高温高压条件下浆态鼓泡床气液传质特性的研究

论文编号:HG007  字数:25168.页数:60

摘 要
浆态鼓泡床反应器具有结构简单、传热、传质性能好以及温度易控制等优点，在化工生产中，例如F-T合成、液相合成甲醇、合成二甲醚等一些强放热的多相反应体系中有着广泛的应用。因此，浆态鼓泡床被认为是最具发展前景的多相反应器之一，对它进行详细的研究具有巨大的现实意义和潜在的应用价值。
传质特性是反应器设计和放大的重要参数之一，也是当今反应器研究的热点和难点。在大多数情况下，传质过程是整个反应过程的控制步骤，它直接影响着反应速率的快慢以及产物分布等。因此，对三相浆态反应器传质特性进行研究有利于了解反应器内的传质特征，使我们能够更好地利用浆态床反应器。
本文针对工业上对二甲苯氧化反应器的特点，建立了高温高压的浆态鼓泡床反应器实验装置，对气体在水体系和液体石蜡体系中传质特性进行了研究。实验采用动态气体吸收法测定了体系的体积传质系数，着重考察了温度（T）、 压力（P）、表观气速（）、固含率（）以及塔径（）等对液相体积传质系数（）的影响；同时，对于有机体系实验还利用床层塌落法测定了反应器内气泡含率（大、小气泡分率）和气泡上升速度，由此根据气泡上升速度与气泡直径的关联式，求取相界面积（）和液相传质分系数（），进而考察了操作条件对相界面积和液相传质分系数的影响，实验结论如下：
在温度（293K~473K）, 压力（1.0MPa~3.0MPa）,表观气速（0.03m/s~0.1m/s），固含率（0%(w)~20%(w)）的实验条件下，液相体积传质系数随着温度、压力、表观气速的增加而增大；随着固含率的增加而减小。对于不同直径的反应器来说，大塔中的传质系数略高于小塔中的传质系数。
在有机体系中，相界面积受压力、表观气速、固含率的影响较大，而受温度的影响较小；而传质分系数受温度、固含率的影响较大，受表观气速和压力影响较小。
在实验范围内得出气体（,,,）在两种体系(水、液体石蜡)中传质系数的计算关联式。
对于水-空气-石英砂体系：

对于气体-液体石蜡-石英砂体系：

实验从流体力学的角度定性地解释了气液传质的变化规律，有利于更加深入地认识传质特性。本实验结果可为浆态床鼓泡反应器的设计和放大提供一些基础实验数据。

关键词    浆态鼓泡床，传质特性，气液传质系数, 液相传质分系数，相界面积
MASS TRANSFER CHARACTERISTICS OF GAS－LIQUID IN A SLURRY BUBBLE COLUMN REACTOR UNDER HIGH TEMPERATURE AND HIGH PRESSURE

ABSTRACT

Slurry Bubble Column Reactor（SBCR）has been widely used in petrochemical, metallurgical, environmental, such as Fischer-Tropsch synthesis, LPMeOH, LPDME and so on. It offers many advantages over other multiphase reactors — simple construction, no mechanically moving parts, good mass transfer properties, high thermal stability, low energy supply and hence low construction and operation costs understood. So SBCR has become one of the most promising multiphase reactors. It has enormous significance and potential application value to study mass transfer of bubble column.
Mass transfer characteristics affect reaction rates and product distribution for chemical processes. Thus, they play an important role in designing and scaling-up the slurry bubble column reactors.
According to the characteristic of p-xylene oxidation reactor, A slurry bubble column reactor operating with water and organic liquid under high temperature and high pressure was set up. The effects of temperature, pressure, superficial gas velocity, solid concentration and diameter of reactors on the volumetric mass transfer coefficients using dynamic method are studied systematically. Moreover, the gas holdup and bubble rise velocities are measured using dynamic gas disengagement technique, which is used to calculate and estimate the Sauter mean bubble diameter and the gas-liquid interfacial area. Experimental study has resulted in the following conclusions:
Gas-liquid volumetric mass transfer coefficients increase with the increase of system pressure, temperature and superficial gas velocity, and decrease with the increase of solid concentration under the ranges of temperature (293K~473K), pressure (1.0Mpa~3.0Mpa), gas velocity (0.03m/s~0.1m/s) and solid concentration (0%(w)~20%(w)). For different reactors,  values in bigger reactor are slightly larger than those in smaller one.
 values are much more affected by pressure, superficial gas velocity and solid concentration, but less by temperature. However,  values are much more affected by temperature, solid concentration, but less by pressure and superficial gas velocity.
Based on analysis of the experimental data, two experiential correlations for predicting  values of gas in different liquids are obtained.
For Air-water- arenaceous quartz system:

For gas- paraffin- arenaceous quartz system:

In this paper, mass transfer characteristics are illustrated on the disciplinarian of hydrodynamics, which makes us understand mass transfer deeply in mass transfer behaviors of SBCR under high temperature and high pressure. The results of the experiment can provide some basic data to the design and scale-up of SBCR.

