Regenerative Thermal Oxidation of Airborne N, N-Dimethylformamide and Its Associated Nitrogen Oxides Formation Characteristics
Abstract In this study, a two-bed electrically heated regenerative thermal oxidizer (RTO) was used to test the thermal destruction and oxides of nitrogen (NOx) formation characteristics in burning airstreams that contain either N, N-dimethylformamide or dimethylformamide (DMF) mixed with methyl ethyl ketone (MEK). The RTO contained two 0.152 m × 0.14 m × 1 m (L × W times] H) beds, both packed with gravel particles with an average diameter of approximately 0.0111 m and a height of up to 1 m with a void fraction of 0.42 in the packed section. The thermal recovery efficiency (TRE) and the gas pressure drop over the beds were also studied. Experimental results reveal that, with a valve shifting time (t s) of 1.5 min, a superficial gas velocity (U g) of 0.39 m/sec (evaluated at an influent air temperature of around 30 °C) and preset maximum destruction temperatures (T S) of 750–950 °C, no NOx was present in the effluent gas from the RTO when it was loaded with DMF-free air. When only DMF was present in the influent air, the average destruction efficiencies exceeded 96%, and increased with the influent DMF concentration from 300 to 750 mg/N∙m3. The “NOx-N formation/DMF-N destruction” mass ratios were in the range 0.76–1.05, and decreased as the influent DMF concentration increased within the experimental range. When both DMF and MEK were present in the influent gas, the NOx formation ratio was almost the same and the DMF destruction efficiency increased with the influent MEK/DMF ratio from 150/300 to 4500/300 (mg/mg) and in the preset temperature range. The NOx formation ratios were in the range 0.75–0.96. The TRE decreased as U g increased but was invariant with T s. The Ergun equation was found to suffice in the estimation of the pressure drop when the gas flowed over the packing beds.
Treatment of VOCs with molecular sieve catalysts in regenerative catalytic oxidizer.
This work prepares molecular sieve catalysts with various metal species and various metal weight loadings by impregnation, and then screens them in a catalytic combustion system. The current study further investigates the molecular sieve catalyst in an RCO system after it performed well in combustion efficiency. This work tests its performances in terms of CO(2) yield, pressure drop, the difference between temperatures of the inlet and outlet gases (T(d)), and thermal recovery efficiency (TRE), with various operational conditions. Experimental results demonstrate that the 10 wt% Cu/(MS) catalyst was the most active because it has the greatest combustion efficiency to treat volatile organic compounds (VOCs) than Co/(MS) catalysts and Mn/(MS) catalysts. The 10 wt% Cu/(MS) catalyst used in an RCO system reaches over 95% CO(2) yields under the heating zone temperature (T(set))=400°C, gas velocity (U(g))=0.37 m/s, isopropyl alcohol (IPA) concentration=200-400 ppm conditions. Moreover, the RCO system performed well in economic efficiency with the RCO with in terms of TRE, T(d) and pressure drop. The TRE ranged from 90.4% to 94.6% and T(d) ranged from 14.0 to 34.2°C under various conditions at T(set)=300-450°C. Finally, the results of the stability test demonstrated that the catalyst was very stable at various U(g) values and various T(set) values.
Advanced Regenerator Media For Industrial And Solar Thermal Applications
The presented advanced composite salt/ceramic thermal energy storage (TES) media concept has the potential of using phase change materials (PCM) via direct contact heat exchange and, therefore, the potentialof significant storage capacity improvement and cost reduction. It opens the windows for new industrial and solar thermal applications. Lab scale materials of Na-Ba-CO3/MgO and of Na2SO4/SiO2 have been successfully developed. With the silicia composite manufacturing in technical scale has been started in cooperation with a German ceramic producer.