Pressure Parts 500MW Boiler

CONSTRUCTION OF 500 MW BOILER (PRESSURE PARTS)

BY ABHAY D. KHOBRAGADE

A. E. (CHANDRAPUR PROJECT)

CONTENTS

WHY TO GO FOR HIGHER CAPACITY BOILER 1’ 1

T

P1

2’-3 = Heat Rejection in condenser 3-4 = Water pumped to boiler

4 P2

3

1’-2’ = Work done in turbine from P1 – P2

2’

2 S

4-1 = Heat addition in eco and boiler.

Theoretically rankine Cycle is the ldeal cycle. But it is having practical difficulties.  For steam power plant, practically thermal cycle used is modified rankine cycle.  The maximum efficiency between two limits of the working fluid as given by the Rankine cycle is  Efficiency = (T1 – T2)/T1  where T1 and T2 are max. and min absolute temp.  Now as T2 is limited by ambient conditions so T1 must be as high as possible.  Thus from the efficiency point of view, the largest gain can be obtained by the use of higher temperature. i.e to increase T1 

SPECIFICATION OF BOILER 500 MW



FURNACE         



TYPE: Balanced Draft Wall: Fusion welded Bottom: Dry Tube arrangement: Membrane Explosion / Implosion withstand Capacity at 67% yield point : +/- 660mmhg Residence time for fuel particles in the furnace : 3 sec. Effective volume used to calculate residence time: 14580 m3 Furnace height(from center of ring header to centre of roof inlet header) : 61.168 meter. Depth : 15.289 meter

SPECIFICATION OF BOILER 500 MW    



Width : 18.034 meter Furnace Volume : 14580 m3 Design Code: IBR Type of Firing: Tilting Tangential

SPECIAL FEATURES OF 500 MW BOILER 

Controlled circulation of feed water in water walls with the help of 3 Nos. of boiler circulating water pumps installed on down comers.



Rifled bore water wall tubes as against smooth bore tubes in 210 MW boiler.



Provision of Orifices for equal distribution of water in water wall tubes from bottom ring header.



All down comers are connected to front header of the bottom ring header.



4 Nos. of bisector air pre heater, two for primary air and two for secondary air.

 

8 Nos. of XRP 1043 bowl mills.

NEED FOR ASSISTED CIRCULATION Densit y of Wat er

Crit ical Point

Densit y of St eam

Pressure (Kg/cm 2)

   

 



Density difference is the driving force for the steam and water mixture. Circulation takes place at such a rate that the driving force and the frictional resistance are balance. But as the pressure increases, the difference in density between the water and steam reduces. Hydrostatic head available may not be able to overcome the frictional resistance for the flow corresponding to the minimum requirement of cooling of water wall tubes. Therefore, natural circulation is limited to Boiler with the drum operating pressure around 175 kg/cm2 Above 175 kg/cm2 of pressure, circulation is to be assisted with mechanical pumps, to overcome the frictional losses. To regulate the flow through various tubes orifice plates are used.

DESIGN FACTOR For the construction of boiler parts subjected to pressure and their integral attachment, the designer takes into account several factors 

CONSTRUCTION OF PRESSURE PARTS

ECONOMIZER TUBES TUBE DETAILS  All economizer tube are of Ø 51mm X 5mm.  Located in the boiler back pass.  It is composed of three banks of 130 parallel tube elements arranged in horizontal rows.  Each row is in line with the row above and below.  All tube circuit originate from the inlet header and terminate at the outlet header.



ECO OUTLET HDR Ø406.4

ECO UPPER BANK

ECO MIDDLE BANK

ECO LOWER BANK

EC0 FEED PIPE

ECO INLET HDR Ø508

WATER WALL TUBES   

TUBEE DETAILS Description Tube Size Ø 159 X 15 Riser Tube Water wall panel Ø51 X 5.6 Ø 63.5 X 7.1 tubes Extended side Ø63.5 X 11 water tube W. W.wall Hanger Ø63.5 X 7.1 tubes W. W. Screen tubesArch Tubes Ø51 X 5.6 Rear 

Ø63.5 X 7.1 Ø63.5 X 7.1 

Material SA – 106 Gr-C SA – 210 Gr-C SA – 210 Gr-A1 SA – 210 Gr-C SA – 210 Gr-A1 SA – 210 Gr-C SA – 210 Gr-C SA – 210 Gr-A1

