USE
OF LIME AND DOLOMITE
Agriculture
Various mixtures of lime, limestone and dolomite are used
in agriculture and forestry, both for correcting acidity in
the soil and for adding nutrients which contain magnesium
and calcium.
These nutrients are essential for healthy plant
growth and for increasing crop yield. SAVINA has supplied
materials to produce and distribute a wide array of fertilising
products.
In forestry, dolomite-based products stimulate
photosynthesis and, by lowering the degree of acidity in the
soil, ensure a better assimilation of nutrients, resulting
in a significant increase in forest productivity.
In addition, lime- and limestone-based products
are used in animal hygiene and animal foodstock
Chemical
Lime has numerous applications in the chemical industry thanks
to its natural properties and competitive price.
It's used in the production of chemicals such as calcium carbide,
propylene oxide, sodium carbonate and glycerine, as well as
being a reagent in the production of calcium-based compounds
and in processes where pH modification is necessary.
Most of the process water in the chemical industry requires
treatment with lime to correct its pH and mineral content.
Acidic waste waters can also be treated with lime before being
recycled or released into the sewage system.
Civil
engineering
Quicklime (and especially low-dust lime) is used to dry out
damp soils and to improve the clay soils used in earthworks.
Lime is also increasingly used to recycle excavated material
(trench spoil) from sites in urban areas.
A recent application of lime is the use of hydrated
lime in the cement filler which consolidates underground works
such as tunnels.
Hydrated lime also improves the performance of
the asphalt mixes used for road surfacing. It increases their
resistance to stripping, rutting and age-hardening.
Construction
Builders have made use of the binding properties of lime for
millennia in structures like the Pyramids of Egypt or the
Great Wall of China. Today, lime-based mortars are often used
in masonry and in plaster mixes for building facades.
In addition, lime is being used increasingly
in modern building materials such as aerated concrete and
lime-sand bricks. These materials are highly valued because
they have excellent thermal and acoustic insulating properties
and are easy to work with.
Gas treament
Waste incineration and many industrial processes
generate flue-gases which often contain pollutants such as
sulphur dioxide (SO2), hydrochloric acid (HCl) as well as
heavy metals, dioxins and furans.
Lime-based products are highly efficient reagents
for capturing these pollutants, depending on the process you
use and the nature of the gases generated.
Glass
Dolomite is mainly used in the float glass industry.
This source of magnesium acts as a stabiliser to improve the
general resistance of glass to natural or chemical attack.
SAVINA also supplies special reagents for industrial
flue-gas treatment.
Iron and steel
Lime and dolime are commonly used in converters and electric
arc furnaces, where they help to form slag which draws off
harmful impurities such as silicon and phosphorus. Lime is
also used to improve productivity in the ore agglomeration
process.
More recently, new products and services have
been introduced in various steps of the steelmaking process.
These have led to major quality improvements in processes
such as hot metal desulphurisation and in effluent handling,
to name but two.
Steelmaking industry also requires large quantities
of water for all its processes. Lime and lime-based products
are a cost-effective way of adjusting the mineral content.
Paper
Lime is traditionally used to reconstitute caustic soda from
the sodium carbonate left over from the pulp-making process.
SAVINA also supplies high-purity lime for the
fabrication of PCC (Precipitated Calcium Carbonate) which
is manufactured via a series of controlled chemical reactions.
Quicklime is usually mixed with water to form a slurry to
which carbon dioxide is added. The resulting reaction produces
a very fine precipitated calcium carbonate (CaCO3). This filler
is used in paper production to enhance the paper's whiteness,
opacity and texture.
Lime is also used as a reagent to soften process
water in paper factories.
Refractories
Dead-burned dolomite is produced when dolomite is calcined
at very high temperatures. It is used both as a refractory
product in granular form to repair linings and for making
the bricks used in the refractory linings of casting ladles
and cement kilns.
In the steel refining process, the use of dolime
instead of pure quicklime will extend the life of refractory
linings. In fact, adding dolime will create MgO in solution
in the slag, which provides an excellent buffering capacity
as MgO particles in suspension provide excellent coating protection.
Any excess MgO precipitates, protecting refractories and tap
holes, reducing the need for gunning and repairs.
Drinking and process water
In both drinking and process water preparation, lime is mainly
used for pH adjustment and/or water purification.
Lime milk, among other products, is a cost-effective
reagent which reduces the water's hardness by precipitating
the bicarbonates dissolved in it, thus preventing the formation
of scale.
Waste water and sludge treatment
In wastewater treatment plants (both urban or industrial),
lime is widely used for correcting the pH balance of acidic
waters, for precipitating heavy metals and phosphates, and
for its flocculating action.
Lime is widely used for stabilising industrial
residual sludge or dredging sludge and for treating urban
biosolids before agricultural re-use or incineration.
Lime helps coagulation, makes sludge easier to
handle, prevents fermentation, limits odours, eliminates pathogens
and holds metallic ions in an insoluble form. It also enriches
the sludge with calcium and magnesium (when dolomitic lime
is used), both of which are beneficial for agricultural use.
In addition, lime is used to treat soils polluted
with hydrocarbons.
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