Ash Aerosol and Deposit Formation from Combustion of Coal and Its Blend with Woody Biomass at Two Combustion Scales: Part 2Tests on a 471 MWe Full-Scale Boiler
Dead trees killed by bark beetles are abundantly available in western US forests. To reduce wildfire risks, it is proposed to collect and use this low-value biomass as a supplementary fuel in existing coal-fired power plants. Burning biomass-based fuel is considered to be carbon neutral and results...
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| Published in: | Energy & fuels Vol. 36; no. 1; pp. 565 - 574 |
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| Main Authors: | , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
American Chemical Society
06-01-2022
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Dead trees killed by bark beetles are abundantly available in western US forests. To reduce wildfire risks, it is proposed to collect and use this low-value biomass as a supplementary fuel in existing coal-fired power plants. Burning biomass-based fuel is considered to be carbon neutral and results in a lowering of net carbon dioxide emissions when it replaces fuels such as coal in the generation of electricity. However, potential impacts to boiler performance when co-firing wood with coal may be caused by changes in ash deposition on heat transfer surfaces. This paper presents results from the second phase of a two-phase project in which the effects of combustion scale on ash deposition from combustion of identical coals and coal/biomass blends were investigated in a 1.5 MWth pilot-scale furnace (part 1) and a 471 MWe operating full-scale boiler (this work). Results presented in this paper, however, can stand by themselves, with a focus on practical effects of biomass addition to coal fired in a full scale unit. The coal/biomass co-fired blend consisted of 15% of torrefied wood made from local dead spruce and 85% of pulverized bituminous coal. Of interest are the effects of addition of woody biomass feedstock to pulverized coal on the ash aerosol and ash deposition. Fly ash and ash deposits were alternatively sampled by an iso-kinetic sampling probe and a surface temperature-controlled deposition probe, respectively, which were inserted to the same boiler penetration in the vertical reheat tube bundles. Measurements include real-time particle size distributions and ash deposition rates during both coal combustion and co-firing cases. The size-segregated (0.0324–15.7 μm) particles and time-differentiated deposits were analyzed in terms of composition and microscopic morphology. Results show no significant changes in ash transformation when switching from coal combustion to co-firing with torrefied wood. The results of this full-scale demonstration are further compared with those obtained in the pilot-scale furnace (part 1) to investigate the scale effect on ash aerosol formation and deposition in coal and co-firing biomass combustion. |
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| ISSN: | 0887-0624 1520-5029 |
| DOI: | 10.1021/acs.energyfuels.1c03522 |