Abstract
Combined cycle power systems offer increased efficiency
of electricity generation and lower environmental
emissions of CO2, SOx and NO2, as well as being adaptable
to most fossil/biofuels. Industrial gas turbines are at
the heart of such power stations and are being developed
to perform at higher firing temperatures and pressures to
achieve even greater efficiencies, with lower emissions.
Fuel gases derived from renewable fuels, such as biogases
from digestors or syngases from solid fuel gasification,
may contain contaminants that are extremely corrosive to
the gas turbine components (e.g. blades and vanes)
located in the hot combusted gas path. Such damage can
result in a gradual loss of turbine efficiency and
reliability. Therefore, it is of paramount importance
that the materials usedfor gas turbine components that
operate in these environments provide acceptable and
predictable in-service life times. Single crystal
superalloys (e.g. CMSX-4) were developed to have improved
mechanical properties (creep and fatigue) at increasing
component operating temperatures, especially in
relatively clean aero-engine operating environments. This
paper describes work carried out to investigate the
development of hot corrosion processes on CMSX-4
(uncoated and Pt-Al coated) in a range of potential
environments for blade materials in industrial gas
turbines fired on biomass derived fuel gases. A series of
laboratory tests has been carried out using the 'deposit
recoat' technique, with exposure conditions covering:
deposits of 80/20 and 50/50 (Na/K)2SO4, with additions
oflead, a gas composition of 100 vpm SOx, 100 vpm HCl in
simulated combustion gases, deposition flux of
15mg/cm2/h, temperature of 700 8C, for periods up to 1000
h. During their exposure the materials were monitored
using traditional mass changemethods. However,
quantitative damage data in terms of metal loss was
obtained using dimensional metrology, pre-exposure
contact measurements combined with post-exposure
measurements of damage observed by optical microscopy on
polished cross-sections. These measurement methods
allowed the distribution of damage to be determined and
the material sensitivity to such hot corrosion processes
to be quantified.
Original language | English |
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Pages (from-to) | 206-216 |
Journal | Materials and Corrosion |
Volume | 65 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2014 |
MoE publication type | A1 Journal article-refereed |
Keywords
- biomass
- CMSX-4
- industrial gas turbines
- Type II hot corrosion