Serious ash deposition and fouling from the synthetic gas cooler in Shell gasifier was studied. The physicochemical characteristics of samples were investigated by X-Ray Fluorescence Spectrometer (XRF)

X-Ray Diffraction (XRD)

Scanning Electron Microscopy and Energy Dispersive Spectrometer (SEM-EDS) respectively to explore the mechanisms of ash accumulation problem. The results showed that the deposition had an obvious layered structure. The inner layer

which presented red color

had the highest degree of crystallization and stiff structure. Its dominant mineral components were calcium sulfate

iron oxide and ferrous sulfide. The middle layer presented yellow color. The amount of Fe and S

the crystallinity and hardness all decreased. The outer layer

which presented grey color and had the lowest amount of Fe and S

was amorphous

soft and porous. The differences of color

hardness and mineral components among three ash layers are due to different interaction of adhesion and sintering as the deposition surface temperature increases with the growth of ash thickness. Ash composition

temperature

reaction atmosphere and pressure are all important factors. And the selective deposition and accumulation of iron-bearing minerals with low melting point in heat transfer surfaces are important sources of initial layer.