基于Aspen Plus的原油常减压蒸馏装置的模拟

在Aspen Plus软件平台上,以标定数据为主要输入数据,以产品控制指标为主要约束条件,建立了某厂原油常减压蒸馏装置的稳态模拟流程。在建立过程中,采取对装置流程进行简化处理、将总板效率作为调节变量等方法,使模拟流程的工艺参数、物料平衡和产品恩氏蒸馏数据与生产基本相符。     

Energy Saving in Crude Oil Atmospheric Distillation Columns by Modifying the Vapor Feed Inlet Tray

Optimization of a typical crude oil atmospheric distillation unit and reduction of energy conservation were carried out through modifying the implementation and change in the flash zone of the tower. A conventional procedure in such units involves the combination of liquid and vapor product of the prefractionation train surge drum upon introduction to the tower. However, it is theoretically illustrated and represented by simulation means that introducing the vapor feed into the upper stages of the distillation column separately can lead to an energy saving of 12.6 % in the condenser duty, an increased liquid‐to‐gas flow (L/G) at certain points of the column, and hence to a reduction in diameter and investment costs of new tower designs of approximately US$ 0.7 million a^–1. The proposal can be put into practice without the need of additional equipments or additional cost of difficult rerouting the streams. An industrial case study of a steady‐state crude oil distillation unit is given by simulation provision of AspenHysys™.     

常减压蒸馏装置的技术改造

介绍中国石化股份有限公司武汉分公司常减压蒸馏装置的技术改造特点及工艺流程,针对常压塔各侧线分离效果差、能耗高、产品分布不合理、轻质油收率低等问题,分别对常压系统、减压系统、电脱盐与精制系统进行改造。装置改造后,总拔出率提高了4.84%,轻油收率提高了3.59%,能耗降低了150.65MJ/t,产品分布趋于合理。     

基于特征选择的常减压装置模型及在计划优化中的应用

常减压装置将原油切割为不同中间产品,其作为炼油工艺的龙头装置,对炼油过程生产计划排产与效益提升至关重要。通过建立一种高精度且具有良好求解效率的常减压模型,用以求解模型关键指标实沸点（TBP）曲线,即综合考虑切割产品的实沸点（TBP）与原油TBP、流量、温度等变量影响,构建非线性方程组模型来表征输入输出间的关系;利用特征选择方法遴选相关变量（包括进料性质、相邻TBP及其二次项等）,并采用鲸鱼优化算法优化方程组系数。仿真结果表明,该多输出相互关系模型与已有文献工作相比,在兼顾求解效率基础上,常减压装置各蒸馏切割产品TBP曲线预测上有更高的精度,将此模型应用到炼厂计划优化中,与传统的悬摆切割模型对比,优化结果优于传统悬摆切割模型。     

Hybrid model for optimization of crude oil distillation units

Planning, scheduling, and real time optimization are currently implemented using different types of models, which causes discrepancies between their results. This work presents a single model of a crude distillation unit (preflash, atmospheric, and vacuum towers) suitable for all of these applications, thereby eliminating discrepancies between models used in these decision processes. Product true boiling point (TBP) curves are predicted via partial least squares model from the feed TBP curve and operating conditions (flows, pumparound heat duties, furnace coil outlet temperatures). Combined with volumetric and energy balances, this enables prediction of crude distillation on par with a rigorous distillation model, with 0.5% root mean square error (RMSE) over a wide range of conditions. Associated properties (e.g., gravity, sulfur) are computed for each product based on its distillation curve and corresponding property distribution in the feed. Model structure makes it particularly amenable for development from plant data. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1065–1078, 2016     

原油常减压蒸馏装置的流程模拟及参数优化

根据某原油常减压蒸馏装置的工艺流程,采用Aspen Plus软件对装置的初馏塔、常压塔和减压塔进行流程模拟计算,获得了各产品的温度、流量等关键参数及减压塔侧线产品的馏程曲线,并与实际数据对比,二者吻合良好. 分析了塔板温度和气液相流量沿塔板的分布,运用灵敏度分析工具对相关参数进行优化,优化后常压塔柴油收率可增加0.22 t/h,常压塔热负荷降低6.3%,减压塔轻油收率上升0.18%,减压塔热负荷降低11.2%.     

常压塔回流取热流程的讨论

根据一套500万t/a常减压蒸馏装置的数据,采用ASPEN PLUS软件对目前常减压蒸馏装置设计中采用的3种常压塔回流取热流程进行了模拟计算,并从产品分离精度、对换热网络终温的影响等方面进行了对比.对比结果认为流程1和流程3产品的分离精度比较好,流程2的换热网络终温较高、但产品的分离精度和常压塔的操作弹性较差.     

Optimization and control of a reactive distillation process for the synthesis of dimethyl carbonate

Dimethyl carbonate is an environmentally benign and biodegradable chemical. Based on integration of reactive distillation and pressure-swing distillation technologies, a novel process for synthesis of dimethyl carbonate through transesterification with propylene carbonate and methanol has been developed by Huang et al. In this work, the optimization of this process was performed by minimizing the total TAC. The results show that the op-timal design flowsheet can save energy consumption by 18.6％with the propylene carbonate conversion of 99.9％. Then, an effective plant-wide control structure for the process was developed. Dynamic simulation results dem-onstrate that the temperature/flow rate cascade control plus with simple temperature control can keep not only product purity but also the conversion of the reactant at their desired values in the face of the disturbance in re-actant feed flow rate and feed composition.     

