Recycling (continued). Project for the manufacture and supply of hydrocracking reactors at the RN-Tuapse Oil Refinery (JSC NK Rosneft) Comparative indicators for product yield at domestic and foreign GKVD installations are given in Table 4

PJSC Orsknefteorgsintez, or Orsky 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 surrounding areas with petroleum products - motor fuel, fuel oil and bitumen. For several years now, the company has been undergoing large-scale modernization, as a result of which the plant will remain among the leaders in the oil refining industry for many years.

Currently, the Orsk Refinery has begun a test launch of the most significant of the newly built facilities, the Hydrocracking Complex. By June, construction, installation and commissioning work “idle” and debugging and adjustment of equipment “under load” were completed at this facility. The total investment in the construction of this Complex will amount to 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 the installation and debugging of all processes to obtain products will begin. The test mode is necessary to debug the technological regime at all facilities of the Hydrocracking complex, obtain products of appropriate quality, and also, among other things, to confirm the warranty indicators laid down by the licensor Shell Global Solutions International B.V. (Shell)

The adjustment of the regime is carried out by ONOS divisions with the involvement of commissioning contractors and in the presence of a representative of the licensor Shell. The main shareholder of ONOS, ForteInvest, plans to complete operation in test mode and bring the facility into commercial operation in July of this year. Thus, despite the difficult economic situation in the country, the Hydrocracking Complex is planned to be built in an extremely short time frame - 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 petroleum 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 commercial product, as it will become a raw material for a hydrocracking unit; The production of aviation kerosene and Euro 5 diesel fuel will significantly increase.

The shareholders of the Orsk Oil 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 - it 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 plant and city workers.

PJSC "Orsknefteorgsintez"‒ an oil refinery with a capacity of 6 million tons per year. The set of technological processes of the plant allows the production of about 30 types of different products. These include class 4 and 5 motor gasoline; RT jet fuel; diesel fuel of summer and winter types of classes 4 and 5; road and construction bitumen; fuel oils. In 2017, the volume of oil refining amounted to 4 million 744 thousand tons.

The Hydrocracking Complex includes a hydrocracking unit, a sulfur production unit with a granulation and loading unit, a chemical water treatment unit, a recycling water supply unit and nitrogen station No. 2. Construction of the vacuum gas oil hydrocracking complex began in 2015, its launch is scheduled for the summer of 2018.

4. Catalytic cracking
Catalytic cracking is the most important oil refining process, significantly affecting the efficiency of the refinery as a whole. The essence of the process is the decomposition of hydrocarbons included in 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 CC installation is a high-octane component of gasoline with an octane number of 90 points or more, its yield ranges from 50 to 65% depending on the raw materials used, the technology used and the mode. The high octane number is due to the fact that isomerization also occurs during cat cracking. During the process, gases are formed containing propylene and butylenes, 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 installations is from 1.5 to 2.5 million tons, but at the factories of the world's leading companies there are installations with a capacity of 4.0 million tons.
The key installation area is reactor-regenerator unit. The unit includes a raw material heating furnace, a reactor in which cracking reactions directly occur, and a catalyst regenerator. The purpose of the regenerator is to burn out the coke formed during cracking and deposited on the surface of the catalyst. The reactor, regenerator and raw material 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 installations 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 installation using ExxonMobil technology.
The catalytic cracking capacity at Russian refineries is currently clearly insufficient, and it is through the commissioning of new units that the problem with the predicted gasoline shortage is being solved. When implementing refinery reconstruction programs declared by oil companies, this issue is completely removed.
Over the past few years, similar, heavily worn-out and outdated installations introduced during the Soviet period have been reconstructed in Ryazan and Yaroslavl, and a new one has been built in Nizhnekamsk. In this case, technologies from Stone&Webster and Texaco companies were used.

Fig. 14. Diagram of the reactor-regenerator unit of a catalytic cracking unit

Raw materials with a temperature of 500-520°C, mixed with a dusty catalyst, move upward through the elevator reactor for 2-4 seconds and undergo cracking. Cracking products go to separator, located on top of the lift reactor, where chemical reactions are completed and the catalyst is separated, which is removed 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 this, the restored catalyst is returned to the raw material input unit. The pressure in the reactor-regenerator unit is close to atmospheric. The total height of the reactor-regenerator unit ranges 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 sent for rectification.
Cat cracking can be part of combined installations, including preliminary hydrotreating or light hydrocracking of raw materials, gas purification and fractionation.

Photos of catalytic cracking units

Fig. 16. Catalytic cracking reactor unit using ExxonMobil technology. On the right side is the reactor, to the left of it is the regenerator.

