脫硫工藝
Desulfurization process
沼氣脫硫是為了避免硫化氫腐蝕設備、硫化氫中毒，以及防止沼氣燃燒時，硫化氫被氧化成二氧化硫或三氧化硫造成更大的危害。其脫除方法如下：
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:
生物降解工藝
Biodegradation process
沼氣中的硫可以通過微生物被去除。大部分的硫氧化細菌都屬于硫桿菌屬，且大多都是自養的，即他們可以利用沼氣中的二氧化碳來滿足其C營養的需要，主要生成物是單質硫，也有部分硫酸根，在溶液中形成硫酸會造成腐蝕。根據沼氣中不同不同的硫化氫含量，可以往沼氣中通入2%-6%的空氣，以滿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.
更直接和簡單的方法是直接往厭氧消化罐或儲氣罐中通入一定量的氧或空氣并保持一定時間，因為硫桿菌隨處可見，所以并不需要接種。消化物的表面可以提供給他們一個微觀好氧環境和必須的營養以供它們生長，并會形成菌落上面附著一層黃色的硫。適當的溫度、反應時間和空氣量可以使硫化氫減少至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.
對于不同的甲烷含量，沼氣在空氣中的爆炸范圍為6%-12%，所以必須采取一定的安全措施以避免給沼氣中通入過量的空氣。
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.
生物濾床工藝
Biofilter Process
在大型厭氧消化罐生產沼氣中，水洗和生物脫硫常常被聯合起來用以去除硫化氫。可以使用廢水或者消化罐中的上清液從濾床頂部通入，沼氣從底部通入，進入濾床前的沼氣中通入4%-6%的空氣，濾床為水吸收硫化氫和脫硫微生物的生長都提供了一個充足的接觸面。在丹麥，有幾家工業污水處理廠和很多農場發酵產沼都在使用此種工藝凈化沼氣。
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.
消化污泥中加氯化鐵工藝
Process of adding ferric chloride to digested sludge
直接往消化污泥中加入氯化鐵，氯化鐵會和硫化氫反應而形成硫化鐵鹽顆粒。這種方法可以使硫化氫的產生量大為減少，但不能減少到天然氣或汽車燃料所要求的水平，需要再進一步處理。這種去除工藝的投資成本較少，只需要一個盛氯化鐵溶液的罐子和一個定量泵，主要成本是氯化鐵產生的。
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.
沼氣脫硫
Biogas desulfurization
氧化鐵吸收工藝
Iron oxide absorption process
硫化氫易于氫氧化鐵、氧化鐵反應成硫化鐵，此反應是略微的吸熱反應，溫度要求12℃，反應溫度需要一定量的水，所以沼氣不能太干，但是應該避免生成冷凝水使球狀氯化鐵粘在一起，減少了反應表面。
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.
產生的硫化鐵可以被空氣氧化再生，生成氧化鐵或者氫氧化鐵和硫單質，再生過程中會放出大量的熱，因此常常會發生自燃。由于在氧化鐵的表面上會覆蓋一層硫單質，所以在經過很多次重復使用后，就需要更換氧化鐵和氫氧化鐵。通常，一個裝置中配有兩個反應床，當一個在進行脫硫的過程中，另一個可以進行再生。
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.
氧化鐵木片吸收工藝
Absorption process of iron oxide wood chips
在木片上覆蓋一層氧化鐵相對于相同量的氧化鐵有更大的比表面積和較低的密度，大約100g的氧化鐵木片可以吸收20g的硫化氫。這種方法在美國很流行，價格相對較低，但是必須注意再生氧化鐵過濾器的時候溫度不能太高。
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.
赤泥顆粒吸收工藝
Red mud particle absorption process
氧化鋁生產中產生的廢物赤泥可以被做成顆粒狀用來吸收硫化氫，它有著更大的比表面積，不足之處就是密度比氧化鐵木片大得多。在德國和瑞士大部分的污水處理廠都使用這種方法。
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.
活性炭吸附工藝
Activated carbon adsorption process
在變壓吸附系統中硫化氫可以通過用碘化鉀浸泡過的活性炭去除，硫化氫被轉化為單質硫和水，硫被活性炭吸收，此反應條件為：壓力7-8×105Pa，溫度50℃到70℃，在壓縮氣體的過程中很容易使溫度到達50℃以上。通常氣體停留時間為4-8小時。在連續運行的情況下，系統要包含兩個吸附裝置，如果硫化氫的濃度在3ppm以上，需要進行再生。
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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