Method for eliminating FCC moisture compressor and gas plant bottlenecks

Abstract

In a fluidized catalytic cracker (FCC) unit operating in petrochemical mode, it has increased dry gas and LPG production, which creates a bottleneck in the product stream, a method is provided for completely or partially separating a light gas component from a moisture compressor suction port stream and directing it directly to an untreated fuel gas header using a system in parallel with an existing moisture compressor that includes an auxiliary compressor and a membrane separation system.

Description

Cross-reference to related applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 508,456, filed June 15, 2023, which is incorporated herein by reference. Technical Field

[0002] The present invention relates to systems and methods for processing hydrocarbons in a fluidized catalytic cracker (FCC) unit, and more specifically, to systems and methods for processing hydrocarbons in an FCC unit that operates in a petrochemical mode rather than a gasoline / diesel-maximizing mode. Background Technology

[0003] Fluid catalytic cracking (FCC) units have long been the primary production units for high-octane gasoline at the heart of refineries. However, with the continued growth in demand for petrochemical products, global demand for engine fuels is declining. Existing FCC units designed to maximize engine fuel (i.e., gasoline and light cycle oil) are operable to maximize petrochemical feedstocks (such as propylene and ethylene) through operational adjustments, minor technology upgrades, and / or catalyst formulation reformulation.

[0004] FCC units designed to maximize gasoline / diesel output typically operate risers in the range of approximately 480°C–520°C. Under these conditions, riser outlet temperatures are low, resulting in low dry gas and LPG production. Product recovery systems (wet gas compressors and gas units) are designed to address these product requirements.

[0005] By increasing operational severity, existing FCC units, originally designed to maximize fuel production, can be operated in petrochemical mode (even with ethylene and propylene maximized). This requires increasing the riser outlet temperature (in one non-limiting example, from approximately 550°C to 650°C), using shape-selective zeolites such as ZSM-5 (0%–100%) in the catalyst formulation, and hardware improvements. This results in a significant increase in dry gas and LPG production from the FCC reactor. However, existing wet gas compressors and gas enrichment section equipment may not be able to handle such increased hydrocarbon loads, thus creating bottlenecks.

[0006] The goal is to operate existing FCC units in a petrochemical manner while avoiding such bottlenecks in hydrocarbon loads with minimal capital investment. Summary of the Invention

[0007] In one non-limiting embodiment, a fluidized catalytic cracker (FCC) unit is provided, comprising a wet gas compressor (WGC) including an inlet; a C3-C4 / naphtha fractionation unit; and a gas section including the effluent from a feed fuel gas system. The FCC unit is characterized by, in parallel with the WGC, an auxiliary compressor including an FCC bypass feed stream from the WGC inlet; and a membrane system receiving compressed FCC wet gas from the auxiliary compressor, wherein the membrane system includes a separated relatively lighter hydrocarbon component effluent stream in fluid communication with the C3-C4 / naphtha fractionation unit and a separated relatively heavier hydrocarbon component effluent stream in fluid communication with the untreated fuel gas system.

[0008] Furthermore, a method for operating an FCC unit in petrochemical mode is provided, wherein the method includes: feeding dry gas and LPG from an FCC fractionator to a WGC; extracting a bypass stream from the feed to the WGC and supplying it to an auxiliary compressor and membrane separation system connected in parallel with the WGC; compressing the bypass stream in the auxiliary compressor to produce a compressed stream; feeding the compressed stream to a membrane system including a membrane; separating the compressed stream via the membrane into a relatively lighter hydrocarbon component effluent stream and a relatively heavier hydrocarbon component effluent stream; directing the relatively lighter hydrocarbon component effluent stream to a C3-C4 / naphtha fractionation unit; and directing the relatively heavier hydrocarbon component effluent stream to an untreated fuel gas system, which in turn feeds the processing section. Attached Figure Description

[0009] Figure 1 This is a non-limiting schematic block flowchart of systems and methods for eliminating bottlenecks when FCC wet gas compressors and gas units operate in petrochemical mode.

