沼氣工程流程沼氣脫硫塔：沼氣作為一種能源,在使用前必須經(jīng)過凈化,使沼氣的質(zhì)量達(dá)到標(biāo)準(zhǔn)要求。《氣工程技術(shù)規(guī)范》NY/T1220.2-2006規(guī)定,沼氣低熱值>18MJ/m3,沼氣中H2S質(zhì)量濃度<20mg/m3,沼氣溫度<35。沼氣凈化主要包括脫硫、脫水和過濾。脫硫:沼氣作為能源利用時(shí),要求H2S的質(zhì)量濃度符合有關(guān)要求,否則對(duì)管道、設(shè)備(如鍋爐、沼氣發(fā)動(dòng)機(jī)等)有腐蝕作用。脫硫方法有干法脫硫、濕法脫硫、水噴淋脫硫等。脫水:水分與沼氣中的H2S反應(yīng)產(chǎn)生氫硫酸,腐蝕管道和設(shè)備;水分凝聚在檢查閥、安全閥、流量計(jì)、調(diào)節(jié)器等設(shè)備的膜片和隔膜上,影響其準(zhǔn)確性;水分能增大管道的氣流阻力;水分能降低沼氣的熱值。脫水方法有冷凍法、吸附法、化學(xué)反應(yīng)法等。過濾:沼氣中含有雜質(zhì),尤其在消化池運(yùn)行初期或消化狀態(tài)不穩(wěn)定時(shí)雜質(zhì)較多。因此,進(jìn)入內(nèi)燃機(jī)前一般應(yīng)采取過濾措施。濾網(wǎng)可設(shè)在沼氣管道上,一些發(fā)動(dòng)機(jī)在設(shè)備內(nèi)部也設(shè)有濾網(wǎng),應(yīng)定期清洗。沼氣脫硫塔脫硫工藝的選擇：干法脫硫干法脫硫中常見的方法為常壓氧化鐵脫硫法。在常溫常壓下沼氣通過脫硫劑床層,沼氣中硫化氫與活性氧化鐵接觸,生成硫化鐵和硫化亞鐵。然后進(jìn)行再生,含有硫化物的脫硫劑與空氣中的氧接觸,當(dāng)有水存在時(shí),鐵的硫化物又轉(zhuǎn)化為氧化鐵和單質(zhì)硫。這種脫硫、再生過程可進(jìn)行多次,直至氧化鐵脫硫劑表面的大部分空隙被硫或其他雜質(zhì)覆蓋而失去活性為止。一旦脫硫劑失去活性,需將脫硫劑從塔內(nèi)卸出,攤曬在空地上,然后均勻地在脫硫劑上噴灑少量稀氨水,利用空氣中的氧,進(jìn)行自然再生。氧化鐵的脫硫反應(yīng)如下:Fe2O.3H2O 3H2S→Fe2S3 6H2OFe2O3.3H2O 3H2S→2FeS S 6H2O氧化鐵的再生反應(yīng)如下：

Biogas engineering process: Biogas desulfurization tower: Biogas, as an energy source, must be purified before use to ensure that its quality meets the standard requirements. According to the Technical Specification for Gas Engineering NY/T1222.2-2006, the low calorific value of biogas is greater than 18MJ/m3, the mass concentration of H2S in biogas is less than 20mg/m3, and the biogas temperature is less than 35. Biogas purification mainly includes desulfurization, dehydration, and filtration. Desulfurization: When biogas is used as an energy source, it is required that the mass concentration of H2S meets relevant requirements, otherwise it will have a corrosive effect on pipelines and equipment (such as boilers, biogas engines, etc.). The desulfurization methods include dry desulfurization, wet desulfurization, water spray desulfurization, etc. Dehydration: The reaction between water and H2S in biogas produces hydrogen sulfate, which corrodes pipelines and equipment; Moisture condenses on the membranes and diaphragms of inspection valves, safety valves, flow meters, regulators, and other equipment, affecting their accuracy; Moisture can increase the airflow resistance of pipelines; Moisture can reduce the calorific value of biogas. Dehydration methods include freezing, adsorption, chemical reaction, etc. Filtration: Biogas contains impurities, especially in the early stages of digestion or when the digestion state is unstable. Therefore, filtering measures should generally be taken before entering the internal combustion engine. The filter can be installed on the biogas pipeline, and some engines also have filters inside the equipment, which should be cleaned regularly. Selection of desulfurization process for biogas desulfurization tower: The common method in dry desulfurization is atmospheric pressure iron oxide desulfurization. At room temperature and pressure, biogas passes through a desulfurizer bed, and hydrogen sulfide in the biogas comes into contact with active iron oxide to produce iron sulfide and ferrous sulfide. Then regeneration is carried out, and the desulfurizer containing sulfides comes into contact with oxygen in the air. When water is present, iron sulfides are converted into iron oxide and elemental sulfur. This desulfurization and regeneration process can be carried out multiple times until most of the voids on the surface of the iron oxide desulfurizer are covered by sulfur or other impurities and lose their activity. Once the desulfurizer loses its activity, it needs to be unloaded from the tower, spread on the open space, and then evenly sprayed with a small amount of dilute ammonia water on top of the desulfurizer, using oxygen in the air for natural regeneration. The desulfurization reaction of iron oxide is as follows: Fe2O.3H2O 3H2S → Fe2S3 6H2OFe2O3.3H2O 3H2S → 2FeS S 6H2O. The regeneration reaction of iron oxide is as follows:

