Secondary distillation of gasoline distillate
AWT + secondary distillation Two-stage vacuum distillation Vacuum secondary distillation plant

Definition and classification of primary distillation plants

Primary oil refining units form the basis of all oil refineries; the quality and yields of the resulting fuel components, as well as raw materials for secondary and other oil refining processes, depend on the operation of these units.

In industrial practice, oil is divided into fractions that differ in boiling point temperature limits. This separation is carried out in the primary distillation of oil using the processes of heating, distillation and rectification, condensation and cooling. Direct distillation is carried out at atmospheric or slightly elevated pressure, and residues under vacuum. Atmospheric and vacuum tubular installations (AT and VT) are built separately from each other or combined as part of one installation (AVT).

Atmospheric tubular installations (AT) are divided depending on technological scheme to the following groups:

  • installations with single evaporation of oil;
  • installations with double evaporation of oil;
  • installations with pre-evaporation in a light fractions evaporator and subsequent distillation.

The third group of installations is practically a variant of the second, since in both cases the oil is subjected to double evaporation.

Vacuum tubular installations (VT) are divided into two groups:

  • installations with a single evaporation of fuel oil;
  • installations with double evaporation of fuel oil (two-stage).

Due to the wide variety of processed oils and the wide range of products obtained and their quality, it is not always advisable to use one standard scheme. Plants with a preliminary topping column and a main distillation atmospheric column are widely used, which are operational with a significant change in the content of gasoline fractions and dissolved gases in oils.

Schemes of primary distillation of oil

The range of capacities of AT and AVT factory units is wide - from 0.6 to 8 million tons of processed oil per year. The advantages of installations with a large unit capacity are known: when switching to an enlarged installation, instead of two or more installations of a smaller bandwidth operating costs and initial costs per 1 ton of refined oil are reduced, and labor productivity is increased. Experience has been accumulated in increasing the capacity of many existing AT and AVT installations through their reconstruction, as a result of which their technical and economic indicators have been significantly improved. Thus, with an increase in the throughput capacity of the AT-6 plant by 33% (wt.) through its reconstruction, labor productivity increases by 1.3 times, and specific capital investments and operating costs are reduced by 25 and 6.5%, respectively.

Combining AVT or AT with other process units also improves the technical and economic performance and reduces the cost of petroleum products. Reducing specific capital and operating costs is achieved, in particular, by reducing the building area and the length of pipelines, the number of intermediate reservoirs and energy costs, as well as reducing the overall cost of purchasing and repairing equipment. An example is the domestic combined unit LK-6u, which consists of the following five sections: electric desalination of oil and its atmospheric distillation (two-stage AT); catalytic reforming with preliminary hydrotreatment of feedstock (gasoline fraction); hydrotreatment of kerosene and diesel fractions; gas fractionation.

The process of primary oil refining is most often combined with the processes of dehydration and desalting, secondary distillation and stabilization of the gasoline fraction: CDU-AT, CDU-AVT, CDU-AVT - secondary distillation, AVT - secondary distillation.

Primary distillation processes

Open superheated steam is used to remove light components from distillates as they pass through stripping columns. In some installations, for this purpose, boilers are used that are heated by a hotter oil product than the distillate withdrawn from the stripping column.

The flow rate of water vapor is: in the atmospheric column 1.5-2.0% (wt.) for oil, in the vacuum column 1.0-1.5% (wt.) for fuel oil, in the stripping column 2.0-2, 5% (mass.) on the distillate.

In the distillation sections of AT and AVT units, intermediate circulating irrigation is widely used, which is located at the top of the section (directly under the side distillate output plate). The circulating phlegm is removed two plates below (no more). In vacuum columns, the overhead reflux is usually circulating and requires 3-4 trays to reduce oil loss through the top of the column.

To create a vacuum, a barometric condenser and two- or three-stage ejectors are used (two-stage are used at a vacuum depth of 6.7 kPa, three-stage - within 6.7-13.3 kPa). Condensers are mounted between the stages to condense the working steam of the previous stage, as well as to cool the exhaust gases. In recent years, surface condensers have been widely used instead of the barometric condenser. Their use not only contributes to the creation of a higher vacuum in the column, but also saves the plant from huge quantities contaminated wastewater, especially in the processing of sour and sour oils.

As refrigerators and condensers-refrigerators, air coolers (AVOs) are widely used. The use of air coolers leads to a reduction in water consumption, initial costs for the construction of water supply, sewerage, treatment facilities and a decrease in operating costs.

A high degree of automation has been achieved at the primary oil refining units. So, at factory installations, automatic quality analyzers (“on stream”) are used, which determine: the content of water and salts in oil, the flash point aviation kerosene, diesel fuel, oil distillates, boiling point of 90% (wt.) sample of light oil product, viscosity of oil fractions, product content in wastewater. Some of the quality analyzers are included in automatic control schemes. For example, the steam supply to the bottom of the stripper column is automatically corrected for the flash point of diesel fuel, which is determined using an automatic flash point analyzer. Chromatographs are used for automatic continuous determination and registration of the composition of gas flows.

Crude oil is a term used to refer to crude oil - a raw material that comes out of the ground as is. Thus, crude oil is a fossil fuel, which means that it is produced naturally from decaying plants and animals living in ancient seas millions of years ago - most of the places where oil is most often found were once the bottom of the seas. Crude oil, depending on the field, is different and varies in color and consistency: from bright black (wet asphalt) and very viscous, to slightly transparent and almost solid.


