脱硫工艺
Desulfurization process
沼气脱硫是为了避免硫化氢腐蚀设备、硫化氢中毒，以及防止沼气燃烧时，硫化氢被氧化成二氧化硫或三氧化硫造成更大的危害。其脱除方法如下：
The purpose of biogas desulfurization is to avoid hydrogen sulfide corrosion of equipment, hydrogen sulfide poisoning, and to prevent hydrogen sulfide from being oxidized into sulfur dioxide or sulfur trioxides when biogas is burned. The removal method is as follows:
生物降解工艺
Biodegradation process
沼气中的硫可以通过微生物被去除。大部分的硫氧化细菌都属于硫杆菌属，且大多都是自养的，即他们可以利用沼气中的二氧化碳来满足其C营养的需要，主要生成物是单质硫，也有部分硫酸根，在溶液中形成硫酸会造成腐蚀。根据沼气中不同不同的硫化氢含量，可以往沼气中通入2%-6%的空气，以满足生物氧化硫化物的需要。
Sulfur in biogas can be removed by microorganisms. Most of the sulfur oxidizing bacteria belong to the genus Thiobacillus, and most of them are autotrophic, that is, they can use carbon dioxide in biogas to meet their c nutrition needs, the main product is elemental sulfur, but also part of sulfate, which will cause corrosion when sulfuric acid is formed in the solution. According to different content of hydrogen sulfide in biogas, 2% - 6% air can be introduced into biogas to meet the needs of biooxidation of sulfide.
更直接和简单的方法是直接往厌氧消化罐或储气罐中通入一定量的氧或空气并保持一定时间，因为硫杆菌随处可见，所以并不需要接种。消化物的表面可以提供给他们一个微观好氧环境和必须的营养以供它们生长，并会形成菌落上面附着一层黄色的硫。适当的温度、反应时间和空气量可以使硫化氢减少至50ppm。
The most direct and simple method is to directly inject a certain amount of oxygen or air into the anaerobic digestion tank or air storage tank and keep it for a certain period of time. Because Thiobacillus can be seen everywhere, it does not need to be inoculated. The surface of digestive products can provide them with a micro aerobic environment and necessary nutrients for their growth, and will form a layer of yellow sulfur on the colony. Appropriate temperature, reaction time and air quantity can reduce hydrogen sulfide to 50ppm.
对于不同的甲烷含量，沼气在空气中的爆炸范围为6%-12%，所以必须采取一定的安全措施以避免给沼气中通入过量的空气。
For different methane content, the explosion range of biogas in the air is 6% - 12%. Therefore, certain safety measures must be taken to avoid excessive air in the biogas.
生物滤床工艺
Biofilter Process
在大型厌氧消化罐生产沼气中，水洗和生物脱硫常常被联合起来用以去除硫化氢。可以使用废水或者消化罐中的上清液从滤床顶部通入，沼气从底部通入，进入滤床前的沼气中通入4%-6%的空气，滤床为水吸收硫化氢和脱硫微生物的生长都提供了一个充足的接触面。在丹麦，有几家工业污水处理厂和很多农场发酵产沼都在使用此种工艺净化沼气。
In the production of biogas in large-scale anaerobic digesters, water washing and biological desulfurization are often combined to remove hydrogen sulfide. Waste water or supernatant in digestion tank can be used to enter from the top of the filter bed, biogas from the bottom, and 4% - 6% air can be introduced into the biogas before entering the filter bed. The filter bed provides a sufficient contact surface for the water to absorb hydrogen sulfide and the growth of desulfurization microorganisms. In Denmark, several industrial wastewater treatment plants and many farms are using this process to purify biogas.
消化污泥中加氯化铁工艺
Process of adding ferric chloride to digested sludge
直接往消化污泥中加入氯化铁，氯化铁会和硫化氢反应而形成硫化铁盐颗粒。这种方法可以使硫化氢的产生量大为减少，但不能减少到天然气或汽车燃料所要求的水平，需要再进一步处理。这种去除工艺的投资成本较少，只需要一个盛氯化铁溶液的罐子和一个定量泵，主要成本是氯化铁产生的。
Adding ferric chloride directly into the digestion sludge, ferric chloride will react with hydrogen sulfide to form iron sulfide particles. This method can greatly reduce the production of hydrogen sulfide, but it can not be reduced to the level required by natural gas or automobile fuel, and further treatment is needed. The investment cost of this removal process is less. Only a tank and a quantitative pump are needed. The main cost is produced by ferric chloride.
