Natural quartz sand is commonly used as an inert fluidizing material for fluidized bed boilers. In a natural sand bed, the problem is the sintering of the fluidizing material, which, according to research, is due to the reaction of quartz with the alkalis, i.e. sodium and potassium that is contained in the fuel ash.
The mutual reaction with Quartz and alkalis forms a mixture with a low melting point. Due to this, the flow of the bed material becomes weaker or stops completely, after which the bed material needs to be replaced.
Bed sintering causes significant problems to incinerators in plant usability and in worst case cause significant costs if energy production had to be stopped altogether due to bed sintering.
The issues caused by the alkali reaction can be significantly reduced by either replacing the bed material more frequently or by switching to a bed sand that contains less silica. There are several sands to choose from, but their commercial use is often limited by the materials’ limited availability and high prices.
Finn Recycling has developed solutions for this problem. Finn Recycling Oy processes recycled materials into bed material for fluidized bed boilers, which are resistant to alkali reactions and thus reduces the consumption of bed material and the generation of waste sand.