Inhibition effects of wetting and corrosion behavior of high-alkali coal using typical additives under gasification conditions

The presence of alkali metal Na in high-alkali coal causes severe corrosion in high-chromium-refractory gasifiers, posing a significant challenge for large-scale gasification. Various additives have demonstrated promise in inhibiting the corrosive properties of high-alkali coals. In this study, the corrosion inhibition mechanisms of Si/Al-based and P-based additives on refractories were explored. The results indicate that these additives decrease water-soluble Na and increase insoluble Na, thereby effectively reducing the release of alkali vapors. Si/Al-based additives were more effective in inhibiting liquid-phase slag corrosion, whereas P-based additives more effectively inhibited alkali vapor corrosion. This difference is primarily due to the higher mass retention of Na-containing species by SiO2 and Al2O3, which also prevent the formation of low-temperature eutectic compounds in coal ash. Phosphates reacted with Na vapor, forming high-melting-point mineral phases. However, the addition of bauxite and TCP increased the flow temperature, leading to slagging and blocking issues. Considering both economic factors and corrosion inhibition performance into account, kaolin was determined to be the most effective and appropriate additive for entrained-flow gasifiers.