目前國內外常用的沼氣脫硫的工藝有濕式催化氧化法脫硫、堿式生物法脫硫、酸式生物法脫硫、濕式絡合鐵催化氧化法和活性碳系或氧化鐵系干法精脫硫等。 下面就不同工藝進行分別介紹并進行比較。

　　At present, the commonly used biogas desulfurization processes at home and abroad include wet catalytic oxidation desulfurization, alkaline biological desulfurization, acid based biological desulfurization, wet chelated iron catalytic oxidation, and activated carbon or iron oxide based dry desulfurization. Below, different processes will be introduced and compared separately.

　　1、不同脫硫工藝介紹

　　1. Introduction to different desulfurization processes

　　（1）干法脫硫工藝?干法脫硫是通過固體有機脫硫劑將氣態硫化物轉化為固體硫化物，該法特點是設備制造簡單、操作簡便，凈化度較高，脫硫劑可再生，但價值很低，達到飽和硫容后就須更換。通常用于氣量小、硫化氫含量低、需要深度脫硫的氣體脫硫，且對氣溫和水分有一定要求的場景。脫硫劑通常分為活性碳系、氧化鐵系、鋅錳系幾類。脫硫塔多為固定床層，多塔串聯使用。用過的脫硫劑通過摻煤燃燒或廠家回收處理再利用。 

　　(1) Dry desulfurization process? Dry desulfurization is the process of converting gaseous sulfides into solid sulfides using solid organic desulfurizers. The characteristics of this method include simple equipment manufacturing, easy operation, high purification degree, and renewable desulfurizers. However, its value is low, and it needs to be replaced after reaching saturation sulfur capacity. Usually used for gas desulfurization with low gas volume, low hydrogen sulfide content, requiring deep desulfurization, and having certain requirements for temperature and moisture. Desulfurizers are usually divided into several categories: activated carbon based, iron oxide based, and zinc manganese based. Most desulfurization towers have a fixed bed and are used in series with multiple towers. Used desulfurizers can be burned with coal or recycled by manufacturers for reuse.?

　　（2）濕式催化氧化法脫硫工藝?濕式催化氧化法脫硫基本原理可概括為堿液吸收、氧化再生和硫的分離等三個過程。基礎脫硫溶液的溶質及溶劑分別為純堿、催化劑和軟水。沼氣中的H2S通過堿性溶液吸收并與OH-反應生成HS-和H2O，同時HS-自由擴散至堿性溶液中液相催化劑表面，發生氧化還原反應，催化劑被還原，HS-被氧化形成單質S。催化劑在有氧供給的條件下，催化劑得以恢復再生并可循環重復使用。簡而言之，利用堿性脫硫溶液吸收硫化氫形成NaHS，NaHS在催化劑的作用下氧化反應形成單質硫，形成單質硫后從脫硫液中分離出來。?

　　(2) Wet catalytic oxidation desulfurization process? The basic principle of wet catalytic oxidation desulfurization can be summarized as three processes: alkali absorption, oxidation regeneration, and sulfur separation. The solute and solvent of the basic desulfurization solution are soda ash, catalyst, and soft water, respectively. H2S in biogas is absorbed by alkaline solution and reacts with OH - to generate HS - and H2O. At the same time, HS - diffuses freely to the surface of the liquid-phase catalyst in the alkaline solution, undergoing oxidation-reduction reaction. The catalyst is reduced, and HS - is oxidized to form elemental S. Under aerobic supply conditions, the catalyst can be restored and regenerated, and can be recycled and reused. In short, using alkaline desulfurization solution to absorb hydrogen sulfide to form NaHS, NaHS undergoes oxidation reaction under the action of catalyst to form elemental sulfur, which is then separated from the desulfurization solution.?

　　具體化學反應如下：?H2S+Na2CO3=NaHS+NaHCO3NaHS+1/2O2=NaOH+S↓?

　　The specific chemical reaction is as follows:? H2S+Na2CO3=NaHS+NaHCO3NaHS+1/2O2=NaOH+S↓?

