《化学工程设计技术》课程教学资源（参考资料，英文版）4 Introduction to Separation Operations

SEPARATION OPERATIONS INTRODUCTION o What are separation operations? o Typical applications of separation operations o Physical basis for separation operations Basic types of separation operations o Performance characterization of separation operations Choice of separation operations 94/99 Separation Operations: Introduction

9/4/99 Separation Operations: Introduction 1 SEPARATION OPERATIONS: INTRODUCTION u What are separation operations? u Typical applications of separation operations u Physical basis for separation operations u Basic types of separation operations u Performance characterization of separation operations u Choice of separation operations

WHAT ARE SEPARATION OPERATIONS A Separation Operation Separates a multicomponent input stream into two or more output streams whose compositions differ from that of the input stream OR Separates a mulitphase stream into its constituent substreams 94/99 Separation Operations: Introduction

9/4/99 Separation Operations: Introduction 2 WHAT ARE SEPARATION OPERATIONS? A Separation Operation u Separates a multicomponent input stream into two or more output streams whose compositions differ from that of the input stream, OR uSeparates a mulitphase stream into its constituent substreams

TYPICAL APPLICATIONS o Separation of a multicomponent stream E Distillation E Gas Absorption and stripping E Liquid-Liquid extraction E Fractional Crystalization E Dialysis E Pressure-Swing Adsorption (PSa) o Separation of a multiphase stream E Filtration(solid-liquid) E Decantation(liquid-liquid E Electrostatic Precipitation(gas-solid E Knock-Out Drum(gas-liquid 94/99 Separation Operations: Introduction

9/4/99 Separation Operations: Introduction 3 TYPICAL APPLICATIONS u Separation of a multicomponent stream ð Distillation ð Gas Absorption and Stripping ð Liquid-Liquid Extraction ð Fractional Crystalization ð Dialysis ð Pressure-Swing Adsorption (PSA) u Separation of a multiphase stream ð Filtration (solid-liquid) ð Decantation (liquid-liquid) ð Electrostatic Precipitation (gas-solid) ð Knock-Out Drum (gas-liquid)

PROCESS EXAMPLE: ETHYLENE OXIDE PFD Steam BFW EO to Recycle Purification Compressor Condenser Re Drum CHA Water C 94/99 Separation Operations: Introduction

9/4/99 Separation Operations: Introduction 4 EO Reactor Gas-Gas Exchanger EO A b s o r b e r Intercooler CW O2 C2H4 CH4 Purge Cycle Water Cooler EO S t r i p p e r CW Condenser Knock Out Drum CO2 A b s o r b e r CO2 S t r i p p b e r CO2 EO to Recycle Purification Compressor BFW HP Steam Steam Drum PROCESS EXAMPLE: ETHYLENE OXIDE PFD

PROCESS EXAMPLE: ETHYLENE OXIDE ◆ Process Chemistry: C2H4+ 1/2 02>C2H40(Ethylene Oxide eod C2H4+302→2CO2+2H2O ◆ Reactor effluent C2H40 (EO product) C2H4 (unreacted raw material) C2H6(impurity in C2H4 feed) (unreacted raw material) (impurity in O2 feed Co2(byproduct) H20(byproduct CH4(diluent 94/99 Separation Operations: Introduction 5

9/4/99 Separation Operations: Introduction 5 PROCESS EXAMPLE: ETHYLENE OXIDE u Process Chemistry: C2H4 + 1/2 O2 ® C2H4O (Ethylene Oxide [EO]) C2H4 + 3 O2 ® 2 CO2 + 2 H2O u Reactor Effluent C2H4O (EO product) C2H4 (unreacted raw material) C2H6 (impurity in C2H4 feed) O2 (unreacted raw material) Ar (impurity in O2 feed) CO2 (byproduct) H2O (byproduct) CH4 (diluent)

EO SEPARATION REQUIREMENTS o Recover product eo and purify 5 Recover Eo from reactor effluent via gas absorption in H20 E Recover eo from absorption H20 via stripping E Reabsorb eo in H20 to separate from dissolved gases E Further purify eo to satisfy downstream requirements o Recover and remove byproduct Co2 and H20 E Recover Co2 using acid gas absorption E Remove via stripping E Recover h2o along with eo in eo absorber o Purge feed impurities(C2H6 and Ar) 94/99 Separation Operations: Introduction

