Super Critical Boiler.ppt

WELCOME TO PRESENTATION ON

SUPERCRITICAL By BOILER

OPERATION TEAM

1

APML,TIRODA

Introduction to Supercritical Technology What is Supercritical Pressure ? Critical point in water vapour cycle is a thermodynamic state where there is no clear distinction between liquid and gaseous state of water. Water reaches to this state at a critical pressure above 22.1 MPa and 374 oC.

2

Rankine Cycle Subcritical Unit            3

1 - 2 > CEP work 2 - 3 > LP Heating 3 - 4 > BFP work 4 - 5 > HP Heating 5 – 6 > Eco, WW 6 – 7 > Superheating 7 – 8 > HPT Work 8 – 9 > Reheating 9 – 10 > IPT Work 10–11 > LPT Work 11 – 1 > Condensing

Rankine Cycle Supercritical Unit  1 - 2 > CEP work  2 – 2s > Regeneration  2s - 3 > Boiler Superheating  3 – 4 > HPT expansion  4 – 5 > Reheating  5 – 6 > IPT & LPT Expansion  6 – 1 > Condenser Heat

rejection 4

VARIATION OF LATENT HEAT WITH PRESSURE

5

Absolute Pressure (Bar)

Saturation Temperature (oC)

Latent Heat (K J/Kg.)

50 150 200 221

264 342 366 374

1640 1004 592 0

Departure from Nucleate Nucleate boiling is a type of boiling that takes place when the surface temp is hotter than the saturated fluid temp by a certain amount but where Boiling heat flux is below the critical heat flux. Nucleate boiling occurs when the surface temperature is higher than the saturation temperature by between 40C to 300C.

DENSITY

WATER

STEAM

175 224 PRESSURE(ksc) 6

Supercritical Boiler Water Wall Rifle Tube And Smooth Tube

7

Natural Circulation Vs. Once Through System

8

5710C To HP Turbine Mixer Header 4230C

4620C

To IP Turbine 5690C

5340C 5260C

Separator

FRH

4730C

FSH Platen Heater From CRH Line 3240C

From FRS Line

NRV

3260C

2830C

2800C

Boiler Recirculation Pump

LTRH

LTSH 4430C

Economizer Phase 1

Bottom Ring Header

Economizer Phase 2

Feed water control  In Drum type Boiler Feed water flow control by

Three element controller  1.Drum level  2.Ms flow  3.Feed water flow.

 Drum less Boiler Feed water control by  1.Load demand  2.Water/Fuel ratio(7:1)  3.OHD(Over heat degree)

10

Difference of Subcritical(500MW) and Supercritical(660MW)

11

COMPARISION OF SUPER CRITICAL & SUB CRITICAL DESCRIPTION

SUPERCRITICAL (660MW)

SUB-CRITICAL (500MW)

Circulation Ratio

1

Feed Water Flow Control

-Water to Fuel Ratio (7:1) -OHDR(22-35 OC) -Load Demand

Latent Heat Addition

Nil

Heat addition more

Sp. Enthalpy

Low

More

Sp. Coal consumption

Low

High

Air flow, Dry flu gas loss

Low

High

Once-thru=1 Assisted Circulation=3-4 Natural circulation= 7-8 Three Element Control -Feed Water Flow -MS Flow -Drum Level

Continue.. DESCRIPTION

SUPERCRITICAL (660MW)

SUB-CRITICAL (500MW)

Coal & Ash handling

Low

High

Pollution

Low

High

Aux. Power Consumption

Low

More

Overall Efficiency

High (40-42%)

Low (36-37%)

Total heating surface area Reqd

Low (84439m2)

High (71582m2)

Tube diameter

Low

High 13

Continue.. DESCRIPTION

SUPERCRITICAL SUB-CRITICAL (660MW) (500MW)

Material / Infrastructure (Tonnage)

Low 7502 MT

High 9200 MT

Start up Time

Less

More

Blow down loss

Nil

More

Water Consumption

Less

More

14

Water Wall Design

15

WATER WALL ARRANGEMENT  Bottom spiral & top vertical tube furnace arrangement  Once through design feature is used for boiler water wall

design  The supercritical water wall is exposed to the higher heat

flux  Spiral tube wall design (wrapped around the unit) with

high mass flow & velocity of steam/water mixture through each spiral  Higher mass flow improves heat transfer between the 16

WW tube and the fluid at high heat flux.

SPIRAL VS VERTICAL WALL VERTICAL WALL  Less ash deposition on 

  

17

wall Less mass flow More number of tubes More boiler height for same capacity No uniform heating of tubes and heat transfer in all tubes of WW

SPIRAL WALL  More ash deposition  More fluid mass flow  Less number of tubes

 Less boiler height  Uniform heat transfer and

uniform heating of WW tubes

Furnace Arrangement

SPIRAL TYPE

VERTICAL TYPE 18

Supercritical Sliding Pressure Boiler Water Wall Design Comparison of Vertical Wall and Spiral Wall

19

20

Ash accumulation on walls Vertical water walls

21

Spiral water walls

Super Critical Boiler Materials

22

Advanced Supercritical Tube Materials (300 bar/6000c/6200c)

23

Material Comparison Description

660 MW

500 MW

Structural Steel

Alloy Steel

Carbon Steel

Water wall

T22

Carbon Steel

SH Coil

T23, T91

T11, T22

RH Coil

T91,Super 304 H

T22, T91,T11

LTSH

T12

T11

Economizer

SA106-C

Carbon Steel

Welding Joints (Pressure Parts)

42,000 Nos

24,000 Nos

24

Steam Water Cycle Chemistry Controls

25

S. Parameter No. 

Silica

< 20 ppb in feed water and steam, Standard value