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REFAWOOD - Reduction of ash-related problems in large-scale biomass combustion systems via resource efficient low-cost fuel additives

Published 2020

Citation: Sommersacher P. REFAWOOD - Reduction of ash-related problems in large-scale biomass combustion systems via resource efficient low-cost fuel additives. 6th Central European Biomass Conference CEBC 2020 (Oral Presentation). 2020.

Abstract

The incineration of waste wood is very often associated with ash-related problems (deposits, slagging and corrosion). This leads to short maintenance intervals, mainly needed to remove ash depositions, which result in significant power generation losses and high downtime costs. To avoid these problems, additives can be used, with particularly cost-effective additives being of great interest. On the one hand, the purpose of the additives is to reduce the Cl concentration in deposits on heat exchangers, which is the main cause for corrosion. On the other hand, the additives shall increase the ash melting temperature of deposits and hereby reduce deposit formation. In a first step the combustion behaviour of 3 different waste wood mixtures without and with the addition of various low-cost additives such as recycled gypsum, coal fly ash and iron sulphide with two different addition ratios were investigated in a laboratory reactor. Using the laboratory reactor allowed the determination of suitable additives and ratios of additivation for further investigations in the industrial plant. This approach represents a cost-effective and time-saving method for determining suitable additives and ratios of additivation. Based on the investigations carried out, the addition of 2% gypsum and 3% coal fly ash was recommended, since an improved ash melting behaviour can be expected with addition of gypsum and coal fly ash. These additives with the recommended mixing rates were then tested in a large scale CHP plant (a 40 MWth grate furnace with additional injection of wood dust above the grate). Extensive test runs were carried out without additive (as a reference), and with the additives focusing on dust formation (aerosols and total dust), deposit formation and the corrosion behaviour of superheaters. These investigations were accompanied by fuel and ash analyses (grate, cyclone and filter).

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