This all started when my interest was sparked by Niels Anso
posting a thoughtful response to the Ricardo Study of SVO emissions. In
his response he mentioned the effects that phosphor in the fuel could
have on combustion. This was the first time I had seen this discussed
and I had since intended to do further research on this topic.
The Ricardo Engineering study was commissioned by the UK
government Department for Transport and was recently used in their
'Towards a UK Strategy for Biofuels - Public Consultation' to show that
"Biofuels potentially have some air quality benefits, provided the fuel
is of appropriate quality (studies have shown that use of unprocessed
vegetable oil can actually lead to considerable increases in
emissions)."
The Ricardo report is at
http://www.dft.gov.uk/stellent/groups/dft_roads/documents/page/dft_roads
_027622.pdf
Niels response posted to the vegoil-diesel yahoo group
http://groups.yahoo.com/group/vegoil-diesel
Fri 18/06/2004 12:10
The Ricardo report is just another useless report!
The Ricardo report, which evaluates emission performance of Straight
Vegetable Oil(SVO, in Europe Pure Plant Oil, PPO), is based on
fundamental mistakes made regarding combustion of SVO in diesel
engines, and the Ricardo authors demonstrates that they know nothing
about SVO engine conversions and SVO fuel requirements.
<SNIP>
To obtain good emissions results, it«s essential to have a real
conversion, including optimisation of the engine performance, and to
have a good quality fuel which meets the limits specified in fuel
standards developed for that specific fuel.
<SNIP>
Ricardo report & SVO Fuel quality.
Rape seed oil as created by nature is an excellent fuel, but can
easily be spoiled by wrong processing, handling and storing. The
report does not describe the SVO fuel well, just that it«s origin was
food grade Canola and from retail supply. The SVO was analysed and
compared to fossil diesel and biodiesel(appendix 2). But analysis
according to fossil diesel standards do not include important fuel
parameters for SVO, so therefore SVO should be analysed according to
SVO fuel standard. Here we can all benefit from very fine German
research work on SVO fuel quality, ending up with the German RK-
standard for rape seed oil as engine fuel. The Ricardo Team found the
data sheet for the RK standard (appendix 3), but they didn«t use it.
If you compare appendix 3 with
http://www.folkecenter.dk/plant-oil/RK-standard-DK.htm, it looks like
they visited our page, so they could
have asked for our support to understand numbers, principles, and
maybe German. The RK-standard describes both characteristic
properties and variable properties. The first group of properties is
created by nature, so it makes no sense to check the SVO for density,
viscosity and sulphur, as they did in the report. The really
important properties are the variable, which are influenced by
processing, handling and storing, but these properties were ignored
by the authors. "Other parameters which are included in the German
specification were not requested for analysis; but it is not expected
that these parameters would have a major influence on emissions". One of
the important parameters regarding emission from SVO, is the
phosphor(P) content, which I will compare the Sulphur(S) content in
fossil diesel. It«s well known that sulphur in fossil diesel creates
SO2 and particle emission, and that the fossil industry fights to
reduce S. In Denmark the fossil industry convinced the government at
least once, to reduce the mineral oil tax on low sulphur diesel, to
compensate for the expenses to reduce S. Now they are trying again
because of the new requirements from EU. SVO contains from nature no
Sulphur.
Both P and S are "strangers" to the combustion process, which itself
only includes C, H and O. If you study the final report from the
German research on SVO fuel quality, Gelbes Heft 69 (link is included
on http://www.folkecenter.dk/plant-oil/RK-standard-DK.htm ), you will
find that the phosphor reduces the combustion temperature, and that
it will create P layers in the engine. Reduced temperature could
reduce the combustion efficiency leading to more unburned fuel and
thereby more emissions. P-layers are naturally harmful to the engine,
and the reduced temperature/combustion efficiency can also lead to
cooking and polymerisation in the engine.
Industrial produced non refined rape seed oil can easily contain 20
times the P limit specified in the RK-standard. Only cold pressed
rape seed oil, or full refined industrial produced rape seed oil, can
meet the P limit of 15ppm. The Ricardo report doesn«t mention if the
canola oil was refined, and no phosphor test was carried out.
<BIG SNIP>
best regards
Niels Ans¿
Folkecenter - DK
Tel.: +45 97 95 66 00
Dir.: +45 97 95 66 55
mob +45 40 14 80 20
fax.: +45 97 95 65 65
----------------
Anyway Niels mention of phosphor levels in the fuel effecting
combustion got me thinking. It shows that it is crucial for fuel
standards to be set to be able to provide any meaningful
emissions/reliability results from SVO. The Weihenstephan rapeseed oil
fuel standards which are the only SVO standards in existence were
produced following extensive consultation and discussion between
scientists, oil mill operators and SVO engine converting companies.
