# Flue Gas Composition and Treatment Potential of a Waste Incineration Plant
## Appendix A Post-Combustion Capture:  
The capture of CO\({}_{2}\) from flue gases made by the combustion of fossil fuels and biomass in air is known as post-combustion capture. The flue gas is passed through equipment which separates most of the CO\({}_{2}\). The CO\({}_{2}\) is fed to a storage tank and the remaining flue gas is relinquished into the atmosphere. The separation process is achieved using a specific chemical sorbent. This technology is mature and is applicable on an industrial scale. Many existing plants around the world are working with post-combustion chamber techniques and approve of this technology including 2261 GWe capacity oil, coal, and natural gas power plants [49], and in particular, 155 GWe supercritical pulverized coal-fired plants [50]. Furthermore, with over 60% of the electricity in the United States (US) produced from fossil fuel power plants, the deployment of post-combustion capture technologies is vital to reduce CO2 emissions [51]. Oxy-fuel Combustion Capture:  
With this type of capturing, almost pure oxygen is used for combustion as an alternative to air, resulting in a flue gas that is mainly CO2 and H2O. If fuel is burnt in pure oxygen, the flame temperature is excessively high, but CO2- and/or H2O-rich flue gas can be recycled to the combustor to justify this. Oxygen is typically produced by low-temperature (cryogenic) air separation and novel techniques to supply oxygen to the fuel, such as membranes and chemical looping cycles. The disadvantage of this process is that it needs a huge amount of oxygen to become separated. This increases operational costs. It is not widely used in MSW incineration plants due to the existence of water inside the waste composition [30; 52]. Pre-combustion Capture:  
This technique is more complicated, and includes reacting a fuel with oxygen or air and/or steam to give mainly a \"synthesis gas\" (syngas) or \"fuel gas\" composed of carbon monoxide and hydrogen. The next stage is the reacting of carbon monoxide with steam in a catalytic reactor called a shift converter, to give CO2 and more hydrogen. CO2 is then separated, usually by a physical or chemical absorption process, resulting in a hydrogen-rich fuel which can be used in many applications, such as boilers, furnaces, gas turbines, engines, and fuel cells [50]. It can be concluded from the brief information mentioned above about post-combustion technology that it is more mature than the other two technologies. There is much detailed research in the literature about the differences between these technologies [50; 53], both technically and economically, but these are beyond the scope of this study. Post-combustion technology was chosen to be simulated in Epsilon and to capture the results of any potential reduction in CO2. The most important point about this technology is the selection of an efficient sorbent. There are a number of criteria that must be met for a successful sorbent material, specifically high selectivity and adsorption capacity for CO2, fast adsorption and desorption kinetics, efficient regeneration of sorbents, and low cost [54]. Different materials have been investigated as solid-state adsorbents for CO2, such as zeolites, silica, porous polymer materials, metal organic frameworks, and carbon materials [55; 56; 57]. The most efficient for CO2 adsorption are carbon materials, which exhibit a high surface area, large porous volume, chemical stability, affinity for carbon dioxide, low cost, and the possibility of modification with heteroatoms [58]. The weak aspect of carbon sorbents is their poor selectivity. There are many behaviors that can overcome this undesirable feature and convert the carbon element into activated carbon with a high rate of selectivity. Polymers, biomass, or resins are widespread and used to produce or to convert these sources of carbon into activated carbon by using potassium compounds, namely, potassium hydroxide or potassium oxalate chemical activators. This leads to increasing selectivity and also enhances the surface area and porous volume.