5. Hydrocracking
Hydrocracking is a process aimed at producing high-quality kerosene and diesel distillates, as well as vacuum gas oil, by cracking feedstock hydrocarbons in the presence of hydrogen. Simultaneously with cracking, the products are purified from sulfur, olefins and aromatic compounds are saturated, which determines the high performance and environmental characteristics of the resulting fuels. For example, the sulfur content in hydrocracking diesel distillate is millionths of a percent. The resulting gasoline fraction has a low octane number; its heavy part can serve as a reforming feedstock. Hydrocracking is also used in the oil industry to produce high-quality base oils with performance characteristics similar to synthetic ones.
The range of hydrocracking raw materials is quite wide - straight-run vacuum gas oil, catalytic cracking and coking gas oils, oil block by-products, fuel oil, tar.
Hydrocracking units, as a rule, are built with a large unit capacity - 3-4 million tons per year of raw materials.
Typically, the volumes of hydrogen produced at reforming units are not enough to ensure hydrocracking, so separate units are built at refineries to produce hydrogen by steam reforming of hydrocarbon gases.
The technological schemes are fundamentally similar to hydrotreating units - raw materials mixed with hydrogen-containing gas (HCG) are heated in a furnace, enter a reactor with a catalyst bed, and 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 VSG into the reaction zone, the flow of which regulates the temperature. Hydrocracking is one of the most dangerous oil refining processes; when the temperature regime gets out of control, a sharp increase in temperature occurs, leading to an explosion of the reactor unit.
The hardware design and technological mode of hydrocracking units vary depending on the tasks determined by the technological scheme of a particular refinery and the raw materials used.
For example, to produce low-sulfur vacuum gas oil and a relatively small amount of light oil (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 maximum light output (up to 90%, including up to 20% of the gasoline fraction for raw materials), the process is carried out in 2 reactors. In this case, 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 again subjected to hydrocracking. In this case, when hydrocracking vacuum gas oil, the pressure is about 180 atm, and when hydrocracking fuel oil and tar - more than 300. The process temperature, accordingly, varies from 380 to 450 ° C and higher.
In Russia, until recently, the hydrocracking process was not used, but in the 2000s, capacities were introduced at plants in Perm (Fig. 16), Yaroslavl and Ufa, and at a number of plants hydrotreating units were reconstructed for the light hydrocracking process. Installation of the installation 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 plants

Sergei Pronin

background information

Increasing demand for motor fuels with lower sulfur content and the release of fewer pollutants into the atmosphere during their production and combustion influenced the birth of such a process as the catalytic process of hydrocracking of raw materials under hydrogen pressure.

The main purpose of the hydrocracking process is the production of hydrotreated gasoline fractions, commercial kerosene and diesel fuels, as well as liquefied gases from heavier petroleum feedstocks than the resulting target products. In addition, if the unreacted residue is not returned to the hydrocracking feedstock, then it can be used as a high-quality feedstock or component of catalytic cracking, coking, and pyrolysis feedstocks.

The hydrocracking process has been successfully used to produce high-index base lubricating oils.

Hydrocracking combines catalytic cracking and hydrogenation. The sequential scheme of reactions that occur in typical heavy petroleum hydrocracking processes is shown in Figure 1.

Hydrogenolysis of non-hydrocarbon compounds occurs faster, which allows heteroatoms in the form of hydrogen sulfide, ammonia and water to be removed from the raw material. Hydrogenolysis of S-organic compounds occurs most easily. The most resistant to it are N-containing compounds.

The rate of hydrogenation desulfurization decreases as the molecular weight increases and the structure of the molecules of compounds containing sulfur becomes more complex.

Hydrogenolysis reactions of nitrogen-containing compounds are characterized by the stage of saturation of the ring with hydrogen. It then breaks down to form a compound, which is converted into hydrocarbon and ammonia by hydrogenolysis.

Hydrocracking of petroleum fractions- the process is exothermic. Since hydrocracking is a complex set of chemical reactions, the composition of which depends on the raw material being processed, the adopted conversion depth and other factors, the heat of reaction cannot be unambiguously determined. For paraffinic raw materials, the thermal effect of hydrocracking is usually 290-420 kJ/kg. For highly aromatic raw materials, the thermal effect can reach 840 kJ/kg. This suggests that the higher the hydrogen consumption for reactions, the more heat is released.

To regulate the process temperature along the height of the reactor, cold hydrogen-containing gas (HCG) is introduced into the zones between the catalyst layers. The height of each catalyst layer is taken such that the temperature in it does not increase by more than 25 °C (approximately).

Since the types of reactions, the levels of deposition of coke and metals on the catalyst and the activity of the catalyst change along the course of the raw material mixture (raw materials, VSG, hydrocracking products), the heat generation correspondingly decreases and the heights of the catalyst layers increase.

