A modeling approach aimed at calculating critical efficiency factors of microwave energy conversion into heat for different operating conditions is presented. In the experimental part, an efficiency factor was determined for microwave heating of 13X zeolites in a multimode microwave cavity. A comparison of the obtained results with the results reported in the literature indicated that microwave heating (MH) can be more energy-efficient than convective heating (CH). Moreover, it follows from the performed simulations that maintaining the same adsorbent bed temperatures in MH and CH for increasing gas flow rates rises energy consumptions in CH and decreases the critical efficiency factors, thereby improving the economic efficiency of MH.
A synthetic wastewater containing an aqueous mixture of disperse dyes was electrolyzed at
different current densities using a Ti/(RhO
x
+ TiO2) anode and stainless steel cathode, with the
objective of investigating the effect of stirring on the reactor operating under isothermal and
isoperibolic conditions. The results showed that the primary mechanism of dye decomposition
was a homogeneous oxidation by electrogenerated “active chlorine”. Under isothermal conditions
at a bulk pH of 4.0, increasing the mixing rate decreased the dyes' decomposition rates
(decolorization) but increased those rates at pH 8.0. The highest decolorization rate, until
approximately 40% conversion was reached, was achieved at a current density of 300 A/m2 and
pH 8.0 with the apparent homogeneous rate coefficient k
2 being 2.93 × 10-4 m3/mol s, while
6.45 × 10-5 m3/mol s was observed at pH 4.0. Conversely, mixing had a detrimental effect on
the performance of the reactor when it was operated under isoperibolic conditions at alkaline
pH. The effect of mixing is explained by considering the possible pH-dependent electrode and
bulk solution reactions, including the chlorine loss reactions and the possible anodic electrooxidation of chlorinated intermediates.
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