内压缩流程空分的换热与精馏研究

分析和讨论了内压缩空分设备的氧氮两组分、氧氮氩三组分及氧氩两组分和氮氩两组分的相平衡,精馏部分的上塔、下塔、粗氩塔、精氩塔的精馏以及高压主换热器、低压主换热器、过冷器及主冷凝蒸发器等换热设备。希望能促进空气分离设备在理论方面的发展。     

空分精馏系统最佳氩馏分位置的确定

指出在同时生产高纯度的氢、氮及粗氩产品，并带粗氩塔的空气分离双级精馏系统中，双级精馏塔的上塔存在最佳抽氩馏分位置，并介绍其确定方法。     

Argon production from air distillation: Use of a heat pump in a ternary distillation with a side rectifier

A ternary feed mixture ABC can be separated into individual components through the use of a main distillation column with a thermally linked side rectifier. To enhance such a separation, a heat pump can be implemented to transfer heat from the condenser at the top of the side rectifier to the reboiler at the bottom of the main column. In this paper, one such heat pump is described and applied to an air distillation system separating the ternary mixture containing nitrogen, oxygen and argon. The separation is performed by a conventional double column with a crude argon side column. When this system is operated at an elevated pressure to obtain higher product pressures, the separation of oxygen and argon becomes very difficult and leads to reduced argon recovery. The proposed heat pump enhances the separation by providing a supplementary crude argon condensing duty through the vaporization of a liquid oxygen stream from the bottom of the low pressure (LP) column. This scheme improves the liquid/vapour ratio (L/V) in the bottom section of the LP column and, more importantly, increases the vapour feed to the crude argon column. This increased feed rate leads to a substantial increase in argon recovery for the elevated pressure air distillation process.     

Production of argon free oxygen by adsorptive air separation on Ag‐ETS‐10

The purification of different components of air, such as oxygen, nitrogen, and argon, is an important industrial process. Pressure swing adsorption (PSA) is surpassing the traditional cryogenic distillation for many air separation applications, because of its lower energy consumption. Unfortunately, the oxygen product purity in an industrial PSA process is typically limited to 95% due to the presence of argon which always shows the same adsorption equilibrium properties as oxygen on most molecular sieves. Recent work investigating the adsorption of nitrogen, oxygen and argon on the surface of silver‐exchanged Engelhard Titanosilicate‐10 (ETS‐10), indicates that this molecular sieve is promising as an adsorbent capable of producing high‐purity oxygen. High‐purity oxygen (99.7+%) was generated using a bed of Ag‐ETS‐10 granules to separate air (78% N₂, 21% O₂, 1% Ar) at 25°C and 100 kPa, with an O₂ recovery rate greater than 30%. © 2012 American Institute of Chemical Engineers AIChE J, 59: 982–987, 2013     

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.     

Profit maximization of the normal hexane recovery process through a thermal integration method

We developed a separation process that can minimize utility consumption in order to obtain normal hexane from crude raffinates for electronic-grade reagents. For the separation of normal hexane from the crude raffinate mixtures, a two-column configuration was selected. The first distillation column removes lighter constituents than normal hexane as a column top product, after which heavier constituents containing normal hexane are put into the middle of the second distillation column. This allows normal hexane with a purity of 95.5 wt% to be obtained from the top of the second distillation column by removing the constituents that are heavier than normal hexane as a second column bottom product. When both distillation columns are operated at approximately atmospheric pressure, it requires about 5.2 tons of steam per hour both for the reboiling heating source. However, when the operating pressure of the second distillation column is increased, the vapor stream coming out of the top of the second distillation column can be used as a heating medium for the reboiling source of the first distillation column. In this way, steam of only 3.1 tons per hour is required, potentially reducing the amount of steam used to 59.6% of the original amount.     

Modeling,Characteristic Analysis and Optimization of an Improved Heat‐Integrated Air Separation Column

Cryogenic air separation as the most important part of an integrated gasification combined cycle is a widely used operation unit for producing large quantities of high‐purity oxygen and nitrogen. However, cryogenic distillation requires a large amount of energy due to the work needed to compress the air feed. An improved heat‐integrated air separation column (HIASC) is proposed. The requirements of high‐purity separation in the industrial cryogenic air separation process are achieved. An optimization model of the heat transfer coefficient (UA), a key parameter in column structure design and operation, is presented. The optimized UA value is obtained within the accepted value range reported in the international open literature, which ensures the practicability of the improved HIASC.     

