CA2113429A1 - Controlled air grate plate - Google Patents

Abstract

The present invention portions to a grate plate (20) utilized in a cooling apparatus. The grate plate has an upper surface divided into an exposed area (20) and an unexposed area (21). The exposed area of the grate plate is defined by a plurality of air distribution passages (30).

Description

W~93/2370~ PCT/U~93/0479 21134~9 CONTROLLED AIR GRAT. PLATE

BAC~GROUN~ OF T~E INVENTION
: The invention relates in general terms to an apparatus for cooling hot material which is, for example, discharged from a kiln.
A cooling apparatu~ of the general class to which the invention relates is used to cool particulate material ~ (e.g., cement clinker or other mineral materials), which has been burnt in a kiln. Such apparatus:can comprise traveling grate coolers, thrust grate :;coolers, and the like. The hot particulate ;10 ~mater~ial :discharge~d~ :from the kiln outlet typically undergoes~quench1ng;~ln thè material inlet part of the coolinq~apparatus and~is then moved, distributed as well as ~possible,~ to~;consecutive rows~ o~ grates on which additional coolin~g is the:n carried out while the material to be cool~d is~ transported along a path~extending from the material inlet ~o the material outlet of the cooler on said grates.~ Typically, the cooling: air which is ~ blown through the~ho~ material in the recuperation zone : ~: of the cooling apparatus is then reused or recycled -;::

r ~ ~

WV93/Z37~8 PCT/US93/~475~

., ....~

2 ~ 1 3 ~ 2 9 further generally as air for combustion in the preceding kiln~
Grates for cooling or com~ustion are generally equipped with overlapping rows of grate plates, of which S some are mounted 'in a fixed position and others are reciprocating~ which generally means that they oscillate in a longitudinal direction, with the forward stroke of the oscillation being the direction in which the particulate ma~erial to be cooled travels through the cool~r, and they thereby serve in part to facilitate the mov~ement of the material through the cooler. The grate plates are mounted on~a carrler beam which is transverse to~;the direction o~ matPrial flow through the cooler, with ~djoining~grate plates abutting. The air needed for cool:ing~or combustio;n:is~introduced from below the grate plates~through port like;openi~ngs to en~er, penetrate ~nd s~ pass~through the~bed~of~material to be cooled or burned, with~said mat~ria~ lying on~top of the yrate plate.
The~:grate~pla~es~ are subject to wear through 20~ ;mechanica~l and thermal~ef;fects. :In:the case of cooling grates forjinstance, the exposed area of the grate, which lies :closer to the discharge end of the cooler, is subject to considerable abrasive wear and thermal :exposure, whereas the:reax, unexposed, part of the grate ~ , , W0~3/2370~ PCT/VS93~047~9 2113 !l 2 9 Docket No. 1016 plate is subject to less wear, and only minimal thermal exposure.
Grate plates are provided in numerous conf igurations . One popular configuration is the so-called flat grate plate style, which, as its name implies, employs a flat surface on which the clinker is supported as it is ~ransported through the cooler. In this style, ports through which cooling air passes are : located on the surface of the grate. Clinker will thereore rest directly on top of the ports. There will always ~exist the~possibllity ~hat clin~er will sift through the ports, clog the air passageways and at times fal~::;on :the underlying supporting structure, causing possible~ damage~to~the supporting structure and, at 15~ : times, an: uneven ~distribution of cooling air flow resulting:~ln~a grate~;~plate system having hot areas which ;can:excéed m~tal:~endurance limits.
Over~the~years~there have been notable variations in~style:from the so-called flat grate configuration.
;20 ~One~such variati~n~, for example, is the we~ge grate style iD~ w~ich~the ~front area,:~ which comprises part of the exposed~area of~the grate, is ben~ or inclined upward at an angle relatLye :to:the flat, horizontal plane of the remaining area of the grate. This design pro~ided a W0~3/23708 PCT/US~3~0475g partially de~ined area, at the point of the bend, in which the clinker could rest on the surface of the grate.
This design also served to slow the flow of clink~r through the cooler, which ultimately was somewhat successful in retarding red river conditions within the cooler~ Air typically was distributed into the clinker ~through openings lo~ated in the upwardly inclined area of the gra~e plate. This design did not contain any anti-sifting features, as smaller particles o hot clinker ;, ~ :
could enter and clog the air distri~ution holes or pass through the holes in~o the air distribution compartments below the grate. In addition, there was only a limited endency for the c:linker to remain static within this particular desi~n of gra~e. This design was utilized lS ~primarily in the mid~1950's through the ~960's.
:With regard to:another design of grate plate, in the early l950~s the asslgnee of the present inveration designed and s~old a ~particular design of a grate plate popularly known~as~a~:l'pan" grate~plate which in essence :~ ~omprisedj~a grate plate h~ving on its upper surface a :large:depression ln whlch clinker could be re~ained. The : primary purpose was to retain the majority of clinker material located within the depression in a basic static condition, which thereby resulted in improved grate plate W~93/237~8 2 1 1 3 ~ 2 9 - P~T/US93/~q759 life through ~ reduction in wear and better resistance to red river thermal shock conditions. The grate plate could be utilized in a reciprocating or a stationary mode.
In cross-section, this prior art grate plate had a pan-like configura~ion, r~sulting in its popular name, with di~fering degrees of depressions with the ~eepest depression locatPd in the rear of the grate plate in the unexposed area of the grate plate. The term 'lunexposed area", r fers to that area on the upper surface of the grate plate that is, at least some of;the time, covered by the o~erlap of a preceding grate plate. The depr~ssion was not as deep toward the front of the grate pl~ate,~that is, the portion of the grate closer to the ~atcrl~al~outlet of the :c~ooler~. , Ai.r:was distributed directly into th~ depre~ion in which the~clinker was~held in a static condition through ` ~: ": : :
a~plurality of: air~ distribution holes looated in the exposed,~ shallow ~portion of the grate plate. In this 20~ ~csign, some of ~the clinker in the: shallow area wo~ld come::to rest directly on top of the~ air distribution holes which would ~ potentially result in some clinker :
sifting into the air distribution holes, particularly ~ during cooler fan: shut down conditions.

