Alkalimetalliyhdisteiden kaasu–hiukkastasapainon tutkiminen aerosolitestireaktorissa

The research topic of this thesis is inorganic gases from combustion that form particles via gas-to-particle conversion. The particles formed in gas-to-particle conversion have an effect on fouling of the super heaters and corrosion in boilers. These are the main reasons for unscheduled shutdowns and tube failure. Aerosol particlesformed from inorganic gases are challenging to study in boiler conditions. To be able to measure the particles formed via gas-to-particle conversion, the related processes need to be isolated from the boiler to a smaller and easily controllable environment. The experiments of this thesis were conducted in laboratory environment. The most important facilities used were high-temperature chambers, particle sampling and particle instruments. The first high-temperature chamber is used for the vaporization of the reactants, and the latter is used to achieve the gas-to-particle equilibrium. Water solution of solid reactants is fed to the chamber in order to control the amount of reactants. In addition, different gases are fed to the chamber. The reactants used in this thesis were selected from black liquor recovery boiler process. Black liquor composition is highly affected by the quality of the wood used in pulping, and that is why the reactant concentrations should be controllable. Black liquor consists mainly of sodium and sulphur but also of chloride from the wood. The chloride has been observed to be problematic since it causes corrosion in recovery boilers. A sample was taken from the second high-temperature chamber by diluting it in three steps before the particle measurement equipment. The measurement results show two mode particle size distributions. Results indicate that one of the mode is formed in high-temperature conditions and the other in the dilution. It was discovered that alkali sulphate formation is the key component of the particle formation in the second high-temperature chamber. Indirect references of alkali chloride formation are observed by studying the nucleation mode. The nucleation mode particle number is decreased when temperature of the second high-temperature chamber is lowered because more alkali chloride compounds is transferred to the particle phase already in high temperature conditions

From Boiler to Atmosphere: Effect of Fuel Choices on Particle Emissions from Real-Scale Power Plants

Fossil fuels, coal and oil are used for energy production around the world. Combustion of these fossil fuels produces gases and particles that affect air quality and climate. The CO2 emissions can be decreased by substituting fossil fuels with biomass and this substitution can further affect the particle emissions of the power plants. This thesis focuses on characterising particles of real-scale power plants with various fuels, from combustion to atmospheric dilution. The studied power plants were a combined heat-and-power (CHP) plant (combusting coal and a coal – wood pellet mixture) and a heating plant with three fuel mixtures. The particles were characterised mainly based on particle number size distribution and number concentration, using aerosol sampling from the superheater area of the boiler of the CHP plant, the stack of the CHP and the heating plant and the atmosphere surrounding the CHP plant.Measurements for the aerosol samples taken from the boiler indicated that the particles from the combustion of coal and the mixture of coal and industrial pellets had already formed in the boiler. The formation of the particles was studied by changing the dilution of the aerosol sample and by comparing the electrical charges of the particles in the boiler. The coal-combustion particles were around 25 nm in diameter. The addition of 10.5% industrial pellets to the coal caused the formation of a second particle mode, the soot mode (120 nm in diameter), in the boiler. In the heating plant, the addition of light fuel oil to heavy fuel oil had a similar effect on the oil-combustion particles. The particles from the combined coal-and-pellet combustion agglomerated and coagulated before reaching the sampling point in the stack. These processes, combined with the effect of an electrostatic precipitator, resulted the mean diameter of the particles to be 80 nm. Further, the flue-gas desulphurisation and fabric filters lowered the particle number concentrations. The particles measured inside the stack were also observed from the atmosphere before they were diluted to background concentrations. The flue-gas plume was measured in four occasions, in three wind directions and with four flue-gas cleaning and fuel combinations. These measurements resulted in the observation of a new particle formation in the diluting plume. In the atmospheric measurements, the concentrations of SO2 and CO2 played an important role in measuring the dilution process. In the heating-plant experiment, the characterization of oil-combustion particles showed that the lower fuel sulphur content decreased the particles’ hygroscopic growth factors.The atmospheric primary emissions of coal-fired power plants can be effectively lowered through flue-gas cleaning technologies. In this study, flue-gas cleaning was shown to affect the flue gas’s particle number and the mass concentration as well as its black carbon concentration. The cleaning did not prevent new particle formation in the flue-gas plume in the atmosphere, but it did reduce the potential for particle formation

