Advanced Ultra Supercritical Steam Generators & Advanced Ultra Supercritical Steam Generators New trends in Boiler Technology M. Anandaraj Deputy General Manager BHEL, Tiruchirappalli

Contents BHEL Steam Generators Emerging Market Requirements Trends in Cycle parameters Supercritical Boilers Major Systems Startup System Pressure part Arrangement Firing System High Temperature Materials Ultra Supercritical Boilers Advanced Ultra Supercritical Boilers

BHEL Utility Units - A Summary 62 % Total Installed Capacity of India is Contributed by BHEL Utility Sets

BHEL Industrial Units - A Summary Contracted Commissioned VU 40 46 45 VU 40 S 15 VU 60 38 19 MU 3 VP 23 16 V2R 17 HRSG 177 121 AFBC 72 59 CFBC 28 10 Others Total 447 333

BHEL is currently adopting Advanced Steam Cycles to Improve the Environmental & Economic Performance of India’s Power Generation

Reference List of Supercritical Boilers NTPC / BARH 2 x 660MW APPDCL / Krishnapatnam 2 x 800 MW PPGCL / BARA 3 x 660 MW RPCL / Yermaras 2 x 800 MW RPCL / Edlapur 1 x 800 MW KPCL / Bellary 1 x 700 MW LPGCL/Lalithpur- BHL 3 x 660 MW DB Power / Singrauli 2 x 660 MW NTPC / Mouda St. II 2 x 660 MW 18 Boilers Contracted

Emerging Market Requirements For Thermal Power Generation High Reliability & Availability Highest Plant efficiency Suitable for differing modes of operation Suitable for varying fuel quality Minimum emission of Pollutants Lowest cost

Higher Plant efficiency for Conservation of fuel resources Reduction of Atmospheric Pollutants - CO2 , SOX & NOX

Measures to improve Plant Efficiency Cycle Parameters : Higher steam parameters with Once Thro’ Boilers Boiler side measures : Highest Boiler Efficiency Minimum RH spray Minimum SH spray (if tapped off before feed heaters) Reduced auxiliary power consumption

Increase of Plant Cycle Efficiency due to Steam Parameters

500 MW Steam Generator Coal Consumption and Emissions

Current Trends in Steam Parameters 1980s : Pressure increased from 175-180 bar to 225 bar; Temperature mostly around 540 °C 1990 : Pressures raised to 285 bar; Temperature raised to 565-580-600 °C 300 bar & 620 °C not unusual today 255 bar & 568/596 °C commonly used presently

Coal will continue to have maximum share towards installed capacity for electricity at least upto 2050 CLEAN COAL TECHNOLOGY Minimise CO2 emissions and environmental impact Extend life of coal reserves Approach: Develop technology for SC, USC & Adv-USC power plants

Efficiency and CO2 Emission Plant type with power rating Steam Pressure (kg/cm2) Steam Temperature (C) Efficiency (%) CO2 Emissions (g/kW-hr) Sub Critical (500 MWe) 170 540 35 900 # Super Critical 247 565 40 830 Ultra Super Critical 250 600 42 784 Advanced Ultra Super Critical 300 700 45 740 # The improvements are with respect to the best units under construction in India Extension of coal reserves by 11% Competitive in electricity cost on deployment

Trend in unit sizes & Cycle parameters SHO Pressure (kg/cm2(a)) SHO/RHO Temperature (Deg.C) Year of Introduction 60 / 70 MW 96 540 1965 110 / 120 MW 139 540/540 1966 200 / 210 MW 137 / 156 1972 250 MW 156 1991 500 MW 179 540/568 1979 1985 660 MW 256 568/596 2008 800 MW

Type of boilers Drum type - for sub-critical parameters Once-through type - for sub/super Critical Parameters

Drum type boiler Steam generation takes place in furnace water walls Fixed evaporation end point - the drum Steam -water separation takes place in the drum Separated water mixed with incoming feed water

Types of Circulation

Drum type boiler Natural Circulation Boiler Circulation thru water walls by thermo-siphon effect Controlled Circulation Boiler At higher operating pressures just below critical pressure levels, thermo-siphon effect supplemented by pumps

Natural Circulation Controlled Circulation

What is Super critical pressure ? Pressure range Sub critical : Below 221 bar Super critical : 221 bar and above

What is a Super critical Steam Generator?

