A control optimization method for biogas purification

Abstract

The present application relates to biogas purification technology, aims to provide a kind of control optimization method of biogas purification.The method comprises: constructing biogas purification system, through the pipeline sequentially connected desulfurization equipment, water removal equipment, gas compressor and membrane separation equipment, flow meter, gas component on-line analyzer, pressure sensor and flow meter are arranged in system;Monitoring data is transmitted to upper computer, and the optimal operating parameter combination of biogas purification system is obtained by establishing function relationship;Adjustment is carried out by PLC or DCS, so that the system operation meets the requirement of the optimal operating parameter combination, thereby realizing the optimization control of biogas purification process.The present application can more intuitively and more comprehensively understand the progress of biogas membrane separation process, and carry out analysis and optimization control according to demand;The present application optimizes process monitoring measures and control process, can improve biogas purification efficiency, reduce process energy consumption.

Description

Technical Field

[0001] This invention relates to biogas purification technology, and particularly to a method for controlling and optimizing biogas purification. Background Technology

[0002] Biogas is a combustible mixture of gases produced by the fermentation of organic matter under anaerobic conditions by microorganisms. Its main components are methane and carbon dioxide, typically with methane (CH4) accounting for about 60% and carbon dioxide (CO2) about 40%. It also contains small amounts of hydrogen (H2), nitrogen (N2), carbon monoxide (CO), hydrogen sulfide (H2S), and ammonia (NH3). Biogas fermentation is the process of organic matter being decomposed by microorganisms under anaerobic conditions. Approximately 400 billion tons of organic matter are produced annually on Earth through photosynthesis, of which about 5% is decomposed by microorganisms under anaerobic conditions to produce biogas. Humans utilize this natural process for biogas fermentation (also known as anaerobic digestion), which not only produces biogas for energy but also treats organic waste to protect the environment. The resulting biogas residue and liquid are high-quality active organic fertilizers. Biogas fermentation is one of the important measures for humans to comprehensively utilize organic waste, protect the ecological environment, and promote the sustainable development of agricultural production. The carbon dioxide produced by burning biogas can be absorbed by plants and regenerated into organic matter through photosynthesis, thus biogas is also a renewable energy source.

[0003] Because biogas contains more than half methane, its economic benefits in chemical product manufacturing far outweigh its use as fuel. However, prior to this, biogas needs purification and upgrading. Biogas purification primarily involves desulfurization, separating H2S from the biogas. Common processes include dry desulfurization, wet desulfurization, and biological desulfurization. Biogas upgrading mainly involves decarbonization, removing CO2 from the biogas, which can increase the methane volume fraction and calorific value. Effectively purified biogas can have a methane volume fraction of over 95%. Currently, the mainstream biogas purification technologies include pressure swing adsorption (PSA), membrane separation, physical absorption, chemical absorption, and cryogenic separation.

[0004] Membrane separation technology has garnered significant attention in biogas purification due to its advantages such as small footprint, low energy consumption, high efficiency, and environmental friendliness. However, the composition of biogas fluctuates depending on factors like raw materials, fermentation technology, season, and location. Therefore, the permeability and separation coefficient of the gas separation membrane material are affected during the actual purification process. Furthermore, the pressure difference of CO2 across the membrane is the driving force behind the separation process; a larger pressure difference results in higher membrane efficiency. Consequently, adjustments to operating parameters are necessary to accommodate fluctuations in biogas composition.

[0005] Because the processing capacity of the equipment is directly related to the system's operational efficiency, it is usually the most important factor in current membrane separation applications. However, the changes in biogas composition during operation, which alter the equipment's operating conditions, have not received sufficient attention from industry professionals. Consequently, due to a lack of targeted research, there are very few reports on related research findings. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a control and optimization method for biogas purification.

[0007] To solve the technical problem, the solution of the present invention is:

[0008] A method for controlling and optimizing biogas purification is provided, comprising the following steps:

[0009] (1) Constructing a biogas purification system:

[0010] The system includes a desulfurization unit, a dewatering unit, a gas compressor, and a membrane separation unit connected sequentially via pipelines. The membrane separation unit has at least two stages. Sampling ports are located at the front end of the desulfurization unit and the rear end of the membrane separation unit, respectively. These sampling ports are connected to an online gas composition analyzer via pipelines. Pressure sensors are installed at the rear end of the gas compressor, at the inlet of each stage of the membrane separation unit, and on the permeate and osmotic sides of the final stage membrane separation unit. Flow meters are installed at the rear end of the gas compressor and the rear end of the membrane separation unit. The online gas composition analyzer, pressure sensors, and flow meters are connected to a DCS or PLC via signal lines. The DCS or PLC is connected to a host computer via signal lines, and the host computer has a built-in monitoring platform software module.

