Modeling of poly(ethylene terephthalate) reactors: 4. A continuous esterification process

A mathematical model has been developed for the direct, continuous esterification process. Influence of process and operational variables, including temperature distribution, residence time distribution, bis(hydroxyethyl)terephthalate recycle, pressure, and ethylene glycol (EG) to terephthalic acid ratio on the reactor performance have been investigated in a range as close to industrial practice as possible. The variables influencing the amount of EG reflux (which governs the energy economy) and side products (which govern the product quality) have been discussed. This investigation provides an analysis of a continuous, direct esterification process, and the results indicate strategies for optimizing productivity and product quality.     

Modeling of poly(ethylene terephthalate) reactors. II. A continuous transesterification process

A comprehensive mathematical model for a continuous transesterification process has been built so as to enable prediction of the influence of different process and operational variables on productivity and by-product formation. The influence of temperatures and temperature profiles, of residence time and residence time distribution, and also of the number of reactors in series has been investigated. The modeling has been done as close to the industrial practice as possible. Important pragmatic implications from the point of view of operation of continuous transesterification are highlighted.     

聚酯（PET）反应过程研究：Ⅶ后缩聚反应过程研究和数学模拟

对聚酯的后缩聚反应过程进行了分析，把该过程分解为反应动力学和反应器内各种传质；对后缩聚反应进行了实验研究。建立了适用于工业装置的后缩聚反应过程的数学模型     

Modelling of poly(ethylene terephthalate) reactors. III. A semibatch prepolymerization process

A mathematical modelling of a semibatch prepolymerization process has been undertaken. Prepolymerization conducted at constant temperature and pressure and with a predetermined variation in temperature and pressure has been studied. Influence of DMT and TPA addition during prepolymerization has also been examined. The focus has been on investigation of the influence of processing and operational variables on productivity and side product formation, which controls product quality. The results of this investigation (which are applicable only up to DP ? to 30) are borne out by the limited experimental data available in the literature. Important pragmatic implications of the results of the work in terms of design and operation of prepolymerization reactors have been emphasized.     

竖炉焙烧过程METSIM动态模拟

竖炉焙烧是我国赤铁矿选矿工业中常见的工艺环节。其关键工艺指标是磁选管回收率, 反映了矿石焙烧的质量。但磁选管回收率无法在线实时测量。在实际生产中, 对竖炉焙烧磁选管回收率的控制一般通过运行优化控制实现。而运行优化控制策略的设计需要进行大量工业现场实验, 建立磁选管回收率相对于主要控制变量的动态响应关系, 这样做的成本高, 风险大。为了解决这一问题, 基于冶金模拟软件METSIM设计了竖炉焙烧工艺动态模型, 并采用与实际一致的过程控制软硬件系统建立了竖炉过程半实物仿真系统。通过仿真实验获得磁选管回收率与燃烧时温度设定值之间的动态关系, 并与实际数据进行了比较验证。表明该平台能够作为运行优化控制方法设计的实验和测试工具。     

加氢裂化装置生产指导系统的研究与应用

加氢裂化工艺中,催化剂温度等过程变量对最终产品的产量质量指标有着至关重要的影响,而在现实的工业生产中,分散控制系统（DCS）测量得到的过程数据和实验室分析得到的质量指标数据由于各种原因并不能有效地整合,从而造成数据和投资的浪费。本文研究开发了一种生产指导系统,通过采集DCS和实验室分析数据,建立过程变量和最终产品质量等指标的数学关系来指导用户调整一些可调过程变量,从而提高产品质量。实践证实了该系统的有效性。     

Effect of Spray-Dryer Operating Variables on the Whole Milk Powder Quality

Abstract

This work aims at identifying the effects of the main operational spray-dryer variables on the milk powder quality. Experiments have been performed in a pilot spray-dryer following the full-factorial design technique to provide data and correlations that predict the whole powder properties as function of the main operational variables of the spray-dryer. The emulsion feed flow rate, the atomization rotation and the inlet air temperature have been chosen as the independent variables while the residual moisture content, the tapped bulk density, the cohesion force enhancement between particles as well as size distribution of agglomerate and its morphology are the response variables that quantify the powder quality. Correlations obtained are analyzed and incorporated into a mathematical model previously developed for simulating the spray-drying of whole milk emulsion.     

