RU2816315C2 - Combined pyrolysis and hydrocracking units for conversion of crude oil into chemical products - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing olefins and/or dienes, involving partial evaporation of non-gasoline crude oil to form a liquid fraction and a vapor fraction; overheating said steam fraction to form a superheated steam fraction; hydrotreating said liquid fraction to obtain a hydrotreated liquid; partial evaporation of said hydrotreated liquid to form a second vapor fraction and a second liquid fraction; partial evaporation of said second liquid fraction to form a third vapor fraction and a third liquid fraction; hydrocracking a third liquid fraction to obtain a hydrocracked effluent stream; separation of said hydrocracked effluent to obtain a light hydrocracked fraction and a heavy hydrocracked fraction; hydrocracking said heavy hydrocracked fraction with conversion of hydrocarbon components contained therein into hydrocarbons of the naphtha fraction and obtaining a second hydrocracked effluent stream; separation of said second hydrocracked effluent to obtain a second light hydrocracked fraction containing hydrocarbons of the naphtha fraction, and a second heavy hydrocracked fraction; partial evaporation of said second heavy hydrocracked fraction to obtain a fourth vapor fraction and a fourth liquid fraction; thermal cracking of (i) said superheated steam fraction, (ii) said third steam fraction, (iii) said second steam fraction, (iv) said fourth steam fraction, (v) said second light hydrocracked fraction and (vi) said fourth liquid fraction to obtain output streams of thermally cracked hydrocarbons, each containing a mixture of olefins and paraffins. Invention also relates to an embodiment of the method of producing olefins and/or dienes.

EFFECT: increased output of olefins, longer duration of working cycle and possibility to process raw material containing heavy hydrocarbons.

11 cl, 2 ex, 2 tbl, 7 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001] The embodiments described herein generally relate to the combined pyrolysis and hydrocracking of hydrocarbon mixtures, such as unstripped crude oils or other hydrocarbon mixtures, to produce olefins and other chemical products.

BACKGROUND OF THE ART

[0002] Hydrocarbon mixtures having a final boiling point above 550°C are generally not processed directly in the pyrolysis reactor to produce olefins, since the reactor cokes quite quickly. Although limiting reaction conditions may reduce the propensity for fouling, less stringent conditions result in significant loss of yield.

[0003] It is generally accepted in the art that hydrocarbon mixtures having a wide boiling range and/or hydrocarbons having a high final boiling point require initial separation of the hydrocarbons into multiple fractions such as gas/light hydrocarbons, naphtha hydrocarbons, gas oil etc., and further cracking of each fraction under conditions specific to these fractions, for example, in separate cracking furnaces. Although fractionation, such as a distillation column, and separate processing can be capital and energy intensive, it is generally accepted that fractionation and individual fractionation are the most cost-effective in terms of process control and yield.

[0004] Today, most crude oil is partially converted into chemical products in large refining-petrochemical complexes. The primary focus of oil refineries is the production of transportation fuels such as gasoline and diesel. Low-value refinery streams such as LPG and light naphtha are sent to petrochemical complexes that may or may not be located near the refinery. The petrochemical complex then produces chemical products such as benzene, paraxylene, ethylene, propylene and butadiene. A typical complex of this type is shown in Fig. 1.

[0005] In the traditional method, crude oil is desalted and preheated, and sent to a crude oil distillation column. Various fractions are formed there, containing naphtha, kerosene, diesel fuel, gas oil, vacuum gas oil and residue. Some fractions, such as naphtha and gas oils, are used as feedstock for the production of olefins. VGO and the residue are hydrocracked to produce fuels. The products obtained from the crude oil column (atmospheric distillation) and from the vacuum column are used as fuel (gasoline, jet fuel, diesel fuel, etc.). They usually do not meet fuel specifications. Therefore, before using these products as fuel, they are subjected to isomerization, reforming and/or hydroprocessing (hydrodesulfurization, hydrodenitrogenation and hydrocracking). Olefins plants may receive pre-refining and/or post-refining feedstock depending on the refinery.

SUMMARY OF THE INVENTION

[0006] Combined pyrolysis and hydrocracking processes have now been developed for the flexible processing of unstripped crude oils and other hydrocarbon mixtures containing high boiling point coke precursors. The embodiments described herein can advantageously reduce coking and fouling during the pyrolysis process, even under very harsh conditions, by efficiently and economically integrating hydrocracking of heavier portions of unstripped crude oils, achieving olefin yields comparable to naphtha crackers, while significantly reducing capital and energy costs associated with pre-fractionation and separate processing, typically associated with the processing of unstripped crude oil.

[0007] In one aspect, the embodiments described herein relate to a combined pyrolysis and hydrocracking process for converting a hydrocarbon mixture to olefins. The method may include mixing untrimmed crude oil and gas oil to form a hydrocarbon mixture. The hydrocarbon mixture may then be heated in a heater to vaporize a portion of the hydrocarbons in the hydrocarbon mixture and form a heated hydrocarbon mixture. The heated hydrocarbon mixture may be further separated in the first separator into a first vapor fraction and a first liquid fraction. The first vapor fraction is optionally mixed with water vapor, and the resulting mixture can be superheated in the convection zone and fed into the first radiant coil in the radiant zone of the pyrolysis reactor. The first liquid fraction, or a portion thereof, may be supplied along with hydrogen to a hydrocracking reactor system to contact the first liquid fraction with a hydrocracking catalyst to crack a portion of the hydrocarbons in the first liquid fraction. The effluent stream obtained from the hydrocracking reactor system may be divided to recover unreacted hydrogen from the hydrocarbons in the effluent stream, and the hydrocarbons in the effluent stream may be fractionated to form two or more hydrocarbon fractions, including a gas oil fraction.

[0008] In another aspect, embodiments described herein relate to a combined pyrolysis and hydrocracking process for converting a hydrocarbon mixture to olefins. The method may include mixing untrimmed crude oil and gas oil to form a hydrocarbon mixture. The hydrocarbon mixture may be heated in a heater to vaporize a portion of the hydrocarbons in the hydrocarbon mixture and form a heated hydrocarbon mixture. The heated hydrocarbon mixture may be separated in the first separator into a first vapor fraction and a first liquid fraction. The first liquid fraction may then be heated in a convection zone of the pyrolysis reactor to vaporize a portion of the hydrocarbons in the first liquid fraction and form a second heated hydrocarbon mixture. The second heated hydrocarbon mixture may be further separated in a second separator into a second vapor fraction and a second liquid fraction. Water vapor may be mixed with the first vapor fraction, the method including superheating the resulting mixture in a convection zone and feeding the superheated mixture into a first radiant coil in the radiant zone of the pyrolysis reactor. Water vapor may also be mixed with the second vapor fraction, the method including superheating the resulting mixture in a convection zone and feeding the superheated mixture into a second radiant coil in the radiant zone of the pyrolysis reactor. The second liquid fraction, or a portion thereof, may be supplied along with hydrogen to the hydrocracking reactor system to contact the second liquid fraction with a hydrocracking catalyst to crack a portion of the hydrocarbons in the second liquid fraction, and to obtain an effluent stream from the hydrocracking reactor system. Unreacted hydrogen may be recovered from the hydrocarbons in the effluent stream, which may be fractionated to form two or more hydrocarbon fractions, including a gas oil fraction and a residue fraction.

[0009] In another aspect, the embodiments described herein relate to a system including an apparatus for performing the above processes.

[0010] For example, in some embodiments, a system for producing olefins and/or dienes in accordance with the embodiments described herein may include a pyrolysis heater having a convection heating zone and a radiant heating zone. A heating coil in the convection heating zone may be provided to partially evaporate the unstripped crude oil to form a liquid fraction and a vapor fraction. A second heating coil in the convection heating zone may be provided to superheat the vapor fraction. In addition, a radiant heating coil may be located in the radiant heating zone to thermally crack the superheated vapor fraction to form a cracked hydrocarbon effluent stream containing a mixture of olefins and paraffins. The hydrocracking reaction zone can be used to hydrocrack at least a portion of the liquid fraction to form a hydrocracked hydrocarbon effluent stream containing additional olefins and/or dienes. Piping, valves, regulators, pumps and other equipment may be included in the system to provide the required connections and flows specified above.

[0011] Systems described herein may include a separator for separating the hydrocracked hydrocarbon effluent stream to produce two or more hydrocarbon fractions, including a gas oil fraction. The systems described herein may also include a means for mixing the gas oil fraction with the untrimmed crude oil before the heating coil. Means may also be provided for mixing the water vapor with the steam fraction before the second heating coil. The mixing means may include, for example, pipeline tees or connections, pumps, static mixers, and the like, among other mixing means known in the art.

[0012] Systems described herein may also include, for example, a third heating coil in a convection heating zone to partially evaporate a liquid fraction to form a second liquid fraction and a second vapor fraction, and/or a fourth heating coil in a convection heating zone to superheat a second vapor fraction. A second radiant heating coil in the radiant heating zone may be used to thermally crack the superheated vapor fraction to form a second cracked hydrocarbon effluent stream containing a mixture of olefins and paraffins. A pipeline may be provided for supplying the second liquid fraction to the hydrocracking step as at least part of the liquid fraction.

