one cycle consisting of steps 1 to 6 is 50 seconds. In sub-steps 3-1 and 6-1, the pressure of the adsorption towers 10B and 10A using the product oxygen gas in the storage tank 23 was not increased. In sub-steps 3-2 and 6-2, the maximum pressure inside the adsorption towers 10B and 10A during the adsorption operation was set to 20 kPaG, and the minimum pressure inside the adsorption towers 10A and 10B during the desorption operation was set to -65 kPaG. At the end of steps 1 and 4, the flow rate adjustment valve 34b was adjusted so that the internal pressure of the adsorption towers 10A and 10B on the mixed gas supply side was 15 kPaG. At this time, the internal pressures of the adsorption towers 10A and 10B at the end of steps 2 and 5 were the same.

In this example, when the average concentration of the product oxygen gas to be obtained was 93%, the mixed gas supply amount was 824 NL / h and the product oxygen gas flow rate was 99 NL / h. Further, when oxygen acquired amount is assumed 1000 Nm ³ / h at a concentration of 100% conversion, required air volume of the vacuum pump 22 is 16582m ³ / h, required air volume of the turbo blower 21 became 8987Nm ³ / h.

Then, the power intensity was calculated for the vacuum pump 22 and the turbo blower 21 under the same operating conditions as in the first embodiment. As a result, the power consumption (per unit of power) per 1 Nm ^{3 of} oxygen was 0.290 kWh.

Example 3
In this embodiment, the product gas production apparatus X1 shown in FIG. 1 is used as a mixed gas under the following conditions by the production method of product oxygen gas comprising the steps described with reference to FIG. Concentrated oxygen gas was obtained as product gas from air.

In this example, at the end of steps 1 and 4, the flow rate adjustment valve 34b was adjusted so that the internal pressure of the adsorption towers 10A and 10B on the mixed gas supply side was 20 kPaG.

In this embodiment, the pressure drop in the adsorption towers 10A and 10B on the mixed gas introduction side at the start and end of steps 1 and 4 is the maximum pressure (20 kPaG) and the minimum pressure (−65 kPaG) of the adsorption towers 10A and 10B. ) And 0% of the pressure difference (85 kPa). Other operating conditions were the same as in Example 1 above.

In this example, when the average concentration of the product oxygen gas to be obtained was 93%, the mixed gas supply amount was 882 NL / h and the product oxygen gas flow rate was 102 NL / h. Further, when oxygen acquired amount is assumed 1000 Nm ³ / h at a concentration of 100% conversion, required air volume of the vacuum pump 22 is 16963m ³ / h, required air volume of the turbo blower 21 became 9269Nm ³ / h.

Then, the power intensity was calculated for the vacuum pump 22 and the turbo blower 21 under the same operating conditions as in the first embodiment. As a result, the power consumption (unit power consumption) per 1 Nm ^{3 of} oxygen was 0.296 kWh.

Example 4
In this embodiment, the product gas production apparatus X1 shown in FIG. 1 is used as a mixed gas under the following conditions by the production method of product oxygen gas comprising the steps described with reference to FIG. Concentrated oxygen gas was obtained as product gas from air.

In this example, at the end of steps 1 and 4, the flow rate control valve 34b was adjusted so that the internal pressure of the adsorption towers 10A and 10B on the mixed gas supply side became 10 kPaG. In this embodiment, the pressure drop in the adsorption towers 10A and 10B on the mixed gas introduction side at the start and end of steps 1 and 4 is the maximum pressure (20 kPaG) and the minimum pressure (−65 kPaG) of the adsorption towers 10A and 10B. ) And 11.8% of the pressure difference (85 kPa). Other operating conditions were the same as in Example 1 above.

In this example, when the average concentration of the product oxygen gas to be obtained was 93%, the mixed gas supply amount was 788 NL / h, and the product oxygen gas flow rate was 97 NL / h. Further, when oxygen acquired amount is assumed 1000 Nm ³ / h at a concentration of 100% conversion, required air volume of the vacuum pump 22 is 16324m ³ / h, required air volume of the turbo blower 21 became 8756Nm ³ / h.

