气液固三相搅拌槽内的气液分散和固液悬浮研究

发布时间：2018-03-22 16:27

本文选题：临界悬浮特性　切入点：通气搅拌功率　出处：《北京化工大学》2015年硕士论文　论文类型：学位论文

【摘要】：搅拌是工业生产一项常见的操作,由于其适用性强的特点,小到实验室操作,大到化工、冶金、制药、生物工程等大型工业都离不开搅拌单元操作。近年来随着搅拌装置的日益大型化,对多层桨搅拌槽的研究成为一个热点。已有研究表明,以径向流桨为底桨,轴流式桨为中、上层桨更利于气液的分散。本文采用前人在气液两相搅拌槽中优化得到的桨径与槽径比D/T为0.33的组合桨型PDT+2CBY(其中底桨为PDT桨,即径向流型的抛物线盘式涡轮桨,上两层桨为轴向流式的长薄叶螺旋桨CBY桨),在气液固三相体系中进行气液分散及固液悬浮性能的深入研究。本研究涉及两种不同的气液固三相体系,首先在空气-水-玻璃微珠(ρ=2500 k·m-3)体系中,研究采用PDT+2CBY组合桨的临界悬浮特性、通气搅拌功率和整体气含率。研究结果表明：1、临界悬浮特性：随着表观气速VS和固含率Cv的增加,临界悬浮转速NJSG和临界悬浮单位质量功率PmJSG皆随之增大。2、通气搅拌功率：随着通气速率和搅拌转速的增大,相对功率需求RPD皆不断减小并最终趋于稳定；在一定的搅拌转速下,RPD随固含率Cv的变化幅度不大,基本在10%以内。3、整体气含率：随着表观气速VS和单位质量功率PTm的增大,气含率随之增大；VS和PTm相同时,搅拌槽中的整体气含率随Cv增加而减小。在空气-水-树脂颗粒(ρ:1300kg·m-3)体系中进行类似研究,结果表明：1、临界悬浮特性：在不同表观气速下,气-液-树脂颗粒体系所需的NJSG及PmJSG均小于气-液-玻璃微珠体系下,且当表观气速较小时(Vs=0.0074 m·s-1),两种体系下NJSG及PmJSG相差较大,随着表观气速的增大(Vs=0.0152,0.0237 m·s-1),差异不断缩小；树脂颗粒作为固相时,固含率对ΔNJSG/NJS的影响小于玻璃微珠作为固相时,可忽略不计。2、通气搅拌功率：颗粒特性(颗粒密度、颗粒粒径分布等)对相对功率消耗的影响很小或没有影响；树脂颗粒作为固相时,固含率和Flg对RPD的影响均更大；不同固体颗粒作为固相时,Fr对RPD的影响差别不大。3、整体气含率：在给定的VS和PTm条件下,气-液-树脂颗粒体系的气含率均略大于气-液-玻璃微珠体系的。利用实验数据拟合得出两种颗粒三相体系中通气功率,临界悬浮特性及气含率计算的关联式,可为相似条件和桨型的三相搅拌反应器工业设计提供参考。
[Abstract]:Agitation is a common operation in industrial production. Due to its strong applicability, it can be used in laboratory, chemical, metallurgical and pharmaceutical industries. In recent years, with the increasing size of agitator, the research on multi-layer impeller tank has become a hot spot. It has been shown that the radial flow propeller is the bottom propeller, and the axial flow propeller is the middle one. The upper propeller is more favorable for gas-liquid dispersion. In this paper, the combined propeller type PDT _ 2CBY (where the bottom propeller is the PDT propeller, that is, the parabolic disk turbine propeller with radial flow pattern), which is optimized by the former in the gas-liquid two-phase stirred tank with D / T = 0.33, is used in this paper. The CBY propeller with long and thin blade with axial flow in the upper two layers is used to study the gas-liquid dispersion and solid-liquid suspension performance in the gas-liquid-solid three-phase system. This study involves two different gas-liquid-solid three-phase systems. At first, the critical suspension characteristics of PDT 2CBY composite propeller were studied in the air-water-glass microsphere system (蟻 ~ (2 500km-3)). Aeration stirring power and overall gas holdup. The results show that the critical suspension characteristic of 1: 1: with the increase of apparent gas velocity vs and solid holdup CV, The critical suspension speed (NJSG) and critical suspension unit mass power (PmJSG) increased with the increase of aeration speed. The relative power demand (RPD) decreased with the increase of aeration rate and stirring speed. Under a certain stirring speed, the range of gas holdup with solid holdup CV is small, which is within 10%. The overall gas holdup increases with the increase of apparent gas velocity vs and unit mass power PTm, and the gas holdup increases with the increase of VS and PTm. The overall gas holdup in the stirred tank decreases with the increase of CV. A similar study was carried out in the air-water resin particle system (蟻: 1300kg m-3). The results show that the critical suspension characteristic of the cell is: at different apparent gas velocities, The NJSG and PmJSG of gas-liquid-resin granular system are lower than those of gas-liquid-glass microbeads system, and when the apparent gas velocity is smaller, the difference between NJSG and PmJSG is larger, and the difference between NJSG and PmJSG decreases with the increase of apparent gas velocity. When resin particles are used as solid phase, the effect of solid holdup on 螖 NJSG/NJS is smaller than that of glass beads as solid phase. The particle size distribution has little or no effect on the relative power consumption, and the solid holdup and Flg have more effect on RPD when the resin particles are used as solid phase. When different solid particles are used as solid phase, the effect of Fr on RPD is not significant. The overall gas holdup: under given vs and PTm conditions, The gas holdup of gas-liquid-resin particle system is slightly larger than that of gas-liquid-glass bead system. Using the experimental data, the correlations of ventilation power, critical suspension characteristics and gas holdup calculation in two kinds of granular three-phase systems are obtained. It can provide reference for the industrial design of three-phase stirred reactor with similar conditions and propeller type.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ027.2

【参考文献】