Skip to main content
SLU publication database (SLUpub)

Research article2020Peer reviewedOpen access

Fate of Phosphorus in Fixed Bed Combustion of Biomass and Sewage Sludge

Falk, Joel; Skoglund, Nils; Grimm, Alejandro; Ohman, Marcus

Abstract

The recovery of phosphorus (P) from societal waste streams, such as sewage sludge, could make a significant contribution to alleviating the global dependency upon non-renewable phosphate sources, such as phosphate rock. This study aims to determine the effect of fuel ash composition, chemical association, and combustion technology on the fate of P in ashes from the combustion of sewage sludge and biomass blends to enable more efficient P recovery from combustion ashes. Experiments were performed in a fixed bed pellet burner (20 kW), combusting two sewage sludge blends and three biomass blends of similar fuel ash composition but with different P source (sewage sludge, dried distiller's grain with solubles, or phosphoric acid). Slag, bottom ash, and particulate matter samples were collected and analyzed by scanning electron microscopy-energy-dispersive X-ray spectroscopy and X-ray diffraction for morphology and elemental and crystalline phase composition and compared to results from experiments in fluidized bed combustion using the same fuel blends reported separately. The distribution and elemental composition of ash fractions indicated that sub-micrometer particles contained a minor share of fuel P, with the significant share of fuel P found in the slag and bottom ash fractions. No apparent difference in phosphate speciation could be observed between the slag and bottom ash from sewage sludge blends and biomass blends, with a range of crystalline Ca, Mg, and K phosphates detected in the ash. By comparison, only Ca-rich phosphates were detected in the ashes from the combustion of the sewage sludge blends in the bench-scale fluidized bed. The difference in P speciation between the technologies was attributed to a difference in the process temperature between the two technologies. In comparison to fluidized bed combustion, fixed bed combustion favored the formation of (Ca, Mg)-K phosphates rather than Ca phosphates for similar fuel blends.

Published in

Energy and Fuels
2020, Volume: 34, number: 4, pages: 4587-4594 Publisher: AMER CHEMICAL SOC

    Sustainable Development Goals

    SDG6 Clean water and sanitation
    SDG7 Affordable and clean energy

    UKÄ Subject classification

    Energy Engineering

    Publication identifier

    DOI: https://doi.org/10.1021/acs.energyfuels.9b03976

    Permanent link to this page (URI)

    https://res.slu.se/id/publ/105422