Diesel

Sampling according to DIN 51750-1 / EN ISO 3170

The requirements for the temperature limits of the filterability (cold behavior) are:
15th April to 30th September CFPP maximum = 0 C
October 1st to November 15th CFPP max = -10 C
November 16 to February 28 CFPP maximum = -20 C
01. March to 14. April CFPP maximum = -10 C

• Cetane number EN 16144, EN 15195

• Cetane index EN ISO 4264

• Density at 15 °C accroding to EN ISO 12185

• Polycyclic aromatic hydrocarbons EN 12916

• Sulfur content EN ISO 20884

• Flash point EN ISO 2719

• Coke residue EN ISO 10370

• Ash content EN ISO 6245

• Water content EN ISO 12937

• Total contamination EN 12662

• Corrosive effect on copper EN ISO 2160

• Fatty acid methyl ester content EN 14078

• Oxidation stability EN ISO 12205

• Lubricity EN ISO 12156-1

• Viscosity at 40 ° C EN ISO 3104

• Distillation EN ISO 3924

• CFPP filterability EN 116

• Cloud point EN 23015

From this results the first and with the most important characteristic of the fuel, the Zündwil-ligkeit. This ignitability is diametrically opposed to the knock resistance of petrol. That the components that are avoided in gasoline because of their poor octane number, are here the most sought-after components: as long as possible, straight-chain paraffins (n-paraffins). The measure of the ignitability of diesel fuel is the cetane number.

The second important characteristic is the cold behavior of the fuel. Unfortunately, these n-paraffins - especially the long-chain ones - have an unpleasant property:
They have a comparatively high freezing point.
An n-paraffin solidifies at a much higher temperature compared to an equally heavy iso-paraffin. Although many n-paraffins give a good ignition, but at low temperatures, they tend to crystallize out of the fuel. Fuel filters designed to remove unwanted debris from the fuel will clog up within a short time. Then the engine is no longer (sufficiently) fueled, it stops.

he boiling range of the diesel is approx. 170 - 350 C. There are several reasons for this:
1. From the invention time and purpose of the machine: The gasoline fraction was already planned, they were looking for machines that could use other distillate shares from the crude oil.
2. The already mentioned ignitability. Especially for n-paraffins, but in a weaker form also for other hydrocarbons applies: the larger the molecule, the more decomposable (= ignitable).
3. The fuel pump, which pumps the fuel under high pressure into the combustion chambers, is also lubricated by this fuel. If the fuel is too thin, that does not work.
4. A pleasant side effect of the boiling cut: At normal room temperature, diesel is not flammable. He is thus much easier to handle than the flammable gasoline.

The most important additives to diesel fuels:
With regard to the ignitability, a satisfactory product can be produced with most types of crude oil. Only particularly naphthenic crude oils from Nigeria or Venezuela require the addition of ignition improvers (cetane number improvers). For this purpose, organic nitrates, e.g. Hexyl nitrate.
In order to prevent the precipitation of paraffin crystals at low temperatures, use is made of flow improvers. These additives form finely dispersed mixtures of paraffin crystals, the fuel remains flowable and filterable.

It provides information about the ignitability of the fuel. The cetane number is determined according to EN ISO 5165: Determination of the ignitability of diesel fuels, cetane method with the CFR engine.

In the event that no test engine is available or the sample quantity is insufficient for a motor determination, the cetane index can be calculated from the density and values from the boiling curve.
EN ISO 4264: Calculation of the cetane index from 4 parameters

Multinuclear aromatic compounds have a poor cetane number, are most prone to soot during driving, and are generally classified as carcinogenic.
The content of PAH is determined according to:
EN 12 916: Determination of aromatic hydrocarbon groups in middle distillates
HPLC method with refractive index detector

A safety aspect, because diesel is subject to much lower safety requirements than gasoline due to its higher flammability during storage, transport and sale.

EN ISO 2719: Pensky-Martens method with closed crucible
Limit at least 55 C
Rejection limit at least 53 C

Evaporated the fuel when burnout complete or verkoct er and is being being back stands.
EN ISO 10 370: Determination of coke residue - micro-process
The coke residue is determined from a 10 vol. Distillation residue. The determined value is related to the boiling residue and given in relation to the original sample.
Limit: maximum 0.30% by weight
Rejection limit: maximum 0.37% by weight

Too much ash can lead to deposits in the combustion chamber and at the valves. The value gives information about the inorganic constituents of the fuel and becomes:
EN ISO 6245: Determination of ash.
Limit value: maximum 100 mg / kg, = 0.01% by weight
Rejection limit: maximum 130 mg / kg = 0.013% by weight

Diesel fuel can only dissolve very limited amounts of water. If the temperature drops, dissolved water may precipitate again and lead to corrosion in the fuel system.
EN ISO 12 937: Determination of water content, Coulometric titration according to Karl Fischer
and
DIN 51 777: Determination of water content according to Karl Fischer, direct method are methods are water determination. Only the coulometric method EN ISO 12 937 is permitted in EN 590.
The limit is 200 mg / kg,
the maximum rejection limit is 258 mg / kg.

In Diesel are very fine-powdery suspended matter, which can remain in suspension due to the viscosity of the fuel for a long time. They can only be identified directly in samples if they are allowed to rest for a few days (weeks) and a thin, loamy or powdery sediment forms on the bottom of the sample bottle.
EN 12662: Determination of pollution in middle distillates
The sample is sucked through ultrafine filters, the filter washed oil-free and determined the mass gain.
Limit: pollution of not more than 24 mg / kg,
Rejection limit: Pollution of a maximum of 28 mg / kg.

