IMPROVEMENTS IN MANUFACTURING SULPHURIC ACID AND COPPER -FROM COPPER ORES, REGULUSES, AND MATTS
Year: 1853

page_text: LETTERS PATENT to William Henderson, of Bow Common, in the
County of Middlesex, Manufacturing Chemist, for the Invention
of. "IMPROVEMENTS IN MANUFACTURING SULPHURIC ACID AND COPPER
-FROM COPPER ORES, REGULUSES, AND MATTS."
Scaled the 7th June 1853, and dated the 8th January -1853.
PROVISIONAL SPECIFICATION left by the said William Henderson
at the Oflice of the Commissioners of Patents, with his Petition, on
the Sth January 1853.
.1, WILLIAM HENDERSON, of Bow Common, in the County of Middlesex,
Manufacturing Chemist, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN MANUFACTURING SULPHURIC ACID AND COPPER
FROM COPPER ORES, REGULUSES, AND MATTS" to be as follows:-
It consists, first, in separating the sulphur from the other matters,
and treating it for the manufacture of sulphuric acid; secondly, in
treating copper ores, reguluses, and matts so as to convert them into
copper by more simple processes than hitherto; and, thirdly, in
dividing copper ores, &c. into three distinct classes, and treating each
class differently, according to the per-centage of sulphur it may contain.
I compose my first class of ores containing all above 25% of sulphur,
the second all between 10 and 25%, and the third all under 10%.

page_text: The difficulties in the way of manufacturing sulphuric acid from the
sulphur in copper ores have been threefold. The first great difficulty
is, that the high heat in common practice, by which the greater
portion of the sulphur is separated from the copper, would destroy the
vitriol chambers; 2d, tlie carbonic acid and other gases, and with
smoke from the fires (supposing the gases cooled down so as not to
injure the chamber,) is so great as to necessitate the use of a ruinous
amount of nitrate of soda, to neutralize them; and, 3d, in common
practice, a large amount of sulphur is sublined unchanged from the
ore, which, if passed into a vitriol chamber in this state, would remain
as sulphur, and very much retard the production of sulphuric acid. The
present improvements propose to remove all these difficulties by very
simple methods.
The first objection is removed by separating all the
available sulphur by calcination at a low heat, and doing away with
roastings as much as possible. The second objection I propose to
remove by calcining a certain class of ores without the aid of fuel,
and another class in close, calciners, by causing the smoke and the
gases from the ore to pass separately from the furnace. The third
difficulty I propose to remove by conveying the gases from the cal-
ciners over the kilns in which the ores of the first class are burning by
their own power of combustion; by this means all the sulphur that has
been sublimed is readily converted into sulphurous acid. I classify all
copper ores under three heads, and treat them differently.
The first class contains all ores above 25 per cent. sulphur.
The second class contains all between 25 and 10 per cent. sulphur
and the small ores of No. 1.
The third class contains all under 10 per cent. sulphur.
The first class are broken into pieces not larger than a goose egg,
and burnt in small cylindrical kilns, after the manner of mundic kilns.
In my complete specification I propose to describe the size and shape
of a kind of kiln I have found to answer best, together with the method
of working these kilns. The ore, when put into these kilns, kindles very
readily, and gives off the greater portion of its sulphur as sulphurous
and sulphuric acid; the residue still contains a portion of sulphur;
the burnt ore is removed from the kilns, crushed, and smelted for

