物料干燥过程—传质传热最优化方法的研究

论述了多孔介质干燥过程中传质传热的数学模型及干燥过程最优化准则的建立；并且动用控制理论产物料干燥过程传热的动态优化方法－－准则约束法，且得到了最优解。     

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。     

固体干燥的物理解释和建模综述

固体干燥的建模一直是干燥技术研究的主要课题之一。自从Luikov体系和Whitaker理论建立以来，这样的努力已历经近三十年。通过回顾过去几十年所发表的数学模型，对固体干燥过程给出一些物理解释。经典的传递过程理论结合多孔介质理论足以在基础层面上解决固体干燥问题。但几乎全部的现有固体干燥模型仅能处理特殊的物料系统。由于缺乏基础数据，模型的通用性依然是一个主要问题。未知参数的测定和模型的实验验证需要进一步加强。工业干燥器的设计、操作和优化期盼一个综合的数学模型，这个模型须兼顾考虑准确性、通用性和复杂性／简单性。     

微波干燥锰碳合金球的响应曲面法优化

为了研究微波干燥锰碳合金球新工艺过程,确定各因素对脱水率的影响情况,得到优化工艺参数,文中采用响应曲面法中心组合设计对工艺过程进行设计并分析了干燥温度、干燥时间、物料质量及其交互作用对相对脱水率的影响,建立了关于相对脱水率的数学模型。方差分析表明,干燥温度、干燥时间对相对脱水率有较显著影响,建立的数学模型拟合度良好,获得优化工艺参数:干燥温度90℃,干燥时间176 s,物料质量150.61 g,相对脱水率达到93.96%。实验验证表明,实际值与模型预测值相差0.71%,干燥后锰碳合金球的含水质量分数为0.26%,达到炼钢用锰碳合金球的水分指标。研究表明:模型预测结果可靠有效,应用响应曲面法优化得到微波干燥锰合金球的工艺条件合理可行,为工业化应用提供必要的工艺参数。     

多效干燥过程的排产调度优化

针对干燥过程是一个高能耗的间歇单元操作,对多效干燥过程进行了排产调度研究。根据干燥速率曲线,将各效干燥过程设计为等操作时间,建立了多效干燥过程排产调度的优化模型。以效数和干燥器干燥时间为决策变量,以年费用最小为目标表达为一个混合整数非线性规划（MINLP）的数学模型,利用GAMS进行求解。以淤泥1～5效干燥为算例进行了优化调度分析,结果表明：在4效时年费用最小;与1效干燥相比,在最优条件下年生产费用可节约26%。同时获得了最优排产调度的Gantt图,从而可以得出干燥设备的最小操作周期,据此对多效干燥过程进行排产,使间歇多效干燥过程可以实现连续化生产,对多效干燥的工业化具有一定的意义。     

竹条干燥特性的实验研究

对竹条的热风对流干燥特性进行了系统的实验研究。讨论了干燥方式， 热风速度和温度等因素对干燥过程的影响； 从干燥过程的基本原理出发， 导出了干燥过程的数学模型； 利用此模型对实验结果进行回归整理， 得到了反映竹条干燥特性的实验关系式。     

油烧辊道窑预干燥带干燥过程微观数学模型的研究

本文分析了辊道窑内预干燥带传热及干燥过程的特点，引入Morgan的蒸发面后退模型，建立了陶瓷制品干燥过程中温度场分布及湿含量计算的微观数学模型。     

探讨物料工业干燥动态特性的新方法

针对小质量物料干燥动态过程恒速率干燥阶段和降速率干燥阶段，提出了用偏差活化能的方法来避免寻找该两个干燥阶段临界湿分点的困难，并从物理化学的概念推导出了理论动态数学模型，建立了物料干燥动态特性实验台，以实验数据验证模拟结果，效果较好。研究结果表明，利用物料干燥过程偏差活化能的变化特性来研究物料的工业干燥动态特性和干燥机理是可行的。     

