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MINISTRY OF EDUCATION AND SCIENCE OF RUSSIA
Federal State Budgetary Educational Institution of Higher Professional Education
"Penza State Technological Academy" (PGTA)
Professional institute
course project
Discipline: "Chemistry and technology of oil and gas"
Topic: "Hydrocracking of crude oil"
Is done by a student:
Emeldyaev V.A.
Checked by teacher:
Pavlova E.A
Penza 2013
- Introduction
- 1. Hydrocracking of crude oil
- 1.1 Features of the chemistry and mechanism of hydrocracking reactions
- 1.2 Hydrocracking catalysts
- 1.3 Basic parameters of hydrocracking processes
- 1.4 Hydrocracking of gasoline fractions
- 1.5 Selective hydrocracking processes
- 1.6 Hydrogenation of kerosene fractions
- 1.7 Hydrocracking of vacuum distillate at 15 MPa
- 1.7.1 Single-stage vacuum distillate hydrocracking process
- 1.7.2 Technological scheme of one-stage hydrocracking with the production of predominantly diesel fuel from vacuum gas oil in a stationary catalyst bed
- Conclusion
- List of sources used
Introduction
The oil refining industry in Russia lags far behind in its development from the industrialized countries of the world. The main problems of the industry are the low depth of oil refining, the low quality of the produced oil products.
Russian refineries are characterized by a low level of conversion of crude oil into more valuable refined products. On average, in the Russian Federation, the output of the main motor fuels (gasoline, diesel fuel) is inferior to the indicators of oil refining in the industrialized countries of the world, and the share of fuel oil production is the highest.
The low quality of produced oil products is due to the backward structure of oil refining at most Russian refineries, in which the share of destructive deepening processes is low,
Recently, there has been a tendency to improve the state of the oil refining industry in Russia. Signs of improvement are a significant increase in investment by Russian oil companies in oil refining, an increase in oil refining volumes, a gradual improvement in the quality of motor fuels produced by refusing to produce leaded gasoline, an increase in the share of production of high-octane gasoline and environmentally friendly. At a number of Russian refineries in recent years, the construction of new deep oil refining complexes (DGR) has been actively underway. In 2004, a vacuum gasoil hydrocracking complex was launched at the Perm Oil Refinery (OJSC LUKOIL), in 2005 CGPN was launched at Slavneft's Yaroslavl Oil Refinery, and a vacuum gasoil hydrotreatment complex at the Ryazan Oil Refinery, owned by TNK-BP. The catalytic cracking complex was launched at the Nizhnekamsk Refinery of TAIF. At the Surgutneftegaz plant in Kirishi, the construction of a vacuum gas oil hydrocracking complex is underway.
At the reconstructed refineries, they began to receive European quality petroleum products, and in the areas where the enterprises are located, it was possible to improve the environmental situation.
1. Hydrocracking of crude oil
The hydrocracking process is intended mainly for the production of low-sulphur fuel distillates from various feedstocks. Typically, vacuum and atmospheric gas oils, thermal and catalytic cracking gas oils, deasphalting oils, and less often fuel oils and tars are subjected to hydrocracking in order to produce motor gasolines, jet and diesel fuels, feedstock for petrochemical synthesis, and sometimes liquefied hydrocarbon gases (from gasoline fractions). Hydrogen is consumed during hydrocracking much more than during hydrotreatment of the same types of raw materials.
Hydrocracking is a catalytic process for the processing of petroleum distillates and residues at moderate temperatures and elevated hydrogen pressures on polyfunctional catalysts with hydrogenating and acidic properties (and in selective hydrocracking processes, also a sieve effect).
Hydrocracking makes it possible to obtain a wide range of high-quality petroleum products (liquefied gases C 3 - C 4 , gasoline, jet and diesel fuels, oil components) with high yields from virtually any petroleum feedstock by selecting appropriate catalysts and technological conditions, is one of the most cost-effective, flexible and the most deepening oil refining processes.
In modern oil refining, the following types of industrial hydrocracking processes are implemented:
1) hydrocracking of gasoline fractions in order to obtain light isoparaffin hydrocarbons, which are a valuable raw material for the production of synthetic rubber, high-octane additives for motor gasoline;
2) selective hydrocracking of gasolines in order to increase the octane number, jet and diesel fuels in order to lower their pour point;
3) hydrodearomatization of straight-run kerosene fractions and catalytic cracking gas oils in order to reduce the content of aromatic hydrocarbons in them;
4) light hydrocracking of vacuum gas oils in order to upgrade catalytic cracking feedstock with simultaneous production of diesel fractions;
5) hydrocracking of vacuum distillates in order to obtain motor fuels and the base of high-index oils;
6) hydrocracking of oil residues in order to obtain motor fuels, lubricating oils, low-sulphur boiler fuels and feedstock for catalytic cracking.
1.1 Features of the chemistry and mechanism of hydrocracking reactions
Hydrocracking can be considered as a combined process in which the reactions of both hydrogenolysis (i.e., breaking the C-S, C-N, and C-O bonds) and dehydro-hydrogenation and cracking (that is, breaking the C-C bond) are simultaneously carried out, but without coke formation, with obtaining products of lower molecular weight compared to the feedstock, purified from heteroatoms, not containing olefins, but less aromatized than in catalytic cracking.
The results of hydrocracking (material balance and product quality) of crude oil are largely determined by the properties of the catalyst: its hydrogenating and acidic activities and their ratio. Depending on the intended purpose, catalysts with a predominance of either hydrogenating or cracking activity can be used. As a result, products of light or deep hydrocracking, respectively, will be obtained.
The catalytic processes of hydrocracking of crude oil are based on the following reactions:
1) hydrogenolysis of heteroorganic compounds of sulfur, nitrogen, oxygen and hydrogenation of aromatic hydrocarbons and unsaturated compounds (that is, all those reactions that occur during hydrofinishing);
2) cracking of paraffinic and naphthenic hydrocarbons, dealkylation of cyclic structures and isomerization of the resulting low molecular weight paraffins.
Aromatization and polycondensation reactions to coke occurring during catalytic cracking in hydrocracking processes carried out at high hydrogen pressure and low temperatures are strongly inhibited due to thermodynamic limitations and hydrogenation of coke with hydrogen.