Improving the load flexibility of industrial air separation units using a pressure-driven digital twin

Air separation units are one of the prime examples for studies on demand side management and (non-)linear model predictive control due to their high power consumption and energy storage potential. These plants separate ambient air into its main components, nitrogen, oxygen, and argon, by means of cryogenic distillation at different pressure levels. Approximately two thirds of the industrially operated air separation units consider the separation of argon either as a value product or for reasons of energy efficiency. However, most of the studies in literature neglect the separation of argon since this requires additional equipment, increases the heat and process integration and, thus, the complexity of process control. In this work, a digital twin of an air separation unit with argon system is used to analyze and to improve load change procedures. Moreover, the potential of applying the digital twin as a soft sensor is demonstrated.     

Membrane/cryogenic hybrid scheme for argon production from air

A novel membrane/cryogenic hybrid scheme is presented wherein crude argon from a cryogenic air separation unit is fed to an oxygen selective membrane unit to remove a substantial portion of the oxygen. The oxygen enriched permeate from the membrane unit is returned to the crude argon distillation column of the cryogenic air separation process. The non-permeate stream is enriched in argon and can be further purified in a catalytic unit to produce an oxygen-free argon stream. The proposed process makes use of the synergy between the two separation units whereby, the cryogenic unit offers high recovery and the membrane provides purification leading to improved argon recoveries at higher argon concentrations. Calculations show that this process, in conjunction with an oxygen removal catalytic process, provides an economical alternative for the production of pure argon as compared to the conventional process using just a cryogenic unit and a catalytic unit to remove oxygen.     

Separation process of butanol-butyl acetate-methyl isobutyl ketone system by the analysis to residual curve and the double effect pressure-swing distillation

The separation of ternary mixture of butanol,butyl acetate,and methyl isobutyl ketone (MIBK) was initially analyzed by the residual curve.In this process,MIBK was chosen as the azeotropic agent during the first step of separation.The optimum mass ratio of extra MIBK was 1.6 in the modified feed stream according to the residual curve.Thus on this condition the top product was butanol-MIBK azeotrope while the bottom product was butyl acetate in the preliminary separation of the mixture.Then the butanol and MIBK azeotrope was separated by the double effect pressureswing distillation with the low pressure column performing at 30 kPa and the atmosphetic pressure column at 101 kPa.The optimal operating conditions were then obtained by using Aspen Plus to simulate and optimize the process.The results showed that the mass purities of butanol,butyl acetate,and MIBK were all more than 99％ and reached the design requirements.Additionally,compared with the traditional distillation with outside heating,the double effect pressure swing distillation saved the reboiler duty by 48.6％ and the condenser duty by 44.6％.     

二次萃取蒸馏法从烟草中提取天然烟碱

烟草中的烟碱用石灰水浸提。在ｐＨ＝１１的条件下,经三氯乙烯二次萃取,常压蒸馏获得烟碱粗品。再在压力为４０～６５ｋＰａ,温度为１６０～１７０℃条件下,减压蒸馏获得天然烟碱,产品含量可达９８％以上,收率达６８７％。     

Production of medium pressure nitrogen by cryogenic air separation

This paper concentrates on cryogenic process cycles for producing medium pressure nitrogen (pressure over 5.5 bar (abs.)) at relatively high purity (oxygen concentration under 5 ppm). The major inefficiencies of the conventional waste-expander cycle in a single distillation column were identified as a starting point. These were removed by synthesizing a series of novel cryogenic nitrogen generators in which the expander bypass flow was reduced and converted to a recycle flow to the distillation column. The novel generators retain the convenient and efficient features of the conventional waste-expander cycle while achieving applicability over a much wider range of production rates and product pressures.     

Simulation of hydrodynamic behaviour and mass transfer efficiency of reduced pressure distillation

A random packing hydrodynamic simulator is designed specially to carry out experiments under reduced pressures with a counter-current flow air/water system. The simulator results (air/water system) compared to those obtained in a real packed distillation column (benzylchloride/ ethylbenzene system) show a good agreement between hydrodynamic parameters like pressure drop, flooding flow rate, and total liquid hold-up. Empirical relationships derived from the simulator experimental results are proposed allowing the calculation of the pressure drop in a packed distillation column, operating in the pressure range between 10 kPa and atmospheric pressure. The influence of reduced pressure on the HETP in the distillation column and interfacial area in the simulator was also investigated.     

减压精馏分离常压塔釜余液中的环氧环己烷

实验采用减压精馏法提取常压精馏塔釜余液中的环氧环己烷,考察了塔顶压强、全回流时间和回流比对环氧环己烷纯度及收率的影响,优化得到较佳精馏操作条件:塔顶压强3.6 kPa,全回流时间150 min,回流比为5,在较佳操作条件下,环氧环己烷纯度为99.2%,收率达80%以上,为工业化分离提纯环氧环己烷提供了实验依据.     