芳烃渣干燥过程最佳操作工艺参数的研究

运用二次通用旋转组合实验设计的方法，对芳烃渣在盘式连续干燥机中的干燥过程进行实验，建立了干燥性能指标(芳烃单位时问蒸发量、最终湿含量)与工艺参数之间的二次回归数学模型，分析了工艺参数对于燥性能的影响，找出了芳烃渣干燥过程的最佳工艺参数。本文所求出的芳烃渣干燥过程的最佳操作工艺参数为T=250℃，N=3．96r／min，U=147．9kg/h，此时对应的最大芳烃单位时问蒸发量为34．6kg／h。本文所建立的二次回归数学模型和最佳操作工艺参数对生产具有实际的指导意义。     

无机纤维板干燥过程的数学模拟研究

本文通过对无机纤维板干燥过程的分析,建立了干燥过程中热量传递和质量传递的数学模型,模拟结果与实测结果有较好的一致性.     

不同加热功率下含油污泥的干燥

辽河油田的含油污泥含有大量的水分,为了更有效地进行油泥热解和减少热解过程中的能耗,需运用干燥技术处理油泥。实验考察了不同干燥功率对油泥干燥速率、湿分比的影响。实验结果表明:油泥干燥可以分成3个阶段,即恒速干燥阶段、第1降速干燥阶段和第2降速干燥阶段;加热功率越大,达到平衡含水质量分数所用的时间越短,恒速干燥速率越大。然后运用干燥方程求得干燥时间。最后运用热分析动力学对实验数据进行处理,得到干燥动力学的数学模型。模拟结果表明修正Page模型符合油泥干燥过程。     

Multiphase modeling of intermittent drying using the spatial reaction engineering approach (S-REA)

Several schemes of energy minimization of drying process including intermittent drying have been attempted. Intermittent drying is conducted by applying different heat inputs in each drying period. An effective and physically meaningful drying model is useful for process design and product technology. The lumped reaction engineering approach (L-REA) has been shown previously to be accurate to model the intermittent drying In L-REA, the REA (reaction engineering approach) is used to describe the global drying rate. In this study, the REA is used to model the local evaporation/condensation rate and combined with the mechanistic drying models to yield the spatial reaction engineering approach (S-REA), a non-equilibrium multiphase drying model. The accuracy of the S-REA to model the intermittent drying under time-varying drying air temperature is evaluated here. In order to incorporate the effect of time-varying drying air temperature, the equilibrium activation energy and boundary condition of heat balance implement the corresponding drying settings in each drying period. The results of modeling using the S-REA match well with the experimental data. The S-REA can yield the spatial profiles of moisture content, concentration of water vapor, temperature and local evaporation/condensation rate so that better understanding of transport phenomena of intermittent drying can be obtained. It is argued here that the REA can describe the local evaporation rate under time-varying external conditions well. The S-REA is an effective non-equilibrium multiphase approach for modeling of intermittent drying process.     

洋葱真空干燥动力学研究

为研究洋葱在真空干燥条件下的干燥特性,选用不同干燥条件对洋葱进行脱水处理,测定不同工艺条件下洋葱的干燥曲线和干燥速率曲线。结果表明,温度和真空度对洋葱真空干燥过程都有明显的影响,且洋葱真空干燥的动力学模型符合Page方程,并得到本试验条件下的动力学模型。     

Mathematical Modeling the Drying of Poplar Wood Particles in a Closed-Loop Triple Pass Rotary Dryer

Closed-loop drying systems are an attractive alternative to conventional drying systems because they provide a wide range of potential advantages. Consequently, type of drying process is attracting increased interest. Rotary drying of wood particles can be assumed as an incorporated process involving fluid–solid interactions and simultaneous heat and mass transfer within and between the particles. Understanding these mechanisms during rotary drying processes may result in determination of the optimum drying parameters and improved dryer design. In this study, due to the complexity and nonlinearity of the momentum, heat, and mass transfer equations, a computerized mathematical model of a closed-loop triple-pass concurrent rotary dryer was developed to simulate the drying behavior of poplar wood particles within the dryer drums. Wood particle moisture content and temperature, drying air temperature, and drying air humidity ratio along the drums lengths can be simulated using this model. The model presented in this work has been shown to successfully predict the steady-state behavior of a concurrent rotary dryer and can be used to analyze the effects of various drying process parameters on the performance of the closed-loop triple-pass rotary dryer to determine the optimum drying parameters. The model was also used to simulate the performance of industrial closed-loop rotary dryers under various operating conditions.     

