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Title: Alkali-activation potential of biomass-coal co-fired fly ash

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Cement and Concrete Composites
Additional Journal Information:
Journal Volume: 73; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-04 21:41:11; Journal ID: ISSN 0958-9465
Country of Publication:
United Kingdom

Citation Formats

Shearer, Christopher R., Provis, John L., Bernal, Susan A., and Kurtis, Kimberly E. Alkali-activation potential of biomass-coal co-fired fly ash. United Kingdom: N. p., 2016. Web. doi:10.1016/j.cemconcomp.2016.06.014.
Shearer, Christopher R., Provis, John L., Bernal, Susan A., & Kurtis, Kimberly E. Alkali-activation potential of biomass-coal co-fired fly ash. United Kingdom. doi:10.1016/j.cemconcomp.2016.06.014.
Shearer, Christopher R., Provis, John L., Bernal, Susan A., and Kurtis, Kimberly E. 2016. "Alkali-activation potential of biomass-coal co-fired fly ash". United Kingdom. doi:10.1016/j.cemconcomp.2016.06.014.
title = {Alkali-activation potential of biomass-coal co-fired fly ash},
author = {Shearer, Christopher R. and Provis, John L. and Bernal, Susan A. and Kurtis, Kimberly E.},
abstractNote = {},
doi = {10.1016/j.cemconcomp.2016.06.014},
journal = {Cement and Concrete Composites},
number = C,
volume = 73,
place = {United Kingdom},
year = 2016,
month =

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.cemconcomp.2016.06.014

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  • Sodium and potassium present in the coal and limestone (or dolomite) in a fluidized bed combustor volatilize primarily as NaCl and KCl. Our earlier studies show that the alkali content of the hot combustion gases in a pressurized fluidized bed combustor/gas turbine (PFBC/GT) combined cycle system can be as much as two orders of magnitude higher than that considered normally acceptable to prevent severe corrosion in oil-fired gas turbines. One possible way to remove alkalis from the gas is by adsorbtion on solid sorbents. Our present experimental studies show that NaCl and KCl are reversibly adsorbed on alumina at 800more » and 900/sup 0/C, and strongly enough to reduce their concentrations to acceptable levels. However, a conventional approach using a packed bed of microporous sorbent particles may be uneconomic because mass transport of NaCl or KCl gas molecules to adsorption sites deep within a sorbent particle will be inordinately slow. This problem can be circumvented by dispersing submicron-sized sorbent particles, generated in a flame or plasma, into the hot gas stream.« less
  • We propose a framework for designing the supply chain network for biomass co-firing in coal-fired power plants. This framework is inspired by existing practices with products with similar physical characteristics to biomass. We present a hub-and-spoke supply chain network design model for long-haul delivery of biomass. This model is a mixed integer linear program solved using benders decomposition algorithm. Numerical analysis indicates that 100 million tons of biomass are located within 75 miles from a coal plant and could be delivered at $8.53/dry-ton; 60 million tons of biomass are located beyond 75 miles and could be delivered at $36/dry-ton.
  • Combustion and co-combustion experiments with four kinds of straw, specially selected for their different alkali, Cl, and Si contents, and Colombian black coal were carried out in a circulating fluidized bed (CFB) reactor at Delft University of Technology. The influence of operating conditions and fuel composition on the release of the alkali compounds to the gas phase was investigated. The amount of the total gas-phase sodium and potassium compounds in the flue gases was measured with excimer laser induced fluorescence (ELIF). The results show that the release of gaseous alkali species depends on fuel composition, in particular the K/Cl andmore » K/Si ratios in the fuel. The fuels with high K and Cl values show higher concentrations of the gaseous alkalis. A synergetic effect of the co-combustion with coal was observed, which led to a strong decrease in gaseous alkali concentrations. Together with experiments, chemical equilibrium modeling was performed to help in interpreting the experimental data. The calculations confirmed that the equilibrium is very strongly influenced by the composition of the fuel blend. Moreover, the simulations provided more information on sequestering of alkali species. 22 refs., 5 figs., 4 tabs.« less
  • Neutron activation analysis (NAA) is a highly sensitive non-destructive, multi-element technique useful for analyzing samples from many sources. Following irradiation of the sample with neutrons in a nuclear reactor, induced radioactivity in the isotopes present is measured with a Ge(Li) $gamma$-ray spectrometer. The method has been applied to coal and ash samples from the Allen Steam Plant in Memphis, Tennessee. Twenty-nine elements have been identified, and a mass balance has been made to indicate the ultimate fate of these elements. Most are removed in either the precipitators or the bottom ash. (auth)
  • In fluidized bed co-combustion of coal and biomass, operational problems may occur due to the deposition of ash components on heat transfer surfaces. Alkali metals, sodium and potassium in, play an important role in the ash deposition process. In this work, the fate of alkali metals in a Multi-Circulating Fluidized Bed Combustor (MCFBC) was studied by means of thermodynamic equilibrium calculations and by practical sampling of gaseous and condensed alkali metal species. The alkali vapor concentrations at 6 different measurement locations were found to vary between 0.1--1.8 ppmv sodium and 0.1--3.7 ppmv potassium. A semi-empirical model was set up formore » the plant, dividing it into characteristic sections in order to predict the quantity and species of the alkali metals present in a given section. The model results were found to correlate with the performed measurements, except in the riser section, where the model predicted higher concentrations of potassium than what was measured.« less