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Design Aspects of the Ultra-Supercritical CFB Boiler

Stephen J. Goidich (steve_goidich@fwc.com; Tel. 908-713-2478; Fax. 908-713-2380) Song Wu (song_wu@fwc.com; Tel. 973-535-2339; Fax. 973-535-2242) Zhen Fan (zhen_fan@fwc.com; Tel.973-535-2548; Fax. 973-535-2242)

Foster Wheeler North America Corp 12 Peach Tree Hill Road, Livingston, NJ 07039

Arun C. Bose (arun.bose@netl.doe.gov; Tel. 412-386-4467, Fax. 412-386-5919)

National Energy Technology Laboratory, P.O. Box 10940 626 Cochrans Mill Road, Pittsburgh, PA 15236

ABSTRACT

Ultra-supercritical boiler technology can significantly increase the efficiency of a Rankine cycle power plant, and reduce fuel consumption for a given output, thus proportionally reduce all pollutant and waste streams including CO2 emissions. However, the benefits of elevated steam conditions must be balanced with plant cost, reliability, and operational flexibility. The current limitations for ultra-supercritical boiler technology have been defined in the high gas temperature, high heat flux environment of suspension-fired boilers. Circulating fluidized bed (CFB) boilers have the potential to extend the limits of the technology and also further reduce emission levels.

CFB boilers have evolved into the utility boiler size range with a number of units as large as 250 MWe - 300 MWe in operation, and are poised to enter into the realm of larger once-through, supercritical units, as indicated by the award of the 460 MWe Lagisza project in Europe. Because of in-furnace limestone addition, low emission levels of SO2 can be achieved without the need for expensive backend scrubbers. Low NOx emissions result because of an inherently low furnace temperature and staged combustion. Because of the low furnace temperature and the vigorous solids circulation, the CFB furnace heat transfer rates are lower, more uniform, and more predictable. The CFB boiler also has many ways to allocate heat transfer surface (in-furnace wingwalls, full or partial division walls, INTREXTM heat exchangers, parallel or series pass heat recovery area), and several options to control main and reheat steam temperature (flue gas proportioning, steam bypass, solids bypass, solids fluidization, spray water attemperation). These options provide the means to give operational flexibility that makes it easier to predict and control where and how heat is absorbed which is crucial to the operation of an OTU boiler.

The paper presents the design of a 400 MWe Ultra-Supercritical CFB boiler, which is a part of an on-going CFB boiler conceptual design study program jointly funded by US Department Energy and Foster Wheeler. The design boundary conditions for the CFB boiler are defined through a power plant system simulation and analysis, including the advanced steam turbine and other balance of the plant components. Design topics such as furnace and separator arrangement, heat duty distribution, reheater arrangement and temperature control, heat exchanger design and material requirements are addressed. _______________________________________________________ International Pittsburgh Coal Conference, Pittsburgh, PA, Sept. 12-15, 2005

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INTRODUCTION Foster Wheeler is currently working on a conceptual design study (Ultra-Supercritical CFB Boiler Conceptual Design Study, DE-FC26-03NT41737) which is jointly funded by the US Department of Energy and Foster Wheeler. The two primary objectives of the study are (1) to determine the economic viability of Ultra-Supercritical OTU CFB Technology and (2) identify pathways for the diffusion of Ultra-Supercritical OTU Technology into CFB Technology. The study consists of evaluating the following cases:

CFB OTU Unit Size and Technology Technology Steam Cycle Conditions Case 1 - Current Current 400 MWe, 593 C (1100 F), 311 bar (4500 psig) Case 2 - Future Current 600 MWe, 593 C (1100 F), 311 bar (4500 psig) Case 3 - Future Future 600 MWe, ~700 C (1300 F),~375 bar (5400 psig)

