Costumer focus12 06-2010

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Costumer focus12 06-2010

  1. 1. ASH HANDLING ARRANGEMENT (ASHA)<br />JISHNU V<br />EMP NO:-6106188<br />BHEL-ISG <br />
  2. 2. Arrangement of Boiler Auxiliaries<br /> Coal bunker: <br /><ul><li>Stores crushed coal from CHP
  3. 3. Made up of welded steel plates
  4. 4. Kept at the top of the mills, so as to assist induced gravity flow
  5. 5. Normally 6 in number</li></ul> Coal feeder: <br /> Drag link mechanism used for the transport of coal from bunker<br />
  6. 6.
  7. 7. Boiler Auxiliaries<br />Mills: <br /><ul><li>For every 200 MW unit, there are 6 mills (25% capacity) which powder the coal to the required fineness
  8. 8. Located at the same elevation as that of furnace
  9. 9. Pulverization is done in the mill and crushing in the bunker</li></ul>Primary Air fans (PA fans):<br /><ul><li>2 fans per 200 MW unit operating at 50% capacity
  10. 10. Heating air up to 50C</li></li></ul><li><ul><li>Located at datum level</li></li></ul><li>Boiler Auxiliaries<br />Air pre-heaters:<br /><ul><li>It is used to preheat primary air and secondary air using regenerative heat exchangers utilizing the flu gases
  11. 11. 2 such heaters for each 200MW unit
  12. 12. 16m elevation from datum
  13. 13. Burners: - to burn the pulverised coal with oil</li></li></ul><li>A short note on various heat exchangers<br />1) Shell and tube heat exchanger: used in suction heaters of oil fired TPPs<br />2) Plate heat exchangers<br />3) Adiabatic wheel heat exchangers<br />4) Plate fin heat exchangers<br />5) Regenerative heat exchangers<br />
  14. 14.
  15. 15. Ljungstrom type Bisector<br />
  16. 16.
  17. 17. Boiler Auxiliaries<br />FD fans: <br /><ul><li>Forced draft fans , 2 per 200MW unit
  18. 18. Used to handle the secondary air
  19. 19. 0 metres elevation, at the same level as of the PA fan</li></ul>Wind box: <br /><ul><li>To supply the excess air, placed on either sides of the furnace facing chimney
  20. 20. Distributing medium</li></ul> Scanner fan: <br />To cool the scanner<br />
  21. 21. Boiler Auxiliaries<br /> Soot blowers: <br />There are 3 types of soot blowers, viz Long retractable soot blowers, air heater blowers, Wall blowers<br /><ul><li>Pressure reducing valves</li></li></ul><li>BOILER AIR AND DRAFT SYSTEM<br />
  22. 22. Why we need a fan<br />The fan is required for 2 purposes: -<br />A) To provide sufficient oxygen to assist the combustion<br />B) To remove the products of combustion<br />C) Evacuation of flue gases<br />
  23. 23. Selection criterion for fan<br />Air or gas flow-mass flow rate (kg/hr)<br />Density of gas (function of state variables like temperature and pressure)<br />System resistance<br />
  24. 24. DRAFT SYSTEM<br />
  25. 25. What is draft?<br />The term draft refers to the pressure difference between the atmosphere and that existing in the furnace<br />It is required to ensure that required amount of oxygen is available for combustion, removal of products of combustion, losses due to flow is to be minimized<br />
  26. 26. Types of draft<br />Various types of drafts are<br />A) Natural draft: Vacuum is created in furnace by making very tall chimneys, this pressure difference draws air to furnace<br />B)Induced draft: The air is sucked into the furnace by the height of chimney and flue gases are pushed out by the ID fans. Negative pressure is created<br />C) Forced draft: It has positive pressure and air is pushed out by the pressurization by FD fan<br />
  27. 27. Requirement of TPP<br />Mechanical drafts (ID and FD) are more advantageous than natural draft because proper combustion is ensured, easy flow of flue gases and more efficiency<br />Air is required to carry coal from mill to furnace<br />To remove the flue gases<br />To ensure proper combustion<br />
  28. 28. CHIMNEY<br />FURNACE<br />MILLS<br />SECONDRY AIR HEATER<br />PRIMERY AIR HEATER<br />FD FAN A<br />FD FAN B<br />ID FAN A<br />Atmospheric air<br />PA FAN A<br />ESP<br />PA FAN B<br />ID FAN B<br />Atmospheric air<br />
  29. 29. Primary air system<br />The primary air is driven by axial flow reaction fan<br />Air discharging from each fan is divided into two parts, one passes first through a air pre-heater then through a gate into the P.A bus duct. The second goes to the cold air duct. The mix of both is used to carry the pulverized coal to the boiler. <br />
  30. 30. Ignitor fan<br />These fans, again two per boiler, are used to supply air for cooling ignitors and combustion of ignitor air fuel mixture. Fan makes the suction from atmosphere directly and supplies air to the wind boxes of individual igniters at a fixed constant uncontrolled rate at ambient temperature.<br />
  31. 31. Burner Box Dampers<br />Coal/Air Dampers<br />Secondary Air Dampers<br />Oil/Secondary Air Dampers<br />Bottom Tier Secondary Air Damper<br />Over Fire Damper<br />
  32. 32.
  33. 33. Secondary air Damper control<br />Fuel Air Dampers: which regulate air surrounding a fuel compartment. Fuel air dampers are modulated in proportion to the rate of fuel fired in that elevation. <br />Auxiliary Air Dampers: which regulate air adjacent to a fuel compartment are termed. Auxiliary air dampers are modulated to maintain a fixed differential pressure between the wind box and the furnace.<br />
  34. 34. Primary and secondary air system<br />
  35. 35.
  36. 36. Tangential Firing System<br />
  37. 37. Variation of Pressure in Boiler<br />
  38. 38.
  39. 39. Hoisting machines used in ASHA<br />Chains:  2 types. Viz coil chains and stud link chains<br />Coil chains are used in hoists, cranes and dredges<br />Made of open hearth steel for smaller ones and high grade wrought iron for larger ones<br />Load capacity equals 1.5 times proof load or load at the elastic limit whichever may be the least<br />FOS=2 for normal applications, 3 for <br />
  40. 40. 3 for intermittent applications, 3.5 for continuous machine operations<br />Stud link chains are used for anchors and moorings<br />Can carry loads which are 20-25% more than open link chains<br />
  41. 41. THANK YOU<br />

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