Aspen Pipeline Modeling · PDF file– Gas Turbine – Steam Turbine ... bypass or recycle take-off Valve dynamics – Size, speed of operation and characteristics of the recycle or

© 2013 Aspen Technology, Inc. All rights reserved

Compressor Modeling Using Aspen HYSYS Dynamics

Glenn Dissinger, Director of Product Management

Martyn Blanchard, Global Practice Director

Engineering Collaboration Webinar Series

April 23, 2013

© 2013 Aspen Technology, Inc. All rights reserved |

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Ongoing Series of Technical Webinars Engineering Webinars for Education and Best Practices

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April 30, 2013: Vea lo Nuevo de aspenONE Engineering V8

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OTHER RECENT WEBINARS:

Recent webinars on many engineering topics can be viewed on-demand on aspentech.com including:

April 2013: Modeling Solids Dryers and Granulators with Aspen Plus V8

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Common Models & Data

aspenONE Integration

Support Manufacturing & Supply Chain

Conceptual Engineering

Basic Engineering

Detailed Engineering

aspenONE Engineering Industry Leading Products

Aspen Simulation Workbook & Aspen Online Deployment

Aspen Petroleum Downstream & HYSYS Upstream

Aspen Equipment Design & Rating

Aspen Basic Engineering Aspen Capital

Cost Estimator (ACCE)

Aspen Plus Dynamics, ACM & Flare System & Energy Analyzer

Aspen Plus

Aspen HYSYS

Aspen Process Economic Analyzer (APEA)

Detailed Engineering

Aspen Plus

Aspen HYSYS


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aspenONE Engineering V8.0

The New HYSYS

Solids Modeling in Aspen

Plus

Activated Economic Analysis

Activated Energy Analysis

Integrated Exchanger

Design

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Easy To Adopt

• Reduce Time to Get Started for New & Occasional Users by 50%

• Increase Engineering Productivity by 20%

• Reduce Capital & Energy Costs by 10%

• Increase Troubleshooting Efficiency by 20%


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The New HYSYS


Plus




Design

Plant Data View

Easy To Adopt


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Compressor Modeling Using Aspen HYSYS Dynamics

Glenn Dissinger, Director of Product Management

Martyn Blanchard, Global Practice Director


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Disclaimer

Aspen Technology may provide information regarding possible future product developments including new products, product features, product interfaces, integration, design, architecture, etc. that may be represented as “product roadmaps.”

Any such information is for discussion purposes only and does not constitute a commitment by Aspen Technology to do or deliver anything in these product roadmaps or otherwise.

Any such commitment must be explicitly set forth in a written contract between the customer and Aspen Technology, executed by an authorized officer of each company.


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Outline

Overview of HYSYS V8

Compressor Overview

– Types

– What’s Important to Consider

– Surge

Modeling Compressors in HYSYS

– Overview

– Demo

Compressor Trip Case Studies

– Best Practices

– Customer Examples

– AspenTech Global Services & Capabilities

Wrap-Up and Q&A


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New Aspen HYSYS: Easier to Use

Faster to Learn


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Multiple Views

Interactive Analysis

Environments

Streamlined Workflow & Easier Access

Easier to Learn

New Aspen HYSYS


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Add Pure or Hypothetical Components from the Same Form

Properties Environment

Workflow Oriented Ribbon -> Left to Right

Navigation Pane to Easily Browse Objects


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Units of Measure

Simulation Options

Home Ribbon

Solver

Summary and Reports

Analysis Tools

Simulation Environment


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Easy Navigation Pane

Status Icons

One Dockable Model Palette


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Stream Analysis Button in Ribbon

One Click to Analyze


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Case Study Button in Ribbon

Drag & Drop Variables Results in Table and Plots


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Outline


Compressor Overview

– Types


– Surge


– Overview

– Demo


– Best Practices



Wrap-Up and Q&A


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Poll Question


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Compressors – Three Typical Types

Centrifugal • Most common compressor

used in industry

Reciprocating Piston • Used for very high pressures

and low flow rates

Axial • Special compressor used for

very high flow rates and low pressures

Inlet Flow

(acfm)

1

0

102

103

104

106

105

1

10

102

105

103

104

Discharge

Pressure

(psia)

Reciprocating

Centrifugal

Axial

Flow

Reference – Compressor Handbook for the

Hydrocarbon Industries, Gulf Publishing Co., 1979

Compressors are mechanical devices commonly used to increase the pressure of a gas and transport it through a pipeline


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Compressors – Why Worry?

