Design of Environmentally Benign Processes: Integration of Solvent Design Separation Process Synthesis

1. Design of Environmentally Benign Processes: Integration of Solvent Design & Separation Process Synthesis Peter M. Harper, Martin Hostrup, Rafiqul Gani CAPEC Dept. of Chem. Eng., Tech. Univ. of Denmark http://www.capec.kt.dtu.dk

2. Clean Products and Processes II 2 Overview Introduction Methodology Problem Formulation Solution Approach Tools needed Application examples Conclusions

3. Clean Products and Processes II 3 Introduction-I: Definitions Environmentally Benign Process All environmental aspects have been considered. The process complies (AT LEAST) with all regulatory requirements. Pollution Causes Solvents, energy use, by-products in effluent streams. Prevention, Treatment & Cure

4. Clean Products and Processes II 4 Introduction -II: Integration Objective: Develop a combined methodology in order to determine (interactively), optimal, environmentally benign processes

5. Clean Products and Processes II 5 Superstructure representation

6. Clean Products and Processes II 6 Methodology-I: Problem Formulation New process (pollution prevention) Existing process (treatment/cure) Variables are fixed Problem more constrained (less degrees of freedom) More difficult to solve

7. Clean Products and Processes II 7 Problem Formulation Steps 1. Analyse process, divide into reaction & separation blocks. 2. List separation techniques to be considered. 3. External mediums? Eliminate if none found. 4. Screen out infeasible separation techniques. 5. Binary mixture analysis: Azeotropes, miscibility, � 6. Generate solvent alternatives. 7. Multicomponent mixture analysis: Separation boundaries, etc. 8. Check separation stream for reactants. Recycle? 9. Formulate optimization problem in terms of superstructure, objective function, constraints, etc.

8. Clean Products and Processes II 8 Methodology-II: Solution Approach

9. Clean Products and Processes II 9 Sub-Problems: Process Design Conditions of operation Temperature / Pressure Separation unit (distillation column) design Separation efficiency curves Product specifications Design parameters (feed location, reflux, �) Reaction synthesis and optimization Volume / Residence time Temperature profile Operational constraints Separation boundaries Solvent/material design (selection) Energy consumption & waste

10. Clean Products and Processes II 10 Process Design: Separation techniques Need for (appropriate) thermodynamic models. Thermodynamic Model Selection Need for Properties (Database/Property prediction)

11. Clean Products and Processes II 11 Sub-Problems: Solvent Design/Selection I Find compounds matching desired properties Performs database search Generates missing data Based on properties controlling the search/design operation Ability to identify novel compounds Suitable for substitution problems

12. Clean Products and Processes II 12 Molecule Generation Multilevel Approach All generation is rule-based (feasibility, method considerations). Increasing complexity on the generated molecular descriptions. Output from previous level is used as input for the next next level.

13. Clean Products and Processes II 13 Generation criteria/properties Group contribution Correlation EOS UNIFAC Rigorous phase calculations Link to database Calculation order optimised for speed

14. Clean Products and Processes II 14 Sub-Problems: Material Design/Selection Designing or selecting the most appropriate membrane material for a particular application. Computer Aided Membrane Design still an emerging field. Database approach combined with shortcut simulations: Allows for realistic input data to be used in the selection process. The choice of material can change the efficiency of a process by several orders of magnitude.

15. Clean Products and Processes II 15 Sub-Problems: Waste/Energy Aspects Local (process-wide) energy aspects can be addressed using the simulation engine. Off-process energy requirements must be handled using LCA techniques - taking local conditions into account. Waste/effluent minimisation can (in part) be handled using the simulator/optimiser. Impact assessment tools must be used��...

16. Clean Products and Processes II 16 Methodology- III: Problem Solution Flexible & interactive solution of the problem Rigorous models used in the NLP-step Linear model generated for the MILP-step Any sub-problem can also be solved independently

17. Clean Products and Processes II 17 Methodology - IV: Tools Needed Process Simulator (steady state, dynamic) & Modelling tool Solvers (NLP, MINLP, AE, DAE, etc.) Flowsheet generation tool (process synthesis) CAMD (solvent selection/design) Physical properties database (> 13000 compounds) Environmental properties database Materials database Properties estimation tool (Pure component & mixture properties) Impact Assessment tools

18. Clean Products and Processes II 18 Application Examples

19. Clean Products and Processes II 19 Example-I: Design criteria Compound type: Acyclic alkanes, ethers, esters, aldehydes, ketones and acids. Pure component properties: Tflash > 310 K, Tboil > 421 K ; Tmelt < 310 K Mixture properties: Sl < 0.01 ; m > 0.1 ; ? > 7 ; B > 1 Solvent must not form azeotrope with acetic acid Liquid-liquid phase behaviour at 298 K

20. Clean Products and Processes II 20 Example-I: Results & performance 2332 Alternatives were found Candidates sorted using m*? as ranking criteria Structure analysis/matching to identify CAS-NO

21. Clean Products and Processes II 21 Example-I: Environmental Aspects D = Drug, S = Primary Irritant, T = Reproductive-Effector, M = Mutagen, C= Tumorigen

22. 22 Example-II: Integrated Problem

23. Clean Products and Processes II 23 Pressure dependence

24. Clean Products and Processes II 24 Pressure dependence

25. Clean Products and Processes II 25 Solvent design sub-problem CAMD problem: 340 < Tboil < 420 Selectivity > 3.5 Solvent power> 2.0 No azeotropes Number of compounds designed: 47792Number of compounds selected: 53 Number of isomers designed: 528 Number of isomer selected: 23 Total time used to design: 57.01 s

26. Clean Products and Processes II 26 Phase behaviour

27. Clean Products and Processes II 27 Phase behaviour

28. Clean Products and Processes II 28 Problem formulation & Solution

29. Clean Products and Processes II 29 Conclusions A systematic, knowledge intensive framework for design for the environment on the process level. Pollution prevention Use of thermodynamic knowledge Synthesis of flowsheets Optimizes operational parameters Cure/Treatment Verification by simulation Uses existing operational constraints Identifies needed changes in operational parameters Use of rigorous models

30. Clean Products and Processes II 30 More information ? CAPEC Web-Sites www.capec.kt.dtu.dk (Primary site) www.capec.kt.dtu.dk/eurecha (EURECHA inf. site) www.escape11.kt.dtu.dk (European Symposium on Computer Aided Process Engineering - 11, May 2001 Denmark)