Evaluation of the adhering layer ratio of iron ore granules and its influence on combustion-generated NO _x emission in iron ore sintering

Abstract

In iron ore sintering, the granulation process is the first and an important step. As the fine particles adhere to the coarse coke particles, the NO _x emission generated from coke combustion may be expected to be influenced by that adhering layer. In this study, the granule size distributions and adhering ratios were evaluated by a granulation model. Granulation experiments were also carried out to obtain the granule size distribution and adhering ratio. The influence of the adhering layer on NO _x emissions from the combustion of S type granules was studied by tube furnace experiments. Conclusions include: (1) The adhering ratio predicted from the granulation model can be used as a qualitative index for the evaluation of NO _x emission from coke combustion. (2) The influence of the adhering layer on NO _x emissions was enhanced with increasing adhering layer thickness of S type granules, and the NO _x reduction was enhanced at higher temperatures (around 1373 K), but weakened at lower temperatures (around 1173 K).

中文概要

目的

铁矿石烧结需要对原料进行制粒,而焦炭被细粉颗粒覆盖,会影响其燃烧。本文旨在建立制粒模型分析粘附比例和粘附层的有效面积,并研究铁矿石制粒粘附层厚度对NO _x 生成的影响。

创新点

1. 建立制粒模型计算多组分原料制粒的粘附比;2. 结合制粒模型计算粘附比和在不同粘附比下进行NO _x 释放实验,并对制粒中的焦炭进行合理分布。

方法

1. 通过理论分析,建立原料颗粒参数与制粒粒径分布的关系(公式(1)~(11));2. 通过实验和制粒模型分析水分以及各种原料的特性对制粒粒径分布的影响(图4~10);3. 通过管式炉实验分析不同粘附层厚度对NO _x 释放的影响(图12和13)。

结论

1. 制粒模型可以用于多组分原料的制粒粒径分布和粘附比预测;2. 粘附层对焦炭氮释放有较大影响,需要对烧结中的燃料进行合理分布;3. 通过原料成分和对粘附比的预测,可定性分析铁矿石烧结过程中NO _x 的排放。