　　氣體流程：原料氣從脫硫塔下部進入，與塔上部噴淋下來的脫硫堿液逆流接觸，實現粗脫硫，氣體從塔頂引出再送往后工序使用。液體流程：吸收了硫化氫的脫硫堿液從脫硫塔底部進入富液槽，經富液泵打入再生槽利用空氣和催化劑進行再生；再生空氣同時將脫硫堿液中的單質硫以硫泡沫的形式浮選出來后放空，硫泡沫經泡沫溢流槽流至泡沫儲槽，由泡沫泵送往過濾機過濾。

　　Gas process: The raw gas enters from the lower part of the desulfurization tower and comes into contact with the desulfurization alkali solution sprayed from the upper part of the tower in reverse flow to achieve coarse desulfurization. The gas is then drawn out from the top of the tower and sent to subsequent processes for use. Liquid process: The desulfurization alkaline solution that absorbs hydrogen sulfide enters the rich liquid tank from the bottom of the desulfurization tower, and is pumped into the regeneration tank by the rich liquid pump for regeneration using air and catalyst; At the same time, the regeneration air floats out the elemental sulfur in the desulfurization lye in the form of sulfur foam and vents it. The sulfur foam flows to the foam storage tank through the foam overflow tank, and is sent to the filter by the foam pump.

　　清液回貧液槽再利用；濾餅——硫膏則直接作為副產品銷售或處置。再生后的脫硫堿液經液位調節器進入貧液槽，由貧液泵加壓送至脫硫塔內上部經噴頭噴淋進行循環使用。?吸收過程化學反應如下：?吸收反應：H2S+Na2CO3=NaHS+NaHCO3?副反應：Na2CO3+CO2+H2O=2NaHCO3再生時脫硫液中的硫氫化鈉與噴射器吸入的空氣中的氧在催化劑的作用下反應如下：?2NaHS+O2=2S+2NaOH?NaOH+NaHCO3=Na2CO3+H2O

　　Reuse of clear liquid in the lean liquid tank; Filter cake - sulfur paste is directly sold or disposed of as a by-product. The regenerated desulfurization alkali solution enters the lean solution tank through the liquid level regulator, and is pressurized by the lean solution pump and sent to the upper part of the desulfurization tower for recycling through spray nozzles.? The chemical reaction during the absorption process is as follows:? Absorption reaction: H2S+Na2CO3=NaHS+NaHCO3? Side reaction: During the regeneration of Na2CO3+CO2+H2O=2NaCO3, the sodium hydrosulfide in the desulfurization solution reacts with the oxygen in the air inhaled by the injector under the action of the catalyst as follows:? 2NaHS+O2=2S+2NaOH? NaOH+NaHCO3=Na2CO3+H2O

　　（3）堿式生物法脫硫工藝?堿式生物法脫硫是指采用排硫桿菌作為脫硫細菌進行生物脫硫的方法。?堿式生物法脫硫的反應機理方程如下：?2H2S+O2→2S0+2H2O?堿式生物法脫硫主要由硫吸收單元、生物反應器單元，硫分離單元三個主要部分組成。

　　(3) Alkaline biological desulfurization process? Alkaline biological desulfurization refers to the method of using sulfur eliminating bacteria as desulfurization bacteria for biological desulfurization.? The reaction mechanism equation of alkaline biological desulfurization is as follows:? 2H2S+O2→2S0+2H2O? The alkaline biological desulfurization mainly consists of three main parts: sulfur absorption unit, bioreactor unit, and sulfur separation unit.

　　?①硫吸收單元?高效的硫化氫吸收塔是沼氣生物脫硫系統中一個重要的組成部分，它主要是用來使氣相中的硫化氫氣體轉為液相。吸收塔的工作過程主要為待脫除硫化氫的沼氣通過吸收塔底部進氣管進入，在壓力的作用下，自下而上通過塔內的填料層。堿性溶液從吸收塔上方的噴淋裝置向下噴撒，與含硫化氫的沼氣發生逆向傳質，硫化氫氣體與堿液發生化學反應轉變為硫化物融入吸收液，在重力作用下，吸收液自流進入生物反應器進行氧化再生。被脫除硫化氫氣體的沼氣則由吸收塔頂部的出氣口離開吸收塔進入下一工序。在吸收塔內發生的化學反應主要有：?H2S+OH-→HS-+H2O?H2S+CO32-→HS-+HCO3-?CO2+OH-→HCO3-?HCO3-+OH-→CO32-+H2O?

　　What? ① Sulfur absorption unit? An efficient hydrogen sulfide absorption tower is an important component of a biogas biological desulfurization system, mainly used to convert hydrogen sulfide gas from the gas phase to the liquid phase. The working process of the absorption tower mainly involves the biogas to be removed of hydrogen sulfide entering through the inlet pipe at the bottom of the absorption tower and passing through the packing layer inside the tower from bottom to top under pressure. The alkaline solution is sprayed downwards from the spray device above the absorption tower, and undergoes reverse mass transfer with the biogas containing hydrogen sulfide. The hydrogen sulfide gas reacts chemically with the alkaline solution to transform into sulfides and merge into the absorption liquid. Under the action of gravity, the absorption liquid flows into the bioreactor for oxidation and regeneration. The biogas that has been removed of hydrogen sulfide gas leaves the absorption tower through the outlet at the top of the absorption tower and enters the next process. The main chemical reactions that occur inside the absorption tower are:? H2S+OH-→HS-+H2O? H2S+CO32-→HS-+HCO3-? CO2+OH-→HCO3-? HCO3-+OH-→CO32-+H2O?

