1 Single-cycle mixed-fluid LNG (PRICO) process Part II: Optimal operation Sigurd Skogestad & Jørgen Bauck Jensen Qatar, January 2009.

Slides:



Advertisements
Similar presentations
Basic Refrigeration, Its Components, and Its Cycle
Advertisements

Refrigeration Cycles CHAPTER 11: PTT 201/4 THERMODYNAMICS
1 Optimal Control of Chiller Condenser Sub-cooling, Compressor Speed, Tower Fan and Pump Speeds, and IGV Omer Qureshi, Hassan Javed & Peter Armstrong,
Moisture to water converter. Out Line : Abstract Introduction Heat Pump Heat Pump Components Conclusion.
Dynamic modeling, optimization and control of a CO 2 stripper Marie Solvik Supervisors : Sigurd Skogestad and Marius Støre Govatsmark.
Entropy balance for Open Systems
Advanced Thermodynamics Note 6 Applications of Thermodynamics to Flow Processes Lecturer: 郭修伯.
Refrigeration Cycles Chapter 11.
C oncerns Ltd ool Energy Efficient Refrigeration Jane Gartshore, Cool Concerns Ltd.
1 Single-cycle mixed-fluid LNG (PRICO) process Part I: Optimal design Sigurd Skogestad & Jørgen Bauck Jensen Quatar, January 2009.
Introduction: What is LNG? When natural gas is cooled to a temperature of approximate (–160 C) at atmospheric pressure it condenses to a liquid,called.
Throttling Thermodynamics Professor Lee Carkner Lecture 22.
Verbal Modeling Anchors: Manganese  Matt Morabito Jamie Polan.
EGR 334 Thermodynamics Chapter 4: Section 9-10
A Vapor Power Cycle Boiler T Turbine Compressor (pump) Heat exchanger
1 M. Panahi ’Plantwide Control for Economically Optimal Operation of Chemical Plants’ Plantwide Control for Economically Optimal Operation of Chemical.
Advanced Thermodynamics Note 8 Refrigeration and Liquefaction
EGR 334 Thermodynamics Chapter 10:
1 Operation of heat pump cycles Jørgen Bauck Jensen & Sigurd Skogestad Department of Chemical Engineering Norwegian University of Science and Technology.
1 Single-cycle mixed-fluid LNG (PRICO) process Part II: Optimal operation Sigurd Skogestad & Jørgen Bauck Jensen Quatar, January 2009.
Refrigeration Cycles Chapter 11: ERT 206/4 THERMODYNAMICS
GHGT-8 Self-Optimizing and Control Structure Design for a CO 2 Capturing Plant Mehdi Panahi, Mehdi Karimi, Sigurd Skogestad, Magne Hillestad, Hallvard.
Vapor and Combined Power Cycles (2)
1 Active constraint regions for optimal operation of a simple LNG process Magnus G. Jacobsen and Sigurd Skogestad Department of Chemical Engineering NTNU.
Optimal operation of distillation columns and link to control Distillation Course Berlin Summer Sigurd Skogestad. Part 3.
1 Coordinator MPC for maximization of plant throughput Elvira Marie B. Aske* &, Stig Strand & and Sigurd Skogestad* * Department of Chemical Engineering,
1 Modelling, Operation and Control of an LNG Plant Jens Strandberg & Sigurd Skogestad Department of Chemical Engineering, Norwegian University of Science.
The First Law of Thermodynamics
Partial Evaporation Example 1/31/2007. Shell and Tube Heat Exchanger.
1 Outline Skogestad procedure for control structure design I Top Down Step S1: Define operational objective (cost) and constraints Step S2: Identify degrees.
Variable-Speed Heat Pump Model for a Wide Range of Cooling Conditions and Loads Tea Zakula Nick Gayeski Leon Glicksman Peter Armstrong.
A Vapor Power Cycle Boiler T Turbine Compressor (pump) Heat exchanger
1 Self-Optimizing Control HDA case study S. Skogestad, May 2006 Thanks to Antonio Araújo.
Last Time Where did all these equations come from?
1 Active constraint regions for optimal operation of chemical processes Magnus Glosli Jacobsen PhD defense presentation November 18th, 2011.
