Thermodynamic Analysis,Simulation and Optimization on Energy Savings of Ideal Internal Thermally Coupled Distillation Columns

Internal thermally coupled distillation columns (ITCDIC) are the frontier of distillation energy saving research. In this paper, a novel energy saving model of ideal ITCDIC and a simulation algorithm are presented,upon which a series of comparative studies on energy savings with conventional distillation columns are carried out. Furthermore, we present an optimization model of ideal ITCDIC, which can be used to achieve the maximum energy saving and find the optimal design parameters directly. The binary system of benzene-toluene is adopted for the illustrative example of simulation and optimization. The results show that the maximum energy saving of ITCDIC is 52.25% (compared with energy consumption of conventional distillation under the minimum reflux ratio operation); the optimal design parameters are obtained, where the rectifying section pressure and the feed thermal condition are Pr=0.3006 MPa and q=0.5107 respectively.

A Novel Thermally Coupled Reactive Distillation Column for the Hydrolysis of Methyl Acetate

A different pressure thermally coupled reactive distillation column(DPT-RD) for the hydrolysis of methyl acetate(Me Ac) is developed, and its design and optimization procedures are investigated. The sensitivity analysis is carried out to minimize the energy consumption, which is associated with the total annual cost(TAC). The influence of the proposed DPTRD scheme on energy consumption and economic efficiency are evaluated in comparison with the conventional reactive distillation column(CRD). Both the DPT-RD and CRD are simulated with the Aspen Plus?, and it can be observed that for the DPT-RD the energy consumption and the TAC are reduced, and the thermodynamic efficiency is increased as compared with the CRD process.

Simulation and Optimization for Thermally Coupled Distillation Using Artificial Neural Network and Genetic Algorithm

In this paper, a new approach using artificial neural network and genetic algorithm for the optimization of the thermally coupled distillation is presented. Mathematical model can be constructed with artificial neural network based on the simulation results with ASPEN PLUS. Modified genetic algorithm was used to optimize the model. With the proposed model and optimization arithmetic, mathematical model can be calculated, decision variables and target value can be reached automatically and quickly. A practical example is used to demonstrate the algorithm.

Design and Control of Thermally Coupled Reactive Distillation Sequence for Biodiesel Production

Decreasing petroleum reserves and growing alternative fuels requirements have promoted the study of biodiesel production. In this work, two thermally coupled reactive distillation designs for biodiesel production were investigated, and the sensitivity analysis was conducted to obtain the appropriate design values. The thermodynamic analysis and economics evaluation were performed to estimate the superiority of the thermally coupled designs over the base case. The proposed biodiesel production processes were simulated using the simulator Aspen Plus, and calculation results show that the exergy loss and economic cost in the two thermally coupled designs can be greatly reduced. It is found that the thermally coupled side-stripper reactive distillation design provides more economic benefits than the side-rectifier one. The dynamic performance of the thermally coupled side-stripper design was investigated and the results showed that the proposed control structure could effectively handle large feed disturbances.

Novel Control Structure Design of Differential Pressure Thermally Coupled Reactive Distillation for Methyl Acetate Hydrolysis

In this paper, the novel control structures of differential pressure thermally coupled reactive distillation process for methyl acetate hydrolysis were proposed. The RadFrac module of Aspen Plus was adopted in the steady-state simulation. Sensitive analysis was applied to find the stable intial value and provide a basis for the improved control structure design. The Aspen Dynamics software was adopted to study the process dynamic behaviors, and two novel control structures provided with feed ratio controllers and sensitive tray temperature controllers were proposed. The reflux ratio controllers were applied in the improved novel control structures. Both control structures abandoned the composition controllers that were replaced by simpler controllers with which the product purity could meet the specification requiring under a ± 20% disturbance to the total feed flowrate / MeAc composition.

Process intensification and energy saving of reactive distillation for production of ester compounds

Reactive distillation(RD) process is an innovative hybrid process combining reaction with distillation, which has recently come into sharp focus as a successful case of process intensification. Considered as the most representative case of process intensification, it has been applied for many productions, especially for production of ester compounds. However, such problems existing in the RD system for ester productions are still hard to solve,as the removal of the water which comes from the esterification, and the separation of the azeotropes of ester–alcohol(–water). Many methods have been studying on the process to solve the problems resulting in further intensification and energy saving. In this paper, azeotropic–reactive distillation or entrainer enhanced reactive distillation(ERD) process, reactive extractive distillation(RED) process, the method of co-production in RD process, pressure-swing reactive distillation(PSRD) process, reactive distillation–pervaporation coupled process(RD–PV), are introduced to solve the problems above, so the product(s) can be separated efficiently and the chemical equilibrium can be shifted. Dividing-wall column(DWC) structure and novel methods of loading catalyst are also introduced as the measures to intensify the process and save energy.

