Activated carbons (ACs) were prepared from Alternanthera philoxeroides (AP) by K2CO3 one-step mixing activation. The effects of the mixing mass ratio of K2CO3 to AP, activation temperature, N2 flow rate, and period on the yield and specific surface area of ACs were investigated. The results showed that the surface area and pore volume of ACs were closely related to activation conditions and that the activation temperature was the main factor influencing the surface area and pore volume. The activation conditions only had a slight effect on the yield of ACs, which varied between 13.5% and 19.5%. The surface area of 1799.8 m2/g was obtained at a K2CO3 to AP mass ratio of 2:1, activation temperature of 900 °C, activation time of 2 h, and N2 flow rate of 60 cm3/min. The surface morphology of ACs were characterized with scanning electron microscopy (SEM), and the recovered K2CO3 was characterized with powder X-ray diffractometry (XRD). The SEM images of the ACs also showed that the activation temperature had an obvious effect on the porous structure.

The purpose of this study is to investigate the characteristics of soot particles in C2H4/CO2/O2/N2 combustion at equivalence ratio of 3.0–5.0. As the oxidant is switched from conventional air to CO2/O2/N2 mixture, the key species C2H2, C3H3 responsible for formation of first aromatic ring, the typical aromatics and 4-ring aromatics total production rate all decrease greatly. In addition, with CO2 mole fraction from 0.2 to 0.5 in the mixture, the soot particle number density, volume fraction, surface area density, which are three most important parameters to soot particle property, are suppressed obviously. Furthermore, the increasing content of CO2 in the oxidizer influences mostly H, OH radical concentrations by two reactions: COOHCO2H and HO2OOH, and the production rate of H, OH from the two reactions declined, which revealed that CO2 in mixture has an inhibiting effect on soot particle generation.

A numerical study was carried out to determine the effects of CO addition on the laminar burning velocity, NOx emission, and extinction strain rate in a premixed CH4/CO/air flame under the lean condition (equivalence ratio of fuel to air phi= 0.60-0.80). When more CO was added to the fuel, the laminar burning velocity decreased, which is different from that observed for H-2 addition. To explain this, we studied the strong correlation between laminar burning velocity and H+OHpeak concentrations. Results showed that the H+ OHpeak concentrations decreased linearly with an increase in CO content. This tendency is in good agreement with that of the laminar burning velocity. For NOx, we observed that increments in CO addition led to a remarkable reduction in the NOx emission. In addition, we investigated the NO formation mechanism and determined the relevant reactions for NO production using a sensitive analysis. The NO concentrations decreased significantly with enrichment by CO and the NO production rate also clearly decreased. We calculated the radial strain rate S-rad and discussed the influence of strain rate on lean flame stability with regards to the addition of different CO mole fractions to the fuel. The extinction strain rates indicated that the lean flammability limits were extended by CO addition in some way.

The method of connectivity method was conducted to the reduction of detailed reaction mechanism for methane. An algorithm for the detection of redundant species was examined based on the inspection of the normalized Jacobian,in which the elements provided information about how the time-derivative of the concentration of a species changes if the concentration of another species is perturbed. Two reduced mechanisms consisting of respectively an 39 species involved 227 reactions and 26 species involved 138 reactions for methane oxidation,was found to mimic the performance of the detailed mechanism with high fidelity.