Gas separation device and method for operating gas separation device

Abstract

Provided is a gas separation device using a separation membrane module, the device being capable of efficiently regenerating a separation membrane without extracting the separation membrane for regeneration of the separation membrane and without preparing special gas for regeneration.　This gas separation device 1 having a regeneration function of an inorganic separation membrane 31 includes: a pretreatment device 10 for removing impurities in a raw material gas; a compressor 20 for adiabatically compressing the raw material gas discharged from the pretreatment device; a separation membrane module 30 for separating the raw material gas discharged from the compressor into a permeated gas and a non-permeated gas by means of the inorganic separation membrane; a permeated gas return line 33 for returning at least a portion of the permeated gas from a permeated gas outlet 32 of the separation membrane module to upstream of the pretreatment device; and a non-permeated gas return line 37 for returning at least a portion of the non-permeated gas from a non-permeated gas outlet 34 of the separation membrane module to the upstream of the pretreatment device.

Description

Gas separation device and method for operating a gas separation device

[0001] This invention relates to a gas separation device and a method for operating a gas separation device.

[0002] Currently, separation membrane modules equipped with inorganic separation membranes such as zeolite membranes are used for the purification of biogas and natural gas. Inorganic separation membranes have better chemical resistance, oxidation resistance, heat stability, and pressure resistance than polymer membranes. Among them, zeolite membranes have regularly arranged sub-nanometer pores and function as molecular sieves, so they can selectively transmit specific molecules and have high separation performance. Even for a brand-new inorganic separation membrane that is completely uncontaminated, as the use progresses, separation gas molecules and impurity molecules adsorb on the membrane surface and inside the pores, resulting in a decrease in separation performance and processing capacity. In order to desorb and regenerate the impurity gas molecules and the like adhering to the surface and inside the pores of the separation membrane, it is necessary to remove the separation membrane from the separation membrane module and perform heat treatment or the like.

[0003] Japanese Patent Publication No. 7358827

[0004] When removing the separation membrane from the separation membrane module for regeneration, the separation membrane may be damaged. In this method, it is necessary to stop the gas separation device and carefully perform the regeneration operation of the separation membrane. The invention described in Patent Document 1 relates to a regeneration method characterized by not requiring the removal of the separation membrane from the separation membrane module, and provides a regeneration method for a zeolite membrane composite that can remove the components adsorbed on the zeolite membrane after gas separation and regenerate at low cost. However, in the invention described in Patent Document 1, it is necessary to prepare a specific component gas at a temperature within a predetermined range and flow this gas separately through the separation membrane module during regeneration, which leads to new consumption of the regeneration gas. In addition, since the gas permeating through the separation membrane is used for regeneration, there is a problem that gas molecules such as impurities adhering to the non-permeating side membrane surface cannot be efficiently desorbed. Furthermore, due to the deterioration of the separation membrane, non-permeating gas (product gas) that does not meet the purity standard becomes defective gas and must be disposed of. If it is not disposed of, the entire amount must be recovered again and passed through the separation membrane module, resulting in a large time loss.

[0005] The present invention has been made in view of the above, and its object is to provide a gas separation apparatus using a separation membrane module that does not require the removal of the separation membrane for regeneration, does not require the preparation of a special gas for regeneration, and can efficiently regenerate the separation membrane.

[0006] (1) The present invention relates to a gas separation apparatus having a regeneration function for an inorganic separation membrane, comprising: a pretreatment device for removing impurities from a raw material gas; a compressor for adiabatically compressing the raw material gas discharged from the pretreatment device; a separation membrane module for separating the raw material gas discharged from the compressor into permeate gas and impermeable gas using the inorganic separation membrane; a permeate gas return line for returning at least a portion of the permeate gas from the permeate gas outlet of the separation membrane module to the upstream of the pretreatment device; and an impermeable gas return line for returning at least a portion of the impermeable gas from the impermeable gas outlet of the separation membrane module to the upstream of the pretreatment device.