Catalystshydrocracking

Several types of catalysts are used in the hydrocracking process. These catalysts combine cracking and hydrogenation activities in varying proportions to achieve the targeted conversion of a specific feedstock into the desired product. Hydrogenation activity is achieved through the use of metal promoters deposited on a catalyst support. Promoters can be metals of groups VI and VIII.

Cracking activity is achieved by varying the acidity of the catalyst support. These options are mainly achieved by using a combination of amorphous and crystalline aluminum and silica or zeolite (molecular sieve) as the carrier material. Crystalline zeolites are used for catalyst supports.

When selecting the type of catalyst, its ability to restore activity during regeneration is of high importance. A catalyst operating period of more than 2 years between regenerations can be considered normal. The main purpose of regeneration is to burn out the coke deposited on the catalyst. Amorphous and zeolite-containing catalysts almost completely retain their activity after burning off the coke.

The choice of catalyst determines the production of the desired product:

The main features of amorphous and zeolite catalysts are given below:

Catalysts are produced mainly in the form of extrudates or sometimes in the form of microspheres with a particle size of 1-2 mm.

Before the plant starts operating on raw materials, the catalyst is subjected to sulfurization to activate its centers. Sulfurization of the catalyst is carried out at a temperature of 150-350 °C and a pressure of 20-50 MPa in a flow of circulating hydrogen-containing gas containing from 0.5 to 5.0 vol. % of sulfur compounds in terms of hydrogen sulfide. Mercaptans, disulfides, light S-containing petroleum products and others are used as sulfurizers added to the circulating hydrogen-containing gas.

For hydrocracking process any hydrocarbon feedstock is suitable, including gasoline fractions of primary and secondary processes, straight-run gas oils, vacuum gas oils, catalytic gas oils, coking gas oils, visbreaking gas oil, deasphalting oil.

Hydrocracking for different types of raw materials:

Straight-run raw materials are the easiest to process. Cracked raw materials are more difficult to process because: it contains more various impurities that settle and poison the catalyst; polycyclic aromatic compounds require a more severe regime, which leads to faster deactivation of the catalyst.

The consequences of using this raw material are expressed in an increase in hydrotreating and cracking temperatures, the degree of catalyst deactivation, and a decrease in catalyst selectivity; as well as the quality of hydrocracking products.

The question of the influence of various components of raw materials on the activity of catalysts is very important. The asphaltenes contained in the raw material have a strong deactivating effect on the catalyst, which sharply slow down the rate of hydrogenolysis of sulfur compounds, with virtually no effect on the formation of coke. The strongest poison for hydrocracking catalysts are nitrogen-containing compounds. It is believed that high-molecular nitrogen compounds are strongly adsorbed on acid sites, blocking them and thereby reducing the decomposition ability. With an increase in the partial pressure of hydrogen, which increases its concentration on the surface of the catalyst, the processes of hydrogenation of molecules of nitrogen compounds are accelerated.

When processing petroleum residues, the metals contained in the feedstock in the form of organometallic compounds pose a great danger to catalysts. Metal deposition on catalysts is almost inevitable. First of all, the sum of the metals nickel and vanadium (Ni + V) has a negative effect on the activity of the hydrocracking catalyst. The problem of slowing down the process of poisoning of hydrocracking catalysts is solved in different ways. When hydrocracking vacuum gas oil, strict requirements are imposed on the vacuum distillation of fuel oil (atmospheric distillation residue), which limits the metal content (Ni + V). When hydrocracking heavy oil residues, preliminary hydrodesulfurization and demetallization of raw materials on a special catalyst are provided. At the preliminary stage, “purification” reactions involving metals, sulfur, nitrogen, oxygen, olefins, aromatic compounds (including polycyclic ones), etc. occur. The “purification” and hydrocracking stages can occur in the same reactor. When hydrocracking heavy petroleum feedstocks in a three-phase fluidized bed, constant catalyst activity is maintained by periodically removing the equilibrium catalyst from the system and introducing fresh catalyst.

Technological parameters of the process

Depending on the processed raw materials and the required products, the hydrocracking process has different technological parameters. The influence of the main technological parameters is as follows:

In addition to the main technological parameters, the hydrocracking process is influenced by: partial pressure of hydrogen, concentration of hydrogen in hydrogen-containing gas (HCG), temperature, volumetric feed rate of raw materials, consumption (chemical and total) of 100% hydrogen, circulation ratio of HCG in relation to the processed raw materials.

Temperature. The characteristic temperature range for the hydrocracking process is 350-405 °C. The temperature rises from the lower boundary to the upper one gradually as the activity of the catalyst decreases. In addition, the higher the conversion of the process, the higher the temperature in the reactor (Fig. 2). When conducting the process on amorphous catalysts, higher temperatures are required (in the range of 390-400 °C) than on zeolite-containing catalysts (350-365 °C).

