(BAT) Reference Document for the Production of Chlor-alkali ...

Chapter 1
[ 6, Euro Chlor 2011 ]. In 2010, 522 kt of chlorine were transported via rail and road which
means that more than 94 % were used on the same or adjacent sites for other chemical processes
[ 8, Euro Chlor 2011 ]. Western European exports of elemental chlorine to outside the region are
negligible. More than 85% of the chlorine produced in EU is used on the same or adjacent sites
for other chemical processes. The production of chlorine and caustic is completely interrelated
with the downstream businesses, including the PVC industry and the intermediates used to
manufacture PVC. [Lindley, 1997]
1.4.2 Consumption of sodium hydroxide
Initially devised for the production of chlorine, electrolysis rapidly produced the caustic soda
needed for numerous new sectors: artificial textiles, detergents, etc. The output of caustic soda
is proportional to that of chlorine, in the ratio of their molecular weight (40.00 / 35.45 = 1.128).
Thus, 1.128 tonnes of caustic soda (100%) are produced by electrolysis per tonne of chlorine.
The output of sodium hydroxide (also called caustic soda) is proportional to that of chlorine.
The ratio is more or less equal to the ratio of the molecular weights (40.00/35.45 = 1.128) but is
influenced by the side reactions taking place at the electrodes and, in the case of the diaphragm
and membrane cell technique, the diffusion of hydroxide through the separator. In practice the
ratio ranges from 1.07 – 1.128 [ 3, Euro Chlor 2011 ].
Due to customers' requirements, sodium hydroxide is produced commercially in two forms: as
50 wt-% solution (most common) and less frequently in the solid state as prills, flakes or cast
shapes. There are also applications where sodium hydroxide in lower concentrations is supplied
and/or directly used. Figure 1.7 shows the applications of caustic soda in EU-27 and EFTA
countries in 2010.
Sodium hydroxide is usually supplied as a 50% aqueous solution and can be stored for long
periods and readily transported (rail, road and ship). The main areas of application of sodium
hydroxide today are:
chemicals: synthesis of organic or inorganic compounds
metallurgy, alumina/aluminium
pulp and paper
textile
soaps, surfactants
water treatment
consumer products.
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WORKING DRAFT IN PROGRESS
10 December 2011 TB/EIPPCB/CAK_Draft _1