[0007] In the present invention (1), there is a permeate gas return line that returns at least a portion of the permeate gas from the permeate gas outlet of the separation membrane module to the upstream of the pretreatment device, and a non-permeate gas return line that returns at least a portion of the non-permeate gas from the non-permeate gas outlet of the separation membrane module to the upstream of the pretreatment device. Therefore, there is no need to remove the inorganic separation membrane from the module, and at least a portion of the permeate gas and at least a portion of the non-permeate gas are returned to the upstream of the pretreatment device, adiabatically compressed by a compressor to raise the temperature and bring into contact with the separation membrane, thereby efficiently regenerating the inorganic separation membrane in an operational state.

[0008] The present invention (2) is a gas separation apparatus according to the present invention (1), further comprising a concentration meter for a predetermined gas component at the permeate gas outlet and / or the non-permeate gas outlet of the separation membrane module.

[0009] In the present invention (2), since a concentration meter for a predetermined gas component is further provided at the permeate gas outlet and / or non-permeate gas outlet, the concentration of the permeate gas and / or non-permeate gas can be monitored by the concentration meter, and losses due to the generation of undesirable gases can be prevented.

[0010] The present invention (3) is a gas separation apparatus according to the present invention (1) or (2), wherein the inorganic separation membrane is a zeolite membrane formed on a porous support.

[0011] In the present invention (3), since a zeolite membrane is used as the inorganic separation membrane, it has good chemical resistance, oxidation resistance, thermal stability, and pressure resistance, and has regular pores of subnanometer size, and acts as a molecular sieve, so it can selectively allow specific molecules to pass through and exhibit high separation performance.

[0012] The present invention (4) is a method for operating a gas separation apparatus having a regeneration function for an inorganic separation membrane, comprising: a pretreatment step (1) for removing impurities from a raw material gas; a membrane separation step (2) for separating the raw material gas that has undergone the pretreatment step (1) into a permeate gas and a non-permeate gas using the inorganic separation membrane; a measurement step (3) for measuring the concentration of a predetermined gas component contained in the non-permeate gas and / or the permeate gas; and a step (4) for temporarily stopping the operation and replacing the impurity removal agent filled in the pretreatment device for removing impurities from the raw material gas when the concentration of the predetermined gas component in the non-permeate gas falls below a predetermined value A% and / or the concentration of the predetermined gas component in the permeate gas exceeds a predetermined value B%. The method for operating a gas separation apparatus includes: restarting steps (1) to (3) after the replacement of the impurity removal agent is completed, pressurizing and heating the raw material gas after the pretreatment step (1) that is sent to the membrane separation step (2), and returning the entire amount of the non-permeable gas and at least a portion of the permeable gas, or at least a portion of the non-permeable gas and the entire amount of the permeable gas, to the pretreatment step (1); and interrupting the return of the non-permeable gas and the permeable gas when the concentration of the predetermined gas component in the non-permeable gas becomes a predetermined value C% or more, which is greater than A%, and / or when the concentration of the predetermined gas component in the permeable gas becomes a predetermined value D% or less, which is less than B%, and interrupting the return of the non-permeable gas and the permeable gas.

[0013] In the present invention (4), in step (4), the operation can be temporarily stopped and the impurity removal agent filled in the pretreatment device can be replaced. Furthermore, in step (5), the operation can be restarted, the raw material gas after the pretreatment step (1) can be pressurized and heated, and the entire amount of the non-permeable gas and at least a portion of the permeable gas that has gone through the separation step (2), or at least a portion of the non-permeable gas and the entire amount of the permeable gas can be returned to the pretreatment step (1) to regenerate the separation membrane. In addition, in step (6), the components of the permeable gas and the non-permeable gas can be measured, and after confirming that the separation membrane has been sufficiently regenerated, the return in step (5) can be interrupted to perform gas separation efficiently.

[0014] The present invention (5) is an operating method for the gas separation apparatus of the present invention (4), wherein in the return interruption step (6), before interrupting the return of the non-permeable gas and / or the permeable gas, a portion of the non-permeable gas and a portion of the permeable gas are returned to the pretreatment step (1), and the return of the non-permeable gas and / or the permeable gas is interrupted after the concentration of the predetermined gas component in the non-permeable gas and / or the permeable gas has recovered to 70% or more of the initial value shown when the impurity removal agent and the inorganic separation membrane are new.

