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Патент USA US2119601

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VJune 7,l 1938.
2,119,601 l
Filed Sept. 1l, 193€
Patented June 7, 1938
A 2,119,601
William Raisch, New York, N. Y., as'signor to
Underpinning ¿tY Foundation Co., Inc., New
York, N. Y., a corporation of New York
Application September 11, 1936, .Serial No. 100,282 y
10` claims. (ci. 11o-_12)
The present invention relates to the treatment or valves adapted to discharge material to the
of material including a step of burning or roast
next lower hearths and at the same time to pre- >
ing, and more particularly to treatment in which vent the passage of gases through the correspond
moisture and volatile constituents are driven oiî
by heating in a preliminary stage of operation
and the solid residue is roasted or burned.
The principal objects of the invention are to
provide novel, advantageous and eflicient appa
ratuses and processes for effecting treatment of
this kind. An important feature- of the appara
tus resides in providing a multiple-hearth fur
nace, in which the material is fed downwardly
from hearth to hearth through outlets for said
hearths, with material-feeding devices or valves
at certain hearths to pass the material through
the corresponding outlets while preventing the
passage of gases. In this Way the zones of treat
ing outlets.
Preheated air is admitted to the burning sec
tion and hot gases drawn from this section are
passed through the uppermost and drying sec
tion to dry the material preparatory to burning.
The gases are cooled considerably in the drying
zone and mixed with vapors and then passed 10
to the lowermost or deodorizing zone. Not all
of the hot gases are passed to the drying zone,
the rest of them being passed to the lowermost
or deodorizing section and serving to raise the
temperature of the gases from the 'drying sec
tion.> To»k assure complete combustionV of the
gases, additional heating for the lowermost sec
ment, corresponding to the _compartments over tion may be provided, as by the use of one or ,
the. various hearths„may be separated into groups more iìuid fuel burners. The proportions of the
of zones, between which there is no direct passage vhot gases 'passing from the burning section to 20V
of gases, for example an uppermost drying group, the drying section and to the deodorizing section
an intermediate or central group and a lower
most deodorizing group.
Correspondingly the
furnace would include an uppermost drying sec
tion, a central burning section and a lo-wermost
final combustion and deodorizing section.
Other features relate to the use of part of the
combustion gases from theburning section to as
sist the drying operation in the drying section and
20 the ñnal burning in the lowermost section, to the
treatment of gases and vapors from the drying
section in the lower section for final burning and
deodorizing, and to the manner in which heat
from one part is` utilized in another.
>While applicable to Vthe treatment of various
materials, the present invention is particularly
adapted for the disposal of waste material such
as sewage solids in the form of sludge or screen
ings having a high moisture content.
In carrying out the invention, especially as ap
plied to the disposal of sewage solids, use may
be made ofy a multiple-hearth furnace compris
ing vertically spaced hearths with outlets at the
center of one and the periphery of the next and
vice versa, and rabbling means comprising a hol
low shaft and rabbling devices extending there
from over the hearths and arranged so as to work
may be varied-as required. Preferably'the draft
in the burning zone and theV drying section is
concurrent with the movement of material in
these zones and in the lowermost section is coun
in supplying tothe burning section air preheated
in the portion of the hollow shaft passing through » 30
the deodorizing section and part of the burning
section. If desired, burners may be used in theV ì
drying hearth and of course in the burning Zone.
« The gases may be discharged from the >lower
most or deodorizing section in any suitable man
ner, as by means including a suction fan con
nected with the outlet of the deodorizing section. 40
There maybe a considerable quantity of heat
in the gases-drawn from the deodorizing section
and this may be 'recovered to a considerable ex
tent, as by passing the gases through a waste
heat boiler installation.
Obviously the raising of temperature, to `pro
which they are associated.
siderable readily combustible be mixed with the
less combustible sewage solids, the amount of
supplementary fuel to be used may be reduced
substantially. In some cases such additional
tion, a central or burning section and a lower
most or `deodorizing section. Such division of
the furnace may be effected by selecting certain
55 hearths and providing at their outlets devices
duce burning in some parts, may be eiîected by
use of other kinds of auxiliary fuel. Also, if con;
ner as by utilization of natural draft. Prefer
ably, however, the draft or flow of gases through
the furnace is established in any suitable man
the material to the outlets of the hearthsV with
For better control inv operation, the furnace
may be divided into an 4uppermost; or drying sec
tercurrent to the'flow of material.
