VAPOUR RECOVERY
Built on a brownfield
site adjacent to
Londonderry port and
harbour facilities, a new
76,000 tonne oil storage
terminal is one of the largest
to be developed in the UK
and Ireland in several
decades. The terminal, which
is owned and operated by
LSS Limited, will distribute
products in Northern Ireland
and Eire. It was designed and
project managed by Project
Design Engineers Limited
(PDE) over a two-year
period, with completion in
December 2005.
Four main products,
unleaded petrol, derv, gas oil
and kerosene are imported by
ship through a private jetty in
Lough Foyle, and distributed
by road tanker. Bottom
loading vehicles use one of
four gantries, two having
seven arms, and the other
two having six. Each loading
gantry has a vapour arm,
which is connected to the
vapour recovery unit (VRU).
Operating conditions
produce a petroleum
saturated vapour containing
up to 1,400 grams of
hydrocarbons (HC) in each cu
m of air, which is extracted
during the loading process.
The site's Industrial Pollution
Control licence requires that
the 'clean' air discharged to
atmosphere must not exceed
35g HC/m³. The VRU installed
at the LSS terminal achieves
an operating level of 10g
HC/m³, this figure having
been approved by the Council
of the European Union some
time ago, and referred to as
the 'Gothenburg Protocol'. It
has not been ratified by
member states and is,
therefore, not mandatory for
countries to adopt it.
During the loading at the
gantry, vapour contained
within the road tanker is
expelled through the vapour
return line. This containment
in itself reduces the potential
for fire, explosion and vapour
inhalation; but in addition,
each of the four lines is
monitored for pressure and
temperature, and includes a
detonation flame arrester to
ensure that in the event of an
explosion it would be speedily
quenched.
To minimise power
consumption, the system
includes an efficient vacuum
process with the pipe layout
being configured to ensure
low-pressure loss. The VRU
adopts a dry vacuum process,
including the vacuum pump,
with this later component
saving up to 50% power
compared with the earlier
used liquid-seal ring pump
designs.
