A New Process for Reducing Sulphuretted Ore into Oxides and Sulphur.
Year: 1893

page_text: Date of Application, 18th Oct., 1893-Accepted, 16th Dec., 1893
A New Process for Reducing Sulphuretted Ore into Oxides and
Sulphur.
LEON BEMELMANS, Civil Engineer of Bruxelles, Belgium, Rue de l'Est 54
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 this new process is to separate metallic sulphurets into metallic
oxides and free sulphur. Besides, should the raw material hold arsenic, antimony
and phosphorus, they are respectively eliminated as sulphurets of arsenic and
antimony which are collected, and phosphoric acid generally lost.
The new process consists in the combination of several operations which we shall
expose in succession. Some of them are new while others are already known and
are not claimed individually.
The first operation is new. It is a roasting of the ore which in a single
continuous operation, presents: first a roasting with sublimated sulphur; second, a
roasting with air; third, a calcination at higher temperature.
First: The roasting with sublimated sulphur means the parting of arsenic and
antimony, as already known and of phosphorus which is new. These three obnoxious
bodies depart as sulphurets. For instance, let M stand for the metals of the ore
and arsenic be the objectionable material to be eliminated, we should have
2 MAs + 5 S = 2 MS + As³S³.
Second The roasting with air presents this new feature that it takes place in
pure air previously heated to a high degree, alternately in the two chambers of a
recuperator, the free chamber of which is reheated by the combustion of some
gaseous fuel. This process makes it unnecessary to otherwise heat either the oven
or the ore.
Third The calcination takes place at a higher temperature; what sulphates
might exist after roasting, are parted as oxides and sulphuric anhydrid SO' or
sulphurous anhydrid SO* and oxygen as usual.
These three operations are better carried on in a single Hasenclever improved
roaster which shall be described further on. The heated air first circulates at the
highest heat, along the calcining or lowest zone of the roaster, parting the sulphates
and perfecting the oxydation of any sulphur which might remain in the ore after
the roasting proper; ascending from flue to flue, it soon meets with ore holding
more and more sulphur, oxy.lizing metals into fixed oxides, and sulphur into gaseous
sulphurous acid SO. This is the roasting zone proper. Continuing to ascend to
still higher flues, the hot gases reach a point, in the oven, where they hold no more
The stream of gases, at
free oxygen. There begins the third or distillating zone.
a high heat, meets ore, in dust or grains, which is yet unaltered.
pyrites it yields free sulphur
If the ore holds
FUS + 20.
If the ore is free from pyrites the coal which, in that case, we add to the ore,
reduces a portion of sulphurous anhydrid and free sulphur is the result.
SO,+C=CO, + S.
In short, the ore is first purified from what arsenic, antimony and phosphorus it
may hold, it is then roasted and lastly calcined.
As already stated, these operations are realized in a modified Hasenclever
n

page_text: pyrites burner represented in vertical section in Fig. 1 of the annexed drawing,
Fig. 2 being a plan.
こ
The roaster is a long rectangular chamber. As represented in this case, half of
it is underground. This chamber is divided into sections by vertical transversal
walls a, perforated on their whole height, with openings z somewhat in the shape of
triangles and corresponding in the several walls a. The homologous members
remaining from the hollowed walls a, in successive partitions, are connected by
light flat arches b bridging over the sections and producing continuous flues from
end to end of the roaster. Said arches are in the same plane with the members
they connect and on which they rest. These light arches do not extend quite
down to contact but leave open an horizontal, longitudinal slit c interrupted only
by partition walls a. Walls a are produced at f, outside of side walls e so as to
bring the thrust to bear on heavy earth work g. In this arrangement, there exists,
between each two consecutive walls fa sort of well y by means of which, holes d
in side walls e can be reached and all parts of the roaster be probed, with suitable
tools, should an obstruction happen. To that effect, wells y may be given any
convenient size between e and g. When the furnace is working, openings d are
naturally closed with the ore inside. The ore laden on the longitudinal hoppers on
top of the roaster slides gradually from flue to flue by slits c, confined as they are
in one section by the ridges m n of partition walls a till it is received below into
hoppers while the hot air is admitted at i from the recuperator, straight through
one of the end walls into the lowest flue z, hence through end passages similar to
those of a Hasenclever roaster, into the higher left hand flue, hence into the right
hand one hence to the middle higher one; then the gas divides and by contracted
section passages, provided with dampers, into the two lateral half flues after which
they meet again into the higher left hand flue and so on to the outlets & for the
middle zone and for the upper zone, which are provided through the end walls
straight with the outlet flues z into outside down comers p & I fitted with dampers.
