This document summarizes a study that tested different mixtures of diesel fuel to improve the temperature limit of filterability. Eight diesel mixtures were prepared with varying percentages of light gas oil, heavy gas oil, kerosene and naphtha. The mixtures were tested for flash point, distillation characteristics, and cold filter plugging point (TLF). Only two summer mixtures met standards for distillation and TLF. For winter mixtures, adding the additive "infenium" was needed to meet the TLF standard of -5°C. The best mixture would meet standards while containing maximum heavy gas oil, minimum naphtha and minimum infenium for economic reasons.

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IMPROVING THE TEMPERATURE LIMIT OF DIESEL FILTERABILITY
Adel OUESLATI(1)
, Anis SMIDA(2)
(1)
Higher Institute of Technological Studies ZaghouanMograne, 1121, Tunisia
(2)
Tunisian Refining Industries Company (STIR), Bizerte, Tunisia
ABSTRACT
Several mixtures were made gasoil and characterized. The most important features are the
diesel volume of distillate collected at 350 ° C, the flash temperature and limited temperature
filterability (TLF). The mixture of diesel must first obey the conditions of distillation and the flash
temperature and finally the limited temperature filterability. If any of the characteristics listed was
not observed when the mixture of diesel will be rejected. Note that the filterability limit temperature
can be improved by adding a fuel additive called “infenium”.
1-INTRODUCTION
Diesel or diesel or gasoline, or diesel is a fuel for diesel engines. Physically, it is light oil and
statutorily, a fuel derived from petroleum refining. [1] The word "diesel" is derived from the word
"diesel" (oil, fuel). [2] This term is mostly used in France. In other countries, such as Belgium,
Canada and Switzerland, the product is known as "diesel", a word derived from the name of Rudolf
Diesel, the inventor of the diesel engine, which usually works with the fuel [3].
Largest emitter of fine particles, diesel fuel is prohibited in Japan, heavily taxed in Denmark
and Switzerland, sold more expensive than gasoline in the United States but still used in France [4].
Its calorific value is of the order of 42.5 MJ / kg, the boiling temperature is in the range 170-390 ° C
[5]. The flash point is 55 ° C according to ISO 2719 [6]. By its very nature, diesel contains paraffin.
These are excellent components for the operation of diesel engine. However, when a strong lowering
of the temperature, they can be transformed into crystals and clog filters, causing the engine to stop.
Two key characteristics define the resistance to cold diesel: Point Trouble and cold filter (TLF) [7].
This is the lowest temperature at which a volume of gas oil can still pass through a calibrated
filter at standard conditions. Physically, the size of wax crystals is such that it becomes sufficient to
clog filters. TLF is on average the lowest temperature at which diesel can operate the vehicle, that is
to say the temperature operability limit. However, a vehicle in excellent condition and well
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maintained bear lower temperatures, while an old or poorly maintained vehicle will not reach this
limit [7, 8 and 9].
To improve the filterability of fuel, several additives may be used. These additives may
prevent the formation of solid crystals in the fuel at low temperature. They are mixed with diesel fuel
to a temperature above 0 ° C, before the formation of wax crystals. If the crystals have already
formed, the additive has no effect on the quality of fuel.
In this article, we will test new blends of diesel and a new additive against the formation of
wax crystals at low temperatures.
2-EXPERIMENTAL PROCEDURE AND METHOD
The fuel used for diesel engines is a mixture of four cups of semi-finished products: kerosene,
naphtha, light gas oil and heavy gas oil well in proportion determined using the simplex method [10].
This operation is performed by a specific method to obtain an optimum mixture of specifications
without additives. These specifications are: The flash point [11], distillation [12] and the limit of
filterability [13] temperature. Mixtures of diesel fuel shall meet the requirements of distillation, flash
point and cold filter plugging.
2-1-Distillation
In the ASTM methoddistillation of oil, the temperature of the liquid increases.It depends on
the evolution of the liquid mixture to be distilled. We note the start point and the end point of the
distillation. These points correspond to minimum and maximum temperatures of the test. Standard,
ISO3405, indicates that the volume of recovered condensate must represent at least 85% of the
volume of fuel mixture, distillation, heated to 350 ° C.
Fig.-1: Distillation apparatus diesel Fig.-2: Apparatus for measuring the flash
point of Diesel
2-2-Flashpoint
It is known, also, the flash point. This is the temperature at which it must carry a liquid
petroleum product to emit under standardized conditions, vapors in sufficient quantity so that they
can be ignited by a flame. The Pensky Martins device close vase is used for petroleum having a flash
point above 50 ° C.
2-3- Cold filter plugging point of diesel
The cold filter plugging point (TLF) is the highest temperature at which a given volume of
product continues through in a short time a standardized filtration device when subjected to cooling
at standard conditions. The aim is to assess the lowest temperature at which the product can flow

