incinerator design

7/29/2019 Incinerator Design

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CHAPTER 2I NCINERATOR DESIGN

EM1110-3-1769 Apr 84

2-1 . Defi ni ti ons . Defi ni ti ons of term i n thei r appl i cati on to thi smanual are as fol l ows :a . I ncinerator . A speci al type of structure for the reducti on ofrefuse to i nert gases and sol i ds by burni ng .b . Furnace . That part of the i ncinerator i n which combusti on takes

pl ace, i ncl udi ng the i gni ti on chamber, mxi ng chamber, combusti onchamber, and chargi ng hood i f provided .

c . Arch . The arched cei l i ng of the furnace over the i gni ti on,mxi ng, and combusti on chambers .

d . Grate . The cast i ron (C. I . ) grate on whi ch the dry materi al i sburned.e . Hearth . An i ncl i ned fl oor on whi ch the wet materi al i s dri ed

and burned . I t may be constructed of f i rebri ck or of cast i ron gratebars .

f . Effecti ve grate area . The grate area pl us the effecti ve area ofthe hearth i n term of grate area .g . I gni ti on chamber . The space between the grate and the arch andbetween the hearth and the arch.h . Mxi ng chamber . The chamber adj acent to the i gni ti on chamberwhere the gases mx before passi ng to the combusti on chamber . Thi s i soften cal l ed the down pass .i . Bri dge wal l . The wall at the end of the grate or hearth between

the i gni ti on chamber and the mxi ng chamber .j . Combusti on chamber . The fi nal chamber of the furnace where

combusti on of the gases i s compl eted.k . Target wal l . The wal l between the mxi ng chamber and thecombusti on chamber .1 . Fl ue . The hori zontal connecti on between the combusti on chamberand the stack.m Damper . The verti cal movabl e refractory slab i n the fl ue for

draft control .


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n . Damper box . The box over the damper for housi ng i t i n i ts openposi ti on .o . Chargi ng hood . A structure di rectl y over the i gni ti on chamberprovi ded wth a door, through whi ch the furnace i s charged wthrefuse .p . Chargi ng throat . An extensi on froman openi ng i n the arch to

the chargi ng f l oor, through whi ch the furnace i s charged wth refuse .2-2 . Types of i nci nerators . Two types of i nci nerators are consi deredi n thi s secti on : type I - garbage and rubbi sh i nci nerators and typeI I - wet garbage i nci nerators . Standard desi gns have been prepared fortypes I and I I , drawngs for whi ch are l i sted i n appendi x B. Type I ofthese standard designs i s a general purpose i ncinerator and i s the mostsui tabl e for the present-day needs at a maj ori ty of i nstal l ati ons . I twl l burn refuse consisti ng of al l rubbi sh or, by proper control of thedamper, a mxture of 65 percent rubbi sh and 35 percent garbage byweight . Type I I wl l burn a mxture of 65 percent wet garbage byweight and 35 percent rubbi sh wthout the use of auxi l i ary fuel .However, thi s type i s not desi gned to wthstand the hi gh heat rel easethat woul d resul t f romburni ng refuse contai ni ng a hi gh percentage ofrubbi sh and wl l not be constructed except when the condi t i ons aredefi ni tel y unsui ted to the use of type I .2-3 . I ncinerator capaci ti es . Requi rements wl l be based on theexpected waste fromthe parti cul ar post . At an average troopcantonment, the per capi ta waste wl l approxi mate 1 . 5 pounds ofrubbi sh, 0. 50 pound of non-edi bl e garbage, (ci trus peel s, coffeegrounds, etc . ) and 2 . 0 pounds of edi bl e garbage per day . Quanti tydetermnati ons, however, wl l be based on an actual survey wheneverpracti cabl e . Capaci ty wl l be provi ded for 25 percent excess over theaverage hourl y needs i n order to make al l owance for i rregul ari ty i n thedel i very of refuse to the i ncinerator . For exampl e, i f 4 tons are tobe burned i n 8 hours, the i nci nerator wl l have a capaci ty of 1, 250pounds per hour . Capaci ty factor for troop expansion wl l not be used,as the i ncinerator can be operated 16 hours per day i f necessary, 8hours remaini ng for cool i ng and cl eani ng Li ttl e or no economy wl lresul t i n desi gni ng special i nci nerators of si zes i ntermedi ate betweenthe sizes i ndi cated on the standard desi gns l i sted i n appendi x B2-4 . Basi c design requi rements . The i ncinerator wl l be desi gned forthe severest condi ti ons that may reasonabl y be expected . For i nstance,a type I i ncinerator may be requi red to burn refuse consisti ng of al ldry materi al and no garbage . The desi gn, therefore, i nsofar as i ti nvol ves heat rel ease, gas quanti ti es, vel oci ti es, etc . , wl l be basedon burni ng onl y dry materi al s . A dryi ng hearth wl l be provi ded forthe occasi ons when wet materi al s are to be burned. The design wl lconform t o the fol l owng basi c requi rements :

