新型搅拌式生物冶金反应器的传递特性研究
文献类型：学位论文
| 作者 | 周宏宝 |
| 学位类别 | 硕士 |
| 答辩日期 | 2012-05-21 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 张广积 ; 李向阳 |
| 关键词 | 生物浸出 搅拌槽 气液传质 离底悬浮 导流筒 |
| 其他题名 | Study on transport characteristics of new type stirred reactors for biohydrometallurgy |
| 学位专业 | 化学工程 |
| 中文摘要 | 矿物生物浸出由于能充分利用资源、低环境污染等优势，已成为矿物加工领域中发展最快、研究最为活跃的领域之一。由于传质、混合效果好，易于放大等优点，搅拌槽式反应器是目前工业生物浸出中最常用的反应器之一，但仍存在一些缺陷，如能耗较高、剪切强度较大以及矿浆浓度受限制等。基于此，本论文设计了新型搅拌式生物冶金反应器，并通过实验系统考察了反应器的固体悬浮和气液传质性能，获得了优化的反应器构型。 提出一种基于光纤法的固体颗粒悬浮特性测量方法。采用该方法测定了水-二氧化硅两相体系临界离底悬浮转速，并和传统目测法、取样法测定结果进行了对比。结果表明，由于目测法判据相对严格，光纤法比目测法测定结果偏低；光纤法与取样法测量结果较接近，但取样法操作较繁琐，光纤法更快速、简便，可应用于不透明容器中，因而具有重要的工业应用价值。 设计了新型搅拌式生物槽浸反应器。该反应器的主要特点：无挡板设计，中间加设直筒状导流筒，流动更加均匀，有效降低剪切力对微生物细胞的损伤。通过实验对反应器内气体分布器尺寸、双层桨构型等进行了优化，主要取得了如下结果： （1）小直径的气体分布器具有更低的泛点转速，大直径的气体分布器气泡没有经过搅拌器剪切直接进入导流筒外区，气泡直径较大，优化的环形气体分布器直径为0.8-1.0 D； （2）桨间距的大小是多层桨搅拌槽反应器的一个重要设计参数。本实验中，桨间距C2/D > 2.0时，在中央位置靠近液面处易于形成漩涡，对混合不利；桨间距C2/D ≤ 1.0时，由于叶轮之间相互作用增强，彼此产生的流场相互干扰，搅拌桨的功效降低。优化的桨间距为1.5-2.0 D； （3）在测定不同组合桨的泛点转速和临界离底悬浮转速时发现，六斜叶圆盘涡轮桨和Techmix335下压式水翼桨作为底层桨时，泛点转速较小，气体分散效果较好；开启式斜叶涡轮桨和六斜叶圆盘涡轮桨作为底层桨时临界悬浮转速较小，固体悬浮效果较好； （4）具有较强轴向循环能力的Techmix335下压式水翼桨作为上层桨，六斜叶圆盘涡轮桨作为下层桨时，气液体积传质系数最高。因此，综合考虑固体悬浮和气体分散因素，选取此种组合为优化的搅拌桨组合； （5）考察了操作条件和固含率大小对优化后的反应器kLa的影响，发现kLa随搅拌转速和通气量的增加而增大，并且通气量变大后，kLa的增加幅度减小；kLa随固含率的增加而减小，但减小的幅度不大，这有利于高矿浆浓度下生物浸出体系保持足够高的氧传递速率。 |
| 英文摘要 | Biohydrometallurgy of minerals has been one of the most active research fields in mineral processing for relatively high recovery of metal and low environmental pollution. Stirred tanks are one type of the reactors most frequently employed in biohydrometallurgy industry as a result of their high mass transfer and mixing efficiency and easy scale-up, but the problems such as higher energy consumption and shear intensity and the limitation of pulp density still remain unresolved. So a novel stirred bioreactor is designed and optimized in this work and the researches on the characteristics of solid suspension and gas-liquid mass transfer are carried out in experiments. An optic technique method is proposed for determination of the characteristic of particle suspension. The critical impeller speed for just complete off-bottom solid suspension Njs in water?silica two-phase system is measured using this method and the popular visual observation method and the withdrawal sampling method are selected for comparison. The results show that because of the stricter criterion for the visual observation method, the Njs obtained by the optic technique is smaller than that obtained by the visual observation method. The Njs obtained by the optic technique is close to that obtained by the withdrawal sampling method in the whole range of solid loadings. The optic technique operates faster and more easily than the withdrawal sampling method and can be applied to opaque vessels, so it is crucial for industrial process control. A novel stirred biohydrometallurgy reactor is proposed in this work and it is characterized by a concentric draft tube and no baffles, which make the flow field more uniform and reduce the shear stress and the damage to the bacteria. The diameter of gas sparger and dual-impeller configurations are optimized by experiments and the main findings are listed as follows: (1) Smaller ring sparger has lower impeller speed to prevent flooding. When the large sparger is employed, the air is not dispersed by the impeller and sparged into the annular zone directly, which results in big air bubbles in the riser zone. The optimized diameter of the gas sparger is 0.8-1.0 D. (2) The clearance between the impellers is an important design parameter for multi-impeller stirred tank reactors. In this work, when the impeller spacing is over twice the impeller diameter, vortex is easily formed in the center near the liquid level, which disfavors the mixing. While the impeller spacing is equal to or less than the impeller diameter, it is not energy-effective for liquid circulation with high aspect ratio. The optimized clearance between the impellers is 1.5-2.0 D. (3) The minimum speed to prevent flooding Nf and the critical impeller speed for off-bottom solid suspension Njsg are measured. It is found that the Nf value is lower for pitched rushton disk turbine downflow (PRDTD) and Techmix 335 hydrofoil impeller downflow (TXD) as the lower impeller. The Njsg value is lower for pitched rushton disk turbine downflow (PRDTD) and pitched blade turbine downflow (PBTD) as the lower impeller. (4) The TXD+PRDTD combination gives the highest kLa value. Thus an optimal dual-impeller configuration with PRDTD as bottom impeller and TXD as top impeller is gained based on the characteristics of ore suspension and air dispersion. (5) The effect of operating conditions and solid loading on kLa value for the optimized bioreactor is studied. It is found that the kLa increases with increasing impeller speed and volumetric gas flow rate and the increasing extent of kLa becomes small for higher volumetric gas flow rates. kLa decreases slightly with increasing solid loading, which is helpful to attain high oxygen mass transfer rate in biohydrometallurgy reactors with high solid loadings. |
| 语种 | 中文 |
| 公开日期 | 2013-09-25 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1859]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 周宏宝. 新型搅拌式生物冶金反应器的传递特性研究[D]. 中国科学院研究生院. 2012. |
入库方式： OAI收割
来源：过程工程研究所
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