Hydrocarbon cuts

It stands to reason that the manufacturing of petroleum products from crude oil and other hydrocarbon resources requires chemical and physical operations and processes. Distillation process is one of these operations that leads to the production of oil cuts which can be separated from raw materials because of the differences between their boiling point range. The materials obtained from the cutting and sweetening units, after being extracted from the distillation tower, according to the density and type of products, are transferred to the production and processing unit for necessary operations in producing heavy and light hydrocarbons. Light and heavy hydrocarbons are only the trading names that can be a result of the blending, cut distillation, or sweetening unit. Blending is generally performed through a combination of specific materials to achieve the desired specifications. These hydrocarbons can also be considered as one of the by-products of refinery inter-distillation cuts with a boiling range of 40 to 400 °C.

Heavy hydrocarbons:

Heavy hydrocarbons, which are one of the intermediate fuels of the refinery, are among the most important products of crude oil components. The carbon chain of these hydrocarbons has more than 12 carbon atoms and their boiling point is between 150 and 380 °C. The density of these types of hydrocarbons is above 810 kg/m3 and their flash point is 50 to 55 °C.

Among the distinctive features of these compounds, we can mention large molecules, low volatility and lower flammability compared to light cutting.

Heavy hydrocarbon production and refining process:

In order to produce hydrocarbons from crude oil, first the crude oil is freed from salt and acid (sweetening), then the crude oil is converted into separate products of light hydrocarbon and heavy hydrocarbon by the fractional distillation process based on the boiling point of different hydrocarbons. For this purpose, crude oil is heated up to 400 °C and then sent to the bottom of the distillation tower by

means of a pump. Lighter and smaller molecules go to the top of the tower and are liquefied by the condensers at the top of the tower and directed to the tanks. Larger and heavier molecules remain at the bottom of the tower due to their high density. The products of this process, through isomerization, cracking and other processes, change the size and structure of hydrocarbon molecules to other usable products. Also, heavy hydrocarbons are converted into more valuable materials during complex and expensive processes.

Application of heavy hydrocarbon:

These hydrocarbons are used to generate heat in boilers and furnaces, household burners, lubricating oils, heavy fuels (ships, trucks, etc.). The production of heavy hydrocarbons, especially heavy paraffinic hydrocarbons such as oils or paraffins with a high molecular weight, is considered as a by- product, and due to the low octane number, hydrocarbons C10 and above cannot be used as gasoline, but due to their long hydrocarbon chains are very important in the synthesis of detergents.

In addition, it is used as a backup fuel for peaking power plants in cases where natural gas is not available. But this type of hydrocarbons is very polluting and more expensive than natural gas fuel.

Disadvantages of using heavy hydrocarbon:

The use of fossil fuels, including heavy hydrocarbons, leaves negative effects, some of which are mentioned below:

The excessive use of these materials causes the earth to become warmer and ultimately causes the polar glaciers to melt.

These fuels also emit harmful gases such as CO2 and SO2, which cause acid rain.

Overconsumption of hydrocarbons depletes their reservoirs significantly, while it takes years for new hydrocarbons to replace them. Also, these types of fuels cause the release of methane and carbon dioxide greenhouse gases, which eventually causes the hole in the ozone layer.

Diesel fuel, which is a derivative of heavy hydrocarbons, produces more air pollution such as sulfur and solid carbon particles. Also, this fuel produces more carbon dioxide per unit than gasoline.

These fuels cause biological effects of oil pollution on the aquatic environment and human body, some of which we mention below:

delayed cell division in floating plants;

Abnormal spawning of fish;

disorder of normal nutrition;

As a result of the contact of this type of hydrocarbon with the body, severe irritations, watery discharge and itching are created in the body;

In case of ingestion, side effects such as nausea, vomiting, burning of the throat, mouth, and abdominal disorder will occur;

Also, the vapors of this substance reduce the efficiency of the central nerves and cause dizziness.


Light hydrocarbon:

hydrocarbons are among the most important products from the separation of crude oil constituents. The boiling point of such compounds is between 40 °C and200 °C. Among the commonly used hydrocarbons in this category are naphtha, kerosene, gasoline, jet fuel and solvents. Light hydrocarbons include petroleum hydrocarbons with 5 to 12 carbon chains and are commonly used to produce aromatic compounds and high-octane gasoline through catalytic reforming processes in the petrochemical industry. Such compounds are highly volatile and, as mentioned, have a low boiling point, which makes them easily flammable.

Application of light hydrocarbon:

Light hydrocarbons can be considered the basic material in the chemical and petrochemical industries as a feedstock for the production of various petrochemical products, including solvents and diluents, but they also have various other uses, for example, lubricants, solvents, industrial chemicals, explosives, raw materials for various paints. and thinner, types of plastics, rubbers, synthetic fibers and industrial alcohol, production of liquid gas and kerosene (for heating and domestic use), production of polishes and varnishes, etc. In addition, using catalytic processes, lighter and more valuable hydrocarbons can be converted into high octane gasoline and other petroleum fuels (jet fuel).

Light hydrocarbon compounds:

Many chemical derivatives and consumable fuels are derived from crude oil. Sometimes these materials contain a higher percentage of a specific product with viscosity and density that are different in subsequent samples or the output of other oil wells. Light hydrocarbon is also obtained from the combination of flammable materials such as light petroleum or gaseous liquids and butyl acetate with an octane close to gasoline. As a result, when refined in the refinery, these materials are divided into different subgroups that have hydrocarbons from C5 to C12, or in other words, the alkane group, alkene, and cycloalkane together with octane, and are known as light hydrocarbons or gasoline.

Light hydrocarbon production methods:

If we have a mixture of different hydrocarbons, they can be separated by distillation. By heating the hydrocarbons, the hydrocarbons that have a lower boiling point vaporize earlier and separate from the mixture. In refineries, crude oil components are separated from each other based on boiling point.By heating the crude oil in the distillation tower, lighter hydrocarbons evaporate and go to the upper parts of the tower, and after being condensed by the condenser, they are directed to the desired tanks.

Light hydrocarbons are created from heavy petroleum compounds using chemical methods with catalyst and high temperature, which has increased the cost of producing lighter products.

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