Kiln Comparison Data
Wet Long Dry 1-Stage SP 2-Stage SP
3-Stage SP* Conversion 4-Stage SP SF SF Conversion Short* L/D Kiln Capacity (Mg·d-1·m-3) 0.45-0.70 0.45-0.75 0.75-0.85 0.9-1.0 1.0-1.3 1.5-2.0 3.0-4.0 3.0-3.5 3.5-4.7 L/D (inside brick) 38-44 36-41 30-40 32-34 23-26 15-18 15-18 15-22 10-12
Kiln speed, oper (rpm) 1.2 1.35 1.4 1.4 1.5 1.6 2.8 2.8-3.8 2.1
Kiln speed, max (rpm) 1.4 1.6 1.7 1.7 1.75 1.9 3.3 3.3-4.5 2.5
Slope (%) 3.65 3.65 3.0-4.0 3.0-4.0 3.0-4.0 4.0 4.0 3.0-4.0 3.5
Fill (%) 10-13 10-13 10-13 10-13 10-13 10-13 10-13 10-13 10-14
Ovality (%) 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20
Retention time (min) 150-200 120-160 110-140 95-120 70-85 40-45 20-25 20-30 20-25 Hertz pressure 62,000 62,000 62,000 62,000 62,000 62,000 59,000 59,000 59,000 SHC (kcal·kgKK-1) 1300-2000 1150-1450 1050-1150 1000-1100 900-1000 750-860 750-860 750-860 720-780 KEG temperature (°C) 250-300 550-600 650-700 750-800 900-950 1000-1100 1000-1100 1000-1100 1050-1200 Feed moisture (%) 28-35 0.5 0 0 0 0 0 0 0 KEG velocity (m·s-1) 4-5 4-5 8-10 8-10 8-10 8-10 4-5 4-5 4-5 BZ load (Gcal·h-1·m-2) 5-6 5-6 4.75-5.75 4.5-5.5 4.25-5.25 4-5 2.5-3.5 2.5-3.5 2-3
Stage 1 exit gas T (°C) --- --- 400-425 375-400 375 350 375 375 325-350
Chain section Yes Yes Yes (short) Yes (short) No No No No No
Wet Long Dry 1-Stage SP 2-Stage SP
3-Stage SP* Conversion 4-Stage SP SF SF Conversion Short* L/D Kiln Capacity (lbm·d-1·ft-3) 28-44 28-44 47-53 56-62 62-81 94-125 187-250 187-218 218-293 L/D (inside brick) 38-44 36-41 30-40 32-34 23-26 15-18 15-18 15-22 10-12
Kiln speed, oper (rpm) 1.2 1.35 1.4 1.4 1.5 1.6 2.8 2.8-3.8 2.1
Kiln speed, max (rpm) 1.4 1.6 1.7 1.7 1.75 1.9 3.3 3.3-4.5 2.5
Slope (%) 3.65 3.65 3.0-4.0 3.0-4.0 3.0-4.0 4.0 4.0 3.0-4.0 3.5
Fill (%) 10-13 10-13 10-13 10-13 10-13 10-13 10-13 10-13 10-14
Ovality (%) 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20
Retention time (min) 150-200 120-160 110-140 95-120 70-85 40-45 20-25 20-30 20-25 Hertz pressure 62,000 62,000 62,000 62,000 62,000 62,000 59,000 59,000 59,000 SHC (MMBtu·tonKK-1) 4.7-7.2 4.1-5.2 3.8-4.1 3.6-4.0 3.2-3.6 3.6-4.0 3.6-4.0 3.6-4.0 3.8-4.3 KEG temperature (°F) 500-600 1000-1100 1200-1300 1400-1500 1650-1750 1400-1600 1400-1600 1400-1600 1300-1450
Feed moisture (%) 28-35 0.5 0 0 0 0 0 0 0
KEG velocity (ft·min-1) 800-1000 800-1000 1600-2000 1600-2000 1600-2000 1600-2000 800-1000 800-1000 800-1000 BZ load (MMBtu·h-1·ft-2) 1.84-2.21 1.84-2.21 1.75-2.12 1.66-2.03 1.57-1.94 1.47-1.84 0.92-1.29 0.92-1.29 0.74-1.11
Stage 1 exit gas T (°F) --- --- 750-800 700-750 700 650 700 700 600-650
Raw Grinding
VRM nozzle ring velocity (AChin-Fatt):
80-90 m/s (w/o external recirc) [15,750-17,700 ft/min] 65 m/s (w/ some material recovery ( 15%)) [12,800 ft/min] 40-45 m/s (w/ external recirc ( 25%)) [7,900-8,850 ft/min]
VRM gas flow (Polysius): 1.64 kggas/kgmeal
VRM vibration:
Frame/reducer mounted sensor: 3 mm/s
Housing mounted sensor: 10 mm/s (e.g. Loesche) VRM (w/ dynamic classifier) exit duct grain loading:
620 g/m3 [270 gr/ft3] (LSingh / Polysius) 500-700 g/m3 [225-300 gr/ft3] (AChin-Fatt / Loesche) 500-700 g/m3 [225-300 gr/ft3] (GLabelle / LVT) VRM bed depth: Typical: 3-4” (75-100 mm) Maximum: 5” (125 mm)
