沼氣提純有四種方法可以實現，分別是吸收法、變壓吸附法、低溫冷凝法和膜分離方法。

　　There are four methods to achieve biogas purification, namely absorption method, pressure swing adsorption method, low-temperature condensation method, and membrane separation method.

　　吸收提純法是利用有機胺溶液（一級胺、二級胺、三級胺、空間位阻胺等）與二氧化碳的物理化學吸收特性來實現的，即在吸收塔內的加壓、常溫條件下與沼氣中的二氧化碳發生吸收反應進行脫碳提純甲烷，吸收富液在再生塔內的減壓、加熱條件下發生逆向解析反應，釋放出高純度的二氧化碳氣體，同時富液得到再生具備重新吸收二氧化碳的能力，從而實現沼氣在吸收塔內的連續脫碳提純甲烷過程，并使得脫碳液進行連續的吸收、再生循環工作。

　　The absorption purification method utilizes the physical and chemical absorption characteristics of organic amine solutions (primary amine, secondary amine, tertiary amine, steric hindrance amine, etc.) and carbon dioxide to achieve decarbonization and purification of methane. It involves an absorption reaction with carbon dioxide in biogas under pressure and room temperature conditions in the absorption tower, and a reverse desorption reaction of the absorbed rich liquid under pressure and heating conditions in the regeneration tower, releasing high-purity carbon dioxide gas, At the same time, the regeneration of the rich liquid has the ability to reabsorb carbon dioxide, thereby achieving continuous decarbonization and purification of methane from biogas in the absorption tower, and enabling continuous absorption and regeneration of the decarbonized liquid.

　　變壓吸附提純法是利用吸附劑（如分子篩等）對二氧化碳的選擇性吸附特點, 即在吸附劑上二氧化碳相對其他氣態組分有較高的分離系數, 來達到對沼氣中二氧化碳進行脫除的目的。在吸附過程中，原料氣在加壓條件下其中的二氧化碳被吸附在吸附塔內，甲烷等其他弱吸附性氣體作為凈化氣排出，當吸附飽和后將吸附柱減壓甚至抽成真空使被吸附的二氧化碳釋放出來。為了保證對氣體的連續處理要求，變壓吸附法至少需要兩個吸附塔, 也可是三塔、四塔或更多。

　　The pressure swing adsorption purification method utilizes the selective adsorption characteristics of adsorbents (such as molecular sieves) for carbon dioxide, which means that carbon dioxide has a higher separation coefficient compared to other gaseous components on the adsorbent, in order to achieve the purpose of removing carbon dioxide from biogas. During the adsorption process, carbon dioxide in the feed gas is adsorbed into the adsorption tower under pressure conditions, and other weakly adsorbed gases such as methane are discharged as purified gas. When the adsorption is saturated, the adsorption column is depressurized or even evacuated to release the adsorbed carbon dioxide. In order to ensure continuous gas processing requirements, the pressure swing adsorption method requires at least two adsorption towers, which can be three, four, or more.

　　低溫冷凝提純法是利用二氧化碳液化溫度高的特點，通過低溫作用使沼氣中的二氧化碳被液化，甲烷組分作為不凝氣以提純產品氣排出。為了降低運行能耗，通常采用回熱技術將剩余冷量進行回收。

　　The low-temperature condensation purification method utilizes the high liquefaction temperature of carbon dioxide to liquefy the carbon dioxide in biogas through low-temperature action, and the methane component is discharged as non condensable gas to purify the product gas. In order to reduce operational energy consumption, regenerative technology is usually used to recover the remaining cooling capacity.

　　膜分離提純法是利用不同氣體組分在壓力驅動下通過膜的滲透性作用的不同來實現的，通常情況下二氧化碳的滲透速度快，作為快氣以透過氣排出，甲烷的滲透速度慢，作為慢氣以透余氣形式獲得提純產品氣。在工程中，為了提高甲烷氣的濃度，常采用多級膜分離工藝。

　　The membrane separation purification method is achieved by utilizing the different permeability effects of different gas components through the membrane under pressure driving. Generally, carbon dioxide has a fast permeation rate, and as a fast gas, it is discharged through the permeable gas, while methane has a slow permeation rate. As a slow gas, it is obtained as a purified product gas in the form of permeable residual gas. In engineering, multi-stage membrane separation technology is often used to increase the concentration of methane gas.

　　目前，沼氣提純工程主要采用的是吸收和變壓吸附這兩種方法，低溫冷凝法和膜分離法由于技術成熟度和經濟性等原因應用得還很少。

　　At present, the main methods used in biogas purification engineering are absorption and pressure swing adsorption. The low-temperature condensation method and membrane separation method are still rarely applied due to their technological maturity and economic feasibility.

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