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oa. 29,1946.
Filed June 27, 1945
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Patented Oct. 29, -_1946
Watford A. Reaney, Delaware, Ohio
--Applìcation June 27, 1945, Serial No. 601,763
vs' cnims. (ci. 263-22)
heating ,air employed in
2 sustaining fuel com
This invention relates to an improved process
and apparatus adapted particularly for effecting
bustion within the kilns.
the calcination of calcareous materials, such as
The present invention constitutes a continua
tion-in-part of the disclosures set forth in my
limestone, marl or the like, a general object of ,
priorapplication, Serial No. 491,962, ñled June
the invention being to-provide a new and im
proved process and apparatus by which such
calcination may be carried out with greater
thermal efüciency .than heretofore has been ob
A further understanding of the invention will
be obtained by reference to the following descrip
tion and the accompanying drawing.
. In the production of lime from limestone. it 10
In said drawing:
is'the ordinary practice to pass limestone through
arotary kiln. While inthe kiln, the'limestone
is iired to temperatures in the order of 1400. to
' Fig. l illustrates in schematic form a typica
system for carrying out the invention;
2000 degrees F.
fied form of heat-exchanging pit.
Fig. 2 is a detail view showing a slightly modi
Such burning of the limestone
liberates its-carbon dioxide content, leaving cal
gThe apparatus disclosed in the accompanying
drawing comprises ‘a pair of kilns, indicated at
I and 2, said kilns bein-g preferably of the rotary
drum type. The drum of leach kiln is mounted
as usual, with its longitudinal axis slightly an
gree _of iineness suitable for various uses. In
this customary operation, the heat contained in 20 gular to the horizontal, each drum being sup
ported and rotated by conventional means. The
the calcinedv lime is lostvto the atmosphere and
upper or material-receiving end of each of the
is notV applied to any useful purpose. v
kiln drums enters a vertical flue orwaste gas
¿_gAccordingly, it is another object of the> inven
outlety stack, shown at 6, the lower portion of
tion to utilize more efûciently the available> heat
each stack being provided with a limestone re
in hot calcined lime by bringing the latter, im
ceiving chute 1. Partially crushed limestone, for
mediately uponY its discharge, from a calcining
example, of such particle size that it will pass
kiln into direct and intimate contact with'an
through a 21/2 inch to 11A; inch mesh screen, is
unheated body of limestone being charged to a
delivered to the chute ’I of the kiln Iv in a manner
calcining operation so that the charging material
willbe preheated by contact withthe hot lime A’ hereinafter dei-ined. while crushed limestone of
finer particle sizesuch as that which would pass
before being introduced into thecalcining kiln.
through ascreen of 1 inch to 1/'2 inch mesh is
y It is still another object of the present in
delivered to the inlet chute 'I of the kiln 2. The
vention to provide a lime-calcining system in
hot lime discharging end of each kiln is provided
which two or more rotary kilns are arrangedmin
with a `fuel burner 8 and the fan or blower 9
adjacent order with> the positions of their ma
of each of these burners has its air inlet side
terial-receiving and discharging ends y reversed
connected with a duct system I6. A portion of
with respect to each other, so that- the hot lime
this system, forming a heat exchanger Illa, is
discharged from one of said kilns may be con
disposed in each of the stacks 6, so thatI the
veniently brought into direct contact with cold
limestone being fed as a charging* material to 40 air r'employed forv fuel combustion purposes in
the kilns will be preheated by the waste gases
the inlet end of the other Of, said kilns.
for more eilicient utilization in thekilns.r
¿i A further object is to provide a system of this
cium oxide or lime as the calcined product. The
heated lime upon its discharge from the kiln is
cooled and thereafter crushed to a required de
character in uwhich crushed limestone ofÍi-lne
AThe outlet end of each kiln is formed With a
lime-discharging chute II, the latter being ar
mesh is employed as a charging material for one
of the duplex kilns and a coarser >lime fed as the 45 ranged over a pair of mixing pits shown at I2
and I3 in order that the hot lime discharged
charging material to the other kiln whereby,
from said kilns may be directly received Within
through a screening operation, »to provide for the
saidpits. The hot lime of coarser particle -size
separation of ñnished lime from the kiln-charging
discharged from the kiln 2 is received in the pit
limestone following heat-exchanging admixture
I3, andis there brought into heat exchanging
contact or relationship with crushed cold lime
_' Still, a `further object of the invention is to
stone of ñner particle size. By this operation,
provide a >lime-calcining system in 'which' ad-y
the temperature of the limestone is raised to pre
ditional-heat economies are obtained by dispos
heat the ñne limestone before it is introduced
meiner-adjacent i0: the Combustioaeas. Outlet.
