Modelling continuous foam fractionation with reflux

An equilibrium stage approach is taken to modelling the performance of a continuous foam fractionation column with reflux. Such an approach has been facilitated by recent developments in the understanding of pneumatic columns of foam that allow liquid rates within the rising column of foam to be predicted with confidence. It is shown that the recovery of surfactant into the product stream increases monotonically with increasing reflux ratio but this is at the expense of reduced product rate.     

Optimization of the sulfolane extraction plant based on modeling and simulation

An optimization system, based on modeling and simulation, was developed for a sulfolane extraction plant. The primary objective of the operation of this plant is to increase benzene composition, which is mostly affected by the recycle streams in the plant. In this work the optimal recycle streams were identified and resulting product compositions were evaluated. In the optimization, suitable parametric models for each process unit were obtained first from the steady-state rigorous modeling and simulation of the sulfolane extraction plant. The parametric models were then employed to develop the optimization system based on the SQP scheme. Results of simulations show promise for further economic improvements over present operation states.     

全电动注塑机混合驱动式合模机构优化分析

以加快合模机构移模速度和优化移模速度曲线为目的,优化设计出一种新型混合驱动式合模机构,并对该合模机构的开合模过程进行运动学仿真和动力学仿真。结果表明,相比于现有全电动注塑机混合驱动合模机构,新型混合驱动式合模结构在移模速度上有了显著提高,移模速度曲线也更接近理想的正弦曲线。新型全电动精密注塑机混合驱动合模结构具有低成本化的优势,同时其机构运动学和动力学的性能也超越了已有全电动混合驱动合模结构。     

Optimal operation of the pressure swing adsorption (PSA) process for CO<Subscript>2</Subscript> recovery

The operation of PSA (Pressure Swing Adsorption) processes is a highly nonlinear and challenging problem. We propose a systematic procedure to achieve the optimal operation of a PSA process. The model of the PSA process for CO₂ separation and recovery is developed first and optimization is performed to identify optimal operating conditions based on the model. The effectiveness of the model developed is demonstrated by numerical simulations and experiments using CO₂ and N₂ gases and zeolite 13X. Breakthrough curves and temperature changes in the bed are computed from the model and the results are compared with those of experiments. The effects of the adsorption time and reflux ratio on the product purity and the recovery are identified through numerical simulations. The optimization problem is formulated based on nonlinear equations obtained from simulations. The optimal operating conditions identified are applied to experiments. The results show higher recovery of CO₂ under optimal operating conditions.     

反应精馏过程模拟优化的研究进展

反应精馏过程的数学模拟是反应精馏塔设计、放大、控制的基础。对反应精馏过程模拟模型、求解方法以及优化的研究进展进行了综述。     

Model based prediction of required cut size diameter for fractionation of fly ash from a grate-fired wood chip incineration plant

Utilization of biomass ash as a soil improvement material is limited by the admissible input of heavy metals. It is well known that heavy metal concentrations are increased in fine ash fractions. In this study, two models are investigated to describe the distribution of various heavy metals in different size fractions of fly ash from a grate-fired biomass incineration plant incinerating wood chips. The second model assuming a dependence of the heavy metal concentration from the reciprocal particle diameter to the power of the variable N correlated well with measured concentrations. This model was then used in the calculation of the required cut size of a classifier for the production of a coarse fraction with heavy metal concentrations below limits from a fly ash sample exceeding the Austrian limits for a soil improvement material. The predicted concentrations of the critical heavy metals Cd and Pb and the total mass of the coarse fraction produced corresponded well with measured values, and although the concentration of Zn was considerably underestimated in the model, the produced coarse fraction was within the limits for utilization.     

催化裂化反再系统计算机模拟与优化

采用离线调优的方法,对石油一厂催化裂化反再系统的操作条件进行了优化计算,建立了较精确的生产过程数学模型。在对生产过程进行模拟与优化的基础上,针对催化裂化装置在原料性质及加工量变化状况,就如何选择各种工艺参数等问题进行了优化处理;为确定生产装置调优指标和改造措施提供了方便可行的方案,同时也为提高催化裂化装置的经济效益提供了可靠信息。     

空气分离装置的模拟与优化

采用ASPEN系统模拟软件对某空分装置的设计工况和实际工况进行了模拟计算,给出了以纯氧产量最大为目标函数的操作参数的优化结果,其结果可以为空气深冷分离设计和操作提供可靠的参考数据。     

