Document wr3jreG7GQDqXV1YERG7kEbYJ

Returning oversized particles, Whig!' kbsslc pulverizing forces shows In Fig. have already been dried, helps generi']'^*- ' .j Here raw coal from o supply hopper operation by reducing average !>, a pushed by a feeder shoe into the ture content of coal entering the p^VV -rinding chamber below the rotating verizer and cuts down any tendency of/'- jjfjrttnt. Incoming fuel particles do not incoming coal to plug at the inlet rothe in contact with the rotor on n- Crushing Action. Fig. 5 and 6 ho^j ^pg the chamber. Instead, the coal pulverizers that grind coal between two'j^ idds to a dormant body of fuel lying surfaces moving in relation to esefa-/-^ other, with crushing as the principal'll pulverizing force. One design, Pig.,3/$| employs os the moving elements balls that are held between two races. Orind.$' log pressure la-adjusted by controlled^'tension of springs shown in cutaway.lv. on the pulverizer bottom. Into this atmosphere, under pull of the rotor, in effect a elosed*end fan, comet the preheated oir stream. This stream whips across the dormant fuel bed and seta up a scouring, sandblast* tag action between coal particles pulled Coal in the raceway between aad,?+> around the balls Is subject to variousV$| pulverizing forces os the balls rotate.''/' The entire mill operates under pres*Y^;; up in the stream os well os those on the surface of the fuel bed. The pulverized product passes on with the air stream into the separator sure. An outside fan blows a stream of''./{l preheated air through it to dry, classify tyi end transport pulverized coal. A. l\ above. There the mixture goes through a spinner cone, where the cool*air stream experiences several sharp The mill of Fig. 0 has a grindlagPl] changes in direction to dislodge heavier ring carried by a revolving bowl whose rim speed Is about 1200 fpm. Button* ary rolls, preloaded by springs, are leftti: so they do not contact the ring. Wheftt/'/J incoming cool reaches the splnnlng>v^|j bowl, centrifugal force throws it.*J; particles from the stream. These fall back for further attrition. Fluid Pulverisation, The unit of Fig. Id, introduced recently, contains no moving parts; the expansive force of steam or air is employed to create against the slant-faced grinding rim: and into contact with the rolls. Qround '-1 coal Is thrown from rim into annuls passage surrounding it. Here partial^! strong attrition action. Raw coal not exceeding H in., either wet or dry, enters the mill through a venturi. For wet coal, steam super clasziflcatlon takes place with heavy' porticles rejected back to the grinding ring by deflecting plates. Remaining coal particles cony along* heated to a total temperature of 750 F serves os the working medium, drying and pulverizing the coal simultaneous ly. As the coal enters the venturi it on the exhauster*induced oir aimin' into the elastifler, where the stream undergoes a whirling motion to dls'-l*^, coma into the steam jet's path and is forced down into the pulverizer onto protection cover. It (alls through this lodge heavier particles. To a large ei> V cover to the pulverization zone in the tent, adjustable vanes on the classifier*'// set the fineness of output. . impact, Attrition. Fig. 7 Illustrates a'Y ` bottom steam-jet block, where it is ' pulverized by steam issuing from sev eral jets. mill combining impact and attrition*1'* From this pulverization zone the fuel forces, working under suction. A series particles are carried with the steam of hammers make up the primaryV'' through the uptake leg, back through pulverizing stage into which flows stream of hot air pulled in by fan i`?v the classifier where the heavier parti cles. drop back for further pulveriza action of the hammers. Partly ground tion. There Is enough energy left in coal passes around the outside of the'^ steam-coal mix for delivery to burners. rotor into the Anal pulverizing stag*, ^ No fan is needed for transport. which consists' of pegs on e rotatingyj1 Fluid forces ora also employed in the disk that travel between stationaryj?. pegs. Coal in the turbulent air stream v rubs against pegs and other coal par*'^ tides to be reduced by attrition. A fan pulls out the fines; rejector ottos l'^. pulverizer of Fig. 11, which is designed for ultra*fine grinding. Row material-- tabus 4-mesh or less-enters under in* spirator action to be broken down still finer. Such fine pulverization goes be- the path of this coal-air stream heavy particles. ! Impart PvfvarUar. The pulverizer Fig. 8 consists of a series of lropa^'i stages wiuj an euwuticr i,, -.. *he..,` * mill outlet. As cool*alr mix proceed* ,/, from stage to stage, Individual parity;/ yond present power-field requirements, tut for gas-turbine applications, end other uses such as grinding coal for coi tal fuel, it may well be the answer. Phk Feeder. The job of delivering an ^interrupted flow of coal to the pul verizer, at the rote set by steam de- 'l-'S'", .0 ctipror'or/oal .flftaneu <rt-pulveriser*'/,,* Mcles become progressively finer. heated air enters at the left to perio^1,^. its usual (unctions of drying / * :; transporting. fhz^-l A rather different treatment of "V* /ud, (alls to the feeder. Although flails vary, feeders fall Into two broad ^uaMs-tuYu^f^P,Watf"-a*n'd drum or roil. Fig, |2 shows a totally enclosed disk made in sizes for feeding from A ;.O.outlet,. Prehaated.atr driei'teol.'i*hc*iMrtoi. can beat righVend rowu * December 1748 PS7J :'.", inf 'fV" -'V'-'-J:' As,"* - ' -4-- - - il li'** ,vTv.I