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

3.3 Consumption levels of all cell plants Inputs in the
production line
3.3.1 Sodium chloride/potassium chloride
Chapter 3
Different types of salt are used to produce the brine for electrolysis (see Section 2.5.1) These
types are vacuum-crystallised salt from solution-mined brine, rock salt and solar salt. The
stoichiometric salt consumption is 1.65 1.66 tonnes per tonne of chlorine produced. In reality,
more salt is consumed because it partly leaves the process via the brine purge which is used to
control the levels of impurities in the brine In fact, 1.75 tonnes per tonne of chlorine produced is
closer to reality because of impurities control of the brine by purge. Reported consumption
levels for plants with brine recirculation are summarised in Table 3.2.
Table 3.2: Salt consumption in chlor-alkali plants with brine recirculation in EU-27 and
EFTA countries in 2008/2009
Salt consumption in kg per tonne of chlorine produced
10th 25th
Salt Minimum
percentile percentile Median
75th 90th
percentile percentile Maximum
NaCl ( 1 ) 1650 1661 1690 1711 1788 2036 2339
KCl ( 2 ) 2098 ND 2100 2117 2145 ND 2200
( 1 ) 57 data from 54 plants. Three of these plants provided separate data for different electrolysis units.
( 2 ) 8 data from 8 plants.
NB: ND = not enough data.
Source: [ 57, EIPPCB 2011 ]
Another particular case which can occur concerns Diaphragm plants sometimes which prefer to
sell the salt from caustic evaporators and buy new feedstock for economic reasons.
In plants which operate with waste brine using a once-through brine process, the consumption
of salt is about 3 times twice as much as in plants using a brine recirculation process. Reported
consumption levels range from 3.1 – 3.8 tonnes of salt per tonne of chlorine produced compared
to a median of 1.7 t/t in the case of plants using a brine recirculation system [ 57, EIPPCB
2011 ]. Therefore, 1.4 – 2.1 tonnes of salt per tonne of chlorine produced are wasted which is
equivalent to 45 – 55 % of the total salt consumption., i.e. about 5 tonnes of salt per tonne of
chlorine produced. Chlor-alkali plants using a waste brine process are located close to big
underground salt deposits and which can be found in Spain, Italy, Portugal and the United
Kingdom. {This information was moved to Section 2.5.4.}
In plants using KCl, the amount of salt needed is a bit higher more than for plants using NaCl
feedstock, due to the higher molecular weight of KCl (stoichiometric salt consumption of
2.10 tonnes per tonne of chlorine produced). Consumption in this case is approximately about
2.1 – 2.2 tonnes of salt/ per tonne of chlorine produced (Table 3.2). Plants using KCl do not use
the waste brine process.
WORKING DRAFT IN PROGRESS
3.3.2 Water
For the production of the required demineralised water, several water sources can be used such
as groundwater, river water and drinking water. The techniques used to produce demineralised
water include ion-exchange, membrane filtration and evaporation [ 3, Euro Chlor 2011 ].
Water is used in mainly added to the process for [ 3, Euro Chlor 2011 ]:
purges
TB/EIPPCB/CAK_Draft_1 December 2011 67