The effect of increasing MgO content in dendromass on ash fusibility and corrosion of corundum refractory castable

Low melting temperatures of the biomass ash at the intensive combustion can generate the slag with a portion of unburned fuel. The portion of imperfectly burned fuel reduces the efficiency of its use. An alternative route to solve the problem without changing the combustion condition is a modification of the chemical composition of the ash with the addition of an agent increasing the melting temperature of the ash/slag. In this paper, we report on the impact of adding the magnesite waste sludge to ash on their melting. Three types of ashes with different SiO₂ and K₂O content were selected for the tests. The melting temperatures of ash and ash mixtures with magnesite sludge (mass ratio 0.5–2:1) have been determined. The addition of magnesite sludge to ash increased the temperature of fusibility index of the mixtures by 50–100 °C. The ash fusibility temperature rose with a decrease of the SiO₂ content in the ash. Subsequently, the interaction of the ash/ash mixtures with the refractory corundum castable was monitored at a temperature of 1450 °C using a static crucible corrosion test. The addition of magnesite sludge to ash reduced the aggression of the slags to the refractory corundum materials. The Al₂O₃ concentration in the post mortem slags of the ash mixtures with the magnesite sludge (2:1) was about 20–23 wt% lower in comparison to the slag without magnesite. The evaluation of the effect of magnesite sludge addition to ash and the elements (K, Ca, Mg, Fe, Si) penetration on the extent of corrosion is the subject of further work aimed at analyses of the corrosion interface of the slag – corundum refractory material.