Patent Application
20240360366
The present invention generally relates to fluidized catalytic cracking of kerogen oils derived from kerogen ores.
Kerogen is an abundant organic resource contained within mineral structures often referred to as oil shale (more appropriately, kerogen ore). The most practiced method for extracting kerogen from its ore is pyrolysis: heating the ore in an oxygen-free environment. The resulting product is a rich mixture of numerous carbon compounds, historically referred to as Synthetic Crude Oil (SCO). Existing kerogen pyrolysis technologies have seen little commercial success for two key reasons. Firstly, pyrolysis using existing technologies produces copious amounts of dilute carbon dioxide and other greenhouse gas emissions. Secondly, the economic case for kerogen pyrolysis has focused on production of fuels in existing refineries. However, SCO has chemical properties that make it difficult and generally uneconomical to process in those refineries.
New technologies and methodologies for pyrolysis of kerogen ore have been developed that can address both issues, namely (1) utilizing a pyrolysis technology that minimizes production of carbon dioxide, and (2) shifting focus of the pyrolysis products from SCO and fuels production to that of chemicals—a process termed Kerogen To Chemicals, or KTC. The pyrolysis product of this process, termed Kerogenate, can be fractionated into cuts (or Kerogenates) that are broadly like those obtained from crude oil refining. However, they tend to be richer in more valuable chemicals. As with crude oil refining, the heavier, high-molecular-weight cuts contain molecules that do not have significant commercial value. In existing refineries, various downstream processes are used to upgrade these products into more valuable molecules. The most important of these processes is Fluidized Catalytic Cracking (FCC).
The FCC process has been studied, patented, erected, and operated by many companies over many decades. Existing crude refinery FCC units are typically built as “standalone” processes; they accept feedstocks from other refinery operations, utilize large quantities of steam generated elsewhere and create products that are separated downstream and sold, or purged to atmosphere. Feedstocks for refinery FCC units tend to be less valuable, high-molecular-weight components, typically atmospheric gas oils (AGO) and vacuum gas oils (VGO) having a boiling range between 550° F. (300° C.) and 935° F. (500° C.). Early designs were based on the hot oil and catalyst mixing in a fluidized bed in a large reactor volume. Over time, the process has been refined to shift the bulk of the cracking reactions to what is called the Riser. The Riser is a vertical cylinder into which the feedstock to be cracked is introduced, along with a lift gas and hot powdered zeolitic catalyst. The feedstock is injected near the base of Riser, conventionally using steam as a dispersal medium, such that the feedstock is atomized, forming tiny droplets. These droplets contact the hot catalyst which has been fluidized by the lift gas, causing the droplets to vaporize. The expanding vapor, lift gas and fluidized catalyst travel up the Riser. The vaporized feedstock, in intimate contact with the hot catalyst undergoes cracking to produce lower molecular weight components.
Catalytic cracking is complex, and many rapid reactions are involved. The overall process is endothermic, and energy must be supplied to maintain the reactions. To avoid excess cracking, contact times in the upper Riser are kept short, typically no more than five seconds. Products of the reaction include smaller hydrocarbon molecules, carbon deposited on catalyst, and other compounds. The carbon, along with some chemically bonded hydrogen, metals and other impurities, is deposited on the catalyst as coke. These coke deposits reduce catalyst activity. To overcome this problem, the coked spent catalyst is transported to a Regenerator. Removal of coke deposits and reactivation of the catalyst occurs by oxidation of the coke in the Regenerator using air introduced via a blower. The coke is combusted and forms carbon monoxide, carbon dioxide, and water, and some other compounds. Combustion of the coke heats the catalyst; the hot regenerated catalyst is returned to the Riser forming a continuous cracking-regeneration cycle.
The dominance of the FCC process is based on its ability to achieve a high conversion of heavy low-value feedstock at high energy efficiency to higher-value products. Beneficially, the process also reduces the sulfur, nitrogen, and metals content of the high-value cracked products. FCC units have become the single most important refinery operation with regards to production and profitability, particularly in the U.S. but also worldwide. For many decades, FCC operation has been focused on maximizing production of high-octane gasoline and other fuels. Recent modifications to the process add value by skewing production towards chemical feedstocks such as olefins (e.g., propylene) instead of fuels. Demand for petrochemical feedstocks, including propylene, is expected to increase while demand for fuels is forecast to decrease. As world reserves of lighter, sweeter crude oils have been depleted, FCC technology and catalysts have been developed to enable direct processing of heavier crudes.
The environmental impact of existing FCC units is significant. Large quantities of carbon dioxide and pollutants such as oxides of sulfur (SOx) and nitrogen (NOx), and particulate matter are released. Energy requirements, typically met by burning fossil fuels, and the need for large quantities of steam exacerbate this problem. Capturing or removing the large quantities of carbon dioxide (CO2) produced is complicated by its relatively low concentration in flue and other waste gases. CO2 emissions from FCC units account for approximately 15% to 20% of total refinery carbon emissions-around 0.5% of total U.S. carbon emissions (as of 2019). Addressing these environmental challenges requires a combination of technological advancements, regulatory compliance, and sustainable practices that can be economically implemented.
The present invention addresses the aforementioned needs in the art, as will now be summarized and then further described in detail below.
Some variations of the invention provide a process of converting kerogen ore to multiple products, the process comprising:
In some embodiments, the vacuum column utilizes a motive gas comprising steam and at least 40 mol % carbon dioxide. In some embodiments, the vacuum column utilizes a motive gas comprising at least 80 mol % carbon dioxide.
In some embodiments, the lift gas contains from about 80 mol % to about 100 mol % carbon dioxide. In certain embodiments, the lift gas contains from about 85 mol % to about 95 mol % carbon dioxide.
In some embodiments, the coke-oxidation gas contains from about 55 mol % to about 85 mol % carbon dioxide. In certain embodiments, the coke-oxidation gas contains from about 60 mol % to about 80 mol % carbon dioxide.
In some embodiments, the heavy cycle oil from step (h) is recycled to the riser reactor. In some embodiments, the heavies (column bottoms) stream from step (h) is conveyed to the vacuum column.
The process is preferably continuous or semi-continuous.
Other variations of the invention provide a process of converting kerogen ore to multiple products, the process comprising:
In some embodiments employing a common main column for steps (d) and (h), the vacuum column utilizes a motive gas comprising steam and at least 40 mol % carbon dioxide. In some embodiments, the vacuum column utilizes a motive gas comprising at least 80 mol % carbon dioxide.