Design Issues • Expensive equipment • Often customized with

long lead times to replace

Operability Issues • Very fast dynamics • Compressor trips are

costly • Compressor surge is very

hazardous • Specialized anti-surge

control systems are common

From both a design and controllability / operability point of view, compressors provide unique issues and challenges


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What is Surge and Why is it Such a Problem?

Results

• Rapid flow reversals (e.g., surge)

• Rapid changes in axial thrust

• High vibration

• Potential damage to rotor seals and bearings

• Catastrophic equipment failures and release of gases to atmosphere

Surge is the point where a centrifugal compressor cannot add enough energy to overcome the system backpressure


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Outline


Compressor Overview

– Types


– Surge


– Overview

– Demo


– Best Practices



Wrap-Up and Q&A


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Two Operating Modes – Centrifugal & Reciprocating

Operating Mode


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Theory - Efficiencies

• Isentropic Efficiency = ratio of isentropic (ideal) power required for compression to the actual power required

Efficiency(%) = (Power Requiredisentropic) / (Power Requiredactual) x 100%

• Polytropic Efficiency = Work for a mechanically reversible (polytropic) process

W = V dP where

W = work

V = volume

dP = pressure difference

For a polytropic compression of a gas from P1 to P2

W = F1 (MW) (n/(n-1)) CF (P1/r1) (P2/P1)((n-1)/n) - 1]

Flow (ACFM) Polytropic Efficiency (%)

Centrifugal 2000 69

5000 72

10,000 73

20,000 74

50,000 75

100,000 76

Pressure Ratio Polytropic Efficiency (%)

Reciprocating 1.5 73

2.0 79

3.0 83

5.0 85


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Centrifugal Compressor Performance Curves

Typically available from the manufacturer as plots of efficiency and head vs. flow capacity of a centrifugal compressor for one or more operating speeds (e.g., RPM)

Head vs. Flow Capacity

Decreasing Speed


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Input for Multiple Head and Efficiency Curves

The Enable Curves checkbox must be clicked

One curve per speed

All curves must use the same efficiency definition (Adiabatic or Polytropic)

Individual curves may be activated or deactivated

Remove any input value for efficiency on the Parameters page


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Input for Multiple Head and Efficiency Curves Able to Add Additional Curves for Other MW Gases

Able to add performance curves for the different molecular weights

Compressor performance impacted by significant shifts in gas molecular weight, particularly for low pressure compressors


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Centrifugal Compressor Performance Limits

Surge Limit – Lower Flow Capacity Limit

– Occurs at the upper end of head vs. flow curve (for a given speed) where the performance curve’s tangent becomes zero

Stonewall Limit – Upper Flow Capacity Limit

– Maximum flow rate for a given speed due to the approach of sonic flow of the gas within the compressor

– Occurs at the lower end of head vs. flow curve (for a given speed)

– Important for capacity control, but not as critical as surge

control


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Surge and Stonewall Curves


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Handling Inertia of Compressor Impeller & Shaft

Used to account for frictional energy loss associated with the impeller and the energy required to accelerate the rotational speed of the shaft Key Equations

I = MR2

EI = I IωI dω/dt Ef = ffric I ω IωI I = rotational inertia EI = power to accelerate impeller Ef = frictional work ω = rotational speed M = mass of impeller and rotating shaft R = radius of gyration


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Surge Controller

Surge controller attempts to maintain a minimum flowrate through the compressor

Surge controller takes more aggressive action if compressor is close to surging

Parameters for surge controller set on Surge Control page on the Parameters tab


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Modeling Linked Compressors & Expanders

Used to model compressors and expanders that are physically connected to the same shaft

• Operate at the same speed or a specified gear ratio

• Total Power Loss can be specified

Notion of upstream and downstream links is arbitrary and determined by the user


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Demonstration


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Outline


Compressor Overview

– Types


– Surge


– Overview

– Demo

Compressor Best Practice & Case Studies

– Best Practices



Wrap-Up and Q&A


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Centrifugal & Axial Compressors – What’s Important

What power will it absorb and what mechanical design does it have? – Back to back casing designs have particular issues

– Axial compressors are not very rugged

– Single small wheel high pressure compressors have less issues than multi-wheel ones

– Surging a 5MW compressor is very different to surging a 40MW one

What driver does it have? – Gas Turbine

– Steam Turbine

– Electric Motor – variable speed or fixed speed

What arrangement are you looking at: – Stages in parallel, series

– Multiple drivers per train or only one?