[0010] It should be understood that the accompanying drawings are illustrative and the invention is not limited to the designs, scales, or specific devices shown in the drawings. Detailed Implementation

[0011] Currently, most refineries switching to petrochemical operation are installing parallel gas units, retrofitting existing wet gas compressors, and / or installing larger wet gas compressors to accommodate increased hydrocarbon loads from reactors. However, all of these methods require significant capital investment.

[0012] It has been found that when FCC wet gas compressors and gas units operate in petrochemical mode to maximize ethylene and propylene production, the resulting increase in dry gas and LPG can be eliminated, avoided, or resolved by completely or partially separating the light gas components from the wet gas compressor (WGC) inlet feed stream and routing them directly to the untreated fuel gas manifold. This can be achieved by providing an auxiliary compressor and membrane system in parallel with the WGC.

[0013] Installing parallel gas units and / or larger wet gas compressors to handle additional LPG and dry gas volumetric flow rates is highly capital-intensive. The implementation of the methods and systems described herein will help existing FCC units adapt to anticipated market changes and operate under harsh conditions, maximizing propylene and ethylene yields with minimal capital investment. In other words, compared to FCC units operating in a gasoline / diesel-maximized mode, FCC reactors can operate in a petrochemical mode to produce additional C3 / C4 and naphtha, but without the parallel gas units.

[0014] More specifically, the invention is referenced in a non-limiting embodiment. Figure 1 The description refers to the entire fluidized catalytic cracker (FCC) unit, where the FCC main fractionator 12 receives hydrocarbon feed 14 from the FCC reactor. The FCC main fractionator 12 produces a main fractionator top gas 16, which is condensed in the main fractionator top air condenser 18. The condensed gas 20 is directed to the main fractionator top distillate micro-condenser 22 and subsequently to the top (O / H) receiver 24, where the product is fed to the KO tank (WGC inlet separator) 26. This front-end indicates the absence of "free water" in the gas stream 28 and before the stream split point 30 in system 10.

[0015] Conventionally, gas 28 in FCC unit 10 is directed to a wet gas compressor (WGC) 32, which includes an inlet that feeds compressed gas 34 to a high-pressure separator air condenser 36 and a high-pressure separator fine-tuning condenser 38. The condensed compressed gas 40 is then separated at a high-pressure separator tank 42. The C3 / C4 LPG 44 separated in the separator tank enters the C3-C4 / naphtha fractionation unit 46. The separated hydrocarbons 48 are directed to a gas unit section 50 and then to a fuel gas system 52.

[0016] The new system and method include an auxiliary compressor 54 and a membrane system 60 installed in parallel with the existing WGC 32.

[0017] The new parallel system draws a bypass flow 56 from the WGC inlet 28 at the branch point 30. In one non-limiting embodiment, the bypass flow 56 is approximately 20% to approximately 25% of the total volume of the WGC inlet 28 (in a non-limiting example). In another non-limiting embodiment, the bypass flow varies independently from approximately 10% to approximately 50% of the total volume of the WGC, based on technical and economic constraints. As used herein with respect to range, the term "independently" means that any endpoint can be used with any other endpoint to give a suitable alternative range. For example, the bypass flow may suitably be approximately 10% to approximately 20% of the total volume of the WGC inlet 28.

[0018] The bypass stream 56 is compressed in a small-capacity auxiliary compressor 54. The auxiliary compressor 54 is simply smaller than the WGC 32, with a volumetric capacity approximately 25% of the existing wet gas compressor capacity. The compressed gas 58 is routed to a membrane system 60, which selectively separates light hydrocarbon components (permeate) 64 from the FCC wet gas stream 58. The separated permeate 64 is routed to the FCC gas unit 50 and / or the untreated fuel gas system 66. The effluent from the untreated fuel gas system 66 can then be sent to the existing fuel gas treatment section 68, and then to the aforementioned fuel gas system 52.