Hydrogenolysis sulfur-, nitrogen- and oxygen-containing compounds proceeds according to the mechanism in the same way as in hydrotreating processes, and ends with the formation of hydrogen sulfide, ammonia, water and the corresponding hydrocarbon. hydrocracking catalyst vacuum distiller
Hydrogenation of aromatic hydrocarbons is carried out by successive saturation of aromatic rings with possible concomitant rupture of the formed naphthenic rings and dealkylation.
Hydrocracking of high molecular weight paraffins on catalysts with high acid activity, it is carried out according to the carbenium-ion mechanism, mainly with a gap in the middle part with the lowest C-C bond energy. As in catalytic cracking, first, dehydrogenation of paraffins occurs on the metal centers of the catalyst to form alkenes. Then alkenes on acid sites are easily converted into carbocations and initiate a chain carbenium-ion process. The rate of hydrocracking also increases with an increase in the molecular weight of alkanes. Isoparaffins with tertiary carbon atoms undergo cracking at a much higher rate than normal alkanes. Since the decomposition of carbenium ions with the elimination of fragments containing less than three carbon atoms is strongly endothermic, methane and ethane are almost not formed during hydrocracking, and the yield of isobutane and isopentanes is high (more than equilibrium). On catalysts with high hydrogenating and moderate acidic activities, intense saturation of carbenium ions occurs, resulting in the formation of paraffins with a large number of carbon atoms in the molecule, but less isomerized than on catalysts with high acidity.
The main differences between hydrocracking and catalytic cracking are that the overall paraffin conversion is higher in the first process than in the second. This is due to the ease of formation of alkenes on the hydro-dehydrogenating sites of hydrocracking catalysts. As a result, the slowest and most energy-intensive stage of the chain mechanism - chain initiation - proceeds faster during hydrocracking than during catalytic cracking without hydrogen. Hydrocracking catalysts practically do not coke, since alkenes undergo rapid hydrogenation and do not have time to enter into further transformations with the formation of polymerization and compaction products.
Naphthenes with long alkyl chains during hydrocracking on catalysts with high acid activity, they undergo isomerization and chain breakdown, like paraffinic hydrocarbons. Splitting of the ring occurs to a small extent. The reactions of isomerization of six-membered into five-membered naphthenes proceed intensively. Bicyclic naphthenes are converted predominantly into monocyclic ones, with a high yield of cyclopentane derivatives. On catalysts with low acid activity, hydrogenolysis mainly proceeds - splitting of the ring with subsequent saturation of the resulting hydrocarbon.
1.2 Hydrocracking catalysts
The range of modern hydrocracking catalysts is quite extensive, which is explained by the variety of process purposes. They usually consist of the following three components: acidic, dehydro-hydrogenating and a binder that provides mechanical strength and porous structure.
As an acid component that performs cracking and isomerizing functions, solid acids are used, which are part of cracking catalysts: zeolites, aluminosilicates and aluminum oxide. To increase the acidity, a halogen is sometimes introduced into the catalyst.
The hydrogenating component is usually those metals that are part of the hydrotreating catalysts: metals of group VIII (Ni, Co, sometimes Pt or Pd) and VI groups (Mo or W). Various promoters are also used to activate hydrocracking catalysts: rhenium, rhodium, iridium, rare earth elements, etc. The binder is often performed by an acid component (aluminum oxide, aluminosilicates), as well as oxides of silicon, titanium, zirconium, magnesium and zirconium silicates.
Significantly better hydrocracking results are achieved using catalysts with high acidity and optimal hydrogenation activity, the advantages of which in relation to industrial types of raw materials are as follows:
the yield of paraffins C, - C 3 and especially methane and ethane is low;
butane fraction contains 60 - 80% isobutane;
pentane and hexane fractions consist of 90 - 96% isomers. Cycloparaffins C 6 contain about 90% methylcyclopentane. As a result, light gasoline (up to 85 °C) containing 80-90 % paraffins, up to 5% benzene and 10 - 20% naphthenes, has fairly high antiknock characteristics: RON is 85--88;
gasolines C 7 and above contain 40-50% naphthenes, 0-20% aromatics and are exceptionally high-quality reforming raw materials;
kerosene fractions due to the high content of isoparaffins and low - bicyclic aromatic hydrocarbons are high-quality fuel for jet engines;
diesel fractions contain few aromatic hydrocarbons and mainly consist of derivatives of cyclopentane and cyclohexane, have high cetane numbers and relatively low pour points;
Great importance is currently being given to zeolite-based catalysts. They have high hydrocracking activity and good selectivity. In addition, they allow the process to be carried out sometimes without preliminary purification of the feedstock from nitrogen-containing compounds. The content of up to 0.2% nitrogen in the feedstock has practically no effect on their activity.
In the case of processing heavy raw materials In addition to nitrogenous bases, asphaltenes and, above all, the metals they contain, such as nickel and vanadium, pose the greatest danger to the deactivation of hydrocracking catalysts. Therefore, the hydrocracking of raw materials containing a significant amount of hetero- and organometallic compounds is forced to be carried out in two or more stages. The first stage mainly involves hydrotreatment and shallow hydrocracking of polycyclic aromatic hydrocarbons (as well as demetallization). The catalysts in this stage are identical to the hydrotreating catalysts. At the second stage, the improved raw material is processed on a catalyst with high acidic and moderate hydrogenating activity.
In the hydrocracking of oil residues it is advisable to subject the feedstock to preliminary demetallization and hydrodesulfurization (as in the Khaival process, etc.) on sulfur- and nitrogen-resistant catalysts with a high metal content and a sufficiently high hydrogenating, but low cracking activity.
In the process of selective hydrocracking, modified zeolites (mordenite, erionite, etc.) with a specific molecular sieve effect are used as catalysts: zeolite pores are accessible only to normal paraffin molecules. The dehydrohydrogenating functions in such catalysts are performed by the same metals and compounds as in hydrotreatment processes.
1.3 Basic parameters of hydrocracking processes
Temperature. The optimal temperature range for hydrocracking processes is 360 - 440°C with a gradual increase from the lower to the upper limit as the catalyst activity decreases. At a lower temperature, cracking reactions proceed at a low rate, but the chemical composition of the products is more favorable: a higher content of naphthenes and the ratio of isoparaffin: n-paraffin. An excessive increase in temperature is limited by thermodynamic factors (hydrogenation reactions of polycyclic aromatics) and an increase in the role of gas and coke formation reactions.