Supercritical Boilers Supercritical pressure boiler has no drum and heat absorbing surface being, in effect, one continuous tube, in which the water & steam generated in the furnace water walls passes through only once hence called ‘Once through Supercritical pressure boilers’ The water in boiler is pressurized by Boiler Feed Pump, sensible heat is added in feed heaters, economizer and furnace tubes, until water attains saturation temperature and flashes instantaneously to dry saturated steam and super heating commences.

The Concept The mass flow rate thru’ all heat transfer circuits from Eco. inlet to SH outlet is kept same except at low loads wherein recirculation is resorted to protect the water wall system

Once Through Boiler Flow Diagram Evaporator Water separator Feedwater Economizer FW- Pump Live steam Superheater Features Increased mass flow through spiral waterwall tubing, or improved heat transfer through rifled vertical wall tubing. No fixed evaporator end point No thick wall components

Supercritical Boilers- Major Systems

General Arrangement of Steam Generator – Elevation

General Arrangement of Steam Generator – Plan

Once through Supercritical Boilers Major differences from Drum type boiler : Evaporator system Low load Recirculation system Separator

Circulation Systems Drum Type Once-through

Once -through Operating Range

Once -thru Boiler Requirements : Stringent water quality Different control system compared to drum type Low load circulation system Special design to support the spiral furnace wall weight High pressure drop in pressure parts Higher design pressure for components from feed pump to separator

Features of Once Through Steam Generator To ensure adequate mass flow rates through water wall, spirally wound water wall tubes are used. Start-up and low load system up to 30-40% BMCR required. Feed water quality requirements are very stringent. Can be designed for both sub-critical and super-critical pressures. Ideally suited for sliding pressure operation due to the absence of thick walled components.

Once -thru Boiler Evaporator system : Formed by a number of parallel tubes Tubes spirally wound around the furnace to reduce number of tubes and to increase the mass flow rate thru’ the tubes Small tube diameter Arrangement ensures high mass velocity thru the tubes

Spiral Tube Arrangement Features Reduced number of tubes with pitch. Increased mass flow. Mass flow rate can be selected by number of tubes.

Once -thru Boiler - Furnace Wall

Spiral Water wall Tubing Lateral Heat Flux Profile

Sliding Pressure Supercritical Design Spiral Wall Windbox

Sliding Pressure Supercritical Design Spiral to Vertical Transition Area - Load Transfer Support Fingers SPIRAL WALL SUPPORT

Furnace Wall Designs Spiral Wall Configuration Vertical Wall Configuration

Supercritical Boiler with Vertical wall Unit Mwe: 750 Max. Continuous Rating: 2522 t/h SH Outlet Press: 262 bar SH Outlet Temp: 568°C RH Outlet Temp: 596 °C Fuel: Sub-bituminous

Vertical Wall Sliding Pressure Supercritical Design FRONT WALL SIDE WALL RIFLED TUBING RIFLED TUBING SCREEN TUBES SMOOTH TUBING HANGER TUBES SMOOTH TUBING ARCH RIFLED TUBING SIDE WALL RIFLED TUBING REAR WALL RIFLED TUBING FRONT WALL RIFLED TUBING SMOOTH TUBING FROM THIS ELEVATION ALL WALLS

Vertical Furnace Wall Design Vertical tube furnace walls will provide all the operational benefits of the currently popular spiral design while significantly reducing the cost and construction time for the furnace and providing some reduction in pressure drop.

Vertical Wall Design - Advantages The tubes are self supporting. Transition headers at spiral/vertical interface are avoided. Ash hopper tubing geometry simplified Corners are easier to form Reduced pressure drop, auxiliary power

Spiral Vs. Vertical Wall Comparison Spiral Furnace System Applicable for all size units Benefits from averaging of lateral heat absorption variation (each tube forms a part of each furnace wall) Simplified inlet header arrangement Large number of operating units Use of smooth bore tubing throughout entire furnace wall system One material utilized throughout entire waterwall system No individual tube orifices – Less maintenance & pluggage potential Vertical Furnace Wall System Limited to larger capacity units .  Less complicated windbox openings Traditional furnace water wall support system Elimination of intermediate furnace wall transition header Less welding in the lower furnace wall system Easier to identify and repair tubes leaks Lower water wall system pressure drop thereby reducing required feed pump power

