Target gas separation and purification system and method based on single-pressurization double-backflow

Abstract

The invention relates to a target gas separation and purification system and method based on single pressurization and double reflux, the system comprises a first-stage membrane, an interstage compressor, a second-stage first-section membrane, a valve, a second-stage second-section membrane, a first reflux pipeline and a second reflux pipeline which are sequentially connected in series, the first-stage membrane carries out first-stage separation on first gas, the first gas at least comprises raw material gas, and the second gas at least comprises raw material gas; the interstage compressor pressurizes second gas, the second gas at least comprises first-stage membrane permeable gas, the second-stage first-stage membrane performs second-stage first-stage separation on the pressurized second gas, the valve adjusts the flow of second-stage first-stage membrane retentate gas, the second-stage second-stage membrane performs second-stage second-stage separation on the second-stage first-stage membrane retentate gas, and the second-stage first-stage membrane performs second-stage second-stage separation on the second-stage first-stage membrane retentate gas. The first backflow pipeline enables second-stage second-section membrane permeation gas to flow back to the inlet of the interstage compressor, the second backflow pipeline enables second-stage second-section membrane permeation residual gas to flow back to the inlet of the first-stage membrane, single-pressurization double-backflow is achieved, the concentration multiple and the yield are greatly improved, pressurization energy consumption is reduced, the backflow proportion is automatically adjusted through a valve, and the separation and purification efficiency is improved.

Description

Technical Field

[0001] This article relates to the field of gas processing, and in particular to a target gas separation and purification system and method based on single-pressurization and dual-reflux. Background Technology

[0002] In recent years, membrane gas separation technology has been widely used in the field of gas separation and purification. Membrane gas separation technology utilizes the difference in permeation rates of different gas components through a separation membrane material driven by a pressure difference to achieve gas separation. For example, when helium-containing natural gas is used as feed gas through a separation membrane, helium has a high permeation rate and can quickly pass through the membrane as permeate gas, while other gases such as methane in natural gas have lower permeation rates and become residual permeate gas. Based on the same separation principle, membrane gas separation technology is also widely used in the separation and purification fields of flue gas carbon dioxide capture, biogas decarbonization and purification, and syngas carbon dioxide removal. It is currently the most promising gas separation technology. The most commonly used technology is two-stage separation membrane technology, which uses a single-pressurization, single-reflux method. The permeate gas passing through the first-stage membrane is introduced into a compressor for pressurization, and then the pressurized gas enters the second-stage membrane for further separation. Both the first-stage and second-stage membranes are multiple membranes connected in parallel. To achieve the desired concentration effect, the compressor needs to generate enormous pressurization energy, resulting in extremely high energy consumption. If the pressurization energy is insufficient, the yield and concentration effect of the target gas will be significantly reduced. Therefore, another membrane separation and purification method is needed to solve these problems. Summary of the Invention

[0003] This application provides a target gas separation and purification system and method based on single-pressurization and double-reflux, which realizes single-pressurization and double-reflux, greatly improves the concentration factor and yield, reduces pressurization energy consumption, and improves separation and purification efficiency by automatically adjusting the reflux ratio through valves.

[0004] On the one hand, embodiments of this application provide a target gas separation and purification system based on single-pressurization dual-reflux, including: a primary membrane, an interstage compressor, a secondary first-stage membrane, valves, and a secondary second-stage membrane connected in series, as well as a first reflux line and a second reflux line; The primary membrane is used to perform primary separation of the first gas to obtain primary membrane permeate gas and primary membrane residual gas, wherein the first gas includes at least feed gas and the primary membrane residual gas is tail gas. The interstage compressor is used to pressurize a second gas, the second gas including at least the first-stage membrane permeate gas; The second-stage membrane is used to separate the pressurized second gas in a second-stage process to obtain second-stage membrane permeate gas and second-stage membrane residual gas, wherein the second-stage membrane permeate gas is the product gas; The valve is used to regulate the flow rate of the residual gas from the second-stage membrane to the second-stage membrane. The secondary two-stage membrane is used to perform secondary two-stage separation of the residual gas from the secondary one-stage membrane to obtain secondary two-stage membrane permeate gas and secondary two-stage membrane residual gas. The first return line is used to return the second stage membrane permeate gas to the inlet of the interstage compressor and merge it into the second gas. The second return line is used to return the residual gas from the second stage membrane to the inlet of the first stage membrane and merge it into the first gas. Wherein, both the raw material gas and the product gas are mixed gases including the target gas.

[0005] On the other hand, this application also provides a target gas separation and purification method based on single-pressurization dual-reflux, wherein the method is executed using the target gas separation and purification system based on single-pressurization dual-reflux as described in the above embodiments, and includes: The first gas is fed to the first-stage membrane for primary separation to obtain the first-stage membrane permeate gas and the first-stage membrane residual gas. The first-stage membrane residual gas is discharged as tail gas. The first gas includes at least the feed gas. The second gas is delivered to the interstage compressor for pressurization, wherein the second gas includes at least the first-stage membrane permeate gas; The pressurized second gas is sent to the second stage membrane for second stage separation, and the second stage membrane permeate obtained from the second stage separation is output as product gas; the second stage membrane residual gas obtained from the second stage separation is sent to the second stage membrane through a valve for second stage separation to obtain second stage membrane permeate and second stage membrane residual gas, wherein the valve is used to regulate the flow rate of the second stage membrane residual gas; The permeate gas from the second-stage membrane is transported to the inlet of the interstage compressor through the first return pipeline and merged into the second gas; the residual permeate gas from the second-stage membrane is transported to the inlet of the first-stage membrane through the second return pipeline and merged into the first gas. Wherein, both the raw material gas and the product gas are mixed gases including the target gas.