The current state-of-the-art (Case 1) conditions were selected based on: o DOE Study "Market Based Advanced Coal Power Systems" (Ref. 1) which compared 400 MWe subcritical, supercritical, and ultra-supercritical pulverized coal (PC) boilers. The site, fuel, sorbent, and steam cycle conditions for this study are the same as for the 1999 DOE study so that balance of plant equipment information can be utilized for potential comparison of PC and CFB plant configurations. o Several PC boilers are in operation in the 600 to 1000 MWe size range with steam temperatures at or slightly above the 600 C/610 C main/reheat steam temperature range with pressures approaching 300 bar. These actual operating conditions are comparable to those used in the DOE study noted above, and reflect the current state-of-the-art for OTU technology. o Largest CFB and first supercritical CFB sold to date is the Lagisza 460 MWe unit ordered by Poludniowy Koncern Energetyczny SA (PKE) in Poland (Ref. 2). The design is essentially complete with financial closing expected in the first quarter of 2006 at which time fabrication and construction will commence. As illustrated in Figure 1, the largest capacity units in operation today are the two(2) 300 MWe JEA repowered units which were designed to fire any combination of petroleum coke and bituminous coals. The physically largest Foster Wheeler boilers in operation are the 262 MWe Turow Units 4, 5, and 6 which were designed to fire a high moisture brown coal. The design and configuration of these units with Compact solids separators and INTREXTM heat exchangers were used as the basis for the Lagisza design as well as for this study. For the Case 1 design described in this paper, the Lagisza design (Figure 2) was adjusted to accommodate a typical bituminous coal (Illinois No. 6) and the steam cycle and site conditions noted above.

YEAR OF INITIAL OPERATION

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Air

Figure 1. CFB Boiler Scale-Up Chronology

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Described in this paper are the features of the 400 MWe Ultra-Supercritical CFB OTU boiler design. DESIGN BASIS The site conditions, fuel, sorbent, and steam cycle conditions, as well as the emission levels to which the CFB boiler was designed are summarized in Table 1. Also included are significant heat and material balance, and plant performance parameters. The emission targets are the same as defined in the 1999 DOE Study. The specified NOx level can be achieved without an SNCR which, if added, can provide additional NOx reduction. The limestone consumption and plant efficiency are values without an ash hydration system or flue gas heat recovery system included. These enhancements are beyond the scope of this study, and are options which can be included for improved performance.

Figure 2. Lagisza 460 MWe Supercritical OTU

Table 1. Design Basis and Performance Parameters

Site Conditions: Steam Conditions: Elevation m (ft.) 152.4 (500) Main Steam Flow Rate kg/s (M lb/h) 341.4 (2710.0) Design Air Pressure bar (psia) 0.99 (14.4) Main Steam Temperature C (F) 597 (1106) Dry Bulb Temperature C (F) 17.2 (63) Main Steam Pressure barg (psig) 327 (4500) Wet Bulb Temperature C (F) 12.2 (54) Relative Humidity % 55 Reheat Steam Flow Rate kg/s ( M lb/h) 276.8 (2197.0)

Reheat Steam Temperature C (F) 594 (1101)Illinois No. 6 Coal Reheat Steam Pressure barg (psig) 54.4 (788)Proximate Analysis Moisture wt. % 11.12 Feedwater Temperature C (F) 299 (570) Ash wt. % 9.7 Volatile Matter wt. % 34.99 H&M Balance Parameters: Fixed Carbon wt. % 4.19 Flow Rates:

Flue Gas kg/s (M lb/h) 414.5 (3290.6)Ultimate Analysis Combustion Air kg/s (M lb/h) 381.0 (3024.5) Moisture wt. % 11.12 Coal kg/s (M lb/h) 36.9 (292.6) Carbon wt. % 63.75 Limestone kg/s (M lb/h) 8.3 (66.0) Hydrogen wt. % 4.5 Total Ash kg/s (M lb/h) 11.7 (92.6) Nitrogen wt. % 1.25 Chlorine wt. % 0.29 Temperatures: Sulfur wt. % 2.51 Furnace Exit C (F) 871 (1600) Ash wt. % 9.7 Flue Gas Entering Air Heater C (F) 355 (671) Oxygen (by difference) wt. % 6.88 Flue Gas Leaving Air Heater C (F) 129 (264)

Bottom Ash C (F) 260 (500)HHV kcal/kg 6481

(Btu/lb) (11,666) Excess Air % 20

Greer Limestone Emissions: Calcium Carbonate wt. % 80.4 Sulfur Capture % 96 Magnesium Carbonate wt. % 3.5 SO2 mg/NM3 (lb/MMBtu) 258 (0.18) Moisture wt. % 0.1 NOx mg/NM3 (lb/MMBtu) 229 (0.16) Inerts wt. % 16 Particulate mg/NM3 (lb/MMBtu) 14 (0.01)

Reactivity Index 2.5

Power Generation Plant Performance Gross Output MWe 443.9 Turbine Back Pressure psia (mm Hg) 1 (50.8) Net Output MWe 404.4 Net Plant Efficiency % HHV Basis 40.1

