预热水槽控制方案的数学模型

本文通过建模分析的方法，针对某厂新建的间歇式氯乙酸生产车间结晶工序使用的预热水罐，证明若将其更换为预热水槽，再对预热水槽水位进行恒值控制，可以达到降低系统耦合度，优化系统设计的目的。     

氯乙酸结晶操作改进方案

介绍氯乙酸结晶工序操作中存在的问题,针对氯乙酸结晶时间长和降温温差控制要求精准的特点,提出自动控制的工艺方案。     

氯乙酸连续结晶过程研究

我国氯乙酸结晶一直沿用的是降温结晶工艺,属于间歇操作,存在结晶颗粒粒度小且不可控、纯度很难提高、质量偏低等问题。研究了氯乙酸在恒温条件下连续结晶的可能性;考察了结晶温度、停留时间及搅拌速度对连续结晶过程产品粒度分布及质量的影响。得出了最适宜的连续结晶条件:结晶温度为28℃,停留时间为30h,结晶釜中搅拌速度为40r/min。结晶颗粒平均粒度大于0.8mm,并且一氯乙酸含量及二氯乙酸含量都能满足化工行业标准一等品的要求。     

模糊-PID在聚合釜温控中的应用

针对被控对象惯性延迟大、被调节信号反馈慢的特点,笔者采用恒流量温度控制方案对原聚合釜温度控制系统的单回路控制方案进行了改造,应用模糊-PID控制使聚合釜夹套水温与聚合反应温度保持较小的温差,将调节温度的过程变得更加平缓,经过实际应用取得了令人满意的效果.     

聚苯硫醚聚合釜温度控制方案

分析聚苯硫醚(PPS)的生产工艺流程。针对PPS聚合釜各阶段温度的特点,提出相应的温度控制方案。各控制方案使聚合釜温度得到了精确控制,使PPS的质量和产量得到了提高。     

熔融结晶分离对硝基氯苯温度控制方案的设计与应用

介绍了对硝基氯苯熔融结晶分离的过程,并在结晶器温度控制方案中通过采用HONEYWELL公司的TPS系统的CL程序和RAMP/SOAK算法来满足熔融结晶的工艺控制要求,提高了结晶工序的控制性能.     

醚化反应釜温度控制方案的优化

分析了醚化反应釜的温度控制现状以及醚化釜装置整体自动化水平较低的原因。以山东HD公司的纤维素醚项目为背景,以人工操作经验数据为依据,对醚化反应釜温度控制方案进行了优化,提高了醚化釜装置的自动化水平,更好地满足了控制要求。     

智能型氯乙酸结晶优化控制器CHACCC-7研制成功

江苏省化工研究所计算机应用研究室将氯乙酸生产结晶过程的优化控制技术与先进的自动控制技术相结合，开发研制成功CHACC－97氯乙酸结晶化优化控制器。该控制器具有性能稳定、可串级调节、带RS－422通信接口及可在面板进行各种控制参数没置等功能，是控制氯乙酸结晶过程的理想智能仪表。智能型氯乙酸结晶优化控制器CHACCC-7研制成功@李建新@祁争健     

酯化釜塔顶温度控制系统改造

介绍了串级控制在仪化研究院半连续聚酯试验装置酯化釜塔顶温度控制上的应用,解决了酯化釜塔顶温度调节滞后问题,提高了调节过程的品质     

横河DCS在聚氯乙烯生产中的应用

介绍了YOKOGAWA公司的CENTUM CS3000在聚氯乙烯生产中的应用情况,简述了工艺流程、控制系统硬件配置。重点对聚合温度控制方案的软件实现进行了分析。聚合釜温度控制采用了批量程序控制和常规控制相结合的控制策略,经过不断改进温度控制程序,不断优化参数,聚合釜温度已基本控制在设定温度±1℃,从而稳定了工艺指标,提高了PVC树脂的质量。     

Ultrasonic characterization of the crystallization behavior of poly(ethylene terephthalate)

On the basis of the previous observations that the ultrasonic signals are sensitive to the crystallization of polymers (Tatibouet and Piché, Polymer 1991, 32, 3147), we have expanded our efforts to study the detail relationship between the ultrasonic signals and crystallization process in this work. The nonisothermal and isothermal crystallization of virgin poly(ethylene terephthalate) (PET) and PET samples after degradation were studied by using a specially designed pressure‐volume‐temperature (PVT) device, with which an ultrasonic detector was combined. The results showed that the evolution of the ultrasonic signals not only can be used to probe the crystallization process but also can qualitatively characterize the crystallization rate, crystallinity, crystallite size, and amorphous. DSC measurement was used to verify such results. Ultrasonic signals could be as a complementary tool to polymer chain movement and well be applied to characterize the crystallization behavior. Furthermore, the ultrasonic measurement has the potential use to characterize crystallization of products in‐line during processing (i.e., injection molding, micromoulding). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

红霉素肟的合成研究

以红霉素硫氰酸盐为原料,通过研究液碱浓度、反应时间、结晶温度等对红霉素肟的影响,筛选出了最佳工艺条件,并应用于生产。     

Predictive control of particlesize distribution of crystallization process using deep learning based image analysis

The challenges to regulate the particle-size distribution (PSD) stem from on-line measurement of the full distribution and the distributed nature of crystallization process. In this article, a novel nonlinear model predictive control method of PSD for crystallization process is proposed. Radial basis function neural network is adopted to approximate the PSD such that the population balance model with distributed nature can be transformed into the ordinary differential equation (ODE) models. Data driven nonlinear prediction model of the crystallization process is then constructed from the input and output data and further be used in the proposed nonlinear model predictive control algorithm. A deep learning based image analysis technology is developed for online measurement of the PSD. The proposed PSD control method is experimentally implemented on a jacketed batch crystallizer. The results of crystallization experiments demonstrate the effectiveness of the proposed control method.     