Thermal hydrocracking is determined by the ratio of hydrogenation and cleavage reactions. Typically, the negative thermal effect of cleavage is offset by the positive thermal effect of hydrogenation. Naturally, the exothermic thermal effect of the overall process is the greater, the higher the depth of hydrocracking. Therefore, its hardware design usually provides for the possibility of removing excess heat from the reaction zone in order to prevent overheating of the reaction mixture. When using reactors with a stationary catalyst, the latter is filled in several layers so that cooling of the stream can be carried out between them (usually part of the cold HSG).
Pressure. It has been established that the limiting step in the overall hydrocracking process is the hydrogenation of unsaturated feedstock compounds, especially polycyclic aromatic hydrocarbons. Therefore, deep hydrocracking catalysts should have, in addition to high acid activity, sufficient hydrogenation activity.
The rate of hydrogenation reactions is significantly affected by the phase state (G + L+T) of the reaction mixture, which is a function of pressure, temperature, hydrogen concentration, conversion depth, and fractional composition of the feedstock. In general, on catalysts of the hydrogenating type, both the rate of reactions and the depth of hydrocracking increase with increasing pressure. The minimum acceptable pressure is the higher, the less active the catalyst and the heavier the hydrocracking feedstock.
Most industrial hydrocracking units operate at a pressure of 15-17 MPa. For hydrocracking of oil residues using relatively expensive catalysts, a pressure of 20 MPa is used. Hydrocracking of straight-run light gas oils with a low nitrogen content can be carried out at relatively low pressures - about 7 MPa.
Volumetric feed rate of raw materials in hydrocracking, due to the preference for carrying out the process at minimum temperatures, it is usually low (0.2 - 0.5 h -1). When running the process in
soft hydrocracking it is higher and reaches up to 1 h -1 . To increase the conversion of raw materials, recirculation of fractions that boil above the target product is used.
The frequency of circulation of hydrogen-containing gas in relation to the raw material being processed, it fluctuates depending on the purpose of the process within the limits of 800 - 2000 m 3 /m 3.
Hydrogen consumption depends on the purpose of the process, the feedstock used, the catalyst, the process mode, the depth of hydrocracking, and other factors. The lighter the hydrocracking products and the heavier the hydrocracked feedstock, the greater the hydrogen consumption and the higher the hydrogen:feedstock ratio should be.
1.4 Hydrocracking of gasoline fractions
The purpose of the process of hydrocracking of gasoline fractions is to obtain isoparaffin hydrocarbons C 5 - C 6 - a valuable raw material for the production of synthetic rubbers. In modern world oil refining, this process is not widely used (only about 10 units are in operation), however, it has the prospect of industrial development due to the need to process low-octane raffinates of catalytic reforming processes of the petrochemical profile and gasoline fractions of gas condensates. The significance of this process should increase with the adoption of restrictions on the content of aromatic hydrocarbons in motor gasolines.
Of the numerous catalysts proposed for this process, zeolite-containing bimetallic catalysts that are resistant to catalyst poisons have received industrial application.
In the process of hydrocracking of gasoline fractions 85 - 180 ° C, carried out at a temperature of 350 ° C, a pressure of 4 MPa and a feed space velocity of 0.5-1.5 h with residue recycling, 31% isobutane, 16% isopentanes and 10% isohexanes can be obtained with a slight output of dry gas (C, -C 2).
For the complex processing of low-octane gasoline, a combined process has been developed (at VNIINP) isoreforming, which is a combination of hydrocracking (at the beginning of the process) and catalytic reforming of the hydrocracking product after separation of isocomponents (fractions of n.k. -85 ° C). An industrial catalyst for the hydrocracking stage GKB-ZM is obtained by introducing molybdenum compounds, then nickel and P33Y zeolite with a sodium content of less than 0.1% into a suspension of aluminum hydroxide. The material balance of the combined isoreforming process carried out on the reconstructed industrial plant L-35-11/300 is shown in Table 1.
Table 1. Material balance of the isoreforming process
The disadvantage of the process is a short cycle (3-4 months) of the operation of the hydrocracking section (while the inter-regeneration run of the second stage is about 1 year) and a large gas yield - the isocomponent:gas ratio is approximately equal to 1:1.
1.5 Selective hydrocracking processes
Designed to improve the operational, primarily low-temperature properties of motor fuels and oils. The decrease in their pour point is achieved by selective splitting of normal paraffins contained in the processed raw materials.
The selectivity of the catalytic action in the processes of selective hydrocracking (SHC) is achieved by using special catalysts based on modified high-silica zeolites with a molecular sieve property. SGC catalysts have a tubular porous structure with entrance windows of 0.5–0.55 nm, accessible for penetration and reaction there only by paraffin molecules of a normal structure. To hydrogenate the resulting cracking products, conventional hydrogenating components (groups VIII and VI metals) are introduced into the zeolite.
Selective hydrocracking, also known as hydrodewaxing, is carried out in plants that are almost similar in terms of instrumentation and technological modes to hydrotreatment processes.
Table 2. Characteristics of the process of hydrodewaxing of various fractions on the SGK-1 catalyst
VNII NP has also developed a bifunctional BFK catalyst that provides simultaneous hydrotreatment and hydrodewaxing of paraffinic and sulphurous fuel distillates and the production of jet and diesel fuels with the required pour point and sulfur in one stage. In the process of simultaneous hydrodewaxing and hydrotreatment of diesel fractions of West Siberian oils on a BFK catalyst, it is possible to obtain arctic or winter grades of diesel fuel with a yield of 74 ... 85%.
At the L-24-7 unit of OAO Ufaneftekhim, a process was introduced for catalytic hydrodewaxing of straight-run diesel fraction of commercial West Siberian oil on a mixture of catalysts: hydrotreatment G9-168Sh (OAO Omsknefteorgsintez) and hydrodewaxing GKD-5n (Novokuibyshev Catalyst Factory), pretreated disulfides and aniline. At a temperature of 350 ... 360 ° C, a pressure of 3.5 MPa, a space velocity of 2.25 ... 2.5 h-1 and a circulation rate of the WSG 800 nm 3 / m 3 from raw materials with a sulfur content of 0.7 ... 0.9% wt . and a pour point from -17 to -20 °C, a stable hydrogenation product with a pour point of -35 °C was obtained.