page_text: regulus, as usual; the regulus contains nearly all the sulphur left in the
The method of treatment so as to obtain the sulphur and
burnt ore.
copper from it shall be described presently.
as muchi
The second class are calcined in close furnaces, of which I will give
ä description in my complete specification, but they are no Invention' of
mine. A dull red heat is all that is required to remove
sulphur as it is politic to remove at this stage of the process. I have
found it advantageous to remove the ore from the furnace so soon as the
sulphur fell to half the quantity of copper in the ore.
The sulphur gases
pass off from the beds of the furnace by flues or pipes, and the exhausted
ore is removed to the smelting furnace, and run down for regulus.
The third class are mixed with the calcined ores of the first and
second class, and also smelted for regulus. The reguluses or matts of
copper produced as above I crush fine enough to pass through a sieve
of S holes to the inch. The crushed regulus I treat in the same kind
of furnace as is used for ores of the second class, the only difference
being, that the reguluses require a strong red heat, and the operation is
continued till the sulphur falls to the proportion of 1 to 20. of copper.
The calcined regulus is removed from the furnace, and, after being mixed
with refinery slags, &c., as is readily understood, it is smelted, the pro-
duce being copper fit refining, and a little regulus, which may be
roasted or re-calcined, as convenient. The sulphur gases obtained from
ores and reguluses in the calcining furnaces I pass through the same
flue that receives the gases from the kilns containing the first class of
ores; the burning sulphur of these readily burns all sublimed sulphur, and
the mixed gases pass then into the nitre oven, and from thence into the
chamber, where they are converted into sulphuric acid, and condensed.
If it is wished to produce sulphuric acid of greater purity, I proceed
exactly as I have already described (taking care that all the ores sup-
plied to the furnaces are quite dry), till the gases leave the nitre oven.
Then, instead of conveying the gases into a chamber with steam, I pass
them into a chamber or chambers perfectly dry, where all the volatile
oxides are condensed, and separated from the gases, which then pass into
a vitriol chamber, and are condensed into sulphuric acid as usual.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said William Henderson, in the Great Seal Patent
Office, on the Sth July 1853.
I,
TO ALL TO WHOM THESE PRESENTS SHALL COME,
WILLIAM HENDERSON, of Bow Common, in the County of Middlesex,
Manufacturing Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighth day of January in the year of
our Lord One thousand eight hundred and fifty-three, in the sixteenth
year of Her reign, did for Herself, Her heirs and successors, give and
grant unto me, the said William Henderson, Her special licence that
I, the said William Henderson, my executors, administrators, and
assigns, or such others as I, the said William Henderson, my executors,
administrators, and assigns, should at any time agree with, and no
others, from time to time, and at all times thereafter during the term
therein expressed, should, and lawfully might, make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
MANUFACTURING SULPHURIC ACID AND COPPER FROM COPPER ORES, REGULUSES
AND MATTS," upon the condition (amongst others) that I, the said
William Henderson, by an instrument in writing under my hand and
seal, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
'cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said William Henderson, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, that is to say:
My Invention consists in improvements in the treatment of copper
ores of all descriptions containing. sulphur, also reguluses or matts of
copper, by means of which I obtain therefrom sulphuric acid, in addition
to the copper and other products usually obtained. My mode of treat-

page_text: ment is such, that, with very little alteration of existing arrangements
in copper works, I am enabled to convert the sulphurous gases into
sulphuric acid, and to remove, to a considerable extent, the nuisance
arising from the dissipation of sulphur, arsenic, and other volatile
bodies into the atmosphere. For the purposes of my livention, I
divide all ores of copper into three classes; to the first class belong
all ores containing more than twenty-five per cent. of sulphur, the
second class embraces all ores containing less than twenty-five per
cent. and more than ten per cent. of sulphur, and the third class
includes all orcs containing less than ten per cent. of sulphur.
In
operating on ores of the first class; I cause them to be broken into
pieces rather larger than those to which copper ores are generally
reduced, say about the size of a hen's egg, and all dust removed, by
sifting through a half-inch sieve. I have a series of kilns constructed
in a similar manner to the kilns commonly in use for burning mundic.
I find by experience, that small circular kilus are the most convénient
for operating on copper ores, since the ores are liable to agglomerate,
when worked in large quantities; the following dimensions are those
which I prefer to adopt for the kilns, viz., five feet from the bars to
the spring of the arch, 20 inches in diameter at the bars, and gradually
widened to 30 inches at the top, with three small working doors of
the usual size, at equal distances above each other in the front, the
grate to be formed of three strong bars built into the brickwork, and
running horizontally over the ashpit. 1 bring these kilns to a red heat
in the way usually adopted in burning mundic, gradually charging
them with the broken ores, stirring the whole with iron rods at every
charge. At the commencement of working, no accurate time can be given
for charging the kilns, it being only nécessary that they should be sup-
plied with fresh ore as they burn up clear; care must be taken, 'how-
ever, not to add too much raw ore at once, as this would cause the
sulphur to sublime to some extent, and, on the other hand, the 'heat in
the kilns should not be allowed to get too low for want of a sufficient
supply of ore; these precautions are to be observed in supplying orc to
the kilns until they have become filled to the height of two or three
inches. above the level of the sole of the top door, when a portion of

