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

Chapter 5
5.4 Water consumption
4. In order to reduce the generation of waste water, BAT is to use a combination of the
techniques given below.
Technique Description Applicability
a Brine recirculation
b
c
d
e
f
Recycling of other
process streams
Recycling of saltcontaining
waste
water from other
production
processes
Use of waste water
for solution
mining
Closed-circuit
direct cooling of
hydrogen and
chlorine with
water
Concentration of
brine filtration
sludges
g Nanofiltration
h
The depleted brine from the
electrolysis cells is
resaturated with solid salt or
by evaporation and fed back
to the cells.
Process streams from the
chlor-alkali plant such as
condensates from chlorine,
caustic and hydrogen
processing are fed back to
various steps of the process.
Salt-containing waste water
from other production
processes is treated and fed
back into the brine system.
Waste water from the chloralkali
plant is treated and
pumped back to the salt
mine.
The gas is cooled by direct
contact with water which is
circulated in a closed loop
and cooled indirectly by
using heat exchangers.
Brine filtration sludges are
concentrated in filter
presses, rotary drum
vacuum filters or
centrifuges. The residual
water is fed back into the
brine system.
A specific type of
membrane filtration with
membrane pore sizes of
approximately 1 nm, used
to concentrate sulphate in
the brine purge, thereby
reducing the waste water
volume.
Techniques to reduce
chlorate emissions are
described in BAT 16. These
techniques reduce the brine
purge volume.
Not applicable to diaphragm cell
plants. Not applicable to
membrane cell plants using
solution-mined brine in the case
of availability of abundant salt
and water resources and a saline
receiving water body which
tolerates high chloride emission
levels.
[Section on
which BAT
conclusion is
based]
[4.3.2.2.2,
4.3.2.3.7.]
Generally applicable. [4.3.2.2.3]
Not applicable to plants where an
additional treatment of this waste
water offsets the environmental
benefits.
Applicable to plants which use
solution-mined brine. Not
applicable when it leads to
significant additional energy
consumption.
[4.3.2.1.3]
[4.3.2.2.6]
Generally applicable. [4.3.2.2.4]
Generally applicable. [4.3.2.2.5]
Applicable to membrane cell
plants with brine recirculation.
[4.3.6.2.2]
WORKING DRAFT IN PROGRESS
Techniques to
reduce chlorate
emissions
Applicable to membrane cell
plants with brine recirculation.
[4.3.6.4]
274 December 2011 TB/EIPPCB/CAK_Draft_1