energy optimisation in ng processing plants_aiche 2016 rev 1

8/16/2019 Energy Optimisation in NG Processing Plants_AIChE 2016 Rev 1

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P I L : T h e e x p e r

t s i n p r o c e s s i m p r o v e m e n t t e c h n o l o g i e s

+44 161 9740090www.processint.com Station House, Stamford New Road, Altrincham, Cheshire, WA14 1EP, UK

Energy

Optimisation

in Natural Gas

Processing Plants

Contact: Leandro Labanca

Dr Yuhang LouTel: 0161 974 0090

[email protected]

www.processint.com


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P I L : T h e e x p e r t s i n p r o c e s s i m p r o v e

m e n t t e c h n o l o g i e s

Outline

1. Overview of Process Integration Ltd (PIL)

2. Natural Gas (NG) plant design

3. Heat Exchanger Network (HEN) design and optimisation

4. Utility system design and optimisation

5. Energy optimisation studies in NG plants

6. Industrial case study

7. Conclusions

8. Questions and Answers


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Spin-out company of The Centre for Process

Integration (CPI) of The University of Manchester

Successfully applied Advanced ProcessImprovement Technologies in flagship

projects across the world

1. Overview of PIL

PIL provides:

• Consultancy services and products to

solve business problems and improve

margins

• Software to provide easy evaluation of

business problems and enable the

solutions

• Technology partnerships to leverageknowledge and experience and provide a

competitive advantage

ProcessIntegration

Ltd

Consultancy

TrainingSoftware


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2. NG Plant Design

Raw Gas Inlet Facilities Acid GasRemoval

Dehydration Unit

Metal RemovalNGL RecoveryFractionation

Train

Utilities & Offsites Gas Sales

Treatedto

removeimpurities

Cleanand safeenergy

fuel

NaturalGas


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3. HEN Design and Optimisation

A process has heating and cooling demans that need to

be satisfied Process-to-Processheat recovery?

Should be heated byUtilities?

Which Utilities?Which is the best

match?

How much duty?What equipment to

choose?


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PinchTechnology

EnvironmentalPolicies

High EnergyPrices

Optimal design of HENs improves heat

recovery and reduces the operating costs

and carbon footprint.


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Capitalcost

Heatrecovery

Multiple operating scenarios

Accurate model needs to be developedto evaluate different configurations and

operating conditions

i-HeatTM

200

220

240

260

280

300

0 20 40 60

F [

t / h ]

Days


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4. Utility System Design and Optimisation

• Meet energy and power demands on site

Combined Heat and Power

• Boiler

• Gas Turbine

• Steam turbine• Letdown

• Deaerator

• BFW preheater

• Etc

Power and SteamImport / Export

Steam Distribution

• Steam pipeline

network

Processes

• Process steam generators

• Process steam heaters

• Process steam drivers

• Etc


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• Meet energy and

power demands onsite

• Different configurations can be

developed depending on:

Availability and costs of

resources

Capital investment

Reliability


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• Requires stable and efficient performance

• Designed to cope with changes in:

ProcessOperations

• Operating load

changes

• Start-up / Shutdown

• Maintenance cycles

AmbientConditions

• Daily

• Seasonal

Economics

• Power tariffs

• Fuel prices

• Contractual

agreements

Leads to over-designsand redundancies

Capital cost


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• Some methodologies to obtain improved designs

Accurate model needs tobe developed to evaluatedifferent configurations

CogenerationAnalysis

Total SiteAnalysis


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• The model should consider interactions with processes

CombinedHeat &Power

(CHP)

SteamDistribution

IndividualProcesses

The Model

i-SteamTM

5 E O ti i ti St di i NG


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5. Energy Optimisation Studies in NGPlants

• Pinch Analysis

• Process-to-process heat exchanger

• Heaters and coolers from site utilities

• Individual process optimisation

Process

• Total Site Analysis

•Co generation targets

• Selection of mechanical drivers

• Site-wide optimisation

Utility Systems

5 E O ti i ti St di i NG


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5. Energy Optimisation Studies in NGPlants

7. Economic evaluation of combined improvements

6. Energy optimisation for site-wide utility system

5. Cross-process heat recovery

4. Heat integration study for individual process units

3. Process unit screening

2. Data review and reconciliation

1. Data collection

Standard procedure for energy optimisation in

Natural Gas processing plants


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r t s i n p r o c e s s i m p r o v e m e n t t e c h n o l o g i e s

Project: New design of NG processing plant that imports steam avarious pressure levels from a co-generation plant nearby.

