Inline mixing and granulation technology designed by engineering company Sandvik is helping fertilizer manufacturers add value to commodity materials and bring profitable new products to market. Using an end-to-end process that mixes liquid and/or solid products then converts them into uniform pastilles, producers are able to upgrade low value products such as sulphur and ammonium sulphate with the addition of urea, adjusting the ratio to suit specific crop needs.
Other mixes and blends successfully produced on this system include ammonium nitrate derivatives, sulphur bentonite and NPK complex fertilizer.
Production begins with accurate dosing and weighing of the materials to be combined, followed by mixing and, if necessary, grinding. The resulting solution is then fed in molten form to Sandvik’s Rotoform system, where it is deposited onto a continuously running steel cooling belt as droplets.
The speed of the Rotoform drop depositor is synchronized with the speed of the belt to create hemispherical pastilles of a uniform size and shape. Cooling water sprayed against the underside of the belt absorbs the heat of the melt, resulting in controlled solidification. After being discharged from the end of the steel belt cooler, the solid pastilles are conveyed away for storage or bagging.
“A single line will deliver throughputs of up to 150 mtpd depend on the product,” explains Sandvik’s Kumar Swamy, Global Product Manager, Fertilizers. “This level of capacity makes it ideal for introducing speciality products, while rapid changeover between different blends enables product development and testing.”
Rotoform is widely used for sulphur solidification in the oil and gas industry, where refineries operate multiple lines in parallel to achieve the high capacities required. This approach offers fertilizers the ability to build a system that grows with market demand, with the flexibility to turn individual lines on or off without halting overall production.
Rotoform is environmentally friendly with low energy consumption, no visible dust emission and vapour levels that can easily be captured in a simple atmospheric absorber.
“Blending sulphur and AS with urea to produce enhanced fertilizers benefits everyone,” says Kumar Swamy. “Sulphur is more than just a vital plant nutrient; its presence enhances the efficiency of nitrogen so these products can significantly boost a farmer’s crop yields. The ability to upgrade low value products opens the door to higher profit margins for producers. And a clean production process benefits the environment at large. It’s a win-win situation.”