Preferably the hollow shaft operating` the rab
bling devices over the various hearths is utilized
combustible material, such as ñne coal or paper,
may be mixed with the sewage solids in con
nection witha screening operation, or in a set
¿ 2,119,601Y
"tling tank, or in connectionrwith'dewatering theVv most
drying section, a central burning sectionY c ‘Í ,
V,and a lowermost section ini-which combustion` ~
sludge by use of añlter.V
Other objects,` features'and advantages vvill ap-Y I of the gases and'other materials'is completed and " Y
' fpear upon consideration of the following descrip
Yoffensive ‘odors areeliminated; VTorthis Yendrthel
Vtion and'- of the /draWi/ngin which the Vligure isV ' hearth I4 may be used to separatejthe'drying
pa~sectional elevation illustratingV an `rapparatus „ section from thercentral burning section, and the
embodying a preferred form of the invention.v 'Y hearth I8 maybe used to separate the central
burning Zone from the lowermost deodoriz'ing Vsec
Referring to the drawing'the invention may be
In orderY to prevent the floWv of gases"
hearth furnace II)y having 'a topY I I,«hearths I2 toV Ythrough the outlets 26 ofsthe hearths I4 andi-I8,
Y Yembodied in an Yappzu‘atusr including a ,multiple-'1
v tion.
20 inclusive, and a peripheralY Wall 2| in whichY Vthere
»valve or
be device
4I which
at eachpermits
of these
a Y j, '
Vthe top'and hearths are supported. Material isY
Y deposited on the uppermost hearth I2 Vthroughra -of thel solid. material Y¿but prevent'sgrrthe passage
hopper 22, and a chute'23 extending through the offgases‘ throughthe'correspondingV outlet 26.'.
Preferably each'feed device 4 IÍV is ofA the screw
top' II of the furnace andprovided‘f'vjvitha pivoted l U
feed ¿typerendYY comprises 'agconveyor- screw V42>
doorV or gate
of 24l
a Weighted
normally arm'
l'íeld 25.1;As
soon as a` - which Working in a suitable’casing Vcarries ythe '
material, Zdropping{through 'theV correspondingV
opening 25,'along for a substantial‘distance to an :Y
counterbalancing _action-ofv the arm 25, collects ony ’ «outlet
Where Vit drops to> a lower casing'containîng'. 20V
sufficient amount vof material, _togoyercomethe
theidoor 24, the dooror gate'swings downwardlyY
>about its pi
a conveyor ’screw 43 Ywhich moves the materialin..
otalsupport and the/«materialen the
the opposite >direction-andV discharges it intoî the il. n
„ door falls tothe hearth-I2.
neX't'loWe'r' compartment.; The Vconveyor screwsV i
J In» orderthat the matenal on each hearth may,
in connectionk with agitation thereof, be¿brought ’ 42 and> 43 maybe caused to move in oppositedi-~V>
rectionsï byintermeshing gears 44 mounted on.
v25 into a layer’Y-and-‘gradually fed downwardly to a
. their‘respective shafts 45Vîand 46. » As indicated
lowerhearth orfout> ofthe furnace f_roIrÍ the hearth ' on the dravnngshaft 46'may be drivenfrom any v
20 whichV forms the/bottom ofïfthelfurn'ace, eachY suitable source of poWer.Í VIt will be evident that
' a of theïhearthsrl?, I_4’,ÍI 6, I8 and V2l) may be provided the
material"passingthrough"the feed Ydevices orVir
Withjone or more discharge openings or'outlets
valves 4I serves to Íprevent the flow Aof gases
26¿adjacent to its periphery, and the hearths I3,
¿I_5¿, IA'Il and .I9A may beípro‘videdat their central
portironsrvvithl outlets, preferably in the formV of
through these devices.MVK
rlî'heV hot gases ,ofA combustion from the burning
section Aare useddirectly in drying theV material
_suppliedtto the ulîwperrnost«V or-'drying section.
¿The agitation ofthe material on the hearths Preferably
preheated` airV is supplied Vto Vtheburîn
and- the movementv ¿of Y_the materialY toward- the
' ’Y
ing section, as already describedjrom the hollow,
Vertical shaftix29> throughoutlets 40Yin the upper ' "
V’discl‘large openingsfor outlets Ymay be effected byVV
providineerereaeh hearth elle >er mere‘rebblìne
devices 2`8`invthe5general ,fformïof an arm?pro-V
gi.; ijecting'radiallyfçfromy'a holloypcentraljshaft. V29
Y >40 .ithat'passes »through the centralpartsfof the> cen-f
'part of the burning section. Theupperendof ,
the shaft 29 mayzbe providedwith adamper' _41 "
Vto `control
the passageV
theV of
air therethrough.