In some embodiments employing a common main column for steps (d) and (h), the lift gas contains from about 80 mol % to about 100 mol % carbon dioxide. In certain embodiments, the lift gas contains from about 85 mol % to about 95 mol % carbon dioxide.
In some embodiments employing a common main column for steps (d) and (h), the coke-oxidation gas contains from about 55 mol % to about 85 mol % carbon dioxide. In certain embodiments, the coke-oxidation gas contains from about 60 mol % to about 80 mol % carbon dioxide.
In some embodiments employing a common main column for steps (d) and (h), the pre-flash unit is present, and step (h) includes (1) conveying the reaction products through the pre-flash unit to generate an overhead vapor and a liquid bottoms, and (2) feeding the liquid bottoms to the main column to generate the kerogenate products.
In some embodiments employing a common main column for steps (d) and (h), the kerogenate products produced in step (h) comprise light ends, heavy cracked naphtha, light cycle oil, and/or heavy cycle oil. In certain embodiments, the kerogenate products produced in step (h) comprise all these streams-light ends, heavy cracked naphtha, light cycle oil, and heavy cycle oil.
In preferred embodiments employing a common main column for steps (d) and (h), the process is continuous or semi-continuous.
Various embodiments may be understood with reference to the drawings, which are not intended to limit the invention in any way.
The processes and systems of the present invention will be described in detail by reference to various non-limiting embodiments.
This description will enable one skilled in the art to make and use the invention, and it describes several embodiments, adaptations, variations, alternatives, and uses of the invention. These and other embodiments, features, and advantages of the present invention will become more apparent to those skilled in the art when taken with reference to the following detailed description of the invention in conjunction with the accompanying drawings.
As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this invention belongs.
Unless otherwise indicated, all numbers expressing conditions, concentrations, dimensions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending at least upon a specific analytical technique.
The term “comprising,” which is synonymous with “including,” “containing,” or “characterized by” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. “Comprising” is a term of art used in claim language which means that the named claim elements are essential, but other claim elements may be added and still form a construct within the scope of the claim.
As used herein, the phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. When the phrase “consists of” (or variations thereof) appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole. As used herein, the phrase “consisting essentially of” limits the scope of a claim to the specified elements or method steps, plus those that do not materially affect the basis and novel characteristic(s) of the claimed subject matter.
With respect to the terms “comprising,” “consisting of,” and “consisting essentially of,” where one of these three terms is used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms, except when used in Markush groups. Thus, in some embodiments not otherwise explicitly recited, any instance of “comprising” may be replaced by “consisting of” or, alternatively, by “consisting essentially of.”
Existing kerogen pyrolysis technologies, and a focus on fuels production, have resulted in poor product quality. Through improved retorting technology combined with new integration with FCC operations, as disclosed herein, product quality can be enhanced. Such integration brings many benefits, such as lower overall capital cost through sharing of common process operations. A lower environmental footprint is realized through a combination of energy integration and alternative operational methods. Reduced transport and associated environmental costs can be achieved by integrating downstream processing directly on-site. While the focus in this patent application is on conversion of kerogen to chemicals, both the retort and FCC have the flexibility to handle alternative feedstocks, such as asphalt and even plastics. Further opportunities for integration exist in the re-use of spent FCC catalyst and spent kerogen ore.
The use of air and steam in existing FCC processes is generally based on historical precedent. The invention described herein provides individuals skilled in the art with an opportunity to use more efficient and environmentally friendly solutions. Replacing air used for combustion with high-purity oxygen will increase the concentration of carbon dioxide in the Regenerator flue gas and KTC retort waste gas streams. High concentrations of carbon dioxide make recovery and use more economical.
Similarly, by replacing or reducing the use of steam, emissions from boilers can be reduced or eliminated. Where steam is still required, use of high-purity oxygen rather than air for combustion can, as with the Regenerator and Retort, simplify recovery of carbon dioxide.
This disclosure teaches the techniques and benefits of integrating a pyrolysis process (Retort) with a fluidized catalytic cracking (FCC) unit. The integrated process is herein referred to as “KFCC” which is an acronym for Kerogen Fluidized Catalytic Cracking. Preferred embodiments of the present invention are based on the use of pyrolysis products from a Retort as feedstock to an FCC unit; within the FCC unit a mixture of high-purity oxygen (≥95 mol %) and carbon dioxide (≥80 mol %) replaces air for coke combustion.
Conventional FCC art utilizes steam for many important functions including riser lift gas, regenerator stripping gas, catalyst fluidization for transfer to and from the regenerator, and new fresh catalyst addition and spent catalyst removal from the process, vacuum ejector jet gas and other utility uses. In all cases, using the disclosed technology, the steam may be substituted wholly, or in part with carbon dioxide.
The Gas Processing and Concentration Unit (111) is responsible for handling the gaseous products of the atmospheric separation columns and pre-flash units. The gases from these units will be composed of many components, light hydrocarbons (C1 through C6), oxides of sulfur and nitrogen, water vapor, carbon monoxide, and carbon dioxide being the most notable. The design of this section will depend on the desired products, such as propylene, fuel gas, light cracked naphtha (LCN) and carbon dioxide. Some of these products such as propylene are becoming increasingly valuable. Others, such as fuel gas, can be burned to generate power and/or steam. As with other embodiments of this invention, combustion may be performed using high-purity oxygen, in which case the combustion gases can be processed along with the Recycle Gas. All the processes required are well understood pre-existing art.
CO2-rich gas streams (105) such as those from the Retort Preheat Effluent (108), Regenerator flue gas (109), and Gas Processing and Concentration Unit (106) would undergo additional treatment to remove SOx, NOx, and H2O (101). Where high-purity oxygen has been used for combustion, such as for CO Boiler, CHP/Energy Recovery, Steam Generation (110), the associated flue gas streams would undergo the same treatment. The treated streams, combined, will have a carbon dioxide concentration of at least 80 mol %, and preferably at least 90 mol %. The treated streams are split into carbon dioxide rich Recycle Gas (104) used by preferred embodiments of this invention, and Net Process Gas (102). The split will depend on process requirements but would typically range in volume from 70% to 98% as Recycle Gas and 2% to 30% as Net Process Gas. The Net Process Gas proceeds to the CO2 recovery system (103).
