Saiccor - The First 50 Years 5.8 MB - Sappi

The First Fifty Years
Simon Carves, which was started in February 1959� In October 1959
the Lurgi ‘roaster’ was converted to burn sulphur, and no further
pyrites came to Saiccor�
The blockage constant (KW) of the pulp produced in the first three
months of Saiccor’s operation averaged 24-28, which exceeded
Courtaulds’ limit of 20� The ash, calcium and silica also exceeded the
limit� Owing to the poor quality, Courtaulds would not accept the
pulp and it all went to SAICI� In March 1956, a 10 t trial lot with a
KW of 22 went to Courtaulds� In July acid water was added to the
slurry going to the continua which improved the ash levels and some
pulp started going to Courtaulds, but when the pulp was used another
problem emerged� Some of the sheets ‘floated’ in the caustic soda in
the Courtaulds’ sheet steeping process� This problem was only
completely solved when a calendar press (from Farrel) was installed
70 per cent through the pulp dryer in 1966� By December 1956, a
large proportion of Saiccor’s pulp was going to Courtaulds�
For almost the first four years of operation, there was a constant
struggle with KW values and not much headway was made� In June
1956 John More from Courtaulds arrived to investigate the problem�
In early 1957, it was recognised that high silica gave high KW’s and a
liquor filter was installed in the liquor making plant (to remove silica
from limestone)� Silicas dropped to 70-90, but KW values remained
just over 20� In February wattle was tried, but the KW value was 85�
In March detergent was tried in the caustic soda bleaching stage,
initially to clear the cloudy viscose that was made from Saiccor pulp�
Not only did the viscose clear, but the KW values dropped below the
Courtaulds’ limit� By June (18 months after start-up), Bill Hastie made
the comment ‘The attainment of the quality standards laid down
originally may be said to be an important milestone passed�’ (Hastie,
1957) This was attributed to 0,1 per cent detergent, the liquor filter
and activated silica being used for incoming water purification� KW
values were 17, ash 0,06 – 0,07 per cent, silica 72-84 ppm, and calcium
354 ppm�
From August 1957 silica and KW’s started to increase, and over the
next two years monthly average silicas varied from 91-208 and KW’s
from 18-24� Pulp quality was marginal until September 1959, when a
battery of centricleaners were added to second screening� Silicas
dropped to around 40 and KW’s to 15� By this time flock pulp was
being made but it did not go through the centricleaning plant and
had silica of 219 ppm and a KW of 34 (varying from 18-76)� However,
the major problem of blockage constant had been solved�
The Board approved the first extension scheme in February 1958
to construct a pilot plant to test a new process proposed by Courtaulds
to flash dry pulp (flock pulp)� The conceptual design for the pilot
plant was done by Courtaulds (Fred Aldred and Bruce Townsend)
while the detailed design work was done at Saiccor with help from
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