The main components of biogas are CH4 and CO2. The high-purity methane gas obtained by separating CO2 from the mixture is called biological natural gas. Biogas can be directly used as an alternative fuel for Petrochemical Natural gas. The development of biogas has become an important direction to increase the supply of natural gas. The increase of human demand for natural gas promotes the development of biological natural gas technology.

沼气提纯生物天然气可高值化利用沼气，有效减少沼气工程因沼气利用不充分而排空造成的温室效应，具有环保和能源双重效益。

Biogas purification of biological natural gas can make high-value use of biogas, effectively reduce the greenhouse effect caused by the emptying of biogas project due to insufficient utilization of biogas, and has the dual benefits of environmental protection and energy.

1、沼气特性

1. Biogas characteristics

沼气是一种混合气体，其组成不仅取决于发酵原料的种类及其相对含量，而且随发酵条件及发酵阶段的不同而变化。当沼气厌氧反应器处于正常稳定发酵阶段时，沼气的体积组成大致为：甲烷（CH4）50%～75%，二氧化碳（CO2）25%～45%，水（H2O，20～40℃下）2%～7%，氮气（N2）0～2%，少量的氧气（O2），以及少于1%的氢气（H2）和硫化氢（H2S）。

Biogas is a kind of mixed gas. Its composition depends not only on the type and relative content of fermentation raw materials, but also on the different fermentation conditions and fermentation stages. When the biogas anaerobic reactor is in the normal and stable fermentation stage, the volume composition of biogas is roughly: methane (CH4) 50% ~ 75%, carbon dioxide (CO2) 25% ~ 45%, water (H2O, at 20 ~ 40 ℃) 2% ~ 7%, nitrogen (N2) 0 ~ 2%, a small amount of oxygen (O2), and less than 1% hydrogen (H2) and hydrogen sulfide (H2S).

与其它可燃气体相比，沼气具有抗爆性良好和燃烧产物清洁等特点。目前，沼气主要应用在发电、供热和炊事方面，沼气中的CO2降低了沼气的能量密度和热值，限制了沼气的利用范围，要去除沼气中的CO2、H2S和水蒸气等将沼气提纯为生物天然气（BNG）。

Compared with other combustible gases, biogas has the characteristics of good explosion resistance and clean combustion products. At present, biogas is mainly used in power generation, heating and cooking. The CO2 in biogas reduces the energy density and calorific value of biogas and limits the utilization range of biogas. It is necessary to remove CO2, H2S and water vapor in biogas and purify biogas into biological natural gas (bng).

生物天然气可压缩用于车用燃料（CNG）、热电联产（CHP）、并入天然气管网、燃料电池以及化工原料等领域。汽车使用生物天然气不仅可以降低尾气排放造成的空气污染，而且温室气体的净排放量减少75%～200%，生物天然气可混入现有的天然气管网，降低对石化能源的依赖。

Biological natural gas can be compressed for vehicle fuel (CNG), cogeneration (CHP), integration into natural gas pipeline network, fuel cell and chemical raw materials. The use of biological natural gas in automobiles can not only reduce the air pollution caused by exhaust emissions, but also reduce the net emission of greenhouse gases by 75% ~ 200%. Biological natural gas can be mixed into the existing natural gas pipeline network to reduce the dependence on petrochemical energy.

2、沼气提纯技术

2. Biogas purification technology

目前填埋气提纯工艺有变压吸附法（PSA）、水洗法、化学吸收法、膜分离法、选择分离法等，在目前世界范围内工艺较为成熟、应用相对较多的方法是变压吸附法（PSA）、化学吸收法（胺法净化）、膜分离法。

At present, landfill gas purification processes include pressure swing adsorption (PSA), water washing, chemical absorption, membrane separation and selective separation. At present, the more mature and widely used methods in the world are pressure swing adsorption (PSA), chemical absorption (amine purification) and membrane separation.