Systematic Process Design and Operation of Intensified Processes Seyed Soheil Mansouri, Jakob Kjøbsted Huusom, John M. Woodley and Rafiqul Gani CAPEC-PROCESS Department of Chemical and Biochemical Engineering Technical University of Denmark, DK-2800 Lyngby, Denmark

Outline Objectives Process Design & Controller Design Computer-aided Framework Case Study Conclusions and Future works 2014 AIChE Annual Meeting Atlanta, GA, USA 2November 19, 2014

Objectives To develop a systematic framework for integrated process design and controller design of intensified processes. To identify and obtain an optimal process design that has the inherent ability to reject disturbances. To identify the solution in a simple and efficient way AIChE Annual Meeting Atlanta, GA, USA 3November 19, 2014

Process Design vs. Controller Design: An Overview 2014 AIChE Annual Meeting Atlanta, GA, USA 4November 19, 2014 Optimal Design Optimal Control ? ? Causes many process control problems: due to poor design of the process May lead to: process overdesign, dynamic constraint violations, not robust process How does process design influence process controllability? Drawbacks

Integrated Process Design and Control 2014 AIChE Annual Meeting Atlanta, GA, USA 5November 19, 2014 Optimal Design Optimal Control Integrated Process Design and Controller Design To assure that design decisions give the optimum economic and the best control performance, controller design issues need to be considered simultaneously with the process design issues.

Intensified Processes: Key Concepts 2014 AIChE Annual Meeting Atlanta, GA, USA 6November 19, 2014 OperationalFunctionalPhenomena Integration of Unit Operations Task enhancement Phenomena enhancement Reactive Distillation Solvent replacement INNOVATION Increased level of complexity Sustainable Process Design Environmental Impact Waste Reduction Energy Consumption Operational Cost Possible Benefits Decreased degrees of freedom

Integrated Process Design and Controller Design of Intensified Processes 2014 AIChE Annual Meeting Atlanta, GA, USA 7November 19, 2014 Integrated approach can be achieved by identifying variables together with their target values that have roles in process- controller design Identifying optimal design together with design-manipulated variables u, process-controlled variables y, their target set points, and their pairing. The solution to this optimization problem must address the trade- offs between conflicting design and control objectives for the intensified processes

Integrated Computer-Aided Framework 2014 AIChE Annual Meeting Atlanta, GA, USA 8November 19, 2014

Case Study: Problem Definition and Formulation Objective: To find the optimal process design and controller design solution for an intensified process (reactive distillation column) to produce methyl-tert-butyl-ether (MTBE) Reactions: Feed specifications: Total feed flowrate = 100 kmole/h 70% isobutene and 30% methanol Temperature = 300K and Pressure = 1 atm 2014 AIChE Annual Meeting Atlanta, GA, USA 9November 19, 2014

Case Study: Step 1 – Process Design A set of design methods for reactive distillation column that are simple, easy to use, and similar in concept to non-reactive distillation design methods are used. The methods are based on the element concept [1]. The element-based method is used to translate a ternary system of compounds to a binary system of elements. [1] Pérez Cisneros, E.S., Gani, R., Michelsen, M.L. (1997). Reactive separation systems—I. Computation of physical and chemical equilibrium, Chem. Eng. Sci., 52, 527– AIChE Annual Meeting Atlanta, GA, USA 10November 19, 2014

Case Study: Step 1 – Process Design Element matrix is constructed as: 2014 AIChE Annual Meeting Atlanta, GA, USA 11November 19, 2014 Element AElement B + Element AB Compound ElementC4H8C4H8 CH 4 OC 5 H 12 O A101 B011

Case Study: Step 1 – Process Design Reactive distillation column design Reactive VLE data is obtained by consecutive calculation of reactive bubble points*. *Tool: ICAS-PDS 2014 AIChE Annual Meeting Atlanta, GA, USA 12November 19, 2014 The ternary compound reactive data points are converted into binary element data points.

