【作者】 黄兵；

【导师】 施哲；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2009， 博士

【摘要】 针对燃煤燃烧、金属冶炼、烟气制酸等过程产生的大量低浓度,无回收价值的SO2烟气,提出了用固定化微生物净化低浓度SO2烟气的治理技术。通过对城市污水处理厂氧化沟采集的菌种进行诱导驯化,培养出对SO2有较好降解性能的脱硫菌,并对脱硫菌进行了16S rRNA测序分析鉴定。完成了脱硫菌的复合固定化微生物技术的开发,进行了固定床反应器的设计以及最佳工艺条件确定。分析了固定化微生物反应器净化低浓度SO2的过程机理,并建立动力学模型。具体研究结果如下：在曝气量0.1m3/h,曝气时间30min,间歇时间60min,每升菌液投加硝酸钠和磷酸二氢钾溶液17.5ml情况下,对城市污水处理厂氧化沟的菌种进行诱导驯化,经过四-五天可驯化培养出生长繁殖速度快、活性高、温度和pH值范围适应宽的高效脱硫菌。它们不仅以硫代硫酸盐、亚硫酸、硫酸盐为硫源,而且还可以SO2为唯一的硫源。脱硫菌在液相降解亚硫酸根的反应速率方程符合M-M方程,最大反应速率Rmax=95818mg/(L.h),米氏常数Km=36364mg/L。体系pH值和温度对降解速率均有明显的影响,在pH=3,温度30℃时,降解速率1440mg/(L.h+)。当体系温度不高于30℃,液相降解SO32-为一级反应,其速率常数k=6.522×108exp(-5902/T),反应活化能Ea=49.07kJ/mol。16S rRNA基因测序分析发现,在驯化的脱硫菌株中主要含有8种优势菌,8条序列中有5条是属于16S rRNA基因片段的V2-V5可变区,有3条是属于16S rRNA基因片段的V6-V8可变区,为此分别构建了两棵系统发育树。8条序列都属于变形菌门的物种,其中4种菌属于α-变形菌纲,4种属于β-变形菌纲。系统发育分析证明上述菌种属于α-变形菌纲中的根瘤菌目(Rhizobiales),慢生根瘤菌科(Bradyrhizobiaceae),红游动菌属(Rhodoplanes)的物种。它们之间相互协同,行使着微生物脱硫的生物学功能。用5%海藻酸钠包埋脱硫菌和0.3g活性炭,在4%氯化钙溶液中固定14h,然后再在0.06mol/L已二胺溶液里交联40min,可以制备得到相对活性251.3%,机械强度高,收缩率小的固定化微生物小球。与游离脱硫菌相比,固定化的脱硫菌具有更好的耐酸碱、热稳定性和抗毒物毒性冲击能力,能满足反应器长期运行的要求。固定化脱硫菌在液相降解亚硫酸根的反应速率方程符合M-M方程,最大反应速率rmax=3311mg/(L.h),米氏常数Km=6613mg/L。固定化微生物小球传质分析表明,对直径不大于2.5mm的固定化微生物小球在液相降解亚硫酸根的梯勒(Thiele)模数(φ)不大于0.628,即在液相以反应控制为主,但存在一定扩散影响。与游离脱硫菌降解S032-(pH=3,T=30℃)速率相比,使用直径为2.5mm的固定化微生物小球可以近似达到游离菌的降解速率。在系统温度小于30℃,液相降解S032-为一级反应,其速率常数k=1.62×109exp(-6077.7/T),反应活化能为Eα=50.53(kJ/mol)。这说明脱硫菌固定化后降解机理与游离菌的降解机理相同。用固定床反应器净化低浓度SO2烟气不仅反应器的启动时间短,而且在间歇喷淋pH=3-4的循环液,操作温度20℃,气体停留时间8s,固定床反应器净化S02气体的效率大于96%,最大生化去除量达6kg/(m3.h)。这一数值明显高于生物膜填料塔和游离菌的生化去除量。当反应器中的固定化微生物达到饱和后,可以采取通空气和适当喷淋液体进行固定化微生物活性的恢复,实现系统连续稳定的操作。该固定床反应器应用于处理S02浓度为2000mg/m3的实际燃煤烟气,反应器运行稳定,净化效率接近100%。这说明用固定床反应器净化低浓度SO2烟气是可行。固定化脱硫菌在固定床反应器降解低浓度S02时,微生物的生长动力学方程与S02气体的浓度(Cg)有关,即rx=(?).而基质消耗动力学方程还与固定床的空隙率有关,即-rs=(1-ε)·(?)。其降解过程机理为SO2从气相通过扩散进入液相,进而又经扩散进入固定化微生物表面供给微生物的生命活动,整个反应体系为气、液和固三相的传质,属于非均相微生物反应过程。固定化脱硫菌净化低浓度S02气体时,气相中SO2为脱硫菌生长的唯一限制性底物。SO2的传质扩散是影响固定化微生物生化反应的主要因素之一。底物SO2在固定化微生物小球内有效扩散与固定化小球的直径相关,其浓度分布的关系式固定床反应器净化SO2过程动力学模型方程参数包括了固定化脱硫菌的性质、内扩散因素和固定床的尺寸及固定床操作条件等因素。经检验与实际检测结果较为一致。该动力学方程模型可用于生化反应器的优化和放大设计,以及对含S02烟气降解能力和效果的预测。论文首次通过对城市污水处理厂氧化沟采集的菌种进行诱导驯化,驯化出具有生长繁殖速度快、活性高、对S02有较好降解性能的脱硫菌群。开发出活性炭吸附-海藻酸钙包埋-已二胺交联的复合固定化制备技术。更多还原

【Abstract】 A new removeal low concentration SO2 technology which aim at the low congcentration dioxide sulfurs (SO2) gas in the coal burning, metal smelting, producing sulfuric acid from gas in metallurgy and other SO2 gas of no recovery worth was study basis immobilization microorganism technology in this thesis. The research focused the domestication of desulfuration bacterium, the technology of preparation immobilization microorganism,16s rRNA sequencing of the desulfuration bacterium, and the operation conditionand, the desulfuration mechanism and dynamics model of removing low concentration SO2 in the fixed bed reactor filled immobilized desulfuration bacterium. The results are as follows:An.dominant desulfuration bacterium, which are a quick growth and propagate in a wide