Because biogas contains a lot of sulfides and water vapor, direct combustion may cause great damage to combustion equipment. In order to avoid this situation, we usually purify biogas, and pressure swing adsorption is a commonly used method. Next, we will introduce the advantages and disadvantages of pressure swing adsorption used in biogas purification.
变压吸附提纯法是利用吸附剂（如分子筛等）对二氧化碳的选择性吸附特点, 即在吸附剂上二氧化碳相对其他气态组分有较高的分离系数, 来达到对沼气中二氧化碳进行脱除的目的。在吸附过程中，原料气在加压条件下其中的二氧化碳被吸附在吸附塔内，甲烷等其他弱吸附性气体作为净化气排出，当吸附饱和后将吸附柱减压甚至抽成真空使被吸附的二氧化碳释放出来。为了保证对气体的连续处理要求，变压吸附法至少需要两个吸附塔, 也可是三塔、四塔或更多。
Pressure swing adsorption (PSA) is a method to remove carbon dioxide from biogas by utilizing the selective adsorption characteristics of adsorbents (such as molecular sieves), i.e. the separation coefficient of carbon dioxide on adsorbents is higher than that of other gaseous components. During the adsorption process, carbon dioxide in the feed gas is adsorbed in the adsorption tower under pressurized conditions, and other weakly adsorbed gases such as methane are discharged as purifying gas. When the adsorption is saturated, the adsorption column is decompressed or even pumped into vacuum to release the adsorbed carbon dioxide. In order to ensure the continuous treatment of gases, PSA requires at least two adsorption towers, or three, four or more towers.
Advantages of the process: The newly developed PSA decarbonization device with main and auxiliary towers has changed the problems of low recovery and low purity of traditional PSA methane. The whole device is easy to operate and has less maintenance. At the same time, it overcomes the shortcomings of chemical decarbonization, such as foaming, corrosion and steam consumption.
Technological shortcomings: In practical engineering operation, molecular sieves in pressure swing adsorption are easily poisoned and deactivated, and the cost proportion of molecular sieves in pressure swing adsorption is relatively high.
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