Environmental Engineering Reference
In-Depth Information
taBle 9.3
viscosity limits at 40
°
c (mm
2
/s) for several countries
united
states
south
africa
countries
eu
Japan
India
thailand
Brazil
Fuel quality
standards
EN 14214
ASTM
D 6751
JIS K
2390:2008
IS 15607
Agricultural
engines
FAME
SANS
342
ANP No 42
Act 05/2005
Viscosity at
40°C
(mm
2
/s)
3.5-5.0
1.9-6.0
3.5-5.0
2.5-6.0
1.9
3.5
2.2-5.3
To report
Source:
Rehnlund, B.,
Outlook on Standardization of Alternative Vehicle Fuels: Global, Regional and National Level.
Prepared by: Atrax Energi AB, Sweden for IEA Advanced Motor Fuels Implementing Agreement, 2008.
as an indicator for the control of the residual heavy impurity removal during the production process
(Rilett and Gagnon 2008).
Another parameter that influences the viscosity of biodiesel is the ambient temperature (Prankl
et al. 2004; WWFC 2006). At low temperatures (less than -20°C) some additives are required to
reduce viscosity (Prankl et al. 2004); otherwise, the high viscosity may compromise the mechanical
integrity of the injection pump drive system (White Paper 2007).
Because viscosity is a very critical factor in engine durability (Bacha et al. 2007), a range of
viscosity is a fuel quality requirement. The EU sets this range between 3.5 and 5.0 mm²/s (EN 1421:
2003)* and the United States between 1.9 and 6.0 mm²/s (ASTM D6751). Table 9.3 lists the viscosity
limits for biodiesel by country. Although Brazil currently has no limits, a range of 3.5-6.0 mm²/s
will be established soon (White Paper 2007).
9.2.3 S
ulfatEd
a
Sh
The inorganic matter content of biodiesel, mainly abrasive solids, soluble metallic soaps, and unre-
moved catalysts (Bacha et al. 2007; White Paper 2007; Rilett and Gagnon 2008), is estimated by
the value of the (sulfated) ash content (Mittelbach 1996). Abrasive solids and unremoved catalysts
are oxidized during the combustion of the fuel, which forms an ash that wears the injector, fuel
pump, pistons, and rings of the engine and may contribute to engine deposits. Soluble metallic
soaps, with their oxidation to ash, contribute to filter plugging and engine deposits (Mittelbach
1996; Prankl et al. 2004; Foon et al. 2005; WWFC 2006). According to the Worldwide Fuel
Charter (WWFC 2006), these effects can worsen from the use of ash-forming additives and there-
fore should be avoided.
The sulfated ash content varies according to process rather than to feedstock, that is, control of
the efficiency of the manufacturing process in removing soaps formed during production (Rilett and
Gagnon 2008) as well as the excess catalyst used in the process (Prankl et al. 2004). In the case of
transesterification of fully refined oils using alkaline conditions, the sulfate ash content is mainly
determined by the remaining soaps (Mittelbach 1996). In the case of unrefined oils, the value of
sulfate ash correlates with the content of phosphorus (Mittelbach 1996). In this case, the sulfate
ash will exceed the minimum allowed level of 0.04% m/m, and additional purification steps are
required for the biodiesel to reach the fuel quality limits (Mittelbach 1996).
The ash limit of biodiesel cannot be compared with that of diesel because the latter is expressed
in oxide and not sulfate ash (Prankl et al. 2004). This difference results from the fact that for
the determination of ash in biodiesel, sulfuric acid is added to the sample before the combustion
*
If CFPP is -20°C or lower, the viscosity measured at -20°C shall not exceed 48 mm
2
/s.
