An exploratory study of phosphorus release from biomass by carbothermic reduction reactions
Artikel i vetenskaplig tidskrift, 2023

Phosphorus (P) from biomass can cause operational problems in thermal conversion processes. In order to explore the release mechanism of P to the gas phase, carbothermic reduction of meta-, pyro-, and orthophosphates of ash elements commonly found in biomass; sodium, potassium, magnesium, and calcium was investigated. Mixtures of each phosphate and activated carbon were heated to 1135 °C in a laboratory-scale reactor, with the CO and CO2 evolving from the sample monitored, and the chemical composition of selected residues analyzed to quantify the release of P. Thermal gravimetric analysis was also performed on selected samples. The alkaline earth phosphates were reduced in steps, following the sequence meta → pyro → ortho → alkaline earth oxide. However, the alkali metaphosphates appear to be reduced in one step, in which both alkali and P are released. Alkali pyro- and orthophosphate appear to undergo a two-step process. In the first step, mainly alkali is released and in the second step both alkali and P. An intermediate is produced in the first step, which has a K:P:O atomic ratio of about 2:1:2.7, indicating it might be a phosphite with the overall stoichiometry; K4P2O5. The reduction of alkaline earth phosphates could be interpreted using available thermodynamic data, whereas thermodynamic equilibrium calculations for the alkali phosphates did not correspond well to the experimental observations. Kinetics were derived for the different reduction reactions, and can be used to compare the reactivity of the phosphates. The work suggests that carbothermic reduction reactions are important for the release of P in the temperature range 850-1135 °C and relevant for biomass combustion, pyrolysis and gasification.

Phosphorus

Phosphate

Biomass

Carbothermic reduction

Thermal conversion

Författare

Emil O. Lidman Olsson

Chinese Academy of Sciences

Sino-Danish Center for Education and Research China

Danmarks Tekniske Universitet (DTU)

Peter Glarborg

Danmarks Tekniske Universitet (DTU)

Henrik Leion

Chalmers, Kemi och kemiteknik, Energi och material

Kim Dam-Johansen

Danmarks Tekniske Universitet (DTU)

Hao Wu

Danmarks Tekniske Universitet (DTU)

Proceedings of the Combustion Institute

1540-7489 (ISSN)

Vol. 39 3 3271-3281

Ämneskategorier

Kemiska processer

Annan kemiteknik

Bioenergi

DOI

10.1016/j.proci.2022.07.087

Mer information

Senast uppdaterat

2023-07-07