在全球能源轉(zhuǎn)型的浪潮中，沼氣作為一種源自生物質(zhì)的可再生能源，正逐漸嶄露頭角。它通常由有機(jī)廢棄物，如畜禽糞便、農(nóng)作物秸稈、工業(yè)有機(jī)廢水以及城市生活垃圾等，在厭氧環(huán)境下經(jīng)微生物發(fā)酵產(chǎn)生。沼氣的主要成分是甲烷和二氧化碳，其中甲烷含量一般在 50% - 70%，其余為二氧化碳以及少量的硫化氫、氮?dú)?、水蒸氣等雜質(zhì) 。然而，這樣的原始沼氣在能源利用的道路上還存在諸多限制，沼氣提純技術(shù)應(yīng)運(yùn)而生，成為提升沼氣能源價(jià)值的關(guān)鍵所在。

In the wave of global energy transition, biogas, as a renewable energy source derived from biomass, is gradually emerging. It is usually produced by microbial fermentation in anaerobic environments from organic waste such as livestock manure, crop straw, industrial organic wastewater, and urban household waste. The main components of biogas are methane and carbon dioxide, with methane content generally ranging from 50% to 70%, and the rest being carbon dioxide, as well as small amounts of impurities such as hydrogen sulfide, nitrogen, and water vapor. However, such primitive biogas still has many limitations in energy utilization, and biogas purification technology has emerged as the key to enhancing the energy value of biogas.

一、沼氣提純的必要性

1、 The necessity of biogas purification

原始沼氣直接利用存在諸多弊端。從能源效率角度看，較低的甲烷含量意味著單位體積沼氣蘊(yùn)含的能量有限，無法滿足一些對能源品質(zhì)要求較高的應(yīng)用場景，例如作為優(yōu)質(zhì)的城市燃?xì)饣蛴糜诟咝У陌l(fā)電項(xiàng)目 。在燃燒過程中，二氧化碳等雜質(zhì)的存在不僅降低了沼氣的熱值，還會增加燃燒設(shè)備的負(fù)擔(dān)，降低能源轉(zhuǎn)化效率 。從設(shè)備維護(hù)層面來說，沼氣中的硫化氫是一種具有強(qiáng)腐蝕性的氣體，它會與水結(jié)合形成氫硫酸，對沼氣輸送管道、儲存設(shè)備以及各類燃燒器具造成嚴(yán)重腐蝕，大幅縮短設(shè)備使用壽命，增加維護(hù)成本和更換頻率 。此外，硫化氫在燃燒時(shí)會轉(zhuǎn)化為二氧化硫排放到大氣中，成為酸雨形成的重要因素之一，對環(huán)境造成嚴(yán)重污染 。水蒸氣的存在則可能導(dǎo)致管道積水、凍脹等問題，影響沼氣的穩(wěn)定輸送 。因此，為了提高沼氣的能源利用效率，保護(hù)設(shè)備安全，減少環(huán)境污染，對沼氣進(jìn)行提純處理勢在必行。

There are many drawbacks to directly utilizing raw biogas. From the perspective of energy efficiency, a lower methane content means that the energy contained in a unit volume of biogas is limited and cannot meet some application scenarios that require high energy quality, such as being used as high-quality urban gas or for efficient power generation projects. During the combustion process, the presence of impurities such as carbon dioxide not only reduces the calorific value of biogas, but also increases the burden on combustion equipment and reduces energy conversion efficiency. From the perspective of equipment maintenance, hydrogen sulfide in biogas is a highly corrosive gas that combines with water to form hydrogen sulfate, causing serious corrosion to biogas transmission pipelines, storage equipment, and various combustion appliances, significantly shortening equipment service life, increasing maintenance costs and replacement frequency. In addition, hydrogen sulfide is converted into sulfur dioxide during combustion and emitted into the atmosphere, becoming one of the important factors in the formation of acid rain and causing serious pollution to the environment. The presence of water vapor may cause problems such as water accumulation and frost heave in pipelines, affecting the stable transportation of biogas. Therefore, in order to improve the energy utilization efficiency of biogas, protect equipment safety, and reduce environmental pollution, it is imperative to purify biogas.

