PTA装置醋酸脱水塔存在问题攻关

分析了洛阳石化PTA装置扩能改造后,溶剂脱水塔存在塔盘效率偏低、塔压降过高、塔顶醋酸含量严重超标等问题,采用复合孔微型阀高效塔盘,消除了醋酸塔运行中出现的问题,溶剂脱水塔取得明显效果。     

洛阳石化PTA溶剂塔改造成功

河南省洛阳石化总厂自行研制成功的精对苯二甲酸(PTA)溶剂脱水装置,不仅破解了PTA溶剂脱水装置外排污水醋酸含量偏高的难题,每月还可为企业节约醋酸费用180万元。据介绍,洛阳石化总厂溶剂脱水塔是对精对苯二甲酸装置氧化单元反应后外排污水和废气中的溶剂——醋酸进行回收的重要装置。     

醋酸-对二甲苯-水体系共沸精馏的模拟分析

采用Aspen Plus11.1化工流程模拟软件,对扬子石油化工有限公司化工厂精对苯二甲酸(PTA)装置的溶剂脱水塔生产过程进行了模拟计算,采用NRTL-HOC热力学计算模型,并进行热力学参数修正,通过调整塔板数、热负荷、进料位置、操作压力、对二甲苯(PX)采出位置等操作参数,得出各塔的最佳工艺条件。在最佳工艺条件下,分析了此分离过程的能耗问题。模拟结果表明,溶剂脱水塔分离得到的醋酸、水、PX均能达到产品质量要求,工艺流程合理、可靠。     

工业醋酸脱水过程五元体系非均相共沸精馏的流程模拟

针对以醋酸正丙酯为共沸剂的醋酸脱水过程,考虑醋酸溶剂中未反应的前体对二甲苯以及反应的副产物醋酸甲酯的影响及回收利用,分别选用HOC和UNIQUAC模型来修正体系中五元混合物系的汽液非理想性,通过拟合醋酸甲酯-对二甲苯和醋酸正丙酯-对二甲苯两体系的二元汽液平衡实验数据获得了该两组体系UNIQUAC模型的二元交互作用参数,借助模拟软件Aspen Plus,结合软件内置其他二元体系参数,对工业醋酸脱水塔系包括溶剂脱水塔、PX回收塔、共沸剂回收塔在内的三塔体系进行系统的分析模拟,得到了与工艺数据误差小于±6%的能正确描述工业醋酸脱水塔系操作特性的工艺机理稳态模型,为工业醋酸脱水过程工艺的进一步研究提供理论基础和依据。     

PTA生产降低醋酸单耗的技术

影响醋酸单耗的主要因素是醋酸损失,装置负荷以及系统中Na+的多少。减少醋酸损失的措施为①氧化反应温度190℃左右;②薄膜蒸发器下料的温度为165～180℃;③溶剂脱水塔的回流比为3.2～3.4,回流温度为80～95℃;④高压吸收塔洗涤水的用量为2t/h。装置应尽量在满足负荷或超负荷条件下运行,清洗碱液要排尽并用水彻底冲洗,减少Na+进入系统以此来降低醋酸单耗。     

PTA装置醋酸脱水存在问题与对策

分析了某精对苯二甲酸装置醋酸脱水塔存在塔压降过高、蒸汽耗用大、塔顶醋酸和塔底醋酸异丁酯含量严重超标等问题,采用复合孔微型浮阀高效塔盘和增加醋酸液-液萃取相结合,消除了醋酸塔运行中出现的问题,醋酸精馏取得明显效果。     

先进控制技术在PTA溶剂脱水塔上的应用

阐述了应用APC-Hiecon先进控制软件建立溶剂脱水塔多变量预测控制系统,解决了PTA溶剂脱水塔控制中存在的主要问题,稳定了溶剂脱水塔的操作,降低了醋酸的消耗,取得了预期的目标。     

络合萃取回收PTA溶剂脱水塔塔顶废水中的醋酸

采用络合萃取法回收精对苯二甲酸(PTA)溶剂脱水塔塔顶醋酸废水,研究了几种因素变化对络合萃取废水醋酸平衡的影响,并探讨了填料塔络合萃取醋酸工艺过程和萃取剂再生过程。结果表明:在络合萃取平衡实验中,随着醋酸初始浓度、水油相比、pH值和温度的增加,分配系数随之下降。在填料塔逆流连续络合萃取操作试验中,随着两相流速和相比的减小,萃取率随之增加。反萃采用减压精馏法,真空度控制在一定的范围(0.06~0.08 MPa)内,釜底温度控制在150~170℃之间,反萃率约为95%,再生后得到的醋酸质量分数可达40%以上。     