Section,` hot>From
gases."» '
1 fromr the ,downdraft‘i mayv beV passedy throughta- ’
duct 4`8`to the upper compartment ofthe Vdrying ' _
Y with ‘relatively little clearance, eesé Seals Ybeing
provided atl=these ypoints torprevent Ypassagefof
` `gases throughV theseY last-mentioned heartlisVV ad
section. Y
. *During the passageV of thegases downwardly
. through the drying'sectionïthe gases are cooled to
a substantial amountìThe fcooled gases >with
yaporsltaken from'lthe >dried materialare dis
'jacent'the ¿central1shafti2r95 Eachof therrab
ï bling devices~28rfmay»berprovidedwithaatseries of
’charged’from thelo’wïermost compartment intoa-Y
.terial' outwardly @peripheral (Sliscldla,ArgeVV V()rpe'r1ir;l}_3"s ""'äucltßg which dlsëhal‘ges into therlow'rermost com#
~ v2li» lor> inwardlyto central discharge-“openings 271,/ 'lY partmentfofthe Vcleodorizing section.V ¿Here the',
1' ,l »The hearth520,»constitutingthe bottomv of: the . gases rmust ~be ¿raised tok a `much-higher tempera-V Y,
with 'a Chute; 3l equippeel'ïvlìith.Y e' riveted ~ gateY 0r
ture to complete the combustion of kkthe gasesandv è ‘ Y "
' .Í iurnace'may havebut a‘single‘r?outlet 26¿_provided
' eliminate noxiousodor's.
" -
dobrßßfurgedg te closingresitierll by suitable j by’supplying
Thisr rise inhot
effeeted com- Í 1
counterbalancin'g Ymeans such» as aweighted arm
Y .Y 34;*serrving :to holdfthe'door closed'until a suflrì
f; cient Weight». of- materialV has kfallen VonY said Ydoor
3,3 andcausesgit toppen'.V
partment'of the burningvsection tojthe lowermost f
sectionY of the.,deodorizing section through a duct v Y
or pipe V5I! provided’4 withV a damper 5I. VV,Neces
be rotated‘in V sary additional heatingmay be provided byburna largebevel gear' 35 ing additional fuel, for example fluid fuel sup
The centralhollovvshaftrZQ
any suitable manner,¿as by
mountedfon `the shaft„Zilgandçmeshingwith a .
bevellgear. orjpinion’ßßjrotatedrby a pulleyk 31 Y
' , '.65
plied to‘burners52.
' The Vburning ?and drying sections `arealsoísup`- I
fixed >on theäsamjeïshaftl'and receiving powerlîromV pliedïwithburners 5.2,for‘ruse when required.Y
a prime mover in any suitable'manner. Air may , The deodorizedhot` gases from the 'deoz?lorizing'»55-Y
be , forced. into, the .lower endv ofV the' shaft4 p29*, by sectionmay bedischarged through a ñue V53 con,
any suitable means:V suchasïa fanj38 _anda con
Y i nectin'glduct 39V.A "The air 'forcedintoî tl’ie’shaft> 29
nected _with the-uppermost? compartmentpf the ,
section andprovided with a suitable damper »545
will be’heateda'nd >may bïe'utiliazed- to'aid the fur- f As umstrated the damper'risiverueauyemovable'
>nace operation as rlOyÍÈdischa'rging- itinto the lcom-Í andisjcounterbalanced by 'aweight 55 connected 70
partrnents VVor ïzonesfabove Acertain.hea'rthsv Asuch ’ì with the; damper byiaiflexible member-or'rope 456Y Y Y
ashearths- I5 ¿ andï" IIi,` _throughVY openingsflor out
; The'jgases may passl directly from
53 .
e ’ An _importantëfeatureo’f the apparatus relates to a stack’53ebut'in vieWÍoi the heat supplied for
75 toithe divísionlóftliel .furnace I0 into an upper-2 " final . burning foffïthe gasesv >and; Lthe consequent
high temperature of the gases, it is desirable to
recover some of this heat. 'I‘his may be done in
any suitable manner as by using the gases to heat
a waste-heat boiler 58 comprising a water drum
of gases and divide the furnace into an» uppermost
drying> section, an intermediate burning section »
and a lowermost section for subjecting the gases
59, steam drums 60 and tubes 6| connecting the
water drum with the steam drums. The hot gases
from the flue 53 pass into the lower part of a
to high temperatures to completev combustion
furnace chamber 62 and between the tubes 6|,
being directed to the tubes by a bridge wall 63
10 extending upwardly from the bottom of the cham
ber to the water drum 59. After passing between
thereof and remove noxious odors- before dis
charge from the furnace, means for supplying
preheated air to the burning sec-tion, a duct con
ducting hot gases from the burning section to the
drying section, a duct connecting the drying sec
tion with the lowermost section of the furnace,
the tubes 6|, the gases pass through a duct 64 to
a fan 65 which delivers them to the stack 53a.
