Sammendrag
ABSTRACT
In this work the ash sintering behaviors and effects of aluminosilicates based additives
(kaolin, zeolite 24A and zeolite Y) during combustion of wheat straw and barley husk were
investigated. The sintering degrees of fuel ashes and corresponding mixtures with additives
were evaluated by performing standard ash fusion tests and laboratory scale sintering tests.
The ash chemistry and microstructures were investigated by a combination of X-ray
diffraction (XRD) and SEM-EDX analyses. It was found that the wheat straw and barley husk
ashes have high sintering and melting tendencies. At elevated temperatures, formation and
fusion of low temperature melting potassium salts and potassium silicates contributed to
severe sintering of the two fuel ashes. Sintering of the barley husk ash is also associated with
the presence of low melting points potassium phosphates with high K/Ca ratios. The
experimental results from investigating the reactions between additives and KCl showed that
kaolin and zeolite 24A can both bind KCl with formation of different potassium aluminum
silicates. No clear reactions between zeolite Y and KCl were observed. Both kaolin and
zeolite 24A were effective to increase sintering temperatures of the wheat straw and barley
husk ashes. The reactions between kaolin and zeolite 24A with potassium containing species
in the two reference ashes were revealed by XRD and SEM-EDX analyses. Identification of
high temperature melting potassium aluminum silicates partially explains the higher sintering
and melting temperatures of the ash-additives mixtures. Zeolite Y showed a poor ability to
abate sintering of the studied ashes in this work.
In this work the ash sintering behaviors and effects of aluminosilicates based additives
(kaolin, zeolite 24A and zeolite Y) during combustion of wheat straw and barley husk were
investigated. The sintering degrees of fuel ashes and corresponding mixtures with additives
were evaluated by performing standard ash fusion tests and laboratory scale sintering tests.
The ash chemistry and microstructures were investigated by a combination of X-ray
diffraction (XRD) and SEM-EDX analyses. It was found that the wheat straw and barley husk
ashes have high sintering and melting tendencies. At elevated temperatures, formation and
fusion of low temperature melting potassium salts and potassium silicates contributed to
severe sintering of the two fuel ashes. Sintering of the barley husk ash is also associated with
the presence of low melting points potassium phosphates with high K/Ca ratios. The
experimental results from investigating the reactions between additives and KCl showed that
kaolin and zeolite 24A can both bind KCl with formation of different potassium aluminum
silicates. No clear reactions between zeolite Y and KCl were observed. Both kaolin and
zeolite 24A were effective to increase sintering temperatures of the wheat straw and barley
husk ashes. The reactions between kaolin and zeolite 24A with potassium containing species
in the two reference ashes were revealed by XRD and SEM-EDX analyses. Identification of
high temperature melting potassium aluminum silicates partially explains the higher sintering
and melting temperatures of the ash-additives mixtures. Zeolite Y showed a poor ability to
abate sintering of the studied ashes in this work.