An apparatus and method for integrated light hydrocarbon separation

Abstract

The application belongs to the field of olefin production device, and discloses a device and method for integrated light hydrocarbon separation, which comprises a catalytic cracking system, a steam cracking system and a shared system; the catalytic cracking system comprises a catalytic cracking unit, a fractionation unit, a compression and pre-separation unit and a catalytic thermal separation unit connected in sequence; the steam cracking system comprises a steam cracking unit, a quenching unit, a compression and pre-ethane removal unit and a steam thermal separation unit connected in sequence; the shared system comprises a carbon one cold separation unit and an ethylene rectification unit connected in sequence; the carbon two outlet of the compression and pre-separation unit and the carbon two outlet of the compression and pre-ethane removal unit are connected to the carbon one cold separation unit inlet. The technical scheme reduces the number of equipment, reduces the land occupation, saves the investment, reduces the energy consumption, and improves the carbon two recovery rate of catalytic cracking. Meanwhile, the products with large property difference are not mixed, the separation and use of high value-added components with relatively concentrated concentration are not affected, and the economic benefits are maximized.

Description

Technical Field

[0001] This invention belongs to the field of olefin production equipment, and more specifically, relates to an integrated light hydrocarbon separation device and method. Background Technology

[0002] Currently, my country faces overcapacity in oil refining and oil product production, while traditional refineries are also impacted by new energy sources. Against the backdrop of "carbon peaking" and "carbon neutrality," the transformation of refineries towards chemical processing is an inevitable path for sustainable development. The integration of refining and chemical processing requires not only addressing the primary contradictions and resolving them, but also paying close attention to the specific characteristics of these contradictions to achieve optimal process configuration.

[0003] There are currently two known methods for integrating and separating catalytic cracking and steam cracking.

[0004] One type is a catalytic cracking unit that uses traditional oil absorption and separation processes such as fractionation, absorption stabilization, dual desulfurization, and gas separation to separate its various heavy products of C3 and above. The light components of C2 and below are produced as a mixture, i.e., catalytic dry gas. The specific process flow is as follows: Figure 1 As shown. Early catalytic dry gas was used as refinery fuel gas, with very low utilization value. Later, it was effectively utilized using the ethylene-to-ethylbenzene / styrene technology, but its application was limited. Subsequently, after impurity removal and C2 enrichment processes such as pressure swing adsorption and shallow-cooled oil absorption, the catalytic dry gas was sent to ethylene units (i.e., steam cracking units) for recovery to increase the production of polymerization-grade ethylene. However, in the oil absorption separation of catalytic dry gas and the C2 enrichment processes in various processes, the C2 component is generally lost by 5-15%, and the recovery rate needs to be improved. This fusion separation method, tentatively called fusion, has a very limited actual degree of fusion.

[0005] Another approach is in heavy oil catalytic thermal cracking (CPP) and naphtha catalytic cracking (such as K-COT) units, where the "reaction-regeneration + fractionation" process of catalytic cracking is separated from the "cracking unit + quench zone" of steam cracking. From the compression of rich gas / cracking gas, the separation system is fully integrated, forming an integrated "two-end-one-tail" structure. The specific process flow is as follows: Figure 2 As shown.

[0006] This fusion separation method achieves the highest level of integration, completely mixing and separating pyrolysis gasoline and its lighter components, resulting in the greatest reduction in the number of equipment units, plant space, and investment. However, it has the following drawbacks: First, catalytic cracking products contain more impurities and very little alkyne / diolefins, while steam cracking products generally contain fewer impurities and more alkyne / diolefins. Mixing them increases the amount of impurities that need to be processed and the required equipment. Second, the compositions of catalytic C4 and steam cracking C4, and catalytic gasoline and steam cracking gasoline, differ significantly. The latter contains a large amount of dienes / alkynes, and mixing them severely affects the fate of these two steam cracking products, reducing their utilization value.