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BOILER CONFIGURATION A CFB boiler can be configured in many ways to optimize performance and minimize cost. As illustrated in Figure 3, the inter-relationships between the selected steam turbine cycle, fuel and sorbent characteristics, emission requirements, as well as site conditions and constraints, will dictate how the boiler is configured. These project specific requirements, and sometimes customer preference for specific features will determine the boiler configuration. Options for locating heat transfer surface and methods for reheat steam temperature control are illustrated in Figure 4. The boiler configuration selected for the 400 MWe Ultra-Supercritical CFB is similar to that for the 460 MWe Lagisza project with adjustments to component size made to account for differences in unit capacity, steam duty distribution, and flue gas volumetric flow which resulted because of the smaller unit size, elevated steam parameters, improvement in overall cycle efficiency, and differences in fuel and sorbent properties. Front and side elevation drawings of the 400 MWe unit are included in Figure 5; a plan view, including baghouse and stack, is included in Figure 6.

Figure 3. Boiler Configuration Parameters

Figure 4. Heat Transfer Surface Location and Reheat Steam Temperature Control Options

HEAT TRANSFER SURFACE LOCATIONS:

123456

1

FURNACE ENCLOSUREFURNACE ROOFSOLIDS SEPARATORINTREX ENCLOSURECROSS-OVER DUCTHRA ENCLOSURE

234

WINGWALLSPLATENSOMEGA PANELSFULL HEIGHT WALLS

1234

INBOARD PARALLEL PASSOUTBOARD PARALLEL PASSCASING ENCLOSURESERIES PASS

5 INTREX

1 HRA HANGER TUBES

ENCLOSURES:

PANELS:

SERPENTINE TUBE COILS:

SUPPORT TUBES:

4

5

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5 62

REHEAT TEMPERATURE CONTROL:ABCD

FLUE GAS PROPORTIONINGSPRAY WATER ATTEMPERATIONSTEAM BYPASS

INTREX FLUIDIZATIONEINTREX SOLIDS BYPASS

5

Figure 5. 400 MWe Ultra-Supercritical OTU CFB - Front and Side Views

Figure 6. 400 MWe Ultra-Supercritical OTU CFB - Plan View

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Boiler Island Components. Main components of the 400 MWe Ultra-Supercritical CFB boiler include:

Fuel Feed. Coal crushed to a nominal topsize of 12 mm (0.5 in) is stored in four(4) day silos positioned along the boiler front wall. Chain feeders under each silo meter the coal feed rate and drop the fuel onto four(4) chain conveyors [two(2) along each furnace sidewall] which deliver fuel to a total of 14 drop chutes/screw feeders.

Sorbent Feed. Limestone crushed to a nominal topsize of 600 microns is stored in two(2) day silos positioned adjacent to each furnace sidewall. Six(6) rotary feeders meter the limestone flow rate into the pneumatic transport system that delivers the sorbent to 12 feed points. The limestone is concentrically injected into the furnace through selected lower level overfire airports.

Draft System. Pairs of radial fans with inlet guide vane control are used for primary and secondary systems. Balanced draft operation is provide by two(2) axial flow fans positioned downstream of a baghouse filter. Start-up burner air, INTREXTM fluidization air, and wall seal aeration air is provide by four(4) centrifugal blowers. A tri-sector regenerative air heater positioned under the HRA is used to preheat primary and secondary air for combustion.

Bottom Ash System. Two(2) stripper/coolers are provided (adjacent to the furnace front and rear walls) to cool and recover heat from ash drained from the furnace to maintain the required solids inventory within the furnace. Cooling and heat recovery is achieved by transferring ash sensible heat into the cold primary air used for fluidization, and by tube bundles through which low temperature condensate is passed. Ash removal rate is controlled by screw conveyers which drop the ash onto two drag chain conveyors that run the length of the furnace. For additional ash removal capacity and for occasional removal of ash from the center of the furnace, two screw coolers are also provided with drain inlets positioned near the center of the furnace.

Furnace Hot Loop. The furnace enclosure utilizes vertical smooth tubes designed using the BENSON Vertical OTU technology licensed from Siemens and jointly developed with Foster Wheeler for CFB boiler application. In addition to the furnace enclosure heat transfer surface, furnace temperature is maintained by six(6) two-side heated full height evaporator panels, eight(8) platen superheaters distributed across the upper furnace, eight(8) steam-cooled Compact separators positioned along each furnace sidewall, and eight(8) INTREXTM heat exchangers which are positioned under each solids separator (refer to the subsequent Design Features Summary section for additional details on furnace, solids separator, and INTREXTM heat exchanger).

