Examples of equipment and installations for oil and gas refineries:
Equipment
聽installations for electric desalination and dehydration of emulsion oil (ELOU)
Efficient desalination can significantly reduce corrosion of process equipment of oil refining plants, prevent catalyst deactivation, improve the quality of fuels, petroleum coke, bitumen and other products.
The main equipment of ELOU is electric dehydrators (cylindrical devices with electrodes mounted inside). In the process of desalination at a temperature of 100-120掳C, through the action of a high voltage current (25 kV or more) on a mixture consisting of water, oil and added demulsifiers, water is collected at the bottom and pumped out.
As a result of this production process, desalted and dehydrated oil (3-4 mg / l of salts and up to 0.1% water) is obtained, from which all motor fuel components, lubricating oils, raw materials for the secondary refining process and petrochemistry.
The heavy residue from distillation – tar goes to thermal and catalytic oil refining units. Gaseous hydrocarbons that cannot be condensed into a liquid phase are transferred to a gas fractionation unit (GFU)
AVT installations (atmospheric vacuum tube)
The unit is designed to produce distillates of gasoline, kerosene, diesel fuel, three oil fractions of different viscosity and tar from oil.
In addition to these products, the unit produces dry and wet gases, liquefied gas (reflux), and light vacuum gas oil.
The distillation usually receives oils or mixtures of oils with a content of light distillates (boiling up to 350 掳 C) from 42 to 50% (wt.).
Modern high-power installations consist of the following blocks:
– preliminary heating of oil in heat exchangers;
– electric desalination and dehydration of oil (ELOU unit);
– subsequent heating in heat exchangers;
– oil topping (pressure column with a heating furnace);
– atmospheric column (with heating furnace and stripping columns);
– fractionation of fuel oil under vacuum (with a heating furnace, stripping columns and a vacuum system);
– stabilization and secondary distillation of gasoline into narrow fractions.
During the production process, the feed oil is pumped in several parallel streams (for example, 4 streams) through a group of heat exchangers, where it is heated to a temperature of 100-130掳C.
The use of such an oil heating system makes it possible to create a more efficient heat exchange.
After heat exchangers for temperature averaging, oil flows are mixed in a common collector.
Further, the oil is again directed in parallel flows to 2 stages of electric dehydrators (ELOU block).
Upon exiting the ELOU unit, oil is heated first in 2 heat exchangers connected in parallel, and then in the next heat exchanger.
Heated to 200-250掳C, oil enters the topping column through 2 tangential inlets.
From this column, gases, water vapor and light gasoline fraction leave from above (with a boiling point of 120-160 掳 C).
To condense vapors and cool the mixture, an air cooler and a water cooler located behind it are used.
Gas and water are separated from the condensed light gasoline fraction in the separator.
The gas, having passed the valve that regulates the pressure in the column-separator system, is sent to the hydrogen sulfide purification section, and the water from the bottom of the separator, which is equipped with an interfacial level regulator (water-gasoline), enters the wastewater treatment system.
The circulating part of gasoline (irrigation) is returned to the column with the help of a pump, and its balance quantity is removed from this unit and transferred to the gasoline stabilization unit, to the stabilizer column.
To maintain the temperature at the bottom of the column, partially stripped oil is taken by the pump, passes through the furnace coils and, heated to 350-370掳C, returns to the bottom of the column.
The balance amount of stripped oil with the help of a pump passes through the coils of the furnace and with a temperature of 370-380 掳 C is fed through 2 tangential inlets into the atmospheric column.
gas fractionation units (GFU)
Gas fractionation units (GFU) – a set of devices for separating a mixture of light hydrocarbons into individual or commercially pure substances. HFCs process gas gasolines obtained from petroleum (associated), natural and refinery gases, liquid products isolated from coking gases of catalytic reforming and thermal cracking. The composition of raw materials mainly includes individual low molecular weight hydrocarbons C1 C6 (both saturated and unsaturated, normal or iso structure) or their high purity fractions, which are components of high-octane motor gasolines, valuable petrochemical raw materials, as well as raw materials for alkylation processes and the production of methyl tert-butyl ether, etc. .d.