The operation may be substantially as follows:
and a flue connected with said lowermost sec
15 In starting the apparatus material is introduced
tion to discharge gases of combustion from the
into the uppermost compartment oi the furnace,
the rotation of the shaft 29 started and the fans
38 and 65 started. The burners 52 associated
2. Apparatus of the class described comprising
a multiple-hearth furnace having vertically
with the burning section may also be started as
20 well as the burner 52 for the> drying section and
one or more burners 52 for the deodorizing sec
spaced hearths with outlets through which the '
material introduced at the top of the furnace may 20
pass downwardly to the lowermost hearth and.
then be discharged from the furnace, means at '
the outlets of two hearths to prevent the passage
of gases and divide the furnace into an uppermost
tion. Ordinarily the burner or burners 52 for
the drying lsection may be turned off after the
furnace is heated up, but some or all'of the burn
25 ers in the burning section will be kept in use. In
drying section, an intermediate burning lsection 25
some-instances, the material being treated may
contain enough easily combustible material of
high caloriñc value- to furnish all the necessary
heat in the burning section, thus making it pos
30 sible to dispense with the use of the burners in
the burning sectionr after the furnace is fully
heated up.
Due to the action of the fan $5` the pressure
in the flue 53 will be below atmospheric pressure
35 and there will be a down draft in the burning
section from the outlets 40 in the shaftl 29 to the
lowermost compartment of the section from
which the hot gases may pass through the duct
48 to the upper part óf the drying section or di
40 rectly to the lower part >of the deodorizing sec
tion through the duct 58 as controlled bythe
damper 5|. From the bottom of the drying sec
tion the gases, substantially cooled in drying the
materiah will ñow through the duct 49 to the
45 lower part of the deodorizing section where they
will be mixed with the hot gases introduced
through the duct 50 and finally burned and de
odorized with the use ofthe burners 52 when
necessary. In normal operation the temperature
50 of the gases flowing through the duct 48 may be
about 1200° F. and the temperature-of the gases
flowing through the duct 49 may be about 350° F.
It should be noted that in the drying and burn
ing section the flow of gases is concurrent with
55 the ñow of material and in the deodorizing sec
tion the ñow vof gases is counter-current to the
flow of material. It will be -evident that the
passing of the preheated air downwardly through
the centrall burning section causes the combus
60 tion gases and vapors to pass through the low
and hottest part of the burning section, thus tend
ing to eliminate odors, and that the passing of
some hot gases from the burning zone downwardly
through the drying section assures the applica
65 tion of the greatest'amount of heat to the ma
terial at the beginning ofthe drying operation.
It should be understood that various changes
may be made and that various features may be
used Without others, without departing from the
70 true scope and spirit oi the invention.
Having thus described my invention, I claim:
1. Apparatus of the, class described comprising
a multiple-hearth furnace having vertically
spaced hearths with outlets through which the
75 material introduced at the top of the furnace may
-pass downwardly tothe lowermost hearth and i
then be discharged from the furnace, means at
the outlets of two hearths to prevent the passage
and a lowermost sec-tion for subjecting the gases
to high temperatures to complete combustion
thereof and remove noxious odors before dis
charge from the furnace, means for supplying
preheated air to the burning section, a duct con
ducting hot gases from the burning section to the
drying section, a second duct connecting the dry
ing section with the lowermost section of the fur
nace, a third duct connecting the burning section
`with the lowermost section, and a ñue connected
vwith said lowermost section to discharge gases of 35
combustion from the furnace.
