The constant improvement of technology and the tightening of environmental standards lead to increased requirements for fuel quality . Much attention is paid sulfur content in petroleum products and oil. This parameter is necessarily reflected in the quality passport.

Sulfur impurities are present in any grade of oil and in all oil products, ranging from 0,05 before 6% from the total mass. Sulfur compounds are unevenly distributed over all fractions, being present even in deeply purified distillates. High sulfur content in fuel is undesirable for many reasons:

• sulfur is toxic and causes bad smell oil products,
• reduces the resistance of gasoline to detonation,
• provokes increased resin formation during cracking,
• increases corrosivity,
• vapors of sulfur compounds irritate the human respiratory tract and worsen the condition of plants.

However, it is not yet possible to completely eliminate sulfur from fuel. For example, if the sulfur content in diesel fuel is below 0.035%, then its lubricity significantly deteriorates, which leads to accelerated wear of the elements. fuel system car. To prevent this, additives are added to diesel fuel that improve lubricating properties. But they are still inaccessible, since mass production has not yet been established. The only way out is to reduce the amount of sulfur in oil products by setting strict standards.

Sulfur oil classification

GOST R 51858-2002 determines oil classes by sulfur content:

• Class 1 - low sulfur - sulfur in the total mass of 0.6%.
• Class 2 - sulfurous - sulfur in the total mass up to 1.8%.
• Class 3 - high sulfur - sulfur in the total mass up to 3.5%.
• Class 4 - especially high sulfur - sulfur in the total mass is above 3.5%.

Oil usually contains pure sulfur (not much) and its derivatives. V quality passport the proportion of total sulfur is indicated (pure sulfur + sulfur-containing impurities). The higher the sulfur content in oil, the lower its cost.

The main share of sulfur compounds (50-80%) in oil products are almost neutral sulfides and disulfides. The most "unpleasant" of the sulfur derivatives are mercaptans. It is they who cause a pungent odor and more than others provoke corrosion and the formation of resins. The content of mercaptans is limited to a few hundredths of a percent depending on the type of fuel and is indicated separately in the quality certificate.

Sulfur content standards for different types of fuel

Sulfur content standards are set for all types of fuel. The most stringent requirements apply to motor gasoline and jet fuel. Permissible sulfur content in them is from 0.02 to 0.1%. The same requirements apply to gasoline-solvents.

Diesel fuel in terms of sulfur content is divided into environmental classes . Today in Russia it is allowed to issue and use only Euro-5 diesel fuel with sulfur content less than 10 mg/kg.

How to reduce sulfur

Sulfur removal from fuel is carried out at refineries in two ways:

Previously, oil is passed through filters to free it from mechanical impurities. And then it is processed by catalytic hydrogenation at high temperature. The cost of sweet oil is about twice as high as the cost of the initial raw material, but in this way it is possible to obtain oil with a sulfur content of up to 1%.

The second method involves the removal of sulfur from part of the heavy oil fractions using vacuum distillation. These fractions are then subjected to hydrogenation with hydrogen. The obtained sulfur-free raw material is mixed with the bulk, and the total sulfur content is reduced by 80-95%.

In 2005, in connection with the adopted state obligations to reduce the environmental burden from exhaust gases, as well as the need to meet the requirements of European customers for export shipments, forced us to develop in Russia new standard for diesel fuel.

GOST R 52368-2005 duplicates all the requirements of the European standard EN 590:2004 (which is why the designation of diesel fuel manufactured in accordance with GOST R 52368-2005 necessarily contains the word "EURO" and a reference to "EN 590:2004").

In autumn 2009, Europe entered into force a new version BS EN 590:2009. The main differenceit from the previous standard is the exclusion of diesel fuels with a sulfur content of 50 mg / kg. Thus, only one standard for sulfur content remains in the EU standard - no more than 10 mg / kg.

In the Russian GOST R 52368-2005, the sulfur content of up to 350 mg/kg existed until December 31, 2011, and 50 mg/kg will exist until December 31, 2014. Diesel fuel with a sulfur content of 10 mg/kg has no release date. limited. So, since 2012, the oil refining industry has been producing diesel fuel with a sulfur content of 10 and 50 mg/kg.

According to GOST R 52368-2005, diesel fuel is classified according to two parameters:

1. The maximum sulfur content, reflected in the indicator "TYPE" of fuel, namely:

type I - sulfur content not more than 350 ppm (mg/kg);

type II - sulfur content not more than 50 ppm (mg/kg);

type III with a sulfur content of less than 10 ppm (mg/kg).