Hydrodewaxing is also used for the production of low setting oils from oil fractions and their raffinates. The process is carried out at a temperature of 300 ... 430 ° C, a pressure of 2 ... 10 MPa, a raw material space velocity of 0.5 ... 2 h-1 The yield of oils is 80 ... 87%. The quality of the hydrodeparaffinizate is close to oils obtained by low-temperature dewaxing with solvents. The pour point of oils can be lowered from +6°С to (40…50) °С.
1.6 Hydrogenation of kerosene fractions
Hydrodearomatization is a reverse catalytic process with respect to catalytic reforming, which is designed to produce high-quality jet fuels with a limited content of aromatic hydrocarbons (for example, less than 10% for T-6) from kerosene fractions (mainly straight-run).
< 0,2 % и азота < 0,001 %. Технологическое оформление одноступенчатого варианта близко к типовым процессам гидроочистки реактивных топлив (типа Л-24-9РТ и секций ГО РТ комбинированных установок ЛК-6у). В двухступенчатом процессе предусмотрена стадия предварительной гидроочистки с промежуточной очисткой ВСГ от сероводорода и аммиака.
The content of the latter in straight-run kerosene fractions, depending on the origin of the oil, is 14 ... 35%, and in light catalytic cracking gas oil - up to 70%. Hydrodearomatization of raw materials is achieved by catalytic hydrogenation of aromatic hydrocarbons to the corresponding naphthenes. At the same time, for jet fuels, such indicators as the height of a non-smoking flame, the luminometric number, the tendency to carbon formation, etc., improve.
High pressure and low temperature are thermodynamically more favorable for hydrogenation reactions. Most industrial processes of hydrodearomatization of jet fuels are carried out under relatively mild conditions: at a temperature of 200 ... 350 ° C and a pressure of 5 ... 10 MPa. Depending on the content of heteroimpurities in the raw material and the resistance of the catalyst to poisons, the processes are carried out in one or two steps.
In two-stage plants, at the first stage, deep hydrogenolysis of sulfur and nitrogen compounds of the feedstock is carried out on typical hydrotreating catalysts, and at the second stage, hydrogenation of arenes on active hydrogenating catalysts, for example, on platinum-zeolite-containing catalysts. The latter allows processing raw materials with sulfur content without preliminary hydrotreatment.< 0,2 % и азота < 0,001 %. Технологическое оформление одноступенчатого варианта близко к типовым процессам гидроочистки реактивных топлив (типа Л-24-9РТ и секций ГО РТ комбинированных установок ЛК-6у). В двухступенчатом процессе предусмотрена стадия предварительной гидроочистки с промежуточной очисткой ВСГ от сероводорода и аммиака.
Table 3 shows the main indicators of domestic processes of hydrodearomatization of jet fuels.
Table 3. Indicators of domestic processes of hydrodearomatization of jet fuels
1.7 Hydrocracking of vacuum distillate at 15 MPa
Hydrocracking is an efficient and exceptionally flexible catalytic process that makes it possible to comprehensively solve the problem of deep processing of vacuum distillates (HVDC) to obtain a wide range of motor fuels in accordance with modern requirements and needs for certain fuels.
Abroad, especially at refineries in the United States, Western Europe and Japan, the processes of high pressure water treatment at a pressure of 15-17 MPa, aimed at obtaining gasoline (developed by the following four companies: UOP, FIN, Shell and Union Oil) have been widely developed. . Evaluation of the economic efficiency of the HCWP process in our country indicates the feasibility of implementing this process with the production of predominantly diesel fuels at a pressure of 10-12 MPa and jet fuels at a pressure of 15 MPa. The technology of two domestic modifications: one- and two-stage GKVD processes (processes 68-2k and 68-Zk, respectively) was developed at the All-Russian Research Institute of Petroleum Engineering. The single-stage HCWP process has been implemented at several Russian refineries in relation to the processing of vacuum gas oils 350–500 °C with a metal content of not more than 2 ppm.
1.7.1 Single-stage vacuum distillate hydrocracking process
The single-stage vacuum distillate hydrocracking process is carried out in a multilayer (up to five layers) reactor with several types of catalysts. In order to ensure that the temperature gradient in each layer does not exceed 25 °C, a cooling HSG (quenching) is introduced between the individual catalyst layers and contact distribution devices are installed to ensure heat and mass transfer between the gas and the reacting flow and uniform distribution of the gas-liquid flow over catalyst layer. The upper part of the reactor is equipped with flow kinetic energy dampers, mesh boxes and filters to trap corrosion products.
Figure 1 shows a schematic flow diagram of one of two parallel-operating sections of the 68-2k single-stage hydrocracking unit for vacuum distillate (with a capacity of 1 million tons/year in the diesel version or 0.63 million tons/year in the production of jet fuel).
Rice. 1 Schematic diagram of a single-stage vacuum gas oil hydrocracking unit; I - raw materials; II - WASH; III - diesel fuel; IV - light gasoline; V - heavy gasoline; VI - heavy gas oil; VII - hydrocarbon gases on HFCs; VIII - exhaust gases; IX - regenerated MEA solution; X - MEA solution for regeneration; XI - water vapor
The feedstock (350 - 500 °C) and the recycled hydrocracking residue are mixed with HSG, heated first in heat exchangers, then in the P-1 furnace to the reaction temperature and enter the R-1 (R-2, etc.) reactors. The reaction mixture is cooled in raw heat exchangers, then in air coolers and with a temperature of 45 - 55 ° C enters the high pressure separator C-1, where it is separated into HSG and unstable hydrogenation product. VSG after cleaning from H 2 S in the absorber K-4 is sent to the circulation by the compressor. The unstable hydrogenation product enters the S-2 low-pressure separator through a pressure reducing valve, where part of the hydrocarbon gases is separated, and the liquid stream is fed through heat exchangers to the K-1 stabilization column for distillation of hydrocarbon gases and light gasoline. The stable hydrogenate is further separated in the K-2 atmospheric column into heavy gasoline, diesel fuel (through the K-3 stripping column) and a fraction >360 °C, part of which can serve as recirculation, and the balance amount - as a raw material for pyrolysis, the basis of lubricating oils etc.
Table 5 shows the material balance of one- and two-stage HPHT with hydrocracking residue recirculation (process mode: pressure 15 MPa, temperature 405--410°C, feed space velocity 0.7 h-1, WSG circulation rate 1500 m3/m3 ).
Comparative indicators for the output of products at domestic and foreign installations of the State Committee for Internal Affairs are given in Table 4.
Table 4. Indicators of vacuum gas oil hydrocracking processes at domestic and foreign plants.