二、主流沼氣提純技術(shù)詳解

2、 Detailed explanation of mainstream biogas purification technology

（一）吸收法

（1） Absorption method

吸收法是利用特定吸收劑與沼氣中二氧化碳等雜質(zhì)的物理或化學(xué)作用來實(shí)現(xiàn)分離提純的方法。根據(jù)吸收原理的不同，又可細(xì)分為物理吸收和化學(xué)吸收 。

Absorption method is a method of separation and purification that utilizes the physical or chemical interaction between specific absorbents and impurities such as carbon dioxide in biogas. According to different absorption principles, it can be further divided into physical absorption and chemical absorption.

物理吸收：物理吸收法利用吸收劑對不同氣體的溶解度差異來實(shí)現(xiàn)分離 。常見的物理吸收劑有甲醇、碳酸丙烯酯等 。在加壓條件下，沼氣中的二氧化碳等易溶氣體被吸收劑吸收，而甲烷則幾乎不溶，從而實(shí)現(xiàn)分離 。當(dāng)減壓時(shí)，吸收劑中的二氧化碳等氣體解吸釋放，吸收劑得以再生循環(huán)使用 。例如，在低溫甲醇洗工藝中，甲醇在低溫高壓下對二氧化碳、硫化氫等酸性氣體有良好的溶解性，能高效脫除沼氣中的雜質(zhì) 。物理吸收法的優(yōu)點(diǎn)是吸收劑一般不與被吸收氣體發(fā)生化學(xué)反應(yīng)，能耗相對較低，且對設(shè)備材質(zhì)要求相對不高 。但它對設(shè)備的密封性要求較高，操作壓力通常較高，設(shè)備投資較大 。

Physical absorption: The physical absorption method utilizes the difference in solubility of absorbents for different gases to achieve separation. Common physical absorbents include methanol, propylene carbonate, etc. Under pressurized conditions, soluble gases such as carbon dioxide in biogas are absorbed by absorbents, while methane is almost insoluble, thus achieving separation. When depressurized, gases such as carbon dioxide in the absorbent are desorbed and released, allowing the absorbent to be regenerated and reused. For example, in the low-temperature methanol washing process, methanol has good solubility for acidic gases such as carbon dioxide and hydrogen sulfide under low temperature and high pressure, and can efficiently remove impurities from biogas. The advantages of physical absorption method are that the absorbent generally does not undergo chemical reactions with the absorbed gas, the energy consumption is relatively low, and the requirements for equipment materials are relatively low. But it requires high sealing performance of the equipment, usually high operating pressure, and significant equipment investment.

化學(xué)吸收：化學(xué)吸收法借助吸收劑與二氧化碳等雜質(zhì)發(fā)生化學(xué)反應(yīng)來實(shí)現(xiàn)吸收 。常用的化學(xué)吸收劑有醇胺類溶液（如乙醇胺、二乙醇胺等）、堿性鹽溶液（如碳酸鉀溶液）等 。以醇胺吸收二氧化碳為例，在吸收塔內(nèi)，醇胺與二氧化碳發(fā)生化學(xué)反應(yīng)生成氨基甲酸鹽，從而將二氧化碳從沼氣中脫除 。在再生塔內(nèi)，通過加熱使氨基甲酸鹽分解，釋放出二氧化碳，醇胺得以再生 。化學(xué)吸收法的脫硫效率高，對二氧化碳的脫除較為徹底，能使沼氣中的甲烷含量大幅提高 。不過，由于化學(xué)反應(yīng)需要消耗一定的能量來實(shí)現(xiàn)吸收劑的再生，所以能耗相對較高，且吸收劑在使用過程中可能會發(fā)生降解，需要定期補(bǔ)充和更換 。