The main value and benefit of oil is that it is Starting point for very many different substances, since it contains hydrocarbons. Hydrocarbons are molecules that obviously contain hydrogen and carbon, and differ from each other only in that they can be of various lengths and structures - from straight chains to branched chains with rings.

There are two things that make hydrocarbons interesting for chemists:

  1. Hydrocarbons contain a lot of potential energy. Much of what is derived from crude oil, such as gasoline, diesel, paraffin, etc. - it is this potential energy that is valuable.
  2. Hydrocarbons can take on many various forms. The smallest hydrocarbon (by number of atoms) is methane (CH4), which is a gas that is lighter than air. Longer chains with 5 or more carbon atoms are in the vast majority of cases liquids. And very long chains are hard, for example, wax or resin. By the chemical structure of the "crosslinking" of hydrocarbon chains, you can get everything from synthetic rubber to nylon and plastic. Hydrocarbon chains are actually very versatile!

The main classes of hydrocarbons in crude oil include:

  • Paraffins With general formula C n H 2n+2 (n is an integer, usually 1 to 20) straight or branched chain can represent gases or liquids that already boil at room temperature depending on the molecular examples: methane, ethane, propane, butane , isobutane, pentane, hexane.
  • Aromatics with the general formula: C 6 H 5 -Y (Y is a large straight molecule that connects to a benzene ring) are ring structures with one or more rings that contain six carbon atoms, with alternating double single bonds between carbon atoms. Vivid examples of aromatics are benzene and naphthalene.
  • Naphthenes or cycloalkanes with the general formula C n H 2n (n is an integer, typically from 1 to 20) are annular structures with one or more rings that contain only simple bonds between carbon atoms. These are, as a rule, liquids: cyclohexane, methylcyclopentane and others.
  • Alkenes with the general formula C n H 2n (n is an integer, usually from 1 to 20) are linear or branched chain molecules containing one carbon-carbon double bond, which can be liquid or gas, for example: ethylene, butene, isobutene .
  • Alkynes with the general formula: C n H 2n-2 (n is an integer, usually from 1 to 20) are linear or branched chain molecules containing two carbon-carbon double bonds, which can be liquid or gas, for example: acetylene, butadienes.

Now that we know the structure of oil, let's see what we can do with it.

How does oil refining work?

The oil refining process begins with a fractional distillation column.


Typical oil refinery

The main problem with crude oil is that it contains hundreds of different types of hydrocarbons all mixed together. And our task is to separate different kinds hydrocarbons to get anything useful. Luckily, there's an easy way to separate these things, and that's what refining does.

Different hydrocarbon chain lengths have progressively higher boiling points so that they can be separated by simple distillation at different temperatures. Simply put, by heating oil to a certain temperature, certain chains of hydrocarbons begin to boil, and thus we can separate the "wheat from the chaff." This is what happens in a refinery - in one part of the process, the oil is heated and the various chains are boiled off at their respective boiling points. Each different chain length has its own unique property that makes it useful in its own way.

To understand the diversity found in crude oil and to understand why crude oil refining is so important in our civilization, look at the following list of products that are derived from crude oil:

Petroleum gases- used for heating, cooking, making plastics:

  • they are small alkanes (1 to 4 carbons)
  • widely known by names such as methane, ethane, propane, butane
  • boiling range - less than 40 degrees Celsius
  • often pressurized gases

Naphtha or naphtha - intermediate product, which will be further processed to later become gasoline:

  • contains 5 to 9 carbon alkanes
  • boiling range - from 60 to 100 degrees Celsius

Petrol- motor fuel:

  • always a liquid product
  • is a mixture of alkanes and cycloalkanes (from 5 to 12 carbon atoms)
  • boiling range - from 40 to 205 degrees Celsius

Kerosene- fuel for jet engines and tractors; starting material for the manufacture of other products:

  • liquid
  • mixture of alkanes (from 10 to 18 carbon atoms) and aromatic hydrocarbons
  • boiling range - from 175 to 325 degrees Celsius

Diesel distillate- used for diesel fuel and fuel oil; starting material for the manufacture of other products:

  • liquid
  • alkanes containing 12 or more carbon atoms
  • boiling range - from 250 to 350 degrees Celsius

Lubricating oils- are used for the manufacture of motor oil, fat, other lubricants:

  • liquid
  • long chain structures (from 20 to 50 carbon atoms) alkanes, cycloalkanes, aromatics
  • boiling range - from 300 to 370 degrees Celsius

fuel oil- used for industrial fuel; starting material for the manufacture of other products:

  • liquid
  • long chain structures (from 20 to 70 carbon atoms) alkanes, cycloalkanes, aromatics
  • boiling range - 370 to 600 degrees Celsius

Remains of processed products- coke, asphalt, tar, paraffins; starting material for the manufacture of other products:

  • particulate matter
  • multiple ring compounds with 70 or more carbon atoms
  • boiling range not less than 600 degrees Celsius.

You may have noticed that all of these products come in different sizes and boiling ranges. Chemists have taken advantage of these properties for oil refining. Let's now further learn the details of this exciting process!

