- Thesis topic: Study on CO2 and air pollution emission for electricity and gas supply industry

- Doi: https://doi.org/10.6840/cycu202301550 

- Abstract: 

        The objective of this study is to investigate the analysis of CO2 and air pollutants (PM, SOx, NOx, and heavy metals) emission with fuels, boiler units, air pollutant control equipment, emission factors, and control efficiency from coal-fired power plants. These data provide valuable information for further control strategies and policy making.
The study analyzed the regular inspection data from various power plants' inspection databases for the years 2016 to 2020. The carbon dioxide emission concentrations and emission factors were calculated. The average CO2 emission concentration for gas-fired power plants was found to be 4.2%, which is lower than coal-fired power plants (13.2%), oil-fired power plants (12.5%), and coal-fired cogeneration plants (13.3%).
Converting the emission factor based on electricity generation, the carbon dioxide emission factor for coal-fired power plants, oil-fired power plants, gas-fired power plants, and coal-fired cogeneration plants were determined to be 822, 836, 539, and 1493 g CO2/kWh. Further comparison of the carbon emission coefficients between mainstream coal-fired and gas-fired power plants revealed that gas-fired power plants have a 34.3% lower carbon emission factor.
Analysis of heavy metal emissions from ultra-supercritical coal-fired power plants and subcritical units reveals that the concentrations of various metals (Pb, Cd, Hg, As, Cr, Ni, Sb, Co, Mn) from ultra-supercritical units are all lower than those from subcritical units. However, even with the implementation of air pollution control devices, coal-fired power plants still face the risk of exceeding the established standards of the United States Environmental Protection Agency's MATS (Mercury and Air Toxics Standards) in the category of the heavy metal manganese (Mn).
The analysis of other pollutant concentrations reveals the following ranges for coal-fired power plants, oil-fired power plants, gas-fired power plants, and cogeneration plants, Particulate matter 0.2-19, 1-26, 0.1-4, and 2 mg/Nm3, Nitrogen oxides 5.3-67.5, 74.9-105, 1.37-67.4, and 59.9-62.0 ppm, Sulfur oxides 3.9-52.8, 101-135, 0.2-6.7, and 5.5-6.9 ppm. Comparing the pollutant concentrations between gas-fired and coal-fired power plants, the results indicate that gas-fired plants emit significantly lower concentrations of particulate matter, sulfur oxides, and nitrogen oxides, with reductions of 75.9%, 92.4%, and 52.5%, respectively.
Regression analysis was conducted on operational parameters. The results indicate a significant correlation between boiler temperature and pressure with carbon emission factor. As the design stream temperatures and pressures increase, the carbon emission factor decrease. If a coal-fired power plant adopts ultra-supercritical boilers and incorporates comprehensive air pollution control equipment, its carbon emission coefficients and pollutant emissions can be comparable to gas-fired power units.

Keywords: Thermal Power Plant, Carbon Emission Factor, Heavy Metals, PM, SOx, NOx