Potassium Migration of Chestnut Shell Ashes Under Oxidizing Atmosphere and Its Modification Mechanism by Additives

ABSTRACT Biomass energy plays a critical role in alleviating environmental pressures. However, its relatively high content of alkali metals (especially for potassium) would cause ash‐related issues during combustion. To mitigate these issues, the potassium migration behaviors during chestnut shell (CS) conversion and the modification mechanisms of solid waste additives (fish bone and fly ash) under oxidizing atmosphere were investigated. When the mass ratio of fish bone ash or fly ash increased from 0% to 40%, the potassium retention both increased (fish bone: 5%–33%; fly ash: 5%–43%), and fly ash showed a better potassium‐fixation performance under the same conditions. The phosphorus and calcium from fish bone reacted with potassium to form high‐melting‐point (MP) K‐Ca phosphates (KCa 2 P 3 O 10 ), which increased potassium retention rate obviously. The replacement of some potassium in silicates by the calcium from fish bone might mitigate potassium retention of CS ashes. With the addition of fly ash, its elevated silicon and aluminum concentrations effectively inhibit potassium leaching through the precipitation of high‐MP potassium aluminosilicate phases (KAlSi 3 O 8 ). The combination of XRD and FactSage analyses provides a mechanistic interpretation of potassium migration behavior under oxidizing atmospheres.