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BOC Immingham Dissolved Acetylene Project Environmental Statement: Vol. 2 Main Text
3.38 The lime settles to the bottom of the Generator from which it passes, as a slurry, through a seal
leg, via a crude filter (to remove solid impurities, e.g. coke, present in the carbide), to the Lime
Sump. From the Lime Sump the slurry is pumped to one of three overhead Lime Storage Tanks.
The lime solids in the slurry settle to the bottom of the Tanks and the water is recovered from the
top of the Tanks for reuse in the manufacturing process. Tankers drive under the Lime Storage
Tanks to load the lime slurry product. There is a bund well area below the Lime Storage Tanks,
which is provided as a containment measure in the event of spills an accidental release.
3.39 In the event that there is a period where there are no customers for the lime in slurry form, it can
be fed through a Rotary Drum Filter v to remove excess water and produce a lime paste (with 70-
80% solids content). The extracted water would be recycled back to the manufacturing process.
The lime paste can either be sold or sent for offsite disposal.
3.40 Prior to filling, all cylinders will undergo an external visual examination at the sort dock.
Periodically, typically every five to ten years, cylinders are examined internally in the Cylinder
Examination Shop.
3.41 For empty cylinders that contained acetylene in acetone solvent, as much gas as possible is
recovered via blowdown rigs and returned to the Gas Holder. The cylinders are then devalved,
inspected, re-valved and repainted. Gas that cannot be recovered to the Gas Holder results in the
release of small amounts of residual acetylene gas which is vented to atmosphere. A vent has
been provided on the roof of the Cylinder Examination Shop for the disposal of this gas and
residual acetylene from third party cylinders that do not contain acetone as the solvent.
3.42 Shot blasting facilities and a Paint Shop are provided within the Cylinder Examination Shop. Dust
emissions from shot blasting and painting activities will be minimised through use of appropriate
filters suppression systems. Solvent emissions from painting and drying will be minimised (so far
as possible) through the selection of the application method and the type of paint, and will be
emitted through vents on the roof of the Cylinder Examination Shop.
Rainwater Harvesting
3.43 The rainwater from the Cylinder and Bundle Filling and Generator Building roofs will be collected
and then stored within an above ground Rainwater Harvesting Tank. The Tank is located adjacent
to the south gable of the Generator Building. The rainwater that collects in the tank will pass
through a filter and be pumped to a water softener (see below) before discharging into the
process water ‘Break Tank’. The water from the Break Tank will then be used to serve the process
requirements of the site. Any excess flow will pass to the Site Drainage System (see paragraph
3.52 onwards).
Water Softening
3.44 Water used in the process plant that generates, purifies and compresses acetylene needs to be
softened. A Water Softener package will be installed, located in the south east corner of the
Generator Building. The water softener will be able to treat all sources of water (i.e. the potable,
non-potable supplies and recovered recycled water). Approximately twice a month the water
softener will need to be regenerated, which will produce hard, salty water (i.e. a brine solution
containing calcium ions), which will discharge to Middle Drain.
v It has not been confirmed whether the Rotary Filter will definitely form part of the final design, however, it is included on the current
layout drawings (see Figure 3.3), and is located adjacent to the Lime Storage Tanks.
5100935.404 Environmental Statement August 2011 22