Table 5. Characteristics of the processes for obtaining middle distillates with one- and two-stage versions of the HKVD process
1.7.2 Technological scheme of one-stage hydrocracking with the production of predominantly diesel fuel from vacuum gas oil in a stationary catalyst bed
The hydrocracking process is exothermic, and to equalize the temperature of the feed mixture along the height of the reactor, cold hydrogen-containing gas is introduced into the zones between the catalyst layers. The movement of the raw mixture in the reactors is downward.
Technological hydrocracking units usually consist of two main units: a reaction unit, which includes one or two reactors, and a fractionation unit, which has a different number of distillation columns (stabilization, fractionation of liquid products, a vacuum column, a fractionating absorber, etc.). In addition, there is often a unit for gas purification from hydrogen sulfide. The capacity of the installations can reach 13,000 m3/day.
The raw material supplied by the pump 1 is mixed with fresh hydrogen-containing gas and circulating gas, which are pumped by the compressor 8. The raw gas mixture, having passed the heat exchanger 4 and the furnace coils 2, is heated to the reaction temperature and is introduced into the reactor 3 from above. Given the large heat release during hydrocracking, cold hydrogen-containing (circulation) gas is introduced into the reactor in the zones between the catalyst layers in order to equalize temperatures along the height of the reactor.
The mixture of reaction products and circulation gas leaving the reactor is cooled in heat exchanger 4, cooler 5 and enters high-pressure separator 6. Here, the hydrogen-containing gas is separated from the liquid, which from the bottom of the separator through the pressure reducing valve 9, then enters the low-pressure separator 10. In the separator 10, part of the hydrocarbon gases is released, and the liquid stream is sent to the heat exchanger 11, located before the intermediate distillation column 15. In the column, at a slight excess pressure, hydrocarbon gases and light gasoline are released.
Gasoline is partially returned to the column 15 in the form of acute irrigation, and its balance amount is pumped out of the plant through the "alkalinization" system. The remainder of the column /5 is separated in the atmospheric column 20 into heavy gasoline, diesel fuel and a fraction >360°C.
Atmospheric column gasoline is mixed with intermediate column gasoline and removed from the unit. Diesel fuel after the stripping column 24 is cooled, "alkaline" and pumped out of the plant. Fraction >360°C is used as a hot stream at the bottom of the column 20, and the rest (residue) is removed from the installation. In the case of the production of oil fractions, the fractionation unit also has a vacuum column.
Hydrogen-containing gas is cleaned with an aqueous solution of monoethanolamine and returned to the system. The required concentration of hydrogen in the cycle gas is provided by the supply of fresh hydrogen (for example, from a catalytic reformer).
Catalyst regeneration is carried out with a mixture of air and inert gas; the service life of the catalyst is 4--7 months.
Table 6. Hydrocracking Process Mode:
Table 7. Material balance of a single-stage process of hydrocracking of sour and sour raw materials (under the following conditions: total pressure 5 MPa, temperature 425°C, feed space velocity 1.0 h -1 , the frequency of circulation of hydrogen-containing gas 600 m 3 /m 3 raw materials) given below.
|
Indicators |
Vacuum distillate sour oils (350-500 o C) |
Vacuum distillate of Arlan oil |
Tar coking distillate of sour crude oils (200-450 o C) |
||
|
Fraction 200-450 about C II |
Fraction 350-450 o C III |
||||
|
Taken, % (wt.) Hydrogen (100% H 2) |
|||||
|
Received, % (wt.) Gasoline (n.k.-- 180 o C) Diesel fuel (180--360 o C) Residue > 360°С hydrogen sulfide Hydrocarbon gases |
|||||
Table 8. Characteristics of the main cracking products obtained from this type of feedstock (sulphurous and high-sulphurous).
|
Indicators |
|||||||||
|
diesel fuel |
diesel fuel |
diesel fuel |
diesel fuel |
||||||
|
Density at 20 o C, kg / m 3 Fractional composition, about С Iodine number, g I/100 g Pour point, o C sulfur, % (wt.) actual resins, mg/100 ml Kinematic viscosity, mm 2 / s Octane (m.m.) or cetane number |
Hydrocracking heavy gas oil is considered as a good pyrolysis feedstock for ethylene production, and C5 fractions - 85 °C and 85--193 °C, rich in naphthenic hydrocarbons - as an excellent feedstock for catalytic reforming aimed at the production of aromatic hydrocarbons. Light gas oil is commonly used as a diesel fuel component.
Conclusion
The general trend of the oil industry is a decrease in light oil reserves, almost the entire increase in reserves is due to heavy viscous sour oil. The potential of high-quality raw materials has been realized by almost 80%, retaining only the prospects of small discoveries. Heavy oil reserves prevail in Russia, Kazakhstan, China, Venezuela, Mexico, Canada, and the USA.
At a time when oil prices were breaking one record after another, Russian oil companies preferred an extensive increase in the resource base to an active transition to the path of innovative development. Most of the world's major oil and gas companies directed significant funds for research, the results of which depend on the effectiveness of their further functioning.
It should be taken into account that in the Russian Federation after the seventies not a single large highly productive field was discovered, and the newly incremented reserves are deteriorating sharply in terms of their conditions.
More than half of the highly productive reserves of large fields have been depleted, and large deposits are experiencing an intensive decline in oil production. A mass commissioning of small, low-productive deposits began.
The further development of the oil and gas industry in Russia largely depends on the creation of new innovative technologies.
New competitive advantages in modern conditions are provided by the use of innovative technologies, which is one of the sources for increasing the technological level of production of oil companies:
ь development of an efficient technology for the processing of heavy oil residues as a transitional technology from the processing of petroleum raw materials to the use of alternative raw materials - heavy and bituminous oils, shale;
ь increasing the octane number of motor gasolines in the conditions of refusal to use lead antiknock agents;
ь increasing the selectivity and reducing the energy intensity of oil refining processes by introducing the latest advances in the field of catalysis, improving heat and mass transfer schemes, utilizing the heat of waste streams, improving instrumentation and creating more efficient energy technology equipment.
The development of the processes under consideration in oil refining schemes necessitates the consumption of hydrogen to increase the H:C ratio in the resulting products compared to the feedstock, remove sulfur and nitrogen compounds, saturate olefins, and hydrogenate aromatic hydrocarbons. Various combinations of catalytic, hydrogenation and thermal processes can achieve one or another degree of fuel oil conversion with a change in the volume and structure of the production of motor fuels in accordance with the need for them.