优化氧化工艺降低PTA醋酸单耗

分析了影响PTA装置醋酸消耗的因素，指出了生产中降低醋酸单耗的方法：（1）尽量降低氧化温度；（2）溶剂脱水塔的回流比控制在3．3－3．5；（3）提高薄膜蒸发器的醋酸回收率；（4）平稳操作。上述方法实施后，PTA醋酸单耗大幅度下降。     

三甘醇脱水装置影响因素定量分析

三甘醇溶剂脱水法因其各种优点已经广泛地应用到天然气脱水处理中。本文运用HYSYS模拟软件对三甘醇脱水装置进行了流程模拟,定量分析了吸收塔的塔盘数量、再生温度、湿气入口温度、湿气含水量和汽提气流量等影响因素对三甘醇脱水装置脱水效果的影响。分析讨论结果为实际生产过程中操作参数的调整提供了依据。     

Simulation and analysis of dehydration distillation column based on distillation mechanism integrated with neural network

In an industrial solvent dehydration distillation column (SDDC) model, the Murphree efficiency represents the separation ability of a distillation tray and the SDDC model’s performance depends on the value accuracy of the Murphree efficiency. Because there are many operation conditions having nonlinear effect on Murphree efficiency, it is difficult to determine its value. To develop a precise and robust SDDC model, a novel hybrid model combining distillation mechanism with neural network is proposed. In the SDDC hybrid model, the neural network is employed to model the nonlinear relationship between the operation conditions and Murphree efficiency, which is embedded into the SDDC mechanistic model. The results showed a good predicting and robust performance of the hybrid model under different operation conditions. Based on the hybrid model, the effect of the operation conditions on SDDC was analyzed to obtain some useful guiding rules for the SDDC operation.     

Effect of two-pass trays on distillation efficiencies

Two important structural factors that affect distillation efficiencies, the outlet weir heigh and the liquid flowpath length, are investigated. Performance and efficiency data of an industrial scale i-butane/n-butane distillation column equipped with two-pass trays are used as a basis for the calculations. A mathematical development for a new method for predicting the numbers of vapor and liquid phase transfer units is given. This method together with some other NTU calculation methods is used to assess the effect of the outlet weir height on efficiencies. The effect of outlet weir height on the Murphree tray efficiencies is investigated using the observed point efficiencies and different point efficiency to the Murphree tray efficiency relation methods. The effect of varying liquid flowpath lengths on efficiencies is studied by calculating the Murphree tray efficiencies for one-pass and two-pass trays. The results obtained using the NTU calculation method presented in this study show that a certain outlet weir height point efficiency reaches its maximum. Most of the other methods give opposite results giving a minimum for point efficiency at a certain outlet weir length. The results also show that the Murphree tray efficiencies for one-pass trays are higher than for two-pass trays. Obviously, this is caused by the longer liquid flowpath length of one-pass trays. The Murphree tray efficiencies are also calculated for an industrial-scale MTBE purification column. The column is equipped with two-pass trays in the stripping section and with one-pass trays in the rectifying section. The Murphree tray efficiencies of one-pass trays are considerably higher than the two-pass tray Murphree tray efficiencies.     

CALCULATING DISTILLATION EFFICIENCIES OF MULTICOMPONENT i-BUTANE/ n-BUTANE COLUMN

This paper presents experimental data and estimated distillation efficiencies of an industrial scale distillation column separating i-butane and n-butane. The data gathered from plant instruments and laboratory analysis were reconciled and compared to distillation simulations. The simulations were performed with a number of real plates using the point and the Murphree plate efficiency calculation model. This matrix model of efficiency at first estimates the point efficiencies using the two-film and multicomponent mass transfer theory. The point efficiencies are then converted into Murphree plate efficiencies using a liquid mixing model. The whole method is implemented in a computer program to simulate an industrial distillation column with real plates. Finally the calculated product compositions are compared with reconciled measurements. The values of overall, section, point and Murphree plate efficiencies of multicomponent i-butane/n-butane system are also calculated. The results show that point efficiencies are not adequate for large industrial scale columns. The results also imply that the plate efficiency calculation method can be utilized and employed in the design and simulation of industrial scale columns.     