Then, the power intensity was calculated for the vacuum pump 22 and the turbo blower 21 under the same operating conditions as in the first embodiment. As a result, the power consumption (unit power consumption) per 1 Nm ^{3 of} oxygen was 0.289 kWh.

Example 5
In this embodiment, the product gas production apparatus X1 shown in FIG. 1 is used as a mixed gas under the following conditions by the production method of product oxygen gas comprising the steps described with reference to FIG. Concentrated oxygen gas was obtained as product gas from air.

In this embodiment, the duration of each step is as follows: Step 1 is 6 seconds, Step 2 is 4 seconds, Sub-step 3-1 is 2 seconds, Sub-step 3-2 is 13 seconds, Step 4 is 6 seconds, Step 5 4 seconds, sub-step 6-1 was 2 seconds, sub-step 6-2 was 13 seconds, and the time cycle of one cycle consisting of steps 1 to 6 was 50 seconds. Other operating conditions were the same as in Example 1 above.

In this example, when the average concentration of the product oxygen gas to be obtained was 93%, the mixed gas supply amount was 923 NL / h, and the product oxygen gas flow rate was 110 NL / h. Further, when oxygen acquired amount is assumed 1000 Nm ³ / h at a concentration of 100% conversion, required air volume of the vacuum pump 22 is 16862m ³ / h, required air volume of the turbo blower 21 became 9016Nm ³ / h.

Then, the power intensity was calculated for the vacuum pump 22 and the turbo blower 21 under the same operating conditions as in the first embodiment. As a result, the power consumption (unit power consumption) per 1 Nm ^{3 of} oxygen was 0.296 kWh.

Example 6
In this embodiment, the product gas production apparatus X1 shown in FIG. 1 is used as a mixed gas under the following conditions by the production method of product oxygen gas comprising the steps described with reference to FIG. Concentrated oxygen gas was obtained as product gas from air.

In this embodiment, the duration of each step is as follows: step 1 is 2 seconds, step 2 is 4 seconds, sub-step 3-1 is 2 seconds, sub-step 3-2 is 17 seconds, step 4 is 2 seconds, step 5 4 seconds, sub-step 6-1 was 2 seconds, sub-step 6-2 was 17 seconds, and the time cycle of one cycle consisting of steps 1 to 6 was 50 seconds. Other operating conditions were the same as in Example 1 above.

In this example, when the average concentration of the product oxygen gas to be obtained was 93%, the mixed gas supply amount was 750 NL / h, and the product oxygen gas flow rate was 90 NL / h. Further, when oxygen acquired amount is assumed 1000 Nm ³ / h at a concentration of 100% conversion, required air volume of the vacuum pump 22 is 16749m ³ / h, required air volume of the turbo blower 21 became 9146Nm ³ / h.

Then, the power intensity was calculated for the vacuum pump 22 and the turbo blower 21 under the same operating conditions as in the first embodiment. As a result, the power consumption (unit power consumption) per 1 Nm ^{3 of} oxygen was 0.293 kWh.

Example 7
In the present embodiment, the product gas production apparatus X1 shown in FIG. 1 is used to concentrate the product gas from the air as the mixed gas by the product oxygen gas production method including the steps described with reference to FIG. Obtained oxygen gas. In this embodiment, when supplying the mixed gas to the adsorption tower below atmospheric pressure, it is assumed that the flow rate of the turbo blower 21 is adjusted by the flow rate adjustment valve 37a of the pipe 37 to increase the discharge pressure, and the discharge pressure of the turbo blower 21 is increased. Was calculated as 20 kPaG. The operating conditions of the other steps were the same as in Example 1 above, and the power intensity was calculated for the vacuum pump 22 and the turbo blower 21 under the same operating conditions as in Example 1 above. As a result, the power consumption (unit power consumption) per 1 Nm ^{3 of} oxygen was 0.278 kWh.

