## 3 Results and Discussion
\[CR_{COS}=\frac{(C_{COS,inlet}-C_{COS,outlet})}{C_{COS,inlet}}\times 100 \tag{14}\]  
Temperature variation inside of the reactor showed a delayed response caused by the transport of the heat energy supplied by the external heater, which changed the reaction rate and affected the reactor performance. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Case**} & **Gas Hourly Space Velocity** & **Length Ratio** & **Temperature** \\  & **(GHV)** [h-1] & **[-]** & **[K]** \\ \hline  
603 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Case for numerical analysis. Figure 4: Predicted results of the COS hydrolysis reactor; (**a**) pressure, (**b**) velocity, (**c**) temperature (Gas Hourly Space Velocity (GHSV) = 1.0, length ratio = 1.0, Temperature = 573 K). Figure 5: _Cont._  
Conversion rate of the reactant gas mixture was estimated and compared using the suggested numerical modeling to analyze the effects of individual parameters. Figure 6 shows conversion rate, concentration, and temperature variation with GHSV. Figure 6a graphically depicts conversion rate variation with GHSV, showing a maximum 50.1% conversion rate with an increase in GHSV. This is attributed to increased GHSV for an equivalent amount of catalyst, thus decreasing the conversion rate. The concentration and temperature variation of Figure 6b clearly illustrates a slow catalytic reaction with GHSV via a reduction in temperature by the increased reactant gas mixture flow, and increased reactant mass renders a slower decrease in reactant gas concentration. All in all, low GHSV increases the reactor temperature and activates the reaction further, resulting in a higher reaction rate. Besides, COS concentration rapidly decreased by the relatively small quantity of reactants. GHSV selection is thus very important for optimized reactor design. Secondly, the effect of the length ratio on the reactor performance was investigated by the variation of diameter and its length. Figure 7 shows the effect of the length ratio on the conversion rate, concentration, and temperature variation. Figure 7a graphically shows the conversion rate, and a maximum 9.2% increase was possible with an increase in the length ratio for the same GHSV and reactor tube wall temperature. Figure 7b shows the effect of the length ratio on the COS concentration inside of the reactor and temperature; the COS concentration rapidly decreased with the length ratio, while temperature increased proportionally. This is attributed to facile heat transfer and radial gas diffusion in the tube via reduction in the reactor diameter and an increased tube length, respectively,  
Figure 5: Predicted results of the COS hydrolysis reactor; (**a**) reactant, (**b**) product, (**c**) concentration profiles (GHSV = 1.0, length ratio = 1.0, Temperature = 573 K). causing an increased reaction rate. Therefore, an optimized length ratio could result in a higher COS conversion rate. Figure 6: Predicted results of the COS hydrolysis reactor according to GHSV; (**a**) COS conversion rate, (**b**) COS concentration and temperature profiles. Lastly, the effect of external heater temperature on the reactor wall was investigated by comparing the external tube wall temperatures. Figure 8 shows effects of the reactor wall temperature on conversion rate, reactant concentration, and inside temperature of the reactor. Figure 8a shows variation of the conversion rate with temperature on the reactor wall (547-603 K), showing a maximum 19.3% increase in the COS conversion rate for the same GHSV and length ratio. Figure 8b also shows the effects of variation of the reactant gas concentration and inside reactor temperature on the reaction rate and conversion rate, mainly confirming the beneficial effects of reactor wall temperature. This cogently  
Figure 7: Predicted results of the COS hydrolysis reactor according to length ratio; (**a**) COS conversion rate, (**b**) COS concentration and temperature profiles. shows that a higher heater temperature is required for a high COS conversion rate.