Approximately 3.5% of table diameter (e.g. Loesche LM36 = 3.6 m × 0.035 = 125 mm) Approximately 6-8% of roll diameter (AChin-Fatt)
Power consumption:
VRM: 3-12 kWh/ton (=f(material grindability))
BM: 9-17 kWh/ton
Typical feed size: VRM: 3-5”
BM: 1¼” max to 80% -¾” Typical feed moisture:
VRM: > 24%
BM: 2-3% w/o drying capability 6-8% w/ drying capability
Typical product fineness: 80% -200M (75 ) 0.1% +50M (300 ) Specific surface area of ball charge:
16-20 m2/Mg (AChin-Fatt) Ball charge volume:
24-28%
Mill sweep (AChin-Fatt):
Not air-swept: 0.8-1.5 m/s Semi air-swept: 2.0-3.5 m/s Fully air-swept: 3.5-6.0 m/s
Dew point:
Minimum 40°F < dry bulb T
Pyroprocess
Clinker production increase = f(Q) or f(SP): KK2 = KK1 × (SP2 / SP1)½
KK2 = KK1 × (Q2 / Q1)
Specific exit gases flow (=f(SHC, fuel characteristics)):
780-830 kcal/kgKK (2.8-3.0 MMBtu/tonKK): 1.95-2.15 kg/kgKK [1.35-1.50 Nm3/kgKK] 830-890 kcal/kgKK (3.0-3.2 MMBtu/tonKK): 2.10-2.30 kg/kgKK [1.45-1.60 Nm3/kgKK] Kiln exit static pressure: 1.5-2.5 inWG (suction)
% Calcination =
100
%
100
100
100
KF KF sample sample KF KFLOI
LOI
LOI
LOI
LOI
LOI
Excess air = O2(final) / (20.9 – O2(final)) × 100%
False air = (O2(final) – O2(initial)) / (20.9 – O2(final)) × 100% Note: w/ respect to inlet gases
False air = (O2(final) – O2(initial)) / (20.9 – O2(initial)) × 100% Note: w/ respect to outlet gases
ESP operation (combustion / explosion):
Set @ 25% of lower flammability limits
CH4: 25% of 5% (50,000 ppm) = 12,500 ppm CO: 25% of X% (YYYY ppm) = ZZZZ ppm Hood velocity: 5-8 m/s (FLS) 5-6 m/s (MMcCabe) 4 m/s (KHD) Cyclone p: 1st stage: 5-6 inWG 2nd stage: 8-10 inWG 3rd stage:8-10 inWG 4th stage: 10-12 inWG Bypass:
- Heat penalty (4-stage SP): 5% BP ≈ 1% KF - 16,000-22,000 Btu/tonKK per % BP
Volatiles:
- KK S/Alk molar ratio 0.8-1.2 (can be higher as long as sulfur (SO3) comes out in KK) - Typical equilibrium time = 150 × kiln retention time [LSingh]
- Volatilization approx. 15-20 gr/ft3 - Chlorides:
o < 1.0% of kiln inlet (raw basis) o < 0.07% in fuel
o kiln inlet approx. 50 ×’s inputs
o precipitate / condense @ 900-1200°F (475-650°C)
Clinker cooler cooling air requirement:
Reciprocating grate cooler: 2.8-3.2 kgair/kgKK
S-F cross-bar cooler: 2.2 kgair/kgKK (as advertised; realistically 2.5)
Secondary (+ tertiary) air mass (=f(1° air, NCA, SHC, EA)): Direct-fired system: 0.9-1.2 kgair/kgKK
Indirect-fired system: 1.2-1.5 kgair/kgKK
SA / TA proportioned according to fuel split & EA
Clinker cooler (grate) loading:
Older grate cooler: 30-40 Mg/d/m2 Modern grate cooler: 40-50 Mg/d/m2
Kiln nose cooling fan [HTseng / Polysius]: 725 acfm/ft-Ø
SP = 7-8 inWG v = 4,500-5,000 ft/min
Manifold v approx 50-60% of nozzle velocity to ensure uniform air distribution Burner tip velocities:
Conveying air: 20-50 m/s (80 m/s if single channel burner) Axial air: 80-170 m/s
Swirl air: 50-90 m/s Gas: 200 m/s
Typical kiln feed densities (Peray p. 178): Preheat zone 75 lb/ft3 (1,200 kg/m3) 10% calcined 73 lb/ft3 (1,170 kg/m3) 20% calcined 70 lb/ft3 (1,120 kg/m3) 40% calcined 65 lb/ft3 (1,040 kg/m3) 80% calcined 60 lb/ft3 (960 kg/m3) Burning zone 92 lb/ft3 (1,475 kg/m3)
