Distribution of heavy metals and nutrients in different size fractions of fly ash from biomass incineration

Activity: Talk or presentationOral presentation

Description

Biomass (especially wood) counts as CO2-neutral fuel and is therefore increasingly used for the generation of heat and electricity (transportation and pre-treatment of the biomass not taken into account). After incineration, the inorganic components remain as ashes (1-3% of the input mass). Bottom and fly ashes contain nutrients for soils and plants (e.g. phosphorus, potassium, calcium and magnesium) but especially the fly ashes are also loaded with heavy metals. This restricts their use on agricultural used soils and in forests and they are usually disposed. In this investigation, fly ashes from an Upper Austrian biomass incinerator plant have been separated in the lab with an air classifier into different grain size fractions to study the distribution of pollutants and nutrients. All ashes (the original ashes and the grain size fractions) were then digested in a microwave assisted digestion unit with hydrochloric acid and nitric acid at around 200°C. For the determination of metals ICP-OES (inductively coupled plasma optical emission spectroscopy) was used. It could be found that some elements (e.g. magnesium) are distributed homogenously throughout the different grain size fractions of the fly ash whereas others (e.g. cadmium and potassium) are found in higher concentrations in the finer the ash fractions. These results are interesting in terms of recycling fly ashes from biomass incineration processes as nowadays they are mostly disposed because of their high heavy metal concentrations. By classification the fly ash can be split into a fine fraction with higheer loads of heavy metals and a coarser fraction which could be used as fertilizing agent for soils thereby reducing the necessary amount of synthetic fertilizers. Also the costs for disposing of fly ashes are minimized.
Period12 Sep 2011
Event titleEuroanalysis 2011
Event typeConference
LocationBelgrad, Serbia