The two traditional power plant technologies for capturing carbon dioxide are the Post-combustion and Oxy-fuel combustion systems. In this study, the post-combustion capture system absorbs carbon dioxide using a solvent called monoethanolamine, which is representative of a family of amine-based solvents, from flue gases of a coal-fired electricity generating plant. The resultant carbon dioxide rich solvent is fed to the regenerator for removal of the carbon dioxide, and the lean monoethanolamine solvent is recycled for further carbon dioxide capture. In oxy-fuel combustion, fuel is combusted in pure oxygen and a recycled flue gas stream is used to dilute the oxygen and provide heat transfer, which results in a high carbon dioxide concentration in the flue gas.
Despite Boundary Dam Power Station’s capacity for preventing 90% of its produced greenhouse gases from emission into the atmosphere, both the post-combustion and oxy-fuel capture processes emit some gases that can be hazardous to human health.
Researchers from University of Regina in Canada evaluated the predicted risk to human health associated with the Boundary Dam Power Station in Estevan, Saskatchewan, Canada. The study, which was published in International Journal of Greenhouse Gas Control, predicted the potential instead of actual risks to human health because real data from the stack of the power plant are unavailable. The study relied on results from a life cycle assessment study published in (Koiwanit et al., International Journal of Greenhouse Gas Control, 2014).
Amine is an effective solvent. However, there are solvent losses during the process of post-combustion capture as well as the emission of toxic gases such as sulfur oxides (SOX), nitrogen oxides (NOX) and particulate matter (PM2,5). The process also emits volatile products, largely degradation products of the amine, such as ammonia (NH3), aldehydes, ketones, formaldehyde, nitrosamines and nitramines, all of which pose health concerns such as an increased risk of cancer.
The study of Koiwanit et al. (2016) adopted the Air Quality Benefits Assessment Tool (AQBAT) software package for conducting health risk evaluation and the pollutants PM2.5, NO2, SO2, O3 and CO were considered.
For modelling air dispersion and risk, the study adopted the regulatory model of the American Meteorological Society and the Environmental Protection Agency (AERMOD) and CALPUFF. AERMOD is a steady-state Gaussian plume model, which assumes the dispersion concentration is described by a normal distribution. The model is designed to calculate pollutants in both simple and complex terrains in the same computational framework. On the other hand, the CALPUFF system is a non-steady meteorological and air quality modelling system for complex terrains; it measures air quality in both near field ranges and as far as hundreds of kilometers away.
Data sources for the study included: (i) Canadian stack data provided by SaskPower, (ii) data from the study (Koiwanit, 2015), (iii) meteorological data specific to Estevan provided by the Saskatchewan Government, and (iv) data on emission rates from life cycle analysis studies of the Canadian lignite coal-fired power plant with and without carbon dioxide capture technology processes. The data were all represented in MS® excel spreadsheets.
Health Canada’s air quality benefits assessment tool was used to estimate human risks or damage related to changes in ambient air quality. The data was analyzed in terms of a function, which is endorsed by Health Canada, for measuring the ambient air concentration response related to both chronic and acute human health outcomes.
The two technologies were compared based on three scenarios: conventional lignite-fired electricity generation station without carbon dioxide capture, lignite-fired electricity generation unit with an amine post-combustion capture system and an oxy-fuel combustion carbon dioxide capture system.
The studied system was located at Unit 3 of the Boundary Dam Power Station in Estevan, Saskatchewan, where emissions of NO2, PM2.5 and SO2 were predicted for an area of 19.625 Km2, which consists of a radial pattern of 100 increments with 25 points of 100m laterally on each increment (up to 2500 m).
Results from modeling with AERMOD showed that even though most of particulate matter from the power plant was a result of the oxidation of SOX and NOX to solid-phased sulfate and nitrate, the oxidation process is slow and formation of particulates can occur outside the 2.5 Km radius from the power plant.
Results from modeling with AQBAT showed the NO2 concentration affected only the change in health endpoint of acute exposure. The AQBAT modeling results on health outcomes of PM2.5 showed that PM2.5 was responsible for 14 health impacts, the five most important being acute respiratory symptom days, restricted activity days, asthma symptoms, child acute bronchitis, and adult chronic bronchitis. The AQBAT results on health outcomes of SO2 showed that the pollutant had health impact only in terms of the acute exposure mortality rate.
The research study concluded that the oxy-fuel system had better performance in terms of environmental impacts when compared to the post-combustion CO2 capture system. The oxy-fuel system showed better results in terms of reduction of acute respiratory problems, asthma, and restricted activity health outcomes. The two capture scenarios also demonstrated fewer adverse impacts on human health when compared to the no capture scenario. From the modeling results, among the pollutants, the PM2.5 was responsible for more health risks than gaseous NO2 and SO2, each of which was associated with only one health outcome.
According to Koiwanit et al. (2016), future work needs to be conducted using the modeling tool of AQBAT to assess health impacts of mercury and heavy metals, which were not taken into account in the study.
Koiwanit, J. (2015). Evaluation of environmental performance of hypothetical Canadian oxy-
fuel combustion carbon capture with risk and cost analyses. (Ph.D Thesis, University of
Regina, Regina, SK).
Koiwanit, J., Manuilova, A., Chan, C., Wilson, M., & Tontiwachwuthikul, P. (2014). A life cycle assessment study of a hypothetical Canadian oxy-fuel combustion carbon dioxide capture process. International Journal of Greenhouse Gas Control, 28, 257-274.
Koiwanit, J., Manuilova, A., Chan, C., Wilson, M., Tontiwachwuthikul, P. Human Health Risks of Post- and Oxy-Fuel Combustion Carbon Dioxide Capture Technologies: Hypothetically Modeled Scenarios. (2016). International Journal of Greenhouse Control, 47, 279-290.
Jarotwan Koiwanit1, Anastassia Manuilova2, Christine Chan1 , Malcolm Wilson2, Paitoon Tontiwachwuthikul1 . Human Health Risks of Post- and Oxy-Fuel Combustion Carbon Dioxide Capture Technologies: Hypothetically Modeled Scenarios. International Journal of Greenhouse Gas Control, Volume 47, April 2016, Pages 279–290.Show Affiliations
- Faculty of Engineering and Applied Science, University of Regina, Regina, Saskatchewan, Canada S4S 0A2
- ArticCan Energy Services, Regina, Saskatchewan, Canada S4S 0A2.
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