盘式连续干燥器中物料与加热盘间的传热

<正> 盘式连续干燥器是一种连续操作的搅拌物料传导干燥设备,它操作弹性大,性能良好,运转可靠,干燥效率高,目前已被许多国家广泛应用于工农业生产中。本文拟将E.U.Schlunder和N.Mollekopf针对间歇式搅拌物料传导干燥提出的“扩散理论”应用于盘式连续干燥器中物料的干燥过程,计算物料的干燥速率及料层温度,并以聚氯乙烯树脂为物料在盘式连续干燥器样机上进行干燥实验。     

盘式连续干燥器的耙叶设计探讨

在所有传导式干燥机中,盘式连续干燥器的有效加热面积最高,理论上可达100%,但如果耙叶设计与选择不当,将导致实际有效加热而积降低,有的共至低至50%以下,盘面上出现大最的裸露面积,严莆影响了盘式连续干燥器效能的正常发挥.通过理论分析和图形解析方法,给出了盘式十燥机耙叶设计的一些准则,可消除盘面的裸露面积,提高干燥机的综...     

盘式连续干燥器干燥速率及耙叶搅拌数

盘式连续干燥器干燥速率及耙叶搅拌数司孟华张继军河北经贸管理干部学院石家庄市０５００１１）（核工业部第四设计研究院石家庄市０５００２１）搅拌物料床层的传热与传质是非常复杂的，ＥＵＳｃｈｌｕｎｄｅｒ和ＮＭｏｌｅｋｏｐｆ对其进行了研究，并采用集总参数的方法...     

盘式连续干燥器在氢氧化钡生产中的应用

介绍了应用于氢氧化钡干燥的盘式连续干燥器。阐述了该干燥器的工作原理及工艺流程,分析了这种干燥形式的特点及应用领域,并与传统的气流管干燥机进行了比较。结果表明,用于氢氧化钡的干燥,盘式连续干燥器优于气流管干燥机。     

盘式连续干燥器在卤水法硫酸钡干燥中的应用

介绍了盘式连续干燥器的主要结构、工作原理及其在卤水法硫酸钡干燥中的应用。     

盘式干燥器设计和应用

盘式连续干燥器发展至今已有几十年的历史,最初它只用于硫铁矿的焙烧及煤粉的干燥,由于其设备投资较大及当时的一些技术问题,一直没有引起人们的重视。近几十年,由于节能、改善工作环境及一些难处理物料干燥的需要,许多国家又开始了盘式连续干燥器的开发和研究工作,进一步改进了其制造加工工艺,降低了成本,提高了干燥性能,将广泛应用于化工、染料、农药、塑料、医药、食品等领域,并取得很高的效益。     

滚筒干燥器内丝状物料的传热传质特性研究

干燥涉及众多生产领域,卷烟加工过程中存在干燥环节,滚筒烘丝机是用于干燥烟丝的主要设备。在滚筒烘丝机内,烟丝与周围环境进行热质交换,不同的运行控制条件,将直接影响烟丝的品质。由于干燥过程受众多因素的影响,至今烟草加工企业对烘丝机内部烟丝的传热传质特性缺乏深层次的认识,不利于烟丝品质的提高。针对上述背景,本文基于传热传质学、流体力学、多相流动等相关理论,通过计算机数值模拟方法,建立并求解滚筒内的传热传质数学模型,获得不同操作条件下烟丝温度、含水率变化的详细信息,并将所得结果与实际生产数据相验证。研究结果表明,烟丝与气流逆流流动条件下,干燥过程存在三个阶段：预热段、恒速段、降速段,烟丝含水率先升后降,烟丝温度经历先升高、后降低、再升高的过程;顺流流动条件下,干燥过程存在两个阶段：预热段与恒速段,烟丝含水率沿程单调下降,烟丝温度在预热段急剧上升,在恒速段平缓上升。     

反丁烯二酸生产中盘式连续干燥器的应用

本文介绍了应用于反丁烯二酸干燥的盘式连续干燥器．阐述了工作原理及工艺流程．分析了这种干燥形式的特点及应舟领域．并重点与气流式干燥器进行了比较。     

盘式连续干燥器与回转窑干燥机干燥镍精矿的比较

介绍了盘式连续干燥器与回转窑干燥机的工作原理和干燥效果,通过对盘式连续干燥器的实验数据和回转窑的实际生产数据的分析比较,证明盘式连续干燥器干燥镍精矿的优越性及节能环保效果。     