By including light hydrocracking processes with catalytic cracking of the hydrocracking residue and coking of tar into the fuel oil processing scheme, it is possible to increase the depth of conversion of fuel oil into motor fuels up to 57%, and taking into account the additional production of high-octane components based on the processing of Cs-C4 fractions and up to 60-61% (mass .) for fuel oil.
List of sources used
1. Chemistry and technology of oil and gas. Verzhinskaya S.V., 2007 (for secondary vocational education)
2. "Technology of deep processing of oil and gas" Akhmetov S. A, 2006. (for higher education)
3. Handbook of the oil refiner: Handbook / Under the editorship of G.A. Lastovkina, E.D. Radchenko and M. Rudin. - L.: Chemistry, 1996.- 648
4. Rudin M.G., Drabkin A.E. A brief guide to the oil refiner. - L.: Chemistry, 2004.- 328s.
5. Technological calculations of oil refining units: Textbook for universities Tanatarov M.A., Akhmetshina M.N., Faskhutdinov R.A. and others - M.: Chemistry, 1997. - 352 p.
6. Album of technological schemes of oil and gas processing processes / Ed. B.I. Bondarenko. - M.: Chemistry, 1998.- 128 p.
7. Lapik V.V. Basic reference data for technological calculations in oil refining and petrochemistry: Textbook. - Tyumen, TSU, 1980. - 124 p.
8. Journals "Technologies of oil and gas"
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4. Catalytic cracking
Catalytic cracking is the most important oil refining process, which significantly affects the efficiency of the refinery as a whole. The essence of the process lies in the decomposition of hydrocarbons that are part of the raw material (vacuum gas oil) under the influence of temperature in the presence of a zeolite-containing aluminosilicate catalyst. The target product of the KK unit is a high-octane component of gasoline with an octane number of 90 points or more, its yield is from 50 to 65%, depending on the raw materials used, the technology and regime used. The high octane number is due to the fact that isomerization also occurs during catcracking. The process produces gases containing propylene and butylenes, which are used as raw materials for petrochemicals and the production of high-octane gasoline components, light gas oil - a component of diesel and heating fuels, and heavy gas oil - a raw material for the production of soot, or a component of fuel oils.
The average capacity of modern plants is from 1.5 to 2.5 million tons, however, there are plants with a capacity of 4.0 million tons at the plants of the world's leading companies.
The key part of the installation is reactor-regenerator unit. The unit includes a furnace for heating raw materials, a reactor in which cracking reactions take place directly, and a catalyst regenerator. The purpose of the regenerator is to burn out the coke formed during cracking and deposited on the catalyst surface. Reactor, regenerator and feedstock input unit are connected by pipelines (pneumatic transport lines) through which the catalyst circulates.
The most successful, although not new, domestic technology is used at plants with a capacity of 2 million tons in Ufa, Omsk, and Moscow. The diagram of the reactor-regenerator unit is shown in Fig.14. Figure 15 shows a photograph of a similar plant using ExxonMobil technology.
The capacity of catalytic cracking at Russian refineries is currently clearly not enough, and it is through the introduction of new units that the problem with the predicted shortage of gasoline is being solved. With the implementation of the programs for the reconstruction of refineries declared by oil companies, this issue is completely removed.
Over the past few years, in Ryazan and Yaroslavl, the same type of heavily worn and outdated installations, commissioned during the Soviet period, have been reconstructed, and a new one has been built in Nizhnekamsk. At the same time, technologies from Stone & Webster and Texaco were used.
Fig.14. Scheme of the reactor-regenerator block of the catalytic cracking unit
Raw materials with a temperature of 500-520°C in a mixture with a pulverized catalyst moves up the riser reactor for 2-4 seconds and undergoes cracking. Cracking products go to separator, located on top of the riser reactor, where chemical reactions are completed and the catalyst is separated, which is discharged from the lower part of the separator and flows by gravity into the regenerator, in which coke is burned at a temperature of 700°C. After that, the recovered catalyst is returned to the raw material input unit. The pressure in the reactor-regenerator block is close to atmospheric. The total height of the reactor-regenerator block is from 30 to 55 m, the diameters of the separator and regenerator are 8 and 11 m, respectively, for a plant with a capacity of 2.0 million tons.
Cracking products leave the top of the separator, are cooled and fed to rectification.
Catcracking can be a part of combined units, including preliminary hydrotreating or light hydrocracking of raw materials, purification and fractionation of gases.
Photos of catalytic cracking units
5. Hydrocracking
Hydrocracking is a process aimed at obtaining high-quality kerosene and diesel distillates, as well as vacuum gas oil by cracking feedstock hydrocarbons in the presence of hydrogen. Simultaneously with cracking, products are purified from sulfur, olefins and aromatic compounds are saturated, which leads to high operational and environmental characteristics of the resulting fuels. For example, the sulfur content of hydrocracked diesel distillate is in the millionths of a percent. The resulting gasoline fraction has a low octane number, and its heavy part can serve as a reforming feedstock. Hydrocracking is also used in the oil industry to obtain high-quality base oils that are close in performance to synthetic oils.
The range of hydrocracking raw materials is quite wide - straight-run vacuum gas oil, catalytic cracking and coking gas oils, by-products of the oil block, fuel oil, tar.
Hydrocracking units, as a rule, are built with a large unit capacity - 3-4 million tons per year in terms of raw materials.
Usually, the volumes of hydrogen produced at reforming units are not enough to provide hydrocracking; therefore, separate units for the production of hydrogen by steam reforming of hydrocarbon gases are being built at refineries.
Technological schemes are fundamentally similar to hydrotreating plants - the feedstock mixed with hydrogen-containing gas (HCG) is heated in a furnace, enters the reactor with a catalyst bed, the products from the reactor are separated from the gases and sent for rectification. However, hydrocracking reactions proceed with the release of heat, so the technological scheme provides for the introduction of cold HCG into the reaction zone, the consumption of which is controlled by the temperature. Hydrocracking is one of the most dangerous oil refining processes, when the temperature regime gets out of control, there is a sharp increase in temperature, leading to an explosion of the reactor block.
The instrumentation and technological regime of hydrocracking units differ depending on the tasks determined by the technological scheme of a particular refinery and the feedstock used.