Detailed oil refining process

As mentioned earlier, a barrel of crude oil has a mixture of all kinds of hydrocarbons in it. Oil refining separates useful substances from this whole "company of multi-racial representatives". At the same time, the following groups of industrial chemical processes take place, which, in principle, are in every oil refinery:

  • The oldest and most common way to separate the various components (called fractions) from oil is to do so using differences in boiling point. This process is called fractional distillation .
  • New methods of using chemical processing in some of the fractions use the conversion method. Chemical processing, for example, can break long chains into shorter ones. This allows the refinery to turn diesel into gasoline depending on demand, for example.
  • Refineries, in addition, after the fractional distillation process, must purify the fractions in order to remove impurities from them.
  • Refineries combine various fractions (processed and unprocessed) into mixtures to make the desired products. For example, different blends from different chains can create gasolines with different octane ratings.

Oil refinery products are sent for short-term storage in special tanks until they are delivered to various markets: gas stations, airports and chemical plants. In addition to creating oil-based products, factories must also take care of the inevitable waste to minimize air and water pollution.

Fractional distillation

Different components of oil have different sizes, weights and boiling points; So, the first step is to separate these components. Because they have different boiling points, they can be separated easily using a process called fractional distillation.

The stages of fractional distillation are as follows:

  • You heat a mixture of two or more substances (liquids) with different boiling points to high temperature. Heating is usually done with high pressure steam up to a temperature of about 600 degrees Celsius.
  • The mixture boils, forming steam (gases); most substances pass in the vapor phase.
  • The steam enters lower part a long column that is filled with trays or plates. Trays have many holes or bubble caps (similar to the perforated lid on plastic bottle) in them to allow steam to pass through them. They increase the contact time between vapor and liquid in the column and help collect liquids that form at different heights in the column. There is a temperature difference in this column (very hot at the bottom and colder towards the top).
  • Thus, the steam rises in the column.
  • As the vapor rises through the trays in the column, it cools.
  • When a vaporous substance reaches a height where the temperature in the column equals the boiling point of that substance, it will condense to form a liquid. In this case, substances with the lowest boiling point will condense at the highest point in the column, and substances with higher boiling points will condense lower in the column.
  • Trays collect various liquid fractions.
  • The collected liquid fractions can go to condensers that cool them further and then go to storage tanks, or they can go to other areas for further chemical processing.

Fractional distillation is useful for separating a mixture of substances with narrow differences in boiling points and is the most important step in the process of oil refining. The oil refining process begins with a fractional distillation column. Very few of the components will leave the fractional distillation column ready to be sold on the petroleum market. Many of them must be chemically processed in order to be converted into other fractions. For example, only 40% of distilled crude oil will become gasoline, however, gasoline is one of the main products produced by oil companies. Instead of constantly distilling large quantities of crude oil, oil companies chemically process other fractions from the distillation column to obtain the same gasoline; and this processing increases the yield of gasoline from each barrel of crude oil.

Chemical transformation

You can convert one faction to another using one of three methods:

  1. Break large hydrocarbons into smaller ones (cracking)
  2. Combine small hydrocarbons to make them larger (unification)
  3. Rearrange or replace different parts of hydrocarbons to get the desired hydrocarbons (hydrothermal alteration)

Cracking

Cracking takes large hydrocarbons and breaks them down into smaller ones. There are several types of cracking:

  • Thermal- You heat large hydrocarbons at high temperatures (sometimes also at high pressures) until they break apart.
  • Steam- high steam temperature (over 800 degrees Celsius) is used to break ethane, butane and naphtha into ethylene and benzene, which are used to produce chemicals.
  • Visbreaking- Residual substances from the distillation column are heated to almost 500 degrees Celsius, cooled and quickly burned in the distillation column. This process reduces the viscosity of substances and the number of heavy oils in them and produces resins.
  • Coking- residual substances from the distillation column are heated to a temperature above 450 degrees Celsius, as a result of which heavy almost pure carbon (coke) remains; coke is cleaned from coking and sold.
  • catalyzation- a catalyst is used to accelerate the cracking reaction. Catalysts include zeolite, aluminum hydrosilicate, bauxite and aluminosilicate. Catalytic cracking is when a hot liquid catalyst (538 degrees Celsius) breaks down a heavy substance into diesel oils and gasoline.
  • Hydrocracking- similar to catalytic cracking, but uses a different catalyst with more low temperatures, high pressure and hydrogen. This allows heavy oil to be broken down into gasoline and kerosene (jet fuel).

Unification

Sometimes you need to combine small hydrocarbons to make them larger - this process is called unification. The main merging process is catalytic reforming and in this case a catalyst (a mixture of platinum and platinum-rhenium) is used to combine low weight naphtha into aromatic compounds that are used in making chemicals and in blending gasoline. A significant by-product of this reaction is hydrogen gas, which is then either used for hydrocracking or simply sold.

hydrothermal alteration

Sometimes the structures of the molecules in one fraction are rearranged to produce another. Typically, this is done through a process called alkylation. In alkylation, low molecular weight compounds such as propylene and butylene are mixed in the presence of a catalyst such as hydrofluoric acid or sulfuric acid (a by-product from the removal of impurities from many petroleum products). Alkylation products are high-octane hydrocarbons that are used in gasoline blends to increase the octane number.

Final processing (cleaning) of petroleum products

The distilled and chemically treated oil fractions are processed again to remove impurities - mainly organic compounds containing sulfur, nitrogen, oxygen, water, dissolved metals and inorganic salts. Final processing is usually done in the following ways:

  • The sulfuric acid column removes unsaturated hydrocarbons (with double carbon-carbon bonds), nitrogen compounds, oxygen and residual solids (tars, asphalt).
  • The absorption column is filled with a desiccant to remove water.
  • Hydrogen sulfide scrubbers remove sulfur and all sulfur compounds.

