| |
|
| Time line |
| |
| |
|
|
| Sasol pioneers virtual-reality training of coal miners |
| |
| 1950 |
Development of the Sigma coal
mine at Sasolburg begins |
| 1952 |
Sasol’s first gasifier inches its way through Mozambique
towards Sasolburg |
| |
Sasolburg’s first gasifiers being built |
| 1975 |
Coal-mine development is launched at Secunda |
| 1991 |
Sigma mine’s annual output reaches
7,4 million tons |
| 1998 |
Sasol pioneers virtual-reality training of coal miners |
|
| |
| Sasol’s achievements begin with the efficient mining of coal;
at Secunda it’s on a massive scale. |
| The challenge concerns not only quantity,
however, but also the quality of coal
needed by Sasol’s huge battery of gasifiers.
Explaining that requires a brief description
of a gasifier - or, more accurately, of a
certain kind of Lurgi gasifier. |
| |
| Though Sasol could have chosen from three different
German gasifiers when it began planning its plant soon
after 1950, it accepted a package deal from a joint
venture (an Arbeitsgemeinschaft) between Ruhrchemie
Aktiengesellschaft, which since 1932 had owned the rights
to and developed the Fischer-Tropsch process, and Lurgi
Gesellschaft für Wärmetechnik. The offer was for the designs
and right to operate the Fischer-Tropsch fixed-tube reactor,
with gas supplied by Lurgi-designed gasifiers. Sasol’s people
lost no time in dubbing the fixed-tube reactor Arge, derived
from Arbeitsgemeinschaft. |
| |
| A Lurgi gasifier is a colossal steel construction. Coal is fed
into a compartment at its top (known as a coal lock) from
a conveyor belt, eight or so tons at a time rather than
continuously. Once loaded, the coal lock’s lid is closed tight
and a gas is fed into it before the bottom of the lock is opened
to feed coal into the body of the gasifier. This strategy
maintains the high pressure that has been built up by the next
step: feeding high-pressure (and therefore high-temperature) steam and oxygen into the gasifier to decompose the coal,
producing what Sasol calls its raw synthesis gas, which is taken
away to be cooled and further treated. |
| |
 |
| Above: Cross-section of gasifier Opposite: Sasol’s first gasifiers |
|
| |
| What’s left behind is ash, accounting for close on one quarter of
the 100 000 tons of coal that daily enter Secunda’s 80 gasifiers.
There it forms a support for the hot coal, known as the fire bed.
Ash is removed from time to time, a mechanical process
involving a rotating grate. |
| |
| Top of page |
