Process for eliminating bottlenecks in FCC wet gas compressors and gas plants

Abstract

A method for completely or partially separating light gas components from a wet gas compressor suction stream and sending them directly to an untreated fuel gas header using a system in parallel with the existing wet gas compressor, in a fluid catalytic cracking (FCC) unit operating in petrochemical mode where dry gas and LPG production increases and a bottleneck occurs in the product flow, wherein the parallel system includes an auxiliary compressor and a membrane separation system.

Description

Detailed Description of the Invention

[0001] [Cross - Reference to Related Applications] This application claims priority to U.S. Provisional Patent Application No. 63 / 508,456, filed on 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 fluid catalytic cracking (FCC) unit, and more particularly, to systems and methods for processing hydrocarbons in an FCC unit operated in petrochemical mode, as opposed to when operated in gasoline / diesel maximization mode. [Background Art]

[0003] Fluid catalytic cracking units (FCC) have long been a major producer of high - octane gasoline at the core of refineries. However, the global demand for automotive fuels is on a decreasing trend, while the demand for petrochemical products is continuously increasing. Existing FCC units designed to maximize automotive fuels (i.e., gasoline and light cycle oil) can be operated to maximize petrochemical feedstocks (e.g., propylene and ethylene) through operational adjustments, minor technical upgrades, and / or catalyst reformulation.

[0004] FCC units designed to maximize gasoline / diesel typically operate the riser in the range of about 480°C to 520°C. Under these conditions, the riser outlet temperature is low, and the production of dry gas and liquefied petroleum gas (LPG) is low. The product recovery system (wet gas compressor and gas plant) is designed for these product requirements.

[0005] Existing FCC units, while originally designed to maximize fuel production, can be operated in petrochemical mode (i.e., maximizing ethylene and propylene) by increasing the operating severity. This requires increasing the riser outlet temperature (approximately 550°C to 650°C in one non-limiting example), using shape-selective zeolite (e.g., ZSM-5) in the catalyst formulation (0% to 100%), and hardware modifications. As a result, the production of dry gas and LPG from the FCC reactor increases significantly. However, existing wet gas compressor and gas concentration section equipment may not be able to cope with such increased hydrocarbon loads, creating a bottleneck.

[0006] It is desirable to operate existing FCC units in petrochemical mode while avoiding such hydrocarbon load bottlenecks with minimal capital investment. [Overview of the prefecture]

[0007] In one non-limiting embodiment provided, a fluid catalytic cracking (FCC) unit is provided, having a wet gas compressor (WGC) including suction, a C3-C4 / naphtha fractionation unit, and a gas plant section including emissions supplied to a fuel gas system. The FCC unit is configured in parallel with the WGC and features an auxiliary compressor including an FCC slipstream from the WGC suction and a membrane system receiving the compressed FCC wet gas from the auxiliary compressor, the membrane system including a separated emissions stream of relatively light hydrocarbon components fluidly communicating with the C3-C4 / naphtha fractionation unit and a separated emissions stream of relatively heavy hydrocarbon components fluidly communicating with an untreated fuel gas system.

[0008] Furthermore, a method for operating an FCC unit in petrochemical mode is provided. This method includes supplying dry gas and LPG from an FCC rectification column to a WGC, extracting a slipstream from the supply to the WGC and supplying it to an auxiliary compressor and a membrane separation system, the auxiliary compressor and membrane separation system being in parallel with the WGC, compressing the slipstream in the auxiliary compressor to produce a compressed stream, supplying the compressed stream to a membrane system including a membrane, separating the compressed stream through the membrane into a stream of emissions of relatively light hydrocarbon components and a stream of emissions of relatively heavy hydrocarbon components, transporting the stream of emissions of relatively light hydrocarbon components to a C3-C4 / naphtha fractionation unit, and transporting the stream of emissions of relatively heavy hydrocarbon components to an untreated fuel gas system and supplying it from there to a treatment section. [Brief explanation of the drawing]

[0009] [Figure 1] This is a non-limiting schematic block flow diagram of a system and method for resolving bottlenecks between FCC wet gas compressors and gas plants when operating in petrochemical mode. [Modes for carrying out the invention]

[0010] The drawings are schematic diagrams, and it should be understood that the present invention is not limited to the designs, proportions, or specific equipment shown in the drawings. Currently, most refineries switching to petrochemical mode are installing parallel gas plants, modifying existing wet gas compressors, and / or installing larger wet gas compressors in response to the increased hydrocarbon load from the reactors. However, all of these approaches require considerable capital investment.

[0011] When operating an FCC wet gas compressor and gas plant in petrochemical mode to maximize ethylene and propylene production, it has been found that increasing the amount of dry gas and LPG produced can be resolved by completely or partially separating the light gas components from the wet gas compressor (WGC) suction stream and sending them directly to the untreated fuel gas header, thereby eliminating, avoiding, or otherwise resolving the bottleneck. This can be achieved by providing an auxiliary compressor and membrane system in parallel with the WGC.