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W093/237~$ PCT/US93/04759 2113~

This prior art design did not have any anti~sifting features, had high discharge velocities of air through the air distribution holes into the clinker, and, in the version sold, consisted of a single grate extending across the entire active width of the cooler which here~ore necessitated replacing the entire grate in the event cf excessive wear in only one area of the grate, resulting in expensive and cumbersome maintenance.

SVMM~RY OP ~HE INVENTION
The present invention relates to a grate plate for ;~:: ~:
transporting particulate and solid material in a prede~ermined direction through a cooling apparatus. The grate plate~of~the present invention is particularly well suited:~to re~eive a controlled supply of air. ~The 15 ~ : invention ~is particularly useful in th`e cooling of cement clink~r after~it~exi:ts~a kiln. The cooling apparatus in which~ he grate~plate~ is~ employed is comprised of a materlal~inlet,~a~material outlet, and a plurality of rows of gratei~plates,~which typica~lly alternat between 2:0~ being~ stationary or~reciprocating.~ Each row of grate : plates~ extends~across the wldth of the cooler in a : direction tra:nsverse to the material flow through the cooler. ; Each~.preceding row of~plates overlaps the : ~:: :: : :

W0~3/~370~ PCT/VS93/Oq759 -7 2113q29 following row of platesO The under surface of each grate plate is attarhed to a carrier beam. The upper surface of the grate plate is divided between an exposed area, which is never overlapped by any portion of a preceding S grate and is loca~ed on the front portion of the grate plate, that is the portion which is closer to the material outlet end of the cooler, and an unexposed area, which is overlapped at least part of the time by a ~: preceding grate. The grate plate of the present invention is suitable for receiving a controlled supply of air.
In one embodiment of the grate plate of th present in~Pntion ~ substantially the entire sur~ace area of the ;ex~os~ed;~surface is~recessed from both the upper edges of 15~ its~outsidP.;perimeter and~the surface of the unexpos~ed area~, which~is substantially level. The recessed area is ener~ally~configurated to receive particulate matPrial `that~ is~be:ing cooled. : Preferably, the majority of material~residing~within the recessed area will ~e in a 20:~ : sta~ic condition.~ The: topography of the exposed area, whether or not recessed, is defined by alt~. ~ating rows of air distribution passages and secondary air :
istribution channels. Specifically, there is a~ least ;one, and preferably a plurality of substantially hollow W093~2370~ P~T~US93/~4759 211342~