[0013] The systems described herein may also include means for mixing water vapor with various hydrocarbon-containing streams. For example, the systems described herein may include means for mixing water vapor with the partially vaporized raw crude oil and separating the mixture to form a liquid fraction and a vapor fraction, and/or means for mixing water vapor with the partially vaporized liquid fraction and separating the mixture to form a second liquid fraction and a second vapor fraction.

[0014] In embodiments of the present invention, the raw crude oil may be sent to a pyrolysis unit after desalting. In the convection section, light material can evaporate in the presence of water vapor and react in the radiant section. Heavy fractions are sent to a hydrocracking unit. Products from a hydrocracker can be sold as fuel and/or processed in a pyrolysis unit to produce additional chemical products. Heavy products from the pyrolysis unit (olefins unit), such as pyrolysis gas oil and heavy fuel oil, can be sent to the hydrocracker for upgrading, along with fresh crude oil feedstock. As necessary, raw materials and products are exchanged between the combined pyrolysis and cracking units to obtain the maximum amount of chemical products and/or fuels. Only a small part is rejected as tar.

[0015] The embodiments described herein do not require a crude oil separation unit. Accordingly, this reduces the costs and energy consumption associated with this installation. One or more hydrocrackers operating under different conditions can be used to optimize the production of chemicals/fuels. Hydrocracker sludge/tar is a very heavy, high-boiling material and can be sold as a product to maximize catalyst life. Since the hydrocracker is designed to process residues, the pyrolysis gas oil and heavy fuel oil produced in the cracker and/or pyrolysis unit can be used as feedstock in the hydrocracker. This maximizes valuable chemical products throughout the system. Light materials such as LPG and naphtha produced in a hydrocracker can be used as feedstock in an olefins unit. Unconverted oil can also be used as feedstock in a thermal cracker.

[0016] The combined pyrolysis and hydrocracking process described herein provides high yields of target olefins, dienes, diolefins and aromatics. At the same time, valuable jet and kerosene fuel can also be produced if necessary. There is no need to install a separate crude oil separation plant. Each fraction can be optimally cracked in accordance with the embodiments described herein. The heavy fuel oil produced from the pyrolysis unit can also be hydrocrackered to produce more feedstock for the olefins unit. Light hydrocracker feedstocks can also be thermally cracked to produce more olefins.

[0017] The flow diagrams shown in the accompanying schematic drawings may be slightly modified for specific crude oils and product compositions. Other aspects and advantages will be apparent from the following description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 shows a simplified flow diagram of a typical oil refining - petrochemical complex.

[0019] FIG. 2 is a simplified flow diagram of an integrated pyrolysis-hydrocracking system for processing hydrocarbon mixtures in accordance with the embodiments described herein.

[0020] FIG. 3 is a simplified flow diagram of an integrated pyrolysis-hydrocracking system for processing hydrocarbon mixtures in accordance with the embodiments described herein.

[0021] FIG. 4 is a simplified flow diagram of an integrated pyrolysis-hydrocracking system for processing hydrocarbon mixtures in accordance with the embodiments described herein.

[0022] FIG. 5 is a simplified flow diagram of an integrated pyrolysis-hydrocracking system for processing hydrocarbon mixtures in accordance with the embodiments described herein.

[0023] FIG. 6 is a simplified flow diagram of a HOPS tower used in coupled pyrolysis-hydrocracking systems for processing hydrocarbon mixtures in accordance with the embodiments described herein.

[0024] FIG. 7 is a simplified flow diagram of an integrated pyrolysis-hydrocracking system for processing hydrocarbon mixtures in accordance with the embodiments described herein.

DETAILED DESCRIPTION

[0025] The embodiments described herein relate generally to the pyrolysis and hydrocracking of hydrocarbon mixtures, such as unstripped crude oils or other hydrocarbon mixtures, to produce olefins. In particular, embodiments described herein relate to the efficient separation of hydrocarbon mixtures using heat obtained from the convection cracking section of a heater.

[0026] Hydrocarbon mixtures used in the embodiments described herein may include various hydrocarbon mixtures having a range of boiling points in which the final boiling point of the mixture may be above 450°C or above 500°C, such as above 525° C, 550°C or 575°C. The amount of high-boiling hydrocarbons, such as hydrocarbons boiling above 550°C, may be at least 0.1 wt.%, 1 wt.%. or 2% wt., but can reach up to 10% wt., 25% wt., 50% wt. or more. The description is given in relation to crude oil, but any hydrocarbon mixture with a high final boiling point, such as crude oils and condensates, can be used. The following examples are described in relation to Nigerian light crude oils for illustrative purposes, but the scope of this application is not limited to these crude oils. The methods described here can be used for crude oils, condensates and hydrocarbons with a broad boiling curve and end temperatures above 500°C. Such hydrocarbon mixtures may include, but are not limited to, untrimmed crude oils, unrefined crude oils, hydrotreated crude oils, gas oils, vacuum gas oils, heating oils, jet fuels, diesel fuels, kerosenes, gasolines, synthetic naphtha, raffinate, reformates, Fischer-Tropsch fluids , Fischer–Tropsch gases, gas condensate gasolines, distillates, straight-run naphtha, natural gas condensates, bottom products of atmospheric tubes, vacuum tube streams, including bottoms product, fractions from wide range naphthas to condensate gas oils, heavy hydrocarbon streams from refineries, vacuum gas oils, heavy gas oils, atmospheric distillation residue, hydrocracker wax and Fischer-Tropsch wax. In some embodiments, the hydrocarbon mixture may include hydrocarbons boiling in the boiling range of naphtha or lighter ends to the boiling range of vacuum gas oil or heavier ends. If necessary, these feedstocks can be preprocessed to remove some of the sulfur, nitrogen, metals and Conradson carbon before implementing the methods described herein.

[0027] The thermal cracking reaction occurs through a free radical mechanism. Accordingly, high ethylene yield can be achieved when cracking occurs at high temperatures. Lighter feedstocks such as butanes and pentanes require higher reactor temperatures to produce high olefin yields. Heavy feedstocks such as gas oil and vacuum gas oil (VGO) require lower temperatures. Crude oil has a distribution of compounds ranging from butanes to VGO and residue (material having a normal boiling point, for example, above 520°C). Exposing unstripped crude oil to high temperatures without separation results in high coke yields (a byproduct of hydrocarbon cracking under high severity conditions) and reactor plugging. The pyrolysis reactor must be periodically shut down and the coke cleaned by decoking using steam/air. The period of time between two purification periods when olefins are formed is called cycle time. When crude oil is cracked without separation, coke may be deposited in the convection section coils (which evaporate the fluid), in the radiant section (where olefin formation reactions occur), and/or in the quencher (where reactions are quickly stopped by cooling to maintain olefin yield).

[0028] The embodiments described herein utilize a convection section of the pyrolysis reactor (or heater) to preheat and separate the hydrocarbon feed mixture into different fractions. Water vapor may be injected at appropriate locations to increase vaporization of the hydrocarbon mixture and to control heating and degree of separation. Evaporation of hydrocarbons occurs at relatively low temperatures and/or adiabatically, due to which coke formation in the convection section will be suppressed.

[0029] Thus, the convection section can be used to heat the entire hydrocarbon mixture to form a vapor-liquid mixture. The vaporous hydrocarbons will then be separated from the liquid hydrocarbons, and only the separated vapors will be fed to the radiant coils in one or more radiant cells of a single heater. The geometry of the radiant coil can be any. The optimal residence time for the coil can be selected to maximize the amount of olefins and cycle time for the required hydrocarbon vapor feed mixture and reaction severity.

[0030] If necessary, multiple heating and separation stages may be used to separate the hydrocarbon mixture into two or more hydrocarbon fractions. This will ensure optimal cracking of each fraction so that throughput, steam to oil ratios, heater inlet and outlet temperatures and other variables can be adjusted at the desired level to achieve the desired reaction results to ensure the desired product composition while limiting coking in the radiant coils and associated downstream equipment.

[0031] Since different fractions, depending on the boiling point of hydrocarbons in the mixture, are separated and subjected to cracking, coke formation in radiant coils and quenching and evaporation apparatuses can be regulated. As a result, heater cycle times can be extended to many weeks instead of hours, with higher olefin production.

[0032] The remaining liquid may be subjected to hydroprocessing (eg, hydrotreating and/or hydrocracking). If the cutoff limit is low, for example around 200°C, then the feed to the hydrocracker is high. If the boiling point is high, the feed to the hydrocracker is low for any crude oil. Regardless of the selected separation boundary, all remaining liquid can be sent to the hydrocracker. Alternatively, the liquid may be sent to a distillation column associated with the separation of hydroprocessing products. Here in this column the jet fuel/kerosene fractions (middle distillates) will be separated and only the VGO+ material will be hydrocracked in the hydrocracker.

