An Insider’s View of Dividing Wall Columns

ADVANCED DISTILLATION

Joseph C. Gentry, Vice President – Licensing & Technology

GTC Technology

2017 Global Petrochemicals Symposium, Athens

Conventional 2-Column Fractionation

Sequence for Separating Three Components

Co

lum

n 1

Feed

(A,B,C)

A

(B,C)

Co

lum

n 2

B

C

Feed

(B,C)

0

5

10

15

20

25

30

35

40

45

0 0.2 0.4 0.6 0.8 1

Tray

Nu

mb

er

Composition : Mole Fraction

Thermodynamic inefficiency as component B is

concentrated, then diluted within the first column

Remixing leads to Thermodynamic Inefficiency

B

Remixing

A

C

Remedy is to Pre-fractionate the widest components first

Page 2

Typical Benefits of GT-DWC® (Dividing Wall Columns)

GT-DWC® CAPEX is lower by 20-30% GT-DWC® OPEX is lower by 20-30%

0102030405060708090

100

Conventional TwoColumn System

GT-DWC℠

Installed Cost

Equipment Cost

0102030405060708090

100

Conventional TwoColumn System

GT-DWC℠

Conventional Two

Column System GT-DWC®

Column 2 1

Reboiler 2 1

Condenser 2 1

Pump 4 3

Plot Space 100% Approximately

30% less

Equipment Count

& Plot Space

Page 3

Typical Dividing Wall Column Applications

• Benzene / Toluene / Xylene / C9 Aromatics

• Deisobutanizer / Debutanizer / Depentanizer

• Reformate Splitter

• Naphtha Splitter

• Isomerate Splitter / Deisopentanizer / Deisohexanizer

LPG Recovery with integrated absorption/stripping

Page 4

GT-DWC® Application –

When high-purity side product required

When high purity middle product is desired, GT-DWC® should be

considered instead of a conventional sidedraw column.

A

C

Feed

(A,B,C)

B

Conventional Sidedraw Column

Intermingling

of feed with

Sidedraw

A

C

Feed

(A,B,C)

B

GT-DWC®

A,B

B,C

B

B

Page 5

Case Study: Commercial Column Retrofit

• Intermixing of Feed with Sidecut

Heavies Product

Feed Overhead Product

Sidecut Product

LCO

HCO

• Sidecut separated from feed

• Better quality product

Heavies Product

Feed

Overhead Product

Sidecut Product

Page 6

Product Specs after Revamp to GT-DWC®

Parameter Units Naphtha Splitter

before Revamp

Naphtha Splitter after

Revamp to GT-DWC®

Side Draw Flow Rate lb/hr 398,000 353,000

D86 (IBP/FBP) Deg˚ F 223 to 376 231 to 356

Overlap (Heart Cut Naphtha D86

95%-Heavy Cut Naphtha D86 5%)

Deg˚ F

99 27

• Client was planning to install a 2nd column in sequence with the existing Naphtha Splitter.

• A spare column was available for this retrofit.

• Cost of Revamp to GT-DWC® was 1/4 of the alternate two-column design being explored

by the client.

Page 7

Case 2: Original 2-Tower System

Revamped to GT-DWC®

Heavy

Naphtha

Feed

Light

Naphtha

LCO

HCO

Heart Cut

Naphtha

Naphtha Splitter-1

Revamped to

GT-DWC®

Naphtha Splitter II

Idled

Heavy

Naphtha 2

HCO /

HP Steam

Heart Cut

Naphtha

LP Steam

Generator

Page 8

Parameter Units Original Design

(NS-I and NS-II)

Naphtha Splitter-I after

Revamp to GT-DWC®

Feed lb/hr 679,000 679,000

C8/C9 (Naphthenes & Aromatics) lb/hr 243,900 243,900

Mid Cut lb/hr 363,700 363,500

C8/C9 (Naphthenes & Aromatics)

Concentration wt% 63.90 66.53

C8/C9 (Naphthenes & Aromatics) lb/hr 232,404 241,860

% Recovery C8/C9 (Napthenes & Aromatics) wt% 95 98

Loss of C8/C9 (Naphthenes & Aromatics) lb/hr 25,280 18,230

Total heating duty MMBtu/hr 151 111

Comparison: Product Recoveries

Original Configuration vs GT-DWC®

Benefits of GT-DWC

• Heating duty reduced by ~ 26%

• HP steam usage eliminated

• Naphtha Splitter-II is idled

• 3% Higher Product recoveries

• Heart Cut Naphtha obtained in Naphtha Splitter-I

• Project Payback (based on Energy Reduction benefits only) = 10 Months

Page 9

GTC Internal Liquid Split Distributer

Provision for external

splitting for future use

Risers for

vapor flow

Liquid split metering box

(maintains fixed liquid ratio

on either side of wall)

Page 10

GT-DWC® Column Internals

Off Center

Dividing Wall

Page 11

Feed

Fuel Gas

(C1,C2)

LPG (C3)

C4, Heavies

Internal Circulation

of Heavies as

Absorption Solvent

GT-LPG MAX® - Combined Absorption &

Distillation in a Single Column

Heavy Oil

• Improved LPG recovery with no refrigeration

• Lower energy consumption

• Better heat integration options

Page 12

Summary

• Unconventional distillation applications are an overlooked means to

reduce refinery energy consumption

– GT-DWC® reduces 20–30% OPEX through energy savings

– GT-DWC® reduces 20–30% CAPEX by requiring a single column for

multi-component separation

GT-TDWC℠ allows new solutions for off gas recovery using absorption/stripping

• Advanced Distillation schemes can offer CAPEX and OPEX reduction of

more than 40% by combining multiple unit operations and heat

integration opportunities.

Page 13

Poll Question

• Can you make high purity products from three cuts

in a Dividing Wall Column?

Page 14