this last test programme for 2009, 23rd November- 3rd December, the Mk6
Andes Class gasifier was prepared for the final phase of gas analysis
across it's operating range, and stability check of the gas making
within each changed increment of output . Unfortunately, the built to
order gas analyser was not delivered on time, which highlights the difficulty
of working to a schedule, when other companies fail to perform to the
expectations they themselves provide. It was possible however to use
the electrical frequency meter of the engine electrical generation, to
observe the gas stability under variable load conditions, which later
will be used to correlate against gas analysis in real time.
results from the August tests were mainly focused on the maximum gas
flow potential, and how the first stage gas cooling design performed as
a integral part of the base hopper. With double the gas flows expected,
and how this affected the temperature changes, a new gas cooler or heat
exchanger was designed, to fit into the new lower profile of
the Mk6 gasifier. By reusing components like the hot filter and
2nd stage gas cooler, gas flow connections were made with stainless
flexible pipes, saving considerable time, but will certainly be
discarded in favour of flanged connections in the MK7 Andes that will
be built early 2010.
added to this test programme, was the automated weight scales linked to
the controlling computer, allowing correlation of the fuel
consumption on the same page as all the other collected information.
Being squeezed into an inadequate space provided a few light hearted
moments until the pneumatic rams were adjusted by restrictor valves,
which reacted with such force as to throw chips across the yard instead
of a gentle tip into the elevator. The final fuel consumption was
measured at 6 lbs/minute (2.7kgs/minute) providing enough gas to
generate 100kWe/hr, which was the original design parameters, and the
maximum we consider reliable for making tar free gas, at least with
this design of gas making.
special interest, and a source of real problems for any gas making, was
the sudden appearance of tar in tests conducted on conclusion of the
August test programme. We fitted larger air nozzles for greater gas
output, then tested a smaller chip supplied from a local forestry
contractor without changing the internal parameters to accommodate the
smaller chip, and compacted char bed. It was a timely reminder not to
cut corners to save time! The tar contaminated surfaces were burnt out
using a large propane torch, and in the freezing temperatures, there
was no problem finding a willing set of cold hands to do the dirty work.
performance in the freezing conditions showed that combustible gas was
available within one minute of ignition, and heat soaking took
approximately 7-10 minutes before output could be lifted to the maximum
of 6 lb/minute. It is not planned to add heated air to the gas making
process, as it has previously been established over a number of years,
that it is detrimental to the gas making with this type of gasifier.
completion of the Mk6 gas analysis test programme, the Mk7 development
programme will deal with the issues of building fuel locks specifically
for the producer gas, and fuel drying incorporated into the fuel
feeding elevator. In preparation for the fuel dryer trials, hot air
ducts were fitted to the Mk6 components, so that all the waste heat
could be collected and directed into the dryer, but are not shown
connected in the photos. The average waste heat temperature is 100-120C
depending on air flows and ambient conditions.
Tecogen CHP generating system has finally received approval for
connection into the grid, but at considerable expense. The power board
work schedule suggests June 2010 as a connection date, not exactly an
indication of welcoming renewables to the generation mix. We will show
more of this system in the next development report, and possibly the
Andes Class in it's final pre-production panel cladding.
reminder, this was the Mk5 Andes Class tested in August 2009. The
height of the main recycled components reinforced the need to focus
on consolidating the design of the core processes.
is the Mk6 version, that sees the gasifier hearth lowered, and new
first stage heat exchanger fitted between the gasifier and filter
housing. The gas is transferred from the heat exchanger into the filter
via the two silver flexible pipes as a compromise to facilitate
recycling of the original components. The gas cooler still sits on top
of the filter box, along with the close coupled condenser for final
cooling, but will be lowered on the Mk7 for trials around March/April
2010. Hot air from the 1st stage heat exchanger exits from the two
vertical high level ducts, and will connect with insulated flexibles to
the bottom two horizontal ducts, which then exit the back into the
dryer. This hot air will be ducted internally for the Mk7 system.
order to bring all the measurable inputs together in real time
correlation, a fuel weighing system was built and controlled from the
computer. Making it all fit in was the main problem, but a plastic
curtain and Duct Tape, solved the issue of chips spilling under full
the tipped position, the chips can just be seen going up the elevator.
Being pneumatically operated, saw chips flung in all directions until
we adjusted the restrictors correctly!
Just to show the full fuel supply bin. At full output, the bin lasts about 20 hours of continuous operation.
close-up of the fuel shows the medium size Laimet chip we chose for
this set of testing. The reason can be seen in the following photo.
conclusion of the August 2009 test programme, smaller chips were tried,
obtained from a chipping contractor. Having fitted larger air nozzles
to facilitate maximum gas flow rate testing in August, the smaller
chips resulted in uncracked tar leakage, which then condensed in the
top levels of the gas cooler. Along with condensed water, it then
dripped down into the hot inlet side of the cooler to form a char like
cake on the tubes. When large volumes of gas move through the system,
there can be zero tolerance to low tar levels in the gas, as this type
of mess will gradually move right through the whole system as the tar
Visiting expertise invited to witness part of this test programme, was
bio-char researcher John Miedema from Oregon. John took delivery of the
spare second Pacific Class gasifier owned by CalForests in early
able to capture the beautiful swirl of the combusting gas, it shows the
gas burning with only aspirated air in not perfect gas/air ratios. The
new high flow air fan was delivered with a bent motor shaft, so not all
best laid plans come to fruition.