1 Single-cycle mixed-fluid LNG (PRICO) process Part I: Optimal design Sigurd Skogestad & Jørgen Bauck Jensen Qatar, January 2009.
1 A Plantwide Control Procedure Applied to the HDA Process Antonio Araújo and Sigurd Skogestad Department of Chemical Engineering Norwegian University.
LHCb VELO Meeting LHCb VELO Cooling System Bart Verlaat (NIKHEF) 25 February 2003.
1 E. S. Hori, Maximum Gain Rule Maximum Gain Rule for Selecting Controlled Variables Eduardo Shigueo Hori, Sigurd Skogestad Norwegian University of Science.
HEAT PUMPS BY: DINESH BAKTHAVATSALAM ID#: M-I.
Pressure-Enthalpy and the Variable Refrigerant Cycle
1 Active constraint regions for economically optimal operation of distillation columns Sigurd Skogestad and Magnus G. Jacobsen Department of Chemical Engineering.
Implementation of Coordinator MPC on a Large-Scale Gas Plant
1 Using Self-Optimizing Control on the Statoil Mongstad HEN Daniel Greiner Edvardsen May 27, 2010 NTNU Confidential.
1 Outline Control structure design (plantwide control) A procedure for control structure design I Top Down Step 1: Degrees of freedom Step 2: Operational.
1 Optimization of LNG plants: Challenges and strategies Magnus G. Jacobsen Sigurd Skogestad ESCAPE-21, May 31, 2011 Porto Carras, Chalkidiki, Greece.
1 Self-optimizing control From key performance indicators to control of biological systems Sigurd Skogestad Department of Chemical Engineering Norwegian.
Model 5 Long Distance Phone Calls By Benjamin Cutting
1 PLANTWIDE CONTROL Identifying and switching between active constraints regions Sigurd Skogestad and Magnus G. Jacobsen Department of Chemical Engineering.
The Rankine Cycle: An Alternate Ideal Thermodynamic Model P M V Subbarao Professor Mechanical Engineering Department IIT Delhi A Feasible Mathematical.
1 Self-optimizing control Theory. 2 Outline Skogestad procedure for control structure design I Top Down Step S1: Define operational objective (cost) and.
1 Control of maldistribution of flow in parallell heat exchangers Magnus G. Jacobsen, Sigurd Skogestad Nordic Process Controi workshop, Porsgrunn
HW2 AHU problems: Book: 8.5, 8.25, 8.27, 8.28, 8.22 Cooling Cycles Problems: - Book: 3.1 (page 69), - Book: 3.5 ((page 70), - Out of book: Same like 3.5.
1 Self-optimizing control From key performance indicators to control of biological systems Sigurd Skogestad Department of Chemical Engineering Norwegian.
1 An Extended Pinch Analysis and Design Procedure utilizing Pressure Exergy for Subambient Cooling A. Aspelund, D. O. Berstad, T. Gundersen The Norwegian.
Refrigeration What's Refrigerated? What makes up a system?
Vapour Compression Cycle You will Learn: 1 Vapour Compression Cycle Actual Vapour Compression Cycle Components in a Vapour Compression Plant Multistage.
Date of download: 9/21/2017 Copyright © ASME. All rights reserved.
Coordinator MPC with focus on maximizing throughput
Date of download: 10/6/2017 Copyright © ASME. All rights reserved.
Refrigeration and Heat Pump Systems
ARAC/H/F Air-cooled water chillers, free-cooling chillers and heat pumps Range: kW.
Innovative He cycle Francois Millet.
Compound VCRS.
Self-optimizing control Theory
Changing between Active Constraint Regions for Optimal Operation: Classical Advanced Control versus Model Predictive Control Adriana Reyes-Lúa, Cristina.
Outline Skogestad procedure for control structure design I Top Down
Step 2. Degree of freedom (DOF) analysis
The Heat Pump-pumps heat from a cold area to a warmer area.
“THERMODYNAMIC AND HEAT TRANSFER”
Presentation transcript:

