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$Page 1: Process simulation based optimization of a commercial ... · PDF filegas sweetening unit ... Total cooling duty, MW Solvent split-flow fraction. 2nd World Congress on Petro chemistry$
2nd World Congress on

Petro chemistry and Chemical Engineering

October 27-29, 2014 Las Vegas, USA

Process simulation based

optimization of a commercial amine

gas sweetening unit

w w w . c p f d - s o f t w a r e . c o m

gas sweetening unit

Dr. Abdallah Sofiane Berrouk

Mr. Satyadileep Dara




Outline

� Introduction

� Process simulation model

� Customization of the model


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�Validation with plant data

�Optimization analysis




� Amine sweetening unit #32, Habshan I, GASCO, Abu Dhabi, UAE

• Sour gas: H2S ~ 7% and CO2 ~ 6%

• Capacity – 400 MMSCFD

• Generic MDEA

� Process simulation model development

Introduction


� Process simulation model development

• ProMax V 3.2

• TSWEET kinetics model

• Amine sweetening SRK

3




Process simulation model


4




Customization of simulation model

�Reaction chemistry

R2NCH3 + H2S ��R2NCH4+ + HS- (Instantaneous)

CO2+ H2O + R2NCH3 ��R2NCH4+ + HCO3

- (Slow)

�TSWEET kinetics models


5

�TSWEET kinetics models

• Sweet gas H2S & CO2 = f (Sour H2S, CO2, T, P, Residence time)

• Developed using wide range of operating data of various plants

�Customized TSWEET kinetic models

• Developed using operating data of a specific plant




Customization of simulation model

�Assign data to ProMax existing model

� Identify properties of data that differs from plant data

�Provide constraint to the kinetic model in accordance with

the trend


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the trend

�Run new ProMax model

�Verify new data against plant data




Validation of customized simulation model


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Average sweet gas H2S prediction error – 2.8 ppm




Validation of customized simulation model


8

Average sweet gas CO2 prediction error – 0.17%




Optimization - Operational changes

External VariablesOperational

Variables

Desired

Specifications

� Solvent rate

� Steam to re-boiler

� Solvent strength

� Sweet gas H2S

� Sweet gas CO2

� Sour gas H2S

� Sour gas T


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� Solvent strength

� Lean solvent T

� Condenser T

� Sweet gas HHV

� Corrosion levels

� Sour gas T

� Sour gas rate

Optimum set of ‘operational variables’ is the key for efficient plant performance




Operating conditions’ significance� Solvent circulation rate

• Sweet gas specs

• Rich amine loading (Corrosion on absorber-flash drum piping)

• Pumping energy

� Steam rate

• Sweet gas specs

• Lean amine loading (Corrosion in re-boiler and piping)


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• Lean amine loading (Corrosion in re-boiler and piping)

� Lean amine temperature

• Increased H2S absorption with CO2 slip

• Reduced load on dehydration

• Foaming and hydrate risks

� Solvent concentration

• Decreases solvent circulation rate

• Corrosion effects




Lean solvent temperature


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Optimized operating conditions

Parameter Operating case Proposed case

Lean solvent temperature, oC 59 47.3

Solvent circulation rate, m3/hr 785 630

Steam consumption rate, tons/hr 117 91

Lean solvent concentration, % 42.4 50

Condenser temperature, oC 32 55


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Condenser temperature, oC 32 55

Sweet gas H2S, ppm 4 4

Sweet gas CO2, % 1.4 2.0

Lean solvent cooler load, MW 44 39

Pumping load, MW 0.70 0.55

Hydrate formation temperature, oC 18.7 18.6

Hydrocarbon dew point, oC 24.4 24.1

Sweet gas temperature, oC 60.4 49.3

Sweet gas H2O content, kg/hr 858 522




DCS look up tables


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Solvent rate and steam rate as function of sour gas H2S+CO2 contents and

sour gas temperature




Optimization - Structural changes

� Split-flow configuration

�Multiple absorber feeds

� Semi lean solvent recycle


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�Heat integration (Rich Lean HX – Condenser loop)

�Mixed solvents




Split-flow configuration


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100

105

110

115

Ste

am

rate

, to

ns/h

r

15

17

19

21

23

25

27

29

Condenser

duty

, M

W

Split-flow configuration - Results


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100

0.00 0.20 0.40 0.60Solvent split-flow fraction

15

0.00 0.20 0.40 0.60Solvent split-flow fraction

Sw

eet gas H

HV

, M

J/m

3

Solvent split-flow fraction

Tota

lcoolin

g d

uty

, M

W

Solvent split-flow fraction




Summary

�Process simulation analysis of a commercial amine

sweetening unit was performed

�Customized simulation model was developed with tailor-

made kinetics correlations and property packages


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�Model was validated with operating data over a period of

one year

�DCS look up tables were developed to provide guidelines

on optimum operating conditions

�Optimization analysis was performed by investigating

various operational and structural changes




THANK YOU


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THANK YOU