activation temperature and acidic condition, high activation and efficiency for removing SO2, were obtained from the oxidation ditch in city waste water treatment plant after inducement domestication by contained SO2 gas four or five day with 17.5ml (NaNO3 and KH2PO42- etc)/L(bacterium liquid) for nutriment of microorganism, at 0.1m3/h of aeration air,30min of aeration time and stop 60min. The dominant desulfuration bacterium can get their sulfur source with the thiosulfate, sulfite, sulfate, and can growth only with SO2. The reaction rate of the desulfuration bacterium degrades SO32- in aqueous solution accord with M-M equation, where the max reaction rate (rmax)=95818mg/L.h, and M-constant (Km)=36364mg/L. The pH value and temperature of system have evident effect to the degradation rate, and the maximal degradation rate is (1440mg/L.h) at pH=3, T=30℃. The degradation kinetics for SO32- is first order reaction under 30"C of the system temperature, and the reaction rate constant is k= 6.522×l08exp(-5902/T), the activation energy is=49.07kJ/mol.The desulfuration bacterium were studied using molecular biology based on 16S rRNA sequence comparison, and the results of the conformation or function of microbial communities with in situ hybridization and in situ PCR were exhibited. There are 8 dominant desulfuration bacterium to be found and they occupy about 70%of all microorganism. Tow phylogenetic trees were got because there are 5 bacterial strain in the V2-V5 variable region and 3 bacterial strain in the V6-V8 variable region of 16S rRNA gene segment. There are 4 desulfuration bacterium to belongα—Proteobacteria, and can be placed in Rhodoplanes, Bradyrhizobiaceae, Rhizobiales, and another 4 belong toβ-proteobacteria. The results indicated there are large of microorganism classification in the the desulfuration bacterium, and they are exertion biology function to transfer SO2 with their synergy. The discovery about the desulfuration bacterium have an important value for devolpment way of microorganism desulfuration from fuel gas.The immobilization desulfuration bacterium ball with 251.3%of comparatively activity, high mechanical strength and acid resistance and heat stability can be made by the technology for complexed immobilized bacterium with adsorption by activated carbon, embedded by 5%of sodium alginate, and immobilized drop in calcium chloride, then crosslinked 40 min in 0.06mol/L of hexamethylene diamine liquid. The immobilization desulfuration bacterium ball can be satisfied long period running in fixed bed, and the immobilized desulfuration bacterium degrades SO32- in aqueous solution satisfied also M-M equation as free desulfuration bacterium, and the parameter of kinetics equation: rmax=3311mg/L.h, Km=6613mg/L. The Thiele modulus (Φ) is 0.628 at 2.5mm the diameter of the mmobilized bacterium ball, and the degradation process of immobilized bacterium to SO32- is mainly controlled by reaction. The diffusion of substrate