coal pulveriser

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Ball and tube mill

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coal pulveriser

  1. 1. FTA PRSENTATION ON BALL AND TUBE MILL RHITESH KUMAR
  2. 2. Presentation Outline 1. COAL – TYPES OF COAL 2. WHY PULVERISATION OF COAL? 3. FIRING – DIRECT FIRING, INDIRECT FIRING 4. PULVERISERS – TYPES, CLASSIFICATION 5. BALL & TUBE MILLS – CONSTRUCTIONAL FEATURES 6. GRINDING PRINCIPLE IN TUBE MILLS
  3. 3. COAL  MOST EASILY AVAILABLE  ABUNDANTLY AVAILABLE  CHEAP FUEL SOURCE  EASILY TRANSPORTABLE
  4. 4. GRADE OF COAL BASED ON CALORIFIC VALUE, GRADING OF COALGRADE KCAL/KG A >6200 B 5600-6200 C 4490-5600 D 4200-4490 E 3360-4200 F 2400-3360 G 1300-2400
  5. 5. WHY PULVERISED FORM OF COAL  IT HAS MADE MODERN STEAM GENERATING UNITS HIGHLY THERMAL EFFICIENT, RELIABLE AND SAFE.  IT HAS MADE EFFICIENT USE OF LOW GRADE COALS.  IT PROVIDES GOOD CONTROL OVER COAL AIR MIXTURE PROPORTION, FLAME STABILITY WITH MINIMUM LEVEL OF UNBURNT CARBON.
  6. 6. FIRING DIRECT FIRING Coal is ground and is directly carried from the Pulverizer to the Furnace by use of Pressurized air. Pressurized Air from Primary Air Fans goes to the Pulverizers. Sufficient temperature is maintained for drying of coal and moving the Pulverised Coal to the furnace without settling.
  7. 7. FIRING INDIRECT FIRING Here coal is ground and is carried from Pulveriser to an Intermediate Bunker. Based on the Unit load demand pulverised coal moves from the Intermediate Bunker to the Furnace. A suction fan helps in sucking the pulverized fuel to the furnace. This system is suitable, where the boiler load varies and the mills consume huge power. But, the disadvantage is that the capital cost is high due to extra bunkers and fans. Also, there is danger of Fire in the Intermediate Bunkers
  8. 8. FUNCTIONAL REQUIREMENTS OF PULVERISER  DRYING OF COAL  GRINDING OF COAL  TRANSPORTATION OF PULVERIZED COAL
  9. 9. MECHANISM OF PULVERISATION  BASED ON PRINCIPLES OF PARTICLE SIZE REDUCTION - IMPACT - ATTRITION - CRUSHING PULVERISERS USE ONE, TWO OR ALL THE THREE PRINCIPLES.
  10. 10. TYPES OF PULVERISERS Speed Type Low 10 to 20 RPM Ball tube mills (16 rpm in Vindhyachal) Medium High 40 to 70 RPM 900 to 1000 RPM Bowl Mill, Impact or Hammer MPS Mill, Mill. Ball and Race Beater Mill mill or Fan Mill.
  11. 11. TYPES OF MILL • Tube or ball mills: These are low-speed machines that grind the coal with steel balls in a rotating horizontal cylinder. • Vertical spindle mill: These are medium-speed machines that include bowl mills, ring roll mills, and ring and ball mills. The bowl mills are further divided into deep bowl or shallow bowl mills. • Impact mill: These are high-speed impact machines that use beater wheels to crush the coal.
  12. 12. Ball & Tube Mills Tube mills: The tube mills are low-speed machines that grind the coal with steel balls in a rotating horizontal cylinder. Due to its shape only, people call it as Tube Mill and due to use of Grinding Balls for crushing, it is called Ball Mill. Hence, is the name Ball Tube Mill
  13. 13. TUBE MILL These are slow speed Mills. The Mills are designated as BBD-4772 Where, B – Broyer (Name of inventor). B – Boulet (French word for Balls). D – Direct firing. 47 – Diameter of shell (in Decimeters) i.e. 4.7m dia. 72 – Length of shell (in Decimeters) i.e. 7.2 m length.
  14. 14. BALL & TUBE MILL Tube mills are employed to pulverize the precrushed raw coal to the required fineness before it is admitted into the boiler furnace for combustion. The operating characteristics i.e. Faster response to Load variation of tube mills make it the best mill available for the direct firing system of the coal.
  15. 15. CONSTRUCTION OF TUBE MILL CYLINDRICAL SHELL LINER SHORT CONICAL LINER LONG CONICAL LINER INLET LINER SCREW CONVEYOR RIBBON HOT AIR TUBE CONNECTING ROD
  16. 16. •The Shells which contain ball and liner are of 7.2 mtr. length. •The Shells are of three pieces. The Intermediate shell connects to the end shells by flange joints. 60 Nos. Bolts in each flange CHEEK TRUNION 40 Nos. Trunion to Cheek Joint Bolts in each end SHELL FLANGE GIRTH GEAR