KINETICS OF THE CLAY ROOFING TILE CONVECTION DRYING

Kinetics of the convection drying process of flat tile has been investigated experimentally in an industrial tunnel dryer. Several velocities of wet tile movement through the dryer were tested to obtain maximum allowable drying rate curve. As there are various models to describe the kinetics of convection drying, finding a model that would fairly well approximate the kinetics of the whole drying process was part of the research. Especially the polynomial and exponential models were tested.

It was found that exponential model of the type: B(t) = (a-B_e. EXP(-bt²) +B_et (-dB(t)/dt) = 2bt(B(t)-B_e significantly correlates the kinetics of the whole tile drying process.

Applying the maximum allowable drying rate curve obtained for flat tile in the first period of drying, a grapho-analytic model for the optimal conducting of the process has been developed.     

Fractal Pore Network Simulation on the Drying of Porous Media

Based on the knowledge of fractal geometry, physics of flow through porous media, and transport process principle, a fractal pore network model for the drying process of a natural porous body was established in this article. This model takes various factors into consideration, such as liquid-phase flow, vapor-phase diffusion, temperature gradient, and pore microstructure characteristic. The drying dynamics characteristics of potato slices were obtained by the simulation of a fractal pore network model. The simulation results of the fractal pore network model were contrasted with those of a regular one and the experimental data, respectively. The wet patches were observed on the potato slices during the drying experiments, and it was validated by the drying simulation. The results indicate that the drying kinetics from the fractal pore network model, as well as the distributions of moisture and temperature inside the porous body, are more consistent with that of the drying experiments than that of the regular one, and the throat size distribution in the pore network of the porous media has a notable influence on the drying process.     

DYNAMIC ANALYSIS OF CONTINUOUS WELL-MIXED FLUIDIZED/SPOUTED BED DRYERS

A diffusion-based mathematical model is presented for the prediction of the dynamics of drying in continuous well-mixed fluidized/spouted beds. Numerical techniques are used to solve the model equations. The outlet solids moisture content, the outlet air humidity and solids temperature are predicted as a function of time for the falling rate drying period. The model is helpful in describing the drying process during the startup periods and in studying open loop behavior of drying process. The model is also useful in designing control system for fluidized/spouted bed dryers.     

Heat and mass transfer during microwave‐convective drying

The article presents a mathematical model of drying that describes the kinetics of combined microwave‐convective drying for the process as a whole. Based on this model, the drying curves and the temperature evolutions of the drying body were constructed by a number of computer‐simulated drying programs, which were chosen to follow the respective experimental processes carried out on a cylindrical sample made of kaolin. The experimental data allowed both the estimate of material coefficients arising in the model and the validation of the theory. A very satisfactory correlation of the theoretical predictions with the experimental data is found. The main novelty of this article is the mathematically complete drying model that describes all periods of the microwave‐convective drying process. Application of such a complete model is necessary if we want to optimize drying processes with respect to drying time and consumption of energy via computer simulations. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Experimental and theoretical research on agitated contact drying of sewage sludge in a continuous paddle dryer

Sludge drying is an important intermediate process for sewage sludge treatment, usage, and disposal. A series of drying experiments were conducted in a continuous paddle dryer in order to have a better understanding of the sludge drying mechanism. The couple model of penetration model and Markov chain was used to simulate the drying kinetics in a continuous paddle dryer. The drying process has been compared in experimental and theoretical results, which show good agreement. The sewage sludge drying process in a continuous paddle dryer can be divided into three stages: the pasty phase, the sticky phase, and the complete-granular phase. The influences of the drying parameters on the sludge drying kinetics in a continuous paddle dryer were investigated. The sludge flow rate, dryer wall temperature, and dryer slope have remarkable influence on sludge drying in the examined range, but the stirrer speed and steam temperature have little influence on the drying kinetics.