in the ball have some influenced at the diameter of the mmobilized desulfuration bacterium ball is over 3mm. The degradation rate of the mmobilized bacterium at the 25mm of ball diameter, pH=3, T=30℃is same with free desulfuration bacterium, and the degradation kinetics for SO32- is first order reaction under 30℃of the system temperature, where the reaction rate constant is k= 1.62xl09exp(-6077.7/T), the activation energy isEa=50.53 (kJ/mol). That showed the. desulfuration mechanism to SO32-is the same with that of free desulfuration bacterium.The fixed bed biochemical reactor with 42mm of tower diameter,100mm of high filled 25mm immobilized desulfuration bacterium ball, have a lesser startup time and a high removing SO2 efficiency over 96%and biochemical removal quantity over 6kg[SO2]/(m3.h) for low concentration SO2 gas at pH=3-4 of cycled spraying liquid,20℃of operation,8s of gas residence time. The result showed that biochemical removal quantity in fixed bed biochemical reactor is higher than that of free desulfuration bacterium. When the activity of immobilized desulfuration bacterium in fixed bed reactor is inactivation, it is effective to spray cycled liuquid and aeration air into the fixed bed reaction. When the tester plants have been used to remove SO2 of 2000mg/m3 from fuel oil tail gas and fuel coal tail gas in a catering industry, it showed that the reactor run stable, there are any SO2 to be detected at outlet (detection limit of 1mg/m3), and the removing efficiency is near to 100%. So the fixed bed biochemical reactor is possible for removal SO2 from fuel gas.The kinetics equation about cell growth of immobilized desulfuration bacterium in this bio-reactor is and that of substrate consumed is The mechanism of removing SO2 by fixed bed bio-reactor is that the SO2 in the gas is that the SO2 is diffluence in liquid, then diffusing into immobilized ball for desulfuration bacterium using. Which the process belong to heterogeneous microorganism reaction include mass tranfer of SO2 and other substance in gas-liquid-solid. It is discover that the SO2 is a alone restricted substance by immobilized desulfuration bacterium removal SO2 from low concentration SO2 gas, and the mass transfer of SO2 in immobilized ball is one of main factor for removing SO2. And the internal diffusion of SO2 in the ball is related with the face concentration of substrate and semidiameter of ball, and the concentration distribution in the ball can be described with The kinetics model for fixed bed bio-reaction removal SO2 can be showed as which include the character of immobilized desulfuration bacterium, internal diffusion factor, dimension of fixed bed bio-reactor, and operation condition and so on. The model prediction results have a good coherence with experiment data. So the kinetics model can provide a theory guide for optimizing of operation condition, enlarge design of the bio-reactor, and forecast of the desulfur ability.更多还原