Design Methods and Algorithms for Multicomponent Distillation Processes

1. Design Methods and Algorithms for Multicomponent Distillation Processes Lei Huang

2. Outline • Introduction • Basic configurations • Mathematical framework for searching basic configurations • Practice

3. Introduction • Is it necessary to search all possible configurations? • If not, can we find a smallest adequate search space? • If so, how to implement it?

4. Basic and Non-Basic Configurations • Each column has a condenser on top. • Each column has a reboiler at the bottom. • There are (n-1) distillation columns, after full consolidation of sections. • There are n product streams, each rich in one component. • Each component is recovered in only one product stream. • Each product is recovered from only one location. • There are no intermediate reboilers or condensers. • There is no thermal coupling between columns.

5. Basic and Non-Basic Configurations Three cases of quaternary distillation configurations • 3 columns (N-1) • Only 1 stream for each product • Each column has 1 condenser at the top and 1 reboiler at the bottom • 4 columns (N) • 2 streams for product C • Each column has 1 condenser at the top and 1 reboiler at the bottom • 3 columns (N-1) • Only 1 stream for each product • Fully coupled Basic Non-Basic Non-Basic

6. Basic and Non-Basic Configurations • Multiplicity: the number of section groupings for a given topology. • Same nodes, same edges, different way of connecting nodes and edges-different graphs. • Multiplicity=1 for all basic configurations

7. How many basic configurations?

8. For quaternary distillations, the best network vapor flow for all basic and non-basic configurations(V*basic / V*non-basic)

9. Extended Basic Configuration Extensible Basic Configuration If the same product is desired at two purities • Same number of columns • Same number of distillation/bottom • 1 more stream for product

10. Mathematical Framework for Searching Basic Configurations • Search for all basic configurations (with external constraints) , and eliminate all non-basic configurations • Incorporate design constraints

11. Mathematical Framework for Searching Basic Configurations • A Configuration-A Directed Graph • Nodes-Streams • Edges-Columns

12. Constraints • Material balance • 1 distillation and 1 bottom for each collumn • Basicity ----------------------------------------------------------- • External Constraints • Thermally Coupled Configurations

13. Examples • ABC • xABCAB + xABCA = xABCDABC • xABCBC + xABCC = xABCDABC • Sum (xout * Componentsout) ≥ Sum (xin) * Componentsnode • xABCDA + 2xABCDAB + 3xABCDABC + 3xABCDBCD + 2xABCDCD + xABCDD ≥ 4 • xBC->B + xBCD->B ≤ 1

14. Examples • ABCD-AB/BCD • XABCD-BCD=1 • XABCD-CD=1 • B distillate • XAB-B=0 • Thermally Coupled Configurations • Let y be the variable represents the backward flow of each non-product edge • y≤x

15. Practice structure = 2 3 4 5 5 6 7 8 8 9 8 9 9 10 • x(1,:)=[0.25 0.25 0.25 0.25]; • x(2,:)=[0.25 0.1591 0.075885 0]; • x(3,:)=[0 0.090901 0.17411 0.25]; • x(4,:)=[0.25 0.081123 0 0]; • x(5,:)=[0 0.077977 0.075885 0]; • x(6,:)=[0 0.090901 0.082905 0]; • x(7,:)=[0 0 0.091209 0.25]; • x(8,:)=[0.25 0 0 0]; • x(9,:)=[0 0.081123 0 0]; • x(10,:)=[0 0.16888 0 0]; • x(11,:)=[0 0 0.15879 0]; • x(12,:)=[0 0 0.091209 0]; • x(13,:)=[0 0 0 0.25];

16. Conclusion • Basic and non-basic configurations • Performance and extensibility of basic configurations • Mathematical framework for searching basic configurations • Practices