Hierarchy of Decisions

LEVEL 3 : purge reactor separator products feeds Liquid ? Liquid / Vapor ? Vapor ? Determined with Flash calculation!

1 ) If only liquid is present: LEVEL 4 : 1 ) If only liquid is present: LEVEL 3 reactor liquid separation system liquid products feeds Liquid recycle

2 ) If both liquid and vapor are present: Vapor Recovery system Phase purge LEVEL 4 : 2 ) If both liquid and vapor are present: Vapor Recovery system vapor gas recycle vapor 35C Phase Split liq. liq. reactor liquid separation system liquid products feeds Liq. recycle LEVEL 3

3 ) If only vapor is present: Vapor Recovery system Phase Split purge LEVEL 4 : 3 ) If only vapor is present: Vapor Recovery system vapor gas recycle 35C Phase Split liquid liquid vapor reactor liquid separation system products feeds Liquid recycle LEVEL 3

LOCATIONS OF VAPOR RECOVERY SYSTEM Gas Recycle Purge 2 1 3 vapor from phase split 1 ) The purge stream 2 ) The gas-recycle stream 3) The flash vapor stream 4 ) None

RULES FOR PLACING THE VAPOR RECOVERY SYSTEM 1 ) Place the vapor recovery system on the purge stream if significant amounts of valuable materials are being lost in the purge. 2 ) Place the vapor recovery system on the gas-recycle stream if materials that are deleterious to the reactor operation (catalyst poisoning, etc.) are present in this stream or if recycling of some components degrades the product distribution. 3 ) Place the vapor recovery system on the flash vapor stream if both 1 ) and 2 ) are valid. 4 ) Do not use a vapor recovery system if neither 1 ) nor 2 ) are important.

TYPE OF VAPOR RECOVERY SYSTEM 1 ) Condensation - low. T and/or high P 2 ) Absorption 3 ) Adsorption 4 ) Membrane separation 5 ) Reaction ADJUST MATERIAL BALANCE ?

Decisions in Synthesizing Liquid Separation System 1. How should light ends be removed, if they might contaminate the products? 2. What should be the destinations of light ends? 3. Do we recycle components that form azeotropes with reactants, or do we split the azeotropes ? 4. What separations can be made by distillation ? 5. What sequence of columns do we use ? 6. How should we accomplish separations if distillation is not feasible ?

Q1: Alternatives for Removing Light ends Phase Splitter — T and/or P ◆ Partial Condenser on Product Column (A) ◆ Pasteurization Section on Product Column (B) ◆ a Stabilizer Column before the Product Column (C) Lower cost Higher (A) lights (B) (C) lights lights product product product

2 ) DESTINATIONS OF LIGHT ENDS a ) vent or flare stacks - if light ends have very little value. b ) fuel - if light ends are flammable. c ) vapor recovery system - if light ends are valuable. 3 ) AZEOTROPES WITH REACTANTS 4 ) APPLICABILITY OF DISTILLATION 5 ) SEQUENCING OF SIMPLE COLUMNS 6 ) COMPLEX COLUMNS

Purge Compressor H2, CH4 Reactor Flash Toluene Benzene H2, CH4 Recycle Product Stablizer Diphenyl

Run ASPEN PLUS to obtain M&E balance data ! Process Simulation Run ASPEN PLUS to obtain M&E balance data !

ECONOMIC POTENTIAL AT LEVEL 4 EP4 = EP3 - annual purge loss - annualized distillation costs - annualized vapor recovery costs 2106 1106 $/yr 0 -1106 -2106 -3106 0.2 0.4 0.6 0.1 0.3 0.5 0.7

2 ) DESTINATION OF LIGHT ENDS a ) vent or flare stacks - if light ends have very little value. b ) fuel - if light ends are flammable. c ) vapor recovery system - if light ends are valuable. 3 ) AZEOTROPES WITH REACTANTS 4 ) APPLICABILITY OF DISTILLATION 5 ) SEQUENCING OF SIMPLE COLUMNS 6 ) COMPLEX COLUMNS

A B C Design 1 : Direct Sequence

A C B Design 2 : Indirect Sequence

A B C Design 3 : Side-stream rectifier

A B C Design 4 : Side-stream Stripper

Prefractionator arrangement A , B B B , C C Design 5 Prefractionator arrangement

A A B B C C Design 6 Design 7 side stream