Ash Fusion Behavior in Gasification Processes

Ash fusion behaviour is a critical determinant of performance and reliability in gasification systems. As solid fuels undergo thermal conversion in reactors—whether fixed‐bed, fluidised‐bed or entrained‐flow gasifiers—the mineral matter within the feedstock transforms through a series of physical and chemical changes. At elevated temperatures, ash components such as silica, alumina, calcium and alkali metals form eutectic mixtures that lower the melting point and produce a viscous molten phase commonly referred to as slag. The viscosity and melting characteristics of this slag influence its mobility, propensity to adhere to reactor walls or downstream heat‐exchange surfaces and the risk of syngas cooler fouling. Control of fusion temperatures and slag rheology is therefore essential to avoid blockages, corrosion and inefficient heat transfer. Thermochemical modelling, high‐temperature microscopy and rheological measurements have advanced understanding of phase equilibria and transport properties, enabling more reliable design and operation of gasifiers. Improved predictive tools and experimental protocols aid in tailoring feedstock blends and operating parameters to mitigate slagging and prolong continuous operation, underscoring the global importance of mastering ash fusion phenomena for clean energy production.

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Ash Fusion Behavior in Gasification Processes publication trend

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Technical terms

Ash fusion temperature (AFT): Temperature range over which solid ash particles deform, soften and flow as a liquid under controlled heating.

Slag viscosity: Measure of the resistance of molten ash to flow, affecting its ability to drain or adhere to surfaces.

Eutectic mixture: Alloy of mineral components that melts at a lower temperature than any of its individual constituents.

Entrained‐flow gasifier: High‐temperature reactor where finely ground fuel particles are carried by a gasifying agent to produce syngas rapidly.

Thermochemical modelling: Computational method for predicting phase transformations, equilibria and fusion behaviour of multicomponent systems.

References

1. FactSage thermochemical software and databases, 2010–2016. Calphad (2016).
2. Alkali metals association in biomass and their impact on ash melting behaviour. Fuel (2020).
3. Slag Behavior in Gasifiers. Part I: Influence of Coal Properties and Gasification Conditions. Energies (2013).
4. A Critical Review of Mineral Matter Related Issues during Gasification of Coal in Fixed, Fluidized, and Entrained Flow Gasifiers. Energies (2015).
5. Slag Behavior in Gasifiers. Part II: Constitutive Modeling of Slag. Energies (2013).
6. Structures and diffusion motions of K and Ca in biomass ash slags from molecular dynamics simulations. Fuel (2021).