KEY WORDS: mass transfer coefficient, slurry bubble column reactor, gas-liquid mass transfer, gas-liquid mass transfer coefficient, gas-liquid interfacial area

目 录

符 号 说 明 .....................................................................1
前 言........................................................................... 3
第一章  文献综述 ................................................................4
1.1  浆态床反应器技术的发展状况..................................................4
1.2  浆态鼓泡床的优点............................................................7
1.3  浆态鼓泡床应用的典型工艺及操作条件..........................................7
1.4  浆态鼓泡床反应器的研究领域..................................................8
1.5  浆态鼓泡床内的混合与操作要求 ...............................................9
1.6  浆态鼓泡床气液传质的研究概况 ..............................................10
1.7  影响传质系数的主要因素 ....................................................12
1.7.1  系统压力 ................................................................12
1.7.2  温  度 ..................................................................12
1.7.3  表观气速 ................................................................13
1.7.4  液体性质 ................................................................13
1.7.5  固含率及固体颗粒性质.....................................................14
1.8  传质系数模型...............................................................15
1.8.1  传质系数的理论模型 ......................................................15
（1）双膜模型 ..................................................................15
（2）渗透模型...................................................................15
（3）表面更新模型...............................................................16
（4）旋涡池理论 ................................................................16
1.8.2  传质系数的经验关联式.....................................................16
1.9  传质系数的测量方法 ........................................................18
1.9.1  物理法...................................................................18
1.9.2  化学法 ..................................................................19
1.10 浆态鼓泡床传质特性的研究趋势 ..............................................19
1.11 课题的意义 ................................................................20
第二章  实验部分................................................................21
2.1  实验物系及实验条件.........................................................21
2.1.1  实验物系 ................................................................21
2.1.2  实验条件.................................................................22
2.2  实验装置及测量方法 ........................................................22
2.3  实验测试方法及分析过程 ....................................................23
2.3.1  气体浓度的测定方法 ......................................................23
2.3.2  气液体积传质系数的测定 ..................................................24
2.3.3  气含率的测定及公式推导...................................................25
2.6.3  相界面积的计算...........................................................27
第三章 空气－水体系中氧气传质系数的研究.........................................29
3.1   引 言.....................................................................29
3.2   气体浓度随时间的变化曲线 .................................................29
3.3   实验结果与讨论 ...........................................................30
3.3.1  系统压力的影响...........................................................30
3.3.2  温度的影响...............................................................30
3.3.3  表观气速的影响 ..........................................................31
3.3.4  固含量的影响.............................................................31
3.3.5  塔径的影响...............................................................32
3.4   传质系数的关联式..........................................................33
3.5   小  结....................................................................34
第四章 有机体系传质特性的研究 ..................................................35
4.1   引  言 ...................................................................35
4.2   气体浓度的测定............................................................35
4.2.1 气体浓度随时间变化的规律 .................................................35
4.3   结果与讨论 ...............................................................36
4.3.1 操作条件对的影响 .........................................................36
4.3.1.1   压力对传质系数的影响..................................................36
4.3.1.2   温度对传质系数的影响 .................................................37
4.3.1.3   表观气速对传质系数的影响 .............................................38
4.3.1.4   固含率对传质系数的影响 ...............................................39
4.3.2 体积传质系数的关联式......................................................39
4.3.3 气液相界面积和气液传质分系数的研究........................................40
4.3.3.1   压力的影响 ...........................................................40
4.3.3.2   温度的影响 ...........................................................41
4.3.3.3   表观气速的影响 .......................................................42
4.3.3.4   固含率的影响 .........................................................43
4.4   小  结 ...................................................................43
第五章 结 论....................................................................45
参考文献........................................................................46
附  录..........................................................................52
致  谢..........................................................................54