[0012] Installing parallel gas plants and / or large wet gas compressors to handle further volumetric flow rates of LPG and dry gas is highly capital-intensive. The methods and embodiments of the systems described herein help existing FCC units adapt to anticipated market changes, operate under extremely harsh conditions, and maximize yields of propylene and ethylene with minimal capital investment. In other words, an FCC reactor can be operated in petrochemical mode to produce further C3 / C4 and naphtha, compared to operating the FCC unit in gasoline / diesel maximization mode, even without the presence of a parallel gas plant.

[0013] More specifically, the present invention will be described with reference to Figure 1 in one non-limiting embodiment. Here, 10 refers to the entire fluid catalytic cracking (FCC) unit, and the FCC main rectification column 12 receives hydrocarbon feed 14 from the FCC reactor. The FCC main rectification column 12 generates main rectification column overhead gas 16, which is condensed in the main rectification column overhead air condenser 18. The condensed gas 20 is sent to the main rectification column overhead trim condenser 22, then to the overhead (O / H) receiver 24, and its product is transported to the KO drum (WGC suction knockout drum) 26. This front end indicates that there is no “free water” in the gas stream 28 and before the stream branch 30 within the system 10.

[0014] Conventionally, the gas 28 in the FCC unit 10 is sent to a wet gas compressor (WGC) 32, which includes suction, where the compressed gas 34 is supplied to a high-pressure separator air condenser 36 and a high-pressure separator trim condenser 38 before condensation, and the compressed gas 40 is separated in a high-pressure separator drum 42. The C3 / C4 LPG 44 separated in the separator drum is sent to a C3-C4 / naphtha fractionation unit 46. The separated hydrocarbons 48 are sent to a gas plant section 50 and then to a fuel gas system 52.

[0015] The new system and method include an auxiliary compressor 54 and a membrane system 60 installed in parallel with the existing WGC32.

[0016] This new parallel system takes in a slipstream 56 from the WGC suction 28 at branch 30. In one non-limiting embodiment, the slipstream 56 is about 25 vol% (in the non-limiting example) independently of about 20% of the total volume of the WGC suction 28. In another non-limiting embodiment, the slipstream varies from about 10% to about 50% independently of the total volume of the WGC, based on technical and economic constraints. Where used herein with respect to range, the term “independently” means that any endpoint can be used with any other endpoint to obtain a suitable alternative range. For example, the slipstream may be suitable from about 10% to about 20 vol% of the total volume of the WGC suction 28.

[0017] The slipstream 56 is compressed in a small-volume auxiliary compressor 54. The auxiliary compressor 54 is simply relatively smaller than the WGC 32, and its volume is about 25% of the volume of the existing wet gas compressor. The compressed gas 58 is sent to a membrane system 60, where light hydrocarbon components (permeate) 64 are selectively separated from the FCC wet gas stream 58. The separated permeate 64 is sent to the FCC gas plant 50 and / or the untreated fuel gas system 66. Emissions from the untreated fuel gas system 66 are then sent to an existing fuel gas treatment section 68 and may then be sent to the aforementioned fuel gas system 52.

[0018] Suitable membranes for use in the membrane system 60 include, but are not limited to, hydrocarbon selective membranes. Other membrane types cannot achieve the desired stream separation 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 hybrid matrix membranes. Suitable glassy polymers include, but are not limited to, polysulfone, polyimide, polyimide / polyaramid, polyimide / polysulfone, cellulose acetate, ethylcellulose, poly(phenylene oxide), perfluoropolymer, 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, plate and frame, and combinations thereof. Manufacturers of these films include, but are not limited to, Air Products, Air Liquide, Ube, Parker-Hannifin, Evonik, Praxair, Grasys, UOP, Kvaerner, WRGrace, MTR, Fuji Film, Schlumberger (Natco), Aquila, ABB / MTR, Generon (MG), and GKSS.

[0019] The C3-C4 LPG and naphtha components (unpermeated) 62 separated from the membrane can bypass the gas concentration section and be sent directly to the existing butane detane system (i.e., the C3-C4 / naphtha fractionation unit 46). Therefore, further drying of the gas from the FCC reactor and the production of C3 / C4 LPG can be handled by the existing system without installing a parallel gas plant, thus avoiding significant capital costs while eliminating the bottleneck in the FCC unit when operating in petrochemical mode. In other words, the bottleneck can be eliminated even without a parallel gas plant.

[0020] In this example, the C3-C4 / naphtha fractionation unit 46 may include a high-temperature, high-pressure separator that separates condensable gases from the upper part of the vessel and heavier components such as naphtha from the lower part. The lower product from the separator can pass through a series of columns (stripper, debutane unit, naphtha splitter) to separate C3, C4, C3-C4 mixtures and various naphtha cut products. The lighter exhaust gas (C3-) is sent back to the gas concentration section and finally to the fuel gas header. Thus, the fractionation unit 46 may have one or more emissions 70.

