Improvements in and relating to the Treatment of Slag for a Variety of Important Uses, such as Making it Cellular for Pavements, Walls, and the like.
Year: 1889

page_text: COMPLEIN SIMULTIOALION.
Improvements in and relating to the Treatment of Slag for a
Variety of Important Uses, such as Making it Cellular for
Pavements, Walls, and the like.
I, ST. GEORGE TUCKER COALTER BRYAN, a citizen of the United States, residing at
Birmingham, in the County of Jefferson, and State of Alabama, United States of
America, Metallurgist, 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 following statement:-
The object of my invention is to prepare slag-which is now chiefly a waste
product of iron furnaces, etc. and troublesome to get rid of--for a variety of
important uses to which it has never before been capable of being applied.
Slags in their ordinary state are not uniform in composition and temperature, as
they come from different furnaces, and are largely admixed with gases, fumes, and
with both solid and liquid matter. The presence of these foreign substances, and the
absence of homogeneous composition and uniform temperature, unfit them for
general use, because of the impossibility of satisfactorily annealing them, which
demands, a temperature substantially uniform throughout the mass, and the absence
of foreign matter during the annealing processes.
To practice one part of any invention I deliver slag in a molten state, as it flows
from the furnace, into a suitable receptacle, where I cause it to be agitated, either by
stirring or by revolving the vessel containing it, so as to give it a rotary motion,
which latter method is preferable. By this means I eliminate ali gases and fumės,
and gas and fue producing matter, and all the solid and molten foreign matter is
collected through centrifugal force and gravity, and then removed, and by continued
agitation or stirring a homogeneous mass of molten slag of uniform temperature is
secured, which conditions, as above stated, are essential to annealing. Rotary
motion of the molten slag, assisted by gravity, will cause the gases, coke, clay, and
all the lighter substances, whether molten or not, to rise to the surface where the
gases will escape, and the solids can readily be removed.
Under the influence of this rotary motion the slag, because of its superior density,
will press towards the walls of the vessel. The inolten iron, or other heavier substance,

page_text: will quickly sink to the bottom of the vessel, and can be drawn off in the usual
manner. The result is that the combinations of lime, silica, alumina, and whatever
particles of iron remain in the slag will be such that the slag will be substantially
uniform and homogeneous in texture, quality, etc. throughout its mass.
This first step is followed by running the purified homogeneous slag into moulds
having their inner surfaces covered with asbestos, or a mixture of asbestos, plumbago,
clay, soapstone, and coal tar, using one or more of these with the asbestos, as I may
elect. When practicable, instead of using metal or other material for making molds,
I use asbestos in its fibrous state, or such a mixture of asbestos with plumbago, etc. as
I have described, and molds can readily be fabricated from these substances. Such
molds prevent a too rapid dissipation of heat, and secure a gradual cooling of the
slag, essential to its proper annealing.
•
As soon as the surfaces of the slag in molds become sufficiently set to admit of
removal, the slag may be taken out and immediately placed in an ordinary annealing
oven. When there is not room on the furnace grounds for the construction of
annealing chambers, near to the mixing vessel, they may be constructed at a reasonable
distance, and the molds adjacent to them, or, when desired, the molds may be built
or set up within the annealing chambers. In such case the mixing vessel may be
mounted on a truck, and when filled with the molten slag from the furnace, drawn
to the annealing chamber, and the slag discharged from it into the mold. The
initial heat of the slag is such that it will be practicable to convey it in suitable
receptacles a considerable distance without causing such a reduction in temperature
as to interfere with the successful practice of my improved method of treating it,
which is a method of purifying and annealing. But it will save one handling of the
slag to build the asbestos or asbestos composition molds within or connected with
the annealing chamber.
By these three steps-to wit: first, the agitation and purification of the slag as it
comes from the furnace in a molten condition; second, delivering it, when purified,
and of substantially uniformn density, temperature, melting and fusing points and
heat-conducting capacity, into asbestos, or asbestos composition molds, or molds
lined with the same, which will prevent too rapid loss of heat; and third, the ordinary
process of annealing in an annealing chamber-I secure a tough, durable, and valuable
slag product, which may be used for building purposes and various other objects.
But that part of my invention which consists in purifying the slag by agitation,
preferably rotation, is of itself a complete and valuable improvement, for the reason
that it brings slag to such a condition that it is without defects of porosity, brittleness,
impurity, and heterogeneity, which render ordinary slag useless for most purposes.
My invention consists, therefore, in a process of purifying slag and rendering it more
dense, tenacious, and homogeneous than it is as it comes in mass from furnaces.
In connection with this purification of slag, the further treatment I have described
becomes practicable and highly useful to produce durable forms of slag for divers uses.
Another part of my invention is to produce a superior cellular slag of tough elastic
quality that shall be light and strong, and adapted for building material, and various
other uses.
In order to accomplish this object I mingle hydrogen and carbonic acid gas with
molten slag. The hydrogen combines with the sulphur in the slag and passes away
in the form of sulphuretted hydrogen. Both these gases, hydrogen and carbonic acid
gas, pass through the molten slag and intimately intermingle with it to give it a
fine cellular structure. The cells or pores of the mass, when cold, will contain
carbonic acid gas and hydrogen gas, which perform important functions after the
slag is applied to use by chemically combining, respectively, the hydrogen with any
remaining sulphur, and the carbonic acid gas with silica and calcium of the slag.
These combinations improve the quality of the slag as it becomes aged, adding to
its strength and increasing its durability.
One method of carrying out this part of my invention is to deliver molten slag,
preferably as it comes from the furnace, into a receptacle in which carbon, preferably
in the form of coke, is deposited and held in place. At the same time I force under

