Roasting Sulphurous Iron-Ore. [Volume: 8, Issue: 4, 1889, pp. 208-218]

No. 4.]

CHARCOAL IRON WORKERS.

215

Per Cent. Total Sulphur Sulphur Per Cent. Total
Temp. 0 F. Duration. Sulphur in as as Sulphur as
Residue. Sulphide. Sulphate. Sulphate.
1200 2 hrs..346.235.111 32.18
1200 4".178.088.090 51.12
1500 1 hr..099..027.072 72.72

Experiments with a very dense New Jersey magnetite show that
the density of this ore so completely excluded air from the interior
of the ore-pieces, as to make futile any attempt to desulphurize it
at a low temperature. It required the use of a high heat.
The action of the heat itself on the ore may either cause a cracking of the ore-piece and allow the entrance of air in that way, or it
may act, as pointed out by Akerman, in enabling the sulphur to
take up oxygen from the ore itself, for its oxidation. It is certain
that the degree of heat required for desulphurization varies with
different ores; but an abundant supply of air should always be
present.
It is certainly possible, however, to use too high a heat. A fused
ore is harder to reduce in the furnace, and heating it to that point
appears to be often exceedingly prejudicial to proper roasting.
To test this point (how far fusion or clinkering of ore affects the
amount of sulphur that can be expelled, -and how far its influence
goes to affect the amount of the sulphur remaining in the clinker
present in the form of sulphate) small pieces of Cornwall ore, similar
to those used before, were heated beyond their sintering point, as
quickly as possible, to intensify the effect. For comparison the
former results, obtained on heating at a low temperature, are added:

No. Tmp Per Cent. Total 'Sulphur Sulphur Per Cent. Total
of ToF. Duration. Sulphur in as as Sulphur as
Heat. Residue. Sulphide. Sulphate. Sulphate.
1 1200 2 hrs. 0.346 0.235 0.111 32.18
2 1200 4 " 0.178 0.088 0.090 51.12
3 1500 1 hr. 0.099 0.027 0.072 72.72
4 2400 45 m in. 2.125.................................................
5 2400... 2.422 2.337 0.085 3.50
Recalling the fact that the raw ore contained 2.664 per cent. of
sulphur, the effect of the sudden fusion can be readily noted in the