Challenges in Fuel Filtration
Challenges in the fuel filtration industry continue to grow.
Changes in fuel and increased fuel efficiency demands persist complicating an
difficult task. Fuel cleanliness demands are not being met. We all want cleaner
air and more efficient engines, but the consequences require developing higher
performance filtration equipment and fuel quality management systems that
address the complex nature of the problems.
HDS removes sulfur from petroleum products as well as
lowering oxidation stability. As a result, fuels tend to have a shorter shelf
life. They are also dryer requiring special additives. This is especially true of diesel fuel. In
order to meet the lubricity requirements and protect equipment, additives are
blended with diesel. These additives
increase the surfactancy of the product changing the stability of water
suspended in the fuel or interfacial tension (IFT). IFT is the relationship
between water and fuel. The lower the IFT, the more difficult it is to remove
water from fuel. The lower the IFT, the smaller the water droplets suspended in
the fuel become. The higher the IFT, the larger the water droplets become.
Larger droplets are easier to remove from fuel. If the IFT is too lower, water
separation can be almost impossible.
Lubricity additives are not the only surfactants creating
problems. Many of the aftermarket products sold have surfactant
properties. If added to fuel, filtration
becomes more difficult. This includes a host of biocides and fuel quality
additives. Emulsifiers encapsulate water droplets and allow them to pass
through the fuel system while demulsifiers cause water to fall out of fuel and
make separation easier. If there is a need to correct for fuel quality issues,
it is always best to introduce additives after filtration is completed and
testing confirms the need.
Biofuels introduce unique challenges to fuel filtration.
Both ethanol and biodiesel require special treatment. Because they are more water soluble than
conventional fuels, water problems are prevalent and more difficult to correct.
Water droplets in biodiesel are believed to be smaller and better distributed
because of the surfactant nature of the fuel. Ethanol actually forms a bond
with water and will draw the water into the fuel until it reaches saturation at
which point the water and most of the ethanol drop out of the fuel to form a
separate layer in the bottom of the tank. This phase separation renders the
fuel out of spec requiring additional actions after water removal and
filtration have been completed.
In many areas, up to 5% biodiesel can be added to ULSD without
notice to the end user. Cross contamination is also a problem. Ethanol is often
found in diesel fuel as a result of switch loading. The combination of these
when water is present make filtration a more difficult task. Understanding the
challenges helps to identify the potential pitfalls in filtration. Creating new
and better methods of filtration to address the issues require integrated
features and flexible approaches in the field. Innovative technologies and
designs to meet the demand for clean fuel will continue to be a priority.