1 Single-cycle mixed-fluid LNG (PRICO) process Part II: Optimal operation Sigurd Skogestad & Jørgen Bauck Jensen Qatar, January 2009

2 Single-cycle mixed fluid LNG process Natural gas: Feed at 40 bar and 30 °C Cool to -157 °C (spec.) ΔP = 5 bar in main heat exchanger

3 Single-cycle mixed fluid LNG process Refrigerant: Partly condensed with sea water Subcooled to ~ -157 °C Expansion to ~ 4 bar Evaporates in main HX Super-heated 10 °C Compressed to ~ 30 bar 30 bar -157 °C 26 bar 4 bar Sup 10 °C Sat. liquid Subcooled

4 Degrees of freedom Manipulated variables: 1.Compressor speed N 2.Choke valve opening z 3.Turbine power 4.Sea water flowrate 5.Natural gas feed flowrate 6-9. Composition of refrigerant (4) 6-9

5 Degrees of freedom Assumptions: 1.Assume maximum cooling in SW cooler Realized by fixing T=30 °C 8 degrees of freedom for optimization 4 degrees of freedom in operation –Assume 4 constant compositions in operation

6 Operational constraints Some super-heating to avoid damage to compressor –But we find that super-heating is optimal anyway…. (constraint not active) Maximum compressor power 120 MW –active Maximum compressor rotational speed is 100 % –active Minimum distance to surge is 0 kg/s (no back-off) –active

7 Optimal operation Minimize operation cost with respect to the 8 degrees of freedom (u) subject to the constraints c ≤ 0

8 Optimal operation: Minimize cost Neglect income of turbine work –The main effect of the liquid turbines is the extra cooling effect, not the power production Neglect cost of cooling with sea water –Sea water requires pumping which is cheap in operation compared with compressors

9 Two modes of operation Mode I: Given production rate (m feed ) Optimization problem simplifies to – Minimize compressor work (W s ) Mode II: Free production rate With reasonably high LNG prices: Optimization problem simplifies to – Maximize production rate (m feed ) while satifying operational constraints (max. compressor load)

10 Two modes of operation

11 Mode I: Nominal optimum Feed flowrate is given (69.8 kg/s) –8 - 1 = 7 steady-state degrees of freedom (incl. 4 compositions) Three operational constraints are active at optimum 1.Given temperature LNG (-157 °C) 2.Compressor surge margin at minimum (0.0 kg/s) 3.Compressor speed at maximum (100 %) Only the four degrees of freedom related to refrigerant compositions are unconstrained

12 Nominal optimum

13 Mode II: Nominal optimum LNG production is maximized –8 steady-state degrees of freedom (incl. 4 compositions) Four operational constraints are active at optimum 1.Given temperature LNG (-157 °C) 2.Compressor surge margin at minimum (0.0 kg/s) 3.Compressor speed at maximum (100 %) 4.Compressor work W s at maximum (120 MW) Note that two capacity constraints are active (3 and 4) Only the four constraints related to refrigerant composition are unconstrained

14 Nominal optimum

15 Nominal compressor operating point for mode II N=100% (max speed) N=50% N=10% * Surge limit

16 Temperature profiles in heat exhanger (mode II) T NG -T C NG in LNG out

17 Optimum with disturbances 4 operational degrees of freedom –Refrigerant composition is constant during operation Optimum with disturbances: 1.Given LNG temperature (all cases) 2.Given load (all cases) –Mode I: The production rate is given –Mode II: The compressor work is at maximum (W s = 120 MW) 3.Max. speed compressor (most cases) 4.Operate at surge limit (most cases)

18 Optimum with disturbances Two additional degrees of freedom were at constraints at the nominal optimum –Compressor rotational speed at maximum (100 %) –Compressor surge margin at minimum (0.0 kg/s) We also find that controlling these constraints gives close to optimal operation with disturbance

19 Optimum with disturbances Strictly speaking we would need to consider the following four regions: This is complicated and we prefer to have the same controlled variables in all four regions Control the nominal active constraints and

20 Check Mode II (production vs. disturbance) Dots are re-optimized Lines are for different controlled variables constant Constant distance to surge (0.0 kg/s) (ALL CASES) N=N max gives highest production (CLOSE TO OPTIMAL) N=N max only feasible structure in increasing load direction

21 Example of control structure TC Max cooling Max speed WC W s,max =120MW SC Δm surge =0 m Alternative: MPC

22 Conclusion Maximum compressor speed and minimum distance to surge is nominally optimal for mode I and mode II –In practice one would have a back-off from surge, but this would still be an active constraint This is also close to optimal or optimal for all disturbance regions  Control the following variables: 1.Maximum sea water cooling (valve fully open) 2.T LNG = -157 °C 3.LNG flowrate = 69.8 kg/s (mode I) or W s = 120 MW (mode II) 4. 5.

23 Additional material 1.Disturbances considered 2.Structure of model equations 3.Data used for the PRICO process

24 Disturbances considered

25 Structure of model equations

26 Data used for the PRICO process