Chemical Engineering Report Series

Process intensification refers to technologies and strategies that enable simpler and more efficient processes compared to conventional processes. Some features of such intensified processes are less recycle streams, reduced need for waste handling and lower investment and operating costs compared to conventional processes. One way of doing this is by making two or more process steps simultaneously and not one after another as it is traditionally done. In this work two such approaches, reactive distillation (RD) and the side reactor configuration (SRC), are studied. RD combines chemical reaction and distillation into a single process unit. In SRC a liquid stream rich in reagents is withdrawn from the distillation and fed into a side reactor. The reactor effluent is returned back into the same column. The final product is then obtained from the distillation column just as in RD processes. Two models for simulation and design of processes combining reaction and distillation were developed. The first model is for the reactive distillation process. The modelling approach is based on a direct account of the diffusion with multicomponent interaction effects, reaction kinetics, and heat transport. The model includes mass transfer in the film region, a catalyst efficiency determination based on the mass transfer inside the catalyst, and hydrodynamic models for reactive trays. This model was successfully tested against experiments from a pilot scale unit. A new reactive distillation process for producing 2-methoxy-2,4,4-trimethyl pentane is discussed. The other model is for the Side Reactor Concept (SRC). The model of the distillation column is derived from the mass and energy balances, equilibrium, and summation relations of a stage in a reactive distillation column. Rigorously calculated Murphree multi-component efficiencies are included to account for non-ideality of the stages. This model also includes a series of continuously stirred tank reactors (CSTR) representing the side reactor stage. Co-current flow and gas and liquid phases and heterogeneous catalyst are allowed in the reactor. The use of SRC and RD is discussed in two case studies, in the production of TAME and isooctene. The study showed that SRC is a potential process option, especially because the reactor conditions can be optimised to improve the performance of the process. PREFACE The research described in this thesis was done in the Laboratory of Chemical Engineering and Plant Design in Helsinki University of Technology during 1996-2004. The main part of the work was accomplished within the frame of BRITE-EURAM Project Reactive Distillation (CEC Project No. BE95-1335). I am very grateful to my supervisor Juhani Aittamaa for his guidance and encouragement during this work. I thank professor Andrzej Gorak for guidance and encouragement during the EU project. I thank all partners of the Reactive Distillation project for giving me the important opportunity to work in the project. I thank my co-authors Tuomas Ouni, Antti Hasanen, Sini Pakkanen, Kari Keskinen, Liisa Struckmann, and Satu Hyvärinen. I warmly thank my colleagues and friends Antti Pyhälahti, Kimmo Klemola, Eugeny Kenig, and Peter Banik for co-operation and advices. I also thank the staff of the Laboratory of Chemical Engineering and Plant Design for creating a good working atmosphere. The support by the European Commission in the frame of the BRITE-EURAM program (CEC Project No. BE95-1335) is greatly acknowledged. The financial support of the PROTEK programme of the Academy of Finland is greatly acknowledged. The financial support of TEKES (National Technology Agency of Finland) is greatly acknowledged. Konrad-Zuse-Zentrum in Berlin is acknowledged for the DAE-solver LIMEX used in DESIGNER. Finally, my warmest thanks to my wife Hanni and to my children Kim, Outi and Eva for giving me a wonderful life, which is much richer than I ever expected.