## 2 Methodology  
In order to reach their purpose, a mass transfer model accompanying a two-film model, thermodynamic data, and an energy duty model were used. The framework used in here is proposed in Figure 1. This study is divided into three parts, as follows: the first part uses sodium glycinate solution to capture CO\({}_{2}\). In order to explore the effects of the process variables on the absorption efficiency (\(E\)), absorption rate (\(R_{A}\)), overall mass transfer coefficient (\(K_{G}a\)), gas-liquid molar flow rate ratio (\(\gamma\)), absorption factor (\(\varphi\)), and CO\({}_{2}\) loading (\(\alpha\)) in a steady state condition, a bubble-column scrubber was adopted to study the capture of CO\({}_{2}\) under a constant pH and constant solution temperature environments. The second part uses the Taguchi experimental design and Taguchi analysis to find the optimum operating conditions and the order of importance, which are validated further. In addition, two optimum operating conditions are used for the uncontrolled experiments. The third part uses the scrubbed liquids collected from optimum conditions for the regeneration experiments, so as to evaluate the energy duty of the sodium glycinate solution. Finally, the correlation equations were obtained for further discussion.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**References** & \begin{tabular}{c} **Mass Transfer** \\ **Coefficient (s\({}^{-1}\))** \\ \end{tabular} & **Conditions** & **Remarks** \\ \hline \multirow{4}{*}{[PERSON] et al. [31]} & \multirow{4}{*}{0.02–0.14} & Gas flow rate = 0–0.43.8 m/s & \multirow{4}{*}{\begin{tabular}{c} \\ Solvent: paraffin oil \\ Slurry concentration (Al\({}_{2}\)O\({}_{3}\)); \\ 0–0.25 \\ \end{tabular} } & \multirow{4}{*}{\begin{tabular}{c} \begin{tabular}{c} \\ \end{tabular} \\ \end{tabular} } & \multirow{4}{*}{\begin{tabular}{c} \\ \end{tabular} } \\  & & & \\ \hline \multirow{4}{*}{[PERSON] et al. [32]} & \multirow{4}{*}{0.01–0.20} & Gas flow rate = 0.01–0.28 m/s & \multirow{4}{*}{\begin{tabular}{c} Absorption of O\({}_{2}\) using \\ tap water \\ \end{tabular} } \\  & & & \(T\) = 25 °C; & \\ \cline{1-1}  & & Solvent: tap water & \multirow{2}{*}{\begin{tabular}{c} Absorption of O\({}_{2}\) using \\ tap water \\ \end{tabular} } \\  & & Gas: N\({}_{2}\)/Air & \\ \hline \multirow{4}{*}{[PERSON] et al. [33]} & \multirow{4}{*}{0.045–0.085} & Gas flow rate = 3.2–10.8 m/s & \multirow{4}{*}{\begin{tabular}{c} Absorption of O\({}_{2}\) using \\ tap water \\ \end{tabular} } \\  & & & \(T\) = 25 °C; & \\ \cline{1-1}  & & Solvent: tap water & \multirow{2}{*}{\begin{tabular}{c} Absorption of O\({}_{2}\) using \\ tap water \\ \end{tabular} } \\ \cline{1-1}  & & Gas flow rate = 0.02167–0.2068 & \\ \cline{1-1}  & & & \(m/s\) & \\ \cline{1-1} \cline{2-4} [PERSON] et al. [34] & 0.01–0.14 & Solvent: tap water, glycerin, and alcohol & \multirow{2}{*}{\begin{tabular}{c} Absorption of O\({}_{2}\) using tap \\ water, glycerin, and alcohol \\ solvents \\ \end{tabular} } \\  & & Slurry concentration (PVC): & \\ \cline{1-1}  & & 25–100 kg/m\({}^{3}\) & \\ \hline \multirow{4}{*}{[PERSON] et al. [35]} & \multirow{4}{*}{0.0342–0.888} & pH = 9.0–11; \(T\) = 25–45 °C; & \multirow{4}{*}{\
\begin{tabular}{c} Absorption of CO\({}_{2}\) using \\ MEA solution \\ \end{tabular} } \\  & & \(G\) = 4–9.5 L/min & \\ \cline{1-1}  & & Solvent: 4M MEA & MEA solution \\ \cline{1-1}  & & CO\({}_{2}\) concentration:15–60\% & \\ \hline \multirow{4}{*}{[PERSON] et al. [36]} & \multirow{4}{*}{0.051–0.305} & pH = 9.5–11.5; \(T\) = 25–60 °C; & \multirow{4}{*}{
\begin{tabular}{c} Absorption of CO\({}_{2}\) using \\ aqueous ammonia solution \\ \end{tabular} } \\  & & \(G\) = 3–5 L/min & \\ \cline{1-1}  & & Solvent: aqueous ammonia & Absorption of CO\({}_{2}\) using \\ \cline{1-1}  & & (28\%) & \\ \cline{1-1}  & & CO\({}_{2}\) concentration:15–60\% & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Mass transfer coefficient for various bubble-columns. MEA—monoethanolamine.