乙烯装置冷箱脱甲烷系统模拟优化

中国石化扬子石化股份有限公司烯烃厂650kt／a乙烯装置因二元制冷系统效率低，无法为冷箱、脱甲烷塔系统提供足够的冷量，加之部分操作控制指标不尽合理，导致乙烯损失大。文中介绍了应用Aspen软件对该系统工艺流程进行模拟计算的过程，分析了存在的问题，提出了最优化操作控制指标。     

Enrichment of Lysophosphatidylcholine in Canola Lysolecithin

Lysophosphatidylcholine (LPC) possesses excellent oil‐in‐water emulsifying properties and health benefits. The objective of this study was to produce an LPC‐enriched fraction from lysolecithin generated during enzymatic degumming of crude canola oil. Three alcohols (methanol, ethanol and isopropanol) were evaluated for their effectiveness at enriching LPC. A 3 × 3 full factorial design was employed to study the effects of two processing parameters (temperature and alcohol/lysolecithin ratio) on three responses (yield and LPC concentration of alcohol soluble fraction, and LPC recovery) with the most effective alcohol. Ethanol was found to be the best solvent to enrich LPC in lysolecithin. An ethanol soluble fraction with more than 50 % LPC was produced. Quadratic models with R² > 0.9 were developed to describe the relationship between the processing parameters and the responses in the 3 × 3 full factorial experiment. Both ethanol soluble fraction yield and LPC recovery increased with increasing temperature and ethanol/lysolecithin ratio. LPC concentration in the ethanol soluble fraction was enhanced with decreasing temperature and ethanol/lysolecithin ratio. According to the analysis, ethanol soluble fractions with LPC concentration higher than 66 % could be obtained at temperatures of 0–40 °C and an ethanol/lysolecithin ratio of 2:1 (v/w).     

离心式气液分离器内流场的数值模拟与结构优化

基于计算流体动力学(CFD)方法,采用Gambit建模,利用Fluent软件,对常规立罐式离心气液分离器进行了模拟仿真。通过流场分析可以看出,流场对称性很差,底流出口附近气体含量较多,说明气液分离效果不好。通过结构优化,包括将底流出口改为正下方排液,单入口改为双入口结构,减小罐体直径,溢流管伸入分离器内部入口管之下,以及将分离器下端改为锥形结构等,改善分离器内部流场的轴对称性及气相体积分数分布情况,并提高分离器的净化程度。     

苯乙烯装置中脱氢尾气吸收系统的建立与优化

阐述了苯乙烯的现状并分析装置脱氢尾气的价值。重点对绝热脱氢法中粗苯乙烯塔进行了模拟设计和优化。通过Aspen Plus软件的模拟,建立了一套脱氢尾气吸收系统,并且探讨了吸收塔的影响因素,确立了最优工况,对实际工业生产起到一定的指导作用。     

A microscopic approach to determine the origin and mechanism of coke formation in fractionation towers

This study investigated the deposition of coke in a fractionation tower following thermal cracking of heavy feedstocks. A simple microscopic technique was used to determine whether the coke formed in situ in the fractionator or was formed elsewhere (e.g. in the reactor vessel) and was subsequently entrained in the vapour phase. The reflectance of coke types, mode of occurrence, and distributions from the bottom to the top of the fractionator were used to interpret the range of temperatures responsible for coke formation. Both isotropic and anisotropic (mosaic) coke was observed in the samples. The anisotropic textural features indicated that asphaltenes carry-over was a minor problem and that the vast majority of the isotropic coke precursors were the maltenes present in the gas phase that entered the fractionator. The formation of perfectly spherical mesophase was attributed to the gas oil stream itself used to quench the vapours exiting the thermal cracking vessel. Microscopic evidence, along with metals concentration in the coke at various locations of the operation provided useful information as to the nature of the coke precursors.     

