浮选柱内不同筛板结构下的气泡运动特性.pdf

硕士学位论文 浮选柱内不同筛板结构下的气泡运动特性 Bubble Behaviors under Different Sieve Plate Structures in Flotation Column 作 者李 娟 导 师闫小康 副教授 中国矿业大学 二○二○年六月 万方数据 学位论文使用授权声明学位论文使用授权声明 本人完全了解中国矿业大学有关保留、使用学位论文的规定，同意本人所撰 写的学位论文的使用授权按照学校的管理规定处理 作为申请学位的条件之一， 学位论文著作权拥有者须授权所在学校拥有学位 论文的部分使用权，即①学校档案馆和图书馆有权保留学位论文的纸质版和电 子版，可以使用影印、缩印或扫描等复制手段保存和汇编学位论文；②为教学和 科研目的，学校档案馆和图书馆可以将公开的学位论文作为资料在档案馆、图书 馆等场所或在校园网上供校内师生阅读、浏览。另外，根据有关法规，同意中国 国家图书馆保存研究生学位论文。 （保密的学位论文在解密后适用本授权书） 。 作者签名 导师签名 年 月 日 年 月 日 万方数据 中图分类号 学校代码 10290 UDC 密 级 公开 中国矿业大学 硕士学位论文 浮选柱内不同筛板结构下的气泡运动特性 Bubble Behaviors under Different Sieve Plate Structures in Flotation Column 作 者 李 娟 导 师 闫小康 申请学位 工学硕士 培养单位 化工学院 学科专业 化工过程机械 研究方向 化工分离设备流体动力学 答辩委员会主席 杨建国 评 阅 人 二○二○年六月 万方数据 致致 谢谢 当我写到这里的时候， 意味着我的学生生涯即将画上句号。 回首研究生三年， 首先要感谢我的导师闫小康副教授，谢谢闫老师这三年来的悉心教导，无私帮 助， 祝愿老师桃李满天下， 生活幸福， 工作顺利。 其次， 要感谢课题组的同学们， 李晓恒博士、 郑恺昕博士、 孟诗淇硕士、 苏子旭硕士、 杨涵曦硕士、 粟文兵硕士、 尧燕萍硕士、王帅杰硕士、刘煜硕士、陈朱应硕士以及张锐博士，谢谢你们在生 活和学习上对我的帮助，谢谢你们让我感知的世界更加温暖，和你们一起度过的 三年是我人生中非常珍贵的回忆。最后，衷心感谢我的父母，感谢你们多年的养 育之恩，感谢你们默默地支持，是你们把我从懵懂小儿，培养成一个独立、身心 健康、有生存能力的成年人。 研究生这三年是收获的三年，是奋斗的三年，是青春的三年。我或许曾经沮 丧，懒惰，自我怀疑，但更多的是刻苦学习，努力向上，尽力做好每一件事。再 见了我的学生时代。雨夜潇潇，这个白衣青年，终于要踏入江湖。未来，我或 是默默无闻，或是有所作为。但此刻，这些都不重要，有什么能阻挡一个初入江 湖的剑客心潮澎湃，踌躇满志呢 万方数据 I 摘摘 要要 旋流-静态微泡浮选柱是我国自主知识产权的大型过程装备，其特有的梯级 优化分选结构使其在微细粒矿物分选中表现出明显的优势。 该浮选柱柱选段常设 有筛板充填用以维持其静态化的分选环境。筛板结构对浮选流场的影响很大，具 体的影响规律以及作用机理尚缺乏全面且系统的研究， 限制了旋流静态微泡浮选 柱浮选效率的提高。本文借助电阻层析成像（ERT） 、粒子图像测速（PIV）及高 速动态测量等技术，研究了实验室规模不同筛板结构（孔径、厚度、充填位置） 对气泡运动特性（气含率、气泡速度、气泡尺寸）的作用规律，揭示了筛板对浮 选流场的影响并探讨了筛板充填下的浮选动力学，主要工作及结论如下 借助 ERT 研究了筛板充填对柱选段气含率的影响。首先，测量了不同循环 量和充气量下无充填旋流静态微泡浮选柱柱选段的气含率分布。结果表明其气 含率在径向上的分布呈现柱中心区域高，近壁面区域低的特征；充气量一定时， 测量截面的气含率随循环量的增大而降低。随后，在柱选段充填不同结构的筛板 （孔径、厚度、充填位置） ，研究筛板结构对气含率的作用规律。结果表明在 研究范围内，当开孔率一致时，筛板孔径越大，气含率在径向上的分布越均匀； 筛板越厚，对向上弥散的气泡抑制作用越强，筛板上游的气含率越低；筛板充填 位置距离旋流段越近，筛板上游气含率分布越均匀。最后，对比同一工况下，筛 板充填前后柱选段的气含率，发现筛板的加入使柱中心区域气含率降低，近壁面 区域气含率升高，表明筛板有效分散了柱中心聚集的气泡群，使气含率在径向上 的分布更为均匀，更有利于气泡与矿粒发生碰撞，提高矿化效率。 采用 PIV、内窥镜与 CCD 相机相结合的方式测量了循环量 1.0m3/h、1.5m3/h 和 2m3/h 三种工况下筛板充填前后柱选段横截面上的气泡切向速度变化规律。 结 果表明 筛板的加入使气泡切向速度的径向分布更趋于均匀且筛板对气泡切向速 度的抑制作用极强。循环量为 2m3/h 时，5mm 厚的筛板就使气泡切向速度的峰 值从 0.41m/s 降至 0.046m/s，削弱了 89，可见经过筛板后的大部分气泡以轴向 向上运动为主，有利于与垂直向下给料的矿物颗粒发生碰撞，强化了柱选段的逆 流矿化。 借助高速动态测量技术探明了筛板充填对气泡尺寸的影响及作用机理。 其一， 固定循环量 1.5m3/h，在 0.7L/min、1.1L/min、1.5L/min 三个充气量下，无充填浮 选柱柱选段的气泡尺寸随充气量的增大而增大。其二，在柱选段充填不同结构的 筛板（孔径、厚度、充填位置）后，筛板结构对气泡尺寸的作用规律表现为气 泡的平均直径随筛板孔径和厚度的增加而增加； 筛板充填在距旋流段 95mm0.5D 处对应的气泡平均直径最小，旋流段次之，距旋流段 190mm1D处最大。其三， 万方数据 II 同一工况下，通过对比筛板充填前后柱选段气泡尺寸分布规律的差异，表明了空 间狭小的筛孔在切割、破碎大气泡的同时，也会迫使小气泡发生聚集、兼并，从 而使得气泡尺寸更均匀。 进一步，综合分析不同筛板结构对气泡运动特性参数的作用规律，从矿物分 选角度，得出以下结论 ①综合考虑筛板充填位置对气含率和气泡平均直径的影响， 认为筛板充填在 距离旋流段 95mm0.5D处充填效果较佳； ②筛板对气泡切向速度的抑制作用极强且筛板越厚，气含率越低，气泡平均 直径越大，故在保证充填效果的同时，尽量选择较薄的筛板； ③结合筛板孔径对气含率和气泡平均直径的影响， 在保证筛板不会发生堵塞 的前提下，尽量选择小孔径的筛板。 最后，根据筛板充填后旋流静态微泡浮选柱柱选段的流场特性，探讨了与其 相适宜的气泡-颗粒碰撞、粘附、脱附概率、浮选速率常数以及停留时间，推导 了适用于筛板充填旋流静态微泡浮选柱柱选段的回收率计算公式。 该论文包括图 26 幅，表 13 个，参考文献 81 篇。 关键词关键词旋流静态微泡浮选柱；筛板结构；气泡运动特性；浮选动力学 万方数据 III Abstract Cyclonic-static micro-bubble flotation column is a kind of large-scale equipment with independent intellectual property rights in China. Because of its unique step-optimized separation structure, it has showed obvious advantages on the fine-grained mineral separation. The column flotation unit of this flotation column was packed with sieve plate to maintain its static separation environment. The structure of sieve plate has a great impact on the flotation flow field, its specific rule and mechanism has been lack of comprehensive and systematic research, which limits the improvement of flotation efficiency in cyclonic-static micro-bubble flotation column. In this paper, using electrical resistance tomography ERT, particle image velocimetry PIV and high-speed dynamic