| Ball Mill Performance & Efficiency |
| S. | Description | Symbol | Formula | Example |
| No. | | | | | | | | |
| 1 | Arm of gravity | a | | | 0.666 * ( 1 – 4 * R2 )1.5 | | h | 0.583 |
| | – | | | TAN-1 [ 0.5 / R * (1 – 4*R2)0.5] – [ 2*R * (1 – 4*R2)0.5 ] | | Deff | 4.18 |
| | | | h | Centre Distance (from mill centre to media top layer), mts | | R | 0.139 |
| | | | Deff | Mill effective diameter, mts | | a | 0.578 |
| | | | R | h/Deff, ratio of centre distance to mill effective diameter | | Target | – |
| 2 | Torque factor matrix | u | | | | | – | – |
| | – | | | | | – | – |
| | | | | | | – | – |
| | | | | | | – | – |
| | | | | | | – | – |
| | | | | | | – | – |
| | | | | | | – | – |
| | | | | | | – | – |
| | | | | | | – | – |
| | | | | | | – | – |
| 2 | Power consumption, net | Pn | | | 0.514 * F * u * n * Deff * a | | F | 175 |
| | kW | | F | Grinding media weight, tons | | u | 0.73 |
| | | | u | Torque factor | | n | 16 |
| | | | n | Mill speed, rpm | | Deff | 4.18 |
| | | | Deff | Mill effective diameter, mts | | a | 0.578 |
| | | | a | Arm of gravity, – | | Pn | 2538 |
| | | | | | | Target | – |
| 3 | Power consumption, gross | Pg | | | Pn * 100 * 100 | | Pn | 2450 |
| | kW | | | Em * Eg | | Em | 95 |
| | | | Em | Motor efficiency, % | | Eg | 95 |
| | | | Eg | Gearbox/girth gear efficiency, % | | Pg | 2715 |
| | | | | | | Target | – |
| 4 | New production rate | NPB | Formula-1 | | OPB | 118 |
| (Mill output Vs. Blaine) | tph | | | OPB | | OB | 4000 |
| | | | | Exp ( ( NB – OB ) * 0.49 / 1000 ) | | NB | 5000 |
| | | | OPB | Old production rate, tph | | NPB | 72 |
| | | | OB | Old blaine, cm2/gm | | Target | – |
| | | | NB | New blaine, cm2/gm | | | |
| | | | | | | | |
| | | Formula-2 | | OPB | 118 |
| | | | | OPB * ( OB / NB )1.3 | | OB | 4000 |
| | | | OPB | Old production rate, tph | | NB | 5000 |
| | | | OB | Old blaine, cm2/gm | | NPB | 88 |
| | | | NB | New blaine, cm2/gm | | Target | – |
| 5 | New production rate | NPR | | | OPR * ( 2 – log ( OR ) ) | | OPR | 150 |
| (Mill output Vs. Residue) | tph | | | ( 2 – log ( NR ) ) | | OR | 11.5 |
| | | | OPR | Old production rate, tph | | NR | 9.5 |
| | | | OR | Old residue, % | | NPR | 138 |
| | | | NR | New residue, % | | Target | – |
| 6 | Gypsum set point | GSP | | | 21500 * ( Scem – Sclk ) | | Scem | 2.1 |
| (at weigh feeder) | tph | | | Pu * ( 100 – Fgyp ) | | Pu | 90 |
| | | | Scem | Target SO3 content in cement, % | | Sclk | 0.3 |
| | | | Pu | Gypsum purity, % | | Fgyp | 4.8 |
| | | | Sclk | SO3 content in clinker, % | | GSP | 4.52 |
| | | | Fgyp | Free moisture in gypsum, % | | Target | – |
| 7 | Maximum ball size | MBS | | | 36 * F0.5 * { ( SG * Wi ) / ( %C * Deff0.5 ) }0.333 | | F | 15 |
| | mm | | F | Feed size (sieve size in mm which retains 20% material), mm | SG | 3 |
| | | | SG | Specific weight of feed material, gm/cm3 | | Wi | 15 |
| | | | Wi | Bond’s work index, kWh/t | | %C | 75 |
| | | | %C | Mill speed as %critical, % | | Deff | 5.1 |
| | | | Deff | Mill effective diameter, mts | | MBS | 90 |
| | | | | | | Target | – |
| 8 | %Filling | %F | | | 112.5 – ( 125 * h / Deff ) | | h | 2.5 |
| | % | | h | Free height, mts | | Deff | 4.155 |
| | | | Deff | Mill effective diameter, mts | | %F | 37.3 |
| | | | | | | Target | – |
| | | | | | | | |
| 9 | Circulation factor | C | Formula-1 | | FF | 150 |
| | – | | | F + G | | CR | 170 |
| | | | | F | | C | 2.13 |
| | | | F | Fresh feed rate, tph | | Target | 2-3 |