[0007] Therefore, this fusion method is only suitable for situations where steam cracking is used as a supplement, the cracking feedstock is relatively light, there are few heavy products of C3 and above, and all C4 products and gasoline products are used as catalytic products. Summary of the Invention

[0008] To address the problems existing in the prior art, the purpose of this invention is to provide a novel integrated separation solution. This solution aims to maximize the integration and separation of common products, improve product recovery rate, and reduce investment; while also separating products with different properties separately so as not to interfere with each other, thereby maximizing economic benefits.

[0009] To achieve the above objectives, the first aspect of the present invention provides an integrated light hydrocarbon separation apparatus, which includes: a catalytic cracking system, a steam cracking system, and a shared system;

[0010] The catalytic cracking system includes a catalytic cracking unit, a fractionation unit, a compression and pre-fractionation unit, and a catalytic thermal separation unit connected in sequence.

[0011] The steam cracking system includes a steam cracking unit, a quenching unit, a compression and pre-ethane removal unit, and a steam thermal separation unit connected in sequence.

[0012] The shared system includes a carbon-1 cold separation unit and an ethylene distillation unit connected in sequence.

[0013] The C2 outlet of the compression and pre-separation unit and the C2 outlet of the compression and pre-ethane removal unit are both connected to the inlet of the C1 cold separation unit.

[0014] A second aspect of the present invention provides an integrated light hydrocarbon separation method, the method comprising the following steps:

[0015] (1) Catalytic cracking feedstock oil is catalytically cracked to obtain reaction oil gas, the reaction oil gas is fractionated to obtain light hydrocarbon components, the light components are compressed, impurities are removed and pre-separated to obtain light component A with C2 and below and heavy component A with C3 and above.

[0016] (2) The C3 and above heavy component A is sent to the catalytic thermal separation unit for separation;

[0017] (3) Steam cracking feedstock oil is steam cracked to obtain cracked gas, and the cracked gas is rapidly cooled, compressed, impurity removed and pre-ethane separation to obtain light components B with C2 and below and heavy components B with C3 and above.

[0018] (4) The C3 and above heavy component B is sent to the steam thermal separation unit for separation;

[0019] (5) The light components A and B of C2 and below are combined and sent to the C1 cold separation unit for separation to obtain the C2 fraction, which is then sent to the ethylene distillation unit for further separation.

[0020] The effects of this invention are:

[0021] (1) In this invention, the light components of C2 and below separated are integrated and separated in a unified manner, including the pre-cooling and C1 cooling separation zone and the ethylene distillation unit. The original propylene refrigeration system and ethylene refrigeration system of the ethylene plant are shared by the two plants, as well as the waste heat, steam, circulating cooling water and other utilities. In this invention, the heavy components of C3 and above obtained by catalytic cracking and steam cracking are still separated independently, and the product quality remains unchanged.

[0022] (2) In the present invention, the catalytic cracking and steam cracking products with different properties (heavy products such as C4 and gasoline) are separated independently and do not mix with each other, so as to facilitate the direct separation and recycling of high-value-added components with concentrated concentrations in each product, thereby maximizing economic benefits.

[0023] (3) This invention optimizes and adjusts the treatment method of light hydrocarbon components in catalytic cracking, and appropriately integrates the separation process of catalytic cracking and steam cracking. Light components such as hydrogen, methane, ethylene and ethane in catalytic cracking are separated together with the common components of the ethylene unit. Among them, the concentration of hydrogen + nitrogen (H2 + N2) in crude hydrogen is ≥95mol%, methane tail gas is used as fuel, ethylene purity (≥99.95mol%) reaches the polymerization grade, and ethane is returned to the steam cracking furnace for recycling cracking to increase ethylene production.

[0024] (4) Compared with the conventional method of oil absorption and separation and catalytic dry gas enrichment and recovery, the present invention can maximize the recovery of high value-added C2 components in catalytic cracking, and its recovery rate can be increased by at least 5-10 percentage points to more than 99.6%; at the same time, it can appropriately reduce the number of equipment, reduce the footprint, and reduce investment; and the scale of the ethylene plant integration unit is more conducive to giving full play to its scale effect.

