Steam generating unit
- 1. STEAM GENERATING UNIT PRESENTED BY: CALI, JONALYN P. CAÑAVERAL, SHIHO B. UCANG, LOVELY T.
- 2. What is Steam? Steam is the gas formed when water passes from the liquid to the gaseous state. The uses for steam are many and varied like: 1. Power Generation 2. Industrial Process 3. Heating
- 3. What is a boiler? A boiler is an enclosed vessel that provides a means for combustion heat to be transferred to water until it becomes heated water or steam.
- 4. Classification of Steam According to the contains of the tube: Fire tube boiler Water tube boiler. ACCORDING TO POSITION OF FURNACE: Internally fired boilers Externally fired boilers
- 5. Classification of Steam ACCORDING TO METHOD OF CIRCULATION OF WATER: Natural circulation boilers Forced circulation boilers ACCORDING TO PRESSURE OF STEAM: High pressure boiler (> 80 bar) Low pressure boiler (≤ 80 bar)
- 6. Types of Boilers 1. Fire Tube Boilers 2. Water Tube Boilers 3. Packaged Boiler 4. Fluidized Bed (FBC) Boiler 5. Stoker Fired Boiler 6. Pulverized Fuel Boiler 7. Waste Heat Boiler 8. Nuclear Steam Generating System
- 7. Types of Boilers Fire tube boiler Flames and hot gases (flue gases: products of combustion) pass through the tubes, and Tubes are surrounded by water.
- 8. Example of Fire Tube Boilers: 1. SIMPLE VERTICAL BOILER Is one whose axis of orientation is vertical with respect to the ground.
- 9. Example of Fire Tube Boilers: 2. COCHRAN BOILER Is a fire tube boiler which is just like the simple vertical boiler with some changes to increase the efficiency of the boiler by increase maximum heating area of the boiler.
- 10. Example of Fire Tube Boilers: 3. LOCOMOTIVE BOILER They are the horizontal boiler and belong from the fire tube class of boilers. Locomotives boiler are divided into three main parts smoke box, shell box and fire box.
- 11. Example of Fire Tube Boilers: 4. LANCASHIRE BOILER Is a simple horizontal boiler and belong from the shell and tube types of boilers.
- 13. Example of Fire Tube Boilers: 5. CORNISH BOILER Is a simple horizontal boiler which belong to the shell and tube class of boilers. Cornish boiler is much like the Lancashire boiler.
- 14. CORNISH BOILER
- 15. Types of Boilers Water tube boiler Water passes through the tube, and Flames and hot gases pass outside the tubes.
- 16. Example of Water Tube Boilers: 1. LA-MONT BOILER is a type of forced circulation water-tube boiler in which the boiler water is circulated through an external pump through long closely spaced tubes of small diameter.
- 17. Example of Water Tube Boilers: 2. LOEFFLER BOILER This is also a modern high pressure water tube boiler using the forced circulation principle and named after Prof.Loeffler.
- 18. Example of Water Tube Boilers: 3. BENSON BOILER The first modern high pressure drumless boiler developed by benson was put into operation in 1927 in west Germany power station.
- 19. Example of Water Tube Boilers: 4. BOBCOCK AND WILCOX BOILER It is a water tube boiler used in steam power plants. In this, water is circulated inside the tubes and hot gases flow over the tubes.
- 20. Types of Boilers Packaged Boiler Is a factory-made boiler that consists of a range of standard designs.
- 21. Example of Packaged Boilers: 1. D-type Package Boiler The D-type boiler has a water drum, steam drum, and generating tubes.
- 22. Example of Packaged Boilers: 2. A-type Package Boiler Has two water drums and one steam drum compared to the D-type package boiler.
- 23. Example of Packaged Boilers: 3. O-type Package Boiler Are a little more simple compared to D-type and A-type. are a little more simple compared to D- type and A-type.
- 24. Types of Boilers Fluidized Bed (FBC) Boiler Rapid mixing ensures uniformity of temperature. A fluidized bed may be defined as the bed of solid particles behaving as a fluid.
- 25. Types of Fluidized Bed Combustion (FBC) 1. Vertical type FBC Their vertical shape reduces the overall dimension of the steam boiler, and is extremely efficient in plants, where space provision is limited.
- 26. Types of Fluidized Bed Combustion (FBC) 2. Horizontal type FBC The high capacity of the horizontal type Fluidized boilers coupled with their high efficiency, makes them an extremely desirable choice for the coal fired thermal power generating station.
- 27. Types of Boilers Stoker Firing Proper and sufficient supply of air and proper mixing of air with fuel are primary requirements. Adequate supply of fuel particles for proper burning of particles also to be maintained.
- 28. Types of Stoker Firing 1. Hand firing Here, coal chips are put into the furnace frequently by shovels.
