An exploratory study of phosphorus release from biomass by carbothermic reduction reactions

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