Ammonium sulfate is a bulk crystalline product with a worldwide production
of 17 million TPA. Most of the marketed ammonium sulfate derives from
by-products of other processes. Ammonium sulfate is crystallized in Forced
Circulation (FC), Draft Tube Baffle (DTB), and Oslo (also known as “Krystal”)
crystallizers. FC units make a small particle, but are inexpensive and simple
to operate. The Oslo can produce very large crystals, but it requires more
process volume and which leads to higher capital costs. The DTB is the best
compromise for large crystal size at lower investment, and most modern
crystallizers producing ammonium sulfate are DTBs. This is due to large crystal
and narrow size distribution produced by DTB crystallizers, which command a
sizeable price premium. GEA Messo supplies all of the above crystallizers, (Download our brochure
for more information) and can help in selecting the right type for a
specific application.
The use of Oslo crystallizers has declined over
the years, and in practice most Oslo crystallizers are operated as FC’s,
producing a smaller crystal size then would be expected from a fluidized-bed
crystallizer. Several of these units have been converted (by GEA Messo) to DTB
crystallizers. GEA Messo provides evaluation services to ammonium sulfate
producers, to analyze present operations and develop optimization strategies
that target improvements in capacity, crystal size or both.
An
expanding area in Ammonium Sulfate production is reaction crystallization of
ammonium sulfate by neutralization of (spent) acid. Energy and investment
savings are the driving force in reaction ammonium sulfate crystallization. GEA
Messo’s reaction crystallization technology is applicable to both byproduct and
pure chemical reactants.
Ammonium sulfate is also produced from
flue-gas scrubbing solutions that contain ammonia (such as urea prilling tower
exhaust scrubber effluent). The design of these crystallizers is influenced by
the effect that urea has on the crystallization kinetics of Ammonium sulfate,
and the need for high energy efficiency, due to the low feed concentration.
Such crystallizers typically employ mechanical vapor recompression to reduce
the energy cost.
Crystallization of ammonium sulfate usually occurs in
solutions that include organic compounds as minor constituents. This
environment leads to more complex crystallization operation, as the impurity
concentration increases. Ammonium sulfate crystal growth and habit are very
susceptible to the presence and amount of impurities in its growth environment.
As a result, impurity presence and concentration will influence product crystal
size and purity. GEA Messo maintains a modern Research Facility where
custom-made solutions to such problems can be tested and refined, and effective
methods to improve crystal size and purity can be developed for specific
installations.