Estimated kiln feed angle of repose (Peray p. 178): Preheat zone 45° 10% calcined 27° 20% calcined 24° 40% calcined 21° 80% calcined 18° Burning zone 50°
Kiln chain unit weight (per Magotteaux): ¾” × 3” Ø: 5.9 lb/ft
7/8” × 3” Ø: 8.6 lb/ft 1” × 3” Ø: 12.52 lb/ft
Typical chain system design criteria (LSingh): Chain Zone
% kiln length, including bare inlet section 20 – 30
Total chain wt
% of daily production (ton/d) 8.0 – 12.0
ton chains / ton KK 2.1 to 2.5
Specific surface area (ft2 / ft3 of chain zone) 2.6 to 3.7 Length of dust curtain chains (ft / ft kiln Ø) 0.66 to +0.77
Kiln chain weight installed (per Duda): Wet process: 120 kgchain/MgKK/d Dry process: 105-110 kgchain/MgKK/d
Fuel volatile matter:
- Decreased VM results in decreased reaction, ergo increased CO (combat via finer grinding & higher temperatures) - Typical values: o Coal (bituminous): 25-40% o Coal (anthracitic): 5-15% o Coke (delayed): 8-18% o Coke (fluid): 3.7-7.0%
Typical gross heating values and LHV:HHV ratios:
- Coal: 12,000 Btu/lbm 0.970
- Coke: 14,000 Btu/lbm 0.980
- TDF: 13,700 Btu/lbm (whole tire w/ 13-15% steel) 0.960
- Fuel oil: 138,000 Btu/gal 0.945
- Natural gas: 1,050 Btu/scfm 0.905
Coal/coke fineness (FLSmidth):
Recommended Fineness of Coal/Coke for Kiln and Calciner
0 5 10 15 20 25 30 0 5 10 15 20 25 30 35 40 45 50
% Volatiles (ash and moisture free)
% R 9 0 m Normal T calciner High T calciner Kiln burner
Solid fuel fineness (PAlsop): 0.5% × %VM –200M
Coal/coke residual moistures (FLSmidth):
Anthracite coal and pet coke: 0.5-1.0%
Bituminous coal: 1.5-2.5%
Coal mill air:fuel ratio (for drying):
Smaller vertical mills: 2.0-2.5 lbair/lbfuel @ 55 HGI 1.0-1.7 lbair/lbfuel @ 100 HGI Larger vertical mills: 1.5 lbair/lbfuel @ 55 HGI
1.0 lbair/lbfuel @ 100 HGI
Ball mills: 0.8-1.0 lbair/lbfuel (lower for lighter materials) (HRoser / KVS)
Coal mill (VRM) exit duct grain loading:
350-380 g/m3 [150-165 gr/ft3] (AChin-Fatt)
Separator (HES) product grain loading:
300-500 g/m3 [125-225 gr/ft3] (GLabelle / LVT)
Maximum 600 g/m3 [260 gr/ft3] before see negative impact on separator performance Mill sweep (fuel ball mill):
Semi air-swept: 1.0-2.0 m/s (typical 1.5)
Fully air-swept: 1.0-2.0 m/s (typical 1.5) [note: CEMEX Brooksville 0.5 m/s] KVS: 2,500-3,000 fpm (13-15 m/s) thru discharge trunnion opening
HES rotor peripheral speed: vT = r = r × 2 / t 16-19 m/s (AChin-Fatt) 14 m/s (GLabelle)
Ball mill discharge duct exit velocity:
16 m/s minimum (KVS – MGallimore) Microscopy:
Heating rate = f(alite size); target = 15-35 m Small = too fast
Large = too slow
Residence time = f(belite size); target = 25-40 m Small = too short
Large = too long
Maximum temperature = f(alite birefringence); target > 3.6 Cooling (quenching) rate = f(belite color); target > 3.6
Calcination:
Reaction starts ~ 700°C (1,292°F)
Reaction fully underway ~ 800°C (1,472°F)
Combustibles in kiln feed:
Organic (volatile) C ~ 250-350°C (482-662°F) Inorganic (fixed) C ~ 650-900°C (1,202-1,652°F) Secondary firing:
1 s retention time in preheater 20% back end firing
VRM grinding pet coke (need to increase friction to increase capacity): Increase dam ring height
Add water
Finish Grinding
