沼气净化有四种方法，即吸收法、变压吸附法、低温冷凝法和膜分离法。
There are four methods for biogas purification, namely absorption method, pressure swing adsorption method, low-temperature condensation method, and membrane separation method.
吸收净化过程是利用有机胺溶液（一级胺、二级胺、三级胺、空间位阻胺等）和二氧化碳的物理和化学吸收财产，即在吸收塔中的压力和常温下与沼气中的二氧化碳发生吸收反应来实现的，并且吸收液在再生塔中在压力和加热条件下进行反分析反应以释放高纯度二氧化碳气体。同时，富液再生具有重新吸收二氧化碳的能力，以实现吸收塔中甲烷的连续脱碳和净化，并使脱碳液进行连续吸收和再生循环。
The absorption purification process is achieved by utilizing organic amine solutions (primary amine, secondary amine, tertiary amine, steric hindrance amine, etc.) and the physical and chemical absorption properties of carbon dioxide, that is, by reacting with carbon dioxide in the biogas at pressure and room temperature in the absorption tower. The absorption liquid undergoes a reverse analysis reaction under pressure and heating conditions in the regeneration tower to release high-purity carbon dioxide gas. At the same time, rich liquid regeneration has the ability to reabsorb carbon dioxide to achieve continuous decarbonization and purification of methane in the absorption tower, and to enable continuous absorption and regeneration of the decarbonized liquid.
压力波动吸附净化法利用吸附剂（如分子筛等）对二氧化碳的选择性吸附财产，即吸附剂上的二氧化碳比其他气体组分具有更高的分离系数，以达到从沼气中去除二氧化碳的目的。在吸附过程中，原料气中的二氧化碳在吸附塔中被加压吸附，甲烷和其他弱吸附气体作为净化气体被释放。当吸附饱和时，将吸附柱加压或甚泵入真空以释放吸附的二氧化碳。为了确保连续的气体处理，PSA需要少两个吸附塔，可以是三个、四个或更多。
The pressure fluctuation adsorption purification method utilizes adsorbent (such as molecular sieve) to selectively adsorb carbon dioxide, which means that the carbon dioxide on the adsorbent has a higher separation coefficient than other gas components, in order to achieve the purpose of removing carbon dioxide from biogas. During the adsorption process, carbon dioxide in the feed gas is pressurized and adsorbed in the adsorption tower, while methane and other weakly adsorbed gases are released as purification gases. When the adsorption is saturated, the adsorption column is pressurized or even pumped into vacuum to release the adsorbed carbon dioxide. To ensure continuous gas treatment, PSA requires at least two adsorption towers, which can be three, four, or more.
低温冷凝净化工艺利用二氧化碳冷凝温度高的特点，通过低温作用将沼气中的二氧化碳液化，甲烷组分作为不凝气体排出，净化产品气。为了减少运行能耗，通常使用再生技术来恢复剩余的冷却能力。
The low-temperature condensation purification process utilizes the high condensation temperature of carbon dioxide to liquefy the carbon dioxide in biogas through low-temperature action, and the methane component is discharged as a non condensable gas to purify the product gas. In order to reduce operational energy consumption, regeneration technology is usually used to restore the remaining cooling capacity.
由于膜在压力驱动下的渗透性不同，膜分离和清洁过程通过使用不同的气体组分来实现。通常，二氧化碳的渗透速率快，而甲烷的渗透速率慢，并且以可渗透气体的形式作为慢气体获得纯化的产物气体。在机械工程中，通常使用多级膜分离工艺来提高甲烷气体的浓度。
Due to the different permeability of membranes under pressure driving, membrane separation and cleaning processes are achieved by using different gas components. Usually, the permeation rate of carbon dioxide is fast, while the permeation rate of methane is slow, and the purified product gas is obtained in the form of a permeable gas as a slow gas. In mechanical engineering, multi-stage membrane separation processes are commonly used to increase the concentration of methane gas.
目前，沼气净化工程主要采用吸附和压力波动吸附，而低温冷凝法和膜分离法由于技术成熟和经济性而很少使用。
At present, biogas purification projects mainly use adsorption and pressure fluctuation adsorption, while low-temperature condensation and membrane separation methods are rarely used due to their mature technology and economic efficiency.
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2023-05-04
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