| Abstract | The use of ozone for treatment of solids such as pulp, sawdust, and straw for animal feed,
for example, needs more study in order to know its reactivity in a dispersed solid medium.
Behavioral analysis of ozone decomposition reactor is one of the steps toward a complete and
detailed modelling of ozone-solid reactor. In addition the self ozone destruction can adversely
affect the yields of reactors such as solid bleaching reactors and its effect should be better
understood. This knowledge is also helpful in order to improve the residual ozone
decomposition.
The fixed bed decomposition reactor behavior is related to the ozone production reactor,
particularly the energy of the ozone production. The first part of the study determines the
energy performances to supply' the ozone generator.
The sand, glass bead, crushed glass bead, silica, and glass wool were the packing materials
used for study to ozone decomposition. The reactivity was considered through diffusion into
gas phase and reaction on the solid surface.The experimental results show that decomposition
is heterogenous reaction of first order in which the chemical kinetic is a strong controlling
process at room temperature. The parameters which have the important influence on ozone
decomposition at room temperature are interfacial area of fixed bed, gas flow rate, and
characteristic shape of particle.
The assumption of first order reaction and a plug flow condition fits very well with the
experimental results. A model is proposed from these results to predict the performance of
destroyed ozone in fixed bed reactor in different conditions (such as various kind of packing
materials, packing material size, reactor size, height of reactor, gas flow rate, and temperature).
The model represents with an accuracy compatible with engineering purpose, a total of 180
experiments conducted under various conditions.
However, detailed analysis of the experiments using the model for each series of
experiments show a slight non-linear behavior. The mass transfer boundary layer effect cannot
explain this difference. The assumption of the production of ground state and excited ozone was
assumed in order to explain this difference.
-i-
The decomposition of ozone at same concentration but produced through different ways:
low voltage and high flow rate or high voltage, low flow rate and dilution by oxygen before
entering the decomposition reactor shows clearly two different behaviors through the identified
decomposition kinetic constants from the model. For these two conditions, they are agreement
with the theoretical assumption from the literature review. The energy intensity supplied to the
ozone generator are different. The energy of activation for decomposition of two cases are
different. Reactivity in liquid phase with methyl red solution also clearly different behavior
supporting assumption. These results support the production of ground state ozone and excited
state ozone. |