振动多层流化床干燥装置在化学工业中的应用

本文介绍了一种用于化工领域的新型振动干燥装置,这种装置具有投资少,高效,节能和适用性广等优点。     

闭路循环干燥装置及其应用

简要介绍了闭路循环干燥装置的原理、特点和工艺流程。文中列举了其工业应用实例 ,并与其他干燥设备进行了对比。     

过热蒸汽流化床干燥装置

结合过热蒸汽干燥和流化床干燥的各自特性，开发出一种新型的过热蒸汽流化床干燥装置，阐述了工作原理。以卧式多室过热蒸汽流化床干燥装置干燥酒糟为例进行了工艺设计和计算，在保证稳定工作的条件下，干燥室内的绝对压力为0．3MPa，干燥室进出口的工作介质温度分别为180℃和140℃，最佳操作流化速度为2．6m／s。试验结果表明：该卧式多室过热蒸汽流化床干燥装置具有干燥速率大、热效率高、被干产品质量好和干燥操作成本低等优点，特别适宜于初始湿分高而加工附加值低的农产物料的干燥。     

振动流化床干燥装置干燥特性计算方法研究

通过对振动流化床（ＶＦＢ） 干燥装置中传热与传质过程的分析,建立了物料在其中的干燥特性模型, 得到了振动流化床干燥装置物料出口含湿量与温度的计算公式。     

陶瓷工业振动流化床干燥装置优化设计

振动流化床干燥是陶瓷干法造粒过程的一个重要操作单元.针对卧式多室振动流化床干燥装置能量利用率不高、耗能较大等问题,基于陶瓷原料在振动流化床干燥中的动力学模型、传热方程及热平衡方程,建立了陶瓷原料干燥所需热量在振动流化床干燥机长度方向上变化的数学模型.该模型表明,干燥过程所需热量沿多孔板长度方向减少.因此讨论了在多孔板长度方向底部用隔板隔开不同区域进行不等温进气,实验结果表明符合数学模型,分区供热方式可降低陶瓷原料干燥过程能耗,成品质量符合陶瓷工业干粉造粒要求.     

射流冲击流化床干燥的试验研究

设计试制了一种可对颗粒物料进行连续与批式干燥的射流冲击综合试验装置。在此基础上，对颗粒物料射流冲击干燥进行了系统试验研究，得出了射流冲击干燥装置的结构参数、工艺参数与干燥机性能间的关系，建立了射流冲击干燥的数学模型。     

浅谈流化床干燥的实验教学

流化床干燥是化工原理实验课中的重要单元,学生对其内容非常感兴趣,但是在操作中受到干燥时间和速率的制约,使学生在短时间内,不能观察到整个流化床干燥的过程,这是本文章要叙述的问题,我们该如何解决。     

Particle-to-particle heat transfer in fluidized bed drying

Particle-to-emulsion and interparticle heat transfer rates were estimated in the range 1.5 ? u/u_mf ?3.5, 0.69 ? d_p ? 2.15 mm by drying wet refractory particles in fluidized beds of similar dry particles of the same sizes. Overall particle-to-emulsion heat transfer coefficients decrease roughly as the inverse of the particle diameter. Particle-to-particle heat transfer coefficients vary with the power-2 of the particle diameter and decrease as the fluidization velocity increases.     

Experimental study and simulation of vibrated fluidized bed drying

The paper addresses numerical simulation for the case of convective drying of seeds (fine-grained materials) in a vibrated fluidized bed, analyzing agreement between the numerical results and the results of corresponding experimental investigation. In the simulation model of unsteady simultaneous one-dimensional heat and mass transfer between gas phase and dried material during drying process it is assumed that the gas-solid interface is at thermodynamic equilibrium, while the drying rate (evaporated moisture flux) of the specific product is calculated by applying the concept of a “drying coefficient”. Mixing of the particles in the case of vibrated fluidized bed is taken into account by means of the diffusion term in the differential equations, using an effective particle diffusion coefficient. Model validation was done on the basis of the experimental data obtained with narrow fraction of poppy seeds characterized by mean equivalent particle diameter (d_S,d = 0.75 mm), re-wetted with required (calculated) amount of water up to the initial moisture content (X₀ = 0.54) for all experiments. Comparison of the drying kinetics, both experimental and numerical, has shown that higher gas (drying agent) temperatures, as well as velocities (flow-rates), induce faster drying. This effect is more pronounced for deeper beds, because of the larger amount of wet material to be dried using the same drying agent capacity. Bed temperature differences along the bed height, being significant inside the packed bed, are almost negligible in the vibrated fluidized bed, for the same drying conditions, due to mixing of particles. Residence time is shorter in the case of a vibrated fluidized bed drying compared to a packed bed drying.     

