While there is no doubt that fertilizer blending is a science, running a successful blend plant is also an art. For a small, but growing group of companies, an unusual type of storage facility is making it easier to combine the two.
El Dorado Chemical in Bryan, TX, and Highland Growers in DeRidder, LA, are two of the latest companies to opt for dome-shaped fertilizer blend plants. Domes are super-insulated, steel-reinforced concrete buildings that are used for everything from schools to churches to homes.
The general contractor for both the El Dorado and Highland Growers plants is Texas-based Monolithic Inc., which has been building both single- and multiple-use storages necessary in the operation of a blend plant since the late 1970s.
There are several factors that make these buildings uniquely positioned to serve as fertilizer storage units. For starters, the materials used in the domes’ construction make them extremely energy efficient. The geothermal properties of the concrete, combined with the super insulation, keep temperature fluctuations to a minimum.
In fact, it is possible to air condition the facilities using small units, which makes it easier for blend plant operators to keep condensation out of their formulas ensuring little or no product loss. It also makes for a much more pleasant working environment for workers.
The dome’s circular design also offers an advantage for fertilizer blending. All of the needed materials are within easy reach, enabling plant operators to quickly place the specialty chemicals into the weigh hopper for transfer into the exterior blender. And since the domes can be virtually any size, the number of bins can be adapted to meet the needs of the operator.
Finally, the structures are disaster-resistant, meeting the Federal Emergency Management Agency’s criteria for near-absolute protection from tornadoes and hurricanes, and they also are fire-proof. The reinforced concrete shell also makes it easy to secure the facility from would-be intruders.
The Dome At Work
El Dorado completed its new concrete dome facility in Bryan in 2010. It consists of two domes connected by a covered work area. One dome measures 95 feet in diameter and has the capacity to store 3,000 tons of phosphorus, potash, nitrogen and other fertilizer components in eight bins. The small dome is 40 feet in diameter and has two bins used for storing micronutrients and crop protection products.
Company spokesman Justin Gough said that El Dorado Chemical opted for the dome design because “we believe this type of facility is the future of the fertilizer industry. It became apparent early on that our products would store better, we would be able to operate more efficiently and our maintenance cost will be less going forward.”
In addition to the Bryan facility, El Dorado Chemical operates 12 more bulk fertilizer plants in Texas and one in Tennessee.
Highland Growers is also nearing completion on a concrete dome fertilizer blend plant in DeRidder to replace a wooden structure built in 1968. The new facility, completed last month, measures 75 feet in diameter and will include six bins.
Company President Donald Smith said the ability to affordably air condition the building was a big selling factor for him, as well as the circular design. “We liked the volume you could get in a small area,” said Smith, whose family has been operating Highland Growers since 1939. “The ability to control the humidity is also important to us.”
Construction of the dome is as unique as the building themselves. It begins with the placement of a ringbeam footing and the pouring of a circular steel-reinforced concrete slab floor. Vertical steel bars embedded in the outer ring later attach to the steel reinforcing of the dome itself. An Airform, a tarp made of tough, single-ply roofing material, is attached to the ring base and inflated, creating the shape of the dome.
Crews then move to the interior of the dome, where they spray polyurethane foam on the Airform and reinforce it with a grid of steel rebar. They then spray the dome with two or three inches of Shotcrete. The result is a safe, permanent and energy efficient structure.
“Because the domes are so insulated, we expect virtually no condensation on the interior surfaces, and that’s good because condensation can enter a pile and lead to corrosion,” said David B. South, president of dome manufacturer Monolithic. “We also used special additives in the concrete to help eliminate any corrosion caused by the fertilizer.”
In building fertilizer blend plants, Monolithic used MetaMax, a high reactivity metakaolin that gives the concrete significantly less porosity than standard concrete and makes it resistant against chemical attack.
Super-strong concrete also means less damage from loaders that accidently ram into walls. Front-end loaders, which play a major role in the loading and unloading of fertilizers, also can be hurt by a corrosive environment.
For plant operators who are willing to blaze a new trail, the concrete dome’s unique features offer them the ability to conduct their business more efficiently while also saving money on utilities and replacement costs.
For more information, visit www.monolithic.com.