[0011] (2) Using an online gas composition analyzer, pressure sensor and flow meter, gas composition, pressure data and flow data at the corresponding locations are detected respectively, and transmitted to DCS or PLC via signal lines; the latter receives the signal, performs preliminary processing and stores the data in the database, or transmits the data to the host computer and stores it in the database.

[0012] (3) The host computer uses sufficient data collected from the database to establish functional relationships Q2=f1(ΔP,α1) between the finished biogas flow rate and the pressure difference across the membrane separation equipment and the biogas composition, and E2=f1(ΔP,α1) between the gas compressor energy consumption and the pressure difference across the membrane separation equipment and the biogas composition. 压缩机 =f2(ΔP, α1); Plot the curves of the two functions in the same coordinate system, and then take their intersection as the energy-saving and efficient operation point; The intersection represents the equilibrium of the gas compressor energy consumption, purified biogas flow rate and the pressure difference on both sides of the membrane separation equipment, which is the optimal combination of operating parameters for the biogas purification system;

[0013] Where Q2 is the purified biogas flow rate, in meters (m³). 3 / h; ΔP is the pressure difference across the membrane separation unit, in kPa; α1 is the volume percentage of methane in the biogas before purification; E 压缩机 f1 represents the instantaneous operating power of the compressor, in kW; f2 represents the relationship between the finished biogas flow rate and the pressure difference and biogas composition on both sides of the membrane separation equipment; f1 and f2 are the relationship between the energy consumption of the gas compressor and the pressure difference and biogas composition on both sides of the membrane separation equipment; f1 and f2 are function formulas obtained by curve fitting of discrete data at the same time point based on the data in step (2).

[0014] (4) The monitoring platform software of the host computer sends a control signal to the PLC or DCS according to the calculation result of step (3). The PLC or DCS adjusts the biogas flow rate and gas compressor supply pressure before purification so that the system operation meets the requirements of the optimal combination of operating parameters, thereby realizing the optimized control of the biogas purification process.

[0015] As a preferred embodiment of the present invention, step (4) further includes:

[0016] (4.1) Using online analysis data of biogas flow rate and biogas composition before and after purification, the methane recovery rate k is calculated according to the following formula:

[0017] k = (Q2 × α2) / (Q1 × α1)

[0018] In this formula, Q1 and Q2 represent the flow rates of biogas before and after purification, respectively, in meters (m³). 3 / h; α1 and α2 are the volume percentages of methane in the biogas before and after purification, respectively;

[0019] (4.2) Based on the biogas flow rate and methane recovery rate k before purification, the compressed gas volume of the gas compressor is adjusted in real time to ensure that the methane recovery rate meets the standard.

[0020] As a preferred embodiment of the present invention, the method further includes:

[0021] (a) Temperature sensors are installed at the front end of the gas compressor and membrane separation equipment respectively. Each temperature sensor is connected to the DCS or PLC through a signal line and transmits the temperature data to the host computer. The host computer receives the data, processes it, and stores the data in the database. If the temperature signal exceeds the set threshold, an alarm signal is sent in real time to ensure that the temperature of the gas entering the compressor and membrane separation equipment meets the process requirements.

[0022] (b) Using sufficient data collected from the database, establish a functional relationship between the purified biogas flow rate and the temperature before the membrane separation equipment: Q2 = f1(T); where T is the biogas temperature before the membrane separation equipment, in °C; based on this function, obtain the membrane temperature value that is beneficial to improving the flow rate of the finished biogas product.

[0023] As a preferred embodiment of the present invention, the method further includes:

[0024] A heat exchanger is installed between the gas compressor and the membrane separation equipment. By adjusting the temperature or flow rate of the heat exchange medium flowing through the heat exchanger, the temperature before the membrane separation equipment can be adjusted, and the flow rate of the finished biogas can be further increased.

[0025] As a preferred embodiment of the present invention, the gas compressor is a screw gas compressor, and its drive motor is equipped with a frequency converter; the host computer sends control commands to the frequency converter to control the speed of the screw gas compressor and keep the gas supply pressure stable within 0.01MPa.

