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

Chapter 3
of chlorine capacity. The first one is economic and the second technical. For economic reasons,
a plant will always prefer to run all its cells because it is the cheapest way of operating and
minimising costs. This is particularly true in countries like Spain or the United Kingdom where
electricity tariffs can vary a lot during the year or even the day. Running at lower current
densities is cheaper than switching off the some cells. The second reason given is the design of
the electrical circuit. The rectifier is specified for a certain voltage and the electrical equipment
may not support a voltage drop, especially for processes plants using a combination of
diaphragm and mercury cell techniques amalgam technologies or amalgam mercury and
membrane cell techniques. In Europe, however, the figures reported refer to 90 % running
capacity.
The industry also reports that production figures on a plant by plant basis are confidential data
for ‘competitivity competitive reasons’.
Contrary to what is described above, a minor share of the mercury emission is indeed dependent
on the production rate. For example, emissions via products or via the brine purge are directly
linked to production [ 83, Euro Chlor 2010 ]. In addition, maintenance frequencies and related
emissions also increase with current densities and thus production rates.
The emissions of pollutants other than mercury depend mainly on the production rate and
should thus preferably be expressed per actual production.
3.5.4 Consumption of mercury
Reported consumption of mercury ranges from 2.6 – 10.9 g/t annual chlorine capacity [ 75,
COM 2001 ]. {These data are contained in Table 3.1 and stem from the original BREF. Please
TWG provide updated data.}
3.5.5 Overall mercury emissions and waste generation
Mercury emissions and waste generation from individual chlor-alkali installations in EU-27 and
EFTA countries in 2010 as reported by Euro Chlor are summarised in Table 3.23. These figures
will be discussed in more detail in the subsequent sections.
Figure 3.3 shows the weighted averages of the total emissions from all chlor-alkali installations
in Western Europe (OSPAR countries) from 1977 – 1998 and Figure 3.4 for EU-27 and EFTA
countries from 1995 – 2009. For the OSPAR countries, emissions decreased by approximately
92 % from 1977 – 1995 while for EU-27 and EFTA countries, emissions decreased by
approximately 66 % from 1995 – 2010. The observed decreases are due to reduced emissions
from individual installations. However, the weighted average may also be influenced by the
shutdown or inclusion of installations with emissions higher or lower than the average. For
example, the slight increase from 2008 to 2009 is caused by a plant with high mercury
emissions to water which in 2009 was for the first time included in the calculations. Otherwise
the weighted average of the total emissions would have decreased to 0.81 g Hg/t annual
chlorine capacity.
WORKING DRAFT IN PROGRESS
The reported figures for mercury emissions and for mercury in waste disposed of are subject to
some uncertainty which is due to several factors such as [ 97, Concorde 2006 ]:
the diffuse nature of the majority of mercury emissions to air;
the temporal variations of these diffuse emissions;
the inhomogeneous nature of mercury-contaminated waste;
the measurement uncertainty related to the monitoring technique;
the uncertainty related to the measurement of the airflow in the cell room;
the differences in applied monitoring techniques.
TB/EIPPCB/CAK_Draft_1 December 2011 105