Energy Saving Olefins Cold Ends DMCplus TM in Record Time

Transcription

1 Energy Saving Olefins Cold Ends DMCplus TM in Record Time David Hokanson } Richard Cutting } ExxonMobil Chemical David Dutschmann } Robert Galloway } [1]

2 Outline A Dynamic Matrix Control (DMC) application was applied quickly on an olefins cold ends unit Used AspenTech s SmartStep with a methodology called Rapid Application Development (RAD) Annualized energy savings are equivalent to 98,287 MMBtu, with associated CO 2 emissions reduction of 6,200 tons. This presentation will cover the following: An introduction to DMC, SmartStep & RAD The scope of Cold Ends DMC application The project timeline / workflow Sample results [2]

3 What is DMC? DMC is a Multivariable, Model-Based, Predictive, Constraint Control Algorithm Multivariable Moves multiple handles (ultimately control valves) to meet multiple targets at the same time. Model-Based Based on empirical dynamic models of the process derived from plant test data. Predictive Uses model and past plant performance to predict future trajectory. Constraint Control - Adjusts plant operations to run against plant limits (constraints) in a safe and stable manner Commercially Available Advanced Process Control (APC) Software The commercial DMC software package used in this application is DMCplus TM from AspenTech [3]

4 TM? What is SmartStep TM SmartStep is automated plant testing software Developed and sold by AspenTech Based on the DMCplus software The parameters and interface are nearly identical Designed to allow reduced supervision of DMC tests Initial application: DMC re-tests [4]

5 What is RAD? Rapid Application Development (RAD) is a methodology to enable SmartStep to be used for new/revamp DMCs Developed collaboratively with AspenTech. 40+ DMCs developed using SmartStep /RAD in ExxonMobil Significantly reduces overall effort (site personnel and outside resources) Also reduces elapsed time of testing / commissioning Increases DMC project Return on Investment (ROI), particularly for energy applications Enables DMCs to be done at sites with limited engineering resources without the need for a significant number of external resources [5]

6 Typical DMC Project 1) Pre-test Base regulatory controls are checked and reviewed. 2) Plant test Plant is manually stepped for a period of 2-4 weeks under close engineering supervision. 3) Model identification / control simulation Analysis done in an office environment, when dynamic models are identified from plant test data, and when the initial DMC application is simulated. 4) Commissioning DMC application is put on-line and tuned. The commissioning phase typically lasts as long as the original plant test. [6]

7 RAD Project Combine Steps 2, 3, and 4 -> a Single 2-4 Week Period Rough dynamic models are obtained from the limited pre-test data Used as seed models for the SmartStep testing package. New model identification technology (particularly the Subspace identification algorithm) in AspenTech s DMCplus Model enables the identification of a good starting model from limited data. During the SmartStep test The engineering test team focuses on model improvement while the software moves the plant. An improving model enables the SmartStep package to make optimum test moves, keeping the plant within operating limits. When the Model is good, SmartStep is put into DMCplus control mode Control performance is the ultimate test of model accuracy/performance. Simulation is done prior and during this period to ensure good performance at various constraints [7]

8 Olefins Cold Ends DMC Scope Cold Ends Inventory (8 levels) Cold Box 5 Towers: Pre-Fractionator DeMethanizer DeEthanizer Topping Still C2 Splitter [8]

9 Timeline Scoping / Design June 2005 Pre-Test 3 weeks - August / Sept 2005 Hurricane Rita late Sept Dec 2005 SmartStep Test / DMCplus Commissioning Feb 2006 [9]

10 Example Results C2 Splitter C2 Splitter Reflux / Feed C2 Splitter Power / Feed Avg Historical Data savings Before Test SmartStep Test [10] On Control

11 Example Results - DeEthanizer C3 in Ovhd, PPM ~18% Energy Reduction Reflux/Feed Reboiler Duty/Feed Press Min against Valve Limit Tower Pressure Before Test SmartStep Test [11] On Control

12 Summary Profitable Cold-Ends DMC commissioned Verified that the SmartStep /RAD methodology can work on large DMC applications Considerably less effort and time compared to conventional DMC projects Control performance has met or exceeded the plant s expectations The plant is more stable Energy savings have been substantial: 98,287 MMBtu / yr Associated CO 2 emissions reductions of 6,200 tons/yr [12]

13 Backup Legal Declarations David Hokanson Short Biography [13]

14 Legal Declarations 2007 Exxon Mobil Corporation To the extent the user is entitled to disclose and distribute this document, the user may forward, distribute, and/or photocopy this copyrighted document only if unaltered and complete, including all of its headers, disclaimers, and other information. You may not copy this document to a Web site without the permission of the copyright owners. The copyright owners do not guarantee the typical (or other) values. The information in this document relates only to the named product, materials or processes when not in combination with any other product, materials or processes. We based the information on data believed to be reliable on the date compiled, but we do not represent, warrant, or otherwise guarantee, expressly or impliedly, the merchantability, fitness for a particular purpose, suitability, accuracy, reliability, or completeness of this information or the products, materials, or processes described. The user is solely responsible for all determinations regarding any use of material, product or process in its territories of interest. We expressly disclaim liability for any loss, damage, or injury directly or indirectly suffered or incurred as a result of or related to anyone using or relying on any of the information in this document. There is no endorsement of any product, material or process, and we expressly disclaim any contrary implication. ExxonMobil Chemical Company is a division of ExxonMobil Corporation. ExxonMobil is a trademark of Exxon Mobil Corporation. DMCplus is a multivariable control product developed by Aspen Technology, Inc. following its merger with Dynamic Matrix Control Corporation and Setpoint, Inc. DMCplus and SmartStep are trademarks of Aspen Technology, Inc. [14]

15 Presenter David Hokanson David Hokanson is currently a process control specialist with ExxonMobil Chemical Company's Engineering group in Baytown, Texas. He currently leads the effort to apply Dynamic Matrix Control (DMC) within ExxonMobil Chemical. He has previously held process control leadership roles at ExxonMobil plants in Singapore, Rotterdam, and Baytown. David Hokanson received a BS and Masters in Chemical Engineering from Rice University in Houston, Texas. He also serves as an adjunct professor at Rice where he teaches a portion of the introductory process control course. David Hokanson is a member of AIChE and ISA, and is a registered engineer in the state of Texas. [15]