[0033] The VGO+ material can be further divided into VGO and residue. Any material boiling above 520°C can be considered a residue. The specified separation limit, 520°C, is given as an example, but can vary, for example, from 480°C to 560°C. In VGO/residue separation, various hydrocrackers can be used to process VGO and residue separately. Hydrocracking of the residue is more difficult than for VGO. Depending on the quality of the crude oil and the amount of residue, separating the heavy liquid into VGO and residue can be cost-effective. If there is no economic benefit, all liquids can be hydrocracked in the same hydrocracker unit.

[0034] The hydrocracker effluent may be separated in a distillation column as noted above. Even with hydrocracking, residue recycling must be carefully considered. Some residue cleaning is necessary to prevent excessive coking in the reactor. This drain represents the tar or resin fraction. When the 200°C+ liquid material or the 350°C+ material obtained from the evaporation system is sent to the hydrocracker directly without entering the hydrocracker effluent distillation column, the severity of the hydrocracker can be adjusted accordingly, e.g. soft conditions or high rigidity conditions. Under mild conditions, only high molecular weight compounds are hydrocracked, retaining most of the light materials in the crude oil (middle distillates) and sending the effluent to a product separation column. This provides the maximum amount of middle distillate fuel. At high hardness, the amount of light components such as LPG and naphtha fractions will be high. For all cases listed here, an optional hydrodesulfurization unit may be used prior to the hydrocracking unit. Products such as LPG, naphtha, middle distillates and crude oils boiling below the cut-off temperature (typically below 540°C) can be sent to the olefins plant as feedstock. If necessary, middle distillates can be sold as a product. When all products are sent to the olefins plant, the yield of chemical products increases. Only a small amount of tar, for example less than 5% of the total crude oil supplied, may be sent as tar. This can be considered the maximum mode for obtaining chemical products. Depending on the amount of middle distillate sold as a product, the production of chemical products will decrease. The olefin complex produces hydrogen, methane, ethylene, ethane, propylene, propane, butadiene, butenes, butanes, C5-gasoline (C5-400°F (204°C)) and pyrolysis gas oil (PGO), as well as pyrolysis fuel oil (PFO >550°F (288°C)). The PGO and PFO fractions are quite hydrogen deficient and are less desirable chemical products. Since a residue hydrocracker is used, all of the PGO and some of the PFO (eg, those with boiling points less than 1000°F (538°C)) may be sent to the residue hydrocracker. This maximizes the amount of olefins produced in the olefin complex. When using a residue hydrocracker, high molecular weight PGO and PFO will be hydrocracked, and low molecular weight LPG and naphtha, in addition to other liquid products, can be used as feedstock for the olefin complex. This maximizes the production of chemical products. All operations described here can be carried out without a crude oil column. Some minor modifications to the embodiments described herein are possible for local situations to improve the economics of the method or the desired product.

[0035] As noted above, crude oils and/or heavy feedstocks with boiling points greater than 520°C or 550°C cannot currently be cracked efficiently and economically without their separation, for example, by pre-distillation or separation into several hydrocarbon fractions. In contrast, the embodiments discussed herein involve limited use or elimination of the use of fractionators for separating various hydrocarbons for crude oil cracking. The embodiments described herein may have low capital costs and consume less energy than methods requiring deep fractionation. In addition, the embodiments described herein convert a large portion of the crude oil to produce high yields of olefins by cracking.

[0036] By separating the hydrocarbon mixture into fractions with different boiling points, coking in each section can be controlled by proper equipment design and control of operating conditions. In the presence of water vapor, the hydrocarbon mixture can be heated to high temperatures without coking in the convection section. Additional water vapor may be added to further adiabatically evaporate the fluid. Thus, coke formation in the convection section is minimized. Since fractions with different boiling points can be processed in separate coils, the severity of the conditions for each fraction can be adjusted. This reduces coke formation in radiant coils and in quenching and evaporation apparatus (QEA). In general, olefin production can be maximized over a single cut by removing heavy tails (high boiling residue). Heavy oil refining schemes or conventional preheating of unstripped crude oil without separating boiling point fractions produce lower total olefins than the embodiments described herein. In the methods described herein, any material with a low boiling point to any final boiling point can be processed under conditions that are optimal for that material. One, two, three or more separate fractions can be separated from crude oil, and each fraction can be processed separately under optimal conditions.

[0037] Saturated and/or superheated dilution steam may be added at appropriate locations to vaporize the feedstock to the desired extent in each stage. The separation of the hydrocarbon mixture of crude oil is carried out, for example, using a flash drum or separator with a minimum number of theoretical stages to separate the hydrocarbons into different fractions. The heavy tails can then be processed (upgrading in accordance with the present invention and hydrocracking and recirculation).

[0038] The hydrocarbon mixture may be preheated using waste heat from process streams, including cracking process effluent streams or flue gas from a pyrolysis reactor/heater. Alternatively, crude oil heaters can be used for preheating. In such cases, to maximize the thermal efficiency of the pyrolysis reactor, other cold fluids (such as boiler feed water (BFW) or preheated air or an economizer) can be used as the uppermost cold heat sinks of the convection section.

[0039] The process for cracking hydrocarbons in a pyrolysis reactor can be divided into three components, namely a convection section, a radiant section and a quenching section, such as in a quench-evaporation apparatus (QEA). In the convection section, the raw material is preheated, partially evaporated and mixed with water vapor. In the radiant section, the raw material is subjected to cracking (the main cracking reaction occurs here). In ZIA, the reaction fluid is rapidly cooled to stop the reaction and control the product mixture. Instead of indirect hardening by heat exchange, direct oil hardening is also acceptable.

[0040] The embodiments described herein effectively utilize a convection section to enhance the cracking process. In some embodiments, all heating may be conducted in the convection section of a single reactor. In other embodiments, separate heaters for the respective fractions may be used. In some embodiments, the crude oil enters the top row of the convective tube bundle and is preheated by hot flue gas generated in the radiant section of the heater under operating pressure conditions to medium temperatures, without adding any amount of water vapor. Outlet temperatures can range from 150°C to 400°C, depending on crude oil and throughput. Under these conditions, between 5% and 70% (by volume) of the crude oil may evaporate. For example, the outlet temperature of this first heating stage may be such that the naphtha (which has a normal boiling point of about 200° C.) evaporates. Other separation boundaries (final boiling points) of fractions can also be used, including such as 350°C (gas oil). Since the hydrocarbon mixture is preheated by the hot flue gas generated in the radiant section of the heater, limited temperature variations and outlet temperature flexibility can be expected.

[0041] The preheated hydrocarbon mixture enters the flash drum to separate the vaporized portion from the non-evaporated portion. The vapors can be sent for further superheating, mixed with dilution water vapor and then fed into a radiant cracking coil. If sufficient material does not evaporate, superheated dilution water vapor may be added to the drum fluid. If enough material has evaporated, then cold (saturated or slightly superheated) water vapor can be added to the vapor phase. Superheated dilution steam can also be used in place of cold steam for proper thermal balance.

[0042] A vapor fraction, such as a mixture of a naphtha fraction, a gas oil fraction, or a light hydrocarbon fraction and dilution water vapor, is further superheated in the convection section and enters the radiant coil. The radiant coil may be located in another cell, or a group of radiant coils in one cell may be used to crack hydrocarbons in the steam fraction. The amount of dilution water vapor can be adjusted to minimize overall energy consumption. Typically, the amount of water vapor is adjusted at a water vapor to oil ratio of about 0.5 w/w, with any value from 0.2 w/w. up to 1.0 wt./mass. is acceptable, such as from about 0.3 wt./mass. to about 0.7 wt./mass.

[0043] The liquid (not evaporated) in the flash drum may be mixed with small amounts of dilution water vapor and may be further heated in a convection section in a second convection zone coil, which may be located in the same or a different heater. The P/M ratio (water vapor to oil ratio) for a given coil can be approximately 0.1 w/w, with any value from 0.05 w/w. up to 0.4 wt./mass. may be acceptable. Since this steam will also be heated along with the crude oil, there is no need to introduce superheated steam. Saturated water vapor is suitable. However, instead of saturated water vapor, superheated water vapor can be used. Superheated water vapor may also be supplied to the second evaporation drum. This drum may be a simple vapor-liquid separation drum or a more complex device such as an internally equipped tower. For most crude oil, the final boiling point is high, and some material will never evaporate as it exits this coil. Typical outlet temperatures may range from about 300°C to about 500°C, such as about 400°C. The outlet temperature can be selected to minimize coke formation in a given coil. The amount of water vapor added to the stream can be such that a minimum dilution stream is used and a maximum outlet temperature is achieved without coking. Since some water vapor is present, coke formation is suppressed. For crude oils with high coke formation, a higher steam flow is preferred.