In diesel, the process describes the reaction of the fuel under the influence of atmospheric oxygen, which is particularly important for the storage of diesel. Oxidation-sensitive components such as polycyclic aromatics or hetero-compounds react with oxygen and form a residue. This residue is filtered off and determined similarly to the total contamination. Such residue-forming oxidation reactions can be postponed by suitable additives.

EN ISO 12 205: Determination of the oxidation stability of middle distillates
Limit: maximum 25 g / m ^ 3;
Rejection limit: maximum 28 g / m ^ 3;

As already mentioned in the introduction to EN 590, the fuel pump, which provides a delivery pressure of up to 2000 bar in modern diesel engines, is lubricated by the fuel itself. If the lubricity of the fuel is insufficient, the pump will wear more or less quickly prematurely. With gasoline as the pumping medium, that can be a matter of minutes, just to describe the effects of a wrong refueling with gasoline instead of diesel. For lubricity or lubricity, the corrected wear calotte diameter, "wear scar diameter" (wsd 1.4) at 60 C is determined by:

EN ISO 12 156-1: Determination of lubricity using a vibration wear tester, Part 1: Test method
Limit: A wear scar of maximum 460 m diameter.
Rejection limit: A wear scar with a maximum diameter of 521 m.

How fluid is the fuel, how well it is atomized by the injectors in the combustion chamber. Information about this property gives the kinematic viscosity, determined at 40 C.
EN ISO 3104: Determination of kinematic viscosity and dynamic viscosity calculation
Limits of kinematic viscosity at 40 C:
Limit value: at least 2.00 mm ^ 2 / s, maximum 4.50 mm ^ 2 / s.
Rejection limit: at least 1.99 mm ^ 2 / s, maximum 4.52 mm ^ 2 / s.

The boiling range of a diesel fuel must be within a certain range. Technical reasons (viscosity, cetane number, flash point in the low-boiling range and, for example, tendency to coke in the high-boiling range) as well as customs regulations provide this framework.

EN ISO 3405: Atmospheric pressure distillation method describes the procedure. It is the same distillation process used for petrol fuel to determine volatility.

In the course of the use of regenerative fuels FAME may be admixed to mineral diesel fuel. This is supported by tax incentives. The proportion of FAME is limited to exclude engine malfunctions on vehicles that are not designed for operation with biodiesel.

EN 14078: Determination of fatty acid methyl esters in middle distillates (IR method)
Limit: maximum 5% by volume FAME in diesel
Refusal limit: maximum 5.5% by volume FAME in diesel

FAME determination by IR spectroscopy:
FAME is chemically an ester. An ester compound differs from pure hydrocarbons by oxygen, which is chemically bound in the molecule.
This difference is evident in the infrared spectrum. FAME shows a striking absorption band at 1745 cm-1, where middle distillate is rather inconspicuous. Based on the strength of this band, FAME can be quantitatively detected in diesel.

Execution:
In cyclohexane dilutions of FAME in the range of 1 - 10 g / l and create a calibration function of extinction to concentration.
The extinctions should be in the range of 0.1 to 1.1 and the coefficient of regression just above 0.99.
Dilute the diesel sample to a range favorable for absorbance (1:10 to 1:20), analyze the IR spectrum, and evaluate the absorbance: peak height at approximately 1745 cm-1, baseline correction at approximately 1670 cm-1, and 1820 cm-1.
Use the calibration function and the selected dilution to calculate the FAME content in the fuel.
Calibration is performed using mass components, for the conversion of the measurement into volumes take a density of 880 kg / m 3; for the FAME.

The behavior at low temperatures:
In regions with temperate climates, the CFPP (Cold Filter Plugging Point) is sufficient.
EN 116: Determination of the temperature limit of filterability

The calendar data for summer, winter and transitional periods are identical to de-nen for gasoline.

In addition, the turbidity point CP (cloud point) is determined for these arctic classes.
In addition, diesel requirements under these conditions are different for density, viscosity, cetane number, cetane index and additional parameters for the boiling range. The changed (mitigated) limit values take account of the fact that the cold behavior at very low temperatures can no longer be set solely by means of additives. Also shorter = smaller = lower viscosity and lower boiling hydrocarbon molecules must be used.

In contrast to the CFR engine, where the compression pressure is controlled via a variable compression ratio, this is regulated in the BASF engine by throttling the intake air quantity. The engine developed by BASF AG in Ludwigshafen (based on MWM / KHD) is a 4-stroke single-cylinder diesel engine with a constant compression ratio of 18.2: 1. The engine speed is 1000 rpm, the ignition delay becomes 20 Grad adjusted. The engine includes means for varying the amount of intake air. This adjustment is measured by measuring the air flow through the Venturi nozzle or by measuring the negative pressure in the intake duct.

Input: The sample is compared to 2 reference fuels, one of which has a higher and a lower CZ. The difference of the CZ may be a maximum of 4 points.

Reference curve: You create a reference curve with reference fuels. During the measurements of the samples, tests with reference fuels shall be carried out so that a reference curve can be created reliably. The measurements must be repeated at least twice.



Reference fuels are:
Cetane, n-hexadecane with a CZ of 100 and 1-methylnaphthalene with a CZ of 0.
From the volumetric mixing ratio of the two substances, the CZ is calculated.
In addition, one still uses control fuels. These are diesel fuels whose CZ is e.g. is reliably determined by interlaboratory tests. The control fuels are not used to determine the CZ, they only serve to check the engine condition of the test engine.

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