This is due to the chemical composition 

There is a difference in the coarseness of the material suited for either pelletisation or sintering. The proportion of fine dust can be larger for pellets.

The iron ore has size - 10 mm is used  for sintering process while the fine size and high quality of the iron ore  is used in pelletization process . 

You may find useful the following reference: Kurt Meyer, "Pelletizing of Iron Ores", Springer-Verlag, 1980.             

Dear Ran Bahadur,

Mineralogy is not the only indicator of the suitability of iron ore for sintering vs pelletising. In Australia, currently mined iron ore are predominantly goethite and hematite as the main ore iron oxides.  As mentioned earlier, other factors to consider are geometallurgical properties such as hardness, texture etc. Goethitic ores may contain either vitreous or ochreous goethite (still only goethite by XRD analysis), but vitreous goethite is much harder and is less likely to produce fines than ochreous goethite.

A recent publication dealing with all aspects of iron ore characterisation, processing etc., is "Iron Ore: Mineralogy, Processing and Environmental Sustainability" 2015, Liming Lu (ed.), Woodhead Publishing Series in Metals and Surface Engineering: Number 66.

Hope you find this useful.  Regards, Martin

I agree Martin's answer.According to  our experience，the iron ore mineralogy will affect the high temperature reaction behavior during sintering process or pelletizing process due to different consolidation methods and different basicity .Such as better assimilation performance of goethite  which is useful for liquid phase formation in sintering, but high high crystal water content of goethite will deteriorate the solid consolidation of pellet. 

But except goethite and siderite,other types iron ore are both suitable for sintering and pelletization if the optimal process and economical is not considered.

Hope it is useful for you.

Regards,

Jian Pan

Dear Ran Bahadur, The responses by Martin and Jian are both correct. The geometallurgical properties of the ores (combining all aspects such as mineralogy, hardness, texture, degree of assimilation etc. all play a significant role in determining which ores are more suitable for different process routes. For more information see Suthers et al (2016) Geometallurgy of Australian iron ores from the the recent Proceedings Geometallurgy 2016. In this paper we emphasise the importance of characterising the geometallurgical properties of iron ores and the impact these may have on sintering of iron ore.

Also, as Martin suggests, see the recent book by Lu (2015). IT has a lot of information that you would find useful.

Regards,

Mark

Martin, Jian and Mark are all correct.  Ores with high goethite content can potentially sinter well as long as there is enough nucleus material present, but the presence of significant goethite in pellet feed results in excessive pellet spalling, which is a major problem.

Regards

Ralph

Sintering of Iron ore depends on sizes of particles and to some extent mineralogical structure of the ore. But pelletization of iron ore only depends  on sizes of particle (- 100 mesh). For detail please ref. Kurt Meyer, "Pelletizing of Iron Ores", Springer-Verlag, 1980.