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

Chapter 4
reduction of costs related to equipment and maintenance;
increased process safety.
Example plants
In 2011, AkzoNobel reported having used approximately 1 Mt/yr of vacuum salt with iron(III)
meso-tartrate since 2005 in its own chlor-alkali plants [ 141, AkzoNobel 2011 ]. In 2010, a
contract was signed between AkzoNobel and another European chlorine producer to deliver
0.5 Mt/yr of vacuum salt with iron(III) meso-tartrate [ 142, AkzoNobel 2010 ].
Reference literature
[ 66, Ullmann's 2010 ], [ 140, Giatti 2011 ], [ 141, AkzoNobel 2011 ], [ 142, AkzoNobel 2010 ],
[ 187, Debelle and Millet 2011 ]
4.3.2.3.7 Once-through brine system
Description
This technique consists in using a once-though brine system in which the depleted brine leaving
the electrolysis cells is treated and discharged directly to a receiving water body instead of
reconcentrating and recirculating it.
Technical description
A flow diagram of brine recirculation and once-through brine processes is shown in Figure 4.6.
WORKING DRAFT IN PROGRESS
Source: [ 37, Euro Chlor 2010 ]
Figure 4.6: Flow diagram of brine recirculation and once-through brine processes
When solution-mined brine is used as a raw material for membrane cell plants, the once-through
brine process allows for a reduction in energy consumption for the brine preparation. This is
because three tonnes of water accompany each tonne of salt. With the usual brine recirculation
process, there would be a need to discard that water to reconcentrate the depleted brine after
electrolysis. This could be done in a vacuum salt plant outside the electrolysis plant or in an
206 December 2011 TB/EIPPCB/CAK_Draft_1