盘式连续干燥器中耙叶的设计

简单介绍了盘式连续干燥器中常见的几种耙叶形式,并根据物料在干燥器中的运动规律,对平面刮板形式耙叶的主要尺寸提出了设计方案。为了使耙叶在干燥器运行的过程中更好地输送及翻炒物料,又对耙叶的结构形式提出了几点改进意见。     

CONVECTTVE HEAT AND MASS TRANSFER AND EVOLUTION OF THE MOISTURE DISTRIBUTION IN COMBINED CONVECTION AND RADIO FREQUENCY DRYING

ABSTRACT

In a previous study (Dostie and Navarri, 1994), experiments indicated that a non-uniform moisture distribution could develop in radio frequency drying depending on the applied power and initial conditions, making the design and scale-up of such a dryer a more difficult task. Consequently, a thorough study of the combined convection and RF drying process was undertaken. Experimental results have shown that the values of the neat and mass transfer coefficients decrease with an increase in evaporation rate caused by RF energy. This effect is adequately taken into account by the boundary layer theory. Furthermore, the usual analogy between heat and mass transfer has been verified to apply in RF drying. Experiments have also shown that a different mass transfer resistance on both sides of the product should not result in non-uniform drying. However, it appears that non-uniform drying is dependent upon the initial moisture distribution and the relative intensity of heal transfer by convection and RF- It was shown that the maximum drying rate occurs at a higher average water content and that the total drying time increases with non-uniformity of the initial moisture distribution.     

干燥过程热质传递的简化模型

对多孔介质体积平均理论进行简化,得到简化的热质传递干燥模型,用一个理论式表达模型中有效扩散系数。对香蕉片千燥的研究表明,模型的预测值与实验结果相     

HEAT,MOMENTUM, AND MASS TRANSFER MEASUREMENTS IN INDIRECT AGITATED SLUDGE DRYER

ABSTRACT

Whereas indirect agitated drying has been extensively studied for granular materials, little is known in the case of pasty products. We describe an experimental set up specially designed for the investigation of drying kinetics, of heat transfer coefficient evolution, and of the mechanical torque necessary for stirring. This device was applied to municipal sewage sludge. Preliminary experiments were performed to investigate the influence of ageing of sludge on the drying kinetics. It appears that ageing does have no effect except for the first two days. The influences of the wall temperature, the stirrer speed, the dryer load and the location of the stirrer against the heated wall were studied. Three different rheological behaviors were observed during sludge drying. In particular, the sludge goes through a “glue” phase, and high levels of mechanical strain are recorded when the compact mass begins to break up. A critical stirrer speed is found within the range 40–60 rpm. To shorten the drying time, it seems better to adjust the wall temperature in accordance with the moisture content of the sludge.     

HEAT, MOMENTUM, AND MASS TRANSFER MEASUREMENTS IN INDIRECT AGITATED SLUDGE DRYER

Whereas indirect agitated drying has been extensively studied for granular materials, little is known in the case of pasty products. We describe an experimental set up specially designed for the investigation of drying kinetics, of heat transfer coefficient evolution, and of the mechanical torque necessary for stirring. This device was applied to municipal sewage sludge. Preliminary experiments were performed to investigate the influence of ageing of sludge on the drying kinetics. It appears that ageing does have no effect except for the first two days. The influences of the wall temperature, the stirrer speed, the dryer load and the location of the stirrer against the heated wall were studied. Three different rheological behaviors were observed during sludge drying. In particular, the sludge goes through a “glue” phase, and high levels of mechanical strain are recorded when the compact mass begins to break up. A critical stirrer speed is found within the range 40-60 rpm. To shorten the drying time, it seems better to adjust the wall temperature in accordance with the moisture content of the sludge.     