FUR REAR HGR TUBE O/L HDR Ø273

RISER TUBES, Ø 159

BOILER DRUM Ø1778

FUR UPPER SIDE WW HDR Ø273

FUR UPPER REAR WW HDR Ø273

REAR WALL HGR TUBES Ø63.5

SUCTION MANIFOLD , Ø508

SCREN TUBES Ø63.5

FURN FRONT WALL TUBES Ø51

FURN SIDE WALL TUBES Ø51

FURN REAR WALL TUBES Ø51

BCW PUMP

FURN SIDE HDR , Ø914.4

WATER WALL DETAILS AND

FURN REAR HDR , Ø914.4

SUPER HEATER TUBES Description

Tube Size

Material

Radiant Roof Tubes



Ø 63.5 X 6.3 Ø 57 X 5.6 Ø 63.5 X 6.3 Ø 51 X 5 Ø 51 X 5 76.1 X 10 Ø 63.5 X 6.3 Ø XX 5.07.1 Ø 51 44.5

SA 213, T11 SA 213, T11 SA 210, Gr C SA 210, Gr C SA 210, Gr C SA 210, Gr C SA 210, Gr C

Ø 51 X 5 Ø 44.5 X 7.1 Ø 47.63 X 8.6

SA 210, Gr C SA 210, Gr C SA 210, Gr C



Steam Cooled Side wall tubes Steam Cooled front wall tubes Front Wall Hanger Tubes Rear Roof Tubes

 

Eco and LTSH Support tubes

SUPER HEATER TUBES Description

Tube Size

Material

Steam Cooled Side Wall tubes

Ø 51 X 5

SA 210, Gr C

Bifurcate Tubes (Bottom Header)

Ø 51 X 5

SA 210, Gr C

LTSH Horizontal Tubes



Ø 51 X 5 Ø 51 X 5.6

SA 210, Gr C SA 210, Gr C

Ø 51 X 5 Ø 51 X 5.6

SA 213, T11 SA 213, T11

Ø 51 X 6 Ø 44.5 X 4.5

SA 210, Gr C SA 210, Gr C

Ø 51 X 6

SA 213, T11

Ø 63.5 X 8 Ø 51 X 5.6 Ø 63.5 X 6.5 Ø63.5 X 7.1 Ø 63.5 X 7.1 Ø 51 X 5.0 Ø 51 X 5.0

SA SA SA SA SA SA SA



Pendent Coil Tubes

 

Divisional Panel inlet loose tubes



Divisional Panel Outlet loose tubes



Steam Cooled Spacer

 

213, 213, 213, 213, 210, 213, 210,

T11 TP347H TP347H T11 Gr C T11 Gr C

SUPER HEATER TUBES  Super

heater tubes is composed of three basic stages of section.



The finishing section is located on the horizontal gas path above the furnace rear arch tubes.  The divisional panel section are located in the furnace between the front wall and the pendent platen section.  It consist of 6 front and 6 rear assemblies.  The low temperature section are located in the furnace rear back pass above the economizer section.  They are composed of 116 assemblies spaced on across the furnace width.  The back pass wall and roof section forms the side, front, rear wall and roof of the vertical gas pass. 

DIV PANEL O/L LINK Ø 508, 2 NOS.

MAIN STEAM

BP UPPER REAR HDR, Ø 273 LTSH UPPE BANK Ø 47.63

SH DIV. PANELETTE, Ø 44.5, 6 ASSY

SH & ECO SUPP TUBES, Ø 51

LTSH I/L HDR, Ø 323.9

SH VERT PLATEN ASSY, Ø 51, 6 ASSY

SH CONN TUBES, Ø 59

SH ROOF O/L HDR, Ø 406.4

SH DESH Ø 508, 2 NOS.

LTSH LWR BANK Ø 47.63

BP LWR FRONT HDR, Ø 406.4

BP LWR SIDE REAR HDR, Ø 406.4

BP LWR REAR HDR, Ø 323.9 BP LWR SIDE REAR HDR, Ø 323.9

REHEATER  

TUBE DETAILS Description Tube Size Reheater Wall Ø 60.3 X 4 Ø 54 X 3.6 tubes Cross over tubes

Material SA 313, T11 SA 213, T11

REHEATER  The

re heater section is composed of three stages or section.

