05_Dynamic Simulations for Safety and Reliability and Efficient Operations_Gautam

8/19/2019 05_Dynamic Simulations for Safety and Reliability and Efficient Operations_Gautam

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Dynamic Simulation for Safety, Reliability Efficient Operations

– Dynamics and Compressor Surge Analysis

Gautam Pradhan, Sr. Principal Business Consultant

Feburary, 2016


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© 2015 Aspen Technology, Inc. All rights reserved.2


Agenda

• Steady State Vs. Dynamic Simulation

• Why use Dynamic Simulation?

• What is Aspen HYSYS Dynamics?

• Dynamic Modeling of Compressors – Challenges and Best Practices

- Data Analysis

- Steady State Model

- Dynamic Model with Control System, Configuring ASC

- Modelling Acceleration and Deceleration of Motor/Turbine Drives

- Result Analysis and Documentation

• Activated Compressor Dynamics in Hysys V8.6 and Above

• Dynamic Modeling of Expanders (Turbines)

• Case Studies /Success Stories


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Steady State and Dynamic simulation

Design/Rating/Optimization

Accumulation = 0

Linear Equations

Flow Driven

Modular non- sequential

algorithm

No Process Control

Rating/DSupport/

Accumu

Different

Pressure

Modular

Algorithm

Process

Steady State Dyn


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Why Dynamic Simulation ?

Process plants are never truly at steady state

- Feed and environmental disturbances

- Heat Exchanger Fouling- Catalyst Deactivation

- Equipment/Instrument Malfunctions

Transient behavior are best studied using Dynamic Simulation

-Transition between operating conditions

- Start-up, Normal/Emergency Shut-down Testing

Design Operational Decision Support

Safety System Evaluation

Operator Training

Advanced Process Control


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• Design / Analysis of Control Schemes

– Design the process and control system simultaneously

– Analyze and improve basic control strategies (e.g., fractionators, compressor surge, location of s

– Pre-tune control loops

– Evaluate, develop and test APC scenarios (DMCplus)

• Operability Engineering Studies

– Understand dynamic plant behavior, including upset propagation (e.g., slugging)

– Operability studies of highly-integrated processes

– Design / analysis of start-up, shutdown and process transition strategies

• Hazard and Safety Studies

– Design / analysis of pressure relief and flare systems

– Safety studies

– Design / analysis of emergency shutdown systems

• Operator Training

– DCS checkout

– Graphics functionality/operability of the operator consoles

Dynamic modeling and simulation can address these issues:




Enabling design and verification of process control sch

• Building a fully representative dynamic model with high level details allows tand start-up scheme to be evaluated onshore rather than offshore.

• Allows controller tuning ahead of start-up to give good control response.

• A faster and safer start-up leads to early production and risk minimization.



Aspen HYSYS® Dynamics

Aspen HYSYSDynamics is t

Standard Dyn

Modeling Soft

Combines ProEngineering a

Engineering

®



Compressors – Why Worry?

Design• Expensive eq• Often custom

lead times to

Operabil• Compressor t• Compressor s

hazardous• Specialized a

systems are c

From both a design and controllability / operabilitycompressors provide unique issues and ch


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Dynamic Modeling of Compressors - Challenges

• Precise modeling required for design/operational decision support

• ASC algorithm requires accurate thermodynamics properties along the surge

• Multiple performance curves ( IGV Opening, MW, Speed, )

• ASC valve ( stroke time, delay, special valve characteristics)

• Modeling start-up with different driver – VS motor, fixed speed motor, turbine

• Start-up from various SOP ( refrigeration compressors) and voltage

• Acceleration and deceleration by Inertia and power balance


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Dynamic Modelling: Compressor Surge Analysis – St


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Performance Curves

• Check The Compressor Performance Curves

– Perform Extrapolation for Stone wall and

Surge area.

• Plot the Surge Line by Joining Left Most points

( Min Flow, Max Head Points) at various

speeds.

Polynomial Surge Curve

Linear Surge Line

Stone Wall Curve


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Performance Curve

• For Fixed Speed Drive, performance

curve should be estimated for other

than Operating Speed Curves foraccurate modeling during coast down

and start-up.

• If multiple speed curves are not

available, extrapolated curves should

be generated and entered to themodel

Extrapolated Performance Curve


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Modeling Special Valve Characteristics

Special Valve Characteristics is modeled using Linear Interpolation

=IF(M27


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EQUIPMENT & PIPING DATA

HEAT EXCHANGERS

P&ID

No.