[0015] In the present invention (5), the return of the non-permeable gas and the permeable gas is interrupted after the concentration of the predetermined gas component in the non-permeable gas and / or the permeable gas recovers to 70% or more of the initial value shown when the impurity removal agent and the inorganic separation membrane are new, so that the gas separation apparatus can be renewed and operated.

[0016] According to the present invention, a gas separation apparatus using a separation membrane module can be provided that does not require the removal of the separation membrane for regeneration, does not require the preparation of a special gas for regeneration, and can efficiently regenerate the separation membrane.

[0017] This diagram shows the overall system of the gas separation apparatus of the present invention. This flowchart shows the operating method of the gas separation apparatus of the present invention.

[0018] Embodiments of the present invention will be described in detail below with reference to the drawings. The following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or its uses.

[0019] Figure 1 is an overall system diagram of the gas separation apparatus of the present invention, and its main equipment includes a pretreatment device 10, a compressor 20, and a separation membrane module 30. The raw material gas to be separated enters the pretreatment device 10 through a valve 40. Inside the pretreatment device 10, the raw material gas is sequentially sent to a scrubber 11 that roughly removes hydrogen sulfide and water-soluble VOCs from the raw material gas, a blower 12 that sucks the raw material gas from the scrubber 11 and pressurizes it to a pressure above atmospheric pressure, a desulfurization tower 13 that removes hydrogen sulfide from the raw material gas, and a cooling tower 14 that cools the gas and condenses some of the water vapor in the raw material gas.

[0020] The raw material gas from the cooling tower 14 is sent to a separator 15 that removes condensed water as drain, a VOC removal tower 16 that removes VOCs from the raw material gas using activated carbon, and a dryer 17 that removes water from the raw material gas and dehumidifies the gas. The raw material gas from the dryer 17 is sent to the compressor 20 as gas that has passed through the pretreatment device 10.

[0021] The raw material gas flowing into the compressor 20 is adiabatically compressed, and the gas temperature rises. The gas temperature after the rise is preferably 60°C or higher, more preferably 80°C or higher, even more preferably 100°C or higher, and even more preferably 120°C or higher. The raw material gas, whose gas molecules have been activated by the rise in gas temperature, is sent to the separation membrane module 30. The gas sent to the separation membrane module 30 is separated into permeate gas that has permeated through the inorganic separation membrane 31 and non-permeate gas that has not permeated. The permeate gas may be the product gas and the non-permeate gas may be the removal gas; conversely, the non-permeate gas may be the product gas and the permeate gas may be the removal gas; or both the permeate gas and non-permeate gas may be the product gas. The following explanation will be based on the case where the non-permeate gas is the product gas and the permeate gas is the removal gas.

[0022] If the non-permeable gas exiting the non-permeable gas outlet 34 of the separation membrane module 30 satisfies the predetermined concentration measured by the concentration meter 36, the valve 41 opens and the non-permeable gas is sent to the product gas tank. The gas that has permeated through the inorganic separation membrane 31 exits the permeable gas outlet 32 ​​and enters the concentration meter 35, where its concentration is measured. If the concentration satisfies the predetermined concentration, the valve 44 opens and the gas is sent to the waste gas tank.

[0023] If the concentration meter 35 and / or concentration meter 36 no longer indicate the predetermined concentration, the operation is temporarily stopped, the impurity removal agent in the pretreatment device 10 is replaced, then valve 41 is fully closed, valve 44 is fully closed or partially open, and valves 42 and 43 are opened, so that at least a portion of the permeate gas passes through the permeate gas return line 33, and the entire amount of non-permeate gas passes through the non-permeate gas return line 37 and is returned to the upstream of the pretreatment device 10. At that time, since valve 41 is closed, the non-permeate product gas is not sent to the product gas tank.