air distri~ution passages that travel substantially the entire distance of the expo~ed area in a direction substantially parallel to the movement of material through the cooling apparatus. An air chamber is located directly below the air distribution passages, and the secondary air channels which connects with a source of cooling air. The air distribution passages have a top surface and two sides upon which some of the material transported through the cooling apparatus comes into contoct. In addition, the cooling air will enter the air distribution passages from the under side of the grate plate into an air chamber and will travel along the le~gth of the passag2s~ and will exit into the secondary air channel via a plurali~y of air portals or outlets 15~ that ~ are located on the side walls of the - air distribution passages.::In the recessed Yersion of the present inven~ion,~ the conveying air is directed through material that is:retained within thP recessed area arldlor through material that is being transported through the 0 : ~ooling ~appara~us by the grate plate. The air :distribution passage :is adjacent on one or more of its longitudinal s~ides, depending upon whether it is located ; at ~the side or toward the center of the grate plate to an ~: ~ open., secondary air distribution channel that travels ~: ::::

W0~3/23708 PCT/US93J04759 2 1 1 3 ~ 2 9 substantially the entire distance of the exposed area in a directior. parallel to the movement of material through : the cooling apparatus. The secondary air distribution channels are either located between two adjaceint air distribution passages or between an air distribution passage and a inner side wall of the exposed area of the grate ~plate. : The alternatlng placement of air : distribution conduits and secondary air distribution channels serves to :create a ridged effect over the 10~ èxposed area. The exposed area is bordered by the front inner :side wall;o~ ~he grate~plate, ~that is, the side wall opp~site the front pusher face, ~he:side inner walls o~the~exposed;~area o~the~grate plate:and the adjacent s~ide~o~:the~unexposed~area~runnin~g parall:el to the front 5~ pusher~face. ~
ne~of:the~advantages of the~ design- of the cooling air~d~stribu~ion:~s~stem of the grate:plate of the present inven~on~ls that~:there:is achieved à reduction, compared t~ a~traditiona~ grate plate~design~, of~the velocity of :0~ the;~cooling air~as~ t~is~both init~ially discharged ~rom the~air~distribut~ion outlets~and~as ~it travels through the~a~ea~where:thé retained:clinker~rests. ~his decrease in~veloc`lty presents a number of adva~a~es, inclu~ing:
(l) enhanced~heat~recuperation, (2~ higher secondary air ,~ , : : :

W093~23708 PCT~U~3/04759 2~13~23 temperatures, (3) no~ promoting a fluidized condition of the clinker during normal and red river states, (4) a greater retention factor of cooling air within the ~: retain~d clinker mass, (5) less abrasive characteristics ~: S to the grate which result from high velocity entrained articles abrading ~he air outlets and the surrounding ; grate plate surface ~and (6) improved quenchinq, to name ~: :
~ a few. The actual air velocity realized is directly , ~ ~
: : influenced in part by the configuration of the primary ;10 coollng air;outlets:~which direct the discharge of cooling aix iDto the secondary;:air channels and the configuration of such secondary air channels, both of which are fur~her des~ri~ed below. It is anticipated that, in the p~eferred;:embodiment~s ~descrlbed below, the velocity of lS~ the~cool~lng air;~will~be~optimized to thereby utilize the minimùm~veloclty~af~cooling~air needed to adequately cool the:materia~1 while;~promoting the desired anti-sifting and anti-~fluidlzati~on~fea~ures. I~ i:s understood, in this regard,~ that the~-~ultimate veloci~y of the air thrcfugh ~he 20; ~ secondary,air channel;is also a function of factors other than~ the ~design~ of the~ primary air outlet and the serondary~ aix :cha~nel, one factor being the packing factor of any material that may come to reside within the secondary air channel. Another ad~antage of the :

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W~93/23708 P~T/USg3/0~7~9 1 1 211342~

preferred design of the present invention is that the recessed area of the exposed area will essentially accommodate the material in a static condition. The reduction of mo~ement of materi~l relative to the exposed metal surface area of the grate plate will significantly reduce the wear in said section.

;~ ~ DESCRIPTION OF TXE DRAWINGS
Figure 1 depicts a ~op view ~f one of the preferred :embodiments of the~present~in~ lon. Figure 2 depicts :10 a sec~ion view of the embodi~i depicted in Figure 1, which~;is taken` along axis~A~A of ~igure 1. Figure 3 depicts;~another séction~view of the embodiment depicted in~Figure~1 taken~along axis: B-B of Figure 2. Like numera~ls in all drawings re~er to like elemen~s.