I'd looked into the standards some years ago and come across a
few German documents which at the time I could not use and having become
proficient with the use of googles' web based translation tools could
not find. Earlier this year Niels put me onto some documents relating
to the fuel standards which included:-
http://www.stmlf-design2.bayern.de/tfz/tec/oel/pdf/gelbesheft69.pdf
It is only now that I have had time to run some parts in the
text through a translator giving the following results:-
For the measurement of the phosphorgehalts in rapeseel oil the organic
portion in the sample is unlocked by strong heating in presence of zinc
oxide. The arrears will become solved in sulfurous acid,
Ammoniummolybdat and Hydraziniumsulfat in addition-given.
Spectrophotometrically the adsorption is based on the molybdenum blue
complex, which runs proportionally to the phosphorus concentration in
the sample. In the testing method ASTM D3231-99 for the phosphorgehalt
the unit is used mg/l. The measuring range of the testing method is
appropriate for 40 between 0,2 mg/l and mg/l. The repeatability amounts
to for the limit value 1.05 mg/l, the reproductibility 1.95 mg/l. In
the planned company ME standard the regulation takes place from
phosphorus according to the method NF T60-705 with ICP. The
phosphorgehalt of rapeseel oil fuel is a variable characteristic. It
affected by process parameters during the oelgewinnung. A high
phosphorgehalt has negative effects on the motor burn by the formation
of deposits. In addition phosphorus is a catalyst poison. Illustration
26 shows the phosphorgehalt of rapeseel oil fuels of different origin.
The phosphorgehalt varies with the high standard deviation of 15,6
around the average value of 11,8 mg/kg. The median is with 5,0 mg/kg.
With three samples a phosphorgehalt is not provable in the oil. In
illustration 27 the influence of sort and cultivation on the
phosphorgehalt is represented. Clear sort differences do not show
themselves. With the two measured values, which exhibit over 40 mg/kg,
the analysis was repeated, in order to exclude an analysis error. These
two high phosphorus values are not explainable. The median of 8,0 mg/kg
the samples from the cultivation attempts shows that the limit value is
well stopable. On very low level the phosphorgehalte of the rapeseel
oil samples from the interlaboratory test are, represented in
illustration 28. It is to be noted that for the determination of the
phosphorgehalts the testing method DIN 51363-1 [ 25 ] was used.
Phosphorus phosphorus is present in vegetable oils and FAME in the form
of phospholipiden. With rising portion of phospholipiden oxidation
stability is reduced, in addition phospholipide are inclined to the
Hydratisierung (swelling in water) and can cause thereby for example
filter blockage. Phosphorus lowers the burn temperature, can in the
combustion chamber to deposits lead and possibly a change of the
emission behavior cause. Oxidation catalysts exhibit besides a high
sensitivity in relation to phosphorus connections regarding its shifting
rate and/or continuous function. The phosphorgehalte in vegetable oils
depend on the refining degree. Phosphorgehalte in not refined vegetable
oils can be kept low by appropriate processing [ 59 ].
[ 59 ] WIDMANN, B.A. (1994): Production and cleaning of vegetable oils
in decentralized plants - factors of influence on the product quality
and the production process. "yellow booklet" No. 51. Munich:
Self-publishing house BayStMELF. Research report: DO Munich, Institut
and Bavarian national institute for agricultural engineering, Freising
Weihenstephan (310 sides)
Phosphorgehalt?? A lower limit value than so far would be possible,
since in the meantime with the testing method ASTM D 3231-94 a method is
available, which makes a substantially higher resolution possible
(detection limit 0.2 mg/kg). Phosphorus in the fuel caused in
rotochamber engines of fewer problems, there the phosphorus?staubartig?
arises and over the valves from the combustion chamber one removes.
Problems arise with certain pre-chamber engines and directinjecting
engines. Therefore a limit value is demanded by max 10 mg/kg
phosphorus, stated as example a passenger car engine, which was
defective after 7000 km with a fuel, which exhibited a phosphorgehalt of
26 mg/kg. The rapeseel oils analyzed so far point % phosphorgehalte
to 90? 10 mg/kg up. The boundary conditions of the sampling are
questioned. It is suggested to provide the limit value with 25 mg/kg
too left and the limit value with a footnote that a reinsurance must be
caught up with the engine manufacturers. Doubts exist over it whether
generally phosphorgehalte can be guaranteed of under 10 mg/kg by the oil
producers. A limit value of 20 mg/kg is suggested. It is assumed
that the output product oil seed already exerts a substantial influence
on the phosphorgehalt in the oil. The new method of analysis offers
the chance to receive more accurate values over the phosphorgehalt in
the rapeseel oil. On the part of the oil mill operators it is doubted
whether a limit value can be kept of 10 mg/kg without subsequent
treatment of the oil, through for example Saeureentschleimung. The
phosphorgehalt is very critical for the motor enterprise of evaluating.
