## 1 Introduction  
Carbon dioxide (CO\({}_{2}\)) accumulation in the atmosphere, from different sources, is a serious global concern. Global mean temperatures are rising much faster and if the rate of CO\({}_{2}\) emission remains the same for the coming years, then the problem of global warming will increase exponentially. According to the Mauna loa observatory, Hawaii [1], which tracks the CO\({}_{2}\) presence in the atmosphere daily, the concentration of CO\({}_{2}\) in the atmosphere was determined to be 415.52 ppm in January 2021. This value is far more than 280 ppm, which is the safest level according to climate scientists. The majority of CO\({}_{2}\) emissions are generated by coal-fired power plants, steel and iron industries, cement industries, and automobiles. In a developing nation like India, the backbone of the power sector is coal, which contributes to 55.65% of the total installed capacity [2]. Therefore, our primary focus should be to reduce the emissions from coal-fired thermal power plants. Although many technologies have already been developed to reduce emissions, such as integrated gasification combined cycle (IGCC) and ultra-supercritical boilers, due to the energy penalty and high initial investment cost of these technologies, their implementation on large scale is economically not feasible. Carbon capture and storage (CCS) is one of the most reliable solutions to cut this increasing rate of CO\({}_{2}\) to the safest level. At least 90% of emissions from the world's largest sources can be captured by this technology [3, 4]. CCS is a three-stage process in which CO\({}_{2}\) is captured from the sources first, and then it is transported to a suitable geological site, where it can be stored for a long time. The technologies used in CCS are well known to the world now, but their implementation on a large scale is still not achieved due to the high energy penalty associated with them. Onthe other hand, the implementation of CCS on a large scale is very important in order to fully develop a sustainable energy system in the future. Chemical looping combustion (CLC) is a modified oxy-fuel combustion technique that is highly efficient and inexpensive as compared to other techniques. The CLC system consists of two interconnected fluidized bed reactors, which are a (1) fuel reactor and (2) an air reactor, as shown in Figure 1. The fuel reactor operates as a bubbling bed and the air reactor operates in a fast fluidization regime. In the CLC process, air and fuel (coal) do not directly mix or react. The oxygen required for the combustion of coal is provided by a metal oxide (Me\({}_{\text{x}}\)O\({}_{\text{y}}\)), which is also called an oxygen carrier (OC). These OCs are continuously circulated from the air reactor to the fuel reactor. In the air reactor, OC is oxidized by the air, while in the fuel reactor, the OC supplies oxygen for the combustion of the fuel. In this way, this process loop continues [5]. The products of this combustion reaction are CO\({}_{2}\) and steam. It is possible to isolate the steam from CO\({}_{2}\) by cooling and condensation. The reactions [6] which took place inside the fuel reactor and the air reactor, respectively, are  
\[\text{Fuel}+\text{nMe}_{\text{x}}\text{O}_{\text{y}}\rightarrow\text{nMe}_{ \text{x}}\text{O}\text{y}\text{-}1+\text{H}_{2}\text{O}+\text{CO}_{2} \tag{1}\]  
\[\text{Me}_{\text{x}}\text{O}_{\text{y}\text{-}1}+\frac{1}{2}\text{O}_{2} \rightarrow\text{Me}_{\text{x}}\text{O}_{\text{y}} \tag{2}\]  
where m and n are the numbers of moles of the reactants and the products. Since the ignition of fuel in the fuel reactor takes place without air, only oxygen is utilized for the combustion, which is given by the OC. The vent stream from the fuel reactor is not polluted or weakened by different gases, for example, nitrogen. This gives a high-virtue CO\({}_{2}\) stream, accessible to retrieve at the fuel reactor outlet without the requirement of an energy-expensive process for separation. The only energy cost associated with CLC is the separation of OC from ash.