[Comparative Example 1]
In this comparative example, using the product gas production apparatus X1 shown in FIG. 1, the method disclosed in Japanese Patent Application Laid-Open No. 11-179133 (the above-mentioned Patent Document 1) is performed with the conditions of the present invention as uniform as possible. It was. In this comparative example, the cycle comprising the steps shown in FIG. 4 was repeated, and concentrated oxygen gas was obtained from air as a mixed gas under the following conditions.

In this comparative example, one cycle consisting of steps 1 'to 6' was repeated. In step 1 ', the automatic valves 31b, 32a, 34a and the flow rate adjusting valve 34b are opened, and the gas flow state as shown in FIG. 4A is achieved. In the adsorption tower 10A, the inside of the tower is decompressed by the vacuum pump 22 and nitrogen is desorbed (DS) from the adsorbent, and the gas in the tower is led out of the tower as an off-gas through the gas passage port 11. The off-gas is discharged out of the system. On the other hand, in the adsorption tower 10 </ b> B, the mixed gas is supplied from the gas passage port 11 via the pipe 31.

Further, in step 1 ′, the gas passage ports 12 of the adsorption towers 10 </ b> A and 10 </ b> B communicate with each other through the pipe 34. After the start of step 1 ′, in the adsorption tower 10 </ b> A, the concentrated oxygen gas remaining in the vicinity of the gas passage port 12 is decompressed (DP) while being released from the gas passage port 12. On the other hand, in the adsorption tower 10B, the residual concentrated oxygen gas released from the adsorption tower 10A is introduced from the gas passage port 12, and pressure increase / recovery (PR / RC) is performed.

In step 2 ', the automatic valves 31b, 32a and 33b are opened, and the gas flow state as shown in FIG. 4B is achieved. In the adsorption tower 10A, following the step 1 ′, the inside of the tower is decompressed by the vacuum pump 22, nitrogen is desorbed (DS) from the adsorbent, and the gas in the tower is led out of the tower as an off-gas through the gas passage port 11. . The off-gas is discharged out of the system. On the other hand, in the adsorption tower 10 </ b> B, the mixed gas is supplied from the gas passage port 11 through the pipe 31 following Step 1 ′.

In Step 2 ', the communication between the adsorption towers 10A and 10B is closed, while the gas passage port 12 of the adsorption tower 10B and the storage tank 23 are communicated with each other via the main line 33' and the branch line 33B. At the start of step 2 ′, the adsorption tower 10 </ b> B is in a relatively low pressure state as compared to the storage tank 23. Therefore, after the start of step 2 ′, the product oxygen gas in the storage tank 23 is released to the main line 33. On the other hand, in the adsorption tower 10B, the product oxygen gas released from the storage tank 23 is introduced from the gas passage port 12, and pressure increase (PR) is performed. At the end of step 2 ', the internal pressure of the adsorption tower 10B and the internal pressure of the storage tank 23 are substantially the same pressure.

In this comparative example, step 3 ′ is performed after sub-step 3-1 ′ that continues from the start of step 3 ′ (immediately after the end of step 2 ′) until the elapse of a predetermined time, and after sub-step 3-1 ′. Sub-step 3-2 ′ is included.

In sub-step 3-1 ', the automatic valves 31b, 32a and 33b are continuously opened, and the gas flow state as shown in FIG. 4C is achieved. In the adsorption tower 10A, following the step 2 ', the inside of the tower is decompressed by the vacuum pump 22 and nitrogen is desorbed (DS) from the adsorbent, and the gas in the tower is led out of the tower as an off-gas through the gas passage port 11. . The off-gas is discharged out of the system. On the other hand, in the adsorption tower 10B, the mixed gas is supplied from the gas passage port 11 through the pipe 31 following the step 2 '. In the adsorption tower 10A that performs desorption, the internal pressure continues to decrease, and at the end of sub-step 3-1 ', the inside of the adsorption tower 10A reaches the minimum pressure.

