Recent Experiences in Applying Process Integration Techniques to Oil - - PowerPoint PPT Presentation

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PIL: The experts in process improvement technologies

Recent Experiences in Applying Process Integration Techniques to Oil Refineries

• Dr. Steve Hall

Tel: +44 161 918 6789 Mob: +44 7534 721862 steve.hall@processint.com www.processint.com

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PIL: The experts in process improvement technologies

This Presentation:

• Process Integration Limited
• A Personal Perspective
• Typical PI Refinery Projects
• Consider 2 Refinery Case studies
• Hydrogen management in a modern refinery
• HEN retrofit including anti-fouling equipment
• Summary

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PIL: The experts in process improvement technologies

PIL uses Advanced Process Improvement Technologies

Process Integration Ltd

• a spin-out company from Manchester University’s

‘Centre for Process Integration’

PIL provides: Software, Training, Consultancy to its clients

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PIL: The experts in process improvement technologies

Personal Perspective:

• Comparing 2013 with 1992, major steps forward:
• Marriage of graphical/insight and mathematical approaches
• Decomposition approaches
• Improved link between process

integration and simulation tools

PI

MIN LP

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PIL: The experts in process improvement technologies

Personal Perspective: Today’s Capabilities

• Today’s tools are more in-line with how

chemical/process engineers work

• Specific important areas of application
• Operational optimisation
• Control of retrofit projects

(still some way to go though)

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PIL: The experts in process improvement technologies

Typical PI Refinery Projects

• Energy savings
• Operational optimisation – process units
• Operational optimisation – utility units
• Hydrogen management
• Water minimisation

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PIL: The experts in process improvement technologies

Typical PI Refinery Projects

• Energy savings
• Operational optimisation – process units
• Operational optimisation – utility units
• Hydrogen management
• Water minimisation
• = This presentation

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PIL: The experts in process improvement technologies

Consider 2 Case Studies:

• Demonstrate the practical application of new process

integration technologies

• Case Study 1: Hydrogen management
• Shows new techniques with practical modifications
• Case Study 2: HEN retrofit techniques used in Crude Unit

Revamp

• Shows both new and old techniques in action

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PIL: The experts in process improvement technologies

Case Study 1: Introduction

• Case Study 1: Applying hydrogen pinch techniques to whole

refinery

• Sinopec refinery:
• Crude 13.5 MTPA, Ethylene 1 MTPA
• Two objectives
• Operational optimisation (no investment)
• Revamping (with investment)
• Project shows both new and modified hydrogen integration

techniques

Acknowledgement: LPEC

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PIL: The experts in process improvement technologies

HCU DHT KHT CNHT NHT HDA SR Import CCR

Fuel

SR steam reformer CCR catalytic reformer HCU hydrocracker DHT diesel hydrotreater KHT kerosene hydrotreater CNHT cracked naphta hydrotreater NHT naphta hydrotreater HDA hydrodealkylation

Case Study 1: Hydrogen Distribution System

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PIL: The experts in process improvement technologies

Gasoline & Diesel Regulations

• Lower sulphur – more hydrotreating
• Lower benzene – less reforming
• Lower aromatics

More hydrogen used, less hydrogen generated

Greater demands on hydrogen system

Case Study 1: Challenges Facing Refineries

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PIL: The experts in process improvement technologies

This is a Process Integration Conference: Let’s do some targeting ! Target minimum hydrogen consumption…

Case Study 1: Targeting Minimum Hydrogen

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PIL: The experts in process improvement technologies

Step 1: Identify sources and sinks of hydrogen:

Simplified diagram of consumer

Purge (P) Liquid feed Liquid product Make-up (M) Recycle (R) Reactor Separator Sink Source

Case Study 1: Targeting Minimum Hydrogen

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PIL: The experts in process improvement technologies 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 50 100 150 200 250 300

Flowrate (MMscfd) Purity (-)

Case Study 1: Targeting Minimum Hydrogen

Step 2: Draw hydrogen purities/flow plot:

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PIL: The experts in process improvement technologies

