Estonian Oil Shale Power Plants’ Ash Handling
Problems
Author(s)
H. Arro, J. Loosaar, T. Pihu & A. Prikk
Abstract
Over 90% of the Estonian basic power supply is covered by oil shale-fired
thermal power plants. Every year about 11 million tons of oil shale (ash content
45-47%) is fired. The old pulverised firing (PF) and the new circulated fluidised
bed (CFB) technologies are used. The PF boilers were commissioned between
1959 and 1973. Due to their age and problems relating to environmental and
economical performance, two old blocks were replaced using the CFB
technology. The new CFB units (2x215 MWel) delivered by Foster Wheeler
started operation in 2003-2004 and are meeting the EU LCP Directive limits of
gaseous emissions without any additional flue gas cleaning equipment.
The most serious problem today is ash handling. Power plants (PP) using big
amounts of water for ash handling are not known in Europe and are
environmentally hazardous. In compliance with the EU directives the oil shale
power plants must be switched over to a technology which minimises high
alkaline liquid waste (dry, semidry or dense slurry technology) from July 2009.
Before taking a final decision, it has to be found out what might be involved in
adopting the new technology and what problems might emerge. Whatever
technology we use for ash removal, ash fields come into contact with millions of
cubic metres of rainwater a year which becomes polluted. The question of how
to neutralise free lime in oil shale ash as one of the most hazardous components
seems to be a particularly important question.
This paper describes the problems relating to the chemical-mineralogical
composition of oil shale ash. The conditions at hydro (wet), dry, or semidry ash
removal are analysed.
Keywords: Estonian oil shale, pulverised firing, circulating fluidised bed
combustion, emissions, land filling.
Keywords
Estonian oil shale, pulverised firing, circulating fluidised bed
combustion, emissions, land filling.
Related Book
Other papers in this volume
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