Fusibility of Agricultural Plant Waste Ash under the Conditions of High-Temperature Processing

Agricultural plant wastes such as wheat straw, rice hulls, and sunflower-seed husks were characterized experimentally. The chemical composition of the ash formed from these wastes at various temperatures was determined by energy-dispersive X-ray microanalysis, X-ray diffraction analysis, and IR spectroscopy. The chemical composition of mineral components of the agricultural plant waste ash varies, but the prevalent components are CaO, SiO2, and K2O. Thermodynamic calculations show that SiO2 prevails in rice hull ash; K2Si2O5 and Ca3Si2O7, in wheat straw ash; and potassium compounds (K2O, K2SiO3, KCl, K2SO4), in sunflower-seed husk ash. The ash melting temperatures were determined by the method of characteristic temperatures. No clear correlation was revealed between the melting temperature and alkali metal content of the ash. The main parameters of slag formation such as base-acid ratio, slag viscosity index, and fouling coefficient were calculated. Wheat straw ash and sunflower-seed husk ash, in contrast to rice hull ash, tend to slagging and fouling of reactor walls.