结晶法提纯对二氯苯的研究

本研究采用一种新型的结晶器对从对二氯苯和邻二氯苯的混合物中分离对二氯苯的过程进行了研究,结晶器的操作过程是通过晶析与吹洗两个步骤来完成的。这种结晶器与其它类型的结晶装置相比具有结构简单,便于操作,能耗低和操作周期短等特点。本文对结晶温度为-10℃～45℃之间、对二氯苯浓度为40%～95%的对二氯苯和邻二氯苯混合物的结晶过程     

水析结晶精制对二氯苯研究

水析结晶精制对二氯苯的新方法 ,即加水使溶解于有机溶剂里的混二氯苯 (对二氯苯、邻二氯苯 )中的对二氯苯优先结晶析出 ,达到分离提纯的目的。文中选用水溶性有机溶剂 ,研究了溶剂量、溶剂配比、结晶温度等因素对晶体产品的收率及纯度的影响 ,并提出在适宜的工艺条件下可将对二氯苯的纯度从 75%一次提高到 99.7%以上 ,收率可达到 67%以上。     

对二氯苯分步结晶精制技术

结合实际生产情况,阐述分步结晶器在生产高含量对二氯苯中的应用情况。     

多段熔融结晶精制技术在对二氯苯生产中的应用

介绍了一种采用套管刮刀或结晶器、离心机及降膜式结晶器等关键设备精制对二氯苯的工艺技术。结合生产实际应用情况对该技术装置进行了剖析。指出其优点及不足之处，提出相应的改进建议     

扩大勒沃库森生产基地的二氯苯产能

特种化学品集团朗盛已投资300万欧元将其位于勒沃库森生产基地的二氯苯产能提高15％以上。该扩产是通过增设一台结晶器而为全球市场生产出更多的高纯度对二氯苯。对二氯苯是用于生产高性能塑料的重要原材料。     

浅谈对二氯苯的开发

介绍了对二氯苯的应用领域、国内外市场情况,对工艺路线、所用反应器、催化剂、提纯分离技术及操作方式进行了述评.在防霉、杀菌、除臭剂方面,对二氯苯国内市场潜力巨大,聚苯硫醚的发展也使对二氯苯的需求量大大增加.指出对二氯苯适合氯碱企业生产,以提高产品的附加值.     

熔融结晶技术用于制备高纯对二氯苯

讨论了以熔融结晶技术制备高纯对二氯苯的工业背景及技术原理，并介绍了国内外已经开发成功且已工业化的三种类型熔融结晶器，对其优缺点进行了评价。     

二氯苯生产分离过程中的含量分析

为配合二氯苯生产的需要,利用气相色谱/火焰离子化检测器,DB-5毛细管气相色谱柱,对二氯苯和对甲苯酚进行了成功的分离,难分离物质对间二氯苯和对二氯苯的分离度R=2;建立了定性定量方法,方法准确度好,RSD<1%。     

杂质对磷酸二氢钾冷却结晶过程的影响

研究了MSMPR结晶器中Cl~-、Ca~(2+)、SO~(2-)_4、NH~+_4对磷酸二氢钾结晶产品的产量、纯度、晶型等的影响。结果表明,杂质浓度的增大不利于晶体产量和纯度的增大;杂质的掺杂会影响晶体的晶型,出现晶体的变形、聚结。研究结果为磷酸二氢钾的结晶分离提纯提供了重要的参考依据。     

二氯苯大型双降膜结晶器结构设计

介绍精制对二氯苯装置核心设备双降膜分步式结晶器的工作原理、选材及关键结构设计等。由于物料中含有一定量的稀盐酸,故设备中与物料接触部分材料选N06600或316L;通过合理设计管内布膜器,提高产品收率和质量;优化结晶器管外布膜器,提高换热能量的利用效率;合理设计管板结构减少设备造价。     

CTA加氢精制单元结晶器系统能量评估及优化

基于闪蒸结晶原理,对三井专利技术的PTA装置加氢精制单元连续结晶器系统进行了分析,建立了该系统的能量评估模型,模型能很好地表征四级连续结晶器的闪蒸汽量。基于结晶器系统模型,对各级结晶器闪蒸汽量进行了评估,并以此对结晶器系统的工艺操作条件进行了优化,合理分配和利用了各级结晶器闪蒸汽。     

Effects of sweating time and cooling strategy on purification of N-vinyl-2-pyrrolidinone using a melt crystallizer

A melt crystallization process is proposed to produce high-purity n-vinyl-2-pyrrolidinone (NVP). To produce high purity products, operation strategy plays key role in the melt crystallizer. We investigated the cooling strategy and optimal sweating time using a batch-type melt crystallizer. A slow cooling followed by a slow heating was found to be an effective temperature profile to produce high purity of NVP. The optimal sweating time was found to be about 20 minutes. For industrial application, a cascade melt crystallizer which consists of four stages was constructed and the proposed crystallization/sweating scheme was applied. Using the new melt crystallizer, NVP more than 99.99% purity can be produced in semi-continuous mode.     

