210 MW boiler description, Thesis of Boiler Design and Material

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210 MW BOILER DESCRIPTION

PPT’s compiled and developed by:

Mr. V.K.Gupta, Ex. Sr. Training officer and

Maintenance Engineer, NPCIL & NPTI

Description of stage-1 boiler : It is a tangentially fired, balanced draught, natural circulation, radiant reheat type, dry bottom with pulverized coal direct fired boiler. Tangentially fired: It means the flame is touching the fire ball tangentially, this being a corner fired boiler. Balanced draught: Furnace draught is always kept balanced at -10 mm of water column by suitably loading the ID fans under different loading conditions. Natural circulation: Flow of water in the boiler and also flow of steam in the water wall tubes and other water wall circuits to the drum is under natural circulation. No pump is used for circulation of water between drum and water walls. Radiant: Furnace heat is absorbed by radiation only. Flame will not touch the water walls. Also roof super heater, platen water walls and platen superheater absorb heat by radiation and convection. Reheat: The boiler is provided with a reheater where the steam in the cold reheat line is sent to the reheater in the boiler and then to the IP turbine after superheating in the reheater. Dry Bottom : The furnace bottom ash is in solid form only but not in molten state; hence it is called a dry bottom boiler. Direct fired pulverized coal: After initial ignition either with HSD or Heavy oil the pulverized coal is fired on its self ignition and the flame is self sustaining, hence it is called a direct fired boiler.

INTRODUCTIONINTRODUCTION

Boiler is any closed vessel exceeding 22.75 liters in capacity used for steam generation under pressure. First boiler was developed in 1725 and its working pressure was 6 to 10 kg/cm2 and was called Wagon Boiler There are mainly two types of Boilers

1. Fire Tube Boiler
2. Water tube Boiler The boiler used for generation of power is somewhat different in construction than the boilers used in other industrial applications. The boiler used for power generation is constructed by the four walls called water walls. These walls are made up of long tubes called water wall tubes through which water flows and the combustion of fuel takes place inside the boiler. The flue gases so formed passes through two passes of the boiler.

Boiler is any closed vessel exceeding 22.75 liters in capacity used for steam generation under pressure. First boiler was developed in 1725 and its working pressure was 6 to 10 kg/cm2 and was called Wagon Boiler There are mainly two types of Boilers

1. Fire Tube Boiler
2. Water tube Boiler The boiler used for generation of power is somewhat different in construction than the boilers used in other industrial applications. The boiler used for power generation is constructed by the four walls called water walls. These walls are made up of long tubes called water wall tubes through which water flows and the combustion of fuel takes place inside the boiler. The flue gases so formed passes through two passes of the boiler.

Boiler design Considerations:-

1.0 Boiler structural: The boiler structural is divided into two parts. · Supporting Structure · Galleries and stair ways

1.1 Supporting Structures: Boilers supporting structure consists of a systematic arrangement of columns stiffened with horizontal beams and vertical diagonal bracings and comprise of low carbon steel material. It is composed of 18 main columns and 12 auxiliary columns. The main columns support the main boiler components viz. drum, water wall membrane, panels, superheaters, reheaters, economisers, air preheater, burners and galleries at various levels.

Boiler design Considerations:-

1.0 Boiler structural: The boiler structural is divided into two parts. · Supporting Structure · Galleries and stair ways

1.1 Supporting Structures: Boilers supporting structure consists of a systematic arrangement of columns stiffened with horizontal beams and vertical diagonal bracings and comprise of low carbon steel material. It is composed of 18 main columns and 12 auxiliary columns. The main columns support the main boiler components viz. drum, water wall membrane, panels, superheaters, reheaters, economisers, air preheater, burners and galleries at various levels.

Galleries and stairways: Galleries and stairways around the combustion and heat recovery areas are provided for proper approach to the boiler. Stairways on both the side of Boiler are provided. All the floors are covered with floor gratings of required depth for walkway and are welded to the structure. The total weight of Galleries and stairway are 900 M.T.

Galleries and stairways: Galleries and stairways around the combustion and heat recovery areas are provided for proper approach to the boiler. Stairways on both the side of Boiler are provided. All the floors are covered with floor gratings of required depth for walkway and are welded to the structure. The total weight of Galleries and stairway are 900 M.T.

The auxiliary columns, supports the boiler platforms and other ducts coming in that region. The total weight of supporting structures is about 970 M.T.

The auxiliary columns, supports the boiler platforms and other ducts coming in that region. The total weight of supporting structures is about 970 M.T.

Furnaces may be classified according to the construction of

four wall.

• Solid refractory setting
• Air-cooled refractory setting
• Water-cooled walls

The furnace must provide the following

• Proper installation, operation and maintenance of fuel burning equipment.
• Sufficient volume for combustion requirements.
• Adequate refractory and insulation.

 (^) Accessibility to the boiler for the maintenance and repair work that must be handled from inside the furnace chamber.

Furnaces may be classified according to the construction of

four wall.

