Study of the pyrolysis reaction mechanisms for dust explosion
Résumé
Dust explosion of organic powders involves particles heating, pyrolysis, oxidation of pyrolytic gases and flame propagation. This work focused on the pyrolysis step, which can be rate-limiting during explosions. To better represent the pyrolysis stage, flash pyrolysis of four organic dust clouds (microcrystalline cellulose, wheat starch, oak and douglas fir) were carried out in a Godbert-Greenwald furnace from 700 to 900ᵒC, at a heating rate of 1000ᵒC.s-1, a solid residence time between 150 and 250 ms and vapour residence time in less than 2 s. Tar condensates analysis verifies the production of levoglucosan as the major product for cellulose and wheat starch pyrolysis. Optic image analysis and residual volatile matter content determination with TGA confirmed low conversions of solid residues. The major gaseous components identified were H2 (Hydrogen), CO (Carbon mono-oxide), CH4 (methane), CO2 (carbon dioxide) along with small yields of C2H2 (acetylene), C2H4 (ethylene) and traces of C6H6 (benzene). The effect of reactor temperature on gas compositions was studied. Experimental results indicated H2, CO, and CH4 increased with increasing reactor temperature whereas CO2 showed a contrary trend. C2H4 and C6H6 also increased at elevated reactor temperature but C2H2 showed a similar trend as CO2. Minimum Ignition Temperature (MIT) test results indicated the smallest hot surface temperatures that could be an ignition source for cellulose, wheat starch and oak dust explosions. Pyrolytic product analysis helped explain the pyrolysis behaviour of organic dust in the Godbert-Greenwald setup, a predictive model can be generated to predict the pyrolysis reaction rate of the dust in another work.
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Licence : Domaine public
Licence : Domaine public