The preferred embodiment of this invention processes oil shale (kerogen ore) in a pyrolysis process (107). The product, termed “Kerogenate” may be fractionated, and one or more fractions (“Kerogenates”) processed in an FCC unit. While this is the preferred embodiment, this invention is not limited to processing kerogen. Other embodiments of the process may utilize a range of alternative or supplemental feedstocks. These feedstocks may include but are not limited to bio-sourced oils, recycled pyrolyzed products, recycled oils and fats, other recycled hydrocarbon products and heavy oils. It is also possible to process suitably prepared hydrocarbon-containing solid feedstocks such as plastics, tires, road asphalt, asphalt tiles, and asphalt paper.
The pyrolysis products of these alternative feedstocks may contain problematic levels of oxygenates, metals, silica, and other contaminants. If these feedstocks are processed alongside kerogen ore, the contaminants could reduce the value of the Kerogenate product. The KFCC process, with its integrated FCC, can assist in reducing or eliminating this problem. Catalytic activity in the FCC can act to pacify these undesirable contaminants and remove them from the final products.
Kerogen ore (also known as oil shale), or alternative hydrocarbon-containing material, is first processed to create a suitable feedstock for the pyrolysis unit. Typically, this would involve crushing the ore; for plastics, solid asphalt products, tires, etc., the initial processing may include shredding. The exact requirements of the form and size of the feedstock will depend on the pyrolysis process used. Some preferred embodiments employ pyrolysis technology taught by commonly owned U.S. Patent App. Pub. No. 20210054290 A1 to Schneider and Owen, published on Feb. 25, 2021, which is hereby incorporated by reference (hereinafter, “Schneider”). The pyrolysis reactor described in Schneider is referred to herein as the KTC Retort (119). For the KTC Retort, kerogen ore is crushed and screened to between ½″ (1.25 cm) and 3″ (7.5 cm). Other embodiments may utilize alternative technologies to process the kerogen ore (or other feedstocks). Such technologies may be taught by existing art created by “Red Leaf”, “Paraho”, “Enefit”, “Petrosix”, “ATP”, “Chevron”, “Shell”, “ExxonMobil” and others. These technologies may involve in situ or ex situ processing of the feedstock materials.
In preferred embodiments using the KTC Retort, prepared kerogen ore first enters a Retort Preheat section (113) to eliminate air and water and to raise the temperature to that just below retorting temperatures. This may be achieved using a portion (112) of the Recycle Gas stream which has been heated to a temperature between 660° F. (350° C.) and 710° F. (375° C.); retorting may be carried out between 7.0 psig (0.5 barg) and 25 psig (1.5 barg). The gas leaving the Retort Preheat section, the Preheat Effluent (108), comprises CO2-rich Recycle Gas with small amounts of water, oxygen, nitrogen, light hydrocarbons, and other volatiles. This stream once cleaned of H2O, NOx and SOx (101), forms part of the Recycle Gas (104) and Net Process Gas (102) streams.
A further portion of the Recycle Gas may be used as a Retort Sweep Gas (128) for the Retort (116). Retorting of kerogen ore occurs within a narrow temperature range, between 660° F. (350° C.) and 840° F. (450° C.). The decomposition temperature range for other feedstocks may be different. Temperature control and residence time are controlled to manage Kerogenate product composition. High temperatures and/or too long a residence time can lead to over-cracking of the Kerogenate and coking of the spent kerogen ore. Conversely, low temperatures and/or too short a residence time may lead to incomplete pyrolysis, leading to a poor Kerogenate product composition and contaminated spent kerogen ore. The Retort Sweep Gas transports the Kerogenate product away from the hot ore, terminating cracking reactions. The mixture exits the retort between 525° F. (275° C.) and 750° F. (400° C.) for further processing (117). Spent kerogen ore exits the bottom of the KTC Retort (123). Energy, recovered from the hot ore in the Retort Heat Recovery section (124), may be used to heat the Recycle Gas feeding the Preheat and Retort sections (122).
In embodiments that do not use the KTC Retort, the configuration of the Recycle Gas stream feeds may be different. For example, the use of a Preheat may not be required. Optional process streams are indicated in
Retort Sweep Gas, from the Retort Heat Recovery section, typically requires further heating to achieve the required temperatures for the Preheat and Retort sections. In the preferred embodiment, electrical resistance heaters are used to provide the additional heat for the Preheat and Retort Sweep Gases. Renewable sources such as solar and wind are preferred suppliers of the electrical energy for these heaters. In another embodiment, all, or part of required additional heat may be provided through energy integration with other suitable streams such as the Regenerator flue gas (109). In yet other embodiments, fired heaters or other sources of thermal energy may be used to attain the required temperatures. In some situations, it may economically or operationally beneficial to combust the spent kerogen ore. KTC Retort art taught by Schneider describes the use of multiple zones for additional operations. One zone could be utilized for combustion of the spent ore with high-purity oxygen. The resulting Retort flue gas, rich in carbon dioxide would be cleaned and combined with the Recycle Gas as described by other embodiments of this invention. The hot combusted ore would pass into a second zone where it would be used to heat the retort and preheat sweep gases, for example.
One embodiment of Kerogenate fractionation is taught in U.S. Patent App. Pub. No. 20180355254 A1, published on Dec. 13, 2018, which is hereby incorporated by reference. Kerogenate from the Retort is processed through a directly coupled Retort Main Column (114), such as shown in
In a different embodiment, depicted in
A unified Main Column can realize economic and operational benefits. Construction of the single, although larger, column will reduce capital cost. Operation and control of the column, with feedstocks that have broadly similar characteristics, and are at similar temperatures and similar pressures, enable tighter management and quality of product fractions. Energy integration of a single column, with larger flows can reduce the overall capital cost of associated heat exchanger networks and improve heat recovery opportunities. As with the use of separate Retort and FCC Main Columns, the bottoms product (206) of the single Main Column would proceed to a Vacuum Column (207).
In preferred embodiments, the Vacuum Column, operating at pressures between 1 mmHg (1.5 mbar) and 50 mmHg (70 mbar) would separate the heavier, higher-boiling-point Kerogenate and FCC Reactor products. Typical fractions obtained from this separation include Sour Gas, Light Vacuum Gas Oil (LVGO), Heavy Vacuum Gas Oil (HVGO) and Residue. Sour Gas would leave the process and undergo additional processing, as would the heavy Residue. Light vacuum gas oil (LVGO) (131) and heavy vacuum gas oil (HVGO) (136) would be recycled to the FCC Riser Reactor (127) for further cracking.
