沼氣的凈化一般應包括沼氣的脫水、脫硫及脫二氧化碳。沼氣中的水分與硫化氫共同作用, 能加速管道及閥門、流量計的腐蝕,硫化氫還對大氣造成污染,所以要脫除。
The purification of biogas generally includes the dehydration, desulfurization and CO2 removal of biogas. The moisture in biogas and hydrogen sulfide work together to accelerate the corrosion of pipelines, valves and flowmeters. Hydrogen sulfide also pollutes the atmosphere, so it should be removed.
沼氣如何進行脫水:從發(fā)酵裝置出來的沼氣含有飽和水蒸氣,可用3種方法將其去除。
How to dehydrate biogas: the biogas from the fermentation unit contains saturated water vapor, which can be removed by three methods.
(1)冷分離法。是利用壓力能變化引起溫度變化,使水蒸氣從氣相中冷凝下來的方法。常用 的有兩種流程:A.節(jié)流膨脹冷脫水法。一般用于高壓燃氣,經(jīng)過節(jié)流膨脹或低溫分離,使 部分水冷凝下來。B.加壓后冷卻法。如凈化氣在08MPa壓力下的冷卻脫水。
(1) Cold separation method. It is a method of condensing water vapor from the gas phase by using pressure energy change to cause temperature change. There are two commonly used processes: A. throttling expansion cold dehydration method. It is generally used for high-pressure gas. After throttling expansion or low-temperature separation, part of the water is condensed. B. Cooling method after pressurization. Such as cooling and dehydration of purified gas at a pressure of 0.8MPa.
(2)溶劑吸收法。屬于這類脫水溶劑的有氯化鈣、氯化鋰及甘醇類。
(2) Solvent absorption method. Calcium chloride, lithium chloride and glycol belong to this type of dehydration solvent.
(3)固體物理吸水法。吸附是在固體表面力作用下產(chǎn)生的,根據(jù)表面力的性質(zhì)分為化學吸附( 脫水后不能再生)和物理吸附(脫水后可再生)。
(3) Solid physical water absorption method. Adsorption is generated under the action of solid surface force. According to the nature of surface force, it can be divided into chemical adsorption (can not be regenerated after dehydration) and physical adsorption (can be regenerated after dehydration).
沼氣的脫硫:沼氣中的有害物質(zhì)主要是硫化氫,它危害人體健康,對管道閥門及應用設備有較強的腐蝕作 用。目前,國內(nèi)大部分用戶均未安裝脫硫器,已造成嚴重后果。為減輕硫化氫對灶具及配套 用具的腐蝕損害,延長設備使用壽命,保證人身健康,必須安裝脫硫器。脫硫原理:在常溫下含有H2S的沼氣通過脫硫劑床層,沼氣中H2S與活性物質(zhì)(如氧化鐵)接觸,生成 硫化鐵和亞硫化鐵,然后含有硫化物的脫硫劑與空氣中的氧接觸,當有水存在時,鐵的硫化 物又轉(zhuǎn)化為氧化鐵和單體硫。這種脫硫和再生過程可循環(huán)進行多次,直氧化鐵脫硫劑表面 大部分被硫或其他雜質(zhì)覆蓋而失去活性為止。脫硫方法:脫硫的方法有濕法脫硫和干法脫硫兩種。干法脫硫具有工藝簡單,成熟可靠、造價低等優(yōu)點 ,并能達到較好的交貨程度。目前家用沼氣脫硫基本上采用這種方法。干法脫硫劑有活性炭、氧化鋅、氧化錳及氧化鐵等,從運轉(zhuǎn)時間、使用溫度、公害、等 綜合考慮,目前采用多的脫硫劑是氧化鐵。
Desulfurization of biogas: the harmful substance in biogas is mainly hydrogen sulfide, which is harmful to human health and has a strong corrosive effect on pipeline valves and application equipment. At present, most domestic users have not installed desulfurizer, which has caused serious consequences. In order to reduce the corrosion damage of hydrogen sulfide to the cookers and supporting appliances, extend the service life of the equipment, and ensure personal health, the desulfurizer must be installed. Desulfurization principle: under normal temperature, the biogas containing H 2S passes through the desulfurizer bed. The H 2S in the biogas contacts with the active material (such as iron oxide) to generate iron sulfide and iron sulfite. Then the desulfurizer containing sulfide contacts with the oxygen in the air. When there is water, the iron sulfide is converted into iron oxide and monomer sulfur. This desulfurization and regeneration process can be repeated many times until the surface of the iron oxide desulfurizer is covered with sulfur or other impurities and becomes inactive. Desulfurization method: there are two desulfurization methods: wet desulfurization and dry desulfurization. Dry desulfurization has the advantages of simple process, mature and reliable, low cost, and can reach a good delivery level. At present, domestic biogas desulfurization basically adopts this method. The dry desulfurizing agents include activated carbon, zinc oxide, manganese oxide and iron oxide. Considering the operating time, operating temperature, public hazards and price, the most commonly used desulfurizing agent is iron oxide.
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