In sub-step 3-1 ′, following the step 2 ′, the adsorption tower 10 B and the storage tank 23 communicate with each other via the main line 33 ′ and the branch line 33 B. At the start of sub-step 3-1 ', the adsorption tower 10B and the storage tank 23 have substantially the same pressure. After the start of sub-step 3-1 ′, the mixed gas is supplied to the adsorption tower 10B to increase the internal pressure of the adsorption tower 10B, while the product oxygen gas is taken out from the storage tank 23 through the pipe 35. As a result, the internal pressure of the storage tank 23 decreases. For this reason, a gas flow is generated from the adsorption tower 10 </ b> B toward the storage tank 23. In the adsorption tower 10B, the internal pressure rises and nitrogen contained in the mixed gas is adsorbed (AS) by the adsorbent. Then, product oxygen gas enriched with oxygen is led out from the gas passage port 12. The product oxygen gas is sent to the storage tank 23 via the branch line 33B and the main line 33 '.

In sub-step 3-2 ', the automatic valves 31b, 32a, 33b, 34a and the flow rate adjusting valve 34b are opened, and the gas flow state as shown in FIG. 4 (d) is achieved. In the adsorption tower 10B, the mixed gas is supplied from the gas passage port 11 through the pipe 31 following the sub-step 3-1 '. In the adsorption tower 10B, the internal pressure is increased, and nitrogen contained in the mixed gas is adsorbed (AS) by the adsorbent. Then, product oxygen gas enriched with oxygen is led out from the gas passage port 12. The product oxygen gas is sent to the storage tank 23 via the branch line 33B and the main line 33 '. In sub-step 3-2 ', the internal pressure of the adsorption tower 10B continues to rise, and at the end of sub-step 3-2', the internal pressure of the adsorption tower 10B reaches the maximum pressure.

In sub-step 3-2 ′, part of the product oxygen gas derived from the adsorption tower 10B is introduced as a cleaning gas into the adsorption tower 10A via the pipe 34, and the adsorbent in the adsorption tower 10A is washed (RS). Is done. At the same time, in the adsorption tower 10A, the inside of the tower is depressurized by the vacuum pump 22, and the gas in the tower is discharged outside the tower.

In subsequent steps 4 ′ to 6 ′, as shown in FIGS. 4E to 4H, the operation performed on the adsorption tower 10A in steps 1 ′ to 3 ′ is performed on the adsorption tower 10B, and the adsorption tower 10B is performed. The performed operation is performed on the adsorption tower 10A. The product oxygen gas from which nitrogen is significantly removed from the mixed gas is continuously obtained by repeatedly performing the cycle including the above steps 1 'to 6' in each of the adsorption towers 10A and 10B.

In this comparative example, the duration of each step is 4 seconds for Step 1 ′, 2 seconds for Step 2 ′, 12 seconds for Sub-Step 3-1 ′, 7 seconds for Sub-Step 3-2 ′, and Step 4 ′ 4 seconds, step 5 ′ is 2 seconds, sub-step 6-1 ′ is 12 seconds, sub-step 6-2 ′ is 7 seconds, and the time cycle of one cycle consisting of steps 1 ′ to 6 ′ is 50 seconds. . In substeps 3-2 ′ and 6-2 ′, the maximum pressure inside the adsorption towers 10B and 10A during the adsorption operation is set to 20 kPaG, and in substeps 3-1 ′ and 6-1 ′, the adsorption tower 10A during the desorption operation is set. , 10B minimum pressure was -65 kPaG. At the end of Steps 1 'and 4', the flow rate adjustment valve 34b was adjusted so that the internal pressures of the adsorption towers 10B and 10A on the mixed gas supply side were the same. In sub-steps 3-2 'and 6-2', the amount of product oxygen gas used as the cleaning gas was 180 NL / h.

In this comparative example, when the average concentration of the obtained product oxygen gas was 93%, the mixed gas supply amount was 807 NL / h, and the product oxygen gas flow rate was 95 NL / h. Further, when oxygen acquired amount is assumed 1000 Nm ³ / h at a concentration of 100% conversion, required air volume of the vacuum pump 22 is 17283m ³ / h, required air volume of the turbo blower 21 became 8964Nm ³ / h.

Then, the power intensity was calculated for the vacuum pump 22 and the turbo blower 21 under the same operating conditions as in the first embodiment. As a result, the power consumption (unit power consumption) per 1 Nm ^{3 of} oxygen was 0.308 kWh.