In existing art, vacuum columns typically use steam ejectors to maintain their high vacuum state; typically, 3 pounds (1.5 kg) of steam are required per pound (kg) of hydrocarbon extracted. In one embodiment of this invention, steam would be replaced as the motive medium for the ejectors by a portion of the Recycle Gas. In a different embodiment, a combination of steam and Recycle Gas could be used. The ratio of steam to Recycle Gas could range widely, from 0.0 to 1.0: where 0.0 indicates no steam, and 1.0 indicates no Recycle Gas. The ejector effluent, termed Sour Gas, is a mixture of light hydrocarbons and other components including some containing sulfur, such as hydrogen sulfide. Sour Gas can cause a variety of maintenance issues: corrosion and fouling being the most prominent. Eliminating the use of steam for the vacuum ejectors will reduce the adverse effects of hydrogen sulfide and other compounds that become more reactive in the presence of water. Alternatively, it may be economically or operationally preferable to replace the use of ejectors with an appropriate liquid ring vacuum pump or compressor.
There is a great deal of prior art relating to the design and operation of FCC units, with different configurations and nuances. However, they all share the same fundamental implementation and objective, and, in most cases, similar equipment in various configurations. Individuals skilled in existing FCC process art will be able to readily identify and understand how changes noted in the various embodiments presented in this invention can be applied to existing designs. An example side-by-side style FCC design is depicted in
With reference to
While there are many different Riser feedstock injector designs, they all have the same objective—atomization of the feedstock. Smaller droplet sizes enable rapid heat transfer from the catalyst and lift medium, leading to faster vaporization. Proper injector placement optimizes the spray pattern across the Riser cross-section, improving mixing, further enhancing vaporization. In existing art, superheated steam is typically used to disperse the feedstock via the injectors. Steam (typically around 2 wt % for gasoil feeds and up to 5 wt % for heavy resid feeds) lowers the hydrocarbon partial pressure, further enhancing atomization of the feedstock. Typical temperatures for injector steam are between 380° F. (195° C.) and 600° F. (315° C.), with pressures between 180 psig (12.5 bar) to 1000 psig (70 bar). The selected injector configuration and operating pressure depends on the design and operational requirements of the FCC; it is a trade-off between sufficient atomization and the energy required to achieve it.
One embodiment of this invention replaces the use of steam in the feedstock injectors with Recycle Gas. Under any sensible injector operating regime, Recycle Gas will be non-condensable. Thus, feedstock injection temperatures and pressures can be varied over a significantly greater range compared to the use of steam. As with other embodiments of this invention, consideration must be given to how the different physical properties of the Recycle Gas and steam may affect equipment design and operation. Recycle Gas has a significantly higher density, and a lower heat capacity than that of steam. This can affect mass flowrates through the injectors. Further consideration should also be given to other properties such as surface tension; injector nozzle designs should be evaluated with these considerations in mind. There are other benefits in eliminating steam, such as reducing issues of corrosion, scaling, and fouling. Similarly, the capacity of equipment necessary to remove condensate and sour water downstream of the reactor can be re-evaluated, and potentially eliminated.
Another embodiment of this invention would replace steam to the injectors with a mixture of steam and Recycle Gas. In this embodiment the ratio of Recycle Gas to steam may vary from as little as 0.0 (all steam), to as much as 1.0 (no steam). Such an embodiment enables the operator to select the mix of dispersion gases to best suit operational and economic considerations. Careful review of injector nozzle design must be performed based on the selected dispersion mixture and required operating conditions.
The atomized feedstock is brought into contact with hot catalyst which has been fluidized by the lift gas (327) within the lower riser (326). In conventional art, the lift gas is steam. The hot catalyst vaporizes the feedstock and the expanding vapors and lift gas along with the fluidized catalyst travel up the Riser. Catalytic cracking occurs mostly in the upper Riser, wherein the heavy feedstock is converted to lighter products.
There is existing art on the type and design of equipment for dispersing the lift gas into the Riser base. Again, the present invention is largely agnostic to the exact design employed. The lift gas accelerates the catalyst up the Riser to the feedstock injectors. This promotes uniform flow over the Riser cross-section. Ensuring uniform flow at the point of feedstock injection limits back-mixing and prevents early excessive coking.
One embodiment of this invention replaces the use of steam as a lift gas with Recycle Gas. Recycle Gas, being predominantly carbon dioxide, at temperatures and pressures typically found at the Riser base, is nearly three times as dense as steam. Typical residence times in the Riser range from as little as 1 second to as much as 10 seconds. This equates to velocities between 6 ft/s (1.8 m/s) to as much as 80 ft/s (24.5 m/s); velocity is not linear through the Riser height. As feedstock is vaporized the expanding vapor, and cracking products accelerate up the Riser. It is expected that residence times would be similar whether steam or Recycle Gas (or a combination thereof) is used, assuming catalyst activity is the same. Selection of residence time, for a given operating temperature and pressure, will define the extent of cracking reactions. Too high a residence time can lead to over-cracking of the feedstock, forming lower-value products.
Existing use of steam may have a beneficial impact on the acid function of the zeolitic catalysts typically used in FCC units by reducing pore plugging by metals. Various catalyst formulations and additives exist that may be used to operate effectively in an anhydrous environment. The higher density of carbon dioxide compared to steam may alter the pressure drop up the Riser. It may also affect uniform distribution of catalyst and dispersion of the feedstock; one skilled in the art can verify whether a conventional Riser design is adequate. Use of existing designs should be evaluated to ensure density and viscosity of the lift gas are within specification.
For a conventional steam-based lift gas system, the pressure and thus the minimum (saturation) temperature of steam is constrained. When using Recycle Gas instead of steam, no such constraint practically exists; a similar benefit arises to that noted for using Recycle Gas instead of steam for the feedstock injectors. This introduces another control variable for Riser temperature management, and uniquely, an ability to reduce the Riser temperature. By reducing the temperature of lift gas, catalyst and riser temperatures will also reduce. Importantly, this is achieved without changing Regenerator operating temperatures, Catalyst Cooler duty, or requiring a change in the Cat/Oil ratio.
