My Metals Handbook says that one of the significant improvements in blast furnace technology in the last forty years is “coal washing.” What is this?
(For an explanation of the subject line, see this thread.)
Part of the residue from coal fired generating plants is called fly ash. It is used in concrete but I still don’t know what the purpose is. Could be just a filler.
Uhhh…a whole thread devoted to me? I don’t know what to say.
Well, unless the term “coal washing” has a site-specific meaning I never heard of, I’m assuming that what you are referring to is it’s use with respect to blast furnaces used for coke and metallurgical coke production. Of course, you have to bear with me since I’m not an expert on blast furnaces or coking.
What it refers to in general is improving the quality of the coal prior to the coking process by washing the coal in a dense media bath - such as a magnetite/water bath. In this bath seperators and centrifuges wash away and collect rocks, large particles of pyrites and minerals, sulfur, and chlorides (esp. in British coals). The efficiency of the coking process is improved greatly by washing the coal prior to coking, but at the added cost and trouble of operating a wash plant. Then after washing, it may be necessary to dewater/dry the coal as well, which is typically done by diverting steam or hot flue gases to the coal stream. In a power plant, this results in a lost efficiency; in a coke plant I’m not sure - it would depend pn if they had any means to productively recover the heat anyways. I know that some plants, such as Indiana Harbor operated by Sun Coke (Sunco), generates 90-95 MW of electric power from it’s waste heat.
Coal washing also helps to greatly reduce sulfur emissions from coke blast furnaces, and also results in a lower annual NOx and CO2 emission rate due to having a greater heating value of coal entering. Since many coke furnaces are going to be subject to new, tighter regulations in 2003, this process might gain much wider acceptance.
Of course, in the US electric arc furnaces currently account for nearly 50% of coke production currently, so maybe use of those furnaces will increase as well and blast furnace use will drop…oh wait, I’m rambling again. Stop snoring!
Well, I would love to type a unique response to you. However, since this question was discussed at length in a previous coal thread, I will have to chicken out and just give you a link.
Look out for Narile’s question and my response to it, near the middle of the thread.
Thanks for asking - if this other thread I linked above doesn’t put you to sleep, and you have additional questions, just ask and I’m happy to answer. 
Thanks, Anthracite! I was talking about blast furnaces used for smelting, so I’m sure your description is what they were talking about. The impurities probably are also a problem in smelting if they get into the steel (depending on what they are).
Yes thanks
You are probably the most knowlegable poster on this board.Thanks for taking the time to explain things. You do it so most everyone can understand.
BTW I didn’t go to sleep reading that link. Not until after;)
Oops
Except for the GREAT ONE of course.
Oh, smelting? Oops! And I rambled on about coke blast furnaces!
Well, your conclusion makes perfect sense to me - there would be a lot of ash and sulfur removed by the washing process, and a lot of that ash has phosphorus compounds in it (P[sub]2[/sub]O[sub]5[/sub], most commonly) which I know are not good for steelmaking.
Well, at least I kept your attention for a while, LOL!
Seriously though - I love to explain what I do to people, if they are honestly interested. Unfortunately, most people are not interested in what I do. But I have come to accept that.
Thank you for the compliment!
Don’t feel so bad, Anthracite. At least what you do has a practical application: You’re one ofthe folks who’s figuring out how to power this country for the next century. What I do won’t help power anything, until we get ourselves a nice black hole in the laboratory.
I know you were being facetious, Chronos, but how could one use a black hole as a power source, assuming it could be contained and controlled? I know that it throws off x-rays, but are these in great enough quantity to heat a boiler or a reaction mass?
Or would you throw water or sand or something into its gravity well, and fix a turbine right next to it to mine the kinetic energy? That seems very wasteful, since you couldn’t recover any of your working fluid.