[Gasification] [WoodGas] Re: Perfect Hearths

[Greg Manning]

 Greetings Arnt, and list..

I wrote most of that original message (I think) and it is now so cut up, I don't remember which parts are mine, and which parts are someone else's...

anyhow, the reduction tube and hearth work for me, everything else is mild steel.

Greg Manning



-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org]On Behalf Of Arnt Karlsen
Sent: Saturday, April 05, 2008 1:42 AM
To: gasification at listserv.repp.org
Subject: Re: [Gasification] [WoodGas] Re: Perfect Hearths


On Mon, 31 Mar 2008 11:52:05 -0500, Greg wrote in message 
<006801c8934f$8d72f580$0201a8c0 at a31new>:

>  
>  
>  Ah... EDSI or EDS >? or could it ... SHL/MCI ?
>  
> LOL,
>  
> Stewart, I have access to a foundry not 2 hours from me, set-up is
> nominal, 5 pc. minimum.
>  
> I'm currently experimenting with some really "radical" thinking (that
> is my "MO" lol), in that making a hearth from 314ss

..precisely _where_ and _why_ do you wanna use 
stainless steels in gasifier hearths? 

..while it makes good sense in tuyeres, the fuel hopper and anywhere
else it sees hot air or hot combustion gases, these steels depend on
their "oxygenated" surfaces for their "stainlessness". Remove that in 
e.g. the reduction zone and downstream, and you're left with a new
expensive way of making "holy pig iron."  ;o)

..for hot dusty gasifier gas piping, I use cheapo rusty mild steel. ;o)

> tubing, and
> drawing the inlet air through that tubing, gas evolution happens just
> above the hearth, and the heat is being drawn down to the hearth,
> therefore my thoughts are two fold.
>  
> 1) With downdraft units, pre-heating of inlet air does one thing,
> assists in the water/gas phase shift, by keeping all things in the
> carbonization area hotter than with no preheat (shift is dependent on
> reaction temp.) 
> 2) Because gas evolution happens just above, and heat rises / cool
> falls, the tubing would act as a "pre-cooler" to gas "cooling" for
> non-dioxin/furan formation, and I believe the CO to CO2/soot shift
> would also be much harder to have happen.

..is more important to have a _small_enough_ reduction zone, shoot 
for a gas exit temporature of about 1050 degrees Celsius ~ 1925 
degrees Fahrenheit ~ 1325 Kelvin, up beyond 1100 doesn't win you
anything worthwhile, as you're left with much less than 2% of 
the steel strength exposed to this, and, you'll see soot shift 
aka "reversial" starting below 850 degrees Celsius.

> With this said, one final thing, we would sure know when a hearth
> cracked or pitted through as the incoming air would ignite the gas
> stream for a short period of time, and then gas evolution would
> cease. (there by telling you "you have a problem") ......

..and then we have subtle ones, where things works, 
and 95% as good as in Gengas.  ;o)

> Greg Manning
>  

-- 
..med vennlig hilsen = with Kind Regards from Arnt... ;o)
...with a number of polar bear hunters in his ancestry...
  Scenarios always come in sets of three: 
  best case, worst case, and just in case.


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