Dave Nelson wrote:
The key point below is the absence of any mention of smelting iron ore. You need coke to do that. The mention of the Open Hearth Furnace is saying they took pig iron and by melting it and adding a bit of this and that changed the iron into a complex compound – steel. Obviously melting the iron requires a lot heat but that could be from any fuel. I’d put my money on natural gas for most of the 20th century (with the chance they used coal before the 1930’s) because there are natural gas wells in the area, including some just on the other side of the Sacramento River opposite Pittsburg.
It's a common misconception that smelting iron from ore requires fuel. The only fuel used is at start-up, when the materials have to be gotten hot. Once the reaction between carbon (in the form of coke) and iron oxide (main part of the ore) begins, it is EXOTHERMIC and no fuel i consumed at all. The oxygen combines with the carbon, leaving iron behind, which is molten. During a furnace campaign, only very minor amounts of fuel, if any, are consumed to make up for heat losses in the furnace.
Melting iron pigs for further processing is another story. It does require fuel, which certainly need not be coke.
Tony Thompson Editor, Signature Press, Berkeley, CA
Publishers of books on railroad history