White TexasEnergy DCW SavingEnergyFractionation 06126

8/10/2019 White TexasEnergy DCW SavingEnergyFractionation 06126

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S av i n g E n er g y i n S av i n g E n er g y i n F r a c t i o n a t i o n O p e r a t i o n F r a c t i o n a t i o n O p e r a t i o n

TexasTechnologyShowcase2006



2006 Texas Technology Showcase

Presenter Presenter Presenter

Doug White

Principal Consultantand Vice President,APC Services

Process Systems andSolutions

Emerson Process

Management

Houston, Texas




F r ac t i o n at i o n E n e r g y F r ac t i o n at i o n E n e r g y F r ac t i o n at i o n E n e r g y

Over 40000 distillation/ fractionation columns in the USalone

Consume 40% - 60% of the total energy used inchemical and refining plants

Consume 19% of the total energy used inmanufacturing plants in the US

Reference: Office of Industrial Technology:

Energy Efficiency and Renewable Energy;

US Department of Energy

Washington, DC

“Distillation Column Modeling Tools”




Pr esentation O bjectives Pr esentation O bjectives Pr esentation O bjectives

Present general approaches to saving energyin fractionation/ distillation through improvedcontrol

Present techniques for economic analysis thatrecognize non-linear character of distillationoperation and effects of product blending




FC

LC

FC

TC

FC

LC

Feed, F

20,000 BPD$60/ Bbl

Bottoms, B 5%C4; $80/ Bbl> 5%C4; $60/ Bbl

Distillate, D 3%C5 ;$60/ Bbl>

%C5; $40/ Bbl

Reflux,

R

Reboiler,E

PC

AC

C as e S t u d y C as e S t u d y C as e S t u d y

AR

C3 – 25%nC4 – 25%nC5 – 25%nC6 – 25%

Steam

10$/MMBTU




S av i n g E n e r g y i n F r ac t i o n at i o n S av i n g E n e r g y i n F r ac t i o n at i o n S av i n g E n e r g y i n F r ac t i o n at i o n

Closer Control to Specifications

Optimize Energy Usage versus Recovery

Minimize Pressure




D is t i l lat i o n C o l u m n C o n t r o l S av i n g s D is t i l lat i o n C o l u m n C o n t r o l S av i n g s D i s t il l at i o n C o l u m n C o n t r o l S av i n g s

Cost Per Year

Excess Reflux

20000 BPD Stabilizer Column

$10/ MM BTU Steam

$0

$100,000

$200,000

$300,000

$400,000

$500,000

$600,000$700,000

5 10 25 50

% Excess Reflux

$/ Yr



Mat erial B alanc e Mat erial B alanc e




P r o d u c t V al u e P r o d u c t V al u e P r o d u c t V al u e

0.5 1.0 1.5 2.0 2.5

Spec

Product

Value;$/ Day

Bottom Product Composition; %

Assumptions:ConstantReflux; NoVariability in

Control

Optimum is to operateas close to the specas possible




Debut anizer – Mat er ial B alanc e Ef f ect s Debut anizer Debut anizer – – Mat er ial Balanc e Ef f ect s Mat er ial Balance Ef f ect s

Debutanizer

20000 BPD

Constant B/F

0.00%

2.00%

4.00%

6.00%

8.00%

10.00%

3 3.2 3.4 3.6 3.8 4 4.2 4.4

R/D Ratio

C o m p o s

i t o n

, %

B

D

Debutanizer

20000 BPD

Constant R/D

0.00%

2.00%

4.00%

6.00%

8.00%

10.00%

12.00%

9 9.5 10 10.5 11 11.5

B/FRatio

C o m p o s

i t i o n ,

%

B

D

Material Balance Control Has Strongest Effecton Composition




Effec t of Variabi l i ty Effec t of Variabi l i ty – – S t an d ar d A n al y s i s S t an d ar d A n a ly s i s

Time

SpecificationLimit

Average

Composition

Composition

y(x)= 1

2

1

2

2

e

x mean

6

1 %

o f p e a k h e i g h t

1 4 %

16% of area

2% of area

Frequencyof

Occurrence

y

Mean

1 SD

2 SD




Effect of Reduced Var iabi l i ty Effect of Reduced Var iabi l i ty

IMPROVED PROFITBY CHANGING

TARGET

REDUCEDVARIABILITY

POOR CONTROL

$PROFIT

SPECIFICATION LIMIT




R ed u c e d V ar i ab i l i t y O p t i o n s

2-Sigma 2-Sigma

NewSet Point

OriginalSet Point

2-Sigma 2-Sigma

Upper LimitPV distribution for original control

PV distribution for improved control

Extra margin withoutimproved control

value




P r o d u c t V al u e w i t h V a r iab i l i t y P r o d u c t V a lu e w i t h V ar i ab i l i t y P r o d u c t V al u e w i t h V a r iab i l i t y

0.5 1.0 1.5 2.0 2.5

SpecProductValue;$/ Day


MeanValue

Initial

Variability

Initial OperatingTarget




P r o d u c t V al u e w i t h V a r iab i l i t y R e d u c e d – S am e S et p o i n t P r o d u c t V a lu e w i t h V ar i ab i l i t y P r o d u c t V al u e w i t h V a r iab i l i t y

Reduced R e d u c e d – – S am e S et p o i n t S am e S et p o i n t

0.5 1.0 1.5 2.0 2.5



New

Mean Value

Reduced

Variability

Initial OperatingTargetOld Mean

Value




P r o d u c t V al u e w i t h V a r iab i l i t y P r o d u c t V a lu e w i t h V ar i ab i l i t y P r o d u c t V al u e w i t h V a r iab i l i t y

0.5 1.0 1.5 2.0 2.5



NewMeanValue

ProfitIncrease

OldValue

ReducedVariability

For any givenstandard deviationit is possible tocalculate the

optimum setpoint.




