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Fig. 1. Tirax coal mill with separator Type STJ Fig. 3. Grinding
Installation for indirect firing. inert operation with
electrostatic precipitator dedusting
oal firing installations in industry are normallyombined with
grinding and drying unitsecause solid fuels require a certain
degree ofrocessing before their latent energy can be
fullytilised.
L. Smidth have designed and supplied grind-g, drying and firing
plants for more than 75
ears, contributing significantly to the technologi-al advances
in this field.
With the experience thus gained, FLS are in aosition to offer a
wide range of equipment andomplete plants for coal grinding, all of
whichre designed to meet individual requirementsoncerning grinding
economy, explosion safety,nd flexibility in operation.
ome of the special features of FLS coal grind-g equipment
are:
Ability to process every known kind of solid
fuel, including the highly abrasive types ofcoal.
! Automatic operation can be adapted to mostcategories of modern
industrial plants.
! Drying and grinding are combined in onemachine.
Design
The Tirax mill is of the tube type made of highquality steel
plate. The inlet end is supported bya self-aligning slide shoe
bearing which permits
the passage of a large amount of hot air to drythe materials
being processed.
The outlet end is fitted with a trunnion supportedon the
bearing. The bearing, trunnion, and slide
shoe are lubricated by means of forced oil circu-lation during
mill operation. High-pressure lubri-cation is used during the
start-up phase.
The Tirax mill is of the air-swept type without out-let grate.
The large passage area of the out- letensures high air velocity
through the mill to raiseits drying capacity.
Mill compartments
The Tirax mill has a drying compartment whichis protected
internally by wear plates with welded-on lifters. These lifters
convey the coal along themill in order to keep the inlet clear and
to ensure
that the coal is thoroughly blended into the flowof hot air.
The Tirax coal mill is designed with a single grind-ing
compartment to provide an unobstructed flowof air through the mill.
A classifying lining ensuresdiminishing sizes of grinding media
towards theoutlet.
Mill drive
The mill has a two-part spur rim bolted onto aflange near the
outlet end. The pinion is directlyconnected to a precision gear
unit. The pinionshaft runs in roller bearings in mills up to a
cer-tain size and in sleeve bearings above this size.
The bearings are supported on a box- shapewelded base plate. The
spur rim and pinion areenclosed in a dust and oil-tight casing.
SeparatorThe robust and uncomplicated separator usedin the FLS
Tirax coal mill has no moving parts. Itis provided with
explosion-relief and requires littlemaintenance. The fineness of
the finish- ground
coal meal is adjustable. When separated, thecoarse material is
returned to the mill inlet via ascrew conveyor and fed into the
mill through afeed chute together with the feed of wet raw
coal.Among other purposes, this prevents the drycoarse returns from
being ignited by the hot dry-ing gas.
Coal grinding Installations
The design of a coal grinding installation dependsgreatly on the
type of coal for firing, the sourceof drying gas, the number of
points at which thecoal meal is consumed, the type of kiln to be
fired,and finally on the spaceavailable especially in cases where a
new millinstallation is to be added to an existing kiln.
Such factors as machinery costs, maintenancecosts, and
operational reliability must be taken
into account when planning the installation of acoal grinding
plant. Decisions must be reachedwith regard to:
! direct or indirect firing
! inert and non-inert operation! dedusting by bag filter or
electrostaticprecipitator
The flow diagram Fig. 2 shows an example of anindirectly fired
coal grinding plant, non-inert op-eration, for a kiln with Fo lax
grate cooler and witha bag filter for dedusting.
The flow diagram Fig. 3 shows an indirectly firedcoal grinding
plant, inert operation, for aprecalciner kiln. Dedusting is by
electrostaticprecipitator.
FLS supply range
Tirax mills are available with nominalthroughput ranging from 12
to 47 tph, or evenhigher if required. The throughputs shown in
thetable apply to coal of normal grindability
with lump sizes up to 25 rnm and ground downto 12-15% residue on
a 90 micron sieve.
