沼氣的主要成分是CH4和CO2,將CO2從混合氣中分離得到的高純度甲烷氣被稱為生物天然氣。生物天然氣可以直接作為石化天然氣的替代燃料,發(fā)展沼氣已成為增加天然氣供應量的一個重要方向。人類對天然氣需求量的增加推動了生物天然氣技術的發(fā)展。
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.
沼氣提純生物天然氣可高值化利用沼氣,有效減少沼氣工程因沼氣利用不充分而排空造成的溫室效應,具有環(huán)保和能源雙重效益。
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、沼氣特性
1. Biogas characteristics
沼氣是一種混合氣體,其組成不僅取決于發(fā)酵原料的種類及其相對含量,而且隨發(fā)酵條件及發(fā)酵階段的不同而變化。當沼氣厭氧反應器處于正常穩(wěn)定發(fā)酵階段時,沼氣的體積組成大致為:甲烷(CH4)50%~75%,二氧化碳(CO2)25%~45%,水(H2O,20~40℃下)2%~7%,氮氣(N2)0~2%,少量的氧氣(O2),以及少于1%的氫氣(H2)和硫化氫(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).
與其它可燃氣體相比,沼氣具有抗爆性良好和燃燒產物清潔等特點。目前,沼氣主要應用在發(fā)電、供熱和炊事方面,沼氣中的CO2降低了沼氣的能量密度和熱值,限制了沼氣的利用范圍,要去除沼氣中的CO2、H2S和水蒸氣等將沼氣提純?yōu)樯锾烊粴猓˙NG)。
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).
生物天然氣可壓縮用于車用燃料(CNG)、熱電聯(lián)產(CHP)、并入天然氣管網、燃料電池以及化工原料等領域。汽車使用生物天然氣不僅可以降低尾氣排放造成的空氣污染,而且溫室氣體的凈排放量減少75%~200%,生物天然氣可混入現有的天然氣管網,降低對石化能源的依賴。
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、沼氣提純技術
2. Biogas purification technology
目前填埋氣提純工藝有變壓吸附法(PSA)、水洗法、化學吸收法、膜分離法、選擇分離法等,在目前世界范圍內工藝較為成熟、應用相對較多的方法是變壓吸附法(PSA)、化學吸收法(胺法凈化)、膜分離法。
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.