Chemical absorption: The chemical absorption method uses absorbents to undergo chemical reactions with impurities such as carbon dioxide to achieve absorption. Common chemical absorbents include alcohol amine solutions (such as ethanolamine, diethanolamine, etc.), alkaline salt solutions (such as potassium carbonate solution), etc. Taking the absorption of carbon dioxide by ethanolamines as an example, in the absorption tower, ethanolamines react chemically with carbon dioxide to form aminoformates, thereby removing carbon dioxide from biogas. In the regeneration tower, the amino formate salt is decomposed by heating, releasing carbon dioxide, and the alcohol amine is regenerated. The chemical absorption method has high desulfurization efficiency and thorough removal of carbon dioxide, which can significantly increase the methane content in biogas. However, due to the fact that chemical reactions require a certain amount of energy to regenerate the absorbent, the energy consumption is relatively high, and the absorbent may degrade during use, requiring regular replenishment and replacement.

（二）變壓吸附法

（2） Pressure swing adsorption method

變壓吸附法（PSA）是基于吸附劑對不同氣體吸附能力的差異，通過周期性的壓力變化來實(shí)現(xiàn)氣體分離提純的技術(shù) 。該方法常用的吸附劑有分子篩、活性炭、硅膠等 。在吸附過程中，原料氣在加壓條件下進(jìn)入吸附塔，其中二氧化碳、硫化氫、氮?dú)獾入s質(zhì)氣體被吸附劑優(yōu)先吸附，而甲烷等弱吸附性氣體則作為凈化氣排出 。當(dāng)吸附劑吸附飽和后，通過降低壓力（減壓）甚至抽成真空，使被吸附的雜質(zhì)氣體解吸釋放，吸附劑得以再生 。為了保證氣體的連續(xù)處理，變壓吸附裝置通常由多個(gè)吸附塔組成，各個(gè)吸附塔在不同的時(shí)間點(diǎn)分別進(jìn)行吸附、解吸等操作，實(shí)現(xiàn)循環(huán)工作 。變壓吸附法的優(yōu)點(diǎn)是工藝流程簡單，操作靈活，自動化程度高，能適應(yīng)不同流量和組成的沼氣 。它可以在常溫下運(yùn)行，能耗相對較低，且能同時(shí)脫除多種雜質(zhì)氣體 。然而，該方法對設(shè)備的密封性和閥門的可靠性要求極高，設(shè)備投資較大，吸附劑的使用壽命有限，需要定期更換 。

Pressure swing adsorption (PSA) is a technology that achieves gas separation and purification through periodic pressure changes based on the differences in adsorption capacity of adsorbents for different gases. The commonly used adsorbents for this method include molecular sieves, activated carbon, silica gel, etc. During the adsorption process, the feed gas enters the adsorption tower under pressurized conditions, where impurity gases such as carbon dioxide, hydrogen sulfide, and nitrogen are preferentially adsorbed by the adsorbent, while weakly adsorbed gases such as methane are discharged as purified gas. After the adsorbent is saturated with adsorption, the adsorbed impurity gas is desorbed and released by reducing the pressure (depressurization) or even vacuuming, allowing the adsorbent to regenerate. In order to ensure continuous gas treatment, pressure swing adsorption devices usually consist of multiple adsorption towers, each of which performs adsorption, desorption, and other operations at different time points to achieve cyclic operation. The advantages of pressure swing adsorption method are simple process flow, flexible operation, high degree of automation, and the ability to adapt to different flow rates and compositions of biogas. It can operate at room temperature, with relatively low energy consumption, and can simultaneously remove multiple impurity gases. However, this method requires extremely high sealing performance of the equipment and reliability of the valves, requires significant equipment investment, and has a limited service life for the adsorbent, requiring regular replacement.