page_text: the burnt ore is raked through the grate into the ashpit, until the level
of the ore is reduced about 6 or 8 inches; the whole contents of the
kiln are then thoroughly stirred with rods, beginning at the bottom door
and going upwards. All pieces that have run together are then broken
up, and if they are cold they are removed from the kiln, if hot they are
allowed to remain, unless the kiln is hot enough to allow of their being
removed without the contents of the kiln suffering any material decrease
of temperature; when the contents have been well stirred, more fresh
ore is added, and the door closed. In this manner, when the kilns are
in average working order, they will each burn out about 8 to 10 cwt.
of ore in 24 hours, the burnt ore being withdrawn through the ashpit
every 6 hours, and fresh quantites supplied every 20 to 30 minutes,
a few shovelfuls at a time. By attending to these particulars, and
supplying dry ore, copper ores of this first class will be readily calcined
without the aid of fuel, beyond what is required to light the kilns at first
starting. The sulphurous gases evolved pass through an aperture in the
dome of the kiln, into a flue, and they are subsequently treated as will be
herein-after described. The burnt ores still contain sulphur, varying in
amount from 3 to 15 per cent., according to the composition of the
ore. On removing the burnt ores from the kilns, I crush the lumps so
as to enable them to pass through an inch sieve, and I afterwards
mix the same with ores of the third class, before mentioned, that is,
those containing a less proportion than 10 per cent. or sulphur, or
I mix them with prepared ores of the second class and ores of the
third class, or with either of them; the mixture, when smelted in a
reverberatory furnace in the usual manner, produces copper regulus,.
and a clean slag. I treat the second class of ores herein-before
mentioned, that is, those containing between 10 and 25 per cent. of
sulphur, in the following manner: I crush the ores sufficiently fine
to pass through a sieve of 4 holes to the square inch, and charge
them into a calcining furnace of the same dimensions as those ordi-
narily in use in copper works, and constructed in a similar männer
but with this difference, that the furnace is built with two beds, one
over the other, and instead of passing the flame of the fire directly
over the ore in the furnace, as is usually done, I pass it through

page_text: flues underneath the ore. I build these flues over and on the cross
arches into which the calcined ore ultimately passes, and cover them
with close-fitting fire tiles, which form the soles of the beds; tubes
of cast-iron or of brickwork communicate across, the flues from the
beds to each other and. to the arches. When the first bed has been
built, I throw an arch over it, as close to the sole as will leave only
the space necessary for working; on the top of this arch I also
form similar flues, which I cover over with fire tiles similar to the
sole of the first bed, and above this second bed I throw another arch,
above which I also construct flues covered in with iron plates or fire-
tiles, preferring the former. The flame from the furnace passes over
the bridge, and through the llues under the first bed, to the end of the
furnace, thence through two chimneys or flues at the corners, and thence
it returns in an opposite direction, under the second bed, and from there
back again, over the top arch, to the chimney. The mode of working
is as follows; the furnace being properly heated, the crushed ore is laid
on the top plates or tiles, to dry; it is then passed, through tubes in the
arch, to the sole of the top bed, where it is evenly spread, and repeatedly
stirred and worked, as is usually done in calcining ores. After calcina-
tion in the top bed for a period varying from 6 to 9 hours, depending
upon the ratio of the sulphur, more time being required as there is
more sulphur, it is passed to the bottom bed, and there calcined until the
sulphur bears a proportion of one to two of the copper present in the
ore. It is then passed through to the cubs, or receptacles for the cal-
cined ore, from which it is removed, and mixed with the calcined ores
of the first class, and with raw ore of the third class, or with either of
them, and smelted in the usual manner. Whenever a charge is
removed from the lower bed of the furnace, that on the top bed is
shifted to its place, a fresh charge from the drying bed is introduced
into the top bed, and another quantity of raw ore supplied to the drying
bed, and so on continuously. The time required to calcine a charge
varies with the proportion of sulphur in the ore relatively to that of
copper, the more sulphur the longer time is required, and an ore
containing about 25 per cent. of sulphur and 10 of copper will require
about 12 hours to reduce it to 5 per cent. of sulphur, the point required.

