2.8m~2流动干燥床

对连铸用耐火材料生产线配套设备2．8m2流动干燥床的工作原理、结构形式进行分析，并阐述了设备的操作过程及特点。     

Modeling and simulation of the drying of thin sheets in a continuous infrared dryer

The model gives the temperature and moisture distributions of the air, and of the moist sheet, as a function of time and distance in the dryer. The influence of the sheet's velocity and that of the radiant energy on the dryer performance as well as the effect of the moisture content of the entering sheet have been studied. A set of 27 experiments was carried out using the infrared dryer in order to calibrate the model. In these, the following three variables each had three operational levels: web velocity, initial web moisture and heating power. The model predictions agreed very well with the experimental data. Model predictions using arithmetic averages for the parameters, and parameters correlated with operational variables, are also presented and discussed.     

搅拌流化床干燥器流体力学性能研究

分析对比了搅拌流化床和普通流化床的流体力学特性,研究了搅拌转速,物料直径,物料密度和床载量对搅拌流化床床层压降和临界流化速度的影响,提出了临界流化速度的准数关联式,计算结果与实验数据吻合较好。     

Modelling and simulation of a continuous process with feedback control and pulse feeding

This paper deals with feedback control of a microorganism continuous culture process with pulse dosage supply of substrate and removal of products. By the analysis of the dynamic properties and numerical simulation of the continuous process, the conditions are obtained for the existence and stability of positive period-1 solution of the system. It is also pointed out that there does not exist positive period-2 solution. The results simplify the choice of suitable operating conditions for continuous culture systems. It also gives the complete expression of the period of the positive period-1 solution, which provides the precise feeding period for a regularly continuous culture system to achieve the same stable output as a continuous culture system with feedback control in the same production environment.     

尼鲁接触式流化床干燥器控制条件初探

介绍了尼鲁接触式流化床干燥器在锦化化工(集团)有限责任公司8万t／a PVC/VCM装置中的运行情况，介绍了其干燥原理和工艺参数的控制，初步分析了运行中出现的问题，并提出了相应的对策。     

Moisture conditioning of wood using a continuous microwave dryer

Lower moisture content in wood, preferably 5–6%, is desirable for many chemical modification reactions. Economically, it is not feasible to dry timber to such low moisture content by conventional drying without drying degrades. Microwave heating was evaluated and found to be effective in reducing the moisture content of radiata pine from 13% to 6% in a microwave cycle of two minutes. The energy consumption is about 55 kWh/m³. Moisture distribution profiles demonstrate very uniform drying across the sample thickness. The findings suggest that microwave heating can potentially be applied to condition wood in a very short period of time.     

脉冲式气流干燥器的模拟与结构优化

针对脉冲式气流干燥器,在以能耗最低为主目标函数的操作优化数学模型的基础上,加入了加速段高度、减速段高度及管径比等参数,建立了结构优化数学模型,以干燥每千克水为主目标函数编制了模型寻优程序,计算得出了物料终湿含量要求范围内的最佳结构参数.     

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.     

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...     

Modelling and simulation of a local solar still

Presented here is a mathematical model study of a prototype solar still built at Jug Island near Gunsan City. A pair of ODE was solved numerically with auxiliary equations to demonstrate that the predicted water productivity was in good agreement with experimental values. Monthly average water absorptance was the major factor that influnced the solar still performence.It was also found that the initial water depth the degree of insulation and the ambient temperature had significant influnce upon the water productivity whereas the wind velocity, the cover slope and the still orientation exhibited and the still negligible effects.     

Modelling a continuous devulcanization in an extruder

An engineering kinetic model is applied to EPDM devulcanization in an extrusion process. Parameters that were included in the model are crosslink density, devulcanizing agent concentration, time, shear rate, and temperature. The extruder is considered as a series of plug flow and stirred tank reactors. The residence time is calculated using solid flow or liquid flow model, depending on the degree of decrosslinking. The model can accurately predict the decrosslinking degree inside the temperature boundary defined by the applied experimental conditions. Outside this boundary, the effect of chemical degradation on the measured conversion becomes more significant.     

