IMPROVEMENTS IN TREATING AND UTILIZING SPENT TAN AND OBTAINING USEFUL PRODUCTS THEREFROM
Year: 1875

page_text: LETTERS PATENT to Hunter Henry Murdoch, of No. 7, Staple Inn,
in the County of Middlesex, Patent Agent, for the Invention of
"IMPROVEMENTS IN TREATING AND UTILIZING SPENT TAN AND OBTAINING
USEFUL PRODUCTS THEREFROM."-A communication from abroad by
Modeste Leonard Honnaij, of Chatelmeau, Belgium, Manufacturer.
Sealed the 6th October 1875, and dated the 16th April 1875.
PROVISIONAL SPECIFICATION left by the said Hunter Henry Murdoch
at the Office of the Commissioners of Patents, with his Petition,
on the 16th April 1875.
I, HUNTER HENRY MURDOCH, of No. 7, Staple Inn, in the County of
Middlesex, Patent Agent, do hereby declare the nature of the said In-
vention for "IMPROVEMENTS IN TREATING AND UTILIZING SPENT TAN AND
OBTAINING USEFUL PRODUCTS THERE FROM," to be as follows:-
In most places where leather is tanned a quantity of spent tan
accumulates without the tanners having the means of utilizing it. Now
the object of this Invention is to utilize spent tan by a process for

page_text: quickly drying and carbonizing the same, and obtaining therefrom divers
useful products, as herein-after described.
The processes in general use for carbonizing wood are inapplicable to
spent tan, for if the carbonization of spent tan out of contact of air were
attempted the ignited tan would be extinguished instead of becoming
carbonized; the idea of carbonizing spent tan like charcoal by kindling a
fire in it must therefore be abandoned.
According to this Invention the carbonization of spent tan is effected
in apparatus somewhat analogous to what is used in the manufacture of
coal gas.
The said apparatus produces from the said spent tan a gas which is
first purified by passing through water; secondly, by cooling so as to
deprive it of the vapour it contains; and, thirdly, by being caused to
pass through lime.
The said apparatus consists of a furnace in which are mounted one or
more tubes or retorts projecting slightly at one end out of the said
furnace, where they are fitted with a door or plate which may be opened
to charge in the spent tan. At the upper side of the projecting end of
cach of the said retorts is an aperture or hole to which is connected a
suitable pipe through which the smoke or vapour emitted by the tan in
the retort escapes, and is conducted to a tank containing water in
which the said pipe is immersed to a depth of 4 or 5 inches. The
said smoke or vapour produces tar and gas which may be employed
usefully. The tar mixing with the water in the tank is deposited at the
bottom of the tank and passes out of the said tank through a suitable
pipe, the gas filters through the water, and by accumulating passes
through an outlet in the upper part of the said tank, the said outlet
being provided with a suitable pipe which conducts the tan gas to an
iron tank partly filled with water, and having above the water a grating
on which is placed a quantity of coke. The gas passing through the
water is further purified of the tar and other impurities it still contains.
The said tar and other matters are deposited in the water, whilst the gas
passes through the layer of coke, is purified thereby, and then passes
through another pipe to a series of double refrigerating tubes bent in
pairs and opening into a closed chest partly filled with water, one leg of
the said tubes dipping into the water, whilst the other leg opens above
the water. The tan gas passes through the said tubes and through the

