recent years, the interest in gasification has seen many researchers
trying to set up projects for fuel testing, with equipment that is out
of sync with the realities of applied gasification principles. Bench
top testing of very small amounts of fuel, certainly provides useful
information, but this often cannot be extended to apply to the
realities of gasification on a usable commercial scale.
Small gasifiers are very rare to find from commercial manufactures, especially for raw biomass, as these sizes were proven to be more suited to charcoal fuels, and this project showing the Microlab gasifier, was prepared as a special favour to add a gasification facility to the University of Ulster, Northern Ireland. It is set up to enable the gas to be blown out hot with only cyclonic cleaning, or pass through a separated second cyclone and gas cooling cleaning system that can be used to run an engine of about 1 litre cylinder capacity (at 1500 rpm). As a micro gasification process, the small dimensions behave exactly as the larger systems, but still must conform to fuel specification in relation to the set parameters. As an opportunity to study gasification at this level, it provided me with a rare chance to compare charcoal and wood at a manageable level, and my own research stumbled a few steps forward during the proving trials.
Gasification gives up it's secrets very reluctantly, and it is my hope that this gasifier will assist to provide a new generation of informed people who choose to pursue this technology from an informed base line. Size might create the impression that it is perfect for domestic application, but that will be for others to decide, as a market cannot be developed building these one at a time. Having built this system to meet the evolving expectations of a modern World with regulations etc, it will provide a safe and reliable tool for many years to the students of Ulster University.
Front view showing the cabinet enclosure of all hot components, with basic instrumentation of three manometers and digital thermometer.
|Interior components R-L Gasifier, Blast tube, Twin Cyclones with single soot pot (changed to separate pots later)|
Rear view showing sawdust filter and main gas cooling fan.
|Hot air exit, and air supply hoses to test flare nozzle, which acts as aspirator for suction ignition of hearth module|
|Test flare nozzle, showing hot gas suction aspirator under nozzle actuated with low pressure air, and tangential combustion air into nozzle.|
|Ready for testing inside building, shows that the instrument panel swings around to suit position of operator. Manometer hoses are concealed in pipe support.|
|First time ignition shows the classical incandescent oxidation zone. While this indicates correct temperatures, it is only one factor of making a tar free gas|
|First gas, but camera flash killed the moment, but you can just see it against the back ground of the door.|
|As our day was long, this shot at night shows the test flare burning with all the fine particulate, which due to a glitch, the hot cyclone ejected.|
|The dust ejection was fixed by separating the cyclones from a single soot box, into separated boxes|
|Now free of dust, the test flare has lost the red ting of burning soot. The temperature was pretty steady (+ or - 10C) over all tests at just under 700C.|
|As the first tests were also to test the gas cooling, the dust ejection also went into the condensate resulting in this very black sample.|
|The first black condensate sample is on the left after a couple of days to settle. The sample on the right is after the soot boxes were fitted, and has only been standing one day. Both samples are particles in suspension which will settle out, not toxic black liquor which has hydrocarbons in solution. The brown colour comes from dissolved ash, giving the aqueous condensate a pH of 8.2|
|The fuel for this size of gasifier can be thick small chips, or these sugar lump size sawn and chopped blocks. It is important that the charcoal formed is from a size that can carbonise, oxidize, and reduce as it shrinks in volume, without closing the interstitial space of the packed bed.|
|This final photo shows the char as it changes both volume and size as it passes through each stage of this gasification process.|