[Gasification] Accelerated deep-bed gasification

[Greg Manning]

 Greetings all,

 I've been working on a downdraft gasification variant, where secondary air
is injected below the hearth and the mixture is then ignited at this point
to from a downdraft "burner" if you will, that runs in refractory after the
gasifier.

 Once this "secondary" or close coupled burn is complete, the now spent
gasses ( at just over 800c ) are fed through a heat exchanger as to heat
water.

 This entire project is to use a downdraft gasifier/close-coupled continuous
run combustor, to replace the common "OWB" (Outdoor Wood Boiler).

 MUCH to my surprise, during the testing of the gasifier/refractory section
of this unit, I observed some unusual phenomena with the gasifier.

 fist off:

 1) The forced draft and tuyere air, "fluffed" the contents of the gasifiers
feedstock, causing me to redesign the tuyere to hearth area somewhat deeper
than standard engine application downdrafts.

 2) The secondary air is admitted via the hearth tubes, thus keeping them
cool, to date, well over 300 hours of testing (cold/hot cycling) and no
visible changes or deformation of the hearth detected during routine
inspections.

 3) Initial gas evolution from a "dead-cold" start, using a K type TC just
3cm above the hearth, ignitable gas is produced at as low a temperature of
only 160c, but as the unit comes up to operating temperature, the run
temperature at the same 3cm above the hearth is 660c, where as, the spent
gases at the end of the secondary burn refractory are over 800c (800-805).

 4) ash content is imperceptible, "it's like the thing annihilates
everything" except when a drastic change of airflow is introduced, then it
will release "tiny" glowing sparks (under 1mm in size) for 10-15 seconds,
but if the airflow is slowly raised, no tiny sparks. I've attempted to
capture ash or soot, with no success, except the tiny glowing sparks, they
are the only thing I can get from the "spent-end" of the refractory tunnel.


 My next work is to couple the heat exchanger to the spent-end, and do some
testing as to fire tube buildup of non-gaseous product from this unit.

 This unit IMO, is anticipated to keep the fire tube heat exchanger clean
due to it's being built of 304ss, and having a total flow length (after
initial refractory burn tunnel) of over 40 feet, of one pipe 2-3/8" internal
diameter.

 The Gasifier's calculated output rate is 250,000 btu/hr when running in
"heating demand mode" and only 8,000 BTU/hr at idle (off cycle).

 For those that wish to see some initial testing findings in video format,
(detailed examination of the char bed between tuyeres and hearth).

 http://www.youtube.com/watch?v=2sCFpCpSTqE  (Part 1 of 3)

 http://www.youtube.com/watch?v=JkyuMqDrpAo (Part 2 of 3)

 http://www.youtube.com/watch?v=arKLqwxbDqI (Part 3 of 3)

 Regards,

 Greg Manning







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