page_text: water contained in the said chest, and thence passes through a suitable
pipe to the purifier which consists of a vessel of a conical shape tapering
slightly from top to bottom and provided with a suitable cover. In the
said purifier are layers of trellis work, one over the other, each layer of
trellis work being covered with a layer of moss covered over with lime;
the tan gas passes through the said trellis work and the moss and lime,
and in frathon
water contained in the said chest, and thence passes through a suitable
pipe to the purifier which consists of a vessel of a conical shape tapering
slightly from top to bottom and provided with a suitable cover. In the
said purifier are layers of trellis work, one over the other, each layer of
5 trellis work being covered with a layer of moss covered over with lime;
the tan gas passes through the said trellis work and the moss and lime,
Land is further purified.
If very pure gas is required a second purifier or several other
similar purifiers may be used. From the last purifier the gas is made
to pass into a suitable holder or gasometer for use.
The drying and carbonization of spent tan in ordinary retorts or
receptacles is a matter of considerable difficulty, especially when the
dried spent tan is intended for any of the uses to which dried wood or
ligneous or fibrous materials are employed, such as the manufacture of
paper pulp, statuary, pasteboard, and other articles, for tho tan being
greatly charged with moisture owing to its having remained for a length
of time in the tanner's pit emits when heat is applied to it a largo
quantity of steam which is unable to escape by the outlet of the
retort.
A supply of air which would be injurious to the carbonization of
wood or other matters, inasmuch as it would cause them to ignite and
burn away, is useful or even necessary for the treatment of tan, and
according to this Invention the vapour produced by the tan is utilized.
in preventing the ignition of the gases emitted by the tan when air is
admitted into the retort to hasten the drying operation, which drying
operation and also the carbonisation is accelerated by the introduction
of air into the retort without loss of the gases cvolved even when great
heat is used. For this purpose, according to this Invention, a fan
placed behind the retort is used to force a blast of air directly into the
said retort or through a perforated pipe inside the retort, the said blast
which may be regulated at pleasure blows out the steam as soon as it is
produced and contributes greatly to dry the tan, and the said tan being
subjected to the double action of the fire outside of the retort and the
blast of air inside is speedily dried and carbonized. Either a hot or a
cold blast may be used, the hot blast being preferable as accelerating
the operation. Or an agitator consisting of a shaft provided with flat
or curved or helical blades or wings may be used to stir the tan, the

page_text: said agitator being mounted in the retort and caused to revolve either
by hand or by power.
The said agitator may be used with or without the blast above
mentioned, or by making the shaft of the agitator hollow and perfo-
rating it with holes within the retort. The blast may be made to pass
through the said shaft into the retort, or the wings or arms of the said
agitator may be combined with tubes perforated on one side so as to
receive the blast from the hollow shaft and discharge it within the
retort. Or the retort itself may be made capable of oscillating or
revolving so as to increase the stirring up of the tan and the emission of
steam. The winged shaft or agitator in this case may be either rotatory
or stationary. If there should be reason to fear that the agitator will
melt or bend from the great heat a small jet of water may be caused to
flow into the agitator shaft by means of a small pipe in connection with
a water tank.
Motion is given to the agitator and other acting parts by any suitable
mechanical means. If preferred the steam from the retort may be
drawn out by suction instead of being forced out by a blast.
By operating upon spent tan according to this Invention the following
products or results may be obtained :-
First. A gas suitable for lighting or heating purposes. When used
for heating purposes the said gas need not be purified by passing
through the purifiers and refrigerators herein-before described, it being
sufficiently cleansed for use by passing through the water in the first
water tank. If the gas be intended for lighting purposes all the smoke 2
and vapour may be evaporated till the tan is thoroughly dry, thus
avoiding any mixture of air with the gas. This evaporation though
necessary when the gas is to be used for lighting is unnecessary when
it is to be used for heating. If desired the vapour may be conducted to
a second water tank.
Secondly. Tar.
93

page_text: Fifthly. The carbonized tan may be used for fuel either alone or com-
bined with other substances.
Sixthly. The carbonized tan may be reduced to powder, and used for
making impalpable black, or for making gunpowder.
Seventhly. When thoroughly dried, according to this Invention, the
spent tan may be used in place of dried wood or ligneous or fibrous
substances for the manufacture of paper pulp, statuary, pasteboard,
buttons, or other articles.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Hunter Henry Murdoch in the Great Seal Patent
Office on the 16th October 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HUNTER
HENRY MURDOCи, of No. 7, Staple Inn, in the County of Middlesex,
Patent Agent, send grecting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixteenth day of April, in the year of
our Lord One thousand eight hundred and seventy-five, in the thirty-
eighth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Hunter Henry Murdoch, Her special
license that I, the said Hunter Henry Murdoch, my executors, adminis-
trators, and assigns, or such others as I, the said Hunter Henry Murdoch,
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 TREATING AND UTILIZING SPENT Tan and OBTAINING USEFUL PRODUCTS THERE-
FROM," a communication to me from abroad by Modeste Léonard
Honnaij, of Chatelmeau, Belgium, Manufacturer, upon the condition
(amongst others) that I, the said Hunter Henry Murdoch, my executors
or administrators, by an instrument in writing under my, or their, or
one of their hands and seals, 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