　　②生物反應器單元?生物反應器也是沼氣生物脫硫的一個重要組成部分，它主要用來完成硫化物的吸附降解過程。其工作過程主要是當含有硫化物的吸收液進入生物反應器后，反應器中的活性脫硫菌將硫化物吸收氧化，硫化物首先被氧化成S單質，同時再生成OH-離子。被氧化成的硫單質在重力重用下壓入硫分離單元進一步與液體分離。富含OH-離子的堿性溶液，在循環泵作用下進入吸收塔中循環吸收H2S氣體。部分單質S進一步被氧化成SO42-，生成H+，需要補充部分堿中和這部分氫離子。生物反應器單元設有鼓風機、曝氣裝置等曝氣系統為反應器內的脫硫細菌提供所需要的氧氣，同時增加脫硫細菌和硫化物的接觸面積，以增加脫硫效率。生物反應器單元設有堿液投加系統及營養鹽投加系統，為脫硫系統補充堿液和營養鹽，用于調節溶液的pH值、堿度和為脫硫細菌提供所需的營養物質。

　　② Bioreactor unit? Bioreactors are also an important component of biogas biological desulfurization, mainly used to complete the adsorption and degradation process of sulfides. The main working process is that when the absorption solution containing sulfides enters the bioreactor, the active desulfurization bacteria in the reactor absorb and oxidize the sulfides. The sulfides are first oxidized to elemental S and then generate OH - ions. The oxidized elemental sulfur is pressed into the sulfur separation unit for further separation from the liquid under gravity reuse. The alkaline solution rich in OH - ions enters the absorption tower under the action of the circulation pump to circulate and absorb H2S gas. Part of the elemental S is further oxidized to SO42-, generating H+, which requires additional alkali to neutralize this hydrogen ion. The bioreactor unit is equipped with an aeration system such as a blower and an aeration device to provide the required oxygen for the desulfurization bacteria inside the reactor, while increasing the contact area between the desulfurization bacteria and sulfides to improve desulfurization efficiency. The bioreactor unit is equipped with an alkali solution feeding system and a nutrient salt feeding system to supplement the desulfurization system with alkali solution and nutrient salts, which are used to adjust the pH and alkalinity of the solution and provide the required nutrients for desulfurization bacteria.

　　③硫分離單元?硫分離單元將生物反應器中單質硫通過斜板沉淀的方式與液體進行分離，濃縮后的硫泥自沉淀器錐底排出，沉淀器的上清液回流回生物反應器。分離后的液態硫泥固含量約為20%，純度可達95-98%，剩余的為細胞物資和微量鹽類。液態硫泥可通過進一步脫水生成60-65%干度的硫餅，硫餅經高溫熔融后可以生成純度~99.8%商品硫磺；分離后的液體也可直接外排進入污水處理系統。

　　③ Sulfur separation unit? The sulfur separation unit separates elemental sulfur from the liquid in the bioreactor through inclined plate precipitation. The concentrated sulfur sludge is discharged from the bottom of the sedimentation cone, and the supernatant of the sedimentation tank flows back to the bioreactor. The solid content of the separated liquid sulfur sludge is about 20%, with a purity of 95-98%, and the remaining is cellular material and trace salts. Liquid sulfur sludge can be further dehydrated to produce 60-65% dry sulfur cake, which can be melted at high temperature to produce commercial sulfur with a purity of~99.8%; The separated liquid can also be directly discharged into the sewage treatment system.

　　（4）酸式生物法脫硫?酸式生物法脫硫是一種常溫常壓下以生物濾池或生物滴濾池方式利用脫硫細菌將硫化物轉化為硫酸鹽的脫硫方法。生物脫硫法的基本原理是：H2S氣體被吸收液吸收轉化為硫化物，然后被脫硫細菌吸收至體內，作為營養物質被脫硫細菌分解、氧化、利用。在脫硫的同時為脫硫細菌的生長繁衍提供能量。生物脫硫的過程主要分為三個階段：H2S氣體的吸收過程：硫化氫氣體由氣相轉移至液相，被吸收液吸收轉變為硫化物；硫化物的吸附吸收過程：溶解至水溶液中的硫化物被脫硫細菌吸收吸附，從水溶液中轉移至脫硫細菌的體內；生物氧化的過程：進入脫硫細菌體內的硫化物被用作能源或養分在細菌體內酶作用下氧化分解和利用，從而達到去除H2S的目的。?酸式生物法脫硫反應方程如下：?H2S+OH-→HS-+H2O?2HS-+O2→2S0+2OH-?2SO+3O2→2SO42-+2H+因其脫硫細菌的生長還需要氧和其他營養物，通常需要在沼氣中混入氧氣、氮氣等雜質氣體，影響熱值和安全性。又由于脫硫菌不斷在濾床上繁殖更替，脫硫塔會定期堵塞，需要頻繁清塔處理。