(BSA1 / BSA2)n = ton/h2 / ton/h1 = kWh/ton1 / kWh/ton2 n = 1.3 for HES
n = 1.6 for 1st gen sep
Separator efficiency (bypass): 1st generation: 40-60% 2nd generation: 20-40% 3rd generation: 8-20% Separator (1st generation) clearances:
Gap between blade top and drum cover: ⅜-½” Blade extension under drum cover: 1½-2”
Separator (HES) feed concentration (Qf/Qa):
O-Sepa: 2.5 kg/m3 [1100 gr/ft3] (higher because of distribution table) SEPAX: 2.0 kg/m3 [875 gr/ft3] (lower because fully air-swept)
Separator circulating factor, C:
C = Rejects (ton/h) / Fines (ton/h) = [fines (x) – feed (x)] / [feed (x) – rejects (x)] CL = Feed (ton/h) / Fines (ton/h) = [fines (x) – rejects (x)] / [feed (x) – rejects (x)] C = CL – 1
Typical C for 1st generation: 200-600% (low end of range for lower Blaine)
Typical C for 3rd generation: 100-200% (low end of range for lower Blaine)
Separator (HES) exit duct grain loading (to D/C):
Slag: 400-500 g/m3 [175-225 gr/ft3] (GLabelle / LVT) Cement: 500-700 g/m3 [225-300 gr/ft3] (GLabelle / LVT) Cement: 0.75 kg/m3 (AChin-Fatt) [325 gr/ft3]
Separator (HES) rotational speed (): 20 m/s (for BSA = 3600 cm2/g) O-Sepa 2 rpm/50 cm2/g
Tromp Curve (FLSmidth):
Cut size: particle size corresponding to the Tromp-value 50% (depends on rotor speed and fineness level; ideally on the steepest part of the curve)
Slope (): slope of the curve in the interval 25-75%, e.g. P25/P75 Normal ranges: HES > 0.5
2nd gen 0.3-0.4 1st gen 0.25-0.35 Bypass (): Tromp value at lowest point on curve
Normal ranges: HES 5-15%
2nd gen 20-40% 1st gen 30-60%
Tromp curve shape affected by:
Material load: excessive loading results in increased bypass and lower value Airflow: insufficient airflow results in higher bypass value and lower value Circulation factor: increase in circulation factor leads to increase in the bypass value
Grinding aid: the use of grinding aid may counteract agglomeration, resulting in reduced bypass value and increased sharpness of separation
Slot sizes:
C1: 6-8 mm C2: 8-10 mm
Slot open area:
6-8% of effective area (AChin-Fatt/Fuller) [excluding center screen] 15% of effective area (PAlsop) [including center screen]
Material size at division head: 4% +2mm (5% +8M) Material size at mill discharge:
1600-1800 cm2/g (approx half of final product BSA) 5% +30M
FM ball charge surface area:
C1: 9.5-10.5 m2/Mg (3.0-3.5 lbm/ball)
C2: 26-29 (AChin-Fatt) or 28-33 (JBump) or 35-38 (PAlsop) m2/Mg Mono: 18-20 m2/Mg (AChin-Fatt)
Power consumption (=f(feed size)):
BM: 32-36 kWh/ton (ideal); 34-38 kWh/ton (typical) [1-1½” feed F80] BM: 35-40 kWh/Mg (ideal); 37-42 kWh/Mg (typical) [25-38 mm feed F80]
Specific power consumption (LSingh):
Mill w/ conventional separator: 1.0 × (BSA/100) = kWh/ton Mill w/ high efficiency separator: 0.9 × (BSA/100) = kWh/ton Mill w/ HES and roller press: 0.75 × (BSA/100) = kWh/ton
Fluorescein mixture:
2 g fluorescein per Mg/h total mill feed 600-800 ml alcohol
2.5 kg mill feed (proportioned for raw KK, gyp and returns)
Fluorescein analysis:
100 ml beakers (10-20) 5 g material
50 ml distilled water
Grinding aid consumption (8.5 lb/gal): T-I: 0.9-1.1 lbm/toncement T-III: 1.2-1.4 lbm/toncement
Typical allowance in tube mill shell length (AChin-Fatt):
