Drying Kinetics Of Rod-like Nesquehonite And Molecular Dynamics Simulation Of Carbon Dioxide

Rod-like nesquehonite is used to produce high purity mg-based materials. Also, It can be directly used for reinforcement and modification of plastic, painting and so on.Moreover, it has excellent interfacial properties which can well dispersed in organic or inorganic solvent for further surface treatment. So it attracts many scholars’attention. In this work, the nesquehonite solution synthesized in certain reaction temperature, stirring rate and aging time by direct precipitation method using MgCl2·6H2O as raw material, NH4HCO3as precipitant and Na2HPO4as dispersant. After suction filtration, washing and drying, rod-like nesquehonite with diameter range of5-10μm and average length of80μm can be obtained. The drying kinetics experiments can be carried out at different hot air temperatures and materials-layer thicknesses, the drying curves and drying rate curves are obtained with the datas recorded by computer. The datas obtained in different conditions show that hot air temperature and material thickness have a similar influence on drying processes, the drying time will be shorter and the drying rate be faster with higher air temperatures or thinner material thicknesses. The drying equation of rod-like nesquehonite can be obtained through analysis of phase transformation kinetic theory. At the increasing stage, the drying equation is MR=exp[-(kt)n1], the drying rate equation is-dMR/dt=kn1MR(-lnMR)n1-1/n1, at the constant rate stage, the drying equation is MR=1.173-0.652kt, the drying rate equation is-dMR/dt=0.652k, at the decelerated stage, the drying equation is MR=exp[-(kt)n2], the drying rate equation is-dMR/dt=kn2MR(-lnMR)n2-1/n2.Using carbon dioxide EPM2potential energy model and ethanol TraPPE-UA potential energy model, vapor-liquid interface characteristics of carbon dioxide, self-diffusion coefficients of supercritical carbon dioxide and infinite dilute diffusion coefficients of ethanol in supercritical carbon dioxide are investigated by molecular dynamics simulation under the NVT ensemble. The simulation results indicate that with the decrease of the truncated radius, the density of liquid bulk decreases, the density of vapor bulk increases, and the interface thickness increases slightly. The number of plies has little effect on the density of vapor bulk, the density of liquid bulk and the interface thickness. The density of vapor bulk and the interface thickness increase as the temperature increases, but the density of liquid bulk and the interface tension show opposite tendency. The self-diffusion coefficient of supercritical carbon dioxide will increase with the higher temperature or lower pressure, as well as the inter-diffusion coefficient of ethanol in supercritical carbon dioxide system.