Pressure. The pressure of the hydrocracking process (more often called the pressure in the high-pressure separator, that is, at the inlet of the circulation compressor) varies widely - from 5.5 to 20.0 MPa. The choice of process pressure mainly depends on the quality of the raw material and the required product (Fig. 3).

The absolute pressure in the reactor depends on the partial pressure of hydrogen in the system, which plays a major role in the hydrocracking process, and depends on the concentration of hydrogen in the circulating hydrogen-containing gas.

In industrial hydrocracking plants, the minimum hydrogen content in hydrogen-containing gas is not lower than 80-85 vol. %. By increasing the hydrogen concentration in the circulating VSG, it is possible to reduce the overall process pressure of the process and, accordingly, the design pressure of the reactor unit equipment.

Conversion. The hydrocracking process improves product quality (Fig. 4) due to the combined effects of hydrogen partial pressure and conversion level in the presence of a catalyst. Very high quality distillate fuels, including Jet A-1 jet fuel, can be produced from heavy feedstocks in traditional hydrocrackers with high conversion or full conversion at process pressures from 14.0 to 17.5 MPa.

Volumetric feed rate of raw materials. The volumetric flow rate of raw materials is the ratio of the volume of liquid raw materials supplied within 1 hour to the volume of catalyst determined by the bulk mass. The volumetric velocity depends on the quality of the raw material, the catalyst used, the process pressure, the type of products obtained and the depth of conversion. Typical volumetric velocities during hydrocracking are in the range of 0.5-2.0 h -1 (for certain types of raw materials and higher). Reducing the duration of contact as a result of increasing the volumetric feed rate of raw materials reduces the depth of desulfurization.

Hydrogen consumption. The consumption of hydrogen, which is determined by the range of products obtained, is of decisive importance for the economic indicators of hydrocracking. The hydrogen consumption for reactions can be determined using a simplified material balance equation:

100 N s + X = N p (100 + X)

where: X is the consumption of hydrogen for the reaction in mass. % on raw materials; H c is the concentration of hydrogen in the raw material; H p is the average concentration of hydrogen in products.

The heavier the resulting products, the lower the hydrogen consumption. In practice, hydrogen consumption is determined experimentally.

The total consumption of hydrogen during the hydrocracking process consists of its consumption for the reaction, for dissolution in the hydrogenation product, for stripping and losses. The main amount of hydrogen is spent on the reaction. The consumption of hydrogen for dissolution in the hydrogenated product can be compensated for by extracting it from the hydrogenated product, using effective technological separation schemes using the characteristics of its solubility in various hydrocarbons at different temperatures and pressures. The consumption of hydrogen with blow-off, which is a circulating hydrogen-containing gas in composition, depends on the amount of this blow-off required by the technology to regulate the optimal partial pressure of hydrogen in the system. The total hydrogen consumption can vary from 1.5 to 4.0 wt. % on raw materials.

Almost all hydrocracking plants are supplied with hydrogen from hydrogen production plants using the steam reforming method of natural gas, plant hydrocarbon gas, gasoline fractions and other petroleum products. Recently, in order to reduce the use of expensive hydrogen from conversion plants, hydrogen-containing gases from reforming and hydrotreating are added to it after preliminary concentration. For example, using the short-cycle absorption process from UOP or Linde. The concentration of fresh hydrogen reaches 99.9 wt. %.

Circulation ratio of hydrogen-containing gas (HCG). The hydrocracking process is carried out with an excess amount of hydrogen, taking into account that with increasing partial pressure of hydrogen, the reaction rates increase. The circulation ratio represents the volume of VSG in relation to the volume of raw materials supplied to the reactor (Nm 3 /m 3 of raw materials). The VSG circulation rate is accepted, depending on the purpose of the process and the purity of the VSG, in the range of 800-2500 nm 3 /h.

The WASH circulation pattern in the reactor block is the main component of energy costs for the entire hydrocracking unit. Therefore, preference should be given to hydrocracking technology that requires the lowest circulation rate, and when designing, it is necessary to strive for minimal hydraulic resistance in the system from the outlet of the circulation compressor to its inlet.

Cleanliness of WASH. In most industrial hydrocracking plants, the concentration of circulating WASH is maintained at 80-85 vol. %, the rest is methane, ethane and other light components. In addition to hydrogen and hydrocarbons, the mixture leaving the reactor also contains hydrogen sulfide, ammonia and water vapor.

