Environmental Aspects of Phosphate and Potash Mining United ...

The Environmental Approach of the Phosphate Rock and Potash Mining Industry
26
Air Emission Control By-Products
Zirconium is recovered as a co-product during phosphate
rock processing at the Phalaborwa operation of
Foskor Limited in South Africa.
Dust emissions from the zirconium plant prompted
the installation of an emission control system. Fine silica
fume generated during processing is recovered by
the system and subsequently sold, producing a revenue
stream. The revenue generated has resulted in
the rapid payback of the installation costs for the air
emission control system.
The system has produced environmental benefits
from the reduction in dust emissions as well as an
additional revenue stream for the company.
The problem of dust emissions may be compounded
by processes such as calcination and drying, which
generate high levels of exhaust particulates and gases.
These emissions are reduced through the use of cleaner
fuels such as natural gas, applying emission control
equipment to exhausts, using more efficient equipment
and making use of cogeneration possibilities and
heat recovery. In some cases, minor adjustments have
improved the efficiency of old equipment.
Steam-Heated Fluidized Bed Dryers for Potash Ore
The installation of steam-heated fluidized bed dryers
to dry potassium chloride at the Hattorf operation of
Kali und Salz GmbH in Germany has resulted in 35%
less energy consumption, with markedly lower flue
gas and dust emissions in comparison to rotary dryers.
Exhaust emissions from vehicle engines, electrical
power generation and product dryers may contain
greenhouse gases such as carbon dioxide (CO 2 ) and
other gases such as NO x . The use of improved fuel or
energy consumption techniques and technologies
reduces the emission of greenhouse gases and other
exhaust particulates and gases.
Dryer Burner Modifications
The IMC Potash Carlsbad operation in New Mexico
(USA) has significantly reduced the exhaust emissions
from an aging product dryer through minor modifications.
A small adjustment to the angle of the burner
fuel injection nozzles created more turbulent flow
conditions, improving the mixing of fuel and air and
hence, the combustion.
The result has been greater fuel efficiency and a significant
reduction in the quantity of carbon
monoxide.
Noise and Vibration
Beneficiation processes may generate high levels of
noise and vibration, especially during crushing and
grinding. Noise pollution has been reduced in many
cases by enclosing the plant, retaining suitable buffer
zones around the plant site, planting greenbelts and
constructing earth bunds. Some of these measures
also assist in reducing the visual impact of the site.
Resource Maximization
The efficiency of resource recovery influences the
environmental impact of other activities such as
extraction or waste disposal.
Product loss during beneficiation through the loss of
ore to waste streams, dust emissions and process
spillages results in both an economic loss as well as the
need to extract and process additional ore to meet
demand. An example of this is the fine particles of
phosphate that are lost to waste, as they cannot be efficiently
separated.
Ultra-Fine Phosphate Recovery
In Brazil, the Tapira mining complex and Uberaba fertilizer
complex operated by Fertilizantes Fosfatados
SA (Fosfertil) are expanding production. A component
of this is the implementation of a process to recover
the ultra-fine phosphate previously lost to the clay
tailings. The system will use column flotation cells to
recover around 200,000 tonnes of ultra-fine phosphate
rock per year. This ultra-fine product will be
used to produce single super-phosphate (SSP) fertilizer.
Recovery of the ultra-fine phosphate rock has provided
an additional source of revenue for the company,
enhancing its competitiveness in the market place.
Environmental benefits are derived from greater
recovery of the resource and consequently, a minor
reduction in the waste volume generated.
Spillage of ore and concentrated product may occur
during beneficiation, prevention or recovery of these
can assist maximizing the resource.
Product Spillage Recovery
In South Africa, Foskor has been using hand shovels
and wheelbarrows to recover small amounts of
spillage associated with the loading of phosphate
rock concentrate into rail cars. Approximately 20,000
tonnes of product were recovered in one year providing
a significant saving.