• Solid refractory setting
• Air-cooled refractory setting
• Water-cooled walls

The furnace must provide the following

• Proper installation, operation and maintenance of fuel burning equipment.
• Sufficient volume for combustion requirements.
• Adequate refractory and insulation.

 (^) Accessibility to the boiler for the maintenance and repair work that must be handled from inside the furnace chamber.

Following selection factors are taken into consideration:-  (^) Lowest capital cost, easy in construction, simplicity safety,

good working condition, easy in maintenance.  (^) Availability of auxiliaries  (^) Efficient operation, effective for heat transfer well insulate

casings, ability to deliver pure steam with effective drum internals, to generate steam of full capacity.

Boiler Construction :- Main parts of Boiler used in Thermal power plant Economizer, Boiler Drum, Down corners, Bottom Ring Header, Water wall, Primary, Superheater, Platen superheater, Final Superheater Reheater Coal firing nozzles, oil Firing nozzles, , Burners Windbox assembly, Igniters, Flame scanners and Soot Blowers. Figures on the next slide shows the basic construction of pulverised coal fired boilers.

Following selection factors are taken into consideration:-  (^) Lowest capital cost, easy in construction, simplicity safety,

good working condition, easy in maintenance.  (^) Availability of auxiliaries  (^) Efficient operation, effective for heat transfer well insulate

casings, ability to deliver pure steam with effective drum internals, to generate steam of full capacity.

Boiler Construction :- Main parts of Boiler used in Thermal power plant Economizer, Boiler Drum, Down corners, Bottom Ring Header, Water wall, Primary, Superheater, Platen superheater, Final Superheater Reheater Coal firing nozzles, oil Firing nozzles, , Burners Windbox assembly, Igniters, Flame scanners and Soot Blowers. Figures on the next slide shows the basic construction of pulverised coal fired boilers.

The flue gas formed by combustion of a fuel in the furnace passes through the following passes

• (^) First Pass
• (^) Horizontal pass
• (^) Second Pass  (^) First pass consist of  (^) Furnace water wall  (^) Platen super heater  (^) Horizontal Pass consist of  (^) Reheater  (^) Water wall screen tubes  (^) Final Superheater  (^) Second pass consist of  (^) LTSH  (^) Economizer

The flue gas formed by combustion of a fuel in the furnace passes through the following passes

• (^) First Pass
• (^) Horizontal pass
• (^) Second Pass  (^) First pass consist of  (^) Furnace water wall  (^) Platen super heater  (^) Horizontal Pass consist of  (^) Reheater  (^) Water wall screen tubes  (^) Final Superheater  (^) Second pass consist of  (^) LTSH  (^) Economizer

Boiler Drum :-

• (^) Drum is a pressure vessel
• (^) It is made of special carbon steel plate, Material of SA-299 grade

A1 or SA- 515 Grade 70.

• (^) Plates thickness having 132 mm
• (^) The function of Boiler Drum is to separate water & steam from the mixture generated in the furnace wall.
• (^) It also provides a water storage for preventing the starvation of tubes.
• (^) Located at 53 meter elevation.

Boiler Drum :-

• (^) Drum is a pressure vessel
• (^) It is made of special carbon steel plate, Material of SA-299 grade

A1 or SA- 515 Grade 70.

• (^) Plates thickness having 132 mm
• (^) The function of Boiler Drum is to separate water & steam from the mixture generated in the furnace wall.
• (^) It also provides a water storage for preventing the starvation of tubes.
• (^) Located at 53 meter elevation.

Parts of boiler drum :-

 Turbo separator

 Screen dryer

 Feed pipe

 Baffle Plate

 Drum level gauge (lower)

 Riser tube (Water walls

Tubes) i.e 6 x 23 rows on

drum

 Chemical dosing pipe

 Main hole & main hole cover

 Safety Valve

 Sampling line

 Vents

Parts of boiler drum :-

 Turbo separator

 Screen dryer

 Feed pipe

 Baffle Plate

 Drum level gauge (lower)

 Riser tube (Water walls

Tubes) i.e 6 x 23 rows on

drum

 Chemical dosing pipe

 Main hole & main hole cover

 Safety Valve

 Sampling line

 Vents

Technical specification of 210 MW boiler drum is given below. Length 15700 mm Weight 123 Tonnes Internal Diameter 1676 mm Outside Diameter 1942 mm Thickness of Metal 132 mm Material Carbon Steel SA 515 Gr. 70 or S.A. 299 A Pressure in Drum 149.7 Kg. /cm^2 (LMW Unit) 168 Kg. /cm^2 (KWU Unit) Total Number of Turbo separator in each row 50

Technical specification of 210 MW boiler drum is given below. Length 15700 mm Weight 123 Tonnes Internal Diameter 1676 mm Outside Diameter 1942 mm Thickness of Metal 132 mm Material Carbon Steel SA 515 Gr. 70 or S.A. 299 A Pressure in Drum 149.7 Kg. /cm^2 (LMW Unit) 168 Kg. /cm^2 (KWU Unit) Total Number of Turbo separator in each row 50