Preparation Of Fly Ash-based Porous Ceramics Material

Fly ash discharged by industry occupys a large amount of land and threatens the environment.How to utilize the fly ash has already become a big problem which we must face in the new century.This thesis explored a new way to use fly ash to produce porous ceramics with high added value,high performance and good solid-fluid-gas separation characterization,which meets the need of comprehensive utilization of fly ash.The porosity and bend strength of the fly ash-based porous ceramic were controlled by selecting adequate binder,suitable pore-making agent and optimizatiing other processing parameter.The effects of binder, pore-making agent,particle size distribution of fly ash,water content, forming pressure,sintering temperature and holding time on the porosity, bend strength,volume density and water absorption of fly ash-based porous ceramic were also studied.The results showed that sintering temperature and dosage of pore-making agent exhibited the most significant effects on the porosity, bend strength,volume density and water absorption of fly ash-based porous ceramic.QM coal powder is the most suitable pore-making agent. With increasing dosage of pore-making agent,the porosity and water absorption increased while the bend strength and volume density decreased.With increasing sintering temperature,the porosity and water absorption fell down,while the bend strength and volume density increased.The holding time,dosage of binder and particle size distribution of fly ash also had the obvious effects on the performace of porous ciramics.The best binder was bentonite blended with small quantity of PA and the best particle size distribution of fly ash is 74～66μm.The water content and forming pressure had the relative weaker influence effects on the porosity,bend strength,volume density and water absorption of fly ash-based porous ceramic.By optimizing the compounding and processing parameters,the best technological conditions were determined.When the water content was 24%,dosage of bentonite was 4%,dosage of PA binder was 1%,dosage of pore-making agent was 35%,forming pressure was 10.2MPa,sintering temperature was 1180℃,soaking time was 60min,the fly ash-based porous ceramic whose porosity was 41.52%,bend strength was 9.37MPa,volume density was 1.14 g/cm³,water absorption was 36.38%,acid resistance was 96.15%,fastness to alkali was 94.77%,degree of aeration was 3.7 m³Â·m^-2·h^-1and heat stability was 900℃.XRD analysis showed that the main phases in fly ash-based porous ceramics were SiO₂,3Al₂O₃·2SiO₂,Fe₂O₃ and CaO·Al₂O₃·2SiO₂.SEM analysis indicated that there were large quantity of three-dimensional pores whose diameters were about 40～70μm.These pores were resulted from the combustion of fly ash particles.In addition,there were also some micropores with diameter of 1～20μm induced from stack of flas ash pores.The fly ash-based porous ceramics had advanced microporosity and high specific area.