1. 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 1 A Comparison of Perturbation Based Approaches for Real-time Optimization Yale Zhang and Fraser Forbes CPC Group, ChE Department University of Alberta Oct. 26, 1998

2. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 2 Outline Introduction  Motivation  Closed RTO Loop RTO Performance Evaluation  Extended Design Cost Perturbation Based Methods for RTO system  Methods Review  Comparison  process modeling; plant/model mismatch compensation; plant perturbation Case Studies  Heat Exchanger Network and A Continuous Bio-reactor Conclusions and Future Work

3. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 3 Motivation for RTO Increasing global competition and economic pressure Increasing industrial focus on improving process economics Improvement and maturity of the advanced process controllers (APC) RTO

4. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 4 Model-based RTO System  Model-based Optimizer Model Update Validation ConditionControllerPlant Sensor Z’Z’ Xm*Xm* r euZ N Scheduling and Planning Three Actions (White, 1997)  Current Plant Assessment  Optimization Execution  Model Updating and Model-based Optimization  Results Implementation

5. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 5 RTO Performance Loss and Evaluation  RTO performance loss consists of: (1) offset; (2)unnecessary variance; and (3) transient behavior

6. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 6 Extended Design Cost Bias Cost Transition Cost Variance Cost Extended Design Cost  Extended Design Cost can be used as an evaluation tool for different RTO design alternatives.

7. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 7 Model Updating and Optimization Two-Phase Approach (Chen and Joseph, 1987) Parameter Estimation Problem Optimization Problem  Effect of plant/model mismatch on RTO performance.

8. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 8 Perturbation Based Methods for RTO How to deal with plant/model mismatch? Optimality ConditionAdaptive Control Techniques Integrated System Optimization and Parameter Estimation (ISOPE) Approach (Roberts, 1979,1991) Linear Adaptive On-line Optimization (LAOO) Approach (McFarlane and Bacon, 1989) Quadratic Adaptive On-line Optimization (QAOO) Approach (Golden and Ydstie, 1989)  Perturbation Based Methods!

9. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 9 Comparison of PBMs for RTO

10. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 10 Example 1: Heat Exchanger Network (Forbes, 1994)  actual heat transfer coefficient:  approximation model: Case Studies Example 2: Continuous Bioreactor (Golden and Ydstie, 1989)  Optimization Model where f(D) is an approximation steady-state model, Fin,Tin r Fout,Tout

11. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 11 Simulation Results for Example 1 RTO Trajectory of MV Extended Design Cost

12. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 12 Simulation Results for Example 2 Bias Cost Transition Cost Variance Cost RTO Optimum Two-Phase ISOPE LAOO QAOO Two-Phase LAOO ISOPE

13. AIChE Annual Meeting 6/2/2015 University of Alberta © Yale Zhang, Nov., 1998 13 Conclusions and Future Work Conclusions Future Work Acknowledgement  Sunoco, Imperial Oil and NSERC  CPC Group at University of Alberta