生物脫硫技術(shù)是利用堿液吸收酸性氣中的硫化氫，然后在硫黃桿菌的生化作用下產(chǎn)生硫黃，再經(jīng)脫水、熔硫等操作，實現(xiàn)酸性氣凈化和硫黃回收的目的。介紹了生物脫硫技術(shù)的原理、工藝流程、操作要點及控制指標、主要設備、運行效果。實際運行結(jié)果表明，生物脫硫技術(shù)脫硫效率高、運行穩(wěn)定，處理后的排放廢氣完全滿足相關(guān)國家標準的要求

Biological desulfurization technology utilizes alkaline solution to absorb hydrogen sulfide from acidic gas, and then generates sulfur under the biochemical action of Thiobacillus. After dehydration, sulfur melting, and other operations, it achieves the purpose of acid gas purification and sulfur recovery. Introduced 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

1酸性氣的產(chǎn)生及來源

1. The generation and source of acidic gas

煤中的硫在水煤漿氣化爐內(nèi)高溫燃燒形成H2S，并隨粗煤氣進入低溫甲醇洗單元。因H2S與甲醇同為極性分子，易形成氫鍵，因此H2S在甲醇中有很好的溶解度。粗煤氣經(jīng)甲醇洗滌塔內(nèi)的甲醇洗滌后，CO2、H2S等氣體均溶解在甲醇中。洗滌后的甲醇經(jīng)減壓閃蒸、低壓解析、N2氣提除去甲醇中大部分的CO2后，富含H2S的甲醇經(jīng)熱再生塔加熱氣提再生，甲醇與H2S之間的氫鍵斷裂。從熱再生塔頂部出來的富含H2S的酸性氣體流量約1870m3/h(標態(tài))，其中H2S為25.38%(體積分數(shù)，下同)、COS為0.02%、CO2為72.35%，經(jīng)冷卻分離后送至硫回收裝置。

The sulfur in coal is burned 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 both polar molecules and are prone to forming hydrogen bonds, H2S has good solubility in methanol. After being washed with methanol in the methanol washing tower, the crude gas dissolves in methanol, including CO2 and H2S. After washing, methanol is subjected to vacuum flash distillation, low-pressure desorption, and N2 gas extraction to remove most of the CO2 in methanol. The methanol rich in H2S is heated and gas extracted in a hot regeneration tower for regeneration, and the hydrogen bond between methanol and H2S is broken. The flow rate of acidic gas rich in H2S coming out 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生物脫硫的原理

2. Principles of Biological Desulfurization

生物脫硫技術(shù)主要是采用硫黃桿菌來處理酸性氣中的H2S，而硫黃桿菌是在自然界中產(chǎn)生，通過遺傳培育或改良而來。硫黃桿菌的繁殖生長很快，4h就可以翻倍且成對數(shù)增長，而且對工藝條件、生產(chǎn)環(huán)境等都有很強的適應性，其生長過程中所需的能量主要來源于硫化物的氧化過程，碳源則來自于酸性氣中的CO2。

Biological desulfurization technology mainly uses Thiobacillus to treat H2S in acidic gas, and Thiobacillus is produced in nature through genetic cultivation or improvement. Thiobacillus proliferates and grows rapidly, doubling and growing logarithmically within 4 hours, and has strong adaptability to process conditions and production environments. The energy required for its growth mainly comes from the oxidation process of sulfides, while the carbon source comes from CO2 in acidic gases.

來自低溫甲醇洗單元的酸性氣進入H2S吸收塔內(nèi)與堿性溶液逆向接觸，酸性氣中的H2S和CO2被堿液吸收分別生成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 generate HS -, CO32-, and HCO3- (H2S+OH -=HS -+H2O, H2S+CO32-=HS -+HCO3-, CO2+OH -=HCO3-, HCO3-+OH -=CO32-+H2O), respectively.

吸收了酸性氣中H2S和CO2的溶液進入生物反應器底部與空氣混合，溶液中的HS-與O2反應生成硫和OH-(2HS-+O2=2S+2OH-，8SxHS-+4O2=S8+8Sx+8OH-)，溶液中的CO32-、HCO3-分解釋放出OH-和CO2(CO32-+H2O=HCO3-+OH-；HCO3-=CO2+OH-)，堿液得到再生后循環(huán)使用。生物反應器內(nèi)若O2過量，會發(fā)生副反應生成硫酸鹽和硫代硫酸鹽(HS-+2O2=SO42-+H+，2HS-+2O2= S2O32-+H2O)。在高濃度硫化物的作用下，生物菌的活性會降低，產(chǎn)生的硫酸鹽和硫代硫酸鹽增多。為減少副反應的發(fā)生，須合理控制生物反應器內(nèi)空氣的通入量，防止O2過剩。同時將硫黃脫水機分離出來的液體排至污水處理裝置，并向生物反應器內(nèi)補充新鮮水和堿液維持系統(tǒng)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 -), and the alkaline solution is regenerated and reused. If there is excessive O2 in the bioreactor, side reactions will occur to generate 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 air intake in the bioreactor to prevent excess O2. At the same time, the liquid separated by the sulfur dehydrator is discharged to the sewage treatment device, and fresh water and alkaline solution are added to the bioreactor to maintain system balance.

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