[Comparative Example 2]
In this comparative example, using the product gas production apparatus X1 shown in FIG. 1, the method disclosed in Example 3 of Japanese Patent Laid-Open No. Hei 2-119915 (Patent Document 2) is compared with the example of the present invention as much as possible. I went with all of them. In this comparative example, the cycle consisting of each step shown in FIG. 5 was repeated, and concentrated oxygen gas was obtained from air as a mixed gas under the following conditions.

In this comparative example, one cycle consisting of steps 1 "to 6" was repeated. In step 1 ', the automatic valves 31a, 32b, 34a and the flow rate adjusting valve 34b are opened, and the gas flow state as shown in FIG. 5A is achieved. In the adsorption tower 10 </ b> A, the mixed gas is supplied from the gas passage port 11 through the pipe 31. Since the adsorption tower 10A has been previously adsorbed (see step 6 ″ shown in FIG. 5 (f)), it is in a relatively high pressure state at the start of step 1, and product oxygen gas is introduced into the tower. On the other hand, in the adsorption tower 10B, desorption is performed first (see step 6 ″ shown in FIG. 5 (f)), and the gas in the tower is continuously removed by the vacuum pump 22. It is led out of the tower as off-gas through the passage port 11. The off-gas is discharged out of the system via the branch line 32B and the main trunk line 32 '.

In Step 1 ″, the gas passages 12 and 12 of the adsorption towers 10A and 10B communicate with each other through the pipe 34. After the start of Step 1 ″, The pressure is reduced (DP) with the release of the residual concentrated oxygen gas (the gas containing a large amount of product oxygen gas). On the other hand, in the adsorption tower 10B, the residual concentrated oxygen gas released from the adsorption tower 10A is introduced from the gas passage port 12. Thus, pressurization / recovery (PR / RC) having a cleaning effect is performed.

In Step 2 ″, the automatic valves 31b, 32a, and 33b are opened, and the gas flow state as shown in FIG. 5B is achieved. In the adsorption tower 10A, the inside of the tower is depressurized by the vacuum pump 22 and adsorbed. Nitrogen is desorbed (DS) from the agent, and the gas in the tower is led out of the tower as an off-gas through the gas passage port 11. The off-gas is discharged out of the system. It is supplied from the gas passage port 11 via the pipe 31.

In step 2 ″, the communication between the adsorption towers 10A and 10B is closed, while the gas passage port 12 and the storage tank 23 of the adsorption tower 10B communicate with each other via the main line 33 ′ and the branch line 33B. At the start of 2 ″, the adsorption tower 10B is in a relatively low pressure state compared to the storage tank 23. Therefore, after the start of step 2 ″, the product oxygen gas in the storage tank 23 is released to the main line 33. On the other hand, in the adsorption tower 10B, the product oxygen gas released from the storage tank 23 is discharged from the gas passage port 12. The pressure is increased (PR). At the end of step 2 ″, the internal pressure of the adsorption tower 10B and the internal pressure of the storage tank 23 are substantially the same pressure.

In step 3 ″, the automatic valves 31b, 32a, 33b are continuously opened, and the gas flow state as shown in FIG. 5C is achieved. In the adsorption tower 10A, the vacuum pump 22 continues the tower with the vacuum pump 22 following step 2 ″. The inside is depressurized and nitrogen is desorbed (DS) from the adsorbent, and the gas in the tower is led out of the tower as an off-gas through the gas passage port 11. The off-gas is discharged out of the system. On the other hand, in the adsorption tower 10B, following step 2 ″, the mixed gas is supplied from the gas passage port 11 through the pipe 31, and nitrogen contained in the mixed gas is adsorbed (AS). In the adsorption tower 10A that performs desorption. The internal pressure continues to drop, and at the end of step 3 ″, the inside of the adsorption tower 10A reaches the minimum pressure.