Principles of palm olein fractionation: a bit of science behind the technology

Dry fractionation is a well‐established and versatile fat modification technology that can produce a broad spectrum of edible oils and fats. Due to its specific chemical composition, especially palm oil can be processed by this technology into fractions that serve as salad oils, frying oils, margarine fats. Whereas the first step of this multi‐stage production process is well understood, the edible oil industry all over the world is much more often confronted with problems in the second stage of the process, when the liquid palm olein is further fractionated. The process of palm olein crystallization is indeed a lot more difficult to control. This article therefore elaborately explains the main, fundamental causes for this sensitivity of palm olein during the fractional crystallization. It further discusses which and how components present in refined palm olein can be responsible for process instability and how they affect the quality of the end products on an industrial scale. The article also highlights which novelties and innovation in dry fractionation technology are currently under investigation.     

头孢氨苄连续结晶研究及应用

头孢氨苄的传统生产方法多为间歇结晶,存在效率低、能耗高等弊端。为节约能耗、提高生产效率、缩短工时、降低成本,针对头孢氨苄等电点结晶的特点,本文设计了两级连续结晶工艺。采用单因素法系统研究了头孢氨苄水溶液初始浓度、停留时间、搅拌速率、结晶终点pH、晶种策略等因素对头孢氨苄连续结晶过程产品的收率、晶习及粒度分布的影响。单因素实验结果显示头孢氨苄水溶液质量分数为14%、最佳停留时间为12min、结晶终点pH控制在4.8附近、晶种添加量为5%时其产品收率、粒度分布均达到了理想的效果。该工艺能将结晶过程的过饱和度有效地控制在介稳区内,避免了爆发成核。与间歇结晶相比,两级连续结晶工艺的工时缩短30%。产品晶习完整,粒度分布均匀,收率可以达到96%。目前该工艺已成功实现单条生产线规模为500t/a的产业化应用。     

高效膜蒸馏结晶过程的研究进展

全球性的水资源短缺及环境污染问题,使得工业废水处理、海水淡化、高价值溶质综合利用的需求日益迫切。膜蒸馏结晶过程可以充分利用低品质热源,实现高纯度水溶剂分离、盐分结晶制备,对于实现分离过程零排放和协同增效有重要意义。同时,膜蒸馏结晶也可以与多级闪蒸,多效精馏、纳滤、正向渗透、反渗透等过程进行耦合,进一步提高整体分离效率。此外,该过程对于调控晶体外部形貌,制备晶体尺寸分布集中、流动性好的晶体产品也有积极作用。基于此,针对膜蒸馏结晶原理、过程调控机制以及创新过程应用几个方面开展论述,总结了膜蒸馏结晶技术在高效分离、结晶过程精准控制等领域的关键问题和发展趋势。     

Research progress of high-efficiency membrane distillation crystallization process

The global shortage of water resources and environmental pollution has made the demands for industrial wastewater treatment, seawater desalination, and comprehensive utilization of high-value solutes increasingly urgent. Membrane distillation crystallization process cannot only make full use of low-quality heat sources, achieve high-purity water-solvent separation, but also achieve salt crystallization preparation, which is of great significance for achieving zero liquid discharge and synergistic efficiency in the separation process. At the same time, membrane distillation crystallization process can also be coupled with multi-stage flash evaporation, multi-effect distillation, nanofiltration, forward infiltration, reverse osmosis and other processes to further improve the overall separation efficiency. In addition, it also has a positive impact on regulating the external morphology of the crystal, preparing crystal products with relatively concentrated crystal size distribution and good flowability. Based on this, this article has discussed several aspects of membrane distillation crystallization principles, process control mechanisms and innovative process applications, and looking forward to the key issues and development trends of membrane distillation crystallization technology in the fields of efficient separation and precise control of the crystallization process.     

Ultrasonic determination of the effect of shear on lipid crystallization

The design and calibration of a novel rheometer incorporating ultrasonic sensors are described. The instrument is capable of the simultaneous measurements of torque, rate of temperature change, and ultrasonic properties of a liquid as a function of time, temperature, and shear rate. The effect of shear rate on the crystallization onset temperature of a sample of confectionery coating fat is studied using this device. The instrument detected the phase transition in the sheared sample as abrupt changes in all of the measured parameters. The onset temperature increased significantly with shear rate, implying lipid crystallization can be accelerated by mixing. There were also significant differences between sensing modalities.     

Characterization of thermal behavior and kinetics of crystallization of a thermotropic rigid-chain copolymer

Thermal analysis was employed to estimate the heat of transition, equilibrium melting temperature and surface free energy of a thermotropic liquid crystal copolyester resin (70 mol% p-hydroxybenzoic acid and 30 mol% 2,6-hydroxynaphthoic acid). Specific heats and melting and crystallization behavior were evaluated using differential scanning calorimetry (DSC). Experiments over a wide range of cooling rates indicate two different crystallization processes: a rapid crystallization process and a slow crystallization process. The kinetics of the rapid crystallization process were evaluated using a non-isothermal method. The analysis indicates that the rapid crystallization process can be suitably described by the non-isothermal Avrami equation. The Avrami exponent is found to be equal to 2, which is in agreement with the nucleation and growth mechanism of the rigid rodlike molecules. The kinetics of the slow crystallization process, which were studied using an isothermal method, indicate that the degree of crystallinity varies linearly with log(time). The equilibrium melting temperature for this process is found to be 372°C. The Arrhenius plot yields a linear relationship in the lower temperature range.