Prepare Mag: August 2018 - page 19

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Cooling:
Once the Syngas is created from the reactor, it is
pulled through a series of cooling tubes to cool the gas. As
the gas cools the condensate from the gas is collected for
removal.
Condensate Collection:
After the gas has cooled, condensate
is collected for later removal. The amount of condensate is
dependent upon the moisture content of the fuel. Charcoal
has less moisture content than wood. Condensate may be
collected at several points in the wood gas generation,
including the top of the reactor, the cooling system, the
filtering system or upon exit of the syngas from the system.
Filtering:
The filtering system removes any contaminants
remaining in the wood gas after passing through the cooling
and condensate collection. The most efficient designs utilize
a multi-stage filtering system that includes several layers of
filtration from course to very fine, much like a water filtration
system. In the case of the wood gas generator, the course
layer may use hay or straw while the fine layers use
increasing fine levels of foam filters.
Suction Blower:
A suction blower is used to ‘pull’ air into the
reactor and to pull the gas through the cooling, condensate
and filtering system and finally to an exit port past the
blower. The suction blower is critical to the entire gas
production process and a blower with sufficient suction
capability must be used. In the case of a high grade fuel
application, the suction blower would pull the gas through
the system and out to a flare port, in which the gas may be
ignited and shown in a visible flame. Once sufficient gas is
being produced, the gas can then be fed into the engine or
generator, which will provide the suction needed to pull the
gas into the engine or generator. A blower may also be used
to ‘push’ air into the system from the air intake as a
supplement or alternative to the suction blower.
The Heart of the Wood Gasifier
The below image is that of the “Choke Plate” and “Reduction
Tube”, the components that funnel the fuel and where the
fuel is consumed. It is this area that reaches the highest
internal temperatures approaching 2,000° F. These Parts are
typically made from ¼” (or greater) stainless steel.
Choke Plate and Reduction Tube
The size of the opening in the choke plate and length of the
reduction tube can vary depending upon the amount of gas
to be generated. In a good system design, this part is
removable so that it can be changed or resized as needed.
Wood Gasifier Designs Examples:
Imbert Downdraft Gasifier Design
Peterson Wood Gas Generator Design (Front View)
Peterson Wood Gas Generator Design (Rear View)
The Build Process
The build process will involve cutting, shaping, bending,
fitting, welding and assembling of the many metal
components. It is very important to check and double check
all measurements prior to cutting and welding and to ‘dry fit’
components before welding or assembly whenever possible.
Regardless of which design you choose, there will always be
some slight modifications and adjustments during the build
process. It is far easier (and less costly) to make these
adjustments during a dry fit process rather than having to
replace and rework portions of the build.
Welding Considerations
There will be 2 types of welding needed for your build; (1)
Critical Flow Welds – Those welds that contain and control
the air intake into the systems, and the movement of the
Syngas through the system, filters, and exit ports and (2)
Structural – Those welds that are structural in nature that
hold things together but do not affect the air or gas flow
through the system. It is imperative that the (1) critical welds
be air tight so as to not introduce uncontrolled air into the
system that can cause internal ignition of the gas and/or
cause the syngas to become diluted making it unusable.
Even the most experienced welders can have problems with
making an airtight weld. Structural welds are not as critical
as they do not affect the function of the gasifier. The main
point here is if you are a home hobby shop welder, take
great care on the critical airtight welds and even consider
contracting out this portion of your welding. Additionally,
perform leak tests as you build to ensure each section is
airtight before completing the build as it will be easier to fix
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