KWS Manufacturing

Weigh Belt Spillage Screw Conveyor for Fertilizer Additive

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End User or Owner

Mosaic Fertilizer
Mulberry, FL

General Description

The Mosaic Company is the world’s largest producer of concentrated phosphate and potash, nitrogen fertilizers and feed ingredients for the agricultural industry. They decided to spend $225 million to expand their fertilizer plant in Mulberry, Florida; this was the largest capital project Mosaic had ever undertaken. Mosaic had developed a new fertilizer called MicroEssentials in the mid-2000s and customer demand had increased four-fold since 2009. A critical component of the new MicroEssentials formulation was the addition of zinc oxide. Recent testing had indicated that most of the wheat and corn grown in the Plains states lacked adequate zinc. Zinc deficiency causes significant decreases in crop productivity and nutritional quality. As part of the project, Mosaic required four high quality screw conveyors that acted as spillage conveyors underneath weigh belt feeders metering zinc oxide.

Design Parameters

  1. Product Type: Zinc Oxide (dry, free flowing powder materials)
  2. Material Density: 35-150 Pounds per Cubic Foot
  3. Capacity: 206 Cubic Feet per Hour
  4. Duty: Intermittent Duty

KWS Advantages

Thayer Scale was selected by Mosaic to provide the belt feeders for the project. Thayer Scale and KWS have had a long standing relationship and worked on many successful projects together. KWS has great relationships with other leading suppliers of bulk material handling equipment and is frequently called upon to partner on projects. Zinc oxide can be a very light product but also can pack under pressure. KWS has the knowledge and expertise to design for the most demanding applications and bulk materials. Mosaic supplied the project specifications and general arrangement drawings, Thayer provided the dimensions to mate to their equipment, and KWS did the rest. KWS designs every piece of equipment using 3D Autodesk Inventor. KWS and Thayer Scale traded 3D CAD models so that all dimensions, interferences, and details could be addressed. The screw conveyors were designed for full upset conditions with the packed density of zinc oxide. The four screw conveyors were shipped to Thayer so they could be inspected and packaged with the weigh belt feeders.

Special Features

KWS designed the screw conveyors with flared troughs so the inlet section would match up to the weigh belt feeders. Access doors were added to make maintenance easier. Flush end discharges were used so the zinc oxide would fully discharge without packing. The screw conveyor trough was designed for easy removal and replacement. Stainless steel fasteners were used for better corrosion resistance. A special Rustoleum epoxy mastic primer and paint was applied for superior protection from the corrosive elements. Severe duty IEEE-841 motors were utilized due to mill and chemical duty environment. The screw conveyor drives were designed to start and operate under the worst case upset conditions to remove any packed zinc oxide.


"Thank you for all the information you provided so we could provide just what the Customer wanted."

Lynne Adler – Project Engineer, Thayer Scale

Zinc Oxide

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