生物脱硫技术是利用碱液吸收酸性气中的硫化氢，然后在硫黄杆菌的生化作用下产生硫黄，再经脱水、熔硫等操作，实现酸性气净化和硫黄回收的目的。介绍了生物脱硫技术的原理、工艺流程、操作要点及控制指标、主要设备、运行效果。实际运行结果表明，生物脱硫技术脱硫效率高、运行稳定，处理后的排放废气完全满足相关国家标准的要求。

　　Biological desulfurization technology uses alkaline solution to absorb hydrogen sulfide in acidic gas, and then produces sulfur through the biochemical action of sulfur bacteria. After dehydration, sulfur melting and other operations, the goal of acid gas purification and sulfur recovery is achieved. This article introduces the principle, process flow, operating points, control indicators, main equipment, and operating effects of biological desulfurization technology. The actual operation results show that the biological desulfurization technology has high desulfurization efficiency and stable operation, and the treated exhaust gas fully meets the requirements of relevant national standards.

　　国内某煤化工项目气化装置选用水煤浆气化工艺，净化采用耐硫变换、低温甲醇洗、液氮洗工艺，净化后的合成气送至氨合成装置。在生产过程中，低温甲醇洗产生的酸性气通过生物脱硫技术进行处理。与传统的硫回收工艺相比，生物脱硫工艺酸性气中硫化氢脱除率高，工艺流程简单，建设费用、维护费用低，日常消耗少，操作弹性大，产生的硫黄亲水性好，不易堵塞设备和管道，装置运行可靠度高，无需增设尾气处理装置，而且酸性气处理过程中无二次污染。

　　The gasification unit of a domestic coal chemical project adopts the coal water slurry gasification process, and the purification adopts sulfur resistant transformation, low-temperature methanol washing, and liquid nitrogen washing processes. The purified synthesis gas is sent to the ammonia synthesis unit. During the production process, the acidic gas generated by low-temperature methanol washing is treated through biological desulfurization technology. Compared with traditional sulfur recovery processes, the biological desulfurization process has a higher removal rate of hydrogen sulfide in acidic gas, a simpler process flow, lower construction and maintenance costs, less daily consumption, greater operational flexibility, good hydrophilicity of the generated sulfur, less likely to block equipment and pipelines, high reliability of device operation, no need to add tail gas treatment equipment, and no secondary pollution during the acidic gas treatment process.

　　1酸性气的产生及来源

　　1. Generation and Source of Acidic Gas

　　煤中的硫在水煤浆气化炉内高温燃烧形成H2S，并随粗煤气进入低温甲醇洗单元。因H2S与甲醇同为极性分子，易形成氢键，因此H2S在甲醇中有很好的溶解度。粗煤气经甲醇洗涤塔内的甲醇洗涤后，CO2、H2S等气体均溶解在甲醇中。洗涤后的甲醇经减压闪蒸、低压解析、N2气提除去甲醇中大部分的CO2后，富含H2S的甲醇经热再生塔加热气提再生，甲醇与H2S之间的氢键断裂。从热再生塔顶部出来的富含H2S的酸性气体流量约1870m3/h(标态)，其中H2S为25.38%(体积分数，下同)、COS为0.02%、CO2为72.35%，经冷却分离后送至硫回收装置。

　　The sulfur in coal burns at high temperature in the coal water slurry gasifier to form H2S, which enters the low-temperature methanol washing unit with the crude gas. Due to the fact that H2S and methanol are polar molecules, they are prone to form hydrogen bonds, thus H2S has good solubility in methanol. After the crude coal gas is washed with methanol in the methanol washing tower, gases such as CO2 and H2S are dissolved in methanol. After washing, the methanol is subjected to vacuum flash evaporation, low-pressure desorption, and N2 gas stripping to remove most of the CO2 in the methanol. The methanol rich in H2S is then heated and gas stripped in a thermal regeneration tower for regeneration, and the hydrogen bonds between methanol and H2S are broken. The flow rate of acidic gas rich in H2S from the top of the hot regeneration tower is about 1870m3/h (standard state), of which H2S is 25.38% (volume fraction, the same below), COS is 0.02%, and CO2 is 72.35%. After cooling and separation, it is sent to the sulfur recovery unit.