For example, to obtain low-sulfur vacuum gas oil and a relatively small amount of light (light hydrocracking), the process is carried out at a pressure of up to 80 atm in one reactor at a temperature of about 350°C.
For the maximum yield of light (up to 90%, including up to 20% of the gasoline fraction for raw materials), the process is carried out on 2 reactors. At the same time, the products after the first reactor enter the distillation column, where the light products obtained as a result of chemical reactions are distilled off, and the residue enters the second reactor, where it is repeatedly subjected to hydrocracking. In this case, during the hydrocracking of vacuum gas oil, the pressure is about 180 atm, and during the hydrocracking of fuel oil and tar - more than 300. The process temperature, respectively, varies from 380 to 450°C and higher.
In Russia, until recently, the hydrocracking process was not used, but in the 2000s, capacities were commissioned at plants in Perm (Fig. 16), Yaroslavl and Ufa, at a number of plants, hydrotreatment units were reconstructed for the light hydrocracking process. Installation of the unit is underway at Kirishinefteorgsintez LLC, construction is planned at the plants of Rosneft OJSC.
The joint construction of hydrocracking and catalytic cracking units within the framework of deep oil refining complexes seems to be the most effective for the production of high-octane gasolines and high-quality middle distillates.
Photos of hydrocracking units
Sergey Pronin
Oil. A new complex for deep oil refining using hydrocracking technology has appeared in Russia. But it is too early to say that oil companies are moving from primary refining to deep refining.
In Perm, a complex for deep oil refining at the Lukoil refinery was put into operation. According to the company's message, the increase in the output of light oil products due to it is comparable to the additional processing of 2.3 million tons of oil per year. But it is still difficult to say how big a role the complex will play. “It is good for Russia that Lukoil is increasing the level of refining at one of its key facilities,” said Marina Lukashova, an analyst at FC Uralsib. “But it has not gained much advantages over other oil companies and there are too many refineries that need upgrade".The new complex includes a hydrocracking unit, which is a fairly modern but expensive technology. More about it told "F." Alexander Yakovlev, director of EPN-Consulting: “Earlier, a hydrocracking unit operated in Russia only in Ufa at Ufaneftekhim. But it worked poorly - it was constantly reconstructed. Now a second unit in Perm has begun to operate using a new, more modern technology, which allows to increase the production of light oil products.However, this process is very expensive, so now they mainly use catalytic cracking.The construction of a plant for processing 2 million tons of oil per year costs about $ 1.5-2 billion, the cost of an oil refinery for 5-6 million tons "The decision on what to build depends on the company's starting capacity. If it has little refining capacity, it builds a new refinery; if it has enough, it can afford to upgrade."
Dmitry Lukashov, an analyst at IG Aton, told F. that hydrocracking is not considered a super technology abroad, but for Russia it is quite progressive. When it is used, the yield of light oil products increases, but on the scale of Lukoil, the changes will not be serious. Yes, the complex is expensive. With this money it was possible to build a new processing plant. However, Lukoil is not the only company that has decided to use hydrocracking. Rosneft plans to use this technology at the Komsomolsk refinery from 2005, while Surgutneftegaz plans to install it at the Kirishi refinery by 2008.
According to Lukoil's calculations, the new complex will increase the production of motor fuel by more than 1 million tons per year, while the quality of oil products will meet European standards. “However, products of low processing are in great demand abroad,” Anastasia Andronova, an analyst at CenterInvest Securities, told F. “In the short term, it would be more profitable to build an enterprise for primary oil refining. In this case, Lukoil focuses on future, but in 3-4 years this technology will be cheaper. It is unlikely that hydrocracking will become very popular now, since there is a lack of processing capacity in Russia."
According to Lukoil, investments in the complex amounted to 10.8 billion rubles. "According to our calculations, additional income from the project will amount to more than 4 billion rubles a year," Dmitry Mangilev, an analyst at Prospekt Investment Company, told F. "Thus, we can talk about a fairly quick payback of the project for the company. On the other hand, the construction of a new refinery, designed to process 2 million tons of oil per year, could cost Lukoil about $ 300-350 million, which is about the same level as the new installation.Therefore, it is doubtful whether other domestic companies will invest in such projects or prefer the construction of new facilities, especially since large companies other than Lukoil are more focused on the export of crude oil.”
Thus, new oil refining technologies are being consolidated in Russia, but now it is difficult to say how widely the oil industry will use them. Large companies still prefer to export crude oil. Moreover, for some, the problem of a shortage of processing capacities is acute and, first of all, they will try to solve it by building refineries. And only then will they think about upgrading and improving product quality. l
Orsknefteorgsintez PJSC, or Orsk Oil Refinery, is part of the industrial and financial SAFMAR Group of Mikhail Gutseriev. The plant operates in the Orenburg region, supplies its region and adjacent areas with oil products - motor fuel, fuel oil and bitumen. For several years now, the enterprise has been undergoing a large-scale modernization, as a result of which the plant will remain among the leaders in the oil refining industry for many years to come.
Currently, the Orsk Oil Refinery has started a test launch of the most significant of the newly built facilities, the Hydrocracking Complex. By June, construction, installation and commissioning work "in idle" and debugging and adjustment of equipment "under load" were completed at this facility. The total volume of investments in the construction of this Complex will be more than 43 billion rubles, both own and borrowed funds are used to finance the project.
In the near future, raw materials will be accepted for installation and debugging of all processes for obtaining products will begin. The test mode is necessary for debugging the technological regime at all facilities of the Hydrocracking Complex, obtaining products of the appropriate quality, and also, among other things, to confirm the warranty indicators laid down by the licensor Shell Global Solutions International B.V. (Shell)
Adjustment of the regime is carried out by the ONOS subdivisions with the involvement of contractors for commissioning and in the presence of a representative of the Shell licensor. ForteInvest, the main shareholder of ONOS, plans to complete operation in a test mode and bring the facility into commercial operation as early as July this year. Thus, despite the difficult economic situation in the country, the Hydrocracking Complex is planned to be built in an extremely short time - the first work on the project began in mid-2015, and hydrocracking will reach its design capacity approximately 33 months after the start of the project.
The commissioning of modernization facilities will bring the Orsk Refinery to a new level of refining, allowing it to increase its depth to 87%. The selection of light oil products will increase to 74%. As a result of this stage of the Modernization Program, the product line of the enterprise will change: vacuum gas oil will cease to be a marketable product, as it will become a raw material for a hydrocracking unit; the output of aviation kerosene and Euro 5 class diesel fuel will increase significantly.
