Steven, Somehow, your answer is about what I expected. The air you describe is very wet. You would have some latitude for drying feedstock, if the exhaust were very hot, however.
Thanks for making the effort! Mark -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Sunday, December 19, 2010 5:35 AM To: [email protected] Subject: Re: [Gasification] Drying fuel with IC exhause and other pleasures... Hi Guys and Gals, I decided to tackle the relative humidity of exhaust question. The answer I got is that GASOLINE burning IC exhaust is 100% relative humidity at 120F. At 140F it is 60% relative humidity. My analysis is at: http://groups.yahoo.com/group/WoodGas/photos/album/118107394/pic/2025686540/ view?picmode=&mode=tn&order=ordinal&start=41&count=20&dir=asc for everyone to critique/inspect/laugh at. I will try to do the woodgas equivalent tommorow. If you don't have access to this yahoo group, email me and I will send the .jpg image of the writeup. Enjoy. Stephen -----Original Message----- From: Ken Calvert <[email protected]> To: Discussion of biomass pyrolysis and gasification <[email protected]> Sent: Sat, Dec 18, 2010 8:39 pm Subject: Re: [Gasification] Drying fuel with IC exhause and other pleasures... -----Original Message----- From: Ken Calvert <[email protected]> To: Discussion of biomass pyrolysis and gasification <[email protected]> Sent: Sat, Dec 18, 2010 8:39 pm Subject: Re: [Gasification] Drying fuel with IC exhause and other pleasures... Heh! How often do us old timers have to come back on and say, forget about your heorising, and will it or won't it? We have done it! At Onesua Mission High School in the Pacific Isllands of Vanuatu, in the iddleof the first Oil Shock in 1978, we had the boys cutting green Leucaena rush as thick as your wrist and filling a hopper which had the exhaust of a onverted Toyota FJ ute engine driving a 25kva generator piped into the bottom ith more than a couple of flame traps in the exhaust line. Even at 30ft down n insulated exhaust pipe the gas is RED HOT. Dull red, but still hot. It took s three fires to learn that lesson! And there is such a thing as countercurrent' flow! The dryest wood comes out the bottom were the hottest as with the lowest relative humidity is going in! Psychometric charts only nto vogue in the last foot or so near the top of the hopper. And then the main ction is heating the wood, not driving out moisture. 50mm x 50mm Wood blocks dripping-sap and moisture went in the top of the opper and three days later they came out the bottom so dry and so shrunken and racked and shattered that you could pull them apart with your fingers. And hey were so dry that you could light them with a match. Didn't have any oisture meters, or what have you then, but they were dry! If you have read ny of the old literature, during the boom time in producer gas firing, during he second World War, ou will know that with dry fuels there is very little hydrogen around to roduce water vapour with. Burning charcoal alone, the gas is so dry that the as will lick all the oil off the cylinder walls and unless you take extra pecial measures with lubrication you will sieze up your engine very rapidly ndeed. When it comes to wood, there is just the right stoichiometrical amount f water vapour available as the cellulose and other carbohydrates break down rom C6H1206 to CO2 and H20 carbon and water vapour. You do need to add extra ater as steam for coal coke and charcoal, but not for wood, even if it has bsolutely zero water content. But don't let me stop you! Keep talking! Listen o Doug Williams. Hes not as old as me, but he's been there and done that! en C. --- Original Message ----- rom: "Mark Ludlow" <[email protected]> o: "'doug.williams'" <[email protected]>; "'Discussion of biomass yrolysis and gasification'" <[email protected]> ent: Sunday, December 19, 2010 8:07 AM ubject: [Gasification] Drying fuel with IC exhause and other pleasures... If the IC exhaust is saturated at 100C, the best the wood can do is reach an equilibrium moisture content with respect to this environment. Best check a psychrometric chart to convince yourself. It's the partial pressure of water in the exhaust that will, ultimately, inhibit drying, even though if the feedstock is cooler that the I.C. exhaust, some heat may be transferred to it via condensation on its surface. One simply need to know the dewpoint of the exhaust gas to determine whether or not this is a fool's errand. Flush a Pyrex Erlenmeyer flask with exhaust and fit a stopper with a penetration for an RTD and observe the temperature of condensation, as a first approximation, and observe the water-carrying capacity along the line of constant water. This is not 100% accurate, of course, because the specific