[0006] Compared with related technologies, the target gas separation and purification system and method based on single-boost double-reflux in this application divides the secondary membrane into two sections, namely the secondary first-stage membrane and the secondary second-stage membrane, which, combined with the primary membrane, achieves three-stage gas separation. The permeate gas from the secondary first-stage membrane is transported to the secondary second-stage membrane for separation, and the permeate gas from the secondary second-stage membrane is refluxed back to the inlet of the interstage compressor. The permeate gas from the secondary second-stage membrane is refluxed back to the inlet of the primary membrane, realizing a single-boost double-reflux gas separation and purification process. Compared with the conventional single-boost single-reflux method, it greatly improves the concentration ratio and yield, reduces the boosting requirements of the interstage compressor, and greatly reduces boosting energy consumption. Moreover, it can convert the secondary membrane, which contains multiple parallel separation membranes in the prior art, into a series separation membrane without adding new separation membranes to achieve the single-boost double-reflux separation and purification method. By setting a valve between the secondary first-stage membrane and the secondary second-stage membrane, the reflux ratio can be automatically adjusted, improving the separation and purification efficiency. It is highly flexible and suitable for raw gas of different qualities and different separation and purification needs.

[0007] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the solutions described in the description and the accompanying drawings. Attached Figure Description

[0008] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0009] Figure 1 This is a schematic diagram of a target gas separation and purification system based on single-pressurization dual-reflux according to an embodiment of this application; Figure 2 This is a schematic diagram of a target gas separation and purification system based on single-pressurization and dual-reflux, which is a specific example of this application. Figure 3 This is a flowchart illustrating a target gas separation and purification method using single-pressurization dual-reflux according to an embodiment of this application; Figure 4 The flowchart for the control valve is shown in Example 2 of this application; Figure 5 This is a schematic diagram of the prior art secondary separation and purification system used in the reference example of Specific Example 3 of this application; Figure 6 The diagram shows the target gas separation and purification system with single-pressurization and double-reflux as shown in Specific Examples 3 and 4 of this application. Detailed Implementation

[0010] This application describes several embodiments, but these descriptions are exemplary and not restrictive, and it will be apparent to those skilled in the art that many more embodiments and implementations are possible within the scope of the embodiments described herein. Although many possible combinations of features are shown in the drawings and discussed in the detailed description, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with, or may replace, any feature or element of any other embodiment.

[0011] This application includes and contemplates combinations of features and elements known to those skilled in the art. The embodiments, features, and elements disclosed in this application can also be combined with any conventional features or elements to form unique inventive solutions. Any feature or element of any embodiment can also be combined with features or elements from other inventive solutions to form another unique inventive solution. Therefore, it should be understood that any feature shown and / or discussed in this application can be implemented individually or in any suitable combination. Therefore, the embodiments are not limited except by the limitations imposed by the appended claims and their equivalents. Furthermore, various modifications and changes can be made within the scope of the appended claims.

[0012] Furthermore, in describing representative embodiments, the specification may have presented methods and / or processes as a specific sequence of steps. However, the method or process should not be limited to the specific order of steps described herein, to the extent that it does not depend on such a specific order. As will be understood by those skilled in the art, other sequences of steps are also possible. Therefore, the specific order of steps set forth in the specification should not be construed as a limitation of the claims. Moreover, the claims concerning the method and / or process should not be limited to the steps performed in the written order, and those skilled in the art will readily understand that these orders can be varied and still remain within the spirit and scope of the embodiments of this application.

[0013] This application provides a target gas separation and purification system based on single-pressurization dual-reflux, such as... Figure 1 As shown, it includes a primary membrane, an interstage compressor, a secondary first-stage membrane, valves, and a secondary second-stage membrane connected in series, as well as a first return line and a second return line; The primary membrane is used to perform primary separation of the first gas to obtain primary membrane permeate gas and primary membrane residual gas, wherein the first gas includes at least feed gas and the primary membrane residual gas is tail gas. The interstage compressor is used to pressurize a second gas, the second gas including at least the first-stage membrane permeate gas; The second-stage membrane is used to separate the pressurized second gas in a second-stage process to obtain second-stage membrane permeate gas and second-stage membrane residual gas, wherein the second-stage membrane permeate gas is the product gas; The valve is used to regulate the flow rate of the residual gas from the second-stage membrane to the second-stage membrane. The secondary two-stage membrane is used to perform secondary two-stage separation of the residual gas from the secondary one-stage membrane to obtain secondary two-stage membrane permeate gas and secondary two-stage membrane residual gas. The first return line is used to return the second stage membrane permeate gas to the inlet of the interstage compressor and merge it into the second gas. The second return line is used to return the residual gas from the second stage membrane to the inlet of the first stage membrane and merge it into the first gas. Wherein, both the raw material gas and the product gas are mixed gases including the target gas.

[0014] In this embodiment, the target gas separation and purification system based on single-pressurization dual-reflux is a gas separation and purification cycle system. Each cycle process performs three separation and purification steps through a series of primary membrane, secondary first-stage membrane, and secondary second-stage membrane. That is, each cycle includes primary separation, secondary first-stage separation, and secondary second-stage separation. Compared with traditional two-stage separation and purification, an additional separation and purification process is added, which increases the content of the target gas in the obtained product gas.

