Sealants sulfur-coated urea with

The process and the related variables depend on whether the plant is producing sulfur-coated urea with or without a sealant and whether the sulfur is being applied with the pneumatic or hydraulic sulfur-spraying system. 

Pneumatic Sulfur-Spraying System. Sulfur-Coated Urea with Sealant. Figure 3 is a flow diagram of the pneumatic sulfur-spraying system. This system provides better atomization than the hydraulic system, which is discussed later. With the pneumatic system less sulfur is required, producing a higher analysis sulfur-coated urea fertilizer. 

Figure 1. Flowsheet of process for coating urea with sulfur and a wax sealant using either pneumatic or hydraulic sulfur-spraying system...

Agronomic Properties and Nutrient Release Mechanisms. The mechanism of nutrient release from SCU is by water penetration through micropores and imperfections, ie, cracks or incomplete sulfur coverage, ia the coating. This is followed by a rapid release of the dissolved urea from the core of the particle. When wax sealants are used, a dual release mechanism is created. Microbes ia the soil environment must attack the sealant to reveal the imperfections ia the sulfur coating. Because microbial populations vary with temperature, the release properties of wax-sealed SCUs are also temperature dependent. 

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