(248m) Targeting Multi-Phase Chemical Reactor Networks in Biochemical Processes: A Superstructure Approach with a View to Innovation and Novel Development

Authors: 
Panayiotou, G. P., National Technical University of Athens, Greece
Mountraki, A. D., National Technical University of Athens, Greece
C. Kokossis, A., National Technical University of Athens, Greece
Keywords: Chemical reactor designs, superstructure optimization, synthesis, biochemical reactions, process development

Biochemical reactions are non-ideal heterogeneous systems that operate at mild temperatures and consist of several paths that are often reversible. Reactions are typically slow and account for new and untested chemistries that one should optimize ahead of design. Apparent reaction rates are cumulative terms that combine transfer across phases, phase-equilibria as well as reaction kinetics [1]. Targeting the reaction performance is usually required to consider mass transfer that in turn stands a major drive in the development of innovative designs. The removal of products often offers a further potential to improve overall yields. Despite well-reported literature and experimental evidence to experiment with innovative schemes, the design of bioreactors is based on intuition and heuristics and the units selected are typically simple agitated vessels. Systems engineering is challenged to offer performance targets and to guide the design towards innovative choices for the process equipment required to deploy.

The paper presents systems methodology using a superstructure approach. The methodology extends previous work in homogeneous [2, 3] and heterogeneous systems [4, 5] building links that promote or deter relative velocities between reaction and mass transfer. Models exploit extensive, still fragmented, work in hydrodynamics as available from experimental rigs and short-cut models. The multiphase systems include gas-liquid reactors (e.g. stirred-tank reactors, bubble columns, gas-lift reactors, ejector-based reactors and thin film reactors), liquid-liquid reactors (e.g. column reactors and stirred-tank reactors), gas-solid reactors (e.g. multi-bed reactors, multi-tubular reactors, fluidized bed reactors and monolithic reactors), gas-solid-liquid reactions (e.g. trickle-bed reactors, slurry reactors, and again monolithic reactors) and liquid-solid reactors (e.g. stirred tank reactors). The methodology is based on shadow-reactor compartment as introduced by Mehta and Kokossis (1997) [5]. The compartments are extended to include degrees of freedom that manipulate reaction over mass transfer selecting compartments with favorable choices for hold ups and mass transfer areas (e.g. bubble sizes). The optimization combines evolutionary methods with mathematical programming.

Results illustrate the impact of mass transfer in the development of reliable targets and the link to non-conventional process equipment. Application examples include multiphase reactions in biochemical operations including cases in algae production. In all cases the methodology calculates performance targets along with a list of designs able to achieve this performance. Extension of the work addresses reactive separation systems and in-situ product recovery (ISPR) featuring products that inhibit reactions and leading to low conversions unless with a gradual removal of streams from the process.

 Acknowledgements

The financial support from Marie Curie European Research Program, RENESENG (FP-607415) is gratefully acknowledged.

References

  1. Klaewkla, R. , Arend, M. and Wolfgang F. Hoelderich, 2011, A Review of Mass Transfer Controlling the Reaction Rate in Heterogeneous Catalytic Systems Chemical Technology and Heterogeneous Catalysis, University of Technology RWTH, Germany.
  2. Kokossis, A.C. and Floudas, C.A., 1990, Optimisation of complex reactor networksâ??I. Isothermal operation, Chem Eng Sci, 45(3): 595â??614.
  3. Balakrishna, S. and Biegler, L.T., 1992, A constructive targeting approach the synthesis of isothermal reactor networks. Ind. Eng. Chem. Res., 31 (1), 300.
  4. Montolio-Rodriguez, D., P. Linke, D. Linke, M.Z. Stijepovic, 2010, Optimal conceptual design of processes with heterogeneous catalytic reactors. Chemical Engineering Journal 163(3), 438-449.
  5. Mehta, V.L. and Kokossis, A.C., 1997, Development of novel multiphase reactors using a systematic design framework, Computers and Chemical Engineering, 21, pp. S325-S330, (XD313/ISSN: 0098-1354).

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