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'''Three-stage co-current gasifier''' separates the pyrolysis, combustion and gasification (reduction) steps. If all goes well, the result is low-tar gas (20-200 mg / Nm3). '''Overview''' Unlike the classical Imberts in the 1940's or FEMA (tar-makers), this type of reactor can output clean producer gas, but requires automatization with pressure sensors and high-temperature thermocouple sensors. ---- '''Operation modes''' This laboratory gasifier has 4 modes of operation. 3 good, and 1 bad (which gives tarry gas, unavoidable during warmup). http://vems.hu/producergas/images/ThreeStageGasifier/ThreeStageReactor_test_6346_m.jpg Notes: * The air must be preheated. Optimally min 400C or rather 500C. (using the exhaust heat and/or the producer gas heat in production). * this test-reactor is too small for straw, because straw bridges easily ** on the good side, slagging was not a problem even when operating on 100% straw. http://vems.hu/producergas/images/ThreeStageGasifier/Three-Phase-Gasifier_lightningport_airinput_6318_m.jpg At this occasion (not always!), the middle-burner burns even with 15C air input. http://vems.hu/producergas/images/ThreeStageGasifier/MiddleBurnerBurningWith20Cair_6341_m.jpg ---- '''Practical size''' * '''50-1000 kWe''' (200 - 3500 kWth) '''is a practical size for now''' (and multiple reactors can always run in parallel) ** 50 kWe appr 4-5 months (~ 2000 EUR / kWe inside Hungary) ** 250 kWe or bigger (~ 1800 EUR / kWe inside Hungary) on 6-8 months notice. * the smaller 4-20 kWe seems more problematic, eg. more prone to fuel-flow "bridging" problems. ** We hope to deploy at least one 12 kWe test unit for evaluation on a friendly farm in 2011 summer, to collect fuel-bridging and fuel-tolerance experience. ** We do not expect as problem-free operation (or near as good return-of-investment) as with the 50kWe and bigger units. * even smaller 2-4 kWe size is beyond aims for now, but not impossible in far-future Q: what do you use for stoichiometric point with the gas mixture? * '''lambda=1.05''' at peak power ** lambda measured with Bosch LSU4 wideband oxygen sensor and [http://shop.vems.hu/catalog/assembled-controller-p-48.html VEMS v3 controller] from exhaust gas O2 content ** 1.05 is used for for low CO. Lambda near 1.00 or 1.01 would raise CO ppm considerably. ** '''Unlike natural gas, wood-gas (with low tar content) likes high compression without knocking'''. We use max 15 (compression ratio, max volume/min volume) but [http://thompsonspaven.com/ TS] uses up to 19 (yes, nineteen) with near-stoich lambda. ** we use lambdatarget=1.2 at low power. 1.2 to 1.25 definitely burns well, but with reduced peak power (we do not know the exact part-load efficiency numbers, efficiency difference between 1.05 and 1.2 lambda is small) Nice project ( applaus :) '''QUESTION''': We are researching the use of maize/wheat straw gasification cogenerators in farms and small-medium sized businesses. We're very interested in your project. Could you please contact us to discuss the possibilities of buying your system? jean.hupperets(that[a]sign)gmail.com. Thanks in advance! * where are you located ? * electric power rating needed ? * fuel ** fuel size ** fuel moisture content (dry base) * if a naturally aspirated spark-ignition genset is available, all parameters are required ** compression ratio ** displacement, cyl arrangement ** make, model ** it is not guaranteed that it is feasible (and cuts project investment), but chances are good if naturally aspirated ** if genset is turbocharged, we don't recommend using it (it is not impossible though if a ''very experienced'' local turbo-engine expert takes the challange and responsibility to install the safety pressure-relief valve(s) and tune it) As of 2011-09 the 4-stage gasifier base system totals 2940 EUR /kW in EU (230/400V 50Hz) for '''45kWe''' (predrier + reactor + filtering system + genset with accessories and automation) * it does not include the moving-floor fuel-container (or other suitable fuel-container, typically for 3-7 days max-load that is kWe rating * 1.2kg/kWhe * 72 hours) normally made in-place, but includes 2kW hydraulic supply for it. * electricity is required (4kW) to start the plant. Diesel or LPG genset is OK (but not included in the price). * '''minimum system is 30 kWe''' (slightly higher per kW cost than the 45 kW). '''Bigger plants costs less (per kW).''' * we currently do not have any plants in planning stage above 500kWe but bigger plants are feasible * wheat straw is planned for 2012 August ** wheat straw has low ash-melting point that causes problems with many types of devices. According to our tests - in complience with Viking tests in Denmark - (ours with manual feed, as our automatic straw plug-feeder is not ready yet and only feasible for ID > 630mm reactor) these multi-stage gasifiers are not prone to slagging. The char-content prevents ash-fusion at the top of the reactor bed and when the char burns out, temps is lower than 850C and no channeling. * most of our experiments used woodchips as fuel, maize tests (4 cm pieces) are carried out 2011 October. ** For ID>630mm reactors (90kWe) it is safe to assume that maize will work. ID=450 mm ... we don't know yet. Bridging is more likely to be a problem than ash-fusion. We are completing the system (including CE paperwork) with experienced technology partners (who can make even an Imbert type reactor operate reliably, at least with wood-chips) and will make advertisement soon.
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