So that the diesel does not freeze .... Freezing point of diesel fuel

pour point diesel fuel should be practically 10 - 15 C below the ambient temperature. When cooled, it can thicken, which adversely affects the supply of fuel from the tanks to the engine cylinders.

The pour point of diesel fuel is a conditional value and serves only as a known guideline for determining possible conditions for the use of fuel. When pumping fuel under pressure, the crystalline structure of high-melting hydrocarbons can be mechanically destroyed, and the fuel becomes fluid for a certain period at a temperature below the pour point. In particular, the above figures for the performance of the booster pump for various temperatures and pressures were obtained using fuel with a pour point of -30 C. But in fact, this fuel was pumped to a temperature of -50 C. It should be noted that the destroyed crystalline structure of the fuel is quickly restored.

The pour point of diesel fuel, determined according to GOST 1533 - 42, has great importance for operation of engines, transportation and storage of fuel. The pour point of diesel fuels is the temperature at which the fuel in a laboratory test tube inclined at an angle of 45 does not change its level for one minute. The fuel may solidify due to the presence of a large amount of paraffin hydrocarbons in it, the release of which causes clouding of the fuel, their deposits on fuel filters and cutting off the fuel supply. Diesel fuels saturated with paraffin are used only in the summer. The pour point of diesel fuel also depends on its fractional composition. Heavier in terms of fractional composition, fuel from the same oil has a higher pour point.

The pour point of diesel fuel is a conditional value and serves only as a guideline in determining the conditions for the use of fuels.

The pour point of diesel fuels must be below the air temperature in winter time(affects the flow of starting without heating); no paraffin should be released.

The pour point of diesel fuels is the temperature at which the fuel in a standard tube loses its ability to change its level when the tube is tilted at an angle of 45 for 1 min. For reliable operation of the engine, this temperature should be 7 - 10 C lower than the ambient air temperature.

After hydrotreatment, the pour point of diesel fuel increases by 1 C. Therefore, in order to eliminate the need for dewaxing diesel fuel of brand L during its complete selection, the distillate obtained in the atmospheric column must have a margin of pour point. For this, it is necessary, as shown above, to increase the clarity of the separation of diesel fuel from gas oil fractions.

To determine the pour point of diesel fuels, the LPAZ device has been developed. In this device, the fuel sample in the cuvette can be cooled down to -20 C with the help of a semiconductor cooler. The fuel cooled in the cell is constantly probed by ultrasonic pulses. The fuel temperature is measured by a thermocouple sensor. The pour point is the temperature at which there is a sharp decrease in the reflected ultrasonic signal. This temperature is fixed by an electronic potentiometer.

To lower the pour point of diesel fuels obtained from paraffinic oils, special depressant additives are used, the choice of which must take into account not only their positive influence on certain fuel qualities, but also to analyze the possible negative consequences of the introduction of this additive; in particular, special attention should be paid to the effect of the additive on the metal parts of the engine.

To determine the pour point of diesel fuels, the LPAZ-69V device is used. In this device, the fuel sample in the cuvette can be cooled down to - 35 C with the help of a semiconductor cooler.

With the onset of cold weather for many owners diesel vehicles the painful question arises of how to eliminate the problems associated with the solidification of diesel fuel. Moreover, it is most relevant in the off-season, when there is no certainty about what kind of fuel - winter or summer - gas stations actually sell.

Several ways to prevent fuel freezing.

One option is to conduct a personal experiment: pour diesel fuel into a transparent bottle and evaluate the reaction of the contents to low temperatures. If already at zero temperature the fuel becomes cloudy, then it is not recommended to refuel at this gas station.

Another option - the well-known "old-fashioned" way - is to dilute diesel fuel with kerosene. But there is an important nuance! Kerosene does not contain lubricants. Therefore, diesel fuel diluted in this way cannot provide the diesel fuel equipment with the necessary lubricating properties. This leads to a decrease in the life of the high pressure fuel pump (TNVD) and injectors, increases the likelihood of their breakdown and, consequently, costly repairs. This is of particular importance for modern diesel systems such as common rail and unit injector. In addition, kerosene reduces the cetane number of fuel, which makes it difficult to start the engine in winter and increases fuel consumption.