system, the effect of sieve plates different in aperture, thickness and packing position on the bubble motion parameters including gas holdup, bubble velocity, bubble size in the column flotation unit was studied to reveal its effect on the flotation flow field. After that, the flotation kinetics was discussed. The main work and conclusions were as follows. The effect of sieve plate on gas holdup in column flotation unit was explored by ERT. First of all, ERT was used to measure gas holdup at different liquid fluxes and air inflows in cyclonic-static micro-bubble flotation column without packing. The results showed that the distribution of gas holdup along the radial direction was uneven, its value was high in the central region and low near the wall region. Under a certain air inflow, gas holdup decreased with the increase of liquid flux. After that, sieve plate which was different in aperture, thickness, or packing position was packed in column flotation unit to explore the effect of sieve plate structure on gas holdup. The results showed that fixing opening percentage, the larger the diameter of sieve plate was, the more uni the distribution of gas holdup was in the radial direction. The thicker the sieve plate was, the stronger the inhibition of upward dispersed bubbles was, and the lower the gas holdup upstream of the sieve plate was. From the view of the uniity distribution of bubble, the closer sieve plate was to cyclone separation unit, the better packing effect was. Finally, the distribution and value of gas holdup in sieve plate packing flotation column was compared with open flotation column at the same operating conditions. The results showed that sieve plate was lower gas holdup in the central region and higher gas holdup near the wall region, which revealed that sieve plate effectively dispersed the group of bubbles and made bubbles evenly distributed in radial direction. It was more conducive to the collision 万方数据 IV between bubbles and the ore particles evenly distributed in the pulp, so as to improve the mineralization efficiency. By the combination of endoscope, PIV and CCD camera, the tangential velocity of bubbles was measured at different liquid fluxes such as 1 m3/h, 1.5 m3/h, 2 m3/h in sieve plate packing flotation column and open flotation column. And the results showed that the addition of sieve plate made the radial distribution of bubble tangential velocity more uni. And sieve plate had a strong effect on weakening the tangential velocity of bubbles, which was conducive to collide with the mineral particles feeding vertically downward and strengthen the countercurrent mineralization in column flotation unit. For example, the 5 mm thick sieve plate reduced the peak value of the tangential velocity of the bubble from 0.41 m/s to 0.046 m/s, which weakened 89 of it. A high-speed dynamic measurement system on bubble size was established to explore the effect of sieve plate on bubble size. At first, fixing liquid flux as 1.5 m3/h, the size of bubble was photographed in open flotation column under three air inflows of 0.7 L/min, 1.1 L/min and 1.5 L/min. The results showed that the diameter of bubble increased with the increase of air inflow. Secondly, sieve plate which was different in aperture, thickness, or packing position was packed in column flotation unit to explore the effect of sieve plate structure on bubble size. The results showed that the average diameter of bubbles in column flotation unit increased with the increase of its aperture and thickness. When sieve plate packed at 95 mm 0.5D from cyclone separation unit, the average diameter of bubbles was