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

Chapter 1
1.5 Environmental relevance of the chlor-alkali industry
The chlor-alkali industry is an energy-intensive industry and consumes large amounts of
electricity during the electrolysis process. Additional energy in the form of steam or electricity
is necessary for auxiliary processes, which depend on the cell technique used. In 2008, the total
electricity consumption of the chlor-alkali sector in EU-27 and EFTA countries amounted to
36 TWh [ 13, Euro Chlor 2008 ]. This was equivalent to 17 % of the total final energy
consumption in the form of electricity of the chemical industry and to approximately 3 % of all
industry sectors in this region [ 14, Eurostat 2010 ].
Inputs and pollutant outputs from the chlor-alkali industry are quite specific to the cell
technology used, the purity of the incoming salt and the specifications of the products. Because
of the huge amount of electricity needed in the process, energy can be considered as a raw
material. The chlor-alkali process is one of the largest consumers of electrical energy.
All three cell techniques (mercury, diaphragm and membrane cell technique) may give rise to
emissions of chlorine to air through leakages during production, handling and storage, as well as
to channelled emissions from the chlorine absorption unit. The substances emitted through
waste water include free oxidants, chlorate, bromate, chloride, sulphate and halogenated organic
compounds.
For many years, the mercury cell technique has been a significant source of environmental
pollution, because some mercury is lost from the process to air, water, products and wastes.
Inorganic mercury can be metabolised to form highly toxic methyl mercury by anaerobic
bacteria, and this organic mercury is bio-accumulated 1 in the food chain. Most of the mercury
which leaves an installation is disposed of with waste. Releases to the environment from the
installation mostly occur to the atmosphere as diffuse emissions from the cell room. Significant
emissions may also occur during decommissioning of the installation.
It is recognised that the main part of the mercury losses is in the different wastes from the
process. Considerable emissions of mercury can also occur with run-off water. The soil at many
sites is contaminated with mercury due to deposition of diffuse emissions and/or historical
disposal of mercury contaminated wastes. The mercury leaks from the soil and ends up in the
run-off water. Another big entry is the ‘Difference to Balance’. The annual mercury balance for
a site is never zero. This is because mercury accumulates in plant equipment and structures
during the life of the plant.
Data on mercury emissions for EU-27 and EFTA countries can be found in the technical
background report to the global atmospheric mercury assessment from AMAP/UNEP for the
reference year 2005 [ 15, AMAP/UNEP 2008 ]. Based on these data, the total annual mercury
emissions of the chlor-alkali industry for EU-27 and EFTA countries amounted to 5.98 t,
equivalent to 5.2 % of the total anthropogenic emissions in this region. The greatest emissions
of mercury originate from stationary combustion (45.4 %), metal production (15.1 %) and
cement production (13.6 %). There is, however, some uncertainty about mercury emissions
from mercury cell chlor-alkali plants due to methodological difficulties in quantifying the
diffuse emissions and in setting up a mercury input-output balance.
WORKING DRAFT IN PROGRESS
The chlor-alkali industry was the largest domestic user of mercury in the years 1989 to 1990 in
the US and this could be expected to be the same in Europe [J. Ind. Ecology, 1997]. Based on
the European Atmospheric Emission Inventory of Heavy Metals and Persistent Organic
Pollutants [UBA (D)-TNO report, 1997] in the 15 EU countries, the highest emitters of mercury
to air in 1990 include: coal burning electric utilities (highest figure of 90.5 tonnes), municipal
1 In the 1950s a chemical plant producing acetaldehyde discharged a spent catalyst containing organic mercury into
Minimata Bay, Japan. A number of people (mostly fishermen) became seriously ill and some were disabled. This event was at the
origin of environmental regulations in Japan and caused changes into mercury free technologies in some industrial sectors.
{Minamata is mentioned with less details in 2.4.1}.
14 December 2011 TB/EIPPCB/CAK_Draft _1