Full resolution (JPEG) - On this page / på denna sida - VI. Mining and Metallurgical Industry. General Survey. By C. Sahlin - 2. Iron and Steel Industry. By J. A. Leffler
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fuels.
273
The output of briquettes in Sweden is shown by the Table 52.
In 1913 there were 19 briquette works in Sweden; one of these works,
that at Hälsingborg, manufactures briquettes out of purple ore.
For the roasting and sintering of slick is employed firstly a flame
furnace with two storeys, constructed by J. G. Wiborgh:
furnaces of this type are found at Baggå, Jädraås, Ljusne, Norn, Riddarhyttan,
Söderfors, Ulvshyttan, Uttersberg and Åg; secondly, the G. O.
Petersson roasting flame furnace with four storeys: at Köping and
Lång-banshyttan. Both of these furnaces are heated with blast-furnace gas.
Provided they are properly managed, they effect a pretty satisfactory
de-sulphurisation and oxidisation of the slick.
Experiments made in Sweden with rotary slick furnaces have not
yielded very encouraging results.
On the other hand, the Gröndal briquette furnace has proved of great
importance for Swedish iron industry, as is indicated by the rapid
development of the briquette industry revealed by Table 52 above.
The Gröndal furnace consists of a brickwork-tunnel from 50 to 60 meters
in length, and from l’is to l’eo meters in breadth. Sometimes two of these
tunnels are built into one, which produces what is known as a "double furnace".
The slick proceeding from the concentrating works and containing from 6 to
8 % of water, is fed down into a briquette press, in which it is pressed without
any special binding medium into briquettes of 150 by 150 by 65 millimeters
in size. These briquettes are then placed in two layers on cars, each of which
takes from 170 to 200 briquettes. At intervals of certain minutes one car
after the other is pushed into the one end of the briquette furnace; this
shoves forward all the cars in the furnace one car-length, and thus one car
with finished briquettes comes out at the other end. The above-mentioned
interval varies according to the quality of the slick: with sulphuriferous slicks
it is about än hour; at Sandviken, for instance, the time is from 40 to 45
minutes. A Car of briquettes weighs there on an average 830 kilograms, and
the output per week of 7 working days is from 190 to 210 tons.
The actual hearth of the furnace is formed by the refractory brickwork upper
frame of the cars. The furnace is heated with producer gas (occasionally with
blast-furnace gas), and the consumption of coal is from 6 to 8 % of the weight
of the briquettes. The producer gas is admitted at about the centre of the
furnace. The combustion gases are carried in the opposite direction to the
cars, and the air used in the combustion of the gas is led in the same way
through the rear part of the furnace, where it cools the briquettes already burnt,
and is itself heated before it reaches the inlet for the gas.
Provided it be properly managed, the Gröndal furnace desulphurises the
briquettes very completely and oxidizes them in an extremely high degree. Thus,
it may be mentioned that sulphur percentages of 0’17 and 1’33 % have been
reduced by it to 0*oo6 and 0’030 % respectively, and that the degree of oxidation in
the former case was raised from 89 to 99’6 %.
The pores take up from 20 to 30 % of the whole volume of the briquettes.
The great importance of briquettes for the Swedish iron industry lies
in the saving of charcoal effected by their use in blast furnaces. It may
be roughly estimated that on an average a saving of 12-5 % of charcoal
has been effected in the works employing briquettes.
18—133179. Sweden. II.
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