Hi Doug,
Good to hear you continue hard at it as well. Congratulations on your
success so far.
We moved to an active grate system in our linear design back in early
2010, based on the reality that real world fuels often contained
contamination in the form of small stones or nails which alas defied any
attempt to vaporise them with the wood or mixed sewerage biosolids we
were working with...:) What then originally was a change wrought by the
need to manage a feed stock issue ended in being an incredibly flexible
package and since have been able to make similar observations to your
own over the positive benefits to consistent gas flows over extended
operating hours, lifting the original packed bed limit from 12hrs to
true 24/7 capable without the need to get down and dirty cleaning out
the gasifier every day.
Looking at your excellent report and photo's on your archives page (yes
we have bowed to pressure and are organising someone to do something
similar for our own work, will post a link to list in due course) I note
the flare colours are similar to what we used to get from our early
models, though if the operation was at the 320Nm3/hr level for the
daylight photos then we have to get better gas flow measurements
ourselves as the flare volumes depicted are what we would expect from
the system with the fan at low speed. Perhaps you did not have the
gasifier at full flow when the pictures were taken?
Real world is so much different to what many envision and it was great
to see pictures in a working environment.
Just a clarification: When you talk about air blown you are referring to
the fan forcing air in rather than drawing gas out? We did play with
this at one stage and whilst it looked promising the level of instrument
control required was beyond our skills and resources at the time and
negated our advances in "open core" operation. Though it did make an
interesting Updraft/Downdraft hybrid blowing gas out both ends when the
top lid was opened! I see you have addressed this somewhat with a
divorced feed system via a cross flow auger. We also looked at ram type
plug feeders as a auger alternative, but all these things increase
complexity, cost, maintenance requirements and parasitic electric loads,
the opposite of our core philosophy of KISS. Though we would stress this
in no way negates their validity or value where the situation warrants.
We are now (finally!) moving to a full commercial design suited to ease
of replication, having spent much of the last 2years on this aspect
rather than gasifier operation itself which has been more than
satisfactory. We are now planning the fabrication of a 250kg/hr model
and +500kg/hr model, the former for retro fitting and dual fueling
diesels and the latter for matching to an optimised low btu gas engine
500kWe genset from our new Malaysian partners later this year. The large
throat size again a concession to material handling of lighter mixed
biomass feed stocks rather than a need to build a single module for the
scale of job, who knows what other break through s this change might
lead to?
I know I am occasionally to frustrated in my writings, the negative
experiences with industry peers in the fair land of Oz coloring my
outlook to a degree, but I remain as others have in their long careers,
eternally optimistic that a new age of gasification is dawning, and even
if it isn't we are enjoying the journey anyway!
Cheers,
Peter
On 22/07/2013 4:00 AM, [email protected] wrote:
Operation of Shasta 1 over the annual seasonal changes while hooked up to a
online gas analyzer, highlighted the variations that can be experienced by the
gas making process, some of which are almost impossible to detect, let alone
control. The stability and natural evolution of the packed bed oxidation and
reduction chars has always been considered the most important aspect to our gas
making philosophy, so a new design feature of Shasta Class, is adjustment of
the bed during operation in responce to gas quality changes. Char extraction is
not used in any way to maintain the process, but some char does exit the
reduction zone naturally with soot's entrained in the gas, and the dropped
larger fraction augured out the bottom. The cyclone then removes most of the
char entrained in the gas stream.
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