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Keywords:

  • film boiling;
  • hydrogen production;
  • nucleation;
  • chemical reaction;
  • conversion;
  • catalysis;
  • heat transfer;
  • mass transfer;
  • transport;
  • fuel cells

Abstract

A new platform, based on film boiling, is described for chemical processing by catalytic decomposition of organic liquids. A model for conversion of pure methanol to hydrogen and carbon monoxide is used to illustrate the operational and performance characteristics of the reactor. The model extends film boiling theory to include catalytic reactions at the surface. The results show that wall temperature exerts a dominant influence on product yields, with tube diameter a secondary effect. The yields of hydrogen increase as tube diameter and wall temperature increase, with the variation being nonlinear. At temperatures > 1200 K, the wall conversion rates reach an asymptote with wall concentrations of hydrogen and carbon monoxide being lower and higher than stoichiometric, respectively, because of the higher diffusion rate of hydrogen compared to carbon monoxide. A dimensional “performance factor,” defined as the ratio of hydrogen yield to the total energy required to maintain the vapor film and drive the reaction, is used to cast the performance of the film boiling reactor in terms of the variables of the problem. For the range of tube diameters examined (1.5 mm to 1.5 cm), the analysis shows the existence of wall temperatures that optimize performance. The advantages of the new reactor system are its simplicity and potentially large product yields, making it ideal for portable applications. © 2006 American Institute of Chemical Engineers AIChE J, 2006