| Phosphogypsum and fly ash are the bulk solid wastes discharged by industry,the total amount of which is up to hundreds of millions of tons every year.However,the comprehensive utilization rate of both is lower than 40%,and long-term accumulation will cause serious water and soil environmental pollution.Therefore,how to realize the resource utilization of phosphogypsum and fly ash has become a research hotspot of scholars.In this paper,analytica pure,fly ash and phosphogypsum are used as raw materials to prepare porous ceramics,and the influence of billet composition and technological parameters on the structure and properties of ceramics and related mechanisms are studied,in order to achieve high quality utilization of fly ash and phosphogypsum.The main conclusions are as follows:(1)Porous ceramics can be prepared by using pure quartz sand and alumina as raw materials and gypsum dihydrate as foaming agent.With the increase of foaming agent dosage and sintering temperature,the water absorption rate of porous ceramics increases and the compressive strength decreases.When the sintering temperature is 1260℃,the dosage of gypsum dihydrate is 6wt%,and the holding time is 30 min,the comprehensive performance of the ceramic sample is better.The water absorption,compressive strength and porosity are6.83%,13.68 MPa and 51.7%,respectively,and the thermal conductivity is 0.315 W/(m·K).(2)Fly ash as the main raw material,phosphogypsum as the foaming agent can be prepared fly ash based phosphogypsum porous ceramics,compared with the analysis of pure raw material prepared porous ceramics,the sample water absorption rate decreased,porosity increased.The analysis shows that the phase composition of porous ceramics is quartz,phosphoalauxite,anorthite,sodium calcium plagioclase and andalusite,with the increase of sintering temperature,holding time and the amount of fly ash and phosphogypsum,the content of anorthite and anorthite increases,which is beneficial to improve the density of ceramics.The optimum technological conditions obtained by the experiment are as follows:Fly ash 35wt%,phosphogypsum 9wt%,sintering temperature 1250℃,holding time 30 min,then the bulk density,water absorption,thermal conductivity and porosity of the sample are1.05 g/cm~3,5.84%,0.517 W/(m·K)and 54.8%,respectively.The compressive strength(12.76 MPa)is much higher than the performance requirement(8 MPa)in GB/T 16533-1996“General technical conditions for porous ceramic products”,which provides a new way for the comprehensive application of fly ash and phosphogypsum.(3)Sodium carbonate,potassium carbonate and basic magnesium carbonate were introduced into the porous ceramics based on fly ash phosphogypsum.The effect of different admixtures on the structure and properties of porous ceramics and the related mechanism were studied.The results showed that the volume density and compressive strength of porous ceramics decreased and water absorption increased with the three admixtures.The addition of potassium carbonate has a better effect on the performance of porous ceramics.The addition of potassium carbonate is 3wt%,the thermal conductivity of the sample is 0.452 W/(m·K).The compressive strength and water absorption of porous ceramics as building wall materials meet the performance indexes.The proper introduction of basic magnesium carbonate can promote the formation of magnesia alumina spinel,improve the mechanical properties of porous ceramics.The addition of sodium carbonate significantly decreased the comprehensive properties of the sample.When the dosage of sodium carbonate increased from 2wt%to 4wt%,the bulk density and compressive strength of the sample decreased from 1.04 g/cm~3and 12.08 MPa to 0.63 g/cm~3and 9.37 MPa,which decreased by 39.42%and 22.43%,respectively.Water absorption increased from 5.44%to 15.81%.Comprehensive performance analysis,the dosage should not exceed 2wt%. |
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