　　2生物脱硫的原理

　　The principle of biological desulfurization

　　生物脱硫技术主要是采用硫黄杆菌来处理酸性气中的H2S，而硫黄杆菌是在自然界中产生，通过遗传培育或改良而来。硫黄杆菌的繁殖生长很快，4h就可以翻倍且成对数增长，而且对工艺条件、生产环境等都有很强的适应性，其生长过程中所需的能量主要来源于硫化物的氧化过程，碳源则来自于酸性气中的CO2。

　　Biological desulfurization technology mainly uses sulfur bacteria to treat H2S in acidic gas, which is produced in nature through genetic cultivation or improvement. The reproduction and growth of sulfur bacteria are very fast, doubling and growing logarithmically in 4 hours, and have strong adaptability to process conditions, production environments, etc. The energy required for their growth mainly comes from the oxidation process of sulfides, and the carbon source comes from CO2 in acidic gas.

　　来自低温甲醇洗单元的酸性气进入H2S吸收塔内与碱性溶液逆向接触，酸性气中的H2S和CO2被碱液吸收分别生成HS-、CO32-、HCO3-(H2S+OH-=HS-+H2O，H2S+CO32-=HS-+HCO3-，CO2+OH-=HCO3-，HCO3-+OH-=CO32-+H2O)。

　　The acidic gas from the low-temperature methanol washing unit enters the H2S absorption tower and comes into reverse contact with the alkaline solution. The H2S and CO2 in the acidic gas are absorbed by the alkaline solution to produce HS -, CO32-, HCO3- (H2S+OH -=HS -+H2O, H2S+CO32-=HS-+HCO3-，CO2+OH-=HCO3-，HCO3-+OH-=CO32-+H2O)。

　　吸收了酸性气中H2S和CO2的溶液进入生物反应器底部与空气混合，溶液中的HS-与O2反应生成硫和OH-(2HS-+O2=2S+2OH-，8SxHS-+4O2=S8+8Sx+8OH-)，溶液中的CO32-、HCO3-分解释放出OH-和CO2(CO32-+H2O=HCO3-+OH-；HCO3-=CO2+OH-)，碱液得到再生后循环使用。生物反应器内若O2过量，会发生副反应生成硫酸盐和硫代硫酸盐(HS-+2O2=SO42-+H+，2HS-+2O2= S2O32-+H2O)。在高浓度硫化物的作用下，生物菌的活性会降低，产生的硫酸盐和硫代硫酸盐增多。为减少副反应的发生，须合理控制生物反应器内空气的通入量，防止O2过剩。同时将硫黄脱水机分离出来的液体排至污水处理装置，并向生物反应器内补充新鲜水和碱液维持系统平衡。

　　The solution that absorbs H2S and CO2 from acidic gas enters the bottom of the bioreactor and mixes with air. The HS - in the solution reacts with O2 to generate sulfur and OH - (2HS -+O2=2S+2OH -, 8SxHS -+4O2=S8+8Sx+8OH -). The CO32- and HCO3- in the solution decompose to release OH - and CO2 (CO32-+H2O=HCO3-+OH -; HCO3-=CO2+OH -). The alkaline solution is regenerated and recycled for use. If there is an excess of O2 in the bioreactor, side reactions will occur to produce sulfates and thiosulfates (HS -+2O2=SO42-+H+, 2HS -+2O2=S2O32-+H2O). Under the action of high concentrations of sulfides, the activity of biological bacteria will decrease, and the production of sulfates and thiosulfates will increase. To reduce the occurrence of side reactions, it is necessary to reasonably control the amount of air introduced into the bioreactor to prevent excess O2. At the same time, the liquid separated from the sulfur dehydrator is discharged to the sewage treatment unit, and fresh water and alkali solution are added to the bioreactor to maintain system balance.

　　3生物脱硫工艺流程

　　3. Biological desulfurization process flow

　　生物脱硫工艺流程见图 1。

　　The process flow of biological desulfurization is shown in Figure 1.