$5~ DESCRIPTION :OF THE~ IEN~IQN
Referling~;to~Figures 1,~2:and: 3, there is depicted one~:~em~odiment ~of ~the gra~e plate of the present invention generally rèferred to by the numeral 20, which can be~util~ized in a stationary or~rec~rocating mode.
Z0 :~ Tha view~of grate plate 20 as set forth in Figure 1 is~ of its upper surface, which upper surface is divided .
~ : into an exposed area generally referred to as 70, the . ~
:: : : : : : :

,:

W093~237~8 PCT/US93~q7~g : ` î2 ~113~29 longitudinal boundaries of which are as defined by the dotted line 61, and an unexposed area 71 as defined by lines 60. Material will travel through the cooler longitudinally in the direction represented by arrow F.
S The boundaries of ~he exposed area are further defined by outer side walls 21 and 22 and front pusher face 23, ~:: which has a top edge 24, and edge 25 of the unexposed area~
:In the depicted version, a significant portion of 0 the exposed area is recessed, with said recession ~: :
: meas~red from ~op edge 24 of front pusher face 23, top : longitudinal edges 26 and ~7 and front surface 28 of the unexposed area.
As material~moves through the cooler it will 15: ~ generally~fall onto the exposed area. Surface 28 of-the unexposed area~will b covered during the operation of the~ cooler at: lea~st ~part af the time by an overlap , cr2ated by~the~grate plate immedi~tely behind it in the covler:, keeping in mind that said preceding grate pla~e ~an be eitherls~ationary or reciprocating.
~ ~ , he recession~of the exposed area of the grate plate ~hich constitutes one embodiment of the present invention can be ~etter appreciated with reference to line 40 in Figure 3, which represents the plane which intersects the , ~ ~

W093/23708 PCr/US93/0~7~9 1 3 2113~2~

highest points located on the upper surface of grate plate 20, which, in the case of the embodiment depicted in Figures 1-3 is on the same plane with top longitudinal edge 26, surface 28 of the unexposed area, and top edge 24.
:~; :There is located on the exposed area 70, at least one, and preferably a plurality of air distribution : : passages 30, through which cooling air travels. Cooling alr is proYided to alr distributlon passages 30 primarily 10~ ~ from an ~air~cham~er:33 which:is open to cooling air flowing~from the carrier beam 80 that is located beneath the~: grate ~ plate ~0~. : Cooling air can enter air distribution passages 30 and air chamber 33 horizontally from~the~ under~portlon of ~the qrate plate near the lS~ junctio:n ~ point of~ the :exposed a~d unexposed areas.
ooling~;air can also~enter~air dis~rlbution passages 30, -and:~air;:~chamber~;3::3~ in~ a vertical~fashion. The air distr~ibution~passages~30~are~hollow~;structures whlch run essential1y ~he entlre exposed length, in parallel to the 1? ~` '2 0 ~flow~:o~ ma~erial ~through the coole~. Cooling air will tra~el~ ~throu~gh~the~:air dis~ributlon pass~ges 30 eng:thwise:in the same~direction as material flow, that i5,~ f~om rear to front.~ Cooling air is discharged from the alr; distribution~ passages 30 through primary air '?~: : :: : :

W093J~3708 PCT/U~93/04759 2113~23 ~ 4 outlets 55 into secondary air channels 56, which, like passages 30, ru~ substantially the entire length of the exposed area, and alternate with conduits 30 to fill substantially the entire recessed area. With reference to Figure 2, the secondary air channels 56 can be either located, between two adjacent air distribution passages 30 ( s depicted~ or between an inner longitudinal edge 29 or 29a o~ grate plate 20 and an adjacent air condult, this latter option not being depicted.
:Air distribution passa~es 30 can either be separated :: from: an inner side wall of the longitudinal edge of exp~sed:area by a secondary~air dist~ibution channel or, in certain embodiments, they may be located flush with sa~id i~nner side wall.
;IS ~ Air ~passing through primary air outlet 55 will'be directed into secondary~ air channel 56. Preferably the air:is~ directed at;a~downward angle, tha~ is, an angle somewhat;~b~elow the~horizonta~1, into said secondary air distribution hannel~56. The configura~ion of th~
~secondary air chànnel 56 will of course be determined by : the:shape of at le~ast one~of the side walls 58 of the adjacent air distri~ution conduits 30.
Figure 2 displays the embodiment of the present nvention wherein top surface 32 of the aix conduit 30 , , ~::: :