板式精馏塔的塔板效率

塔板效率包括:点效率、莫夫里效率和全塔效率,它们的值主要受流体多相流动时的动力学体系特性的影响;点效率可由双膜理论推出,莫夫里效率和全塔效率存在一定的内在关系。     

Murphree and vaporization efficiencies in multicomponent distillation

A quantitative comparison between Murphree and vaporization efficiencies is presented based on ternary distillation data for the systems acetone/methanol/ethanol, acetone/benzene/chlorobenzene, benzene/toluene/mxylene and n-hexane/methylcyclopentane/benzene. The influence of experimental errors on calculated values of Murphree efficiencies is also analysed.It is shown that the vaporization efficiency model fails to describe the behaviour of distillation plates and it is suggested that Murphree's model gives a more useful representation of the behaviour of distillation columns.     

背包式反应器与精馏塔耦合合成醋酸甲酯的模拟

针对背包式反应器与精馏塔耦合过程循环流股多,模拟计算收敛难度大的缺点,在Aspen P lus的RadFrac模型中引入Murphree板效率,仅用一个精馏塔模型就描述了这个复杂耦合过程的模拟模型。在固定精馏塔塔板数的情况下,讨论了背包反应器个数和间隔位置、进料位置、回流比和催化剂量等因素对醋酸甲酯合成的影响。初步探索了反应能力和分离能力的匹配问题。模拟结果表明,当采用5个背包反应器,反应器之间间隔4块分离塔板的配置时,在适宜条件下醋酸总转化率可达到96.3%。     

人工免疫网络多Agent的分馏装置建模

分馏过程是石油化工流程模拟中的重要模块之一。在分馏装置的模拟计算中,塔板Murphree效率直接影响模型质量,且随装置的原料、工况不同而有所改变,因此探索Murphree效率的准确确定方案是分馏建模的关键。本文提出用人工免疫网络多Agent(Maopt-aiNet)确定最佳的Murphree效率。不同于其他智能算法,Maopt-aiNet结合人工免疫网络的核心思想与多Agent技术,搜索算子包括:邻域克隆选择、邻域竞争、自信度激励、自信度邻域学习和邻域协作算子,算法有机结合全局与局部搜索能力,实验表明其对高维系统搜索能力较强。在分馏装置建模应用中,用Maopt-aiNet确定的Murphree效率,能够使分馏塔的塔板温度分布及塔顶、塔釜主要产品的产出与实际吻合得较好,表明用Maopt-aiNet建立的分馏塔模型能较好地描述实际分馏塔的生产过程,可以用来指导分馏装置的操作优化。     

Efficiency of Distillation Columns Containing Packed Sieve Trays

Abstract

The Murphree efficiency of the fifth tray in a six-sieve tray distillation column, 7.8 cm in diameter and 85 cm high, was increased from 37.5 to 90% when three disks of a wire mesh pad, 9 cm high, were placed on the tray. An acetone-methanol test system was used in this investigation. The pressure drop across the tower corresponding to this packing increased by 33%. Nine disks of Raschig rings of similar height increased the tray efficiency to 75% and the pressure drop by 16%. A model was used for the azeotropic system, and the overall tower efficiency was found to increase by about 20% due to the presence of packing on a single tray.     

BEHAVIOR OF A MINUTE AMOUNT OF DIETHYL SULFIDE IN HYDROCARBON DISTILLATION

Vapor-liquid equilibria of 2,2,4-trimethylpentane(T)-hexane(H), T-cyclohexane(C) and T-methylcycIo-hexane(M) systems containing a minute amount of diethyl sulfide(D) were measured at atmospheric pressure. Continuous distillation experiments of the above systems were carried out in an Oldershaw type column. The Murphree vapor efficiencies of the major and the trace components were obtained.

In the T-H-D system, in which the trace component is a typical “intermediate volatility” component, the Murphree vapor efficiency of the trace component varies remarkably and exhibits an unreasonable value, in contrast to that in T-C-D and M-T-D systems.     

预测非理想多元混合物精馏点效率的新模型

提出一个新的计算非理想多元元精馏物系Murphree点效率的方法,在计算塔板上鼓泡液体中汽液两相间的传质通量时,充分考虑了在扩散路径上混合物组成的变化所产生的影响,同时根据多相湍流动力学的原理计算了鼓泡液体中汽、液相的接触面积．利用这个新模型对6个多元非理想混合物的计算,表明它能够准确地预测某些组元点效率的奇异性,而且预测的精度明显地优于现有其他方法,证明它是一个有效的、可靠的非理想多元精馏点效率预测方法.