INVESTIGADORES
BUCALA Veronica
capítulos de libros
Título:
Production of Granular Urea as NitrogenousFertilizer
Autor/es:
COTABARREN, IVANA; BERTIN, DIEGO; VELIZ MORAGA, SUSSY; MIRAZÚ, LEONARDO; PIÑA, JULIANA; BUCALÁ, VERÓNICA
Libro:
Urea: Synthesis, Properties and Uses
Editorial:
Nova Publishers
Referencias:
Año: 2012; p. 1 - 63
Resumen:
The demand for urea is continuously growing and entwined with the need for fertilizers
and animal feed additives.
Industrially, urea is initially produced in liquid form as a concentrated solution. Then, it
can be converted into particulate material either through granulation or prilling processes.
Since granules have better attributes than prills, nowadays granulation is the preferred
production route. Urea granulation is a multifaceted process that requires several operation
units, which constitute the granulation circuit, to produce the solid form (granules) with the
desired attributes. The main unit of the circuit is the granulator, where small urea particles
known as seeds are continuously fed and sprayed with a urea concentrated solution. The
seeds grow through deposition of the solution droplets onto the solids surface, followed by
water evaporation and urea solidification. The granules that leave the size enlargement unit
are size classified into product, oversize and undersize streams. The product is transported
to storage facilities, while the oversize fraction is fed to crushers for size reduction. The
crushed oversize particles are then combined with the undersize granules and recycled back
to the granulator as seeds.
Focusing on urea, the advantages of granules over prills are discussed by exploring the
physical properties of both solid forms. Then, the current available technologies for urea
granulation are presented in a comparative manner. From this analysis, the fluidized-bed
granulator appears as the most widely used equipment for granular urea production. Due to
this preference, different approaches to model fluidized-bed granulators are presented
aiming to give a comprehensive picture of the fundamental phenomena that occurs within
these granulation units. Special attention is placed on the granules growth mechanism, and
its proper representation. Although coating is the preferred urea growth mechanism,
unexpected operating situations may favor size enlargement by agglomeration that is an
undesired phenomenon. Therefore, based on experimental data obtained in a pilot-scale
fluidized-bed batch granulator for urea production, the influence of the operating variables
on both granules quality and growth mechanisms is discussed. Finally, mathematical
models for peripheral circuit units (crusher, cooler and screens) are presented. By coupling
all the involved units, a complete granulation circuit simulator is reported. Steady-state and
dynamics results obtained by means of the urea granulation simulator are provided to show
the influence of different circuit operating variables on the marketable product size
distribution and the plant throughput. Summarizing, this chapter gives an introduction to
the main features of the urea granulation process and remarks operation problems that face
the granular urea production together with possible strategies to overcome them.