[0024] The refluxed permeate gas passes through the pretreatment device 10 again, is pressurized and heated in the compressor 20, and enters the separation membrane module 30. There, it passes through the pores of the inorganic separation membrane 31, and can be purified by desorbing impurity molecules and the like that attached to the pores. Furthermore, the refluxed non-permeate gas passes through the pretreatment device 10 again, is pressurized and heated in the compressor 20, and enters the separation membrane module 30. There, it comes into contact with the surface of the inorganic separation membrane 31, and can be purified by desorbing impurity molecules and the like that attached to the surface.

[0025] Figure 2 is a flowchart showing the operation method of the gas separation apparatus of the present invention. A pretreatment process (S1) is performed on the raw material gas introduced in the raw material input process (S0). This process is performed in the pretreatment apparatus 10 shown in Figure 1. Subsequently, a membrane separation process (S2) is performed. This process is performed in the separation membrane module 30, but the raw material gas sent to the separation membrane module 30 is adiabatically compressed in the compressor 20 beforehand.

[0026] In step (S3-1), the concentration of the non-permeable gas emitted from the separation membrane module 30 is measured to determine whether the concentration of a predetermined gas component in the non-permeable gas (i.e., the product gas component concentration) is less than A%. If NO is A% or greater, in step (S3-2), the concentration of the predetermined gas component in the permeable gas is measured to determine whether it is greater than B%. If NO is B% or less, the non-permeable gas is stored in the product gas tank in the product gas storage step (S7).

[0027] If the result in step (S3-1) is YES (the concentration of the predetermined gas component in the non-permeable gas is less than A%), or if the result in step (S3-2) is YES (the concentration of the predetermined gas component in the permeable gas is greater than B%), then in step (S4), the operation is temporarily stopped and the impurity removal agent is replaced. After the impurity removal agent in the pretreatment device 10 is replaced, the valve is operated so that all of the non-permeable gas and at least a portion of the permeable gas are returned to the upstream of the pretreatment device 10, and the operation is restarted in step (S5). Subsequently, after the pretreatment step in step (S1) and the membrane separation step in step (S2), the concentration of the predetermined gas component in the non-permeable gas is measured in step (S6-1) to see if it is C% or higher. If the result is YES (the concentration of the predetermined gas component in the non-permeable gas is C% or higher), then in step (S6-2), the concentration of the predetermined gas component in the permeable gas is measured to see if it is D% or lower. If the concentration of a predetermined gas component in the permeate gas is D% or less, the return process is interrupted in step (S6-3), and the product gas is stored.

[0028] If NO is detected in step (S6-1), the process is returned to step (S5). Similarly, if NO is detected in step (S6-2), the process is returned to step (S5) to regenerate the separation membrane.

[0029] In the above embodiment, it was explained that product gas storage in step (S7) is not performed when the answer in step (S3-2) is YES or in step (S6-2) is NO (i.e., when the concentration of the predetermined gas component in the permeate gas exceeds B% or D%). However, product gas storage in step (S7) may be performed when the answer in step (S3-1) is NO or in step (S6-1) is YES (i.e., when the non-permeate gas contains sufficient product gas components).

[0030] Furthermore, even if the answer is YES in steps (S6-1) and (S6-2), it is preferable to return a portion of the non-permeable gas and / or the portion of the permeable gas to the pretreatment step (S1) until the concentration of the predetermined gas component in the non-permeable gas and / or the permeable gas recovers to 70% or more of the initial value shown when the impurity removal agent and the inorganic separation membrane are new. In this case, it is possible to regenerate the membrane while performing the normal separation operation.

[0031] In the above embodiment, the case where the non-permeable gas is the product gas and the permeable gas is the removal gas was described. However, if the non-permeable gas is the removal gas and the permeable gas is the product gas, after the impurity removal agent in the pretreatment device 10 is replaced in step (S4), the valve is operated so that at least a portion of the non-permeable gas and the entire amount of the permeable gas are returned to the pretreatment device 10, and operation is restarted in step (S5). Also, if both the permeable gas and the non-permeable gas are product gases, after the impurity removal agent in the pretreatment device 10 is replaced in step (S4), the valve is operated so that the entire amount of the non-permeable gas and the entire amount of the permeable gas are returned to the pretreatment device 10, and operation is restarted in step (S5). By performing such operations, it is possible to prevent product gas that does not satisfy the predetermined concentration from being sent to the product gas tank.

