Environmental Aspects of Phosphate and Potash Mining United ...

Environmental Aspects of Phosphate and Potash Mining
Beneficiation plants frequently implement measures
to contain and recover process spillages, in order to
minimize environmental effects and product loss.
Water Consumption
Beneficiation operations generally consume large
quantities of fresh water for processes such as washing
and flotation. The water is usually sourced from nearby
surface and ground water supplies. In arid areas,
local water supplies may be limited, requiring water to
be piped considerable distances.
Water piped in from distant sources may provide a
suitable source for other users.
Provision of Water Resources to Other Users
In New Mexico, the Mississippi Chemical Corporation
pipes water from a distant freshwater aquifer to their
Carlsbad potash operation. Local groundwater in the
vicinity of the operation is high in total dissolved
solids and not suitable for human or livestock consumption.
The freshwater pipeline has provided a
water source available for local ranchers, reducing
reliance on variable rainfall in this arid area.
Electrostatic Separation and Pneumatic Flotation
for Potash Ore
The Kali und Salz GmbH operation in Germany has
developed the ESTA electrostatic separation process
and the pneumatic flotation cell to improve the recovery
of potash from complex mineralized ores.
Implementation of these techniques has also created
additional environmental benefits through reduced
energy consumption and waste water production.
The ESTA electrostatic separation process requires
that complex potassium/magnesium ores are dry
ground to less than 1 millimetre to separate the different
minerals. The particles are conditioned to
create differential positive and negative charges
between them. Separation occurs as the mineral particles
are subject to a 125,000-volt potential drop
during free fall. A multi stage separation process
allows the various product and waste minerals to be
isolated and concentrated. Environmental and economic
benefits arise from the dry separation process
that produces no waste brines and the relatively low
energy requirements.
A non-mechanical, pneumatic flotation cell has been
developed for the separation of kieserite (magnesium
sulphate) from halite. In comparison to conventional
mechanical flotation cells the pneumatic cells consume
less energy and recover more kieserite.
Water management is an important aspect of the
operation and is usually integrated with waste disposal.
Where possible, recirculation or recovery of the
waste process water/brine is effected. In many cases
the process waters/brines are used to transport the
wastes as a slurry to the disposal areas. Typically, they
are recovered for reuse, minimizing the need for additional
fresh water input.
Where fresh water sources are not available for phosphate
rock beneficiation, salt water has been used for
processing. A clean water wash is required afterwards,
to reduce the chloride content of the ore concentrate.
Utilizing dry beneficiation processes reduces water
consumption. However, it can create additional dust
problems.
Water Contamination
Contamination of surface and ground water may
occur from the spillage of process water, brines, ore
concentrates, wastes or chemical reagents during processing.
A variety of methods to contain spills are
used, including drains, bunds around storage and processing
tanks and dams for major process spills.
Pneumatic flotation cell - Kali und Salz GmbH,
Germany
These allow spills to be recovered and returned to the
process or be disposed of safely.
Air Contamination
Dry processing operations may generate significant
quantities of dust during operations such as crushing,
grinding, compaction and drying. This can be controlled
to some extent through the use of emission
control equipment such as baghouses and wet scrubbers.