HYDRODYNAMICS AND MASS TRANSFER IN A SPOUTED BED DRYER

ABSTRACT

The disposal of sludge generated by water treatment plants poses major financial and environmental problems. Drying of the sludge is an essential pan of any disposal process which may include incinerating, landfilling or upgrading. In the present study, experiments were carried out to investigate the drying of sludge in a spouted bed and to characterize the hydrodynamics and mass transfer mechanisms. The effect of bed moisture content on the minimum spouting velocity (U_ms) was examined for sludge granules. U_ms was found to increase with increasing the moisture content of the sludge particles. The gas phase mass transfer coefficient in the dryer was determined using porous calcined alumina particles and the results were compared with predictions by correlations available in the literature. The existing correlations gave poor predictions for the mass transfer coefficient. A new correlation for the mass transfer coefficient in a spouted bed dryer was developed based on the experimental results.     

ANALOGY BETWEEN HEAT AND MASS TRANSFER IN THREE SPOUTED BED ZONES DURING THE DRYING OF LIQUID MATERIALS

This work, presents an experimental study of simultaneous heat and mass transfer in spouted bed zones during the drying of liquid materials. Distilled water was used as the liquid material and glass beads as inert material. The effect of the inlet gas temperature (100 to 140 °C), the feed air flow rate relative to air flow at minimum spouting (1.1 to 1.3), and liquid feed flow rate to the bed were investigated. The similarity between heat and mass transfer was analyzed using the Lewis and Chitton-Colburn analogies. Results showed that the ratio between the heat and mass transfer Chilton-Colbum factors lay between 1,31 and 1.74.     

搅拌槽内气－液体系的分散、传质和传热

综述了搅拌槽内气－液体系分散、传质和传热特性，比较了搅拌器类型、通气方式和多级搅拌器对混合性能的影响。对文献中观点的分歧进行了探讨，由此得到两个传质系数关联式，并揭示出给热系数随操作条件变化的机理。     

MASS TRANSFER IN A RECIPROCATING PLATE BIOREACTOR

An experimental program has been initiated to evaluate the performance of a reciprocating plate bioreactor for its use in viscous fermentations. The investigation is divided into three parts: (1) to study the hydrodynamics within the bioreactor, (2) to determine the axial dispersion coefficient and the overall oxygen mass transfer coefficient as a function of the operating conditions, and (3) the evaluation of a reciprocating plate column as a bioreactor for viscous fermentations. This paper reports on the determination of the axial dispersion coefficient and on the measurement of the overall oxygen transfer coefficient. Experiments were done in water on a semi batch scheme (no water flow) in a 1.26m high and 101.6mm internal diameter column.

It was found that the axial dispersion coefficient is a strong function of the reciprocation speed whereas it is relatively unaffected by the aeration flow rate. The overall oxygen transfer coefficient was determined with two separate methods: (1) the sulfite oxidation method which is based on the conversion of sulfite into sulfate to calculate the overall oxygen transfer coefficient, and (2) the gassing-out method which uses dissolved oxygen responses at various locations inside the column to determine the local mass transfer coefficient. It was found that higher values of the oxygen transfer coefficient prevail within the reciprocating plate bioreactor than in other types of mixing devices, for an identical volumetric power input.     

EXPERIMENTAL RESEARCH ON MASS TRANSFER IN A CENTRIFUGAL FLUIDIZED BED DRYER

Abstract

The influences of bed thickness, particle diameter, rotating speed of the basket and operating gas velocity on the mass transfer between gas and particles in the centrifugal fluidized bed dryer (CFBD) were examined. The experimental correlation used to calculate the mass transfer coefficient in the centrifugal fluidized bed dryer was obtained.     

ANALOGY BETWEEN HEAT AND MASS TRANSFER IN THREE SPOUTED BED ZONES DURING THE DRYING OF LIQUID MATERIALS

ABSTRACT

This work, presents an experimental study of simultaneous heat and mass transfer in spouted bed zones during the drying of liquid materials. Distilled water was used as the liquid material and glass beads as inert material. The effect of the inlet gas temperature (100 to 140 °C), the feed air flow rate relative to air flow at minimum spouting (1.1 to 1.3), and liquid feed flow rate to the bed were investigated. The similarity between heat and mass transfer was analyzed using the Lewis and Chitton-Colburn analogies. Results showed that the ratio between the heat and mass transfer Chilton-Colbum factors lay between 1,31 and 1.74.