The most reliable way is to add anti-gels with each filling. Unlike kerosene, anti-gel does not reduce the lubricating properties and does not affect the cetane number of diesel fuel! The antigel is easy to use, it is poured into the tank immediately before refueling. The action of antigels is aimed at reducing the limiting filterability temperature and the freezing point of diesel fuel. But they must be filled in before the fuel has thickened or solidified, because no anti-gel can defrost it.

Why ASTROhim® Antigel?

Since 2003, ASTROhim® Antigel has been produced according to German technology and from BASF® (Germany) raw materials. The use of high-quality imported components made it possible to dramatically increase the efficiency of the additive and ensure stable quality.

Below are the results of some tests of different brands of anti-gels, organized by reputable automotive publications.

The results of testing antigels by the journal “Consumer. Avtodela (No. 27, 2003)

The results of testing antigels by the magazine "Behind the wheel" (No. 1, 2008)

Investigation of the effect of antigel on the low-temperature properties of fuel.

VNII NP, Protocol No. 29/14-3-846 dated 12/24/2012

It should be noted that the effect of the use of anti-gels (reducing the limiting filterability temperature and pour point) directly depends on the grade and quality of diesel fuel.

ASTROhim® antigel features.

Antigel ASTROhim® was developed specifically for Russian diesel fuel and fully complies with the requirements for servicing modern diesel systems. The additive effectively improves the fluidity of diesel fuel when operating a car in winter - significantly reduces the limiting filterability temperature and the freezing point of diesel fuel. Due to the content of dispersants in the additive, it prevents paraffin crystals from settling to the bottom of the fuel tank and fuel stratification. This improves the pumpability of fuel through fine filters. In addition, Antigel ASTROhim® extends the life of the injectors and the high pressure fuel pump, makes it easier to start the engine and reduces fuel consumption.

In the event that it is impossible to accurately determine how much fuel is contained in the tank, it is allowed to exceed the concentration of antigel. In this case, a slight improvement in temperature values ​​is possible.

ASTROhim® Antigel is available in vials and canisters with different concentrations, specially designed for fuel tanks of various sizes:

It has a higher efficiency when compared with a gasoline unit. This increases its power and mileage. And this fuel is cheaper than gasoline. These two reasons attract users to purchase diesel cars.

However, this does not mean that such an engine is ideal. Problems with its use can arise in winter, when frost sets in. Inexperienced drivers often find themselves in a situation where the fuel is frozen and the car engine has stalled.

How does diesel fuel freeze?

DF includes hydrocarbons of various groups - naphthenic, aromatic and paraffinic. At the same time, the latter are to blame for the freezing of the fuel. The positive function of these hydrocarbons is to increase the rate of ignition of the fuel. But at low temperatures(about -5 ºС for summer diesel fuel), they begin to crystallize into a solid phase in the form of flakes and the fuel becomes cloudy.

At the cloud point of the fuel, the engine continues to operate normally. It also works at the limiting filterability temperature (-7 ºС), but at this stage the paraffin crystals begin to coagulate (stick together). With a further decrease in temperature (-10 ºС), agglomerates are formed, which no longer pass through the filter cells and clog it. The engine stalls without getting fuel. This occurs at the freezing point of diesel fuel.

Features of the fight against frost

The fight to lower the freezing point of the fuel, allowing the engine to operate in frost, is underway. different ways. The most expensive is the replacement of summer fuel with winter fuel. The latter, intended for cold climates, is obtained by the dewaxing process - the removal of hydrocarbons with a high melting point at the production stage.

Since the yield of fuel from crude oil is halved, the price also increases. The freezing point of such winter diesel fuel is - 45 ºС, it becomes cloudy at -35 ºС, it is recommended to use it at a temperature not lower than -30 ºС.

More in a simple way get winter diesel fuel for the temperate climate zone.
In summer, pour point depressants are added, which prevent paraffin crystals from sticking together. The freezing point of this summer diesel fuel, which has actually become winter, is -35 ° C, cloudiness - -25 ° C. It is recommended to use it up to -15 °C.

Every motorist can make summer fuel into winter fuel in this way outside the factory conditions. To do this, when frost sets in, add a depressant additive in accordance with the instructions. It is important that during this operation the temperature of the fuel is not lower than +5°C, otherwise the effect will be zero.