After the fractions have been processed, they are cooled and then mixed together to make various products such as:

  • Gasoline of various grades, with or without additives.
  • Lubricating oils of various brands and types (eg 10W-40, 5W-30).
  • Kerosene of various grades.
  • jet fuel.
  • Fuel oil.
  • Other chemical substances various grades for the manufacture of plastics and other polymers.

Oil refining is a rather complicated process, which requires involvement. Many products are obtained from the extracted natural raw materials - various types of fuel, bitumen, kerosene, solvents, lubricants, petroleum oils and others. Oil refining begins with the transportation of hydrocarbons to the plant. The production process takes place in several stages, each of which is very important from a technological point of view.

Recycling process

The process of oil refining begins with its specialized preparation. This is due to the presence of numerous impurities in natural raw materials. An oil deposit contains sand, salts, water, soil, and gaseous particles. Water is used to extract a large number of products and save energy deposits. This has its advantages, but significantly reduces the quality of the resulting material.

The presence of impurities in the composition of petroleum products makes it impossible to transport them to the plant. They provoke the formation of plaque on heat exchangers and other containers, which significantly reduces their service life.

Therefore, the extracted materials are subjected to complex cleaning - mechanical and fine. At this stage of the production process, the resulting raw material is separated into oil and. This happens with the help of special oil separators.

To purify the raw material, it is mainly settled in hermetic tanks. To activate the separation process, the material is subjected to cold or high temperature. Electric desalination plants are used to remove salts contained in raw materials.

How does the process of separating oil and water take place?

After primary purification, a sparingly soluble emulsion is obtained. It is a mixture in which particles of one liquid are evenly distributed in the second. On this basis, 2 types of emulsions are distinguished:

  • hydrophilic. It is a mixture where oil particles are in water;
  • hydrophobic. The emulsion mainly consists of oil, where there are particles of water.

The process of breaking the emulsion can be mechanical, electrical or by chemical means. The first method involves settling the liquid. This happens under certain conditions - heating to a temperature of 120-160 degrees, increasing the pressure to 8-15 atmospheres. The stratification of the mixture usually occurs within 2-3 hours.

In order for the process of separation of the emulsion to be successful, it is necessary to prevent the evaporation of water. Also, the extraction of pure oil is carried out using powerful centrifuges. The emulsion is divided into fractions when reaching 3.5-50 thousand revolutions per minute.

The use of a chemical method involves the use of special surfactants called demulsifiers. They help to dissolve the adsorption film, as a result of which the oil is cleaned of water particles. The chemical method is often used in conjunction with the electrical method. The last cleaning method involves the impact on the emulsion electric current. It provokes the association of water particles. As a result, it is more easily removed from the mixture, resulting in the highest quality oil.

Primary processing

Extraction and processing of oil takes place in several stages. A feature of the production of various products from natural raw materials is that even after high-quality purification, the resulting product cannot be used for its intended purpose.

The starting material is characterized by the content of various hydrocarbons, which differ significantly in molecular weight and boiling point. It contains substances of naphthenic, aromatic, paraffinic nature. Also, the feedstock contains sulfur, nitrogen and oxygen compounds of the organic type, which must also be removed.

All existing methods of oil refining are aimed at dividing it into groups. During the production process, a wide range of products with different characteristics is obtained.

Primary processing of natural raw materials is carried out on the basis of different temperatures boiling of its constituent parts. For the implementation of this process, specialized installations are involved, which make it possible to obtain various oil products - from fuel oil to tar.

If natural raw materials are processed in this way, it will not be possible to obtain a material ready for further use. Primary distillation is aimed only at determining the physical and chemical properties of oil. After it is carried out, it is possible to determine the need for further processing. They also set the type of equipment that needs to be involved to perform the necessary processes.

Primary oil refining

Oil distillation methods

There are the following methods of oil refining (distillation):

  • single evaporation;
  • repeated evaporation;
  • distillation with gradual evaporation.

The flash method involves the processing of oil under the influence of a high temperature with a given value. As a result, vapors are formed that enter a special apparatus. It is called an evaporator. IN this device cylindrical pairs are separated from the liquid fraction.

With repeated evaporation, the raw material is subjected to processing, in which the temperature is increased several times according to a given algorithm. The last distillation method is more complex. Processing of oil with gradual evaporation implies a smooth change in the main operating parameters.

Distillation equipment

Industrial oil refining is carried out using several devices.

Tube furnaces. In turn, they are also divided into several types. These are atmospheric, vacuum, atmospheric-vacuum furnaces. With the help of equipment of the first type, shallow processing of petroleum products is carried out, which makes it possible to obtain fuel oil, gasoline, kerosene and diesel fractions. In vacuum furnaces, as a result of more efficient operation, the raw materials are divided into:

  • tar;
  • oil particles;
  • gas oil particles.

The resulting products are fully suitable for the production of coke, bitumen, lubricants.

distillation columns. The process of processing crude oil using this equipment involves heating it in a coil to a temperature of 320 degrees. After that, the mixture enters the intermediate levels of the distillation column. On average, it has 30-60 chutes, each spaced at a certain interval and equipped with a liquid bath. Due to this, the vapors flow down in the form of droplets, as condensation forms.

There is also processing using heat exchangers.

Recycling

After determining the properties of the oil, depending on the need for a particular final product, the type of secondary distillation is selected. Basically, it consists in a thermal-catalytic effect on the feedstock. Deep processing of oil can occur using several methods.

