Recovery of Chemicals from Spent Liquors of Pulp Digesters.
Year: 1887

page_text: Recovery of Chemicals from Spent Liquors of Pulp Digesters.
We JOHN EBENEZER WARREN, Agent, and FRANCIS AUGUSTUS CLOUDMAN, Foreman,
both of Cumberland Mills, Maine, in the United States of America 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 or furnace for reclaiming chemicals from the
spent liquors of pulp mill digesters, the said apparatus comprising an evaporating
chamber, a combustion furnace and a rotary calcining furnace between the said
evaporating chamber and combustion furnace.
One of the features of our invention consists in providing the evaporating chamber
with preferably a series of screw conveyors located near the bottom or hearth of the
said chamber and by means of which the liquid, which in most cases will be in a
sirupy consistency when it reaches the bottom of the said chamber, may be fed
forward toward the inlet to the rotary calcining or incinerating furnace.
Our invention further consists in providing the rotary calcining furnace with an
agitating device, herein shown as a screw-conveyor, or worm, by means of which the
soda or other chemical therein may be detached from the walls of the said furnace,
thereby preventing the inner walls of the furnace from becoming coated or lined with
chemicals.
Another feature of our invention consists in providing the combustion furnace, near
the outlet of the calcining furnace with a hollow throat, adapted to have the spent
liquor circulated through it before entering the evaporating chamber, the said spent
liquor serving to somewhat cool the said throat, thereby permitting the latter to be
made of iron and to be projected into the outlet of the rotary caleining furnace, iron
being the most desirable material from which to construct the said throat, but which
could not be used to advantage hitherto on account of the intense heat in the fire
chamber, the iron, if used in furnaces made hitherto without the hollow throat having
liquid circulating therethrough, being burnt out in short time, thereby rendering
necessary repairs, which occasioned delay and expense

page_text: Figure 1 is a longitudinal section of our improved apparatus for reclaiming
chemicals in spent liquors from pulp digesters.
Figure 2 a section on line a-a, Figure 1, and
Figure 3 a sectional detail showing the form of the hollow iron throat, the section
being taken on the line ac, looking toward the right.
The rotary calcining furnace A as shown is provided with tracks a, running on
pulleys a and is located between the evaporating chamber A¹ and the combustion
furnace A².
The combustion furnace A² constructed in the main of brick or other refractory
material, is provided with a hollow throat a² made of iron, the said hollow iron throat
projecting into the axial outlet of the calcining furnace and being shaped as a
segment of a circle to form, for the product in the caleining furnace, a discharge
passage between the chord of the segment and the axial outlet of the said calcining
furnace, as shewn in Figure 3.
The hollow iron throat a² has connected to it near its bottom, a pipe a³ communi-
cating, as shown with the bottom of a tank or reservoir B to contain spent liquor, the
said hollow iron throat having connected to it near its top a pipe a extended into the
evaporating chamber A', the said pipe a being shown as extended to near the rear
wall of the said evaporating chamber.
The spent liquor containing the chemicals to be recovered flows from the tank B
through the pipe a³ into the hollow iron throat, from which it passes through the
pipe a into the evaporating chamber, it falling upon a tray 63, thence upon a second
tray arranged zig-zag to cause the liquor to pass over a large evaporating surface,
the said liquor descending from the tray 4 upon the bottom of the evaporating
chamber.
As the liquor circulates around the hollow iron throat it is heated and the iron of
the said throat is cooled sufficiently to prevent it from being burnt out.
The liquid issuing from the pipe a' is heated on its passage around the hollow iron
throat, so that it readily yields up its water as it flows through the chamber A',
thereby hastening the evaporation of the said liquid, so that when it reaches the
bottom of the said evaporating chamber it is substantially of a sirupy consistency.
The sirupy liquid on the bottom of the evaporating chamber is fed forward from its
rear end toward the discharge or outlet c of the said chamber, by means of screw
conveyors c driven by a belt, not shown, but which is passed about pulley c² at one
end of the said screw conveyors outside the evaporating chamber.
The discharge or outlet passage e is controlled by a valve or gate; herein shown as
a plug attached to an arm 2 of a crank shaft, e13, which projects through the walls
of the evaporating chamber, and receives a crank or handle not herein shown by
which the said valve may be operated.
The sirupy liquid fed into the rotary chamber A is calcined therein, and in order
to prevent the soda or other chemical salts from adhering to the inner walls of the
said calcining furnace, an agitating device is located therein.
The agitation device is herein shown as a screw conveyor or worm d which is
independent of the calcining chamber and is free to move therein.
The screw conveyor or worm d normally rests upon the bottom of the calcining
furnace, and as the latter is rotated the said screw conveyor or worm is carried up on
one revolution to a certain distance when it falls back again.
The screw conveyor or worm serves to cut off or detach the soda or chemical salt
adhering to the inner wall of the calcining furnace, the said screw conveyor or worm
at the same time feeding the soda or other chemical salt in the furnace forward toward
the outlet, the said soda or other chemical salt passing from the calcining furnace
between the chord and axial outlet and into a suitable receptacle, not shown,
located beneath the said discharge or outlet or the said soda may be discharged
directly upon the floor.
The soda or other chemical salt in the calcining furnace is freed from organic
matter, which is burnt off by the products of combustion from the furnace A², they