[0044] Superheated steam can be added to the drum and will further vaporize the hydrocarbon mixture. The vapors are additionally overheated in the convection coil and enter the radiant coil. To avoid any vapor condensation in the pipeline, a small amount of superheated dilution water vapor can be added at the drum outlet (steam side). This will avoid condensation of heavy material in the pipelines, which could eventually turn into coke. The drum can be designed to perform this function too. In some embodiments, a heavy oil processing tower system (“HOPS”) may be used to provide condensation of heavy materials.

[0045] The unevaporated liquid can be further processed or sent for fuel. If the non-evaporated liquid is further processed, a HOPS tower can be used preferably. If some of the unevaporated liquid is sent to fuel, the unevaporated hot liquid can be replaced by other cold fluids, such as hydrocarbon feedstock or the first liquid fraction, maximizing energy recovery. Alternatively, the unevaporated liquid may be processed as described herein to produce additional olefins and higher value products. In addition, the thermal energy available in this stream can be used to preheat other process streams or to generate steam.

[0046] The radiant coil arrangement can be of any type, with a total residence time ranging from 90 ms to 1000 ms, using multi-row or multiple parallel pass and/or split coil configurations. They can be vertical or horizontal. Coil material can be high-strength alloys with bare and finned or enhanced internal heat transfer tubes. The heater may consist of one radiant box with several coils and/or two radiant boxes with several coils in each box. The geometry and dimensions of the radiant coil and the number of coils in each box can be the same or different. If cost is not a factor, multi-flow heaters/heat exchangers can be used.

[0047] After cracking in radiant coils, one or more quenchers can be used to very quickly cool the products and generate (ultra)high pressure water vapor. One or more coils may be combined and connected to each heat exchanger. The heat exchanger(s) may be a two-pipe heat exchanger or a composite shell-and-tube heat exchanger(s).

[0048] Instead of indirect cooling, direct quenching can also be used. In such cases, oil can be pumped at the outlet of the radiant coil. After oil quenching, water quenching can also be used. Instead of oil quenching, entirely water quenching is also acceptable. After hardening, the products are sent to the extraction section.

[0049] FIG. 2 is a simplified flow diagram of one integrated pyrolysis and hydrocracking system in accordance with the embodiments described herein. The combustion tube furnace 1 is used to crack hydrocarbons in a hydrocarbon mixture to form ethylene and other olefin compounds. The combustion tube furnace 1 has a convection section or zone 2 and a cracking section or zone 3. Furnace 1 contains one or more process pipes 4 (radiant coils), with the help of which part of the hydrocarbons introduced into the system through the hydrocarbon supply pipeline 22 is subjected to cracking to form gaseous products when heated. Radiant and convection heat is provided by the combustion of coolant introduced into the cracking section 3 of the furnace 1 through coolant inlets 8, such as hearth burners, bottom burners or wall burners, and exited through outlet 10.

[0050] Hydrocarbon feedstock 22, which may be a mixture of unstripped crude oil 19 and gas oil 21 and which may contain hydrocarbons boiling in the range from naphtha hydrocarbons to hydrocarbons having a normal boiling point greater than 450°C, may be introduced into the heating coil 24 , located in the convection section 2 of the pyrolysis heater 1. For example, hydrocarbon feedstock with components having a normal boiling point greater than 475°C, greater than 500°C, greater than 525°C, or greater than 550°C may be introduced into the heating coil 24. In the heating coil 24, the hydrocarbon feedstock may be partially vaporized, resulting in to the evaporation of lighter components of hydrocarbon feedstock, such as hydrocarbons of the naphtha fraction. The heated hydrocarbon feedstock 26 is then fed into the separator 27 for separation into a vapor fraction 28 and a liquid fraction 60.

[0051] Steam may be supplied to the process via conduit 32. Various sections of the process may use low temperature or saturated steam, while other sections may use high temperature superheated steam. Water vapor for superheating can be supplied through pipeline 32 to the heating coil 34, heated in the convection zone 2 of the pyrolysis heater 1 and discharged through pipeline 36 in the form of superheated water vapor.

[0052] A portion of the steam may be supplied through conduit 40 and mixed with the steam fraction 28 to form a steam/hydrocarbon mixture in conduit 42. The steam/hydrocarbon mixture in stream 42 may then be fed to heating coil 44. The resulting superheated mixture may then supplied through pipeline 46 to one or more cracking coils 4 located in the radiant zone 3 of the pyrolysis heater 1. The cracked hydrocarbon product may then be removed through conduit 12 for heat recovery, quenching, and product recovery (not shown) as described above.

[0053] Superheated steam 36 may be pumped through conduit 72 directly into separator 27. Pumping superheated steam into the separator may reduce the partial pressure and increase the amount of hydrocarbons in steam fractions 28. Steam or superheated steam may also be injected into one or both streams 22, 26.

[0054] Hydrogen 59 and liquid fraction 60, which includes high-boiling hydrocarbons (residue) in feed mixture 22, can then be fed to hydrocracking reactor system 61. The hydrocracking reactor system 61 may include one or more reaction zones, and may include fixed bed reactor(s), fluidized bed reactor(s), or other types of reaction systems known in the art.

[0055] In the hydrocracking reactor system 61, hydrogen 59 and hydrocarbons in the liquid fraction 60 may be contacted with a hydrocracking catalyst to hydrocracker a portion of the hydrocarbons in the liquid fraction to form lighter hydrocarbons, including olefins, among other products. The effluent stream 63 may be recovered from the hydrocracking reactor system 61 and may include unreacted hydrogen and various hydrocarbons. A separator 65 may then be used to separate unreacted hydrogen 67 from hydrocarbons 69 in the effluent stream. Unreacted hydrogen may be recycled to continue the reaction in the hydrocracking reaction system 61 if desired. The hydrocarbon effluent stream 69 may then be fractionated in a fractionation system 71, which may include an atmospheric distillation column and/or a vacuum distillation column, dividing the hydrocarbon effluent stream into two or more hydrocarbon fractions, which may include one or more light petroleum gas fractions 73, naphtha fraction 75, jet fuel or kerosene fraction 77, one or more atmospheric or vacuum gas oil fractions 79, and residue fraction 81. The gas oil fraction(s) 79, or portion(s) thereof, in some embodiments, may then be used as stream 21 and combined with unstripped crude oil 19 to form a mixed hydrocarbon feedstock 22, combining the hydrocracking reaction system with the pyrolysis unit. Other gas oil fractions, including those from external sources, may also be used as feed stream 21, in addition to or as an alternative to gas oil fraction(s) 79. Additionally, although not shown, feed 22 may include other feed streams similar to unstripped crude oil 19 and/or gas oil fraction(s) 79. Residue fraction 81 or a portion thereof may be returned to the hydrocracking reaction system for additional conversion and production of additional olefins.

[0056] FIG. 3 is a simplified flow diagram of a combined pyrolysis and hydrocracking system in accordance with the embodiments described herein. The fired tube furnace 1 is used to crack hydrocarbons to form ethylene and other olefinic compounds. The combustion tube furnace 1 has a convection section or zone 2 and a cracking section or zone 3. The furnace 1 contains one or more process pipes 4 (radiant coils), with the help of which a portion of the hydrocarbons supplied through the hydrocarbon supply line 22 is cracked to form gaseous products when heated. Radiant and convection heat is provided by the combustion of coolant introduced into the cracking section 3 of the furnace 1 through coolant inlets 8, such as hearth burners, bottom burners or wall burners, and exited through outlet 10.

[0057] Hydrocarbon feedstock, such as unstripped crude oil or a hydrocarbon mixture containing hydrocarbons boiling in the range from naphtha hydrocarbons to hydrocarbons having a normal boiling point greater than 450°C, can be introduced into the heating coil 24 located in the convection section 2 heater 1 pyrolysis. For example, hydrocarbon feedstock with components having a normal boiling point greater than 475°C, greater than 500°C, greater than 525°C, or greater than 550°C may be introduced into the heating coil 24. In the heating coil 24, the hydrocarbon feedstock may be partially vaporized, resulting in to the evaporation of lighter components of hydrocarbon feedstock, such as hydrocarbons of the naphtha fraction. The heated hydrocarbon feedstock 26 is then fed into the separator 27 for separation into a vapor fraction 28 and a liquid fraction 30.

[0058] Steam may be supplied to the process via conduit 32. Various sections of the process may use low temperature or saturated steam, while other sections may use high temperature superheated steam. Water vapor for superheating can be supplied through pipeline 32 to the heating coil 34, heated in the convection zone 2 of the pyrolysis heater 1 and discharged through pipeline 36 in the form of superheated water vapor.

[0059] A portion of the steam may be supplied through conduit 40 and mixed with the steam fraction 28 to form a steam/hydrocarbon mixture in conduit 42. The steam/hydrocarbon mixture in stream 42 may then be fed to heating coil 44. The resulting superheated mixture may then supplied through pipeline 46 to the cracking coil 4, located in the radiant zone 3 of the pyrolysis heater 1. The cracked hydrocarbon product may then be removed through line 12 for heat recovery, quenching, and product recovery.