Novel design of lubricant-type vacuum distillation process for lube base oils production from hydrocracking tail oil

Dividing-wall columns(DWCs)are widely used in the separation of ternary mixtures,but rarely seen in the separation of petroleum fractions.This work develops two novel and energy-efficient designs of lubricant-type vacuum distillation process(LVDP)for the separation of hydroisomerization fractions(HIF)of a hydrocracking tail oil(HTO).First,the HTO hydroisomerization reaction is investigated in an experimental fixed-bed reactor to achieve the optimum liquid HIF by analyzing the impact of the operating conditions.A LVDP used for HIF separation is proposed and optimized.Subsequently,two thermal coupling intensified technologies,including side-stream(SC)and dividing-wall column(DWC),are combined with the LVDP to develop side-stream vacuum distillation process(SC-LVDP)and dividing-wall column vacuum distillation process(DWC-LVDP).The performance of LVDP,SC-LVDP,and DWC-LVDP are evaluated in terms of energy consumption,capital cost,total annual cost,product yields,and stripping steam consumption.The results demonstrates that the intensified processes,SC-LVDP and DWC-LVDP significantly decreases the energy consumption and capital cost compared with LVDP.DWC-LVDP further decreases in capital cost due to the removal of the side stripper and narrows the overlap between the third lube oils and fourth lube oils.This study attempts to combine DWC structure into the separation of petroleum fractions,and the proposed approach and the results presented provide an incentive for the industrial implementation of high-quality utilization of HTO through intensified LVDP.

歧化装置与芳烃装置二甲苯塔分离热耦合工艺

针对歧化装置和芳烃装置的C_(8)和C_(9)物料被重复冷凝与加热,以及设备数量多、投资大、占地多、开工程序复杂等缺点,中海石油宁波大榭石化有限公司将歧化装置的重芳烃塔与芳烃装置的二甲苯塔合并为1个新二甲苯塔,开发出满足C_(8)芳烃深度分离和C_(9)芳烃烷基转移的低成本分离热耦合精馏技术。结果表明:通过Petro-SIM软件模拟,该二甲苯塔分离热耦合工艺获得的C_(8)芳烃产品中甲苯质量分数小于0.98%,C≥9重芳烃质量分数小于2.51%,获得的C_(9)芳烃产品中C_(8)芳烃质量分数小于0.21%,C≥10重组分质量分数小于0.07%;与传统工艺相比,热耦合工艺装置建设投资约减少2700万元,节省占地6666.7 m^(2),减少二氧化碳排放9600 t/a。

低温设备故障工况下的热应力分析

低温精馏系统是通过冷源将原料气进行冷却液化,然后再利用原料气中各组分的沸点差不同,利用精馏的方法将各组分分离开来,以获得所需要的目标组分。本文针对所涉及的低温精馏系统,根据设备安装布置的特殊性,对在生产运行过程中可能因冷源失效或者停机这一现象,对低温精馏塔在结构上产生的热应力进行计算。针对可能出现的冷源故障,进行不同组合模式的模拟计算,获取该工况下最严重位置处的应力水平值,并进行评价,验证该结构的合理性,为可能出现的故障提供技术依据。

低温设备热应力模拟分析

低温精馏系统通过同位素组分富集,将目标组分从原料气中分离出来。低温精馏塔外部与大气环境接触,内部流体与塔体对流换热,因此整个换热过程引起的热量损失和热应力大小是验证结构设计合理性的关键。本文利用模拟软件,通过对连接冷凝器和塔节的真空过渡箱的热分析,获得连接箱处的温度梯度以及热量损耗,并进行温差应力和机械应力的耦合应力分析,评定连接箱的应力强度,确定强度设计的合理性。通过温度线性化处理和热损耗计算分析,提出较优化的改进措施,并对其进行热分析,评定热损耗,验证改进结构的合理性。

分子蒸馏技术在高沸点热敏性油脂分离中的应用进展

在蒸馏体系中,具有高沸点和热敏性特征的物质在分离过程中会因长时间所受高温而发生结构变化,如何解决这一问题是分离与纯化的难点。分子蒸馏作为一种特殊的高新分离技术,常用于对高沸点热敏性物质的分离。对分子蒸馏原理及特点进行介绍,并概述了分子蒸馏在不饱和脂肪酸、维生素E、长链脂肪烷醇和角鲨烯提取中的应用,探讨了其实际应用时的不足,对未来的发展方向进行展望,为后续分子蒸馏技术在实际生产过程中提供理论指导。

