Carbon dioxide, the main cause of the greenhouse effect, has attracted much attention in recent years. Thermal power plants that consume large amounts of coal are one of the main causes of the greenhouse effect, but it is difficult to replace them with alternative power plants due to their high energy production efficiency. For this reason, the removal process of flue gas including carbon dioxide from coal-fired power plants has been widely.

The International Energy Agency (IEA) reported that CO2 emissions dropped by 5.8% during the COVID-19 pandemic, and coal-based CO2 emissions declined by 0.6 Gt CO2. However, coal-based electricity generation contributes 35% of production, which is still larger than renewables, oil, and nuclear. Further, they have identified that Carbon Capture and Storage (CCS) technology will be essential to meet the global goal of limiting global temperature increase. At least 90% of CO2 could be captured from the power plant and energy industries. More than 80% of energy comes from the combustion of fossil fuels, which contributes to global warming. However, after CO2-capturing processes, CO2 can be turned into fuels such as methanol, formic acid, dimethyl carbonate, and methyl formate. There are various ways to capture carbon dioxide, including absorption, adsorption, membrane, cryogenic, and CO2/O2 combustion. Absorption is divided into two methods: chemical and physical absorption. Chemical absorption uses an aqueous solution, such as of amines or sodium hydroxide and sodium carbonate. Absorption has the advantage that the solvent is regenerated and returned to a continuous carbon dioxide removal process. CCS technology still faces some challenges, however. Large scale CCS has a high energy demand, leading to high operating costs. Optimization of the process is required to reduce energy demands and cost. Various CO2 capture processes have been developed with amine solvents, such as MEA (monoethanolamine). However, MEA has drawbacks: the high solvent cost, thermal degradation, and low CO2 absorption efficiency. Therefore, NH3 has been identified as a new absorption solvent. Comparisons of amines and ammonia as CO2 capture solvents have been undertaken. By theoretical values, NH3 can capture carbon dioxide twice as effectively as MEA. 5 wt% ammonia solvent has at least 23% to 29% lower reboiler duty than 30 wt% amine solvent in carbon dioxide capture.