Chemical and physical characterization of oil shale combustion emissions in Estonia

In this study, oil shale combustion emission measurements were conducted in a 60 kW(th) Circulating Fluidized Bed combustion test facility located in a laboratory-type environment. A comprehensive set of instruments including a nitrate-ion-based Chemical Ionization Atmospheric Pressure interface Time-of-Flight Mass Spectrometer, a Soot-Particle Aerosol Mass Spectrometer, and a Potential Aerosol Mass (PAM) chamber was utilized to investigate the chemical composition and concentrations of primary and secondary emissions in oil shale combustion. In addition, the size distribution of particles (2.5-414 nm) as well as concentration and composition of gaseous precursors were characterized. Altogether 12 different experiments were conducted. Primary emissions were studied in seven experiments and aged emissions using PAM chamber in five experiments. Combustion temperatures and solid fuel circulation rates varied between different experiments, and it was found that the burning conditions had a large impact on gaseous and particulate emissions. The majority of the combustion particles were below 10 nm in size during good burning whereas in poor burning conditions the emitted particles were larger and size distributions with 2-3 particle modes were detected. The main submicron particle chemical component was particulate organic matter (POM), followed by sulfate, chloride, nitrate, and ammonium. The secondary particulate matter formed in the PAM chamber was mostly POM and the concentration of POM was many orders of magnitude higher in aged aerosol compared to primary emissions. A significant amount of aromatic volatile organic compounds (VOCs) was measured as well. VOCs have the potential to go through gas-to-particle conversion during the oxidation process, explaining the observed high concentrations of aged POM. During good combustion, when VOC emissions were lower, over 80% of SO2 was oxidized either to gaseous H2SO4 (37%) or particulate sulfate (46%) in the PAM chamber, which mimic the atmospheric processes taken place in the ambient air after few days of emission.Peer reviewe

New particle formation in the fresh flue-gas plume from a coal-fired power plant: effect of flue-gas cleaning

Atmospheric emissions, including particle number and size distribution, from a 726 MWth coal-fired power plant were studied experimentally from a power plant stack and flue-gas plume dispersing in the atmosphere. Experiments were conducted under two different flue-gas cleaning conditions. The results were utilized in a plume dispersion and dilution model taking into account particle formation precursor (H2SO4 resulted from the oxidation of emitted SO2) and assessment related to nucleation rates. The experiments showed that the primary emissions of particles and SO2 were effectively reduced by flue-gas desulfurization and fabric filters, especially the emissions of particles smaller than 200 nm in diameter. Primary pollutant concentrations reached background levels in 200–300 s. However, the atmospheric measurements indicated that new particles larger than 2.5 nm are formed in the flue-gas plume, even in the very early phases of atmospheric ageing. The effective number emission of nucleated particles were several orders of magnitude higher than the primary particle emission. Modelling studies indicate that regardless of continuing dilution of the flue gas, nucleation precursor (H2SO4 from SO2 oxidation) concentrations remain relatively constant. In addition, results indicate that flue-gas nucleation is more efficient than predicted by atmospheric aerosol modelling. In particular, the observation of the new particle formation with rather low flue-gas SO2 concentrations changes the current understanding of the air quality effects of coal combustion. The results can be used to evaluate optimal ways to achieve better air quality, particularly in polluted areas like India and China

Alkalimetalliyhdisteiden kaasu–hiukkastasapainon tutkiminen aerosolitestireaktorissa