When cooling the reactor mixture, ammonia reacts with hydrogen sulfide, forming ammonium sulfide, which upon further cooling may precipitate in the air cooler. To avoid this undesirable process and remove the balance amount of ammonia from the system, ammonium sulfide is dissolved in the wash water supplied to the system before the air cooler. Then, in a low-pressure separator, this acidic solution is removed from the system for stripping, which can again produce hydrogen sulfide and ammonia. As the amount of hydrogen sulfide in VSG increases, the efficiency of the hydrocracking process decreases, so in modern installations it is continuously removed before the circulation compressor in the amine absorber. Aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA) of different concentrations are used as a regenerable hydrogen sulfide absorbent. A saturated amine solution, when regenerated in a stripper by stripping, releases absorbed hydrogen sulfide, which is utilized in plants for the production of sulfuric acid or for the production of elemental sulfur using the Claus method.

With the development of new, more selective hydrocracking catalysts, increasing attention is being paid to the purity of VHC and increasing its hydrogen content.

Industrial hydrocracking processes

Hydrocracking is characterized by a variety of types and technological schemes:

1. by process pressure - high-pressure hydrocracking and “soft” hydrocracking;
2. on the conduct of the process in the reactor - in a stationary catalyst bed (the vast majority of industrial installations) and in a three-phase fluidized bed with periodic replacement of catalyst portions;
3. according to technological schemes:

• single-stage single-pass (“per pass”);
• single-stage with residue recirculation;
• two-stage;
• with a parallel system.

The choice of technological scheme depends on many factors mentioned above. The most widely used in industry is the single-stage recirculation scheme (Fig. 5), which significantly exceeds other schemes in the number of implementations.

Hydrocracking units in a three-phase fluidized bed are designed for processing heavy oil residues (fuel oil, tar, etc.), but have been implemented on an industrial scale in small quantities. This was due to high capital investment, high consumption of expensive catalyst and the difficulty of maintaining its constant activity. Constant activity is maintained by periodically introducing fresh catalyst into the system and removing equilibrium catalyst from the system. The technological scheme of this process is similar to the schemes of hydrocracking in a stationary layer.

Exploiting synergies between hydrocrackers and other process units

The hydrocracking process is particularly well suited for the production of high quality, low sulfur middle distillate fuel components and can be combined to achieve synergies with other conversion processes, particularly fluid catalytic cracking (FCC) and coking. This circumstance has brought single-stage “on-pass” hydrocracking at different pressures to the leading position. The “per pass” technological scheme has a number of significant advantages:

• lowest cost;
• maximum productivity for raw materials (up to 3-3.5 million tons per year);
• the ability to process very heavy raw materials with a high boiling point;
• production of a high-quality bottoms product for further use in other installations.

Fractionation Features:

• stripping the side stream to remove hydrogen sulfide;
• atmospheric fractionation with fired heater;
• stripping of gasoline fractions at the request of the customer;
• heated vacuum fractionation for high-boiling end products (need assessed on a project-by-project basis).

Single stage high pressure hydrocracking for several options is given in the table below.

Mild hydrocracking

The construction of hydrocracking units with a high degree of conversion requires large capital expenditures. In this regard, some refineries increased the depth of oil refining at their enterprises by reconstructing existing vacuum gas oil hydrotreating units into mild hydrocracking units. These units are operated at process pressures from 5.5 to 8.5 MPa, which corresponds to the standard approach when choosing the design pressure of vacuum gas oil hydrotreating units. In these cases, the yield of diesel fuel and its quality are limited by the maximum permitted characteristics of existing equipment, and most often the main goal of such projects is to increase the depth of oil refining, rather than improve the quality of products.

Operation of a mild hydrocracking unit at relatively low pressure and conversion does not allow obtaining high-quality products. The cetane index of the resulting diesel fuel ranges from 39 to 42 points. Very often the smoke-free flame height of the resulting kerosene is only 10 mm, which is significantly lower than the 19 mm required by current jet fuel specifications.

The table below shows the operating parameters of a conventional mild hydrocracker and a single-stage, single-pass hydrocracker designed to produce diesel fuel at the same conversion of 40%.

Single-pass medium-pressure hydrocracking schemes with partial conversion of raw materials. Traditional high pressure hydrocrackers are very difficult to break even. Operating equipment with incomplete conversion of raw materials can make it possible to optimize the relationship between pressure, degree of conversion, catalyst service life, hydrogen consumption and the quality of the resulting product, which can significantly reduce the required capital costs and increase profits.

The process of medium pressure hydrocracking (MPHC) with the brand name "MAK". The MAK-MRNS process was developed by Mobil, Akzo Nobel and M.W. Kellogg." The main differences between the MAK-MRNS process (Table 3) and traditional hydrocracking are the use of a new effective design of internal reactor devices called “Spider-Vortex” and the inclusion of a high-temperature separator in the technological scheme of the reactor block.