[0060] In the same or a different heater, the liquid fraction 30 may be mixed with water vapor 50 and supplied to a heating coil 52 located in the convection zone 2 of the pyrolysis reactor 1. In heating coil 52, the liquid fraction may partially evaporate, resulting in evaporation of the remaining lighter components in the hydrocarbon feed, such as hydrocarbons ranging from middle ends to gas oil. Injecting water vapor into the liquid fraction 30 may help prevent coke formation in the heating coil 52. The heated liquid fraction 54 is then fed to a separator 56 to be separated into a vapor fraction 58 and a liquid fraction 60.

[0061] A portion of the superheated steam may be supplied through conduit 62 and mixed with the steam fraction 58 to form a steam/hydrocarbon mixture in conduit 64. The steam/hydrocarbon mixture in stream 64 may then be fed to heating coil 66. The resulting superheated the mixture can then be supplied through line 68 to the cracking coil 4 located in the radiant zone 3 of the pyrolysis heater 1. The cracked hydrocarbon product may then be discharged through conduit 13 for heat recovery, quenching, and product recovery.

[0062] Superheated steam may be pumped through conduits 72, 74 directly into separators 27, 56, respectively. Injecting superheated steam into separators can reduce the partial pressure and increase the amount of hydrocarbons in the steam fractions 28, 58.

[0063] In addition to heating the hydrocarbon and steam streams, convection zone 2 may be used to heat other process and steam streams, such as through coils 80, 82, 84. For example, coils 80, 82, 84 may be used, among etc., for heating BFW (boiler feedwater) and preheating SHP (super high pressure) steam.

[0064] The placement and number of coils 24, 52, 34, 44, 66, 80, 82, 84 may vary depending on the design and expected raw materials available. Thus, the convection section can be designed to maximize energy recovery from the flue gas. In some embodiments, it may be desirable to locate superheat coil 44 in a location with a higher flue gas temperature than superheat coil 66. Lighter hydrocarbons may be cracked under more severe conditions, and by appropriate placement of superheat coils, cracking conditions may be enhanced or adjusted. for a specific vapor fraction. Likewise, when vapor fractions are processed in separate heaters, coil locations, heater conditions, and other variables can be independently adjusted to match cracking conditions to the desired severity.

[0065] In some embodiments, the first separator 27 may be a flash drum, and the second separator 56 may be a heavy oil handling system (HOPS) tower, as shown in FIG. 6 described below.

[0066] Liquid fraction 60 can then be processed in an integrated hydrocracking system as described above with reference to FIG. 2. Hydrogen 59 and liquid fraction 60, which includes high boiling point hydrocarbons (residue) in feed mixture 22, may then be supplied to hydrocracking reactor system 61, which may include one or more reaction zones, and may include reactor(s) ) fixed bed, fluidized bed reactor(s), or other types of reaction systems known in the art.

[0067] In hydrocracking reactor system 61, liquid fraction 60 may be contacted with a hydrocracking catalyst to crack a portion of the hydrocarbons in the liquid fraction to form lighter hydrocarbons, including olefins, among other products. The effluent stream 63 may be recovered from the hydrocracking reactor system 61 and may include unreacted hydrogen and various hydrocarbons. A separator 65 may then be used to separate unreacted hydrogen 67 from hydrocarbons 69 in the effluent stream. The hydrocarbon effluent stream 69 may then be fractionated in a fractionation system 71, which may include an atmospheric distillation column and/or a vacuum distillation column, dividing the hydrocarbon effluent stream into two or more hydrocarbon fractions, which may include one or more light petroleum gas fractions 73, naphtha fraction 75, jet fuel or kerosene fraction 77, one or more atmospheric or vacuum gas oil fractions 79, and residue fraction 81. The gas oil fraction(s) 79 or portion(s) thereof may then be used as stream 21 and combined with unstripped crude oil 19 to form a mixed hydrocarbon feedstock 22, combining the hydrocracking reaction system with the pyrolysis unit. Residue fraction 81 or a portion thereof may be returned to the hydrocracking reaction system for further conversion and production of additional olefins.

[0068] Although not shown in FIG. 2 or FIG. 3, additional hydrocarbons in liquid fraction 60 may be vaporized and cracked, maximizing olefin production in the process. For example, liquid fraction 60 may be mixed with steam to form a steam/oil mixture. The resulting steam/oil mixture can then be heated in the convection zone 2 of the pyrolysis reactor 1 to evaporate some of the hydrocarbons in the steam/oil mixture. The heated stream can then be fed to a third separator to separate a vapor fraction, such as vacuum gas oil range hydrocarbons, from a liquid fraction. Superheated steam may also be introduced into the separator to aid separation, as well as into the recovered vapor cut to prevent condensation in the transfer lines before introducing the vapor cut into the cracking coils to produce olefins. The liquid fraction recovered from the separator may contain the more difficult boiling components of the hydrocarbon mixture 22, such as hydrocarbons having a normal boiling point above 520° C. or 550° C., and this resulting liquid fraction can then be processed in an integrated hydrocracking system as described above with with reference to FIG. 2 and FIG. 3.

[0069] The configuration of FIG. 2 and FIG. 3 provides significant advantages over the traditional method of pre-fractionating the entire mixed hydrocarbon feedstock into separately processed fractions. Additional process flexibility, such as the ability to process a wide range of feedstocks, can be achieved using the embodiment illustrated in FIG. 4.

[0070] As shown in FIG. 4, where like numerals denote like parts, mixed hydrocarbon feedstock 22 may be supplied to heater 90. At heater 90, the hydrocarbon feedstock may be brought into contact by indirect heat exchange with heat exchange medium 96 to raise the temperature of the hydrocarbon feedstock. 22, resulting in the formation of heated feedstock 92. Heated feedstock 92 may remain in a liquid state or may partially evaporate. The heat transfer medium 96 may be a heat transfer oil, steam, process stream, or the like used to provide heat to the mixed hydrocarbon feedstock 22.

[0071] The heated feed 92 may then be introduced into the separator 27 to separate lighter hydrocarbons from heavier hydrocarbons. Water vapor 72 may also be introduced into separator 27 to enhance evaporation of lighter hydrocarbons. The vapor fraction 28 and liquid fraction 30 may then be processed as described above in relation to FIGS. 2 and 3 to crack one or more of the vapor fractions to produce olefins and recover a heavy hydrocarbon fraction containing hydrocarbons having very high normal boiling points. eg above 550°C.

[0072] When crude oil preheating is performed externally in a heat exchanger or preheater as shown in FIG. 4, economizers or BFW coils 83 may occupy the top row(s) of convection section 2. To further improve efficiency, flue gas from the two or more heaters may be collected, and the combined flue gas may be used to recover additional heat, for example, by preheating feedstocks, preheating combustion air, generating low pressure steam, or heating other process fluids.

[0073] Water vapor has a very low heat capacity, and the heat of vaporization of oil is also significant. In addition, the thermal energy available in the convection zone of a pyrolysis reactor is not infinite, and the multiple tasks of evaporating hydrocarbon feedstock, superheating water vapor, and superheating hydrocarbon/steam mixtures fed to the radiant coils may result in large amounts of high-boiling material not being used. A separate heater can be used to preheat the hydrocarbon feedstock and/or dilution steam, resulting in a greater degree of flexibility for the overall process in processing hydrocarbon mixtures containing both low and high amounts of heavier hydrocarbons and increasing the overall olefin yield from the hydrocarbon feed. mixtures.

[0074] This embodiment is disclosed in FIG. 5, where a dedicated heater 100 is used only for preheating the hydrocarbon feedstock. Heater 100 preferably does not crack any feedstock into olefins, but rather acts as a convection section to perform the heating described above. The temperatures indicated in relation to FIG. 5 are for exemplary purposes only and may be modified to obtain desired hydrocarbon fractions.

[0075] Crude oil 102 is supplied to heating coil 104 and is preheated in heater 100 to a relatively low temperature. The heated feed 106 is further mixed with water vapor 108, which may be dilution steam or superheated dilution steam. Preheating and contact with steam may result in the vaporization of hydrocarbons having a normal boiling point of approximately 200°C or less (ie naphtha fractions). The vaporized hydrocarbons and water vapor can then be separated from the non-vaporized hydrocarbons in drum 110 to produce a vapor fraction 112 and a liquid fraction 114. The vapor fraction 112 can then be further diluted with water vapor if necessary, superheated in the convection section, and directed to the radiant coils. pyrolysis reactor (not shown).

[0076] Liquid fraction 114 may be mixed with dilution steam 116, which may be saturated dilution steam, supplied to heating coil 117, and heated in combustion heater 100 to medium temperatures. The heated liquid fraction 118 may then be mixed with superheated dilution water vapor 120 and the mixture introduced into a flash drum 122. Hydrocarbons boiling in the range of about 200°C to about 350°C are vaporized and recovered as a vapor fraction 124. Steam fraction 124 can then be superheated and sent to the radiant section of the pyrolysis reactor (not shown).

