Potash, an abundantly popular mined element, is primarily used for agricultural purposes. It is a source of soluble potassium, one of three primary plant nutrients required to ensure the growth of healthy and nutritious crops. Mined potash requires processing in order to make the potassium readily available for plant consumption. Drying is a vital aspect of processing potash into a usable form. The following article highlights the basics of potash drying, including benefits, equipment, and material considerations.
Benefits of Drying Potash
The drying process accomplishes many benefits for potash such as:
- Reduced Moisture
The drying process reduces moisture in potash, diminishing material handling issues such as clumping.
- Round, Polished Granules
Rough granule edges wear down other granules and produce a large amount of fines (called attrition). Drying rounds and polishes granules, reducing occurrences of this issue.
- Hardened Granule Surface
Potash drying flashes residual moisture off quickly, leaving a hardened, more robust potash granule with a re-crystallized surface.
Why Dry Potash?
After potash is mined, it undergoes processing to extract potassium from minerals and create a final potassium product in a readily available form. Agglomeration is part of the overall processing used to achieve an optimal potash product, with compaction granulation or pelletization being the primary techniques. Drying complements both processes.
Compaction Granulation and Drying
Compaction granulation is the most frequently used solution to agglomerate mined potash into a readily available product. A double roll press, or compactor, compresses the potash into a compacted form. Next, a granulator fractures the material into coarse granules.
Compaction is a dry process; consequently, this procedure does not always include the use of an industrial dryer. However, even when using a seemingly straightforward process such as compaction, there are special material considerations that need to be addressed. For instance, the issue of attrition mentioned earlier. To improve resistance to attrition, the compacted granules are wetted and then dried in an industrial dryer. The goal is to fill cracks inside the particles and eliminate sharp granule edges, reducing dusting problems that would otherwise occur when the material is shipped and handled. Both rotary dryers and fluid bed dryers can be used to dry the potash granules after they are wetted.
Pelletization and Drying
Potash pelletization, while not as common as compaction granulation, is also used to agglomerate potash. A disc pelletizer gradually builds the potash to the desired pellet size in a process known as tumble growth agglomeration.
Pelletizing requires a binder to adhere the potash to itself in pellet form. Because the binder also adds moisture, a drying phase is necessary. As with granulated potash, rotary dryers and fluid bed dryers are excellent industrial dryer choices for pelletized potash.
Potash Drying Equipment: Rotary Dryers vs Fluid Bed Dryers
A rotary dryer is a robust, long-lasting equipment choice for drying potash. Flights within the rotating drum lift and cascade material as it tumbles through the drum, preventing material clumps and promoting an evenly dried final product. Rotary dryers accept a wide variability in feedstock, a high volume of material, and are ideal for rounding the sharp edges of compacted potash.
Fluid bed dryers use pneumatic conveying to dry materials. By suspending potash in a fluidized state, they expose the entire surface of each granule, increasing a material’s cooling efficiency in certain applications. These dryers have the advantage of being smaller than rotary dryers, which is beneficial in processing facilities with limited space. Fluid bed dryers are also modular, which is well-suited for operational growth in the future. However, their downfall is that they are unable to accept a wide range of variability in feedstock, and do not round or polish granules.
In terms of energy, the most efficient equipment choice varies. Material considerations such as volume, weight, and feedstock variability should be considered when determining which machine will be the most suitable and energy efficient solution.
Material Considerations When Drying Potash
Potash is a demanding material that requires robust equipment to handle the product’s challenging characteristics. Examples of equipment adjustments for handling potash are listed below.
- High processing temperatures are used to remove moisture from potash efficiently. In addition, a co-current air flow, meaning the potash and air stream flow in the same direction, proficiently dries the material.
- Potash is corrosive. Consequently, stainless steel is often used at the front end of equipment in order to counteract the product’s eroding characteristics.
- Because potash can clump together during drying, knocking systems are included as a means of breaking up lumps in the material. Another solution to avoid lumps is to use a screw conveyer. The feed trajectory of a screw conveyer will ‘fling’ or ‘throw’ the potash into the dryer, breaking up lumps in the process.
Drying potash creates a multitude of benefits, resulting in an optimal final product with minimal moisture, clumping, and dusting issues. However, with so many challenging material considerations, it is clear that potash drying requires well-designed equipment to get the job done right. FEECO has over 60 years of experience engineering a range of potash processing solutions, including rotary dryers, compactors, pelletizers, and material handling equipment. For more information on potash dryers, as well as FEECO’s other potash processing equipment, contact us today!
Preview of: Potash Processing Handbook
|Download our FREE Potash Processing Handbook|