在全球能源转型的浪潮中，沼气作为一种源自生物质的可再生能源，正逐渐崭露头角。它通常由有机废弃物，如畜禽粪便、农作物秸秆、工业有机废水以及城市生活垃圾等，在厌氧环境下经微生物发酵产生。沼气的主要成分是甲烷和二氧化碳，其中甲烷含量一般在 50% - 70%，其余为二氧化碳以及少量的硫化氢、氮气、水蒸气等杂质 。然而，这样的原始沼气在能源利用的道路上还存在诸多限制，沼气提纯技术应运而生，成为提升沼气能源价值的关键所在。

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、沼气提纯的必要性

1、 The necessity of biogas purification

原始沼气直接利用存在诸多弊端。从能源效率角度看，较低的甲烷含量意味着单位体积沼气蕴含的能量有限，无法满足一些对能源品质要求较高的应用场景，例如作为优质的城市燃气或用于高效的发电项目 。在燃烧过程中，二氧化碳等杂质的存在不仅降低了沼气的热值，还会增加燃烧设备的负担，降低能源转化效率 。从设备维护层面来说，沼气中的硫化氢是一种具有强腐蚀性的气体，它会与水结合形成氢硫酸，对沼气输送管道、储存设备以及各类燃烧器具造成严重腐蚀，大幅缩短设备使用寿命，增加维护成本和更换频率 。此外，硫化氢在燃烧时会转化为二氧化硫排放到大气中，成为酸雨形成的重要因素之一，对环境造成严重污染 。水蒸气的存在则可能导致管道积水、冻胀等问题，影响沼气的稳定输送 。因此，为了提高沼气的能源利用效率，保护设备安全，减少环境污染，对沼气进行提纯处理势在必行。

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、主流沼气提纯技术详解

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剂与沼气中二氧化碳等杂质的物理或化学作用来实现分离提纯的方法。根据吸收原理的不同，又可细分为物理吸收和化学吸收 。

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剂对不同气体的溶解度差异来实现分离 。常见的物理吸收剂有甲醇、碳酸丙烯酯等 。在加压条件下，沼气中的二氧化碳等易溶气体被吸收剂吸收，而甲烷则几乎不溶，从而实现分离 。当减压时，吸收剂中的二氧化碳等气体解吸释放，吸收剂得以再生循环使用 。例如，在低温甲醇洗工艺中，甲醇在低温高压下对二氧化碳、硫化氢等酸性气体有良好的溶解性，能高效脱除沼气中的杂质 。物理吸收法的优点是吸收剂一般不与被吸收气体发生化学反应，能耗相对较低，且对设备材质要求相对不高 。但它对设备的密封性要求较高，操作压力通常较高，设备投资较大 。

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.

化学吸收：化学吸收法借助吸收剂与二氧化碳等杂质发生化学反应来实现吸收 。常用的化学吸收剂有醇胺类溶液（如乙醇胺、二乙醇胺等）、碱性盐溶液（如碳酸钾溶液）等 。以醇胺吸收二氧化碳为例，在吸收塔内，醇胺与二氧化碳发生化学反应生成氨基甲酸盐，从而将二氧化碳从沼气中脱除 。在再生塔内，通过加热使氨基甲酸盐分解，释放出二氧化碳，醇胺得以再生 。化学吸收法的脱硫效率高，对二氧化碳的脱除较为彻底，能使沼气中的甲烷含量大幅提高 。不过，由于化学反应需要消耗一定的能量来实现吸收剂的再生，所以能耗相对较高，且吸收剂在使用过程中可能会发生降解，需要定期补充和更换 。

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）变压吸附法

（2） Pressure swing adsorption method

变压吸附法（PSA）是基于吸附剂对不同气体吸附能力的差异，通过周期性的压力变化来实现气体分离提纯的技术 。该方法常用的吸附剂有分子筛、活性炭、硅胶等 。在吸附过程中，原料气在加压条件下进入吸附塔，其中二氧化碳、硫化氢、氮气等杂质气体被吸附剂优先吸附，而甲烷等弱吸附性气体则作为净化气排出 。当吸附剂吸附饱和后，通过降低压力（减压）甚至抽成真空，使被吸附的杂质气体解吸释放，吸附剂得以再生 。为了保证气体的连续处理，变压吸附装置通常由多个吸附塔组成，各个吸附塔在不同的时间点分别进行吸附、解吸等操作，实现循环工作 。变压吸附法的优点是工艺流程简单，操作灵活，自动化程度高，能适应不同流量和组成的沼气 。它可以在常温下运行，能耗相对较低，且能同时脱除多种杂质气体 。然而，该方法对设备的密封性和阀门的可靠性要求极高，设备投资较大，吸附剂的使用寿命有限，需要定期更换 。

