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.