[0025] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0026] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0027] Figure 1 This is a process flow diagram of the existing conventional catalytic cracking and steam cracking fusion separation method.

[0028] Figure 2 This is a process flow diagram of the existing fusion separation method of catalytic cracking and steam cracking.

[0029] Figure 3 This is a process flow diagram of an integrated light hydrocarbon separation method according to the present invention. Detailed Implementation

[0030] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0031] This invention provides an integrated light hydrocarbon separation device, which includes: a catalytic cracking system, a steam cracking system, and a shared system;

[0032] The catalytic cracking system includes a catalytic cracking unit, a fractionation unit, a compression and pre-fractionation unit, and a catalytic thermal separation unit connected in sequence.

[0033] The steam cracking system includes a steam cracking unit, a quenching unit, a compression and pre-ethane removal unit, and a steam thermal separation unit connected in sequence.

[0034] The shared system includes a carbon-1 cold separation unit and an ethylene distillation unit connected in sequence.

[0035] The C2 outlet of the compression and pre-separation unit and the C2 outlet of the compression and pre-ethane removal unit are both connected to the inlet of the C1 cold separation unit.

[0036] In this invention, the catalytic cracking reaction-regeneration furnace and the steam cracking furnace, i.e., the "two heads", are still separate.

[0037] In this invention, the fluidized bed reaction products of catalytic cracking contain catalyst powder and include carbon dioxide (CO2), hydrogen sulfide (H2S), organic sulfur, and nitrogen oxides (NO). x The catalytic cracking gas contains various impurities, such as water vapor, alkynes / dienes, small amounts of carbon dioxide (CO2) and hydrogen sulfide (H2S), and very few other impurities. Therefore, the fractionation, compression, and impurity removal / pre-fractionation units of catalytic cracking are still set up separately from the quenching, compression, and pre-ethane removal and pre-hydrogenation units of steam cracking.

[0038] In this invention, pre-separation refers to the separation of catalytic cracking or steam cracking before entering the C1 cold separation unit. Pre-separation can adopt a sequential pre-ethane removal process. The separation processes used for catalytic cracking and steam cracking can be the same or different. Here, catalytic cracking and steam cracking use similar separation processes, but the operating values ​​(pressure, temperature) will vary depending on the composition.

[0039] According to the present invention, the propane outlet of the catalytic thermal separation unit, the propane outlet of the steam thermal separation unit, and the ethane outlet of the ethylene distillation unit are connected to the steam cracking unit.

[0040] According to the present invention, the catalytic cracking unit is selected from any one of a fluidized catalytic cracking unit, a deep catalytic cracking unit, a heavy oil high-efficiency catalytic cracking unit, and a heavy oil catalytic thermal cracking unit.

[0041] This invention also provides an integrated light hydrocarbon separation method, the method comprising the following steps:

[0042] (1) Catalytic cracking feedstock oil is catalytically cracked to obtain reaction oil gas, the reaction oil gas is fractionated to obtain light hydrocarbon components, the light components are compressed, impurities are removed and pre-separated to obtain light component A with C2 and below and heavy component A with C3 and above.

[0043] (2) The C3 and above heavy component A is sent to the catalytic thermal separation unit for separation;

[0044] (3) Steam cracking feedstock oil is steam cracked to obtain cracked gas, and the cracked gas is rapidly cooled, compressed, impurity removed and pre-ethane separation to obtain light components B with C2 and below and heavy components B with C3 and above.

[0045] (4) The C3 and above heavy component B is sent to the steam thermal separation unit for separation;

[0046] (5) The light components A and B of C2 and below are combined and sent to the C1 cold separation unit for separation to obtain the C2 fraction, which is then sent to the ethylene distillation unit for further separation.

[0047] According to the present invention, the catalytic thermal separation unit separates refinery-grade polymerized propylene, propane, C4 fraction and catalytic cracked gasoline; the steam thermal separation unit separates polymerized propylene, propane, mixed C4 and crude cracked gasoline.

[0048] According to the present invention, the C2 fraction is separated into polymer-grade ethylene product and ethane in the ethylene distillation unit.