REHEATER  The

finishing section is located above he furnace arch between the furnace screen tubes and the super heater tubes.  It consists of 46 tubes assemblies.  The reheater front and side radiant wall is composed of tangent tubes on 63.5 centres across the furnace width.

SH ROOF O/L HDR, Ø 406.4

SH CONN TUBES, Ø 59

RH VERT PLATEN O/L HDR, Ø 558.8

RH VERT PLATE I/L HDR, Ø 457.2

RH VERT PLATE I/L HDR, Ø 457.2

RH VERT PLATEN O/L HDR, Ø 558.8

MAIN STEAM

COMPLETE CYCLE 500 MW

BOILER DRUM  The

function of the boiler drum internals is to separate the water from the steam generated in the furnace walls.  To reduce the dissolved solid contents of the steam to below the prescribed level.

BOILER DRUM  Separation

is generally performed in three stages.

Boiler Drum Internals Boiler Int ernals Mainly Consist s of: -

Separating Chamber 

 



From the riser tube steam and water mixture flows into the Drum through a narrow annulus formed by a shroud extending along the length of the Drum Shell called the Separating Chamber. This is a welded construction formed by Baffles. These surfaces direct the flow of substances either to prevent or o improve it’s flow. It directs the steam and water mixture entering the drum to the turbo separator.

Turboseparator From the lower end of the separating chamber the steam and water mixture is forced upward in the turboseparator.  Turbo separator is a main separating device. 

Spinner Blades Cans

Primary stage  

The primary stage is formed by two concentric cans and a spinner blade located inside the inner can. The fixed spinner blade of turbo separator which is located inside the inner can imparts a centrifugal motion to the mixture of steam and water flowing upward through the inner can.

Secondary st age  The

secondary st age consist s of t wo opposed banks of closely spaced t hin corrugat ed sheet s.  It direct s t he st eam t hrough a curved pat h and separat es t he rem aining ent rained wat er.  Since t he velocit y is relat ively low t his wat er is not picked up again but runs down t he plat e and flows down t o t he drum wat er.  This st age of separat ion is called secondary separat ion or st eam scrubbing.

Third stage 









The third and final stage of steam/water separation takes place in the screen dryer. It removes residual moisture from the steam leaving turbo separator. The screen dryer box consists of wire mesh of different gauges. Exterior meshes are of thicker wire rod, which have better mechanical rigidity to the screen box. The steam passing between the strips making one or more sharp changes of direction and throwing the heavier water particle coming in contact with the strips.

Chemical Composition of tubes used in 500 MW boiler Sr. No. Materila spec.

C

Mn

P

S

Si

Ni

Cr

Mo

V

Cb

Used in

1

SA 210, Gr- 0.27 A1

0.93

0.048

0.058

0.10

Extended side WW tube, WW screen tube arch tube

2.

SA 210, Gr 0.35 C

0.29 to 1.06

0.048

0.058

0.10

3.

SA 213, T11

0.15

0.30 to 0.60

0.03

0.03

0.5 to 1.0

1.0 to 1.5

0.44 to 0.65

WW Panel & corner transition tube, hanger tubes, rear arch tube, Eco tube, steam cooled wall, rear roof, SH hanger tube, LTSH divisional Panel loose Radiant roof pendent coil divisional panel, S, C, tube. spacer, SH Platen coil, re heater wall , re heater coil.

4.

SA 213, T91

0.15

0.3 to 0.60.03

0.03

0.5

1.9 to 2.6

0.87 to 1.13

Divisional Panel, SH Platen coil, RH Platen Coil, RH rear coil.

5.

SA 213, T91

0.08 to 0.12

0.3 to 0.60.02

0.01

0.2 to 0.4 0.5

8.0 to 9.5

6.

SA 213 TP 0.04 to 304-H 0.10

2.0

0.04

0.03

0.75

8.0 to 11.0

0.85 to 0.18 0.06 to Platen SH coil, platen RH Coil. 1.05 to 0.10 0.25 18.0 to Divisional Panel, RH platen coil. 20.0

7

SA 213, TP 0.04 304-H

2.0

0.04

0.03

0.75

9.0 to 13.0

17.0 to 20.0

Divisional panel, SH platen coil, steam cooled spacer.

THANK YOU