  17. 17. DETAILS FOR SCREW CONVEYOR ASSEMBLY RIBBON SHAFT ANGLE CHAIN & CHAIN LINK
  18. 18. MILL DETAILS • • • • • • • • Design coal capacity- 83.15 Tons/Hr Ball charged- 90 Tons (50 mm, 40 mm, 30 mm) Speed – 15 to 16 rpm Screw assembly- Right hand helix(DE side) Left hand helix (NDE side) Direction of rotation of Shell from NDE end-AntiClockwise. Shell door opening- two numbers. Shell liners- 600 nos. weight of liners- 60.26 MT
  19. 19. MILL LUBRICATION SYSTEM TRUNION SUPPORT BEARING H P OIL TANK BS LP FILTER COOLER Pum p
  20. 20. MILL LUBRICATION DETAILS • • • • • • • • • • LP PUMP FLOW – 137 Ltrs/min. LP PUMP PR.- 10 Bar. LP PUMP SPEED – 750 rpm. B&S PUMP FLOW – 6 Ltrs/min. B&S PUMP PR.- 70 Bar. B&S PUMP SPEED – 1450 rpm. HP PUMP FLOW – 40 Ltrs/min. H PUMP PR.- 80 Bar. HP PUMP SPEED – 965 rpm. TANK CAPACITY- 1800 Ltrs.
  21. 21. MAIN REDUCER Output Shaft
  22. 22. DETAILS OF MAIN REDUCER LOW SPEED SHAFT 118.98 rpm LUB. OIL LINES HIGH SPEED SHAFT 1487 rpm
  23. 23. MAIN REDUCER DETAILS • • • • • • CAPACITY- 300 Ltrs. OIL- SERVO MESH SP 460. HIGH SPEED SHAFT- 1487 rpm LOW SPEED SHAFT- 118.98 rpm. DE SIDE- RESILIENT (BIBBY) COUPLING NDE SIDE – GEARED COUPLING.
  24. 24. REDUCER LUBRICATION • This is closed cycle lubrication system • This is required for the lubrication of gears and bearings • The oil is pumped to the different points in the reducer by motorized pumps. • Oil is sprayed to the gears by means of nozzles in the gearbox at the mating plane. • The bearings get oil through nozzles inside the gearbox • The pumps are screw pump. • Oil coolers are used to cool the lubricant coming out of the reducer. • After the filter the oil goes to the reducer.
  25. 25. Schematic Diagram of Main Reducer Lube Oil System MILL FILTER MAIN REDUCER P COOLING WATER OIL COOLER M
  26. 26. PUMP DISCHARGE/ OIL INLET TO REDUCER PUMP SUCTION/OIL OUTLET TO REDUCER OIL COOLER ASSEMBLY OIL FILTER ASSEMBLY LUB.OIL PUMP
  27. 27. MAIN REDUCER LUB. OIL DETAILS • SCREW PUMP. • SPEED- 1500 rpm • FLOW RATE- 79 Liters/Min. • PRESSURE- 2 Bars. • WATER FLOW THROUGH COOLERS- 60-65 LPM • COOLER WATER I/L & O/L TEMP.- 35 & 45 deg. • FILTER RATING- 160 Microns.
  28. 28. GIRTH GEAR GREASING NOZZLE NOZZLE GREASE DISTRIBUTOR GREAS PUMP M GREASE BARREL ELECTRICAL SHUT OFF VALVE COMPRESSED AIR SUPPLY AIR FILTER
  29. 29. GIRTH GEAR GREASE PUMP • NO.OF DISCHARGE: 06 • SPEED- 1400 rpm. • FLOW RATE- 0-18M3 /24 Hrs. • MAX. PRESSURE- 100 Bars. • OIL: Servo Tak-40 • SPRAY INTERVAL- 30Sec.
  30. 30. VIEW OF SEAL AIR FAN MOTOR GEARED BEARING COUPLING HOUSING IMPELLER HOUSING
  31. 31. TRUNION SEAL AIR FAN • CAPACITY – 3.9 m3/sec. • SPEED- 2880 rpm. • HEAD DEVELOPED- 1650 mmWCL. • MEDIUM HANDLING- Atmospheric air. • ORIENTATION- Axial suction & vertical delivery.
  32. 32. VISCOUS FILTER DRIVING GEAR COARSE MAT FILTER OIL SUMP Behind the Coarse mat filter, the fine mesh filter is present. It is also called Oil drop eliminator. This is present to prevent carry over of oil drops to the Impeller. Both the Coarse mat filter and the Oil drop eliminator screens rotate intermittently as per the Timer settings. Normally, it is 30 sec. rotation after every 20 minutes
  33. 33. MILL CLASSIFIER ARRANGEMENT MULTIPORT OUTLET CLASSIFIER CONE INTERNAL CONE HEX. CONE ASSEMBLY REFUSAL DUCT P.F. DISCHARGE TO CLASSIFIER
  34. 34. BALL FEEDING DETAILS
  35. 35. PRINCIPLES OF GRINDING Raw Coal is fed into the Mill for Grinding. Grinding takes place by Impact and attrition.
  36. 36. MAINTENANCE PRACTICES • Ball Charging when current goes below 95 Amps. for which current data is collected from UCB on First day of every week. • Monthly Preventive Maintenance of Mills, R C Feeders and Seal Air fans • Minor Overhaul of Mills in 4-6 months in which P/M works, Servicing & Replacement of CADs, Girth Gear Grease Pumps servicing is carried out.
  37. 37. Problems faced in the Mills at Vindhyachal •Failure of Liners • Explosion in the Mills • Girth Gear Greasing trouble • Frequent Jamming of CADs • Frequent Filter Choking • Firing of Wet coal in the Mills • Non-operation of Viscous filters

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