Heat Recovery Area (HRA). Flue gas leaving the solids separators is directed to the HRA via two(2) steam-cooled ducts formed by the continuation of the Compact separator tubing. Each of these separator outlet ducts directs the flue gas into two(2) steam-cooled cross-over ducts which then direct the flue gas into the series pass HRA. The modularly constructed HRA includes a convection reheater (RH I) and the primary superheater (SH I) which are supported by steam-cooled hanger tubes. A smooth tube economizer is housed within an un-cooled casing enclosure and is positioned at the bottom of the HRA. Standard features for convection tube bundles (sootblowers, tube spacing, erosion baffles, etc.) consistent with the specified bituminous fuel specified are incorporated in configuration of the HRA.

Start-Up Burners. To preheat the furnace bed material to the fuel ignition temperature, ten(10) above-bed, oil-fired start-up burners are provided. There are two(2) burners on the furnace front and rear walls, and three(3) on each side wall.

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Steam/Water Circuitry. The circuitry configuration is schematically illustrated in Figure 7.

Preheat. Feedwater from the preheater system enters the boiler in a bare tube economizer which is positioned in the lower, un-cooled casing section of the series pass heat recovery area (HRA). Water leaving the economizer is directed through a single transfer pipe to the enclosure walls of the INTREX™ fluidized bed heat exchangers to ensure that a uniform temperature fluid (and subcooled liquid at reduced load, sub-critical conditions) is received for distribution to the walls. From the INTREXTM enclosure, the heated feedwater is again brought together to a common transfer line before the flow is distributed to the inlet headers of the evaporator (furnace) walls to ensure uniform fluid conditions so that the potential for flow unbalances is minimized. Surfacing of the economizer and INTREXTM enclosure walls is selected to ensure that subcooled, single-phase water enters the evaporator circuits over the load range as illustrated in Figure 8.

Evaporation. The subcooled water is then heated in the furnace enclosure walls, as well as in full height internal panels at approximately the quarter points along the center of the furnace, and is eventually converted to superheated steam before it reaches the top of the furnace. The full height internal panels are included because the furnace enclosure wall area is not sufficient to provide the required evaporation duty with a reasonable furnace height. Sufficient evaporator heat transfer surface is provided to ensure that dry, superheated steam is leaving the furnace over the once-through operational load range as illustrated in Figure 8. To accommodate a range of fuel qualities which can shift the duty distribution between furnace hot loop and HRA, an evaporator bypass is included that can direct some water to the attemperator station upstream of the radiant platen superheater (SH II) to ensure that superheated steam leaves the evaporator circuitry. Steam from the evaporator panels is then piped to three (3) in-line steam/water separators which are part of the start-up system.

Figure 7. Steam/Water Circuitry Diagram

INTREXWalls

FurnaceWalls

Economizer

HRAWalls

Hanger Tubes

SH IIRadiantPlatens

SH IVINTREX

HP- Bypass

To Turbine

Feed Water Pump

FurnaceRoof & Cross-Over

To Flash Tank

Water/Steam Separators

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HP-HeatersHP-HeatersFrom feed tank

From TurbineRH I

RH IIINTREX To Turbine

SH IIISolids Separators

Water CollectingVessel

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Superheat. Steam leaving the tangential steam/water separators is piped to the furnace roof and then through the cross-over ducts which connect the two(2) solids separator flue gas outlet ducts to the HRA. The steam is then passed down through the HRA serpentine tube coil support (hanger) tubes which feed steam into the lower HRA enclosure inlet headers. From the HRA enclosure, the steam is passed through the convection superheater (SH I) which is positioned in between the upper and lower tube bundles of the convection reheater (RH I). Steam is then directed to eight (8) radiant platen superheater panels (SH II) located in the upper furnace where the solids density is lowest. The bottom of the panels is covered with refractory as is standard practice to protect against any possible erosion. From SH II steam is directed down in parallel through the eight (8) Compact solids separators (SH III). The separator walls are formed with gas tight membrane walls and are covered with a thin, high conductivity refractory lining. Final superheat is then achieved with the steam passing in parallel flow through four(4) of the INTREXTM superheaters positioned on one of the furnace sidewalls. Spray water attemperators are located in the piping upstream of the Compact separators (SH III) and upstream of the INTREXTM superheaters (SH IV).