Multi-objective optimization of seeded batch crystallization processes

The optimization of a batch cooling crystallizer has been traditionally sought with respect to the cooling profile and seeding characteristics that keep supersaturation at an optimum level throughout the operation. Crystallization processes typically have multiple performance objectives and optimization using different objective functions leads to significantly different optimal operating conditions. Thus different temperature profiles and seeding characteristics impose a complex interplay on the crystallizer behavior and there is a trade-off between the performance objectives. Therefore, a multi-objective approach should be adopted for optimization of a batch crystallizer for best process operation. This study presents the solution of various optimal control problems for a seeded batch crystallizer within a multi-objective framework. A well known multi-objective evolutionary algorithm, the elitist Nondominated Sorting Genetic Algorithm, has been adapted here to illustrate the potential for the multi-objective optimization approach.     

Micromixing limits in an MSMPR crystallizer

The effect of micromixing limits on a process of crystallization in an MSMPR crystallizer is studied with respect to power law growth and nucleation kinetics. Three limiting cases corresponding to maximum mixedness and complete segregation in an MSMPR crystallizer and plug flow configuration were analyzed for processes in which supersaturation is generated by conventional techniques. The sensitivity of these three limiting cases to the supersaturation generation term in each mode of operation was investigated using several numerical examples. The study demonstrates the effects of mixing on the overall crystallizer performance and, in particular, the enormous micromixing influence at high supersaturation generation rates. The difference in the product CSD arise from the variations of supersaturation profiles experienced by the elementary volumes throughout their sojourn. Characterization of mixing in a real crystallizer at some intermediate levels is emphasized with the aid of relevant industrial examples.     

PX氧化反应器-结晶器串联过程的数学模型

在对二甲苯（PX）氧化反应器研究的基础上，建立了考虑结晶器中的反应、蒸发、杂质扩散等过程的反应器-结晶器串联的数学模型。模拟表明，该模型计算结果与工业实测数据吻合。串联操作在催化剂用量、燃烧消耗、产品收率等方面均优于单一反应器；通过提高结晶器温度。强化结晶器氧化作用，并调整氧化反应器和结晶器的负荷分配，可以达到增产效果。     

固定床电化学反应器研究进展

本文主要就垂直到固定床电化学反应器研究的进展情况进行了综述，阐明了该类反应器开发、设计及操作优化的关键，指出了研究方法及研究方向．     

Mathematical modelling and experimental validation of a novel periodic flow crystallization using MSMPR crystallizers

The challenges of insufficient residence time for crystal growing and transfer line blockage in conventional continuous mixed‐suspension mixed‐product removal (MSMPR) operations are still not well addressed. Periodic flow crystallization is a novel method whereby controlled periodic disruptions are applied to the inlet and outlet flows of an MSMPR crystallizer to increase its residence time. A dynamic model of residence time distribution in an MSMPR crystallizer was first developed to demonstrate the periodic flow operation. Besides, process models of periodic flow crystallizations were developed with an aim to provide a better understanding and improve the performance of the periodic flow operation, wherein the crystallization mechanisms and kinetics of the glycine‐water system were estimated from batch cooling crystallization experiments. Experiments of periodic flow crystallizations were also conducted in single‐/three‐stage MSMPR crystallizers to validate the process models and demonstrate the advantages of using periodic flow operation in MSMPR stages. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1313–1327, 2017     

Product quality improvement of batch crystallizers by a batch-to-batch optimization and nonlinear control approach

Batch crystallization is one of the widely used processes for separation and purification in many chemical industries. Dynamic optimization of such a process has recently shown the improvement of final product quality in term of a crystal size distribution (CSD) by determining an optimal operating policy. However, under the presence of unknown or uncertain model parameters, the desired product quality may not be achieved when the calculated optimal control profile is implemented. In this study, a batch-to-batch optimization strategy is proposed for the estimation of uncertain kinetic parameters in the batch crystallization process, choosing the seeded batch crystallizer of potassium sulfate as a case study. The information of the CSD obtained at the end of batch run is employed in such an optimization-based estimation. The updated kinetic parameters are used to modify an optimal operating temperature policy of a crystallizer for a subsequent operation. This optimal temperature policy is then employed as new reference for a temperature controller which is based on a generic model control algorithm to control the crystallizer in a new batch run.     

Analysis of the Operating Conditions of a Continuous Linear Crystallizer

Theoretical Foundations of Chemical Engineering - The operation of a linear crystallizer, which performs crystallization extraction of uranium from a nitric acid solution of uranyl nitrate during...     

Methanol synthesis from CO2 and H2 in multi-tubular fixed-bed reactor and multi-tubular reactor filled with monoliths

This work investigates the impact of catalyst structuring into particles or monoliths on methanol production from only CO₂ and H₂ at a large scale. Methanol synthesis in multi-tubular reactors is evaluated using packed-bed and monolithic reactors by modeling heat and mass transfer in each reactor. The obtained simulation results show that, at low gas hourly space velocity (GHSV = 10,000 h⁻¹), the performances of both reactor technologies are similar. In this case, the packed-bed reactor technology is the most appropriate technology due to its simplicity of installation and operation. At high GHSV (25,000 h⁻¹), the packed-bed reactor technology is limited by a considerable pressure drop that causes an important loss in productivity due to thermodynamic equilibrium, whereas the monolithic reactors exhibit negligible pressure drop and achieve far better performances.