[0015] In this embodiment, the valve is an electric valve. By adjusting the valve opening, the ratio of the permeate gas and the residual gas from the second-stage membrane can be adjusted. The larger the valve opening, the greater the flow rate of the residual gas from the second-stage membrane, and the smaller the flow rate of the permeate gas. Since the residual gas from the second-stage membrane is transported to the second-stage membrane for second-stage separation, both the permeate gas and the residual gas obtained from the second-stage separation are reflux gases. This achieves the adjustment of the reflux ratio in the system. The greater the flow rate of the residual gas from the second-stage membrane, the more reflux gas there is. More reflux gas participates in the next cycle, further increasing the content of the target gas in the obtained product gas.

[0016] In this embodiment, the second gas is pressurized by an interstage compressor so that the inlet pressure of the second stage membrane is at least 200 kPa higher than that of the first stage membrane. This ensures that the permeate gas from the second stage membrane flows smoothly back to the compressor inlet and that the residual permeate gas from the second stage membrane flows smoothly back to the inlet of the first stage membrane.

[0017] In this embodiment, the secondary two-stage membrane includes two outlets. One outlet outputs secondary two-stage membrane permeate gas, and the first return line connects this outlet to the inlet of the interstage compressor, so that the secondary two-stage membrane permeate gas and the primary membrane permeate gas are used together as the second gas to pass through the secondary one-stage membrane. The other outlet outputs secondary two-stage membrane residual gas, and the second return line connects this outlet to the inlet of the primary membrane, so that the secondary two-stage membrane residual gas and the feed gas are used together as the first gas to pass through the primary membrane.

[0018] In this embodiment, only when the target gas separation and purification system based on single-pressurization dual-reflux is first started up, that is, during the first cycle, the first gas only includes raw material gas and the second gas only includes primary membrane permeate gas; once the subsequent cycle steps are entered, the first gas includes raw material gas and secondary membrane permeate gas, and the second gas includes primary membrane permeate gas and secondary membrane permeate gas.

[0019] In this embodiment, the primary membrane can be a single separation membrane; or it can be a group of multiple separation membranes connected in parallel. The multiple separation membranes connected in parallel can be of the same type or include multiple types of separation membranes.

[0020] In this embodiment, the secondary first-stage membrane can be a single separation membrane; or it can be a separation membrane group composed of multiple parallel separation membranes. The multiple parallel separation membranes can be of the same type or include multiple types of separation membranes.

[0021] In this embodiment, the secondary two-stage membrane can be a single separation membrane; or it can be a separation membrane group composed of multiple parallel separation membranes. The multiple parallel separation membranes can be of the same type or include multiple types of separation membranes.

[0022] In this embodiment, the primary membrane, the secondary first-stage membrane, and the secondary second-stage membrane can be the same or different; for the primary membrane, the permeability of the residual gas in the primary membrane is lower than the permeability of the permeable gas in the primary membrane; for the secondary first-stage membrane, the permeability of the residual gas in the secondary first-stage membrane is lower than the permeability of the permeable gas in the secondary first-stage membrane; for the secondary second-stage membrane, the permeability of the residual gas in the secondary second-stage membrane is lower than the permeable gas in the secondary second-stage membrane.

[0023] In this embodiment, the material of the primary membrane can be one or more of polyimide, polysulfone, polyester, or cellulose derivatives; the material of the secondary first-stage membrane can be one or more of polyimide, polysulfone, polyester, or cellulose derivatives; and the material of the secondary second-stage membrane can be one or more of polyimide, polysulfone, polyester, or cellulose derivatives.

[0024] This embodiment of the target gas separation and purification system based on single-boost double-reflux divides the secondary membrane into two sections: a primary secondary membrane and a secondary secondary membrane. Combined with the primary membrane, this achieves tertiary gas separation. The permeate from the primary secondary membrane is transported to the secondary secondary membrane for further separation. The permeate from the secondary secondary membrane is refluxed back to the inlet of the interstage compressor, and the permeate from the secondary secondary membrane is refluxed back to the inlet of the primary membrane. This achieves a single-boost double-reflux gas separation and purification process. Compared to the conventional single-boost single-reflux method, this significantly improves the concentration ratio and yield, reduces the pressure requirements of the interstage compressor, and greatly reduces pressure energy consumption. Furthermore, it converts the existing technology, which involves multiple parallel separation membranes, into a series separation membrane, eliminating the need for additional membranes to achieve the single-boost double-reflux separation and purification method. By installing valves between the primary and secondary secondary membranes, the reflux ratio can be automatically adjusted, improving separation and purification efficiency. This system offers high flexibility and is suitable for different qualities of raw materials and various separation and purification requirements.

[0025] In one exemplary embodiment, the target gas separation and purification system based on single-pressurization dual-reflux may further include: The first monitoring instrument, located at the inlet of the primary membrane, includes a first flow meter and a first component analyzer. The first flow meter is used to monitor the flow rate q1 of the first gas in real time, and the first component analyzer is used to monitor the content c1 of the target gas in the first gas in real time. The second monitoring instrument, located at the product gas outlet of the secondary membrane, includes a second flow meter and a second component analyzer. The second flow meter is used to monitor the flow rate q2 of the product gas in real time, and the second component analyzer is used to monitor the content c2 of the target gas in the product gas in real time.

[0026] In this embodiment, the first flow meter and the second flow meter can be one of a vortex flow meter, an orifice plate flow meter, or an ultrasonic flow meter, respectively. In order to reduce the error caused by using different types of flow meters, as a preferred embodiment, the first flow meter and the second flow meter can be set to the same type of flow meter. The above examples of flow meters are all exemplary descriptions and are not intended to limit this application. They will not be described in detail hereafter.