Hydrocracking with partial conversion of raw materials. Hydrocracking units with partial conversion of raw materials from UOP, as well as the MAK-MRNS process, provide a higher yield of better quality products compared to mild hydrocracking units. Traditional 35-70% partial conversion hydrocracking flowsheets are similar to full conversion hydrocracking flowsheets, except that the operating pressure range is about 10.5 MPa instead of 14.0-17.5 MPa. Due to the lower process pressure, there is some deterioration in the quality of the distillate product. In addition, the quality of the distillate product is also limited by the degree of conversion. Even with higher feed conversion, the quality of the distillate product obtained in a traditional hydrocracker with partial conversion of feedstock remains insufficiently high to meet the requirements for diesel fuel with high cetane characteristics.

UOP has developed three new technological schemes for hydrocracking with partial conversion of raw materials at the same pressure. The quality of distillate fuels produced using these new schemes is much better - the sulfur content is less than 50 ppm, the cetane index is above 50 points.

Flow diagrams of the UOP company are presented in Fig. 5, 6, 7. In all three schemes there are two identical technological solutions. Firstly, all schemes provide two reactors. Second, in each flowsheet, hydrotreating and hydrocracking are separated into separate reaction zones, so not all feedstocks that undergo hydrotreating must undergo hydrocracking. This feature of the technological scheme is very important, and it is only possible if the installation has two reactors.

The first technological scheme is a modification of the two-stage hydrocracking scheme with complete conversion, general separation and fractionation of reaction products (Fig. 6). The second scheme provides for the use of two parallel single-pass reactors, also with common separation and fractionation of reaction products (Fig. 7). The third technological scheme uses two-stage hydrocracking developed by UOP with modified flow patterns (Fig. 8). Each of these schemes has certain advantages compared to the traditional scheme of a hydrocracking unit with partial conversion of raw materials.

The key to ensuring high quality products with low overall process conversion is the separation of hydrotreating and hydrocracking functions into separate reactors. Using conversion to achieve product quality is a more efficient process solution compared to using higher process pressures.

Synergy of a combined catalytic cracking unit (FCC) with pre-treatment of raw materials

When replacing the FCC raw material preparation section by hydrotreating with hydrocracking with partial conversion of raw materials, the density of the FCC raw material decreases. Thus, the combined effect of higher pressure and higher conversion during the hydrocracking process with partial conversion of feedstock allows us to obtain higher quality FCC feedstock with almost the same level of feedstock desulfurization as in the traditional hydrotreating process. The synergy from the hydrotreatment of catalytic cracking feedstock is confirmed by the improvement of the technical and economic indicators of the refinery and the increase in the production of high-quality motor fuels.

The presented technological schemes for hydrocracking with partial conversion of raw materials make it possible to increase the flexibility of refineries in terms of the production of high-quality commercial diesel fuel from low-quality gas oils (without using variants of the hydrocracking scheme at high pressure with full conversion). By separating the hydrotreating and hydrocracking reactions into different reactors, these new technological schemes make it possible to increase the flexibility of the process, which has certain limitations when carried out in the modes of mild hydrocracking and traditional hydrocracking with partial conversion of raw materials.

HyCLE-Unicracking process from UOP

The HyCYCLE-Unicracking process is a step forward in technology for producing maximum quantities of distillates through the hydrocracking process. The process is an optimized flowsheet designed to maximize yield of high-quality diesel fuel. The process utilizes a combination of several unique technologies, including an improved hot separator, a back-flow reactor system, and a newly designed fractionator with a vertical baffle. A feature of the reactor block design is that the recycle is first sent to the hydrocracking catalyst zone, and then to the hydrotreating catalyst zone. The advantages are that the purer feedstock enters the cracking catalyst at a higher partial pressure of hydrogen. The end result is increased catalyst activity per unit volume and therefore less catalyst required.

The process is characterized by lower pressure and higher volumetric velocity compared to traditional installations. By minimizing secondary cracking reactions, less hydrogen is consumed. Another synergistic benefit can be realized where upgrading of low quality secondary distillates is required. In this case, for example, light catalytic gas oil is loaded directly into the advanced HighCYCLE separator. As a result, the plant will not need to build a separate unit for upgrading light catalytic cracking gas oil.

Place of hydrocracking in a refinery

At most foreign oil refineries with deep oil refining, the presence of a hydrocracking process is important. In addition to increasing the depth of oil refining, hydrocracking is the main process that affects the flexibility of the enterprise’s technological scheme and the quality of its commercial products. In the absence of other processes for processing residues from oil distillation at the refinery, hydrocracking with complete conversion is mainly used for the intended purpose of a specific product.

In cases where refineries already have residue conversion processes in place, the most attractive option is to use hydrocracking with partial conversion and combine it with other conversion processes. In this case, hydrocracking uses low-quality gas oils from other processes as raw materials and produces a high-quality residue, which serves as an upgraded raw material or a component of the raw materials of the same installations. Vacuum gas oil hydrocracking residue is an excellent feedstock for ethylene plants, outperforming other feedstocks.