[0077] The liquid fraction 126 recovered from the flash drum 122 is reheated with saturated (or superheated) dilution steam 127 and passed through coils 128 and further superheated in the fired heater 100. The superheated dilution steam 130 may be added to the heated liquid stream 132 /steam and fed to separator 134 for separation into a vapor fraction 136 and a liquid fraction 138. This separation will separate the 350-550 °C (VGO) fraction, recovered as a vapor fraction 136, which can be superheated with additional dilution steam if this is necessary and is directed to the radiant section of the pyrolysis reactor (not shown).

[0078] In some embodiments, separator 134 may be a flash drum. In other embodiments, separator 134 may be a HOPS tower. Alternatively, the separation system 134 may include both a flash drum and a HOPS tower, wherein the vapor fraction 136 may be recovered from the flash drum and further heated with dilution steam and supplied to the HOPS tower. In cases where a HOPS unit is used, only the evaporating material will be cracked. The non-evaporated material 138 may, for example, be recovered and sent to fuel or further processed to produce additional olefins, as described below. Additional dilution water vapor will be added to the vapor phase before it is sent to the radiant section of the pyrolysis reactor (not shown). Thus, using a separate fired heater, many fractions can be produced, and each fraction can be optimally cracked.

[0079] For each of the embodiments described above, a conventional heater design is possible. To increase the thermal efficiency of such a heater, the top row (cold heat sink) can be any low temperature fluid or BFW or economizer, as shown in FIG. 4. Heating and superheating of fluids with or without the use of steam can be accomplished in the convection section or the radiant section or both sections of the fired heater. Additional superheating can be carried out in the convection section of the cracking heater. In heaters, maximum heating of the fluid must be limited to temperatures that are lower than the coking temperatures of the crude oil, which for most crude oils can be around 500°C. At higher temperatures, sufficient dilution water vapor must be present to suppress coke formation.

[0080] The dilution steam can also be superheated so that the energy balance of the cracking heater does not significantly affect cracking severity. Typically, dilution steam is superheated in the same heater (called a complex heater) where the cracking of the feedstock occurs. Alternatively, dilution water vapor can be superheated in separate heaters. The use of an integrated or separate dilution steam superheater depends on the amount of energy available in the flue gas.

[0081] A simple diagram of a HOPS tower 150 is shown in FIG. 6. Various modifications of this scheme are possible. In a HOPS tower, superheated dilution steam 152 is added to hot liquid 154, and a separation zone 156, comprising 2 to 10 theoretical stages, is used to separate volatile hydrocarbons from non-volatile hydrocarbons. As a result of this process, the entrainment of small droplets into the overhead fraction 160 is reduced, while the entrainment of high-boiling liquids into the steam will cause coke formation. Heavy non-volatile hydrocarbons are recovered into bottoms fraction 162, and vaporized hydrocarbons and dilution water vapor are recovered into overhead fraction 164. The HOPS tower 150 may include any internal distributors with and/or without packing. When using a HOPS tower, vapor/liquid separation can be almost perfect. The end boiling point of steam is predictable depending on operating conditions, and any entrainment of liquid into the vapor phase can be minimized. Although this option is more expensive than a flash drum, the benefits of reduced coking greatly outweigh the additional cost. The liquids in stream 162 may be recycled to an appropriate process step for further processing.

[0082] In the embodiments described herein, all vapor fractions may be cracked in the same reactor in different coils. In this manner, a single heater can be used for different fractions, and optimal conditions for each fraction can be achieved. Alternatively, multiple heaters can be used.

[0083] The resulting nonvolatile material, such as in streams 60, 138, can be fed to an integrated hydrocracker unit as shown and described above in relation to FIG. 2 and FIG. 3.

[0084] In some embodiments, it may be desirable to further treat one or more liquid fractions, such as liquid fraction 30 or 60, to remove metals, nitrogen, sulfur, or Conradson carbonaceous residue prior to further processing in the combined hydrocracking and pyrolysis system. One configuration for this additional processing and combining in accordance with the embodiments described herein is shown in FIG. 7.

[0085] As shown in FIG. 7, a hydrocarbon mixture 222, such as raw crude oil or raw crude oil mixed with gas oil, as described above for feed 22, for example in relation to FIG. 2 and FIG. 3, is sent to convection zone 202 of the pyrolysis heater 201. The heated mixture 224 is flashed in a separator 203 and the vapor fraction 204 is sent to the pyrolysis heater 201 of the reaction section (radiant zone) 205, where the vapor stream is converted to olefins. The resulting effluent stream 206 is then sent to an olefin recovery section 208, where the hydrocarbons can be separated by fractionation into various hydrocarbon fractions, such as a light petroleum gas cut 209, a naphtha cut 210, a jet or diesel fuel cut 211, and a heavy cut 212.

[0086] The liquid portion 214 recovered from the separator 203 may be hydrotreated in a fixed bed reactor system 216 to remove one or more of the metals, sulfur, nitrogen, CCR, and asphaltenes and to produce a lower density hydrotreated liquid 218. The liquid 218 is then directed to the convection zone 220 of the pyrolysis heater 221. Separator 219 may be used to remove vapors 245 from hydrotreated liquid 218 in some embodiments, where vapors 245 may react in reaction section 205 of pyrolysis heater 201 in the same or a different coil as vapor 204.

[0087] The heated mixture 243 resulting from heating the liquid 218 in the convection zone 220 is then flashed in the separator 226, and the steam 227 is sent to the reaction zone 228 of the pyrolysis heater 221, where the vapor stream is converted to olefins and sent through conduit 247 to olefin recovery section 208.

[0088] Liquid 229 from separator 226 is sent to hydrocracking reactor 250 (fluidized bed or slurry) for near complete conversion of the liquid boiling nominally above 550°C, converting hydrocarbons to products <550°C. The effluent stream 253 from the hydrocracking reaction zone 250 may be fed to a separation zone 255, where the lighter products 251 from the reactor effluent stream are stripped and sent to the respective pyrolysis reactor zones in the heaters 201 and 221, and may be sent through hydrotreaters 216 or simply combined with streams with a similar boiling range fed into the pyrolysis reactor zones.

[0089] Liquid 212 from fractionation section 208 (substantially at temperatures of 370-550°C) is sent to a full conversion hydrocracker 260 combined with the rest of the hydrocracking system 250 (fluidized bed or slurry) for complete conversion to naphtha 261 or mixture 261 naphtha and unconverted oil streams. In the case where all of the product in stream 261 is naphtha, naphtha 261 may be processed in the reaction zone of a separate pyrolysis heater (not shown) or heater coil in one of the reaction zones 205, 228. In other embodiments, the mixture 261 of naphtha and the unconverted oil stream may be separated in one or more separators 270, 272 into various fractions 274, 276, which may be fed to reaction zones 205, 228 for separate or co-processing with steam fractions 204, 245, 227 in respective reaction zones 205, 228. Heating and separation of the unconverted oil stream or a portion thereof may occur in the convection section 290 of the pyrolysis heater 292. The liquids 280 in the unconverted oil stream may then be sent to their own pyrolysis reaction section 294 in the pyrolysis heater 292 for conversion to olefins. The pyrolysis effluent stream 296 may then be supplied to the olefin recovery zone 208 .

[0090] The embodiments described herein can eliminate the refinery entirely while still making the process of converting oil into chemicals highly flexible relative to crude oil. The processes described here are flexible for crude oils with high contaminant contents (sulphur, nitrogen, metals, CCR), and this distinguishes them from unstripped crude oil processes, which can only process very light crude oils or condensates. In contrast to hydrotreating whole crude oil, which can involve very large reactor volumes and is inefficient at adding hydrogen, in the processes described here hydrogen is added only as needed and at the right location in the process.

[0091] Additionally, the embodiments described herein utilize a unique combination of convection and reaction pyrolysis zones to process various types of feedstocks resulting from the selective hydrotreating and hydrocracking of crude oil components. Complete conversion of crude oil can be achieved without a refinery.

[0092] Vapor and liquid generated in the convection section can be effectively separated using HOPS separators. The embodiments described herein use a convection section of the first heater to separate light components that can be easily converted to olefins and do not require hydrotreating. The liquid can then be effectively hydrotreated to remove heteroatoms that affect the yield/extent of contamination before further pyrolysis using a fixed bed catalytic system for HDM, DCCR, HDS and HDN. The embodiments described herein may also use a fluidized bed hydrocracking or slurry hydrocracking reaction and a catalyst system to convert the heaviest components in the crude oil in an intermediate step.

[0093] Embodiments described herein may also use a fixed bed hydrocracking system to convert low density aromatic products resulting from the conversion of the heaviest components of crude oil into high hydrogen content products, which can then be sent to pyrolysis. The embodiments described herein can also minimize the production of pyrolysis liquid fuels by accurately adding hydrogen and by conducting the pyrolysis reaction in special heaters tailored to the feedstock being processed. The production of pyrolysis oil is minimized due to the fact that hydrogenation systems are able to process different fractions of raw materials, for example, by separating the raw materials in HOPS separators. The pyrolysis oil produced in accordance with the embodiments described herein is recovered and hydroprocessed in various hydrocracking sections, thereby avoiding the discarding of low value pyrolysis oil.

