## 4 Case Analysis
### Analysis of the Optimization Results  
To maintain the steel production capacity of the S steel plant, the production and consumption levels of the secondary energy sources in the main production system must remain unchanged. The heating furnace is considered an energy conversion device, where part of the consumed gas can be replaced by another gas. The model can be used to optimize the distribution of energy source in the energy conversion process according to two different schemes. The first scheme keeps the original process configuration without changing the energy conversion equipment, thus only modifying the energy source distribution. The second scheme adds new energy conversion equipment, changes both the original process and the distribution of the energy source, and forms a new process. The energy conversion equipment introduced in the latter scheme includes the CCPP, the CHF system, and the production of hydrogen, urea, and methanol. Table 3 shows the power distribution schemes of the S steel plant before and after model optimization. After optimizing the energy source distribution under the condition of the original energy conversion equipment, the steam boiler with a low power generation rate (power generation efficiency of 26%) no longer generates electricity. At the same time, the amount of electricity generated by the pulverized coal/gas mixed combustion boiler is also reduced. The analysis shows that the power generation efficiency of the pulverized coal/gas mixed combustion boiler is low, and the consumption level of steam coal is reduced after considering the pollution. Thus, the power \begin{table}
\begin{tabular}{c c c} \hline
**Energy Source** & **Market Price** & **Unit** \\ \hline BOG & 0.05 & CNY/m\({}^{3}\) \\ COG & 0.10 & CNY/m\({}^{3}\) \\ LDG & 0.40 & CNY/m\({}^{3}\) \\ Electricity & 0.50 & CNY/kWh \\ Oxygen & 0.55 & CNY/m\({}^{3}\) \\ Nitrogen & 0.25 & CNY/m\({}^{3}\) \\ Argon & 1.75 & CNY/m\({}^{3}\) \\ Liquid oxygen & 0.74 & CNY/kg \\ Liquid nitrogen & 0.65 & CNY/kg \\ Steam & 0.10 & CNY/kg \\ Compressed air & 0.15 & CNY/m\({}^{3}\) \\ Hydrogen & 1.76 & CNY/m\({}^{3}\) \\ Urea & 2.15 & CNY/kg \\ Methanol & 2.14 & CNY/kg \\ Steam coal & 0.40 & CNY/kg \\ Demineralized water & 5.6 & CNY/m\({}^{3}\) \\ \hline \end{tabular}
\end{table} 
Table 1: Market prices of the energy source. \begin{table}
\begin{tabular}{c c c c} \hline
**Energy Source** & **Surplus State** & **Amount** & **Unit** \\ \hline BFG & surplus & 599.36 & m\({}^{3}\)/t steel \\ COG & surplus & 98.03 & m\({}^{3}\)/t steel \\ LDG & surplus & 49.05 & m\({}^{3}\)/t steel \\ Electricity & demand & 339.05 & kWh/t steel \\ Oxygen & demand & 124.35 & m\({}^{3}\)/t steel \\ Nitrogen & demand & 109.94 & m\({}^{3}\)/t steel \\ Argon & demand & 2.66 & m\({}^{3}\)/t steel \\ S1 steam & demand & 105.29 & kg/t steel \\ S2 steam & surplus & 132.46 & kg/t steel \\ S3 steam & demand & 3.31 & kg/t steel \\ Compressed air & demand & 232.12 & m\({}^{3}\)/t steel \\ Demineralized water & demand & 1.85 & m\({}^{3}\)/t steel \\ \hline \end{tabular}
\end{table} 
Table 2: The surplus or demand amounts of the energy source. generation of the pulverized coal/gas mixed combustion boiler is reduced. After the introduction of new power generation equipment (CCPP and CHP) and energy conversion technology (urea production, methanol production, and hydrogen production), the BFG, LDG, and COG are fully utilized, and the utilization rates of the energy source are improved. The CCPP realizes the maximum power generation, and the remaining BFG and LDG are distributed to the CHP system and pulverized coal/gas mixed combustion boiler for power generation. Due to the addition of new energy conversion technology, more electric energy needs to be consumed. Therefore, it is necessary to purchase steam coal and electricity to maintain the balance between the supply and demand of electricity. Table 4 shows the gas distribution plans of the S steel plant before and after optimization.