3. Apparatus of the class Adescribed compris
ing a multiple-hearth furnace. having vertically.
spaced hearths with outlets through which the 40
material introduced at the top of the furnace may
pass downwardly to the lowermost hearth and
then be discharged from the furnace, means at
the outlets of two hearths to prevent the passage
of gases and divide the furnace into an upper
most Adrying section, an intermediate burning sec 45
tion and a lowermost section for subjecting the
gases to high temperatures to complete combus
tion thereof and remove noxious odors before dis
charge from the furnace, means for supplying
preheated air to the burning section, a duct con
ducting ~hot gases from the burning section to
the drying section, a duct connecting the drying
section with the lowermost section of the furnace,
and means for drawing the final gases of com
bustion from said lowermost section.
4. Apparatus of the class described comprising
furnace _ having
spaced hearths with outlets through which the
material introduced at the top of the furnace may
pass downwardly to the lowermost hearth and 60
then be discharged from the furnace,means at the
outlets of two hearths to prevent passage of gases
through these outlets and divide the furnace into
an uppermost drying section, an intermediate
burning section and a lowermost section for sub V65
jecting the gases to high temperatures for com
plete combustion thereof and removal of noxious
odors before discharge from the furnace, means
for supplying preheated air to the upper part of
the burning section, a duct conducting hot gases 70
fromthe lower part of the burning section to the
upper part of the drying section, a, duct connect
ing the lower part of the drying section with the
lower part of the lowermost section of the fur
ai i
_ 2,119,601'
eiimin'até‘?oxîous odors, andrmeans 'for
"nace, Tand? a'riiuèiiconnêcted with" said ‘lowermost' and
drawing the final gases `of combustion. from‘said'
'Y section to discharge gases of .combustion from theA
lowermost section. i
~ 8.'- Apparatus of the classdescribed comprising“
furnace. '
Y '
5; 'Apparatus of theclass’describedr‘comprising
-multiple-hearth furnace Ahaving a verticallyY
a Vmultiple'-lriearth ‘furnacefhaving v._vertically', laspacedfhearths
with .outlets throughrwhich the
Vspacedïheartl'is Vwithfoutlets through’ which the
gmaterialïintroduced at' the top ofthe furnacemay'
pass ,downwardly Vto the ll'owermost'hearthrand
then be discharged from the ¿furnacegmeansat
material introduced'at the top‘of thefurnace mayV Y `
pass downwardly tothe lowermost heartha‘n‘vd'vj
then be discharged from'the'furnaca'meansat Y
the outlets of two> hearths to’prevent thepassage
' Y
the »outlets off4 two hearths to prevent‘passage >of Y of gases and divide> the furnace into an uppermost? Q
gases-through these’ outlets and 'olivvìdeftheffur-v drying section, anV interme’diateburning section i Y»
nace vinto ran uppermost'drying section, 'an inter
and a lowermost section for subjecting’the gases `
mediatefburning section V4and a' lowermost section to
high temperatures tofcomplete combustionv
for subjecting thegases to highV temperatures t0
Y thereof 'and remove noxious-’coders ibeforeïîdisá
charge from the furnace'grabbling means toffeedv
l ,noxious 'odors before dischargerfrom the furnace, VVmaterial on said hearthsto their' outlets includ;Y Y
175 complete ' combusti-on ,thereofv and Aremoval Aof
meansfforrsupplying preheatedïairV to theupper
part ofthe burning section,-a duct-conducting hot
ing a hollow shaft and devices extending radiallyVV Y ,
therefrom over .the AVariousrhearths;means for>
Y gasesfromrthe lower‘part ofthe burning section l" passing
to the upper' ypart of¿tlî1efdrying> sectionja vsecond` Ãheated asìairit lupwardly,"through
VductV conductingrhot gases from ‘the lowerpartlof
f '
and part of said burning section, vsaid'hollo‘w shaft'
' vthe burning section tothe Ylowermost section, Va ' havingoutletsthroug'h- whichrair is supplied to the; y
third duct conductingl gases fromthe lower part
upper partzofrïthe burning section, means-'con->` 'i il ~
2'5; ~
ofthe 'drying Vsection to the lower partV ofV the loW-Y v' ducting, hot gases Y fromV :the v,lower fpartf'of: .the
ermost section of the'furnace, vandV a-f'flue con;
`burning section VtoV the drying’ section; means for
necteld withsaid -’lowermost section'to discharge Yeonductìng gasesV and vapors from said drying`
