Experimental and Kinetic Studies on Steam Gasification of a Biomass Char

The maximum gasification rate of corn stalk char (CSC) appeared at high conversion range, and its quite different gasification behaviors from other carbonaceous materials are all derived from the catalytic effect of alkali and alkali earth metals (AAEMs), so it is necessary to study the effect of AAEMs and gasification kinetics of such biomass char. However, there are few systematic discussions about this effect and kinetic modeling. Thus, in this study, CSC samples were prepared in a fast pyrolysis fixed-bed reactor, and its gasification experiments were conducted on a pressurized magnetic suspension balance at various total pressures (0.1–0.7 MPa), steam concentrations (10–70 vol.%) and temperatures (725–900 °C). Moreover, a water-leached CSC (H2O-CSC) was also prepared to evaluate the impact of AAEMs on the gasification performance of CSC, and some well-known models were adopted to describe the gasification behaviors. On the basis of these results, the effect of primary AAEMs on the gasification behaviors of CSC and gasification kinetic modeling were obtained. Results showed total pressure had no obvious influence on the gasification rate of CSC, and the reaction order varied at 0.43–0.55 with respect to steam partial pressures. In addition, the modified random pore model (MRPM) and Langmuir–Hinshelwood (L-H) model were satisfactorily applied to predict the gasification behaviors of CSC. The catalytic effect of AAEMs on CSC gasification was weakened due to water-leaching treatment. A random pore model (RPM) could describe the gasification behavior of H2O-CSC well, followed by grain model (GM) and volumetric model (VM).

Kinetic Study of Low Temperature Sulfur Dioxide Removal Reaction By Sodium Carbonate Using Random Pore Model

An experimental investigation of low temperature SO2 removal by porous sodium carbonate was carried out by thermogravimetry. As well as, applied mathematical modeling based on the random pore model was employed to kinetic study of this reaction. The experiments were performed at various temperatures (100-250 oC) and different SO2 concentrations (0.13-1.12 vol%). The initial slopes procedure was used to determine dependency of the reaction rate constants versus temperature. First-order kinetic with respect to gaseous reactant was found and value of activation energy was attained as 22.5 kJ mol-1. Product layer diffusion coefficients were evaluated by the best fitting of experimental data with the model predictions. These random pore model predictions indicated good agreement with experimental conversion-time data at various conditions. The resulted kinetic parameters were avail abled for engineering calculations of SO2 abatement from the coal-based power plants by low-temperature flue gas desulfurization.