Design and application of a millistructured heat exchanger reactor for an energy-efficient process

• The use of millistructured HEX reactors enables new options for heat integration.
• A comprehensive optimization of an energy-efficient flow synthesis is presented.
• Pinch analysis was applied to determine energy targets for heat recovery.
• The feasibility of the approach was demonstrated by proof-of-concept experiments.

Flow chemistry in milli- and microstructured reactors exhibits great potential for process intensification. In the present work, this potential has been demonstrated through the process development for a solvent-free production process including a Michael addition and following product purification. Process simulation was used to maximize the material and energy efficiency of the overall process by recycling unconverted reactants and a catalyst (water) and by utilizing heat from the exothermic reaction to substitute external energy supply in the heat demanding process steps. As a proof-of-concept experiment, millistructured equipment was designed, manufactured and tested at a laboratory scale. A three-stream counter-current heat exchanger for reactant preheating and a plate heat exchanger reactor with zigzag reaction channels were investigated regarding the maximum transfer of reaction heat available for further process steps via a heat carrier cycle. The experiments showed stable reactor control in steady state operation and efficient heat transfer with a small driving temperature difference at the outlet of the heat exchanger reactor.