2. Application temperature (climatic zone in which diesel fuel can be used). For a temperate climate zone, diesel fuel is divided into six grades: A, B, C, D, E, F.

Fuel requirements for temperate climates

For areas with a cold climate, diesel fuel is conditionally divided into five classes: 0, 1, 2, 3, 4.

The term “filterability temperature” was also introduced for the first time by the new GOST R 52368-2005 and denotes the temperature below which diesel fuel does not pass at the required speed (flow rate) through a standard reference filter.

Fuel requirements for cold and arctic climates

Name of indicator	Class
Limiting filterability temperature,°С, not higher
cloud point,°С, not higher
Density at 15 °С, kg/cu. m	800-845	800-845	800-840	800-840	800-840
Kinematic viscosity at 40°С, sq. mm/s	1,50-4,00	1,50-4,00	1,50-4,00	1,40-4,00	1,20-4,00
Cetane number, not less than	49,0	49,0	48,0	47,0	47,0
Cetane index, not less than	46,0	46,0	46,0	43,0	43,0
Fractional composition:
Up to 180°С, % (by volume), no more
Up to 340°С, % (by volume), no more
Flash point in a closed cup,°С, not lower

It is important to remember: "GRADE" or "CLASS" is a temperature characteristic parameter, and "TYPE" is a parameter of sulfur content in diesel fuel.
Here are a few examples of the fuel symbol and its decoding.

Example 1 "DT Euro grade F, VIEW II". From this designation, we learn that diesel fuel is intended for a temperate climate zone (grade F) - a winter grade, and the sulfur content in this fuel is not more than 50 ppm (mg / kg).

Example2. "DT Euro class 2, type I". The word "CLASS" means that this fuel is intended for the cold and arctic climate zone. Class "2" indicates that the limiting filterability temperature is minus -32 °C. Type I indicates that the sulfur content is not more than 350 ppm (mg/kg).

Seasonal use of diesel fuels in the regions Russian Federation in accordance with the requirements for the limiting temperature of filterability

Central Federal District	The use of diesel fuel according to the maximum filterability temperature
	summer period			transitional spring/autumn periods			winter period
	grade A	grade B	grade C	grade D	grade E	grade F and class 0	class 1	class 2	class 3	class 4
	not higher than +5 °С	not higher than 0 °C	not higher	not higher than -10 °С	not higher than -15 °С	not higher -20 °С	not higher -26 °C	not higher than -32 °С	not higher than -38 °С	not higher than -44°C
Belgorod region
Bryansk region
Voronezh region
Kursk region
Lipetsk region
Oryol region

In accordance with climatic conditions, it is allowed to change the number of days of the spring and autumn transitional periods towards winter or summer by agreement of the local administration with the regional services of the Hydrometeorological Center.

The requirements for diesel fuel according to GOST R 52368-2005 (EN 590:2009) are as follows:

Name of indicator	Meaning
1. Cetane number, not less than	51,0
2. Cetane index, not less than	46,0
3. Density at 15 °С, kg/cu.m.	820 - 845
4. Polycyclic aromatic hydrocarbons, % (by mass), no more
View I	350,0
View II	50,0
View III	10,0
6. Flash point in a closed crucible, °C, above
7. Coking capacity of 10% distillation residue, % (by mass), no more	0,30
8. Ash content, % (by mass), no more	0,01
10. General pollution, mg/kg, no more
11. Corrosion of a copper plate (3 hours at 50 °C) 6), units on a scale	Class 1
12. Oxidative stability: total sediment, g / cu. m, no more
13. Lubricity: corrected wear scar diameter at 60 °C, microns, not more
14. Kinematic viscosity at 40 °C, sq. mm/s	2,00 - 4,50
15. Fractional composition:
At a temperature of 250 °C,% (by volume), less than
At a temperature of 350 °С, % (by volume), not less than
95% (by volume) is distilled at a temperature, °C, not higher

(No. 8 for 2010)
Vladimir SHLYAKHOVOY

Sulfur

Diesel fuel is characterized by a number of sufficiently important parameters and one of the main among them is the sulfur content. Theoretically, the presence of sulfur improves the lubricity of the fuel, but this is nothing compared to the problems that arise when it is burned during engine operation. The resulting sulfur oxides react with water vapor to form sulfuric and sulphurous acids, which in one quantity or another necessarily enter the engine lubrication system. But, besides, what kind of "Euro" can we talk about, if from exhaust pipe pouring sulfuric acid fumes? Yes, and exhaust gas aftertreatment systems, and particulate filters when using sulphurous fuel, they quickly fail. Therefore, along with the growth of requirements for the purity of exhaust gases, the requirements for fuel quality also naturally grow. Including the content of sulfur in it.

