Increasing quality with innovative design

With fertilizer granules, size matters


The chemical fertilizer market has become increasingly competitive, which is why it is essential for suppliers to ensure they can deliver a premium quality product while still maintaining a competitive price. Part of what determines granular fertilizer’s quality is the granule’s size and distribution, the acceptable size range of granular fertilizer having evolved in recent years.

Today granular fertilizer is typically expected to be between 2mm and 4mm in size with an acceptable distribution of between 95% and 98% in this range. This is quite high considering 90% was once considered acceptable.

Undersized granules, commonly known as fines, cause caking which can affect fertilizer handling equipment and create blockages for the end user out in the field. Additional to this, a uniformly sized granule ensures consistent and sustained release of nutrients into the soil. Fertilizer fines reduce efficiency as the dust is easily blown away or dissolved and carried away by first rains.

In a granulation system, fines and oversize screens are generally installed after the dryer in order to recycle over- and undersized product back into the system. Market pressure has resulted in most granulation facilities installing additional “polishing screens” which are installed downstream of the cooler in order to ensure a good particle size distribution.

Despite these improvements on the side of the manufacturer, fertilizer quality can be negatively affected by factors such as transport, handling systems, air temperature and humidity.

This makes it essential for blending or bagging operators to ensure they have the appropriate screening systems in place to ensure a quality final product. Incorporating a fines screen into a warehouse receiving process is fundamental to ensuring your operation has a premium quality product as a starting point. Precision Metal Products (PMP) have developed rotary screens specific to the fertilizer industry that are very gentle on product, efficient and require minimal maintenance. These screens can accommodate a wide range of capacities, and are easily incorporated into a warehouse distribution system. They have also designed mobile screening systems which offer versatility and allow operators to pre-screen problematic products prior to blending or bagging.

During storage it is still likely that the granules will create further undersized particles even after screening. Again, this depends on multiple factors such as how the product is handled, air conditions and duration between the pre-screening and the blending or bagging process. Additional rotary screens can be incorporated in line with the blending or bagging process; however, a rotary screen is not always feasible due to space constraints or cost. For this reason, with its experience and knowledge of blending and bagging operations, PMP have developed a wedge wire gravity screen as a more compact and cost-effective solution. The innovative wedge wire screen design can be easily incorporated into a bagging or blending system without greatly increasing the system’s footprint. The wedge wire screen can also be used in conjunction with a dust-extraction system to increase efficiency and air quality.

Another process which can contribute significantly in reducing complications from dust is to coat the fertilizer with a dust suppressant. PMP has developed a coating system which gently and efficiently coats the granular fertilizer with a dust suppressant liquid with the use of a paddle mixer and automated spray system. This process is beneficial as it greatly reduces product breakdown between the bagging facility and the end user. The coating systems can also be used to add a wide range of liquid additives which can increase fertilizer efficiency and stability and optimize product yield for the end user.

The fertilizer industry has shifted its market expectations for increased product quality to improve efficiency and yield for the end user. Screening and coating systems have become essential in meeting market demand and end user requirements. This is why PMP continues to design and develop equipment capable of meeting market demand. PMP keeps the end user in mind and assures that the best solutions are implemented in a cost-effective manner. If quality fertilizer is your main concern, then PMP will be able to assist you, from small operations to large volume distributors. Visit or contact them directly so they can tailor a solution to suit your requirements. 

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Issue 45


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