.~ :

W093/23~08 PCT/~S93/0~75~

1 5 21134~

overhangs, in a shroud like manner, primary air condui~s 55 to thereby promote the anti-sifLing fe tures of the present invention. In addition, b2tter air distribution is also the result of there being an overhang which shrouds the primary air outlets and creates an exterior cooling air flow path which extends essentially the full length of the exposed area inside the secondary air ~ distribution channelO Should one location in front of :: the shroud become blocked with clinker the air is free to 0 migr~te to a locat1on where a blockage does not occur.
The primary air ou~lets 55 appear, on the side walls 58 :of~ air distribution passages 30, preferably as rectangularly shaped s;1Ots 60 with the longer sides of the s~lots: being substantially~parallel to the direction 15~ o~f~ow~of material~through the cooler. The 510ts ~re preferab1y located~in;the lower~ section of the secondary air:~distribution: channe1 56. Since slots 60 are positioned on~the s ide walls 58 of air distribution passages 3Q, air is initially discharqèd from the primary , 20 air outleti~55~ in a direction transverse to the clinker f1:ow through the cooier. Rather than there being one 510t in each sidewall that runs~ the length of the air distribution conduit, there: is a plurality of slots positioned along the length of each side wall 58. It has , ~ , :;

WO 93/2370~ PCI`/I~S93/0475~

211~'~23 been found that this configuration has a number of advantages. For instance, the struc~ural integrity of the grate plate is enhanced. The slots maintain a transport velocity which will minimize the backflush of 5 materia~l into the air conduit. Furthermore, by minimizing the discharge velocity the potential for fluidization will be reduced. Figure 3 shows a preferred ~ :
embodiment of the placement of slots 60.
In another embodiment of the invention, the width and length of the slots may vary.
A~:~ particularly advantageous feature of this invention~is~the lnclusion~of a secondary air discharge channe~ 56 immediat~ely ad~oining and in fluid co~munlcation with the: primary air outlet 55. As ;15 ~ ~ indicated,~ there are~a plurality of secondary channel that~essentially;run parallel to the directly of material f:low~across virtually the~entire length of the exposed area of~ the: grate~plate. The secondary air channels :f~unct:ion:as nozzles~and serve to redu~e the Yelocity sf h`~ ' 20 ~he: cooling air d~ischarged into the clinker retention area thereby~:reduc1ng~the posslbility of:fluidization of the clinker. ~
ir dis~ribution passages 30 will generally be narrower than~ secondary air channels 56. In this regard, ~V093~2370~
PCT/US9~/~759 .
1 7 2113~2~

it has been determined that a preferred configuration for the secondary air channels is when their length to width ratio ranges from about 4:1 to about 12:1 and more preferably from about 6:1 to about lO:l. If the : secondary air channels have a length to width ratio greater than 12:ll the velocity of the air passing through these channels will be higher t l preferred. If the ratio is less than 4:1, ~he per~ormance of the ; secondary air channel may be adversely affected and will - lO ~: not function as a :nozzle.
: When there are a plurality of air distribstion ass~ges or secondary air channels within a given grate . ~ ~
plate~one or more may optionally have variable widths a~nd/or~heights from a corresponding passage or channel~

5~ In another~embodiment,~al~ of the secondary air chann~ls may~be~of the same depth:and/or width and/or all of the alr~pas~sa~ges may:be of the same height and/or width.

: T~e~top surfac~e 3:2~o:f each of ~he air distribution : passages~ 30 are; preferably récessed from the plane ~ dépicted bylline 40, preferably in a sufficl~t amount so : that~at least some,~but preferably a majo~s~ty, of the : clinker within the recessed a~ea will remain in a static ~ condition.

: :;

WO93/2370B ` PCT~US93/04759 : ` 18 2113~3 In the embodiment depicted in Figure 2, side edge 27 is recessed from surface 40 to such an extent so that edge 21 of an adjoining grate plate will overlap :~ therewith so that bottom edge 26a will mate with edge 27 to create an overlapping joint to thereby virtually eliminate clinker from falling between adjacent grate , :~ plates. Alternatively, the longitudinal edges of the grate plate can be identical in height and shape to each :: : other so that adjoining grate plates would abut rather ; 10 : than ove~lap~
The grate plates of the present invention may be modified in such a:manner as known to those skilled to be utilized in any row of the cooler without changing the unique features thereof.