　　详见文章全文：

　　Please refer to the full article for details:

　　生物脱硫技术在煤化工酸性气脱硫中的应用

　　Application of biological desulfurization technology in acid gas desulfurization in coal chemical industry

　　4生物脱硫工艺的操作要点及

　　4. Key points of operation for biological desulfurization process and

　　控制指标

　　Control indicators

　　生物脱硫工艺的操作要点包括H2S吸收塔的气液比、溶液的pH和溶液的缓冲能力、氧化还原电位和生物反应器空气通入量、排放和电导率、系统中固体(单质硫)的浓度、温度。

　　The key operating points of the biological desulfurization process include the gas-liquid ratio of the H2S absorption tower, the pH and buffering capacity of the solution, the oxidation-reduction potential and air flow rate of the bioreactor, emissions and conductivity, the concentration of solid (elemental sulfur) in the system, and temperature.

　　详见文章全文：

　　Please refer to the full article for details:

　　生物脱硫技术在煤化工酸性气脱硫中的应用

　　Application of biological desulfurization technology in acid gas desulfurization in coal chemical industry

　　5主要设备工作原理及作用

　　5. Working principles and functions of main equipment

　　生物脱硫装置的主要设备有H2S吸收塔、生物反应器、硫黄沉降槽、熔硫釜等。

　　The main equipment of the biological desulfurization device includes H2S absorption tower, bioreactor, sulfur settling tank, sulfur melting kettle, etc.

　　H2S吸收塔内装填鲍尔环和必要的内件，以确保吸收液从塔顶部均匀地喷洒到填料塔内，气体在塔内与吸收液逆向接触，使酸性气中的H2S和部分CO2从气相转移至液相。为了防止吸收液发泡，塔顶设有喷淋装置。

　　The H2S absorption tower is filled with a Bauer ring and necessary internal components to ensure that the absorption liquid is evenly sprayed from the top of the tower into the packed tower. The gas in the tower comes into reverse contact with the absorption liquid, causing H2S and some CO2 in the acidic gas to transfer from the gas phase to the liquid phase. In order to prevent the absorption liquid from foaming, a spray device is installed at the top of the tower.

　　生物反应器是脱硫工艺最关键的设备。空气从底部通入，使HS-转化为硫。为了提高HS-转化率，在生物反应器内配置特殊的内件，保证了系统的气液完全混合。同时顶部安装喷嘴，以防止生物反应器内的溶液发泡。

　　Bioreactors are the most critical equipment in desulfurization processes. Air is introduced from the bottom to convert HS - into sulfur. In order to improve the HS conversion rate, special internal components are installed in the bioreactor to ensure complete gas-liquid mixing in the system. At the same time, a nozzle is installed at the top to prevent the solution inside the bioreactor from foaming.

　　硫黄沉降槽是底部为锥形的容器，内部设有溢流堰，塔顶设有喷嘴等，使贫液与硫黄颗粒通过静态沉降的方式予以分离。

　　The sulfur settling tank is a cone-shaped container with an overflow weir inside and a nozzle at the top of the tower, which separates the lean solution from sulfur particles through static settling.

　　熔硫釜内温度按上低下高的梯度分布，硫浆进入釜内后被逐渐加热，硫泡沫破裂，细小的硫颗粒聚集变大沉降至釜底高温区熔融，硫水分离后的清液上浮从熔硫釜上端旁侧连续排出。

　　The temperature in the sulfur melting kettle is distributed according to the gradient of upper, lower and higher. The sulfur slurry is gradually heated after entering the kettle. The sulfur foam breaks, and the small sulfur particles gather and settle to the high temperature area at the bottom of the kettle for melting. The clear liquid after sulfur water separation floats up and is discharged continuously from the side of the upper end of the sulfur melting kettle.

　　6生产中其他操作及注意事项

　　6 Other operations and precautions in production

　　(1) 经常观察H2S吸收塔和生物反应器内溶液的颜色。在操作正常时，生物反应器内的溶液外观呈灰白－黄色，类似硫黄产品的颜色，此时表明系统具有高的生物活性和硫黄产量。当系统不正常时，生物菌的生物活性被抑制，硫化物在装置内累积并与元素硫反应生成多硫化物，氧化还原电位会降低，H2S吸收塔和生物反应器内的液体将变成暗绿色。

　　(1) Regularly observe the color of the solution in the H2S absorption tower and bioreactor. When operating normally, the appearance of the solution in the bioreactor is gray white yellow, similar to the color of sulfur products, indicating that the system has high biological activity and sulfur production. When the system is abnormal, the biological activity of the bacteria is inhibited, and sulfides accumulate in the device and react with elemental sulfur to produce polysulfides. The oxidation-reduction potential will decrease, and the liquid in the H2S absorption tower and bioreactor will turn dark green.

