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- Biogas combustion: chemiluminescence fingerprintPublication . Quintino, Filipe; Trindade, Teodoro; Fernandes, Edgar C.A numerical and experimental study was conducted, with the purpose of inferring the influence of the CO2 concentration (xCO2) for different equivalence ratios (ϕ) on CH4/CO2/air (biogas) flames chemiluminescence. A thorough analysis on the signals of OH∗, CH∗, C∗2 and CO∗2 was performed. Typical biogas compositions were tested under laminar atmospheric flame conditions, within the unburned equivalence ratio of 0.9 and 1.14 with CO2 concentrations up to 40% in the blend. Experimental measurements of chemiluminescence were done using spectroscopy in the UV–visible region of the spectra. Simulations were performed with the GRI-Mech 3.0 mechanism without accounting for the nitrogen chemistry, extended with a chemiluminescence kinetics of OH∗, CH∗, C∗2 and CO∗2, in a burner-stabilized frame in CANTERA. Experimental measurements and numerical simulations are compared and generally are in good agreement. It was verified that CO2 dilution leads to a regular decrease in the emission intensities of OH∗, CH∗, C∗2 and CO∗2. Relations between chemiluminescence intensity ratios and xCO2 and ϕ were found. It was shown that OH∗/CO∗2 and C∗2/CO∗2 have the potential predict xCO2 in CH4/CO2/air flames. Moreover, it was verified that OH∗/CH∗, OH∗/C∗2 and CH∗/C∗2 are well suited to infer ϕ for the blends tested. It was verified that xCO2 does not cause relevant changes in the chemiluminescence ratios when inferring ϕ.
- Coal fly ash waste, a low-cost adsorbent for the removal of Mordant Orange dye from aqueous mediaPublication . Rosa, Teresa; Martins, Angela; Santos, Maria Teresa; Trindade, Teodoro; Nunes, NelsonIn this study, a coal fly ash material generated in a Portuguese coal thermal powerplant was tested as a low-cost adsorbent to remove dye molecules. Pre-treatment of the coal fly ash samples was not performed in order to reduce end use cost. Physical and chemical characterization revealed their inert nature and low effects lixiviation in aqueous media. Preliminary adsorption studies include adsorbent quantity, and adsorption kinetics. The adsorption studies focused on Mordant Orange 1 (Mo1) dye, but two other molecules, Rhodamine B (RhB) and Methylene Blue (MeB) were also included for comparison reasons. The adsorption isotherms were tested with different models including Langmuir, Freundlich and modified Langmuir-Freundlich. The effect of temperature, pH and unburn carbon in the adsorption process were also studied. The results show that adsorption capacity of the coal fly ash occurs mainly due to electroestatic interactions between the adsorbent surface and the adsorbate, which depends on the pH of the aqueous media and the surface chemistry of the material, quantified by the point of zero charge, pHpzc. These joint effects are responsible for the higher retention of Mo1 that is about 16 times higher, when compared to the other two molecules tested.