although biodiesel is a clean-burning
environmentally-friendly renewable
substitute to petroleum diesel water
contamination may degrade biodiesel
quality
this video will help you understand
problems caused by water and sediment in
biodiesel the common sources of water
and finally we will show the ASTM
approved method of measuring water and
sediments in a biodiesel sample improper
biodiesel processing such as inadequate
drying after a water wash or by storing
biodiesel at high temperature and
relative humidity can cause biology so
to have a water content higher than the
allowable limit water and sediment and
fuel tend to cause following and
corrosion and make it trouble in the
fuel system of a burner or an engine an
accumulation of sediment in storage
tanks and on filter screens can obstruct
the flow of fuel if the amount of soap
is also high in biodiesel water can
cause emotions or hazy appearance water
and fuel supports microbial growth which
can be another cause of fuel filter
plugging the ASTM standard d 6751 limits
the water content in biodiesel 2.0 5% by
volume water and biodiesel can exist in
three states dissolved water emulsified
water and free water dissolved water is
like the humidity and air and cannot be
seen when the amount of water rises it
reaches the saturation point and water
molecules collect as suspended droplets
which appear as an emulsion the emulsion
is similar to fog and make fuel appear
too
good or hazy as water droplets grow in
size phase separation occurs because of
gravity and water settles to the bottom
of the storage tank biodiesel can pick
up water during storage research
conducted at the University of Idaho's
biodiesel laboratory showed that the
amount of water picked up by biology so
could be 25 times higher than for
regular diesel the amount of the water
picked up by biodiesel mainly depends on
the relative humidity of the surrounding
air the storage temperature and the
biodiesel blend level the research found
that it takes only about a day for
biodiesel to reach equilibrium with the
surrounding air humidity water and
biodiesel at equilibrium is proportional
to the relative humidity of the air in
order to reduce the amount of water
entering into the storage tank from air
it is important to keep the storage tank
full of fuel and seal the tank other key
variables in water absorption are the
storage temperature and the blend level
with diesel fuel the graph here shows
the effect of blend level and
temperature on saturated water content
the x axis of this chart is the
biodiesel mass fraction each line
represents the equilibrium moisture at a
particular temperature the top line with
the star symbol represents 50 degrees
centigrade or about a hundred and
twenty-two degrees Fahrenheit whereas
the black squares at the bottom
represent 10 degrees centigrade or 50
degrees Fahrenheit the intermediate
lines are at 10 degrees c intervals if
we look at the case for pure biodiesel
which is the group of points on the far
right there is more effective
temperature than for the pure diesel
which are the group of points on the far
left
out in general the higher the percentage
of biodiesel the greater the effect of
temperature for be 100 on average the
saturation moisture increases at 12.3
parts per million per degree fahrenheit
if biodiesel is exposed to higher
temperature fluctuations in storage safe
from 40 degrees Fahrenheit at night up
to 70 degrees Fahrenheit during the day
the water-holding capacity of the
biodiesel from day-to-night is reduced
by 370 parts-per-million the excess
water precipitates at night and
accumulates at the bottom of the tank
the next day at a higher temperature
biodiesel may pick up some water from
the air to make up the difference
instead of from the precipitates from
what the last night and as a result
water may continue to accumulate at the
bottom of the tank this situation can be
avoided by having storage at constant
cool temperatures and possibly at a
lower blend level and underground tank
would have a much lower temperature
fluctuation that in a and above-ground
tank ASTM d 6751 is the main
specification for all be 100 the
document specifies the limits and
testing procedures for water and
sediment in biodiesel ASTM d 2709 is the
referee method for measuring water and
sediment in biodiesel the ASTM d 2709
method is used to determine mainly free
water in biodiesel this is a simple
method in which a hundred milliliters of
sample is centrifuged 800 G's of force
for 10 minutes at a temperature of
between 70 and 90 degrees Fahrenheit the
equation shown here can be used to
determine the
needed RPM to produce 800 G's at the tip
for the swing in this video we want to
show you the use of a centrifuge in
order to detect free water that's
present biodiesel samples for this test
we need to measure the inside diameter
that the these different pear-shaped
class end up receiving a given RPM in
order to calculate the g-force that the
receipt so the distance between the tip
and the center of the centrifuge the
radius is approximately seven and a half
inches so we just measure the radius
which we can double and get the diameter
we need to calculate the g force is
exerted on into the pear-shaped class
next thing we're going to do is
determine the RPMs we're going to now
turn the power on started the lowest
power setting turn on the centrifuge
inside of each of these cups will add a
hundred milliliters of our sample of
biodiesel with water present this is a
fuel sample that we intentionally added
moisture to we've added a hundred
milliliters of fuel that had moisture in
it so you can see this is cloudy in
comparison to the biodiesel sample here
which is much higher in clarity it's
important when using a centrifuge to
make sure both rotors are correctly
balanced that will reduce the vibrations
to counterbalance the sample we wanted
to use just some just used water seal
run run the sample
we can see that there's a little bit of
sediment present in the sample is still
would pass this only measures the free
water so we can tell visually that
there's moisture president sample if
there's water that dissolved in the fuel
that still miscible it won't necessarily
come out and so will show you some other
analytical techniques of our next videos
that will help to determine that there's
a way to use saturated toluene to
extract that water out and use the
centrifuge like this other way is to use
a carl fischer and use iodine
electrochemically in order to detect the
presence of that water visit our website
at www biodiesel education dot org for
more information
the biodiesel education program is
sponsored in part by a USDA grant