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 50 100 150 200 250 300

Flowrate (MMscfd) Purity (-)

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 10 20 30 40 50

Hydrogen surplus (MMscfd) Purity (-)

+ _

Case Study 1: Targeting Minimum Hydrogen

Step 3: Draw purity vs hydrogen surplus diagram Actual Hydrogen Surplus

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PIL: The experts in process improvement technologies

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 10 20 30 40 50

Hydrogen surplus (MMscfd) Purity (-)

Target minimum hydrogen flow:

Hydrogen Pinch

Case Study 1: Targeting Minimum Hydrogen

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PIL: The experts in process improvement technologies

How should we exploit purification units (pressure swing adsorption, membranes)?

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

2

4

6 8 10 12

No Benefit Possible Benefit

Hydrogen surplus / MMscfd

Certain Benefit Purifier

Case Study 1: Using the pinch curves

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PIL: The experts in process improvement technologies

This provides us with an “ultimate” target, but ignores :

• pressure constraints
• compressor requirements
• piping requirements
• practical constraints
• network complexity
• impurities (lumped as CH4)

Case Study 1: Hydrogen Pinch Analysis

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PIL: The experts in process improvement technologies



Use MINLP to model other factors



Combine graphical and mathematical techniques to produce practical retrofit designs



Include constraints, e.g.

• H2/Oil ratio entering reactor ≥ lower bound
• H2 partial pressure in the gas mixture (makeup hydrogen + recycle)

≥ lower bound

Case Study 1: We need to consider the impurities

Reactor

Recycle Makeup hydrogen Liquid

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PIL: The experts in process improvement technologies

Case Study 1: Modified Hydrogen Network Optimisation

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PIL: The experts in process improvement technologies

Case Study 1: Hydrogen technology Enabled in Software

Embedded physical properties models improve accuracy

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PIL: The experts in process improvement technologies

A basic design from the feasibility study

• f de-bottlenecking project

1.2 MPa main 2.4 MPa main 4.5 MPa main

Case Study 1: Base Case Network

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PIL: The experts in process improvement technologies



Hydrogen supply very close to target

• Based on the current hydrogen purifying strategy



BUT, over 25000 Nm3/h pure hydrogen is lost

Increase purification

H2 Surplus H2 Purity

Case Study 1: Hydrogen Pinch Diagram

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PIL: The experts in process improvement technologies

 Objective: minimise total operating cost (TOC)

• TOC = H2 generation + compression - Fuel gas value
• Fuel gas = H2 from providers – Net H2 used by consumers

 H2 consumption in each consumer is assumed to be fixed  Value of fuel gas based on net heating value  H2/Oil ratio and H2 partial pressure in each hydro-processor cannot

be decreased

 Other constraints

• Keep certain parts of the hydrogen network as they are in the

existing network (guided by plant engineers)

• Priority given to recovering hydrogen in purges from various

hydrogen consumers

Case Study 1: Optimisation

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PIL: The experts in process improvement technologies



# 4 HTU is changed from once-through to complete recycle



Higher compression duty



Lower total hydrogen supply



Total operating cost reduced by 3.45 MM$/yr.



No investment

No new purification unit Case Study 1: Optimisation Scenario 1

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PIL: The experts in process improvement technologies

New PSA + existing membrane



Optimised new PSA capacity: around 10000 Nm3/h



Total hydrogen supply can be reduced by 14500 Nm3/h



Capital cost estimated: 4.9 MM$/yr



Total operating cost reduced by 10.1 MM$/yr



Simple payback = 0.5 yrs

Case Study 1: Optimisation Scenario 2

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PIL: The experts in process improvement technologies



Optimised new PSA capacity: around 16000 Nm3/h



Total hydrogen supply can be reduced by 14627 Nm3/h



Capital cost estimated: 7.0 MM$/yr



Total operating cost reduced by 10.2 MM$/yr



Simple payback = 0.7 yrs

Larger PSA + turn off existing membrane Case Study 1: Optimisation Scenario 3

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PIL: The experts in process improvement technologies

