隨著我國對可再生能源的開發和利用的不斷深入發展, 利用畜禽糞便厭氧發酵產沼氣是一種非常有前景的能源利用途徑，但所產生的沼氣中都含有H2S氣體，由于它是一種腐蝕性很強的化合物，所以沼氣脫硫是沼氣利用的關鍵環節。本文以某工程調試與運行實例分析了大型沼氣工程中的生物脫硫技術，以為同類型工程提供參考。

With the continuous development and utilization of renewable energy in China, anaerobic fermentation of livestock and poultry manure to produce biogas is a very promising energy utilization pathway. However, the biogas produced contains H2S gas, which is a highly corrosive compound. Therefore, biogas desulfurization is a key link in biogas utilization. This article analyzes the biological desulfurization technology in large-scale biogas projects through a case study of commissioning and operation, providing reference for similar projects.

目前沼氣脫硫的方法有兩大類，即物理化學法和生物法。物理化學法包括干法脫硫和濕法脫硫，已被廣泛地應用且積累了豐富的經驗，但該方法存在運行費用高、投資大、產生二次污染等缺點；而生物法以不需催化劑和氧化劑、不需處理化學污泥、少污染、低能耗、率、可回收單質硫等優點，引起了人們的廣泛關注。為此，筆者以某公司熱電聯產沼氣工程為例，介紹了該沼氣工程調試與運行時生物脫硫技術的具體運用。

At present, there are two main methods for desulfurization of biogas, namely physical and chemical methods and biological methods. Physical and chemical methods, including dry desulfurization and wet desulfurization, have been widely applied and accumulated rich experience. However, this method has disadvantages such as high operating costs, large investment, and secondary pollution; Biological methods have attracted widespread attention due to their advantages such as no need for catalysts and oxidants, no need to treat chemical sludge, low pollution, low energy consumption, high efficiency, and recyclability of elemental sulfur. Therefore, the author takes a company's cogeneration biogas project as an example to introduce the specific application of biological desulfurization technology during the commissioning and operation of the biogas project.

生物脫硫的裝置主要由生物脫硫塔和曝氣水箱構成，從厭氧罐內導出的沼氣由脫硫塔底部進入，脫硫循環水由泵打入脫硫塔頂，兩者在塔內逆向接觸反應，且塔內充有填料以供脫硫菌附著生長，同時也利于氣水均勻分布以充分接觸。生物脫硫塔及曝氣水箱都采用耐酸玻璃鋼制作，循環泵也使用耐酸性泵。脫硫塔的負荷為8m3 (沼氣) /（m3·h）左右。

The device for biological desulfurization mainly consists of a biological desulfurization tower and an aeration water tank. The biogas exported from the anaerobic tank enters from the bottom of the desulfurization tower, and the desulfurization circulating water is pumped into the top of the desulfurization tower. The two react in reverse contact inside the tower, and the tower is filled with packing material for the attachment and growth of desulfurization bacteria. At the same time, it is also conducive to the uniform distribution of gas and water for sufficient contact. The biological desulfurization tower and aeration water tank are made of acid resistant fiberglass, and the circulation pump also uses acid resistant pumps. The load of the desulfurization tower is about 8m3 (biogas)/(m3 · h).

本工程采用生物脫硫的方法對沼氣進行脫硫處理，主要利用無色硫細菌在適宜的溫度、濕度和微氧條件下的代謝作用將H2S氧化成單質硫或亞硫酸。生物脫硫分為3個階段 :

This project adopts the method of biological desulfurization to desulfurize biogas, mainly utilizing the metabolic action of colorless sulfur bacteria under suitable temperature, humidity, and micro oxygen conditions to oxidize H2S into elemental sulfur or sulfurous acid. Biological desulfurization is divided into three stages:

1.H2S 氣體的溶解過程，即由氣相轉化為液相；

The dissolution process of H2S gas, that is, the transformation from gas phase to liquid phase;

2.溶解后的H2S被微生物吸收，轉移微生物的體內；

2. The dissolved H2S is absorbed by microorganisms and transferred into their bodies;

3.進入微生物細胞內的H2S作為營養物被微生物分解、轉化和利用，從而達到去除H2S的目的。

3. H2S entering microbial cells is decomposed, transformed, and utilized by microorganisms as nutrients, thereby achieving the goal of removing H2S.