（三）低溫冷凝法

（3） Low temperature condensation method

低溫冷凝法是利用沼氣中各組分沸點(diǎn)的差異，通過低溫冷卻使二氧化碳等雜質(zhì)氣體液化，從而與甲烷分離的技術(shù) 。由于二氧化碳的沸點(diǎn)（-78.5℃）遠(yuǎn)高于甲烷的沸點(diǎn)（-161.5℃），在低溫條件下，二氧化碳首先被液化成液體，而甲烷則保持氣態(tài) 。為了降低能耗，通常采用回?zé)峒夹g(shù)，將低溫尾氣中的冷量回收利用，用于冷卻原料氣 。低溫冷凝法的優(yōu)點(diǎn)是提純后的沼氣純度高，甲烷回收率也較高，且可以同時(shí)脫除硫化氫和水蒸氣等雜質(zhì) 。但是，該方法需要配備制冷設(shè)備，投資成本高，運(yùn)行能耗大，對設(shè)備的保溫性能和低溫材料要求嚴(yán)格，操作條件較為苛刻 。

Low temperature condensation method is a technology that utilizes the difference in boiling points of various components in biogas to liquefy impurities such as carbon dioxide through low-temperature cooling, thereby separating them from methane. Due to the boiling point of carbon dioxide (-78.5 ℃) being much higher than that of methane (-161.5 ℃), at low temperatures, carbon dioxide is first liquefied into a liquid, while methane remains in a gaseous state. In order to reduce energy consumption, regenerative technology is usually used to recover and utilize the cooling capacity in low-temperature exhaust gas for cooling the feed gas. The advantage of low-temperature condensation method is that the purified biogas has high purity, high methane recovery rate, and can simultaneously remove impurities such as hydrogen sulfide and water vapor. However, this method requires refrigeration equipment, high investment costs, high operating energy consumption, strict requirements for insulation performance and low-temperature materials of the equipment, and harsh operating conditions.

（四）膜分離法

（4） Membrane separation method

膜分離法是利用不同氣體在膜材料中滲透速率的差異來實(shí)現(xiàn)沼氣提純的技術(shù) 。常用的膜材料有高分子材料（如聚酰亞胺、聚二甲基硅氧烷等）、無機(jī)材料（如陶瓷膜、分子篩膜等）以及高分子 - 無機(jī)復(fù)合材料 。在壓力差的驅(qū)動下，沼氣中的二氧化碳、硫化氫等小分子氣體作為快氣，能夠較快地透過膜，而甲烷作為慢氣則透過較慢，從而在膜的兩側(cè)分別得到富含二氧化碳等雜質(zhì)的透過氣和高純度的甲烷透余氣 。為了提高甲烷的純度和回收率，工程上通常采用多級膜分離工藝，將多個(gè)膜組件串聯(lián)或并聯(lián)使用 。膜分離法的優(yōu)點(diǎn)是工藝流程簡單，設(shè)備緊湊，占地面積小，操作方便，可實(shí)現(xiàn)連續(xù)化生產(chǎn) 。它的能耗較低，對環(huán)境友好，且膜組件的模塊化設(shè)計(jì)便于安裝、維護(hù)和擴(kuò)容 。但膜材料的成本較高，膜的使用壽命有限，且容易受到沼氣中雜質(zhì)的污染和損壞，需要對沼氣進(jìn)行嚴(yán)格的預(yù)處理 。

Membrane separation method is a technology that utilizes the difference in permeation rate of different gases in membrane materials to achieve biogas purification. The commonly used membrane materials include polymer materials (such as polyimide, polydimethylsiloxane, etc.), inorganic materials (such as ceramic membranes, molecular sieve membranes, etc.), and polymer inorganic composite materials. Under the driving force of pressure difference, small molecule gases such as carbon dioxide and hydrogen sulfide in biogas can pass through the membrane quickly as fast gases, while methane, as slow gases, can pass through more slowly, resulting in permeate gas rich in impurities such as carbon dioxide and high-purity methane permeate gas on both sides of the membrane. In order to improve the purity and recovery rate of methane, multi-stage membrane separation processes are commonly used in engineering, where multiple membrane modules are connected in series or parallel. The advantages of membrane separation method are simple process flow, compact equipment, small footprint, easy operation, and the ability to achieve continuous production. It has low energy consumption, is environmentally friendly, and the modular design of the membrane components facilitates installation, maintenance, and expansion. However, the cost of membrane materials is high, the service life of membranes is limited, and they are easily contaminated and damaged by impurities in biogas, requiring strict pretreatment of biogas.