The gases would follow the shorter way p to the common steam jets did not the damper
contract P. The disposition of partition walls a, admits of several kinds of ore
being worked at once without mixing, as they are raised in flues z, high enough, as
at mn to separate the ore right and left. This is an important consideration as
will be seen directly.
I said, higher up, that while roasting non pyritous ore, coal is added to the ore,
whereby a portion of sulphurous gas SO is reduced, evolving the needed
sulphur. However such ore may disagree with carbon. It is the case with
blende ZnS, because some zinc might be reduced and volatilize. In order to purify
such ore from arsenic &c., roasting with sulphur is required which is easily obtained
by loading pyrites in some sectious and blende into the others as the ore in different
sections never mix. The especial disposition which prevents mixing is simply a
ridge of masonry m n, raised as high as the ore reaches in flues z, said ridge being
part of partition walls a.
Having thus described the roaster, I shall now proceed with the process,
resuming where I left it.
We have no more concern with the ore, which is roasted
into oxides. The gases from the upper or distillating zone are made up of
nitrogen, sulphurous acid SO³, sublimated sulphur and eventually carbonic
acid CO, sulphurets of arsenic As 'S' and antimony Sb'S³ besides perhaps some
phosphoric acid Ph²0 (seldom present with sulphurets. Sulphurated phosphorus
with carbonic and sulphurous acids, would yield phosphoric acid). Below said
distillating zone, we find nitrogen and sulphurous anhydrid SO' with more or less
sulphuric anhydrid SO)³,
Now comes in order, the reduction of sulphurous anhydrid SO³ into sulphurated
hydrogen H'S so that sulphur may be ultimately recovered. To this effect, the
gases from the distillating zone are injected with hot producer gas and steam, into
a reducing apparatus which may be either a) a kiln similar to a closed lime kiln or a
cylinder, holding incandescent coke, at the base of which said gases are injected;
1) alternately the two chambers of a recuperator whose free chamber is reheated

page_text: by combustion of some gaseous fuel; c) a recuperator as specified at 6), followed
with a kiln holding coal as specified at a), the steam and producer gas being alone
superheated in the recuperator and then injected with the sulphurous gas, at the
base of the kiln. In the first case a), the heat required for the reactions specified
below, results from the action of sulphurous acid on carbonic monoxyde CO and
hydrogen,
by combustion of some gaseous fuel; c) a recuperator as specified at 6), followed
with a kiln holding coal as specified at a), the steam and producer gas being alone
superheated in the recuperator and then injected with the sulphurous gas, at the
base of the kiln. In the first case a), the heat required for the reactions specified
below, results from the action of sulphurous acid on carbonic monoxyde CO and
hydrogen,
SO* + 2 CO : 8+2CO; SO + 2 H
S + 2 H2O.
In the second b) and third c) cases, the heat is also furnished from outside com-
bustion. The first process is cheapest but the last ones are easier to manage.
The apparatus presents no new feature although the process does. In this
reduction, the gases from the roasting mix with reducing gases, steam and, in
processes a) &c.), with coal at a red heat. The following reactions take place and
the free sulphur, as well as the sulphurous acid SO* are transformed into
sulphuretted hydrogen H'S, as follows:"
At a cherry red heat, SO + C = S + CO'; SO' + 2 CO = S + 2 CO²;
SO +2 HS + 2 H'O; 2 H2O + C = 2H² + CO²; H³O + CO = H³+ CO' ;
SO + 3 H'H'S + 2 H2O; S + CO + H2O = H³S + CO²; S + C + 2 H³O
H'S + CO2 + H²; S + H2 = H³S.
-
At higher heat, SO2 + 2 C = 8+2 CO; H2O + C = H' + CO; CO' + C
= 2 CO.
The gas mixture must hold a considerable excess of carbonic monoxyde CO, in
order to prevent a partial decomposition of sulphurated hydrogen H'S by carbonic
anhydrid CO. Very likely the sulphurets of arsenic and antimony experience
some changes in the reducer but it does not matter as these compounds shall con-
dense further on when the gases cool down; and such condensation taking place
in an excess of damp sulphurated hydrogen, can only yield hydrated sulphurets of
arsenic and antimony easy to collect. The phosphoric acid Ph30, if phosphorus
is present in the ore, combines with the alumina and iron oxide in the reducer.
It shall appear, further on, that the ultimate reaction of this new process, is
that taking place between one volume of sulphurous acid SO* and two volumes of
sulphurated hydrogen H'S in presence of water or steam.