常减压装置初馏塔侧线投用分析

常减压装置是炼化企业的重要组成部分,随着科学技术的发展,越来越多的企业开始投用初馏塔侧线以达到增产航煤的目的。某炼化企业3^#常减压装置加工混合原油8.0Mt/a,通过Aspen Plus进行装置的流程模拟及操作优化,确定了初馏塔侧线最佳抽出位置为第22块塔板,抽出量为16t/h,常压塔最佳取热比为塔顶+顶循∶一中∶二中=0.387∶0.233∶0.380。结果不仅使常二中增加取热8.11GJ/h,为后续换热网络优化提供了有利的条件,而且还在保证各侧线产品质量合格的基础上增产航煤16t/h,常压塔的拔出率也从35.5%提高到了36.3%。说明了常压塔在中段取热优化基础上,投用初馏塔侧线对航煤的增产效果较为明显,常压塔的拔出率也会增加。并且随着我国航空航天事业的飞速发展,市场对航煤的需求量日益提高。因此对于初馏塔侧线的投用具有很大的现实意义。     

Design and Control of Extraction Distillation for Dehydration of Tetrahydrofuran

Design and control of an extractive distillation system for tetrahydrofuran (THF) dehydration with ethylene glycol as entrainer is investigated. The main module is a two‐column system containing an extractive distillation column, whose top stream is the desired product THF, and an entrainer recovery column. Economic analysis with total annual cost as the objective function is developed. Two kinds of control strategies are explored for THF dehydration. The responses reveal that the control structure with fixed reflux ratio cannot maintain the bottom liquid level of the entrainer recovery column, while the control scheme with fixed reboiler heat duty/feed flow ratio exhibits good control performance in spite of large deviations in feed flow rate and feed composition.     

Falling film distillation column with heat transfer by means of a vapor chamber – part I: isothermal operation

We describe a new configuration for falling film distillation columns: a heating system provided by a vapor chamber along the entire column with the operation at atmospheric pressure. Experimental tests were carried out with an ethanol–water mixture by providing isothermal while varying the feed flow rate and the temperatures of the feed and vapor chamber. This heating proposal allowed the formation of a temperature gradient inside the distillation column, which was attributed to the mass and heat axial transfer that occurred along the entire length of the unit. Different from the usual recommendation for film units, higher flow rates are more suitable for distillation of ethanol and water, which was attributed to the heat transfer method and the operation being held at atmospheric pressure. Also, it was observed that there is a strong relationship between the feed temperature and vapor chamber temperature. The results are promising and encourage further studies with this new heat transfer proposal.     

塔河石化常减压装置减压蒸馏模拟分析与改进

塔河石化减压蒸馏装置为A级沥青产品生产提供满足其指标要求的减压渣油原料。当前生产存在的主要问题是：减压渣油闪点指标偏低且波动较大;蜡油馏分中沥青质和重金属含量较高,影响了A级沥青产品的正常生产。为此,调研收集塔河石化常减压蒸馏装置的生产数据,通过建立其工艺计算模型,进行模拟计算数据与装置标定数据、液相产品分离精度的对比,分析影响减压渣油作为沥青产品原料闪点不合格等问题;并利用SULPAK3.0工具分段对减压塔进行水力学计算,分析影响减压蒸馏分离精度的塔结构问题,提出了改进措施和方案,为减压深拔操作生产A级沥青产品提供依据。     

环氧丙烷尾气甲醇吸收及纯化工艺

针对环氧丙烷生产中环氧丙烷尾气难回收问题，提出了甲醇吸收和环氧丙烷萃取精馏解吸回收的环氧丙烷回收新工艺。该工艺同时考虑无催化环氧丙烷水解和与甲醇反应，并采用共沸精馏分离获得高附加值产品丙二醇单甲醚。选用NRTL热力学方法，对上述流程进行了全流程模拟和优化设计，分析了溶剂比、理论塔板数、吸收剂进料温度等主要工艺参数对分离的影响规律，发现新工艺对环氧丙烷质量回收率达到99.99%。研究结果对环氧丙烷工业装置产能提升、节能降耗和挥发性有机物(VOC_S)治理具有指导作用。     

Comparison between the design of experiments and simulation in the three-phase distillation in a sieve tray column for glycerine dehydration

Design of experiments (DOE) is a value scientific approach used to understand the processes in a better way and to determine how the inputs affect the response(s). In this work, this method has been applied to study the behavior of the three-phase distillation in a sieve tray column, through the effects of the process and geometrical variables. The experimental values were compared with predicted values obtained by simulation using the equilibrium and nonequilibrium models. Three-phase distillation has been used for glycerine dehydration using toluene as entrainer, in order to avoid the glycerol degradation by distillation at atmospheric pressure. The best conditions found were: vapor flow rate of toluene = 23.5 kg/h, feed flow rate = 2.2 kg/h and feed concentration = 50 wt% glycerol, using the layout L₄ with fractional hole area = 0.04 and weir height = 70 mm. The nonequilibrium model based on Eckert and Vanek's approach (2001) and Chen–Chuang's correlation (1993) have been used to estimate the binary coefficients of mass transport. The predicted values obtained by the experimental model and by the nonequilibrium model have represented the behavior of the dehydration in the sieve tray column studied. Both models underpinned the experimental results obtained for this column.     