聚酯(PET)反应过程研究Ⅴ预缩聚反应过程分析和反应动力学研究

对乙二醇和对苯二甲酸预缩聚反应过程进行了分析，把该过程分解为反应动力学和反应器内各种传质，对预缩聚反应过程的反应动力学进行了实验研究。得到了不同温度下的反应速率及其参数     

对苯二甲酸（PTA）间歇酯化反应计算机模拟

为了研究不同的工艺操作参数对ＰＴＡ转化率和副产物形成的影响，针对ＰＴＡ间歇酯化建立了一较完善的反应模型．模拟过程中考虑了重要工艺参数如乙二醇（ＥＧ）与ＰＴＡ配比、温度等的影响，对既能达到最高生产效率又能最小限度减少副产物的工艺参数范围提出了建议．     

聚酯（PET）反应过程研究：Ⅱ.酯化反应过程动力学研究

对乙二醇和对苯二甲酸直接酯化反应过程的主反应动力学和生成ＤＥＧ副反应的动力学进行了研究，得到了不同温度下的反应速率，进而获取了各反应的活化能和频率因子。     

PRODUCT QUALITY MULTI-OBJECTIVE DRYER DESIGN

Design of conveyor-belt dryers constitutes a mathematical programming problem involving the evaluation of appropriate structural and operational process variables so that total annual plant cost involved is optimized. The increasing need for dehydrated products of the highest quality, imposes the development of new criteria that, together with cost, determine the design rules for drying processes. Quality of dehydrated products is a complex resultant of properties characterizing the final products, where the most important one is color. Color is determined as a three-parameter resultant, whose values for products undergone drying should deviate from the corresponding ones of natural products, as little as possible. In this case, product quality dryer design is a complex multi-objective optimization problem, involving the color deviation vector as an objective function and as constraints the ones deriving from the process mathematical model. The mathematical model of the dryer was developed and the fundamental color deterioration laws were determined for the drying process. Non-preference multi-criteria optimization methods were used and the Pareto-optimal set of efficient solutions was evaluated. An example covering the drying of sliced potato was included to demonstrate the performance of the design procedure, as well as the effectiveness of the proposed approach.     

PRODUCT QUALITY MULTI-OBJECTIVE OPTIMIZATION OF FLUIDIZED BED DRYERS

Design of fluidized bed dryers constitutes a mathematical programming problem involving the evaluation of appropriate structural and operational process variables so that total annual plant cost involved is optimized. The increasing need for dehydrated products of the highest quality, imposes the development of new criteria that, together with cost, determine the design rules for drying processes. Quality of dehydrated products is a complex resultant of properties characterizing the final products, where the most important one is color. Color is determined as a three-parameter resultant, whose values for products undergone drying should deviate from the corresponding ones of natural products, as little as possible. In this case, product quality dryer design is a complex multi-objective optimization problem, involving the color deviation vector as an objective function and as constraints the ones deriving from the process mathematical model. The mathematical model of the dryer was developed and the fundamental color deterioration laws were determined for the drying process. Non-preference multi-criteria optimization methods were used and the Pareto-optimal set of efficient solutions was evaluated. An example covering the drying of sliced potato was included to demonstrate the performance of the design procedure, as well as the effectiveness of the proposed approach.     

PRODUCT QUALITY MULTI-OBJECTIVE OPTIMIZATION OF FLUIDIZED BED DRYERS

ABSTRACT

Design of fluidized bed dryers constitutes a mathematical programming problem involving the evaluation of appropriate structural and operational process variables so that total annual plant cost involved is optimized. The increasing need for dehydrated products of the highest quality, imposes the development of new criteria that, together with cost, determine the design rules for drying processes. Quality of dehydrated products is a complex resultant of properties characterizing the final products, where the most important one is color. Color is determined as a three-parameter resultant, whose values for products undergone drying should deviate from the corresponding ones of natural products, as little as possible. In this case, product quality dryer design is a complex multi-objective optimization problem, involving the color deviation vector as an objective function and as constraints the ones deriving from the process mathematical model. The mathematical model of the dryer was developed and the fundamental color deterioration laws were determined for the drying process. Non-preference multi-criteria optimization methods were used and the Pareto-optimal set of efficient solutions was evaluated. An example covering the drying of sliced potato was included to demonstrate the performance of the design procedure, as well as the effectiveness of the proposed approach.     

Atmospheric Freeze Drying—Modeling and Simulation of a Tunnel Dryer

Drying is an important unit operation in processing of foods and other biotechnological products. Vacuum freeze drying is said to be the best drying technology regarding product quality of the end product, but the disadvantages are, among others, expensive operational costs and batch drying. Atmospheric freeze drying was introduced to lower the production costs of high-quality dried foods, and the need of simulation tools became important in estimations of the industrial drying processes.