Another embodiment would use a mixture of steam and Recycle Gas as the lift gas. The ratio of Recycle Gas to steam could vary from 0.0 (all steam) to 1.0 (no steam). Such a mixture can yield better overall results than the use of steam or Recycle Gas alone. Retaining the use of at least some steam may mitigate issues with zeolite catalyst acid function. This would reduce or mitigate the need for catalyst additives or special formulations as may be required when using Recycle Gas alone. Other issues related to dispersion of the catalyst may also be mitigated as the steam/Recycle Gas mixture density is decreased versus Recycle Gas alone.
Internal devices (e.g., 304) at the top of the Riser (305) are designed to ensure cracking reactions are quickly terminated. There are many different configurations for the Riser termination equipment; two such examples are UOP's Vortex Separation System (VSS) and Vortex Disengager Stripper (VDS). The invention described here is agnostic to the configuration of the termination device.
The Riser vapors with entrained catalyst, at between 900° F. (482° C.) and 1,000° F. (538° C.), enter the Reactor body (302). In typical designs, the Reactor can be thought of more as a separation and disengaging vessel than as a chemical reactor. It contains a series of gas cyclones (301), usually comprising at least two stages; processed through these, catalyst load in the vapor is significantly reduced. The product vapor, largely free of entrained catalyst, exits the top of the Reactor (300) where it proceeds to fractionation (118). Recovered catalyst exits via the cyclone dip legs (303) to the top of the Stripper section (308) where it combines with catalyst separated via the Riser termination equipment. In the embodiment depicted in
An alternative embodiment, depicted in
When using an embodiment of this invention that replaces or augments the use of steam as a lift gas in the Riser (or dispersant in the feedstock injectors) with Recycle Gas, attention must be given to potential effects on design and operation of the termination system. Termination systems such as VSS and VDS essentially operate by rapidly changing the direction of flow. It is considered unlikely that a change of lift gas (or feedstock injector dispersant) will have much effect on the terminator efficiency of conventional designs. However, physical properties such as the effects of the density and viscosity of the recycled flue gas on cyclone efficiency must be considered. Given catalyst particle size is unchanged whether using steam or Recycle Gas, the denser flue gas should result in improved separation due to inertial and centrifugal effects. Further, the higher density gas will incur a higher pressure drop through the upper reactor and cyclones, which may be beneficial.
The Stripper section recovers hydrocarbons remaining on the catalyst. As with all aspects of the FCC, there are many different conventional designs and implementations for the Stripper; this invention is agnostic to design choice. In the version depicted in
In one embodiment steam is replaced as the stripping agent by high-CO2 Recycle Gas. Design or selection of the stripping section internals including baffles and dispersion ring should consider associated changes in physical properties versus steam. Effects to be considered include catalyst holdup times and reduced heat capacity.
Spent (coked) catalyst flows from the Stripper to the Regenerator (322) via a standpipe (313), its flowrate controlled by a slide valve (316). A critical safety consideration here is ensuring no hydrocarbon vapors from the Riser Reactor can escape into the Regenerator. If they were to do so, they could proceed further downstream where additional particulate removal processes such as electrostatic precipitation create an explosion hazard.
Those skilled in the art will be aware of the role of the Regenerator in FCC units. Catalytic cracking of high molecular weight feedstock in the Riser (318) results in the deposition of coke on the catalyst. This coke, comprising mostly carbonaceous material, deactivates the catalyst by blocking active sites. In the Regenerator, coke on catalyst is removed by combustion returning the catalyst to a high level of activity. The combustion reactions form carbon monoxide and carbon dioxide, along with some water and other products.
From the standpipe (313), the spent catalyst is distributed into the Regenerator. There is a significant quantity of existing art concerned with implementation of the spent catalyst feed device (324); the present invention is agnostic to the specific design. Within the Regenerator the spent catalyst contacts and is fluidized by a gas which contains an oxidizing agent. In existing art, this gas generally takes the form of air, and oxygen is the oxidizer; the gas typically is supplied by an air blower at pressures of about 35 psig (2.5 barg) to 50 psig (3.5 barg) and ambient temperature. In recent art, enriched air, containing oxygen at a higher concentration than found normally may enhance the burning capacity of the Regenerator. The flowrate of air is typically set at the rate needed to maintain an appropriate Regenerator operating pressure. The oxygen level in the flue gas is measured and continuously controlled to be about 1 mol % to 3 mol %. An insufficient flow of oxygen will result in incomplete combustion of carbon and increased carbon monoxide levels. Too high an excess of oxygen will result in harmful afterburning of carbon monoxide. Typical oxygen-to-coke ratios ranges from 0.5 to 1.5 on a mass basis. As with the catalyst distributor, there is significant existing art describing the design and operation of the oxidizing medium distributor (323) and this invention is largely agnostic to its design subject to certain considerations.
Once coke has been burned off the catalyst, it returns to near original activity. After multiple circuits through the Reactor and Regenerator, metals (such as vanadium, nickel, and sodium) build up on the catalyst blocking access to zeolite matrix pores, reducing activity. Metal deactivation is essentially irreversible in the Regenerator. Physical attrition of the catalyst also occurs and is likewise irreversible. These and other similar effects result in a gradual decline in catalyst activity. To counter this, catalyst is withdrawn, and fresh catalyst added. Though this can be done batchwise, continuous replacement is preferred, since a constant mass of catalyst maintains stable operation. Depending on the size of the unit, the amount of catalyst added and withdrawn can range from less than 1 ton to more than 30 tons per day. Although it is increasingly common for FCC catalyst to be sent for metals recovery, used in cement or other products, or recycled, most is simply sent to landfill.
In one embodiment of this invention, all, or a portion of the spent catalyst is mixed with raw crushed kerogen ore fed to the Retort process. Adding spent FCC catalyst to the retort feed will impact the types of molecules produced. The effect on molecular type distribution may or may not be beneficial. The decision to do this will be based on operational and commercial objectives.
Air is approximately 78 mol % nitrogen and 21 mol % oxygen; the remaining 1 mol % comprises mostly argon with smaller quantities of carbon dioxide, carbon monoxide, neon, and helium. The typical operating temperature of the Regenerator ranges between 1,300° F. (700° C.) and 1,380° F. (750° C.). At these temperatures, nitrogen does not play a significant role in the combustion reactions. Thus, while significant quantities of carbon dioxide (and carbon monoxide) are produced during combustion of the coke, the CO2 and CO remain dilute relative to this large quantity of inert nitrogen, typically 10 mol % to 20 mol % carbon dioxide. This significantly complicates recovery of the carbon dioxide from the Regenerator flue gas. Further, although nitrogen does not play a significant role in the combustion process, the N2 is still reactive. The products of N2 reaction—oxides of nitrogen (NOx)—can react with water created during combustion to form nitric acid. Nitric acid can react further to form ammonium salts which can cause fouling, corrosion, erosion, and other issues in downstream equipment.
