Duodan mill

Application, operation and designAPPLICATION

With very few exceptions, new cementplants are designed to operate on the dryprocess principle. Most cement raw materi-als, however, have a moisture content of 3-8%, in some cases even more than 20%. Toobtain effective grinding in a ball mill it istherefore necessary to dry before grinding.

To achieve simplicity of mill installationthe drying and grinding processes can be di-rectly connected by passing the exhaust gasesfrom the kiln through a semi-airswept rawmill. The air velocity through the mill andtrunnion must be kept as low as possible toavoid a heavy pressure drop through the mill,with correspondingly high mill fan power con-sumption.

The advantages of low pressuredrop, as provided by a one compartment

mill, and the high grinding efficiency of atwo compartment mill, are combined in asingle unit in the Duodan mill.

The Duodan offers a number of designadvantages over conventional ball mills:! High drying capacity! High grinding efficiency! Low pressure drop

OPERATING PRINCIPLEThe Duodan, which is used for drygrindingof raw materials, is a semiairswept millequipped with a drying chamber and twogrinding compartments: a pregrinding com-partment containing large steel balls, and afinegrinding compartment using small steelballs or Cylpebs as grinding media. Thesetwo compartments are separated by dia-phragms and a peripheral outlet.The material to be ground passes through thedrying chamber before entering the

pregrinding compartment. The drying cham-ber is fitted with lifters which cascade the rawmaterial through the hot air current during millrotation. The mill is designed with large flowareas for the drying air drawn through the dry-ing chamber and pregrinding compartment tomaintain a flow of hot gas at relatively highvelocity while at the same time ensuring lowair velocity through the finegrinding compart-ment.The mill discharge material is conveyed to theseparator by Fluxoslides or screw conveyors,elevators, and to a lesser extent, by the millvent air. On leaving the separator the finishedmaterial is passed into cyclones. The rejectmaterial is returned to the fine- grinding com-partment, except for a small amount which issent to the pregrinding compartment.

DESIGNThe Duodan mill is equipped with one trun-nion bearing and one slide-shoe bearing and isarranged for central drive. The mill is pro-vided with inlets at both ends for the first and

second grinding compartments, respectively.Mill body. All-welded shell with a cast steelconical mill head at the secondary inlet end,welded to the shell. A cast steel trunnion isfastened to the mill head and the slide ring tothe mill flange by tight-fitting bolts.The drying chamber is cantilevered from theslide ring and consists of an all-welded shellflanged to the web of the slide ring by meansof tight-fitting bolts. At the inlet end, a steelfront plate is bolted to the shell flange.Trunnion bearing. The mill trunnion restsin a self-aligning ball-and-socket type bearinglined with white metal. This oil-lubricatedbearing is bolted to a heavy base plate.Slide-shoe bearing. The slide ring runs in abearing fitted with two self-aligning slideshoes which are supported on rollers mountedon a robust bedplate to allow for the longitu-dinal expansion and contraction of the millbody. Slide ring and bearing are enclosed in adust-tight casing.Both bearings are water-cooled and providedwith a self-contained oil

pumping unit enclosed in a metal casing. Thisunit comprises an oil circulation pump forgeneral lubrication, and a high-pressure oilpump to ensure lubrication during mill startand barring.Drive. A welded-up, flanged, cylindricalconnection piece for the Symetro gear driveis attached to the trunnion by tight-fittingbolts.Inlets. At the primary inlet a large diameterplate steel funnel is provided to channel thefeed and drying air into the drying chamberthrough a large opening in the steel frontplate. An air seal between funnel and frontplate, and a funnel support, are also pro-vided.

At the secondary inlet the connec-tion piece is provided with a large scoop-ing device and internal flights to trans-port tailings from the separator to thefine-grinding compartment. Additionalopenings are provided in the connec-tion piece for passage of ventilation ordrying air into the fine grinding com-

partment. Also included are a casingwith support and seals forthe rotary parts, as well as steel plate liningsfor connection piece and trunnion.Outlet. The drying air and ground materialfrom the first and second grinding compart-ments leave the mill through a peripheral out-let in the form of oblong openings in themill shell between the two compartments.

The outlet section of the mill, which isprotected by bolted-on wear plates betweenthe openings, is separated from the grindingcompartments by diaphragms, described be-low. Also included is a stationary, airtightoutlet easing with supports, seals at the millshell, outlet flange at the bottom, and an open-ing in the upper part fitted with an expansionjoint for connection to an exhaust duct.Internal fittings. The drying chamber is linedwith bolted-on carbon steel plates and isequipped with highgrade cast steel lifters.

The first grinding compartment has asteplining of highchromium cast steelbolted to the mill shell, while the second

compartment is fitted with bolted-onhighchromium cast steel and grouted-in castDragpeb lining plates.

