Improvements in Leaching Apparatus, chiefly Designed for the Leaching of Tan-bark.
Year: 1899

page_text: Date of Application, 4th Apr., 1899-Accepted, 2nd June, 1899
[Communicated from abroad by THE VAUGHN MACHINE COMPANY, of Peabody,
Massachusetts, United States of America, Manufacturers.]
Improvements in Leaching Apparatus, chiefly Designed for the
Leaching of Tan-bark.
I, DAVID YOUNG, Patent Agent, of the Firm of D. Young & Co., of 11 and 12,
Southampton Buildings, London, W.C., 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:
This invention relates to an apparatus for leaching, especially designed and
adapted for leaching tan bark, but which is also well adapted for leaching other
materials.
The invention has for its object to provide an apparatus for leaching tan bark,
whereby a maximum amount of tannin may be extracted from the bark in a
minimum time and at a minimum expense.
For this purpose the tan bark is agitated or put in motion as will be described,
and while in motion is subjected to the action of heat and water in a rotatable
vessel or drum, which results in all or substantially all the tannin in the bark
being extracted in a minimum time and at a minimum expense by the water
as it descends or percolates through the mass of tan bark, while the particles of
bark are in motion.
These and other features of this invention will be pointed out in the claim at
the end of this specification.
Figure 1 is a vertical longitudinal or axial section of a rotatable leaching
apparatus embodying this invention.
Figure 2, a transverse section through one of the extract outlets, taken on the
line 4-4, Fig. 1 and looking toward the right.
Figure 3, a similar section through the same extract outlet taken on the
line 3-3, Fig. 1.
Figure 4, a transverse section through the apparatus shown in Fig. 1, the
section being taken on the line 4-4, looking in the direction of the arrow thereon.
Figure 5, a detail of the heating apparatus, and
Figure 6, a detail to be referred to.
In the present instance, I have shown this invention as embodied in a rotatable
leaching apparatus comprising a rotatable drum a having hollow journals a¹ a
and preferably provided with a partition wall or false head a³, which separates
the drum into a leaching chamber at and a liquor chamber a³.
The leaching chamber at is provided with preferably a plurality of separate
outlets for the extract or percolated liquor, and with lifting devices for the tan
bark, and in the present instance said lifting devices form side walls for the
liquor outlets.
The leaching chamber at is provided as hereinshown with six separate liquor
outlets a extended as shown longitudinally or axially of the said chamber and
disposed about the inner circumference of the drum at substantially equal distances

page_text: apart, but this number of outlets may be varied. In the present instance, the
liquor outlets a assume the form of substantially trough-shaped channels, having
side walls a a¹0 and closed at the top by a strainer or screen and as shown at the
bottom by the circumference of the drum.
The strainer or screen referred to, is preferably made as hereinshown and con-
sists of a series of substantially V-shaped bars or slats a¹³ of wood or other suitable
material extended the length of the outlet passage as hereinshown and secured
to the side walls a al⁰ as by bolts or stay rods a (see Fig. 3), the said bars or
slats being secured in position preferably with the base of the V outermost so as
to reduce the size of the entrance for the liquor into the outlet passage and obtain
a better clearing or cleaning action of the extract liquor upon the strainer as will
be described.
The strainer or screen is preferably closed to the passage of the extract at
suitable intervals by substantially V-shaped slats or bars a20, which are inserted
between the slats or bars a¹³ as shown in Fig. 3, and which are held in place by
the stay rods or bolts a¹5.
The bars or slats a 20 serve to re-enforce or strengthen the strainer or screen and
prevent its warping under the influence of heat and moisture, when made of
wood, which is preferred. The length of the slats or bars a is indicated by the
distance between the points 10-12, Fig. 1. The slats or bars a¹ may and
preferably will be supported at their ends and at suitable points throughout their
length by substantially arch-shaped cross-bars a² (see Figs. 1, 2 and 3). The
outlet passages a in the present instance discharge into the chamber a through
holes or openings a25 in the partition wall a³, and the discharge opening a for
each liquor outlet pasage is of less area than the area of the said passage and is
preferably located at one side of the transverse center of the outlet passage as
shown in Figs. 2 and 3, for a purpose as will be described.
