Feasibility Study of Flare Reduction Concept for Operating LNG Trains by Dynamic Simulation

© Chiyoda Corporation 2017, All Rights Reserved.

Presented by Kyoko Kamei

6 April, 2017

2

1. Introduction

2. Qatargas Flare Reduction Project (Off-spec Recycle)a) Overviewb) Conceptc) Upset Scenariod) Expected Concerns

3. Dynamic Simulationa) Model Scopeb) Simulation Resultsc) Key Results

4. Conclusion

5. Acknowledgements

Agenda

1. Introduction

4

EPC Contractor

Est. 1948

HQ - Yokohama, Japan

Designed and constructed LNG (Liquefied Natural Gas) plants for 35 years

Completed six mega LNG trains in Qatar in 2010

Developing efficient LNG process and protecting the environment

Yokohama-Minatomirai

1. Introduction

5

Dynamic Simulation

Concerns

✓ Troubleshooting

✓ Environmental Requirement

✓ Operation / Profit Improvement

Plant Design by Steady State

Simulation

Design

VerificationChiyoda’s Solutions

Data Review

Planning

FEEDOperationEPC

Design Know-how

1. Introduction

FEED: Front End Engineering Design, EPC: Engineering Procurement and Construction

Utilize Dynamic Simulation

Valuable Solution Providing Tool

2. Qatargas Flare Reduction Project (Off –spec Recycle)

7

Overview

• Qatar National Vision 2030 and Qatargas Direction Statement provide direction to reduce flaring.

• Qatargas and Chiyoda Almana are carrying out a “Flare Reduction Project” to mitigate CO2

emissions since 2009.

• Dynamic simulation verified feasibility of one of the concepts (Off-Spec Recycle).

Dynamic Simulation is

a good solution!

Scope includes 4 LNG trains including upstream

facilities

Complicated self-heating recovery systems and

control systems affecting each other

Expander-Compressor process in NGL system

CO2: Carbon Dioxide, Spec: Specification

2. Qatargas Flare Reduction Project (Off –spec Recycle)

8

Concept

Current OperationFlaring during start-up

takes several hours

Huge amount of gas

is flared leading to

higher CO2 emission

2. Qatargas Flare Reduction Project (Off –spec Recycle)

AGR: Acid Gas Removal, NGL: Natural Gas Liquid

Inlet

Facility

Feed

Gas

(QG 3&4)

AGRNGL Recovery

& Liquefaction

Normal Operating Train-7 FFF

NGL

LNG

Off-Spec Gas

Acid Gas

Inlet

Facility

Feed

Gas

(QG 2)

Starting up Train-4

Dehydration

Water

AGRNGL Recovery

& Liquefaction

Normal Operating Train-5 FFF

NGL

LNG

Acid Gas

Dehydration

Water

AGRNGL Recovery

& Liquefaction

Normal Operating Train-6 FFF

NGL

LNG

Acid Gas

Dehydration

Water

AGR NGL Recovery

FFF

NGL

LNG

Acid Gas

Dehydration

Water

9

Recycle off-spec gas

instead of flaring

Need to assess the impact of a

sudden loss of off-spec recycle gas

due to a trip of the start-up train

×

Concept

2. Qatargas Flare Reduction Project (Off –spec Recycle)

Inlet

Facility

Feed

Gas

(QG 3&4)

AGRNGL Recovery

& Liquefaction

Receiving Train-7 FFF

NGL

LNG

Acid Gas

Inlet

Facility

Feed

Gas

(QG 2)

Starting up Train-4

Dehydration

Water

On/Off

valve

Off-Spec Recycle Gas

AGRNGL Recovery

& Liquefaction

Normal Operating Train-5 FFF

NGL

LNG

Acid Gas

Dehydration

Water

AGRNGL Recovery

& Liquefaction

Normal Operating Train-6 FFF

NGL

LNG

Acid Gas

Dehydration

Water

AGR NGL Recovery

FFF

NGL

LNG

Acid Gas

Dehydration

Water

10

Upset Scenario: Loss of Recycle Gas from Starting-up Train

What happens to the operation of the receiving Train (Train-7)?

Tr-7 inlet flow reduces ⇒Recovered by increasing flow from Inlet facility

Tr-7 inlet gas composition becomes heavier

2. Qatargas Flare Reduction Project (Off –spec Recycle)

Inlet

Facility

Feed Gas

(QG 3&4)

AGRNGL Recovery

& Liquefaction

On/Off

valveReceiving Train-7 FFF

NGL

LNG

Off-Spec Recycle Gas from NGL

Acid Gas

Normal Operating Train-6

Dehydration

Water

60% Heavy Flow→100%

40% Lean Flow→0%

Flow & composition disturbance

(Rapid change) @ Train-7 AGR inlet!

11

Inlet

Facility

Feed Gas

(QG 3&4)

AGRNGL Recovery

& Liquefaction

On/Off

valveReceiving Train-7 FFF

NGL

LNG

Off-Spec Recycle Gas from NGL

Acid Gas

Normal Operating Train-6

Dehydration

Water

60% Heavy Flow→100%

40% Lean Flow→0%

Concerns in Inlet Facility, AGR, and Dehydration

• Determine if stable pressure and flow rate are maintained for good

separation performance

Evaluate Controller

Performance

2. Qatargas Flare Reduction Project (Off –spec Recycle)

12

Feed Gas

NGL

Lean Gas

Expander/Compressor

Deethanizer

J-T Valve

Concerns in NGL Recovery (Typical Scheme)