Case Study 1: Summary of Results

Base case Optimisation scenarios Scenario 1 Scenario 2 Scenario 3 Total H2 supply, Nm3/h 271935 267786 257393 257308 Net H2 loss, Nm3/h 25247 21202 11069 10986 Membrane inlet, Nm3/h 10460 10460 10460 Membrane outlet, Nm3/h 5518 5518 5518 PSA inlet, Nm3/h 22541.9 28060 PSA outlet, Nm3/h 10711 15477 Fuel gas flow, Nm3/h 37433 33284 22891 22806 H2 concentration in fuel gas, v% 67.40% 63.70% 48.40% 48.20% Makeup compression duty, kW 38627 37740 39205 39062 Recycle compression duty, kW 17647 18005 18005 18005 Total operating cost: MM$/yr 379.6 376.2 369.6 369.4 Capital investment: MM$/yr 4.87 7.00 Pay back time: year 0.48 0.69

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PIL: The experts in process improvement technologies

 Combine pinch analysis and mathematical programming for a

practical hydrogen network retrofit

 Fully understand practical constraints in refinery hydrogen

network design and retrofit

 Add physical property library for maximum accuracy  Some further work needed on impurities modelling  Ensure that the user drives the optimisation

Case Study 1: Summary

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PIL: The experts in process improvement technologies

• Case Study 2: Applying PI techniques to revamp a crude

preheat train and mitigate fouling

• Petrochina refinery
• Retrofit design required to save energy
• Ultra-sonic antifouling units used
• Project shows both new and old heat integration techniques
• Acknowledgement: Dr Lu Chen, PIL

Case Study 2: Introduction

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PIL: The experts in process improvement technologies

Retrofit of the HEN is complex:

• MINLP problem
• Non-convex behaviour
• Most difficult to solve
• Practical constraints only make it more difficult
• Ref: Biegler and Grossmann, Comp Eng Chem 2004

Change flows in stream splits Re-order some heat exchangers Add shell to heat exchangers Change stream temperatures where possible

Case Study 2:

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PIL: The experts in process improvement technologies

• Smith, Jobson and Chen, 2010
• Builds on Network Pinch Approach of Asante and Zhu
• Considers:
• non-constant thermal properties in design decisions
• stream split ratios
• potential modifications based on cost
• Search for structural changes and capital-energy optimisation

combined into a single step

• Used in this case study for retrofit

Case Study 2: ‘Modified Network Pinch Approach’

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PIL: The experts in process improvement technologies

Fouling makes it harder:

• Energy costs
• Pressure drops
• Corrosion
• Operability
• Equipment failure
• Throughput
• Costs

Case Study 2: Fouling

Time CIT, Deg.C 284 281 280

After Cleaning Mid Period Fouled

Coil Inlet Temperature

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PIL: The experts in process improvement technologies

Case Study 2: Mitigating Fouling

There are things we can do:

• Provide more HX area
• Clean HX’s
• Design carefully
• Use additives
• Tube/shell side enhancement
• Choose carefully

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PIL: The experts in process improvement technologies

Ultrasonic Antifouling Units (UAUs)

• Produce a variety of pulsed ultrasonic signals to transducers
• Transducer emits series of low power, low frequency

(inaudible) sound waves

• Resonance within HX keeps liquid moving at metal surfaces
• Clean, easy to install, cheap to run

Case Study 2: Another Option Under Trial

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PIL: The experts in process improvement technologies

Ultrasonic transducers in place

Case Study 2: Ultrasonic Antifouling Units

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PIL: The experts in process improvement technologies

• Typical performance of test unit
• Slurry decant oil / reactor feed HX in FCC unit

Case Study 2: UAUs in Practise

0,002000 0,004000 0,006000 0,008000 0,010000 0,012000 0,014000 0,016000 0,018000 0,020000

Fouling resistance (hr·m2·K)/kcal

Date

No increase in fouling over 9 months

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PIL: The experts in process improvement technologies

• Typical crude unit has 20-30 heat exchangers
• Not economic to install UAU on all HXs
• Use UA or A sensitivity analysis to identify

candidate UAU locations:

