Karen N. Finney

Ash deposit characterisation in a large-scale municipal waste-to-energy incineration plant

The deposition of ash - combustion residues - on superheaters and heat exchanger surfaces reduce their efficiency; this phenomenon was investigated for a large-scale waste-to-energy incineration facility. Over a period of six months, ash samples were collected from the plant, which included the bottom ash and deposits from the superheater, as well as flyash from the convective heat exchanger, the economiser and fabric filters. These were analysed for particle size, unburned carbon, elemental composition and surface morphology. Element partitioning was evident in the different combustion residues, as volatile metals, such as cadmium, antimony and arsenic, were found to be depleted in the bottom ash by the high combustion temperatures (1000+°C) and concentrated/enriched in the fabric filter ash (transferred by evaporation). Non-volatile elements by contrast were distributed equally in all locations (transported by particle entrainment). The heat exchanger deposits and fabric filter ash had elevated levels of alkali metals. 82% of flyash particles from the fabric filter were in the submicron range.

Experimental Investigation of Indoor Air Pollutants in Residential Buildings

Indoor air quality is affected by many factors, including energy provision/use. The main objective of this research was to investigate indoor air pollutant emissions due to energy use in residential buildings, with a specific focus on particulate matter (PM). Three environments were compared: (a) a rural house with an electric cooker; (b) a city-centre flat with a gas cooker; and (c) an urban flat on a main road, also with gas appliances. Concentrations of PM, CO, NO2 and VOCs were measured in the kitchens and emission rates were calculated for cooking periods. Although there has been a great deal of research examining the effects of gaseous pollutants in the indoor environment, this is one of the first studies to specifically focus on PM. Most particles were small (≤2.5 µm) and thus respirable. The elemental analysis of the PM revealed high metal concentrations (Fe/Na/Zn), whilst their morphologies indicated these were present as salt, skin and particles of biological origin. Gaseous emissions, particularly NO2 and CO, were more prevalent in homes with gas appliances, since these are a significant source of both pollutants.

The Sustainable Option of Power from Fossil Fuels with Carbon Capture and Storage: An Overview of State-of-the-Art Technology

To limit the global rise in temperature to 1.5–2 °C, considerable reductions in greenhouse gas emissions, especially CO2, are needed—challenging because of the continuous increases in energy demand and the large contribution from fossil fuels. Gas-fired power plants will be a significant part of power generation over the next few decades, and whilst CO2 emissions are significantly lower than for coal, they must still be addressed to lower carbon intensity. This can be achieved through carbon capture and storage (CCS) as a key enabling technology. This chapter aims to summarize the key research on state-of-the-art gas turbine technologies for enhanced post-combustion capture and oxy-turbine gas-CCS cycles, including the technical challenges and opportunities. For post-combustion systems, supplementary firing, humidification, exhaust gas recirculation and selective exhaust gas recirculation will be assessed, which outline the CO2 increases and electrical efficiencies achievable when considering the capture penalty. An alternative to post-combustion capture is the use of oxy-turbine cycles, where the relative merits are assessed. Lastly, this chapter discusses the impacts of the technical, policy, financial and social challenges on scaling-up these technologies for full-chain commercial-level deployment. Overcoming these will be a necessity to enable CCS to decarbonize energy for a sustainable future.

Entrained Metal Aerosol Emissions from Air-Fired Biomass and Coal Combustion for Carbon Capture Applications

Biomass energy with CO2 capture could achieve net negative emissions, vital for meeting carbon budgets and emission targets. However, biomass often has significant quantities of light metals/inorganics that cause issues for boiler operation and downstream processes; including deposition, corrosion, and solvent degradation. This study investigated the pilot-scale combustion of a typical biomass used for power generation (white wood) and assessed the variations in metal aerosol release compared to bituminous coal. Using inductively coupled plasma optical emission spectrometry, it was found that K aerosol levels were significantly greater for biomass than coal, on average 6.5 times, with peaks up to 10 times higher; deposition could thus be more problematic, although Na emissions were only 20% of those for coal. Transition metals were notably less prevalent in the biomass flue gas; with Fe and V release in particular much lower (3–4% of those for coal). Solvent degradation may therefore be less severe for biomass-generated flue gases. Furthermore, aerosol emissions of toxic/heavy metals (As/Cd/Hg) were absent from biomass combustion, with As/Cd also not detected in the coal flue gas. Negligible Cr aerosol concentrations were found for both. Overall, except for K, metal aerosol release from biomass combustion was considerably reduced compared to coal.