Fuel. The use of this method of secondary distillation makes it possible to obtain a number of high-quality products - motor gasoline, diesel, jet, and boiler fuels. Recycling does not require a lot of equipment. As a result of applying this method, a finished product is obtained from the heavy fractions of raw materials and sediment. The fuel distillation method includes:

  • cracking;
  • reforming;
  • hydrotreating;
  • hydrocracking.

Fuel oil. As a result of this distillation method, not only various fuels are obtained, but also asphalt, lubricating oils. This is done using the extraction method, deasphalting.

Petrochemical. As a result of applying this method with the involvement of high-tech equipment, we obtain a large number of products. This is not only fuel, oils, but also plastics, rubber, fertilizers, acetone, alcohol and much more.

How objects around us are obtained from oil and gas - accessible and understandable

This method is considered the most common. With its help, the processing of sour or sour oil is carried out. Hydrotreating can significantly improve the quality of the resulting fuels. Various additives are removed from them - sulfur, nitrogen, oxygen compounds. The material is processed on special catalysts in a hydrogen environment. At the same time, the temperature in the equipment reaches 300-400 degrees, and the pressure - 2-4 MPa.

As a result of distillation, organic compounds contained in raw materials decompose when interacting with hydrogen circulating inside the apparatus. As a result, ammonia and hydrogen sulfide are formed, which are removed from the catalyst. Hydrotreating makes it possible to recycle 95-99% of raw materials.

catalytic cracking

Distillation is carried out using zeolite-containing catalysts at a temperature of 550 degrees. Cracking is considered very effective method processing of prepared raw materials. With its help, high-octane motor gasoline can be obtained from fuel oil fractions. The yield of pure product in this case is 40-60%. Liquid gas is also obtained (10-15% of the original volume).

catalytic reforming

Reforming is carried out using an aluminum-platinum catalyst at a temperature of 500 degrees and a pressure of 1-4 MPa. At the same time, a hydrogen environment is present inside the equipment. This method is used to convert naphthenic and paraffinic hydrocarbons to aromatics. This allows you to significantly increase the octane number of products. When using catalytic reforming, the yield of pure material is 73-90% of the feedstock.

Hydrocracking

Allows you to get liquid fuel when exposed to high pressure(280 atmospheres) and temperature (450 degrees). Also, this process occurs with the use of strong catalysts - molybdenum oxides.

If hydrocracking is combined with other methods of processing natural raw materials, the yield of pure products in the form of gasoline and jet fuel is 75-80%. When using high-quality catalysts, their regeneration may not be carried out for 2-3 years.

Extraction and deasphalting

Extraction involves the separation of the prepared raw materials into the desired fractions using solvents. Subsequently, deparaffinization is carried out. It allows you to significantly reduce the pour point of the oil. Also, to obtain high quality products, it is subjected to hydrotreatment. As a result of the extraction, distilled diesel fuel can be obtained. Also, using this technique, aromatic hydrocarbons are extracted from the prepared raw materials.

Deasphalting is necessary in order to obtain resinous-asphaltene compounds from the end products of the distillation of petroleum feedstock. The resulting substances are actively used for the production of bitumen, as catalysts for other processing methods.

Other processing methods

Processing of natural raw materials after primary distillation can be carried out in other ways.

Alkylation. After processing the prepared materials, high-quality components for gasoline are obtained. The method is based on the chemical interaction of olefinic and paraffinic hydrocarbons, resulting in a high-boiling paraffinic hydrocarbon.

Isomerization. The use of this method makes it possible to obtain a substance with a higher octane number from low-octane paraffinic hydrocarbons.

Polymerization. Allows the conversion of butylenes and propylene into oligomeric compounds. As a result, materials are obtained for the production of gasoline and for various petrochemical processes.

Coking. It is used for the production of petroleum coke from heavy fractions obtained after the distillation of oil.

The oil refining industry is a promising and developing one. The production process is constantly being improved through the introduction of new equipment and techniques.

Video: Oil refining

Oil is a mineral that is an oily liquid insoluble in water, which can be either almost colorless or dark brown. The properties and methods of oil refining depend on the percentage of predominantly hydrocarbons in its composition, which varies in different fields.

So, in the Sosninskoye deposit (Siberia), alkanes (paraffin group) occupy a share of 52 percent, cycloalkanes - about 36%, aromatic hydrocarbons - 12 percent. And, for example, in the Romashkinskoye deposit (Tatarstan), the share of alkanes and aromatic hydrocarbons is higher - 55 and 18 percent, respectively, while cycloalkanes have a share of 25 percent. In addition to hydrocarbons, this raw material may include sulfur, nitrogen compounds, mineral impurities, etc.

Oil was first "refined" in 1745 in Russia

In its raw form, this natural resource is not used. To obtain technically valuable products (solvents, motor fuels, components for chemical industries), oil is processed using primary or secondary methods. Attempts to transform this raw material were made as early as the middle of the eighteenth century, when, in addition to candles and torches used by the population, “garne oil” was used in the lamps of a number of churches, which was a mixture vegetable oil and refined oil.

Oil refining options

Refining is often not included directly in oil refining processes. It is rather a preliminary stage, which may consist of:

Chemical cleaning, when oil is treated with oleum and concentrated sulfuric acid. This removes aromatic and unsaturated hydrocarbons.

adsorption cleaning. Here, resins and acids can be removed from oil products by treatment with hot air or by passing oil through an adsorbent.