Disturbances in feed

flow & composition

Performance of Deethanizer

Heavy component in LNG

Light component in NGL

Stability of Controllers

Multiple pressure controllers

Expander-Compressor speed controller

Deethanizer liquid level controller

Temperature excursions in Aluminum

Blazed Heat Exchangers

2. Qatargas Flare Reduction Project (Off spec Recycle)

3. Dynamic Simulation

14

Dynamic Simulation Model Scope

Prepared for Train-4 and 7

Adjusted process variables of Train-7 to

meet actual operating conditions during

start-up when off-spec gas is recycled

from Train-4 NGL Recovery Unit

Tested whether Train-7 can maintain

stable operation & Train-4 can safely

shutdown without problems in case of

loss of recycle gas to receiving train

3. Dynamic Simulation

×

Inlet FacilityFeed Gas

(QG 3&4)

AGR &

Dehydration

NGL Recovery

& Liquefaction

Receiving Train-7

Normal Operating

Train-6

FFF

NGL

LNG

Recycle Gas

Acid Gas

& Water

Inlet FacilityFeed Gas

(QG2)

Starting up Train-4

AGR &

DehydrationNGL Recovery

NGLAcid Gas

& Water

Normal Operating

Train-5

On/Off

valve

15

3. Dynamic Simulation

16

Simulation Results with Current Configuration

System ResultsRecommendations

(software modification)

AGRAGR Absorber pressure decreases below the allowable minimum

Control system should be updated

NGLLean gas pressure decreases, which opens the expander IGV leading to JT operation

NGLDeethanizer bottom (NGL) flow reduces to zero for a while (below the minimum turndown rate of 40% flow) Deethanizer reboiler operation

should be modified to respond to the rapid change of feed gas composition

NGLDeethanizer bottom liquid level fluctuates

LiquefactionHeavy component in LNG exceeds the allowable range

Found that operational disturbances of the receiving

train could not be avoided

3. Dynamic Simulation

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Key Results

(a) Pressure Fluctuations in AGR Unit

0

20

40

60

80

100

80

85

90

95

100

0 180 360 540 720 900 1,080O

utp

ut

(%)

PV

(%

No

rma

l P

ress)

Time (sec)

AGR Pressure ControllerPV

OP

0

20

40

60

80

100

80

85

90

95

100

0 200 400 600 800 1,000

Outp

ut

(%)

PV

(%

Norm

al P

ress)

Time (sec)

AGR Pressure ControllerPV

OP

Min P = 81% Normal Press.

Min P = 98% Normal Press.

Original Modified Controller

0

20

40

60

80

100

80

85

90

95

100

0 180 360 540 720 900 1,080

Ou

tpu

t (%

)

PV

(%

No

rma

l P

ress)

Time (sec)

AGR Pressure ControllerPV

OP

0

20

40

60

80

100

80

85

90

95

100

0 200 400 600 800 1,000

Outp

ut

(%)

PV

(%

Norm

al P

ress)

Time (sec)

AGR Pressure ControllerPV

OP

Min P = 81% Normal Press.

Min P = 98% Normal Press.

Stable operation achieved!Decreases below the allowable pressure, leading to

unacceptable disruption!

3. Dynamic Simulation

PV: Process Variable, OP: Output

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Feed Gas

NGL

Lean Gas

Expander/Compressor

Deethanizer

J-T Valve

Key Results

(b) Deethanizer Bottom Liquid Level

Modified Reboiler Operation

3. Dynamic Simulation

0

20

40

60

80

100

0

20

40

60

80

100

0 200 400 600 800 1000 1200

Outp

ut (%

)

Liq

uid

Level (%

)

Time (sec)

Deethanizer Bottom Level ControllerPV

OP

0

20

40

60

80

100

0

20

40

60

80

100

0 200 400 600 800 1,000 1,200

Outp

ut (%

)

Liq

uid

Level (%

)

Time (sec)

Deethanizer Bottom Level ControllerPV

OP

0

20

40

60

80

100

0

20

40

60

80

100

0 200 400 600 800 1000 1200

Outp

ut (%

)

Liq

uid

Level (%

)

Time (sec)

Deethanizer Bottom Level ControllerPV

OP

0

20

40

60

80

100

0

20

40

60

80

100

0 200 400 600 800 1,000 1,200

Outp

ut (%

)

Liq

uid

Level (%

)

Time (sec)

Deethanizer Bottom Level ControllerPV

OP

Unstable Operation! Stable operation maintained!

Original

4. Conclusion

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Findings

1. Dynamic Simulation verified the feasibility of Flare Reduction Concept

• It is not feasible with the current design configuration

• It was found feasible with some software modification

2. Dynamic Simulation suggested solutions for Flare Reduction

4. Conclusion

Effective and fit-for-purpose Dynamic Simulation

with given schedule and cost!

No hardware modification necessary!

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What Chiyoda Provides

• Solutions to problems that occur during operation: “Flare Reduction.”• All in consideration of safety, availability, operability, controllability, and maintainability,

including dynamic aspects of operation

• We identify possible scenarios with large impacts to the operation for the proposed

modification and propose an effective approach using advanced technology.

• Close communications with the Client every step of the process allowed us to define issues, develop scope and scenarios, suggest countermeasures, change the scenario if necessary—all in a timely manner.

4. Conclusion

5. Acknowledgements

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Qatargas Operating CompanyMr. Hassan Sawan, Project Division Manager

Mr. Abdulla Radi Al-Hajri, Surveillance Division Manager

Mr. Fadi Ghaya, Head of Project Engineering

Ms. Ranya Gornass, Senior Process Engineer

Mr. Krishnakumar Raghunatha Rao, Senior Process Engineer

Chiyoda Almana Engineering LLCMr. Kei Masuda, Deputy Engineering Dept. Manager

Mr. Shinya Endo, Engineering Manager

Mr. Shankar Dharmadas, Lead Process Engineer

5. Acknowledgements

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Thank You

© Chiyoda Corporation 2017, All Rights Reserved.