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BOC Immingham Dissolved Acetylene Project Environmental Statement: Vol. 2 Main Text
Operation
Process Emissions
Air Quality
6.83 The Dissolved Acetylene Project will require an EP to operate and as a consequence will be
required to demonstrate that it has been designed, and will be managed and operated, in
accordance with BAT. The new facilities will also be accredited under ISO 14001 EMS.
6.84 As described in Chapter 3, emissions to atmosphere will consist of acetylene, ammonia,
phosphine, hydrogen sulphide and acetone. The main emission is acetylene. Ammonia,
phosphine and hydrogen sulphide are only present as a result of the impurities in the raw carbide
and acetone is only present as a result of its use as a solvent for dissolving the acetylene gas.
6.85 An estimate of the likely emissions from the proposed facility has been produced using the EIGA
methodology and spreadsheet 16 for the calculation of air emissions from an acetylene plant. The
emissions were estimated based on an acetylene production rate of 1,200 t/yr, which gave the
following approximate values:
� acetylene 22,000 kg/yr;
� acetone 118 kg/yr;
� ammonia 2.2 kg/yr;
� hydrogen sulphide 0.06 kg/yr; and
� phosphine 1.9 kg/yr.
6.86 These estimates are relatively generic and since as much acetylene as possible is routed back to
the Gas Holder it is likely that the emissions from the proposed BOC facility could be lower than
those listed above. Over 80% (18 tonnes) of the emissions of acetylene arise from the internal
examination of cylinders and from the compression, drying and filling operations.
6.87 The EA has set EALs for phosphine, acetone, ammonia and hydrogen sulphide on account of
their potential health effects. There are no such EALs for acetylene, which is essentially nontoxic
31 . The EALs are presented in Table 6.7.
6.88 Acetylene is, however, a volatile organic compound (VOC) and is categorised as a Class B VOC
on account of its low toxicity and low ozone depletion potential. As a result of the vapour pressure
of acetylene, it will exist solely as a gas in the atmosphere. Gas-phase acetylene will be degraded
in the atmosphere by reaction with photochemically produced hydroxyl radicals and the half-life for
this reaction in air is estimated to be 20 days.
6.89 The Environment Agency Environmental Permit Regulations 1 guidance for the large volume
organics sector (EPR 4.01) 32 sets emission limits for Class B VOCs emitted in quantities of more
than 5 tonnes per year or 2 kg per hour. The guidance notes state that the use of a concentration
limit is not normally appropriate in the case of an emission from non-point sources such as
storage tanks or process vessels and that an approach based on limiting total mass released or
mass per unit of production is likely to be more effective. This issue will be dealt with in the
application for the EP for the facility.
5100935.404 Environmental Statement August 2011 84