Interpretation of the hydrodynamic behaviour in a conical fluidized bed dryer

Wet batches of placebo pharmaceutical granule were dried at inlet superficial gas velocities of 0.64 and 1.3 m/s in a Glatt GPCG-1 fluidized bed. Using pressure fluctuation analysis, the hydrodynamic behaviour indicates a transition from a multiple bubbling regime to a coalescence dominated regime as drying proceeds. The transitional fluidization behaviour is linked to the physical mechanisms associated with the constant and falling rate periods of drying porous materials. Excess surface moisture present during the constant rate period increases interparticle forces through liquid bridging. These liquid bridges stabilize the bed structure which limits bubble formation in the bed. Once the falling rate period is reached, the liquid bridges cannot be maintained and bubble coalescence increases. The resulting bubbling bed hydrodynamics can be explained using the simple two-phase model proposed by Toomey and Johnstone [1952. Gas fluidization of solid particles. Chemical Engineering Progress 48, 220-226] using the full support velocity and bed voidage characteristics of the granule at varying moisture contents.     

Numerical analysis of spouted-bed hydrodynamics

Some of the basic concerns in the analysis of spouted-bed hydrodynamics are the flow pattern and the pressure field of the fluid and the spout shape. These are closely related with other design concerns such as spoutability, minimum spouting velocity and maximum spoutable bed depth. A computer program was developed in order to determine the flow pattern, pressure distribution in the fluid phase and the spout shape for a given operational condition. The computer program relies upon a two region model with a spout and annulus element for an axisymmetric bed. The paper presents some results for grain drying beds and compares them with the existing experimental data qualitatively.     

Radioactive particle tracking in a lab‐scale conical fluidized bed dryer containing pharmaceutical granule

Radioactive particle tracking (RPT) has been used to study the motion of the particulate phase in a bench‐scale conical fluidized bed containing dried pharmaceutical granule. RPT revealed that there is a distinct circulation pattern of the granule with particles moving upwards at high velocities near the centre of the bed and falling slowly near the walls. There was also a localized region near the centre of the bed where particles moved downward rapidly. The particle size distribution (PSD) of the granule had an appreciable impact on particle motion with a wide PSD leading to larger fluctuations in particle velocity as well as poorer granule mixing.     

Performance of heat pump drying system integrated into a blood dryer

ABSTRACT

In general, most heat losses in industrial dryers arise due to the discharge of humid air. Using heat pump drying systems, heat from the exhaust humid air can be recovered, thus improving the energy efficiency substantially. In this study, the performance of heat pump integration in a blood dryer was examined. Computer simulation models of the original high-temperature (180°C) dryer and the proposed system with heat pump integration and auxiliary heating were developed. Different heat pump systems and working fluids were investigated to determine the best performing heat pump system. In this case, it was found that an R245fa heat pump system with a subcooler is the best solution. When using an absorption heat pump, the results showed that a type I absorption heat pump with H₂O–LiBr as working fluid pair performs the best. In addition, the economic benefit as well as the optimum operating conditions of the dryer with integrated heat pump were also determined.     

Drying of industrial sludge waste in a conical spouted bed dryer. Effect of air temperature and air velocity

To determine the performance of a conical spouted bed dryer for the drying of sludge waste, an experimental study of drying in a spouted bed regime was performed under different experimental conditions. The drying performance was determined based on the time evolution of solid moisture content, and the influence of operating conditions (inlet air temperature, air flow rate, and bed mass) on the drying rate of sludge waste in spouted beds of a conical geometry was analyzed.     

An adsorption-sublimation model for a freeze dryer

A model has been constructed using material and energy balances in the dried and frozen regions of a material undergoing freeze drying. Both sublimatio and adsorption are accounted for in the set of coupled non-linear partial differential equations that constitute the model. Numerical solutions to thes equations are shown to agree quite closely with experimental data over the entire drying period.     

Conductivity method for the control of a soap dryer

Conclusion Data reported in this paper show that a conductivity method may be used for the computation of fatty acid contents of soap in the range of 78 to 83%. The method is adaptable to the control of soap dryers.     