激光加工多孔端面机械密封结构参数的协调优化

通过建立激光加工多孔端面机械密封的理论分析模型,采用有限差分法求解雷诺方程,得到不同微孔结构参数下密封端面间的膜压分布,进而可以计算多目标优化方法构建的液膜刚度与泄漏量之比的协调函数,获得了最佳的微孔结构参数值。研究表明,当微孔深径比ε为0.1069和微孔密度sp为0.492时,刚漏比最大。     

茂名乙烯裂解汽油加氢操作工艺的优化

分析了造成茂名石化裂解汽油加氢装置混合芳烃产品损失率以及能耗较高的原因,介绍了茂名石化乙烯裂解汽油加氢装置在工艺操作方面采取的优化措施。通过操作工艺的优化达到了降低裂解汽油加氢装置的能耗和混合芳烃产品损失的目的。     

等值渗流阻力法在整体压裂优化设计计算中的应用

压裂改造技术是油气井增产、水井增注的一项重要技术措施,随着压裂技术的发展,从单井的增产增注逐渐发展到整个油藏的总体压裂优化设计。目前整体压裂优化设计计算大多采用数值模拟的方法,该方法适应性强但计算方法复杂。本文提出一种简单的优化设计计算方法:利用水电相似原理,建立等效渗流阻力优化计算模型。该方法计算简单适用,能够分析井网及压裂参数对压裂生产井产能的影响。     

基于CFD的三相分离旋流器流场分析与结构优化

基于计算流体动力学(CFD)方法,采用FLUENT软件对三相旋流分离器进行了流场分析和结构优化。通过对该旋流器的脱气和除砂功能开展数值模拟分析,研究了不同结构参数对脱气和除砂效果的影响。研究发现,溢流管伸入长度、倒锥结构高度、入口截面面积以及出液孔高度等的变化对脱气除砂效果均有较大影响。     

氨合成系统工艺操作参数的优化

对小化肥厂氨合成系统工艺操作进行优化，以每小时的得经济收益为目标函数，取入合成塔气的氨含量，惰性气含量、氢氮比、压力、温度空速６个工艺参数为变量，采用正交试验法进行优化。探讨不同情况下（如催化剂不同使用期，原料、产品市场价格的变化）最大效益一氨合成工艺操作参数间的关系及最佳操作区域。为工艺操作参数的合理确定提出了一些思路。     

Understanding the operation of industrial MSF plants Part II: Optimization and dynamic analysis

This paper is a continuation of Part I, which aims at widening the knowledge about MSF operation. The investigation includes studying the set-point optimization of an MSF plant. This is achieved by optimizing the steady-state model of the plant to determine the optimal operating conditions. The objective function is designed such that it determines the feasible values for the plant operational parameters that maximize the performance ratio. The investigation also includes studying the dynamic behavior of the process during open-loop and closed-loop operations. The dynamic analysis in both cases focuses on investigating the source and existence of operation stability due to blow-through or liquid pile-up. The entire analysis is based on simulation of a previously validated model for an MSF plant.     

Characterization of uncertainties in the operation and economics of the proposed seawater desalination plant in the Gaza Strip

In the Gaza Strip, the available freshwater sources are severely polluted and overused. Desalination of seawater through reverse osmosis (RO) has become the most realistic option to meet a rapidly growing water demand. It is estimated that the Gaza Strip will need to develop a seawater desalination capacity of about 120,000 m³/d by the year 2008, and an additional 30,000 m³/d by the year 2016 in order to maintain a fresh water balance in the coastal aquifer and to fulfill the water demand for different uses in a sustainable manner. Cost and reliability of a large RO facility are still subject to much uncertainty. The cost of seawater desalination by RO systems varies with facility size and lifetime, financing conditions, intake type and pre-treatment requirements, power requirements, recovery rate, chemicals cost, spare parts cost, and membrane replacement cost. The permeate salinity is a function of feed water temperature, recovery rate, and permeate flux. The quantity of water produced depends mainly on plant size, recovery rate, and operating load factor. Many of these parameters are subject to a great deal of uncertainty. The objective of this work is to develop a probabilistic model for the simulation of seawater reverse osmosis processes using a Bayesian belief network (BBN) approach. This model represents a new application of probabilistic modeling tools to a large-scale complex system. The model is used to: (1) characterize the different uncertainties involved in the RO process; (2) optimize the RO process reliability and cost; and (3) study how uncertainty in unit capital cost, unit operation and maintenance (O&M) cost, and permeate quality is related to different input variables. The model utilizes information from journal articles, books, expert opinions, and technical reports related to the study area, and can be used to support operators and decision makers in the design of RO systems and formulation of operational policies. The structure of the model is not specific to the Gaza Strip and can be easily populated with data from any large-scale RO plant in any part of the world.