[0027] In this embodiment, the first component analyzer and the second component analyzer can be one of semiconductor gas sensors, electrochemical gas sensors, and optical gas sensors, respectively. In order to reduce the error caused by using different types of component analyzers, as a preferred embodiment, the first component analyzer and the second component analyzer can be set to the same type of gas sensor. The accuracy of the first component analyzer and the second component analyzer needs to be at the ppb level. The above examples of gas sensors are all exemplary descriptions and are not intended to limit this application. They will not be described in detail hereafter.

[0028] In one exemplary embodiment, the target gas separation and purification system based on single-pressurization dual-reflux may further include: The controller includes a processor and a user interface; The user interface is used to obtain the target concentration factor K1', target yield K2', and valve adjustment step size input by the user. The processor is used to acquire q1, q2, c1, and c2 in real time, calculate the concentration factor K1 = c2 / c1 and compare the magnitudes of K1 and K1'. When K1 < K1', it sends an adjustment command to the valve; or, it calculates the yield K2 = (c2 × q2) / (c1 × q1) and compares the magnitudes of K2 and K2'. When K2 < K2', it sends an adjustment command to the valve. The adjustment command is used to instruct an increase in valve opening, and the amount of increase is equal to the valve's single adjustment step size.

[0029] In this embodiment, the controller can be a personal computer, a microcontroller, a programmable logic controller, an industrial computer, a digital signal processor, a smartphone, a tablet computer, or a cloud computing platform. The examples of the controllers described above are all exemplary descriptions and are not intended to limit this application. They will not be described in detail hereafter.

[0030] In this embodiment, the valve single adjustment step size can be set to 1%-20% of the total valve opening. For example, if the valve single adjustment step size is set to 5%, then the valve opening will increase by 5% every time it receives an adjustment command.

[0031] In this embodiment, the target concentration factor K1' can be set to 10-2000, and the target yield K2' can be set to 50%-95%.

[0032] In one embodiment of this invention, after the valve completes one operation to increase its opening degree, the processor can continuously acquire q1, q2, c1, and c2. Each time c1 and c2 are acquired, the concentration factor K1 = c2 / c1 is calculated. If K1 reaches stability within a predetermined time period, the last acquired K1 and K1' within the predetermined time period are compared. If K1 < K1', an adjustment command is sent to the valve, and the valve, upon receiving the adjustment command, performs the next operation to increase its opening degree; for example, if the fluctuation range of K1 is less than 5 within 10 consecutive minutes. If the percentage is %, then compare the last obtained K1 and K1' within 10 minutes. If K1 < K1', then send an adjustment command to the valve. In this embodiment, q1 and q2 can be used as auxiliary data for a target gas separation and purification system based on single-pressurization double-reflux. For example, if the flow rate of the raw gas is constant, q1 can be used to determine the flow rate of the residual gas in the second stage membrane refluxed to the first stage membrane, and q2 can be used to determine the flow rate of the product gas. Moreover, after the valve opening is increased, whether q2 decreases can be used to determine whether the effect of increasing the residual gas flow rate in the second stage membrane has been achieved.

[0033] In another embodiment of this invention, after the valve completes one operation to increase its opening degree, the processor can continuously acquire q1, q2, c1, and c2. Each time q1, q2, c1, and c2 are acquired, the concentration factor K1 = c2 / c1 and the yield K2 = (c2 × q2) / (c1 × q1) are calculated. If K1 reaches stability within a predetermined time period, the last acquired K2 and K2' within that time period are compared. If K2 < K2', an adjustment command is sent to the valve. Upon receiving the adjustment command, the valve performs the next operation to increase its opening degree. For example, in a continuous... If the fluctuation range of K1 is less than 5% within 10 minutes, then the last obtained K2 and K2' within 10 minutes are compared. If K2 < K2', then an adjustment command is sent to the valve. In this embodiment, q1 and q2 can also be used as auxiliary data for a target gas separation and purification system based on single-pressurization double-reflux. For example, if the flow rate of the raw gas is constant, q1 can be used to determine the flow rate of the residual gas in the second stage membrane refluxed to the first stage membrane, and q2 can be used to determine the flow rate of the product gas. Moreover, after the valve opening is increased, whether q2 decreases can be used to determine whether the effect of increasing the residual gas flow rate in the second stage membrane has been achieved.

[0034] In this embodiment, a controller is used to automatically adjust the valve, which can intelligently ensure that the system is in the best operating state, improve the flexibility and adaptability of operation, reduce manual intervention, reduce human error in operation, and improve the reliability and stability of production.

[0035] In one exemplary embodiment, the primary membrane may include a tail gas outlet for discharging the residual gas from the primary membrane as the tail gas; the secondary membrane includes a product gas outlet for conveying the permeate from the secondary membrane as the product gas to a product gas collector.

[0036] In this embodiment, the exhaust gas outlet of the primary membrane can be connected to an exhaust gas collection and treatment device to further collect and treat the residual gas from the primary membrane. In this embodiment, the product gas collector can be a gas container or a production device that utilizes product gas.

[0037] In one exemplary embodiment, the primary membrane, the secondary first-stage membrane, and the secondary second-stage membrane may each comprise one or more of hollow fiber membranes, spiral wound membranes, flat sheet membranes, or tubular membranes.

[0038] In one exemplary embodiment, the interstage compressor may be a reciprocating compressor, a centrifugal compressor, a rotary compressor, an axial compressor, or a mixed-flow compressor.

