Improvements in Processes of Manufacturing Mineral Wool, also called "Slag Wool" and "Silicate Cotton."
Year: 1899

page_text: Date claimed for Patent under Sect. 103 of Act,
being date of first Foreign Application 19th Nov., 1898
(in United States),
Improvements in Processes of Manufacturing Mineral Wool, also
called "Slag Wool" and "Silicate Cotton."
I, ALEXANDER DANIEL ELBERS, of 418, Hudson Street, Hoboken, in the County
of Hudson and State of New Jersey, United States of America, Industrial Chemist,
do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in the manufacture of the substance
known as mineral wool," "slag wool, and silicate cotton," and has for its
object the production of "mineral wool" that is more free from sulphur, and there-
fore of a better quality, than can be produced by the methods heretofore and
now in use.
"
The invention consists in desulphurizing the material that is to be converted
into mineral wool by smelting it in a cupola-furnace in admixture with
gypsum or with other sulphates of the alkaline earths.
Mineral wool is usually made from blast-furnace slag that is more or less
sulphurous and by the following methods:-
First. The fresh-tapped slag is either flushed or conveyed from the blast-
furnace to the blowing device where it is made to flow in a small stream into a
jet of steam or air. The resulting mineral wool is nearly as sulphurous as the
slag from which it is blown, the term "sulphurous" meaning that the material
contains soluble and easily-decomposable sulphides chiefly those of calcium:
Second Hardened blast-furnace slag is remelted in a cupola-furnace, with or
without admixture of either basic or acid fluxes such as limestone and quartz,
and with coke as fuel, and the blowing device is adjusted under the taphole of
the cupola from whence the " smeltings," as I call the molten charges, flow
into the steam jets. The mineral wool produced by this method is less sulphur-
ous than that of the preceding method, even when the hardened slag is remelted
without fluxes, because some of the sulphide contents of the slag become oxidized
by the blast of the cupola in remelting it. The consequent loss of sulphur, how-
ever, is not likely to amount, under the most favourable conditions, to as much
as one-half of the total contents: .
rock
Third: In order to obtain mineral wool quite free from sulphur it has also been
attempted to produce it entirely from non-sulphurous material such as quartz.
limestone, oyster-shells, etc., and the resulting product is usually called
wool" but as it is not practical to smelt such charges with charcoal, and as coke
contains always more or less of sulphur chiefly in the form of spent pyrites

page_text: lime under formation of calcium sulphide, the rock wool produced in
is also slightly sulphurous;
that manner
My improvement applies to the second and third of the methods named and
it consists in adding to the cupola charges, gypsum or other sulphates of the
alkaline earths. As gypsum is the cheapest and most abundant of these materials,
the others which react in a similar manner need not be herein considered.
The action of the gypsum is as follows:-At the high temperature that obtains
in the cupola-furnace near the tuyeres it melts, intermixes with the other con-
stituents of the melting charge, and then reacts on the contained sulphides under
evolution of sulphurous oxide gas. The respective reactions are expressed by the
equation:-
Ca (Mg, Fe) S+ 3 Ca So.
+
==
Ca (Mg, Fe) 0 + 3 Ca 0 + 4 So,
The theoretical requirement for desulphurizing the charges with calcium sulphate
amounts therefore, to about twelve and three-fourths parts, by weight, of
anhydrous or dehydrated gypsum for each per cent. of sulphur that is still retained
by the smeltings. Thus if the sulphur-free composition for a rock wool takes
up 0.1% of sulphur from the coke, the smeltings might be completely desul-
phurized by adding to the charge about one and one-third per cent. of calcined
gypsum, and a charge of hardened slag that carries one and one half per cent. of
sulphur might be desulphurized by adding about 13 %, allowing that one-
third of the sulphur will become oxidized by the blast of the cupola. The actual
requirement may be somewhat larger because some of the gypsum is apt to
become superficially reduced to calcium sulphide by contact with red hot coke:
but it is not likely that the reducing action of the fuel will amount to much
when the charged gypsum is in suitable condition.
The invention may be carried out as follows:-The cupola is charged with
layers of coke, slag, gypsum and slag, in the order named or, when mineral
wool is to be made from other materials than slag, with layers of coke alternating
with lavers of other materials including the gypsum. This as well as other
ails of charging and smelting operations, as well as the suitable arrangements
for converting the smeltings into mineral wool, are however well known and need
not be here described. excepting as follows:-The gypsum rock should be dry
nd hard and should be crushed to a somewhat smaller size than the slag. If
it crumbles to powder in going down with the burden of the cupola, it is apt
to become so intimately intermixed with the fuel that it may become reduced to
sulphide to a considerable extent. The natural anhydrite (CaSO) would pro-
bably be the most suitable kind: but where that cannot be obtained it is best
to try whether the natural hydrate (CaSO, 2 H,O) or the calcined rock gives the
best results. If however it should be found that by the application of either
method appreciable portions of the gypsum become reduced to sulphide, then it
should not be charged with the other materials, but should be introduced into the
furnace by charging it into a hopper that is attached to one of the tuveres, so
that it will be blown into the melting charge. For this purpose only calcined
or anhydrous gypsum should be used, ground to about pea size. The proportions
in which the gypsum is to be added to the charges are easily determined by a few
trials, beginning with a small quantity and increasing it with the subsequent
runs of the furnace. A slight excess does no harm inasmuch as the sulphate that
goes undecomposed into the mineral wool is not as injurious as the sulphides.
Instead of gypsum the sulphates of magnesium and barium may also be used:
but they offer no especial advantages and are more expensive.
Dated this 2nd day of June 1899.
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London,

