Engineering

Polymer chemistry

Materials science

Chemical engineering

Sphericity

Organic chemistry

Urea

Dispersity

Granule (geology)

Composite material

Chemistry

Granulation

Advanced Materials Interfaces

Urea melt droplets (UMDs) spontaneously spheronize and form large urea granules after condensation on superhydrophobic surfaces without dust generation. However, they break and coalesce when colliding with each other; moreover, they adhere to the surface and form tails when rolling. These problems limit the practicality of the process using UMDs for large urea granulation directly. Urea melt marbles (UMMs) are introduced to overcome these drawbacks by enwrapping UMDs with superhydrophobic polytetrafluoroethylene (PTFE) powder, thus enhancing the elasticity and maintaining the sphericity. A premixing–melting process is developed to obtain UMMs and lower the PTFE powder consumption to half of that required in the traditional liquid marble preparation. The best determined elasticity modulus of UMMs reaches 44.9 ± 3.6 Pa, and the sphericity is 0.9992. No adhering or tailing occurs during rolling granulation. Large urea granules obtained through UMMs meet all requirements for the commercial urea products and exhibit additional advantages of protection against moisture and slow release of fertilizer.

Urea Melt Marbles Developed by Enwrapping Urea Melt Droplets with Superhydrophobic Particles: Preparation, Properties, and Application in Large Urea Granule Production