What methods of lowering the freezing point should be feared?

Along with established methods for lowering the pour point, there are many fraudulent methods. Most often, summer diesel fuel is diluted almost by half with kerosene or other petroleum products and the resulting composition is passed off as a normal winter one. It really works at low temperatures, but kerosene sharply reduces the lubricity of fuel - in just one season, a car engine can fail.

It is impossible to know what freezing point the purchased diesel fuel has. We recommend that you do not buy fuel from random sellers, but refuel at reliable and trusted gas stations.

Every winter, owners of cars and other equipment with diesel engine faced with such a problem as the freezing of fuel. In Russia, and especially in its northern parts, it is particularly acute. In order to figure out how to cope with this problem, it is necessary to understand the mechanisms of its occurrence.

Diesel fuel contains heavy hydrocarbons. Some of them are representatives of the paraffin group. Under the influence of low temperatures, these hydrocarbons crystallize, which increases the viscosity of the fuel and, subsequently, leads to its partial or complete solidification.

Types of diesel fuel

There are several types of diesel fuel: summer, winter and arctic.

. Summer diesel fuel. It freezes at -5 degrees Celsius. It is quite problematic to use it at temperatures below -7

. Winter diesel fuel. It begins to harden at a temperature of -35 degrees Celsius. The production of this fuel is much more expensive and its price is correspondingly higher.

. Arctic diesel fuel. It starts to freeze at -50 degrees Celsius. It contains special additives, thanks to which the fuel does not freeze at low temperatures.

Frozen diesel

There are ways to help avoid freezing diesel fuel:

.Diesel fuel dewaxing- this is the process of removing normal paraffinic hydrocarbons from kerosene-gas oil and oil fractions of oil. This is an industrial way to create a winter and arctic diesel engine, performed at the production stage. There are two dewaxing technologies. Solvent and catalytic. Deparaffinization is an expensive method and extremely difficult to implement under normal conditions.

.Diesel antigel- depressant additive for diesel fuel, which allows to improve the low-temperature properties of the fuel. This is a more practical method of dealing with diesel freezing. The depressant additive is introduced into the composition of diesel fuel and due to this, the size of paraffin crystals is reduced to such that they can freely pass through the filters of the fuel system, without affecting the operation of the engine. The mechanism of their action lies in the fact that at the moment of crystallization they envelop the formed paraffin particles and do not allow them to combine into clots, and this is enough to ensure the pumpability of the fuel through the filter and expand the temperature range of using summer fuel or improve the low-temperature properties of winter fuel. However, it must be remembered that antigels cannot prevent crystallization, they modify the dissolved paraffins. Therefore, they should be added exclusively to "warm" fuel, before it starts to freeze. At the time of anti-gel refueling, the temperature of the fuel should be from 0 to + 5 ° C, that is, 5-10 degrees more than the thickening temperature of summer fuel. Otherwise, there will be no result. The antigel itself should be warm at the time of injection. It does not lose its properties when it freezes, but in case of freezing it must be heated.

. Adding quality kerosene to fuel- an old but proven method. At a temperature of minus 20-30 degrees Celsius, about 10% of kerosene (from the entire fuel mixture) is added to winter fuel at minus 10-15 - 50% of kerosene. When the temperature drops below minus 15, 60-70% of kerosene is added. This method is considered temporary, but effective.

. Heating of diesel fuel- a way to defrost a frozen diesel engine using external heat sources. In emergency situations, if diesel fuel is frozen, you can use any available heat source. For example, you can use the exhaust gases of another car. Please note that it is not recommended to send open source flames on the tank, as this can cause an explosion of fuel.

Some believe that blending gasoline and diesel fuel is the most effective way to prevent fuel from freezing at low temperatures. But still, it must be borne in mind that gasoline worsens the lubricating qualities of diesel fuel, spoils fuel pumps and jets. It also increases the combustion time of the fuel and increases carbon formation.