[0039] In one exemplary embodiment, the target gas separation and purification system based on single-pressurization dual-reflux may further include: A first independent pipeline is used to deliver the second gas to the interstage compressor; A second independent pipeline is used to deliver the pressurized second gas to the second stage membrane. A third independent pipeline equipped with the valve is used to transport the residual gas from the secondary stage 1 membrane to the secondary stage 2 membrane through the valve.

[0040] In one exemplary embodiment, the raw material gas may be helium-containing natural gas, and the target gas may be helium. Alternatively, the raw material gas may be a combustion gas containing carbon dioxide, and the target gas may be the carbon dioxide.

[0041] To illustrate the target gas separation and purification system employing single-pressurization dual-reflux in this application embodiment, a specific example is provided below for detailed description, such as... Figure 2 As shown.

[0042] This specific example includes: a primary membrane, an interstage compressor, a secondary first-stage membrane, valves, and a secondary second-stage membrane connected in series. The feed gas enters the single-pressurization, double-reflux target gas separation and purification system from the primary membrane inlet. The primary membrane permeate is the tail gas, and the secondary first-stage membrane permeate is the product gas. A first independent pipeline connects the primary membrane permeate outlet to the interstage compressor inlet, a second independent pipeline connects the interstage compressor outlet to the secondary first-stage membrane inlet, and a third independent pipeline with valves connects the secondary first-stage membrane permeate outlet to the secondary second-stage membrane inlet. A first monitoring instrument is installed at the primary membrane inlet, and a second monitoring instrument is installed at the secondary first-stage membrane permeate outlet. The first monitoring instrument monitors the flow rate q1 of the first gas and the content c1 of the target gas in the first gas. The second monitoring instrument monitors the flow rate q2 of the product gas and the content c2 of the target gas in the product gas. The first gas is the feed gas during the first cycle of separation and purification. Outside of the first cycle, the first gas is both the feed gas and the secondary second-stage membrane permeate. The second gas... The first cycle after purification uses primary membrane permeate gas. The second gas, excluding the first cycle, consists of primary membrane permeate gas and secondary membrane permeate gas. The controller acquires q1, q2, c1, and c2, and obtains the user-inputted target concentration factor K1', target yield K2', and valve single adjustment step size via the user interface. The controller also calculates the concentration factor K1 = c2 / c1 and compares the values ​​of K1 and K1'. When K1 < K1', it sends an adjustment command to the valve, or calculates the yield... The rate K2 = (c2 × q2) / (c1 × q1) is calculated and compared with the magnitude of K2 and K2'. When K2 < K2', an adjustment command is sent to the valve. After receiving the adjustment command, the valve opening is increased according to the valve's single adjustment step size. The residual gas from the second stage membrane is separated into the second stage membrane permeate gas and the residual gas from the second stage membrane after passing through the second stage membrane. The second stage membrane permeate gas is returned to the inlet of the interstage compressor through the first return pipe, and the residual gas from the second stage membrane is returned to the inlet of the first stage membrane through the second return pipe.

[0043] This application also provides a target gas separation and purification method using single-pressurization dual-reflux. The method is based on the target gas separation and purification system using single-pressurization dual-reflux as described in the above embodiments. The target gas separation and purification method using single-pressurization dual-reflux is a cyclic method, and each cycle includes steps S100-S400, as follows: Figure 3 As shown: S100: The first gas is delivered to the primary membrane for primary separation to obtain primary membrane permeate gas and primary membrane residual gas. The primary membrane residual gas is discharged as tail gas. The first gas includes at least the feed gas. S200: The second gas is delivered to the interstage compressor for pressurization, wherein the second gas includes at least the first-stage membrane permeate gas; S300: The pressurized second gas is delivered to the second stage membrane for second stage separation, and the second stage membrane permeate obtained from the second stage separation is output as product gas; the second stage membrane residual gas obtained from the second stage separation is delivered to the second stage membrane through a valve for second stage separation to obtain second stage membrane permeate and second stage membrane residual gas, wherein the valve is used to regulate the flow rate of the second stage membrane residual gas; S400: The permeate gas from the second stage membrane is transported to the inlet of the interstage compressor through the first return pipeline and merged into the second gas; the residual permeate gas from the second stage membrane is transported to the inlet of the first stage membrane through the second return pipeline and merged into the first gas; Wherein, both the raw material gas and the product gas are mixed gases including the target gas.

[0044] In this embodiment, the target gas separation and purification method using single-pressurization dual-reflux includes multiple cycles. Each cycle executes steps S100-400. In the first cycle, the first gas is the feed gas and the second gas is the primary membrane permeate gas. In other cycles besides the first cycle, the first gas includes the feed gas and the secondary membrane permeate gas, and the second gas includes the primary membrane permeate gas and the secondary membrane permeate gas.

[0045] In this embodiment, when performing step S200, the second gas is pressurized by the interstage compressor so that the inlet pressure of the second stage membrane is at least 200 kPa higher than the inlet pressure of the first stage membrane. This ensures that the permeate gas from the second stage membrane flows smoothly back to the compressor inlet and that the residual permeate gas from the second stage membrane flows smoothly back to the inlet of the first stage membrane.

[0046] In this embodiment, when performing step S300, the flow rate of the residual gas from the second-stage membrane is adjusted by a valve. When the valve opening increases, the flow rate of the residual gas from the second-stage membrane increases, and the flow rate of the permeate gas from the second-stage membrane decreases, that is, the flow rate of the product gas decreases; when the valve opening decreases, the flow rate of the residual gas from the second-stage membrane decreases, and the flow rate of the permeate gas from the second-stage membrane increases, that is, the flow rate of the product gas increases.