[0026] In a preferred embodiment of the present invention, in the biogas purification system, each operating device and signal acquisition device is connected to the computer in any of the following ways:

[0027] (1) If the device has a communication interface, it can be directly connected to the host computer: the communication interface is a serial port or Ethernet interface that can realize real-time communication, etc.

[0028] (2) The equipment has a 485 / 232 interface and can be connected to a host computer through an industrial gateway to realize data acquisition and reporting;

[0029] (3) The device connects to the host computer through the IO module. After the IO module obtains the data signal from the acquisition device, it converts it into data and uploads it to the host computer through the network.

[0030] As a preferred embodiment of the present invention, the host computer is also connected to a cloud server via wired or wireless means, and the collected data can be stored in a local or cloud database; the biogas purification system also includes a mobile terminal device that can be wirelessly connected to the host computer via the cloud server.

[0031] As a preferred embodiment of the present invention, the mobile terminal device is a laptop computer, a tablet computer, or a smartphone.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. This invention adds multiple signal acquisition devices such as flow rate, pressure, and temperature to the traditional biogas purification system and adds a frequency converter to the gas compressor; it can establish relevant functional relationships using various monitored parameters, thereby providing a more intuitive and comprehensive understanding of the biogas membrane separation process and enabling analysis and optimization control according to requirements.

[0034] 2. Based on the collected parameter data, this invention adjusts the flow rate, pressure, and temperature of the gas supplied by the system, which can improve the biogas purification efficiency and reduce process energy consumption.

[0035] 3. Compared with the overly simple purification process in existing technologies, this invention optimizes process monitoring measures and control procedures, and provides new ideas for energy-saving operation of biogas. Attached Figure Description

[0036] Figure 1 This is a schematic diagram illustrating the optimization of biogas purification process control in this invention.

[0037] The reference numerals in the figure are as follows: 1. Gas composition online analyzer; 2. Temperature sensor; 3. Compressor controller; 4. Frequency converter; 5. Temperature sensor; 6. Pressure sensor; 7. Flow meter; 8. Pressure sensor; 9. Flow meter; 10. Pressure sensor; 11. Desulfurization equipment; 12. Water removal equipment; 13. Gas compressor; 14. Membrane separation equipment. Detailed Implementation

[0038] First, it should be noted that this invention relates to industrial control technology, specifically an application of computer technology in industrial production. The implementation of this invention involves the application of multiple software functional modules. The applicant believes that, after carefully reading the application documents and accurately understanding the implementation principles and objectives of this invention, and in conjunction with existing publicly known technologies, those skilled in the art can fully utilize their software programming skills to implement this invention. The aforementioned software functional modules include, but are not limited to, monitoring platform software modules built into the host computer, etc. All those mentioned in this application fall within this scope, and the applicant will not list them all further.

[0039] Those skilled in the art will understand that, besides implementing a portion of the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, enabling the system and its various devices, modules, and units to function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered both software modules implementing the method and structures within the hardware component.

[0040] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0041] The control and optimization method for biogas purification in this invention will be described in detail below with reference to the accompanying drawings.

[0042] Part 1: Constructing a Biogas Purification System

[0043] Traditional biogas purification processes typically include desulfurization, water removal, compression, and membrane separation. To optimize process control, this invention proposes adding biogas composition analysis and other online monitoring devices to the traditional process flow. This allows for real-time acquisition of relevant operating parameters, providing data for subsequent process adjustments.

[0044] The biogas purification system of this invention includes: a desulfurization device, a water removal device, a gas compressor, and a membrane separation device connected sequentially via pipelines, wherein the membrane separation device has at least two stages. A heat exchanger is installed between the gas compressor and the membrane separation device. Sampling ports are respectively provided at the front end of the desulfurization device and the rear end of the membrane separation device, and the sampling ports are connected to an online gas composition analyzer via pipelines. Pressure sensors are installed at the rear end of the gas compressor, the inlet of each stage of the membrane separation device, and the permeate and osmotic sides of the final stage membrane separation device. Flow meters are respectively provided at the rear end of the gas compressor and the rear end of the membrane separation device. Temperature sensors are respectively installed at the front end of the gas compressor and the membrane separation device. The online gas composition analyzer, pressure sensors, flow meters, and temperature sensors are respectively connected to a DCS or PLC via signal lines. The DCS or PLC is connected to a host computer via signal lines, and the latter has built-in monitoring platform software. The DCS, PLC, and built-in monitoring platform software can all directly adopt existing mature system or software function modules, and can be modified, set, or adjusted accordingly according to the control or calculation requirements of this invention.