Vertical Wall Wind box Straight Tubes Only a Few Bends at the Top and Bottom

Supercritical Boilers- Start-up and Low load recirculation Systems

Low load system with circulating pump

Once -thru Boiler Separator : Separates steam and water during the circulating mode operation Runs dry during once-thru flow mode Smaller in size compared to drum in a drum type boiler

Start-up System

Overview of Firing Systems Close-Coupled Overfire Air CFS Air Nozzle Tips Flame Attachment Coal Nozzle Tip NOx < 0.18 – 0.30 kg/Mkcal* Furnace Diagonal Separated Overfire Air HP Pulverizer with Dynamic Classifier *NOx at furnace outlet

Wind Box arrangement

Plan View for SOFA arrangement Lower SOFA in Corners Tilt +/-30o Yaw +/-20o Upper SOFA on Walls

Materials in 660 MW (Typical)

Material Comparison Pressure part 660 MW OTSC (Supercritical) 500 MW (Sub-critical) Drum Not applicable SA 299 (Carbon Steel) Vertical Separator SA 335 P91 Water Walls SA 213 T22 SA 210 Gr C Economiser Sa 210 Gr C SH T91, TP 347H T11/T22/T91/ TP 347H RH T12/T23/T91/TP347H/ Super 304H T22, T91, TP 347H

Boiler Parameters Description Unit 660 MW (Supercritical) 500 MW (Sub critical) Boiler Parameters - BMCR SH steam flow t/h 2120 1625 SHO pressure kg/cm2(a) 256 179 SHO/RHO temp. oC 568/596 540/540 Feed water temp. 294 254

Description (Source/Type) Fuel Analysis - Coal Description (Source/Type) Unit Design Coal Worst Coal Best Coal Proximate Analysis Fixed Carbon % 26.00 23.00 32.00 Volatile matter 19.00 18.00 22.00 Moisture 15.00 17.00 12.00 Ash 40.00 42.00 34.00 Total 100 HHV kcal/kg 3300 2800 4000 Ultimate Analysis Carbon 31.37 28.93 40.08 Hydrogen 3.40 2.40 3.50 Sulphur 0.40 0.5 0.36 Nitrogen 1.5 1.45 1.78 Oxygen(difference) 7.75 7.26 8.03 15.0 17.0 12.0 40.0 42.0 34.0 Carbonates + Phosphorous 0.58 0.46 0.25 Hard Grove Index 55 50 60

General Arrangement of Steam Generator – Plan

ULTRA SUPER CRITICAL TECHNOLOGY & ADVANCED ULTRA SUPER CRITICAL TECHNOLOGY

The Basic Heat Cycle Sub-critical units: Main steam pressure < 221. 1 bar Super-critical units: Main steam pressure > 221. 1 bar Ultra-supercritical units: Higher steam pressure and temperature than supercritical units Japan: Main steam pressure >242 Bar, or Steam temperature >593 ℃ Demark: Main steam pressure >275 Bar China: Main steam pressure >270 Bar USA (EPRI) : Main steam temperature>593 ℃

STEAM PARAMETERS Plant with steam pressure exceeding 225 kg/cm2 is said “Supercritical” Supercritical plant with main steam temperature  600C is said “Ultra Super-Critical” Supercritical plant with main steam temperature  700C is “Advanced Ultra Super-Critical

Evolution of Steam Power Stations Efficiency Worldwide

EUROPEAN PERSPECTIVE AND ADVANCEMENT FOR ADVANCED USC Pulverised Fuel-importance in World Power Generation Background of Development Of USC Plant with Steam Temperature around 600 0C Immediate Possibility of going to 650 0C & 700 0C with Nickel Alloy Best Strategy for reduction of CO2 Emission 64

AD700 TECHNOLOGY USC steam parameters-700 0C and 350 bar This can be achieved only by using Nickel based alloys In July 2005 :COMTES 700 testing most important components – started operation in power plant Scholven in Gelchen-kirchen Completed in 2009. During operation phase, valuable operational experience and processing technical knowledge were gained Welding of thick walled materials must be improved More test needed for improved welding techniques for 617 or Alloy 740 or Nimonic 263 66