At oil and gas refineries, the following physical processes for the separation of hydrocarbon gases into individual or narrow technical fractions are most widely used: condensation, compression, rectification and absorption. At HFCs, these processes are combined in various combinations. Prior to fractionation, hydrocarbon gases are first sent to the hydrogen sulfide removal and drying units.
Hydrocarbon mixtures are separated by distillation in HFC column apparatuses. Rectification is the final stage in the separation of hydrocarbon gases. A feature of the rectification of liquefied gases, in comparison with the rectification of petroleum fractions, is the need to separate components or fractions of raw materials that are very close in boiling point at a high degree of fractionation.
The main indicators of the operation of HFCs are the clarity of the separation of raw materials into constituent components and the concentration of target components in fractions. Their quality must meet the requirements of technical specifications and standards.
For each unit, its own flow chart is developed, which indicates: the optimal mode of operation of all equipment – the limits of changes in the main process parameters – the pressure in the columns and irrigation tanks, the temperature of the top and bottom (on the control plate) of the columns, the consumption of raw materials, the consumption of irrigation, levels in boilers, irrigation tanks and the chemical composition of the products obtained.
At refineries, mainly 2 types of gas fractionation units are used to separate refinery gases, each of which includes compression and condensation units: rectification – abbreviated HFC, and absorption-rectification AGFU.
A gas fractionation unit (GFU) is used to separate a mixture of light hydrocarbons into individual, or technically pure, substances.
HFC is a part of gasoline, gas processing, petrochemical and chemical plants. The HFC capacity reaches 750 thousand tons of feedstock per year.
For processing, HFCs receive raw materials – gas gasolines obtained from natural and refinery gases, oil stabilization products, pyrolysis and cracking gases. The composition of raw materials includes mainly hydrocarbons containing from 1 to 8 carbon atoms per molecule. The separation of mixtures of hydrocarbons is carried out by distillation in column apparatus.
Propane vapor is discharged from the top of the column, which condenses in a condenser-refrigerator and enters the irrigation tank. Part of the propane is returned to the top of the column as reflux, while the excess is removed as a finished product. The liquid from the bottom of the column after heating enters the next column for further separation according to the same scheme, where a mixture of butanes is separated from it as an upper product, and gasoline is discharged from the lower part. Similarly, butanes are separated into isobutane and normal butane, and gasoline – into isopentane, normal pentane, hexanes, etc. Approximate content of pure substance (in%) in a commercial product of the same name during the processing of gas gasoline: propane 96; isobutane 95; normal butane 96; isopentane 95; stable gasoline 74.
gas absorption and fractionation unit (AGFU)
AGFU is designed for refinery gas processing and unstable gasoline. The unit consists of the following units: actual fractionation, compression, purification of wet gas and a wide fraction of light hydrocarbons with a solution of monoethanolamine, as well as with the final purification of the latter with a 10% alkali solution and drying with an aqueous solution of diethylene glycol, then the solutions of monoethanolamine and diethylene glycol are regenerated.
Absorption allows converting the extracted gases into a liquid state at relatively low pressures. The quantity and quality of the absorbent, as well as the absorption temperature and pressure, depend on the composition of the gas to be separated and the desired depth of extraction of the individual components; 97.8% extraction of the propane-propylene fraction can be carried out at a pressure of 12 atm and the supply of 7 liters of absorbent per 1 cubic meter. m of gas without resorting to artificial cold. The absorption method of extracting gases began to be successfully used after the development of the head, combined absorption-stripping column, also called the fractionating absorber.