[0047] In this embodiment, by executing step S400, the recirculation of the second-stage membrane permeate gas and the second-stage membrane residual gas is realized. Since the second-stage membrane permeate gas and the second-stage membrane residual gas both originate from the second-stage membrane residual gas, the flow rate of the second-stage membrane residual gas is adjusted by the valve, thereby achieving the effect of adjusting the gas recirculation ratio.

[0048] This embodiment employs a single-boost double-reflux target gas separation and purification method based on a series configuration of a primary membrane, a secondary first-stage membrane, and a secondary second-stage membrane. This achieves three-stage gas separation and purification, optimizing the separation and purification process. The permeate from the secondary first-stage membrane is transported to the secondary second-stage membrane for separation, while the permeate from the secondary second-stage membrane is refluxed back to the inlet of the interstage compressor. The permeate from the secondary second-stage membrane is refluxed back to the inlet of the primary membrane, thus realizing a single-boost double-reflux gas separation and purification process. Compared to the conventional single-boost single-reflux method, this significantly improves the concentration ratio and yield, reduces the pressure requirements on the interstage compressor, and greatly reduces pressure energy consumption. Furthermore, it simply converts the existing technology, which involves multiple parallel separation membranes, into a series separation membrane, eliminating the need for additional separation membranes to achieve the single-boost double-reflux separation and purification method. By installing valves between the secondary first-stage and secondary second-stage membranes, the reflux ratio can be automatically adjusted, improving separation and purification efficiency. This method offers high flexibility and is suitable for different qualities of raw materials and various separation and purification requirements.

[0049] In one exemplary embodiment, before step S300, a step of adjusting the valve opening may be included, specifically steps S210-S230: S210: Obtain the flow rate q1 of the first gas, the content of the target gas in the first gas c1, the flow rate q2 of the product gas, and the content of the target gas in the product gas c2; S220: Calculate the concentration factor K1 = c2 / c1 and compare the magnitudes of K1 and K1'. If K1 < K1', send an adjustment command to the valve; or, calculate the yield K2 = (c2 × q2) / (c1 × q1) and compare the magnitudes of K2 and K2'. If K2 < K2', send an adjustment command to the valve; where K1' is the target concentration factor and K2' is the target yield. S230: Increase the valve opening according to the adjustment command, wherein the amount of the increase in valve opening is equal to the valve adjustment step size in a single operation.

[0050] In this embodiment, the target concentration factor K1', target yield K2', and valve single adjustment step size are input by the user through the user interface and saved in the controller. When executing step S220, after calculating the concentration factor K1, the controller's processor compares the magnitudes of K1 and K1' according to a pre-set program, or after calculating the yield K2, the controller's processor compares the magnitudes of K2 and K2' according to a pre-set program. The adjustment command sent by the processor to the valve carries the single adjustment step size.

[0051] In this embodiment, when step S210 is executed, the processor can acquire the monitoring data q1, q2, c1 and c2 of the first and second monitoring instruments in real time.

[0052] In this embodiment, when executing step S220, it may further include: when K1=K1', it means that separation and purification with the current valve opening can achieve the target concentration factor K1', and there is no need to send an adjustment command to the valve. The target gas separation and purification system with single pressure boosting and double reflux can be used to maintain the current state for separation and purification; or when K2=K2', it means that separation and purification with the current valve opening can achieve the target yield K2', and there is no need to send an adjustment command to the valve. The target gas separation and purification system with single pressure boosting and double reflux can be used to maintain the current state for separation and purification.

[0053] In this embodiment, the valve is an electric valve. In actual production, the initial opening of the valve can be set to 0. Each time the valve receives an adjustment command, it will perform an operation to increase the valve opening once. This process continues until multiple cycles are completed. The valve will then perform an operation to increase the valve opening by the number of cycles, thereby achieving the target concentration factor K1' or the target yield K2'. The opening increase each time is equal to the valve's single adjustment step size, which can be set to 1%-20% of the total valve opening.

[0054] To illustrate the steps of controlling the valve in the embodiments of this application in detail, a specific example two is provided below. Figure 4 As shown: S1: The controller acquires q1, c1, q2, c2, target concentration factor K1', target yield K2', and valve single adjustment step size; S2: The controller calculates K1=c2 / c1 or yield K2=(c2×q2) / (c1×q1); S3: The controller determines whether K1 < K1' or K2 < K2'. If yes, proceed to steps S4-S5; otherwise, proceed to step S6. S4: The controller sends a regulating command to the valve; S5: The valve opening is increased according to the single adjustment step size; S6: Control ends.

[0055] To illustrate the technical effects of the target gas separation and purification system and the target gas separation and purification method using single-pressurization dual-reflux in the embodiments of this application, two specific examples are described in detail below.

[0056] Specific Example 3 To demonstrate the effectiveness of the embodiments of this application, this specific example uses a reference example and an experimental example. The reference example is an example of two-stage separation and purification in the prior art, while the experimental example is an example using the embodiments of this application. Both the reference example and the experimental example involve the separation and purification of helium-containing natural gas with a helium content of 1%, meaning the feed gas is natural gas with a helium content of 1%. The composition of the feed gas is shown in Table 1. The operating conditions are: temperature 20°C, hollow fiber membranes, polyimide material, and a single membrane area of ​​300 m². 2 .

