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TECHNICAL PAPERS: Gas Turbines: Industrial and Cogeneration

High-Pressure Turbine Deposition in Land-Based Gas Turbines From Various Synfuels

[+] Author and Article Information
Jeffrey P. Bons, Jared Crosby, James E. Wammack, Brook I. Bentley

Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602

Thomas H. Fletcher

Department of Chemical Engineering, Brigham Young University, Provo, UT 84602

J. Eng. Gas Turbines Power 129(1), 135-143 (Sep 06, 2005) (9 pages) doi:10.1115/1.2181181 History: Received August 30, 2005; Revised September 06, 2005

Ash deposits from four candidate power turbine synfuels were studied in an accelerated deposition test facility. The facility matches the gas temperature and velocity of modern first-stage high-pressure turbine vanes. A natural gas combustor was seeded with finely ground fuel ash particulate from four different fuels: straw, sawdust, coal, and petroleum coke. The entrained ash particles were accelerated to a combustor exit flow Mach number of 0.31 before impinging on a thermal barrier coating (TBC) target coupon at 1150°C. Postexposure analyses included surface topography, scanning electron microscopy, and x-ray spectroscopy. Due to significant differences in the chemical composition of the various fuel ash samples, deposit thickness and structure vary considerably for each fuel. Biomass products (e.g., sawdust and straw) are significantly less prone to deposition than coal and petcoke for the same particle loading conditions. In a test simulating one turbine operating year at a moderate particulate loading of 0.02 parts per million by weight, deposit thickness from coal and petcoke ash exceeded 1 and 2mm, respectively. These large deposits from coal and petcoke were found to detach readily from the turbine material with thermal cycling and handling. The smaller biomass deposit samples showed greater tenacity in adhering to the TBC surface. In all cases, corrosive elements (e.g., Na, K, V, Cl, S) were found to penetrate the TBC layer during the accelerated deposition test. Implications for the power generation goal of fuel flexibility are discussed.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Ash particle size distribution from Coulter Counter measurement

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Figure 2

ESEM images of (a) coal and (b) straw ash after processing. Images are approximately 150μm×150μm.

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Figure 3

Schematic of Turbine Accelerated Deposition Facility (TADF) at BYU

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Figure 6

ESEM cross-section of coal surface deposit and coal/TBC interface. (a) Coal surface deposit structure (b) Coal deposit penetration into TBC.

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Figure 9

Comparison of element weight percent for fuel ash vs. deposit: (a) coal (b) petoke (c) sawdust (d) straw

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Figure 8

ESEM cross-section of straw deposit

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Figure 7

ESEM cross-section of petcoke deposit inclusions

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Figure 5

Surface topographies of 3 different deposits from Hommel profilometer measurements. (a) 8mm×21mm section of straw deposit surface—peak height ∼400μm (b) 3mm×3mm section of coal deposit surface—peak elevation ∼600μm (c) 8mm×22mm section of residual coal deposit after deposit separated—peak ∼350μm.

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Figure 4

Average deposit thickness vs. net particle loading for 4 fuels

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