[0019] Non-limiting examples of suitable membranes for use in membrane system 60 include, but are not limited to, hydrocarbon-selective membranes. Other membrane types do not provide the desired separation of the feed stream required by the present invention. Suitable hydrocarbon-selective membranes are commercially available, and suitable examples include, but are not limited to, glassy polymers, rubbery polymers, and mixed matrix membranes. Suitable glassy polymers include, but are not limited to, polysulfone, polyimide, polyimide / polyaramid, polyimide / polysulfone, cellulose acetate, ethyl cellulose, poly(phenylene ether), perfluoropolymers, tetrabromopolycarbonate, and combinations thereof. Suitable rubbery polymers include, but are not limited to, poly(ether-β-amide) copolymers, polysiloxanes, and combinations thereof. Suitable membrane module types include, but are not limited to, hollow fiber, spiral wound, plate, and frame, and combinations thereof. Manufacturers of these films include, but are not limited to, Air Products, AirLiquide, Ube, Parker-Hannifin, Evonik, Praxair, Grasys, UOP, Kvaerner, WRGrace, MTR, Fuji Film, Schlumberger (Natco), Aquila, ABB / MTR, Generon (MG), and GKSS.

[0020] The C3-C4 LPG and naphtha components (permeate) 62 separated from the membrane can bypass the gas concentration section and be directly routed to the existing butanizer system, namely the C3-C4 / naphtha fractionation unit 46. Therefore, the additional dry gas and C3 / C4 LPG generated from the FCC reactor can be processed in the existing system without the need for a parallel gas unit, resulting in significant capital cost savings and eliminating the FCC unit bottleneck when operating in petrochemical mode. In other words, bottleneck elimination is achieved without a parallel gas unit.

[0021] In this example, the C3-C4 / naphtha fractionation unit 46 may include a hot high-pressure separator to separate condensable gas and naphtha from the top of the vessel and heavier components from the bottom. The bottom product from the separator may pass through a series of towers—stripping towers, butanizers, and naphtha separators—to separate C3, C4, C3-C4 mixtures, and different naphtha fractions. The lighter exhaust gas (C3-) is returned to the gas connection section and ultimately to the fuel gas header. Therefore, the fractionation unit 46 may have one or more effluents 70.

[0022] In the foregoing description, the invention has been described with reference to specific embodiments thereof. However, this description should be considered illustrative rather than restrictive. For example, compressors, reactors, membranes, exchangers, furnaces, units, other devices, process streams, processes, reactants, catalysts, products, and operating conditions that fall within the claimed or disclosed parameters but have not been specifically identified or attempted in particular instances are contemplated within the scope of the invention.

[0023] This invention can be practiced without any undisclosed elements. Furthermore, the invention may suitably include, consist of, or consist substantially of the disclosed elements. For example, a fluidized catalytic cracker (FCC) unit may be provided, comprising, substantially consisting of, or consisting of: a wet gas compressor (WGC) including an intake; a C3-C4 / naphtha fractionation unit and a gas section including the effluent from a feed fuel gas system, wherein the FCC unit is characterized by, in parallel with the WGC, an auxiliary compressor containing an FCC bypass feed stream from the WGC intake; and a membrane system receiving compressed FCC wet gas from the auxiliary compressor, wherein the membrane system comprises, substantially consisting of, or consists of: a separated relatively lighter hydrocarbon component effluent stream in fluid communication with the C3-C4 / naphtha fractionation unit and a separated relatively heavier hydrocarbon component effluent stream in fluid communication with an untreated fuel gas system.

