How does the Bessemer Process work?


Ok as far as I can tell, the Bessemer process works by pumping air through raw iron that has been rendered molten through a previous process and poured it. Various impurities react with oxygen to form slag, and even more additives like Manganese and more carbon is added.


1. Does the initial burst of air before the additives remove *all* carbon in the form of carbom monoxide, or is it just *some* carbon and turns all impurities into slag?
2. Air is blown in through pipes on the bottom of the Bessemer process. Why aren’t these pipes getting jammed by the molten metal?
3. How is the slag removed from the Bessemer furnace?

In: Engineering

1. It doesn’t remove all the carbon, just most of it. Over time, you can get more and more out but not all the way to zero. You need fancy lab-grade stuff to get to “zero”.
2. Molten metal is just a liquid…as long as you pump the air in at higher pressure than the liquid, it will move out of the way.
3. You tap the furnace from the bottom so you get pure iron, the slag floats on top. You can remove it after tapping the furnace. Once you cool it, slag becomes a kind of scuzzy glass and you can grind it up for use in other industrial production.

1. Nearly all the carbon is burnt off. I gather it’s pretty exciting to see. The point is to reduce the level from that of cast iron to close to that of wrought iron. Steel is two percent carbon, or thereabouts?

2. The air pressure is sufficient. I think they start off with something blocking the pipes, like a stopper in a bottle.

3. Poured off, after (I think) the steel is tapped.

Maybe you know this, but it’s important to note that the Bessemer processes hasn’t been used on an industrial scale for at least a century. Modern steel mills use a Basic Oxygen Furnace (BOF) to remove carbon from pig iron and then produce steel. A BOF injects pure oxygen through a pipe from above into the top layer of the iron in order to burn out most of the carbon from the melt. A BOF also uses a different type of ceramic lining which can resist erosion from a basic (as in non-acidic) slag, which improves the BOF’s ability to remove phosphorus, which is a significant impurity in steel.