　　(2) 生物菌的备份。当上游气体成分严重偏离设计工况或本装置操作维护不当等出现极端情况时，可能会对生物脱硫系统造成不可逆的破坏。如出现气体携有过量的HCN、NH3、CH3OH，液相中重金属超标，系统pH和温度过低等问题，生物菌就有可能会被杀死。因此须对生物菌进行备份，以便装置快速重启。在正常运行时，一般每隔3个月对生物菌重新备份一次。进行生物菌备份时，首先根据溶液的颜色判断是否适宜进行取样，然后用4个200L的无毒塑料桶在硫浆泵出口取样，再密闭置于常温(25~40℃)贮藏室内保存。

　　(2) Backup of biological bacteria. When the upstream gas composition deviates significantly from the design conditions or when there are extreme situations such as improper operation and maintenance of this device, it may cause irreversible damage to the biological desulfurization system. If there are problems such as excessive HCN, NH3, CH3OH in the gas, excessive heavy metals in the liquid phase, low system pH and temperature, etc., biological bacteria may be killed. Therefore, it is necessary to backup the biological bacteria in order to quickly restart the device. During normal operation, the biological bacteria are usually backed up again every 3 months. When backing up biological bacteria, first determine whether it is suitable to take samples based on the color of the solution, then use four 200L non-toxic plastic buckets to take samples at the outlet of the sulfur slurry pump, and then store them in a sealed room at room temperature (25-40 ℃).

　　(3) 系统通过生物菌来处理酸性气中的H2S，生物菌活性数量将严重影响装置负荷及生产情况。在前系统负荷波动较大时，酸性气量突然减少或增多，会导致生物菌死亡或因生物菌数量与负荷不匹配造成系统紊乱，对装置运行影响较大。当系统开车时，先培养装置内的生物菌菌落，根据系统生物菌状况缓慢提高负荷，否则容易因生物菌数量较少、酸性气量过大，导致排放气中的H2S含量超标。因此，在前系统负荷波动或开停车时，应密切关注硫回收装置的操作界面，严格控制H2S吸收塔的气液比、pH、氧化还原电位和生物反应器通入的空气量、排放量、电导率、温度，若指标出现异常应及时处理，防止工况恶化。

　　(3) The system uses biological bacteria to treat H2S in acidic gas, and the activity of biological bacteria will seriously affect the load and production situation of the equipment. When there is a large fluctuation in the load of the front-end system, a sudden decrease or increase in the amount of acidic gas can lead to the death of biological bacteria or system disorder caused by the mismatch between the number of biological bacteria and the load, which has a significant impact on the operation of the device. When the system is running, first cultivate the bacterial colonies inside the device, and slowly increase the load according to the condition of the system's biological bacteria. Otherwise, it is easy for the H2S content in the exhaust gas to exceed the standard due to a small number of biological bacteria and excessive acidic gas. Therefore, when the load of the front-end system fluctuates or starts and stops, close attention should be paid to the operating interface of the sulfur recovery unit, and the gas-liquid ratio, pH, oxidation-reduction potential of the H2S absorption tower, as well as the air volume, emissions, conductivity, and temperature of the bioreactor should be strictly controlled. If there are any abnormalities in the indicators, they should be dealt with in a timely manner to prevent deterioration of the working conditions.

　　7运行效果分析

　　7. Analysis of Operational Effectiveness

　　生物脱硫装置投产后，设备可靠度高，运行稳定，硫黄产量可达13.5t/d，能够满足生产需求。

　　After the biological desulfurization device is put into operation, the equipment has high reliability and stable operation, and the sulfur production can reach 13.5t/d, which can meet the production demand.

　　8结语

　　8 Conclusion

　　与其他硫回收技术相比，生物脱硫技术具有投资费用低、工艺流程简单、操作方便、运行成本低、设备和管道不易堵塞、对酸性气要求低、适用范围广等特点，装置运行稳定可靠，无二次污染，脱硫效果良好。

　　Compared with other sulfur recovery technologies, biological desulfurization technology has the characteristics of low investment cost, simple process flow, convenient operation, low operating cost, less likely to block equipment and pipelines, low requirements for acidic gas, and wide applicability. The device operates stably and reliably, without secondary pollution, and has good desulfurization effect.

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