MICRO-REACTORS
Micro-reactors have micrometer-size channels in which reaction takes place. Heat is exchanged through the channel walls to the heat exchange medium. Because of the small channel size both the specific heat transfer areas and the heat transfer coefficients are very high. Because of this feature, very exothermic and very fast reactions can take place under isothermal conditions. The reaction time is thereby very short, which results in a very small reactor. Extensive descriptions of micro-reactor types and potential application are provided by Ehrenfeld [4].
Micro reactors have not been applied so far in the oil refining and base chemical industries. Commercial scale applications are rare even in the fine chemicals and pharmaceutical industry. I could find only one clear commercial scale implementation in DSM [5]. Other literature references even with scale-up in the title appeared to be, on close examination, lab scale or pilot plant scale applications. Poechlauer and others of GSK and Astra Zenica came to the same conclusion [5].
The main reason for the absence of micro reactor implementations in oil refineries and base chemicals is probably the high investment cost relative to conventional reactors[1, 2]. Additional reasons may be fouling and plugging of the micro channels, as well as how to obtain a uniform distribution over the micro channels, as mentioned by Seyfert of BASF [3]. These latter reasons may also be the explanation for the very low number of commercial scale implementation in the fine chemical and pharmaceutical industry.
I have found no other reasons known for this lack of implementation of micro reactors. Concept design knowledge for micro reactors is available [6] and several technology providers have been on the market for a long time. To mention a few: Institute for Micro-Technology Mainz (IMM), Velocys, and Microinnova.
By Jan Harmsen (Harmsen Consultancy BV)
References
[1] J. Harmsen, Implementation of Process Intensification in Industry, in “Process Intensification for Green Chemistry, KVK Boodhoo and AP Harvey (Eds.)“, J. Wiley, Chichester, 2013, p.393-400.
[2] Z. Rabiei, Hydrogen management in refineries, Petroleum & Coal, 54 (2012) 357-378.
[3] W. Seyfert, Upwind, trends and challenges in Process Engineering Research, plenary lecture. BASF Senior Vice President, ECCE10, Nice, 2015.
[4] W. Ehrfeld, V. Hessel, V. and V. Haverkamp, V. Microreactors, in Ullmann's Encyclopedia of Industrial Chemistry. J. Wiley, Hoboken 2000.
[5] P. Poechlauer et.al., Continuous Processing in the Manufacture of Active Pharmaceutical Ingredients and Finished Dosage Forms: An Industry Perspective, Org. Process Res. Dev., 16, 2012, 1586–1590.
[6] S.Borukhova, V. Hessel, Micro Process Technology and Novel Process Windows – Three intensification fields, in “Process Intensification for Green Chemistry, KVK Boodhoo and AP Harvey (Eds.)", John Wiley & Sons, Chichester, 2013, p. 91-156.
