Abstract:

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.

Key words: gasification, syngas cooler, fouling, layered structure, sintering, initial layer

摘要：

以某Shell气化炉合成气冷却器严重积灰结垢区域的灰样为研究对象，通过X射线荧光光谱仪、X射线衍射仪、扫描电子显微镜等对其物化特性进行表征，并分析积灰的形成机制。结果表明，灰样内部存在明显的分层结构：最底层呈红色，结晶程度最高且质地坚硬，主要矿物组成有CaSO₄、Fe₂O₃、FeS等；中间层呈黄色，Fe、S含量降低，结晶程度和硬度下降；最外层呈灰色，Fe、S含量最低，为非晶体结构且松软多孔。各灰层间颜色、硬度和内在矿物组分的较大差异，主要是由于在积灰发展过程中，沉积表面温度升高导致沉积层的黏附作用和烧结作用不同。而低熔点含铁矿物的选择性沉积和富集，是初始灰层形成的主要原因。

关键词: 气化, 合成气冷却器, 结垢, 分层结构, 烧结, 初始灰层