<div dir="ltr">Hi Julien and All,<div><br></div><div>Any serious researcher is welcome to come to the Aprovecho lab and pursue the open source description of natural draft TLUD operation. We have a nice dorm room, hot lunches, good coffee and offer a stipend of $500/month. I think a minimum of three months would result in some good data but six months (or more) would be better. Scientific investigation can be tedious but, as you say, it's very much needed.</div><div><br></div><div>We're doing an Open House the week after ETHOS again (January 27-29) and it would be a good time to look at our lab and talk to the staff.</div><div><br></div><div>All Best,</div><div><br></div><div>Dean<br><div><br></div><div><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Dec 14, 2014 at 3:17 PM, Julien Winter <span dir="ltr"><<a href="mailto:winter.julien@gmail.com" target="_blank">winter.julien@gmail.com</a>></span> wrote:<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>Dear Crispin et al;</div><div><br clear="all">It would be nice if I had some good gear for my experiments, but what I used was sufficient for my purpose. I need to get some very basic performance characteristics for a natural draft, top-lit updraft gasifier (ND-TLUD). </div><div><br></div><div>The take-home message from my graphs is just how sensitive the reaction is to small alterations of primary air at low rates. Anybody designing a ND-TLUD will see that the knob that adjusts primary air should move a manageable distance to regulate primary air at low to nil rates. As for people who want to make biochar, or use the reactor as manufacturing furnace, for the first time there is publically available observations on what temperatures to expect when gasifying softwood pellets.</div><div><br></div><div>What I used for this research is (1) a scale to measure fuel and char, (2) an overhead scale to measure mass loss during gasification, (3) a four channel thermocouple data logger, and (4) an oven I can hold to 105°C to measure fuel moisture content. For unfunded, recreational research, that is not bad. </div><div><br></div><div>What would have been the biggest improvement for my experiment would be to set-up a more sophisticated method of feeding primary air, and measuring the primary air superficial velocity (SV). Expressing my results in terms of grate aperture is very useful for TLUD design, but SV would have allowed me to compare directly my results to published papers on FD-TLUDs. If I had SV, for the first time, we would have known exactly were ND-TLUDs lie on the range of primary air flow rates for top lit gasifiers and combustors. For research on gas burners, the flow rate of secondary air and monitoring emissions are important. Gear like that needs a full-time laboratory.</div><div><br></div><div>As for trying to explain my observations, just about all explanations for ND-TLUDs are speculative, because ND-TLUD SCIENCE DOES NOT EXIST. There are at least 50 peer-reviewed papers on 'FD-TLUDs' dating back to 1947. No all of them are appropriate to cookstoves, but a lot of them are. For ND-TLUDs there is nothing. </div><div><br></div><div>For the moment, that means that my graph showing the regression of temperature on specific gasification rate is there mostly for "gee-wiz, that is a high R²." If someone was burning softwood pellets, and knew their gasification rate, they could estimate the temperature. If this kind of regression is common across fuels, then it will beg an explanation. </div><div><br></div><div>For now what we need are some very basic empirical studies on ND-TLUD performance, so that builders of stoves can make more deliberate decisions, so that rural extension workers can have confidence that their advise is well-grounded, and so that both can respond effectively to unexpected situations.</div><div><br></div><div>We need to start building ND-TLUD science at a very basic empirical level. Nobody has actually measured primary and secondary air flow, so nobody really knows the their optimum proportions for low emissions and how that changes with gasification temperature, types of burner and fuel. Nobody has actually proven that preheating secondary air is effective; it is just assumed to work, even though we are taking heat from the reactor to create more viscous and less dense air. If preheating makes no difference, then it becomes easier to design the gas burner and the gasification reactor as separate modules, that are mixed and matched according to need. Nobody has shown that TLUD biochar has safe levels of polycyclic aromatic hydrocarbon and dioxins. All this, and more, needs clarification in replicated, controlled experiments ... and open access publication.</div><div><br></div><div>Cheers,</div><div>Julien.<span class="HOEnZb"><font color="#888888"><br>-- <br></font></span></div><span class="HOEnZb"><font color="#888888"><div><div dir="ltr">Julien Winter<br>Cobourg, ON, CANADA<br></div></div>
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