CFD simulation of corn drying in a natural convection solar dryer

A computational fluid dynamics model was developed to simulate the corn drying process in a solar cabinet dryer. Incident solar radiation was modeled using a dual-band spectrum to simulate the absorption of shortwave radiation by corn and account for the greenhouse effect caused by glazing materials. The performance of the dryer was simulated at fair and overcast weather conditions. The model allowed visualization of temperature, humidity, and air velocity profiles in the dryer. The model was validated with experimental results, which showed an overprediction of temperature (8.5%) and humidity (21.4%). The experimental humidity profile suggests that there was stagnation in the airflow of the dryer, which was accurately predicted by the model. The model was used to simulate the dryer’s performance under overcast conditions, and the predicted moisture removal was 32% less than the simulated fair-weather case.     

Modelling and experimental validation of a fluidized-bed reactor freeboard region: Application to natural gas combustion

A theoretical and experimental study of natural gas–air mixture combustion in a fluidized bed of sand particles is presented. The operating temperatures are lower than a critical temperature of 800 °C above which the combustion occurs in the vicinity of the fluidized bed. Our study focusses on the freeboard zone where most of the methane combustion takes place at such temperatures. Experimental results show the essential role of the projection zone in determining the global thermal efficiency of the reactor. The dense bed temperature, the fluidizing velocity and the mean particle diameter significantly affect the thermal behaviours.A model for natural gas–air mixture combustion in fluidized beds is proposed, counting for interactions between dense and dilute regions of the reactor [P. Pré, M. Hemati, B. Marchand, Study of natural gas combustion in fluidised beds: modelling and experimental validation, Chem. Eng. Sci. 53 (1998) (16), 2871] supplemented with the freeboard region modelling of Kunii–Levenspiel [D. Kunii, O. Levenspiel, Fluidized reactor models: 1. For bubbling beds of fines, intermediate and large particles. 2. For the lean phase: freeboard and fast fluidization, Ind. Eng. Chem. Res. 29 (1990) 1226–1234]. Thermal exchanges due to the convection between gas and particles, and due to the conduction and radiation phenomena between the gas-particle suspension and the reactor walls are counted. The kinetic scheme for the methane conversion is that proposed by Dryer and Glassman [F.L. Dryer, I. Glassman, High-temperature oxidation of CO and CH₄, Proceedings of the 14th International Symposium on Combustion, The Combustion Institute, Pittsburg (1973) 987]. Model predictions are in good agreement with the measurements.     

承压型盘式连续干燥器在聚磷酸盐中的开发及应用

介绍了正压盘式连续干燥器在聚磷酸盐中的应用,阐述了其设备设计过程中应注意的事项。结果表明,正压盘式连续干燥器在聚磷酸盐中的开发是成功的。     

Numerical simulation on mixing kinetics of slender particles in a rotary dryer

The mixing processes of slender particles in a rotary dryer fitted with lifters were simulated in three dimensions. Particle motion was modeled by the Discrete Element Method (DEM) and a three dimensional collision model for slender particles was developed. Contact force, friction force and gravitational force acting on an individual slender particle were considered when establishing mathematics models. The influences of rotational velocity on the mixing of slender particles were discussed and compared with those of spherical particles under identical operating conditions. It was found that the mixing characteristics of slender particles and spherical particles all followed a constant rate until a completely mixed state was encountered. But there were still certain differences between these two kinds of particles. The influences of the lifters with different shapes were further discussed for slender particles. Selected stimulation results were obtained and would provide consults for the further study of slender particles.     