Reheat. Initial steam reheat is accomplished in the series pass HRA in the upper and lower tube bundles of RH I. During high load operation a portion of the reheat steam flow is bypassed around RH I to control final reheat steam temperature. The full reheat steam flow is then passed in parallel through four (4) of the INTREXTM heat exchangers positioned on the left furnace sidewall. The primary means for reheat steam temperature control is by modulation of the amount of reheat bypass flow. The amount of modulation necessary can be adjusted by variation of INTREXTM fluidizing velocities and the amount of solids bypass, both of which can be used to regulate the amount of heat absorbed in the reheat circuitry.

Start-Up System. Before fuel can be fired in a once-through boiler, a minimum fluid mass flow rate must be established within the evaporator tubes that form the furnace enclosure to protect the tubes from overheating. This minimum flow can be provided by the feedwater pump or preferably (as shown in Figure 7), by a recirculation pump that returns the heated water back to the boiler in a closed loop for maximum heat recovery. During this start-up phase the boiler is controlled similar to a drum unit by having in-line steam/water separators (Figure 9) downstream of the evaporator to separate liquid and vapor phases. The load at which boiler control is switched from drum type control to a once-through mode is called the

Figure 8. Pressure-Enthalpy Diagram

Figure 9. Steam/Water Separator

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BENSON load (40% load for this project). Separated water is drained to a water collecting vessel from which the water is pumped back to the economizer. To ensure that subcooled water enters the pump, a small amount of cold feedwater is piped to the pump inlet line. The proposed design includes three (3) tangential type separators and a single water collecting vessel. The separator design is an optimized configuration developed to minimize pressure loss and also, vessel size. During initial firing, the inventory of water within the evaporator expands. Excess water is drained from the water collecting vessel to a flash tank to maintain an acceptable water level within the water collecting vessel. DESIGN FEATURES SUMMARY BENSON Vertical Evaporator. The furnace evaporator utilizes the BENSON Vertical OTU technology (Ref. 3,4) which features low fluid mass flow rates in a single up-flow pass through the furnace that gives a self compensating “natural circulation” characteristic, i.e., strongly heat tubes have more flow drawn into them to minimize tube-to-tube temperature variations. Unique for CFB boiler application are the following:

o Heat fluxes in a CFB boiler are less than half of those typically experienced in a typical PC boiler (Figure 10). The highest heat flux occurs just above the refractory covered zone in the lower furnace where the fluid is at a low temperature for supercritical pressures and is a sub-cooled liquid when at reduced load sub-critical steam pressure. Because of the low heat flux, smooth enclosure tubes can be used to achieve proper cooling so that excessive temperature excursions are not experience when passing near the critical pressure.

o The two(2) side heated full height evaporator panels used to minimize furnace height, require standard rifled tubes to provide adequate cooling when load is passed near the critical pressure. Optimized rifled tubes with a steeper lead angle and more pronounced ribs are not required, as would be used for all the tubes in the lower furnace of a PC BENSON Vertical boiler.

o Because of the low heat fluxes in a CFB furnace, the full load mass flow rate can be in the 500 to 700 kg/m2-s (370-520 M lb/h-ft2) range (Ref. 2), as compared to about 1000 kg/m2-s (738 M lb/h-ft2) for a PC unit. This reduced mass flux will give the CFB boiler a greater “natural circulation” characteristic, and with the flywheel of circulating solids giving a more uniform heat flux distribution (Figure 11), will result in reduced tube-to-tube temperature differentials (Ref. 2).

Figure 10. PC vs CFB Heat Flux Comparison

kW/m2

Figure 11. CFB Heat Flux Distribution

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CFB

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Compact Solids Separators. The solids separators feature a flat panel, steam-cooled design which is optimized to give high solids collection efficiency with low flue gas pressure loss. The advanced separator inlet design, with a tall and narrow shape, provides a uniform flow of flue gas and solids that avoids localized high velocities (Figure 12). This results in equal collection efficiency, compared to optimized cyclone configurations, with considerably lower pressure loss (Ref. 2).

The separators are designed with panel wall sections and have a thin refractory lining anchored with a high density pattern of studs. This minimizes the amount of refractory, allows it to operate at a cooler temperature for improved durability, and contributes a significant amount of heat absorption for superheat steam circuitry (SH III). The separators are manufactured with welding machines eliminating the need for extensive manual welding. The extension of the separator tubing to form two(2) flue gas ducts provides a convenient means to direct flue gas to the HRA. In addition to being part of the superheater heat absorbing circuitry, the down-flow steam configuration provides a convenient means to route the superheater steam from the upper furnace platen superheater (SH II) to the INTREXTM finishing superheater (SH IV)

INTREXTM Heat Exchanger. The INTREXTM heat exchangers (Figure 13) are bubbling fluidized beds with immersed steam-cooled serpentine tube coils which extract heat from externally circulated solids that are collected in the solid separators. Additional bed material is internally circulated from the furnace into the INTREXTM chambers directly through slots in the lower furnace sidewalls. The combination of internal and external circulation provides a sufficient amount of bed material over a wide load range to achieve full final steam temperatures.