Line

No. From To

Associated

Pipe Length

Nom.

Dia.

Inner

Dia.

45 deg

elbows

Long

radial

elbows

Short

radial

elbows

Soft

tees

Hard

tees

Ball

Valves

PIPING ISOMETRICS

VESSEL

DIAMETER

VESSEL

HEIGHT

VESSEL

VOLUME

SHELL

VOLUME

TUBE

VOLUME OVER-ALL UA

SHELL SIDE

DESIGN FLOW &

PRESSURE DROP

VESSELS

HOLD-UP OVER-ALL UA DESIGN FLOW AND

PRESSURE DROP

AIR COOLERS CONTROL VALVE

Delay time for sensor/transmitters/control valve should be taken into account for p


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INERTIA OF DRIVER AND COMPRESSORSTOTAL SYSTEM INERTIA OF THE DRIVER AND COMPRESSOR SYSTEM IS REQUI

ACCURATE MODELING OF START-UP AND SHUT-DOWN and ESD OF COMPRESS

No. Equipment Speed GD2 /4 (=J) at LS shaft

[rpm] [kgm2]

1 Motor

2 Low Speed Coupling (Incl. Hub)

3 Gear Shaft (Incl. Pinion Shaft)

4 Pinion Shaft

5 High Speed Coupling (Incl. Hub)

6 Compressor

Total


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ASC Configuration

• Surge control systems are designed to

– Detect the imminent start of surging

– Prevent the compressor from reaching this condition

• Basic Strategy of Anti Surge Controller (ASC):

– Open a recycle valve to provided increased throughput

– A surge curve is used to detect imminent start of surging

– Quick opening recycle valve controlled directly by ASC

• Additional Possible Strategies:

– Decrease speed, reducing surge flow limit

– Reduce outlet pressure, reducing compressor head

• Specialized surge controller technology

– From compressor vendors

– Other technology providers


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ASC Configuration

• Surge controllerattempts to maintain

a minimum flow ratethrough thecompressor

• Surge controller takesmore aggressiveaction if compressor

is close to surging

• Parameters for surgecontroller set onSurge Control pageon the Parameterstab


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ASC Configuration - Other Technology Providers

• Specialized surge controller algorithm can be emulated for use in Hysys.

– From compressor vendors

– Other technology providers

• Information required for emulating third party surge controller algorithm

– Details of the operation/features of the ASC, Details on Input signals/connections, m

line characterization

– Details on output signals/connections, Details on configuration/tuning parameters

– Details on control algorithms (closed loop/open loop responses and transitions betwe – Specific details on the application (if known/available), such as: Input data used, Inp

Algorithms employed

– Configuration parameters (or how to calculate them),Output connection.

• DLL can be created and registered as extension into HYSYS.


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Modelling Acceleration/Deceleration of Motor/Turbine

• The rate of Acceleration/Deceleration is calculated from the total rotational

consumption, and driver power and friction losses. The rate of Acceleration

re-calculated at each time-step by a rigorous torque balance equation:

Where:

P = change in shaft power in each time-step

ILSS = inertia with respect to the low speed shaft

Nmotor = motor speed

Ncomp = compressor speed


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=IF(M16


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Rated Torque = Rated Power*60*1000/(2*π*Motor Speed)

T = Rated Torque * ESD Trip * Speed Controller OP *Reduced Torque/100

Available Power = 2**N*T/ (60*1000)

Required Power = Power Consumed in Gas Compression + Power Losses

Power Losses = Power Loss Constant * Speed* Speed

Power consumed in gas compression is dynamically imported to spread sheet at each tim

compressor performance data in HYSYS.

Power Imbalance Available Power Required Power

Power Imbalance is used for calculating Acceleration or deceleration using the torque ba

Integrator Setting


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Integrator Setting

• Step Size should be reasonably setto capture the Desired Operating

Locus 0.001 – 0.05 Sec Typical• Do not play with the Acceleration

factor, should be 1

• Set Execution rate for P-F Solver,Control and Logic Operations,Composition and Flash calculationto 1

• In the Integrator Option, uncheck‘Truncate large volume integrationerror’

• Enable Static head contribution asdesired

Scenario Configurations Event Scheduler


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Scenario Configurations – Event Scheduler

• Configure all Required Test

Scenario, ESD, Start-up, Etc.using Event Scheduler

Result Analysis and Report


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For Generating Report, Create a Strip Chart and addall important variables:

- Compressor speed, Head, Flow

- Total Available Power, Torque

- Flow Through ASC, HGB

- Suction Temperature, Pressure, Flow

- Discharge Temperature, Pressure Flow

- Any Other Important Variables, Calculated Match

No. through HGB etc.