[0045] In practical engineering applications, data from various instruments or equipment is typically first connected to a PLC or DCS (which supports data processing), and then the data is transferred from the PLC or DCS to a computer. Data from the computer, PLC, or DCS can all be connected to a cloud server. The common practice is to perform simple data processing on the PLC or DCS, then build a relatively complex mathematical model on the local computer or cloud server, and finally send some adjustment commands back to the PLC or DCS for control.

[0046] To regulate the operation of the gas compressor according to the control strategy, the gas compressor of this invention is a screw gas compressor, and its drive motor is equipped with a frequency converter. By sending control commands to the frequency converter using a computer, the speed of the screw gas compressor can be controlled to maintain the gas supply pressure stable within 0.01 MPa.

[0047] In the biogas purification system, each signal acquisition device (i.e., detection device or analysis device) can be connected to the DCS or PLC in any of the following ways:

[0048] (1) The device has a communication interface that can directly connect to the platform:

[0049] For data acquisition in production equipment with a high degree of informatization, the equipment's own communication interface protocols, such as serial port and Ethernet, can enable communication with the host computer and real-time data acquisition. Without adding intermediate devices, it can directly connect with the local area network and the system platform of the host computer to achieve real-time communication.

[0050] (2) Industrial gateways directly collect device data:

[0051] Currently, most PLC / CNC equipment mainly uses gateways for data acquisition because these devices do not have Ethernet communication interface modules and do not support the addition of secondary Ethernet communication. Therefore, the host computer connects to the device's 485 / 232 interface through an industrial gateway to realize the acquisition and reporting of device data.

[0052] (3) Data acquisition via the IO module:

[0053] For traditional and outdated physical devices, the host computer can connect to the device via I / O modules, collect relevant parameter data from the device, convert the parameter data into network data, and upload it to the host computer's system platform in real time via the network.

[0054] (4) Data acquisition is achieved using external sensors:

[0055] For some particularly outdated equipment that lacks both interfaces and automated data acquisition capabilities, external sensors can be used to collect data, which is then aggregated and reported to a host computer platform system via a gateway device.

[0056] To meet the needs of online monitoring, the host computer in this system can optionally connect to a cloud server via wired or wireless means. Furthermore, the system also includes mobile terminal devices that can connect to the host computer wirelessly via the cloud server. These mobile terminal devices can be laptops, tablets, smartphones, or similar devices.

[0057] Part Two: Control Optimization for Biogas Purification

[0058] 1. Using an online gas composition analyzer, pressure sensor, flow meter, and temperature sensor, gas composition, pressure data, flow data, and temperature data at corresponding locations are detected and connected to a DCS or PLC via signal lines. The PLC receives the signals, performs preliminary processing, and stores the data in a database, or transmits the data to a host computer and stores it in a database. If the temperature signal exceeds a set threshold, an alarm signal is sent in real time to ensure that the gas temperature entering the compressor and membrane separation equipment meets the process requirements.

[0059] The compressor controller acquires real-time current and voltage data from the gas compressor to calculate its energy consumption, which is then stored in a database. Compressor operation monitoring primarily involves monitoring the compressor's supply pressure, operating status, operating current, and voltage. These parameters are typically built into existing air compressor controllers and can be read via communication. For older equipment lacking current or voltage data, additional monitoring instruments can be added; these are all standard, general-purpose instruments.

[0060] 2. Using sufficient data collected from the database, the host computer establishes the following three functional relationships:

[0061] Q2=f1(ΔP,α1) (1)

[0062] E 压缩机 =f2(ΔP, α1) (2)

[0063] Q2=f1(T) (3)

[0064] Equation (1) is the functional relationship between the finished biogas flow rate and the pressure difference and biogas composition on both sides of the membrane separation equipment; Equation (2) is the functional relationship between the gas compressor energy consumption and the pressure difference and biogas composition on both sides of the membrane separation equipment; Equation (3) is the functional relationship between the purified biogas flow rate and the temperature in front of the membrane separation equipment.

[0065] Plot the curves of the two functions (1) and (2) in the same coordinate system, and then take their intersection point as the energy-saving and efficient operation point; the gas compressor energy consumption, purified biogas flow rate and pressure difference on both sides of the membrane separation equipment represented by the intersection point are balanced, which is the optimal combination of operating parameters for the biogas purification system. Based on equation (3), the membrane inlet temperature value that is conducive to increasing the flow rate of finished biogas can be obtained.