热泵干燥装置的调控分析

热泵干燥具有节能、低温干燥及环境友好等特点，控制热泵干燥装置运行在较佳的状态，是保证热泵干燥装置效率和可靠性的基础。以带循环空气旁通的封闭式热泵,干燥装置为例，对热泵干燥装置的调控方法进行了分析，给出了装置的被控参数和一组较佳的控制参数，并建立了各控制参数的计算公式。     

Integral methods for flow in a conical centrifuge

A set of through-thickness averaged equations for momentum and strain rate are derived for the problem of axi-symmetric free-surface flow within a spinning cone. The expressions are independent of the choice of constitutive law and can therefore be used for modeling the flow of a variety of materials within an industrial conical centrifuge. By assuming a through-thickness velocity profile the distribution of flow thickness and average velocity over the internal surface of the cone can be obtained. The approach has been validated for thin Newtonian viscous flow by comparison with full three-dimensional solutions of the Navier–Stokes equations obtained with a commercial CFD package. The averaged equations provide an accurate prediction of the flow thickness, velocity and the length of the zones of influence of inlet and outlet boundary conditions.     

Modeling and simulation of a beet pulp dryer for a training simulator

This paper deals with the modeling of a high-temperature rotatory sugar beet pulp dryer for training simulators. This model adds some aspects to traditional drum dryer models; particle size distribution, detailed modeling of the solid phase, and the inclusion of malfunctions in the model. An object-oriented simulation package is selected to implement this model in a library, together with models of other components of a drying plant. Using this library, the complete plant and its control system are built and simulated. Finally, the simulation of the plant integrated together with a SCADA makes up the training simulator.     

粒状过磷酸钙烘干机的技改

2002年,为适应粒状过磷酸钙市场销售的需求,我厂利用硫酸生产线闲置的烘干系统,建成了以含有效P2O5为12%,w(H2O)12%~15%已熟化后的过磷酸钙为原料生产粒状过磷酸钙的车间,设计能力为20 kt/a。工艺流程:行车将原料提至加料平台,通过加料导管加至圆盘造粒机(2 800 mm),制成的颗粒     

多层水平气流带式干燥机的数学模型

根据干燥传质传热学原理和干燥动力学特性，建立了水平气流带式干燥机干燥过程的数学模型。该模型可以预测干燥机合理的通风道高度、带翻转最佳时间和热风风速等。为优化多层带式干燥机的结构或设计新的水平气流带式干燥机提供了理论依据。     

Modeling a multiple-zone air impingement dryer

A complete model for the simulation of the drying process of a binary system in a modular air impingement dryer is presented. The underlying equations and the numerical scheme were chosen such that large-scale parameter studies could be performed efficiently with an ordinary PC. The influence of the operating parameters on the drying progress and the energy efficiency was investigated, considering a wide range of technically important constraints such as proper web handling, the risk of explosion or the generation of bubbles in the coating.     

干燥机进料箱的改造

几乎所有复混肥生产线的干燥机进料箱都存在积料严重且清理困难的问题,现将我公司改造经验介绍如下。1　干燥机进料箱积料严重的原因(1)　进料溜管结构不合理　进料溜管为方形管,两底角处易粘料,且一旦有粘料就会越粘越多,导致从造粒系统来的物料溢出溜管而塞满进料箱。(2)　机头倒料　一般复混肥干燥机最始端都是由斜弧形板组成的导料区,斜弧形板与机头挡料圈结合处也易粘料,导致进入的物料溢出挡料圈,进入进料箱。(3)　进料箱结构不合理　干燥机的原进料箱结构如图1所示,进料溜管和机头倒料溢出的物料易进入进料箱,由于干燥机进口温度…     

Mathematical model and optimization of drying process for a through-circulation dryer

A mathematical model of a through-circulation dryer is proposed. This model approximates the drying time of constantrate drying and fallingrate drying processes. Based on the proposed model, the optimal drying conditions of maximizing the drying production rate in a continuous through-circulation dryer are obtained. The drying production rate, in terms of the independent operating variables, is a nonlinear objective function, and is optimized under the nonlinear inequality constraint functions by a differential algorithm.     

蒸汽管回转干燥机在褐煤干燥上的应用

针对褐煤高水分、高挥发分、热稳定性差以及易自燃等特点,经过对比分析,选择适合褐煤干燥的技术方案,同时在传统蒸汽管回转干燥机的基础上,根据试验研究结果,摸索出适合褐煤干燥的蒸汽管回转干燥机结构和工艺参数,并成功地运用于高水分印尼褐煤的干燥。     

滚筒式煤泥干燥系统的改进

对滚筒式煤泥干燥系统中往复式燃烧炉在生产中出现的问题进行了分析,找出了燃烧炉砌体缝隙生成的原因;采用新型浇注材料烧结整体密封耐磨陶瓷对炉体进行密封后,煤泥干燥系统生产稳定,燃烧炉热工效率大大提高,节约了能源消耗,干燥机的生产能力增加。