- Drag and Drop variable from flow-sheet into strip

chart

Drag and



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• After the scenario runs, savehistorical data as .CSV file for

analysis and report generation.

• A Template can be created toavoid repeated task formultiple scenarios



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A HYSYS V8 6+ A ti t d D i


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Aspen HYSYS V8.6+ – Activated DynamicsEliminate Compressor Damage by Compressor Surge Analysis

Activated Compressor Dynamics in Hysys V8 6+


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Activated Compressor Dynamics in Hysys V8.6+

Dynam ic analy

the process

safety, op erab

effective

Empow er everyone to use dynam ics

New users supp ly m in imal inputs

Pre-made templates, scenarios & results forms

Experienced users can imp rove the template

DynamicSimulation

Models

SteadyState

SimulationModels

Process Engineer Controls E


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Activated Compressor Surge Analysis

Dynamic model automatically built from steady state compressor mod

Pre-definedEmergency scena

Automatically generate results forms

Feedback


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Feedback Activated Compressor Dynamics (1 of 2)

Customer Reference: Atkins (Ian Wyatt, Principal Engineer)

Impressed with how quickly the flowsheet can likes the automation and how quickly you can

Liked the custom templates and the rewind funrecycle block is not reflective of a true dyna

Scenarios and input summary form useful. Vsizing should not be based on steady state

options to include hot bypass line and to stavalve partially open

“… an innovative screening tool before fucompressor modeling. A good starting poin

compressor study across a range of scenariopresented in a well-organized manner, and pdisplays are convenient.”

Modeling Expanders ( Turbines) in Hysys


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g p ( ) y y

• Expander is an important piece of equipment in many process plants

• Expanders are often used in refrigeration units, LNG plants, gas pla

separation plants and ethylene plants.

• Expanders are also often used as the driver for compressors or pumhere are expanders running on steam or expanders that are part of a

• Unlike Compressors, Getting Detailed Performance Curves for ExpaHead & Efficiency at various speed is difficult as expander vendor do

such curve.• For a compressor the feed actual volume flow is a good parameter t

compressor head and efficiency, however, for an expander, it is rathactual volume flow that is the parameter of choice.

• Most often, a single Mass Flow Vs Power Curve is provided by expaonly a point efficiency is generally provided rather than a curve.

M d li E d ( T bi ) i H


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Modeling Expanders ( Turbines) in Hysys

Recommended Modeling Approach:

Step 1: Size a Control Valve so that at steady state with same pressure difference betwthe turbine, gives same flow rate as the Turbine Design Flow .Inlet and outlet prvalve is dynamically manipulated (at each time steps). This is done by first impooutlet pressure of the turbine to a spread sheet and then exporting these pressoutlet of the control valve.

Step 2: The flow rate [ACT_m3/h] through the Control Valve (sized in step 1 above) isspread sheet and then exported to the capacity of turbine.

Step 3: The Adiabatic Efficiency is calculated in spreadsheet using Mafi-Trench meth

E = 100*SQRT {(3.14 *D*N/60)/SQRT (H*1000)}Where

E = Adiabatic Efficiency

D = Wheel Diameter of the Turbine

N = RPM of Turbine

H = Adiabatic Fluid Head of the turbine (imported from turbine in Hysys model)

Case Studies


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• PETRONAS – Malaysia LNGDynamic Simulation for LNG Plant Revamp

• JGC

Compressor Anti-Surge Valve design using HYSYS Dynamics simula

• Wintershall and InProcess Assessing safer Blow-down option by Using Dynamic Process Simula

• Production Services Network

Perform operability analysis

PETRONAS Malaysia LNG


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Challenge Solution Results Challenge

Liquefied Natural Gas (LNG) plant revampdesign verification

Ensure compressor anti-surge system willprovide adequate protection from the riskof damage under all scenarios

Verify controllability of the compressorsduring unit upsets, start-up, shutdown and

normal operation scenarios

Check the start-up and shutdownprocedures for compressors

Verify compressor systems and equipmentdesign conditions

Ref: Siti Rafidah Moslim, Petronas, Vikas Singh, AspeaspenONE Global Conference, Boston, May 201

PETRONAS – Malaysia LNGDynamic Simulation for LNG Plant Revamp



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Challenge Solution Results


Challenge

Aspen HYSYS Dynamics model to representactual equipment, piping arrangements andcontrols

