Study On The Process Of Urea-nitric Acid Decomposing Phosphate Rock

Phosphorus is an essential element for the growth of plant.In China,80%of phosphate rock were used in the production of fertilizer.However,high quality phosphate rock is becoming less and less.Most of the phosphate rock are low grade.The increasing demand for fertilizer in current society makes it urgent to use the low grade phosphorus rationally.In this article,we firstly analyzed the process status of the decomposing of phosphate rock with nitric acid.In laboratory studies and determine the process condition of the decomposing of phosphate rock with nitric acid and the condition as control base on the decomposition of phosphate rock with urea nitrate Secondly,studied the preparation process condition of an acid solution of urea nitrate,and determination the characterization data and physical properties of urea nitrate.On the basis of,we researched the reaction principal and process condition of the decomposition phosphate rock with urea nitrate.After program calculation the slurry made by decomposing the phosphate rock with urea nitrate can be used in a variety ratio of functional fertilizer preparation.In this article,we take the“15-15-15”compound fertilizer for example and study the preparation process and the nature of the compound fertilizers.The conclusions are as follows.?1?Phosphorus conversion rate acted as the index of Urea nitric acid decomposing phosphate rock preferably ore process conditions.The supplementary conditions are free acid,the difference value of measured nitrogen content and theoretical nitrogen content,water soluble rate,citrate acid soluble rate,viscosity and density.The preferential conditions we get from the experiment are that the reaction time is 60 min,the stirring intensity?expressed as linear velocity?is 3.43m/s,the nitric acid dosage is the theoretical dosage which is 90%,the nitrate concentration is45%,and the reaction temperature is room temperature.Under this condition,the phosphate conversion rate of the 1#phosphate rock decomposition can reach to98.20%.There is only 11.01%free acid and the measured nitrogen content and theoretical nitrogen content has almost no difference which means the generation of without the nitrogen oxides pollution.Meanwhile,we decomposed the 2#phosphate rock with this condition and we also achieved the high conversion rate of 99.75%.For the slurry we get,we do the thermo gravimetric analysis and X-ray diffraction analysis.According to the X-ray diffraction analysis,the product we get from the decomposing phosphate rock with urea nitric acid is?NO₃?₂Ca₃?P₂O₇?·6H₂O,NH₄NO₃,and no easy to moisture absorption calcium nitrate.By thermo gravimetric analysis,we can see that between 160?to 280?,the trend of the mass decrement is relatively mild.We consider it relatively pure product.There is only one product in this process.?2?Urea nitrate yield is the inspection standard of urea nitrate preparation conditions.The conclusions are,the molar ratio of urea and nitric acid is 1:1,the reaction temperature is 18?,the reaction time is 20min and the concentration of the nitric acid is 45%.The urea nitrate we get from the characterization analysis is a compound which is totally different from other substances,the acidity of the urea nitric acid is higher than citric acid of the same concentration,lower than that of nitric acid.?3?Through program calculation,Urea,potassium chloride,MAP,Ammonium bicarbonate,calcium magnesium phosphate fertilizer and the different proportion of slurry is made into a variety of functional compound fertilizer.We took“15-15-15”for example and researched the sequence of adding the material in detail.We harvested qualified fertilizer and the water content of the fertilizer is below 2%.We compared the compound fertilizer dried and not dried with calcium nitrate hygroscopic and came to the conclusion that the hygroscopic of mixed fertilizer without drying is mild,the hygroscopic of the dried mixed fertilizer is far lower than the calcium nitrate.The development of nitric acid decomposing phosphate rock has been nearly a century.But there exists calcium nitrate easy to moisture absorption in product has been a problem difficult to solve.The technology in these days exists a lot of problems such as complex equipment,high cost and time consuming etc.The conversion rate of urea nitric acid decomposing phosphate rock is 98.20%and there is no easy to moisture absorption calcium nitrate and nitrogen loss.The process of nitric acid decomposing phosphate rock will make contribution to the development of nitrate class phosphate fertilizer.