A simplified mathematical model (AFDsim) is developed based on uniformly retreating ice front (URIF) considerations. The model is used to calculate theoretical drying curves of atmospheric freeze dried foods in a tunnel dryer. Studies of thermal and mass transfer properties during drying are essential for understanding the changes in product quality and for designing and dimensioning the drying process. The model can be used to simulate industrial atmospheric freeze drying of different foodstuff in a tunnel. The results from AFDsim modeling are in good accordance with the experimental results.     

PRODUCT QUALITY MULTI-OBJECTIVE DRYER DESIGN

ABSTRACT

Design of conveyor-belt dryers constitutes a mathematical programming problem involving the evaluation of appropriate structural and operational process variables so that total annual plant cost involved is optimized. The increasing need for dehydrated products of the highest quality, imposes the development of new criteria that, together with cost, determine the design rules for drying processes. Quality of dehydrated products is a complex resultant of properties characterizing the final products, where the most important one is color. Color is determined as a three-parameter resultant, whose values for products undergone drying should deviate from the corresponding ones of natural products, as little as possible. In this case, product quality dryer design is a complex multi-objective optimization problem, involving the color deviation vector as an objective function and as constraints the ones deriving from the process mathematical model. The mathematical model of the dryer was developed and the fundamental color deterioration laws were determined for the drying process. Non-preference multi-criteria optimization methods were used and the Pareto-optimal set of efficient solutions was evaluated. An example covering the drying of sliced potato was included to demonstrate the performance of the design procedure, as well as the effectiveness of the proposed approach.     

Atmospheric Freeze Drying—Modeling and Simulation of a Tunnel Dryer

Drying is an important unit operation in processing of foods and other biotechnological products. Vacuum freeze drying is said to be the best drying technology regarding product quality of the end product, but the disadvantages are, among others, expensive operational costs and batch drying. Atmospheric freeze drying was introduced to lower the production costs of high-quality dried foods, and the need of simulation tools became important in estimations of the industrial drying processes.

A simplified mathematical model (AFDsim) is developed based on uniformly retreating ice front (URIF) considerations. The model is used to calculate theoretical drying curves of atmospheric freeze dried foods in a tunnel dryer. Studies of thermal and mass transfer properties during drying are essential for understanding the changes in product quality and for designing and dimensioning the drying process. The model can be used to simulate industrial atmospheric freeze drying of different foodstuff in a tunnel. The results from AFDsim modeling are in good accordance with the experimental results.     

Physical-chemical characterization and statistical modeling applied in a chlor-alkali diaphragm-cell process

Between the asbestos diaphragms, asbestos with polymer or only polymer for use in the chlor-alkali industry, the diaphragm technology is still known for contributing the most in industrial production being responsible for the operational security and energetic efficiency. The objective of this work is the quantitative understanding of the influence of the effects that the variables involved in the diaphragms manufacturing have on the performance of this process. The major variables considered in this work are: the specific weight, the relationship between the length of the asbestos fibers and the concentrations of NaCl, NaOH and the SM2™ polymer. From a statistical mathematical model, it was possible to establish quantitative relationships between these variables and the parameters that characterize the diaphragm, such as the MacMullin number and permeability associated to a phenomenological model proposed by Van Zee [Van Zee, J.W., 1984. Sodium-Hydroxide Production in Diaphragm-Type Electrolyzers, Ph.D. Dissertation, Texas A&M University]. Therefore, it was possible to compare experimental and calculated data from this model for current efficiency and the concentration of NaOH produced for a group of 34 industrial cells in operation. Finally, it was possible established a mathematical relationship between the variables involved in the manufacturing process with the performance of the diaphragm in an industrial electrolytic cell.     

Modeling of poly(ethylene terephthalate) reactors. I. A semibatch ester interchange reactor

A comprehensive model for a semibatch ester interchange reactor has been developed with a view to investigate the effect of various process and operational variables on the DMT conversion rate as well as the by-product formation. The influence of important variables such as EG-to-DMT ratio, catalyst concentration, and operational variables such as temperature and pressure has been considered. Definite conclusions concerning the choice of the desirable range of process and operational variables to maximize productivity and minimize by-product formation have been reached.     

A simulation study of industrial vegetable oil hydrogenation reactors

A mathematical model has been developed to predict the course of industrial vegetable oil hydrogenation reactors. The model assumes that the reaction is mass-transfer-controlled. Suitable empirical equations have been used to describe rate of hydrogenation in preference over a mechanistic approach. The agreement between theoretical predictions from the model and plant data is generally satisfactory. Temperature, pressure and agitation intensity have strong effect on the kinetics of the reaction and on selectivity ratio under conditions of industrial reactors. The product quality is determined by overall selectivity which is governed by operating conditions, as well as the catalyst selectivity. D.N. Saraf, Currently on leave at the Petroleum Recovery Institute, Calgary, Alberta, Canada.