page_text: Office within six calendar months next and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that I, the said Hunter Henry Murdoch, do hereby
declare the nature of the said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained in
and by the following statement thereof, that is to say :-
In most places where leather is tanned a quantity of spent tan accu-
mulates without the tanners having the means of utilizing it. Now the
object of this Invention is to utilize spent tan by a process for quickly
drying and carbonizing the same, and obtaining therefrom divers useful 1
products, as herein-after described.
The processes in general use for carbonizing wood are inapplicable
to spent tan, for if the carbonization of spent tan out of contact with
air were attempted the ignited tan would be extinguished instead of
becoming carbonized; the idea of carbonizing spent tan like charcoal 1
by kindling a fire in it must therefore be abandoned.
According to this Invention the carbonization of spent tan is effected
in apparatus somewhat analogous to what is used in the manufacture of
coal gas.
The said apparatus produces from the said spent tan a gas which is 2
purified, firstly, by passing through water; secondly, by cooling so as to
deprive it of the vapour it contains; and, thirdly, by being caused to
pass through lime.
The said apparatus consists of a furnace in which are mounted one or
more tubes or retorts projecting slightly at one end out of the said 2
furnace, where they are fitted with a door or plate which may be opened
to charge in the spent tan. At the upper side of the projecting end of
each of the said retorts is an aperture or hole, to which is connected a
suitable pipe, through which the smoke or vapour emitted by the tan in
the retort escapes and is conducted to a tank containing water, in which 3
the said pipe is immersed to a depth of four or five inches. The said smoke
or vapour produces tar and gas, which may be employed usefully. The
tar mixing with the water in the tank is deposited at the bottom of the
tank, and passes out of the said tank through a suitable pipe. The gas
filters through the water, and by accumulating passes through an outlet 3
in the upper part of the said tank, the said outlet being provided with a

page_text: suitable pipe which conducts the tan gas to an iron tank partly filled
with water, and having above the water a grating on which is placed a
quantity of coke. The gas passing through the water is further purified
of the tar and other impurities it still contains. The said tar and other
matters are deposited in the water, whilst the gas passes through the
layer of coke, is purified thereby, and then passes through another pipe
to a series of double refrigerating tubes bent in pairs and opening into a
closed chest partly filled with water, one leg of the said tubes dipping
into the water, whilst the other leg opens above the water. The tan gas
passes through the said tubes and through the water contained in the
said chest, and thence passes through a suitable pipe to the purifier,
which consists of a vessel of a conical shape tapering slightly from top
to bottom, and provided with a suitable cover. In the said purifier are
layers of trelliswork, one over the other, each layer of trelliswork being
covered with a layer of moss covered over with lime. The tan gas passes
through the said trelliswork and the moss and lime, and is further
purified.
If very pure gas is required a second purifier or several other similar
purifiers may be used. From the last purifier the gas is made to pass
into a suitable holder or gasometer for use.
The drying and carbonization of spent tan in ordinary retorts or recep-
tacles is a matter of considerable difficulty, especially when the dried
spent tan is intended for any of the uses to which dried wood or ligneous
or fibrous materials are applied, such as the manufacture of paper pulp,
statuary, pasteboard, and other articles, for the tan being greatly charged
with moisture owing to its having remained for a length of time in the
tanner's pit, emits when heat is applied to it a large quantity of steam,
which is unable to escape by the outlet of the retort.
A supply of air, which would be injurious to the carbonization of
wood or other matters, inasmuch as it would cause them to ignite and
burn away, is useful or even necessary for the treatment of tan, and
according to this Invention the vapour produced by the tan is utilized in
preventing the ignition of the gases emitted by the tan when air is
admitted into tho retort to hasten the drying operation, which drying
operation, and also the carbonization, is accelerated by the introduction
of air into the retort without loss of the gases evolved even when great
heat is used. For this purpose, according to this Invention, a fan placed