脫硫劑一次裝入后,平時(shí)不需維護(hù),當(dāng)出口沼氣的硫含量超標(biāo)時(shí),應(yīng)更換脫硫劑。更換出來的脫硫劑可以再生,再生的次數(shù)與脫硫劑的品質(zhì)有關(guān),一般可以再生2~3次。濕法脫硫濕法脫硫有直接氧化法、化學(xué)吸收法、物理吸收法。目前國內(nèi)常用的主要是直接氧化法脫硫,將硫化氫在液相中氧化成單質(zhì)硫,流程比較簡單,可以直接得到單質(zhì)硫。這種方法主要用于處理硫化氫濃度較低而二氧化碳濃度較高的氣體。這種脫硫方法的缺點(diǎn)是溶液吸收硫化氫的硫容量低,因此溶液循環(huán)量大、回收硫的處理量大。適用于脫硫量<10t/d的氣體。濕法脫硫反應(yīng)如下:

After the desulfurizer is loaded once, it does not need to be maintained normally. When the sulfur content of the exported biogas exceeds the standard, the desulfurizer should be replaced. The replaced desulfurizer can be regenerated, and the number of regenerations depends on the quality of the desulfurizer. Generally, it can be regenerated 2-3 times. Wet desulfurization includes direct oxidation method, chemical absorption method, and physical absorption method. At present, the commonly used method in China is direct oxidation desulfurization, which oxidizes hydrogen sulfide into elemental sulfur in the liquid phase. The process is relatively simple and can directly obtain elemental sulfur. This method is mainly used to process gases with low hydrogen sulfide concentration and high carbon dioxide concentration. The disadvantage of this desulfurization method is that the sulfur capacity of the solution to absorb hydrogen sulfide is low, resulting in a large circulation volume of the solution and a large processing capacity for sulfur recovery. Suitable for gases with desulfurization capacity<10t/d. The wet desulfurization reaction is as follows:

原料氣進(jìn)入脫硫塔底部,通過塔內(nèi)填料層時(shí),與塔頂噴淋而下的脫硫液(堿液)逆流接觸,堿液吸收硫化氫生成NaHS,塔頂出來的凈化氣中硫化氫質(zhì)量濃度下降到20mg/m3,脫硫氣體由塔頂流出,經(jīng)氣液分離后進(jìn)入下一工序。吸收了硫化氫的溶液經(jīng)循環(huán)泵送入再生槽進(jìn)行再生,再生后溶液經(jīng)液位調(diào)節(jié)器進(jìn)入脫硫塔頂部循環(huán)使用。干濕結(jié)合法脫硫干濕結(jié)合法脫硫效率高,管理一體化,綜合運(yùn)行費(fèi)用低,保養(yǎng)維護(hù)簡單,設(shè)備壽命長、運(yùn)行可靠,脫硫劑價(jià)格低廉,可將脫硫脫水置于一體,設(shè)備可長期連續(xù)進(jìn)行脫硫、脫水。用pH值來控制一級(jí)脫硫效率。采用干法脫硫進(jìn)行二級(jí)脫硫,使脫硫率提高到99.8%。與干法脫硫相比,干濕結(jié)合法脫硫運(yùn)行費(fèi)用低,但因設(shè)備復(fù)雜,需要較高的運(yùn)行維護(hù)操作水平。

When the raw gas enters the bottom of the desulfurization tower and passes through the packing layer inside the tower, it comes into countercurrent contact with the desulfurization solution (alkali solution) sprayed from the top of the tower. The alkali solution absorbs hydrogen sulfide to generate NaHS. The mass concentration of hydrogen sulfide in the purified gas coming out of the tower top drops to 20mg/m3. The desulfurization gas flows out of the tower top and enters the next process after gas-liquid separation. The solution that has absorbed hydrogen sulfide is pumped into the regeneration tank through a circulation pump for regeneration. After regeneration, the solution enters the top of the desulfurization tower through a liquid level regulator for circulation. The wet dry combined desulfurization method has high desulfurization efficiency, integrated management, low comprehensive operating costs, simple maintenance, long equipment life, reliable operation, low desulfurizer price, and can integrate desulfurization and dehydration into one. The equipment can perform desulfurization and dehydration continuously for a long time. Use pH value to control the efficiency of primary desulfurization. Using dry desulfurization for secondary desulfurization, the desulfurization rate was increased to 99.8%. Compared with dry desulfurization, wet dry combined desulfurization has lower operating costs, but due to the complexity of the equipment, it requires a higher level of operation and maintenance.

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