Effects of Additives on Barley Straw and Husk Ashes Sintering Characteristics

Abstract

A growing interest has been observed for producing sustainable heat and power by combustion of residues from local agricultural production. However, ash related problems are inclined to occur due to high contents of problematic ash forming matter in such residues. The aims of this work were to examine ash characteristics of barley straw and husk and to find mixtures of fuels and additives that can be used as basis for producing pellets giving minimal problems during combustion. Influence of kaolin and calcite additives on the two fuel ashes’ sintering behaviors were investigated by X-ray fluorescence (XRF), ash fusion analyzer and X-ray diffraction (XRD) analysis. The results showed that, compared to barley straw ash, the barley husk ash has a higher sintering tendency, with observation of severe melting during combustion. Kaolin and calcite addition increased the melting temperatures of ashes from both barley straw and husk. Reactions between kaolin and potassium containing species in the barley straw and husk ashes were revealed by XRD analyses. With formation of high temperature melting species due to kaolin addition, the severe sintering of barley straw and husk ashes were significantly reduced. The dilution effect from calcite is supposed to be a main reason for improved barley straw and husk ash sintering behaviors. In addition, calcite addition led to formation of more calcium rich phases, which have higher melting points and contribute to low ash sintering degrees. Therefore, by using the additives, agricultural residues can be competitive for energy production in the future.