The impact of an additive on fly ash formation/transformation from wood dust combustion in a lab-scale pulverized fuel reactor

The quality of fly ash from wood dust combustion with an alumina-silicate additive in a laboratory scale pulverized fuel reactor is assessed. Fly ash analyses include XRD, SEM-EDX, micro-Raman spectroscopy, ICP-OES, and mobility of elements. XRD results show that the addition of the additive change the fly ash to a pozzolanic nature, improving its quality for applications that follow strict material provisions. SEM analyses showed the morphology of fly ash particles changed to having more spherical smaller particles that involves much fewer larger particles covered by sticky fly ash particles on the surface too. The reduction of irregular particles and the increase in spherical particles improve the fly ash quality in concrete use. Mobility results showed a decrease in the amount of some potentially hazardous elements leached from the fly ash generated with the additive. Results from micro-Raman spectroscopy had the added value of identifying mineral phases for particles associated with a scale size, giving rise to determination of mineral phases for the different fly ash size fractions or particles. The study shows that an expansion of EN 450-1 is warranted for consideration to include an additive with combustion of higher amounts of a greenwood, or only with a greenwood, or with co-firing lower amounts of other biomass types in order to acquire fly ash in compliance with the standard. (C) 2019 Elsevier Ltd. All rights reserved.