Preparation of high purity methylal by extractive distillation using N,N-dimethylformamide (DMF) as solvent

通过溶剂选择原理粗选出萃取精馏制备甲缩醛产品的溶剂,既而通过Chemcad软件模拟和汽液平衡实验确定合适的溶剂及溶剂比。结果表明,N,N-二甲基甲酰胺（DMF）能够消除甲缩醛-甲醇共沸物系的共沸点;采用UNIQUAC模型对常压下甲缩醛-甲醇物系和加入溶剂N,N-二甲基甲酰胺的汽液平衡进行模拟,模拟结果和实验数据吻合较好。用间歇萃取精馏实验对甲缩醛粗品进行了分离,在实验条件下,可以从塔顶得到质量浓度为99.9%的高纯度甲缩醛产品。     

热泵精馏在三氯氢硅提纯过程中的模拟

运用化工模拟软件Aspen Plus,选用NRTL-RK物性模型和RADFRAC精馏模型,对三氯氢硅精馏塔的两种热泵流程进行了模拟计算,分别是塔顶气体直接压缩式和塔釜液体闪蒸再沸式热泵精馏。对比热泵精馏流程和常规精馏流程,结果表明：对三氯氢硅提纯而言,塔釜液体闪蒸再沸式热泵流程更有利。本研究采用双塔串行流程提纯三氯氢硅,运用塔釜液体闪蒸再沸式热泵精馏技术,优化后的主要操作参数为：T1塔回流比20,节流阀压力180 kPa,压缩机出口压力309 kPa;T2塔回流比5,节流阀压力227 kPa,压缩机出口压力310 kPa。优化后三氯氢硅的一次收率为88.75%,纯度超过99.9999%;在处理量相同情况下,与常规精馏相比,能耗费用节约82%。     

C5馏分萃取精馏模拟研究

以异戊二烯为目标产物,采用Aspen plus模拟软件对C5的萃取精馏过程进行模拟与优化。以乙腈为萃取剂,重点研究了萃取塔进料位置、理论板数、回流比以及剂料比对产品收率及纯度的影响。优化二次萃取工艺为一次萃取工艺,得到聚合级异戊二烯。萃取塔的适宜操作条件为：压力200 kPa,理论塔板数60块,进料位置为第25块塔板,回流比4,剂料质量比5.0。该操作条件下,异戊二烯收率及纯度分别为99.48%、99.70%。     

变压精馏分离甲醇-丙酮的工艺模拟及优化

采用Aspen Plus软件,以塔釜能耗为目标,以甲醇、丙酮纯度为约束函数,对双效变压精馏分离甲醇-丙酮工艺过程进行模拟。分析了操作压力、理论板数、回流比、进料位置和进料温度等参数对精馏过程的影响。确定了最优工艺参数：减压塔操作压力40 kPa,理论板数37,回流比2.4,进料塔板数26,进料温度25 ℃;常压塔理论板数30,回流比4.2,进料塔板数23。减压塔所得甲醇质量分数为99.0%,常压塔所得丙酮质量分数为99.7%。对比变压精馏和萃取精馏过程,变压精馏更容易得到高纯度丙酮产品,节能约13.4%。模拟结果对工业设计和设备改造具有一定指导意义。     

甲基氯硅烷精馏流程的模拟与优化

采用Aspen plus软件对工业七塔精馏过程进行全流程建模与模拟,优化工艺参数,研究了新的精馏节能工艺。对一甲塔等7个精馏塔采用双因素水平的灵敏度分析,考察了塔釜采出率、回流比、进料位置和塔顶压力对产品浓度和热负荷的影响,确定一甲塔最优的工艺参数：塔釜摩尔采出率为0.92,摩尔回流比为130,塔顶压力为0.18 MPa,总理论板数为400,在210块理论板位置进料。在此基础上,针对高能耗的脱高塔/脱低塔,模拟研究了双效精馏新工艺,新工艺可节省39.70%的年总成本;针对一甲塔模拟研究了热泵精馏新工艺,新工艺可降低41.42%的年总成本。     

分子蒸馏法从异氰酸酯热解液中分离多亚甲基多苯基多异氰酸酯

采用分子蒸馏技术从异氰酸酯热解液中分离多亚甲基多苯基多异氰酸酯(PMPPI),通过设计L25(56)正交实验对PMPPI-氯苯的模拟热解液进行分离,得到最佳工艺条件为：进料速度2 mL/min、蒸馏温度100℃、转子速度120 r/min、蒸馏压强4.0 kPa,该条件下PMPPI的分离纯度高达99.65%. 使用上述最佳分离条件对多亚甲基多氨基甲酸甲酯(PMDC)热解分离PMPPI的真实热解液进行分离,分离高效液相色谱检测不到氯苯,证明分子蒸馏可从异氰酸酯热解液中高效分离PMPPI.