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Biogas is a green energy source with great potential for development. It mainly consists of organic substances such as straw, leaves, and human and animal waste; under certain conditions of temperature, humidity, and acidity, and in an environment free from air, these materials produce flammable gases through microbial action or fermentation. Depending on actual needs, biogas can be purified to produce natural gas of higher quality, which can be directly integrated into urban gas supply networks, or it can be turned into compressed liquefied natural gas after compression and liquefaction, thereby offering better economic benefits. So, do you know the methods for purifying biogas? Pressure Swing Adsorption (PSA) 1. Working principle: Pressure Swing Adsorption is a gas separation technique based on pressure changes. It achieves separation by taking advantage of the differences in the adsorption capacity of different gases on the adsorbent (such as the separation of nitrogen and oxygen) or the differences in the size of gas molecules (such as the molecular sieve effect). The entire process takes place at room temperature, with the cycle of adsorption and desorption being achieved by periodically changing the system pressure. 2. Cycling process: Adsorption stage: Biogas passes through the adsorption tower under high pressure; impurities are adsorbed, while CH4 is discharged from the top of the tower. Depressurization stage: Pressure is reduced, and the adsorbent releases impurities (such as CO₂). Rinsing/evacuation: Flush the adsorption tower with some of the product gas or using a vacuum pump to completely desorb impurities. Pressurization stage: The adsorption tower is re-pressurized to prepare for the next cycle. 3. Biogas purification process: Pretreatment: Dehydration (condensation or adsorption) to prevent the adsorbent from becoming ineffective. Desulfurization (such as activated carbon or chemical washing) protects the adsorbent. PSA main system: Multiple towers in parallel (usually 3–6 towers) to ensure continuous gas production. Operating pressure: 0.3–1.0 MPa (optimized based on the properties of the adsorbent). Post-treatment: The methane product gas is compressed or directly integrated into the pipeline network. The desorbed CO₂ can be recycled or released. 4. Technical advantages: (1) High product purity, meeting automotive fuel standards ； (2) Operation at normal temperature and low pressure results in lower energy consumption, and no additional heating is required for bed regeneration ； (3) The equipment structure is relatively simple, making operation and maintenance convenient ； (4) It can achieve fully automatic continuous operation ； (5) Environmentally friendly, as it does not cause secondary pollution such as wastewater. 5. Application scenarios: (1) Bio-CNG: The purified methane can be used as a fuel for vehicles ； (2) Gas power generation: Increase the calorific value of gas and reduce corrosion ； (3) Carbon reduction projects: CO₂ can be recovered, achieving negative emissions.