Rotary drums are the industry standard for everything from granulating fertilizers, to drying, cooling, and even coating them. Throughout the US – and the world – this diverse type of equipment dots the landscape at both mine sites and fertilizer production facilities of all kinds.
The potash industry is no exception and perhaps most exemplifies the extensive capabilities of rotary drums; rotary drums are a critical piece of equipment in many of the processes used to process mined potash into a premium fertilizer product.
Here’s a look at how and why rotary drums are so prolifically employed in bringing mined potash to market as a fertilizer.
How Rotary Drums are Applied in Processing Potash
Rotary Drums at the Potash Mine
Potash can be mined in various ways. In almost all settings, however, a rotary drum can be found somewhere in the process, helping to convert potash ore into a market-ready product.
Drying Potash at the Mine Site
Potash is frequently extracted through brine operations which ultimately produce a crystallized product that requires drying prior to transportation. Drying at the mine site not only reduces shipping costs, but also helps to ensure that potash does not cake during shipment, and that fertilizer plants receive the material in the form they require to produce their fertilizer products.
While other types of dryers are available, the industry favors the rotary dryers for drying potash.
Potash Coarse Conditioning Drums
Flotation is a widely used technique in potash beneficiation. When coarse ore particles are present, a conditioning or reagentizing step is employed to maximize the effectiveness of froth flotation.
This conditioning step serves to homogeneously combine the coarse ore particles with reagents to enhance the hydrophobic or hydrophilic qualities of the material for improved separation. This process is carried out in a rotary drum referred to as a process mined potash.
Desliming Potash With Rotary Scrubbers
Also in preparation of froth flotation, deslimining potash is often necessary to remove fine clay particles that would otherwise hinder effective flotation. Here again, rotary drums, referred to as rotary scrubbers in this setting, are the preferred approach.
Rotary Drums in Potash Fertilizer Production
Once mined and beneficiated potash reaches the fertilizer plant, it is again subject to a range of processing techniques in which rotary drums are essential.
Traditional NPK Granulation
The granulation drum has been the standard approach to granular NPK fertilizer production since its inception by the Tennessee Valley Authority (TVA) in the mid-20th century.
Drying Potash Granules
When a potash fertilizer product, be it a straight or complex fertilizer, is granulated in any way outside of compaction granulation (such as the drum granulation mentioned above, or through the increasingly popular pelletizing method method), the produced granules are dried as part of the finishing process.
In this setting, drying plays a critical role in preventing caking, as well as mold or bacterial growth as product is stored and moved from plant to farm. It also helps to ensure granules hold their newly-formed shape.
Rotary dryers are the preferred approach to drying for many reasons, but in this setting, they are also favored for the tumbling action they impart, which further encourages granule rounding and polishing.
Cooling Potash Granules
When potash is dried, it is often also subsequently cooled. Cooling further discourages caking and allows the product to be bagged immediately without issue.
While other types of coolers exist, the rotary cooler is the industry’s preferred approach.
Glazing (Polishing) Potash Granules
Compaction granulation may not require a drying step, but one may be used as a finishing technique to help prevent attrition and create a more attractive product. glazing, which involves flashing off moisture, creates a recrystallized surface on the granules and is typically in a rotary dryer.
Coating Potash Fertilizers
Potash’s hygroscopic nature often mandates a coating process to inhibit granules from picking up moisture from the atmosphere, which would cause caking. Recently, coating has also become a way of changing the properties and even the formulation of standard fertilizers, transforming them into specialty products.
Here again, coating drums have proven superior.
Why Rotary Drums are the Potash Industry’s Preferred Equipment
There are a number of reasons why the potash industry favors rotary drums for accomplishing a litany of process objectives:
High Throughput
Most potash operations are working with high tonnages. Whether at the mine site or the fertilizer plant, potash producers need high-capacity processing capabilities and rotary drums provide just that.
Heavy-Duty Design
Potash is notoriously corrosive and abrasive. Combined with the high throughput characteristic of the industry, and potash can quickly wreak havoc on equipment.
Well-designed rotary drums are incredibly durable. Their already-rugged design and fabrication is often further enhanced through various customizations to produce a system that is capable of withstanding the harshest of processing conditions. Customizations often include options in shell thickness and opting for stainless steel or other specialty alloys over carbon steel for a portion or all of the drum’s construction.
Long-Term Reliability
In part due to their rugged design and construction, rotary drums are also known for their longevity. When well cared for, these diverse machines can provide decades of trouble-free operation.
Proven in the Industry
The prolific use of rotary drums in both the fertilizer and mining industries makes them a familiar and proven technology. Paired with their simple operation, this ubiquity translates to easy adoption and accessible maintenance.
Tolerance to Variation in Feedstock
Variation in moisture content, particle size, and other feedstock characteristics is not uncommon at mine sites. In the case of drying, such changes would bring other types of dryers to a shutdown. In contrast, rotary dryers are widely recognized for their ability to tolerate such variation.
Tumbling Action
The tumbling action imparted by a rotating drum has benefits in several settings. When used in the glazing process, a rotary drum helps to knock off edges and polish granules. In the conditioning process, the tumbling motion promotes a thorough mixing of ore with the reagents. In coating, it ensures uniform distribution of the coating throughout the material bed. And in traditional granulation operations, it fosters particle agglomeration and growth of granules.
Conclusion
The potash industry relies on rotary drums for everything from ore beneficiation to finishing fertilizer products, and for good reason; their high throughput, rugged build, and long-term reliability, among other benefits, has made them the industry standard wherever they can be applied.
FEECO is the potash industry’s preferred provider for all types of rotary drums, from dryers to coating drums. All FEECO rotary drums are designed specifically around potash’s unique and often-challenging qualities for a lifetime of reliable processing. Process development and testing services, as well as a comprehensive parts and service program, are also available. To learn more about why the potash industry’s top players rely on FEECO, contact us today!