[0057] For example Figure 5 As shown: A primary membrane and a secondary membrane are installed. The primary membrane consists of 5 parallel separation membranes, and the secondary membrane consists of 2 parallel separation membranes. The primary membrane, interstage compressor, and secondary membrane are connected in series. The feed gas is separated into primary membrane permeate and primary membrane residual gas after passing through the primary membrane. The primary membrane residual gas is discharged from the tail gas outlet of the primary membrane. The primary membrane permeate is pressurized by 2 MPa by the interstage compressor and enters the secondary membrane for separation, which is further separated into secondary membrane permeate and secondary membrane residual gas. The secondary membrane permeate is used as the product gas, and the secondary membrane residual gas is returned to the primary membrane inlet through the reflux pipeline and merged into the feed gas. The separation and purification effect is shown in Table 1. Comparing the helium content in the feed gas with the helium content in the product gas of the reference example, the helium content increased from 1% to about 11%, the concentration factor was 11 times, and the corresponding yield was 86%.

[0058] For example, comparison Figure 6 As shown: a primary membrane, a secondary first-stage membrane, and a secondary second-stage membrane are set up. The primary membrane consists of 5 parallel separation membranes, the secondary first-stage membrane consists of 1 separation membrane, and the secondary second-stage membrane consists of 1 separation membrane. After pressurization by the interstage compressor, the inlet pressure of the secondary first-stage membrane is at least 200 kPa higher than the inlet pressure of the primary membrane. The separation and purification effect is shown in Table 1. Comparing the helium content in the feed gas with the helium content in the product gas of the reference example, the helium content increased from 1% to about 22%, the concentration factor was 22 times, and the corresponding yield was 98%.

[0059] As can be seen from the reference example and the comparative example, the concentration factor increased from 11 times in the reference example to 22 times in the comparative example, an increase of 100%. With the number of separation membranes remaining unchanged, i.e. without increasing consumables, and using the same pressurization operation, the system and method of this application achieved a significant concentration effect, greatly increasing the helium proportion in the product gas obtained after separation and purification. At the same time, the helium yield increased from 86% to 98%, an increase of 12 percentage points. In addition, the interstage compressor in the reference example required a pressurization of 2 MPa, while the comparative example only required a pressurization of 200 kPa, greatly reducing the need for pressurization and saving a significant amount of pressurization energy.

[0060] Table 1. Comparison of Separation and Purification Effects

[0061] Specific Example 4 To demonstrate the effects of the embodiments of this application, specific examples 4-1 and 4-2 are used, both of which are examples of embodiments of this application. Both involve the separation and purification of combustion exhaust gas containing carbon dioxide, employing methods such as... Figure 6 The target gas separation and purification system shown employs a single-pressurization, double-reflux design, operating at 20°C. All separation membranes are hollow fiber membranes made of polyimide, and each membrane has an area of ​​300 m². 2 It is equipped with a primary membrane, a secondary first-stage membrane, and a secondary second-stage membrane. The primary membrane consists of five separation membranes arranged in parallel, the secondary first-stage membrane consists of one separation membrane, and the secondary second-stage membrane consists of one separation membrane.

[0062] Example 4-1: The feed gas is combustion exhaust gas containing 5% carbon dioxide. The target concentration factor K1'=6, the target yield K2'=90%, and the valve adjustment step size is 10%. The separation and purification effect is shown in Table 2. Comparing the carbon dioxide content in the feed gas and the product gas, the helium content increases from 5% to about 33.5%, the concentration factor is 6.7 times, the valve opening is 20%, and the corresponding yield is 90.4%.

[0063] Example 4-2: The feed gas is combustion exhaust gas containing 8% carbon dioxide. The target concentration factor K1'=6, the target yield K2'=90%, and the valve adjustment step size is 10%. The separation and purification effect is shown in Table 2. Comparing the carbon dioxide content in the feed gas and the product gas, the helium content increased from 8% to about 52.8%, the concentration factor was 6.6 times, the valve opening was 60%, and the corresponding yield was 90.9%.

[0064] As can be seen from Examples 4-1 and 4-2, the embodiments of this application can separate and purify raw materials containing different amounts of target gases, and the separation and purification effects can all achieve the target concentration factor and target yield. By controlling the opening of the valve by the controller, the reflux ratio can be automatically adjusted, thereby achieving the separation and purification effect for raw materials containing different amounts of target gases. The embodiments of this application can adapt to the separation and purification requirements of different raw materials.

[0065] Table 2 Comparison of Combustion Exhaust Gas Separation and Purification Effects with Different Carbon Dioxide Contents

[0066] It will be understood by those skilled in the art that all or some of the steps, systems, or apparatuses disclosed above, and their functional modules / units, can be implemented as software, firmware, hardware, or suitable combinations thereof. In hardware implementations, the division between functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed collaboratively by several physical components. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit (ASIC). Such software may be distributed on a computer-readable medium, which may include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term "computer storage medium" includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and can be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

Claims

1. A target gas separation and purification system based on single-pressurization dual-reflux, characterized in that, include: The system consists of a primary membrane, an interstage compressor, a secondary membrane, valves, and a secondary membrane connected in series, along with a first return line and a second return line. The primary membrane is used to perform primary separation of the first gas to obtain primary membrane permeate gas and primary membrane residual gas, wherein the first gas includes at least feed gas and the primary membrane residual gas is tail gas. The interstage compressor is used to pressurize a second gas, the second gas including at least the first-stage membrane permeate gas; The second-stage membrane is used to separate the pressurized second gas in a second-stage process to obtain second-stage membrane permeate gas and second-stage membrane residual gas, wherein the second-stage membrane permeate gas is the product gas; The valve is used to regulate the flow rate of the residual gas from the second-stage membrane to the second-stage membrane. The secondary two-stage membrane is used to perform secondary two-stage separation of the residual gas from the secondary one-stage membrane to obtain secondary two-stage membrane permeate gas and secondary two-stage membrane residual gas. The first return line is used to return the second stage membrane permeate gas to the inlet of the interstage compressor and merge it into the second gas. The second return line is used to return the residual gas from the second stage membrane to the inlet of the first stage membrane and merge it into the first gas. Wherein, both the raw material gas and the product gas are mixed gases including the target gas.

