芳烃抽提装置芳烃分离模拟及设计优化

采用PRO/Ⅱ流程模拟软件对某新建项目40万t/a芳烃抽提装置，混合芳烃中苯、甲苯、二甲苯（BTX）分离进行常规双塔精馏和双塔差压热耦合精馏进行稳态模拟，在产品质量规定要求下，分别对苯塔和甲苯塔进行设计优化，对比不同分离方案用能要求及能耗，旨在工厂公用工程条件限制下，选择最合适的分离工艺，提高低温热利用效率，达到最佳节能降耗的效果。     

苯-甲苯分离节能新工艺

针对现苯-甲苯塔热集成工艺的不足,提出了苯-甲苯分离的双效热集成节能新工艺。采用化工模拟软件Aspen one V7.2,选取Peng-Robinson热力学模型,分别对苯-甲苯分离的传统精馏流程、苯-甲苯塔热集成精馏流程及苯-甲苯塔双效热集成精馏流程进行了模拟计算和分析。结果表明,在产品质量和收率相同的条件下,采用双效热集成精馏新工艺和现工业装置苯-甲苯热集成精馏工艺相比,其总加热量降低了13.4 MW,节能率40.22%,节能效果显著;所增加的甲苯塔第一效精馏塔操作真空度不高,塔顶蒸汽可采用空冷器冷却,其余设备和现有苯-甲苯塔热集成精馏工艺相同,装置改造投资少,容易推广实施。     

基于Aspen Plus的二甲苯塔优化及应用

二甲苯塔在芳烃联合装置中作为关键设备,是能源消耗较高的分离塔器。中国石化海南炼化公司二甲苯塔含有对二甲苯、间二甲苯、邻二甲苯等同分异构体,组分之间沸点值相近,产品纯度要求非常严格,意味着精馏分离需要高热量与高回流比操作。为降低能耗,本文利用芳烃生产数据建立了Aspen Plus二甲苯塔模型,经对比计算值与实际值验证了可行性,其准确性能够应用于实际生产。通过利用模型中的约束与优化及灵敏度分析,在保证二甲苯塔顶底控制指标的前提下,研究了回流比与塔压操作参数的变化对塔底热负荷与分离效果的影响,然后选择最优参数,提供运行优化方向,结果表明,降低回流比操作来降低塔底热负荷,可以达到节能降耗的目的。     

分壁精馏塔分离苯/甲苯/二甲苯的模拟工艺研究

分壁精馏塔（简称分壁塔）在节能和节约投资方面都有很大的优势和潜力,因此近几年来人们对它的深入研究也越来越多。以等比例的苯、甲苯和二甲苯为原料,通过模拟工艺流程,研究分析了分壁塔的进料位置、隔板位置、回流比、侧线采出位置以及液汽相分流比与能耗、组分纯度的关系。研究结论显示,分壁塔的最适宜液相分流比和汽相分流比分别为0.65和0.45,与常规精馏塔相比,分壁塔分离所得的苯、甲苯和二甲苯的纯度高,冷凝负荷和热负荷分别比常规精馏塔降低31.066 9%和34.167 5%。     

轻苯精制工艺的几点改进

莱钢焦化厂苯精制装置于１９９１年投产，年加工轻苯１万t，采用连续吹苯后半连续精馏工艺。２００１年实施了吹苯塔和纯苯塔气相串联新工艺，并对操作和部分设备进行了改进。通过改进，不但降低了生产成本，而且使多年在８５％左右的三苯收率，提高到８９％以上，取得了显著的经济效益。１改进措施（１）分离甲苯、二甲苯的精制塔是半连续间歇釜式精馏塔，在每次分离完甲苯、二甲苯后需向塔内通直接蒸汽４～６h，清扫塔体、塔盘，去除残余成分，为下一次生产做好准备。由于频繁地通蒸汽清扫塔，造成精制塔内壁、塔盘、浮阀等腐蚀严重，个别…     