变压精馏分离丙酮和环己烷的动态特性

基于丙酮-环己烷共沸体系的压力敏感性，利用Aspen Plus软件，以年度总费用(TAC)最小为目标函数对常规、部分及完全热集成变压精馏工艺进行稳态模拟与优化，并以经济最优的完全热集成变压精馏工艺为基础，借助Aspen Plus Dynamics软件建立多种不同控制结构，通过改变进料流量和进料组成考察了控制结构的有效性，并提出塔底热负荷/进料量比例控制与组成-温度串级控制相结合的改进控制结构。稳态模拟与优化结果表明，常规、部分和完全热集成三种工艺的最小TAC分别为3.64×105, 2.83×105, 2.76×105 $/y，经济最优工艺为完全热集成变压精馏。动态响应结果表明固定回流量/进料量控制结构在响应时间方面优于固定回流比控制结构，但产品纯度未达到设计值99.9wt%；而塔底热负荷/进料量比例控制与组成-温度串级控制相结合的改进控制结构能够有效保证产品纯度在99.9wt%及以上。     

混合溶剂间歇萃取精馏分离过程的模拟

由于混合溶剂存在"混合溶剂效应",能够解决简单溶剂选择性与互溶性相互矛盾的问题,因此混合溶剂间歇萃取精馏技术可以大大拓宽传统单一溶剂间歇萃取精馏分离技术的应用空间。文章建立了反映常规混合溶剂间歇萃取精馏过程的恒摩尔持液数学模型,并运用2点隐含法对其求解,结果表明,模拟计算结果与实验结果吻合较好。随后运用该模型探讨了塔身持液量、混合溶剂进料位置等因素对混合溶剂常规间歇萃取精馏的影响。得出以下结论,产品馏出速率随塔身持液量的增大而减小,塔顶馏分产量与塔身持液量的关系不大。另外,混合溶剂进料位置的选定对分离效果也有较大的影响,需要正确选择。     

Product tri-section based crude distillation unit model for refinery production planning and refinery optimization

Accuracy of a crude distillation unit (CDU) model has a significant impact on refinery production planning. High accuracy is typically accomplished via nonlinear models which causes convergence difficulties when the entire refinery model is optimized. CDU model presented in this work is a mixed-integer linear model with a modest number of binary variables; its accuracy is on par with rigorous tray to tray CDU models. The model relies on the observation¹² that a line through the middle of the product true boiling point (TBP) curve depends on the crude feed properties and the yields of the adjacent products. Novelty of the product tri-section CDU model is that it does not require models of individual distillation towers comprising the CDU, thereby leading to a much simpler model structure. Significant reduction in the computational effort required for the optimization of nonlinear refinery models is illustrated by comparison with previous work.     

Fuzzy cognitive approach of a molecular distillation process

Takagi-Sugeno fuzzy model is presented as an alternative modeling tool for the molecular distillation process of heavy liquid petroleum residues. A nonlinear phenomenological model formed by partial differential equations involving temperature and composition is regarded as a virtual working plant for the generation of data required to build the fuzzy models. Furthermore, experimental data from the molecular distillation process of an atmospheric residue 673.15 K upward (673.15 K+) at different operating conditions were used to develop the fuzzy representations. In this work, the system was simulated through the development of software in Fortran 90/95 and the numerical solution by using the finite-difference method. In the fuzzy approaches, the distillation temperature and the feed flow rate are the input variables, while the liquid interface temperature, the film thickness, the concentration profiles, and the distillate flow rate were considered as the output responses. The fuzzy models obtained were compared with the results generated from the phenomenological model, showing an excellent agreement.     

Theoretical study of sequential centrifugal partition chromatography

Sequential centrifugal partition chromatography (sCPC) is a novel cyclic liquid–liquid chromatographic process. Each cycle comprises two steps, which differ by the liquid phase used as a mobile phase (upper or lower phase) and its flow direction. The feed is continuously separated into two product streams, which are collected alternately. The process includes six (four flow rates and two‐step durations) interconnected operating parameters. In this work, by imposing a complete separation of a binary feed mixture and using the assumption of instantaneous solutes partition equilibrium, a set of constraints on the sCPC unit operating parameters is derived. Using these constraints, a region of complete separation, composed of a set of combinations of the two‐step times, can be defined for a preselected feed and mobile phase flow rates. The approach is validated by simulation of a binary mixture separation in a sCPC using the cell model. © 2012 American Institute of Chemical Engineers AIChE J, 59: 241–249, 2013