Study On The Preparation And Properties Of Phosphogypsum And Plaster Gypsum

Phosphogypsum is to produce industrial waste residue in the production of wet process phosphoric acid. Similar to the nature of natural gypsum and FGD gypsum, the main component of dihydrate calcium(CaSO4?2H2O), also contains amount of fluorine compound, acid insoluble matter, iron aluminum compounds and other impurities.In recent years, with the production of high concentration phosphorus compound fertilizer, the annual emissions of phosphogypsum is about 68000000 tons, the effective utilization rate is less than 20%. A large number of emissions and accumulation of phosphogypsum has brought tremendous pressure on the environment and farmland,which seriously affect the sustainable development of phosphate fertilizer industry. In order to improve the comprehensive utilization of phosphogypsum and ensure the sustainable development of the phosphate fertilizer industry and propose the phosphogypsum for comprehensive application of building materials, not only solve the national infrastructure for building materials demand, but also for the sustainable development of phosphorus fertilizer industry possible. However, there are many harmful impurities in the phosphogypsum, which lead to the uncertainty of the quality of the phosphorgyp-sum, which is extremely unfavorable to the development of the building material resources.This thesis hope that through the reasonable production process and additive to improve the comprehensive utilization rate of phosphate gypsum resources.(1) Phosphogypsum is fried into building gypsum, the influence of calcination system on the macroscopic properties of the phosphorus gypsum, through building gypsum setting time, mechanical properties and thermal analysis test and economic considerations, and the optimum calcination temperature, constant temperature time and aging time were optimized, so as to provide reference for industrial production.(2)Regulating phosphorus gypsum setting time research, by potassium sulfate, sodium sulfate, natural gypsum and phosphorus gypsum four coagulant; citric acid, bone glue, D-50 and PE four retarder, required for the production of phosphorous gypsum products and different construction, providing optimal control agent and its dosage.(3) Improve phosphorus gypsum on water resistance, by adding silicone directly improve phosphorus gypsum product water resistance and with white cement and potassium carbonate, impurities in the phosphogypsum neutralized and excited silicone, of phosphorus gypsum products water further improved.(4) Study on the preparation of gypsum plaster,through various admixtures, plastering gypsum proportion optimization.Results show:(1) Effect of calcination system on macro properties of phosphorus gypsum, aging time about 9d phosphogypsum standard thick gradually stabilized, improved the strength and the effect of aging effect is obvious; calcination temperature in 180?~190?, constant temperature time in 2h~2.5h, Calcined phosphogypsum performance is better.(2) Coagulant sulphate ratio of dihydrate calcium sulphate in phosphogypsum setting time was shortened, and the more obvious effect, but sulfate loss is bigger, the strength of phosphorus gypsum and sodium sulfate make phosphogypsum whiskering phenomenon is very serious.(3) D-50 retarder in 60 min has better controllability, strength of phosphogypsum loss compared with citric acid, and bone glue and so on; PE retarder on phosphorus gypsum setting time within 60 min to 200 min, had a certain linear change, but the strength loss of phosphogypsum is bigger.(4) Silicone water repellent agent can significantly improve the water resistance of phosphorus gypsum products in 24 h.when the silicone content of 1.0%, the water absorption of phosphogypsum are 0.75% at 2h and 13.84% at 48h; when the white cement and K2CO3 content is 0.15% with content 1.0% silicones compound, phosphogypsum of water absorption significantly reduces to 11.11% at 72 h, softening coefficient increases to 0.60; SEM analysis shows that the phosphogypsum hydration product crystalline structure of activator and organic silicon compound array more closely than single-doped silicones of phosphogypsum.(5) Bottom phosphgypsum plaster formulations, retarder D-50 dosage of 0.3%, water gypsum ratio 40%, redispersible latex powder dosage of 1.0%, methyl cellulose ether content of 1.0%, phosphgypsum: sand = 40:60, preparation of bottom layer plastering gypsum water retention rate is very good, high bonding strength, the intensity values is also higher than the national standard requirements.