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a . Total furnace vol ume . The total furnace vol ume wl l be suchthat the heat rel ease per cubi c foot of furnace vol ume wl l not exceed18,000 Btu per hour .b . Hearth area . The hearth area wl l be approximatel y equal to the.grate area for types I and I I i nci nerators .c . Effecti ve grate area . For type I i nci nerators - 0 . 022 square

foot for each pound of refuse per hour ; and for type I I - 0.04 squarefoot for each pound of refuse per hour . I n determni ng effecti ve gratearea, the hearth may be consi dered t o be 60 percent effecti ve i f madeof f i rebri ck and 80 percent i f made of grate bars .d . Gas vel oci ty . Amaxi mumof 15 fps through the combusti onchamber and a maximumof 35 fps through the mxi ng chamber, f l ue, and

stack.e . Combusti on-chamber volume . At l east 30 cubi c feet per pound of

gas produced per second, i ncl udi ng excess ai r requi red for cool i ngpurposes .f . Combusti on-chamber temperature . Suff i ci ent for compl etecombusti on but not to exceed 1,600 degree F . (2,059 degrees F .absolute) . Thi s can be control l ed by use of the damper and by thei ntroducti on of excess ai r .g . Combusti on time . Amnimumof 1 . 5 seconds, total time requi red

for the gases to pass through the furnace .h . Stack hei ght . Suff i ci ent to provi de the necessary draft anddetermned by the formul a :

DH - 0.52B

C1 -Ta Ts

i . Draft . Suff i ci ent to di scharge the gases of combusti on andrequi red excess ai r . The total draft requi rements wl l be determnedi n accordance wth the fol l owng al l owances for l osses expressed i ni nches of water :

Vel oci ty head : 0 .119BV214.7Ts

Fri cti on l oss through the stack and f l ue : (1 . 1 x 10 -6)T sWLP

Loss through each 90 degree turn i n the gas passage : computed as astack or condui t, the l ength of which i s 12 times the square root of

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A3


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the area of the openi ng Loss through grate : vari es accordi ng to typeof grate, quanti ty, and type of refuse burned, quanti ty of ai r andattenti on gi ven to stoki ng Under average condi ti ons thi s l oss may beconsi dered t o be 0 . 25 i n type I i nci nerator and 0 . 15 i n type I I whenthe furnace i s operati ng at rated capaci ty .Abbrevi ati ons of term used i n the precedi ng formul as are :Ta - Atmospheri c temperature i n degrees F . (absol ute) .Ts - Average stack-gas temperature i n degrees F . (absol ute) .H - Stack hei ght above t he grate (f eet) .A - Average i nside cross-secti onal stack area (square feet) .B - Barometri c pressure (psi ) .

D - Stati c stack draft (i nches of water) .V - Gas vel oci ty (fps) .W - Wight of gas i ncl udi ng excess ai r (pounds per second) .L - Stack hei ght above f l ue pl us l ength of f l ue (feet) .P - I nside stack perimeter (feet) .2-5. Prel imnary desi gn . A prel imnary desi gn wl l be made fi rst andthen checked and adj usted t o assure compl i ance wth the basi c desi gnrequi rements . For thi s purpose, tabl e 2-1 may be uti l i zed . The desi gnof an i nci nerator i s i l l ustrated i n appendi x A

Tabl e 2-1 . Prel imnary Design Factors

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Type of i nci nerator

Ef fecti ve grate area per pound of refuseper hour (square feet) 0 . 022 0 . 04Rati o of hearth area t o grate area 1 1Ef fecti veness of hearth area i n termof grate area (percent) :

Fi rebri ck hearths 60 60C . I . grate bars 80 80

Hori zontal cross-secti onal area of mxi ngchamber i n term of ef fecti ve grate area 25 20(percent)Hori zontal cross-secti onal area ofcombust i on chamber i n term of ef fecti vegrate area (percent) 60 30Cross-secti onal area of f l ue i n term ofef fecti ve grate area (percent) 25 10


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Tabl e 2-1 . Prel imnary Desi gn Factors (Cont' d)Type of i ncinerator

Corps of Engi neers2-6. Desi gn anal ysi s . A desi gn anal ysi s wl l accompany al l requestsfor authori ty to construct i nci nerators and al l i ncinerator pl ans andspeci f i cati ons, other than standard pl ans and speci f i cati ons . Theanal ysi s w l l i ndi cate the type of materi al to be i ncinerated and thebasi s upon whi ch the capaci ty requi rements were establ i shed .

EM1110-3-1769 Apr 84

. Cross-secti onal area of stack i n term ofef fecti ve grate area (percent) 22 10Rati o of height of arch above grate towdth of furnace not to exceed 1 1

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