# Flue Gas Composition and Treatment Potential of a Waste Incineration Plant
## 3 Results
### Adopted Flue Gas Cleaning System for the Proposed Plant  
Two main categories are available for flue gas cleaning; either dry or wet [27]. The main issue which must be considered if using the wet cleaning facility is water usage. For example, if NaOH suspension is applied, the scrubber system must have an additional water treatment plant in which the sulfate ions of the Na\({}_{2}\)SO\({}_{4}\) solution are precipitated as gypsum. As the MENA region is one of the most water-scarce areas in the world [32; 33], the dry cleaning system would be much better than the wet system despite the corresponding increase in operational costs because of the increased consumption of chemicals. Dry and semi-dry flue gas cleaning systems are similar. In both systems, the acid gases react with hydrated lime (Ca(OH)\({}_{2}\)). In this process, the gases are converted to solid substances such as calcium chloride, calcium sulfite, and calcium fluoride. The reaction products are precipitated in a subsequent bag house filter. The difference between the two systems is that in dry flue gas cleaning, the lime is injected in a solid form, whereas in semi-systems, it is injected in the form of an aqueous suspension. To calculate the amount of lime required to interact with the emitted amount of acids and sulfate emissions (HCl, SO\({}_{2}\), and HF), the molar weight of these compounds was used. According to [34], hydrated lime and one mole of Ca(OH)\({}_{2}\) captures two moles of HCl and one mole of Ca(OH)\({}_{2}\) captures one mole of SO\({}_{2}\) (see the chemical equations below). \[\text{Ca(OH)}_{2}+2\text{HCl}\rightarrow\text{CaCl}_{2}+\text{H}_{2}\text{O}\]  
\[\text{SO}_{2}+\text{Ca(OH)}_{2}\rightarrow\text{CaSO}_{3}+\text{H}_{2}\text{O}\]  
According to the simulated results in Epsilon for emissions and the molar weights of the related compounds, the amount of lime required to reach a certain level of emissions (see Table 12) matched the limitations on emissions stated in the 2018 BREF, which is 293 g of lime. The lime is injected as dry material into the flue gas stream in the reactors. It should be noted that the flue gas mass flow rate was around 340 m\({}^{3}\)/s where the temperature of the flue was around 1000 \({}^{\circ}\)C, which decreases the flue gas density and increases its mass flow. In recent years, the international community has paid more attention to climate change. It has promoted the study of technologies to reduce the emission of greenhouse gases such as CO\({}_{2}\), SO\({}_{2}\), HCl, and HF, among others, which is said to be responsible for contamination of the atmosphere and climate change. The increase in CO\({}_{2}\) has been generated by the growth in demand for energy, which makes it difficult to reduce. In the short term, one of the most viable options to reduce emissions is capture and storage, as agreed by the IPCC, which has set an ambitious objective of reducing CO\({}_{2}\) emissions by 50% by 2050 [35]. There are three main technologies currently available on the market to treat and reduce CO\({}_{2}\) emissions (an explanation about each of them can be found in Appendix A). Post-combustion technology was chosen to be simulated in Epsilon and to ascertain the results of any potential CO\({}_{2}\) reduction. It is most important when using this technology to select an efficient sorbent, so in this model, spherical nano carbon materials were used. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Compound** & **Molar Weight (g/mol)** & \
\begin{tabular}{c} **Epsilon Emissions** \\ **Before Treatment (mg/m\({}^{3}\))** \\ \end{tabular} &
\begin{tabular}{c} **Epsilon Emissions** \\ **After Treatment (mg/m\({}^{3}\))** \\ \end{tabular} \\ \hline Ca(OH)\({}_{2}\) & 74.093 & reagent & Reagent \\ SO\({}_{2}\) & 64.06 & 451.96 & 22.53 \\ HCl & 36.45 & 364.07 & 3.64 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Molar weights and emissions concentrations of sulfur oxides and hydrochloric acids.