## 3 Key Component Update
### HI Decomposer with Heat Recovery Utilization  
During early experiments, it was found that activated carbon had poor thermal conductivity, making it difficult for a large flow of HI to achieve both superheating and decomposition within the reactor. Therefore, an evaporator was added before the HI catalytic decomposer to gasify HI, and a superheater was installed to heat HI to the reaction temperature (773.15 K). In previous experiments, the decomposed HI was directly cooled by a cooler, resulting in significant heat loss. In this modification, to verify the feasibility of internal heat recovery, the high-temperature gas from decomposition is used to preheat the HI vapor before entering the superheater. This optimization aims for a hydrogen \begin{table}
\begin{tabular}{c c c} \hline  & **Power (kW)** & **Deviation from Heat Exchange Tube Power** \\ \hline Heat released by hot air & 4.99 & 1.46\% \\ Heat absorbed by boiling H2 SO4 & 4.77 & 5.92\% \\ \hline \end{tabular}
\end{table} 
Table 6: Results of energy conservation calculation. Figure 7: Temperature cloud map distribution: (**a**) Overall distribution; (**b**) Central section distribution. production rate of 1000 L/h, based on relevant data obtained from prior experiments. The relevant parameters for the HI decomposer are shown in Table 7.  
Through thermodynamic calculations, the heat absorption and release for heating the distilled HI solution to 773.15 K and cooling the high-temperature gas from decomposition to 473.15 K were determined, as shown in Table 8.  
Based on the thermodynamic calculation results, the HI decomposition reaction module was redesigned and manufactured as shown in Figure 8. All equipment is made of TC4 alloy. The distilled HI solution first enters the evaporator from the top. The evaporator has dimensions of \(\Phi\)700 \(\times\) 900 mm and is equipped with 54 kW adjustable-power titanium heating rods (108 kW at full load). In the evaporator, the H\({}_{2}\) solution undergoes heating and vaporization. The resulting gas then enters the HI shell-and-tube heat exchanger (\(\Phi\)273 \(\times\) 1500 mm), where it exchanges heat with the high-temperature gas flow from decomposition, heating the HI to about 653.15 K. The fluid then enters a \(\Phi\)273 \(\times\) 1500 mm superheater to heat to the required decomposition temperature of 773.15 K before entering the catalytic decomposition reactor filled with an activated carbon-based catalyst, where it decomposes to produce H\({}_{2}\) and I\({}_{2}\). The dimensions of the catalytic decomposer are \(\Phi\)377 \(\times\) 1900 mm. The generated products and undecomposed HI solution enter the heat exchanger tube side, exchanging heat with the gaseous HI solution in the shell side, cooling to about 473.15 K, and then entering the condenser and gas-liquid separator to produce hydrogen as the product. \begin{table}
\begin{tabular}{c c c} \hline
**Item** & **Unit** & **Value** \\ \hline HI decomposer reaction temperature & K & 773.15 \\ HI decomposition conversion rate & \% & 20 \\ Mass fraction of HI solution at outlet of distillation tower & \% & 38 \\ Density of HI solution at outlet of distillation tower & g/cm\({}^{3}\) & 1.35 \\ Flow rate of decomposition machine HI & mol/h & 446.43 \\ Steam flow rate into decomposer & mol/h & 5643.74 \\ Decomposer HI flow rate & mol/h & 401.78 \\ H\({}_{2}\) flow rate of decomposer & mol/h & 44.64 \\ Flow rate of decomposer I\({}_{2}\) & mol/h & 44.64 \\ H\({}_{2}\)O flow rate of decomposer & mol/h & 5643.74 \\ \hline \end{tabular}
\end{table} 
Table 7: Relevant parameters of HI decomposer.