– How is it controlled?

– What protection is there for high or low pressures, low flows

What range of operating conditions will it be expected to cope with? – Differing gas molecular weights

– Differing ambient temperatures (gas turbine driver)

– Continuous recycle?

– Special start-up conditions (nitrogen, de-frost gas)


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Best Practices for Modelling Compressors What is Needed in a Dynamic Model

Compressor dynamics

– Accurate modelling of speed lines to at least minimum governed speed (don’t just assume the fan laws apply)

– Inertia of all items on the string, must be related to the same speed (watch the units used)

– Driver power decay rate

Accurate capacities/holdups in all pipelines to/from compressor

– Return location of the recycle or hot gas bypass line

– Piping details of the recycle line, both up and down stream in case choking occurs

– Discharge volume up to the NRV after the compressor and the hot gas bypass or recycle take-off

Valve dynamics

– Size, speed of operation and characteristics of the recycle or hot gas bypass valve

– Relative timings and delays if these can be assessed

Valid Boundary Conditions


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Best Practices for Modelling Compressors Compressor Trip Tests on the Dynamic Model

Discuss the basis for the trip tests. Possible scenarios are: Trip from design?

Trip from the surge line just out of recycle ?

Trip at maximum power?

– Depends on expected operation and possible consequences

Examine simulation results with a critical eye

– First make sure you can trust them

If the trajectory isn’t very smooth or there seems to be any sign of instability, halve the sample time and repeat it. Continue to do this until there is no discernible difference between results. If you are inexperienced in dynamics you may want to do this in any case.

– Next gather the facts from the model

How long before it enters surge (if it does)

What is the power at the time it enters?

Does the model predict recovery within a very short period (1 second or so)


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Best Practices for Modelling Compressors Modelling the Compressor under Surge Conditions

The only details you can rely on are the time and power of entry into surge

– No commercially available dynamic compressor model accurately predicts behavior in surge

You may draw some tentative conclusions from the time spent in surge according to the model

– Less than 0.5 seconds on a HYSYS Dynamics model is often unlikely to be real based on feedback from operations

Always discuss with the Compressor Vendor, in the end it is their decision on whether action needs to be taken

Ideally surge should be totally prevented in all cases


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Best Practices for Modelling Compressors Possible Design Changes to Avoid Surge

Minimize the discharge volume

Increase the recycle valve size (within the limits of controllability)

Increase the speed of opening of the recycle valve

Consider a parallel cold gas bypass valve around the recycle valve

Consider a hot gas bypass valve

– Considerations such as leakage, vibration etc. often make this an unattractive option


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Best Practices for Modelling Compressors Modelling the Anti-Surge Control System

Surge control systems are designed to detect the imminent start of surging, and prevent the compressor from reaching this operating condition

Basic Strategy – Open a surge recycle valve that will allow outlet flow from the compressor to recycle back to the compressor inlet, thus providing a flow rate through the compressor above the minimum surge limit.

For conceptual and FEED studies, use the HYSYS Anti-Surge controller

For detailed design, there may be a need to use a proprietary system:

– CCC, Dresser Rand, Man-Turbo, Solar, Triconex etc

Most of these systems use multiple control lines, linking between serial and parallel units, surge protection by moving lines, various characterizers, algorithm selection etc. and can be quite complex to set up

In some cases the Vendor will provide software (at a cost) or an emulator; in others just the algorithms are used and settings


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Challenge Solution Results Challenge

Liquefied Natural Gas (LNG) plant revamp design verification

Ensure compressor anti-surge system will provide adequate protection from the risk of damage under all scenarios

Verify controllability of the compressors during unit upsets, start-up, shutdown and normal operation scenarios

Check the start-up and shutdown procedures for compressors

Verify compressor systems and equipment design conditions

Ref: Siti Rafidah Moslim, Petronas, Vikas Singh, AspenTech, aspenONE Global Conference, Boston, May 2010

PETRONAS – Malaysia LNG Dynamic Simulation for LNG Plant Revamp


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Challenge Solution Results


Challenge

Aspen HYSYS Dynamics model to represent actual equipment, piping arrangements and controls

