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The workshop weekend was great fun and good learning as usual– and this time with a gasifier-genset running through the whole event.  Thank you again to all who joined us, and for the many new friends that came out of the process.  The full gallery of the weekend is here:

Longest distance award this time goes to Abau who flew in all the way from the Congo, and flew back with many plans for gasification in central Africa.  The most interesting new contributors were Kyoung Ro with his talk on animal manure biochars and Devinder Mahajan for his survey of liquification pathways and related liquification technology.  Mixing in talks during Saturday and Sunday building/running was a great addition, which we’ll continue.


In terms of hands-on activities, we had a very successful two day run of the GEK Power Pallet gasifier-genset.  The details are below.  The BEK biochar unit ran cleanly and interestingly for much of Sunday afternoon.  Alex brought a pelletizing machine and densified most everything found to be loose.  Walt and Opalyn separated oxygen from air with a presssure swing absorption unit.  Lots of learning time too on a standalone GEK, with flare burning to grilled cheese sandwiches out.

GEK Power Pallet Endurance Runs

We ran the Power Pallet for two 10+hour days over the weekend.  This followed two similar days of 10 hours total at the Maker’s Faire two weeks previously.  Thus we actually put a total of about 30 hours over 4 days on the rig before the teardown pictures shown below.

We’re very pleased to report that things ran wonderfully both weekends.  We ran common wood chips in, to varied electricity out, with fully automated hands-off operation.  Mixture and grate shaking were controlled by the GCU, as well as all temps, pressures and particulars of electricity produced monitored and logged.

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A tear down after the two weekends showed tar production to be minimal, with still clean gas tubes and engine filter after the long run.  This includes about 5 hours on the workshop Sunday running between 1 – 1.5kw– a pull rate well below what a gasifier will usually tolerate.

It appears the TOTTI architecture is in fact doing what was intended, and the thermal augmentation is extending downward the minimum pull rate for good tar conversion and clean running.  We ran for hours and hours at “Lister-like” pull rates, and the gas stayed clean.

Here’s s photo gallery of the conditions inside the reactor, filters and engine after the 30 hours: Notice the clean filter element and filter housing on the engine.  There is no tar or soot deposition.  Yes, there is some mild darkening of the filter from condensate– but for a gasifier, this is a white table cloth. . . 😉   These results were achieved with no exotic filtration, only a single stage packed bed filter, filled with wood chips and sawdust.

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These are the pleasures won by solving the tar problem in the reactor, not just transferring it downstream to expensive and complicated filtering.  Producing clean gas in the reactor also also keeps your heat transfer surfaces, cyclone, and general distribution tubes clean too.  Notice the toasty brown air preheating ss tubes around the reactor.  There is no soot or crust build up on the air preheating lines.  Similarly the inside of the cyclone and tube to the filter are only mildly soot covered.


Later in the summer we’ll be doing more testing and datalogging to document the numbers of this thermal recycling system.   The logic of why, what and how we are doing it is explained in the Tower of Total Thermal Integration info here:  But for now, the pleasing takeaway is that we are in fact solving the tar problem in the reactor, and not relying on either a large filter train to cover sins, or a large fuel prep system to support a fussy reactor.

Yes, there is in fact a better way to peel the onion of small scale biomass thermal conversion.  And the result makes possible a small and compact total system like the Power Pallet.

Things Learned and What to Improve Next:

1. Check your plugs and caps for tightness:

On Saturday of the workshop we had an air leak soon after startup, which was combusting some of the gas by the grate.  We shut down and found we forgot to tighten one of the ash port plugs.  Doh!.  Remember, always put your bilge plug in before launching your boat . . .

2. Follow Calibration Maintenance on wide band O2 sensor:

Late Sunday the mixture started wandering and the engine died.  We fussed a bit, reread the O2 sensor manual, and realized we were supposed to recalibrate it after a few hours of first running and burn in.  This was a new O2 sensor and we were near 30 hours without doing so.  The one time recalibration is easy– hold the sensor in open air and press the button on its control box.  Once we did, it went back to its regular smooth operation.

3. Screen out large chips:

The first day of Maker’s Faire we had one bridge caused by a 6″ long wood chip.  Actually, it wasn’t really a bridge, but rather a wedge that stuck the fuel level switch and prevented the auger from operating.  Somehow this long piece made it through our chip screening.   Watch out for unusually out of spec chips.  Otherwise, we had zero mechanical bridges over the two weekends.  Solving bridging issues for consistent fuel flow has been a big challenge over the last two years.  At times, it has seemed more worrying than the tar challenge.  We’ve done quite a bit of testing on this lately, with some deeply interesting revelations.  I presented the details on the learning at the workshop.  I’ll write it up soon and post it to the wiki for others having problems in these parts.  What we’ve learned is incorporated into all current GEKs and can be backward installed into older GEKs.

An added treat of the workshop was Tom Jopson showing up with a real time gas analysis rig.  We of course hooked it up to the GEK, sampling the gas after the filter, and found the following.  This is with the GEK in TOTTI form, pulled around 8″ of h2o vac at the reactor.  These numbers wandered a percentage point or so up or down, but were surprisingly stable.  Tom believed his machine to be well calibrated, but we did not have any reference onsite to confirm the readings.

CO-     22.5%
H2-     19.5%
CH4-   2.4%
CO2-   9.5%
O2-     1.3%

All this adds up to our being happy.  We’re well over the main hurdle of an integrated and automated small scale gasifier-genset.  Details will continue to refine and improve, but we’ve successfully arrived at the main goal– an advanced and realistic to use biomass-to-energy system, for $1-$2/watt.


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