Fuel heating systems

There are also self-regulating fuel heating systems. Thanks to them, the fuel does not become viscous and the likelihood of fuel freezing is reduced. Another advantage of these systems is the absence of the need to use anti-crystallizers and kerosene. The essence of the operation of such systems is that they heat the diesel fuel and thanks to this, the fuel can get from the tank into the engine without interference. This type of devices can be conditionally divided into two types: pre-start and flow. The main function of both systems is to ensure the free passage of diesel fuel through the fine filter, because in cold weather, the precipitated paraffin clogs this particular filter. Prestarting devices do their work before starting the engine, and flow devices - during the supply of fuel to the cylinders. In order for the engine to start in any frost and to work confidently at low temperatures, it is recommended to install both heaters.

There is another type of heating systems - a nozzle on a standard fuel collector, which is installed in the car's tank. As a rule, such nozzles are used in northern latitudes, but this unit can also be useful for those who often go to nature in winter.

Modern diesel-fueled vehicles, for the most part, have a fuel heating system. A similar system can be installed in a car in which it is not. But this device is not suitable for all cars and installation requires a highly qualified specialist who performs it.

The pour point of fuels must be taken into account when carrying out storage operations for unloading, loading and pumping through pipelines.
The pour point of the fuel, or, more precisely, the temperature at which normal filtration is disturbed, is of decisive importance for the operation of diesel engines in winter. This is due to the extreme sensitivity of fine filters to an increase in the viscosity of the fuel and the precipitation of sludge and solids from it. According to Hagemann-Hammerich, the filtration time of 200 cm3 of fuel at -15 C should be less than 60 seconds.
Device for determining the limiting filterability temperature. The pour point of the fuel, determined according to GOST 20287 - 74, only to some extent characterizes the behavior of the fuel in the engine power system.
The pour point of fuels (samples 4 and 5) with the introduction of 0 1% additive noticeably decreases, however, after a month of storage, the effect of the additive ceased. Thus, the VES-6 additive, even when introduced at a concentration of 0–5%, does not have a noticeable effect on the stability of the pour point of fuels obtained from highly paraffinic oils.
The pour point of the fuel (GOST 20287 - 74) is determined by cooling the fuel in a test tube placed in the cooling mixture. The fuel tube is kept in the cooling mixture until the product in the tube reaches the temperature indicated for the solidification test. Then the tube is tilted at an angle of 45 and left in this position for 1 min. If the meniscus of the test product has not shifted, the product in the test tube is heated to 50 1 C and a new determination is made, but already at a temperature 4 C higher than the previous one. And so the definitions continue until, at a certain temperature, the meniscus moves. When the freezing point is established, the determination is repeated. The pour point of the product is taken as the arithmetic mean of the temperatures established in two parallel tests.
The pour point of the fuel is reduced to minus 45 - minus 60 С.
The pour point of fuel, as is known, is not a constant value, but is determined by the nature and type of fuel and the method of its production. Naturally, the pour point of fuel-water emulsions depends, on the one hand, on the pour point of the fuel itself, and on the other hand, on the presence of water. Generally, increasing the water content of a fuel increases its pour point.
The pour point of the fuel determines the possibility of its use at a given air temperature. In practice, the pour point of the fuel should be 10 - 15 C lower than the ambient air temperature.
The pour point of the fuel depends on its fractional composition. Heavier fuel has a higher pour point.
The pour point of the fuel determines the possibility of its use at a given air temperature. In practice, the pour point of the fuel should be 10 to 15 degrees lower than the ambient air temperature.
The pour point of fuel for high-speed units located in a cold room must be at least 10 ° C below the minimum local temperature. For other installations, the type of fuel used depends on the operating conditions of the engine and the availability of fuel heaters at the stations.
The pour point of the fuel corresponds to such a limiting temperature at which the fuel loses its fluidity. This indicator serves as an approximate guideline in determining the possible limiting conditions for the use of fuels, and to a greater extent, this indicator is used to judge the possibilities of refueling, transporting, draining and loading fuel.
The pour point of the fuel should be 5 - 10 C below the temperature environment, in which the engine is running, otherwise the fuel filtration deteriorates and its supply may stop.

