[bechen]

What is marketable coal tar and non-saleable coal tar when it is produced in steel industry as by-product?
How to determine? And what is the process?

[Enthalpy]

I'm not quite sure...

Maybe said "steel industry" includes the production of pig iron, the precursor to steel.

Pig iron production consumes coke, obtained from coal, with tar as a by-product.

[bechen]

I'm not quite sure...

Maybe said "steel industry" includes the production of pig iron, the precursor to steel.

Pig iron production consumes coke, obtained from coal, with tar as a by-product.

I already know coal tar is a by-product of iron production from iron ore... that but the by-products coal tar has different specifications: some coal tar can't be sold i'm curious about the reason behind this.

[Enthalpy]

Just a hypothesis: some tar evolves at the beginning when coal is pyrolysed, and some tar later, which is less volatile.

Customers may prefer one type. To coat roads for instance, tar with a higher melting point and a low vapour pressure seems better. So the pig iron industry would separate tar evolving early from tar evolving late in order to sell at least one fraction.

Tar is unhealthy as it comprises many aromatics. If it has a higher vapour pressure, the vapour ends in lungs.