Case Study: Step 1 – Process Design Reactive McCabe-Thiele method The binary reactive element-based data are used to generate reactive equilibrium curve. The reactive McCabe-Thiele method [2] is used to calculate the number of stages AIChE Annual Meeting Atlanta, GA, USA 13November 19, 2014 Reflux ratio: 2 Theoretical number of stages: 5 Assumptions: Total condenser Partial reboiler Chemically saturated liquid reflux [2] Daza, O.S., Pérez Cisneros, E.S., Gani, R. (2003). Graphical and stage-to-stage methods for reactive distillation column design, AIChE J., 49,

Case Study: Step 1 – Process Design Reactive driving force (DF) diagram 2014 AIChE Annual Meeting Atlanta, GA, USA 14November 19, 2014 A design method of distillation separation system based on identification of the largest driving force. The idea is to design the reactive distillation column at the maximum of the driving force. At the maximum driving force, separation becomes easier and energy required is at the minimum. The optimal feed location is found to be at stage 1 from top of the column

Case Study: Step 2 – Optimal Design-Control Solutions 2014 AIChE Annual Meeting Atlanta, GA, USA 15November 19, 2014 Selection of controlled variables -W A,max – primary controlled variable (uncontrolled output) -W A d or W A B – secondary controlled variable (desired output) Set-points value for controlled and manipulated variables -The calculated value of y and u at Point ( I ) are the optimal set- points.

Case Study: Step 2 – Optimal Design-Control Solutions 2014 AIChE Annual Meeting Atlanta, GA, USA 16November 19, 2014 Sensitivity of controlled variables with respect to disturbances in the feed -It is verified that disturbance rejection in the feed is the best at the maximum driving force (Point I) than other points. -At Point ( I ),

Case Study: Step 2 – Optimal Design-Control Solutions 2014 AIChE Annual Meeting Atlanta, GA, USA 17November 19, 2014 Optimal process design: the lowest energy required [3] Optimal controller design the lowest sensitivity of d y /d d and the highest sensitivity of d y /d u.[4] [3] Bek-Pedersen, E., Gani, R. (2004). Design and synthesis of distillation systems using a driving-force-based approach, Chem. Eng. Process., 43, 251–262 [4] Hamid, M. K. A., Sin, G., and Gani, R. (2010). Integration of process design and controller design for chemical processes using model-based methodology. Comput. Chem. Eng., 34,

Case Study: Step 2 – Optimal Design-Control Solutions Selection of the controller structure (pairing between controlled-manipulated variables) -It is verified that at the maximum point of the driving force diagram, pair of secondary controlled variable or with manipulated variable is always the best controller structure. -At Point ( I ), 2014 AIChE Annual Meeting Atlanta, GA, USA 18November 19, 2014

Case Study: Step 3 – Final Selection and Verification Rigorous dynamic simulation* -A rigorous reactive distillation dynamic model based on elements is used. -The chemical reactions occurring are fast enough to reach the equilibrium. -Chemical equilibrium condition is implicitly incorporated into the element mass balances. *Tool: ICAS-Process Simulation 2014 AIChE Annual Meeting Atlanta, GA, USA 19November 19, 2014

Case Study: Step 3 – Final Selection and Verification Rigorous dynamic simulation: Open-loop 2014 AIChE Annual Meeting Atlanta, GA, USA 20November 19, 2014 Step Disturbance: +15 kmole change in Isobutene flowrate in the feed

Case Study: Step 3 – Final Selection and Verification Controller structure verification -Controller structure at the maximum driving force: -The relative gain array (RGA): 2014 AIChE Annual Meeting Atlanta, GA, USA 21November 19, 2014 Candidate design alternatives to the maximum driving force

Case Study: Step 3 – Final Selection and Verification Rigorous dynamic simulation: Closed-loop -Controller structure implementation 2014 AIChE Annual Meeting Atlanta, GA, USA 22November 19, 2014 Proportional – Integral (PI) controller

Case Study: Step 3 – Final Selection and Verification Rigorous dynamic simulation: Closed-loop 2014 AIChE Annual Meeting Atlanta, GA, USA 23November 19, 2014

Conclusions and Future Works Conclusions -A computer-aided framework for integrated design and control/operation of intensified processes is proposed. -The application of the framework is demonstrated through a reactive distillation case study. -It is illustrated that designing a reaction-separation operation at the maximum driving force results in optimal design in terms of controllability. Future works -To extend the application of the framework to include variety of intensified operations. -To illustrate the application of the framework for systems involving more compounds AIChE Annual Meeting Atlanta, GA, USA 24November 19, 2014

Thank you! Acknowldegments Prof. Mauricio Sales-Cruz, UAM, Mexico Contact Seyed Soheil Mansouri PhD student CAPEC-PROCESS Department of Chemical and Biochemical Engineering Technical University of Denmark Kongens Lyngby, Denmark AIChE Annual Meeting Atlanta, GA, USA 25November 19, 2014