A Review on Technologies for Reducing CO2 Emission from Coal Fired Power Plants

In recent years, global warming has been a major issue due to continuous growth of greenhouse gas emissions from different sources. It has been estimated that the global average temperature will rise between 1.4 –5.8 °C by the year 2100 (Williams, 2002). The contributors to greenhouse effects are carbon dioxide (CO2), chlorofluorocarbons (CFCs), methane (CH4), and nitrous oxide (N2O). The contribution of each gas to the greenhouse effects is CO255%, CFCs 24%, CH4 15%, and N2O 6% (Demirbas, 2008). Carbon dioxide (CO2), a major greenhouse gas which is mainly blamed for global warming occupies a large volume of the total emissions. Figure 1 shows the trend of CO2 emissions over the years (Demirbas, 2005). Different industrial processes such as power plants, oil refineries, fertiliser, cement and steel plants are the main contributors of CO2 emissions. Fossil fuels such as coal, oil and natural gas are the main energy sources of power generation and will continue to generate power due to the large reserves and affordability. It is expected that coal utilisation in power generation will continue to increase in this century too. Demirbas (2005) reported that about 98% of CO2 emissions result from fossil fuel combustion, and 30%–40% of world CO2 emissions are generated by coal combustion among all the fossil fuels. The coal fired power plants generate the majority of the electricity and produce the highest rate of CO2 per kilowatt hour (Department of Energy and Environmental Protection Agency, Washington DC, 2000). Table 1 shows the CO2 emissions and power generation from various sources. It can be seen from Table 1 that the coal-fired power plants are responsible for a large percentage of CO2 emission among other process plants around the world, including Australia. About 46% of the world’s power generation is estimated to be from coal combustion, including 50%, 89% and 81% of the electricity generated in the United States, China and India respectively (Parker et. al., 2008). It is estimated that combustion of coal for power generation will be responsible for about 41% of the world’s CO2 emissions by 2025. Table 2 shows the world wide large stationary sources of CO2 emissions and Figure 2 shows the stationary sources of CO2 in Australia. In Australia 75% of the total electricity is produced from coal fired power plants, so coal fired power plants have a great impact on the Australian economy (ESAA, 2003; ABS, 2001). In Australia, power plants contribute about 64% of the total CO2 emissions generated from stationary sources (AGO, 2006).