Catalytic purification - mild hydrogenation to remove nitrogen and sulfur compounds.

Physical and chemical cleaning. In this case, excess components are selectively isolated by means of solvents. For example, the polar solvent phenol is used to remove nitrogenous and sulfurous compounds, and non-polar solvents - butane and propane - release tars, aromatic hydrocarbons, etc.

No chemical changes...

Oil processing through primary processes does not involve chemical transformations of the feedstock. Here, the mineral is simply divided into its constituent components. The first oil distillation device was invented in 1823, in Russian Empire. The Dubinin brothers guessed to put the boiler in a heated oven, from where a pipe went through a barrel of cold water into an empty container. In the furnace boiler, the oil was heated, passed through the “cooler” and precipitated.

Modern methods of preparation of raw materials

Today, at oil refineries, oil refining technology begins with additional purification, during which the product is dehydrated on ELOU devices (electric desalination plants), freed from mechanical impurities and light-type carbohydrates (C1 - C4). Then the raw material can be sent to atmospheric distillation or vacuum distillation. In the first case factory equipment according to the principle of action, it resembles what was used back in 1823.

Only the oil refining unit itself looks different. At the enterprise there are stoves resembling windowless houses in size, made of the best refractory brick. Inside them are many kilometers of pipes, in which oil moves at high speed (2 meters per second) and is heated up to 300-325 C by a flame from a large nozzle (at higher temperatures, hydrocarbons simply decompose). Today, the pipe for condensation and cooling of vapors is replaced by distillation columns (they can be up to 40 meters in height), where the vapors are separated and condensed, and entire towns from different reservoirs are built to receive the resulting products.

What is material balance?

Oil refining in Russia gives different material balances during the atmospheric distillation of raw materials from one or another field. This means that different proportions can be obtained at the output for different fractions - gasoline, kerosene, diesel, fuel oil, associated gas.

For example, for West Siberian oil, the gas yield and losses are one percent each, gasoline fractions (released at temperatures from about 62 to 180 C) occupy a share of about 19%, kerosene - about 9.5%, diesel fraction - 19% , fuel oil - almost 50 percent (is released at temperatures from 240 to 350 degrees). The resulting materials are almost always subjected to additional processing, since they do not meet the operational requirements for the same machine motors.

Production with less waste

Vacuum oil refining is based on the principle of boiling substances at a lower temperature with a decrease in pressure. For example, some hydrocarbons in oil only boil at 450°C (atmospheric pressure), but they can be made to boil at 325°C if the pressure is lowered. Vacuum processing of raw materials is carried out in rotary vacuum evaporators, which increase the speed of distillation and make it possible to obtain ceresin, paraffins, fuel, oils from fuel oil, and use the heavy residue (tar) further for the production of bitumen. Vacuum distillation, compared to atmospheric processing, produces less waste.

Recycling allows you to get high-quality gasoline

The secondary oil refining process was invented in order to get more motor fuel from the same feedstock by influencing the molecules of petroleum hydrocarbons, which acquire formulas more suitable for oxidation. Recycling includes different types so-called "cracking", including hydrocracking, thermal and catalytic options. This process was also originally invented in Russia, in 1891, by engineer V. Shukhov. It is the breakdown of hydrocarbons into forms with fewer carbon atoms per molecule.

Oil and gas processing at 600 degrees Celsius

The principle of operation of cracking plants is approximately the same as that of atmospheric pressure vacuum plants. But here, the processing of raw materials, which is most often represented by fuel oil, is carried out at temperatures close to 600 C. Under such influence, the hydrocarbons that make up the fuel oil mass break down into smaller ones, which make up the same kerosene or gasoline. Thermal cracking is based on high temperature treatment and produces gasoline with a large amount of impurities, catalytic cracking is also based on heat treatment, but with the addition of catalysts (for example, special clay dust), which allows you to get more good quality gasoline.

Hydrocracking: main types

Oil production and refining today may include various types of hydrocracking, which is a combination of hydrotreating processes, splitting large hydrocarbon molecules into smaller ones, and saturation of unsaturated hydrocarbons with hydrogen. Hydrocracking can be light (pressure 5 MPa, temperature about 400 C, one reactor is used, mainly diesel fuel and material for catalytic cracking are obtained) and hard (pressure 10 MPa, temperature about 400 C, there are several reactors, diesel, gasoline and kerosene are obtained). fractions). Catalytic hydrocracking makes it possible to produce a range of oils with high viscosity coefficients and a low content of aromatic and sulphurous hydrocarbons.

Secondary oil refining, in addition, can use the following technological processes:

Visbreaking. In this case, at temperatures up to 500 C and pressures ranging from half to three MPa, secondary asphaltenes, hydrocarbon gases, gasoline are obtained from raw materials due to the splitting of paraffins and naphthenes.

Coking of heavy oil residues is a deep processing of oil, when raw materials are processed at temperatures close to 500 C under a pressure of 0.65 MPa to obtain gas oil components and petroleum coke. The process steps end in a "coke cake" preceded (in reverse order) by compaction, polycondensation, aromatization, cyclization, dehydrogenation and cracking. In addition, the product must also be dried and calcined.

Reforming. This method processing of petroleum products was invented in Russia in 1911 by engineer N. Zelinsky. Today, catalytic reforming is used to produce high-quality aromatic hydrocarbons and gasolines from naphtha and gasoline fractions, as well as hydrogen-containing gas for subsequent processing in hydrocracking.

