Influence of additives on potassium retention behaviors during straw combustion: A mechanism study

The potassium retention behaviors of wheat stalk and its modification mechanisms in an oxidizing atmosphere by three additives [kaolinite, fly ash from Jincheng coal fluidized-bed gasification (JFA), and ammonium dihydrogen phosphate (ADP)] were investigated. The potassium retention ratios (PRRs) increased with increasing additive mass ratio. The ADP was the optimal selection for wheat stalks combustion when the three additives at the same mass ratio because of its highest PRR and a slow decrease in PRR with an increase in temperature. With the increasing three additive mass ratios, the PRRs of their mixed ashes showed a similar trend [rapid increase (<12%) and then a slow increase (12%-15%)]. The mass ratios of three additives were all <1.0% and their mixed ash reached an appropriate PRR. For kaolinite or JFA, the formations of K-Al/Fe silicates prompted an increase in the PRR. For ADP, K-Ca/Mg phosphate generations increased the PRR.