Fertilizer and soil amendment producers face many obstacles. One of their greatest challenges lies in controlling dust. As a top priority, there are many options available on the market to aid in dust management. And while some producers opt for dust collection systems, dust prevention is a much more reliable, effective, and efficient means of managing dust.
For this reason, coating has become the method of choice for fertilizer and soil amendment producers looking to maximize their dust suppression efforts.
What Causes Dust?
When working with fertilizers and soil amendments, there are a number of ways through which dust is generated.
Product Degradation
Product degradation is the primary culprit in the production of fugitive dust. Here, dust is generated by the breakdown of product into fines (known as attrition). This can happen for several reasons:
Inadequate Production Techniques
Production techniques are crucial in creating a product with as little attrition as possible. Proper crush strength and particle shape must be achieved in order to maintain product integrity and minimize attrition.
Additionally, the type of granulation employed also has an effect on the amount of degradation that occurs; pellets produced via compaction granulation have jagged edges that are more likely to rub together and break down, while pellets produced via agitation/tumble-growth agglomeration are round and much less likely to experience this.
Improper Storage and Handling
Storage and handling practices can also cause dust due to product degradation. Transfer and drop points should be minimized to create as little opportunity for breakage as possible. Additionally, temperatures and humidity should be carefully managed.
The Material
Some materials are generally more prone to dusting than others due to their natural characteristics. Potash, for example, is notoriously dusty, requiring extra attention to dust management.
The Impact of Fugitive Dust
Despite its small particle size, dust causes big issues. The effects of fugitive dust are incredibly widespread and costly, representing significant liability in the form of:
Health and Safety Hazards
Depending on the material(s) being handled, dust may pose health and safety risks in the form of respiratory problems, illness resulting from long-term exposure, and even combustion.
As a result, producers are required to meet a myriad of regulations designed to keep workers and the surrounding community safe. Meeting these requirements demands strategic and careful planning.
Increased Maintenance Costs
In addition to being a safety hazard to workers, dust is also a hazard to equipment. Dust that is allowed to pervade the production area can damage equipment and even halt production, causing excessive unplanned downtime.
A buildup of dust easily clogs equipment, and if left unresolved, can cause severe damage to mechanical components. Similarly, dust that is allowed to sit for long periods of time corrodes and abrades equipment and infrastructure.
Product Loss
Dust also results in product losses, which can be significant; even if only 1% of material were lost as dust, this still represents a substantial loss. For example, if a fertilizer product worth $350 per ton accrued 1% dust loss during rail transfer at a rate of 1,000 tons per day, that would equate to a loss of:
- $3,500 per day
- $105,000 per month (assuming seven days per week in operation)
- $1,277,500 per year (assuming 365 operating days per year
Dust not only causes a loss of the product from which it came, but it can also impact other products in the facility. Dust migrating from one area of the plant to another has the potential to contaminate raw materials or change product composition, spoiling product and adding to the initial loss.
On application, dust that becomes windblown also represents a loss to the customer.
Increased Potential for Caking
Because dust dissolves more readily in water, a dusty product is more likely to experience caking, devaluing the product and adding to product losses. Caking also presents a host of additional issues that require management.
Difficult to Handle, Transport, and Apply
In addition to the problems listed above, dusty products are generally difficult to handle, transport, and apply. Those in the fertilizer and soil amendment industry have generally come to expect a certain level of quality when it comes to such products, and dust is simply not acceptable. The market demands products with minimal dust. Products that are prone to dusting are therefore less marketable and cannot be sold as a premium product.
The Coating Process
Coating fertilizers and soil amendments provides an effective solution to dust suppression, preventing the generation of dust from the start, satisfying market demands, and mitigating the need to manage dust downstream. The coating drum is the preferred type of equipment for dust suppression efforts, offering superior results.
Unlike other coating methods, the coating drum provides uniform coating distribution – an essential aspect of dust prevention. Uniform coating is achieved as a result of a well-designed spray distribution system, combined with the tumbling action that occurs in the material bed of the coating drum; as material tumbles in the rotating bed, a spray bar distributes coating at predetermined points. The granule-to-granule contact then works to evenly distribute the coating throughout the bed. The result is a uniform coating on each and every granule.
The coating drum also aids in polishing and smoothing granules when applicable, knocking off any loose edges and incorporating the resulting fines into the coating.
Coating drums can be integrated into a new fertilizer production line, or retrofitted into an existing facility.
Dust Suppression/De-Dusting Agents
A wide variety of dust suppression/de-dusting agents are available, with oils, waxes, and polymers being typical choices. Dust control coating agents are available by the hundreds and can even be customized to suit the needs of a given application.
Coatings may also be formulated to serve multiple purposes, coloring, de-dusting, preventing moisture absorption from the air, and preventing caking all at once.
Coating Process Development
Uniformly coating each granule in a coating drum is achieved by carefully balancing a wide range of process and material parameters. For this reason, when developing a new coating line, testing is often recommended.
Testing programs such as those carried out in the FEECO Innovation Center evaluate both material and coating behavior in the coating drum to identify the specific combination of parameters necessary for a unique application. Coating type and formulation can also be explored.
Some of the process and material parameters assessed during testing include:
- Spray method and location
- Coating application rate
- Material feed rate
- Nozzle type
- Drum fill percentage
- Retention time
- Drum speed
- Surface characteristics of the material to be coated
- Coating temperature
Testing in the Innovation Center is conducted on a scalable process to gather data for designing a commercial-scale coating drum. Material samples may also be produced for further testing.
Conclusion
Dust suppression is a crucial priority when working with fertilizer and soil amendment products due to the many issues dust can present. And while dust is caused by many factors, coating with anti-dusting agents is the most effective way to prevent dust generation, with the coating drum offering the best results.
FEECO produces the industry’s most reliable and effective coating drums. For more information on our coating drums or testing programs, contact us today!