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Old   October 20, 2009, 11:55
Default Coal Slurry Injection
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Andy Robertson
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Folks,
Has there been any progress in coal slurry injection modeling?? This is typically used in coal gassification.

So you have a liquid phase carrying particles at a very very high loading factor being injected into a gas. Which then of course one would like to have react/combust!

As far as I can determine this seems well beyond the capabilities of any of the commercial codes, but perhaps someone in academia has made at least a dent in the problem.

So far my internet searches haven't yeilded anything too pertinent, but I am still searching.

Seems like you need a three phase model (eularian/eularian/lagrangian) that can handle a high volume fraction of a discrete phase. Simple eh ??

Any references would be appreciated.

Thanks
- Andy R
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Old   October 22, 2009, 07:05
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Hi sounds very complicated. Can I clear something up. I may have a lead for the first part.

So you start off with a high volume fraction of particles suspended within a fluid yes? The biggest problem here is that crystallization is likely to occur it there is must viscosity within the suspending fluid (which I would imagine there is in this situation). What sort of VF are we talking about?

What kind of Re are we talking about here? If you are heading towards a Stokes flow and if the particles can be modeled as spheres to model this suspension you should look at Stoksian dynamics by J.F Brady, there have been a lot more advances since this paper but it's a good starting point.

@ARTICLE{Brady:1987,
AUTHOR={Durlofsky, L and Brady, J F and Bossis, G},
TITLE="Dynamic Simulations of Hydrodynamically Interacting Particles",
JOURNAL={Journal of Fluid Mechanics},
VOLUME=180,
PAGES=21,
YEAR=1987
}

However as stated above if crystallization is occurring this model is probably too computationally expensive.

I may have completely misunderstood the problem though.
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Old   October 22, 2009, 11:56
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Andy Robertson
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Yes it is very complicated
Various people have used various models which treat the coal slurry as a non-newtonion fluid. These approaches have had some success when the analysis goal is to look at overall combustion or gassification behavior in a furnace/reactor.

I am trying to see if anyone has had success modeling the near injector behavior.

Essentially within the injector you have high volume fraction (50%) coal particles (dust or powder really) in your carrier fluid, which is generally a mixture itself. This gets blown into the reactor volume and atomizes.

Its not clear to me if you can still treat the coal slurry as a fluid. I suspect that the initial atomization may occur in a mixed state but very quickly the carrier fluid is vaporized and you are left with wet clumps of coal dust which then will burn.

Currently it appears that there is some model bases cfd being done, but a lot of cut and try at the injector detail level.

Interesting
-Andy
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