Research On Reactive Crystallization And Polymerization Of Urea Phosphate-base Products

Urea phosphate is a complex salt of amino structure,can be regarded as containing N,P element of the entire water-soluble compound fertilizer,and can be coupled with spray irrigation and drip irrigation technologies to achieve the double effect of saving water resources and control the release of fertilizer of eco-environmental protection.Take urea phosphate as the main object of study,studies its building-up reactions, the crystallization process.The entire water-soluble ternary NPK fertilizers were prepared by mixing potassium chloride in the reaction system or the crystallization process,or urea phosphate and urea are polymerized by heating to produce ammonium polyphosphate.The ammonium polyphosphate with low degree of polymerization is a high concentration of N,P binary compound fertilizer,The ammonium polyphosphate with high degree of polymerization is an excellent environmentally friendly flame retardant,the market prospects are both good,and the products are urgent need of development.The study is the main component of education department of "Research and development on water-soluble NPK compound fertilizer technology serve as spray irrigation and drip irrigation"(item number 2007530007) of Henan Province Natural Science Research Project.The main findings are as follows:(1) By studying the compose experiments of phosphate and urea,the optimum conditions were achieved:mixing speed rate 200 r/min,phosphate concentration was 55%～60%,reaction temperature 55℃,reaction time 30 min,phosphoric acid and urea in molar ratio of 1:1,cooling crystallization time was 12～15 h.(2) The properties of urea phosphate were determined,the pH value increases along with urea phosphate mass fraction increases,when the mass fraction of urea phosphate greater than 4%,pH≤1.27;The melting point and specific heat of urea phosphate were determined by thermal analysis,the values of which are 117.45℃, and 3.4819 J/(g·K),and made the DSC curve;Urea phosphate crystals were analyzed by IR and X-ray diffraction and the spectrums was compared with standard patterns, and add the basis data of urea phosphate.(3) Urea Phosphate solubility in water was measured,the result showed that urea phosphate solubility in water was larger,the curve of urea phosphate in the water solubility was accordant with mathematical model:Y= 0.001T³-0.010T²+1.531 T+ 46.95,r=0.996(Y express solubility,T express temperature).(4) The effects of different factors on Urea Phosphate metastable zone width was found,When the cooling rate was 8℃/h,the metastable zone width of the saturation temperature(15,30,45℃) were 7.8,4.6,3.3℃;when the saturation temperature was 30℃,the metastable zone width of the cooling rate(6,8,10℃/h) were 4.9,4.6, 4.0℃.(5) In the metastable zone width,when the(?)T decrease,the quality growth rate decrease,when the temperature of saturated solution of urea phosphate was 35℃,the cooling temperature was 31.5℃,the quality growth rate of urea phosphate was 40.29×10^-3 g / min.(6) The size of phosphate urea product by different cooling methods was determined,the product was optimal by use of 8℃/h constant speed cooling means to cool the crystallization,the quality of product that the size is bigger than 0.83 mm was 45.38%,the quality of product that the size is between 0.35 and 0.83 mm was 48.16%.(7) Joining in different molar potassium chloride in optimum condition,the content of K₂O would increases with the amount increasing of potassium chloride, however,the increasing was slowly down after reaching 9.32 percent.(8) Ammonium polyphosphate was synthesized use of box-type resistance furnace and microwave reactor by urea phosphate and urea,The best conditions with box-type resistance furnace:polymerization temperature of 200℃,polymerization time 1 h,urea phosphate and urea in molar ratio of 1:1;The best conditions with microwave reactor:power 140 w,polymerization time 20 min,urea phosphate and urea in molar ratio of 1:1.4.(9) The solubility and pH value of ammonium polyphosphate which obtained were determined,the solubility of ammonium polyphosphate increases along the degree of polymerization decreases,and less than 0.05 g/mL,the pH values close neutrality when the degree of polymerization increase;the thermal stability of product was determined,results show that the thermal stability of ammonium polyphosphate was good,and decomposition temperature was greater than 250℃;By IR and X-ray diffraction analysis,it show that the obtained products was mainlyⅠ-ammonium polyphosphate structure,and high purity.