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This document has not been fully peer reviewed and <strong>the</strong> <strong>information</strong> within is not validated nor endorsed by <strong>the</strong> TWG
on LVIC-S or by <strong>the</strong> European Commission, it is meant for <strong>information</strong>, only
Solid products have a concentration of between 7 – 9.3 % Al with a typical concentration of
9.1 % equivalent to 14 crystal water. Concentration in liquid products is 3.5 – 4.5 % Al. The
iron content in <strong>the</strong> substances can typically vary between 0 – 3 % as Fe.
Solid products are produced in every fraction from fine powder up to blocks of about 10 kg.
Product Name : Aluminium sulphate Al2(SO4)3
Derivatives: Low iron aluminium sulphate, iron containing aluminium sulphate,
aluminium basic sulphate.
As illustrated in Table 1.4, aluminium sulphate is a very common product that is used in <strong>the</strong>
following major areas:
Use Share Application
Drinking water treatment ~ 30 % Coagulant for purification
Sewage water treatment ~ 10 % Coagulant for purification and phosphorus removal
Paper industry ~ 40 % Coagulant for water purification and paper sizing
O<strong>the</strong>r applications ~ 20 % Pigment production, cement industry, detergent, fire
extinguishers, etc.
Table 1.4: Major applications of aluminium sulphate
[50, CEFIC-INCOPA, 2004]
Due to its low value and high production volumes, aluminium sulphate is produced in most
European countries to cover <strong>the</strong> local demand. The number of production units within Europe is
about 65 plants. From <strong>the</strong>se, about 15 units are outside <strong>the</strong> EU-15. The total capacity is at <strong>the</strong>
level of 1.2 million tonnes calculated as solid equivalents of 9.1 % Al. The capacity utilisation is
on average 50 %, which would bring <strong>the</strong> total European market to about 600000 tonnes, i.e.
20 – 25 % of <strong>the</strong> total world market [50, CEFIC-INCOPA, 2004].
1.2.2 Process description
Aluminium sulphate comes directly from <strong>the</strong> digestion of aluminium containing raw materials
with sulphuric acid.
2Al(OH)3 + 3H2SO4 F Al2(SO4)3 + 6H2O
The most common aluminium raw material is by far aluminium hydroxide, a product
originating from <strong>the</strong> Bayer process, where bauxite is used as a raw material for <strong>the</strong> production
of pure aluminium hydroxide or oxide. For <strong>the</strong> production of iron containing aluminium
sulphate products, bauxite is also used as a source for aluminium raw material.
The digestion with sulphuric acid normally takes place at atmospheric pressure and at a
temperature between 110 – 120 ºC. In some cases pressure digestion is also used with a
temperature up to about 170 °C. The heat necessary for <strong>the</strong> process comes from <strong>the</strong> exo<strong>the</strong>rmic
reaction. The normal Al-concentration in <strong>the</strong> digester is in <strong>the</strong> ratio of 7 – 9 %, which means
that <strong>the</strong> boiling temperature is around 120 °C and <strong>the</strong> crystallisation temperature 105 – 110 °C.
A small amount of steam is sometimes used to avoid crystallisation and prolong <strong>the</strong> reaction.
O<strong>the</strong>rwise <strong>the</strong> energy consumption of <strong>the</strong> process is limited to pumps and agitators.
After digestion, <strong>the</strong> product is ei<strong>the</strong>r diluted with water for a liquid product or, in a solidification
unit, cooled directly or indirectly with air or water to a solid form, which is <strong>the</strong>n ground and
screened to <strong>the</strong> required particle size. Dust coming from this process is handled by filters or
scrubbers. This dust is commonly recycled through a dilution step in <strong>the</strong> production of
aluminium sulphate solution.
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