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

Chapter 3
3.2 Overall Overview of emission and consumption levels of
all cell plants
Emission and consumption levels Inputs and pollutant outputs of the chlor-alkali industry are
quite specific to the cell technique technology used but also depend on the specifications of the
products (O2 or CO2 content, for example), the purity of the incoming salt and the geographical
location of the plant. The inputs are primarily salt and water as feedstock, acids and chemical
precipitants used to remove impurities in the input brine or output chlorine/caustic soda, as well
as refrigerants cooling agents (CFCs, HCFCs, HFCs, ammonia, etc.) for liquefying and
purifying the chlorine gas produced. The chlor-alkali process needs huge amounts of electricity
and electrical energy is a major input.
The main pollutant outputs which are common to all three electrolytic processes are emissions
of chlorine and refrigerants to air, emissions of noise, emissions of free oxidants, chlorate,
bromate, chloride, sulphate and halogenated organic compounds to water as well as the
generation of spent acids from chlorine drying and sludges from brine purification. chlorine gas
emissions, spent acids, cooling agents, impurities removed from the input salt or brine.
The major pollutant in terms of environmental impact, originating from the mercury cell
technique amalgam technology, is mercury. Due to the process characteristics, mercury can be
released emitted from the process to through air, water, wastes and in the products. The
diaphragm cell and membrane cell techniques are more concerned with spent materials
generation, such as asbestos waste in the case of asbestos diaphragms. because of the
replacement of the cell materials needed for the process. In the diaphragm process, deterioration
of the asbestos-based diaphragms is the main reason for cell renewal. In view of the potential
exposure of employees to asbestos and releases into the environment, special care must be
taken. In addition, the improvement in cell component materials such as metal anodes and
modified diaphragms, which are more stable, has helped to reduce the formation of undesirable
and polluted by-products. {This information is too detailed for an introducing section.}
Mercury outputs have decreased in the last twenty years as amalgam cell plant operators have
been more active in reducing mercury emissions, although the attention paid to this may vary
from one country to another. According to Euro Chlor, mercury emissions to air and water per
tonne chlorine capacity in western Europe were 27 g in 1977, 8 g in 1987 and around 2 g in
1997. Furthermore, the industry moved away in the 1990s from the mercury process to the more
efficient (in terms of material and energy inputs and outputs) membrane cell process (first
European membrane plant in 1983 at Akzo in Rotterdam). {The information was updated and
moved to Section 3.5.5.}
Table 3.1 gives an overview of the main emission and consumption levels inputs and outputs of
the three chlor-alkali techniques technologies, using a brine recirculation process. The
information is collected from available sources and is not complete. Chlorine liquefaction is not
included, nor are emissions from cooling systems. This table represents a summary of
Chapter 3.
WORKING DRAFT IN PROGRESS
64 December 2011 TB/EIPPCB/CAK_Draft_1