| | | | G | Coarse return, tph | | | |
| | | | | | | | |
| | | Formula-2 | | Rg | 54.92 |
| | | | | Rg – Rf | | Rf | 3.52 |
| | | | | Rg – Rm | | Rm | 34.16 |
| | | | Rg | Residue of coarse return, % | | C | 2.48 |
| | | | Rf | Residue of fines, % | | Target | 2-3 |
| | | | Rm | Residue of separator feed, % | | | |
| 10 | Circulation load | CL | | | ( C – 1 ) * 100 | | C | 2.48 |
| | % | | C | Circulation factor, – | | CL | 148 |
| | | | | | | Target | – |
| 11 | Separator efficiency | SE | Formula-1 | | Ro | 100 |
| | % | | | [log(Ro/Rf) – C * log[{Ro+(C-1)*Rg} / {Rf+(C-1)*Rg}]]*100 | | Rf | 3.52 |
| | | | | log(Ro/Rf) – C * log[{Ro+(C-1)*100} / {Rf+(C-1)*100}] | | C | 2.48 |
| | | | Ro | Residue of fresh feed, % | | Rg | 54.92 |
| | | | Rf | Residue of fines, % | | SE | 68.8 |
| | | | C | Circulation factor, – | | Target | 70-80 |
| | | | Rg | Residue of coarse return, % | | | |
| | | | | | | | |
| | | Formula-2 (Fines Efficiency) | | Rf | 3.52 |
| | | | | ( 100 – Rf ) * 100 | | Rm | 34.16 |
| | | | | ( 100 – Rm ) * C | | C | 2.48 |
| | | | Rf | Residue of fines, % | | SEf | 59.1 |
| | | | Rm | Residue of separator feed, % | | Target | 70-80 |
| | | | C | Circulation factor, – | | | |
| | | | | | | | |
| | | Formula-3 (Coarse Efficiency) | | Rg | 54.92 |
| | | | | Rg * ( C – 1 ) * 100 | | C | 2.48 |
| | | | | C * Rm | | Rm | 34.16 |
| | | | Rg | Residue of coarse return, % | | SEc | 95.9 |
| | | | C | Circulation factor, – | | Target | 70-80 |
| | | | Rm | Residue of separator feed, % | | | |
| 12 | Critical speed | nc | | | 42.3 / Deff0.5 | | Deff | 4.15 |
| | rpm | | Deff | Mill effective diameter, mts | | Pn | 20.8 |
| | | | | | | Target | – |
| | | | | | | | |
| | | | | | | | |
| | | | | | | | |
| 1 | New production rate | NPR | Formula-1 | | OPB | 118 |
| (Mill output Vs. Blaine) | tph | | | OPB | | OB | 4000 |
| | | | | Exp ( ( NB – OB ) * 0.49 / 1000 ) | | NB | 5000 |
| | | | OPB | Old production rate, tph | | NPR | 72 |
| | | | OB | Old blaine, cm2/gm | | | |
| | | | NB | New blaine, cm2/gm | | | |
| | | | | | | | |
| | | Formula-2 | | OPB | 118 |
| | | | | OPB * ( OB / NB )1.3 | | OB | 4000 |
| | | | OPB | Old production rate, tph | | NB | 5000 |
| | | | OB | Old blaine, cm2/gm | | NPR | 88 |
| | | | NB | New blaine, cm2/gm | | | |
| 2 | New Specific power cons. | | Formula | | | | |
| (sp. power Vs. Blaine) | NPR | | E1 | E (S1 / S)n | | | |
| | kWh/TC | | | | | | |
| | | | E1 | New specific power | | E | 32.5 |
| | | | E | Old specific power | | S1 | 5000 |
| | | | S1 | New Blaine | | S | 4000 |
| | | | S | Old Blaine | | n | 1.3 |
| | | | n | Mill exponent for close ckt = 1.3 | | E1 | 43.44 |
| | | | | | | | |
| | | | | | | | |
| | | | | | | | |
| | | | | | | | |
| | | | | | | | |
| | | | | | | | |
| | | | | | | | |
| | | | | | | | |
| 1 | New production rate | NPR | Formula | | OPB | 118 |
| (Mill output Vs. Blaine) | tph | | | OPB * ( OB / NB )1.3 | | OB | 4000 |
| | | | OPB | Old production rate, tph | | NB | 5000 |
| | | | OB | Old blaine, cm2/gm | | NPR | 88 |
| | | | NB | New blaine, cm2/gm | | | |
| | | | | | | | |
| 2 | New Specific power cons. | | Formula | | | |
| (sp. power Vs. Blaine) | NPR | | E1 | E (S1 / S)n | | | |
| | kWh/TC | | | | | | |
| | | | E1 | New specific power | | E | 32.5 |
| | | | E | Old specific power | | S1 | 5000 |
| | | | S1 | New Blaine | | S | 4000 |
| | | | S | Old Blaine | | n | 1.3 |
| | | | n | Mill exponent for close ckt = 1.3 | | E1 | 43.44 |
| | | | | | | | |
