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

Chapter 3
3.3.4.5 Energy consumption for auxiliary equipment
The amount and complexity of equipment varies from one installation to another. The electrical
energy consumption for electrical equipment other than the electrolysis cells and without
chlorine liquefaction ranges from approximately 60 to 600 kWh/t Cl2 produced, the median
being approximately 200 kWh/t Cl2 produced (Table 3.8). There is no major difference between
the three cell techniques.
For the treatment of the brine and to maintain the electrolysis process in the best operating
conditions with respect to current efficiency, the brine and the equipment are usually heated
with steam. For this process, energy consumption is higher at low current densities and higher
for membrane cell plants than for diaphragm cell plants due to lower Joule heating. Reported
consumption figures range from approximately 0.1 to 1.3 t steam/t Cl2 produced, the median
being approximately 0.2 t steam/t Cl2 produced (Table 3.8).
Liquefaction of chlorine is used to facilitate the transportation of the product and/or to remove
inert gases such as oxygen and carbon dioxide, especially in the case of the diaphragm and
membrane cell techniques. Reported electrical energy consumption figures for chlorine
liquefaction range from approximately 10 to 200 kWh/t Cl2 liquefied, the median being
approximately 50 kWh/t Cl2 liquefied. Steam consumption for chlorine evaporation ranges from
approximately 0.1 to 0.8 t steam/t Cl2 vaporised, the median being approximately
0.2 t steam/t Cl2 vaporised (Table 3.8) [ 63, Euro Chlor 2010 ].
Table 3.8: Energy consumption for auxiliary processes of chlor-alkali installations in EU-27
and EFTA countries
All cell techniques ( 1 Parameter
Electrical energy use
by other electrical
Unit
Min.
)
Max. Average Median
equipment, except for
chlorine liquefaction
(pumps, compressors,
etc.) ( 2 )
AC kWh/t
Cl2
60 596 191 177
Brine and equipment
heating
t steam/t Cl2 0.080 1.270 0.292 0.226
Temperature of steam °C 133 285 208 190
Pressure of steam bar 0.6 18.0 9.2 8.8
Energy use for
chlorine liquefaction
( 3 )
Steam consumption
AC kWh/t
Cl2
8 200 67 53
for chlorine
evaporation
t steam/t Cl2 0.058 0.830 0.214 0.160
( 1 ) Data from 80 plants in EU-27 and EFTA countries. Reference year 2008: 75 plants; reference year 2009:
4 plants; reference year 2010: 1 plant.
( 2 ) 44 plants measured electricity consumption and 32 estimated it.
( 3 ) 23 plants measured electricity consumption and 36 estimated it.
Source: [ 58, Euro Chlor 2010 ]
WORKING DRAFT IN PROGRESS
3.3.4.6 Comparison of the three cell techniques
When attempting to deal with comparisons of energy consumption, it is fundamental to define
both the reference conditions and the boundaries of the comparison. In this section, energy
consumption for the mercury, diaphragm and membrane cell techniques is based on the energy
necessary to produce one tonne of dry and compressed chlorine with its co-products: dry
78 December 2011 TB/EIPPCB/CAK_Draft_1