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Nitrogen in SL/RN direct reduced iron: Origin and effect on the electric steelmaking process.

机译：SL / RN中的氮直接还原铁：起源和对炼钢过程的影响。

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摘要

Direct Reduced Iron (DRI) is used as an alternative feedstock in electric arc furnaces, making up 50% or more of the total iron charge. DRI produced with coal based reductants (for example in rotary kilns) make up roughly 25% of DRI produced in the world. It was found that SL/RN DRI samples from a kiln cooler had high nitrogen contents (50-250ppm, depending on particle size), higher than DRI from gas-based reduction. The higher nitrogen content of SL/RN DRI would increase the levels of nitrogen of liquid steel produced in the EAFs. The problem is exacerbated by the fact that the SL/RN DRI contains virtually no carbon (which would aid in preventing nitrogen pickup). The proposed mechanism of nitrogen pick-up by the SL/RN DRI is one where nitrogen present within the atmosphere of the rotary cooler (where hot DRI, discharged at 1000°C from the rotary kiln, is cooled to approximately 100 °C in ca. two hours) penetrates the solids bed and nitrides DRI particles. Possible rate-determining steps for nitriding in the cooler have been evaluated. Nitriding of DRI particles is predicted to be rapid: the most plausible location for rapid nitrogen pickup is the first 5 meters of the rotary cooler, where the high temperature, nitrogen-rich gas atmosphere and rapid solids bed mixing are conducive to nitriding; solid-state and pore diffusion of nitrogen into DRI particles are predicted to be rapid too. The most plausible rate determining step for nitriding of DRI particles is that of nitrogen dissociation on the DRI surface, which can be further retarded by the presence of sulphur. A strong correlation was found between the amount of "melt-in" carbon in the liquid steel and the final tap nitrogen content, with 0.3% C resulting in nitrogen levels as low as 50 ppm (80 ppm or less is desired on the plant in question) at tap, even with DRI material that is high in nitrogen and contains virtually no carbon. Proposals to increase the melt-in carbon are included.
机译：直接还原铁（DRI）在电弧炉中用作替代原料，占总铁装料的50％或更多。用煤基还原剂生产的DRI（例如在回转窑中）约占世界生产的DRI的25％。发现来自窑冷却器的SL / RN DRI样品的氮含量较高（50-250ppm，取决于颗粒大小），高于基于气体还原的DRI。 SL / RN DRI较高的氮含量会增加电弧炉生产的钢水的氮含量。 SL / RN DRI实际上不含碳（这将有助于防止氮吸收），这一事实使问题更加严重。 SL / RN DRI提出的氮吸收机制是一种在旋转冷却器的大气中存在氮的机制（其中，从旋转窑以1000°C排放的热DRI在大约1000°C下被冷却至大约100°C）。 2小时）渗透到固体床和氮化物DRI颗粒中。已经评估了在冷却器中进行氮化的可能的速率确定步骤。预计DRI颗粒的氮化将很快：最合理的氮气吸收位置是旋转冷却器的前5米，高温，富氮气体气氛和固体床快速混合有助于氮化；氮在DRI颗粒中的固态和孔扩散也被认为是快速的。用于DRI颗粒氮化的最合理的速率确定步骤是在DRI表面上的氮离解速率，这可以通过硫的存在进一步阻止。液态钢中的“熔化”碳含量与最终出钢氮含量之间存在很强的相关性，其中0.3％的C导致氮含量低至50 ppm（在工厂中希望达到80 ppm或更低）。问题），即使使用氮含量高且几乎不含碳的DRI材料。包括增加熔化碳的建议。

著录项

  • 作者

    Erwee, Markus Wouter.;

  • 作者单位

    University of Pretoria (South Africa).;

  • 授予单位 University of Pretoria (South Africa).;
  • 学科 Materials science.
  • 学位 M.Eng.
  • 年度 2013
  • 页码 80 p.
  • 总页数 80
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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