气相中的稳态分子扩散 (28).pdf
DistillationPrinciples of Chemical Engineering-CDUT*1.What is distillation?Overview【Definition】It is one of the unit operation of seperating liquid components.【Example】(1)Crude oil is distilled to gasoline,kerosene,diesel and heavy oil；(2)BTX aromatics are distilled to benzene,toluene and xylene；(3)Liquid air is distilled to pure liquid oxygen and liquid nitrogen.Principles of Chemical Engineering-CDUT*Atmospheric Distillation of PetroleumOverviewPrinciples of Chemical Engineering-CDUT*2.Distillation Basis(1)Different volatility of each component in the liquidmixture；(2)In seperation equipment,heat energy can be used asthe medium in the separation equipment to partiallyvaporize the liquid mixture to form a vapor-liquid two-phase system;(3)To enrich light components in vapor phase and to enrichheavy components in liquid phase,thus to separate theliquid mixture.OverviewPrinciples of Chemical Engineering-CDUT3.Light Component&Heavy Component【Light Component】Components with low boiling point and highvolatility;【Heavy Component】Components with high boiling point and lowvolatility.【Example】EthanolWater System ethanol(boiling point:78.4)isa light component,water(boiling point:100)is a heavy component;BenzeneTolueneSystembenzene(bolingpoint:80.1)is a light component,toluene(boling point:110.8)is a heavycomponent.OverviewPrinciples of Chemical Engineering-CDUT*benzene+waterheatingliquid phase:ethanol enrichmentliquid phase:water enrichmentcondensationcoolingethanol productsewageBenzeneDistillation and Seperation of Water SystemOverviewPrinciples of Chemical Engineering-CDUT*OverviewPrinciples of Chemical Engineering-CDUTSimple Distillation and Equilibrium Distillation【Characteristic】The process of single-stage distillation；【Usage】The volatility of each component in the mixture varies greatly;The system without high separation requirement.*4.Classification of Distillation(1)According to Principles of DistillationOverviewPrinciples of Chemical Engineering-CDUT*【Characteristic】Multi-stage distillation process；【Usage】It is used in difficult separation systems(withlow relative volatility)or high separation requirements;RectificationSpecial Rectification【Charactertisic】Rectificationwithspecialmethods(such as:extractive distillation,constant boilingrectification);【Usage】Special distillation is applicable to somesystems that are difficult or impossible to be separated byOverviewPrinciples of Chemical Engineering-CDUT*(2)According to the ways of distillation【Characteristics】B a t c hd i s t i l l a t i o nhas someadvantageslikeflexibleoperation,strong adaptation,which is mainly used in small-scale,multi-variety,or someoccasions with specialrequirements.The process is inan unsteady state.【Batch Distillation】It is an operation in which the liquid of raw material is added to the separation equipment at one time and it will not be added again during the whole process.OverviewPrinciples of Chemical Engineering-CDUT*【Continuous Distillation】Adding raw material liquid continuously into the separation equipment to obtain a variety of products constantly.【Characteristics】Continuous distillation hasthe advantages of large production capacity,stable product quality and convenientoperation,which is mainly used in therequirements for large scale of productionand high quality of products,continuousdistillation is a steady-state operation.OverviewPrinciples of Chemical Engineering-CDUT*(3)According to the number of components in the separation system【Two-component Distillation】There are two components in aseperated liquid mixture.【Multi-component Distillation】There are three or morecomponents in a seperated liquid mixtureOverviewPrinciples of Chemical Engineering-CDUT*【Instruction】In the industrial production,the majority ofdistillations is multi-component distillation,but the principle andcalculation of two-component distillation is also applicable tomulti-component distillation,it is more complicated to deal withthe process of multi-component distillation.Therefore,the relatedproblems will be discussed on the basis of two-componentdistillation later in this course.OverviewPrinciples of Chemical Engineering-CDUT*(4)According to operating pressure【Atmospheric Distillation】It is suitable for liquid mixtures with abubble point from room temperature to 150 at atmospheric pressure,and the operating pressure is(about 1atm)when distillation.【Pressurized Distillation】It is suitable for mixtures with gaseous state(such as air,petroleum gas)or with a bubble point of room temperatureat atmospheric pressure,the operating pressure is(higher than 1atm)when distillation.【Vacuum Distillation】It is suitable for thermosensitive mixtures withhigh bubble point at atmospheric pressure,or easy to decompose andpolymerize at high temperature,the operating pressure is(less than1atm)when distillation.OverviewPrinciples of Chemical Engineering-CDUT*【Brief Introduction of CrudeOil Distillation Process】Schematic Diagram of Atmospheric and Vacuum Distillation Process of Crude OilThe pressure at the top ofthe tower is about 130170kPaThe pressure at the topof the tower is about 15kPaOverviewPrinciples of Chemical Engineering-CDUT*2.5 Million Tons ofAtmospheric and Vacuum Unit Used in Petroleum RefiningAtmospheric towerVacuum towerOverview
