[Gasification] Re: [Stoves] Big Wood Burner

[Arnt Karlsen]

On Sun, 20 Feb 2005 15:46:26 -0600, Paul wrote in message 
<4.3.1.2.20050220123740.00d896d0 at mail.ilstu.edu>:

> Stovers and Gasifier-folk,
> 
> As Dick said, I visited his location last year.  His description in
> his  message matches perfectly with what I saw.  We have here a
> situation that,  if solved, would be important for innumerable
> communities that need to  dispose of tree stumps and "big brush." 
> Dick has the equipment to handle  this type of big biomass.
> 
> The question is:  How can stumps and big biomass be consumed 
> ("burned/gasified/etc.) in bulk (no or minimal pre-processing like
> chipping  or sawing) in a way to produce heat that is usable?  Dick
> can drop entire  7-foot diameter tree stumps into a tall 10-foot
> diameter thick-steel 

..the "thick-steel", what kinda steel?  316 type SS?  What kinda 
product was this tank made for?  Damage history? (Just so we 
don't wind up killing people etc.)

> tall  cylinder.  He can modify it in any way he wants.  Forced air can
> be  arranged at any location on the cylinder.  He has access to both
> the top  and bottom of the 30 foot cylinder because of the embankment
> and retaining  wall.  He must be able to "top-load" the cylinder by
> placing the stumps  into the top and letting gravity feed them
> downward.
> 
> I hope I have stated it correctly.  Dick can clarify if there are any 
> questions.
> 
> My suggestion to Dick last year was oral but now I have written it
> below  for others to examine.  Would others please comment on it. 
> Feel free to  politely blast it as a bad idea if that is what you
> think.  Or give  suggestions.  I am hoping for at least comments from
> Tom Reed and Dan  Dimiduk and Alex English.
> 
> Note:  What follows is a long and detailed message about one possible 
> solution.
> 
> A "Big Wood TLUD Gasifier".  This would be an enlarged version of what
> Tom  Reed and I are doing with the small gasifiers that are Top-Lit
> Up-Draft or  also called IDD Inverted DownDraft).  The largest one
> thus far (I believe)  was by Alex English.  You can see it at
> http://www.repp.org/discussiongroups/resources/stoves/English/phaltan.htm
> 
> 1.  We might not need to use the full 30 foot height of the cylinder. 
> If  it would work with 15 feet of cylinder (plus the base), Dick could
> have 2  units side by side for continuous operation by alternating the
> two  batch-process gasifiers.  Also,  the base of the device could be
> made to  our specifications (discussed below).

..the base could be a "battery grate" of 7 or more "gasifier spools", 
Gatling gun style, but no need to spin it, each gasifier spool needs 
about 5 feet height, less if more but smaller spools are used, but at
least 2 feet, thermochemical gasifier up--n-downscaling is not linear.  

..this makes your big ass tank, "a canister holding 7+ gasifiers sharing
a common fuel hopper."  Cut the tank in 2, and rest each half on the
"gasifier spool honeycomb battery grate" and you can run continously.

..a kinkier way is "jacked cook stove rings", with a throttle range of
200kW thru 90MW thermal in a second, if your steel can handle it.  ;o) 

> 2.  The vertical cylinder is to have a removable lid.  (Dick can pick
> it up  with his tree moving crane, or eventually the cylinder can have
> its own  small crane for lifting it and swinging the lid to the side
> while loading  the tree stumps and fuel.)  The weight of the lid is
> sufficient to hold it  in place (or have some brackets in case of very
> strong winds).  It is not  air tight, but reasonably well sealed.

..and sneezes?  Size it for sneezes, we prefer shooting smoke rings
rather than steel shrapnel.

> 3.  Being a pyrolysis device (a "pyrolyzer"?), when in operation the 
> pyrolysis gases will rise to the top and exit through a lateral
> opening  (perhaps 2 ft diameter) that has appropriate controls
> (doors/gates/flaps)  to control the passage of the hot and dense
> "smoke" (pyrolysis  gases).  There could be a drafting fan or an
> "ejector" to entrain those  gases to the secondary combustion area,
> which should be close  by.  

..I disagree, draw the vapors off at the top, pipe it down and torch 
it off above the combustion lens, to thicken it, and watch the tar 
vapor problems vaporize. ;o)  

..3, 5 or 7 tar flares per fuel hopper this big, should do the job.
http://crest.org/discussion/gasification/199903/gif00019.gif (from
http://crest.org/discussion/gasification/199903/msg00055.html )

..point them in immediately above the gasifier spools, right into the 
charcoal, "tuyere style."   These can also be used to light up the
gasifier, just hook up blow torches to the tar flares.  Also preheat 
the tuyere air, use tin cylinders around the fuel hopper tank to 
cool it and preheat tuyere air.

