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TECHNICAL PRESENTATIONTECHNICAL PRESENTATION

CETHAR LIMITED

Types of boilers

�Sub critical boilers� Drum type natural circulation boilers

� Drum type controlled circulation boilers

� Once through boilers

�Super critical boilers� Once through boilers

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Evaporator systems

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Design Criteria

Description OT Super critical Sub-Critical

Furnace sizing Decided by Fuel and Gas side parameters

Same

Evaporator Supercritical fluid;Variable evaporation end point; Superheated steam at evaporator outlet;

(Supported by BENSON

Water and Steam mixture;Fixed evaporation end point;Saturated steam at evaporator outlet

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Technology) Natural / controlled circulation

Drum Replaced by smaller Separators and collecting vessel. Required only during low loads (about 35-40%)

Required for water and steam separation at all loads

Start up and low load circulation system

Required.(Supported by BENSON Technology)

Not applicable

Design Criteria

Description OT Supercritical Sub-Critical

SH and RH sizing Same for both sub critical and sup ercritical

Economiser Same for both sub critical and supercriti cal

Pulveriser sizing Same for both sub critical and sup ercritical

Fans. RAPH & ESP and ducts

Same for both sub critical and supercritical

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and ducts

Controls Feed water flow is controlled based on loadSH steam temperature is controlled by spray followed by firing rate.

Feed water flow is controlled by drum level.SH outlet temperature is maintained by spray.

Water treatment and water chemistry

AVT and Oxygenated water treatment (mandatory)

Generally AVT

Furnace Design

FEGT = IDT - 50 K

FEGT = Furnace exit gas temperature

IDT = Initial deformation temperature of ash

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IDT = Initial deformation temperature of ash

Furnace design and size are decided by coal and ash quality

Evaporator wall design

� Heat absorption variation and resulting temperature difference at furnace wall outlet

Key Issues

� Boiling crisis like DNB and Dry out and associated wall temperatures

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Evaporator systems

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Steam temperature at furnace wall outlet

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Heat flux variation in furnace

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Sliding pressure operation

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Operating regimes

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Fluid Density

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Flow pattern

Flow pattern at different pressures:Supercritical Subcritical

Insignificant density differenceat Supercritical pressure results

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at Supercritical pressure resultsin single phase supercritical fluid. Consequently there is no DNB andDry Out which exist in sub-criticalpressure regime of operation.

Boiling Crisis

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Evaporator Designs

� High mass flux design (2000 to 2400 kg/ m2 s)

� Spiral wall arrangement with smooth tubes

� Medium mass flux design (1500 to 2000 kg/m2 s)

� Vertical wall arrangement with rifle tubes and orifices� Vertical wall arrangement with rifle tubes and orifices

� Low mass flux design (900 to 1000 kg/m2 s)

� Vertical wall arrangement with optimised multilead rifled tubes

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Furnace wall designs

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CETHAR’s 660 MW boiler

LTSH

HTSH HTRH

Screen Low mass flux design

Furnace with Vertical tubes

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Econ

LTRH

RSH

Optimised Multi Lead Rifled tubes for lower furnace (OMLR tubes)

Spiral wall arrangement

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Spiral wall construction reduces the number of eva porator wall tubes and thereby increases mass flux through the tubes.

This ensures a minimum water wall flow and protects water wall tubes.

Changes in mass flux

%16

12

8

4

.

.∆mmm ean

Change of mass flowin a tube with 25%increased heat input

%16

12

8

4

.

.∆mmm ean

Change of mass flowin a tube with 25%increased heat input

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600 800 1200 kg/m2s1000 1400 1800Mass flux (at full load)

4

0

-4

-8

-12

-16

Naturalcirculation

Once-through

600 800 1200 kg/m2s1000 1400 1800Mass flux (at full load)

4

0

-4

-8

-12

-16

Naturalcirculation

Once-through

Impact of flow characteristic on fluid temperatures

High mass fluxHigh mass flux Low mass fluxLow mass flux

100%

85%420°C

524°C100% 101%

420°C461°C

∆ = 104°C∆ = 41°C

High mass fluxHigh mass flux Low mass fluxLow mass flux

100%

85%420°C

524°C100% 101%

420°C461°C

∆ = 104°C∆ = 41°C

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Mass flux Mass fluxOutlettemperature

Outlettemperature

1308 // Tubesda 29.65 mm; di 16.65 mmMass flux 1805 kg/m²s

1298 // Tubesda 34.92 mm; di 21.91 mmMass flux 1050 kg/m²s

Mass flux Mass fluxOutlettemperature

Outlettemperature

1308 // Tubesda 29.65 mm; di 16.65 mmMass flux 1805 kg/m²s

1298 // Tubesda 34.92 mm; di 21.91 mmMass flux 1050 kg/m²s

Flow Features of a Water Wall Tube with 25% Excess Heat Input

Evaporator wall design

� Heat absorption variation and resulting temperature difference at furnace wall outlet

Key Issues

� Boiling crisis like DNB and Dry out and associated wall temperatures

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Rifle tube

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Smooth Vs Rifle tubes

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Optimised Multilead Rifled Tube

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Comparison of various designs

Parameter High mass flux

Spiral wall

Medium mass flux, vertical wall

Low mass flux

Vertical wall

Flow Characteristic

Once through characteristic Once through characteristic

Natural circulation flow characteristic

Mass flux High

(around 2000 kg/m2-s

at full load or above)

Medium to High (around 1500 to 2000 kg/m2-s at full load)

Low

(around 1000 kg/m2-s

at full load)

Furnace wall tube Smooth tubes Rifled tubes with orifices

Optimized Multi Lead Rifled Tubes (OMLR)