iiiioiheiraletchgte orthgkiln I» ._ ..
of the kiln a heat exchanging meansgfor. p_re-`
two kilns serves to preheat the fuel and intake
After such heat exchange has taken place, the
combustion air of each opposite kiln.
coarse lime is separated -from the smaller sized
particles of preheated limestone. Advantage
ously, this may be accomplished by providing the
I claim:
1. Process for heat-treating materials, which
comprises advancing a stream of materials of
relatively coarse particle size through a coniined
pit I3 with a conveyor type elevator I4, the upper
or discharge end I5 of this elevator being dis
posed in registration with an inclined screen I6,
heating zone, simultaneously therewith advanc
ing a second stream of materials of relatively
iiner particle size through a separate heating
heated limestone will pass through the meshes 10 zone, bringing the heated materials discharged
from each of said zones into direct heat-exchang
of the screen for delivery to the inlet chute of
so that as the mixture of coarse lime and ñne
limestone passes over the screen, the íine pre
The coarser lime gravitates to the
ing and preheating relationship with previously
lower end of the screen and from that point is
conducted in any suitable mannerto aposition
unheated materials of a particle size diiîering
from that rof both said streams of materials
the kiln I.
of storage.
A corresponding arrangement is provided for
introducing the coarse limestone into the kiln 2.
destined for delivery to each of the other zones,
and separating the preheated materials from the
finally heated materials prior to the introduction
of the preheated materials into their respective
Coarse limestone in an unheated state and at a
heating zones.
controlled rate of ilow is dropped into the pit I2
from a valved spout I1, where the coarse lime
stone comes into intimate heat exchanging rela
tionship with the hot lime of iine particle size
discharge‘d‘from the lime outlet II` of 'the kiln I.
As this-mixture of lime and limestone cf 4dii?
ferent particle size gravitates to the bottom of
the pit I2, the same is engaged by the conveyor
elevatorv I9 andliftedithereby for deposit on an
inclined screen 2S.
2. Process for heating dry bulk materials dif
fering >in particle size which comprises advancing
a stream of materials ’of relatively coarse particle
size through a conñned heating zone, simultane
ously >therewith ‘advancing’ a `second stream of
such materials possessing a iiner particle size
through a separate heating zone, bringing the
heated materials discharged from said'zones finto
direct heat-exchanging and preheatingrelation
The mesh of this screen is
ship with the unheated materials undergoing
such that as the mixture passes thereover, the
calcined lime of fine particle size will pass through 30 charging advancement to said zones, and screen
ing the preheated zone-charging vmaterials from
the screen for delivery to storage as a finished
the finally heated'materi'als prior to the intro
product, while the preheated coarse limestone
duction of said charging materials into their >re
will be discharged from the lower end of the
spective heating zones.
screen 2Q into the inlet chute‘of the kiln 2.
Thus, by utilizing the dual kilns, each handling
3. Process for heat treating loose bulk granular
limestone of determined particle size and differ
ing from that handled by the other, I am enabled
to obtain thermal eñiciencies and economies sub
stantially in excess of systems now in general
materials dii'îering in particle size which com
prises advancing a stream of 'such materials com
posed of 'relatively large or coarse particles
uselfor the purpose set'forth.
through a heating kiln, simultaneously therewith
40 advancing a second stream of such materials
Thus the hot lime, while it possesses its high
est temperature, and immediately upon its dis
charge from the kilns, is brought into intimate
admixture with the charging limestone, usefully
possessing relatively smaller Íand finer particle
size through a second heating kiln, bringing the
ñnally heated materials discharged from each ci
said kilns into directheat exchanging relation
absorbing’the heat of the lime and minimizing ‘
heat losses in a system of this kind. Another
ship with the previously unheated charging ma
terials undergoing delivery to each of said kilns,
and following such commingling of the heated
advantage accruing from the dual and reversely
unheated materials, separating the charg
disposed kilns is the fact that combustion air,
ing materials from the finally heated materials
used in sustaining fuel combustion, may be ef
fectively preheated in the gas outlet stack of each 50 and delivering the preheated charging materials
to their respective kilns.