[0094] In addition, a feature of the embodiments described herein is hydrocracking of pyrolysis fuel oil and thermal cracking of hydrocracked material. A typical VGO contains approximately 12–13 wt%. hydrogen, while PFO contains approximately 7% wt. hydrogen. In addition, PFO may contain significant amounts of polynuclear aromatic compounds, including hydrocarbon molecules having more than 6 rings. Accordingly, vacuum gas oil is easier to hydrocrack than PFO. The hydrocracking unit in the embodiments described herein may be configured to process such heavy feedstocks.

[0095] EXAMPLES

[0096] Example 1: Arabian Crude Oil

[0097] Table 1 shows the calculated yields obtained for crude oil cracking. All calculations are based on a theoretical model. Provided that cycle time (even several hours) is not a critical factor, outputs at high stringency conditions are shown, although other severity levels may be used.

[0098] This example considers Nigerian light crude oil. Crude oil has properties and distillation curve as shown in Table 1.

Table 1

Specific Gravity 0..79 Sulfur,% wt. 0.04 Microcarbon residue (MCRT), wt.% 0.67 Metals, ppm 2.1 C7 asphaltenes, wt.% 0.11 End boiling point TBP, °С Total yield (wt.%) < 80 11.7 150 30.2 200 43.5 260 58.1 340 78.2 450 93.6 570 97.7 Residue (570°C +) 100

[0099] The simulated pyrolysis yields for crude oil cracking, calculated based on the theoretical model, are shown in Table 2. In this example, three cases were studied, including: Case 1 - unstripped crude oil plus gas oil product; case 2 – crude oil together with gas oil and residue hydrocracker product, and control case, case 3 – full range naphtha pyrolysis.

[00100] Naphtha fraction (<200°C), gas oil fraction (200-340°C) and VGO+ (>340°C) are considered. In case 1, the naphtha and gas oil fractions are the same as during cracking in pyrolysis coils. The VGO+ material is sent to the residue hydrocracking unit. The products of the hydrocracking unit are sent to the pyrolysis unit. A small portion is removed from the hydrocracker as effluent to minimize the fouling rate of the hydrocracker.

[00101] In case 2, the resulting pyrolysis gas oil and pyrolysis liquid fuel (205°C+) are sent to the residue hydrocracking unit, and the products from the hydrocracking unit are sent to the pyrolysis unit, similar to case 1.

[00102] For all cases, the feedstock is cracked under high severity conditions to minimize feedstock consumption. A typical full range naphtha is considered as a control. The properties of naphtha are as follows: specific gravity = 0.708, initial boiling point = 32°C, 50 vol.% = 110°C, final boiling point = 203°C; paraffins=68 wt%, naphthenes=23.2 wt%, and aromatics=8.8 wt%.

[00103] For all cases, the ethane and propane produced in the olefin production unit are recycled until complete production. Ethane is cracked at a conversion rate of 65%. This example uses a highly selective dual SRT heater. The coil outlet pressure is selected at 1.7 bar abs. (0.17 MPa).

[00104] The following table shows the material balance for a typical 1 million metric ton ethylene production at high severity.

table 2

RAW MATERIALS Case 1 Case 2 Case 3 Crude oil in complex (% wt.) 3130.7 2937.9 Nafta to the complex 2970 Water vapor reaction 3.5 3.5 3.3 Total raw materials 3134.2 2941.4 2973.3 RIGIDITY High High High Products, H2+fuel gas 456 457.8 516.2 C2H4 1000 1000 1000 C3H6 448.1 454.3 422.1 Unrefined C4 276.9 279.8 245.9 Pyrobene C5 up to 240°C 651.1 666 631.5 PGO/PFO 174.9 –– 155.9 Acid gases 1.8 1.8 1.7 Remainder 125.2 –– 0 PFO drain –– 81.8 0 Total 3134.2 2141.4 2973.3 Final yield of C2H4, wt.% 31.94 34.03 33.67 Final yield of C3H6, wt.% 14.31 15.46 14.21 Final yield of C2H4+C3H6, wt.% 46.25 49.5 47.88

[00105] Hydrocracking the heavy ends and sending the products to an olefins unit as a feedstock produces final yields comparable to a naphtha cracker. When the residue hydrocracker is not used, not only is the residue hydrocrackered, but also the heavy fuel oil produced in the olefin complex can be hydrocracked and integrated as a feedstock for the olefin complex. This improves the final yield and proves to be better than a typical naphtha cracker. Without separating the crude oil into different fractions, the crude oil can be processed into an olefin complex by combining with a conventional hydrocracker and/or a residue hydrocracker. This increases final olefin production, minimizes feedstock consumption and improves the economics of crude oil cracking. The production of less valuable heavy fuel oil is significantly reduced, thereby conserving resources.

[00106] When high-value fuels such as kerosene and/or diesel are required, these products can be obtained from a distillation column used in a hydrocracker. They may not be routed to the olefin complex - since they have been through the hydrocracker, they will also meet the fuel specifications, avoiding the need for separate hydroprocessing units required in conjunction with a crude distillation unit when fuels are obtained from a crude oil distillation column. This reduces capital costs. In addition, the process flowsheets proposed here can be modified to provide the required olefin to fuel ratio.

[00107] Example 2

[00108] When using Arabian crude oil, the following material balance is formed.

Material balance for 11564 thousand t/y of crude oil feedstock without LPG HAPPENING 1A 2A 3A 1B 2B 3B Vacuum residue cracking No Yes Yes No Yes Yes Recycling of heavy fuel oil No No Yes No No Yes Cracking Hardness High High High Low Low Low Light gas 668.4 668.4 668.4 668.4 668.4 668.4 Light naphtha 2889.2 2889.2 2889.2 2889.2 2889.2 2889.2 Heavy naphtha 2390.0 2390.0 2390.0 2390.0 2390.0 2390.0 Heavy mix 2 4052.4 4052.4 4052.4 4052.4 4052.4 4052.4 Vacuum residue 1564.3 1564.3 1564.3 1564.3 1564.3 1564.3 Methanol 114.3 136.3 150.7 198.9 231.0 255.2 Total amount of reacted water vapor 11.9 13.8 15.0 13.1 15.1 16.5 TOTAL 11690.5 11714.4 11730.0 11776.3 11810.4 11836.0 PRODUCTS, thousand t/y Hydrogen 35.9 39.9 42.6 10.3 11.4 12.2 Fuel gas 1706.9 1937.6 2088.3 1528.8 1732.4 1885.5 Ethylene 3637.8 4114.8 4426.5 3435.5 3884.6 4222.5 Propylene from cracking unit 1572.7 1822.3 1985.3 1926.7 2205.0 2414.3 1,3-Butadiene 512.3 588.6 638.5 540.1 618.9 678.2 MTBE 314.5 375.0 414.5 547.3 635.5 701.9 1–Butene 57.9 67.3 73.5 119.9 134.0 144.5 C9+ Gasoline 238.9 289.6 0.0 261.9 315.1 0.0 Benzene 697.5 819.0 898.3 435.8 502.9 553.4 Toluene 527.1 575.4 607.0 518.6 561.3 593.5 Xylene 208.6 247.8 273.5 242.0 278.4 305.9 Pyrolysis gas oil 172.3 256.8 0.0 175.3 284.7 0.0 Pyrolysis liquid fuel 435.5 570.9 0.0 461.1 636.2 0.0 Remainder 1564.3 0.0 0.0 1564.3 0.0 0.0 Liquid fuel recycling
Flue gases 0.0 0.0 32.1 0.0 0.0 37.0 Liquid fuel recycling
Oil residues 0.0 0.0 240.0 0.0 0.0 276.4 Acid gases 8.3 9.3 9.9 8.9 9.9 10.7 TOTAL 11690.5 11714.4 11730.0 11776.3 11810.4 11836.0 RECIRCULATES, thousand t/y Recycle C ₂ 555.1 635.9 688.6 638.9 724.6 789.0 Recycle C ₃ 123.2 175.3 209.4 140.3 193.1 232.9 Recycle THU C ₄ –C ₅ 534.6 666.3 752.3 1073.9 1254.4 1390.2 Recycle _C6 – _C8 non-aromatic substances 223.5 274.9 308.5 687.2 770.5 833.2 Recycle liquid fuel for cracking 0.0 0.0 969.8 0.0 0.0 1116.8 Recirculate liquid fuel for flushing 0.0 0.0 52.0 0.0 0.0 59.9

[00109] For this balance, 10,000 thousand t/y of liquid crude oil, free of residue and without LPG, is selected as the basis, and mixed with the corresponding 1,564.3 thousand t/y of residue. The residue-free part is the traditional raw material. Under conditions of high rigidity (case 1A), it produces 3637.8 thousand t/g of ethylene and 1572.7 thousand t/g of propylene. Under conditions of low hardness (case 1B), the same amount of raw material produces 3435.5 thousand t/g of ethylene and 11926.7 thousand t/g of propylene. Crude oil contains residue, and to obtain 10,000 thousand tons/year of cracked material, 11,564.3 thousand tons/year of crude oil must be used, and 1,564.3 thousand tons/year of residue will be rejected. Currently used cracked feedstocks are light gases (668.4 thousand tons/year), light naphtha (2889.2 thousand tons/year), heavy naphtha (2390 thousand tons/year) and heavy oils (4052.4 thousand t/y). Cases 1A, 2A, 3A represent the cracking of the entire feedstock of an olefin production unit at high severity. Cases 1B, 2B, and 3B represent the corresponding low-stringency cases.