page_text: Hot air is .supplied to the beds by iron pipes passing through the hot
flues of the smelting furnace, and built into the end of the calcining
furnace next the fire; the air might also be introduced through one
large pipe, but I prefer to use several pipes of small size. The
sulphurous gases evolved pass away through pipes or flues opening into
the beds of the furnace, close under the arch and opposite the points
where the hot air is introduced, so that the hot air is allowed to
traverse the whole surface of the ore under operation.
A charge for
a furnace of the internal dimensions of 16 feet by 8 feet will be about
2 tons. In treating ores of the third class, that is, containing less
than 10 per cent. of sulphur, I cause them to be crushed or broken
into pieces of from to inch sieve, and then mix them, without
previous calcination, with calcined ores of the first or second class, or
with both, in equal or other convenient proportions; I then cause the
mixed ores to be smelted in the usual manner, the product being a regulus
of copper, and a clean slag. Having obtained reguluses or matts of
copper by treating the ores in the several modes described, I next pro-
ceed to calcine the same, in such manner as to obtain all, or nearly all, of
their sulphur, in a state available for producing sulphuric acid, and at
the same time that a clean slag is produced, and copper fit for refining
at one smelting, as follows: I take the reguluses or matts of copper,
produced as before described, or in any other manner, and crush them
fine enough to pass through a sieve of 16 meshes to the square inch;
I then calcine the crushed reguluses in furnaces similar to those de-
scribed as employed for operating on the second class of ores; the heat
in the last bed should be gradually increased towards the end of the
calcination, and hot air admitted freely during the whole
process;
twelve hours in each bed, when the furnaces are carefully managed, will
be a suflicient time to reduce the sulphur present to about 2 per cent.,
beyond which stage the calcining process should not be carried. Cal-
cining the regulus dead, or free from sulphur, must be carefully avoided,
as the success of the subsequent smelting will depend greatly on this
point; and, as a general rule, it might be advisable that one part of
sulphur should be left for every twenty parts of copper, although the
proportion of two per cent. is sufficient when the ore to be mixed with
about

page_text: the regulus, as below stated, is poor in copper and rich in silica. When
the regulus has been calcined, it is removed from the furnace, and mixed
with an ore free from sulphur, but having a large excess of silica; slags
from the refining furnace are also added, with a little coal, to reduce
them more readily, as is well understood, and the whole then smelted,
when the produce will be copper fit for refining, and a small proportion
of regulus, more or less pure, which may be re-calcined or roasted, as
may be most convenient. When the impurities in the ore to be smelted
are of small amount, I, in every case, consider the following method to be
much more economical; after selecting as much ore of the first class as
I find necessary for the supply of the kilns, I calcine, in the close
calcining furnaces above described, the remainder of the first class and
all of the second and third classes, all of which have been previously
crushed to a sieve of eight meshes to the inch; I continue the calcina-
tion till all the ores are "dead," or free from sulphur. The evolved
sulphurous gases are treated as those evolved by the previous processes,
in the manner to be hereafter described. When the ores are calcined
dead, they are mixed with ores containing no sulphur, and large excess
of silica, in such proportions that the protoxide of iron and of other
bases may form with the silica protosilicates. For every four parts of
copper in the mixture, one of coal or coke, or other carbonaceous matter,
must be used. The mixture is then smelted in the usual manner. By
these means, metallic copper fit for refining is produced by two opera-
tions. The sulphurous gases arising from the calcination of the ores,
and from the calcination of the reguluses and matts, as above described,
I employ to produce sulphuric acid; and in this process I have the
further advantage of condensing the volatile oxides of zinc, arsenic,
lead, &c., when present in the ores, and of obtaining them for use.
The gases from the calcining furnaces, when collected in flues or
pipes, as has been already mentioned, are almost always contaminated
with sublimed sulphur, which would very much retard, if not altogether
prevent, the subsequent formation of sulphuric acid in the vitriol
chamber. To convert this sublimed sulphur into sulphurous acid, I
cause it to pass, while in the state of gas, direct from the calcining
furnace into the flue on the top of the kilns herein-before described,