雖然生物脫硫具有能耗少、去除率高等特點，但必須給硫細菌營造一個適宜的環境，才能確保其具有較高的生物活性，以達到的脫硫效果。而在該工程調試與運行中影響生物脫硫效率的主要因素有pH值、DO、溫度、H2S負荷，因此必須對這些因素進行控制。

Although biological desulfurization has the characteristics of low energy consumption and high removal rate, it is necessary to create a suitable environment for sulfur bacteria to ensure their high biological activity and achieve the best desulfurization effect. The main factors that affect the efficiency of biological desulfurization during the commissioning and operation of the project are pH value, DO, temperature, and H2S load, so these factors must be controlled.

1、pH值的控制

1. Control of pH value

硫細菌種類繁多，且各自具有不同的生理學、形態學和生態學特性，對環境條件的要求也各異。有研究表明，硫細菌可生存的范圍很廣，在pH值為1.0～9.0、溫度為 4～95℃的條件下都可生長和運動，但各自都有適宜的pH值范圍，如硫化葉菌屬的硫細菌在pH值為2～3下生存才有較好的生物活性，若環境的pH值不在其適宜的范圍，其活性將會 受到很大的影響，一般大多數硫細菌適宜的pH值范圍為6～8。

There are various types of sulfur bacteria, each with different physiological, morphological, and ecological characteristics, and different requirements for environmental conditions. Studies have shown that sulfur bacteria can survive in a wide range, growing and moving under conditions of pH 1.0-9.0 and temperature 4-95 ℃, but each has a suitable pH range. For example, sulfur bacteria belonging to the sulfur leaf fungus genus have good biological activity only when they survive at pH 2-3. If the pH value of the environment is not within their suitable range, their activity will be greatly affected. Generally, the pH range suitable for most sulfur bacteria is 6-8.

本工程試運行初期，將脫硫循環水的pH值維持在2～3之間，達到了較好的脫硫效果，可能是硫化葉菌屬的硫細菌起的作用，但隨著產氣量的增加，循環水中有限的DO濃度難以將pH值維持在較低水平，所以在試運行后期將循環水的pH值維持在5～7之間，在此期間主要通過控制較小的曝氣量(即較低的DO)和更換新鮮循環水來防止pH值的波動。因為當pH值發生較大波動時，硫細菌的活性急劇下降甚失去活性，如本工程中當pH值由2～3調整到5～7時，生物脫硫塔幾乎完全失去了脫硫效果。所以在生物脫硫中，維持穩定的pH值是關重要的，它將直接影響脫硫效果的好壞。

In the early stage of the trial operation of this project, the pH value of the desulfurization circulating water was maintained between 2 and 3, achieving good desulfurization effect, which may be due to the role of sulfur bacteria in the sulfur leaf fungus genus. However, with the increase of gas production, the limited DO concentration in the circulating water makes it difficult to maintain the pH value at a low level. Therefore, in the later stage of the trial operation, the pH value of the circulating water was maintained between 5 and 7. During this period, the main measures to prevent pH fluctuations were to control the aeration rate (i.e., lower DO) and replace fresh circulating water. Because when the pH value fluctuates significantly, the activity of sulfur bacteria decreases sharply or even loses its activity. For example, in this project, when the pH value is adjusted from 2-3 to 5-7, the biological desulfurization tower almost completely loses its desulfurization effect. Therefore, maintaining a stable pH value is crucial in biological desulfurization, as it will directly affect the effectiveness of desulfurization.

2、DO濃度的控制

2. Control of DO concentration

氣相中H2S和O2難以發生反應，生物脫硫反應過程主要發生在液相中，所以脫硫塔內循環噴淋水中的DO（溶解氧）濃度是影響生物脫硫的一個重要因素。C.J.N.Busiman等在生物脫硫反應器中研究了單質硫產生的條件，在硫化物濃度為90mg/L、停留時間為45 min、DO濃度低于1mg/L時，產生極少的硫酸（<10%）；在DO濃度超過5mg/L 時，生成的硫酸鹽穩定在52%；而在DO濃度為1mg/L時，單質硫產率。所以控制噴淋水中的DO濃度是氣相中H2S能否變為單質硫的關鍵因素之一。經過該工程試運行發現，在不同的H2S負荷下，循環液中都存在一個的DO濃度。

H2S and O2 are difficult to react in the gas phase, and the biological desulfurization reaction mainly occurs in the liquid phase. Therefore, the dissolved oxygen (DO) concentration in the circulating spray water inside the desulfurization tower is an important factor affecting biological desulfurization. C. J.N. Busiman et al. studied the optimal conditions for the production of elemental sulfur in a biological desulfurization reactor. When the sulfide concentration was 90 mg/L, the residence time was 45 min, and the DO concentration was below 1 mg/L, very little sulfuric acid (<10%) was produced; When the DO concentration exceeds 5mg/L, the generated sulfate remains stable at 52%; At a DO concentration of 1mg/L, the yield of elemental sulfur is highest. So controlling the DO concentration in the spray water is one of the key factors determining whether H2S in the gas phase can be converted into elemental sulfur. After the trial operation of the project, it was found that there is an optimal DO concentration in the circulating liquid under different H2S loads.

