Hi GF, This is the only time I have over the next few days to myself, and it is nice to be guilt free to peck away at these discussions. Unfortunately, I cannot access the book you referred until my son becomes available to "join me up". He wants to ensure I don't link to anything that invites more junk into the mail box.
>I can appreciate the inconvenience of metering steam to the "reaction zone" on >modern setups. With gasification development, you can do whatever you wish if you have the resources, the only limitation being, some sound base line of performance that you work from to improve the outputs. >Even so, there is a deficiency in monitoring the quality of gas produced >during a run. other than listening to noises from the engine. I would agree with the difficulty of seeing gas quality change as they happen, but for most, the engine and output, is the only guide most have available. Unless you are in a situation that demands qualified results, you can certainly in a DIY project, tell a lot from the gas flares, by how easily they ignite with a flint gun, the sound of the poof when they are lit, the temperature of the flare, radiance and colour. >This book mentions the distillation of "wood waste" together with the >exceptable moisture content of the raw fuel."biomass". >There was however, NO reference to utilizing the "Exhaust & waste heat" from >the the ICE. >The steam was obtained from heat generated by the hot gas leaving the >"Reaction Zone" For us as a group, the variations of gasifier design and the resulting experiences, can bring our thinking and individual understanding, into sharp conflict at times. In saying that, some facts do apply that affect all our designs. The gas temperature leaving the "reaction zone" at a point where the gas making stops, or reduction slows to a point where the reduction carbon no longer shrinks in size, is around 800-850C. If the gas continues through deeper char beds, the temperature plunges quickly, so if you wish to tap this steam raising potential at it's best, it has to be adjacent to this area of the design. If there is a problem, it has to be the choice and cost of the material you use as a steam generator. This year we have been using this high temperature to pre-heat our incoming air to the oxidation zone, and I see the run on the 21 December 2010, the air gradually built up to 350C. This heat exchangers tubes, are directly in the blast of the exiting gas, and being made of steel, really stress out in such high temperatures (850-1,000C). There is a price and servicing cost to all good ideas, and you need to prove that the benefits out- weigh the costs. In our case, we saw an improvement to the H2 and CO content, but you can write a book on the behaviour of the char evolution. and the side issues of keeping the bed within operational parameters (:-) >The reclamation of heat from the engine was probably not worth the trouble as >these long stroke engines were renowned for efficiency, their exhaust >temperatures being far lower than that of >the modern "Square engine",and were >probably sited several buildings away. There seems to be no reference to the >temperature expectations here. This probably is due to the system being discussed, but I have several historical papers showing engine exhaust wood block dryers in the files. >Your reference to "the inconvenience" of reclaiming ICE exhaust heat is surely >a design failure. I read what I last wrote to you, and didn't say that at all, but it might be something referred to, or taken out of context. If you are talking stationary engines, the distance to the engine from the gasifier can steal the benefits, not all engines can be close coupled. Exhaust heat I said was easy to be in awe of, because it's there for free in very large quantities, and you just need ways to use it in your particular situation. >There has been a lot said about moisture content of raw fuel on recent >contributions,would you not agree that the temperature of the reaction zone >becomes lowered by wet fuel ,due to the >endothermic effect of "to much water" >being present, leading to gas of deficient quality and tar?. The short answer is yes, but first define "to much water". Most traditional designs state that 15% MC acceptable as a standard for biomass. Literature is full of fuel moisture references, but be careful of taking them as gospel. >If so, additional heat needs to be applied to this area in order to convert >the "water trapped within the fuel" in to super heated steam, just before >being drawn through the "reaction zone". Speaking for myself, I can see no way of making super heated steam out of trapped water in a conventional gasifier. You don't specify which reaction zone you are referring, but getting the heat into the fuel mass is not as easy as one might think, unless the extra heat flows through the fuel. You cannot transfer small dimensional heating experiences into larger scale gas making either, as the fuel can become it's own best insulation. There can be no single answer, but I am sure you get the drift, unless your thinking is coming from a more innovative direction. >Perhaps we should consider the ICE as the primary provider of heat for >pyrolization, and build the gasifier around it. Isn't this where we came from, more or less with this discussion? Get the water out of the fuel before it goes into the gasifier and keep it simple. Gone for my afternoon holiday nap. Happy Holidays. Doug Williams. Hi GF, There has to be a minute available to make comment on this subject; > I found the information quite enlightening in The Linsay Publication Issue > > of: > “Gas Engine& producer Gas Plants” By R.E.Mathot. > This book describes various systems of early gasification processes. > There was one item which seems to have been neglected in the construction > > of the modern equivalents. > It played an important role on “Pressure” gasifiers and was also included > > on “suction systems of many types. > The enrichment of the gas produced by cracking water was highly valued; > > notes are included of BTU improvement of gas quality, using calorimeters. > The inclusion of the VAPORIZER seems to be of little importance today. Without splitting hairs, most of those historic gasifiers were coal or charcoal, to which the addition of steam improved their gas quality. Biomass gasification based on more recent experience, shows it is not required. You can of course find exceptions to this rule of thumb, where-by, the very dry dead wood of ring barked eucalyptus in Australia, did work better if a bit of steam was added. Steam works best into incandescent carbon beds. Our modern gasification technologies separate steam gasification into the pressurized Syngas plants which we all know is far superior in BTU content, compared to producer gas. While many working with gasifiers describe their work making "syngas", it is in fact fraudulent to do so, when the difference is like night and day. > With the high exhaust temperatures of gasifier fuelled ICE combos > It would be a simple modification to wrap a few turns of metal tube around > > the exhaust manifold and meter water according to demand, there through > and > conduct said flow of >super heated steam to the reaction area of the > > gasifier. This is a description of how Brisbane Taxi drivers in the 1940's improved their engine performance on rationed gasoline. Mobile gasifiers are usually mounted some distance from the engine, and if charcoal, which is the smallest and lightest choice of gasifiers design is used, then heat losses are not an issue, but need the addition of steam to provide H2. > In this way it would be possible to claim some waste heat from the engine > > and use it to cancel out the endothermic losses of the FT reaction. I am not sure if you are still talking gasification or liquid fuels with this comment, but it is easy to be in awe of the waste heat from engines. Doug Williams. _______________________________________________ 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