The research topic of this thesis is inorganic gases from combustion that form particles via gas-to-particle conversion. The particles formed in gas-to-particle conversion have an effect on fouling of the super heaters and corrosion in boilers. These are the main reasons for unscheduled shutdowns and tube failure. Aerosol particlesformed from inorganic gases are challenging to study in boiler conditions. To be able to measure the particles formed via gas-to-particle conversion, the related processes need to be isolated from the boiler to a smaller and easily controllable environment. The experiments of this thesis were conducted in laboratory environment. The most important facilities used were high-temperature chambers, particle sampling and particle instruments. The first high-temperature chamber is used for the vaporization of the reactants, and the latter is used to achieve the gas-to-particle equilibrium. Water solution of solid reactants is fed to the chamber in order to control the amount of reactants. In addition, different gases are fed to the chamber. The reactants used in this thesis were selected from black liquor recovery boiler process. Black liquor composition is highly affected by the quality of the wood used in pulping, and that is why the reactant concentrations should be controllable. Black liquor consists mainly of sodium and sulphur but also of chloride from the wood. The chloride has been observed to be problematic since it causes corrosion in recovery boilers. A sample was taken from the second high-temperature chamber by diluting it in three steps before the particle measurement equipment. The measurement results show two mode particle size distributions. Results indicate that one of the mode is formed in high-temperature conditions and the other in the dilution. It was discovered that alkali sulphate formation is the key component of the particle formation in the second high-temperature chamber. Indirect references of alkali chloride formation are observed by studying the nucleation mode. The nucleation mode particle number is decreased when temperature of the second high-temperature chamber is lowered because more alkali chloride compounds is transferred to the particle phase already in high temperature conditions

From Boiler to Atmosphere: Effect of Fuel Choices on Particle Emissions from Real-Scale Power Plants

Fossil fuels, coal and oil are used for energy production around the world. Combustion of these fossil fuels produces gases and particles that affect air quality and climate. The CO2 emissions can be decreased by substituting fossil fuels with biomass and this substitution can further affect the particle emissions of the power plants. This thesis focuses on characterising particles of real-scale power plants with various fuels, from combustion to atmospheric dilution. The studied power plants were a combined heat-and-power (CHP) plant (combusting coal and a coal – wood pellet mixture) and a heating plant with three fuel mixtures. The particles were characterised mainly based on particle number size distribution and number concentration, using aerosol sampling from the superheater area of the boiler of the CHP plant, the stack of the CHP and the heating plant and the atmosphere surrounding the CHP plant.Measurements for the aerosol samples taken from the boiler indicated that the particles from the combustion of coal and the mixture of coal and industrial pellets had already formed in the boiler. The formation of the particles was studied by changing the dilution of the aerosol sample and by comparing the electrical charges of the particles in the boiler. The coal-combustion particles were around 25 nm in diameter. The addition of 10.5% industrial pellets to the coal caused the formation of a second particle mode, the soot mode (120 nm in diameter), in the boiler. In the heating plant, the addition of light fuel oil to heavy fuel oil had a similar effect on the oil-combustion particles. The particles from the combined coal-and-pellet combustion agglomerated and coagulated before reaching the sampling point in the stack. These processes, combined with the effect of an electrostatic precipitator, resulted the mean diameter of the particles to be 80 nm. Further, the flue-gas desulphurisation and fabric filters lowered the particle number concentrations. The particles measured inside the stack were also observed from the atmosphere before they were diluted to background concentrations. The flue-gas plume was measured in four occasions, in three wind directions and with four flue-gas cleaning and fuel combinations. These measurements resulted in the observation of a new particle formation in the diluting plume. In the atmospheric measurements, the concentrations of SO2 and CO2 played an important role in measuring the dilution process. In the heating-plant experiment, the characterization of oil-combustion particles showed that the lower fuel sulphur content decreased the particles’ hygroscopic growth factors.The atmospheric primary emissions of coal-fired power plants can be effectively lowered through flue-gas cleaning technologies. In this study, flue-gas cleaning was shown to affect the flue gas’s particle number and the mass concentration as well as its black carbon concentration. The cleaning did not prevent new particle formation in the flue-gas plume in the atmosphere, but it did reduce the potential for particle formation

Finland's energy system for 2030 as envisaged by expert stakeholders

To reach the 2030 decarbonization targets, EU Member States develop national strategies. We examine the views of key stakeholders in Finland to outline how those responsible for developing, steering and implementing the energy system assess the various solutions. The Finnish choices are of interest owing to the mixture of assets, constraints and path-dependencies shaping them. Our Q methodological analysis uncovers three main views: international competition and smart solutions; active consumers; national competitiveness and local solutions alongside a consensus upon which the implementation of Finland's own 2030 strategy can be built. The key stakeholders in Finland are ready for solutions comprehensively shaping the energy system, which can also influence several vested interests, existing business models and eventually break existing path-dependencies. Keywords: Energy strategy, Decarbonization, Finland, Stakeholder, Q methodolog