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

Chapter 2
Table 2.5: Possible Trade-offs in chlorine gas liquefaction
Liquefaction system
High pressure (7 – 16 bar)
and high temperatures
(~ 40 °C)
Medium pressure
(2 – 6 bar) and medium
temperatures (between -
10 and -20 ºC)
Normal pressure (~ 1 bar)
and low temperatures
(below -40 ºC)
Refrigerant
Cooling medium
Water High precautions
Water, HCFC/
HFC or ammonia
Mainly
HCFC/HFC or
ammonia
Safety aspect Storage Costs ( 1 )
Lowest energy costs but
high material costs
Moderate precautions Moderate energy and
material costs
Precautions ( 2 )
Cryogenic storage of liquid
chlorine is possible. High
energy and lower material
costs
( 1 ) Globally, the costs for equipment are comparable.
( 2 ) Attention must be paid to the increased solubility of other gases at low temperatures, especially carbon dioxide.
Source: [ 1, Ullmann's 2006 ], [ 3, Euro Chlor 2011 ], [ 17, Dutch Ministry 1998 ] [Ullmann’s, 1996], [Dutch
report, 1998]
The residual chlorine in the tail gas can be used to produce hypochlorite, iron(III) chloride or
hydrochloric acid. The residual chlorine which cannot be valorised is then led to the chlorine
absorption unit (see Section 2.6.12). In some cases, it is recovered by an absorption-desorption
process with carbon tetrachloride [ 36, Euro Chlor 2010 ]. The latter has the disadvantage of
using a toxic substance with high ozone depletion and global warming potential.
2.6.9 Handling and storage
Chlorine is liquefied and stored at ambient or low temperature. The pressure corresponds to the
vapour pressure of the liquefied chlorine at the temperature in the storage tank. Pressure storage
at ambient temperatures (~ 7 bar at 20 °C) has advantages of simplicity of operation, ease of
visual external inspections as well as lower energy and investment costs. Low-pressure storage
operating around the boiling point of liquid chlorine (-34 °C) requires more complex
infrastructure, particular safety measures and higher energy costs [ 1, Ullmann's 2006 ], [ 40,
Euro Chlor 2002 ], [ 41, Euro Chlor 2002 ].
Within a plant and over distances of several kilometres, chlorine can be transported by
pipelines, either as gas or liquid. The liquid chlorine from the bulk tank can be used as a
feedstock for on-site processes or loaded into containers, road or rail tankers. Because of the
high toxicity of chlorine, the storage area must be carefully monitored and special care must be
taken during loading operations.
2.6.10 Vaporisation
Liquid chlorine is usually vaporised prior to its use. The easiest option is to use ambient heat by
which approximately 5 kg of chlorine per hour and square metre of container surface can be
vaporised. For higher flowrates, it is necessary to use a chlorine vaporiser [ 56, Euro Chlor
2008 ].
WORKING DRAFT IN PROGRESS
52 December 2011 TB/EIPPCB/CAK_Draft_1