沼气工程流程沼气脱硫塔：沼气作为一种能源,在使用前必须经过净化,使沼气的质量达到标准要求。《气工程技术规范》NY/T1220.2-2006规定,沼气低热值>18MJ/m3,沼气中H2S质量浓度<20mg/m3,沼气温度<35。沼气净化主要包括脱硫、脱水和过滤。脱硫:沼气作为能源利用时,要求H2S的质量浓度符合有关要求,否则对管道、设备(如锅炉、沼气发动机等)有腐蚀作用。脱硫方法有干法脱硫、湿法脱硫、水喷淋脱硫等。脱水:水分与沼气中的H2S反应产生氢硫酸,腐蚀管道和设备;水分凝聚在检查阀、阀、流量计、调节器等设备的膜片和隔膜上,影响其准确性;水分能增大管道的气流阻力;水分能降低沼气的热值。脱水方法有冷冻法、吸附法、化学反应法等。过滤:沼气中含有杂质,尤其在消化池运行初期或消化状态不稳定时杂质较多。因此,进入内燃机前一般应采取过滤措施。滤网可设在沼气管道上,一些发动机在设备内部也设有滤网,应定期清洗。沼气脱硫塔脱硫工艺的选择：干法脱硫干法脱硫中常见的方法为常压氧化铁脱硫法。在常温常压下沼气通过脱硫剂床层,沼气中硫化氢与活性氧化铁接触,生成硫化铁和硫化亚铁。然后进行再生,含有硫化物的脱硫剂与空气中的氧接触,当有水存在时,铁的硫化物又转化为氧化铁和单质硫。这种脱硫、再生过程可进行多次,直氧化铁脱硫剂表面的大部分空隙被硫或其他杂质覆盖而失去活性为止。一旦脱硫剂失去活性,需将脱硫剂从塔内卸出,摊晒在空地上,然后均匀地在脱硫剂上喷洒少量稀氨水,利用空气中的氧,进行自然再生。氧化铁的脱硫反应如下:Fe2O.3H2O 3H2S→Fe2S3 6H2OFe2O3.3H2O 3H2S→2FeS S 6H2O氧化铁的再生反应如下：

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:

脱硫剂一次装入后,平时不需维护,当出口沼气的硫含量超标时,应更换脱硫剂。更换出来的脱硫剂可以再生,再生的次数与脱硫剂的品质有关,一般可以再生2~3次。湿法脱硫湿法脱硫有直接氧化法、化学吸收法、物理吸收法。目前国内常用的主要是直接氧化法脱硫,将硫化氢在液相中氧化成单质硫,流程比较简单,可以直接得到单质硫。这种方法主要用于处理硫化氢浓度较低而二氧化碳浓度较高的气体。这种脱硫方法的缺点是溶液吸收硫化氢的硫容量低,因此溶液循环量大、回收硫的处理量大。适用于脱硫量<10t/d的气体。湿法脱硫反应如下:

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:

原料气进入脱硫塔底部,通过塔内填料层时,与塔顶喷淋而下的脱硫液(碱液)逆流接触,碱液吸收硫化氢生成NaHS,塔顶出来的净化气中硫化氢质量浓度下降到20mg/m3,脱硫气体由塔顶流出,经气液分离后进入下一工序。吸收了硫化氢的溶液经循环泵送入再生槽进行再生,再生后溶液经液位调节器进入脱硫塔顶部循环使用。干湿结合法脱硫干湿结合法脱硫效率高,管理一体化,综合运行费用低,保养维护简单,设备寿命长、运行可靠,脱硫剂低廉,可将脱硫脱水置于一体,设备可长期连续进行脱硫、脱水。用pH值来控制一级脱硫效率。采用干法脱硫进行二级脱硫,使脱硫率提高到99.8%。与干法脱硫相比,干湿结合法脱硫运行费用低,但因设备复杂,需要较高的运行维护操作水平。

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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