page_text: passing through the calcining and the evaporating furnaces to the chimney, not
shown.
Instead of the screw conveyor or worm d, we may employ any other agitating or
detaching device, such for instance, a harrow provided with teeth to scrape the
adhering salt from the walls of the furnace.
The combustion furnace inay be made stationary or movable with respect to the
calcining furnace, as desired.
As shown in Figures 2 and 3, the chord b is made in two parts, forming an angle
between them to enable the water leg or throat to be more clearly shown, but in
practice the chord will preferably consist of but a single straight line or part."
Having now particularly described and ascertained the nature of our said Invention,
and in what manner the same is to be performed, we declare that what we claim is :-
1. In an apparatus for recovering chemicals from the spent liquors of pulp digesters,
the combination with a rotary calcining furnace, of a combustion furnace provided
with a hollow throat a² extended into the rotary calcining furnace and adapted to
have the spent liquor passed through it, substantially as and for the purpose specified.
2. In an apparatus for recovering chemicals from the spent liquors of pulp digesters,
a rotary calcining furnace, combined with a loose agitating device located therein, and
independent of the said calcining furnace whereby the recovered chemicals are
prevented from adhering to the inner walls of the said furnace, substantially as
described.
3. In an apparatus for recovering chemicals from the spent liquors of pulp digesters,
a combustion furnace, a rotary calcining furnace and an independent evaporating
chamber, combined with a screw conveyor located near the bottom of the said
chamber to feed the material forward toward the calcining furnace, substantially as
described.
4. In an apparatus for recovering chemicals from the spent liquors of pulp digesters,
a rotary calcining furnace, a combustion furnace provided with a hollow iron throat
extended into the calcining furnace, combined with an evaporating chamber provided
with screw conveyors located near the botton thereof to feed the chemicals forward
toward the calcining furnace, substantially as described.
5. In an apparatus for recovering chemicals from the spent liquors of pulp digesters,
a rotary calcining furnace and an independent agitating device located therein, a com-
bustion furnace provided with a hollow iron throat extended into the calcining furnace,
combined with an evaporating chamber provided with screw conveyors located near
the bottom thereof, to feed the chemicals forward toward the calcining furnace
substantially as described.
6. In an apparatus for recovering chemicals from the spent liquors of pulp digesters,
the combination with a rotary calcining furnace, of a combustion furnace provided
with a hollow throat a extended into the rotary calcining furnace and capable of
containing a fluid, as and for the purpose specified.
7. In an apparatus for recovering chemicals from the spent liquors of pulp
digesters, a rotary calcining furnace, a combustion furnace provided with a hollow
iron throat extended into the calcining furnace, a tank B connected to the said
hollow throat, combined with an evaporating chamber also connected with the said
hollow throat, whereby the spent liquors are circulated around and heated in
the hollow throat before entering the evaporating chamber, substantially as described.
Did the 5th of An 1287
WM. BROOKES & SON,
55 & 56, Chancery Lane, London,
Agents for the Applicants.