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

Chapter 4
removal of conductive components via special adsorption beds in the chlor-alkali plant
(modified equipment).
Achieved environmental benefits
The achieved environmental benefits of this technique include the following:
reduction of salt consumption;
reduction of water consumption;
reduction of chloride emissions.
Environmental performance and operational data
At the AkzoNobel plant in Bitterfeld (Germany), approximately 8 % of the consumed brine is
obtained by neutralising a hydrochloric acid stream from a customer with sodium hydroxide
[ 57, EIPPCB 2011 ]. {Please TWG provide more information.}
At the Arkema plant in Saint Auban (France), waste water generated during a chlorination
process and containing hydrochloric acid is neutralised with caustic soda and fed back to the
electrolysis unit after stripping organic contaminants [ 3, Euro Chlor 2011 ], [ 33, Euro Chlor
2011 ].
At the Dow plant in Stade (Germany), waste water generated during the production of
propylene oxide is sent back for solution mining after biological and physico-chemical
treatment. This results in savings of approximately 10 000 000 m 3 /yr of fresh water and the same
volume of waste water not discharged [ 33, Euro Chlor 2011 ]. Previously, a total water
consumption of 30 000 000 m 3 /yr was reported. Waste water recycling resulted in conservation
of 7 000 000 m 3 /yr of river water and 600 000 t/yr of salt, as well as a 23 % reduction of annual
salt discharge [ 129, Euro Chlor 2007 ].
At the SABIC plant in Bergen op Zoom (Netherlands), 73 % of the NaCl leaving the
polycarbonate production unit is recycled, which is equivalent to vacuum salt savings and
related emissions of approximately 72 000 t/yr. Moreover, water consumption is reduced by
225 000 m 3 /yr [ 128, SABIC 2008 ].
At the Zachem plant in Bydgoszcz (Poland), hydrochloric acid obtained during the production
of epichlorohydrin and toluene diisocyanate is neutralised with the caustic liquor from the
diaphragm cells and recycled [ 220, Polish Ministry 2011 ].
Cross-media effects
Some raw materials and energy are consumed for the installation and operation of the additional
waste water treatment units.
Technical considerations relevant to applicability
The recycling of salt-containing waste water is restricted by two major factors. First, it is
necessary to ensure that no contaminants with a detrimental effect on the electrolysis process are
introduced into the brine system. This includes heavy metals, which negatively affect the
lifetime of the diaphragm or membrane as well as the energy consumption, in particular for the
membrane cell technique (see Table 2.4). High residual concentrations of organic compounds
are also unwanted in the membrane cell technique (see Table 2.4) and may lead to the formation
of halogenated organic compounds (see Section 3.4.2.3.7). Second, the water balance of the
electrolysis unit has to be respected [ 33, Euro Chlor 2011 ].
WORKING DRAFT IN PROGRESS
Economics
{Please TWG provide more information.}
At the SABIC plant in Bergen op Zoom, investment costs for the waste water recycling system
amounted to EUR 11 million. Annual cost savings due to reduced consumption of salt and
TB/EIPPCB/CAK_Draft_1 December 2011 187