Solving the deliquescence problem in blended fertilizers

Some blended fertilizers may be prone to an undesired chemical process: deliquescence. Deliquescence typically becomes an issue when fertilizer granules are transported or as they are applied to the soil at the farm. This undesired moisture uptake negatively affects the economics of both the companies handling these fertilizers and the growers using them. Let us look at what deliquescence is, the damage it can cause, and how to avoid it.

The Science Behind Deliquescence

In the middle of the 20th century, manufacturers developed high-analysis fertilizers, which typically contain more than 30% nutrients. These complex fertilizers were developed and then blended to achieve higher yields and improve farm productivity. One undesired consequence of some blended fertilizers is deliquescence at the surface of the fertilizer granules.

Deliquescence is a chemical process that begins when a single layer of water forms on the surface of a solid substance as it adsorbs moisture from the air. This water then dissolves the solid and forms a solution. The creation of this solution on the surface starts a cycle where more water is absorbed and more of the solid is dissolved. If this goes on long enough, the solids will completely dissolve and turn into a liquid.

The disadvantages of deliquescence in fertilizers

The deliquescence point, or critical relative humidity, is the relative humidity level above which a given fertilizer begins to liquefy. This threshold can vary widely. Typical ammonium sulfate and urea blends, for example, have a deliquescence point of 55%, meaning this blend readily absorbs moisture from the atmosphere in many climates, while the deliquescence point of potassium sulfate is over 90%, meaning it will not deliquesce until humidity reaches oppressive levels. In situations where the relative humidity rises and falls, it can lead to cycles of liquefaction and crystallisation, contributing to caking and dust generation as well.

When handling granular fertilizers, deliquescence is always an undesirable trait, and in certain conditions can occur in a matter of hours. The altered granules cause interruptions of fertilizer flow in blending and storage facilities or when passing through application equipment to the fields. This results in decreased operational efficiency during the narrow fertilizer application windows in the spring and fall, leading to higher costs. In more severe cases, it can actually cause work stoppages. In addition, nutrients may not be applied to the field as intended, resulting in missed nutrient application targets and crop yield losses. In extreme cases, deliquescence can result in fertilizer blends that are no longer usable, causing a complete loss of valuable product. Traditional fertilizer dust control and anti-caking coatings provide limited deliquescence improvement to fertilizer blends, and until recently, efforts to specifically address moisture uptake in blended fertilizers have not been able to significantly improve performance over traditional coatings.

Coating technology from ArrMaz can help reduce deliquescence

In response to industry need, ArrMaz scientists began focusing efforts on better understanding the fundamental mechanisms which lead to moisture uptake in fertilizers and deliquescence interactions, developing better test methods to improve lab scale replication of real world systems, and leveraging research from adjacent industries also struggling with this issue.

The result is a new GALORYL^® coating technology, which reduces deliquescence when high-analysis dry granular fertilizers are bulk blended together. When applied to granular fertilizer bulk blends, the coating delays the onset of deliquescence, effectively reducing the blend’s propensity for moisture uptake and hence extending the time available from blending to field application. This new coating technology is compatible with many traditional coating application systems.

For fertilizer blenders, the application of this GALORYL^® coating solution to mitigate deliquescence reduces the risk of blender operation interruptions due to poor fertilizer flow, thus reducing costs and improving operational efficiency. Growers benefit from increased longevity of stable fertilizer storage and decreased risk of plugging equipment during field application, ensuring that fertilizer isn’t over- or under-applied when compared to desired rates in the field. As a result, fertilizer growers benefit by increasing the yield potential of every acre, while managing input cost.

Read the article online at: https://www.worldfertilizer.com/special-reports/30012019/solving-the-deliquescence-problem-in-blended-fertilizers/