[0049] Preferably, the method further includes the following steps:

[0050] (6) The propane separated from the catalytic thermal separation unit and the steam thermal separation unit, and the ethane separated from the ethylene distillation unit are sent back to the steam cracking unit for cyclic cracking.

[0051] The separated light components of C2 and below are integrated and separated in a unified manner, including the pre-cooling and C1 cooling separation zone and the ethylene distillation unit. The original propylene refrigeration system and ethylene refrigeration system of the ethylene plant are shared by the two plants, as well as utilities such as waste heat, steam, and circulating cooling water.

[0052] By optimizing and adjusting the treatment method of light hydrocarbon components in catalytic cracking and appropriately integrating the separation processes of catalytic cracking and steam cracking, light components such as hydrogen, methane, ethylene and ethane in catalytic cracking are separated together with the common components of the ethylene unit. The concentration of (H2+N2) in crude hydrogen is ≥95mol%, methane tail gas is used as fuel, ethylene purity (≥99.95mol%) reaches the polymerization grade, and ethane is returned to the steam cracking furnace for recycling cracking to increase ethylene production.

[0053] According to the present invention, the pre-separation adopts a cryogenic separation process with pre-ethane removal.

[0054] The pre-deethane removal process employs a cryogenic separation process involving pre-deethane removal followed by pre-hydrogenation.

[0055] Preferably, the reacted oil and gas are further fractionated to obtain oil slurry and cracked light oil components.

[0056] The pyrolysis gas, after rapid cooling, yields pyrolysis diesel and pyrolysis fuel oil components.

[0057] Heavy components with C3 and above from catalytic cracking and steam cracking are still separated independently, and the product quality remains unchanged.

[0058] Catalytic cracking and steam cracking can be used to separate products with different properties (heavy products such as C4 and gasoline) independently and prevent them from being mixed back into each other. This allows for the direct separation and recycling of high-value-added components with high concentrations in each product, thereby maximizing economic benefits.

[0059] Preferably, the carbon-cold separation unit also separates crude hydrogen and methane.

[0060] The present invention will be described in more detail below through embodiments.

[0061] Comparative Example

[0062] Adopting such Figure 1The process flow shown is a conventional fusion separation of catalytic cracking and steam cracking. A petrochemical DCC with a capacity of 2.4 million tons / year of heavy oil and other feedstocks produces oil and gas from catalytic cracking. After the fractionation unit removes heavy fractions such as slurry and light diesel, the rich gas and crude gasoline enter the absorption and stabilization unit to separate catalytic gasoline. The light gas / liquid fraction undergoes dual desulfurization to obtain desulfurized catalytic dry gas and liquefied petroleum gas (LPG). The LPG is sent to a gas separation unit to separate propylene products, propane, and catalytic C4, etc. The catalytic dry gas is processed by a dry gas recovery unit to obtain enriched ethylene-rich gas and methane / hydrogen tail gas. The propane and ethylene-rich gas are sent to the steam cracking unit as feedstock. Meanwhile, a certain petrochemical 600,000-ton / year ethylene unit (i.e., steam cracking unit) mainly uses naphtha and other raw materials. The cracked gas obtained from steam cracking is separated into heavy products such as cracked fuel oil (PFO), cracked diesel (PGO) and heavy cracked gasoline by a quench unit. After the cracked gas is compressed, cold separated and hot separated, products such as crude hydrogen, methane tail gas, polymer-grade ethylene, polymer-grade propylene, mixed C4 and crude cracked gasoline can be obtained.

[0063] Example

[0064] Adopting such Figure 3 The apparatus shown is for the separation of light hydrocarbons, and includes: a catalytic cracking system, a steam cracking system, and a shared system;

[0065] The catalytic cracking system includes a catalytic cracking unit, a fractionation unit, a compression and pre-fractionation unit, and a catalytic thermal separation unit connected in sequence.

[0066] The steam cracking system includes a steam cracking unit, a quenching unit, a compression and pre-ethane removal unit, and a steam thermal separation unit connected in sequence.

