ECONOMIZER

• Purpose: Preheat the boiler feed water and recover some of the heat from the flue gases.

• Location: Rear gas pass below the rear horizontal SH.

• Staggered arrangement.

• Continuous finned tube.

ECONOMIZER

• Tube size:

OD 44.5 mm X 4.5 mm (thick).

Material – SA 210 Gr A1.

• Probable failure causes.

WJF

Erosion

DRUM• FUNCTION:To separate steam and water from the mixture

generated from water walls.Reduce the dissolved solid contents into acceptable

limits.• Size:ID – 1676 mm; Thickness – 133 mmLength – 15700 mm; hemisphere – 940 mmMaterial SA 299

DRUM

• Steam drum internals:

Feed pipe.

Separating chamber.

Turbo separators.

Screen dryers

Chemical dosing.

Blow down.

Welded Wall Construction• Water cooled furnace.

Combustion and heat transfer takes place.

Construction:

Furnace walls Membrane type.

Radiant roof is of pegfin welded construction.

Rear pass roof, and rear, front and side steam cooled wall are of fin welded construction.

WATER WALL

• Bottom construction:

Depends on fuel and ash condition.

Mostly open hopper type, often referred as dry bottom. Leakage of air between furnace and hopper is prevented by either a water impounded or a mechanical seal expansion joints.

WATER WALL• Corner/tangential fired.• Tube Dia -63.5 mm Thickness – 5.2 mm

Material – SA 210 Gr A1.• Probable failure causes.

Blistering

Erosion

Corrosion

AWF/WJF.

SUPERHEATERS

• Composed of four basic stages:Pendant section, Platen section, Rear

horizontal section, and the steam cooled wall and roof sections.

Location:Platen Section is located just above the

furnace in front of the furnace arch. Heat absorbs mainly by radiation.

SUPERHEATERS

• Pendant section is located behind the screen tubes. Predominant mode of HT is convection.

• LTSH is located in the rear vertical gas pass above economizer. This is the primary SH of the convective, counter flow type.

• SCW sections form the side, front and rear walls and roof of the vertical gas flow path.

REHEATER

• Reheater is composed of two sections namely front pendant and rear pendant vertical spaced section.

• Location:Rear pendant is located above the furnace arch

between water cooled screen and rear water wall hangers.

Front pendant is located between water wall hangers and platen section.