- 29. Types of Stoker Firing 2. Mechanical stroke firing Under Feed Mechanical Stoker Firing Travel Grate Stoker Solid Coal Firing
- 30. Types of Boiler Pulvarized Fuel Firing For getting most calorific value of coal, the coal is pulvarized in fine powder and then mixed with sufficient air.
- 31. Types of Boilers Waste Heat Boiler Auxiliary fuel burners used if steam demand is more than the waste heat can generate. Used in heat recovery from exhaust gases from gas turbines and diesel engines.
- 32. Types of Boilers Nuclear Steam Generating System Steam generators are heat exchangers used to convert water into steam from heat produced in a nuclear reactor core. They are used in pressurized water reactors (PWR) between the primary and secondary coolant loops.
- 33. BOILER DRUM AND ITS INTERNALS
- 34. Function Boiler Drum is a pressure vessel it is used to Separate steam and water mixture Mixing feed water with water separated from steam-water mixture and re-circulate through the evaporating tubes. Reduce dissolved solid contents of the steam ( Blow down) Storage of water
- 35. Types of steam separators: Baffle Separator - are used to reverse flow direction of the mixture and acts as impact plate. Centrifugal Separator - Mixture passes through the Turbo separator. Mechanical Coalescing/Centrifugal Separator - To arrest the residual moisture if any steam is passed through the screen dryer before leaving the drum
- 36. Drum Internal
- 37. Arrangement Of Drum Internals
- 38. Seperation Procedure Wet steam entering the drum from the riser tubes is collected in a compartment called separating chamber. From this compartment the steam is first led through two rows of turbo separators. Each turbo-separator consists of a primary stage and a secondary stage
- 40. 600 MW Unit Drum Features Length : 27998 mm ID : 1778 mm Wall Thk. : 185 mm / 155mm Weight : 247.67 MT Material : SA 299 Turbo separators : 110 Nos. Screen Dryers : 148 Nos. Riser Connections : 80 nos. Super Heater Connection: 26 Nos. Down comers : 6 nos. Safety valve : 6 nos. Feed Nozzle : 3 nos. Drum Elevation: : 80.561 m
- 41. Objectives of boiler drum: The main purpose of the boiler drum is to provide necessary space for separating steam from steam-water mixture at a certain pressure. It provides a point for chemical dosing in order to maintain the concentration of the impurities and the ph of the water It provides a point for blow down to maintain the concentration of the impurities as well as in case of emergencies like high drum level; it helps to drain out the excess water. It provides necessary space for housing the drum internals.
- 42. Connections To Drum MAIN CONNECTIONS 1. Feed Lines 2. Down Comers 3. Risers 4. Super heater supply tubes AUXILLARY CONNECTIONS 1. Blow Down Lines 2. Chemical Dosing Lines 3. Instrumentation Tappings 4. Air Vents 5. Safety valves 6. Nitrogen Filling Line 7. High & Low level trips
- 43. Main Connections Feed Lines Feed water from economiser outlet is supplied to drum through feed lines and connected to the feed nozzles mounted with the drum. Feed nozzles in turn are connected to the feed header provided inside the drum.
- 44. Main Connections Downcomers The downcomer pipe are connected to the bottom of the drum. The water from drum is circulated to the evaporating tubes through the downcomers which are kept external to the heating zone of the boiler.
- 45. Main Connections Riser Tubes The water steam mixtures formed inside the evaporating tubes is collected in the top headers from where water steam mixture enters the drum through risers tubes.
- 46. Main Connections Super Heater Supply Tubes The dry saturated steam separated inside the drum is circulated to Superheaters through these tubes connected at the top of the drum.
- 47. Anti Vortex Spider The water entry from drum to down comers connected at the bottom leads to the formation of vortex at the inlet. This may cause drawl of steam into down comers and water hammering. To prevent this vortex formation anti-vortex spider in the form of cruciform are located at the down comers inlet.
- 48. Auxiliary Connections Air Vents Vent pipes fitted with valves and open to atmosphere are mounted on the top of the drum. The vents are required to evacuate the air while filling water in drum and to kill the vacuum during shutdown due to condensing of steam in drum. Nitrogen filling line: To charge nitrogen into drum when boiler is under shut down for preservation purpose.
- 49. Auxiliary Connections Safety Valve To prevent drum explosion from excessive pressure, drum is provided with spring loaded safety valve. Constructions & Location Boiler drum is a heavy wall pressure vessel having hemispherical ends Heavy thickness plate are rolled/pressed and welded to construct the drum It consists of cylindrical portion with two hemispherical end
- 50. Important Aspects The fitting and alignment of drum internals are very important for its efficient performance. Any misalignment with gap will lead to heavy carry-over of impurities into steam which will get deposited in the super heater. The alignment should be checked and drum internals should be set right at every annual overhaul. In between also, it is desirable to check the drum internals fit up during any shut down for a few days.