热旁路控制精馏塔冷凝系统设备布置要点分析

在精馏操作中,保持精馏塔压力稳定是确保产品组成的关键。热旁路控制是一种常用的精馏塔压力调节方式。以某烯烃装置中丙烯分离塔为例,详细阐述了热旁路控制精馏塔压力的原理、优点及关键点,并对塔顶冷凝系统的设备布置要点进行了重点分析。结果表明,冷凝系统的设备布置方式对于热旁路控制系统的性能至关重要。在平面布置中,应实现冷凝器工艺侧管线的对称布置,以防止偏流。在立面布置中,需要满足配管对空间的需求,并确保回流罐下方产品泵的有效汽蚀余量符合供货商要求。同时,冷凝器出口液体应具有足够的过冷度,以克服冷凝器和回流罐之间的高差及管道的阻力损失。

乙醇-环己烷-乙酸乙酯混合物的分离模拟

基于Aspen Plus对乙醇-环己烷-乙酸乙酯三元共沸体系进行了模拟分离,提出了五塔变压精馏分离工艺流程,对精馏塔的进料位置进行了优化并确定了最佳的工艺参数,同时对多个精馏塔进行了热耦合。最终结果表明乙醇、环己烷、乙酸乙酯的纯度均能达到99.90%,热耦合后节约蒸汽43.97%,节约冷却水45.53%。

隔壁塔技术进展

在简要介绍隔壁塔结构特点、节能原理、形式以及适用范围的基础上,着重阐述了隔壁塔的工业应用状况,并分析了国内外反应精馏隔壁塔、萃取精馏隔壁塔及共沸精馏隔壁塔研究的若干最新进展。

完全能量耦合精馏塔的设计、模拟与优化

本文针对完全能量耦合精馏塔,基于Fenske-Underwood-Gilliland方程建立了完整的简捷设计方法,得到了各塔的实际理论板数、适宜的进料和侧线液相采出位置以及各塔回流比等参数。并在此基础上通过严格模拟,对完全热耦合精馏塔的中间组分分配比β、气相分割比Rv和液相分割比Rl等参数进行了优化,得出了它们对再沸器热负荷的影响规律。

隔壁塔四塔模型的设计计算

在对分离三组分混合物的隔壁塔结构进行分析的基础上,为隔壁塔的设计建立简捷计算的四塔模型,以最佳中间组分分配比为基础,以汽相分配比和液相分配比为设计变量,对汽相、液相流量进行平衡,将其作为设计计算的模型约束条件,计算此时全塔的最小汽相流率;基于Underwood-Fenske-Gilliland-Kirkbride计算方法,确定塔的最小回流比、理论塔板数、实际塔板数以及进料和采出位置。以分离正己烷、正庚烷和正辛烷的混合物为例,对隔壁塔进行简捷计算,得到汽、液相分配比的初值;再进行严格计算,对汽、液相分配比进行优化分析,得到最优的设计参数。

热偶精馏技术与应用进展

热偶精馏比常规精馏流程节能30%,还可降低设备投资。其中的分隔壁精馏塔已有40座以上工业化。本文介绍了热偶精馏的各种流程、节能原理、适用范围。同时介绍了热偶精馏的设计方法及工业应用现状,并对分隔壁精馏塔的应用前景进行了展望。

甲苯氯化连串反应的RD和SRC过程分析与比较

侧反应器与精馏塔集成(SRC)是塔内耦合反应精馏(RD)的新拓展,同时适用于反应与精馏处于相同工况和不同工况两种情形。以甲苯氯化连串反应为研究对象,分别建立了RD和SRC过程的数学模型,在相同总塔板数和塔釜上升蒸气量条件下,计算了相同工况下(反应与精馏压力均为101.3kPa),RD与SRC过程的气/液流率、温度、组成分布,发现两者性能具有一致性。在此基础上,以产品氯化苄的生产成本为目标函数、标志系统产能的氯气进料流率和分配比例为优化变量,对甲苯氯化连串反应的相同工况RD与SRC过程、不同工况SRC过程(反应压力为101.3kPa、精馏压力为10kPa)进行优化,结果表明,相同压力工况下,优化得到的RD与SRC的装置产能与产品质量一致;但在不同压力工况下,SRC的产能明显提升、产品质量也有所提高,反映出不同工况SRC明显的优势。

差压热耦合蒸馏节能技术

开发了一种广泛适用于蒸馏分离过程的新型差压热耦合蒸馏技术,该技术将精馏塔分割为两个压力不同的塔,利用高压塔顶蒸汽作为低压塔底的热源,实现热能的耦合匹配,达到蒸馏过程大幅度节能的目的。利用计算机模拟方法对该技术应用在丙烯-丙烷分离和混合C4分离过程中的节能效果进行了计算和分析,结果表明与现有常规蒸馏过程相比,差压热耦合低能耗蒸馏过程能耗可以分别降低92.3%和87.1%,节能效果显著。

热耦蒸馏技术进展

热耦蒸馏作为一种新型蒸馏技术 ,与常规蒸馏相比 ,热耦蒸馏平均可节省能耗 30 %左右 ,同时还可降低设备投资。本文介绍热耦蒸馏塔的构造、分类、特点以及设计和应用。