Hi Peter and Colleagues, As it happens, my work this last few months has been pretty involved around these packed beds and charcoal, so naturally I am focus on how these differing systems work.
On Fri, 14 Mar 2014 09:48:15 +1100 Peter Davies <[email protected]> wrote: > Thanks Doug, given the level of prior art reinventing the wheel is an > occupational hazard. Yes we have observed what you describe, the point > of differentiation though is where we were starting on straight (dry) > wood chips each run rather than charcoal from the previous run. The key thing about all these systems is what your main need is from the process. If you were planning on running an engine, then no way do you start-up on raw fuel, as it will contaminate your gas cleaning system with tar. Process heat and charcoal however is different, unless you have a blown system. >It became clear that substantial improvements in gas calorific value and > useful volume were possible that we seemed to be missing out on. Naturally raw fuel will always create high calorific gas, due to the pyrolysis gases tar chemistry, and no oxidizing charcoal to create the necessary exothermic heat, so you end up with a low temperature bed, higher carbon content to the char, and a rich gas to burn in a furnace. It was > study of this that led to the refinements in design we now enjoy the > benefits of. As it may be of interest to others that, when you mix the phenomena of low temperature packed beds with charcoal extraction, the raw chip is only torrified, charred on the outside, raw on the inside. The low temperatures are around say, <900C without free oxygen and a reducing atmosphere, enough to char and make crude gas, as the hydrocarbon content is still locked inside. As the chip drops, the 900C gas flow sets the conditions that fix the hydrocarbons, hence the better char. If you want to improve the gas quality, because it will be low in H2 but have CO,CH4,C2H5/6 from being low temperature distillation gases released from the surface charring, you need a deeper bed to increase the contact time, BUUUT, if you do this, you begin to initiate CO reversion into soot and CO2 while the bed is above 500C Then if your char extraction rate is not quite right, you can also get H2 reversion and are back to mediocre gas. Peter has obviously sorted this out, but more than a few are chasing shadows for the wrong reason. I heard a whisper that there is a failed gasifier project in Sydney Australia, supplied from a USA manufacturer. Can anyone of our Forum members offer more comment about this project? Doug Williams, Fluidyne. > > Cheers, > Peter _______________________________________________ Gasification mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org for more Gasifiers, News and Information see our web site: http://gasifiers.bioenergylists.org/
