Hi , given the google doc it seems you continued your work after this post , it is uneasy to suggest because you are giving very few clue on what you want but maybie
https://en.wikipedia.org/wiki/List_of_i ... _processes will help , there is a dedicated section for iron and steel where they list different process used through ages and geography , such as crucible steel , bloomery , open hearth furnace , Bessemer process.
Most of those include carbon in a form or another , as you mentionned a mod that emphasize coal , so that can create an evolution from early to mid game as you discover new process through science and make a more efficient use of your ressources.
Some of the process involve temperature which is also something that exist in factorio, some requires pressure , that you can deal with a liquid called " pressurized [Liquid] " , " [highly] pressurized [XX] " " [ Highlier ] pressurized "
otherwise you will find pictures of the different machines in use or that were used in heavy industy maybie one will intrigue you enough that you will want to have it in factorio
https://en.wikipedia.org/wiki/Bacterial_oxidationI had to drop this one too it is within the list of the first one ; it is your cell identifier that made me think of that ;it states that there is a method to use micro organism to eat the minerals that surround the iron ore , creating sulfuric acid in the process.
If you are into adding new mechanism here is a an idea : what about having new kinds of science , like " iron science " " copper science " " oil science " " nuclear science " , you create them in " small experiment lab " , " medium scientific unit " , " fully equiped R&D system " each requires iron or copper or oil , uranium , to produce their new science pack , because you need to test the new stuff on something, like for the nuclear industry IRL where they have reactors that exist only to produce stuff that will be used for research purposes
the research you do will unlock better way to handle each ressources , so that for example if you have a lot of copper and few iron , you can research a process that is energy efficient but has poor yield for copper , and if you have few iron you will have to take a decision between using it for the actual base , or give it to the scientist so that they can increase the yield in the future , even at cost of energy , or other additives.
hoping that could help , good luck