Alternative solutions for the physicochemical evaluation and improvement of the caking properties of calcium ammonium nitrate fertilizer as a quality problem under atmospheric conditions

ABSTRACT Fertilizers are very sensitive to climatic conditions due to their hygroscopic nature. They tend to absorb moisture, weaken and accordingly lose their free-flowing property depending on the ambient conditions. In this study, the influence of storage conditions on a commercial grade calcium ammonium nitrate (CAN/26) fertilizer was investigated using methods that included simulation of storage and handling. The mechanical properties of CAN/26 fertilizer were observed by friability and crushing strength tests. Granule structure begins to weaken especially above a temperature of 40°C and a pressure of 0.33 kg/cm2. Sudden changes in ambient temperature enhance the caking propensity by 4.8%. Fertilizers above 65% relative humidity start to absorb moisture and degrade at very high temperatures. The phase transition of ammonium nitrate between crystalline forms plays an important role in the caking of CAN/26, as its tendency to agglomerate at about 32°C is greatly reduced. The results show that the granule degradation in CAN/26 fertilizer increases almost linearly with increasing temperature, humidity, and pressure but there is a sharp limit for each parameter for degradation to start. With these limits, it may be possible to carry out the protection and control of the good quality of fertilizers in the sector.