U.S. Department of EnergyOffice of Scientific and Technical Information
Ash fouling and erosion of silicon-based ceramic expanders in coal-fired power plants
Abstract
Lysholm-type helical-screw engines (expanders) are proposed as a means of generating electrical power from coal-fired power plants (topping cycle). Ash erosion and deposition (fouling) of silicon-based ceramic materials exposed to coal ash at topping-cycle temperatures (approximately 1270 K) was studied at the Lawrence Livermore Laboratory to select suitable expander materials. Silicon carbide (SiC) or silicon nitride (Si/sub 3/N/sub 4/) blocks exposed to an ash-injected flame at 1270/sup 0/K fouled; however, fouling was prevented when blocks or wheels of the material were rubbed or spun against each other, simulating expander rotors. The sliding friction coefficient between contacting SiC or Si/sub 3/N/sub 4/ surfaces was 0.5 at room temperature, increased to 0.9 at 1270/sup 0/K, but returned to approximately 0.5 when hot, soft ash was injected between the surfaces. When rubbed together, blocks of SiC wore 9.5 mg/h at topping temperatures, 25 times greater than at room temperature. Increase in wear with temperature likely occurs because the SiC surface oxidizes to soft and easily worn silicon oxide. The cooler, harder ash downstream of the expander outlet could erode plant boiler parts. In our tests, high-speed, hard fly ash particles eroded Si/sub 3/N/sub 4/ blocks at 0.2 to 1 mg per g ashmore »
- Authors:
- Publication Date:
- Research Org.:
- California Univ., Livermore (USA). Lawrence Livermore Lab.
- OSTI Identifier:
- 5190796
- Report Number(s):
- UCRL-52390
- DOE Contract Number:
- W-7405-ENG-48
- Resource Type:
- Technical Report
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 20 FOSSIL-FUELED POWER PLANTS; 36 MATERIALS SCIENCE; FOSSIL-FUEL POWER PLANTS; FLY ASH; GAS TURBINES; EROSION; SILICON CARBIDES; WEAR; SILICON NITRIDES; ABRASION; CERAMICS; COAL; COMBUSTION PRODUCTS; OXIDATION; TEMPERATURE DEPENDENCE; TOPPING CYCLES; VERY HIGH TEMPERATURE; AEROSOL WASTES; CARBIDES; CARBON COMPOUNDS; CARBONACEOUS MATERIALS; CHEMICAL REACTIONS; ENERGY SOURCES; FOSSIL FUELS; FUELS; NITRIDES; NITROGEN COMPOUNDS; PNICTIDES; POWER PLANTS; SILICON COMPOUNDS; THERMAL POWER PLANTS; TURBINES; TURBOMACHINERY; WASTES; 200104* - Fossil-Fueled Power Plants- Components; 360205 - Ceramics, Cermets, & Refractories- Corrosion & Erosion
Citation Formats
Taylor, R W, and Shell, T E. Ash fouling and erosion of silicon-based ceramic expanders in coal-fired power plants. United States: N. p., 1978.
Web.
Taylor, R W, & Shell, T E. Ash fouling and erosion of silicon-based ceramic expanders in coal-fired power plants. United States.
Taylor, R W, and Shell, T E. 1978.
"Ash fouling and erosion of silicon-based ceramic expanders in coal-fired power plants". United States.
@article{osti_5190796,
title = {Ash fouling and erosion of silicon-based ceramic expanders in coal-fired power plants},
author = {Taylor, R W and Shell, T E},
abstractNote = {Lysholm-type helical-screw engines (expanders) are proposed as a means of generating electrical power from coal-fired power plants (topping cycle). Ash erosion and deposition (fouling) of silicon-based ceramic materials exposed to coal ash at topping-cycle temperatures (approximately 1270 K) was studied at the Lawrence Livermore Laboratory to select suitable expander materials. Silicon carbide (SiC) or silicon nitride (Si/sub 3/N/sub 4/) blocks exposed to an ash-injected flame at 1270/sup 0/K fouled; however, fouling was prevented when blocks or wheels of the material were rubbed or spun against each other, simulating expander rotors. The sliding friction coefficient between contacting SiC or Si/sub 3/N/sub 4/ surfaces was 0.5 at room temperature, increased to 0.9 at 1270/sup 0/K, but returned to approximately 0.5 when hot, soft ash was injected between the surfaces. When rubbed together, blocks of SiC wore 9.5 mg/h at topping temperatures, 25 times greater than at room temperature. Increase in wear with temperature likely occurs because the SiC surface oxidizes to soft and easily worn silicon oxide. The cooler, harder ash downstream of the expander outlet could erode plant boiler parts. In our tests, high-speed, hard fly ash particles eroded Si/sub 3/N/sub 4/ blocks at 0.2 to 1 mg per g ash at room temperature. This erosion rate is expected to decrease significantly with increasing temperature, particularly above the ash-softening temperature, 870/sup 0/K. Relative to other ceramics and metals, SiC and Si/sub 3/N/sub 4/ are resistant to high temperatures, ash erosion, and fouling under simulated expander conditions and would be equally suitable materials for a topping-cycle Lysholm-type engine.},
doi = {},
url = {https://www.osti.gov/biblio/5190796},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 26 00:00:00 EST 1978},
month = {Thu Jan 26 00:00:00 EST 1978}
}