minimum, following by the cyclone separation unit and 190 mm 1D from cyclone separation unit. On the basis of the previous research, in order to directly reveal the influence of sieve plate on bubble size, the size of bubble in sieve plate packing flotation column was compared with open flotation column. The results showed that sieve plate maintained the uniity of bubble size by forcing small bubbles to gather and merge while cutting and breaking large bubbles. By analyzing the effects of sieve plate on bubble motion parameters, the conclusions were as follows. ①Considering the influence of sieve plate packing position on gas holdup and the average diameter of bubbles, it was considered that the packing effect of sieve plate was better at 95 mm 0.5D from cyclone separation unit. 万方数据 V ②Sieve plate had a strong inhibition on the tangential velocity of bubbles, and the thicker sieve plate was, the lower gas holdup and the larger the average diameter of bubbles was. Therefore, while ensuring the packing effect, the thinner sieve plate should be selected as far as possible. If the swirl was too strong, it could be considered to use a multi-layer thin sieve plate for packing. ③Considering the influence of sieve plate aperture on gas holdup and the average diameter of bubbles, it was considered that after ensuring sieve plate would not be blocked, try to select the sieve plate with small aperture. Based on the flow field characteristics of sieve plate packing cyclonic static micro bubble flotation column, the ula of bubble particle collision, adhesion, desorption probability, flotation rate constant and residence time were established. And the ula of recovery rate which was suitable for column flotation unit in this flotation column was derived. The paper includes 26 figures, 13 tables and 81 references. Keywords Cyclonic static micro bubble flotation column; different sieve plate structures; bubble behaviors; flotation kinetics 万方数据 VI 目目 录录 摘摘 要要............................................................................................................................ I 目目 录录......................................................................................................................... VI 图清单图清单........................................................................................................................... X 表清单表清单........................................................................................................................ XII 变量注释表变量注释表 ............................................................................................................. XIII 1 绪论绪论............................................................................................................................ 1 1.1 研究背景与意义 .................................................................................................................1 1.2 文献综述 .............................................................................................................................2 1.3 存在的问题 .......................................................................................................................10 1.4 研究内容与技术路线 .......................................................................................................11 1.5 本章小结 ...........................................................................................................................12 2 不同不同筛板筛板结构下柱选段的气含率结构下柱选段的气含率 ......................................................................... 