Accelerated carbonation technology granulation of industrial waste: Effects of mixture composition on product properties.

The use of accelerated carbonation technology in combination with a granulation process was employed to produce aggregates from a variety of industrial wastes, which included municipal solid waste incineration fly ash and air pollution control residue, oil shale ash, cement kiln dust, and quarry fines that have been produced in Estonia. Focusing mainly on the effects produced by the content of municipal solid waste incineration ash in the admixtures, the granule compositions were varied in order to tailor granule properties on the basis of CO2 uptake, strength development, leaching behaviour, microstructure, and morphology. All the steps involved in the accelerated carbonation technology granulation process, from mixing with additives to granulation and carbonation treatment, were carried out in the same apparatus - an Eirich EL1 intensive mixer/granulator. The amount of CO2 that was bound ranged from 23 to 108 kg per tonne of waste. The granules that included the optimised mixture of municipal solid waste incineration air pollution control residue, oil shale ash, cement kiln dust, and ordinary Portland cement were characterised by the highest compressive strength (4.03 MPa) and water durability for the size range of 4-10 mm. In addition, the process was found to be effective in reducing alkalinity (pH < 11.5) and immobilising heavy metals (especially zinc) and chloride. The composition and properties of the respective waste materials and mechanisms associated with the characteristics of the resulting granules were also addressed.

PAHs in leachates from thermal power plant wastes and ash-based construction materials.

The focus of the current study is to characterise the leaching behaviour of polycyclic aromatic hydrocarbons (PAHs) from oil shale ashes (OSAs) of pulverised firing (PF) and circulating fluidised-bed (CFB) boilers from Estonian Thermal Power Plant (Estonia) as well as from mortars and concrete based on OSAs. The target substances were 16 PAHs from the EPA priority pollutant list. OSA samples and OSA-based mortars were tested for leaching, according to European standard EN 12457-2 (2002). European standard CEN/TC 15862(2012) for monolithic matter was used for OSA-based concrete. Water extracts were analysed by GC-MS for the concentration of PAHs. Naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene were detected. Still, the release of PAHs was below the threshold limit value for inert waste. The amount of the finest fraction (particle size <0.045 mm), the content of the Al-Si glass phase and the surface characteristics were the main factors, which could affect the accessibility of PAHs for leaching. The mobility of PAHs from OSA of CFB and PF boilers was 20.2 and 9.9%, respectively. Hardening of OSA-based materials did not lead to the immobilisation of soluble PAHs. Release of PAHs from the monolith samples did not exceed 0.5 µg/m(2). In terms of leaching of PAHs, OSA is safe to be used for construction purposes.

CO2 mineral sequestration in oil-shale wastes from Estonian power production.

In the Republic of Estonia, local low-grade carbonaceous fossil fuel--Estonian oil-shale--is used as a primary energy source. Combustion of oil-shale is characterized by a high specific carbon emission factor (CEF). In Estonia, the power sector is the largest CO(2) emitter and is also a source of huge amounts of waste ash. Oil-shale has been burned by pulverized firing (PF) since 1959 and in circulating fluidized-bed combustors (CFBCs) since 2004-2005. Depending on the combustion technology, the ash contains a total of up to 30% free Ca-Mg oxides. In consequence, some amount of emitted CO(2) is bound by alkaline transportation water and by the ash during hydraulic transportation and open-air deposition. The goal of this study was to investigate the possibility of improving the extent of CO(2) capture using additional chemical and technological means, in particular the treatment of aqueous ash suspensions with model flue gases containing 10-15% CO(2). The results indicated that both types of ash (PF and CFBC) could be used as sorbents for CO(2) mineral sequestration. The amount of CO(2) captured averaged 60-65% of the carbonaceous CO(2) and 10-11% of the total CO(2) emissions.

Predicting CO2 and SO2 emissions in the Baltic States through reorganization of energy infrastructure.

The paper deals with predicting carbon dioxide and sulphur dioxide emissions generated by power production sector in the Baltic States in period up to year 2020. The economies of Lithuania, Latvia and Estonia are rapidly growing therefore forecast of emissions related with this occurrence becomes very important. The Ignalina Nuclear Power Plant (INPP), one of the largest in the world, is situated in the region. Two power production scenarios are modelled to investigate changes in power sector's emissions expected as the consequences of the coming closure of Ignalina NPP. Power market was assumed to be common for all three Baltic countries and was modelled by applying the Balmorel model. The planned closure of Ignalina NPP will bring restructuring of Lithuania power production sector and will change also power transmission between countries. Predictive identified the potential of investments for new modern power generation technologies. At the same time, modelling results show in both scenarios that CO(2) and SO(2) emissions from power production in the Baltic region will increase. The increment of emissions is discussed in the context of meeting requirements of UNFCCC Kyoto protocol and EC Directives. Despite of CO(2) emissions increase the Kyoto protocol's requirements may be expected. At the same time, SO(2) formation in Lithuania power sector may exceed the limits of the EU Council Directive 2001/80/EB therefore the additional measures to control SO(2) emissions have to be investigated.