Particle pulverization issue in coal chemical urea plants

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A set of coal chemical urea production plants with a capacity of 52 wt/year experiences particle fragmentation (the particles breaking apart) as soon as the urea leaves the tower; after being stored in a silo for one night before packaging, the fragmentation phenomenon can be even more severe. An analysis of the reasons points to the following factors: 1. Poor evaporation vacuum, especially in the second stage, with a difference of 5–6 kPa (absolute pressure), which results in high levels of moisture and free ammonia; these substances escape during granulation or storage, leading to particle degradation. 2. The pressure-rated nozzles from a factory in Zhejiang were used; the high outlet pressure of the melt pump caused the urine to be ejected at high pressure, leading to the release of water and free ammonia, which in turn resulted in the particle fragmentation. 3. In summer, the air humidity is high, with plenty of moisture; this moisture moves between the air and particles. Some other details: the net height of the granulation tower is 68 meters, the particle temperature is controlled at 60 degrees, the ambient temperature is 32 degrees, and the humidity is 60%. Particle moisture: 0.35–0.4%, free ammonia: 120–300 ppm. I was wondering if any of my colleagues have encountered similar situations? How was it solved? Or what should be the key issue to address?