The pour point of fuels must be determined after their dehydration, since the presence of water, especially for low-viscosity fuel oils, affects the correctness of the determination. This can be seen from the following figures.
A device for determining the freezing point and cloudiness of gasoline. The pour point of the fuel is the temperature at which the fuel thickens so much under experimental conditions that when the test tube is tilted at an angle of 45, the level remains stationary for 1 min.
The pour point of fuels is the temperature at which the test fuel cooled in the test tube under experimental conditions freezes so much that when the test tube is tilted at an angle of 45 it remains motionless for 1 min.
The pour point of a fuel is the temperature at which crystals visible to the naked eye form in the fuel.
The pour point of fuels is the maximum temperature at which the fuel thickens to such an extent that when the tube with it is tilted at an angle of 45, the product level remains stationary for 1 min.
The pour point of the fuel is the temperature at which the fuel thickens so much under experimental conditions that when the test tube is tilted at an angle of 45, the level remains stationary for 1 min.
According to the pour point of the fuel, they correspond to summer grades.
A sharp increase in the pour point of fuel when small amounts of high-melting normal paraffin hydrocarbons are added to it is explained by their low solubility in hydrocarbons of other classes at low temperatures. With an increase in fuel temperature, the solubility of paraffinic hydrocarbons increases slowly at first, and then, as the temperature of the medium approaches the melting point, they increase sharply. The solubility of paraffinic hydrocarbons also depends on their melting point and the nature of the solvent. With an increase in the melting point, the solubility of paraffinic hydrocarbons in the fuel decreases. The closer in structure the hydrocarbons that make up the fuel to paraffinic hydrocarbons, the better their solubility in the fuel. Along with purely paraffinic hydrocarbons, the crystallization of higher-boiling fractions of jet and especially diesel fuels is also caused by monocyclic naphthenic and aromatic hydrocarbons, which have long side chains of a normal structure.
US specification for diesel fuel for city and intercity buses. The specification does not regulate the pour point of the fuel, but, like the ASTM specification, stipulates that it should be 5 6 C below the ambient temperature.
It is most expedient to reduce the pour point of fuels by using depressants. Significantly improving the pour point and viscosity at low temperatures of boiler fuels, it has practically no effect on their other physical and chemical properties.
Influence of paraflow additive on the pour point of fuels. /, 2, 3 - a mixture of Grozny and Balakhan solar distillates (ratio, and, respectively. 4 - a mixture of Grozny solar distillate with Bibieybat sulfonated (1. 2. 5-mixture of Grozny solar distillate with Emben sulfonated (1. 2.
The ability of depressants to lower the pour point of fuels depends on the concentration of the depressant and the nature of the fuel.
The dependence of the pour point (/ and exit (2 deparaffinate) on the temperature of complex formation. | fuel and its yield increase, which indicates incomplete complexation.
Influence of paraflow on the filterability of fuels. However, due to the fact that the pour point of fuels decreases quite significantly when depressants are added, the difficulties associated with the transportation, storage, pumping and refueling of such fuels are significantly reduced. Therefore, it should be recognized that the addition of depressants to jet and diesel fuels will certainly improve their low-temperature properties, although it will not completely solve the problem of fuel filtration at low temperatures.
Consequently, the use of such additives that lower the pour point of fuels makes it possible to carry out work on draining, loading and pumping fuels through pipelines at lower temperatures, but these additives do not affect the expansion of low-temperature limits for the use of fuels on engines, since they practically do not change the temperature cloudiness of the fuel.
The size and shape of wax crystals also affect the pour point of fuels. However, according to D. L. Goldstein, this does not improve the fluidity of fuels in the fuel-conducting system. The experiments of this author have established that the filtration of initial fuels and fuels containing paraflow is interrupted at approximately the same temperature (Fig.
Influence of paraflow on the viscosity of fuels. More often, the structure is formed at a temperature several degrees higher than the pour point of the fuel.
Influence of paraflow on the pour point of fuels. Paraflow and other studied depressants, while reducing the pour point of fuels more or less effectively, have practically no effect on the cloud point of fuels.
Typically, PTF is lower than the cloud point and higher than the pour point of the fuel.
The pour point of fuel such as kerosene is equal to - 50 C, slightly lower than the pour point of a similar fuel isolated from oil before refining; its value reaches - 38 - 40 C. As in the case of fuels such as kerosene, the pour point of diesel fuel obtained after oil cracking, equal to - 7 - 9 C, is lower than the pour point of diesel fuel (: - 3, - 5 C) isolated from oil before refining. Attention is drawn (Table 64) to the high yields of isobutane in the process of refining Romashkino oil. Under optimal conditions, catalytic cracking gases contain 20–23% isobutane.
The use of depressant VES-241 with a concentration of up to 0 1% allows to reduce the pour point of the fuel to -15 C. It is a low molecular weight copolymer of ethylene with vinyl acetate, which is a by-product of the production of sevilen.
When studying the depressant activity of compounds such as polyalkyl methacrylates, an assumption was made about another mechanism for reducing the pour point of fuels. It is believed that the pour point depressant is involved in the crystallization of paraffinic hydrocarbons, penetrating into the resulting chains with the formation of eutectic crystals. This co-crystallization theory explains well some of the results of studies on the effectiveness of polyalkyl methacrylates.