Phosphorgehalte of 100 mg/kg with full load enterprise do not cause
problems, only with intermittent enterprise or partial load operation
already arise with substantially smaller phosphorgehalten damage to the
engine. Possibly these damage is favoured by low burn temperatures and
an engine oil dilution exerted by it. The damage to the engine by
phosphorus is temperature and pressure independent. It is considered
to indicate graduated limit values for the phosphorgehalt for
differently targeted applications of the engine. The task of the
adjustment of the engine to the natural fuel does not lie on sides of
the engine manufacturers, after present level of knowledge is suitable
for example directinjecting engines for the use of vegetable oils as
fuel. Different oil mills are to be kept able a limit value of 10
mg/kg. A limit value of 10 mg/kg is to be only accepted for the oil
mills, if over interlaboratory tests the stop barness of the limit value
is examined. The sampling must be specified exactly. In addition a
if possible low phosphorgehalt is to be demanded with the use from
catalysts to, since phosphorus?Katalysatorgift as? works. Appendix 3:
Minutes to 5. Ltv working group meeting 187?? It is discussed whether
a limit value is to be fixed, or whether the phosphorgehalt in
arrangement between supplier and engine manufacturer can be specified.
Influences of the oil production process on the phosphorgehalt
discusses. A proposal for compromise for the limit value reads max.15
mg/kg. The influence of the phosphorgehalts in the fuel on the motor
enterprise is to be examined by the engine manufacturers more near. A
footnote to the limit value max. 15 mg/kg?25 mg/kg with the employment
in stationary engines? as meaningfully one does not judge. For the
retention of the past limit value of max. 25 mg/kg one pleads, since the
past data basis is too small due to the insufficient analysis procedure.
It will suggested, which methods of analysis to test and examine whether
the limit value can be kept, afterwards is the limit value again to be
discussed. The limit value max. 15 mg/kg phosphorus proves as
consentable phosphorgehalt?? variable characteristic?? In place of the
testing method DIN the more highly dissolving testing method ASTM D
3231-94 steps 51,363 T1. The limit value is lowered on max. 15 mg/kg.
Phosphorgehalt: For engine damage frequently the phosphorus in the
vegetable oil is made responsible. Also phosphorus works as catalyst
poison. The analysis of practice oil samples results in that with an
exception all phosphorgehalte lie underneath the limit value of 15
mg/kg. More as 2/3 of the oil samples have a PGehalt of less than 6
mg/kg.
13.Phosphorgehalt collection of the statements and suggestions of the
participants: From an engine manufacturer the demand of a limit value
of 10 is present ppm for phosphorus. Indications exist for a direct
connection of phosphorus deposits in the engine compartment and the
phosphorgehalt in the fuel. Phosphorus lowers the burn temperature in
the engine, the vegetable oil burns therefore incompletely, deposits
themselves at walls and can by the piston rings into the engine oil be
brought. In particular during low engine extent of utilization
abrasive materials can develop. It must be paid attention to the fact
that no defaults are made for the oil mill operators, which are not
stopable in practice therefore are a participant against a sinking of
the limit value and points out that certain engines stand also
substantially more phosphorus, than the past limit value permits. It
is reported that the p-content in the vegetable oil depends strongly on
the contamination and is influenceable by the sampling. Schleimstoffe
do not have to be specially limited, since the Schleimstoffe settles as
phospholipide in the p-content. One agrees to maintain the limit value
for phosphorus. Resolution: Phosphorgehalt?? Testing method ASTM D
3231-99?? The limit value remains unchanged on max. 15 mg/kg
---------------
It appears from the translated notes above that the 15mg/kg was
a compromise between the conversion companies wishes for 10mg and the
oil mills worrying about feasibility of providing fuel at a level below
20mg.
DI engines are more likely to suffer from high P levels.
Also the report contains a table of biodiesel specifications
from around the world that show that most limit phosphor to 10mg/kg,
Austria and Czech 20mg and USA has no requirements. This report was
written August 2000 so things may well have changed.
Also Of note one of the most advanced SVO conversion companies
United Vegetable Oil Workshops - VWP suggests using only oils with less
than 10mg/kg phosphor - see FAQs at www.pflanzenoel-motor.de
Still this is, I think, an important issue which has gone
largely unreported.
Best
Darren
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