Isomerization. The processing of oil and gas in this case involves the production of chemical compound isomer due to changes in the carbon skeleton of the substance. So, high-octane components are isolated from low-octane oil components to produce commercial gasoline.

Alkylation. This process is based on the incorporation of alkyl substituents into the molecule organic plan. Thus, components for high-octane gasolines are obtained from hydrocarbon gases of an unsaturated nature.

Striving for European standards

The technology of oil and gas processing at refineries is constantly being improved. Thus, domestic enterprises noted an increase in the efficiency of processing raw materials in terms of the following parameters: the depth of processing, an increase in the selection of light oil products, a decrease in irretrievable losses, etc. The plans of plants for the 10-20s of the twenty-first century include a further increase in the depth of processing (up to 88 percent) , improving the quality of manufactured products to European standards, reducing the technogenic impact on the environment.

Crude oil compounds are complex substances, consisting of five elements - C, H, S, O and N, and the content of these elements ranges from 82-87% carbon, 11-15% hydrogen, 0.01-6% sulfur, 0-2% oxygen and 0 01-3% nitrogen.

Conventional well crude oil is a greenish-brown flammable oily liquid with a pungent odor. The oil produced in the fields, in addition to the gases dissolved in it, contains a certain amount of impurities - particles of sand, clay, salt crystals and water. The content of solid particles and water complicates its transportation through pipelines and processing, causes erosion of the internal surfaces of oil pipeline pipes and the formation of deposits in heat exchangers, furnaces and refrigerators, which leads to a decrease in the heat transfer coefficient, increases the ash content of oil distillation residues (fuel oil and tars), promotes the formation persistent emulsions. In addition, in the process of oil production and transportation, a significant loss of light components of oil occurs. In order to reduce the cost of oil refining, caused by the loss of light components and excessive wear of oil pipelines and processing equipment, the produced oil is subjected to pre-treatment.

To reduce the loss of light components, oil is stabilized, and special hermetic oil storage tanks are also used. From the main amount of water and solid particles, oil is released by settling in tanks in the cold or when heated. Finally, they are dehydrated and desalted in special installations. However, water and oil often form an emulsion that is difficult to separate, which greatly slows down or even prevents oil dehydration. There are two types of oil emulsions:

oil in water, or hydrophilic emulsion,

and water in oil, or hydrophobic emulsion.

There are three methods for breaking up oil emulsions:

Mechanical:

settling - applied to fresh, easily broken emulsions. The separation of water and oil occurs due to the difference in the densities of the emulsion components. The process is accelerated by heating to 120-160°C under a pressure of 8-15 atmospheres for 2-3 hours, preventing water evaporation.

centrifugation - separation of mechanical impurities of oil under the influence of centrifugal forces. It is rarely used in industry, usually with a series of centrifuges with a speed of 350 to 5000 rpm, with a capacity of 15-45 m3 / h each.

Chemical:

the destruction of emulsions is achieved by the use of surfactants - demulsifiers. Destruction is achieved a) by adsorption displacement of the active emulsifier by a substance with a higher surface activity, b) by the formation of emulsions of the opposite type (vas inversion) and c) by dissolution (destruction) of the adsorption film as a result of its chemical reaction with a demulsifier introduced into the system. The chemical method is used more often than the mechanical one, usually in combination with the electrical one.

Electric:

when an oil emulsion enters a variable electric field water particles, which react more strongly to the field than oil, begin to oscillate, colliding with each other, which leads to their association, enlargement and faster stratification with oil. Installations called electric dehydrators.

An important point is the process of sorting and mixing oil. Oils similar in physical, chemical and commercial properties are mixed in the fields and sent for joint processing.

There are three main options for oil refining:

  • - fuel,
  • - fuel oil,
  • - petrochemical.

According to the fuel option, oil is processed mainly into motor and boiler fuels. There are deep and shallow fuel processing. At deep processing oil companies strive to obtain the highest possible yield of high-quality and motor gasolines, winter and summer diesel fuels and jet fuels. The output of boiler fuel in this variant is reduced to a minimum. These include catalytic processes such as catalytic cracking, catalytic reforming, hydrocracking and hydrotreating, as well as thermal processes such as coking. The processing of factory gases in this case is aimed at increasing the yield of high-quality gasolines. With shallow oil refining, a high yield of boiler fuel is provided.

According to the fuel-oil variant of oil refining, along with fuels, lubricating oils, distillate oils (light and medium industrial, automotive, etc.) are obtained. Residual oils (aviation, cylinder) are recovered from the tar by its deasphalting with liquid propane. In this case, deasphalt and asphalt are formed. The deasphalt is further processed and the asphalt is processed into bitumen or coke. The petrochemical option for oil refining - in addition to producing high-quality motor fuels and oils, not only is the preparation of raw materials (olefins, aromatic, normal and isoparaffinic hydrocarbons, etc.) for heavy organic synthesis, but also the most complex physical and chemical processes associated with the large-tonnage production of nitrogen fertilizers, synthetic rubber, plastics, synthetic fibers, detergents substances, fatty acids, phenol, acetone, alcohols, esters and many other chemicals. The main method of oil refining is its direct distillation.

Distillation - distillation (dropping) - the separation of oil into fractions differing in composition (individual oil products), based on the difference in the boiling points of its components. The distillation of petroleum products with boiling points up to 370°C is carried out at atmospheric pressure, and with higher ones - in a vacuum or with the use of water vapor (to prevent their decomposition).

