Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1890-10-10


and from repeated observation at the furnace
itself, confirmed by the fact that the gases at
tne tuyeres contain quantity OF oxygen,
ABOUT cWts. per ton of metal produced, ana
something like IL cwts. of carbon; the former
not being accounted for by the atmospheric air
used, nor the latter by the weight of fuel burnt
In the hearth. Whether it is the actual carbon
precipltated from the carbonic oxide or coke
user which completes re e1uction or not, IN a
neat-producfng point OF view, is lmmateriai;
What seems proved is, shat it is reserved 1or
the crucible to complete this work at or ABOUT
the period when fusion takes place.
AS theoretical proposition. we have been re-
mlnded that the exact quantity OF carbon re-
CURED to deoxidize 20 cwts. of iron: IN the
form OF ferric oxide, is 438 cwts. 1t is 1urther
assumed that this mixture of ore and carbon
must be raised to temperature OF SOU' Y, Ior
which, provided the entire carbon used is
purnt, half to monoxide and half to dioxlde,
LIZ cwts. ought to suffice. II is suggested not
that the work can be done for these 56o cwts.,
may work
So far as my observations, experimental and
otherWlse, have enabled me to judge, the maxi
mum quantity of oxygen representing the
second equivalent in carbon dioXide in the
gases, is that corresponding with the equlva-
lent contained in the ferric oxide OF the ore.
From this it might be inferred that reduction
Is completed in what has been generally known
as the reducing zone, j. e., the uppermost anu
cooler portions of the furnace. We know,
however, that the deposition of carbon, ac-
companied by the generation of some carbon
dioxide. as already mentioned, is also most
abundant at moderate temperatures.
A CONDITION DETERMINED.
These facts might reasonably lead US to ex-
pect quantity of carbon dioxide in excess OF
that due to the reduction of ferric oxide by car
bon monoxide. 1t will, however, be shown i'm
medlately that condition of equilibrium in
the gases is determined not alone by the rela-
tive quantities of the two carbon oxides, but
also by the amount of oxygen still remaining
IN combination with iron. Now, having regard
to the quantity of carbon required to be burnt
at the tuyeres, in order to fuse the Stag and
iron, added to that rendered necessary to re-
duce the metalloids found in the pig, is such
that at the various temperatures through
which the ore descends, position of equilibri-
um is reached, when the gases contain at the
outside about six hundred weight of carbon
per ton of iron, in the form of dioxide, and
when the metal still retains about one-fOurth
OF its original quantity of oxygen.
IhlS observation refers to ores of the type of
Cleveland, but with those of a different char
acter the composition of the gases may be
materially modified, Thus, in certain Swedish
furnaces. the fuel consumed does not greatly
exceed two-thirds of the quantity necessary for
smelling the Cleveland ironstone The volume
OF carbon monoxide for every ton of iron is
correspondingly diminished, the result being
that, instead of having two volumes of this sub
stance in the escaping gases for each volume Of
carbon dioXide the two gases are found in
almost equal volumes. In one respect, how
ever, all furnaces agree. viz, in there being an
increase OF carbon and oxygen in the gases at
the tuyeres, as compared with that found
short distance above this level
Thus it will be seen that at no time during
the descent of the ore in properly constituted
blast furnace is il, with one exception, ever ex-
posed to high temperature, IN an atmosphere
Of gases, capable of oxldlzing iron. The ex-
ception is when carbon monoxide is split up
into carbon and carbon dioxide; and then the
alreaQV
observed, to remove the oxygen. taken up by
the iron during the act of dissertation, when
the ore arrives at the tuveres.
SOME REVERSE CONDITIONS.
Now it is not too much to say the conditions
of every reverberatory furnace are the very re-
verse of those Just laid down. If coal is the
fuel burnt. which generally is the case, we have
vapor of water, carbon dioxide. and very often
good deal of free atmospheric air, heated
probably at least to l50Uo c., passing over the
materials. (Of course. it would be quite posi-
BILE to maintain an excess of the reducing gas
carbon monoxide-in the furnace, but this
merely means great waste of fue.) Thus ex-
posed, spongy iron, when formed by direct re-
duction. as proposed. could not fail to be very
readily oXidized. But the circumstances under
which it is now expected to produce spongy
oxide and the other half to monoxide. From
the information contained in the table
Just given, we learn that while carbon mon-
oxide is a reducing agent, the product of
reduct;on--caEb0n -dioxide-is of an opposite
character, and, in consequence, is able to re-
oxidize the metallic iron by the production of
which it was generated. The cause which de-
termInes this reflex action is difference of tenn
perature, and, as might be expected when both
gases are present there IL brought about po-
sition of equilibrium deterpined. as has been
said, not by temperature alone, but also by the
extent of the oxygen still remaining united
with the iron.
Thus, if mixture of two volumes of carbon
monoxide and one volume of carbon doXide is
passed over calcined Cleveland ore at about
ALTO G., one-third only of the oxygen can be re-
moved, j. e., the ferric is reduced to ferrous
oxide,
If, on the other hand. the gas consists in
equal volumes of the oxidizing and reducing
gases, the same effect is produced, provided the
is raised to a bright red; and
spongy iron similarly exposed is oxidized, and
becomes also ferrous oxide.
At white heat the attraction of the metal
for oxygen is SO intensified that further action
ceases when Il per cent of the combined oxygen
is removed from the ore. At the same time ten
volumes of carbon dioxide are able to keep in
check the reducing power of 80 volumes of car
bon monoXide.
see no reason, however, why a close ap-
to complete reduction in the d.
rect process, should not be effected by using
sufficient quantity of carbon mixed with the
ore, in the manner already described The diff
ticulty to be apprehended is the reoXidation of
the spongy iron when, by the revolution of the
furnace, fresh surface is exposed to the fame
which is serving TO heat the materials under
treatment. Certain it is that Siemens failed to
reduce the loss of metal to within reasonable
limits.
UNABLE TO CHANGE RESULTS.
Forty-five years ago labored for some time
with Mr.. William Neale Clay. who was very
sanguine of beng able to dispense, wholly or
with the blast furnace. The results
in our case. were the same as those obtained by
others who have followed US in the same path
since that time. AS regards the carbon re-
quired as source of heat, for raising the
of the mixture of ore and carbon,
see no prospect of reducing this with any ap-
l.T cwts per ton of iron. Not only theo-
but practically, in the Bessemer
the combustion OF the metal
loids and portion of iron suffices to raise
the bath of melted cast iron TO proper tenn
perature, for keeping malleabe iron in state
of fusion. Attempt the same thing in a pud-
ding furnace. rotating or otherwise, and the |
oxidation of the same metallods and iron, pro-
1ucing the same quantity of heat as in the con-
verter, requires to be supplemented by the heat |
afforded by 10 cwts of COAL in each case COM
with iron In a fluid state. In both
there is a great loss of heat at the chimney but
this we will neglect, and regard the remainder
in each as due to radiation. convection, etc.. in
separable from the larger size of the furnace |
and the small amount of work turned out as |
with Bessemer's apparatus.
Sir Lowthian, proceeding, discussed the
question OF the capabilities of reverbera-
tory furnace, as compared with the united |
action of blast furnace and Bessemer con.
verter, and the amount of labor required |
BY the two systems.
AN INTERESTING DISCUSSION.
discussion on Sir IoWthian Bells nal Der
participated in by Professor |
Howe, of Boston, G. W. Maynard and Mr.. |