[0066] In each formula, Q2 represents the purified biogas flow rate, in meters (m³). 3 / h; ΔP is the pressure difference across the membrane separation unit, in kPa; α1 is the percentage of methane in the biogas before purification; E 压缩机 1 is the instantaneous operating power of the compressor, in kW; T is the biogas temperature before the membrane separation equipment, in °C.

[0067] f1 and f2 are function formulas derived by curve fitting of discrete data obtained at the same time point based on the aforementioned database. f1 represents the relationship between the finished biogas flow rate and the pressure difference across the membrane separator and the biogas composition, while f2 represents the relationship between the gas compressor energy consumption and the pressure difference across the membrane separator and the biogas composition. Software such as Excel can be used when fitting the data curves. The time points can be set manually; the shorter the time interval, the more accurately the fitted function relationship reflects the actual situation.

[0068] 3. The monitoring platform software of the host computer sends control signals to the PLC or DCS according to the calculation results of step (3). The PLC or DCS adjusts the biogas flow rate and gas supply pressure of the gas compressor before purification so that the system operation meets the requirements of the optimal combination of operating parameters, thereby realizing the optimized control of the biogas purification process.

[0069] 4. Furthermore, the compressed gas volume of the gas compressor can be optimized in the following ways:

[0070] (1) Based on the online analysis data of biogas flow rate and biogas composition before and after purification, the methane recovery rate k is calculated according to the following formula:

[0071] k = (Q2 × α2) / (Q1 × α1)

[0072] In this formula, Q1 and Q2 represent the flow rates of biogas before and after purification, respectively, in meters (m³). 3 / h; α1 and α2 are the percentages of methane content in biogas before and after purification, respectively;

[0073] (2) Based on the biogas flow rate and methane recovery rate k before purification, the compressed gas volume of the gas compressor is adjusted in real time to ensure that the methane recovery rate meets the standard.

[0074] 5. Furthermore, by adjusting the temperature or flow rate of the heat exchange medium flowing through the heat exchanger, the temperature before the membrane separation equipment can be adjusted, and the flow rate of the finished biogas can be further increased.

[0075] Practical application example:

[0076] For newly built or existing biogas purification plants, the following equipment can be added as follows:

[0077] Infrared monitoring and other online detection equipment are installed on the main biogas inlet pipeline and the finished biogas pipeline. A frequency converter is provided for the compressor motor. Flow meters are installed on the main exhaust pipe of the biogas compressor and the finished gas pipeline. Pressure sensors are installed at the biogas compressor outlet, the inlet of each stage of membrane separation equipment, and the permeate and osmotic sides of the final membrane separation stage. Temperature sensors are installed on the pipelines before the biogas compressor inlet and the separation membrane equipment. The operating data of the compressor and frequency converter can be connected to a host computer via a communication interface; data from the flow meters, pressure sensors, and temperature sensors can be directly connected to a DCS or PLC via a gateway, and then communicated to the host computer.

[0078] As data is gradually integrated into the database, once each data type has more than 100 sets of valid data, software such as Excel can be used to fit function formulas and gradually establish the functional relationship Q2=f1(ΔP,α1) between the flow rate of the separated biogas and the pressure difference across the membrane, and the functional relationship E between the compressor energy consumption and the pressure difference across the membrane. 压缩机 =f2(ΔP, α1), and the functional relationship between the flow rate of the separated biogas and the temperature before the separation membrane is Q2 = f1(T). When the operating parameters are adjusted, it is necessary to re-collect data to fit the above functions.

[0079] In practical applications, various detection and control models can be built according to preset control schemes to achieve a more intuitive and comprehensive understanding of the entire separation process and make corresponding adjustments according to needs.

