In 1963, following research carried out on a number of missions spread out
between 1953 and 1962, the Union Chimique Belge (Belgian Chemical Union) set up
a gas extraction plant for Lake Kivu at Cape Rubona, 8km to the south-west of
Gisenyi. The operation of this installation is based on the auto-pump principle.
Water is taken from a depth of around 300m using two 300mm diameter columns set
actually on the lake bed. These columns are about 850 metres long and emerge at
the base of the separator at an angle of about 40°, just under the surface
of the lake. The degassified water is expelled directly at the lake surface and
the gas is injected into the base of two washing columns, allowing the multiplication
by three of the methane content of the gas. The enriched gas is then compressed
and transported by gas pipeline for about 3 kilometres to the boilers of the Bralirwa
power plant has worked reasonably well for forty years, but some major defects
need to be mentioned : The untreated gas goes through a blower in order to be
injected into the first washing column. Because of the presence of a high concentration
of H2S, the formation of sulphuric acid considerably reduces the working life
of the motors.
- The unanchored positioning of the catchment pipes on the
ground has led to serious deterioration caused by friction against the ground
on a number of occasions.
- The oblique angle of the catchment columns as well
as the angle of 40° formed with the separator are at the origin of serious
load losses, thus diminishing the intrinsic output of the system.
- Since the
whole system is situated at the lake, the volumes of gas to be treated are large
and the transporting machinery for the gas correspondingly significant.
1977 these defects, taken together, have led the UCB to undertake costly maintenance
work time after time, failing which the output of the plant would have fallen