Screening machines for phosphate fertilizers

Efficient fertilizers are needed worldwide to compensate for nutrient deficiencies in modern agriculture. Today, the majority of phosphates are used as fertilizers. The hardly soluble rock phosphates are processed in combination with ammonia to water-soluble fertilizers such as mono and diammonium phosphate or in combination with sulfuric acid to special superphosphates (double and triple superphosphates) to supply crops quickly and effectively with the required nutrients.

Challenges in phosphate screening

Typical phosphate fertilizers are subject to specifications that allow particle sizes ranging from 2 mm to 4 or 5 mm (10 Me. to 5 Me.). In addition, these products are often expected to have a quality of more than 90 percent, which means that only 10 percent of the particles may be outside the specialized range. Moreover, phosphate fertilizer production plants have a production rate of several hundred tons per hour. So the biggest challenge of a phosphate screening machine is to obtain a high quality material with high throughput while ensuring low downtime for maintenance.

On the other hand, phosphate granules tend to form agglomerates which close the screen mesh and reduce the effective screening area to the point of complete clogging. If this occurs, production must be stopped to allow cleaning or replacement of the mesh. 

How to screen phosphate fertilizer efficiently

For top quality screening of phosphate fertilizers, RHEWUM recommends its directly excited screening machine RHEmoto^®) with up to 5 screen decks. Direct excitation of the screen allows high-frequency vibration of the screen with accelerations of up to 15 g, thus preventing clogging of the mesh. In addition, automatic cleaning cycles can be set to remove stuck material from the screen mesh and ensure continuous production.

To further optimize the screening process, the RHEside distribution chute with static housing and vibrating inner part is installed upstream. It ensures optimal feeding onto the machine even of sticky screenings and is available with optional pre-screening of the product. With this system, the material is fed evenly over a screening machine width of up to 4.4 m (173″) via a dust-tight flange connection, while very coarse material is removed before the actual screening process. In this way, the machine is further relieved and the fractions are separated even more precisely.