[00110] In cases 1A, 1B, gaseous feedstock, naphtha feedstock and high boiling point material are used in a conventional manner. A portion of the high boiling point material is hydrocracked to produce feedstock for the olefin production unit.

[00111] In Cases 2A, 2B, the same feedstock is used and the residue is hydrocracked in a residue hydroprocessing unit, and the products of the hydrocracker are cracked in addition to the feedstock used in Cases 1A or 1B.

[00112] Cases 3A, 3B use all the feedstocks used in Cases 2A or 2B and also crack hydroprocessed pyrolysis fuel oil (PFO). This pyrolysis liquid fuel is hydrocracked in a special hydrocracking unit. PFO is generated in the cracker and recycled back to the cracker after hydrocracking.

[00113] By cracking the residue and hydrocracking the PFO recycle, the production of ethylene and propylene increases significantly, as shown in the table below. All values are given in thousand tons/year.

Case 1A Case 1B Case 1C Case 2A Case 2B Case 2C HC raw materials 10000 10000 10000 10000 10000 10000 Remainder 1564.3 1564.3 1564.3 1564.3 1564.3 1564.3 Total 11564.3 11564.3 11564.3 11564.3 11564.3 11564.3 _{C2H4 ​} 3637.8 4114.8 44426.5 3435.5 3884.6 4222.5 _{C3H6 ​} 1572.7 1822.3 1985.3 1926.7 2205 2414.3 C ₂ H ₄ + C ₃ H ₆ 5210.5 5937.1 6411.8 5362.2 6089.6 6636.8 Output C ₂ +C ₃ , % 45.06 51.34 55.44 46.37 52.66 57.39

[00114] As a result of cracking the residue as well as pyrolysis liquid fuel, olefin yields increase significantly. Crude oil consumption is reduced to produce a fixed amount of ethylene or olefin. This is an advantage of cracking residue and pyrolysis liquid fuels after hydroprocessing. In industry, % C ₂ + C ₃ shown in the table is designated as the final yield.

[00115] Some of the above examples use high severity cracking. The embodiments described herein are not limited to high rigidity. The pyrolysis heater can be modified to match the desired ratio of propylene to ethylene. When very high propylene contents are required, olefin conversion technology can be used, for example using the resulting butene and ethylene to produce propylene (eg metathesis). Additional butene can be produced using ethylene dimerization technology when the butene produced by pyrolysis is insufficient for olefin conversion. Accordingly, if necessary, it is possible to obtain 100% propylene with 0% ethylene. Using reverse olefin conversion technology, propylene can be converted into ethylene and butene. Thus, 100% ethylene and 100% propylene can be produced from crude oil by combining pyrolysis, residue hydrocracker, olefin conversion technology and/or dimerization technology.

[00116] As described above, embodiments discussed herein can provide flexible processing of raw crude oil and other hydrocarbon mixtures containing high boiling point coke precursors. The embodiments described herein can advantageously reduce coking and fouling during preheating, superheating, and cracking processes, even under high severity conditions. The embodiments described herein can achieve desired yields while significantly reducing the capital and energy costs associated with prefractionation and separate processing of fractions in multiple heaters.

[00117] Suppressing coke formation throughout the cracking process and combining pyrolysis and hydrocracking in accordance with the embodiments described herein provides significant benefits, including increased olefin yield, longer cycle times (reduced downtime), and the ability to process feedstocks containing heavy hydrocarbons . In addition, significant energy efficiency can be achieved compared to traditional processes involving distillation separation and the use of separate cracking reactors.

[00118] Although the description of the invention includes a limited number of embodiments, those skilled in the art taking advantage of the present invention will appreciate that other embodiments may be developed that do not depart from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the appended claims.

Claims (32)

1. A method for producing olefins and/or dienes, including: partial evaporation of unstripped crude oil to form a liquid fraction and a vapor fraction; overheating said vapor fraction to form a superheated vapor fraction; hydrotreating said liquid fraction to remove one or more of metals, sulfur, nitrogen, Conradson carbonaceous residue or asphaltenes to produce a hydrotreated liquid; partial evaporation of said hydrotreated liquid to form a second vapor fraction and a second liquid fraction; partially evaporating said second liquid fraction to form a third vapor fraction and a third liquid fraction; hydrocracking the third liquid fraction with the conversion of the hydrocarbon components contained therein, having a boiling point of more than 550°C, into hydrocarbons having a boiling point of less than 550°C, and obtaining a hydrocracked effluent stream; separating said hydrocracked effluent to produce a light hydrocracked fraction and a heavy hydrocracked fraction; hydrocracking said heavy hydrocracked fraction to convert the hydrocarbon components contained therein into naphtha fraction hydrocarbons and producing a second hydrocracked effluent stream; separating said second hydrocracked effluent to produce a second light hydrocracked fraction containing naphtha hydrocarbons and a second heavy hydrocracked fraction; partially evaporating said second heavy hydrocracked fraction to obtain a fourth vapor fraction and a fourth liquid fraction; thermal cracking of (i) said superheated vapor fraction, (ii) said third vapor fraction, (iii) said second vapor fraction, (iv) said fourth vapor fraction, (v) said second light hydrocracked fraction, and (vi) said fourth liquid fraction to produce thermally cracked hydrocarbon effluent streams, each of which contains a mixture of olefins and paraffins. 2. The method according to claim 1, wherein the thermal cracking includes joint thermal cracking of a superheated steam fraction, a second steam fraction and a second light hydrocracked fraction, wherein the method further includes mixing said superheated steam fraction, a second steam fraction and a second light fraction hydrocracked fraction. 3. The method of claim 1, wherein the thermal cracking comprises joint thermal cracking of a third vapor fraction and a fourth vapor fraction, wherein the method further includes mixing said third vapor fraction and a fourth vapor fraction. 4. The method according to claim 1, wherein the hydrotreating further includes hydrotreating the light hydrocracked fraction. 5. The method of claim 1, further comprising separating the thermally cracked hydrocarbon effluent streams to produce one or more light olefin fractions and a liquid boiling at a temperature of from 370 to 550°C. 6. The method according to claim 5, in which hydrocracking the third liquid fraction and/or hydrocracking the heavy hydrocracked fraction further includes hydrocracking a liquid boiling at a temperature of from 370 to 550°C. 7. A method for producing olefins and/or dienes, including: partial evaporation of unstripped crude oil to form a liquid fraction and a vapor fraction; overheating said vapor fraction to form a superheated vapor fraction; hydrotreating said liquid fraction to remove one or more of metals, sulfur, nitrogen, Conradson carbonaceous residue or asphaltenes to produce a hydrotreated liquid; partial evaporation of said hydrotreated liquid to form a second vapor fraction and a second liquid fraction; partially evaporating said second liquid fraction to form a third vapor fraction and a third liquid fraction; hydrocracking the third liquid fraction with the conversion of the hydrocarbon components contained therein, having a boiling point of more than 550°C, into hydrocarbons having a boiling point of less than 550°C, and obtaining a hydrocracked effluent stream; separating said hydrocracked effluent to produce a light hydrocracked fraction and a heavy hydrocracked fraction; hydrocracking said heavy hydrocracked fraction to convert the hydrocarbon components contained therein into naphtha fraction hydrocarbons and producing a second hydrocracked effluent stream; separating said second hydrocracked effluent to produce a second light hydrocracked fraction containing naphtha hydrocarbons and a second heavy hydrocracked fraction; thermally cracking (i) said superheated steam fraction, (ii) said third steam fraction, (iii) said second steam fraction, (iv) said second heavy hydrocracked fraction, and (v) said second light hydrocracked fraction to produce thermally cracked hydrocarbon effluent streams , each containing a mixture of olefins and paraffins. 8. The method according to claim 7, wherein the thermal cracking includes joint thermal cracking of a superheated steam fraction, a second steam fraction and a second light hydrocracked fraction, wherein the method further includes mixing said superheated steam fraction, a second steam fraction and a second light fraction hydrocracked fraction. 9. The method of claim 7, wherein the hydrotreating further includes hydrotreating the light hydrocracked fraction. 10. The method of claim 7, further comprising separating the thermally cracked hydrocarbon effluent streams to produce one or more light olefin fractions and a liquid boiling at a temperature of from 370 to 550°C. 11. The method according to claim 10, in which hydrocracking the third liquid fraction and/or hydrocracking the heavy hydrocracked fraction further includes hydrocracking a liquid boiling at a temperature of from 370 to 550°C.

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