kiln and by a short transfer line delivered to
4. Process for burning limestone, comprising
the-fuel burner of each adjacent kiln. If the
placing limestone of relatively coarse particle
dual kilns were not used, the transfer line for
size’through a kiln which is maintained at such
the preheated air would necessarily extend the
temperatures as to effect calcination of the lime
full length Vof a single kiln, and heat losses there
stone, simultaneously therewith passing lime
fore would be such as to render the air-pre
stone of relatively fine >particle size through a
heating element ineiiicient.
second kiln maintained at calcination tempera
As shown in Fig. 2, the bottom of the heat
tures, admixing the hot calcined lime of coarse'
exchanging pits, in which a bed of heat-exchang 60 particle `size immediately upon itsv discharge from
ing lime and limestone is maintained, may be
said ñrst kiln with quantities of unheated lime
funnel-shaped to> maintain intimate ' engagement
stone of ñne particle size and which servesas the
between the hot lime and limestone, and the
charging material for the second-named» kiln,
restricted outlet 2i of the pit may be arranged
subjecting said admixture to a screening opera
immediately over the table of a vibratory feeder 65 tion to remove in'a separated state the preheated
23, by> which the heated materials maybe fed'by
limestone of ñne particle size, delivering such
a controlled feed to the elevator.
preheated fine limestone to the inlet ofthe sec
ond-named kiln, admixing with the hot calcined
invention provides a system or mechanical proc
lime of iine particle size discharged from said
ess whereby hot burned lime, discharged from 70 second kiln with bodies of unheated limestone
each of two rotary kilns placed in adjacent order
of coarse particle size», screening said last-named
with their material-receiving and discharging
admixture to remove the calcined lime of fine
ends reversed, acts as a preheating medium for
particle size therefrom, and delivering the _pre-_
In summary, it will be evident that the present
the cool limestone charged to each opposite kiln,
and whereby the ñue kor-stack gases >of each ofthe
heated coarse limestone to the inlet o‘ffsaid'ñr‘st
named kiln.A
5. Process for heat-treating loose bulk mate
rials, which comprises advancing a stream of
such materials composed of particles relatively
coarse in size through a confined heating zone,
simultaneously therewith advancing a second
stream of such materials composed of particles
of finer size -through a separate heating zone,
admixing with the hot coarse materials im
mediately upon their discharge from the first
6. A process of heat treating materials as de
ñned in claim 5 and wherein the material streams
advancing through the separate heating zones
move longitudinally in opposite directions with
respect to each other.
7. A process whereby hot burned lime dis»
charged from each of two rotary kilns placed in
juxtaposition with their receiving and discharge
ends reversed, acts as a preheating medium for
named heating zone quantities of unheated ma-- 10 the charging limestone of each opposite kiln, and
whereby simultaneously the llue gases of each
terial of fine particle size, the latter constituting
of the two kilns so placed acts as the preheating
the charging material for the second heating
element for the fuel and intake combustion air of
zone, following heat exchange between said ad"
each opposite kiln.
mixed materials screening the same to separate
8. In combination, a pair of juxtaposed, cylin-v
the heat treated materials of coarse particle size 15
drical kilns disposed with the material receiving
from the preheated liner materials and deliverend of one kiln adjacent the material discharg
ing the latter to said second-named heating zone,
ing end of the other, a fuel burner of the blast
admixing with hot materials of ?lne particle size
type at the material discharging end of each
immediately upon their discharge from the said
second-named heating zone quantities of un» 20 kiln, a stack at the material receiving end of
each kiln, and an air conduit in heat exchange
heated coarse material to preheat the latter ma -
terial, prior to its delivery to the inlet side of the
first-named heating zone, and screening said last»`
named admixture to remove therefrom the heatedr
relation with the gases passing through the stack
of each kiln, said conduit delivering air directly
to the burner of the other kiln, whereby such air
material of fine particle size and delivering the 25 is preheated, and travels over a relatively short
preheated material of coarse particle size to the
first-named heating zone.
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