Transcript Summer School Individual Project

Summer School Individual
Project
Bio-Energy Summer School 2009
Taylor Norrell
Project Goal
Make an anaerobic
digester that
combines the gas
storage unit and the
digestion tank into
one unit, using as
little materials as
possible.
Anaerobic Digestion
Breakdown of complex organic materials
into a methane/carbon dioxide “biogas”
and a nutrient rich effluent
Biomass Magazine, February 2009, http://www.biomassmagazine.com/article.jsp?article_id=2410&q=&page=all
Benefits of Anaerobic Digestion
• Biogas can be used for
heating and cooking
applications
• Effluent can be applied to
crops as fertilizer
• Anaerobic conditions are
effective treatment for
pathogen elimination
Digester Design
Original
Simplified
Agitation
• Essential for proper digestion
• Helps prevent slurry layering
• Well mixed digester is a healthy digester
First Attempt
• Agitates by moving the
gas collector up and down
• It was found that it was
hard to move the collector
up and down
• It was also found to be
very messy, contents from
the digester would
overflow when the gas
collector was being
pushed
• Structure required a lot of
pieces and was not very
simple to make
Second Attempt
•
•
•
Agitator consists of the top
of the gas collector
attached to 4 ropes which
run through a series of
pulleys. When the ropes
are pulled, it lifts the top
through the digester,
stirring the contents. A brick
was added so the top can
sink to the bottom after
being lifted.
Ropes became easily
tangled
Without the right pulleys, it
was difficult to pull the
ropes.
Final Attempt
• Took two 2”x4” and
screwed them together
to make an ‘L’ shape.
Screwed on the top of
the gas collector to the
bottom.
• Agitates by the user
lifting it up and down.
• This was the simplest
to make and the most
effective mixer.
Gas Collector
• The inverted barrel acts
as the gas collector
• Methane is formed in the
digester and rises up out
of the slurry, and gets
caught in the collector
• On top of the collector, a
PVC pipe with a ball valve
acts as the gas outlet
Cage
• The cage is the
wooden structure
surrounding the
digester, attaching four
ropes to the gas
collector
• Helps stabilize the
collector and promotes
gas production by
creating a lower
pressure environment
in the digester
Oil
• A layer of vegetable oil
separates the slurry from the
open air
• This serves to keep conditions
in the digester anaerobic
– Acid forming bacteria are
facultative anaerobes,
methane forming bacteria
are obligate anaerobes
• Helps to manage odor and
pests.
Problems/Solutions
• As gas collector rises, it brings some contents out
with it, attracting pests
• Possible solution: incorporate some sort rubber
lining/brush to wipe off the collector as it rises
• As scum forms, it rises above the oil layer and
can attract pests
• Regular agitation should maintain any scum
problems, otherwise the oil layer can be skimmed
to remove scum
Thank You For Your Time!
Questions?