Chemical Engineering December 2013 - 11

For the first story, the diagram refers to " SOP " (sulfate of potash), which another name for potassium sulfate (K2SO4). So I think we either have to substitute K2SO4 for SOP in the diagram (Dave,
Edited by Gerald Ondrey
December 2013
Leonite crystals
First commercial process for K2SO4
from polyhalite completes pilot
Crushed
P
ilot plant operation has been
completed for a process that proPolyhalite
ore
duces
the fertilizer potassium sulfate
from the mineral polyhalite,
a hydrated sulfate of potassium,
magnesium and calcium. The process,
developed by Intercontinental
Potash Corp. (ICP; Golden, Colo.;
www.icpotash.com), resurrects a
route to K2SO4 that was first explored in a
push to develop a domestic source of potash
and washed
ore
Crushing
and washing
Crush ore to
appropriate size
Remove sodium
chloride to protect
downstream
equipment
Calcined
ore
Fluid bed
calcination
Calcine ore to
increase
solubility
of potassium
sulfate during
leach stage
Leach
tank
Produce potassium
sulfate brine using
counter-current
leach process
Remove calcium
sulfate
after a German embargo in World War I.
" Although it was evaluated decades ago,
but not pursued, our process represents the
first commercially viable potassium sulfate
process using mined polyhalite as a feedstock, "
says Randy Foote, chief operating
officer at ICP. " After validating the decadesold
data, ICP developed a patented hybrid
crystallization system designed to maximize
production of K2SO4, " explains ICP process
engineer Mike Morrison.
The ICP process avoids the cost fluctuations
of conventional potassium sulfate production,
where feedstocks potassium chloride
and sulfuric acid must be purchased.
ICP's polyhalite route is less expensive than
using mined sylvite, a naturally occurring
mineral composed of KCl, Foote says.
The process (flowsheet) begins with a
crushing and washing stage to remove sodium
chloride, then enters a calcination
step in a fluidized-bed reactor, where the
polyhalite undergoes changes to its crystal
structure that dramatically increase solubility.
The calcined solids then enter a countercurrent
leaching process that removes
potassium and magnesium sulfate from the
mineral, forming a brine.
The next stage of the process involves a
hybrid crystallization system that combines
mechanical vapor recompression (MVR)
and multiple effect evaporation (MEE). The
patented circuit features a leonite dissolver,
which takes a potassium- and magnesiumcontaining
mineral (leonite) from later in the
process and uses it to increase production of
potassium sulfate. An MVR evaporator removes
water until the K2SO4 crystallizes,
recovering 90% of the material. The mother liquor
then enters a series of MEEs, which produce
the leonite that is then recirculated (U.S.
Patent 8,551,429; other patents pending).
The final stage of the process is a drying
and granulation step, where three potassium
sulfate products are produced - standard,
granular and soluble-grade.
Improving extraction yields of Ni and Co from laterite
L
K2SO4 crystals
Granulation
Modify SOP to
marketable form
Granular
K2SO4
Standard
K2SO4
Soluble
K2SO4
Leach
brine
Concentrated
brine
Preconcentration
K2SO4
mother
liquor
K2SO4
crystallization
Leonite
crystallization
Magnesium-rich
brine to
evaporation
pond
Acetic acid from syngas
A new process for the production
of acetic acid claims to be
more efficient and cost-effective
than current technologies.
Carbonylation of methanol
has been the leading acetic
acid technology for several
decades, but BP plc (London,
U.K.; www.bp.com) has introduced
the new three-step
SaaBre process to produce
acetic acid directly from synthesis
gas (syngas; a mixture
of H2 and CO).
Unlike current acetic acid
ow-grade nickel (less than 1.5 wt.%) laterite
ores represent about 70% of global
reserves but account for only 40% of nickel
production. Increasing demand for nickel in
recent years has created the need to process
such ores. Atmospheric acid leaching of these
ores presents difficulties due to the presence
of high-acid-consuming serpentinized and
clay minerals, leading to pulp gelation and
poor mixing, and low metal recovery. Now a
team from the Ian Wark Research Institute,
University of South Australia (Adelaide:
www.unisa.edu.au), led by professor Jonas
Addai-Mensah, has shown how to increase
Ni and Co recoveries from these ores.
The team studied the influence of time
Note: For more information, circle the 3-digit number
on p. 68, or use the website designation.
and temperature on atmospheric acid-leaching
behavior of saprolitic nickel laterite ores.
It carried out isothermal (at 70°C and 95°C),
batch, sulfuric acid leaching studies on 40
wt.% solid dispersions of 2-mm saprolitic
nickel laterite ore for 4 h at pH=1.
There was a sharp decrease in particle
size within the first 5 min. of shearing in
both water and sulfuric acid. This was accompanied
by an increase in the amount of
finer particles in the pulps. Further increase
in time led to a gradual decrease in size for
the particles sheared in water with a marginal
change in the acidic solution.
The specific surface areas at 120 and
(Continues on p. 12)
technologies, the SaaBre
process requires no CO purification,
and no methanol
needs to be purchased. Also,
there are no iodides present,
reducing the need for any
metallurgical considerations.
In fact, experts believe that
SaaBre will cut variable operating
costs over BP's current
methanol-carbonylation technology
to produce acetic acid,
Cativa XL, by up to $50 per
metric ton.
Another feature of the process
is its ability to use simple,
ample feedstocks. Creating
products directly from
syngas allows for numerous
suitable feedstock sources in
any region around the world.
The inaugural deployment
of the SaaBre technology is
expected for the first half of
2014, with future plans includ(Continues
on p. 13)
CHemICAL engIneerIng www.CHe.COm DeCemBer 2013 11

http://www.icpotash.com http://www.bp.com http://www.unisa.edu.au http://www.CHe.COm

Chemical Engineering December 2013

Table of Contents for the Digital Edition of Chemical Engineering December 2013