隔板塔特性模拟研究

文章以三元系统苯-甲苯-二甲苯的三组分分离体系为例,分析对比了常规蒸馏塔和隔板塔的系统特性、分离效果、过程耗能,并对模拟结果进行能耗以及经济效益分析,结果表明,隔板塔的节能百分率可达67%。并由以上的分析结果创新地选择隔板塔的控制结构和控制方法。为隔板塔设计和工业操作提供参考依据。     

乙苯回收塔、苯/甲苯塔操作对乙苯脱氢反应的影响

分析了乙苯脱氢反应苯乙烯收率低的原因,提出了乙苯回收塔塔底的循环乙苯中甲苯含量高会影响脱氢反应苯乙烯收率,苯/甲苯塔顶回收苯中的甲苯含量高会增加乙苯产品中二甲苯的含量,进而影响苯乙烯的收率。通过优化操作条件,可降低循环乙苯中的甲苯含量,稳定回收苯中甲苯含量,脱氢反应中苯乙烯的收率提高了0.13%,年可增加苯乙烯产量198t,增收158万元人民币。     

芳烃抽提工艺流程的模拟与优化

采用SIMSCI公司开发的流程模拟软件PRO/Ⅱ对实际生产中预分离塔、抽提精馏塔、溶剂回收塔、苯塔、甲苯、二甲苯塔进行逐塔模拟并优化,进而对全流程进行模拟,给出了模拟结果,最终获得最佳的工艺操作参数,所得产品符合国家质量要求。     

隔壁塔流程模拟及节能效益的研究

隔壁塔技术是一种效果优良的过程强化与精馏节能技术。具有特殊结构的隔壁塔相比常规精馏塔具有较高的热力学效率。对于相同的分离任务,隔壁塔所需的能耗较低,同时隔壁塔技术的应用也降低了设备数量和投资。文中通过对隔壁塔内部结构的讨论和热力学有效能转化的分析,阐释了隔壁塔的节能原理;并以粗苯精制流程中甲苯-二甲苯-重苯的分离为例,在三组元精馏流程的分析之上设计了2套精馏流程方案,对其进行了严格计算和优化,相比于传统的顺序分离双塔流程,隔壁塔可节省能耗41.5%,同时减少了设备的数目和投资。     

内部热耦合空分塔的节能优化分析

内部热耦合精馏是迄今为止所提出的节能效果最好,而唯一没有商业化的节能技术。将内部热耦合技术用于空分塔,可以带来良好的节能效果。根据低温空气分离过程以及三组分精馏的特点,提出了一种新的内部热耦合空分精馏塔优化模型。在优化模型基础上,对热耦合塔进行了深入的节能优化与分析,并且与常规空分仿真结果进行了比较分析,压缩机能耗下降20.75%,产值增加17.46%,单位产值能耗下降32.53%。内部热耦合空分塔的提取率以及能耗均优于常规热耦合空分塔,节能效果显著。     

外部热耦合复合精馏塔的经济性与可控性评价

外部热耦合复合精馏塔系统是一种新型的精馏塔系统,通过操作在不同压力下的两个精馏塔的精馏段和提馏段之间的热传递来提高热力学效率。根据精馏段和提馏段热耦合的相对位置不同,外部热耦合复合精馏塔系统可分为对称型和非对称型两种结构。为便于设计和实现,可用外部换热器替代外部热耦合得到简化的结构。本文以乙烯乙烷物系分离过程为对象,通过对外部热耦合复合精馏塔系统建立了静动态模型,采用四点控制的方法,对三种结构的外部热耦合复合精馏塔的经济性和可控性两方面做了分析,证明了非对称型优于对称型外部热耦合复合精馏塔。同时,对使用外部换热器简化外部热耦合结构的方法提供了理论依据和参考。     

Internally heat-integrated distillation system for quaternary separation

A new internally heat-integrated distillation column for quaternary separation modified from a conventional three-column system is proposed, and its performance is examined here. Two sets of heat integration between the rectifying section and the stripping section of two adjacent columns are placed in the conventional three-column system. The proposed system has been applied two example processes, the hexane and BTX processes, for the performance evaluation of energy saving and reduction of entropy production. In the hexane process, the duty reductions in reboilers and condensers are 28.5% and 30.5%, respectively, and the entropy production is reduced by 12.2% compared with the conventional system. In the BTX process, the duty reductions are 27.8% and 31.6%, respectively, and the entropy production is decreased 9.8%. The compressor utilized in the existing internally heat-integrated distillation column is not used in the proposed system leaving no difficulty of its operation and maintenance. Also, the structural similarity of the new system to the conventional system gives the column operation as easy as the conventional system.     