In Step 3 ″, following Step 2 ″, the adsorption tower 10B and the storage tank 23 communicate with each other via the main line 33 ′ and the branch line 33B. At the start of step 3 ″, the adsorption tower 10B and the storage tank 23 have substantially the same pressure. After the start of step 3 ″, the mixed gas is supplied to the adsorption tower 10B, so that the adsorption tower 10B While the internal pressure rises, the product oxygen gas is taken out from the storage tank 23 through the pipe 35, so that the internal pressure of the storage tank 23 decreases. For this reason, a gas flow is generated from the adsorption tower 10 </ b> B toward the storage tank 23. In the adsorption tower 10B, the internal pressure rises and nitrogen contained in the mixed gas is adsorbed by the adsorbent. Then, product oxygen gas enriched with oxygen is led out from the gas passage port 12. The product oxygen gas is sent to the storage tank 23 via the branch line 33B and the main line 33 '. At step 3 ″, the internal pressure of the adsorption tower 10B continues to rise, and at the end of step 3 ″, the inside of the adsorption tower 10B reaches the maximum pressure.

In subsequent steps 4 ″ to 6 ″, as shown in FIGS. 5D to 5F, the operations performed on the adsorption tower 10A in steps 1 ″ to 3 ″ are performed on the adsorption tower 10B, and the adsorption tower 10B is performed. The performed operation is performed on the adsorption tower 10A. The product oxygen gas from which nitrogen is significantly removed from the mixed gas is continuously obtained by repeatedly performing the cycle including the above steps 1 "to 6" in each of the adsorption towers 10A and 10B.

In this comparative example, the duration of each step is as follows: Step 1 ″ is 4 seconds, Step 2 ″ is 2 seconds, Step 3 ″ is 19 seconds, Step 4 ″ is 4 seconds, Step 5 ″ is 2 seconds, Step 6 ″. Was 19 seconds, and the time cycle of one cycle consisting of steps 1 "to 6" was 50 seconds. In steps 3 ″ and 6 ″, the maximum pressure inside the adsorption towers 10B and 10A during the adsorption operation was set to 20 kPaG, and the minimum pressure inside the adsorption towers 10A and 10B during the desorption operation was set to −65 kPaG. At the end of steps 1 ″ and 4 ″, the flow rate adjustment valve 34b was adjusted so that the internal pressure of the adsorption towers 10B and 10A on the mixed gas supply side became 1 kPaG.

In this comparative example, when the average concentration of the product oxygen gas to be acquired was 93%, the mixed gas supply amount was 814 NL / h and the product oxygen gas flow rate was 90 NL / h. Further, when oxygen acquired amount is assumed 1000 Nm ³ / h at a concentration of 100% conversion, required air volume of the vacuum pump 22 is 18047m ³ / h, required air volume of the turbo blower 21 became 9677Nm ³ / h.

Then, the power intensity was calculated for the vacuum pump 22 and the turbo blower 21 under the same operating conditions as in the first embodiment. As a result, the power consumption (unit power consumption) per 1 Nm ^{3 of} oxygen was 0.318 kWh.

Table 1 shows the relationship between the amount of product oxygen gas generated per unit time (product oxygen gas flow rate) and the power intensity for the above examples and comparative examples.

Next, assuming an apparatus with a flow rate of 5000 Nm ³ / h (100% oxygen concentration conversion), the electricity price is 15 yen / kWh, the annual apparatus operating time is 8000 hours, and the adsorbent price is 1700 yen / kg. Table 2 shows a list of annual electricity charges and the price of the adsorbent used.

As is apparent from Table 1, according to the method for producing product oxygen gas (product gas) of the present invention, the power intensity can be reduced (less than about 0.3 kwh / Nm ³ ).

In addition, by setting the cleaning time using the residual concentrated oxygen gas in the adsorption tower (the time of each step of steps 1 and 4 in Examples 1 to 4 above) to 6 to 14% of the cycle time, high product oxygen The amount of gas generated can be realized, and the amount of adsorbent required is reduced. Accordingly, it is possible to reduce the device manufacturing cost while reducing the power consumption rate.

