Storing fertilizer is one thing, but handling it properly is quite another.
The first step for handling success is to consider the big picture—hourly and annual tonnage requirements, throughput needs, and more. The standard handling mechanism outside the storage facility is straightforward—usually conveyance via belt and reclaim via front-end loader—so major material-handling decisions must be made for systems within the structure. Here are five considerations when planning a project:
1. Select the right storage facility.
Because fertilizer is hygroscopic, some companies opt for wooden warehouses since wood is naturally inert; however, a concrete dome designed to hold the same amount of material is significantly less expensive, said engineer for Dome Technology Adam Aagard.
Two major perks for storing fertilizer in a dome are economy and longevity. Much of the cost savings in a dome comes from humidity control and finish options that protect the product. As far as longevity, a dome is built to last decades, and with the necessary finishes, the structure can withstand corrosion.
Many companies store bulk amounts within separate domes, then mix them in smaller batching facilities outside the storage areas. Domes offer the most economical value for large dry-bulk storage, so other types of small structures are commonly used for storing smaller quantities or when mixing fertilizer within the structure.
2. Understand the product.
Regardless of the product being stored and handled, an understanding of all physical and chemical properties is a must, said Charles Formisani, vice president of sales for A.J. Sackett and Sons Company, an industry leader in fertilizer-handling systems. With a basic understanding engineers can begin delivering on other requests—upstream and downstream processes, hourly and annual tonnage requirements, site-specific safety requirements, accommodating preferred vendors for mechanical components, and more, he said.
Whether or not the stored product has been prilled will affect the handling-system design. Prilled product is more susceptible to degradation, so gentle handling is a must—but “the more gently you handle it, the more it costs,” Aagard said. Unformed or unprilled product doesn’t require gentle handling, so a low-tech, less expensive option is one way to cut costs. Both prilled and unprilled fertilizers are corrosive, so stainless or non-corrosive finishes are the standard.
3. Control humidity.
Water wreaks havoc on fertilizer; since most fertilizers are hygroscopic, they attract moisture that dissolves the product and corrodes it too, producing weak acids that break down steel and damage concrete. Dome customers are advised to allot a portion of the budget to corrosive-resistant rebar and/or additional concrete over rebar.
To protect product from humidity, a dehumidifier is highly recommended. Humidity monitors can also be installed, allowing site managers to survey and adjust interior conditions.
4. Deal with fines.
Smaller particles ought to be evenly dispersed in the storage; if not, fines will concentrate in the middle of the pile and glue together more firmly than solid, larger particles—and that can cause serious reclaim problems. Selecting the right distribution spout can ensure that solid, larger particles are more evenly mixed with fines. A common solution is an umbrella spout that dumps fertilizer onto an umbrella-like structure and fans out the product. Not only is this option effective, but it’s fairly inexpensive, Aagard said.
5. Identify maximum stacking depth.
When stacked too tall, some fertilizers will crystal-bridge together, making reclaim difficult. A point-level monitor tracks the stack so site managers know how much they’re storing and can adjust throughput as needed.
This is an excerpt from a feature published in the September 2016 issue of World Fertilizer.