Hướng dẫn vận hành máy nghiền bi Operation of the Cement grinding plant Preconditions: The switch on conditions of the auxiliary units must be fulfilled. • Auxiliary units of the tube mill • Conveying equipment for cement transport • Recirculation transport incl. the foreign body trap • Grits conveyors • SEPOLSeparator • Dedusting system • Mill drive • Mill feed system • Water injection
Page Operation of the Cement grinding plant Training Polysius Headquarters / Germany 19 May – 13 June 2008 Training THALOFA Page Training THALOFA Training THALOFA Page Control Loops • Fresh fee (F) + Grits (G) = constant • ball mill sound level / mill feed Training THALOFA Page Control Loop • Temperature mill outlet / water injection chamber & Training THALOFA Page Additional monitoring: Pressure behind ball mill [mbar] • Pressure behind Separator [mbar] • Amount of grits [t/h] • Electrical ear for mill noise [%] • Power of Bucket Elevator [A or kW] • Speed of Separator rotor [rpm] • Water flow chamber & [l/h] Training THALOFA Page Start up of the Cement Mill Preconditions: The switch- on conditions of the auxiliary units must be fulfilled • Auxiliary units of the tube mill • Conveying equipment for cement transport • Recirculation transport incl the foreign body trap • Grits conveyors • SEPOL-Separator • De-dusting system • Mill drive • Mill feed system • Water injection Training THALOFA Page Start up of Cement Mill, process adjustments • Material feed rate 60% of nominal • Pressure after tube mill 15 mbar • Position of guide fans at SEPOL 65 – 70 ° • SEPOL Rotor speed 70 -75 % of max • Damper before system fan: 60 – 80 • Jalousie dampers before SEPOL: 100 % • Fresh air damper before SEPOL: 30 – 50 % Training THALOFA Page Ball Mill Ball Charge Diaphragm Training THALOFA Page Ball Mill Components - Intermediate Diaphragm Adjustment tool knee lever Lifter adjustment Training THALOFA Page 10 Intermediate Diaphragm • for equal material flow of material from 1st to 2nd compartment • adjustable scoops to influence flow characteristics of mill • can be set to reduce or accelerate flow of material to second compartment • Scoops adjustment influences material filling degree of compartment • Longitudinal samples should be taken to determine if scoops need adjusting Training THALOFA Page 16 Ball Charge • Mills for cement grinding normally operate at a 25-32% “filling degree” • “Filling degree” is defined as volume of grinding media as percentage of total mill internal volume • Mill speed, liner shape and mill diameter are normally constant parameters • Therefore, only an adjustment to filling level and ball size distribution can be made Training THALOFA Page 17 Ball Mill Liners • Protect the mill shell and assist in grinding action • First Compartment – Lifting liners: “impact” grinding action for large particle reduction • Second Compartment – Classifying Liners – shifting finer media to discharge end of mill where fine grinding is required; “friction” grinding Chamber 1: Lifting liners Chamber 2: Classifying liners Training THALOFA Page 18 Lifting Liners - Most commonly used in cement industry - Used mainly for coarse grinding in first compartment - Lifting liners must lift media high enough to allow sufficient impact force for coarse grinding Training THALOFA Page 19 Classifying Liners • Used in second or fine grinding compartment • The liner shape causes a classification of grinding media • Decreasing ball size along grinding path • Grinding efficiency is increased Theory is, that ball size should decrease with particle size being ground Training THALOFA Page 20 Liner Shape Classifying Liners • Greater impact forces cause larger ball “jumps” over the lining hill • Smaller balls retained by the lining hill Result: larger balls in the front of second compartment Smaller balls at discharge end of mill Training THALOFA Page 21 Mill Optimisation Optimise Chamber 1!!! If chamber is O.K -> Optimization of Chamber Training THALOFA Page 22 SEPOL - Initial Settings • Guide Vanes – 65 - 70 degrees • Fresh Air Inlet Damper 30 -50 % Training THALOFA Page 23 SEPOL - Inlet Damper NOTE: Dedusting system should be set to 1-2 mbar negative pressure exists at SEPOL inlet Louvers are being adjusted to wear pattern at the rotor Separating Air Air channels Training THALOFA Page 24 SEPOL - Guide Vanes clockwise rotation counter-clockwise rotation Training THALOFA Page 25 SEPOL settings • Guide vanes setting acc to the drawing or to 65 -70° ~65 70° 60 - -65° • Maximum separating air • Speed of separator rotor set to suit the required cement fineness Training THALOFA Page 26 SEPOL - Setting of Guide Vanes • if residue ratio too low… set guide vanes more tangentially • if residue ratio too high… set guide vanes more radially Adjustments should be carried out in 5-10 degree steps After each adjustment samplings are necessary Training THALOFA Page 27 SEPOL - Separator Formulas Circulation Factor = SA / SF = (f - g) / (a - g) S A (a) SA, SF SG [t/h]: separator feed, separator fines, separator grits a, f, g: fineness feed, fines, grits (Blaine or residue) SG (g) F (100 - f) (g - a) SEOPL efficiency = -(100 – a) (g – f) S F (f) Training THALOFA Page 28 Separation TROMP Curve Fines Coarse X –Particle Size Training THALOFA Page 29 Typical TROMP Curve Separation 100% 90% 80% Fines 70% 60% 50% 40% Coarse 30% 20% 10% 0% 10 100 Particle Size (Microns) 1000 Page 30 Training THALOFA