Case Study 2: Sensitivity Analysis

249 100 100 259 128 128 96 170 170 106 270 270

2

182.9 *Q :697 A:39

2

183.4 *Q :697 A:39

C

100 *Q :875 A:36

1

249 *Q :127 A:11

1

214.1 *Q :127 A:11

3

186 *Q :798 A:95

3

239 *Q :798 A:95

4

132.5 *Q :677 A:109

4

170 *Q :677 A:109

C

128 *Q :57 A:3

205.7

H

270 *Q :838 A:64

HOT 1 HOT 2 COLD 1 COLD 2

May choose to install UAU on Exch 2

Note: Sensitivity analysis was

• ne of the first UMIST PhDs

Overall heat transfer coefficient * Area

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PIL: The experts in process improvement technologies

• PetroChina refinery crude unit, > 100,000 bbl/d

Case Study 2: Back to the Study

• 2 stage desalter

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PIL: The experts in process improvement technologies

• HEN: Total Area > 20,000 m2

Case Study 2: Existing HEN

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PIL: The experts in process improvement technologies

• Operating data for HXs collected over 3 operating regimes:
• After cleaning
• Mid period
• Extremely fouled
• Conclusions – HEN already

fouled during mid period

Time CIT, Deg.C 285 281 280

After Cleaning Mid Period Fouled

Coil Inlet Temperature

Case Study 2: HEN Fouling Character

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PIL: The experts in process improvement technologies

• HEN retrofit using Modified Network Pinch Approach
• Energy targeting suggests CIT can be increased from

280 to 298 Deg.C

• Furnace duty can be reduced by 9.4 MW
• 3 revamp options possible:
• Add 1000, 2000 or 4000 m2 area
• Options discussed with site --- 2000 m2 option chosen

Case Study 2: HEN Retrofit

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PIL: The experts in process improvement technologies

• Add 1 new HX 1010 m2, re-allocate 2 HXs w/ extra area
• Add 1800 m2 in 1 new HX and increase area in 3 others

Actual CIT increased to 291.4°C Reduced Furnace Duty by 6.3 MW

Case Study 2: Retrofit Design

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PIL: The experts in process improvement technologies

Use UA sensitivity graphs to decide candidate UAU locations

Case Study 2: UAU Placement

• Units with largest ∆CIT / ∆A
• Units with history of significant fouling

4 UAUs selected (shaded)

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PIL: The experts in process improvement technologies

270,00 275,00 280,00 285,00 290,00 295,00 300,00 305,00 01-10-2011 31-10-2011 30-11-2011 30-12-2011 29-01-2012 28-02-2012 29-03-2012

Daily average CIT °C Date

On-line optimisation increased CIT at start No real drop in performance over monitored period (6 months)

Case Study 2: HEN Performance after Revamp

Save $2.8 mill/yr, Implemented Oct 2011

Note: No change made to distillation

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PIL: The experts in process improvement technologies

Performance after revamp significantly improved and sustainable

275 280 285 290 295 300 305 1 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 Monthly average CIT °C Operating month after start-up

before after

Case Study 2: Comparison of Performance

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PIL: The experts in process improvement technologies

• Crude unit revamping has been done over many years
• Modified Network Pinch design method (new) has been used

effectively

• UA sensitivity analysis (old) helps assess how area changes

affect the overall HEN

• Ultrasonic antifouling units (UAUs) provide a new technology to

address fouling

• UA sensitivity analysis helps identify where to locate UAUs
• Combining these new technologies provides an exciting new

approach to crude unit revamping

Case Study 2: Summary

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PIL: The experts in process improvement technologies

• Significant advances for a practising engineer over recent years
• Marriage between graphical and math programming
• Decomposition techniques to simplify the maths
• Closer link with simulation tools
• Major advances in terms of refineries
• Hydrogen management
• Operational optimisation
• Energy reduction and fouling mitigation using new

equipment solutions

Overall Summary

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PIL: The experts in process improvement technologies

• Ongoing challenge – keep

developing the maths while keeping the engineer in the driving seat

A Final Note

MINLP

Thank You