Dear Stephan and all I agree with Stephen that the practical aspects of operating suction or pressure gasifiers are major. I only wanted to say that the actual pressure inside the gasifier is very close to 1 atmosphere, no matter which mode you run.
In suction mode, any leak brings air into the system and may actually burn a small amount of gas if there is a source of ignition. Otherwise, small leaks don't matter. In Pressure mode, a small leak can be seen and smelled, so even a suction gasifier can be tested by putting a positive pressure pulse on it to test for leaks. I suppose all of this was common knowledge in the 1940s when a million cars were operated on Woodgas. Now we need to re-learn these quirks. Thomas B Reed Woodgas.com On Mar 19, 2012, at 6:41 AM, [email protected] wrote: > Luke, > > I am going to challenge the statement that pressure vs. suction is the same > thing. I thought the same thing three years ago, but after running my > machine in both modes I've come to the conclusion that it's just not true. I > now think of the flows going into the nozzles like a rope. If you push a > rope into the machine until it come out the exit flange it's going to go in, > bunch up, pack up, and go in many different directions before finally > exiting. From a flow standpoint it will be a mess. > > If you run the machine under suction, it's like pulling the rope through the > machine from the exit flange. Everything is straight, smooth, and directed > toward the exit. The result is that the pyrolysis zone is thinner and there > are fewer up drafts carrying heat up into the fuel hopper. The thinner > pyrolysis zone means that there is less tar for the available oxygen to > incinerate(or "crack" if you like that theory) so everything runs cleaner. > > When I used to run my machine under pressure I would see a "sea" of flammable > thick tar gas in the hopper when I would refuel it. Now under suction I > don't see any smoke in the hopper. > > Just my experiences. > > Stephen Abbadessa > -----Original Message----- > From: Luke Gardner <[email protected]> > To: Discussion of biomass pyrolysis and gasification > <[email protected]> > Sent: Sun, Mar 18, 2012 10:22 pm > Subject: Re: [Gasification] On the subject of H2 and O (was N2 removal) > > Greg, > I don't have a lot of time today, but I have been loosely following along, > and I Can't help but wonder if things might not be a little easier to > understand if a Guy stops thinking in temperature and pressure, and started > thinking about the material of discussion in terms of its kinetic energy. > 14.7, or 101.325 aren't magical universal pivot points that natural laws > swing upon, "normal" Air pressure, isn't hardly ever " normal" at all. It > is as much a figment of our human imagination as monday, or leap day, or > the millenium. The only difference between a "suction" and "pressure" > gasifier is a few PSI and your point of view. > resectfully, > Luke > > -----Original Message----- > From: Greg Manning > Sent: Sunday, March 18, 2012 12:30 PM > To: Discussion of biomass pyrolysis and gasification > Subject: Re: [Gasification] On the subject of H2 and O (was N2 removal) > > meant NOT at a great amount (as in very small) sorry all. > > G. > > On Sun, Mar 18, 2012 at 2:26 PM, Greg Manning <[email protected]> wrote: > > KELBURN, > > > > THANK YOU ! > > > > This is the EXACT thing I needed to see.... proves my point, EXACTLY. > > > > I am now of the firm beleif that we CAN (And DO) water gas shift in > > suction type gasifiers, where as, blown (pressureized) gasifiers can > > NOT do W/G shift. > > > > I think the W/G shift is at a great amount, BUT, it sure proves my > > caclulations, almost dead on. > > > > Thank you Thank you Thank you Thank you > > > > Greg > > > > > > > > On Sun, Mar 18, 2012 at 12:14 PM, Kelburn Koontz <[email protected]> > > wrote: > >> Making Ice with Vacuum > >> http://www.youtube.com/watch?v=pOYgdQp4euc > >> > >> Check out the ideal gas law. > >> > >> Thanks, > >> Kel > >> > >> > >> On Sun, 2012-03-18 at 08:10 -0700, Mark Ludlow wrote: > >>> “The steam produced in cavitation is like putting water in a bell jar > >>> and pulling a vacuum. If there is enough vacuum the water will boil, > >>> converting it's temperature into energy for the phase change. > >>> Eventually you end up with a chunk of ice in the bell jar.” > >>> > >>> > >>> > >>> Not so! Not enough latent heat is lost. Sensible heat must be removed > >>> also. In outer space, where there are huge radiative heat losses this > >>> applies. If folks could make ice with simple vacuum pumps, who would > >>> mess with refrigeration? It takes energy to evaporate water, not just > >>> vacuum. > >>> > >>> > >>> > >>> Plus, when a gas is adsorbed onto a sieve, energy is released. It > >>> takes the same energy (and then some) to regenerate the sieves. No > >>> free lunch; no where. > >>> > >>> > >>> > >>> > >>> > >>> From: [email protected] > >>> [mailto:[email protected]] On Behalf Of > >>> [email protected] > >>> Sent: Sunday, March 18, 2012 7:55 AM > >>> To: [email protected] > >>> Subject: Re: [Gasification] On the subject of H2 and O (was N2 > >>> removal) > >>> > >>> > >>> > >>> Hi Greg, > >>> > >>> > >>> > >>> > >>> > >>> Sure. Let's to a simple example so my feeble mind can follow it. > >>> When I drop cold chips in my gasifier there is some moisture content > >>> in the chips...this is liquid water in the wood cells. As the chips > >>> burn down into the hearth they get hot and the water