> Insulation of the larger cylinder and the lateral exit pipes might be 
> needed if too much cooling of the gases occurs prior to the secondary 
> combustion.
> 
> 4.  Dick says "Tree trimmers dump hundreds of truck loads of chips
> here, at  no charge, but I use them for bedding and then into the
> compost piles."  We  want some of those chips to be sufficiently dry
> to be loaded as part of the  fuel of the large gasifier.  The purpose
> of the chips is to loosely fill in  the air spaces between the brush
> and branches that are also loaded in with  the tree stumps.  In other
> words, the column of fuel is loose enough for  forced air from the
> bottom to pass through the fuel but sufficiently full  to prevent
> sparks and embers from falling from the pyrolysis zone down into  the
> area of the un-pyrolyzed fuel.  (Falling embers could ignite the lower
> biomass that would then utilize the incoming primary air to have
> standard  combustion, with the racing away of the fire and the
> production of bad and  too-cool smoke, resulting in problems for the
> proper functioning of the  system.)

..if it's small enough to auger in, auger it in, using gas tight augers,
means no need to shut down.
 
> 5.  There are several ways to ignite appropriately the top of the
> column of  biomass.
> 
> 6.  The up-coming  (up-draft, or inverted down-draft) primary air

..clustered down drafts with tarflares.  ;o)
<snip>

> 7.  Some of the larger stumps and logs will only pyrolyze on the outer
> inches of the wood.  Tom or someone once told me to expect X inches
> per Y  unit of time, but I have forgotten those numbers.  (If you
> know, please  send them to us.)   Even so, a 7-foot diameter stump has
> many root stubs to  make the 7 foot diameter, but those root stubs are
> only 3 to 6 inches in  diameter, just like some of the other wood in
> the fuel chamber.  But the  tree base (lowest part of the tree trunk
> at the ground level) and any  amount of the trunk might be 3 or 4 feet
> in diameter.  Pyrolysis will not  reach the inner part of that
> big-wood.  Even the attached char will  eventually help insulate the
> innermost part of the big-wood and prevent  pyrolysis.  There are at
> least 2 options:
> 
>    a.  The inner un-pyrolyzed wood will smolder even after the main 
> pyrolysis has reached the bottom of the cylinder and finished.  That 
> smolder-smoke will be insufficient to sustain the supply of pyrolysis
> gases  at the top.  The options are to extract the stumps while
> smoldering or to  consume them if there is to be combustion of the
> char that now is in the  fuel cylinder.  (to be discussed below).

..another reason to use tar flares is, torch those logs.

>    b.  Cut the "big-wood" into smaller wood of 4 to 6 inch
> measurements (or whatever final diameter is defined to be appropriate
> for the major branches  and root stubs.).  Note:  bigger diameter root
> stubs, etc (use 6 inch for  the example) will have a longer time to
> pyrolyze if they are near the top  of the fuel column.  And place only
> smaller diameter root stubs, etc.  (maybe up to 3 inch diameter) in
> the lowest (first fuel into the cylinder)  part of the cylinder, lets
> say the lowest 5 feet of fuel.  This would need  to be determined. 
> Therefore, this option b would require some chain-saw  work (or some
> monster trunk splitter) to break apart the largest of the  "big-wood."
> (If Dick can get a $35 tipping fee per truck load of big wood  (and
> maybe add on a surcharge on the "stumps" part that could be easily 
> counted), he could pay some local person to do a few hours of
> chain-saw  work to get the big stumps to be small enough.  (or simply
> tell those who  have stumps to deliver that, in addition to cutting
> down the whole tree  with chain saws, they must cut some more on the
> stump to bring it into  acceptable size.  For example, no more than 2
> inches of tree trunk above  the soil-line at the base of the stump.) 
> Summary:  There are solutions to  these problems concerning the size
> of the fuel.  Do not forget that option  "a" is still open.
> 
> 8.  Pyrolysis occurs at temperatures of 500 to 900 degrees C. 

..say 400 to 900 Centigrades, some traditionalists say 400-800, 
with my tar flares, I simplify and say 25 thru 1000.  ;o)

> (some help here please:  I keep confusing these numbers, and the
> corresponding temps  in deg F.)    At least I can say that the
> pyrolysis is at "relatively"  lower temperatures than occur with the
> combustion/gasification of the  char.  This is good, because those
> pyrolysis temperatures are not so  damaging to the steel of the
> cylinder.  Pyrolysis temperatures will not  make the steel glow red or
> orange.  And the railroad tank car that Dick  intends to use has 1
> inch thick steel walls.  Therefore, we are hoping that  there is no
> need to line the inside of the cylinder with refractory  bricks.  That
> will need to be determined, and if needed, they can be added  later.
> 
> 9.  Well, at this point in the discussion, we are faced with a tall 

..or 2...

> cylinder partially filled with hot char plus some remnants of
> incompletely  charred stumps and logs, plus some inert dirt and stones
> that stuck to the  roots.  It is NOT sufficient to simply close off
> the air supply and wait  for it to extinguish and cool.  That would be
> too long and, if there are  any air leaks, never ending.  