Feed end liners 75 mm
Central diaphragm 500 mm
Discharge diaphragm 350 mm Typical shell liner thickness (AChin-Fatt):
Lifting (step) liner 95 mm
Classifying liner 90 mm
Lifting (compt 2) 63 mm
Torque factor in 2nd compt ( in FLS power consumption equations) (AChin-Fatt): Classifying liners 0.65
Lifting liners 0.67
DUO-3 liners 0.66
Ball mill absorbed power design notes (AChin-Fatt):
For dry grinding raw mill, add power for the drying compartment For air swept raw mill, increase the calculated power draw by 1.08
For wet grinding raw mill, decrease the calculated power by 0.75 to 0.9 (low for lower % solids) For wet grinding raw mill, use balls no less than 1" in 2nd compt as finer balls tends to float For slag grinding mill, decrease the calculated power draw by 0.95
Typical power losses:
Gear & Pinion 3.5%
Reducer 1.5%
Motor 3.0%
Ball volume (%) ≈ 113 – 126 × (H / D)
Ball mill operating rotational speed (% of critical): 75-78%
Dust Collection
Air-to-cloth ratio:
Pulse Jet (process D/C): 4.0-4.5 acfm/ft2
Pulse Jet (nuisance D/C): 5.0-6.0 acfm/ft2 R/A: 2.0-2.5 acfm/ft2
“Star” bags: 4.0-4.5 acfm/ft2 Pleated elements: 4.0-4.5 acfm/ft2 D/C can (or thimble) velocity: < 250 ft/min
D/C p:
Pulse Jet: 3.5-4.5 inWG (bags blinded at 7 inWG) R/A: 2.0-3.0 inWG (bags blinded at 5 inWG) “Star” bags: 4.0-5.0 inWG (bags blinded at 7 inWG)
D/C off-time: 8-15 s (higher the better; low off-time contributes to internal bag wear) D/C on-time: 0.10-0.12 s (dependent on “bang”)
Blow pipes:
Number of holes per pipe 16
Hole Ø: hole areas pipe cross-sectional area
1½” Ø pipe (sched 40): I.D. = 1.610”, A = 2.036 in2 1¼” Ø pipe (sched 40): I.D. = 1.380”, A = 1.496 in2 1” Ø pipe (sched 40): I.D. = 1.049”, A = 0.864 in2 ¾” Ø pipe (sched 40): I.D. = 0.824”, A = 0.533 in2 Stagger firing sequence: e.g. 1-4-7-10-2-5-8-11-3-6-9-12-etc.
Gravel Bed Filter (GBF):
Gas flow per module: 20,000 acfm [LSingh]
Based on 128 acfm/ft2 total filter area (comes to 15,000 acfm) [Rexnord]
Backflush flow: 8,400 acfm (some specs call for 7800 acfm) [Rexnord, Lurgi] Based on 145-150 acfm/ft2 (flux), 9 ft Ø screen, 2.5-3.0 ft Ø dip tube, 57-59 ft2 screen area Lower: improper cleaning
Design p: 8-9 inWG (typical is 9-12 inWG)
Gravel bed depth: 4.5 in
Rake clearance above screen: 3/8 in Design inlet grain loading: 4-6 gr/ft3 Cyclone dimensioning: 600 , 3 · · · 6 . 2 · 4 n V d
where: d = nominal cyclone diameter [m]
V = total airflow [m3·h-1] n = number of cyclones [---] Fans Fan power: P [kW] = Q [m3/s] × p [kPa] / [%] BHP [hp] = Q [cfm] × SP [inWC] / 6356 / [%] ( = static efficiency)
Note: fan p is total pressure difference across fan
Fan laws:
Density Change Speed Change Size Change
Q2 = Q1 Q2 = Q1 × (N2 / N1) Q2 = Q1 × (D2 / D1)3
p2 = p1 × (2 / 1) p2 = p1 × (N2 / N1)2 p2 = p1 × (D2 / D1)2 P2 = P1 × (2 / 1) P2 = P1 × (N2 / N1)3 P2 = P1 × (D2 / D1)5
Note: valid only for speed changes up to 25% because of assumption that fan efficiency remains constant Tip speed, u:
u [fpm] = × D [ft] × N [rpm]
Rule of thumb for calculating fan total pressure w/ straight impeller vanes:
g u ptotal 0.6 2
where: ptotal = fan total pressure [Pa] = gas density [kg·m-3]
