CERTAIN IMPROVEMENTS IN PROCESSES FOR ELIMINATING PHOSPHORUS FROM IRON
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by John B. Kunkel at the Office of
the Commissioners of Patents on the 27th December 1876.
JOHN B. KUNKEL, of Catoctin Furnaces, Frederick County, Maryland, United
States of America. " CERTAIN IMPROVEMENTS IN PROCESSES FOR ELIMINATING
PHOSPHORUS FROM IRON."
My Invention relates to methods of purifying iron from the phosphorus which
has heretofore been practically inseparable from it, and producing in a cheap and
simple manner iron free from any tendency to "cold shortness" when caused
by the presence of phosphorus, and admirably adapted for use in the Bessemer
converter.
The said Invention consists in the abstraction of the phosphorus from the iron by
means of magnesian compounds, in the manner and under the conditions herein-
after more fully set forth, and is applicable alike to the production of iron free from
phosphorus direct from the ore, and to the purification of pig iron.
The rationale of my process consists in taking advantage of the great affinity
exhibited by phosphorus for magnesia, which affinity seems not to be disturbed by
any possible elevation of temperature.
In carrying out my Invention I proceed as follows:-When operating upon
phosphatic ores, I use instead of the ordinary limestone flux, dolomite, or magnesian
limestone a well known double carbonate of lime and magnesia. The charges of
ore, dolomite, and carbonaceous matter are fed into the ordinary blast furnace in
the usual way, the proportions of ingredients being substantially the same as when
ordinary limestone is used as a flux, and goverened by like conditions, namely, the
relative amounts of oxide of iron, silica, and lime naturally present in the ore.
Should the ore be extraordinarily phosphatic it is advisable to increase the charge of
dolomite from ten to one hundred per cent. A portion of the dolomite should be
introduced through the tuyères, although this is not essential.
The working of the furnace being under the above conditions in no wise different
from the ordinary practice, and being well understood by those practising the art,
need not further be adverted to.
When operating upon metallic iron to eliminate its phosphorus I apply the
dolomite either in the cupola or puddling furnace as follows:-I charge first into
the cupola a quantity of coarsely ground dolomite sufficient to form a layer from
two to ten inches deep, and then charge the fuel and pig iron in proper proportions
11

page_text: for melting, so that the iron as melted will pass through the dolomite, whereby it is
purified from all estimable amounts of phosphorus.
"
When used in the puddling furnace I apply the dolomite directly to the charge of
pig iron in quantities varying, according to the amount of phosphorus in the iron,
from ten to fifty per cent. of the weight of the iron, so that in the process of
boiling" the iron is thoroughly brought into contact with the dolomite. I also
" fettle or "fix" the sides and bottoin of the furnace with a mixture of iron ore
aud dolomite in about the proportions of four of ore to one of dolomite, the mass
being speedily bound by the slag, and forming a durable and excellent fix, and one
moreover which acts chemically upon the molten charge to purify it.