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New chemical mechanism explaining the breakdown of protective oxides on high temperature steels in biomass combustion and gasification plants

机译：新型化学机制，解释了生物质燃烧和气化植物高温钢对保护氧化物的击穿

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Biomass is considered a replacement fuel over fossil fuels to mitigate climate change. The switch to biomass in the combustors changes the inorganic chemistry of the flue gases and leads to more severe corrosion of the construction materials of the combustors. The integrity of most high temperature steels relies on the formation of a protective Cr2O3 layer on the steel surface at a high temperature environment. The ash compound found on the heavily corroded steel in biomass combustion and gasification plants is KCl, but the mechanism, which triggers the breakdown of the protective Cr2O3 layer under the KCl salt is not known. We studied the chemical reactions involved with furnace exposure of KCl and KOH with Cr2O3 and identified the formed reaction products with XRD analysis. The amount of reaction products was analyzed from the leachates of the salt-oxide mixtures by UV/VIS spectroscopy. We also used thermodynamic Gibbs energy minimization calculations to evaluate the evolution of reactions as a function of temperature. The results suggests that the reaction of KCl with Cr2O3 involves a KOH reaction intermediate that forms before K2CrO4 is formed. The amount of reacted potassium as a function of temperature follows the trend of KCl decomposition to KOH and HCl(g) as predicted by thermodynamics calculations. Therefore, we argue that the suggested overall reaction of KCl with Cr2O3 as found in the corrosion literature: , starting with the initiation step: KCl + H2O(g) double right arrow KOH + HCl(g) and then the formed KOH reacts with Cr2O3 to form K2CrO4. This explains the initial breakdown of the protective Cr2O3 under KCl salt in water containing high temperature atmospheres. The result is essential for the development of new alloys for biomass fired combustors.
机译：生物质能被认为是在化石燃料，以减轻气候变化的替代燃料。在燃烧器的开关，以生物量变化的烟道气，导致燃烧器的构造材料的更严重的腐蚀的无机化学。最高温钢的完整性依赖于在高温环境下形成的钢表面上形成保护层的Cr2O3的。在生物质燃烧和气化植物严重腐蚀钢中发现的灰化合物为KCl，但其作用机理，这触发氯化钾盐下保护的Cr2O3层的击穿是未知的。我们研究了参与KCl和KOH的炉曝光Cr2O3和鉴定所形成的反应产物XRD分析的化学反应。反应产物的量从盐氧化物的混合物的通过UV / VIS光谱法分析沥出液。我们还用热力学吉布斯能量最小化计算，以评估作为反应温度的函数的演变。结果表明，氯化钾与的Cr2O3的反应涉及KOH反应中间体，K2CrO4之前的形式被形成。反应钾作为温度的函数的量如下的KCl分解到KOH和如通过热力学计算预测HCl（气体）的趋势。因此，我们认为，如在腐蚀文献中找到用的Cr2O3的KCl建议的整体反应：，开始于起始步骤：氯化钾+ H 2 O（克）双右箭头KOH + HCl（气体），然后用的Cr2O3所形成的KOH发生反应形成K2CrO4。这解释下的KCl盐在水中含有高温度气氛保护的Cr2O3的初始击穿。其结果是新合金开发生物质燃煤燃烧器是必不可少的。

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  • 来源
    《RSC Advances》 |2019年第18期|共15页
  • 作者

    Blomberg Tom; Tripathi Tripurari; Karppinen Maarit;

  • 作者单位

    Aalto Univ Dept Chem &

    Mat Sci Kemistintie 1 Espoo 02150 Finland;

    Aalto Univ Dept Chem &

    Mat Sci Kemistintie 1 Espoo 02150 Finland;

    Aalto Univ Dept Chem &

    Mat Sci Kemistintie 1 Espoo 02150 Finland;

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  • 正文语种 eng
  • 中图分类 化学;
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