Claims (13)

From the mixed gas containing the target gas and the unnecessary gas, the target gas is obtained by a pressure fluctuation adsorption method using a first adsorption tower and a second adsorption tower filled with an adsorbent that selectively adsorbs the unnecessary gas. Is a method for producing a concentrated product gas,
While the first adsorption tower and the second adsorption tower are in communication with each other, the mixed gas is supplied to the first adsorption tower, and the gas in the tower is exhausted from the second adsorption tower. Step 1 and
While the first adsorption tower and the second adsorption tower are in communication, the gas in the tower is exhausted from the first adsorption tower, and the mixed gas is supplied to the second adsorption tower. Step 2 to
While the first adsorption tower and the second adsorption tower are not in communication with each other, the gas in the tower is exhausted from the first adsorption tower, while the mixed gas is supplied to the second adsorption tower. Step 3 for recovering the product gas from the second adsorption tower in at least part of the time;
While the first adsorption tower and the second adsorption tower are in communication with each other, the mixed gas is supplied to the second adsorption tower, and the gas in the tower is exhausted from the first adsorption tower. Step 4 and
While the first adsorption tower and the second adsorption tower are in communication, the gas in the tower is exhausted from the second adsorption tower, while the mixed gas is supplied to the first adsorption tower. Step 5 and
While the first adsorption tower and the second adsorption tower are not in communication with each other, the gas in the tower is exhausted from the second adsorption tower, while the mixed gas is supplied to the first adsorption tower. Step 6 for recovering the product gas from the first adsorption tower in at least part of the time;
A method for producing a product gas, comprising repeatedly performing a cycle including The method for producing a product gas according to claim 1, wherein at least part of the supply of the mixed gas to the first adsorption tower and the second adsorption tower is performed using a turbo blower. In each of the steps 1 and 4, the pressure drop of the adsorption tower on the mixed gas introduction side at the start and end of the step is the maximum of the adsorption tower through the steps 1 to 6. The method for producing a product gas according to claim 1 or 2, wherein the pressure difference is in the range of -5 to 25% of the pressure difference between the pressure and the minimum pressure. In each of the steps 1 and 4, the pressure drop of the adsorption tower on the mixed gas introduction side at the start and end of the step is the maximum of the adsorption tower through the steps 1 to 6. The method for producing a product gas according to claim 3, wherein the pressure difference is in the range of 0 to 15% of the pressure difference between the pressure and the minimum pressure. The product gas according to any one of claims 1 to 4, wherein a time ratio occupied by each step of the step 1 and the step 4 is 2 to 18% with respect to a cycle time of the steps 1 to 6. Production method. 6. The method for producing a product gas according to claim 5, wherein a time ratio occupied by each step of the step 1 and the step 4 is 6 to 14% with respect to one cycle time of the steps 1 to 6. The product according to any one of claims 1 to 6, wherein a pressure difference between the first adsorption tower and the second adsorption tower is within 5 kPa at the end of each of the steps 2 and 5. Gas production method. The product gas production method according to any one of claims 1 to 7, wherein the product gas derived from the adsorption tower in each of the steps 3 and 6 is temporarily stored in a storage tank. In each of the steps 3 and 6, the adsorbing tower into which the mixed gas is introduced communicates with the storage tank in the initial stage of each step, and in addition to the introduction of the mixed gas, the storage The method for producing a product gas according to claim 8, comprising an operation of increasing the pressure by sending the product gas in the tank to the adsorption tower. In each of the steps 3 and 6, the adsorption tower is introduced only by introducing the mixed gas without communicating the adsorption tower into which the mixed gas is introduced and the storage tank at the initial stage of each step. The method for producing a product gas according to claim 8, comprising an operation of increasing the pressure. 11. The optimum duration for performing the step 3 and the step 6 is calculated according to the temperature of the mixed gas, and the duration of each step of the step 3 and the step 6 is updated. A method for producing a product gas according to any one of the above. 12. The method for producing a product gas according to claim 1, wherein the target gas is oxygen and the unnecessary gas is nitrogen. The method for producing a product gas according to claim 2, wherein the discharge pressure of the turbo blower is made higher than the atmospheric pressure.

Images