Course: BFM 202 Biodiesel Production

Lecture

Corrosion and Sedimentations
Credits
BFM 202 Biodiesel Production Unit 2 Lecture has been adapted from "ENGY 131 Unit 2 Commentary: The Diesel Engine" by Southeastern Illinois College.

ENGY 131 Biodiesel Production course content by Southeastern Illinois College is licensed under a Creative Commons Attribution 3.0 Unported License. Except where indicated otherwise.

Corrosion and Sedimentation

Corrosion

High carbon steel is used in the diesel fuel injection systems and is
susceptible to corrosion upon contact with water. Water damage is the
most widely known cause of fuel injection failures and causes
irreversible damage quickly.
Diesel engines are designed with water separators to remove water from
the fuel flow although there seems to be evidence that they are not
effective when biodiesel fuel is used.
Water is found in diesel fuel in two forms: dissolved water and free water.
Dissolved water effects fuel stability but free water is responsible for
most corrosion. Petroleum-based diesel fuel absorbs ~50 ppm of dissolved water.
Biodiesel fuel absorbs up to 1500 ppm dissolved water.
In diesel fuel samples, ASTM D 2709 uses a centrifuge to collect and
measure the total free water and sediment. The limit is 0.05% for both
petroleum-based diesel and biodiesel.
Copper is highly susceptible to sulfur corrosion. Since sulfur also
corrodes diesel engine components, ASTM D 130 prescribes the use of
copper strips soaked in diesel fuel to determine the fuel's corrosive
tendencies. Tarnish is allowed but corrosion will fail the fuel.
Biodiesel normally is not found to be corrosive.

Sediment

Diesel fuel filters limit particles >10 μm with newer engines further
reducing particle size to 2 μm.
Diesel engines operate at high temperatures causing chemically compounds
to form. These compounds are insoluble and create varnish deposits that
coat moving parts or sediments that lead to plugged orifices.
ASTM D 2274 measures diesel fuel tendencies toward sediment creation but
have not been accepted into diesel fuel specification ASTM D 975.
ASTM D 6751 does provide an oxidative stability test for biodiesel since
it tends to degrade through oxidation more rapidly due to its higher
concentration of unsaturated compounds.
ASTM D 482 tests for ash in that may be produced from the inorganic
materials in diesel fuel. Ash is abrasive and can lead to piston and
cylinder wear.
ASTM D 874 is referenced in the biodiesel specification ASTM D 6751 as
the measurement standard for sulfated ash. Sodium and potassium
catalysts are used in biodiesel production and are the main sources for
this ash.
ASTM D 189, D524, and D 4530 are tests used to predict a fuel's tendency
to form in-cylinder carbon deposits.
In-cylinder carbon deposits occur when the fuel is at a high temperature
in the absence of oxygen. This condition pyrolyzes the fuel to a
carbon-rich residue that collects around the injection nozzle and limits
its moving parts.