沼气提纯工艺
Biogas purification process
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 not only depends on the type and relative content of fermentation raw materials, but also changes with 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, 20 ~ 40 ℃) 2% ~ 7%, nitrogen (N2) 0 ~ 2%, a small amount of oxygen (O2), and less than 1% hydrogen (H2) and hydrogen sulfide (H2S).
沼气提纯工艺,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)。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。
Compared with other combustible gases, biogas purification process is characterized by good explosion resistance and clean combustion products. At present, biogas is mainly used in power generation, heat supply and cooking. The CO2 in the biogas reduces the energy density and calorific value of the biogas, and limits the utilization range of the biogas. It is necessary to remove CO2, H2S and water vapor from the biogas to purify the biogas into biological natural gas (BNG). Biological natural gas can be compressed and used in such fields as vehicle fuel (CNG), cogeneration (CHP), incorporation into natural gas pipeline network, fuel cell and chemical raw materials. The use of bio natural gas in automobiles can not only reduce the air pollution caused by exhaust emissions, but also reduce the net greenhouse gas emissions by 75%~200%. Bio natural gas can be mixed into the existing natural gas pipeline network, reducing 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, the purification processes of landfill gas include pressure swing adsorption (PSA), water washing, chemical absorption, membrane separation, selective separation, etc. At present, the more mature and widely used methods in the world are pressure swing adsorption (PSA), chemical absorption (amine purification), and membrane separation.
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