A scooping device with carbon steel scoopsfor lifting the feed into the mill proper is fittedbetween the drying chamber and first grindingcompartment. The scooping device is boltedto a heavy double supporting plate joined tothe web of the slide ring, forming the inlet endplate of the first grinding compartment

This inlet end plate and the mill head areprovided with bolted-on, wear-resistant liningplates of high- chromium cast steel.

The diaphragms at the outlet end of thetwo grinding compartments each comprise amild steel front plate

bolted to cast steel segments, which in turnare bolted to the mill shell. Welded onto thefront plates are stiffening flatirons and tubespacers. The front plate supports cast-steel,wear- resistant grates via bolts through the tubespacers.

Self-aligning trunnion bearing Slide ring and slide shoe bearing

FLS Separator, Type RTE Installation for grinding raw material

Dimensioning

Approx.Capacity

t/h

*) Not including grinding media and Symetro gear **) Depends on length of compartment II

Dimensions (m)Mill size

48X 7.5+3.2 19,5 4,9 8,3 4,9 3,3 10,9

48X 8.5+3.2 20.5 4.9 8.3 5.4 3.3 11.8

48X 9.5+3.2 21.5 4.9 8.3 5.4 3.3 12.8

48X 10.5+3.2 22.5 4.9 8.4 5.9 3.3 13.7

56X 8.0+4.4 22,0 5.7 9.1 5.1 4.6 11.5

56X 9.0+4.4 23.0 5.7 9.3 5.6 4.6 12.5

56X 10.0+4.4 24.1 5.7 9.4 6.0 4.6 13.4

56X 11.0+4.4 25.0 5.7 9.7 6.6 4.6 14.5

OPTION. As an alternative the mill can be fitted with a side drive with one or two pinions.

125-165 48X 7.5+3.2 2500 14.0 157 305

140-185 48X 8.5+3.2 2800 14.2 174 320

155-205 48X 9.5+3.2 3120 14.1 197 330

175-235 48X 10.5+3.2 3500 14.2 223 340

200-265 56X 8.0+4.4 3960 12.9 230 425

225-300 56X 9.0+4.4 4480 13.0 260 440

250-335 56X 10.0+4.4 5050 13.0 290 460

275-370 56X 11.0+4.4 5540 12.8 324 480

Mill sizeMotor

kWRPM

Maximumcharge

of grindingmedia

t

*) Weightof mill

t

A B C D**) E F

Data in this brohure is only intended for preliminary project Planning. Manufacturer reserves the right to modify equipment details and/or specifications without notice.

DENMARK: F.L. Smidth & Co. A/S Vigersley A11é 77, JAPAN: F.L.Smidth & Co. (Japan) Ltd., Togeki Building, 1-1, Tsukiji 4-chome,DK-2500 Valby Copenhagen Chuo-ku, Tokyo 104, Postal address: Kyobashi P.O. Box 78, Tokyo 104-91

MEXICO: F.L. Smidth & Cia., S.A. de C.V., Ave. Campos Eliseos, 385,BRAZIL: F.L Smidth S.A., Comérelo c Indùstria, Rua Nebraska, 443, 5' piso, Torre B, Chapultepee Polanco, 11560 Mexico City, D.EBrooklin Paulista - CEP 04560, Caixa Postal 3506, 01000 Sdo Paulc - SP PR OF CHINA: F.L. Smidth & Co. A/S, Beijing Representative Office,CANADA: F.L.Smidth & Co. of Canada, Ltd., 2000, Yanjing Hotel, Suite 801218014, Fuxing Men Wai, BeijingRue Mansfield, Suite 800, Montreal, Quebec, Canada H3A 2Z5 SOUTH AFRICA: F.L. Smidth & Co. (S.A.) (Pty.) Ltd., Craighall Mews, 347FEDERAL REPUBLIC OF GERMANY : F.L.Smidth & Co. GmbH, Jan Smuts Ave, Craighall Park, Transvaal. Postal address: PO. Box 41455,Geniner Strasse 133-135, Postfach 1632, D-2400 Lübeck 1 2024 Craighall, TransvaalFRANCE: F.L. Smidth & Cie-France, S.A.R.L., 55, Rue Ampére, F-75017 Paris SPAIN: F.L.Smidth & Cia. Espanola, S.A., Ay. General Peron, 38,17O E-28020 MadridHONG KONG: Representative Office of F.L.Smidth & Co. A/S UNITED KINGDOM: F.L. Smidth & Co. Limited, 17, Lansdowne Road,25 Floor Hop Hing Centre, 8-12 Hennessy Road, Wanchai Croydon, CR9 2JTITALY: F.L.Smidth & C. Itailana S.rl., Via Lucilio, 25, 1-00136 Rome USA: F.L. Smidth & Co., 300 Knickerbocker Road, Cresskill, N.J. 07626