volume of the gas will change as it cools. Plus, if the dryer is "direct" the gas will quickly mix with surrounding air. What about home-made heat pipes? I use the commercial versions for sensible heat extraction on industrial heat pump systems. Best, Mark -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of doug.williams Sent: Saturday, December 18, 2010 10:29 AM To: Discussion of biomass pyrolysis and gasification Subject: Re: [Gasification] Gasifiers and greenhouses and CO2 augmentation. Hi Toby and Colleagues, You ask a couple of curly questions: >We seem to have moved on from the direct heating (drying) of fuel without really answering the original question of water content in IC exhaust. I understand the indirect heating, like Doug's >nearly horizontal heat exchanger, but what about the direct introduction of engine exhaust gas for drying incoming fuel? Of course not all H2 is converted into H2O in an IC engine, but one >would hope a significant portion is. Same with CO and CO2. If 15% is H2, is 15% of the exhaust water vapor? I am sure there are equations that will confirm a "perfect" answer, other than mine, which is more H2, more water vapour. So long as the gas is hotter than 100C, wood can be dried down without any problems by direct contact. >Has anyone tried putting a producer gas fired engine exhaust directly into a stock of wood fuel? You have possibly missed the exchanges of discussing direct exhaust heat into a fuel pile to make torrified wood. Ken Calvert specifically used this to overcome the problems of gasification in the tropics, and I had to use it in Papua New Guinea just to get enough dry fuel to start a gasification project for the first time. We also used it on our first project back in 1978 in New Zealand, resulting in the wood blocks catching fire as we learnt the hard way, gaining experience. It's as simple as a drum with a gas space in the bottom, connected to the exhaust as close to the engine as possible to reduce heat loss. It's best to try it and learn by experience if it is for you, but, I would not want to promote this type of direct drying, for anything commercial. >One final thought on greenhouse. Engine exhaust would presumably make most of the CO into CO2 (but not all) and H2 into H2O, benefiting the plants. Without question, it has been already established, that using producer gas through an engine without first scrubbing the gas, could place the crop at risk. I do however see a lot of potential to used scrubbed and compressed CO2, used in a system of micro-porous support tubing to control white fly and aphids. >This would seem to be an argument for having not only a gasifier, but an engine or combustor in greenhouse application. That is how it might appear, but there is very little demonstrated and tested using producer gas to support any argument. >But is there any way to assure a safe level of CO for direct exhaust into a greenhouse? Does it rise or fall in a collum or can one assure a complete reaction in some way? Issues of CO and human safety usually resort to badge monitoring for the individual. Plants however only thrive, I have been advised, in a 10% CO2 atmosphere. I cannot imagine it piling up as layered slug of inert gas, as the greenhouse should have a circulation capability if heated. Not sure what you mean by a complete reaction. Does this help or hinder? Doug Williams, Fluidyne. _______________________________________________ The Gasification list has moved to [email protected] - please update your email contacts to reflect the change. Please visit http://info.bioenergylists.org for more news on the list move. Thank you, Gasification Administrator _______________________________________________ The Gasification list has moved to [email protected] - please update your email contacts to reflect he change. Please visit http://info.bioenergylists.org for more news on the list move. Thank you, Gasification Administrator ______________________________________________ he Gasification list has moved to [email protected] - please update your email contacts to reflect he change. lease visit http://info.bioenergylists.org for more news on the list move. hank you, asification Administrator _______________________________________________ The Gasification list has moved to [email protected] - please update your email contacts to reflect the change. Please visit http://info.bioenergylists.org for more news on the list move. Thank you, Gasification Administrator _______________________________________________ The Gasification list has moved to [email protected] - please update your email contacts to reflect the change. Please visit http://info.bioenergylists.org for more news on the list move. Thank you, Gasification Administrator
