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17
The average sulphur content of the heavy fuel oil used at the Bankside "B" Station is 3.8%.
The average elimination of the sulphur compounds from the flue gases is 97.1%. The weight
of the sulphur dioxide emitted to the atmosphere, calculated on the tonnage of fuel used in 1954
was 91.6 tons, or an average of approximately 5 hundredweights per day. The whole of this is
ultimately washed down by rain as very dilute sulphuric acid. Much of this emission makes no
contribution to the sulphur pollution of the City's atmosphere since the chimneys of the power
station are of such a height as to ensure its discharge and dispersal beyond the zone of turbulence
which exists downwind of buildings or high ground. In addition there are long periods of the
year when winds from directions other than the south blow the gases away from the City. But
with the wind from a southerly direction, coupled with a very humid atmosphere, the flue gases,
cooled as a result of the washing process, sink to ground level before they have become adequately
diluted, and then cause a higher local concentration than would occur if the gases were not
washed and so, being hot, rise high above the level of the top of the chimney.
How does the quantity of sulphur emitted from Bankside compare with that emitted from
the chimneys of other premises within the City boundaries? Sulphur dioxide is discharged
wherever solid or oil fuel is burnt, whether in industrial or domestic premises. The degree of
efficiency of combustion does not affect the quantity of sulphur dioxide evolved, and although
a relatively small proportion of the sulphur is retained in the ashes the bulk goes into the
atmosphere. Gas for public supply is excluded from consideration since nearly all the sulphur
compounds are removed before distribution.
The approximate annual consumption, in tons, of fuel, solid and oil, in the City of London
is set out below. The figures for solid fuels relate to 1953 and for oil to 1954.
Bituminous Anthracite and Coke. Other smokeless Oil.
coal. other Welsh coals. fuels.
23,100 7,000 41,900 300 20,000
The approximate total tonnage of solid fuels consumed is 72,300, and oil fuel 20,000. The
amount of sulphur in solid fuels varies between 0.5 and 3.0%. The average is generally taken to
be 1.5%. In oil the percentage varies between 3 and 4. For the purpose of the* following
calculations the average taken is 3%, i.e. 0.8% less than the figure of the average sulphur
content of the oil used at the Bankside Power Station.
From these figures it will be seen that the quantity of sulphur emitted without any treatment
at low level from premises in the City is as follows:—
in tons
annually. daily.
Solid fuel 1084.5 2.97
Oil fuel 600.0 1.64
Hence the sulphur emitted from the Bankside Station annually 91.6 tons, and daily,
approximately 5 cwts. is equal to about 5.4 per cent. of the sulphur dioxide discharged from all
the chimneys in the City of London."