Modelling the combustion of micron-sized zinc particles
: for the application of a zinc metal fuel cycle

Student thesis: Master

Abstract

Metals are high-density energy carriers and have the potential to contribute to the energy transition towards a sustainable future. This thesis reviews zinc combustion for the discharge stage of a new concept: The metal fuel cycle. For this application of zinc, no specific research was found, and thus a particle model for the combustion of zinc microparticles is proposed. This model describes how, while heating a micro-sized zinc particle, a protecting (sub)-oxide layer is created which impedes the ignition of the zinc particle. However, at evaporation temperature, zinc vapour is released due to the evaporation of excess zinc from this (sub)-oxide layer, or by micro-explosions, occurring upon evaporation of the zinc core. The reaction mechanism of the released zinc vapour with oxygen is still up for debate, but it is clear that the product of this reaction mainly consists of nano-zinc oxide particles. In an attempt to confirm this hypothesis, experiments in a drop tube furnace were conducted. With SEM analysis, traces of surface oxidation and sub-oxide layers are found along with zinc oxide nanoparticles. When using a nitrogen flow, micro-explosions were observed at the exit of the furnace where particles came in contact with air. Not enough experiments were conducted to confirm the hypothesis with certainty. However, from the analysis, it can be concluded that several different combustion regimes - homogeneous and heterogeneous - are addressed in the combustion process. The total conversion of the zinc micro-particles and the capturing performance of the cyclone used in these experiments, were considered insufficient for an efficient metal fuel cycle. Therefore, future work on the capturing of the - by homogeneous combustion produced - zinc nanoparticles is needed. Modelling
Date of Award28 Feb 2019
Original languageEnglish
SupervisorL.P.H. (Philip) de Goey (Supervisor 1)

Keywords

  • metal fuels
  • zinc
  • combustion
  • sustainability

Cite this

'