'gases of combustion' from the'furnace. ' L , Y Y»
section to said lowermost section,‘and'means"for
f 6.7'Apparartus of the class described comprising heating
said lower section' to complete“cVoxnbus-Í‘Y
a multiple-'hearth furnace having >vertically
tion of the gases’and eliminate noxious odors.Y
9. Apparatus for treating material which “come
spaced hearths with ooutlets through whichY the Y
material introduced at the topV of the furnace may
Y pass, downwardly to "the ‘lowermost rl‘ie'arthîand»
then be Vdischarged from Vthe 'furnace„~rnean's' at
lprises passing the material downwardlyf:from4
zone to zone through aplurality offzorfiesjY means Y
for detaining'theim’aterial temporarily‘inv-îeach"Y ‘
Y the outlets of two hearths to prevent passage of`
_means for preventing 4the` direct‘flow’fof
gasesY through theseY outlets and3 divide th'efurnacefY zone',
gases between a centralV burning Ygroup of zones;
into an uppermost drying sectiongfan 'interme-4
an upperidrying group offzonesV and aV lowerfde
air group.ofïzones,`
through the central
for passing coni
pre'- ‘, "
diatefburning sectionA and ’a 'lowermost section
Y for subjecting thefgrases rto
` completegrcombustion » thereof v.j andVIV removal' of
noxious odors before discharge from'the furnace, Y
currentlyïwith themateri'alfor burning said ma#V
terialwhile in'othis group, mean-s foripa'ssinggho't 4 ~
"means for supplying’preheatedair to «the lupper ' exhaustrga‘ses from the central group through the'
¿part oftherburning section, a'duct' conducting
upper,groupzcon‘currentlyï'with'the material for"
hot gases from the‘lower part of 'the burning sec# VVdrying
materiaL'means'forpassing?gases'iand 1
part of "their drying section,V _,a vapors the
from th'e'upperg'roupjand hotïgases from“l 45 '
second'rduct conducting'h'ot gases'from'the'lower'- Y
VVtion Y to the>V upper
the central group through the ' lower >group courr-VA
„ "most _part of 'the burning 'sectionïto' the lower
tercurrently- to the material",I and me'ansïfor‘burr'iv-`r`
ing the gases insaid lower group therebyfelimi-'f
’ section,î aV third duct conducting gases'fromrthe o
lower part ofthe drying section to the lower part'
nating odors. v
of ¿the lowermost sectionîof îtherfurnace, means
10. VVAppâg?atiis
means' ’forl
for’ passing
f the 'material down'èî*
which; 507
V50 for> controlling the -flowofïhotgases through said"
` secondV duct, and a flue' connected Vwith Vsaidlowrg
Ywardly fromrzone to' Zone througha plura‘lit'yof
"ermost, section' Ato _discharge
f i
" VVNl»zones,Vmeansf‘for 'd’e'taiifiing'4 the'nrate'rial’'tempo-v
» from thje furnace. ~
rarilyf"-1n~ each 'zonegì means 'fori preventing. the f Y' Y
direct ilowïof gases Vbetweenr a'rcentr‘a’l burning
and a of
Zone/s, anrupper group
‘of Az_onesymean's’ Y Y l
a VVmultiple-hearth, furnace Yhaving `»vertically
material 'introduced at thetop of theV furnace may Vfor'passing ypreheated air through fthe'r centrali*
y ' pass',doiilnwardlyY to Vthe "lowerm'ost hearth and
Abu'rningfg'ro'up concurrentlyA withf'th'e material for'
then be‘discharged froml the furnace, meansat
the outlets of two hearths'lto prevent ,theV passage Vburningvsaid material while inithisr group‘;îmeans`
of gases and divideî the
furnace into an uppermost
` for passinghot' exha'lust’gasesÍfrom'the»centralV
drying section,` an intermediateburningY sectionV 1
and a lowerm'ostfsection
for subjecting the; gases
v and
‘ the material'for'drying'the'material‘fm‘eans‘for» l'
remove noxious odors before dis
passing gases' and vapors from thei upperïgroup'
and' hot gasesfromfthe 'cent-rar group‘throughfitlre 65
Vrmeans for ‘supplying
means Vforfvarying the proportionsfoffhot' gases
Yto high' temperatures to completev combustion
‘groupl through the‘upper
group/'concurrently' with'"
burning section, a duct con
ducting hot gasesmfrom. the-> burning section 'to
» thexdrying sectlon, a duct connecting the drying
lower group „countercurrently“ tof-the‘fmaterlal, ~
passing from the' central 'groupqtof the «drying
group-¿and the lower~group to» control' the- drying', i
section with theilowermost section of the furnace, and means-for -burningrthe _gases in the lower i 7o
ï’ l Í
means including'a burner for raising the tem-w group and eliminating( odors. ì
perature in said lowermost section toV complete
>theburning'of,the gases fromr'the other sections
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