[0024] Alternatively, a method for operating a fluidized catalytic cracker (FCC) unit in a petrochemical mode can be provided, wherein the method comprises, substantially comprises, or comprises the following steps: feeding dry gas and LPG from an FCC fractionator to a wet gas compressor (WGC); extracting a bypass stream from the feed to the WGC and supplying it to an auxiliary compressor and membrane separation system connected in parallel with the WGC; compressing the bypass stream in the auxiliary compressor to produce a compressed stream; feeding the compressed stream to a membrane system including a membrane; separating the compressed stream into a relatively lighter hydrocarbon component effluent stream and a relatively heavier hydrocarbon component effluent stream; conveying the relatively lighter hydrocarbon component effluent stream to a C3-C4 / naphtha fractionation unit; and directing the relatively heavier hydrocarbon component effluent stream to an untreated fuel gas system, which in turn feeds the processing section.

[0025] The terms “comprising” and “comprises” used throughout the claims should be interpreted as “including but not limited to” and “including but not limited to”, respectively.

[0026] As used in this article, the word “basically” should mean “mostly, but not entirely, of the specified terms.”

[0027] As used herein, unless the context clearly indicates otherwise, the singular forms “a”, “an”, and “the” are intended to also include the plural forms.

[0028] As used herein, the term “about” with respect to a given parameter includes the stated value and has the meaning prescribed by the context (e.g., it includes the degree of error associated with the measurement of the given parameter).

[0029] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

Claims

1. A fluidized catalytic cracker (FCC) unit, comprising: A wet gas compressor (WGC) includes an intake port; C3-C4 / Naphtha Fractionation Unit; as well as The gas processing section includes the effluent fed into the fuel gas system; Its characteristic is that, connected in parallel with the WGC: The auxiliary compressor includes an FCC bypass feed stream from the WGC inlet; and A membrane system that receives compressed FCC moisture from the auxiliary compressor, the membrane system comprising: The relatively lighter hydrocarbon components separated and discharged from the feed stream are in fluid communication with the C3-C4 / naphtha fractionation unit; and The relatively heavier hydrocarbon components, separated from the untreated fuel gas system, flow out of the material stream.

2. The FCC unit according to claim 1, wherein the FCC bypass flow is at least 10% of the volume of the WGC inlet.

3. The FCC unit according to claim 1, wherein the separated relatively light hydrocarbon components comprise C3, C4 and naphtha.

4. The FCC unit according to claim 1, wherein the separated relatively lighter hydrocarbon component effluent stream is subsequently in fluid communication with a butanizer.

5. The FCC unit of claim 1, further comprising an FCC reactor operating in petrochemical mode that produces additional C3-C4 and naphtha compared to an FCC reactor operating in gasoline / diesel maximization mode, and wherein the FCC unit does not have a parallel gas device.

6. A method for operating a fluidized catalytic cracker (FCC) unit in petrochemical mode, the method comprising: Dry gas and LPG from the FCC fractionator are fed into the wet gas compressor (WGC); A bypass flow is drawn from the feed of the WGC and supplied to an auxiliary compressor and membrane separation system connected in parallel with the WGC; The bypass feed stream is compressed in the auxiliary compressor to produce a compressed feed stream; The compressed feed stream is fed into a membrane system including a membrane; The compressed feed stream is separated into a relatively lighter hydrocarbon component outflow stream and a relatively heavier hydrocarbon component outflow stream via the membrane. The relatively lighter hydrocarbon component effluent is fed to the C3-C4 / naphtha fractionation unit; as well as The relatively heavy hydrocarbon component outflow is fed to an untreated fuel gas system, which in turn feeds the treatment section.

7. The method of claim 6, wherein the FCC bypass flow is at least 10% of the feed volume of the WGC.

8. The method of claim 6, wherein the separated relatively light hydrocarbon component comprises C3, C4 and naphtha.

9. The method of claim 6, wherein the separated relatively lighter hydrocarbon component effluent is fed into a butanizer.

10. The method of claim 6, further comprising operating the FCC reactor in a petrochemical mode, wherein the operation produces additional C3-C4 and naphtha from the FCC fractionator compared to operating the FCC reactor in a gasoline / diesel maximization mode, and wherein the FCC unit does not have a parallel gas device.

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