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Along with the phase-out of CF3Br (Halon 1301), several agents have been proposed as halon replacements for use in suppressing fires in aircraft cargo bays. However, these potential drop-in replacements were found to have a promotion effect on the explosion of an aerosol can, which tested by the US Federal Aviation Administration. Motivated by this problem, we measured the laminar burning velocity of premixed methane/air flames with added one of these agents, C6F12O (Novec 1230), in the counterflow configuration, for fuel/air equivalence ratios of 0.63, 0.68, 0.74, and 0.82. C6F12O was added at levels up to 3.5% by volume fraction to each mixture. Numerical simulations were performed using the detailed kinetic mechanism. The predicted results were in good agreement with the experimental measurements. The burning velocity for the very lean flames ( Φ = 0.63) was increased with C6F12O added at low concentrations due to the additional heat release from C6F12O reaction, whereas for higher equivalence ratios ( Φ = 0.68–0.82), it always decreased with all added agent concentrations. The extinction stretch rates have also been measured using the counterflow technique to gain further insight into the promotion/inhibition behavior of C6F12O in ultra-lean ( Φ < 0.63) flames. The results showed that C6F12O has larger promotion effect for the ultra-lean conditions. Sensitivity analyses showed that lean flames are more sensitive to the fluorinated reactions compared to the rich. In addition, direct images of hydrocarbon flame inhibition by fluorinated ketone were provided for the first time to help interpret the experiments.

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Previous experimental and numerical studies have demonstrated the unwanted promotion effect caused by potential halon replacements added to hydrocarbon–air mixtures. To explore this abnormal phenomenon, the chemical and physical contributions of the addition of C6F12O (Novec 1230) and C2HF5 (HFC-125) on the laminar flame speeds of the CH4–air mixtures are numerically investigated. Numerical simulations are conducted using the CHEMKIN-PRO software with newly developed fluorinated compounds’ mechanisms. Based on the interaction between the chemical effect and the physical effect, the equivalence ratio zone is divided into synergistic zone and antagonistic zone. Furthermore, the fuel-like characteristics of C6F12O and C2HF5 are also studied. In the lean CH4–air condition, the agents contribute to increasing the equivalence ratio, thus increasing the flame speeds chemically but cooling the mixture physically. When the actual equivalence ratio of the agent–CH4–air mixture is larger than 1.10 (for the C2HF5 addition) or 1.20 (for the C6F12O addition), the agents create an over-rich fuel mixture, thus decreasing the flame speed chemically. The contribution of the chemical effect is studied under different initial temperature and pressure conditions. The results indicate that increasing the temperature slightly lowers the chemical contribution, whereas increasing the pressure largely increases the chemical contribution. Additionally, a sensitivity analysis is conducted to interpret the large chemical component increase under high pressure conditions.

In this paper, a new magnetic molecular imprinting-cyclodextrin (MMIPs-CD) material was prepared by connecting β-cyclodextrin (CD) on the surface of the magnetic molecular imprinting polymers (MMIPs), which was used for...

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The reaction models employed in the kinetic studies of biomass pyrolysis generally do not include the secondary charring reactions. The aim of this work is to propose an applicable kinetic model to characterize the pyrolysis mechanism of medium density fiberboard (MDF) and to evaluate the effects of secondary charring reactions on estimated products yields. The kinetic study for pyrolysis of MDF was performed by a thermogravimetric analyzer over a heating rate range from 10 to 40 °C/min in a nitrogen atmosphere. Four stages related to the degradation of resin, hemicellulose, cellulose, and lignin could be distinguished from the thermogravimetric analyses (TGA). Based on the four components and multi-component parallel reaction scheme, a kinetic model considering secondary charring reactions was proposed. A comparison model was also provided. An efficient optimization algorithm, differential evolution (DE), was coupled with the two models to determine the kinetic parameters. Comparisons of the results of the two models to experiment showed that the mass fraction (TG) and mass loss rate (DTG) calculated by the model considering secondary charring reactions were in better agreement with the experimental data. Furthermore, higher product yields than the experimental values will be obtained if secondary charring reactions were not considered in the kinetic study of MDF pyrolysis. On the contrary, with the consideration of secondary charring reactions, the estimated product yield had little error with the experimental data.

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