- 51. Mud Drum A drum beneath a boiler, into which sediment and mud in the water can settle for removal. It is related with “bottom” blow down which reduces the quantity of un-dissolved solids (sludge) which collect in the lower parts of the boiler (mud drum)
- 52. Superheater Coils Super heater coils are used in a boiler to generate saturated steam. The super heater coils are specially used in Boilers of Power plant.
- 53. Re-heaters They are the same as the super-heaters but as their exit temperature is a little bit less than super-heaters and their pressure is 20%-25% less than the super-heater, they can stand less quality material alloys.
- 54. Economiser Coils Economizer coils are used in downstream of Boiler bank to preheat the feed water absorbing heat from hot exhaust gases. Economizers are always water tube type.
- 55. Headers Form an important part of all types of boilers. Steam from the generating tubes is collected in headers which are therefore always under pressure.
- 56. WATER WALL PANEL Water wall panels are used in Waste Heat recovery boilers. These are tubes in the boiler where water is evaporated to steam and are also called steam generating tubes.
- 57. Air Preheater An air preheater (APH) is a general term used to describe any device designed to heat air before another process (for example, combustion in a boiler) with the primary objective of increasing the thermal efficiency of the process.
- 58. Soot Blower Is a device for removing the soot that is deposited on the furnace tubes of a boiler during combustion.
- 59. Classification of Soot Blower Long Retractable Soot Blower This type of soot blower is located in area superheater and reheater.
- 60. Classification of Soot Blower Wall / Short Retractable Soot Blower. This type of soot blower is located in area furnace. There is not temperature limitation in its use
- 61. Classification of Soot Blower Rotary Soot Blower This type of soot blower is located in area boiler bank, economizer, and air heater.
- 62. Classification of Soot Blower Rake Soot Blower This type of soot blower is located in area fin tube economizer and vertical tubular air heater.
- 63. Furnace Is a device used for high- temperature heating. The name derives from Greek word fornax, which means oven.
- 64. Burners The burner is the device that permits controlled burning of fue inside the furnace. The burner mixes the fuel with the required amount of air and directs the flame into the combustion area. The burner comprises of gas burner and oil burner with atomizing steam connection.
- 65. Burner consists of: Air Register Used to given an enough quantity of air to the burner for good combustion. Ignition Gun Used to give ignition spark to the burner for firing. Flame Detector Used to monitor the flame.
- 66. Oil Burners Pressure Jet Burners - These burners consist of an orifice at the end of the pressurised tube. The pressure of the fuel oil ranges from 7 to 15 bar. These burners are easy to maintain and have less cost.
- 67. Oil Burners Swirl oil burner In swirl oil burner, oil is pressurized to about 7-10 bar. This pressurized fuel enters tangentially through the slot at a high velocity in the oil swirl chamber. It flows in the form of vortex and escapes through a nozzle at the other end of the chamber.
- 68. Oil Burners Rotary cup Burner This burner has a rotary cup and a fan. The cup and the fan are rotated by an electric motor with a shaft. Oil is feed to the oil distributer to throw at the inner surface of the cup.
- 69. Oil Burners Dual fuel burners These are burners designed with gas as main fuel and have additional facility for burning fuel oil.
- 72. Boiler Draft System Natural draft: When air or flue gases flow due to the difference in density of the hot flue gases and cooler ambient gases. Forced draft: When air or flue gases are maintained above atmospheric pressure. Induced draft: When air or flue gases flow under the effect of a gradually decreasing pressure below atmospheric pressure. Balanced draft: When the static pressure is equal to the atmospheric pressure, the system is referred to as balanced draft. Draft is said to be zero in this system.
- 73. Boiler Drains & Vents System
- 74. Boiler Drains & Vents System Vents are provided on different pressure parts of the Boiler. They are used during depressurizing, filling and charging the system. All drains and vents are manual operated and are used during startup and shutdown. The purpose of this system is to vent and drain the superheater, Reheater, Boiler drum, Economizer, Deaerator and Boiler convection pass during startup and shutdown activities of the Boiler as required. The cool down the high temperature drains in the Blowdown Tank before sending the water to the waste water system.
- 75. Use of drains: Superheater Drains – During shutdown, these drain valves are usually opened to depressurize during shutdown. Reheater drains – These drains are usually opened for depressurizing the Reheaters during shutdown. Drum level gauge drain – This drains is usually opened when the gauge is required to place in service. Economizer inlet drain – these drains are used for draining the boiler after shutdown.
- 76. Use of drains: Lower convection pass header drain – These drains are used for draining the boiler after shutdown. Downcomer header drains – These drains are used for draining the boiler adter shutdown or cycling the feedwater system during normal operation. Continous Blowdown – This arrangement is used to remove the silica & another impurities fro the steam drum water. Drum Vent – During depressurizing the boiler, open the vent at 2kg pressure Superheater vents – Keep these vents open until steam comes out of those during startup.
- 77. Thank You !!!