[0067] The shared system includes a carbon-1 cold separation unit and an ethylene distillation unit connected in sequence.

[0068] The C2 outlet of the compression and pre-separation unit and the C2 outlet of the compression and pre-ethane removal unit are both connected to the inlet of the C1 cold separation unit.

[0069] The process flow of the integrated light hydrocarbon separation method in this embodiment is as follows:

[0070] (1) The light hydrocarbon components obtained after catalytic cracking and fractionation are compressed, impurities are removed and pre-separated. The pre-separation adopts a cryogenic separation process route with pre-ethane removal. The cracked gas from steam cracking is quenched and then compressed and pre-ethane removal with pre-hydrogenation cryogenic separation process route. The separated light components of C2 and below are combined and subjected to pre-cooling, demethanization and ethylene distillation similar to ethylene plants to obtain crude hydrogen and methane tail gas, which are further used to produce polymer-grade ethylene and ethane in the ethylene distillation unit.

[0071] (2) The heavy components of C3 and above separated by catalytic cracking compression and pre-separation / pre-deethanement are sent to the thermal separation zone of catalytic cracking (similar to gas separation unit) to separate their own C3, C4 and cracked gasoline products, namely the polymer grade propylene, propane, catalytic C4 and catalytic gasoline of oil refining.

[0072] (3) The heavy components separated by steam cracking compression and pre-deethaner hydrogenation are sent to the thermal separation zone (hot zone) of the ethylene unit to separate their own C3, C4 and gasoline products, namely, the chemical polymer grade propylene, propane, mixed C3 and crude cracked gasoline.

[0073] (4) The separated ethane and propane are sent back to the ethylene cracking furnace for circulating steam cracking to increase the yield of ethylene and propylene.

[0074] In this embodiment, the two units of catalytic cracking and fractionation, and steam cracking and quenching remain unchanged (i.e., the light diesel oil and slurry oil of catalytic cracking and the cracked diesel oil and cracked fuel oil of the ethylene unit remain unchanged).

[0075] Test Example 1

[0076] The yields of the main products from the catalytic cracking and steam cracking fusion separation processes in the examples and comparative cases were tested. The product yields were measured in tens of thousands of tons per year. The yield comparisons of the main products are shown in Table 1.

[0077] Table 1 Comparison of Production Volume of Major Products

[0078]

[0079]

[0080] As shown in Table 1, using a conventional separation process, the dry gas from catalytic cracking needs to be enriched with C2 before it can be recovered in the ethylene unit. The enrichment and recovery methods include pressure swing adsorption (PSA) and oil absorption, with C2 recovery rates ranging from 85% to 95%. In any case, some ethylene and ethane will be lost to the methane / hydrogen tail gas.

[0081] Using the device integration method described in this embodiment, hydrogen produced by catalytic cracking can also be directly recovered from the crude hydrogen in the ethylene unit, increasing crude hydrogen production (from 25,200 tons / year to 34,800 tons / year), while the total hydrogen + nitrogen (H2 + N2) content remains at around 95 mol%. The C2 recovery rate can be increased to over 99.6%, almost completely recovering the ethylene, thus increasing ethylene production by at least 12,000 tons annually, equivalent to an economic benefit of over 100 million yuan. Polymer-grade propylene remains divided into refining grade and chemical grade.

[0082] Test Example 2

[0083] The number of equipment units required for the fusion separation process of catalytic cracking and steam cracking in the examples and comparative examples was compared and tested. The equipment unit number comparison test data is shown in Table 2.

[0084] Table 2 Comparison Test of Equipment Quantity

[0085]

[0086] As shown in Table 2, the main changes to the integrated units after integration using the embodiment method are the absorption stabilization, dual desulfurization, C2 recovery, and gas separation of the catalytic cracking unit, while the cold separation and refrigeration systems of the ethylene unit are mainly scaled up. Compared with conventional separation processes, the embodiment can reduce the number of equipment by approximately 125 units, accounting for more than 17% of the total equipment in the two sets of units.