Usually, the wet gas from the catalytic cracking unit I goes to the absorption-gas fractionation unit, from where the individual fractions are sent for further processing. For the most part, the butane-butylene fraction is the raw material of the alkylation unit, where alkyl-benzo3, a valuable component of aviation gasoline, is obtained from butylenes and isobutane.
If there is a significant amount of ethane and ethylene in the feedstock supplied for gas fractionation, as a rule, refineries use units in which the preliminary separation of gases into light and heavy parts by the absorption method is combined with rectification of the resulting streams. Absorption-gas fractionation units (AGFU) are used at gas processing plants, refineries and petrochemical enterprises. In some cases, they are combined with an oil stabilization unit.
The operation of this unit is closely related to the operation of the catalytic cracking unit. The connection lies not only in the fact that light products from the catalytic cracking unit are supplied to the absorption gas fractionation unit, but also in the technological interdependence of both units. Thus, with an increase in the amount of gas generated during cracking, it is necessary to put into operation an additional compressor in the absorption gas fractionation unit in order to avoid pressure increase in the catalytic cracking unit. With an increase in the end point of boiling of unstable gasoline, it is necessary to change the mode of the butane column in order not to reduce the depth of selection of the butane-butylene fraction.
Catalytic cracking units
The catalytic cracking unit provides „breakdown“ of the gas oil fraction after distillation. Cracking is carried out by the action of a catalyst aerated by steam and acting as a liquid.
These plants typically process atmospheric gas oil, vacuum gas oil or coker gas oil. The hot product comes into contact with the steam and then with the catalyst. In this case, products of lower molecular weight are released. The produced products of catalytic cracking units are further processed in alkylation units (propylene, isobutene, gasoline, diesel fuel).
alkylation plants
Alkylation unit (alkyl) is one of the conversion processes used in refineries. It is used to convert isobutane and low molecular weight alkenes (primarily mixtures of propene and butene) to alkylate, the high-octane component of gasoline. The process takes place in the presence of an acid such as sulfuric acid (H2SO4) or hydrofluoric acid (HF) as a catalyst. Depending on the acid used, the plant is called a sulfuric acid alkylation unit (SAAU) or a hydrofluoric acid alkylation unit (HFAU). In short, alkyl produces a high quality gasoline blend by combining two shorter hydrocarbon molecules into one long chain gasoline range molecule by blending isobutane with a light olefin such as propylene or butylene produced in a fluid catalytic cracking unit (FCCU) refinery in the presence of an acid catalyst .
Because crude oil typically contains only 10-40% hydrocarbon components in the gasoline range, refineries typically use FCCUs to convert high molecular weight hydrocarbons into smaller, more volatile compounds, which are then converted to gasoline-sized liquid hydrocarbons. By-products of the FCC process also create other low molecular weight alkenes and isoparaffin molecules that are undesirable. Alkylation converts these by-products into larger molecules of high octane isoparaffins. While FCCU units are very common equipment in modern refineries, an alkylation unit in refineries is not common.
hydrocracking units
Hydrocracking units are capable of processing a wide range of feedstocks with different characteristics to produce a wide range of products. They can be designed and operated to maximize gasoline blending component production or to maximize diesel fuel production.
Hydrocracking is a catalytic chemical process used in refineries to convert the high-boiling hydrocarbon constituents of oil (heavy residues) into more valuable low-boiling products such as: gasoline, kerosene, jet fuel, diesel fuel. The process takes place in a hydrogen environment at elevated temperatures (260-425 掳C) and pressures (12-17 MPa). In the hydrocracking process, high boiling, high molecular weight hydrocarbons are first broken down into low boiling, low molecular weight olefinic and aromatic hydrocarbons, and then they are hydrogenated.
Any sulfur and nitrogen present in the hydrocracking feed is also largely hydrogenated to form hydrogen sulfide (H2S) and ammonia (NH3) gas, which are subsequently removed. As a result, hydrocracking products contain practically no sulfur and nitrogen impurities and consist mainly of paraffinic hydrocarbons.