**2.1 Separation**

At present there are basically four cases where the concentration of CO2 emissions makes its separation for geological sequestration technically and commercially viable. The first is related to the processes of extraction of natural gas, which depending on where and how it is extracted brings with it a varying percentage of CO2 along with a series of other gases and impurities. The second case the process of gasification of coal, which generates large amounts of CO2. The third is the generation of hydrogen, in which CO2 is generated as a byproduct. And the fourth situation, which contributes most to emissions, is the generation of CO2 from industrial processes involving combustion. Figure 5 presents, as an example of this fourth case, a coal-fired power plant. The coal is burned to heat a boiler to generate steam, which drives the turbines coupled to the generators. The exhaust gases, composed of roughly 15% CO2, 85% N2 and under 1% of other compounds such as sulfur oxides (SOx) and nitrogen oxides (NOx), pass through a desulfurization system for removal of most of the sulfur-based compounds. The exhaust gases then go to the capture unit, where the CO2 is separated from the other constituents, which are discharged into the atmosphere. The part discharged is mainly composed of nitrogen (N2).

Fig. 5. Coal thermoelectric plant with carbon capture

Today there are a series of CO2 separation methods already developed or under development, among them the more used are:


242 Fossil Fuel and the Environment

At present there are basically four cases where the concentration of CO2 emissions makes its separation for geological sequestration technically and commercially viable. The first is related to the processes of extraction of natural gas, which depending on where and how it is extracted brings with it a varying percentage of CO2 along with a series of other gases and impurities. The second case the process of gasification of coal, which generates large amounts of CO2. The third is the generation of hydrogen, in which CO2 is generated as a byproduct. And the fourth situation, which contributes most to emissions, is the generation of CO2 from industrial processes involving combustion. Figure 5 presents, as an example of this fourth case, a coal-fired power plant. The coal is burned to heat a boiler to generate steam, which drives the turbines coupled to the generators. The exhaust gases, composed of roughly 15% CO2, 85% N2 and under 1% of other compounds such as sulfur oxides (SOx) and nitrogen oxides (NOx), pass through a desulfurization system for removal of most of the sulfur-based compounds. The exhaust gases then go to the capture unit, where the CO2 is separated from the other constituents, which are discharged into the atmosphere. The part

**2. CCS steps – Involved technologies** 

 Separation Dehydration; Compression Transport; Injection;

**2.1 Separation** 

Storage and monitoring.

The CCS process can be divided into six basic steps:

discharged is mainly composed of nitrogen (N2).

Fig. 5. Coal thermoelectric plant with carbon capture

Various factors influence the choice among these separation methods: available space for allocation and consumption of energy by the separation plant, concentration of CO2 in the gases to be processed, pressure of these gases, level of purity and percentage of CO2 separation.