當DO濃度過低時主要發生個反應，因S2-轉化為S0的過程是一個產堿的過程，會引起循環水pH值的上升; 當DO濃度過大時發生第二個反應，產生的酸過多，循環液的 pH 值會加速下降。pH值的上升與下降都會對脫硫效果有影響，所以合適的DO濃度是控制反應進行到哪一步的關鍵，也是使產物主要為單質硫，并使循環液的pH值穩 定維持在5～7，即脫硫效果的關鍵。由于理論上氧化1分子H2S生成單質硫需要1/2分子的O2 ，所以在工程調試與運行中, 需要根據不同的H2S負荷對循環液中的DO 濃度進行調整，以防止DO過少pH值上升、DO過量生成大量酸，造成pH值劇烈變化而影響脫硫效果。而DO控制主要是通過調整曝氣風量加以控制。

When the DO concentration is too low, the first reaction mainly occurs, as the process of S2- conversion to S0 is an alkali production process, which can cause an increase in the pH value of the circulating water; When the concentration of DO is too high, a second reaction occurs, producing too much acid and accelerating the decrease in pH value of the circulating solution. The rise and fall of pH value will have an impact on the desulfurization effect, so the appropriate DO concentration is the key to controlling which step of the reaction is carried out, and it is also the key to making the product mainly elemental sulfur and maintaining the pH value of the circulating liquid stable at 5-7, which is the best desulfurization effect. Due to the theoretical requirement of 1/2 molecule of O2 for the oxidation of 1 molecule of H2S to produce elemental sulfur, it is necessary to adjust the DO concentration in the circulating liquid according to different H2S loads during engineering debugging and operation, in order to prevent the pH value from rising due to insufficient DO and the generation of a large amount of acid due to excessive DO, which may cause a drastic change in pH value and affect the desulfurization effect. And DO control is mainly controlled by adjusting the aeration air volume.

3、H2S負荷的控制

3. Control of H2S load

H2S負荷對脫硫產物也有較大影響。當脫硫塔在低負荷的條件下運行時，H2S容易被過氧化，生成大量的酸使循環水pH值急劇下降；當反應器在高負荷的條件下運行時，脫硫產物主要為單質硫，循環液pH值穩定甚還會上升。生物脫硫塔在啟動時需向循環水中加入約1%的厭氧罐發酵液，以提供生物脫硫所需的菌種；啟動初期菌種有將近30d適應過程，期間脫硫效果會出現較大的波動；但調試運行穩定后，經過脫硫后的沼氣中 H2S濃度可維持在200×10-6以下，去除率將達到90%以上。

The H2S load also has a significant impact on desulfurization products. When the desulfurization tower operates under low load conditions, H2S is prone to peroxidation, generating a large amount of acid and causing a sharp drop in the pH value of the circulating water; When the reactor operates under high load conditions, the main desulfurization product is elemental sulfur, and the pH value of the circulating liquid remains stable or even increases. When starting the biological desulfurization tower, about 1% of anaerobic tank fermentation broth needs to be added to the circulating water to provide the required bacterial strains for biological desulfurization; During the initial start-up phase, the bacterial strain undergoes an adaptation process of nearly 30 days, during which there may be significant fluctuations in desulfurization efficiency; But after stable debugging and operation, the H2S concentration in the desulfurized biogas can be maintained below 200 × 10-6, and the removal rate will reach over 90%.

實際工程運行發現，在硫細菌所能承受范圍內，H2S容積負荷越高，微生物脫硫反應越能保持良好的運行效果，且不易發生循環水急劇酸化的現象。有研究發現，無色硫細菌在營養物質受限制而有足夠硫化物時，可在幾乎無明顯生長的情況下，地將硫化物氧化。所以在工程運營中，當H2S負荷發生變化時，主要通過控制pH值、DO濃度等運行條件就能確保運行效果的穩定。

In actual engineering operation, it has been found that within the range that sulfur bacteria can withstand, the higher the H2S volumetric load, the better the microbial desulfurization reaction can maintain good operating efficiency, and the phenomenon of rapid acidification of circulating water is less likely to occur. A study has found that colorless sulfur bacteria can efficiently oxidize sulfides with almost no significant growth when there are sufficient sulfides due to nutrient limitations. So in engineering operation, when the H2S load changes, the stability of the operating effect can be ensured mainly by controlling operating conditions such as pH value and DO concentration.