Oil under pressure is fed by pumps into a tubular furnace, where it is heated to 330...350°C. Hot oil, together with vapors, enters the middle part of the distillation column, where, due to pressure reduction, it evaporates and the evaporated hydrocarbons are separated from the liquid part of the oil - fuel oil. Vapors of hydrocarbons rush up the column, and the liquid residue flows down. Plates are installed in the distillation column along the path of vapor movement, on which part of the hydrocarbon vapors condenses. Heavier hydrocarbons condense on the first trays, light hydrocarbons have time to rise up the column, and the most hydrocarbons, mixed with gases, pass the entire column without condensing, and are discharged from the top of the column in the form of vapors. So hydrocarbons are separated into fractions depending on their boiling point.

During the distillation of oil, light oil products are obtained: gasoline (bp 90-200 ° C), naphtha (bp 150-230 ° C), kerosene (bp 180-300 ° C), light gas oil - solar oil (bp 230-350 ° C) , heavy gas oil (bp 350-430°C), and the remainder is a viscous black liquid - fuel oil (bp above 430°C). Oil is subjected to further processing. It is distilled under reduced pressure (to prevent decomposition) and lubricating oils are recovered. Flash distillation consists of two or more single distillation processes with an increase in operating temperature at each stage. Products obtained by direct distillation have high chemical stability, since they do not contain unsaturated hydrocarbons. The use of cracking processes for oil refining makes it possible to increase the yield of gasoline fractions.

Cracking is a process of refining oil and its fractions, based on the decomposition (splitting) of molecules of complex hydrocarbons under conditions of high temperatures and pressures. There are the following types of cracking: thermal, catalytic, as well as hydrocracking and catalytic reforming. Thermal cracking is used to produce gasoline from fuel oil, kerosene and diesel fuel. Gasoline obtained through thermal cracking has an insufficiently high octane number (66 ... 74) and a high content of unsaturated hydrocarbons (30 ... 40%), i.e. it has poor chemical stability and is mainly used only in as a component in the production of commercial gasoline.

New installations for thermal cracking are no longer being built, since the gasolines obtained with their help are oxidized during storage to form resins, and it is necessary to introduce special additives (inhibitors) into them, which sharply reduce the rate of resinification. Thermal cracking is divided into vapor phase and liquid phase.

Steam-phase cracking - oil is heated to 520...550°C at a pressure of 2...6 atm. Currently not applicable due to poor performance and great content(40%) unsaturated hydrocarbons in the final product, which are easily oxidized and form resins.

Liquid-phase cracking - oil heating temperature 480 ... 500 ° C at a pressure of 20 ... 50 atm. Productivity increases, quantity (25…30%) of unsaturated hydrocarbons decreases. Thermal cracking gasoline fractions are used as a component of commercial motor gasolines. However, thermal cracking fuels are characterized by low chemical stability, which is improved by introducing special antioxidant additives into the fuels. The yield of gasoline is 70% from oil, 30% from fuel oil.

Catalytic cracking is a process for producing gasoline based on the splitting of hydrocarbons and changing their structure under the influence of high temperature and a catalyst. The splitting of hydrocarbon molecules proceeds in the presence of catalysts and at temperature and atmospheric pressure. One of the catalysts is specially treated clay. Such cracking is called pulverized catalyzed cracking. The catalyst is then separated from the hydrocarbons. Hydrocarbons go their way to rectification and refrigerators, and the catalyst goes to its reservoirs, where its properties are restored. As feedstock for catalytic cracking, gas oil and solar oil fractions obtained by direct distillation of oil are used. Catalytic cracking products are essential components in the production of A-72 and A-76 gasolines.

Hydrocracking is a process of refining petroleum products that combines cracking and hydrogenation of raw materials (gas oils, oil residues, etc.). This is a type of catalytic cracking. The process of decomposition of heavy raw materials occurs in the presence of hydrogen at a temperature of 420...500°C and a pressure of 200 atm. The process takes place in a special reactor with the addition of catalysts (W, Mo, Pt oxides). As a result of hydrocracking, fuel is obtained.

Reforming - (from the English reforming - to remake, improve) an industrial process for processing gasoline and naphtha oil fractions in order to obtain high-quality gasolines and aromatic hydrocarbons. As a raw material for catalytic reforming, gasoline fractions of the primary distillation of oil are usually used, which boil away already at 85 ... 180 "C. Reforming is carried out in a hydrogen-containing gas environment (70 ... 90% hydrogen) at a temperature of 480 ... pressure of 2 ... 4 MPa in the presence of a molybdenum or platinum catalyst.To improve the properties of gasoline fractions of oil, they are subjected to catalytic reforming, which is carried out in the presence of catalysts from platinum or platinum and rhenium.During the catalytic reforming of gasoline, aromatic hydrocarbons (benzene, toluene, xylene, etc.) from paraffins and cycloparaffins. Reforming using a molybdenum catalyst is called hydroforming, and using a platinum catalyst is called platforming. The latter, which is a simpler and safer process, is currently used much more often.

Pyrolysis. This is the thermal decomposition of petroleum hydrocarbons in special apparatuses or gas generators at a temperature of 650°C. It is applied to receiving aromatic hydrocarbons and gas. Both oil and fuel oil can be used as raw materials, but the highest yield of aromatic hydrocarbons is observed during the pyrolysis of light oil fractions. Yield: 50% gas, 45% resin, 5% soot. Aromatic hydrocarbons are obtained from the resin by distillation.