The Princess Royal opens BP's KG (Kinneil Grangemouth) ethylene plant
on Monday. It is the latest and most expensive single investment in the
company's 72-year history of commitment to Scotland. This five-page
feature by Maurice Baggott reports on the background to its latest
venture
BP CHEMICALS' new #300m KG Ethylene plant at Grangemouth is
world-scale in every respect. It gives BP Chemicals the lowest cost base
in Europe for ethylene, the basic building-block for a whole family of
the most important petrochemicals.
Work on the huge plant, capable of producing 350,000 tonnes of
ethylene, began in early 1990 and has been completed on time and on
budget by a construction force that peaked at 2200 people and put in a
total of four million man-hours.
The plant has a permanent workforce of around 100, and about 3000 work
within the BP complex in total.
In just over two years, 6250 piles, 36,000 cubic metres of concrete,
6800 tonnes of steelwork, 230 kilometres of pipework, 565 kilometres of
cable, and more than 500 individual pieces of equipment have been
installed at the 77-acre site.
Major items include compressors, pumps, five furnaces, 14 distillation
columns (three of which are over 90 metres high), two 22-metre diameter
propylene spheres, and a bridge over the river Avon.
Apart from the construction of the new ethylene plant, substantial
modifications and other work had to be done within the BP refinery and
other parts of the chemical plant.
The main contractor for the design work was Stone & Webster. The main
construction contractor was Laing Construction; offsite work was carried
out by Foster Wheeler Engineering; and modifications to existing plant
were carried out by Matthew Hall Engineering.
Other major contractors included Press Construction, UK Construction,
and Wimpey. In total there were 42 major contractors, half from
Scotland, but dozens of other smaller companies, mostly Scottish, were
involved at various stages in the project.
The ethylene plant is the centrepiece of an even bigger investment
programme by BP, involving their Exploration, Oil Refining, and
Chemicals Divisions in Scotland over the past three years.
Projects ranged from a new platform in the central North Sea to handle
oil and gas from a number of fields, the #162m renewal of the pipeline
from the Forties Field, the #310m expansion of the Kinneil Gas
separation plant, an extra pipeline from Grangemouth to the Hound Point
export tanker terminal, and a second berth and extra tankage at the
terminal.
The ethylene plant is not only central to BP Chemicals' operations,
but is exported ''over the Fence'' to a number of other major chemical
companies in Grangemouth including GE Plastics, who produce ABS Polymer
plastics, Rohm & Hass, (MBS rubbers), and Enichem (Polybutadiene
Rubbers).
Ethylene is used in a huge range of products, including solvents,
anti-freeze, and pharmaceuticals, but its most important use is in the
production of plastics, most notably polyethylene.
Polyethylene in found in products ranging from cables to ducting, car
components to packaging, and computer casings to plastic buckets.
Ethylene has been produced at Grangemouth for more than 40 years and
existing plants at the complex have a capacity of 270,000 tonnes for use
as a feedstock for the polyethylene and ethanol plants.
By the late eighties demand for ethylene had outstripped supply, but
at the same time the expansion of the Kinneil gas-separation plant at
Grangemouth owned by BP Exploration was given the go-ahead, providing
new supplies of the raw material for ethylene production -- ethane gas.
Although ethylene is a hydrocarbon, it is not present in crude oil and
gas but has to be processed by taking hydrocarbon gases separated from
crude and restructuring them to form new compounds, using a process
called steam cracking.
The incoming feedstock gas is mixed with steam and is passed into a
furnace where it is heated to 800 deg. C, which cracks the molecular
structure and makes it form new combinations, one of which is ethylene.
The cracking process is stopped by rapidly cooling the hot gases with
water, which produces large amounts of steam. The energy in the steam is
used in various parts of the plant to drive turbines and provide heat.
At this stage, the ethylene is one gas within a mixture of several,
each of which has to be separated as a product in its own right or for
use in the process.
Separation is achieved by cooling the gas until it condenses as a
liquid. Heat is then applied and, as each gas has a different
boiling-point, each one separates in sequence and is drawn off from the
giant distillation columns.
Absolutely nothing is wasted: some of the gases are used as fuel to
operate the plant, others are used in the process, and others are
returned as feedstock.
The KG plant has been built to exacting design standards, which
incorporate advanced safety features. With the completion of the
ethylene plant, Grangemouth has become one of the biggest and most
sophisticated petrochemical complexes in the world, putting Scotland at
the leading edge of chemical process technology.
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