Thus, the presence of hydrocracking in the technological scheme of a refinery significantly increases the flexibility and, accordingly, the efficiency of its operation.

The information in this section is provided for reference purposes only. You will find information about the products and services of NPP Neftekhim LLC in the sections “

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 deep oil refining complex was put into operation at the Lukoil oil refinery. As stated in the company's statement, the increase in the production of light petroleum products due to it is comparable to the additional refining of 2.3 million tons of oil per year. But it’s difficult to say how big a role the complex will play. “It’s good for Russia that Lukoil is increasing the level of refining at one of its key facilities,” says Marina Lukashova, an analyst at FC Uralsib. “But it has not gained any special advantages over other oil companies and there are too many factories left that need upgrade".

The new complex includes a hydrocracking unit, which is a fairly modern, but expensive technology. "F" told us more about it. Alexander Yakovlev, director of the EPN-Consulting company: “Previously, in Russia, a hydrocracking unit operated only in Ufa at Ufaneftekhim. But it worked poorly - it was constantly reconstructed. Now a second unit has begun operating in Perm using a new, more modern technology, which allows you to increase the production of light petroleum products. However, this process is very expensive, so now catalytic cracking is mainly used. The construction of a plant for processing 2 million tons of oil per year costs about $1.5-2 billion, the same as the cost of an oil refinery for 5-6 million tons. “The decision about what to build depends on the company’s starting capabilities. If it has little refining capacity, then it builds a new refinery, but if it has enough, it can afford modernization.”

Dmitry Lukashov, an analyst at Aton Investment Group, told F. that hydrocracking is not considered a super technology abroad, but for Russia it is quite progressive. When using it, the yield of light petroleum products increases, but on the scale of Lukoil the changes will not be serious. And 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 since 2005, and 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 petroleum products will meet European standards. “However, low-processed products 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 is focusing on the 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 revenues from the project will amount to more than 4 billion rubles per year,” Dmitry Mangilev, an analyst at Prospekt Investment Company, told F. “Thus, we can talk about a fairly quick payback for 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 approximately the same level as a new installation. Therefore, it is doubtful whether other domestic companies will invest in it. similar projects or will prefer the construction of new capacities, especially since large companies besides Lukoil are more focused on the export of crude oil.”

Thus, new oil refining technologies are taking hold in Russia, but now it is difficult to say how widely oil companies will use them. Large companies still prefer to export primary oil. Moreover, for some, the problem of lack of refining capacity is acute and, first of all, they will try to solve it by building refineries. And only then will they think about modernizing and improving product quality. l

Rather, the connection of things will be broken In Shakespeare's Macbeth

Hydrocracking is a later generation process than catalytic cracking and catalytic reforming, so it more efficiently accomplishes the same tasks as these two processes. Hydrocracking can increase the yield of gasoline components, usually by converting feedstocks such as gas oil. The quality of gasoline components that is achieved in this way is unattainable by re-passing gas oil through the cracking process in which it was obtained. Hydrocracking also allows the conversion of heavy gas oil into light distillates (jet and diesel fuel). And, perhaps most importantly, hydrocracking does not produce any heavy non-distillable residue (coke, pitch or bottoms), but only light boiling fractions.

Process

The word hydrocracking is explained very simply. This is catalytic cracking in the presence of hydrogen. The combination of hydrogen, catalyst and appropriate process conditions allows cracking of low-quality light gas oil, which is formed in other cracking plants and is sometimes used as a component of diesel fuel. The hydrocracking unit produces high-quality gasoline.

Consider for a moment how beneficial the hydrocracking process can be. Its most important advantage is its ability to switch refinery capacity from producing large quantities of gasoline (when the hydrocracker is running) to producing large quantities of diesel fuel (when it is off).

The well-known joke of a sports coach who disparagingly declares about the transfer of his player to the opposing team: “I think this will strengthen both teams”, is largely applicable to hydrocracking. Hydrocracking improves the quality of both gasoline components and distillate. It consumes the worst of the distillate components and produces an above average quality gasoline component.

Another point to note is that the hydrocracking process produces significant amounts of isobutane, which is useful for controlling the amount of feedstock in the alkylation process.

There are about ten different types of hydrocrackers in common use today, but they are all very similar to the typical design described in the next section.

Hydrocracking catalysts are fortunately less valuable and expensive than catalysts. Typically these are sulfur compounds with cobalt, molybdenum or nickel (CoS, MoS2, NiS) and aluminum oxide. (You've probably been wondering for a long time why these metals are needed in general.) Unlike catalytic cracking, but just like catalytic reforming, the catalyst is located in the form of a fixed bed. Like catalytic reforming, hydrocracking is most often carried out in two reactors, as shown in the figure.