page_text: a second water tank.)
Secondly. Tar.
Thirdly. An essential oil in admixture with the tar. (The said oil
may be used for lubricating machinery.)
Fourthly. A carbon similar to charcoal, and which may be used as
charcoal.
Fifthly. The carbonized tan may be used for fuel either alone or
combined with other substances.
Sixthly. The carbonized tan may be reduced to powder and used for
making impalpable black or for making gunpowder.
Seventhly. When thoroughly dried, according to this Invention, the
spent tan may be used in place of dried wood or ligneous or fibrous
substances for the manufacture of paper pulp, statuary, pasteboard,
buttons, or other articles.
Having now explained the nature of this Invention I will proceed to
describe with reference to the accompanying Drawings the manner in
which the same is to be performed.
Figure 1 represents a perspective view of the general arrangement
of apparatus used for the treatment of spent tan according to this
Invention.
a is the furnace for the distillation and carbonization of the spent tan;
b is the furnace door, and c is the ash-pit; d, d, d, are the retorts, of
The said retorts project
which there may be any suitable number.
slightly from the face of the furnace, and the spent tan is charged into
them through the projecting ends of the said retorts, which are then
closed by a plate or door. In the upper side of the projecting end of
each of the retorts d, d, d, is an aperture, in which is fixed a bent tube
or pipe e, which conducts the smoke or vapour produced by the com-
bustion or carbonization of the tan in the retorts to a reservoir or tankƒ
containing water, in which water the ends of the pipes e are immersed to
a depth of about four or five inches. The smoke or vapour from the retorts
contains tar and gas. The tar mixing with the water in the reservoir or
tank falls to the bottom and passes off by the pipef¹. The gas filters
through the water and passes into the pipe f, which conducts it to the

page_text: iron tank g partly filled with water, and having above the water a grating|
on which is placed a quantity of coke g'. The gas passing through the
water in the tank g is further purified of the tar and other matters it
contains. The said tar and other matters are deposited in the water,
whilst the gas passes through the coke g¹, is purified thereby, and then
passes through the pipe g² to a closed chest partly filled with water,
which chest is provided with a series of double refrigerating tubes
h³, h³, h¹, bent in pairs closed at their upper ends and opening at their
lower ends into the closed chest h. The lower end of the pipe g³ dips
into the water in the chest h, and one leg of each of the double tubes /¹
dips also into the water in the chest h, whilst the other leg opens above
the water. 2, 1, are diaphragms. The tan gas passes through the
tubes h³, ½³, and through the water contained in the chest h, and
thence passes through the pipe i to the purifier J, which consists of a
vessel of conical shape tapering slightly from top to bottom, and
provided with a suitable cover. In the purifier j are layers of trellis-
work, one over the other, each layer of trelliswork being covered with a
layer of moss covered over with limic, as indicated at j.
passes through the said trelliswork and the moss and lime, and is
further purified, and thence it passes through the pipe / underground to
the gasometer 1, whence it may be allowed to pass out for use through
the pipe m.
The tan gas
When the tan gas is to be used for heating purposes it is unnecessary
to purify it thoroughly, and it may be taken directly from the water tank
or reservoir without further purification.
Figures 2 and 3 represent arrangements for the introduction of a blast
of air into the retorts for the purpose of carrying off the vapour emitted
by the spent tan in the process of carbonization. In Figure 2 a repre-
sents the retort, and 6 a fan by which a blast of air is forced through the
retort, as shown. In Figure 3 a represents the retort, and b a perforated
pipe or tube through which a blast from a suitable blowing machine is
forced through the retort.
Figure 4 represents a retort a provided with an agitator composed of
a central rotatory shaft b, from which projects a series of arms or blades c,
which arms or blades stir up the tan in the retort and facilitate the escape
of the vapours emitted thereby.
Figure 5 represents a retort a provided with a rotatory agitator b, as

page_text: shown in Figure 4, and receiving a blast of air at e from a suitable
fan.
Figure 6 represents a retort a provided with a hollow rotatory agitator b,
the arms of which agitator are perforated with holes, through which
holes a blast from a suitable fan or blower is admitted into the retort, as
shown.
Having now described the nature of this Invention and the manner
in which the same is to be performed, I wish it to be understood that I
do not limit myself to the precise details herein-before described and illus-
trated in the accompanying Drawing, as the same may be varied without
departing from the nature of the said Invention; but I claim as the said
Invention,―
Firstly. Distilling and carbonizing spent tan and purifying the
resulting gas (either wholly or partially), and obtaining tar and essential
oil and carbon or charcoal as residual products, essentially as described
and illustrated in the accompanying Drawing.
Secondly. Drying or carbonizing spent tan in a retort and passing
through the said tan during the process of drying or carbonization a
blast of air, either hot or cold, essentially as and for the purposes
described.
In witness whereof, I, the said Hunter Henry Murdoch, have here
unto set my hand and seal, this Sixteenth day of October, in the
year of our Lord One thousand eight hundred and seventy-
foun
Witness,
B. WILLCOX,
His Clerk.
H. H. MURDOCH.
(L.S.)