Objective: Heat integration and Energy Optimisation Study

6. Industrial Case Study

NG ProcessingPlant

Co-generationPlant

Condensate

Steam


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Step 3: Process unit screening

• Process units containing heat exchangers were identified

• Thirteen out of 23 units were selected for the energy optimisation study

Step 4: Heat integration study for individual process units

• Three units discussed to demonstrate the benefits of heat integration

Inlet facilities

Acid gasremoval units

Dehydrationunits

NGLrecovery

units

Fractionationunits


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6. Industrial Case Study – Unit 1


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Utility Type UtilityHeat

Exchanger Duty [kW]

Hot LP Steam

SH 01 1,865

SH 02 20,950

SH 03 2,452

Total 25,267

Cold Air

AC 01 19,490

AC 02 3,012

Total 22,502


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Pinch analysis carried out to identify the minimum energy targe

for both the hot and cold utilities

Pinch

Cold Utility Target


Hot Utility Target

Duties Existing [kW] Target [kW]

Hot 25,267 20,030

Cold 22,502 17,265

Saving Potential: 5,237 kW


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• Four heat exchangers found to have cross pinch heat transfer

• Design improvement achieved by reducing cross pinch duties within HEN

PROJECT1Reduce cross pinch heat transfer in AC 01


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Air cooler duty reduced by 1,865.4 kW

New Heat Exchanger


PROJECT1: New heat exchanger ‘‘New HX 01’’ added to recove

heat between Hot Stream 2 and Cold Stream 2.

SH 01

SH 01 removed


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Unit 2 composed of 20 HXs

• Practical constraints limiting opportunities of heat integration were considered

Simplified HEN:


Heat Exchanger Cross PinchDuty [kW]

SH 01 1,409

SH 02 642


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New Heat Exchangers

Duty reduced by 642 kW

Duty reduced by 1,409 kW

Duty reduced by 2,051kW

PROJECT2

Reduce cross pinch heat transfer in SH 01 and SH 02


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CapitalInvestment of

3.92 MM$

EnergySaving of

2.77 MM$/yr

Considering all trains:

The project was found economically attractive• 20-year Net Present Value (NPV) = 38.8 MM$

• Internal Rate of Return (IRR) = 72.8%

PROJECT2 was recommended for further investigation.


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Pinch analysis: Existing HEN design meets energy targets.

Process modification: Pre-heating feed reduces reboiler LP steamconsumption by 2,198 kW.

Air Cooler

Preheater(heat recoveredfrom Process)

LP SteamReboiler

6 C S 3


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EnergySaving of0.37 MM$/yr

Energy Savingof 0.37 MM$/yr

Considering all trains:

CapitalInvestment of

0.20 MM$

EnergySaving of

0.37 MM$/yr

The project was found economically attractive• 20-year Net Present Value (NPV) = 6.0 MM$


PROJECT3 was recommended for further investigation.

6 I d t i l C St d


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Step 5: Cross-process heat recovery

• Thermodynamically, there is potential to reduce utility usage• Practical constraints and operating independence of processes limited the

opportunities to recover heat across processes

Step 6: Energy optimisation for site-wide utility systemProcess SteamGenerators

HP Header

LP SteamImport

LP Header

Process SteamConsumers

Steam TurbineGenerators


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6 I d t i l C St d


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Other options to improve the overall performance and economics

of the natural gas processing plant• Driver selection

• Optimisation of refrigeration systems

• Chilled water integration


6. Industrial Case Study–

Combined


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Step: 7 Economic evaluation of combined improvements

Combined overall performance of the site including the energy

saving projects:

• Annual operating costs reduced by more than 16 MM$

• 20-year Net Present Value (NPV) = 284.1 MM$


y

improvements

23 Individual

Processes

13 Process

Screening11 Energy Saving

Projects7 Cost-Effective Projects

7 Concl sions


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• Natural Gas processing plants used for removing impurities, such as water,

carbon dioxide and hydrogen sulphide.

• Energy optimisation procedure has been developed that significantly

enhances the economic benefits:

Optimisation considering the integration between individual processes and

utility systems

Cost-effective projects identified and evaluated to save energy consumption in

individual process units.

Impact of energy saving projects evaluated on the utility system.

Industrial case study illustrates the benefits of the integrated procedure.

• Advanced design tools for heat integration and energy optimisationsignificantly improves the energy performance and process economics of a

NG Processing Plant.

7. Conclusions

7 Questions and Answers


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7. Questions and Answers

THANK YOU

energy optimisation in ng processing plants_aiche 2016 rev 1

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