The chamber a constitutes a liquor chamber or well, in which the extract liquor
may accumulate, and from which the said liquor may be discharged through the
depending stationary leg 6 of the liquor outlet pipe 61 extended through the hollow
journal a².
The leaching chamber a¹ is provided with a liquid inlet, shown as a substantially
large pipe 63 provided with perforations & in its upper side, and extended to near
the partition wall a³, where it is supported by a spider or frame 65 bolted or other-
wise attached to said partition wall. The liquor inlet pipe 3 is stationary with
relation to the drum as hereinshown and is closed at its inner end by a suitable
stopper or plug 66, through which loosely extends a steam inlet pipe 67, which
passes through the liquid inlet pipe to the outside of the drum as shown in Fig. 1.
The hollow journals a¹ a² are provided with suitable stuffing boxes 68 69, and are
mounted to turn in suitable supports B B¹.
In the present instance, the leaching chamber contains the heating apparatus,
which is closed to the passage of steam into the leaching chamber, thereby avoiding
dilution of the extract liquor, and the said heating apparatus is preferably made
as hereinshown so as to obtain a superior heating of the tan bark and leaching
liquor. The heating apparatus is best shown in Fig. 5, and consists of a two-
way fitting 60 provided with four mouths 2, 3, 4, 5. The mouth 2 has connected
to it the steam inlet pipe 67, the mouths 3, 4, pipes 612, 613, and the mouth 5,
pipe 614
The fitting 610 is located close to the partition wall a³ and the heating apparatus
may be secured to said wall in any suitable manner as by straps 750, so that the
heating apparatus within the leaching chamber may revolve with the drum. The
pipes is are extended to near the circumferential wall of the drum in sub-
stantially diametrically opposite directions, and one of said pipes as 612 is connected
to two branch pipes 615 616 extended substantially at right angles to near the
circumferential wall of said drum, where they are connected to pipes 618 619 extended
longitudinally of the leaching chamber to near the side of the drum opposite to

page_text: the partition wall a³, where they are respectively connected to branch pipes 620, 21
extended substantially at right angles to each other and parallel to the branch
pipes 616, 15, the pipes 60, 62 being connected to a pipe extended longitudinally
of the drum and joined to the pipe 613.
The pipe 6 is extended through the partition wall and into a stuffing box 21
in the liquor outlet pipe 61, where it meets or abuts against a pipe 625 extended
through the said liquor outlet pipe, the pipe constituting the steam outlet pipe
for the heating apparatus.
The steam inlet pipe extends through the liquor inlet pipe into a stuffing
box wherein it meets or abuts against a steam supply pipe 27. It will be seen
that the steam pipes b, are free to turn in the stuffing boxes 626, 621, which
construction permits the heating apparatus within the leaching chamber to revolve
with the drum. The course of the steam through the heating apparatus may be
traced as follows, viz. :-through the pipe 67 to the fitting 610, thence by the
pipe branch pipes 15, 61, pipes 68, 69, branch pipes 620, 62, pipes 62, 613 to
the fittings 610, thence through the pipe and outlet pipe 62. It will thus be
seen that the interior of the leaching chamber is thoroughly heated and that the
heat is well distributed throughout the contents of the chamber, which results in
a more uniform and superior heating of the tan bark and leaching liquor, thereby
quickening the leaching process.
The heating apparatus referred to, creates a steam pressure within the drum
and to prevent this pressure exceeding a predetermined point, the drum may
be provided with preferably a series of vent openings normally closed by relief
valves of any suitable or desired construction, which may operate automatically
or which may be positively operated, which latter method of operating said valves
is herein illustrated.
In the present instance, the vent openings are made in the circumferential wall
of the liquor chamber a³, and each of said openings is controlled by a valve d
normally seated by a spring encircling its stem d², which is extended outside
of the drum, and, as shown, is adapted in the revolution of the drum to meet an
actuating device shown as a bar, which acts in the nature of a cam to open
the relief valve and maintain it open until in the travel of the drum the valve
stem is removed from engagement with said bar or cam, whereupon the
spring closes the valve.
