od of taking the fluid pig iron direct from the various blast
furnaces to the converter have been obviated. At Hoerde the mixing and
desulphurizing plant shown in the accompanying engravings is employed.
This apparatus holds 70 tons of pig iron. It is, however, advisable to
have an apparatus of greater capacity, say 120 tons. The apparatus has
the shape of a converter, and the hydraulic machinery by which it is
moved is simple and effective. An hydraulic pressure of eight
atmospheres is sufficient to set it in motion. The vessel is provided
with a double lining of firebricks of the same quality as those used
for the lining of blast furnaces. This lining is gradually attacked
only along the slag line, and does not require repair until it has
been in use for some six weeks. Further repairs are then necessary
every three weeks. Only the few courses of spoilt bricks are renewed,
and for the repairs, including the cooling of the vessel, a period of
two or three days is required. At the end of the week the vessel is
kept filled, so that its contents suffice for the last charge to be
blown on Saturday. On Sunday night the vessel is again filled. The
consumption of manganese is very low; theoretically, it is the
quantity required for the formation of manganese sulphide, and in
practice it has been found that this amounts to about 0.2 per cent.
The proportion of manganese which the desulphurized pig iron coming
from the vessel should contain is best kept at about 1.5 per cent. in
order to render the desulphurization as complete as possible. Thus, a
mean proportion of 1.7 per cent. of manganese in the pig iron passing
into the vessel is more than sufficient to effect a thorough
desulphurization. Indeed, 1 to 1.2 per cent. of manganese is
sufficient to effect a satisfactory desulphurization. For the extent
of the removal of the sulphur, the temperature and the duration of the
reaction are of importance. It has been found that if highly
sulphureted pig iron is poured from the blast furnace into the
desulphurizing vessel, fifteen to twenty minutes are sufficient to
effect the desulphurization requisite for the steel process. The part
played by the duration of the process is seen from the results
obtained with the last charges, if the vessel is emptied at the end of
the week without fresh pig iron being added from the blast furnace.
If, for example, 60 tons of pig iron with 0.065 per cent. of sulphur
remain in the vessel, the proporti