13 2.1 概述 ...................................................................................................................................13 2.2 电阻层析成像仪测量气含率 ...........................................................................................13 2.3 结果分析 ...........................................................................................................................15 2.4 本章小结 ...........................................................................................................................26 3 筛板充填前后筛板充填前后柱选段的气泡速度柱选段的气泡速度 ......................................................................... 27 3.1 概述 ...................................................................................................................................27 3.2 无充填旋流静态微泡浮选柱横截面的 PIV 测量 ...........................................................27 3.3 筛板充填旋流静态微泡浮选柱横截面的 PIV 测量 .......................................................31 3.4 筛板充填前后柱选段气泡切向速度对比 .......................................................................33 3.5 本章小结 ...........................................................................................................................34 4 不同不同筛板筛板结构下柱选段的气泡尺寸结构下柱选段的气泡尺寸 ..................................................................... 36 4.1 概述 ...................................................................................................................................36 4.2 高速动态测量气泡大小 ...................................................................................................36 4.3 结果分析 ...........................................................................................................................38 4.4 本章小结 ...........................................................................................................................46 5 筛板充填筛板充填对对浮选动力学浮选动力学过程的影响过程的影响 ..................................................................... 47 5.1 概述 ...................................................................................................................................47 5.2 浮选动力学 .......................................................................................................................47 万方数据 VII 5.3 浮选速率常数 ...................................................................................................................48 5.4 颗粒停留时间 ...................................................................................................................53 5.5 筛板充填浮选柱柱选段的回收率 ...................................................................................54 5.6 本章小结 ...........................................................................................................................54 6 结论与展望结论与展望 ............................................................................................................. 56 6.1 结论 ...................................................................................................................................56 6.2 未来工作展望 ...................................................................................................................58 参考文献参考文献 ..................................................................................................................... 59 作者简历作者简历 ..................................................................................................................... 64 学位论文原创性声明学位论文原创性声明 ................................................................................................. 65 学位论文学位论文数据集数据集 ......................................................................................................... 66 万方数据 VIII Contents Abstract ...................................................................................................................... III Contents ........................