Preferred embodiments of this invention replace the use of air in the Regenerator with Recycle Gas mixed with high purity oxygen; Recycle Gas thus acts as a Diluent (134). In this specification, “high-purity oxygen” (135) is defined as being no less than 95 mol % and up to 100 mol % oxygen. While nitrogen does not play a significant role in combustion within the Regenerator, N2 does act to carry heat away from the reaction. This effect influences the maximum combustion temperature. Recycle Gas achieves the same effect, preventing excessive and potentially uncontrolled temperatures which may cause unwanted reactions or even damage or destroy the catalyst, components, or the vessel. Further, by using high-purity oxygen and Recycle Gas, the production of nitrous oxides in the regenerator will be significantly reduced. As the coke on catalyst will contain some nitrogen it is unlikely that production of nitrous oxides can be fully eliminated.
High-purity oxygen for all the embodiments presented herein can be obtained as one product of air separation. Air separation is a process for which there are many existing technologies; cryogenics and adsorption being two such examples. Electrolysis of water offers another potential route to production of oxygen. In all cases by using renewable energy to produce the oxygen, the environmental cost of production can be significantly reduced. Alternatively, oxygen could be provided via pipeline, tanker, railcar, or other off-site solution. Economics would typically be the prime driving factor in determining how and where the oxygen is obtained. In the case of electrolysis, access to a plentiful supply of water would also play a significant role in selection of the technology. In all cases, this invention only uses one component of the separation, oxygen. Other separation products could be used elsewhere in the plant or sold. For air separation such products would include nitrogen, argon, and neon. Where electrolysis is used, hydrogen (H2) would be a valuable co-product. Preferred embodiments of this invention are agnostic to which process technology or delivery method is used to obtain the high-purity oxygen.
Although Recycle Gas replaces the nitrogen component of air, oxides of nitrogen (NOx) may still be produced during pyrolysis of the feedstock. Likewise, oxides of sulfur (SOx) may be created during pyrolysis and FCC operations. If these are allowed to build up in the Recycle Gas stream, they react with water forming compounds that can foul and corrode downstream equipment. The Recycle Gas stream is thus processed (101) to remove NOx, SOx, and water. The cleaned gas (102, 104) contains approximately 90 mol % to 95 mol % Carbon Dioxide. Composition of the balance will vary depending on Retort and FCC operation but will typically comprise light hydrocarbons, and small quantities of hydrogen, nitrogen, oxygen, and other gases.
In one embodiment of this invention, the carbon dioxide component of the Recycle Gas (104) replaces the nitrogen found in air on a mole-for-mole basis, 1 mol of carbon dioxide for 1 mol of nitrogen. Recycle Gas as Diluent (134) is combined with high-purity oxygen (135) to form Oxidation Gas (125) (also referred to as coke-oxidation gas). Depending on the desired concentration of oxygen, the resulting composition of the Oxidation Gas will range from 9.5 mol % to 35 mol % high-purity oxygen and 58 mol % to 86 mol % carbon dioxide. The balance includes light hydrocarbons, unconsumed oxygen and small quantities of nitrogen and other gases. This gas composition should enable use of known gas separation technology designed for existing FCC units as gas velocities therein should be similar.
Oxidation Gas is sent to the Regenerator. It is necessary to consider how differences in the properties of Oxidation Gas versus that of air may impact FCC operation. Carbon dioxide is 1.5× the molecular weight, 1.5× the density, and 1.3× the heat capacity, relative to nitrogen. Like nitrogen, carbon dioxide does not play a significant role in Regenerator combustion. Thus, it follows, given its higher molecular weight and larger heat capacity, carbon dioxide will remove more heat from the Regenerator than nitrogen would in a conventional FCC on a like-for-like basis. As a result, under otherwise similar process operating conditions temperatures in the Regenerator will be lower than those in a conventional FCC operated with nitrogen-rich air.
Operating the Regenerator at lower temperatures may have both beneficial and detrimental effects on overall performance for a given feedstock at otherwise comparable operating conditions. Unless otherwise compensated for, lower temperatures may lead to incomplete combustion of carbon monoxide which would require additional afterburning at the Regenerator outlet. Also, unless otherwise compensated for, lower Regenerator temperatures may mean lower Riser catalyst temperatures. These lower temperatures will have an impact on cracking within the Riser, reducing both conversion and coking. Lower temperatures can also be seen as an advantage—by increasing capacity to burn coke for a given Regenerator size as compared to existing FCC regenerator art. In a Regenerator, more coke may be burned, and temperatures can be maintained in a more typical operating range of 1,290° F. (700° C.) to 1,380° F. to (750° C.). In turn, this may have a beneficial effect on catalyst maintenance, particularly in operations running high Conradson Carbon Residue (CCR). The overall effect of replacing nitrogen with Recycle Gas can enable an increase in FCC throughput of between 25% and 35% for the same size regenerator vessel. Thus, the capital costs of a Regenerator may be significantly lower than for a conventional FCC operating at the same feedstock quality and quantity. Alternatively, it may be possible to increase use of lower cost, high Conradson Carbon Residue (CCR) feedstocks, renewable organic feedstocks, or synthetic feedstocks such as derived from kerogen-thereby improving FCC profitability.
It has been noted that this invention is agnostic to the equipment (323) used to distribute the oxidizing gas within the Regenerator, subject to certain conditions. The use of recycled flue gas/oxygen instead of air may impact the performance of conventional air grid designs. Typically, these designs consist of a plate grid, dome grids with skirt, a flat grid with skirt or a pipe grid. Air grids are designed to operate at temperatures up to 1,250° F. (675° C.), higher operating temperatures may see metal creep become an issue. As such, the design of conventional structures should be reviewed before implementation of this invention: stress analysis, non-linear finite element (NL-FEA) and heat transfer analysis may be required.