沼气脱硫
Biogas desulfurization
氧化铁吸收工艺
Iron oxide absorption process
硫化氢易于氢氧化铁、氧化铁反应成硫化铁，此反应是略微的吸热反应，温度要求12℃，反应温度需要一定量的水，所以沼气不能太干，但是应该避免生成冷凝水使球状氯化铁粘在一起，减少了反应表面。
Hydrogen sulfide is easy to react with iron hydroxide and iron oxide to form iron sulfide, which is a slight endothermic reaction. The minimum temperature is required to be 12 ℃, and the optimum reaction temperature requires a certain amount of water, so biogas cannot be too dry, but condensate should be avoided to make the spherical iron chloride stick together and reduce the reaction surface.
产生的硫化铁可以被空气氧化再生，生成氧化铁或者氢氧化铁和硫单质，再生过程中会放出大量的热，因此常常会发生自燃。由于在氧化铁的表面上会覆盖一层硫单质，所以在经过很多次重复使用后，就需要更换氧化铁和氢氧化铁。通常，一个装置中配有两个反应床，当一个在进行脱硫的过程中，另一个可以进行再生。
The iron sulfide produced can be oxidized and regenerated by air to form iron oxide or iron hydroxide and sulfur. During the regeneration process, a lot of heat will be released, so spontaneous combustion often occurs. Since the surface of iron oxide will be covered with a layer of sulfur, it is necessary to replace iron oxide and iron hydroxide after repeated use for many times. Generally, one unit is equipped with two reaction beds. When one is in the process of desulfurization, the other can be regenerated.
氧化铁木片吸收工艺
Absorption process of iron oxide wood chips
在木片上覆盖一层氧化铁相对于相同量的氧化铁有更大的比表面积和较低的密度，大约100g的氧化铁木片可以吸收20g的硫化氢。这种方法在美国很流行，价格相对较低，但是必须注意再生氧化铁过滤器的时候温度不能太高。
Covering a layer of iron oxide on the wood chip has a larger specific surface area and a lower density than the same amount of iron oxide. About 100g of iron oxide wood chip can absorb 20g of hydrogen sulfide. This method is very popular in the United States, the price is relatively low, but it must be noted that the temperature of regeneration iron oxide filter cannot be too high.
赤泥颗粒吸收工艺
Red mud particle absorption process
氧化铝生产中产生的废物赤泥可以被做成颗粒状用来吸收硫化氢，它有着更大的比表面积，不足之处就是密度比氧化铁木片大得多。在德国和瑞士大部分的污水处理厂都使用这种方法。
Red mud, a waste produced in alumina production, can be made into granules to absorb hydrogen sulfide. It has a larger specific surface area, but its density is much larger than that of iron oxide wood chips. This method is used in most sewage treatment plants in Germany and Switzerland.
活性炭吸附工艺
Activated carbon adsorption process
在变压吸附系统中硫化氢可以通过用碘化钾浸泡过的活性炭去除，硫化氢被转化为单质硫和水，硫被活性炭吸收，此反应条件为：压力7-8×105Pa，温度50℃到70℃，在压缩气体的过程中很容易使温度到达50℃以上。通常气体停留时间为4-8小时。在连续运行的情况下，系统要包含两个吸附装置，如果硫化氢的浓度在3ppm以上，需要进行再生。
In PSA system, hydrogen sulfide can be removed by activated carbon soaked in potassium iodide. Hydrogen sulfide is converted into elemental sulfur and water, and sulfur is absorbed by activated carbon. The optimum conditions for this reaction are: pressure 7-8 × 105Pa, temperature 50 ℃ - 70 ℃. In the process of compressed gas, it is easy to make the temperature above 50 ℃. Generally, the gas residence time is 4-8 hours. Under the condition of continuous operation, the system shall include two adsorption devices. If the concentration of hydrogen sulfide is above 3ppm, regeneration is required.
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2020-06-10
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