内嵌锥筒连续式多晶硅固渣干燥机的流动行为

设计了一种新型的内嵌锥筒且有内外2层螺带的连续式多晶硅固渣干燥机,通过对干燥机的流场进行Fluent模拟和实验验证,分析了示踪粒子的停留时间和示踪粒子在外筒的移动轨迹,以及干燥机的流场,得出如下结论:对流场进行模拟的方法是正确的,且在模拟粒子轨迹时用的DPM模型和嵌入的UDF源代码也是可靠的。示踪粒子在锥筒内的停留时间大约是在外筒的15.8%—25.4%,相对于传统连续式干燥机延长了停留时间。锥筒、辐杆、螺带组成的旋转结构可以带动物料运动:其一是向出口处流动;其二绕壁面旋转,形成漩涡,强化传热,且转速越快,强化程度越高。出口速度对流场结构的影响很小,只影响物料的处理量:速度越大,物料在筒内的停留时间越短,干燥程度越低。     

Three-dimensional simulation of humid-air dryer using computational fluid dynamics

A three-dimensional (3-D), mathematical model for the analysis of the flow distribution in a humid-air dryer was developed employing a computational fluid dynamics package, FLUENT^®. A thin-layer drying approach for a sphere-shaped object was coupled with 3-D modeling framework. The model was validated by comparing the simulated moisture content (MC) of red pepper with experimentally measured MC with drying time. The present model was employed to obtain optimized dryer design with the most homogeneous flow distribution inside the drying trays. Consequently, two parametric studies are presented and discussed: (i) varying inner structure, and (ii) varying drying objects in the dryer.     

Modelling and control of a continuous distillation tower through fuzzy techniques

This paper presents a methodology for the design of a fuzzy controller applicable to continuous processes based on local fuzzy models and velocity linearizations. It has been applied to the implementation of a fuzzy controller for a continuous distillation tower. Continuous distillation towers can be subjected to variations in feed characteristics that cause loss of product quality or excessive energy consumption. Therefore, the use of a fuzzy controller is interesting to control process performance.A dynamic model for continuous distillation was implemented and used to obtain data to develop the fuzzy controller at different operating points. The fuzzy controller was built by integration of linear controllers obtained for each linearization of the system. Simulation of the model with controller was used to validate the controller effectiveness under different scenarios, including a study of the sensibility of some parameters to the control.The results showed that the fuzzy controller was able to keep the target output in the desired range for different inputs disturbances, changing smoothly from a predefined target output to another. The developed techniques are applicable to more complex distillation systems including more operating variables.     

Modelling and simulation of polymerisation processes

In order to model the effects of uneven spatial distribution of components and temperature a computational fluid dynamics (CFD) model has been developed for a living polymerisation reaction in a tubular reactor. The low moments of the molecular weight distribution (MWD) and the dispersiry index of the product as well as the more usual spatial concentration of species and temperature have been calculated. The modelling and simulation work was carried out using the CFD code PHOENICS version 2.1 on Pentium PCs. Additionally, a novel algorithm is described which makes the design of reactor control strategies more tractable by providing a very rapid route to a qualitative approximation of the MWD of products from living polymerisation processes. Numerically simulated data generated using this new procedure are compared with slower but more rigorous approaches to the same problem. The examples cover living polymerisations in an isothermal batch reactor, a steady-state continuous stirred tank reactor (CSTR) and feed-perturbed CSTR. It is demonstrated that, although the novel algorithm comprises only four differential equations, it provides the essential information concerning the position and relative intensity of the peak(s) in a MWD plot needed for the design of reactor control strategies for the production of tailored MWDs.     

Measurement and simulation of the contact drying of sewage sludge in a Nara-type paddle dryer

Contact drying experiments were carried out in a Nara-type paddle dryer to study the drying kinetics of sewage sludge in the presence of air. In order to have a better understanding of the sewage sludge drying mechanism, a penetration model developed by Tsotsas and Schlünder is used to simulate the drying kinetics of the pasty, lumpy and granular phase which the sludge experiences during the drying process. The pasty phase is assumed to be a saturated particulate phase, and the granular phase is considered as a mono-dispersed particulate phase whose diameter was experimentally determined. In the lumpy phase, a sludge wall sticking still to the paddle-shaft surface was formed, and the heat transfer resistance from the sludge wall is considered during the model calculation. The influence of the drying parameters (temperature, stirrer speed and air flowrate) on the drying process is investigated experimentally and theoretically. The result indicates that the penetration theory is able to describe the sludge drying kinetics of the three distinct phases. Experimental and calculated drying kinetics are in satisfactory agreement for different drying parameters.