[0021] In the above specification, the present invention is described with reference to specific embodiments thereof. However, this specification should be considered illustrative rather than restrictive. For example, compressors, reactors, membranes, exchangers, furnaces, units, other equipment, process streams, processes, reactants, catalysts, products, and operating conditions are within the scope of the claimed or disclosed parameters, but are also expected to be within the scope of the invention even if they are not specifically identified or tested in particular examples.

[0022] The present invention can be implemented even if no undisclosed elements are present. In addition, the present invention may appropriately include, be composed of, or essentially be composed of the disclosed elements. For example, a fluid catalytic cracking (FCC) unit may be provided, comprising, essentially comprising, or consisting of, a wet gas compressor (WGC) including suction, a C3-C4 / naphtha fractionation unit, and a gas plant section including emissions supplied to a fuel gas system. The FCC unit features a membrane system, comprising, essentially comprising, or consisting of, an auxiliary compressor in parallel with the WGC, including an FCC slipstream from the WGC suction, and a membrane system receiving the compressed FCC wet gas from the auxiliary compressor, comprising a separated emissions stream of relatively light hydrocarbon components fluidly communicating with the C3-C4 / naphtha fractionation unit and a separated emissions stream of relatively heavy hydrocarbon components fluidly communicating with an untreated fuel gas system.

[0023] Furthermore, a method for operating a fluid catalytic cracking (FCC) unit in petrochemical mode may be provided. This method comprises, or comprises, essentially comprising, the following: supplying dry gas and LPG from an FCC rectification column to a wet gas compressor (WGC); extracting a slipstream from the supply to the WGC and supplying it to an auxiliary compressor and a membrane separation system, the auxiliary compressor and membrane separation system being in parallel with the WGC; compressing the slipstream in the auxiliary compressor to produce a compressed stream; supplying the compressed stream to a membrane system including a membrane; separating the compressed stream into an emissions stream of relatively light hydrocarbon components and an emissions stream of relatively heavy hydrocarbon components; transporting the emissions stream of relatively light hydrocarbon components to a C3-C4 / naphtha fractionation unit; and transporting the emissions stream of relatively heavy hydrocarbon components to an untreated fuel gas system, from which it is supplied to a treatment section.

[0024] The terms "comprising" and "include" when used throughout the claims shall be construed to mean "comprising but not limited to" and "include but not limited to", respectively.

[0025] As used herein, the term "substantially" shall mean "being mostly but not completely the specified content".

[0026] As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise.

[0027] As used herein, the term "about" with respect to a given parameter shall include the recited value and have the meaning determined by the context (e.g., including the degree of error associated with the measurement of a given parameter).

[0028] As used herein, the term "and / or" shall include any and all combinations of one or more of the associated listed items.

Claims

1. A fluid catalytic cracking (FCC) unit, A wet gas compressor (WGC) including suction, C3-C4 / Naphtha fractionation unit, Includes a gas plant section containing emissions supplied to a fuel gas system, In parallel with the aforementioned WGC, An auxiliary compressor including an FCC slipstream from the WGC suction, A membrane system that receives FCC-moistened gas compressed from the auxiliary compressor, wherein the membrane system is A stream of separated, relatively light hydrocarbon components is fluidly connected to the C3-C4 / naphtha fractionation unit, A fluid catalytic cracking (FCC) unit comprising a membrane system containing a separate, relatively heavy hydrocarbon component emissions stream that fluidly communicates with an untreated fuel gas system.

2. The FCC unit according to claim 1, wherein the FCC slipstream is at least 10 vol% of the WGC suction.

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

4. The FCC unit according to claim 1, wherein the separated, relatively light hydrocarbon component exhaust stream is then fluidly connected to a debutane unit.

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

6. A method for operating a fluid catalytic cracking (FCC) unit in petrochemical mode, wherein the method is: The supply of dry gas and LPG from the FCC rectification column to the wet gas compressor (WGC), The process involves extracting a slipstream from the supply to the WGC and supplying it to the auxiliary compressor and the membrane separation system, wherein the auxiliary compressor and the membrane separation system are in parallel with the WGC. The slipstream is compressed within the auxiliary compressor to generate a compressed stream, The compressed stream is supplied to a membrane system including a membrane, The compressed stream is separated through the membrane into a stream of emissions containing relatively light hydrocarbon components and a stream of emissions containing relatively heavy hydrocarbon components. The aforementioned stream of relatively light hydrocarbon components is transported to the C3-C4 / naphtha fractionation unit, A method comprising transporting the aforementioned stream of relatively heavy hydrocarbon components to an untreated fuel gas system and supplying it from there to a treatment section.

7. The method according to claim 6, wherein the FCC slipstream is at least 10 vol% of the supply to the WGC.

8. The method according to claim 6, wherein the separated relatively light hydrocarbon component includes C3, C4, and naphtha.

9. The method according to claim 6, wherein the separated stream of relatively light hydrocarbon components is supplied to a butane removal unit.

10. The method according to claim 6, further comprising operating the FCC reactor in petrochemical mode, wherein, compared to operating the FCC reactor in gasoline / diesel maximum mode, more C3-C4 and naphtha are produced from the FCC rectification column, and the FCC unit does not have a parallel gas plant.

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