For example, in accordance with the current standards, the type of fuel must be indicated depending on the sulfur content in it. In Russia, since 2005, the GOST R 52368-2005 (EN 590:2004) standard has been in force. Fuel diesel EURO. Specifications”, and in Ukraine from January 1, 2008 a similar standard DSTU 4840:2007 “Diesel fuel of improved quality. Specifications”, corresponding to the same standard EN 590:2004. However, DSTU 3858-99 “Diesel fuel. Specifications”, which replaced GOST 305-82 in Ukraine from September 1, 1999, has not yet been canceled, it will operate along with DSTU 4840:2007 until the end of 2010.

Table 1. Cetane number and maximum sulfur content in diesel fuels different kind, mg/kg, depending on the standard

Characteristic	DSTU 3868-99	GOST R 52368-2005	DSTU 4840:2007
cetane number

*Fuel with a sulfur content of not more than 10 mg / kg in the accompanying documents may be designated as "sulfur-free" .

Table. 2 Cetane number and maximum sulfur content in diesel fuels of various environmental norms and standards

	cetane number	Sulfur, mg/kg
DSTU 3868-99**
GOST R 52368-2005*
EN 590 (up to 1.01.2005)
DSTU 4840:2007**
EN 590 (from 1.01.2005)

*Standard valid in Russia.

**Standards in force in Ukraine.

Thus, in Ukraine it is now possible to refuel with equal success both with diesel fuel of the Euro-5 level, containing sulfur in an amount of 10 mg / kg, and with “Soviet” diesel fuel, in which the concentration of sulfur is 500 (!) times higher.

Frost resistance

Perhaps the second most important parameter of diesel fuel is its frost resistance, which is inversely proportional to the amount of paraffins in it. When the temperature drops, paraffins tend to crystallize, as a result of which diesel fuel first becomes cloudy, then turns into “jelly”, and then completely freezes. Therefore, the integral characteristics of diesel fuel are its parameters such as cloud point and limiting filterability temperature, which are specific for each type of diesel fuel and are separated from each other by about 10 ºС.

At the same time, both of the above parameters are rather conditional, and therefore one should not think that cloudy fuel can be used painlessly. Especially if fuel filters do not have heating. Indeed, in this case, their filter elements will very quickly become tightly clogged with paraffin, which cannot be removed by anything. We will keep silent about the fact that in such a case further operation of the engine is in principle impossible. And to solve the problem, you will have to change very expensive filter elements.

The reason for the cloudiness of diesel fuel is the appearance of groups of oriented paraffin molecules, which become centers for the formation of crystals. At the same time, the minimum allowable temperature for the use of diesel fuel, at which its normal pumpability through the fuel system through the filter elements is ensured, is at least 2 ºС higher than its cloud point.

As for such a concept as "limiting diesel fuel filterability temperature", it means the limit at which cooled diesel fuel is able to pass through a standard filter element at a certain speed. This indicator is used only to determine the possibility of starting the engine. But if unheated fuel filters are used in this case, they will immediately be blocked by paraffin.

To this we can add that such a parameter as the “pour point of diesel fuel” is also normalized, the cause of which is the coalescence of hydrocarbon crystals to each other into a rigid crystal lattice. The pour point determines the possibility of transporting, refueling, draining and pouring diesel fuel into tanks and has no practical significance for determining the possibility of starting the engine or its operation.

And in order to be able to easily determine in what temperature ranges one or another diesel fuel can be used, according to the requirements of the standards, its symbol must indicate the grade (depending on the values ​​​​of the limiting filterability temperature, or class), determined by both the filterability temperature and the temperature turbidity.

In this case, the grade is set for fuel intended for use in areas with a temperate climate, and the grade is set for the arctic zones.

Table 3. Requirements for low-temperature properties of diesel fuel (GOST R 52368-2005)

Name of indicator
Limiting filterability temperature, ºС, not higher
Cloud point, ºС, not higher
Cetane number, not less than

* N / N - not standardized.