Optimal design of cryogenic distillation columns with side heat pumps for the propylene/propane separation

Propylene is one of the most important products in the petrochemical industry, which is used as raw material for a wide variety of products. The propylene/propane separation is a very energy-intensive process because their boiling points are quite similar. In addition, at atmospheric conditions, their boiling points are −47.6 °C and −42.1 °C, respectively. To separate this mixture conventional columns which operate at high pressure and cryogenic distillation columns which operate at low pressure have been used, however, this approaches are still energy-intensive. This work presents energy-efficient and intensified distillation columns which are adiabatic such as the vapor recompression column (VRC) or diabatic such as columns with heat-integrated stages. A design and optimization procedure, which minimizes the energy consumption in the propylene/propane separation is presented. Conceptual design, superstructure representation, rigorous simulations and mathematical programming techniques are effectively combined to assess all the candidate distillation structures, refrigeration cycles, and heat integration possibilities simultaneously. Results showed that VRC and diabatic distillation columns with heat-integrated stages can reduce the energy consumption between 58 and 75% when compared with conventional distillation at high pressure. Furthermore, the proposed synthesis procedure derived simplified optimal distillation structures with few heat-integrated stages and still attained important energy savings.     

Energy saving and thermodynamic efficiency of a double-effect distillation column using internal heat integration

The existing internally heat-integrated distillation column with the problem of utilizing a compressor is modified to propose a new heat-integrated distillation column without the compressor. Two identical columns of a conventional binary distillation are implemented to the heat integration. The energy used in the reboiler is recovered by the internal heat integration between the stripping section of one of the columns at lower pressure and the rectifying section of the other higher pressure column. The heat integration is similar to double-effect distillation, but internal heat integration requires less pressure elevation. The performance of energy saving and thermal efficiency improvement of the proposed system is evaluated with the two examples of the benzene-toluene and methanol-ethanol processes. The performance comparison indicates that the proposed system requires 17.4% less of reboiler duty for the benzene-toluene process and 15.8% less of heating duty for the methanol-ethanol process. The thermal efficiencies are 16.3% and 23.8% for the benzene-toluene and methanol-ethanol processes, respectively. Elimination of the compressor makes the column operation easy and the separate reboilers and condensers for the two columns in the proposed system provide flexible control, when the controllability of the proposed system is compared with that of the existing internally heat-integrated distillation column.     

醋酸甲酯和甲醇热集成变压精馏分离工艺模拟与优化

基于对醋酸甲酯与甲醇二元共沸特性的分析,提出热集成变压精馏分离醋酸甲酯和甲醇的工艺. 利用Aspen Plus软件对该分离过程进行模拟,以NRTL活度系数方程为物性计算方法,其二元相互作用参数由气液相平衡数据回归,分析了加压塔和常压塔的理论板数、进料位置及回流比对分离效果的影响,并进行了能耗比较. 结果表明,该工艺能很好地分离醋酸甲酯和甲醇,较佳的工艺条件为：加压塔操作压力909 kPa,理论板数32,第21块板进料,回流比4.2,塔釜醋酸甲酯纯度99.8%;常压塔操作压力101 kPa,理论板数30,第20块板进料,回流比4.6,塔釜甲醇纯度99.0%. 与常规变压精馏相比,热集成变压精馏可节能达45.8%;与以水为萃取剂的萃取精馏分离工艺相比,热集成变压精馏分离工艺更适合醋酸甲酯与甲醇体系的分离.     