In another embodiment of this invention the oxygen concentration of the Recycle Gas/high-purity-oxygen mixture may be increased from 20 mol % to 35 mol %. Oxygen concentrations greater than 35 mol % are unlikely to be desirable as the resulting temperatures may compromise catalyst function. By increasing the oxygen concentration, Regenerator temperatures will rise; in turn so will the Riser temperature. High-severity conditions in the Riser may be beneficial for those operations where increased cracking to lighter products such as propylene is desired. Conversely, higher Riser temperatures and increased cracking of product may be undesired. One possible solution is the use of lower activity catalyst. However, this may place significant limits on both feedstock and product qualities. Typically, the Cat/Oil (catalyst to oil) ratio is used to manage the Riser catalyst temperature; reducing the Cat/Oil ratio reduces the reaction temperature in the Riser. However, this reduces conversion rate and yield of desired products. In these situations, a Catalyst Cooler (319) may be beneficial in enabling high temperature operation of the Regenerator without a need for significant Cat/Oil ratio changes or increased Riser temperatures.
In one embodiment a Catalyst Cooler is utilized to manage the catalyst temperature to the Riser. A Catalyst Cooler (319) is, essentially, a vertical heat exchanger. Those skilled in the art will recognize that like all aspects of FCC design, catalyst coolers come in various configurations;
As in existing art, it is necessary when using preferred embodiments of this invention to clean the Regenerator flue gas. Within the Regenerator, combustion gases will contain entrained catalyst particles. Without removal, these particulates will cause significant damage in downstream operations such as power recovery turbines and flue gas recycle compressors. Existing art employs gas cyclones (307 and 309) to separate the catalyst from the gas. As with cyclones in the Riser Reactor, consideration must be given to how changing, in this case, the flue gas composition may affect separation efficiency. When using a 1-to-1 replacement ratio of Recycle Gas to nitrogen operational impacts should be minimal as velocities should remain similar; density and viscosity differences may still have an operational impact. If the ratio is altered, changes in superficial velocities within the vessel and cyclones may change separation efficiency. Flue gas, largely cleaned of catalyst particles, exits the Regenerator (306) where it will undergo additional cleanup. It is not uncommon to utilize a third or even fourth stage separator. Further downstream processing may include electrostatic precipitation to remove the finest particles.
Typically, Regenerator flue gas will contain carbon monoxide due to incomplete combustion. Depending on the eventual disposition of the carbon monoxide stream, its presence may be beneficial. For example, commercial processes exist for the conversion of carbon monoxide to useful chemicals, such as methanol. In other cases, a CO Boiler (110) can be used to convert carbon monoxide to carbon dioxide by high temperature combustion. In existing art, air is used for combustion. A different embodiment would use Combustion Gas (135). The ratio of high purity oxygen to carbon monoxide in the combustion gas should be carefully managed at near stoichiometric ratio. A small excess would be maintained, as with the Regenerator to account for some residual oxidation of minor components. This will minimize excess oxygen and un-combusted carbon monoxide at the CO boiler outlet. As with other aspects of this invention, replacing the use of air and the nitrogen it contains will greatly simplify recovery of the carbon dioxide. Care should be taken in designing the CO Boiler with high ratios of high purity oxygen to Recycle Gas. If 100 mol % high-purity oxygen was used, temperatures could exceed 4,500° F. (2,500° C.). Using between 20 mol % and 35 mol % oxygen, more-typical temperatures may range from 1,200° F. (650° C.) to 1,800° F. (980° C.).
The Regenerator flue gas would, like other combustion gases in the KFCC process undergo further cleanup such as removal NOx, SOx, and water. The presence of these components can lead to corrosion and fouling of downstream equipment. The flue gas, having been processed through these stages will be at least 90 mol % carbon dioxide; combining with other source high concentration carbon dioxide waste gases to form the Recycle Gas stream.
The regenerated catalyst is returned to the Reactor Riser (318) by a standpipe (320), flowrate is controlled by a slide valve (325). Here, the catalyst is maintained in a fluidized state by a gas introduced by a dispersion ring (310). In conventional FCC art, air or steam is used as fluidizing gas. In one embodiment this would be replaced with a combination of air or steam and recycle gas in a ratio of between 0.0 (no air or steam) to 1.0 (all air or steam). As in other embodiments where air or steam have been substituted, consideration must be given to the effects of changes in physical properties for the associated device.
Energy recovery is common to existing FCC art, and it remains preferred for this invention. Hot flue gas exiting the Regenerator (or CO boiler, if employed) can be used to drive one or more power recovery turbines, generating electrical energy. This electrical energy can be used throughout the plant, but replacement of fossil fuel fired heaters with electrical resistance heaters may significantly improve efficiency and further reduce environmental impact. Additional energy may be recovered and used to generate steam for use elsewhere in the plant. In some embodiments, it may be beneficial to combust some of the cracked products. In these cases, combined heat and power (CHP) may be employed to maximize energy recovery. In some embodiments, Combustion Gas (135) may be used for combustion in the CO Boiler, CHP/Energy Recovery, Steam Generation (110) section rather than air. In this scenario the CHP flue gas would undergo similar cleanup (101) as the Regenerator and other combustion and waste gases and be combined with the Recycle Gas stream.
A key environmental concern for both existing and new process and energy technologies is reducing release of carbon dioxide. Carbon Capture, Utilization, and Storage (CCUS) is the umbrella term for techniques and technologies to achieve this goal. There is significant existing art that can teach suitable methods for recovering carbon dioxide from industrial process. The most common approach is DEA/MEA (amine) absorption/desorption, other approaches include cryogenic, supersonic, pressure-swing adsorption, calcium-looping, and membrane separations.
Selection of a suitable CCUS technology would typically be driven by economics; this invention is agnostic to the method used. However, those aware of the art involved will see that certain techniques may be preferable. Amine based absorption of carbon dioxide requires significant resources, water, energy, capital cost and MEA/DEA replacement and treatment costs. As the carbon dioxide concentration increases, these requirements and costs become uneconomical; 40 mol % carbon dioxide is typically considered the maximum economically viable concentration for amine-based recovery. Preferred embodiments of this invention will result in a carbon dioxide stream of over 90 mol % carbon dioxide concentration. At this point cryogenic, pressure-swing and other methods bring economic and environmental benefits.
By avoiding the use of air (with its nitrogen and other components) for combustion, the volume of gas sent to the carbon dioxide recovery unit (103) will be reduced by up to 80%. Thus, regardless of the selected technology, capital cost will be reduced as a smaller plant will be required than if nitrogen were present.
