The Science Symposium “Smart Energy for a Sustainable Future” March 9-10 is all about the importance of new energy technologies.
Professor Andrzej Górak, takes a close look at the most common and most energy-intensive separation technique: distillation. It is used in refining crude oil or the manufacture and purification of nitrogen, oxygen and other gases. Górak leads the Laboratory of Fluid Separations at the Department of Biochemical and Chemical Engineering at the Technical University of Dortmund, Germany, and has edited the most comprehensive work on distillation ever published: Distillation: Fundamentals and Principles . Join him in discussing opportunities on how to improve the energy consumption and efficiency of distillation.
Ancient But Still Interesting
For more than 5,000 years distillation has been used as a method for separating binary and multicomponent liquid mixtures into pure components. Even today, it is amongst the most commonly applied separation technologies and is used on such a large scale worldwide that it is responsible for up to 50 % of both capital and operating costs in industrial processes. It absorbs about 50 % of the total process energy used by the chemical and petroleum refining industries every year.
Distillation seems to be a mature technology, but it will continue to interest researchers and practitioners for the next decades because of its significant practical relevance as well as unsolved questions such as how to substantially reduce the energy footprint of chemical processing.
Current and Future Trends
Distillation columns – large cylindrical columns packed with trays, plates, or packing material to allow better contact between two phases – are typically used for industrial distillation. During the last twelve years, the column internals have been continuously and substantially improved by equipment providers. These include, for example, the Raschig Super-Ring , sandwich packing , and high performance distillation trays .
Academia has developed very sophisticated mathematical tools for conceptual distillation design. Many of these tools have been adopted by end users in the chemical and petrochemical industries and open new pathways for identifying optimal separation schemes, process modelling, and optimization.
Reactive distillation, which is the simultaneous realization of a chemical reaction and a distillative separation, has also been improved extensively. Today it is possible to recover carboxylic acids produced by fermentation  or to separate chiral substances using enzymatic bioreactive distillation . However, for bioproduct processing in particular, reactive distillation still needs further study.
The big challenge, however, is the development of mega-equipment and better integration of distillation with other unit operations such as pervaporation (a membrane process for the purification of liquid mixtures), vapour permeation, organic solvent nanofiltration, and extraction . For this, more detailed models and design tools are needed that can handle multicomponent and multireaction systems as well as manage the complexity that comes with the large number of potential process configurations and large sets of potential solvent–membrane candidates.
Smart Use of Energy
Given that the chemical industry consumed 19 % of the energy in Europe in 2009, distillation is clearly a significant driver of overall energy consumption. We need to reduce its energy consumption through
- further improvement of the overall performance of column internals;
- use of better solvents for extractive or azeotropic distillation;
- placement of several distillation columns in one shell (divided wall columns);
- integration of distillation with other separations such as reactive agents, adsorbents, and membranes.
Alternative energy sources such as microwave, plasma, ultrasound, electric fields, and light have the potential to improve chemical syntheses in terms of energy and resource efficiency. Currently, practical applications of alternative energy sources such as microwaves are far from ready for application in distillation. Ultrasound can be used to increase the mass-transfer area rather than as a source for energy input. Fundamental research is needed here and is being carried out as part of some European and national projects. One of them is the European research project Alternative Energy Forms for Green Chemistry (ALTEREGO) . It aims to develop new methods to use alternative energy technologies in processes for advanced pharmaceutical synthesis, green fuels, and bulk chemicals synthesis.
Please share your opinion.
Which approaches to improve the energy consumption and efficiency of distillation seem promising to you?
 Distillation: Fundamentals and Principles (Eds: Andrzej Gorak, Sorensen), 1st ed., Academic Press – Elsevier, Amsterdam, The Netherlands, 2014. ISBN: 978-0-123-86547-2; Distillation: Operation and Applications (Eds: Andrzej Gorak, Hartmut Schoenmakers), 1st ed., Academic Press – Elsevier, Amsterdam, The Netherlands, 2014. ISBN: 978-0-123-86876-3; Distillation: Equipment and Processes (Eds: Andrzej Gorak, Zarko Oluji´c), 1st ed., Academic Press – Elsevier, Amsterdam, The Netherlands, 2014. ISBN: 978-0-123-86878-7
 Michael Schultes, The Impact of Tower Internals on Packing Performance, Chem. Ing. Tech. 2014, 86, 658–665. https://doi.org/10.1002/cite.201300166
 N. Kashani, M. Siegert, T. Sirch, A New Kind of Column Packing for Conventional and Reactive Distillation – The Sandwich Packing, Chem. Eng. Technol. 2005, 28, 549–552. https://doi.org/10.1002/ceat.200407153
 T. Cai, M. Resetarits, A. Y. Ogundeji, Trays for distillation and absorption, Liaison Functions 2014 – Core Programming Area at the 2014 AIChE Spring Meeting and 10th Global Congress on Process Safety 2014, 482–488. ((accessed February 2015))
 C. S. López-Garzón, A. J. J. Straathof, Recovery of carboxylic acids produced by fermentation, Biotechnol. Adv. 2014, 32(5), 873–904. https://doi.org/10.1016/j.biotechadv.2014.04.002
 P. H. Au-Yeung, S. M. Resnick, P. M. Witt, T. C. Frank, F. A. Donate, L. A. Robbins, Horizontal reactive distillation for multicomponent chiral resolution, AIChE J. 2013, 59(7), 2603–2620. https://doi.org/10.1002/aic.14138
 P. Lutze, A. Gorak, Reactive and membrane-assisted distillation: Recent developments and perspective, Chem. Eng. Res. Desig. 2013, 91(10), 1978–1997. https://doi.org/10.1016/j.cherd.2013.07.011
 Alternative Energy Forms for Green Chemistry (ALTEREGO), European cooperation project funded within the 7th Framework Programme (accessed February 2015)