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freely. The volume drawn through the metal filter (whose mesh size is 45µm) is 20 ml. TLF is
reached when the suction fluid time becomes greater than 60 seconds. According to EN 116, TLF
has a value of -5 ° C in the period from November 1 to March 31. It has the value 5 ° C during the
period 1 April to 31 October.
Other specifications such as fuel are required. Corrosivity, pollution, ash contents and water,
the cetane number, etc., will not be discussed in this article.
Eight diesel mixtures are prepared from the light gas oil, heavy gas oil, kerosene and naphtha. We
prepared mixtures used in the winter season and others in the summer season. The mixtures are listed
in the following table:
Table-1: Mixtures gasoil as percentages by volume [10]
2-4-The infenium
Infenium is a long carbon chain of polymer added to the mixtures to prevent, on the one hand,
paraffin, formed of long chains contained in the fuel and prevent clogging of the filters on the other
hand. Figures 3 and 4 explain the formation of crystals and the role against particle agglomeration
paraffin.
Fig.-3: Effect of wax crystals on the Fig.-4: Effect of the Infenium on the wax
filter [10] crystals [10]
Winter Season SummerSeason
M1 H M2 H M3 H M4 H M5 E M6 E M7 E M8 E
% Naphta 0 0 0 25 25 25 30 30
% kerosene 20 20 20 20 20 20 20 20
% light gasoil 75 73 70 45 40 41 35 33
% HFO 5 7 10 10 15 14 15 17

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3-RESULTS AND DISCUSSION
Flashpoint: The results of measuring the flash point are shown in Table-2.
Table-2: Flash Points of fuel mixtures [10]
Mixture M1 H M2 H M3 H M4 H M5 E M6 E M7 E M8 E
flash point(°C) 87,0 86,0 87,0 64,5 63,0 64,0 62 ,0 64,0
We recall that the Tunisian standards require that the value of the flash point is greater than at
55 ° C. Hence the analysis of these results shows that all flash points of mixtures studied obey the
Tunisian standards.
It is found that mixtures containing in its composition of naphtha have low flash points. This
is explained by the fact that the compound is light naphtha; it emerges on the surface of a vapor
mixture to a temperature less than the other component of the product mixture.
Distillation: The measurement results of the distillation are detailed in Table-3.
Table-3: Volume of condensate collected at 350 ° C [10]
As the volume recovered at 350 ° C should be at least 85% of the original volume; following
the Tunisian standards, so both summer mixtures (M5 and M8) and the wintry mix M3 are not
following the standards, so these mixtures will not be used for the remaining analyzes.
M7 and M8 mixtures have the same proportions naphtha and kerosene, but the M8 mixture
contains more heavy fuel mixture M7 which explains the outlier distillation. The same applies to the
mixture M3.
Temperature limit of filterability: To our blends the initial filterability limit temperature are
included in the following table:
Table-4: Initial TLF mixtures without additive
Mixture M1 H M2 H M3 H M4 H M5 E M6 E M7 E M8 E
TLF (°C)
without
additive
-1 0 1 0 +3 +3 +2 +4
Since the standards require that the limit of filterability of diesel summer temperature must be
below 5 ° C, where all summer mixtures obey the standards for TLF.
On summer blends, only two mixtures M6 and M7 are ready to be marketed as both mixtures
obey the standards of the distillation.
Similarly Tunisian standards require that the limit temperature filterability of winter fuel must
be less than -5 ° C implying that all winter blends are extraordinary on the cold filter plugging.
Mixture M1 H M2 H M3 H M4 H M5 E M6 E M7 E M8 E
Volume of
condensate
recovered at 350 °
C.
86,3 85,4 83,5 88,0 84,8 85,8 85,4 83,9

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Mixtures that do not follow the norms and standards of distillation flash point will be
eliminated for the rest of our analyzes.
As both summer blends are following all standards even they will be eliminated in the future.
Winter mixtures standardized by flash point and distillation will be our focus in the following order
to optimize these mixtures in terms of cold filter plugging.
We will proceed to the processing of mixtures one by one.
Fig.-5: Cold filter blends with diesel Infenium [10]
4-CONCLUSIONS
Our study is to optimize the diesel engine, that is to say, obtaining a fuel mixture that meets
all the requirements of the Tunisian standards.
We went eight mixtures after various analyzes, we found only five among these mixtures
obey the standards of density, flash point and distillation.
The mixture M3 is extraordinary because distillation of excess heavy gasoil which makes
recovery volume at 350 ° C is less than 85% of the initial volume, and this is the case even for
mixtures M5 and M8.
During summer seasons STIR increase the rate of diesel heavy in the marketed product.
These require correction with naphtha. Even with a large amount of heavy fuel oil, the summer
mixtures obey the standards TLF (+5 ° C).
For winter blends, a single mixture is extraordinary distillation due to excess weight diesel.
Note that with increasing percentage of fuel weight in the mixtures studied, the amount necessary to
achieve ainfenium of TLF (-5 ° C) increases.
As our goal is to achieve an optimal mix of quality meeting all standards, one must take into
account economic factors that is to say, the estimated price of these mixtures.
Recall that the studied mixtures contain naphtha, kerosene, light gas oil and heavy gas oil. Some of
them contain infenium. The best of these mixtures should contain the maximum fuel weight, the
minimum naphtha and minimum infenium.

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ACKNOWLEDGEMENT
We thank the Directors of the Company Refining Industries "STIR" to support and availability.
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