– A high fidelity emulation of CCC controllerto reproduce the precise behavior of anti-surge control

– Torque and power characteristics of the gas

turbines to reproduce precise conditionsduring start-up and shut down

Over 45 Scenarios were simulated andanalyzed in an iterative process using HYSYSEvent Scheduler




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Challenge

• Better sizing of recycle valves andbypass valves based on all failurescenarios compared to steady state

• Relieving loads confirmed for variousscenarios which form the basis for keyrelief valve sizing

• Start-up and shutdown procedurestested in advance of actual plant start-up

Safe Comp

Operating P

(outside sur

Final Results(after implementing recommendations)


Compressor Anti-Surge Valve design using HYSYS Dynam


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Compressor Anti Surge Valve design using HYSYS Dynamsimulation

• Better design for safety and reliability of compressor systems, especially:

– Anti Surge Valve Sizing

– Anti Surge Valve Stroke Time

– Anti Surge Controller parameters

• Aspen HYSYS Dynamics model with high level of detail(compressor performance curves, isometrics, anti-surge valves,and controllers)

• More reliable compressor anti-surge circuit design andverification of design

– Pressure controller set-points

– Design conditions

– ControllabilityRef: Mr. Kuroda (JGC Corporation), Aspen User Group Meeting, Japan, May 2006

Business Challenges & Objectives

Solution Overview

Results & Benefits

Test Run-a Suction Blockag

Temperature

40

0

20

40

60

80

100

0 5 10 15Time

C o m p - 2 o u t -

T e m p e r a t u r e C

Test Run-a Suction Block

Percentage ope

00

20

40

60

80

100

0 5 10 15Time

A S V -

P e r c e n t a g e

o p e n %

Test Run-a Suction Blockag

0

1000

2000

3000

4000

5000

6000

7000

0 5000 10000 15

Flow m^3/h

H e a d N - m / K g

Wintershall and InProcess


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Challenge Solution ResultChallenge

Plant revamp required a revision ofthe blow-down strategy

Different simultaneous blow-downscenarios evaluated

What measures are required to allowa complete blow-down within 15

minutes following the API 521directive of blowdown to 50% ofoperating pressure or 6.9 barg within15 minutes.

Ref: Michael Brodkorb Inprocess Group,

AspenTech Global Conference, Washington, D.C., M

Assessing safer Blow-down option by Using Dynamic Process Simulation



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Challenge Solution Result

Aspen Flare System Analyzer to modelthe complete flare header system andmodelling of multiple Flare Tips topredict correct pressure drop

Model the flare header in Aspen HYSYSDynamics for validation of pressuredrop and mass flows

Integrate the Aspen HYSYS Dynamicsmodels of the different processsections with the flare header model



Wintershall and InProcessSafer Blow-down by Using Dynamic Process Simulation



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Challenge Solution Result

Complete Dynamic Model gives a

max flare load of75% (of total capacity)

Dynamic simulation can be usedfor modelling the completeprocess plant as well as the flareheaders and shows additionalcapacity of the existing flare

system.

Low investment solution identifiedreducing the investment for theflare system upgrade significantly(-70%)



Wintershall and InProcessSafer Blow-down by Using Dynamic Process Simulation

Production Services Network


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Production Services NetworkPerform operability analysis

Challenge

Using dynamic simulation to modelemergency system response

Provide evaluation of alternateprocess configurations orequipment failures

Improve safety

Ref: David Francis, PSN

AspenTech User Conference, Houston, May 2



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Challenge

Compressor modeling with AspenHYSYS Dynamics

Emergency Shutdown (ESD) andEmergency Depressuring (EDP)systems via Aspen HYSYSDynamics Cause & Effects





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Challenge

Increased safety margin for compressoruntil confirmed protected against surge.

Eliminated need for Hot Gas Bypassinstallation- Saving @ £ 2 Million capitalexpenditure

Easy identification of trapped inventories

Operator training tools revised based onnew understanding of ESD and EDPsystems

Zone 10 Blowdown curves

0

10

20

30

40

50

60

70

80

90

100

110

120

0 4 8 12 16 20 24

Time (minutes)

P r e s s u r e ( b a

r g )

Zone 10A Zone 10B Zone 10D Zone 10C Fla



Conclusion


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• Numerous Dynamic Simulation Case Studies and Success S• Improved Operability, Safety, Reliability

• Cost Saving – both Capex and Opex

• Proven Benefit


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AspenTech is ranked as a topinnovative growth company

Thank You

05_Dynamic Simulations for Safety and Reliability and Efficient Operations_Gautam

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