R&D PROGRAM FOR A-USC MATERIAL DEVELOPMENT WITH CREEP STRENGTH/DEGRADATION ASSESMENT STUDIES Japanese programme 2007 & 2008 (finding out and stabilising the structure parameters affecting creep strength and degradation for accurately estimating 1,00,000 hr creep strength) New alloys Fundamental studies on creep strength degradation assessment needed to ensure long term safe use.(FS->650 0C AS ->700 0C Ni-> 750 0C) FS->100 MPa @ 650 0C beyond 30000 hrs without any type IV degradation AS->generated by means of inter metallic compound precipitation strength grain boundary, strongest creep. 67

USC POWER PLANT DEVELOPMENT IN JAPAN 68

METI/NEDO MATERIAL R&D PROGRAM 69

China first established use with parameters 600 0C/25 MPa in 2006 STRUCTURAL STABILITY STUDY ON USE POWER PLANT ADVANCE HEAT RESISTANCE STEELS AND ALLOYS IN CHINA China first established use with parameters 600 0C/25 MPa in 2006 TP347FGH & Super304H GH984, Nimonic 80A Ni-Cr-Co Inconel 740 studied with Special Metal Corp. USA for steam temperature of 700 0C 70

ECONOMIC ANALYSIS (EPRI) A cost effective CO2 emission reduction option Engineering design study(EPRI) Cost and performance of USC with conventional coal power plants Slightly more expensive Cost of avoided CO2 emission was less than $25 per metric ton of CO2 capture and storage 71

MATERIAL SELECTION STEAM SIDE OXIDATION FIRE SIDE CORROSION CREEP STRENTH 72

GKM TEST RIG 73

GKM TEST RIG 74

ADVANCES IN MATERIAL TECHNOLOGY Strengthening and degradation of long term creep properties and the relevant microstructural evolution in advance high Cr-Ferritic steels and Austenitic steels at high temperature GKM TEST RIG Investigation of the long term operation behaviour tubes and forgings made of alloys for future high nuclear power plants Qualification of key materials for 700°C fossil fuel power plant Demonstration of material performance with special consideration of oxidation and corrosion behaviour Creep damage development Early detection of damage in new material in connection with advance calculation tools for components 75

ADVANCES IN MATERIAL TECHNOLOGY ADVANCE CONCEPT FOR MAINTANENCE AND REPAIR FOR COMPONENTS MADE OF NEW MATERIALS SH Test Track Creep Test Track (upto 630 °C Austenite steel & upto 725 °C Ni based alloys) Monitoring devices for evolution of ongoing damage 76

OPTIMIZATION OF INCONEL ALLOY 740 BY SPECIAL METALS CORPORATION Developed for operating with 700°C steam temperature and higher pressure. EUROPEAN TARGET Stress rupture requirement of 1,00,000 Hrs rupture life at 750°C and 100 MPa stress. Metal loss of less than 2 mm in 2,00,000 hrs of Superheater service. DISADVANTAGE OF INCONEL ALLOY 740 Thick section fabrication posed weldability challenges. Grain boundary microfissuring occurred in the heat affected zone (HAZ) of the base metal. 77

Robust Roadmap for Success of Mission BHEL Development, Design & Manufacture of Power Cycle Equipment, System Engineering, Test Facility and Evaluation NTPC Detailed Project Report Project Management Operation and Maintenance Testing of Real Life Components in an existing plant IGCAR Advanced Design Analysis Materials Development Manufacturing Technology Testing and Evaluation 800 MWe Advanced Ultra Super Critical Power Plant MoU & Synergy

Advanced Ultra Super Critical Plants Gearing-up to introduce Advanced Ultra supercritical boilers (AUSC) AUSC Boilers (300 ata, 700 C / 700 C) will be developed based on OTSC technology Test Facility (400 bar, 700 Deg. C) installed and tests are on to collect critical design data BHEL is one among the Five MNC’s to have this facility Member of the National Technology Mission program to install AUSC plant by 2017

SUMMARY OTSC plants offer better cycle efficiency Proven technologies leading to lower GHG emissions and lesser fuel burnt BHEL has the technology for offering 660/700/800 MW supercritical units

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