Hi ironman, The more iron you put into a blast furnace the more...

Hi ironman,

The more iron you put into a blast furnace the more you get out.

The main difference tho is due to the higher level of contaminants in the 58% Fe
If the iron content drops then the Silica, Alumina, Phosphorous and Manganese grades increase which is bad. Other contaminants are Sulfur and lately Chlorine and Cesium have been all the hype.
65% Fe thus has very low contaminants and it is therefore far easier and cheaper to burn these off when producing pig iron in the blast furnace.

Silica produces more slag in the blast furnace.
Alumina effect's the viscosity of the slag. Too much and its too runny. Too little and its not runny enough. I think 1.7% is about the number they like.
Phosphorous makes steel brittle.
Sulfur does not make steel brittle - but the Phos loves it and sticks to it. And it will carry it into the pig iron if it isn't burnt off properly.
Manganese isnt too much of an issue however it makes the slag black.
The slag is the waste product - mainly Si - they sell it to the brick makers - brick makers dont like black slag because they cant add color to it.
Chlorine is bad for the environment - it can form deadly toxins which you definitely dont want to be breathing in. The Chinese living in the worst areas need to wear masks its that bad.
Cesium is a hot one - It vastly increases the decrepitation of the ore. The decrepitation index measures the thermal degredation of the ore in the blast furnace. In other words the ore is more volatile and comes with costly problems.

Other factors to consider is the moisture of the ore. If the moisture is through the roof at say 18% - then china will only pay for 82% weight in the ship. They don't pay for the water. 10 - 12% for fines is normal.

Lump also attracts a premium - it got up to $20/tonne a while back when china declared war on Polution. It usually sits around $10 i think. The only two companies that produce lump are BHP and RIO. FMG and Vale dont have good enough ore - it is too friable.
Lump totally by passes the sintering process which is costly and highly polluting.
All fines must be first sintered into an artificial lump product before entering a blast furnace.
If you put fines straight into a furnace it would snuff it out. It would be like throwing sand on a fire.
The furnace requires porosity and permeability for the heat to flow.

Dont quote me on any of this - all of the top of my head