Segmentation of Urea Melt Marbles and Application of One-Shot Segmentation in Batch Production of Large Urea Granules

Abstract

Steel strip granulation is a promising technology for preparing large urea granules; however, easy blocking of the feeding nozzle by urea melt limits its industrial applications. In this study, a dust-free and anticlogging urea granulation process for the mass production of large urea granules is proposed by introducing a urea melt marble (UMM) formed by covering urea melt with super-urea-phobic poly­(tetrafluoroethylene) (PTFE) particles to improve steel strip granulation. Large urea granules are obtained by directly cutting a large-sized cake-shaped mother-UMM into segments. These segments shrink into spherical baby-UMMs and solidify after condensation to form rigid particles. The results confirm that the PTFE powder distribution density for constructing a stable mother-UMM by the segmentation process is crucial. The PTFE powder distribution density for obtaining usable baby-UMMs and subsequent qualified large urea granules should be within 0.0009–0.0011 g/cm2. Super-urea-phobic honeycomb-shaped cutters are used for the batch preparation of qualified urea products with adequate quality distribution. This study provides a promising strategy for improving the production of urea granules.

Preparation of Oriented Superhydrophobic Surface to Reduce Agglomeration in Preparing Melt Marbles

“…Liquid marbles were first discovered and proposed by Aussillous and Quéré, which are nonwetting droplets that are wrapped by hydrophobic powder particles . The process of preparing liquid marbles is simple, and the special structure of liquid marbles shows typical properties such as nonadhesion, − elasticity, , mechanical stability, , and divisibility properties, − which are widely used in the fields of droplet microfluidics, , controlled release, − microreactors, − granulation and energy storage. − …”

“…Melt marbles should belong to a category of liquid marbles. The difference is that the material inside the melt marble is not in a liquid state at room temperature and only becomes a conventional liquid marble when heated above its melting point. − Owning to superhydrophobic particles of melt marbles, it has good mechanical impact stability and elasticity. However, the particles on the surface of the droplet are not fixed, , so the stability and elasticity of the marbles are limited.…”

“…However, the existing process of preparing the anisotropic superhydrophobic surface is complex, expensive, and challenging to implement on an industrial scale. − Moreover, the anisotropy depends mainly on the specific arrangement of micronano structures on the surface, limiting its ability to control the directional movement of larger droplets. , For “droplets” with significant particle size, the influence of particle size becomes paramount, where the kinetic energy arising from solid/solid contact surpasses the energy barrier imposed by the micronano architecture. − Consequently, the anisotropic superhydrophobic surface prepared by the traditional method is unsuitable for the batch-directional transportation of large-sized liquid/melt marbles.…”