Ensuring normal fuel supply, start-up and operation of the engine at low temperatures is determined by the pour point of the fuel. In practice, the pour point of the fuel should be 10 to 15 degrees lower than the ambient air temperature. With the increase in fuel viscosity caused by cooling, the booster pump is unable to supply fuel to the fuel pump, and at very low temperatures, the fuel may completely lose fluidity. When the temperature drops, paraffin crystals are released from the fuel, clogging filters and fuel lines. Corrosion of engine parts is determined by: a) the sulfur content in the fuel; b) the content of water-soluble acids and alkalis.
The effect of the content of diesel fractions in marine fuel oil F-5 and depressant additive VES-6 on the pour point of fuel during storage has been studied.
To ensure a reliable supply of fuel to the engine cylinders in winter, the pour point of the fuel is also of great importance. The pour point of diesel fuels is the temperature at which the fuel in a standard test tube loses the ability to change its level within 1 minute. For reliable operation of the engine, this temperature should be 5-10 C lower than the ambient air temperature during vehicle operation. Additionally, GOST provides for the determination of the cloud point of diesel fuel. This definition according to GOST 5066 - 49 consists in cooling the tested fuel and establishing the temperature at which it becomes cloudy due to the onset of crystallization of the hydrocarbons that make up its composition.
When carrying out urea dewaxing of diesel fuel using settling-washing centrifuges at the pilot plant of the State Oil Refinery, a decrease in the pour point of fuel from -9 to -48 G was achieved, and high-quality synthetic fatty acids and alcohols were obtained by oxidizing the paraffin separated from the fuel.
The latter is achieved by dewaxing distillates in the production of winter grades of fuel, in which, as a result of the extraction of paraffin or the introduction of special additives, the pour point of the fuel decreases and clogging of pores and the formation of a layer of paraffin on the filter partition are excluded in the filters. During their production, fuels must be cleaned of all contaminants (tars, sulfur, naphthenic acid soaps, water, mechanical impurities), which also cause blockage of filter pores and interfere with the operation of fuel equipment.
For all high-melting hydrocarbons, regardless of the melting point, there is a limit to their percentage in solution, above which paraflow has no effect on the pour point of the fuel.
In diesel fuels, the presence of normal alkanes is desirable, since they have good flammability (maximum H:C ratio), but at the same time increase the pour point of the fuel. Therefore, in diesel fuels, the permissible amount of normal paraffinic hydrocarbons is determined by the pour point according to GOST.
By modern technology from distillates of diesel fuels, when grades 3 and A are obtained, n-alkanes C 2 - C 2o are deeply extracted (up to 95% of the potential) in order to lower the pour point of the fuel and at the same time obtain a valuable product for petrochemistry - liquid paraffin (see further section

Depending on the conditions of use, three grades of diesel fuel are installed: L (summer) - for operation at ambient temperature C and above; 3 (winter) - minus 20 C and above (fuel pour point not higher than minus 35 C) and minus 30 C and above (fuel pour point not higher than minus 45 C); A (arctic) - minus 50 C and above.
Diesel fuel grades are subdivided into types: L (summer) - for operation at an ambient temperature of 0 C and above; 3 (winter) - for operation at an ambient temperature of - 20 C and above (fuel pour point not higher than - 35 C) and - 30 C and above (fuel pour point not higher than - 45 C); A (arctic) - for operation at an ambient temperature of 50 C and above.
The pour point characterizes the temperature limits of the use of fuel without preheating. The pour point of the fuel should be 5 to 10 times lower than the temperature at which the fuel is supposed to be used.