Study on the mass transfer behavior of single CO2 bubbles in sodium silicate solution

Abstract

This study investigated in depth the mass transfer behavior of a single CO₂ bubble in sodium silicate solution. The dynamics of the bubble were accurately tracked using high-speed camera technology, and key parameters such as velocity, drag coefficient and mass transfer coefficient during the bubble rising process were analyzed in detail with the data processing ability of MATLAB. The results showed that the concentration of sodium silicate solution had a significant impact on the dissolution behavior of the CO₂ bubble. With the increase of concentration, the initial dissolution rate of the bubble was significantly accelerated, and the bubble in sodium silicate solution disappeared more quickly than that in deionized water. Meanwhile, an increase in liquid level would lead to a decrease of CO₂ dissolution rate. In the study on the influence of solution pH value on CO₂ absorption, it was found that the absorption rate at pH = 11.0 was significantly higher than that at pH = 10.5, and the whole absorption process conformed to the rapid pseudo-first-order reaction model. The kinetic parameters calculated by the model fully revealed the profound influence of solution pH value on the mass transfer and chemical reaction mechanism. Further research on the relationship between CO₂ absorption rate and static pressure indicated that the increase of static pressure could effectively promote CO₂ absorption in the initial stage of the reaction, and there was a significant linear positive correlation between them. However, with the progress of the reaction, due to the coupling effect of various complex factors, the deviation from linearity became pronounced with time. The absorption process could be clearly divided into the initial stage dominated by surface adsorption and preliminary reaction, the intermediate stage with accelerated absorption rate, and the later stage where the absorption rate tended to be stable. Furthermore, by comparing the liquid film mass transfer coefficients in the chemical absorption and physical absorption processes and combining with the relevant theoretical model calculations, the enhancement factor was evaluated. It reflects the enhancing effect of the chemical reaction on the mass transfer process. The empirical correlation established in this study took into account the influence of bubble size and sodium silicate concentration. The research results of this study provide a solid theoretical foundation and important data support for the process optimization of carbonization preparation of white carbon black, and have important reference value for the research and practice in related fields.