Biogas membrane-based purification system

Thread Content

I. Application Areas: The biogas membrane purification equipment is a device used in biogas projects that relies on advanced hollow fiber gas separation membrane technology to remove carbon dioxide from biogas (or landfill gas). It is suitable for the purification of biogas and landfill gas. After purification, biogas can be used as a substitute for natural gas, with a methane concentration of over 97%. By using integrated compression/gasification equipment to increase the pressure, it is possible to produce standard 25MPa CNG for use in vehicles, or to raise the pressure to the standards required by natural gas networks so that the gas can be fed into local gas networks. II. Working Principle The membrane-based biogas purification equipment is designed based on the fact that gas membranes have different permeation rates for various components in a mixed gas. Figures 1 and 2 illustrate the selective permeation of various components in a mixed gas by gas membranes. The main components of biogas are methane and carbon dioxide. The purification of biogas involves separating and removing carbon dioxide from it. As can be seen from the graph, the permeation rate of CO2 in biogas is higher than that of CH4. By taking advantage of the selective permeability of gas membranes, it is possible to rapidly separate components such as CH4 and CO2 in biogas, thereby achieving its purification. file:///C:/Users/ThinkPad/AppData/Local/Temp/msohtmlclip1/01/clip_image002.gif Figure 1: Selective permeability of gas separation membranes. Figure 2: Principle of gas separation between methane and carbon dioxide. The process flow for purifying biogas using membrane technology is shown in Figure 3. The entire system has a simple structure; aside from the primary compressor, there are no other gas-handling devices, resulting in a low failure rate and lower overall energy consumption. file:///C:/Users/ThinkPad/AppData/Local/Temp/msohtmlclip1/01/clip_image003.jpg Figure 3: Process flow diagram for membrane-based biogas purification. III. Characteristics of membrane separation technology: ü The process flow is simple, operation and management are easy, and the number of workers required is reduced by more than 50% ； ü Low investment and operating costs, 15-25% lower than those of chemical absorption and pressurized water washing methods ； ü It occupies a small area, utilizes standard containers for integration, and allows for modular expansion ； ü The product has a high purity and high recovery rate; CH4 purity ≥97%, recovery rate ≥97% ； ü It has a synchronous dehydration function, eliminating the need for pre-dehydration. IV. System Composition The components of the biogas membrane purification equipment are as follows: biogas compression system, gas purification system before the membrane, membrane separation system, biogas pressurization system, gas addition system, etc. 4.1 Biogas compression system: To achieve the optimal separation performance of the membrane module, the feed gas must be compressed to a process pressure suitable for its operation. The system uses oil-free lubrication compressors to ensure that biogas is not contaminated again by lubricating oil, thereby providing clean gas for the membrane separation unit. 4.2 Pre-membrane gas purification system: In addition to gases such as methane and carbon dioxide, biogas generally contains various impurities such as free liquids, solid particles, and microorganisms. The gas purification system removes these impurities such as water, oil, and solid particles from the biogas, thereby meeting the operational requirements of the membrane separation system. The gas purification system is a condition that ensures the stable operation of the purification device, and it can also extend the service life of the membrane separation system. 4.3 Membrane separation system: The world’s most advanced imported membrane modules are used to separate carbon dioxide and water vapor from biogas, thereby obtaining methane gas of high purity. Through a scientifically designed multi-stage separation process, the methane purity at the outlet of the membrane separation system can reach over 97%, with a methane recovery rate of over 97% as well. The application of membrane separation systems provides optimal performance for biogas purification processes, and it has the following advantages: ü It offers a higher recovery rate compared to other physical methods used for biogas purification ； The membrane group separation system itself consumes no energy and does not require regeneration ； The membrane module separation system is equipped with pressure override safety devices and an air intake shutdown system; in case of an emergency, the air intake is automatically shut off to protect the fiber membrane modules ； ü At the outlet of the membrane separation system, a check valve is used to prevent issues such as backflow and excessive pressure. 4.4 The biogas pressurization system is used to ensure that the purified biogas meets the pressure requirements of vehicle fuel systems or other applications that require gas supply; it involves further pressurizing the purified biogas. The system utilizes compressors that are stable and reliable in operation, enabling the biogas to be pressurized to 25 MPa or to the pressure level required by other gas-consuming systems. 4.5 Gas filling system: The system is equipped with one gas filling column, which is used to transport the high-pressure gas discharged by the biogas compression system to the CNG tank truck for storage. When the filling pressure in the tank truck reaches the set value, the biogas compression system automatically stops compressing and supplying gas. V. Technical Parameters – Table of Main Models and Technical Specifications
Serial Number | Model and Specifications | Equipment Dimensions (L×B×H in m) | Air Inlet Volume (m3/d) | Purity of Feed Gas CH4 (%) | Purity of Product CH4 (%) | CH4 Recovery Rate (%)
1 | TRJH-25 | 2500 m3/d | 12.3×2.4×2.5 | 2500 | 50–70 | ≥96.8 | ≥99.09
2 | TRJH-50 | 5000 m3/d | 12.3×2.4×2.5 | 5000 | 50–70 | ≥96.5 | ≥99.57
3 | TRJH-80 | 8000 m3/d | 12.3×2.4×2.5 | 8000 | 50–70 | ≥96.5 | ≥99.35
4 | TRJH-100 | 10000 m3/d | 2×12.3×2.4×2.5 | 10000 | 50–70 | ≥96.6 | ≥98.31

Note: The equipment configuration should be designed based on the specific air inlet volume, CO2 content, and other relevant parameters, including the selection of primary and auxiliary equipment. Additional equipment and instruments such as advanced desulfurization systems and online analysis monitoring devices can also be included as needed