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1. ASH HANDLING ARRANGEMENT (ASHA) JISHNU V EMP NO:-6106188 BHEL-ISG

3. Made up of welded steel plates

4. Kept at the top of the mills, so as to assist induced gravity flow

5. Normally 6 in number Coal feeder:  Drag link mechanism used for the transport of coal from bunker

8. Located at the same elevation as that of furnace

11. 2 such heaters for each 200MW unit

12. 16m elevation from datum

15. Ljungstrom type Bisector

18. Used to handle the secondary air

20. Distributing medium Scanner fan: To cool the scanner

22. Why we need a fan The fan is required for 2 purposes: - A) To provide sufficient oxygen to assist the combustion B) To remove the products of combustion C) Evacuation of flue gases

23. Selection criterion for fan Air or gas flow-mass flow rate (kg/hr) Density of gas (function of state variables like temperature and pressure) System resistance

24. DRAFT SYSTEM

25. What is draft? The term draft refers to the pressure difference between the atmosphere and that existing in the furnace 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

26. Types of draft Various types of drafts are A) Natural draft: Vacuum is created in furnace by making very tall chimneys, this pressure difference draws air to furnace 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 C) Forced draft: It has positive pressure and air is pushed out by the pressurization by FD fan

27. Requirement of TPP Mechanical drafts (ID and FD) are more advantageous than natural draft because proper combustion is ensured, easy flow of flue gases and more efficiency Air is required to carry coal from mill to furnace To remove the flue gases To ensure proper combustion

28. CHIMNEY FURNACE MILLS SECONDRY AIR HEATER PRIMERY AIR HEATER FD FAN A FD FAN B ID FAN A Atmospheric air PA FAN A ESP PA FAN B ID FAN B Atmospheric air

29. Primary air system The primary air is driven by axial flow reaction fan 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.

30. Ignitor fan 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.

31. Burner Box Dampers Coal/Air Dampers Secondary Air Dampers Oil/Secondary Air Dampers Bottom Tier Secondary Air Damper Over Fire Damper

33. Secondary air Damper control 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. 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.

34. Primary and secondary air system

36. Tangential Firing System

37. Variation of Pressure in Boiler

39. Hoisting machines used in ASHA Chains:  2 types. Viz coil chains and stud link chains Coil chains are used in hoists, cranes and dredges Made of open hearth steel for smaller ones and high grade wrought iron for larger ones Load capacity equals 1.5 times proof load or load at the elastic limit whichever may be the least FOS=2 for normal applications, 3 for

40. 3 for intermittent applications, 3.5 for continuous machine operations Stud link chains are used for anchors and moorings Can carry loads which are 20-25% more than open link chains

41. THANK YOU