随着我国对可再生能源的开发和利用的不断深入发展, 利用畜禽粪便厌氧发酵产沼气是一种非常有前景的能源利用途径，但所产生的沼气中都含有H2S气体，由于它是一种腐蚀性很强的化合物，所以沼气脱硫是沼气利用的关键环节。本文以某工程调试与运行实例分析了大型沼气工程中的生物脱硫技术，以为同类型工程提供参考。

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.

目前沼气脱硫的方法有两大类，即物理化学法和生物法。物理化学法包括干法脱硫和湿法脱硫，已被广泛地应用且积累了丰富的经验，但该方法存在运行费用高、投资大、产生二次污染等缺点；而生物法以不需催化剂和氧化剂、不需处理化学污泥、少污染、低能耗、率、可回收单质硫等优点，引起了人们的广泛关注。为此，笔者以某公司热电联产沼气工程为例，介绍了该沼气工程调试与运行时生物脱硫技术的具体运用。

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.

生物脱硫的装置主要由生物脱硫塔和曝气水箱构成，从厌氧罐内导出的沼气由脱硫塔底部进入，脱硫循环水由泵打入脱硫塔顶，两者在塔内逆向接触反应，且塔内充有填料以供脱硫菌附着生长，同时也利于气水均匀分布以充分接触。生物脱硫塔及曝气水箱都采用耐酸玻璃钢制作，循环泵也使用耐酸性泵。脱硫塔的负荷为8m3 (沼气) /（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).

本工程采用生物脱硫的方法对沼气进行脱硫处理，主要利用无色硫细菌在适宜的温度、湿度和微氧条件下的代谢作用将H2S氧化成单质硫或亚硫酸。生物脱硫分为3个阶段 :

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 气体的溶解过程，即由气相转化为液相；

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，转移微生物的体内；

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

3.进入微生物细胞内的H2S作为营养物被微生物分解、转化和利用，从而达到去除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.

虽然生物脱硫具有能耗少、去除率高等特点，但必须给硫细菌营造一个适宜的环境，才能确保其具有较高的生物活性，以达到的脱硫效果。而在该工程调试与运行中影响生物脱硫效率的主要因素有pH值、DO、温度、H2S负荷，因此必须对这些因素进行控制。

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

硫细菌种类繁多，且各自具有不同的生理学、形态学和生态学特性，对环境条件的要求也各异。有研究表明，硫细菌可生存的范围很广，在pH值为1.0～9.0、温度为 4～95℃的条件下都可生长和运动，但各自都有适宜的pH值范围，如硫化叶菌属的硫细菌在pH值为2～3下生存才有较好的生物活性，若环境的pH值不在其适宜的范围，其活性将会 受到很大的影响，一般大多数硫细菌适宜的pH值范围为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.

本工程试运行初期，将脱硫循环水的pH值维持在2～3之间，达到了较好的脱硫效果，可能是硫化叶菌属的硫细菌起的作用，但随着产气量的增加，循环水中有限的DO浓度难以将pH值维持在较低水平，所以在试运行后期将循环水的pH值维持在5～7之间，在此期间主要通过控制较小的曝气量(即较低的DO)和更换新鲜循环水来防止pH值的波动。因为当pH值发生较大波动时，硫细菌的活性急剧下降甚失去活性，如本工程中当pH值由2～3调整到5～7时，生物脱硫塔几乎完全失去了脱硫效果。所以在生物脱硫中，维持稳定的pH值是关重要的，它将直接影响脱硫效果的好坏。

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浓度的控制

2. Control of DO concentration

气相中H2S和O2难以发生反应，生物脱硫反应过程主要发生在液相中，所以脱硫塔内循环喷淋水中的DO（溶解氧）浓度是影响生物脱硫的一个重要因素。C.J.N.Busiman等在生物脱硫反应器中研究了单质硫产生的条件，在硫化物浓度为90mg/L、停留时间为45 min、DO浓度低于1mg/L时，产生极少的硫酸（<10%）；在DO浓度超过5mg/L 时，生成的硫酸盐稳定在52%；而在DO浓度为1mg/L时，单质硫产率。所以控制喷淋水中的DO浓度是气相中H2S能否变为单质硫的关键因素之一。经过该工程试运行发现，在不同的H2S负荷下，循环液中都存在一个的DO浓度。

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.

当DO浓度过低时主要发生个反应，因S2-转化为S0的过程是一个产碱的过程，会引起循环水pH值的上升; 当DO浓度过大时发生第二个反应，产生的酸过多，循环液的 pH 值会加速下降。pH值的上升与下降都会对脱硫效果有影响，所以合适的DO浓度是控制反应进行到哪一步的关键，也是使产物主要为单质硫，并使循环液的pH值稳 定维持在5～7，即脱硫效果的关键。由于理论上氧化1分子H2S生成单质硫需要1/2分子的O2 ，所以在工程调试与运行中, 需要根据不同的H2S负荷对循环液中的DO 浓度进行调整，以防止DO过少pH值上升、DO过量生成大量酸，造成pH值剧烈变化而影响脱硫效果。而DO控制主要是通过调整曝气风量加以控制。

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负荷的控制

3. Control of H2S load

H2S负荷对脱硫产物也有较大影响。当脱硫塔在低负荷的条件下运行时，H2S容易被过氧化，生成大量的酸使循环水pH值急剧下降；当反应器在高负荷的条件下运行时，脱硫产物主要为单质硫，循环液pH值稳定甚还会上升。生物脱硫塔在启动时需向循环水中加入约1%的厌氧罐发酵液，以提供生物脱硫所需的菌种；启动初期菌种有将近30d适应过程，期间脱硫效果会出现较大的波动；但调试运行稳定后，经过脱硫后的沼气中 H2S浓度可维持在200×10-6以下，去除率将达到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%.

实际工程运行发现，在硫细菌所能承受范围内，H2S容积负荷越高，微生物脱硫反应越能保持良好的运行效果，且不易发生循环水急剧酸化的现象。有研究发现，无色硫细菌在营养物质受限制而有足够硫化物时，可在几乎无明显生长的情况下，地将硫化物氧化。所以在工程运营中，当H2S负荷发生变化时，主要通过控制pH值、DO浓度等运行条件就能确保运行效果的稳定。

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.