The false head or partition wall ³ may and preferably will be provided with
a suitable manhole normally closed by a door 10 (see Fig. 4) through which access
may be had to the liquor chamber; and the leaching chamber may be entered
through a suitable manhole in its circumferential wall, which is normally closed
by a cover or door d¹ and preferably said leaching chamber will be provided with
two manholes substantially diametrically opposite.
In operation, tan bark preferably in a fine or comminuted state, is placed in
the leaching chamber until the latter is preferably substantially two-thirds full;
and water or a weak leaching liquor is then admitted into said chamber through
the liquor inlet pipe a³, from which the said leaching liquor passes upward into
the leaching chamber through the perforations 6 in said pipe, and preferably
fills the space above the mass or body of tan bark. Steam is then circulated
through the heating apparatus and the drum is set in motion, which may be
accomplished in any suitable manner, as for instance by suitable chains 20" (see
Fig. 6). The leaching liquor percolates down through the mass of tan bark and
the extract or percolated liquor passes through the strainer or screen of each
outlet passage, and in the construction hereinshown flows through said passage
into the liquor chamber, from which it may be drawn off through the liquor
outlet pipe by a suitable pump not hereinshown, by means of which a continuous
circulation of the leaching liquor through the tan bark is effected.
As the drum revolves, for instance, in the direction indicated by arrow 40,
Fig. 4, a portion of the lower part of the mass or body of the tan bark, is carried

page_text: up with the drum by the lifting devices, which in the present instance, are the
side walls of the outlet passages for the leaching chamber, and the bark thus
lifted is carried above the upper surface of the mass of bark and discharged upon
the upper surface of the said mass, passing down through the body of leaching
liquor which rests upon the mass of bark.
As the lower portion of the mass of bark is elevated as described, the mass or
greater part of the bark descends by gravity into position to have another portion
lifted by the next lifting device. it will thus be seen that the mass of tan bark
is put in motion so that all its particles are exposed to the action of the leaching
liquor, while at the same time, the greater portion of the bark is maintained in
a compact form and presents a body of substantially uniform density, so that
the leaching liquor percolates through the bark at a uniform rate, which results
in a maximum extraction of the tannin matter in a minimum time at a minimum
expense, and with a uniform strength of extract liquor.
By reference to Fig. 4, it will be seen, that the discharge opening a for the
liquor outlet passage a is located at one side of the transverse center of said
passage, which construction is preferred, as a substantially large amount of the
extract or percolated liquor will remain in the outlet passage a' and will he
discharged back into the leaching chamber when the outlet passage has been
carried to a sufficient elevation.
When the extract or percolated liquor is thus discharged back into the leaching
chamber, it passes through the screen or strainer in a reverse direction, and
thereby washes the strainer clean and removes any of the fine bark, which might
clog up the outlet passage, so that when this outlet passage is again brought
under the mass of tan bark a free outlet is afforded for the extract.
In other words, the outlet passage for the extract liquor is self-cleaning, and
the V-shaped spaces between the bars or slats facilitate the cleansing action of
the extract liquor discharged back into the leaching chamber.
From the above description, it will be seen that the tan bark confined in the
leaching chamber a, and the leaching liquor therein, are subjected to heat in
a closed chamber, which facilitates increased extraction of the tannin, avoids
loss of heat and tannin matter by evaporation, thereby economizing in the cost of
leaching. Furthermore, it will be noticed that the rotary motion of the drum
and the lifting devices attached thereto, serve to tumble or agitate the comminuted
tan bark, and thus expose all particles of bark to the action of the leaching liquor;
prevent the bark from packing thereby enabling fine bark to be used; and avoid
the formation of channels down through the mass of bark, which would result
in an imperfect leaching.
°
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondents, I declare that what I claim is:
1. A leaching apparatus comprising a rotatable normally closed drum to
contain the material to be leached, a partition wall or false head within said drum
to form a leaching chamber and a liquor chamber or well, means to effect com-
munication between said chambers near the circumference of the drum for the
passage of the extract or percolated liquor from the leaching chamber into the
liquor chamber, a liquid inlet for the feaching chamber, and a liquid outlet for
the liquor chamber, for the purpose specified.