At the same time, Ukrainian DSTU 4840:2007 provides for the same six grades (AF), but only two classes (0-1) of diesel fuel, as GOST R 52368-2005, regulates a lower sulfur content and a higher cetane number (at least 51 ). Whereas DSTU 3868-99, which will be valid in Ukraine until 01/01/2011, provides for only two grades of diesel fuel: L - summer and Z - winter.

Table 4. Requirements of DSTU 3868-99 for low-temperature properties of diesel fuel

In this regard, diesel fuel can be labeled as follows:

- "Diesel fuel EURO according to GOST R 52368-2005 (EN 590:2004), grade A, type I";

- "Diesel fuel of high quality (Euro) class 1, type II in accordance with DSTU 4840:2007".

In a word, it is quite difficult to understand all this variety of varieties, classes and types of diesel fuel. Theoretically, as a substitute for winter and arctic diesel fuel for diesel engines you can use kerosene. But in practice this cannot be done, since kerosene has two significant shortcomings. Firstly, its cetane number is about 40, which is too low for normal engine operation. And secondly, kerosene, unlike diesel fuel, does not have lubricating properties, so all rubbing parts in the fuel system (high-pressure fuel pump, plunger pairs, etc.) will quickly become unusable.

This is allowed only in exceptional cases and only as a temporary remedy, especially on older engines with a mechanical injection pump. But even in this case, it is necessary to introduce anti-wear and cetane-boosting additives. It is believed that without damage to the engine, up to 20% of kerosene can be added to summer diesel fuel to reduce its pour point. But this, too, should be considered only as an extreme measure, unacceptable on modern engines with high injection pressure.

cetane number

An important indicator for diesel fuel is the cetane number (CN), which characterizes the flammability rate of the fuel - from the moment it is injected into the cylinder to the start of combustion (the self-ignition delay period). And the higher the CC, the faster the diesel fuel ignites.

The numerical value of the CN is equal to the percentage of cetane (C16H34, the CN of which is taken as 100) in its mixture with α-methylnaphthalene (its cetane number is 0), the flammability of which is equivalent to the tested diesel fuel. In this case, the CC is determined by testing on a motor installation.

With a cetane number of less than 40, due to the long ignition delay period, the fuel in the cylinder has time to warm up well, so the ignition is explosive, the pressure in the cylinder rises sharply, which leads to knocks in the engine. This operation of a diesel engine is called rigid, since it causes shock loads on the piston and crankshaft bearings, which leads to their accelerated wear.

The higher the cetane number, the shorter the ignition delay, the smoother the burn fuel mixture, the smoother the engine runs and the cleaner the exhaust. But it's good up to certain limits. Diesel fuel with a CC above 55, which has a short self-ignition delay period, having entered the cylinder, does not have time to warm up well, so the pressure in the cylinder increases evenly and the engine runs smoothly. However, in this case, the mixture formation process deteriorates, since the fuel does not have time to mix well with air, which leads to incomplete combustion of the fuel, a decrease in engine power and efficiency, and an increase in exhaust smoke. In addition, diesel fuel with a high CN is much more expensive. Therefore, unlike the octane number, which the higher the better, the cetane number has its own operating range of 40 - 55 units, the optimum of which is 51 - 53 units.

At the same time, standard diesel fuel is characterized by a cetane number of 40 - 45, and top quality fuel has a cetane number of 51 - 55. According to modern standards, the CN of summer and winter diesel fuel should be at least 49 units. (According to the EN 590:2004 standard, the CN must be at least 51, and the cetane index (the same, but determined by calculation) must be at least 46.)

To this we can add that the cetane number indirectly indicates the low-temperature characteristics of the fuel - the lower it is, the lower the pour point. Therefore, summer and winter diesel fuels usually have different CNs, and for Arctic diesel fuel, it is completely on the verge of hard engine operation. But here the soft work of a diesel engine is often deliberately sacrificed in order to ensure its normal start-up and fuel pumpability through filters in severe frosts. At the same time, diesel High Quality lighter, contains more flammable light fractions and is therefore more suitable for starting the engine in cold weather. In addition, the ratio of hydrogen to carbon in light fractions is higher, so less smoke is generated during the combustion of such diesel fuel.

Coking capacity, ash content and others…

Other standardized parameters of diesel fuel include its coking capacity, which contributes to the formation of deposits in the combustion chamber and on piston rings, and ash content, which determines the non-combustible fuel residue. Thus, the coking capacity of the 10% residue remaining after distillation of the volatile fractions of diesel fuel should be within 0.3%, and the ash content should not exceed 0.01%, while according to the previous standards, this value was ten times higher.