Claims

1. A method for controlling and optimizing biogas purification, characterized in that, Includes the following steps: (1) Constructing a biogas purification system: The system includes a desulfurization unit, a water removal unit, a gas compressor, and a membrane separation unit connected sequentially via pipelines. The membrane separation unit has at least two stages. The gas compressor is a screw-type gas compressor, and its drive motor is equipped with a frequency converter. A host computer sends control commands to the frequency converter to control the speed of the screw-type gas compressor, maintaining the gas supply pressure stable within 0.01 MPa. A heat exchanger is installed between the gas compressor and the membrane separation unit. By adjusting the temperature or flow rate of the heat exchange medium flowing through the heat exchanger, the temperature before the membrane separation unit is adjusted, further increasing the flow rate of the purified biogas. Sampling ports are provided at the front end of the desulfurization equipment and the rear end of the membrane separation equipment, and the sampling ports are connected to an online gas composition analyzer through pipelines. Temperature sensors are installed at the front end of the gas compressor and the membrane separation equipment. Pressure sensors are installed at the rear end of the gas compressor, the inlet of each stage of the membrane separation equipment, and the permeate and osmotic sides of the final stage membrane separation equipment. Flow meters are installed at the rear end of the gas compressor and the rear end of the membrane separation equipment. The online gas composition analyzer, temperature sensors, pressure sensors, and flow meters are connected to a DCS or PLC through signal lines. The DCS or PLC is connected to a host computer through signal lines, and the latter has a built-in monitoring platform software module. (2) Using an online gas composition analyzer, pressure sensor and flow meter, gas composition, temperature data, pressure data and flow data at the corresponding locations are detected respectively, and transmitted to DCS or PLC via signal line; the latter receives the signal, performs preliminary processing and stores the data in the database, or transmits the data to the host computer and stores it in the database; if the temperature signal exceeds the set threshold, an alarm signal is sent in real time to ensure that the temperature of the gas entering the compressor and membrane separation equipment meets the process requirements; (3) The host computer uses the sufficient data collected from the database to establish the following three functional relationships: The functional relationship between purified biogas flow rate and the pressure difference across the membrane separator and biogas composition is as follows: Q 2 = f 1(D P， a1); The functional relationship between gas compressor energy consumption and pressure difference across membrane separation equipment and biogas composition E 压缩机 = f 2(D P， a1); The functional relationship between the purified biogas flow rate and the temperature before the membrane separation equipment: Q 2 = f 3( T )； Drawing in the same coordinate system f 1 and f 2. Find the curves of these two functions, and then take their intersection point as the energy-efficient operation point; the intersection point represents the balance of the gas compressor energy consumption, purified biogas flow rate and the pressure difference on both sides of the membrane separation equipment, which is the optimal combination of operating parameters for the biogas purification system. in, Q 2 represents the purified biogas flow rate, in meters (m³). 3 / h; Δ P α1 represents the pressure difference across the membrane separation unit, expressed in kPa; α1 represents the volume percentage of methane in the biogas before purification. E 压缩机 This is the instantaneous operating power of the compressor, measured in kW. f 1. f 2. f 3 are all functions obtained by curve fitting of discrete data at the same time point in step (2); T The biogas temperature before the membrane separation equipment is expressed in °C. Based on this function, the in-membrane temperature value that is beneficial for increasing the flow rate of purified biogas is obtained. (4) The monitoring platform software of the host computer sends a control signal to the PLC or DCS according to the calculation result of step (3). The PLC or DCS adjusts the biogas flow rate and gas compressor supply pressure before purification so that the system operation meets the requirements of the optimal combination of operating parameters, thereby realizing the optimized control of biogas purification process. Furthermore, it also includes online control of methane recovery rate, including the following steps: (4.1) Using online analysis data of biogas flow rate and biogas composition before and after purification, calculate the methane recovery rate k according to the following formula: k = (Q2×α2) / ( Q1×α1) In this formula, Q1 represents the flow rate of biogas before purification, in cubic meters per second (m³). 3 / h; α2 is the volume percentage of methane in the purified biogas; (4.2) Based on the biogas flow rate and methane recovery rate k before purification, the compressed gas volume of the gas compressor is adjusted in real time to ensure that the methane recovery rate meets the standard.

2. The method according to claim 1, characterized in that, In the biogas purification system, each operating device and signal acquisition device is connected to the computer in any of the following ways: (1) If the device has a communication interface, it can be directly connected to the host computer: the communication interface is a serial port or Ethernet interface that can realize real-time communication. (2) The equipment has a 485 / 232 interface and connects to a host computer through an industrial gateway to realize data acquisition and reporting; (3) The device connects to the host computer through the IO module. After the IO module obtains the data signal from the acquisition device, it converts it into data and uploads it to the host computer through the network.

3. The method according to claim 1, characterized in that, The host computer is also connected to a cloud server via wired or wireless means, and the collected data can be stored in a local or cloud database; the biogas purification system also includes a mobile terminal device that can be wirelessly connected to the host computer via the cloud server.

4. The method according to claim 3, characterized in that, The mobile terminal device is a laptop computer, a tablet computer, or a smartphone.

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