2. A leaching apparatus comprising a rotatable drum provided with an inlet
opening for the material to be leached, a partition wall within said drum forming
a leaching chamber and a liquor chamber or well, a strainer interposed between
said chambers near the circumference of the drum, a liquid inlet for the leaching
chamber, and a liquor outlet for the liquor chamber, for the purpose specified.
3. A leaching apparatus comprising a rotatable normally closed drum provided
with a leaching chamber to contain the material to be leached and with a liquor

page_text: chamber in communication with the leaching chamber near the circumferential
wall of the drum for the passage of the extract from the leaching chamber into
the liquor chamber, substantially as described.
4. A leaching apparatus comprising a rotatable drum to contain the material to
be leached, a liquid inlet for said drum, a stationary outlet pipe for the extract
or percolated liquor having a leg within the drum extended to near the circum-
ferential wall of the drum, and a strainer interposed between said liquid inlet and
the leg of said outlet pipe.
5. A leaching apparatus comprising a rotatable drum to contain the material
to be leached, a lifting device attached to said drum on its inner side, a heating
apparatus within the drum, a liquid inlet, a liquid outlet for the drum, and a
strainer interposed between said inlet and outlet near the circumferential wall of
the drum, for the purpose specified.
6. A leaching apparatus comprising a rotatable drum to contain the material
to be leached, and provided with means within it for lifting a portion of the
said material, a liquid inlet for said drum, an outlet for the extract liquor, and a
strainer interposed between said inlet and outlet near the circumferential wall
of the drum, for the purpose specified.
7. A leaching apparatus comprising a rotatable drum to contain the material
to be leached, and provided with means within it for lifting a portion of the
said material, a liquid inlet for said drum, an outlet for the extract liquor, a
strainer interposed between said inlet and outlet near the circumferential wall of
the drum, and a heating apparatus within said drum for the passage of the
heating medium through the drum out of contact with the material to be
leached.
S. A leaching apparatus comprising a rotatable drum having a partition wall
forming a leaching chamber and a liquor chamber, and provided with a liquid
inlet for the leaching chamber and with a plurality of separate outlets located
within the leaching chamber near the circumferential wall of the drum to move
with the same and pass below the body of material being leached for the passage
of extract or percolated liquor from said leaching chamber into said liquor cham-
ber, strainers for said outlets affixed to the drum to pass below the said body
of material, and means within the leaching chamber to lift a portion of the material
to be leached, substantially as described.
9. A leaching chamber comprising a rotatable drum having a partition wall
forming a leaching chamber and a liquor chamber, and provided with a liquid
inlet for said leaching chamber, and with a plurality of separate outlets located
within the leaching chamber near the circumferential wall of the drum to move
with the same and pass below the body of material being leached for the passage
of extract or percolated liquor from said leaching chamber into said liquor chamber,
strainers for said outlets affixed to the drum to pass below the said body of
material, means within the leaching chamber to lift a portion of the material to
be leached, and a heating apparatus within said leaching chamber, substantially
as described.
10. A leaching apparatus comprising a rotatable drum to contain the material
to be leached provided at its periphery with a strainer affixed to the drum to pass
below the body of material being leached and covering an outlet passage for the
extract, having a separate discharge opening for said extract, and means within
the drum to lift the material being leached, substantially as described.
11. A leaching apparatus comprising a rotatable drum to contain the material
to be leached, provided with a liquid inlet, and with a liquid outlet passage having
side walls projecting inwardly from the inner circumference of the drum and
having a discharge opening for the extract from said passage, and a strainer
covering said outlet passage, substantially as described.
12. A leaching apparatus comprising a rotatable drum provided with a partition
wall forming a leaching chamber and a liquor chamber, and having an outlet

page_text: passage for the extract from the leaching chamber into the liquor chamber,
extended longitudinally of said drum within said leaching chamber, a strainer for
said outlet passage, and a liquor outlet for said liquor chamber, substantially as
described.
1 11
1
1000
D. YOUNG & Co.,
11 and 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.