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

– Torque and power characteristics of the gas turbines to reproduce precise conditions during start-up and shut down

Over 45 Scenarios were simulated and analyzed in an iterative process using HYSYS Event Scheduler



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Challenge

• Better sizing of recycle valves and bypass valves based on all failure scenarios compared to steady state

• Relieving loads confirmed for various scenarios which form the basis for key relief valve sizing

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

Safe Compressor

Operating Points

(outside surge line)

Final Results

(after implementing recommendations)



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Challenge Solution Results Challenge

Compressor operation and control critical to success of the overall gas processing project

Customer determined that a dynamic simulation study was essential to verify the performance of the compressors and the associated control systems

JGC – Ourhoud Algeria Gas Processing Facility Verification of Compressor Performance


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Challenge

AspenTech Global Services commissioned to develop a Aspen HYSYS Dynamics model to represent actual equipment, piping arrangements and controls

– 5-stage compression train

– Detailed vendor (Nuovo Pignone) compressor curves implemented

– Production manifold & injection manifold modeled to match piping holdups

Many scenarios were simulated and analyzed covering trips, feed changes, start-ups etc.

The project was completed to a fixed budget and was executed within 12 weeks. This met JGC's design and construction schedule and enabled equipment changes to be ordered.


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Challenge

• The study revealed many aspects that were significant to the operation and control of the compressors, one example below:

• In the original control scheme the recycle from the Lift Gas Compressor (LGC) was taken downstream of the cooler. With a large pressure drop a large Joule Thomson effect was observed so that the feed to the Booster Compressor (BC) cooled and the heavy components dropped out in the suction drum. In order to avoid this it was recommended that the recycle be taken upstream of the cooler with a smaller valve on temperature control to prevent the suction temperature increasing too much. This modification was subsequently agreed, implemented and proved to work well.


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Global Services Expertise

AspenTech Professional Services is organized around five regions and four global technology practices to deploy process and business solutions based on aspenONE products

Service Areas

Process Engineering/ Real-time Optimization

Advanced Process Control

Production Management & Execution

Supply Chain Management

Regions

Asia Pacific (APAC)

Europe (EURA)

Middle East Africa (MENA)

North America (NORAM)

Latin America (LATAM)


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AspenTech has 29 office locations in 20 countries and 142 Professional Services employees to effectively serve our customers

on a global basis. Partner locations further expand our global delivery network.

NALA

56

EMEA

48

APAC

38

142 Total

* As of April 2013 AT office locations

Key partner locations

Service Delivery Centers


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Outline


Compressor Overview

– Types


– Surge


– Overview

– Demo


– Best Practices



Wrap-Up and Q&A


49


The New HYSYS


Plus




Design

Plant Data View

Easy To Adopt


50

Online Training at Your Fingertips

aspenONE Engineering


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New Online Training Courses for aspenONE Engineering V8


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Learn More

http://www.aspentech.com/


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OPTIMIZE™ 2013 Global Conference

Join us in Boston for the industry’s must-attend event!

OPTIMIZE 2013 6 – 8 May 2013

The Westin Waterfront Hotel

Boston, MA USA

For more information, visit www.aspentech.com/agc

http://www.aspentech.com/agc


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Optimize 2013 Global Conference

Foster Wheeler UK Refinery wide modeling with Aspen HYSYS

Jord International Optimization of a mixed refrigerant LNG process

Kuwait National Petroleum Company Refinery energy reduction using Aspen HYSYS

May 6-8, 2013

See these and over 50 additional presentations and training sessions

Inprocess Reliability of Dynamic Simulation to Reproduce Plant Dynamics


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What Next?

Get more information now

– Additional resources available at:

http://www.aspentech.com/products/aspen-hysys.aspx

http://www.aspentech.com/products/aspen-hysys-dynamics.aspx

– Videos also available at: www.youtube.com/user/aspentechnologyinc

Contact info for today’s presenters and hosts – Glenn Dissinger [email protected]

– Martyn Blanchard [email protected]

– Luisa Herrmann [email protected]

– Ron Beck [email protected]









http://www.youtube.com/user/aspentechnologyinc

mailto:[email protected]





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Questions?

Documents

Aspen Pipeline Modeling · PDF file– Gas Turbine – Steam Turbine ... bypass or recycle take-off Valve dynamics – Size, speed of operation and characteristics of the recycle or