【作者】 刘金艳；

【导师】 陶秀祥；

【作者基本信息】 中国矿业大学 ， 矿物加工工程， 2010， 博士

【摘要】 煤炭是中国的主要能源。随着煤炭资源的日益消耗与机械化采煤程度的提高,高硫、高灰、细粒煤炭含量在原煤中的比例不断提高,细粒煤的燃前脱硫技术成为洁净煤技术的研究重点之一。由于煤炭生物脱硫具有低成本、低能耗、环境友好等优点,因此,开展煤炭生物脱硫相关的基础研究对提高煤的洁净利用和改善生态环境具有重要的经济和社会意义。本文从脱硫微生物氧化亚铁硫杆菌的优化培养研究入手,探讨了电化学方法与生物反应器放大培养模式对细菌细胞代谢亚铁离子的影响;分析了氧化亚铁硫杆菌与单质硫、黄铁矿作用过程中的溶液性质变化,优化了煤炭生物脱硫的工艺参数条件;利用硫的K边X射线近边结构光谱等新型手段,探讨了氧化亚铁硫杆菌与固体基质(单质硫、黄铁矿与煤样)的表面特性;通过分析微生物与煤炭、浸出液及气相的界面作用,提出了氧化亚铁硫杆菌脱除煤中黄铁矿硫的界面生物氧化模型,为煤炭生物脱硫工艺的设计提供了理论支持。具体研究结果包括以下几部分:(1)在摇瓶培养氧化亚铁硫杆菌的过程中,分析了溶液中氢离子与铁离子的变化规律,优化了初始pH值、初始亚铁离子浓度与外加电位等反应条件;利用单因素方差分析方法讨论了细菌接种量、培养温度、初始亚铁离子浓度对细菌放大培养的影响;实验得出了在培养液中补加能源物质维持(4-5) g/L亚铁离子浓度的最佳补料-分批培养策略。实验结果证明了外加负电位对细菌生长的促进作用,通过补料-分批放大培养,氧化亚铁硫杆菌在70 h达最大浓度2.30×109个/mL,实现了细菌的高密度快速培养。(2)探讨了铁离子与L-半胱氨酸对氧化亚铁硫杆菌活化氧化单质硫的影响;分析了氧化亚铁硫杆菌对黄铁矿的浸出行为与L-半胱氨酸对黄铁矿生物浸出的影响;利用K边XANES、FTIR、SEM、XRD、Zeta电位与接触角等测试手段研究了细菌作用后单质硫与黄铁矿的表面特性变化。实验结果表明,铁离子促进细菌在固体基质上的生长代谢,L-半胱氨酸中的巯基在细菌与固体基质的接触中起到“桥梁”作用,与细菌分泌的含巯基蛋白质一起发挥硫的解环作用。(3)在煤炭生物脱硫工艺研究中,讨论了煤浆浓度、煤样粒度与细菌接种量对煤炭生物脱硫效果的影响;通过正交试验确定了外加负电位的最佳脱硫条件,处理7天后煤炭脱硫率为59.47%;利用生物反应器补料-分批技术进行煤炭脱硫,第7天黄铁矿硫脱除率为80.45%,灰分脱除率为44.80%。实验结果表明,外加负电位促进了铁离子向亚铁离子的还原,一方面补充了氧化亚铁硫杆菌的能源供应,另一方面减少了黄铵铁矾沉淀的生成,对细菌生长活性与煤炭表面改性具有积极作用,利用生物反应器进行煤炭浸出脱硫的技术具有可行性,并在此基础上设计了一套细菌电化学催化、放大优育与逆流浸滤的煤炭脱硫方法与装置。(4)研究了氧化亚铁硫杆菌在煤炭表面的吸附行为;对比分析了在不同基质上生长的氧化亚铁硫杆菌的表面特性;利用多种检测手段分析了煤炭经氧化亚铁硫杆菌作用后的表面特性。综合分析微生物浸出脱硫体系中的界面作用,提出了氧化亚铁硫杆菌脱除煤中黄铁矿硫的界面生物氧化模型:煤炭生物浸出脱硫过程中,氧化亚铁硫杆菌分泌更多的蛋白质、多糖、类脂等胞外多聚物,通过静电吸引、疏水作用、氢键及化学键合等作用接触吸附到煤炭表面,催化氧化煤中黄铁矿溶解;溶液中的铁离子作为氧化剂继续与浸出体系中的黄铁矿和单质硫反应,产生亚铁离子供细胞循环利用,同时一部分铁离子生成黄铵铁矾沉淀并释放氢离子;黄铁矿中的硫在细菌的催化氧化作用下形成单质硫、链状硫、硫代硫酸盐与连四硫酸盐等中间产物。论文共包含92幅图,27个表格,156篇参考文献。更多还原