..use CO2 flooding to shut down these beasts.

> We do NOT want to consume the char inside the  cylinder because it
> would substantially reduce the life of the device, and  the resultant
> heat would be produced in the cylinder and not where the  pyrolysis
> gases were being burned with the secondary air.  The solution is  to
> remove the hot char.  Not a simple task, but possible.

..opening these while hot is "ok" if CO2 flooded, without, you're
playing with fire, even shooting smoke rings up the log feed hole, 
cause shock load stresses to the steel.

> 10.  I propose that the base of the cylinder be imbedded/supported in
> a  concrete "bunker" designed to receive the load of hot char and
> remnants of  the stumps.  The char is now quite friable (breakable)
> and the action of  moving it (see below) will cause it to crumble and
> therefore fill in the  empty spaces between the char pieces.  The char
> around the stumps and big  wood will partially crumble off, but might
> need some assistance to free up  the inner un-pyrolyzed parts of the
> stumps.
> 
> 10.  To remove the char, open the top or side door of the bunker, and
> then  open the grate upon which the fuel was held in place.  The char
> and stump  remnants fall into the cement bunker that has ample room. 
> (If the char  does not fall, then some "shaking" via some poking rods
> from underneath or  from a side "port" would be used.)  The bunker
> door is then closed and  sealed as well as possible, but it should not
> be air tight because of  contraction and expansion of the gases. 

..eh, it should both be airtight and allow for thermal expansion
of the gases and the steel.  Steel bellows is an option.

> Without access to additional  oxygen, the char will extinguish.  To
> accelerate the cooling process, some  water could be sprayed onto the

..you really wanna risk your ass playing rocket scientist???  
Use CO2 flooding, or watch your rocket fly.

> char, and the resultant steam can escape  safely.  It might take hours
> or a day for it to cool, but it will  cool.    When cool, a side or
> bottom door can be opened and the cooled char  examined.  Perhaps a
> heavy rake or roller might be handy.  Basically,  remove the quality
> char that can be sorted by size if it is to be  sold.  The large
> pieces will be the remnants of the stumps.  Hit or crush  or otherwise
> assist the attached char to fall off.  The remaining core of  the
> stump is to be loaded into a later batch of fuel.
> 
> By the way, a ton of char is worth about $25 in Kyoto-type CDM 
> credits.  And you could sell it as wood charcoal for much more than 
> that.  And any char fines and ash are good for building up weak soils.
> 
> 11.  The cylinder is to be allowed to cool before being reloaded. 

..means heat cycling, and heat cycle stresses.  Is why I ask 
"_Which_ steel???", some can take it, some cannot.

> This  will be relatively fast (one or two hours?) because ambient air
> can flow  freely through the cylinder when the top is removed and the
> bottom door  (through which the char was removed) is opened.  Then
> close the grate,  close the bottom door, refill with stumps and
> biomass, replace the top lid,  ignite at the top of the biomass, and
> repeat the process.
> 
> Note:  I am not an engineer and I cannot calculate the amount of heat
> from  the pyrolysis of a pile of stumps and big biomass.  I am not a
> builder and  I have no information about blowers or trap-door-grates
> or cement for the  char-receiving bunker or the secondary combustion
> arrangements and heat  transfer devices that Dick wants for heating
> his greenhouse and other  buildings.  But I do know that what is
> described above should work.
> 
> My proposal would include making first a smaller version, say 4 or 5
> or  even 7 feet in diameter.  But because Dick already has so many of
> the  components of the full-sized "system" at his location, he might
> be inclined  to "go for it".  But lets hear what some of the others
> have to say.

..play with smaller models first, to prove the ideas, oil drums are
nice, if a bit thin walled.  ;o)

> If any reader has not seen Dick's message (which I have deleted
> because of  length), please check the archives or request a copy from
> Dick.
> 
> Awaiting your comments.
> 
> Paul
> 
> At 10:20 PM 2/19/05 -0600, Dick Gallien wrote:
> >May l8, 2004, I wrote the gasifier list for suggestions on what I
> >called a  Big Wood Gasifier.  I have a 30'Xl0' dia., l" thick
> >cylinder (r.r. tank  car), which this summer, I plan to set on end,
> >next to a l6' retaining  wall, so I can top load brush and logs, with
> >my log truck.
> >
> >Thanks to the 3 that responded.  Paul Anderson visited.  Doug
> >Williams,  very thoughtfully, said it wouldn't work and mentioned
> >something similar  in Uruguay, that had polluted a ll acre lake.  Ken
> >Calvert thought it  could and generously drew plans, where everything
> >would be funneled down,  so the most intense heat would be at the l'
> >dia. outlet and then into the  boiler.
> << snipped >>
> 

-- 
..med vennlig hilsen = with Kind Regards from Arnt... ;-)
...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.