9/4/99 Separation Operations: Introduction 6 EO SEPARATION REQUIREMENTS u Recover product EO and purify ð Recover EO from reactor effluent via gas absorption in H2O ð Recover EO from absorption H2O via stripping ð Reabsorb EO in H20 to separate from dissolved gases ð Further purify EO to satisfy downstream requirements u Recover and remove byproduct CO2 and H2O ð Recover CO2 using acid gas absorption ð Remove via stripping ð Recover H2O along with EO in EO absorber u Purge feed impurities (C2H6 and Ar)

PHYSICAL BASIS FOR SEPARATIONS All separations are based on a difference in some property of the materials being separated. 9 Size[Particle sieving, sort by length or diameter, filtration/ ◆ Color/ sort be color/ ◆ Physical properties E vapor Pressure /Distillation, gas absorption, drying/ E Solubility/Crystallization/ E Magnetic Susceptibility Ferrous metal separation/ E Density Decantation, flotation, sedimentation/ 94/99 Separation Operations: Introduction

9/4/99 Separation Operations: Introduction 7 PHYSICAL BASIS FOR SEPARATIONS All separations are based on a difference in some property of the materials being separated. u Size [Particle sieving, sort by length or diameter, filtration] u Color [Sort be color] u Physical Properties ð Vapor Pressure [Distillation, gas absorption, drying] ð Solubility [Crystallization] ð Magnetic Susceptibility [Ferrous metal separation] ð Density [Decantation, flotation, sedimentation]

BASIC TYPES OF SEPARATIONS o Phase Creation Equilibrium Phase Separations] E Energy Separating Agent(ESA)/Simple distillation/ E Mass separating Agent MSA)/Gas absorption, liquid-liquid extraction, extractive distillation/ o Use of a barrier /Membrane separations E Gas/Gas permeation E Liquid ialysis, reverse osmosis E Liquid-solid [ Ultrafiltration o Use of a Solid /Adsorption/ E Gas or liquid adsorption E> Chromatography o Use ofa field or gradient E Gravity /decantation, sedimentation, flotation/ E Electric Field Electrostatic precipitation, electrodialysis 94/99 Separation Operations: Introduction

9/4/99 Separation Operations: Introduction 8 BASIC TYPES OF SEPARATIONS u Phase Creation [Equilibrium Phase Separations] ð Energy Separating Agent (ESA) [Simple distillation] ð Mass Separating Agent (MSA) [Gas absorption, liquid-liquid extraction, extractive distillation] u Use of a Barrier [Membrane Separations] ð Gas [Gas permeation] ð Liquid [Dialysis, reverse osmosis] ð Liquid-solid [Ultrafiltration] u Use of a Solid [Adsorption] ð Gas or liquid adsorption ð Chromatography u Use of a field or gradient ð Gravity [decantation, sedimentation, flotation] ð Electric Field [Electrostatic precipitation, electrodialysis]

SEPARATIONS PERFORMANCE CRITERIA ◆ Product Purity E Must meet product specs to be saleable product E Must meet regulatory specs to be disposable(byproducts ◆ fractional Recovery E fractional recovery of all important components must be high enough to make process operable and economic E Generally a trade off between equipment cost and operating penalties(loss of product, disposal costs, etc. 94/99 Separation Operations: Introduction

9/4/99 Separation Operations: Introduction 9 SEPARATIONS PERFORMANCE CRITERIA u Product Purity ð Must meet product specs to be saleable (product) ð Must meet regulatory specs to be disposable (byproducts) u Fractional Recovery ð Fractional recovery of all important components must be high enough to make process operable and economic ð Generally a trade off between equipment cost and operating penalties (loss of product, disposal costs, etc.)

SEPARATION SYSTEM Product: P Feed F Byproduct B 94/99 Separation Operations: Introduction

9/4/99 Separation Operations: Introduction 10 Feed: WF Zi Product: WP Yi Byproduct: WB Xi SEPARATION SYSTEM