A unique feature of the INTREXTM superheater is its ability to control the heat transfer by changing the fluidization velocities. This special capability is utilized, for example, during load changes to trim the steam temperatures and to control reheat steam temperature. Control of the solids flow rate through the tube bundles is simply done by proper aeration of the liftleg that returns solids back to the furnace. High temperature valves or other mechanical devices are therefore not required.

Another important INTREXTM feature is that it provides enhanced protection against corrosion by keeping the tubes with high metal temperature out of the path of chlorine bearing flue gas when firing fuels with a high chlorine content.

A total of eight (8) INTREXTM heat exchangers are included in the design, one (1) for each solids separator. Four (4) heat exchangers serve as final superheater (SH IV); four (4) as final reheater

m/s

Figure 12. Separator Velocity Profile

Figure 13. INTREXTM Heat Exchanger

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(RH II). The INTREXTM enclosures are water-cooled with feedwater that leaves the economizer. This cooled configuration allows the integration of the INTREXTM casings to the furnace thus eliminating expansion joints and minimizing distances to transfer hot solids. The enclosure walls are lined with a thin layer of refractory to reduce heat absorption to ensure that subcooled feedwater enters the furnace evaporator circuits.

Another benefit of the INTREX heat exchanger is a high heat transfer rate, which decreases the amount of heat surface required thus making the actual dimensions smaller.

BOILER MATERIALS

For the Case 1 steam conditions, the material requirements for most sections of the boiler are very conventional, and normal boiler materials can be used (Table 2). The furnace and solids separator panels, for example, can be manufactured of materials that do not require post-weld heat treatment. Austenitic steel Super 304H is required for the final superheater, and TP347HFG for other high-temperature superheaters and reheaters. Material limitations will be evaluated as part of Case 3 for which steam temperatures and pressures will be increased to practical limits based on the selected design heat fluxes for the CFB furnace and INTREXTM heat exchangers. CFB design enhancements required to maximize steam temperature and minimize pressure part design temperature will be evaluated. CONCLUSIONS

The 400 MWe Ultra-Supercritical boiler described in this paper integrates the current state-of-the-art for both CFB (Second Generation Compact) and OTU (BENSON Vertical) boiler technologies. The integration of these technologies provides fuel firing flexibility, low grade fuel firing capability, low pollutant emissions, and high efficiency for cost effective power production. Component selection options and several means to adjust where and how much heat is absorbed give the CFB boiler the advantage to push OTU technology to its limits for cost effective and environmentally friendly power production.

Table 2. Pressure Part Materials for Case 1 400 MWe Boiler

Heat Surface Tube Material Header MaterialEconomizer SA-210 C SA-106 C

Furnace Walls SA-213 T12 SA-106 C

Superheater/Reheaters SA-213 T12 SA-335 P12SA-213 T23 SA-335 P91

SA-213 TP304H SA-335 P911SA-213 TP347HFG

Super 304HSteam Piping

Main Steam Pipe SA-335 P911

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ACKNOWLEDGEMENT The financial support of this study by U.S. Department of Energy National Energy Technology Laboratory under Contract DE-FC-26-03NT41737, and Foster Wheeler North America Corp., is appreciatively acknowledged.

REFERENCES

1. "Market Based Advanced Coal Power Systems", U.S. Department of Energy, Office of Fossil Energy, DOE/FE-0400, May 1999.

2. I. Venäläinen, R. Psik, "460 MWe Supercritical CFB Boiler Design for Lagisza Power Plant", POWER-GEN Europe, Barcelona, Spain, May 25-27, 2004.

3. S.J. Goidich, "Integration of the BENSON Vertical OTU Technology and the Compact CFB Boiler", POWER-GEN International, Orlando, Florida, November 14-16, 2000.

4. R. Lundqvist, R. Kral, P. Kinnunen, K. Myöhänen, "The Advantages of a Supercritical Circulating Fluidized Bed Boiler", POWER-GEN Europe, Dusseldorf, Germany, May 6-8, 2003.