Urea warehouse at Donaldsonville
Close-up of urea granules
CF Industries produces granular urea at its Donaldsonville, LA
and Medicine Hat, Alberta complexes. There are minor differences
between the two operations, but the basic process involves three
major steps. These are urea synthesis, urea purification, and
granulation.
Urea Synthesis: synthesis begins by chemically reacting
liquid ammonia and gaseous CO2 in a condenser to form ammonium carbamate. The carbamate flows into the urea reactor, where about
half of it is converted to urea and water. Unconverted carbamate
undergoes further processing to become urea.
Urea Purification: the urea solution next flows to the
rectifying column, where more ammonia, CO2, and water are removed.
After that, the purified solution moves through a series of vacuum
evaporators, where removal of additional water produces a
concentrated molten urea.
Granulation: granulation produces a moisture-resistant
product well suited for blending with other fertilizer materials.
Molten urea is first sprayed onto a moving bed of urea granules.
Cool air drawn through the granulator “freezes” a new layer of urea
onto the surface of the granules, which are then removed from the
granulator and screened to the desired size. Air leaving the
granulators is scrubbed with water to remove dust before venting to
the atmosphere.