u = tip speed [m·s-1]
g = gravitational constant [9.80665 m·s-2]
Wheel inertia:
wr2 [lbm·ft2] = W [lbm] × (0.35 × D [ft])2
Round duct equivalent of rectangular duct:
5 3 265 . 1 b a ab Dr Environmental
Dioxin / Furan formation 450-800°F (230-425°C) Water injection (NOx control):
~ 1 gpm per ton of fuel 10-15% NOx reduction
SNCR:
Up to 85% NOx reduction 0.40-0.80 USD/tonKK
Auxiliary Equipment
HEX tube design: 2000-2500 fpm tube velocity (HTseng)
Conditioning (spray) tower:
air-to-water pressure ratio: > 1.1:1 (empirical @ DEM)
air-to-water pressure bias: 10-35 psi (supercedes above note based on LYO & BAL) air rqmt: 95-110 acfm/lance
inlet duct: 15° slope (to the vertical)
ensure nozzles / spray pattern doesn’t overlap (creates large droplets) soft mist spray desirable, hard spattering spray undesirable
Engineering / Miscellaneous
Pipe conveying velocities: 3,500-4,000 fpm (18-20 m/s) to transport fine material (raw meal, clinker dust, cement)
Pyroline conveying velocities [PAlsop]: Upper limits:
Through cooler grate: 5 m/s
Kiln hood: 6 m/s
Under cooler bull nose: 15 m/s
Burning zone (1,450°C): 9.5 m/s
Kiln feed end transition (1,000°C): 13 m/s
Preheater riser duct: 24 m/s
Preheater gas ducts: 18 m/s
Lower limits:
Tertiary air duct: 25 m/s
Pulverized coal conveying: 20 m/s [PAslop]; 16 m/s [GLabelle, Pillard]
Ball mill conveying velocities [Lafarge]:
Discharge trunnion: 23-25 m/s (max)
Discharge housing: 4-5 m/s
Discharge duct: 10-15 m/s
Steel erection: $3.00/lb steel (stiffeners, etc. multiply by 1.25-1.75) [HTseng] Refractory installation: $1.75/lb refractory [MGower]
Refractory demolition: $0.44/lb refractory [MGower]
Power consumption by P (damper or other):
kW = Q (ft3/min) × 0.30483 (ft3 to m3) / 60 (s/min) × P (inWC) × 0.24884 (inWC to kPa) note: Pa = kg·m-1·s-2 and W = kg·m2·s-3
Motors:
If designed for 0.8 PF () and a given hp, can incr to 1.0 and get more hp as long as stay below FLA kVA = 3 × E × I /1000
kW = 3 × E × I × /1000
= kW / kVA = cos ( = phase angle)
Transfer point dust collection vent line sizing: Assume 1 ft3 per 1 ft/min belt speed (???)
e.g. 24” belt = 24” × 6” (height of air above belt) = 2’ × ½’ = 1 ft2 × 1000 ft/min = 1000 cfm Hardness scales:
Solid fuels: Hardgrove grindability index (HGI) – lower value represents harder to grind material Minerals: Mohs scale (1 = talc, 10 = diamond)
Metals and alloys (penetration tests):
Brinell hardness number (HBN)
Rockwell hardness test (Rc) [note: scales A, B, C, D, E, F, G) higher value = harder
Also: Vickers, Meyer, Meyer-Vickers, Knoop
Kiln nose ring cooling air flow (HTseng / Polysius):
Total air flow requirement = 725 acfm/ft-Økiln [Duda approx 20% higher] Nozzle velocity = 4,500-5,000 ft/min
Fan SP = 6.5-8.0 inWG
Manifold velocity approx 50-60% nozzle velocity
Kiln shell/tire thermal gradient (T between the two): Typical (floating tire): 180°C Modern (splined/fixed tire): 360°C
Calculation of shaft diameters (Polysius):
n N Md 71,620 where: Md = torque [cm·kg] N = power [hp] n = rotational speed [rpm] 3 2 . 0 d d K M d
where: d = shaft diameter [cm] Kd = torsional stress [kg·cm-2]
Wrought iron 120
Mild steel 200-400
Forged steel 300-480
