氧浓度对自燃硫化亚铁钝化行为的影响

Effect of oxygen concentration on the passivation behavior of the spontaneous combustion of the active ferrous sulfide

为揭示自燃活性硫化亚铁(FeS)气相钝化的机理,使用自主搭建的FeS气相钝化试验装置对实验室合成的自燃活性FeS进行了气相钝化试验。借助拉曼光谱仪对钝化前后的样品进行了分析测试。结果表明:钝化剂氧体积分数大于1.25%时,钝化过程中会放出大量热,具有较高的火灾爆炸风险;钝化剂氧体积分数小于1.25%时,钝化过程中放出热量较少,较为安全。研究表明:在低氧浓度氛围下,钝化后表面的FeS与钝化剂(低浓度氧气)反应产生了自燃活性较低的铁的氧化物,隔离了空气,从而阻止内部自燃活性强的FeS接触空气发生氧化放热甚至自燃,达到了钝化的目的;在较高氧浓度氛围下的FeS钝化是高自燃活性硫化亚铁与充足的氧气完全反应生成不燃的氧化铁。

This paper is inclined to trace and identify the mechanism of the gas phase passivation of the active ferrous sulfide with the self-ignition,ferrous sulfide through the spontaneous combustion activity synthesized under the simulated field working conditions in laboratory.And,for the said purpose,we have conducted a series of gas phase passivation experiments by means of a self-built gas passivation apparatus with the passivized gas in different concentration rates of oxygen.Moreover,we have also analyzed and tested the samples before and after passivation via the Raman spectrometers.The experimental results we have gained so far indicate that the samples through the passivation with different oxygen concentrations would fail to get spontaneously ignited once in contact with air,for it has lost spontaneous combustion activity with better passivation effect.And,then,the iron oxide may tend to get formed on the surface of passivated samples whereas with the decrease of oxygen concentration in passivated gas,the temperature rise of the samples may get decreased gradually in the process of the passivation.At the same time,it would be possible for a large amount of heat can be released in the process of the agent passivation with the oxygen concentration rate of over 1.25%,when the temperature rise of the sample may tend to get over 120℃,which tends to suggest or link up us or join us with the high fire and explosion risks.On the other hand,the passivation is also linked us with the oxygen concentration rate less than 1.25%,which tends to suggest less heat releasing during the passivation,whilst the temperature of the sample tends to fall below 60℃,which implies comparatively safe.It can thus be concluded through the experiment analysis and the current literature revision that the gas phase passivation of the ferrous sulfide at low oxygen concentrations was that the iron oxide with low spontaneous combustion activity can be produced as a reaction of the ferrous sulfide on the sample surface after passivation and the agents being passivated,which tends to isolate the air and prevent the ferrous sulfide with the high spontaneous combustion activity from getting contact with oxygen,and hence it tends to prevent the exothermic oxidation and self-ignition.Thus,the goal of the passivation has been achieved.The gas phase passivation of the ferrous sulfide in the atmosphere of higher oxygen concentration rates has been mainly caused by the entire and comprehensive reaction of the ferrous sulfide with high spontaneous combustion activity and the sufficient oxygen,and,when most of the ferrous sulfide can be converted into the incombustible iron oxide,the goal of passivation can be expected to get fully realized.