Companies today are realizing the benefits of dome storage for fertilizer, starting with the fact that domes boast an indefinite lifespan.

A concrete structure like a DomeSilo by Dome Technology is ideal for fertilizer storage because corrosion is highly unlikely. In fact, some fertilizer domes built by Dome Technology have been around for 30 years and are still structurally sound.

Concrete may develop hairline cracks that can be penetrated by fine fertilizer dust. This concern can be mitigated by spraying a polyurea coating on the interior surface of the dome. A corrosive-resistant powder can also be mixed into the concrete when pouring the floor.

Water wreaks havoc on fertilizer, and since most fertilizers are hygroscopic, they attract moisture that dissolves the product and corrodes it too, producing weak acids that break down steel. To account for this, corrosive-resistant rebar and/or additional concrete over rebar are used.

To protect product from humidity, a dehumidifier is also highly recommended. Housed on top of the dome, humidity in the headspace can be controlled, and the ideal interior climate can be maintained. Humidity monitors can also be installed, allowing site managers to survey and adjust interior conditions.

Protection from rust and moisture on the storage side is one thing, but there are ways to extend a facility’s life span by protecting other components from corrosion too. While many fertilizer companies utilize front-end loaders, those who select integrated reclaim systems can protect metal components from rust in multiple ways. Stainless steel is always an option, especially ideal for food- or pharm-grade fertilizer products, but can be cost prohibitive. Another route is to paint the metal so corrosion isn’t an issue; the main thing is to keep up on maintenance so chips and scratches in the surface don’t allow an access point for moisture.

Decisions about moving product require their own attention. When done right, an efficient handling system promises a boosted bottom line and fewer system hiccups. By striking the right combination of features, fertilizer companies can achieve a completely custom, efficient handling system that functions seamlessly and yields a greater return on investment.

Five key benefits of dome storage + the right handling system

Once a storage facility has been selected, the customer’s next step is to analyze handling options — 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 configuration. Many companies store bulk amounts within separate domes, then mix them in smaller batching facilities outside the storage areas. Domes also 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. With a basic understanding of the stored product, 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.

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 gentle can cost more. 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. Housed on top of the dome, humidity in the headspace can be controlled, and the ideal interior climate can be maintained. 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 relatively inexpensive.

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.

Case study: Fabrication for a facility upgrade at one Idaho mine

Fabrication is a necessity for massive projects like upgrading a fertilizer storage facility. For decades, Dome Technology has specialized in bulk storage, but in recent years the team has turned up the dial on fabrication know-how. Today, Dome Technology builds structural-steel features — ladders, catwalks and the like — to support fertilizer-storage facilities.

In early 2023 one longtime fertilizer-mining company in Idaho chose to transition from truck unload — the model they’d used for decades — to rail unload. Instead of trucking and dumping with smaller conveyors to the stacker, a rail pit was installed; Dome Technology, then, increased the capacity by fabricating a new upgraded trans conveyor and the stacker system.

“The additional capacity of the new rail unloading was way beyond what the existing conveyors for the facility could accommodate,” Dome Technology sales manager Heath Harrison said. “We built replacement conveyors that could increase the rate to handle the rail receiving as opposed to the original truck transfer the mine had depended on.”

Product stacking in this new configuration was also a major consideration. The mining company utilizes an outside pile, allowing their plant to stockpile product when operations pause for the winter. The previous configuration featured a hammerhead stacker that moved back and forth. Dome Technology’s scope of work also included upgrading the stacker equipment, including everything from the rail pit to the stacker. These improvements will allow the company to control how product is stored, building up the pile where necessary and boosting operational flexibility. The new version tilts and spans the entire front side of the storage.

Additionally, a sampler was installed for pulling and testing material, and a front-end loader hopper feed allows entry for cleanup. Trucks and front-end loaders have full access to the facility for reclaim.

The company now has a state-of-the-art staging area that complements anticipated business growth and provides a year-round buffer. “What this allows the mine to do is stockpile material to get them through the winter,” Harrison said.

Dome Technology collaborates frequently with bulk-handling expert Bruks-Siwertell. For this project, Bruks-Siwertell completed the design work, then handed over plans to Dome Technology for fabrication and installation. Additionally, Dome Technology provided assembly and erection of the boom tower and fabricated steel components like ladders, staircases, decking and handrails.

“We do build domes, but this is a great example of how we are a turnkey facility provider and can supply storage, conveyance and fabrication,” Harrison said.

Turnkey construction: Simplifying a project

Large storage projects can seem daunting — they require significant time and a considerable financial investment. That’s why many fertilizer companies opt to partner with a turnkey construction company to manage the full project scope. By working with a one-stop shop, customers receive an innovative facility because each element is planned with the others in mind.

Here are the typical first steps in building a turnkey facility — the initial items a customer defines:

1. A company provides the basics: capacity, geographical and geological position, existing or new facility, potential for growth, product consideration and desired or required operations.

2. This information will drive the dome dimensions, and “because the dome is so flexible, that is where we’ll find the most economical dimensions,” Harrison said.

3. Once plans are approved, it’s full steam ahead. Dome Technology provides geotechnical analysis to determine foundation type; deep foundations aren’t the only option. The team is also knowledgeable in stored-product considerations, optimal design for product integrity and subcontractor management. In addition to the storage structure itself, the team can provide the conveying systems as well as the structural steel, manufactured in its shop located on the corporate campus.

Working alongside an expert team can result in a completely custom facility where serious business goals can be achieved.

Editor’s note: The preceding is an article published in the May/June 2024 issue of World Fertilizer.