Shareholders of the Orsk Refinery pay great attention to the development of the enterprise for the long term. The global modernization of production, which has been underway since 2012, is of great importance not only for the enterprise, but also for the region, because the plant is one of the city-forming enterprises of Orsk. Currently, about 2.3 thousand people work at the refinery - residents of the city and nearby villages. The renewal of production is of great importance for the social sphere of the city - this is the creation of new jobs, an increase in the number of qualified personnel involved in production, and, consequently, increasing the overall standard of living of the workers of the plant and the city.
PJSC "Orsknefteorgsintez"‒ an oil refinery with a capacity of 6 million tons per year. The set of technological processes of the plant allows to produce about 30 types of different products. Among them are motor gasolines of class 4 and 5; jet fuel RT; diesel fuel of summer and winter types of class 4 and 5; road and construction bitumen; fuel oil. In 2017, the volume of oil refining amounted to 4 million 744 thousand tons.
The Hydrocracking Complex includes a hydrocracking unit itself, a sulfur production unit with a granulation and offloading unit, a chemical water treatment unit, a water recycling unit and nitrogen station No. 2. The construction of the Vacuum Gas Oil Hydrocracking Complex began in 2015, and its launch is scheduled for the summer of 2018.
Hydrocracking is a catalytic process for the processing of petroleum distillates and residues at moderate temperatures and elevated hydrogen pressures on polyfunctional catalysts with hydrogenating and acidic properties (and in selective hydrocracking processes and sieve effect).
Hydrocracking makes it possible to obtain a wide range of high-quality petroleum products (liquefied gases C 3 -C 4 , gasoline, jet and diesel fuels, oil components) with high yields from virtually any petroleum feedstock by selecting appropriate catalysts and technological conditions and is one of the most cost-effective, flexible and the most deepening oil refining processes.
Light Hydrocracking of Vacuum Gas Oil
Since 1980, due to the steady trend of faster growth in demand for diesel fuel than for motor gasoline, the industrial implementation of light hydrocracking units (LTC) of vacuum distillates has been launched abroad since 1980, which makes it possible to obtain significant amounts of diesel fuel simultaneously with low-sulphur feedstock for catalytic cracking. The introduction of JIGC processes was initially carried out by the reconstruction of previously operated units for the hydrodesulfurization of catalytic cracking feedstock, then by the construction of specially designed new units.
The domestic technology of the LGK process was developed at the All-Russian Research Institute of Petroleum Research in the early 1970s, but has not yet received industrial implementation.
Advantages of the LGD process over hydrodesulfurization:
High technological flexibility, which allows, depending on the demand for motor fuels, to easily change (adjust) the ratio of diesel fuel: gasoline in the mode of maximum conversion into diesel fuel or deep desulfurization to obtain the maximum amount of catalytic cracking feedstock;
Due to the production of diesel fuel at LGK, the capacity of the catalytic cracking unit is accordingly unloaded, which makes it possible to involve other sources of raw materials in processing.
The domestic one-stage process of vacuum gas oil LGD 350...500 °C is carried out on the ANMC catalyst at a pressure of 8 MPa, a temperature of 420...450 °C, a feed space velocity of 1.0...1.5 h -1 and a WSG circulation rate of about 1200 m 3 / m 3.
When processing raw materials with a high metal content, the LGD process is carried out in one or two stages in a multilayer reactor using three types of catalysts: wide-pore for hydrodemetallization (T-13), with high hydrodesulfurizing activity (GO-116) and zeolite-containing for hydrocracking (GK-35 ). In the process of vacuum gas oil LGD, up to 60% of summer diesel fuel with a sulfur content of 0.1% and a pour point of 15 ° C can be obtained (Table 8.20).
The disadvantage of the one-stage LGC process is a short cycle of operation (3...4 months). The next version of the process developed at VNII NP is a two-stage LGK with an interregeneration cycle of 11 months. - recommended for combination with catalytic cracking unit type G-43-107u.
Hydrocracking of vacuum distillate at 15 MPa
Hydrocracking is an efficient and exceptionally flexible catalytic process that makes it possible to comprehensively solve the problem of deep processing of vacuum distillates (HVDC) to obtain a wide range of motor fuels in accordance with modern requirements and needs for certain fuels.
One-Stage Vacuum Distillate Hydrocracking Process carried out in a multilayer (up to five layers) reactor with several types of catalysts. In order to ensure that the temperature gradient in each layer does not exceed 25 °C, a cooling HSG (quenching) is provided between the individual catalyst layers and contact distributing devices are installed to ensure heat and mass transfer between the gas and the reacting flow and uniform distribution of the gas-liquid flow over the catalyst bed. The upper part of the reactor is equipped with flow kinetic energy dampers, mesh boxes and filters to trap corrosion products.
On fig. 8.15 shows a schematic flow diagram of one of the two parallel operating sections of the unit for single-stage hydrocracking of vacuum distillate 68-2k (with a capacity of 1 million tons / year for the diesel version or 0.63 million tons / year for jet fuel production).
Feedstock (350...500 °C) and recycled hydrocracking residue are mixed with HSG, heated first in heat exchangers, then in a furnace P-1 to the reaction temperature and fed into the reactors R-1 (R-2 etc.). The reaction mixture is cooled in raw heat exchangers, then in air coolers and with a temperature of 45...55°C is sent to a high pressure separator C-1, where separation into WSG and unstable hydrogenate occurs. WASH after purification from H 2 S in the absorber K-4 the compressor is circulated.
Unstable hydrogenated product is sent through a pressure reducing valve to a low pressure separator C-2, where part of the hydrocarbon gases is separated, and the liquid stream is fed through heat exchangers to the stabilization column K-1 for distillation of hydrocarbon gases and light gasoline.
The stable hydrogenate is further separated in an atmospheric column K-2 for heavy gasoline, diesel fuel (through the stripping column K-3) and a fraction >360 °C, part of which can serve as recirculation, and the balance amount - as a raw material for pyrolysis, the basis of lubricating oils, etc.
In table. 8.21 shows the material balance of one- and two-stage HPHT with recirculation of the hydrocracking residue (process mode: pressure 15 MPa, temperature 405 ... ).
The disadvantages of hydrocracking processes are their high metal consumption, high capital and operating costs, the high cost of a hydrogen plant and hydrogen itself.