page_text: the molten mass, and against the carbon, (which may be held down by a cage) a jet
or jets of steam. The effect of forcing the steam against the hot carbon is that the
oxygen of the steam combines with the carbon and greatly raises the temperature, so
that perfect fusion of any matter in the slag is effected. Carbonic acid gas is thus
produced, and hydrogen is evolved, which gases pass into and throughout the molten
mass, and intimately intermingle with it. The hydrogen gas combines with the
sulphur of the slag and forms sulphuretted hydrogen gas, which passes away. The
result is that the sulphur is mostly eliminated from the slag by such combination.
The elimination of the sulphur adds to the toughness and diminishes the brittleness
of the slag, so that an exceedingly valuable, light, strong, porous substance is produced.
The intimate intermingling of the carbonic acid and hydrogen gases with the slag
may be aided, if desired, by mechanical appliances, such as stirrers, etc. These
operations may be continued until the slag is sufficiently stiff to prevent the rising
and escape of the gases from it, and to render it throughout uniform in composition,
and prevent adhesion of the slag to the walls of the vessel. On account of the
presence of hydrogen gas and carbonic acid gas in the pores of the slag, certain
chemical combinations, above referred to, take place gradually, and are aided by
exposure to moisture, so that the lapse of time improves the quality of the cellular
slag product.
Other means for producing the gases mentioned and for distributing them through
the slag for the objects stated may be employed.
In some cases I desire to produce slag in part cellular, and in part solid. From
such slag, blocks may be cut, or they may be molded of any required dimensions for
the manufacture of floors, pavements, walls, etc. These blocks of slag may be used
alone, or they may form a base to receive a covering of cement, or other suitable
plastic or mobile substance which will adhere to them and become hard.
The advantage of using cellular slag, as I manufacture it, is that it is a uniform,
light, strong, elastic, durable substance, readily molded, and also easily cut or sawed
for the purposes of making pipe, blocks for paving or building, etc. These, before
being laid, or after being laid in place, may be covered with any substance that will
enter their pores, and thus form a perfect bond with and also furnish a protection and
finish to the surfaces of the slag when desired.
By means of the cells which contain the cement, two closely fitting surfaces of
porous slag may be firmly united with one another without necessarily any intervening
space for the cement. It is a matter of great importance that the bond and fixedness
between the upper or outer layer (material used to cover the slag) and the base or
sub-structure be as intimate as possible.
According to my invention such bond is made more intimate and fixed than is the
union of any other form of stone, block, or other solid base, not fused with a plastic
or mobile covering, because the cell structure offers the greatest exposed surface of
slag for bond with the cement or other matter covering it. It also permits the
cement, by filling the exposed cells, to form part of the original body of the mass,
and gives to the surface greater strength and lasting quality.
In order to make a mass or block of slag solid in one part and cellular in
another, there are several methods that may be practiced, some of which I will
mention-
1. Slag in part solid and in part cellular may be produced by discharging upon
molten, or semi-molten, or heated solid slag, molten cellular slag, the conditions of
fusion and temperature being such that union will take place between the surfaces of
these masses.
2. Slag in part solid and in part cellular may be produced through the action of
centrifugal force, in which by rotating the vessel, or mold containing cellular slag, or
by rotation of the slag in the vessel or mold, it will, because of its superior weight
and density, under the influence of centrifugal force, displace the gas or vapor cells
near to the walls of the containing vessel, and make a solid exterior crust.
3. Slag in part solid and in part cellular may be produced by discharging molten
slag into a vessel or mold which may contain, in addition to its confining walls,

page_text: partitions, all of which may be solid or hollow, fixed or movable, and which may be
heated as desired and found best. The exterior or containing walls serve the purpose,
in connection with the interior partitions, of chilling and making solid the contiguous
portions of the slag. The molten slag discharged into such a vessel or mold may be
allowed to chill, forming a solid crust on all the walls before the slag is made
cellular by blowing or liberating vapor, gas, etc. into it and intermingling it through
the molten mass.
4. Slag in part solid and in part cellular may be produced by discharging cellular
slag, made so by gaseous or vapor expansion in the molten mass into a mold when the
viscid condition of the slag is such as, in a slight degree, to allow the upward rise of
the gas or vapor cells, and the subsidence of solid slag, by which means the bottom
will become solid, and the upper portion remain cellular.
The use of a cellular slag base, covered with a plastic substance, is of great
advantage as applied to floors, walls, pavements, and the like. Blocks of slag, partly
solid and partly cellular; may, of themselves, form an excellent pavement. The
cellular part serves to lighten the parts and render their transportation and handling
convenient; and the solid part will form a surface, offering greater resistance to wear
and breakage, and being smoother for use, as, for example, in a foot path. It will be
practicable to color the solid surfaces of such slag blocks, and use them either for
exterior or interior finish and decoration of building walls, etc.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. The herein described process of treating slag mechanically by rotating it in a
suitable vessel when in a molten siate so as to separate impurities from it through the
action of gravity and centrifugal force, and after the removal of such impurities
stirring the slag so as to make the fused mass practically homogeneous and of uniform
temperature and quality, substantially as set forth.
2. The method of treating slag herein described, for the purpose of making it
cellular, which consists in forcing into it and intimately mingling with it, when in a
molten state, carbonic acid gas and hydrogen gas, substantially as set forth.
3. As a new article of manufacture, an artificial paving or building block of slag,
made in part solid and in part cellular, substantially as set forth.
4. The combination with a cellular artificial block of slag, made for paving or
building purposes, of a plastic substance or covering forming a bond with the slag by
entering its cells, substantially as set forth.
121000