Debu tanizer - Net Pr ofi t Cur v e Debutanizer Debutanizer - - N et P r o f i t C u r v e N et P r o f i t C u r v e

D e b u t a n i z e r

2 0 0 00 B P D

5 % B t m C o m p

0

5 0 0 0 0

1 0 0 0 0 0

1 5 0 0 0 0

2 0 0 0 0 0

2 5 0 0 0 0

0 .0 0 1 .0 0 2 .0 0 3 .0 0 4 .0 0 5 .0 0 6 .0 0

D i s t il la t e C o m p o s i t io n s , %

N

e t P r o

f i t , $ / D a y




Debutanizer – O p t i m u m S et p o i n t W i t h Variabil i ty Debutanizer Debutanizer – – Op t i m u m S et p o i n t W i t h O p t i m u m S et p o i n t W i th

Variabil i ty Variabil i ty

Debutanizer

20000 BPD

5% Btm Comp

Variability Effect on Optimum Setpoint

150000

175000

200000

225000

250000

0 0.5 1 1.5 2 2.5 3

Distillate Compositon, %

P r o f i t , $ / D a y

0

0.3

0.6

Standard

Deviation

Optimum Setpoint Depends on Variability




E ff ec t o f B l en d i n g E ff ec t o f B l en d i n g E f fec t o f B l en d i n g

Column Product

Shipped Product

Proposition: Since actual specification is on shippedproduct rather than column product directly, smallexcursions over the specification don’t matter andcan be handled by blending.Is this correct?






Non -Lin ear Effects No n No n - - Lin ear Effects L inear Effects

EnergyCost

Composition

For nonlinear relationship, theexpected value of the energy cost isNOT at the value equivalent to themedian of the composition; It’svalue depends on the standarddeviation of the composition

Less PureMore Pure

ProbabilityDistribution

ExpectedValue




Var iabi l i ty Vs Ener gy Var iabi l i ty Vs Ener gy Var iabi l i ty Vs Ener gy

Debutanizer 20000 BPD

5% Btm Co mp; 3% Distil Com p

Variability Effect on Energy Usage

12300

12400

12500

12600

12700

12800

12900

13000

13100

13200

0 0.2 0.4 0.6 0.8 1

Distillate Composition Standard Deviation, %

E

n e r g y

C o s

t , $ / D a y



E n er g y B al an c e E n er g y B al an c e C o n t r o l C o n t r o l




LowEnergyCostOptimum

Profi tabi l i ty Prof i tabi l i ty Prof i tabi l i ty

Reflux

$/ Day

Low Energy Cost,$/day

Product Value,$/day

Low EnergyCost Profit$/day

High EnergyCost, $/day

High EnergyCost Profit$/day

HighEnergyCostOptimum




P r o f i t ab i l i t y w i t h v ar i ab i l i t y P r o f i t ab i l i t y w i t h v a ri ab i l i t y P r o f i t ab i l i t y w i t h v ar i ab i l i t y

RefluxBPD

$/ Day

Profit

$/day

Optimum

Assumptions:ConstantBottomsComposition

MeanValue

Current

Variability




P r o f i t ab i l i t y w i t h v ar i ab i l i t y P r o f i t ab i l i t y w i t h v a ri ab i l i t y P r o f i t ab i l i t y w i t h v ar i ab i l i t y

RefluxBPD

$/ Day

Profit

$/day

Optimum

Assumptions:ConstantBottomsComposition

OldValue Reduced

Variability;

Same Mean

NewValue

ProfitIncrease

For locally quadraticobjective functionthe benefits of reduced variabilitycan be calculatedanalytically



P r es s u r e E f f ec t s P r es s u r e E f f ec t s




C o l u m n P r es s u r e E ff ec t C o l u m n P r es s u r e E ff ec t C o l u m n P res s u r e E ff ec t

Relative Reboiler Cost Per Year

Column Pressure Effect

Constant Separation

20000 BPD Stabilizer

$0

$1

$2

$3

$4

$5

$6

100 120 140 160 180 200

Pressure, PSIA

$ MM/ Yr




S u m m ar y - Sa v i n g E n e r g y i n F r ac t i o n a t i o n S u m m a r y S u m m a r y - - S a v i n g E n e r g y i n F r a c t i o n a t i o n S a v i n g E n e r g y i n F r a c t i o n a t i o n

Closer Control to Specifications

Optimize Energy Usage

Minimize Pressure




Q u e s t i o n s ? C o m m e n t s ? Q u e s t i o n s ? C o m m e n t s ? Q u e s t i o n s ? C o m m e n t s ?

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White TexasEnergy DCW SavingEnergyFractionation 06126