page_text: where, coming in contact with the flame and hot air of the kilns, it is
readily converted into sulphurous acid, and mixed with the gases evolved
from the material under operation in the kilns. These mixed gases,
whether from the first or the second class, or from the regulus, are next
passed through the nitre oven, which is a flat-arched oven, having placed
in it cast-iron pots, containing the usual quantity of nitrate of soda and of
sulphuric acid, in proportion to the sulphur volatized, so as to produce
sufficient nitrous acid to effect the conversion of the sulphurous fumes into
sulphuric acid; the hot gases passing over the nitre pots in the oven give
out sufficient heat to decompose all the nitrate of soda, and produce
nitrous acid, which mixes with the hot gases. The sulphurous and
nitrous gases are then conducted by a flue or flues into the condensing
chambers, where, coming in contact with steam, they are converted into
sulphuric acid, after the manner commonly practised. When sulphuric
acid of greater purity is required, I proceed as follows: I take care that
all the ore supplied to the calcining, furnaces and to the kilns shall be
as dry as practicable, and that the sulphuric acid supplied to the nitre
pots shall be concentrated. I then follow the same mode of working
as just described, until the gases leave the nitre oven, when, instead of
passing them direct into the vitriol chamber, I introduce them into
another chamber, which may be of brick, iron, or lead, kept perfectly dry,
where the greater part of the oxides of the volatile metals will be depo-
sited, and by using two or more chambers before passing the gases into
the vitriol chamber, the volatile impurities which are capable of being
condensed will be entirely deposited. On leaving the dry chamber or
chambers, the gases pass into the vitriol chamber, where they are con-
verted into sulphuric acid by the aid of steam, in the usual manner,
Mundic, or iron pyrites, may also be used in the kilns, to produce sul-
phurous gas for converting the sublimed sulphur, combined with the
fumes from the calcining furnaces, into sulphurous acid, and where
this method is inconvenient, the fumes from one or more sulphur
ovens in which sulphur is burning may be employed, or, instead of
adopting either of these plans, the gases from the calcining furnaces
may be passed through a red-hot pipe or cylinder of fire clay, heated
from the outside, and kept at a red heat. Where this latter mode of

page_text: proceeding is used, the gases should be freely mixed with air, admitted
through apertures in the flues, before they enter the pipe or cylinder,
in order to supply oxygen to support the combustion of the sublimed
sulphur; in the other cases, the excess of air that generally enters the
kilns or ovens will be found sufficient for that purpose.
And having now described the nature of my said Invention, and in
what manner the same is to be performed, I declare that I do not
claim the particular form of furnaces employed, though I have
described those which I have found the most suitable for this pur-
pose; but what I claim is,-
First, the combination of kilns, or sulphur ovens, or hot cylinders
with calcining furnaces, for the purpose of oxidizing the sublimed
sulphur in such a manner as to ensure its complete conversion into
sulphuric acid in the subsequent operations.
Secondly, the use of nitrous acid, with or without the use of dry
ores, for the purpose of converting the sublimed metals which are
mixed with the sulphurous gases into a higher degree of oxidation,
and thereby facilitating their separation before passing into the vitriol
chambers.
Thirdly, the use of dry condensing chambers between the furnaces and
kilns and the vitriol chambers, for the purpose of freeing the sulphurous
gases from their condensible impurities, and thereby producing sulphuric
acid of greater purity.
Fourthly, the short and economical process, herein-before described, of
producing sulphuric acid and copper from sulphuret copper ores, where
the impurities are of small amount.
In witness whereof, I, the said William Henderson, have hereunto
set my hand and seal, this Seventh day of July One thousand
eight hundred and fifty-three.
WILLIAM HENDERSON. (L.S.)