| 1. |
- Chansa, Oris, et al.
(författare)
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Behavior of alkali minerals in oxyfuel co-combustion of biomass and coal at elevated pressure
- 2021
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Ingår i: Journal of Zhejiang University: Science A. - 1673-565X. ; 22:2, s. 116-129
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Tidskriftsartikel (refereegranskat)abstract
- Combustion of biomass or coal is known to yield aerosols and condensed alkali minerals that affect boiler heat transfer performance. In this work, alkali behavior in the pressurized oxyfuel co-combustion of coal and biomass is predicted by thermodynamic and chemical kinetic calculations. Existence of solid minerals is evaluated by X-ray diffraction (XRD) analysis of ashes from pressure thermogravimetric combustion. Results indicate that a rise in pressure affects solid alkali minerals negligibly, but increases their contents in the liquid phase and decreases them in the gas phase, especially below 900 °C. Thus, less KCl will condense on the boiler heat transfer surfaces leading to reduced corrosion. Increasing the blend ratio of biomass to coal will raise the content of potassium-based minerals but reduce the sodium-based ones. The alkali-associated slagging in the boiler can be minimized by the synergistic effect of co-combustion of sulphur-rich coal and potassium-rich biomass, forming stable solid K2SO4 at typical fluidized bed combustion temperatures. Kinetics modelling based on reaction mechanisms shows that oxidation of SO2 to SO3 plays a major role in K2SO4 formation but that the contribution of this oxidation decreases with increase in pressure.
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| 2. |
- Oris, Chansa, et al.
(författare)
-
Forms of potassium and chlorine from oxy-fuel co-combustion of lignite coal and corn stover
- 2019
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Ingår i: Carbon Resources Conversion. - : Elsevier BV. - 2588-9133. ; 2:2, s. 103-110
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the forms of potassium and chlorine from oxy-fuel co-combustion of lignite coal and corn stover under atmospheric pressure were investigated. In order to check transitional stage, the feedstocks were combusted stepwise, first by pyrolysis to form coke under N2 environment and later by coke combustion into the ash at 850 °C in O2/CO2 atmosphere. The results show that an increase in blend ratio from 15% to 40% results in an increase in water-soluble potassium in the feedstock and the ashes from 0.15% to 0.4% and 0.015% to 0.038 % in weight respectively. The water-soluble potassium is present mainly as KCl and K2SO4. For ammonium acetate soluble potassium, a similar trend to water-soluble potassium is presented but with a much lower content of potassium. The bound potassium in the fuel matrix exists, likely in the form of AlKSi2O6. Chlorides are present mainly in the form of KCl which is the dominant water-soluble compound.
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