From my understanding of the process impure hydrogen would be ok...

From my understanding of the process impure hydrogen would be ok however the level of impurity would ideally be low or tailored for the carbon content required in the steel.

Any CH4 which was not already cracked in the reductant gas stream at 1300 degrees and in contact with iron ore would crack into hydrogen and solid carbon, the hydrogen would react with the oxides in the ore to form H2O but the carbon, if formed as a solid graphitic form may if excessive increase the carbon content of the steel beyond ideal levels.

Mild steel requires around 1-1.5 kg of carbon per ton while high carbon steel requires around 12kg. A Nm3 of CH4 weighs around 0.68kg of which 0.51kg is carbon. Based on this you could have 23.5kg of methane/t in the hydrogen feed to a plant producing high carbon steel.

The 23.5kg of methane would contain around 4kg of hydrogen therefore a further 41kg of hydrogen would be required to provide for the reduction needs of a ton of steel.

Total gas feed would be 64.5kg, 36% methane and 64% hydrogen by weight

So yes the low purity hydrogen could in some cases be used direct from the hazer RTR process, for lower carbon steel production the hydrogen would need to go through something like a molecular sieve to reduce the methane content