SO +2 H'S:
= 3 S + 2 H2O.
This reaction is not new but it has never yet succeeded on a large scale. In
order to succeed, it is necessary, and these conditions are new: 1st that the two gases
should be dry when brought together; 2d that the mixture of the dry gases should
be made perfectly homogenous 3d that sulphurous acid SO' should not be in
excess; 4th it is safer that the intimate mixture of the dry gases should be at
about 212° F. before 5th steam is given.
I realize these conditions as follows:
The gases holding sulphuretted hydrogen and eventually volatile compounds of
arsenic and antimony with steam and flying dust, are first cooled, whereby all con-
densable products and dust are abated. To this effect, I use cement flues immersed
in water. The gases so cooled are next made to ascend and descend, at low speed,
towers filled with porous pieces of calcium chloride CaCl2 which effects a percola-
tion as well as a sufficient drying of the gases. These gases must be thoroughly
mixed with dry sulphurous acid SÖ. The sulphurous gases SO are also separately
cooled, dried and filtered if they are not dry and clean; the drying and filtering
being, in that case, done in Glover's towers fed with concentrated sulphuric acid.
Then only are they allowed to mix with the sulphurated hydrogen purified as afore-
said. The stream of united gases is made to circulate alternately up and down' a

page_text: series of vertical flues, whereby an intimate mixture is obtained. These flues con-
stitute also a recuperator to raise the temperature of the gases to about 212° F.
To that effect, this apparatus is duplex, one of the series of flues being reheated by
the combustion of some gaseous fuel while the other series is in use. When the
sulphurous acid is naturally dry and clean as it comes from the roaster, it only
requires to settle what dust it carries, before mixing with the purified sulphurated
hydrogen and it may still be hot enough to raise the mixture of the gases to the
desired heat. No duplex recuperator is then needed.
At the end of the mixer, the gas is caught by steam jets and injected into the
condenser. These steam jets draw the gases from the roaster by outlets p &
regulated by dampers.
In the condenser is realized the ultimate reaction already alluded to, namely
present.
The reaction is complete if the ratio between the gases, stand as two volumes of
sulphuretted hydrogen H2S to one volume of sulphurous acid SO. There may be
no excess of the last gas, as thionic acids would result, but there may be an excess
of the former, which excess takes no part in the reactions. It is well to keep this
excess as small as practicable for safety, which is easily obtained, after testing the
mixture, by regulating a valve which controls the outlet of sulphurous anhydrid SO*
below the distillating zone of the roaster at p.
The thionic acids decompose as the heat increases, hence it is a caution as well
as a convenience in order to prevent condensation of steam, to operate at a high
convenient degree of heat.
Said condenser may be of any shape, however I prefer the shape represented
in plan by Fig. 4 of the annexed drawing, Fig. 3 being a vertical section.
The construction is composed of two chambers F & B contiguous and connected,
near their common floor, by low, arched apertures E. The floor slopes towards one
or several open canals G and is provided with ridges on which filtering canvas T is
stretched. Both chambers dip into the same bath I of calcium chloride CaCl³
solution, boiling at about 260° F. and kept at that degree of heat by hot gases
circulating in flues H provided into the base. B is the reaction chamber; it is
arched and provided with apertures R for introduction of tools, and with one or
several entries A, anywhere in B for the gas and steam. Chamber F is open on
top or connected with a chimney. It is provided with one or more entries V
anywhere near the surface of bath I for fresh air, to revivify the iron oxide with
which chamber F is filled. This iron oxide is bog iron ore (hydrated sesquioxide
of iron) in clean porous lumps. The gases expand into chamber F and surrender to
the hydrated sesquioxide of iron, any sulphur that might be carried so far by the
gases as well as that from any excess of sulphuretted hydrogen H,S. The gases
spend themselves in the atmosphere, at last, from the open top of chamber F or up
a chimney. As to the sulphur, if liquid, it falls into bath I, filters through
canvas T and runs along the inclined floor, into canal G whence it is drawn and
cast by means of a valve, heated when needed. If the precipitated sulphur is in a
solid state and fails to fall on its own accord into bath I, it is made to fall by means
of wooden rods and holes R. What sulphur settles on the iron ore, is melted and
washed down by pumping over the ore, some of the solution I. From time to time
or continuously, a jet of fresh air or several such jets are admitted on the iron ore
in order to liberate any sulphur combined to the iron. I must add that the use of
calcium chloride is not new. However it is not used here in the same way as -in
Schaffner and Van Helbig's process for instance as it takes no part in the reactions
but only keeps the sulphur in a convenient molten state for collecting and
drawing out,

page_text: 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. A process for reducing mineral and artificial metallic sulphurets into oxides
and free sulphur, said process first roasting the ore with volatilized sulphur in order
to eliminate what arsenic, antimony and phosphorus may be present; next
roasting it with pure, highly heated air and last calcining; the sulphurous acid SO²
and free sulphur held in the gas from the roaster being first reduced into sulphurated
hydrogen H2S by steam, carbon, hydrogen carbonic monoxyde CO and hydro-
carbons, at a red heat; next freed by cooling, from dust and condensable materials;
the remaining gases being dried and filtered and then intimately mixed with dry,
clean sulphurous acid SO³, taken, as I prefer, from the same roaster, below the
distillating zone, in order to, lastly, precipitate the free sulphur from the intimate
mixture at about 212° F., in presence of steam, said steam being given only after
an intimate mixture is obtained with the two dry gases; the recovered sulphur
being gathered into a bath of calcium chloride CaCl solution, which takes no part
in the reactions but is only of use in order to eventually melt the sulphur and keep
it in a molten state for convenience in collecting and casting.
