Moisture profile determination in urea prill. I

Abstract

Using Karl Fischer titration, the moisture profile along the radius in urea prill was determined. Having verified that during dissolution in methanol the urea grains diminish in radius linearly with time, it was possible to calculate that the layer with the highest water content is at a depth of one-third of the radius. The moisture profile is linear, with the central moisture content equal to four times the global moisture content of the grain.

Moisture profile determination in urea prill. II. Fertiliser caking implications

“…In a previous study, 8 using KF titrations, the linear moisture profile in urea prill was determined experimentally. The obtained data show that the moisture content is zero at the surface and increases towards the interior, reaching a maximum (four times greater than the global moisture content) in the centre.…”

“…In order to determine the function V KF = f (t), we have previously demonstrated that the water mass detected by the burette in a time interval dt comes solely from the dissolution of a concentric layer of urea grains of thickness dr. 8 The urea mass in this layer is dm = 4πρr 2 dr(g)…”

“…8 In order to do this, two modifications of the commonly used method were applied: 9 (a) the urea prill samples were sifted and separated according to size, so the size of the titrated grains was known; (b) during the titration the consumption of KF reagent was measured every 5 s.…”

“…Since the moisture profile is linear and the prill radius diminishes proportionally with time, 8 i.e.…”