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Join Date: Apr 2012
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### Blast Furnace

04/25/2012 12:47 PM

What means term RAFT in blast furnace and formulas to calculate it which parameters affect RAFT in blast furnace?

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#1

### Re: Blast furnace

04/25/2012 1:12 PM

RAFT = raceway adiabatic flame temperature

There's a nifty calculator for adiabatic flame temperatures, but I'm not sure if the added word "raceway" makes it completely irrelevant or not.

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#2

### Re: Blast Furnace

04/26/2012 2:10 PM

I'm thinking that you will probably still want to know what those words mean.

The raceway is the zone at the entrance of the tuyere to the shaft. It is the zone where the tuyere's blast and injections react and do work. The figure below will help you visualize what is going on inside the furnace. For those of you who haven't worked a blast furnace, these tuyeres are located evenly around the circumference of the furnace several feet above the hearth. They are where the hot blast enters the furnace interior to react with the coke.

Remember that there may be injection lances situated (coaxially) in the tuyeres as well. Oxygen, Oil or powdered (pulverized) coal can be injected.

There are two kinds of adiabatic temperatures for a process: constant volume or constant pressure.

When holding either volume or pressure constant reactants can result in different temperatures that will be achieved by stoichiometrically efficient combusition.

By knowing what the temperature is in the raceway, compared to the theoretical flame temperature for the reactant combination, furnace operators can alter their Ore, burden, fuel, injectant, Oxygen, blast, flux, or coke rate.

This is not the only factor however, as size variation of coke at the bottom of the furnace and reactants can affect the gas permeability resistance, and thus efficiency and yield. Too much powder injectants for example can "clog' the permeability of the column, increasing both the birdsnest and deadman and result in a lower weight fraction of iron slag over coke ratio than if a lesser amount were used.

RAFT temperature provides the furnace man with insights into extent of raceway, permeability, and likely yield, giving him signals to alter his process. Operators who have done studies and know correlations between coke size at tuyere level and furnace efficiency. These can be affected by improper or optimum injection of proper reactants.

Rather than looking for a free zippy calculator on the web, You instead should be doing the thermodynamics calculations.

Questions for you: What is the fuel theoretical temperature for the blast furnace reactants without injectants, what are the temperatures for the injectants reactions? Do You want to increase the volume of the raceway? If so what should you inject? Then why do most furnace men inject oil or pulverized coal?

If the RAFT increases- Is that good or bad? What about the birdsnest? How could you tell from the production data? Which data would be important in order for you to determine? What ratios would you watch or alter if the raft temperature increases? What else should you pay attention to? What if it goes down, or if gas permeability decreases (or gas permeability resistance increases (different shops may use the reciprocal...) dramatically? What could that mean to the safety of your crew and the integrity of the furnace?

While I can appreciate the convenience of having someone doing your research for you, in the absence of sensemaking and perspective, I wonder if by providing that information they are truly helping or providing a hazard to the OP by giving them tools without understanding??

Milo

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#3

### Re: Blast Furnace

04/26/2012 2:14 PM

What could possibly go wrong?

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#4

### Re: Blast Furnace

04/26/2012 2:29 PM

That's pretty close!

That just looks like one helluva slag tap...

Hope its not a breakout!

If so congrats for not being caught in it.

Milo

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#5

### Re: Blast Furnace

05/22/2012 1:49 AM

Dear sir kindly explain in details ,how to calculate heat balance in blast furnace.

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#6

### Re: Blast Furnace

05/23/2012 5:03 AM

The principle is simple:

• Look at all the streams and the heat going into the plant. Look at all the chemical processes absorbing heat and releasing heat. Look at all the streams flowing heat out of the plant. Assign an appropriate sign (+/-) to each flow. Add 'em all up and the answer is zero.
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