【Abstract】 Coal is the main energy resource in China. This comes a time when coal energy has been consumed too fast and mechanized coal mining developed rapidly resulting in more proportion of high-sulfur, high-ash and fine particles coals. Research on coal biodesulfurization before combustion,which is of low cost, low energy consumption and environmental friendship, will contribute to the clean coal processing and efficient utilization and the ecological environment protection, and have very important economic and social significance.With the research of Acidithiobacillus ferrooxidans (A.f) optimum cultivation as a start, the bacterial oxidation of ferrous ions and the influences of electrochemistry and bioreactor scale-up culture to A.f growth were analyzed. On the basis of solution chemistry studies of medium with A.f and element sulfur or pyrite, the processing parameters in coal biodesulfurization were optimized. The surface characteristics of A.f and solid substrates were investigated with the employment of integrated approaches such as sulfur K-edge X-ray near structure spectrums. The research of interface effects in coal desulfurization system with A.f leaching was concluded and the interface bio-oxidation model was proposed to support the design of coal biodesulfurization process theoretically. The detailed research contents and results were summarized to four aspects as follow.(1) The optimum flasks cultivation of A.f with ferrous ions as energy source were tested by varying the conditions of initial pH, initial ferrous ions concentration and applied potential. In the scaled-up batch cultivation of A.f with ferrous ions as energy source, culture temperature and initial ferrous ions concentration were analyzed to be the more important influence factors by factor variance analysis. Adding energy source FeSO4 into the medium to maintain ferrous ion concentration of (4-5) g/L were experimented to be the optimum feeding strategy. The results above proved the promotion of applied negative potential to A.f growth and the high-density and fast cultivation of A.f in bioreactor with the maximum bacterial concentration of 2.30×109 cells per mL in 70 hours.(2) The additions of ferric ions and L-Cysteine into the medium were discussed for the influence of bacterial growth activities on element sulfur. The bioleaching behaviors of pyrite were experimented. After A.f oxidation, the surface characteristics of element sulfur and pyrite changed significantly through the methods of K-edge XANES, FTIR, SEM, XRD, Zeta potential and contact angle. The results above indicated that the extracellular proteins with sulfhydryl group played a big role in the activation of circular sulfur to linear sulfur, and the sulfhydryl group of L-Cysteine served as the bridge between A.f and solid substrates.(3) The coal slurry concentration, coal size and bacterial incubation were explored for the influence of coal biodesulfurization effects. The orthogonal experiments for gaining optimum desulfurization conditions with applied potential were carried out and in 7 days bioleaching, the desulfurization ratio of coal reached 59.47%. The fed-batch experiments using bioreactor for coal desulfurization achieved good results of depyritization ratio 80.45% and deash ratio 44.80%. Experimental results demonstrated that, the utilization of applied potential methods positively influenced A.f growth activity and coal surface modification, as well as the feasibility of coal bioleaching using bioreactor was proved. On these theoretical basis above, a set of apparatus including electrochemical catalyzed culture of A.f, scaled-up optimized culture of A.f and coal desulfurization by bioleaching was designed.(4) The adsorption behavior of A.f cells to coal surfaces was studied. Comparison of A.f cells grown in ferrous ion solutions and on solid substrates showed different surface characters. After the coal bioleaching for depyritization, SEM, XRD, FTIR and sulfur K-edge XANES methods were used to compare the coal surface characteristics. The research of interface effects in coal desulfurization system with A.f leaching was concluded and the interface bio-oxidation model was proposed: planktonic cells with more extra-secretion become sessile on coal surface through electrostatic attraction, hydrophobic interaction, hydrogen bonding and chemical bonding. Pyrite is dissolved to ferric ions and a series of sulfur compounds by A.f. The ferric ions act as a mediator to oxidize sulfur compounds and pyrite producing ferrous ions, which is utilized as energy source by A.f and form the precipitation of jarosite. The catalytic oxidation of sulfur in pyrite by A.f results in the formation of the intermediate products of element sulfur, linear sulfur, tetrathionate and persulfate.The thesis contains 92 figures, 27 tables and 156 references.更多还原