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

Chapter 4
Cross-media effects
Some raw materials and energy are consumed for the manufacture of the electrodes and
coatings.
Technical considerations relevant to applicability
Generally, there are no technical restrictions to the applicability of this technique for new
electrolysis units. In the case of existing electrolysis units, some equipment suppliers offer the
possibility to retrofit the cells [ 22, Uhde 2009 ]. The coatings can often be improved depending
on their availability from the respective equipment provider [ 63, Euro Chlor 2010 ].
Economics
The costs for electrode recoatings may amount to several thousand EUR/m 2 depending on a
potential removal of the mesh [ 3, Euro Chlor 2011 ].
Due to investment costs, upgrades of electrodes and coatings are usually carried out when the
electrodes require recoating.
Driving force for implementation
The driving forces for implementation of this technique include the following:
recoating of electrodes;
reduction of costs related to energy consumption;
increased production rate;
improvement of product quality;
reduction of costs related to equipment and maintenance.
Example plants
Arkema in Fos-sur-mer (France), chlorine capacity of diaphragm cell unit 150 kt/yr;
Arkema in Lavera (France), chlorine capacity of diaphragm cell unit 175 kt/yr.
Reference literature
[ 1, Ullmann's 2006 ], [ 3, Euro Chlor 2011 ], [ 21, Kirk-Othmer 1995 ], [ 22, Uhde 2009 ], [ 63,
Euro Chlor 2010 ], [ 134, INEOS 2011 ]
4.3.2.3.5 High-purity brine
Description
This technique consists in purifying the brine to a level so that it strictly complies with the
manufacturers' specifications of the electrolysis unit, in order to avoid contamination of
electrodes and diaphragms/membranes which may increase energy consumption.
Technical description
Several types of impurities can have a detrimental effect on electrodes, diaphragms and
membranes. The membrane cell technique is particularly sensitive to brine impurities
(see Table 2.4). The required brine purity is usually set out in the equipment specifications of
the manufacturer.
WORKING DRAFT IN PROGRESS
Prior to designing the brine purification system, a full characterisation of the brine is usually
carried out followed by pilot trials for brine purification. Techniques for the removal of the most
important impurities via primary and secondary brine purification are applied in all chlor-alkali
plants (see Section 2.5.3). Some specific impurities such as strontium and aluminium can be
taken into account during the design of the purification process. The temporary removal of
mercury impurities might be necessary in the case of a conversion of a mercury cell plant to a
membrane cell plant [ 143, Healy 2011 ].
TB/EIPPCB/CAK_Draft_1 December 2011 203