Application of biomass gasification fly ash for brick manufacturing

Abstract Biomass gasification technology offers an attractive way to use low-grade fuels in energy production with high efficiency and low environmental impact. However, an issue calling for further development is the volume and quality of fly ash, since biomass gasification fly ash contains more un-reacted carbon compounds than fly ash from direct combustion of similar fuels. This restricts direct gasification ash utilisation for many applications and makes some pre-treatment necessary, representing a significant share of the overall operating cost of gasification-based systems for energy production. Therefore, economical methods for the management of this type of ash without any pre-treatment are attractive. In this paper, we present an initial study on the manufacture of bricks made of gasification ash. Our goal was to come up with a product which satisfies two basic requirements: (a) it has elevated percentages of fly ash; and (b) it enables utilisation of ash without any pre-treatment. We have manufactured bricks by means of conventional moulding and curing methods, using ash percentages of up to 20 wt.%. No special additives were added to provide the bricks with acceptable mechanical and/or insulating properties. The fly ash used was generated in a fluidised bed pilot plant for processing olive mill cake, a by-product of the olive oil industry produced in large quantities in several EU countries. Some mechanical and environmental properties of ash gasification bricks were studied and compared with typical values for commercial bricks. The results lead us to conclude that the bricks could be used commercially as low density clay masonry units with a good thermal insulating capacity and, therefore, the potential for commercial development is promising. In addition, the environmental benefit of waste gasification added to the ash utilisation makes the overall process more attractive.