Recovered carbon dioxide can be used either on site in other processes, stored, sequestered, or sold as a valuable industrial gas. The availability of processes for the efficient conversion of carbon monoxide and carbon dioxide to methanol is particularly attractive. Methanol is an increasingly important feedstock, as it fits in well with the range of chemicals manufactured using the KFCC process. Certain recovery technologies can bring the final concentration of carbon dioxide to over 99 mol %. At this concentration it becomes attractive for further downstream processing and use in industrial applications including use as a chemical reactant, use in food and beverages, and for medical supply. In situations where the process is near oil extraction facilities, sequestration can be combined with enhanced oil recovery. Some level of on-site storage of the carbon dioxide would typically be maintained to provide a ready volume for startup, purging and other operations.
Variations of the invention provide a process of converting kerogen ore to multiple products, the process comprising:
Related variations provide a process of converting a hydrocarbon-containing feedstock to multiple products, the process comprising:
The hydrocarbon-containing feedstock may be selected from the group consisting of plastics, tires, road asphalt, asphalt tiles, asphalt paper, bio-sourced oils, recycled pyrolyzed products, recycled oils and fats, recycled hydrocarbon products, heavy oils, and combinations thereof.
In some embodiments, the vacuum column utilizes a motive gas comprising steam and at least 40 mol % carbon dioxide. In some embodiments, the vacuum column utilizes a motive gas comprising at least 80 mol % carbon dioxide. In various embodiments, the vacuum column utilizes a motive gas comprising about, or at least about 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99 mol % CO2, including any intervening range.
In some embodiments, the lift gas contains from about 80 mol % to about 100 mol % carbon dioxide. In certain embodiments, the lift gas contains from about 85 mol % to about 95 mol % carbon dioxide. In various embodiments, the lift gas contain about, or at least about 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, or 99 mol % CO2, including any intervening range.
In some embodiments, the coke-oxidation gas contains from about 55 mol % to about 85 mol % carbon dioxide. In certain embodiments, the coke-oxidation gas contains from about 60 mol % to about 80 mol % carbon dioxide. In various embodiments, the coke-oxidation gas contains about, or at least about, or at most about 50, 55, 60, 65, 70, 75, 80, 85, or 90 mol % CO2, including any intervening range, and any intervening sub-range in 1-mol % increments (e.g., 63-88 mol % CO2).
In various embodiments, the coke-oxidation gas contains about, or at least about, or at most about 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 25 mol % O2, including any intervening range.
In some embodiments, the heavy cycle oil from step (h) is recycled to the riser reactor. In some embodiments, the heavies (column bottoms) stream from step (h) is conveyed to the vacuum column.
The process is preferably continuous or semi-continuous.
Other variations of the invention provide a process of converting kerogen ore to multiple products, the process comprising:
Related variations provide a process of converting a hydrocarbon-containing feedstock to multiple products, the process comprising:
In processes using a common main column for steps (d) and (h), the hydrocarbon-containing feedstock may be selected from the group consisting of plastics, tires, road asphalt, asphalt tiles, asphalt paper, bio-sourced oils, recycled pyrolyzed products, recycled oils and fats, recycled hydrocarbon products, heavy oils, and combinations thereof.
In some embodiments employing a common main column for steps (d) and (h), the vacuum column utilizes a motive gas comprising steam and at least 40 mol % carbon dioxide. In some embodiments, the vacuum column utilizes a motive gas comprising at least 80 mol % carbon dioxide.
In some embodiments employing a common main column for steps (d) and (h), the lift gas contains from about 80 mol % to about 100 mol % carbon dioxide. In certain embodiments, the lift gas contains from about 85 mol % to about 95 mol % carbon dioxide. In various embodiments, the vacuum column utilizes a motive gas comprising about, or at least about 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99 mol % CO2, including any intervening range.
In some embodiments employing a common main column for steps (d) and (h), the coke-oxidation gas contains from about 55 mol % to about 85 mol % carbon dioxide. In certain embodiments, the coke-oxidation gas contains from about 60 mol % to about 80 mol % carbon dioxide. In various embodiments, the coke-oxidation gas contains about, or at least about, or at most about 50, 55, 60, 65, 70, 75, 80, 85, or 90 mol % CO2, including any intervening range, and any intervening sub-range in 1-mol % increments (e.g., 63-88 mol % CO2).
In various embodiments employing a common main column for steps (d) and (h), the coke-oxidation gas contains about, or at least about, or at most about 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 25 mol % O2, including any intervening range.
In some embodiments employing a common main column for steps (d) and (h), the pre-flash unit is present, and step (h) includes (1) conveying the reaction products through the pre-flash unit to generate an overhead vapor and a liquid bottoms, and (2) feeding the liquid bottoms to the main column to generate the kerogenate products.
In some embodiments employing a common main column for steps (d) and (h), the kerogenate products produced in step (h) comprise light ends, heavy cracked naphtha, light cycle oil, and/or heavy cycle oil. In certain embodiments, the kerogenate products produced in step (h) comprise all these streams-light ends, heavy cracked naphtha, light cycle oil, and heavy cycle oil.
In preferred embodiments employing a common main column for steps (d) and (h), the process is continuous or semi-continuous.
In this detailed description, reference has been made to multiple embodiments and to the accompanying drawings in which are shown by way of illustration specific exemplary embodiments of the invention. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that modifications to the various disclosed embodiments may be made by a skilled artisan.
Where methods and steps described above indicate certain events occurring in certain order, those of ordinary skill in the art will recognize that the ordering of certain steps may be modified and that such modifications are in accordance with the variations of the invention. Additionally, certain steps may be performed concurrently in a parallel process when possible, as well as performed sequentially.
All publications, patents, and patent applications cited in this specification are herein incorporated by reference in their entirety as if each publication, patent, or patent application were specifically and individually put forth herein.
The embodiments, variations, and figures described above should provide an indication of the utility and versatility of the present invention. Other embodiments that do not provide all of the features and advantages set forth herein may also be utilized, without departing from the spirit and scope of the present invention. Such modifications and variations are considered to be within the scope of the invention defined by the claims.
Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that the disclosure is not to be interpreted as limiting. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read this disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alterations and modifications as fall within the spirit and scope of the invention.
This patent application is a non-provisional application claiming priority to U.S. Provisional Patent App. No. 63/462,420, filed on Apr. 27, 2023, which is hereby incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 63462420 | Apr 2023 | US |