page_text: Improvements in Processes of Manufacturing Mineral Wool, also
called "Slag Wool" and "Silicate Cotton."
I, ALEXANDER DANIEL ELBERS, of 418, Hudson Street, Hoboken, in the County
of Hudson and State of New Jersey, United States of America, Industrial Chemist,
do hereby declare the nature of this invention and in what manner the same is
to be performed, to be particularly described and ascertained in and by the follow-
ing statement:-
-
This invention relates to improvements in the manufacture of the substance
known as "mineral wool," "slag wool," and "silicate cotton," and has for its
object the production of mineral wool that is more free from sulphur, and there.
fore of a better quality, than can be produced by the methods heretofore and
now in use.
The invention consists in desulphurizing the material that is to be converted
into mineral wool by smelting it in a cupola-furnace in admixture with
gypsum or with other sulphates of the alkaline earths.
Mineral wool is usually made from blast-furnace slag that is more or less
sulphurous and by the following methods:-
First. The fresh-tapped slag is either flushed or conveyed from the blast-
furnace to the blowing device where it is made to flow in a small stream into a
jet of steam or air. The resulting mineral wool is nearly as sulphurous, as the
slag from which it is blown, the term sulphurous" meaning that the material
contains soluble and easily-decomposable sulphides chiefly those of calcium.
Second. Hardened blast-furnace slag is remelted in a cupola-furnace, with or
without admixture of either basic or acid fluxes such as limestone and quartz.
and with coke as fuel, and the blowing device is adjusted under the taphole of.
the cupola, from whence, the smeltings, as I call the molten charges, flow
into the steam jets. The mineral wool produced by this method is less sulphur-
ous than that of the preceding method, even when the hardened slag is remelted
without fluxes, because some of the sulphide contents of the slag become oxidized
by the blast of the cupola in remelting it. The consequent loss of sulphur how-
ever, is not likely to amount, under the most favourable conditions, to us much
as one-half of the total contents.
Third. In order to obtain mineral wool quite free from sulphur it has also been
attempted to produce it entirely from non-sulphurous material-such as quartz,
limestone, oyster-shells, etc., and the resulting product is usually called "rock
wool" but as it is not practical to smelt such charges with charcoal, and as coke
contains always more or less of sulphur, chiefly in the form of spent pyrites,
which either go into the smeltings undecomposed or are reacted upon by free
lime under formation of calcium sulphide, the rock wool produced in that manner
is also slightly sulphurous.
:
My improvement applies to the second and third of the methods named, and
it consists in adding to the cupola charges gypsum or other sulphates of the
alkaline earths. As gypsum is the cheapest and most abundant of these materials
the others, which react in a similar manner, need not be berein considered.
The action of the gypsum is as follows: At the high temperature that obtains
in the cupola-furnace near the tuyers it melts, intermixes with the other con-
stituents of the melting charge, and then reacts on the contained sulphides under
evolution of sulphurous oxide gas. The respective reactions are expressed by the
equation;—