The drying chambers of the mills indicated in thetable are
dimensioned fordrying coal with a mois-
ture content of 10%, but mills for process ing coalwith a
considerably higher moisture content canalso be supplied.
The type designation TM 40 x 5 + 3.8, for in-stance, refers to
atirax mill with an inner diam-eter of 4 m, the lengths of the
grinding compart-ment and drying chamber being 5 m and 3.8
m,respectively.
Mill sizing
The specific grinding energy consumption de-pends on the
grindability of the coal in question- this often being specified by
the Hard- groveindex - and the required fineness of the coal
meal,see grindability diagram. The degree of finenessdepends on the
gaseous con- tent of the coaland its origin, see recommended
fineness dia-gram.
Applications and design
Fig. 5. Slide ring and slide shoe Fig 6. Separator Type ST for
Tirax coal mill
Fig 4. Tirax coal mill with Folaphone feed control.
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Data in this brochure series is only intended for preliminary
project planning. Manufacturer reserves the right to modify
equipment details andlor specifications without notice
DIMENSIONING
Rated Capcity Mill Size Motor, kW Charge, tonnes Separator type
A B C D
12 TM 24 x 4.0 +2.4 221 19.2 ST 16/137.5 9968 2440 2920 500014
TM 26 x 4.0 _ 2.4 258 21.8 ST 160/137.5 10333 2644 2920 5000
18 TM 28 x 4.0 + 2.4 330 26.4 ST 190/160 10365 2850 2970
6000
22 TM 30 x 4.5 + 2.8 405 31.8 ST 190/160 11454 3050 2970
6000
28 TM 32 x 4.5 + 2.8 500 39.3 ST 230/190 11770 3254 3120
7100
35 TM 34 x 5.0 + 2.8 630 47.0 ST 230/190 12306 3454 3420
7100
40 TM 36 x 5.0 + 2.8 730 52.0 STJ 250 12775 3654 3720 7400
47 TM 40 x 5.0 + 3.8 900 57.0 STJ 280 13850 4060 4100 8400
DIMENSIONING
Dimensioning
Denmark
F. L. Smidth & Co. A/S
Vigerslev All 77, DK-2500 Valby Copenhagen
United Kingdom
F. L. Smidth & Co., Ltd.
17, Lansdowne Road, Croydon, GB-CR9 2JT
France
F. L. Smidth & Cie - France
55, Rue Ampre. F-75017 Paris
Federal Republic of Germany
F. L. Smidth & Co. GmbH
Geniner Strasse 133-135. D-2400 Lbeck 1
Italy
F. L. Smidth & C. Italiana. S.r.l.
Via Lucilio, 25,1-00136 Rome
Spain
F. L. Smidth & Cia. Espaola, S.A.
Calle de Jorge Juan, 46, E-28001 Madrid
Canada
F. L. Smidth & Co. of Canada, Ltd.
1500 De Maisonneuve Blvd. West,
Montreal. Quebec, Canada H3G 1H1
U.S.A.
F. L. Smidth & Co.
300 Knickerbocker Road. Cresskill. N.J. 07626
Mexico
F. L. Smidth & Cia., S.A. de C.V.
Ave. Campos Eliseos, 385, 5 piso.
Torre B, Polanco, Mexico City 5, D.F.
Brazil
F. L. Smidth, S.A., Comrcio e Indstria
Rua Nebraska, 459, Brooklin Paulista - CEP-04560
Caixa Postal 3506. 01000 So Paulo - SP
South Africa
F. L. Smidth & Co. (S.A.) (Pty) Ltd.
Craighall Mews, Cr. Jan Smuts/Rothesay Ave.,
Craighall Park, Transvaal
P.O. Box 41455, Craighall 2024, Transvaal
Japan
F. L. Smidth & Co. (Japan) Ltd.
Togeki Building 1-1. Tsukiji 4-chome,
Kyobashi P.O. Box 78, Chuo-ku. Tokyo 104-91
