TPi July 2009

Measurement of the scale at the duration of the test revealed a surface film of about 1.2 microns for both alloys. 7 The European AD700 project has advanced through component demonstration (phase 3) to full-scale demonstration plant status. E.On has committed to erecting a 550 MWe demonstration plant at Wilhelmshaven, Germany to be operational in 2014. A major incentive of this effort is the ability of higher efficiency of this plant (53% LHV basis) to offset the penalties that carbon capture technology might impose. A worldwide effort to increase the efficiency of power boilers has resulted in more demanding alloy requirements within the power boiler. Thus, advanced alloys will be required to meet the rigours of this service. Nickel-base alloys can meet these challenges. Among them is newly developed Inconel alloy 740 that exhibits the properties required for advanced ultra supercritical boilers designed to operate at significantly increased temperatures and pressures. Report #:DOE/EIA-0484, 2008, US Department of Energy/US Energy Information, Release Date: June 2008. International Energy Outlook 2008 Wright, IG, Maziasz, PJ, Ellis, FV, Gibbons, TB, and Woodford, DA, ‘ Material Issues for Turbines for Operation in Ultra- Supercritical Steam ’, 29 th International Technical Conference on Coal Utilization & Fuel Systems, Clearwater, FL, 18-22 April 2004 McDonald, DK, ‘ Coal Ash Corrosion Resistant Materials Testing Program ’, presented at 16 th Annual Conference on Fossil Energy Materials, Baltimore, MD, 22-24 April 2002 Smith, GD and Sizek, HW, ‘ Introduction of an Advanced Superheater Alloy for Coal-Fired Boilers ’, Corrosion 2000, Paper #00256, NACE International, TX Shingledecker, JP, Swindeman, RW, Klueh, RL, and Maziasz, PJ, ‘ Mechanical Properties and Analysis of Ultra-Supercritical Steam Boiler Materials ’, 29 th International Technical Conference on Coal Utilization & Fuel Systems, Clearwater, FL, 18-22 April 2004 Smith, G and Shoemaker, L, ‘ Advanced Nickel Alloys for Coal- Fired Boiler Tubing ’, Advanced Materials & Processes, July 2004 Baker, BA and Smith, GD, ‘ Corrosion Resistance of Alloy 740 as Superheater Tubing in Coal-Fired Ultrasupercritical Boilers ’, Corrosion 2004, Paper #04526, NACE International, TX [2] [3] [4] [5] [6] [7] References [1]

Figure 3 ▲ ▲ : Coal-ash corrosion resistance for alloy 740 at 700°C (1,290°F) vs time to 4,000 hours with linear and parabolic extrapolations to 200,000 hours

was met. This was achieved with the composition shown in Table 1 .

To determine the corrosion resistance of Inconel alloy 740, a flue gas and coal ash composition was chosen that produces a Type II hot corrosion mode of attack when the alkali trisulfates are molten between about 600°C and 750°C (1,110°F and 1,380°F). Attack is reduced when the trisulfates are solid below 600°C (1,110°F) and above 750°C (1,380°F) as the trisulfates tend to evaporate upon formation. Figure 3 depicts both a linear and a parabolic projection for the metal loss of Inconel alloy 740 in 200,000 hours based on data at 700°C (1,290°F) to 4,000 hours. 6 A linear projection equates to a metal loss of about 1.3mm (0.051") and parabolic projection leads to a metal loss of about 0.25mm (0.001"), both in 200,000 hours. Figure 4 depicts the weight change (mg/cm 2 ) in steam oxidation at 750°C (1,380°F) for times up to 10,000 hours for alloys 740 and 263.

Figure 4 ▼ ▼ : Depiction of the weight change (mg/cm 2 ) in steam oxidation at 750°C (1,380°F) for times to 10,000 hours

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Tube Products International July 2009

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