page_text: The theoretical requirement for desulphurizing the charges with calcium sulphate
amounts, therefore, to about twelve and three-fourths parts, by weight, of
anhydrous or dehydrated gypsum for each per cent. of sulphur that is still retained
by the smeltings. Thus if the sulphur-free composition for a rock wool takes
up 0.1 per cent. of sulphur from the coke, the smeltings might be completely desul-
phurized by adding to the charge about one and one-third per cent. of calcined
gvnsum, and a charge of hardened slag that carries one and one halfer cent. of
sulphur might be desulphurized by adding about thirteen per cent., allowing that
one-third of the sulphur will become oxidized by the blast of the cupola. The
actual requirement may be somewhat larger, because some of the gypsum is apt to
become superficially reduced to calcium sulphide by contact with red hot coke:
but it is not likely that the reducing action of the fuel will amount to much
when the charged gypsum is in suitable condition.
The invention may be carried out as follows:-The cupola is charged with
layers of coke, slag, gypsum and slag in the order named, or, when mineral
wool is to be made from other materials than slag with layers of coke alternating
with layers of other materials including the gypsum. This, as well as other details
of the charging and smelting operations, as well as the suitable arrangements
for converting the smeltings into mineral wool, are however, well known and need
not be here described. excepting as follows: The gypsum rock should be dry
and hard and should be crushed to a somewhat smaller size than the slag. If
it crumbles to powder in going down with the burden of the cupola, it is apt
to become so intimately intermixed with the fuel that it may become reduced to
sulphide to a considerable extent. The natural anhydrite (CaSO) would pro-
bably be the most suitable kind: but where that cannot be obtained it is best
to try whether the natural hydrate (CaSO, 2 H,O) or the calcined rock gives the
best results. If, however, it should be found that by the application of either
method appreciable portions of the gypsum become reduced to sulphide, then it
should not be charged with the other materials, but should be introduced into the
furnace by charging it into a hopper that is attached to one of the tuyers, so
that it will be blown into the melting charge. For this purpose only calcined
or anhydrous gypsum should be used, ground to about pea size. The proportions
in which the gypsum is to be added to the charges are easily determined by a few
trials, beginning with a small quantity and increasing it with the subsequent
runs of the furnace. A slight excess does no harm inasmuch as the sulphate that
goes undecomposed into the mineral wool is not as injurious as the sulphides.
Tustead of gypsum the sulphates of magnesium and barium may also be used:
but they offer no especial advantages and are more expensive.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is-
-
1. The process of manufacturing mineral wool, consisting of remelting hardened
blast-furnace slag in a cupola-furnace in admixture with sulphates of the alkaline
earths and blowing the same into mineral wool.
2. The process of manufacturing mineral wool, consisting of remelting
hardened blast-furnace slag in a cupola-furnace in admixture with gypsum, and
blowing the same into mineral wool.
3. The process of manufacturing mineral wool, consisting of melting silicious
and calcareous substances in a cupola-furnace in admixture with sulphates of the
alkaline earths, and blowing the same into mineral wool.
4. The process of manufacturing mineral wool, consisting of melting silicious
and calcareous substances in a cupola-furnace in admixture with gypsum, and
blowing the same into mineral wool.

page_text: 5. The herein described process of manufacturing mineral wool, consisting in
remelting hardened blast-furnace slag with an admixture of granulated gypsum,
and then blowing the same into mineral wool, as set forth.
6. The process herein described of desulphurizing silicious and calcareous sub-
stances that are to be converted into mineral wool, consisting in melting said sub-
stances in a cupola-furnace, and delivering gypsum into the melting mass in the
furnace, as set forth.
Dated this 19th day of February 1900
A. M. & WM. CLARK.
Chartered Patent Agents, 53, Chancery Lane, London.