Measurement Of The Physicochemical Properties Of Acidic Ammonium Phosphate Slurry And Its Concentrating

Ammonium phosphate is an important compound fertilizer. It is a new way to produce ammonium phosphate by concentrating acidic ammonium phosphate slurry. The dependence of the density,thermal conductivity,boiling point of the acidic ammonium phosphate slurry on both neutralization degree and water content is very important to the industrial realization of the new process.The acidic ammonium phosphate slurries with different neutralization degrees were obtained by neutralizing dilute pure phosphoric acid (P2O523.68%) or wet process phosphoric acid (P2O5l9.41%) with ammonium. They were concentrated to different water contents. The dependence of the density boiling point fluorine volatility and thermal conductivity on neutralization degree and water content were measured.The results indicate that the density of slurry increases with the reduction of water content and/or neutralization degree. The density of the slurry from wet process phosphoric acid is slightly higher than that from dilute pure phosphoric acid. The density of acidic ammonium phosphate slurry can be calculated by the equation p = k(psxv+pL(l-xv)).The experiments shows that the boiling point of slurry rises with the reduction of water content and/or neutralization degree. When water content is below 40%,the boiling point strongly depends on the water content. The boilingpoint can be calculated by equation T = Tb+Tb.The fluorine volatilizes in the concentration of the slurries from wet process phosphoric acid. The volatilization was enhanced in low water content and low neutralization degree range. When the neutralization degree is below 0.4,the fluorine volatility sharply increases with decreasing neutralization degree. While,at a neutralization degree over 0.6,the volatility drops to a very low level.The experiments also show that the thermal conductivity ranged from 0.434 to 0.630 w/m. When no crystalline exist in solution,the thermal conductivity increases with increasing temperature,water content or neutralization degree. However,when crystalline appears,it increases with decreasing water content. The thermal conductivity of the slurries from wet process phosphoric acid is slightly less than that of the slurries from dilute pure phosphoric acid.An industry test for the concentration of acidic ammonium phosphate slurry was conducted in an existing modified concentrating system. According to the test results and process parameters,acidic ammonium phosphate slurry with a neutralization degree of 0.4-0.5 can be directing concentrated to water content 20%. It is further neutralized by ammonia to produce ammonium phosphate. The secondary neutralization releases a large amount of heat which can be used to vaporize water. It will be a simply energy saving process.