2. The use of pure highly heated air for roasting ore, making it unnecessary to
otherwise heat the burner or the material, although the retorts might also be
heated outside if desired.
3. Roasting ore at a single continuous operation first with volatilized sulphur,
next in air and last calcining.
4. Roasting monosulphurets in vapour of sulphur by driving hot gases on
pyritous ore yielding free sulphur by heat in a stream of gas, before said gas
reaches the monosulphurets which are to be purified from arsenic, antimony and
phosphorus.
5. The following improvements of a Hasenclever roaster consisting in dividing
the oven into sections by vertical partition walls a hollowed with passages z for the
gas, the homologous members of the partition walls a being united by light flat
arches b bridging over the sections and bearing on said members so as to constitute
with passages 2, continuous horizontal flues from end to end of the roaster; the
light arches being produced not quite down to contact at their lower end but
leaving a slit c for the ore to slide from each flue into the lower ones, said slit c
being only interrupted by walls a, which walls present, in each flue a ridge as high
as the ore reaches in said flue, in order to prevent any mixing of ore from the two
sides of wall a; slit being reproduced at d, in side wall e for introduction of
suitable tools to probe the flues.
6. The reduction of sulphurous anhydrid and free sulphur at a red heat, into
sulphurated hydrogen H'S by hot producer gas and steam, either in a kiln holding
incandescent coal or in a recuperator or first superheating the steam and producer
gas in a recuperator and driving them together with sulphurous gas at the foot of
a kiln.
7. The reduction of sulphurous anhydrid and free sulphur into sulphurated
hydrogen by hot producer gas and steam and coal kept at a red heat by the reaction
itself of carbonic monoxyde CO on sulphurous anhydrid SO².
8. The use of a recuperator as a medium for reducing sulphurous anhydrid SO'
into sulphurated hydrogen H'S, by means of steam and producer gas, the free
chamber of the recuperator being reheated while the operation is progressing in
the other chamber.
9. A process for realizing the known but so far impracticable reaction
SO +2 H'S = 3 S + 2 H2O which consists; first, in drying separately the
sulphurous acid SO* if damp and sulphurated hydrogen if damp, before they come

page_text: together; second, in mixing intimately the two dry gases into an homogenous
mixture, care being taken to have no excess of sulphurous acid SO' present; third,
in heating the intimate mixture of dry gases to about 212° F. should they be at a
lower temperature; fourth, in giving in steam.
10. A convenient apparatus for realizing the precipitation and collection of
sulphur from a mixture of sulphurous acid SO2 and sulphurated hydrogen H'S.
It is composed substantially of two contiguous chambers, one of which is arched,
receives the mixture of gases and steam, and presents small apertures in the arch
for tools; it acts as the reaction chamber. The other chamber is open at the top
or connected to a chimney and is filled with blocks of bog iron ore (hydrated
sesquioxide of iron) and provided with entries for fresh air; both chambers dipping
into a common bath of chloride of calcium CaCl solution, boiling at about 260° F.
and connected by low arched passages close to the surface of the bath; the
floor of both chambers sloping towards one or several open canals from which the
molten sulphur can be tapped; said floor being provided with ridges on which
filtering canvas is stretched and with flues into which circulating hot gases furnish
the required heat for the bath.
Dated this Seventeenth day of October 1802
LEON BEMELMANS.