As for various additives, they are usually added industrially only to special grades of diesel fuel, primarily to the Arctic. Although sometimes manufacturers throw special grades of fuel onto the market.

These include, for example, Shell V-Power Diesel.

For the first time this fuel was presented in Italy in 2002. And now it has appeared in Ukraine. At the same time, neither Russian nor Belarusian drivers can yet refuel with such fuel, despite the fact that Shell came to Russia much earlier than to Ukraine. In Belarus, there are no Shell gas stations at all.

The new fuel is produced on the basis of Eurodiesel that meets Euro-4 (type II) standards, with the addition of a special detergent additive NEMO 2010. At the same time, as the manufacturer declares, the composition of Shell V-Power Diesel helps to remove existing deposits and prevents the formation of new deposits in combustion chamber of the engine, which contributes to the extension of its resource, stable power and improvement of environmental parameters. This fuel contains no more than 0.05% (50 mg / kg) of sulfur, but it also costs the same as AI-95.

According to Shell representatives, a run of 2400 km on Shell V-Power Diesel fuel is enough to almost completely clean the combustion chamber and injector. Naturally, the benefits of this fuel can be most pronounced when used on used cars, while on new cars the difference will not be noticeable.

Diesel fuel is obtained by refining oil, so sulfur compounds remain one of its components. Although there is no pure sulfur in the composition of the fuel, its derivatives are still present in a fairly large amount (up to 7%). To remove part of the sulfurous substances and improve the environmental friendliness of diesel fuel, various types of purification are used - hydrocracking and alkaline treatment with caustic soda.

Reasons for limiting sulfur content in fuels are:

1. corrosive effect on piston elements;
2. the appearance of soot and deposits;
3. premature wear fuel and exhaust system;
4. exhaust smokiness;
5. emission of sulfur compounds and other harmful substances into the atmosphere;
6. non-compliance with standards, which limits the use of cars.

To extend the life of diesel engines and avoid environmental pollution, restrictions on the sulfur content in diesel fuel have been adopted.

The effect of sulfur in diesel fuel on the engine

The current standards strictly regulate the fractional composition of fuel, including sulfur compounds. However, a certain percentage of such substances still remains, despite the purification and processing of the feedstock. Complete removal of sulfides and other sulfur elements is very expensive and uneconomical.

The presence of such sulfurous substances, when interacting with water vapor, leads to the formation of sulfurous and sulfuric acid. The result is corrosion of metal parts. piston group, fuel and exhaust systems. The formation of deposits impairs heat dissipation, reduces compression, and limits the mobility of the rings.

The effect of sulfur on fuel properties limits and specifications diesel engines themselves, namely:

• power is reduced;
• increased fuel consumption;
• deteriorating power and overclocking characteristics.

Due to the high sulfur content in marine fuel or fuel for other diesel engines, the process of combustion of the mixture itself changes. As a result, a loss of power, a decrease in efficiency and a deterioration in the dynamics of a diesel engine are possible.

Keep in mind that low sulfur content is also not very good for diesel. With a decrease in sulfur compounds below 0.035%, the lubricating properties of the fuel deteriorate. The result is premature wear and reduced fuel system life. To eliminate this problem, special additives are used.

Diesel environmental standards

A certain balance between the content of sulfur substances and the environmental friendliness of the fuel was achieved with the advent of the relevant standards (Euro 0-6). These standards regulate the emission of harmful elements and technical characteristics diesel fuel. The latest adopted options are Euro 5 and 6 (2009 and 2015 respectively), according to which harmful emissions should not exceed the following values:

1. carbon monoxide - 0.5;
2. nitric oxide - 0.18 - 0.08;
3. suspended particles - 0.005.

The presence of hydrocarbons and volatile organic substances is not allowed at all.

Specifications of diesel fuel

Cars, trucks, buses and special vehicles are refueled according to climatic conditions. There are summer, winter and arctic fuels. According to the temperature of use, the fuel is divided into grades (A-F) and classes (0-4). Such fuel is characterized by the following indicators:

• cetane number 45–51;
• sulfur content in diesel fuel Euro 5 and 6 - no more than 10 mg;
• filtration temperature - up to -55 °С;
• density in the range of 0.830-0.860 g/cm 3 .

According to Russian GOST, the sulfur content in diesel fuel should also not exceed 10 mg.

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