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）低温冷凝法

（3） Low temperature condensation method

低温冷凝法是利用沼气中各组分沸点的差异，通过低温冷却使二氧化碳等杂质气体液化，从而与甲烷分离的技术 。由于二氧化碳的沸点（-78.5℃）远高于甲烷的沸点（-161.5℃），在低温条件下，二氧化碳首先被液化成液体，而甲烷则保持气态 。为了降低能耗，通常采用回热技术，将低温尾气中的冷量回收利用，用于冷却原料气 。低温冷凝法的优点是提纯后的沼气纯度高，甲烷回收率也较高，且可以同时脱除硫化氢和水蒸气等杂质 。但是，该方法需要配备制冷设备，投资成本高，运行能耗大，对设备的保温性能和低温材料要求严格，操作条件较为苛刻 。

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）膜分离法

（4） Membrane separation method

膜分离法是利用不同气体在膜材料中渗透速率的差异来实现沼气提纯的技术 。常用的膜材料有高分子材料（如聚酰亚胺、聚二甲基硅氧烷等）、无机材料（如陶瓷膜、分子筛膜等）以及高分子 - 无机复合材料 。在压力差的驱动下，沼气中的二氧化碳、硫化氢等小分子气体作为快气，能够较快地透过膜，而甲烷作为慢气则透过较慢，从而在膜的两侧分别得到富含二氧化碳等杂质的透过气和高纯度的甲烷透余气 。为了提高甲烷的纯度和回收率，工程上通常采用多级膜分离工艺，将多个膜组件串联或并联使用 。膜分离法的优点是工艺流程简单，设备紧凑，占地面积小，操作方便，可实现连续化生产 。它的能耗较低，对环境友好，且膜组件的模块化设计便于安装、维护和扩容 。但膜材料的成本较高，膜的使用寿命有限，且容易受到沼气中杂质的污染和损坏，需要对沼气进行严格的预处理 。

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、技术对比与应用选择

3、 Technical comparison and application selection

不同的沼气提纯技术在甲烷回收率、提纯气甲烷浓度、运行能耗、设备投资以及技术成熟度等方面各有优劣 。吸收法的甲烷回收率和提纯气甲烷浓度较高，技术成熟度也高，但运行能耗中等；变压吸附法运行能耗低，操作灵活，但设备投资较高；低温冷凝法提纯效果好，但投资和能耗都很高；膜分离法能耗低、设备紧凑，但膜材料成本和维护成本相对较高 。在实际应用中，需要综合考虑多方面因素来选择合适的提纯技术 。例如，对于小型沼气工程，若对投资成本较为敏感，且对沼气纯度要求不是特别高，吸收法中的化学吸收法可能是一个不错的选择，因为其技术成熟，能满足基本的提纯需求 。而对于大型沼气发电项目，对沼气的纯度和稳定性要求较高，同时考虑到长期运行成本，变压吸附法或膜分离法可能更为合适 。如果沼气中二氧化碳含量特别高，且有冷量供应或回收条件，低温冷凝法也可以作为一种备选方案 。此外，还可以根据实际情况将多种技术组合使用，以达到最佳的提纯效果和经济效益 。

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.

沼气提纯技术作为提升沼气能源品质的关键环节，在可再生能源领域具有广阔的发展前景 。随着技术的不断进步和创新，未来沼气提纯技术将朝着更加高效、节能、环保和低成本的方向发展 。例如，新型吸附剂和膜材料的研发、多技术耦合集成工艺的优化等，都将为沼气的大规模、高价值利用奠定坚实的基础，助力全球能源转型和可持续发展目标的实现 。

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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