沼氣凈化有四種方法,即吸收法、變壓吸附法、低溫冷凝法和膜分離法。
There are four methods for biogas purification, namely absorption method, pressure swing adsorption method, low-temperature condensation method, and membrane separation method.
吸收凈化過程是利用有機胺溶液(一級胺、二級胺、三級胺、空間位阻胺等)和二氧化碳的物理和化學吸收財產,即在吸收塔中的壓力和常溫下與沼氣中的二氧化碳發生吸收反應來實現的,并且吸收液在再生塔中在壓力和加熱條件下進行反分析反應以釋放高純度二氧化碳氣體。同時,富液再生具有重新吸收二氧化碳的能力,以實現吸收塔中甲烷的連續脫碳和凈化,并使脫碳液進行連續吸收和再生循環。
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.
壓力波動吸附凈化法利用吸附劑(如分子篩等)對二氧化碳的選擇性吸附財產,即吸附劑上的二氧化碳比其他氣體組分具有更高的分離系數,以達到從沼氣中去除二氧化碳的目的。在吸附過程中,原料氣中的二氧化碳在吸附塔中被加壓吸附,甲烷和其他弱吸附氣體作為凈化氣體被釋放。當吸附飽和時,將吸附柱加壓或甚至泵入真空以釋放吸附的二氧化碳。為了確保連續的氣體處理,PSA需要至少兩個吸附塔,可以是三個、四個或更多。
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.
低溫冷凝凈化工藝利用二氧化碳冷凝溫度高的特點,通過低溫作用將沼氣中的二氧化碳液化,甲烷組分作為不凝氣體排出,凈化產品氣。為了減少運行能耗,通常使用再生技術來恢復剩余的冷卻能力。
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.
由于膜在壓力驅動下的滲透性不同,膜分離和清潔過程通過使用不同的氣體組分來實現。通常,二氧化碳的滲透速率快,而甲烷的滲透速率慢,并且以可滲透氣體的形式作為慢氣體獲得純化的產物氣體。在機械工程中,通常使用多級膜分離工藝來提高甲烷氣體的濃度。
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,沼氣凈化工程主要采用吸附和壓力波動吸附,而低溫冷凝法和膜分離法由于技術成熟和經濟性而很少使用。
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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