2. The target gas separation and purification system based on single-pressurization dual-reflux as described in claim 1, characterized in that, Also includes: The first monitoring instrument, located at the inlet of the primary membrane, includes a first flow meter and a first component analyzer. The first flow meter is used to monitor the flow rate q1 of the first gas in real time, and the first component analyzer is used to monitor the content c1 of the target gas in the first gas in real time. The second monitoring instrument, located at the product gas outlet of the secondary membrane, includes a second flow meter and a second component analyzer. The second flow meter is used to monitor the flow rate q2 of the product gas in real time, and the second component analyzer is used to monitor the content c2 of the target gas in the product gas in real time.

3. The target gas separation and purification system based on single-pressurization dual-reflux as described in claim 2, characterized in that, It also includes the controller; The controller includes a processor and a user interface; The user interface is used to obtain the target concentration factor K1', target yield K2', and valve adjustment step size input by the user. The processor is used to acquire q1, q2, c1, and c2 in real time, calculate the concentration factor K1 = c2 / c1 and compare the magnitudes of K1 and K1'. When K1 < K1', it sends an adjustment command to the valve; or, it calculates the yield K2 = (c2 × q2) / (c1 × q1) and compares the magnitudes of K2 and K2'. When K2 < K2', it sends an adjustment command to the valve. The adjustment command is used to instruct an increase in valve opening, and the amount of increase is equal to the valve's single adjustment step size.

4. The target gas separation and purification system based on single-pressurization dual-reflux as described in claim 2, characterized in that: The primary membrane includes an exhaust gas outlet, which is used to discharge the residual gas from the primary membrane as the exhaust gas. The secondary-stage membrane includes a product gas outlet, which is used to deliver the permeate gas from the secondary-stage membrane as the product gas to a product gas collector.

5. The target gas separation and purification system based on single-pressurization dual-reflux as described in claim 1, characterized in that: The primary membrane, the secondary first-stage membrane, and the secondary second-stage membrane each comprise one or more of hollow fiber membranes, spiral wound membranes, flat sheet membranes, or tubular membranes.

6. The target gas separation and purification system based on single-pressurization dual-reflux as described in claim 1, characterized in that: The interstage compressor is a reciprocating compressor, centrifugal compressor, rotary compressor, axial compressor, or mixed-flow compressor.

7. The target gas separation and purification system based on single-pressurization dual-reflux as described in claim 1, characterized in that, Also includes: A first independent pipeline is used to deliver the second gas to the interstage compressor; A second independent pipeline is used to deliver the pressurized second gas to the second stage membrane. A third independent pipeline equipped with the valve is used to transport the residual gas from the secondary stage 1 membrane to the secondary stage 2 membrane through the valve.

8. The target gas separation and purification system based on single-pressurization dual-reflux as described in claim 1, characterized in that: The raw material gas is helium-containing natural gas, and the target gas is helium; Alternatively, the raw material gas may be a combustion gas containing carbon dioxide, and the target gas may be the carbon dioxide.

9. A method for separating and purifying target gases based on single-pressurization and double-reflux, characterized in that, The method is performed based on the target gas separation and purification system based on single-pressurization dual-reflux as described in any one of claims 1-8, comprising: The first gas is fed to the first-stage membrane for primary separation to obtain the first-stage membrane permeate gas and the first-stage membrane residual gas. The first-stage membrane residual gas is discharged as tail gas. The first gas includes at least the feed gas. The second gas is delivered to the interstage compressor for pressurization, wherein the second gas includes at least the first-stage membrane permeate gas; The pressurized second gas is sent to the second stage membrane for second stage separation, and the second stage membrane permeate obtained from the second stage separation is output as product gas; the second stage membrane residual gas obtained from the second stage separation is sent to the second stage membrane through a valve for second stage separation to obtain second stage membrane permeate and second stage membrane residual gas, wherein the valve is used to regulate the flow rate of the second stage membrane residual gas; The permeate gas from the second-stage membrane is transported to the inlet of the interstage compressor through the first return pipeline and merged into the second gas; the residual permeate gas from the second-stage membrane is transported to the inlet of the first-stage membrane through the second return pipeline and merged into the first gas. Wherein, both the raw material gas and the product gas are mixed gases including the target gas.

10. The target gas separation and purification method based on single-pressurization dual-reflux as described in claim 9, characterized in that, Before the pressurized second gas is delivered to the second-stage membrane for second-stage separation, the process further includes: Obtain the target concentration factor K1', target yield K2', and valve single adjustment step size input by the user; Obtain the flow rate q1 of the first gas, the content of the target gas in the first gas c1, the flow rate q2 of the product gas, and the content of the target gas in the product gas c2; Calculate the concentration factor K1 = c2 / c1 and compare the magnitudes of K1 and K1'. If K1 < K1', send an adjustment command to the valve; or, calculate the yield K2 = (c2 × q2) / (c1 × q1) and compare the magnitudes of K2 and K2'. If K2 < K2', send an adjustment command to the valve. The valve opening is increased according to the adjustment command, wherein the amount of the increase in valve opening is equal to the valve adjustment step size in a single operation.

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