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Claims (16)

WE CLAIM:

1. A grate plate for transporting particulate material in a predetermined direction through a cooling apparatus that has a material inlet, a material outlet, and a plurality of rows of grate plates, with each preceding row of plates overlapping a portion of the following row of plates, said grate plate having an outer edge, an upper surface and under surface which is attached to a carrier beam, said upper surface being divided between an exposed area which is never overlapped, and a non-exposed area which is overlapped at least part of the time by a preceding grate, wherein:
wherein said exposed area is defined by alternating rows of (a) substantially hollow air distribution passages that travel substantially the entire distance of said exposed area in a direction parallel to the movement of material through the cooling apparatus, said air distribution passages having a top surface with which some particulate material being transported through the cooling apparatus comes into contact, and two side walls and (b) narrow, open, secondary air distribution channels that travel substantially the entire distance of said exposed area in a direction parallel to the movement of particulate material through the cooling apparatus;

wherein there are a plurality of air chambers that are located underneath said air passages and said air distribution channels; wherein said side walls of said air distribution conduit each have a plurality of primary air outlet located thereon through which cooling air passes from the interior of the air chambers to the air distribution passages and finally through a primary air outlet into an adjacent secondary air distribution channel.

2. The grate plate of claim 1 wherein substantially the entire exposed area is recessed from the upper surface of its outer edges in order to accommodate a volume of particulate material therein.

3. The grate plate of claim 2 wherein substantially all the material that resides within the exposed area is in a static condition.

4. The grate plate of claim 1 wherein the longitudinal edges of adjoining grate plates in a row are fitted to overlap with one another.

5. The grate plate of claim 1 wherein at least some of the primary air outlets are in the form of rectangular slots on the side walls of the air passages, said slots having their longitudinal side parallel to the direction the material moves through the cooler.

6. The grate plate of claim 5 wherein the slots are located in the lower section of the air distribution channel.

7. The grate plate of claim 1 wherein the cooling air passes through the primary air outlet in a downward direction into the adjacent secondary air distribution channel.

8. The grate plate of claim 1 wherein there is a plurality of air distribution passages having varying widths.

9. The grate plate of claim 1 wherein there is a plurality of air distribution passages of varying heights.

10. The grate plate of claim 1 wherein the ratio of the length and width of the secondary air distribution passages ranges from about 4:1 to about 12:1.

11. The grate plate of claim 1 wherein the air distribution passages are separated from the longitudinal side walls of the exposed area by a secondary air distribution channel.

12. The grate plate of claim 1 having at least one air distribution passage that is located against the longitudinal side walls of the exposed area.

13. The grate plate of claim 1 wherein the top surface of the air distribution passage overhangs the primary air distribution outlet.

14. The grate plate of claim 1 wherein the material is cement clinker.

15. A grate plate for transporting particulate material is a predetermined direction through a cooling apparatus that has a material inlet, a material outlet, and a plurality of rows of grate plates, with each preceding row of plates overlapping a portion of the following row of plates, said grate plate having an outer edge, an upper surface and an under surface which is attached to a grate support, said upper surface being divided between an exposed area which is never overlapped, and a non-exposed area which is overlapped at least part of the time by a preceding grate, wherein the longitudinal edges of adjoining grate plates in a row are fitted to overlap with one another, wherein:
substantially the entire exposed surface is defined by alternating rows of (a) a plurality of substantially hollow air distribution passages that travel substantially the entire distance of said exposed area in a direction parallel to the movement of particulate material through the cooling apparatus, said air distribution passages having a top surface with which some particulate material being transported through the cooling apparatus comes into contact, and (b) a plurality of narrow, open, secondary air distribution channels that travel substantially the entire distance of said exposed area in a direction parallel to the movement of particulate material through the cooling apparatus;
wherein there are a plurality of air chambers that are located underneath said air passages and said air distribution channels; wherein said side walls of said air distribution passage each having a plurality of primary air outlets located thereon through which cooling air passes in a downward direction from the interior of the air distribution passage through a primary air outlet into an adjacent secondary air distribution channel;
wherein at least some of the primary air outlets are in the form of rectangular slots on the side walls of the air conduit, said slots having their longitudinal side parallel to the direction the material moves through the cooler.

16. The grate plate of claim 15 wherein substantially the entire exposed area is recessed from the upper surface of its outer edges in order to accommodate a volume of particulate material therein.