[0032] As described above, according to the present invention, when performing gas separation using a separation membrane such as an inorganic membrane, even if the separation membrane deteriorates over time, it is possible to provide a high-performance gas separation apparatus that can efficiently regenerate the separation membrane without removing the separation membrane from the separation membrane module or preparing a special gas for regeneration. Furthermore, in addition to operation specifically for separation membrane regeneration, it is also possible to regenerate the membrane while performing normal separation operations by raising the temperature of the gas supplied to the separation membrane module 30 to prevent the adsorption of impurities onto the membrane and to desorb impurities that had adhered to the membrane.

[0033] 1; Gas separation unit 10; Pretreatment unit 11; Scrubber 12; Blower 13; Desulfurization tower 14; Cooling tower 15; Separator 16; VOC removal tower 17; Dryer 20; Compressor 30; Separation membrane module 31; Inorganic separation membrane 32; Permeate gas outlet 33; Permeate gas return line 34; Impermeable gas outlet 35, 36; Concentration meter 37; Impermeable gas return line 40, 41, 42, 43, 44; Valves

Claims

1. A gas separation apparatus having a regeneration function for an inorganic separation membrane, comprising: a pretreatment device for removing impurities from a raw material gas; a compressor for adiabatically compressing the raw material gas discharged from the pretreatment device; a separation membrane module for separating the raw material gas discharged from the compressor into permeate gas and impermeable gas using the inorganic separation membrane; a permeate gas return line for returning at least a portion of the permeate gas from the permeate gas outlet of the separation membrane module to the upstream of the pretreatment device; and an impermeable gas return line for returning at least a portion of the impermeable gas from the impermeable gas outlet of the separation membrane module to the upstream of the pretreatment device.

2. The gas separation apparatus according to claim 1, further comprising a concentration meter for a predetermined gas component at the permeate gas outlet and / or the non-permeate gas outlet of the separation membrane module.

3. The gas separation apparatus according to claim 1 or 2, wherein the inorganic separation membrane is a zeolite membrane formed on a porous support.

4. A method for operating a gas separation apparatus having a regeneration function for an inorganic separation membrane, comprising: a pretreatment step (1) for removing impurities from a raw material gas; a membrane separation step (2) for separating the raw material gas that has undergone the pretreatment step (1) into a permeate gas and a non-permeate gas using the inorganic separation membrane; a measurement step (3) for measuring the concentration of a predetermined gas component contained in the non-permeate gas and / or the permeate gas; and a step (4) for temporarily stopping the operation and replacing the impurity removal agent filled in the pretreatment apparatus for removing impurities from the raw material gas when the concentration of the predetermined gas component in the non-permeate gas falls below a predetermined value A% and / or the concentration of the predetermined gas component in the permeate gas exceeds a predetermined value B%. A method for operating a gas separation apparatus, comprising: restarting steps (1) to (3) after the replacement of the impurity removal agent is completed; a return step (5) in which the raw material gas after the pretreatment step (1) sent to the membrane separation step (2) is pressurized and heated, and the entire amount of the non-permeable gas and at least a portion of the permeable gas, or at least a portion of the non-permeable gas and the entire amount of the permeable gas, is returned to the pretreatment step (1); and a return interruption step (6) in which the return of the non-permeable gas and the permeable gas is interrupted when the concentration of the predetermined gas component in the non-permeable gas becomes a predetermined value C% or greater than A% and / or when the concentration of the predetermined gas component in the permeable gas becomes a predetermined value D% or less than B%.

5. The method for operating a gas separation apparatus according to claim 4, wherein, in the return interruption step (6), before interrupting the return of the non-permeable gas and the permeable gas, a portion of the non-permeable gas and a portion of the permeable gas are returned to the pretreatment step (1), and the return of the non-permeable gas and the permeable gas is interrupted after the concentration of the predetermined gas component in the non-permeable gas and / or the permeable gas has recovered to 70% or more of the initial value shown when the impurity removal agent and the inorganic separation membrane are new.

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