Dear Andrew To me this a kiss of the death. I started my carier developing screew pyrolysis units at the technical universty of Copenhagen for two purposes - one the Viking gasifier - 2 a starw pyrolysis unit. 1. It is limited in temperature bedause of material limitations in the steel - 2. It is limited in capacity due to heat tarnsfer limitations om both sides 3. It is hot mowing part inside that has a limited lifetime due to reduced strenght 4. Everywhere you cool eg for bearings tar condenses and cause problems. 1. Maks temperature on the steel plate is 600 oC if you expect life times of years even for soem of the most expensive types of refracotory metals. The consequense of that is that mea temperatue inside the biomass will be well below 600 oC having the consequense that almost no gasification takes place. 2. Energy transfer is in the order of 3-4 KW/m2 havinf the consequense that you can pyrolyse 5-10 kg pr hour pr m3 at a mean temperature of 500 oC - thus a Range fuel pyrolyser should have been 4-800 m2 to PYROLYSE (not gasifiy) 4000 kg pr hours. Assuming this made of a 600 mm pipe with a screew inside it is a 2-400 meter long pipe !!! - imagine the termal stresses in such a construction - and even worse thermal transients!! 3. Imagine 18 pipes in series stacked on top of each other you feed into the top and it falls in to the pipe below - each equipped with a screew and 36 - 36 pressurised axel sealings!! and 18 drive mechanisms!! The maintenance cost will far exeed the income from each line in a commercial market 4. Tars are not easy to handle Here in Denmark we have designed 2 real staged gasifiers one is the Viking and the other is the TKE 3 stage gasifier. The Viking has a screew pyrolyser very similar to the one that Range use. The TKE gasifier uses an internally heated plug pyrolyser. The reason the I went a way from the Screew pyrolyser was that i could 1. Not see how upscale it 2. Not see hw to make a safety approval 3. See too high maintenance costs But for both gasifiers electricity made from biomass cost s around 50-75 cent US pr kWh in a 3-800 KW gasifier. The answer to your last question is -- YES Best regards Thomas Koch www.tke.dk
________________________________ Fra: [email protected] på vegne af andrew schofield Sendt: on 26-01-2011 05:25 Til: [email protected] Emne: Re: [Gasification] Range Fuels Closing Plant Dear Thomas Koch, How much of a problem for the scaled up Range Fuels plant, was heat transfer from the hot fluid outside the auger-tubes to the celluose inside each parallel screw-tube? we gather a hint of the problem from your description, and Range Fuels needing to consult you about your experience with hot-fluid jacketed screw-pyrolizers. Dr Reed said he saw the liquid fuel process working at small scale. May I guess this success was with a jacketed single-screw? Inside the radiation, and convection sections of water-tube boilers steel surface temperatures can vary widely, as water vigorously circulates inside. Water, being more fluid than wood chips screwing along in a tube, keeps steel temperature within certain limits throughout the entire boiler setting. May we use this analogy to describe one problem experienced with Range Fuels attempt at system scale up? A culinary anology for heat-jacketed auger-tubes is stir-frying vegitables in a Chinese wok. The chef adroitly presents new surfaces of the food to the hot steel to transfer heat by conduction. The chef can only make a batch of food under a certain size. Size beyond which he may choose to use a pressure cooker which can feed an army. Would not direct-contact heat exchange between the hot fluid, and the wood be more practical at 4 ton/hr? Andrew Schofield Renewable Fuel Systems Thomas Koch wrote: Tom Range fuel gasification technology was an externally heated pressuries pipe with a transport screew inside when I saw it. It was very similar to the pyrolysis unit on the wiking gasifier but they had ideas to upscale it to 4 tons pr hour by stacking pipes with screew conveyers. Thinking of the challenges of making the 1 tons pr hour screew pyrolyser in Haslev i have doubts this principle will ever be competitive for energy production - even for atmospherich applications. Thomas Koch From: Thomas Reed <[email protected]> I attended a few of the formative meetings of Range Fuels back about 2007 when I lived in Denver. I have known Bud Klepper since about 1988 when we worked together on a methanol project. Too bad that many $millions couldn't solve at a large scale what Bud had solved at a small scale. Tom Reed, Pyrologist Jim of All Power Labs wrote: thomas, why did you think a stacked array of skinny auger retorts won't work? this seems a known solution that tends to work as far as i know. of course the proof is in the material handling with specific fuels. did you find it difficult to keep the auger straight and working? difficult to keep the heat out of the motor and bearings at the ends? any secret cautionary tales we should know of? jim
_______________________________________________ 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/