三、技術(shù)對比與應(yīng)用選擇

3、 Technical comparison and application selection

不同的沼氣提純技術(shù)在甲烷回收率、提純氣甲烷濃度、運(yùn)行能耗、設(shè)備投資以及技術(shù)成熟度等方面各有優(yōu)劣 。吸收法的甲烷回收率和提純氣甲烷濃度較高，技術(shù)成熟度也高，但運(yùn)行能耗中等；變壓吸附法運(yùn)行能耗低，操作靈活，但設(shè)備投資較高；低溫冷凝法提純效果好，但投資和能耗都很高；膜分離法能耗低、設(shè)備緊湊，但膜材料成本和維護(hù)成本相對較高 。在實(shí)際應(yīng)用中，需要綜合考慮多方面因素來選擇合適的提純技術(shù) 。例如，對于小型沼氣工程，若對投資成本較為敏感，且對沼氣純度要求不是特別高，吸收法中的化學(xué)吸收法可能是一個(gè)不錯(cuò)的選擇，因?yàn)槠浼夹g(shù)成熟，能滿足基本的提純需求 。而對于大型沼氣發(fā)電項(xiàng)目，對沼氣的純度和穩(wěn)定性要求較高，同時(shí)考慮到長期運(yùn)行成本，變壓吸附法或膜分離法可能更為合適 。如果沼氣中二氧化碳含量特別高，且有冷量供應(yīng)或回收條件，低溫冷凝法也可以作為一種備選方案 。此外，還可以根據(jù)實(shí)際情況將多種技術(shù)組合使用，以達(dá)到最佳的提純效果和經(jīng)濟(jì)效益 。

Different biogas purification technologies have their own advantages and disadvantages in terms of methane recovery rate, methane concentration in purified gas, operating energy consumption, equipment investment, and technological maturity. The methane recovery rate and purified gas methane concentration of the absorption method are relatively high, and the technological maturity is also high, but the operating energy consumption is moderate; The pressure swing adsorption method has low energy consumption and flexible operation, but requires high equipment investment; The low-temperature condensation method has good purification effect, but it requires high investment and energy consumption; Membrane separation method has low energy consumption and compact equipment, but the cost of membrane materials and maintenance is relatively high. In practical applications, it is necessary to consider multiple factors comprehensively to select the appropriate purification technology. For example, for small-scale biogas projects that are sensitive to investment costs and do not have particularly high requirements for biogas purity, the chemical absorption method in the absorption process may be a good choice because its technology is mature and can meet basic purification needs. For large-scale biogas power generation projects, high purity and stability of biogas are required, and considering long-term operating costs, pressure swing adsorption or membrane separation methods may be more suitable. If the carbon dioxide content in biogas is particularly high and there are cooling supply or recovery conditions, low-temperature condensation method can also be used as an alternative solution. In addition, multiple technologies can be combined and used according to the actual situation to achieve the best purification effect and economic benefits.

沼氣提純技術(shù)作為提升沼氣能源品質(zhì)的關(guān)鍵環(huán)節(jié)，在可再生能源領(lǐng)域具有廣闊的發(fā)展前景 。隨著技術(shù)的不斷進(jìn)步和創(chuàng)新，未來沼氣提純技術(shù)將朝著更加高效、節(jié)能、環(huán)保和低成本的方向發(fā)展 。例如，新型吸附劑和膜材料的研發(fā)、多技術(shù)耦合集成工藝的優(yōu)化等，都將為沼氣的大規(guī)模、高價(jià)值利用奠定堅(jiān)實(shí)的基礎(chǔ)，助力全球能源轉(zhuǎn)型和可持續(xù)發(fā)展目標(biāo)的實(shí)現(xiàn) 。

Biogas purification technology, as a key link in improving the quality of biogas energy, has broad development prospects in the field of renewable energy. With the continuous advancement and innovation of technology, future biogas purification technology will develop towards higher efficiency, energy conservation, environmental protection, and lower cost. For example, the research and development of new adsorbents and membrane materials, as well as the optimization of multi technology coupling integration processes, will lay a solid foundation for the large-scale and high-value utilization of biogas, and help achieve global energy transformation and sustainable development goals.

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