沼氣提純有四種方法可以實(shí)現(xiàn)，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 for biogas purification, namely absorption method, pressure swing adsorption method, low-temperature condensation method and membrane separation method.
一、吸收提純法
1、 Absorption purification
吸收提純法是利用有機(jī)胺溶液與二氧化碳的物理化學(xué)吸收特性來實(shí)現(xiàn)的，即在吸收塔內(nèi)的加壓、常溫條件下與沼氣中的二氧化碳發(fā)生吸收反應(yīng)進(jìn)行脫碳提純甲烷，吸收富液在再生塔內(nèi)的減壓、加熱條件下發(fā)生逆向解析反應(yīng)，釋放出高純度的二氧化碳?xì)怏w，同時富液得到再生具備重新吸收二氧化碳的能力，從而實(shí)現(xiàn)沼氣在吸收塔內(nèi)的連續(xù)脫碳提純甲烷過程，并使得脫碳液進(jìn)行連續(xù)的吸收、再生循環(huán)工作。
The absorption and purification method is realized by using the physicochemical absorption characteristics of organic amine solution and carbon dioxide, that is, it reacts with carbon dioxide in biogas under pressure and normal temperature in the absorption tower to decarbonize and purify methane, and the absorbed rich solution reacts reversely under decompression and heating conditions in the regeneration tower to release high-purity carbon dioxide gas, At the same time, the rich liquid is regenerated and has the ability to reabsorb carbon dioxide, so as to realize the continuous decarburization and purification of methane in the absorption tower, and make the decarburized liquid carry out continuous absorption and regeneration cycle.
二、變壓吸附提純法
2、 PSA purification
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(diǎn),即在吸附劑上二氧化碳相對其他氣態(tài)組分有較高的分離系數(shù),來達(dá)到對沼氣中二氧化碳進(jìn)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(nèi)，甲烷等其他弱吸附性氣體作為凈化氣排出，當(dāng)吸附飽和后將吸附柱減壓甚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(xù)處理要求，變壓吸附法少需要兩個吸附塔,也可是三塔、四塔或更多。
PSA purification method uses the selective adsorption characteristics of adsorbents (such as molecular sieves) for carbon dioxide, that is, carbon dioxide has a higher separation coefficient than other gaseous components on the adsorbent to achieve the purpose of removing carbon dioxide from biogas. During the adsorption process, the 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 purified gas. When the adsorption is saturated, the adsorption column is depressurized or even vacuumized to release the adsorbed carbon dioxide. In order to ensure the continuous treatment of gas, PSA requires at least two adsorption towers, or three towers, four towers or more.
三、低溫冷凝提純法
3、 Low temperature condensation purification
低溫冷凝提純法是利用二氧化碳液化溫度高的特點(diǎn)，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(chǎn)品氣排出。為了降低運(yùn)行能耗，通常采用回?zé)峒夹g(shù)將剩余冷量進(jìn)行回收。
Low temperature condensation purification method uses the characteristics of high liquefaction temperature of carbon dioxide to liquefy carbon dioxide in biogas through low temperature, and methane component is discharged as non condensable gas to purify product gas. In order to reduce operation energy consumption, regenerative technology is usually used to recover the remaining cooling capacity.
四、膜分離提純法
4、 Membrane separation and purification
膜分離提純法是利用不同氣體組分在壓力驅(qū)動下通過膜的滲透性作用的不同來實(shí)現(xiàn)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(chǎn)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 and purification method is realized by using the different permeability of different gas components through the membrane under pressure. Generally, the penetration rate of carbon dioxide is fast, which is discharged as fast gas through gas, and the penetration rate of methane is slow. As slow gas, purified product gas is obtained in the form of residual gas. In engineering, multistage membrane separation process is often used to improve the concentration of methane.
沼氣提純工程主要采用的是吸收、變壓吸附以及膜分離法，低溫冷凝法由于技術(shù)成熟度和經(jīng)濟(jì)性等原因應(yīng)用得還很少。
Biogas purification project mainly adopts absorption, pressure swing adsorption and membrane separation methods. Low temperature condensation method is rarely used due to technical maturity and economy.
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2021-08-30
