Hierarchy of Decisions

LEVEL 3 : reactorseparator products purge feeds Liquid ? Liquid / Vapor ? Vapor ?

LEVEL 4 : 1 ) Liquid reactor liquid separation system Liquid recycle products liquid feeds LEVEL 3

LEVEL 4 : 2 ) Liquid / Vapor reactor liquid separation system Liq. recycle products liquid feeds LEVEL 3 Phase Split Vapor Recovery system 35  C gas recycle vapor liq. vapor purge

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

LOCATIONS OF VAPOR RECOVERY SYSTEM 21 3 Gas Recycle Purge 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 ?

DECISION IN SYNTHESIZING LIQUID SEPARATION SYSTEM 1. How should light ends be removed, if they might contaminate the product ? 2. What should be the destination of light end ? 3. Do we recycle components that from 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 ?

1 ) ALTERNATIVES FOR LIGHT-ENDS REMOVAL  Phase Splitter — T T and/or PP  Partial Condenser on Product Column   Pasteurization Section on Product Column   a Stabilizer Column before the Product Column  Lower cost Higher cost  lights product  lights product  lights product

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

ReactorFlash Recycle Product Stablizer Diphenyl Toluene H 2, CH 4 Compressor Benzene H 2, CH 4 Purge

Process Simulation Run ChemCAD to obtain M&E balance data !

ECONOMIC POTENTIAL AT LEVEL 4 EP4 = EP3 - annual purge loss - annualized distillation costs - annualized vapor recovery costs 2   10 6 $/yr 0 -1   

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

AB C Design 1 : Direct Sequence

A B Design 2 : Indirect Sequence C

B Design 3 : Side-stream rectifier C A

Design 4 : Side-stream Stripper C A B

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

AA C Design 6 Design 7 side stream B C B