Pressure drop in

furnace wall

Higher Higher Lower

Good savings in BFP power consumption

Furnace wall attachments & buck stays

Complex

Typical increase in weight for a 660 MW boiler is approx. 400 t

Simple,

Self supporting

Simple

Self supporting

Manufacturing &

Construction

Difficult compared to vertical design Easier Easier

Maintenance Difficult due to presence of vertical supporting straps

Easier Easier

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Waterwall flow

WATER WALL FLOW

50

60

70

80

90

100

FLO

W %

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0

10

20

30

40

50

0 10 20 30 40 50 60 70 80 90 100

LOAD %

FLO

W %

WW FLOW

Start up and low load circulation system

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Materials

SectionSection Sub criticalSub critical Super criticalSuper critical

EconomiserEconomiser SA 210 Gr A1 / CSA 210 Gr A1 / C SA 210 Gr A1 / CSA 210 Gr A1 / C

Water wallWater wall SA 210 Gr CSA 210 Gr C SA 213 T11 / T12/T22 SA 213 T11 / T12/T22

SA 213 T11, T22, T91, SA 213 T11, T22, T91, T92, T92,

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Super heaters and Super heaters and re heaterre heater

SA 213 T11, T22,T91 and SA 213 T11, T22,T91 and TP 347 HTP 347 H

SA 213 T11, T22, T91, SA 213 T11, T22, T91, T92, T92, Super 304HSuper 304H, and TP 347 H, and TP 347 H

Headers and Headers and pipingpiping

SA 106 Gr B, Gr C, P11, SA 106 Gr B, Gr C, P11, P22 and P91P22 and P91

SA 106 SA 106 GrGr B, B, GrGr C, P11, C, P11, P22, P22, 302 302 GrGr C C and P91, and P91, P92P92

Control concepts specific to Once through boilers

� Feed water flow control:� Feed water flow is controlled by drum level in drum type boilers. In

once trough boiler, feed flow depends directly on the load.

� SH steam temperature control� In drum type boiler, SH outlet temperature is maintained by spray.

In once through boiler, SH steam temperature is controlled by spray followed by firing rate.

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� Water collecting vessel level control� Swell during start up is discharged by two quick acting control

valves into a flash tank.

� During low load operation, water level is maintained over a range by a flow control valve located downstream of circulating pump.

Water treatment

� Stringent water quality requirements. Water quality requirements are

to be strictly adhered to as there is no blow down from drum

� Oxygenated water treatment is used

� Oxygen is injected to reduce the formation of magnetite layer

(Fe3O4) and form more of hematite layer (Fe2O3) which will reduce

the deposits and the pressure drop

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the deposits and the pressure drop

� To achieve this, oxygen in feed water is to be maintained within 0.03

to 0.15 mg/L and the conductivity of feed water at 25 deg C

downstream of cation exchanger is to be maintained less than 0.15

micro Siemens/cm

� During Start up : All Volatile Treatment (AVT)

� During Normal Operation : Oxygenated water treatment

Benson experience

167 m

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Aghios Dimitrios Power Plant, Greece286 kg/s - lignite242 bar / 540°C / 540°C

Lippendorf Power Plant, Germany672 kg/s - lignite285 bar / 554°C / 583°C

Hekinan Power Plant, Japan639 kg/s - imported coal255 bar / 543°C / 569°C

Hemweg Power Plant, Netherlands530 kg/s - imported coal261 bar / 540°C / 540°C

NordjyllandsvaerketPower Plant, Denmark270 kg/s - imported coal310 bar / 582°C / 580°C

Ibbenbüren Power Plant, Germany600 kg/s - anthracite220 bar / 530°C / 530°C

Pressures are maximum allowable working pressures

Low mass flux design references

(PC fired boilers)

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Long view has been commissioned and has reached ful l load in June 2011.

No thermo hydraulic problem

Low mass flux reference

CFBC boilers

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Low mass flux references

Anthracite fired boilers

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Why CETHAR need to be qualified?Experience of Riley in the design, supply and commi ssioning of 1290 t/hr constant pressure supercritical boiler

Availability of long term collaboration agreement w ith Siemens for sliding pressure supercritical evaporator system at the han ds of Riley and CETHAR

Royalty payment obligations of CETHAR ensures the s upport of Collaborators for design review, support for Erecti on & Commissioning and trouble shooting.

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and trouble shooting.

Experience of Riley in the design, supply and commi ssioning of sub critical boilers in excess of 500 MW and with var ied fuels

Readily available manufacturing infrastructure for boilers with an annual capacity of 8000 MW

Availability of qualified and experienced world cla ss human resource

Why CETHAR need to be qualified?

25 years presence in boiler industry

CETHAR’s self belief on technology development

Role played by CETHAR in the introduction of fluid bed boilers

Computerisation and centralising the knowledge for consistent

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Computerisation and centralising the knowledge for consistent performance in design , manufacture and constructio n of power plants.

CETHAR’s willingness to offer high level transparen cy in project execution

Substantial reduction in boiler price & delivery ti me.

CETHAR’S Request

� Inclusion of yet another route for supercritical

steam generator bidders:

Indian Boiler manufacturer with already established manufacturing

facility for an annual capacity of at least 5000 MW and having

technology through a collaborator who has already d esigned and

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technology through a collaborator who has already d esigned and

commissioned at least one number of coal fired con stant pressure

supercritical steam generator which is in successfu l operation for a

period of not less than one (1) year as on the date of bid opening. The

collaborator should also have a valid collaboration for variable

pressure evaporator from a technology Owner and a 5 00 MW coal fired

sub critical steam generator in operation.

THANK YOU

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