Under the experimental condition of lower liquid/solid ratio(5∶1)

the A-type and P-type zeolites were successfully obtained utilizing circulating fluidized bed(CFB) fly ashes by hydrothermal reaction in an open or close system.The effects of different synthesizing conditions

composition of raw materials

crystallizing time

NaOH concentration

temperature

stirring

open or close system

on the crystal type

degree of crystallinity

and the shape of obtained zeolites have been investigated.The results show that in shorter reaction time and lower synthesizing temperature A-type and P-type zeolites products can be obtained without pretreating raw materials by baking

which demonstrates that CFB ashes are active chemically.The NaOH concentration is a key factor which affects the types and crystallinity of obtained zeolites.With the increasing of the NaOH concentration

the zeolite will transform from type P into type A(or type X)

and finally into type HS.Quartz phase in the raw ashes will not be transformed and has no significant effect on crystallization.Different composition of raw ashes can affect the types of obtained products.Alumina-rich CFB ashes are suitable for synthesizing A-type zeolite

whereas silica-rich CFB ashes suitable for P-type and X-type zeolites.Using open system in synthesizing reaction can simplify the process and keep higher crystallinity of the products

which is beneficial to controlling reaction and industrial production.