热耦合精馏工艺的模拟

为了进一步了解热耦合精馏工艺的适用范围,同时寻找其中经济性较优的工艺流程,本文利用Aspen Plus流程模拟软件,针对相对挥发度依次递增的四组二元物系(苯-氟苯、苯-正庚烷、苯-甲苯、苯-氯苯)分别开展了常规精馏和4种热耦合精馏工艺(热泵精馏塔、理想内部热耦合精馏塔、内部热耦合精馏塔简化构型、差压热耦合精馏塔)的模拟研究,过程优化的目标函数为年均总费用最低。通过优化结果的对比可知,热耦合精馏工艺在分离相对挥发度较小的物系时能耗相对较低,经济性相对较好,其中又以热泵精馏塔和差压热耦合精馏塔的效果最为显著;而在相对挥发度较大的物系分离中,常规精馏则是较为合适的工艺选择。此外,随着投资回收期的减小,热耦合精馏工艺相对于常规精馏工艺的优势也有所下降。     

带有中间热集成的精馏塔序列及其性能

提出一种带有中间热集成的精馏塔序列(IHISDC)的流程,针对三组元混合物分离的简单塔直接序列,对该流程进行了分析。与传统热集成精馏序列(HISDC)相比,提出的IHISDC通过中间换热器将高压塔的精馏段与低压塔的提馏段进行局部热集成,使能量集成精馏塔之间的压力差更小,进而使能耗费用下降。同时发现,IHISDC中的高压塔再沸器热负荷和低压塔冷凝器热负荷增加,由于换热器数量的增加,IHISDC的投资费用较大。为了进一步降低IHISDC的年度总费用,需要对其设计参数进行优化。     

简化外部热耦合双精馏塔的控制与优化

针对具有3个换热器结构的外部热耦合双精馏塔(S-EHIDDiC),提出了一种新型的控制与优化策略。顶部与底部换热器的热负荷能够改变高压精馏塔的回流量和低压精馏塔的上升汽量,因而可以用来控制高压精馏塔塔顶和低压精馏塔塔底的产品质量。这种控制方法与常规精馏塔的LV控制结构相似。S-EHIDDiC还有多余的决策变量(如进料分流比,高压精馏塔塔压和中间换热器的热负荷),可以对稳态操作进行优化。闭环仿真证明了这种控制结构的可行性,稳态优化也提高了系统的热力学效率。     

Comparing three configurations of the externally heat-integrated double distillation columns (EHIDDiCs)

In terms of separation of a binary mixture of ethylene and ethane, three configurations of externally heat-integrated double distillation columns (EHIDDiCs), including a symmetrical EHIDDiC (S-EHIDDiC), an asymmetrical EHIDDiC (A-EHIDDiC), and a simplified asymmetrical EHIDDiC (SA-EHIDDiC), are compared with respect to aspects related to process design and controllability. It has been found that the A-EHIDDiC and SA-EHIDDiC are superior to the S-EHIDDiC in terms of thermodynamic efficiency as well as in terms of process dynamics and controllability. As for the comparison between the A-EHIDDiC and SA-EHIDDiC, the latter shows somewhat comparable behaviors with the former in terms of process design and controllability. These results demonstrate that the asymmetrical configuration should generally be favored over the symmetrical one for the development of the EHIDDiC. It is feasible to approximate external heat integration using three heat exchangers between the high- and low-pressure distillation columns involved.     

一种外部热耦合反应蒸馏系统的模拟研究

根据常规反应蒸馏塔的热力学特性提出并研究了一种外部热耦合反应蒸馏系统（EHIRDS）。EHIRDS由一个高压的反应塔和一个低压的分离塔组成,且前者的精馏段与后者的提馏段进行热交换。引入四元理想放热反应体系A + B ? C + D,并以年总费用（TAC）最小为目标函数,对EHIRDS进行了研究,发现EHIRDS能够降低操作费用。采用三个换热器简化EHIRDS的设计（即S-EHIRDS）还可以进一步降低设备投资和操作费用。这些仿真结果初步确认了EHIRDS相比于常规设计具有更高的优越性。