Self-heat recuperative fluidized bed drying of brown coal

Brown coal drying based on self-heat recuperation (SHR) technology which recovers effectively both latent and sensible heat was developed to reduce energy consumption which is required during drying. A fluidized bed dryer (SHR–FBD) with heat exchanger immersed inside the bed was adopted as the evaporator. To evaluate the energy efficiency of the proposed SHR–FBD system, a comparison to the available mechanical vapor recompression (MVR) based drying system concerning the effect of the fluidization velocity and bed aspect ratio to the required energy input for brown coal drying was conducted. From the results, the proposed SHR–FBD system was found to be able to drastically reduce the drying energy consumption at all evaluated fluidization velocities and bed aspect ratios. Numerically, the proposed system reduced the energy consumption to about 15% and 75% of that required in hot air and MVR drying systems.     

A mathematical model for continuous fluidized bed drying

A mathematical model for continuous drying process in a fluidized bed-dryer is presented.To describe the heat and mass transfer in gas phase, a Kunii—Levenspiel type, three-phase model representing a dilute (bubble) phase, interstitial gaNumerical computation based on this model was done to study the effects of the process parameters as particle and bubble-size, gas velocity, inlet gas     

流化床氛围下多孔物料干燥传热传质的数值模拟

用有限差分法数值求解一个热、质传递耦合模型,理论研究多孔物料流化床干燥过程。方程离散采用全隐格式的控制容积方法,三对角矩阵法（TDMA）用来求解线性方程组。选用球形的苹果丁作为多孔物料。在典型操作条件下,通过分析温度、饱和度和压力的分布侧形,讨论了物料内部的热、质传递机理。在对比条件下,考察了气体入口温度、气速和床面积因子对干燥过程的影响。结果表明：干燥过程受气、固相间的耦合传热传质的影响十分明显,干燥时间随气体入口温度和气速的提高而减少;随床面积因子的增大而增加。     

旋流振动流化床干燥性能的研究

文章以聚四氟乙烯粒子和蔗糖为物料研究了旋流振动流化床的流体力学及干燥特性,并与振动流化床的各种特性进行了对比。实验在一个干燥室直径为240 mm的小型圆筒振动流化床中进行,采用斜孔分布板使床内产生旋流。实验结果表明:在空气分布板开孔率相差不多的情况下,物料流化以前,旋流振动流化床的床层压降要大于普通振动流化床,一旦物料达到正常流化状态以后,2种振动流化床的床层压降相差不多;旋流振动流化床可以降低物料的临界含湿质量分数。     

An optimization model of the operating costs of a fluidized bed steam‐drying plant

A model is developed to determine an optimum apparatus geometry and, for given apparatus dimensions, a financially optimal fluidized bed height. The parameters that effect the operating costs are the bed mass, the apparatus diameter and the gas mass flow rate. To implement such cost optimization, a physics‐based mathematical model for describing the thermodynamic processes in fluidized bed steam‐drying is briefly explained and presented. The most important conclusion is not to operate the fluidized bed for a drying process below a certain minimum cost, calculated with the help of the modelling. The problem, when describing the drying process and consequently the mass transfer, is that in the superheated steam drying case studied here, water is evaporated as moisture and withdrawn into an atmosphere of vapor water.     

磁场流化床的研究与应用

介绍了磁场流化床的基本原理以及近年来在基础研究和应用研究两个方面取得的进展及成果,综述了磁场流化床在化工环保、生化工程、能源三个领域的应用现状并分析了其工业化前景及存在的问题。     

旋涡压力喷嘴及其在流化床喷雾造粒中的应用

研制了一种旋流室为半空心球形的旋涡压力喷嘴 ,具有结构紧凑、零部件少、旋流效率高、高速流道短、摩擦损耗小、雾炬张角大等优点。应用于流化床喷雾涂布造粒 ,在节省动力和单喷嘴覆盖面积大从而可减少喷嘴数量等方面显示出优越的性能。     

Experimental and numerical analysis of oil shale drying in fluidized bed

The main objective of this work was to experimentally and numerically investigate the Liu Shu River oil shale drying by the means of flue gas in a fluidized bed dryer. Several experiments were performed under different temperatures conditions. The moisture content of oil shale was measured during the experiments. The two-stage drying model was incorporated in computational fluid dynamics (CFD) package FLUENT via user-defined functions (UDF) and utilized for simulation of heat and mass transfer of oil shale drying in the fluidized bed dryer. The simulation results for solid moisture content agreed well with experimental data. The effects of the temperature and velocity of flue gas, initial bed height, and the particle size on the drying characteristics were predicted and analyzed. It is shown that the gas temperature and velocity are the important parameters in the whole drying process. The particle size has more obvious influence in the falling drying period than the constant drying period. The temperatures of gas and solid phases were monitored. It is shown that the so-called “near gas distributor zone” is the most effective heat transfer zone, which agrees well with the calculated value. The system quickly reached thermal equilibrium, characterizing a nearly isothermal bed. The developed model provides a very good demonstration to describe the oil shale drying in the fluidized bed dryer, and may provide important information for design, optimization of operation conditions.