The Study Of Synthesized Wollastonite Use Phosphgypsum

Phosphogypsum(PG)is a solid waste generated in the manufacture of phosphoric acid by wet process and is one of the greatest mass solid waste in chemical factory.Normally PG contains more than 90%CaSO₄·2H₂O which is a material for building industry.However,as PG also contains some harmful impurities,such as phosphate,fluoride and organic matters,if it is indirectly used. And PG brings severe pollution for atmosphere and ground water.Achieve a new technology for a successful synthesis utilization of PG is possess commercial worthiness and practical signification for environmental security,resource's effective utilize and phosphorus fertilizer industry continuable development.Using phosphogypsum,reducing agent C and SiO₂ as the raw materials,this paper invest the decomposition of phosphogypsum and the composition of wollastonite by calcining at high temperature.The decomposition mechanism of phosphogypsum and the effect factors were discussed.The process conditions(such as temperatures,admixture percent,soaking time,accumulation state and impurity) which influence the decomposition of phosphogypsum and the composition of wollastonite were researched.Weight loss rate Decomposition rate and decomposition rate of phosphogypsum were used to characterize the decomposition of phosphogypsum and the composition of wollastonite.The wollastonite which had been synthesized was tested by XRD,SEM and chemical method.The properties of wollastonite were discussed.Existing Way of S in the whole experimental process and the factors which influence the SO₂ content in the tail gas were invested. Combined with Experiment,the design of compounded stove was discussed.The results show that the decompounded reaction between phosphogypsnm and carbon is gas-solid reaction,and temperature is the most primary factor which affects the decompoundaton of phosphogypsum and the composition of wollastonite.The subordinate factors are the contents of reducer,impurity,heat preservation's time and deposit's state,which is not very obvious.The best techniques for wollastonite synthesized by phosphogypsum are as follows:the temperature is 1200℃,and heat preservation's time is 150min,and the content of carbon is 7%.Wollastonite got from the condition appears yellow because of impurities.We can get from the XRD analysis that the impurity isα-CaSiO₃.It can't level off and can dissolve in vitriol of 10%and make CaSO₄.After experiences,S is in form of SO₂,S,and a little of CaSO₄.which doesn't decompound fully.After desiccation,the quality of SO₂ in material will increase,and it achieves the highest mass when the content of carbon is 7%.But,there are some distance between the result and relative theory result.