　　(4) Acid based biological desulfurization? Acid based biological desulfurization is a desulfurization method that uses desulfurization bacteria to convert sulfides into sulfates at room temperature and pressure through biological filters or biological drip filters. The basic principle of biological desulfurization method is that H2S gas is absorbed and converted into sulfides by the absorption solution, and then absorbed into the body by desulfurization bacteria as nutrients, which are decomposed, oxidized, and utilized by desulfurization bacteria. Provide energy for the growth and reproduction of desulfurization bacteria while desulfurizing. The process of biological desulfurization is mainly divided into three stages: the absorption process of H2S gas: hydrogen sulfide gas is transferred from the gas phase to the liquid phase, and is absorbed by the absorption liquid to transform into sulfides; The adsorption and absorption process of sulfides: sulfides dissolved in aqueous solution are absorbed and adsorbed by desulfurization bacteria, and transferred from the aqueous solution to the bodies of desulfurization bacteria; The process of biological oxidation: Sulfides entering the desulfurization bacteria are used as energy or nutrients, and are oxidized, decomposed, and utilized by enzymes in the bacteria to achieve the goal of removing H2S.? The reaction equation for acid based biological desulfurization is as follows:? H2S+OH-→HS-+H2O? 2HS-+O2→2S0+2OH-? 2SO+3O2 → 2SO42-+2H+Due to the growth of desulfurization bacteria requiring oxygen and other nutrients, it is usually necessary to mix impurities such as oxygen and nitrogen into biogas, which affects the calorific value and safety. Due to the continuous proliferation and replacement of desulfurization bacteria on the filter bed, the desulfurization tower will be regularly blocked and requires frequent cleaning.

　　（5）濕式絡合鐵氧化法脫硫?濕式絡合鐵催化氧化法的基本原理是，H2在堿性溶液中被Fe3+的絡合物Fe3+Ln氧化成單質硫，而本身被H2S還原成Fe2+Ln，然后用空氣氧化再生，生成Fe3+Ln，循環使用。濕式絡合鐵催化氧化法系統采用堿性絡合鐵催化劑的氧化還原性質，吸收酸性氣中的H2S。H2S被絡合鐵直接氧化生成單質硫，絡合鐵轉化為絡合亞鐵，然后在再生沉降槽鼓入空氣，以空氣氧化堿性吸收劑中的絡合亞鐵，使吸收劑中的絡合亞鐵轉化為絡合鐵，再生回用。同時，在再生沉降槽對硫磺進行沉降分離形成硫磺漿，將硫磺漿送至過濾機中脫水成硫磺餅。?濕式絡合鐵氧化法脫硫反應方程式如下：吸收氧化總反應方程式：H2S(g)+2Fe3+(l)→2Fe2+(l)+2H+(l)+S0再生還原總反應方程式：0.5O2(g)+H2O(l)+2Fe2+(l)→2Fe3+(l)+2OH-(l)

　　(5) Wet chelation iron oxidation method for desulfurization? The basic principle of wet chelated iron catalytic oxidation method is that H2 is oxidized to elemental sulfur by the Fe3+complex Fe3+Ln in alkaline solution, while it is reduced to Fe2+Ln by H2S, and then regenerated by air oxidation to generate Fe3+Ln, which is recycled. The wet complexed iron catalytic oxidation system utilizes the redox properties of alkaline complexed iron catalysts to absorb H2S from acidic gases. H2S is directly oxidized by chelated iron to produce elemental sulfur, which is then converted into chelated ferrous. Air is then blown into the regeneration settling tank to oxidize the chelated ferrous in the alkaline absorbent, converting it into chelated ferrous for regeneration and reuse. At the same time, sulfur is settled and separated in the regeneration settling tank to form sulfur slurry, which is then sent to the filter machine for dehydration into sulfur cake.? The reaction equation for wet chelation iron oxidation desulfurization is as follows: absorption oxidation total reaction equation: H2S (g)+2Fe3+(l) → 2Fe2+(l)+2H+(l)+S0 regeneration reduction total reaction equation: 0.5O2 (g)+H2O (l)+2Fe2+(l) → 2Fe3+(l)+2OH - (l)

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