Influence of sintering parameters of different sintering layers on NOx emission in iron ore sintering process

• Three layered structure of iron ore sinter bed was implemented.
• The influence of the important sinter parameters on the NOx emission was investigated.
• Permeability is the main factor on the NOx emission during iron ore sintering.
• Middle layer of sinter bed would influence the NOx emission of lower layer.

In iron ore sintering process, coke combustion can influence the NOx emission. At the same time, there are other sintering parameters which can also affect the NOx emission, such as water content, limestone particle size, MgO content and return fines content. This work focuses on the influence of these parameters on the NOx emission in sintering process by pilot scale tests. 14 experiments were designed for testing the influence of these parameters at different locations of the sinter bed. Three layer sintering method was used and the NOx emission from different layers was measured. These parameters influence the granule properties, permeability of the sintering bed, and calcium ferrites formation and distribution, and then influence the NOx emission. The return fine content has the greatest impact. The conversion ratio of char nitrogen to NOx increased by about 7%, when the return fine content increased from 10% to 30% in the middle layer, and the conversion ratio of the upper and lower layers increased by about 3% and 11%, respectively. The permeability of the middle layer would influence NOx emission from lower layer.