changes to steam. > >>> This phase change absorbs some amount of energy. Then as the steam > >>> goes through the char, some of it does the water gas shift if there is > >>> enough heat. This absorbs even more energy. The remaining steam ends > >>> up as condensate in the cooler. > >>> > >>> > >>> > >>> > >>> > >>> The steam produced in cavitation is like putting water in a bell jar > >>> and pulling a vacuum. If there is enough vacuum the water will boil, > >>> converting it's temperature into energy for the phase change. > >>> Eventually you end up with a chunk of ice in the bell jar. > >>> > >>> > >>> > >>> > >>> > >>> The water gas shift will not happen in the phase change because there > >>> isn't sufficient activation energy availble to make the reaction go. > >>> If it did work that way, there would be hydrogen bubbles coming off > >>> boat propellers. That would make a COOL rooster tail! > >>> > >>> > >>> > >>> > >>> > >>> Gasifiers do not run a low enough pressure to vaporize the water, like > >>> the bell jar. I can get the numbers if you want, but you need to be > >>> in -13psi range. That's way more than we pull. > >>> > >>> > >>> > >>> > >>> > >>> Any clearer or still muddy?? > >>> > >>> > >>> > >>> > >>> > >>> Stephen > >>> > >>> > >>> -----Original Message----- > >>> From: Greg Manning <[email protected]> > >>> To: Discussion of biomass pyrolysis and gasification > >>> <[email protected]> > >>> Sent: Sun, Mar 18, 2012 10:09 am > >>> Subject: Re: [Gasification] On the subject of H2 and O (was N2 > >>> removal) > >>> > >>> Hi Stephen, thanks for the reply. > >>> > >>> OK, I somewhat understand you, BUT, wouldn't water be doing a phase > >>> change in the core of a gasifier as well ? > >>> > >>> What I was getting at, is if steam is produced in cavitation in cold > >>> water, then wouldn't the shift effect also happen within the core > >>> during phase transition (from water as a liquid, to water as a vapor, > >>> when heated by the core) within the same boundaries of effect as water > >>> to steam in the trailing edge of a propeller ? (all of these > >>> situations involve lower that normal pressure zones). > >>> > >>> Aren't contrails produced in water vapor on the wing tips of an > >>> airplane because of this same pressure drop phase shift, causing a > >>> dew-point change? > >>> > >>> The core of most gasifiers runs in a dynamic lower than atmospheric > >>> pressure ( a very low internal barometric pressure) (suction based > >>> units), so the same shifts should apply during phase transition, > >>> shouldn't they ? > >>> > >>> I understand that a pressure fed gasifier would behave differently > >>> (and I've personally observed this) than a suction based one, I'm > >>> speaking about suction based gasifiers. > >>> > >>> Somewhat lost, > >>> Greg > >>> > >>> > >>> On Sun, Mar 18, 2012 at 8:26 AM, <[email protected]> wrote: > >>> > Greg, > >>> > > >>> > The energy doesn't change. The bond energy in the water is constant > >>> > regardless of pressure. > >>> > > >>> > The cavitation issue is different. It is a phase change phenomenon, > >>> > not a > >>> > chemical change one. > >>> > > >>> > Stephen > >>> > -----Original Message----- > >>> > From: Greg Manning <[email protected]> > >>> > To: Discussion of biomass pyrolysis and gasification > >>> > <[email protected]> > >>> > Sent: Sun, Mar 18, 2012 9:02 am > >>> > Subject: [Gasification] On the subject of H2 and O (was N2 removal) > >>> > > >>> > Greetings List. > >>> > Since we are speaking input air, I thought I might ask a somewhat > >>> > related question. > >>> > Water gas shift. I know there are many that have talked about this, > >>> > and I understand the basics. > >>> > However, here is the question. > >>> > At what negative pressure ( negative in/wc) does the shift move down > >>> > the temperature scale, to the point of being within the 1000 - 1200 c > >>> > area ? > >>> > We all know that propeller cavitation produces steam in water that is > >>> > 10 c (or there abouts), I have to assume (not being a chemist) that > >>> > the same negative pressure effect would also apply to other principals > >>> > when dealing with water. > >>> > -- > >>> > Regards, > >>> > Greg Manning, > >>> > Brandon, Manitoba, Canada > >>> > _______________________________________________ > >>> > 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/ > >>> > > >>> > > >>> > _______________________________________________ > >>> > 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/ > >>> > > >>> > >>> > >>> > >>> -- > >>> Regards, > >>> > >>> Greg Manning, > >>> Brandon, Manitoba, Canada > >>> > >>> _______________________________________________ > >>> 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/ > >>> _______________________________________________ > >>> 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/ > >> > >> > >> > >> _______________________________________________ > >> 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/ > > > > > > > > -- > > Regards, > > > > Greg Manning, > > Brandon, Manitoba, Canada > > > > -- > Regards, > > Greg Manning, > Brandon, Manitoba, Canada > > _______________________________________________ > 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/ > > > _______________________________________________ > 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/ > _______________________________________________ > 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/
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