The feedstock is mixed with hydrogen heated to 290-400°C (550-750°F) and pressurized at 1200-2000 psi (84-140 atm) and sent to the first reactor. During passage through the catalyst bed, approximately 40-50% of the feedstock is cracked to form

Products with boiling points similar to gasoline (boiling point up to 200°C (400°F)).

The catalyst and hydrogen complement each other in several ways. Firstly, cracking occurs on the catalyst. In order for cracking to continue, heat is required, that is, it is an endothermic process. At the same time, hydrogen reacts with the molecules that are formed during cracking, saturating them and generating heat. In other words, this reaction, called hydrogenation, is exothermic. Thus, hydrogen provides the heat necessary for cracking to occur.

Another aspect in which they complement each other is the formation of isoparaffins. Cracking produces olefins that can combine with each other to form normal paraffins. Due to hydrogenation, the double bonds are quickly saturated, often producing isoparaffins, and thus preventing the re-production of unwanted molecules (the octane numbers of isoparaffins are higher than in the case of normal paraffins).

When the hydrocarbon mixture leaves the first reactor, it is cooled, liquefied and passed through a separator to separate the hydrogen. Hydrogen is again mixed with the raw material and sent to the process, and the liquid is sent for distillation. The products obtained in the first reactor are separated in a distillation column, and depending on what is required as a result (gasoline components, jet fuel or gas oil), a portion of them is separated. The kerosene fraction can be separated as a side stream or left together with gas oil as a distillation residue.

The distillation residue is again mixed with a stream of hydrogen and put into the second reactor. Since this substance has already undergone hydrogenation, cracking and reforming in the first reactor, the process in the second reactor proceeds in a more severe mode (higher temperatures and pressures). Like the products of the first stage, the mixture leaving the second reactor is separated from hydrogen and sent for fractionation.

Imagine the equipment required for a process running at 2000 psi (140 atm) and 400°C. The wall thickness of a steel reactor sometimes reaches cm. The main problem is to prevent cracking from getting out of control. Since the overall process is endothermic, a rapid rise in temperature and a dangerous increase in the cracking rate are possible. To avoid this, most hydrocrackers have built-in provisions to quickly stop the reaction.

Products and outputs. Another remarkable property of the hydrocracking process is the increase in product volume by 25%. The combination of cracking and hydrogenation produces products whose relative density is significantly lower than the density of the raw material. Below is a typical distribution of yields of hydrocracking products when gas oil from a coking unit and light fractions from a catalytic cracking unit are used as feedstock. Hydrocracking products are two main fractions that are used as gasoline components.

Volume fractions

Coking gas oil 0.60 Light fractions from the plant cat. cracking 0.40

Products:

Isobutane 0.02

N-Butane 0.08

Light hydrocracking product 0.21

Heavy hydrocracking product 0.73

Kerosene fractions 0.17

The table does not indicate the required amount of hydrogen, which is measured in standard cubic feet per barrel of feed. The usual consumption is 2500 st. Heavy hydrocracking product -

It is naphtha that contains many aromatic precursors (that is, compounds that are easily converted into aromatics). This product is often sent to a reformer for upgrading. Kerosene fractions are a good jet fuel or feedstock for distillate (diesel) fuel because they contain little aromatics (as a result of saturation of double bonds with hydrogen). More detailed information on this topic is contained in Chapter XIII “Distillate Fuels” and Chapter XIV “Petroleum Bitumen and Residual

Hydrocracking of the residue. There are several models of hydrocrackers that have been designed specifically to process residue or vacuum distillation residue. Most of them operate as hydrotreaters, as described in Chapter XV. The output is more than 90% residual (boiler) fuel. The objective of this process is to remove sulfur as a result of the catalytic reaction of sulfur-containing compounds with hydrogen to form hydrogen sulfide. Thus, the residue with a sulfur content of no more than 4% can be converted into heavy liquid fuel containing less than 0.3% sulfur.

Resume. Now that we can integrate hydrocrackers into the overall oil refining scheme, the need for coordinated operations becomes clear. On the one hand, the hydrocracker is the central point as it helps to establish a balance between the amount of gasoline, diesel fuel and jet fuel. On the other hand, feed rates and operating modes of catalytic cracking and coking units are no less important. In addition, alkylation and reforming should also be considered when planning the distribution of hydrocracking products.

EXERCISES

Analyze the differences between hydrocracking, catalytic cracking, and thermal cracking in terms of raw materials, process driving forces, and product composition.

How do hydrocracking and catalytic cracking complement each other? Reforming and hydrocracking?

Draw a flow diagram of an oil refinery, including a hydrocracking unit.