Development of a fertilizer particle accelerator

Testing of fertilizer spreaders is traditionally carried out by using the collecting tray method, requiring a large hall to eliminate the influence of wind and rain. The Dutch government has announced mandatory periodic testing of fertilizer equipment which could require a significant number of these costly halls. Therefore, an alternative method has been developed which is based on scanning the spreading zone and measuring the velocity vector and diameter of individual fertilizer particles, emanating from the spreader. A model then predicts the landing spot of each particle and accumulation of these spots gives the desired spread pattern. To test the proper functioning of the sensors that are used to measure the velocity and diameter of the particles, it was found necessary to develop a test device which is capable of discharging fertilizer particles with a realistic velocity and a fixed direction. The desired maximum launch velocity of the device is 70 m/s, the most extreme value that particles reach in practice. The principle of the accelerator that was developed is similar to that of a disc type spreader which has been fitted with an encapsulating housing. The machine was tested in combination with an optical device for the measurement of velocity and diameter, at ejection velocities up to 52 m/s. At higher velocities, virtually all fertilizer particles fragmented owing to the severe forces on particles when being accelerated. (C) 1997 Silsoe Research Institute.