[0087] Test Example 3

[0088] The investment and land occupation of the catalytic cracking and steam cracking fusion separation process in the examples and comparative examples were compared. The investment was in hundreds of millions of yuan and the land occupation was in hectares. The data comparing investment and land occupation are shown in Table 3.

[0089] Table 3 Comparison of Investment and Land Acquisition

[0090]

[0091]

[0092] As can be seen from Table 3, the implementation example saves approximately RMB 170 million in investment and about 1.3 hectares of land, which are about 4% and 8% less than the traditional separation method, respectively.

[0093] Test Example 4

[0094] The energy consumption required for the fusion separation process of catalytic cracking and steam cracking in the examples and comparative examples was compared and tested.

[0095] In terms of energy consumption, due to the increased recovery rate of products such as ethylene and the increase in product output, the unit energy consumption based on ethylene products will decrease by 2.1%.

[0096] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. An integrated light hydrocarbon separation device, characterized in that, The device includes: a catalytic cracking system, a steam cracking system, and a shared system; The catalytic cracking system includes a catalytic cracking unit, a fractionation unit, a compression and pre-fractionation unit, and a catalytic thermal separation unit connected in sequence. The steam cracking system includes a steam cracking unit, a quenching unit, a compression and pre-ethane removal unit, and a steam thermal separation unit connected in sequence. The shared system includes a carbon-cold separation unit and an ethylene distillation unit connected in sequence. The C2 outlet of the compression and pre-separation unit and the C2 outlet of the compression and pre-deethane removal unit are both connected to the inlet of the C1 cold separation unit. The propane outlet of the catalytic thermal separation unit, the propane outlet of the steam thermal separation unit, and the ethane outlet of the ethylene distillation unit are connected to the steam cracking unit.

2. The apparatus according to claim 1, characterized in that, The catalytic cracking unit is selected from any one of a fluidized catalytic cracking unit, a deep catalytic cracking unit, and a heavy oil catalytic thermal cracking unit.

3. An integrated light hydrocarbon separation method using the apparatus described in any one of claims 1-2, characterized in that, The method includes the following steps: (1) The catalytic cracking feedstock oil is catalytically cracked in the catalytic cracking unit to obtain reaction oil gas. The reaction oil gas is fractionated in the fractionation unit to obtain light hydrocarbon components. The light hydrocarbon components are compressed, impurities are removed and pre-separated in the compression and pre-separation unit to obtain light component A with C2 and below and heavy component A with C3 and above. (2) The C3 and above heavy component A is sent to the catalytic thermal separation unit for separation; (3) The steam cracking feedstock oil is steam cracked in the steam cracking unit to obtain cracked gas. The cracked gas is then rapidly cooled, compressed, impurity removed and pre-ethane removed in the rapid cooling unit and the compression and pre-ethane removal unit to obtain light components B with C2 and below and heavy components B with C3 and above. (4) The heavy component B with C3 and above is sent to the steam thermal separation unit for separation; (5) The light components A and B of C2 and below are combined and sent to the C1 cold separation unit for separation to obtain the C2 fraction, which is then sent to the ethylene distillation unit for further separation. (6) The propane separated from the catalytic thermal separation unit and the steam thermal separation unit, as well as the ethane separated from the ethylene distillation unit, are sent back to the steam cracking unit for cyclic cracking.

4. The method according to claim 3, characterized in that, The steam thermal separation unit separates polymer-grade propylene, propane, mixed C4, and crude cracked gasoline products.

5. The method according to claim 4, characterized in that, The C2 fraction is separated into polymer-grade ethylene and ethane in the ethylene distillation unit.

6. The method according to claim 3, characterized in that, The pre-separation process employs a cryogenic separation process involving pre-ethane removal. The pre-deethane removal process employs a cryogenic separation process involving pre-deethane removal followed by pre-hydrogenation.

7. The method according to claim 3, characterized in that, The reacted oil and gas were further fractionated to obtain oil slurry and cracked light oil components. The pyrolysis gas, after rapid cooling, yields pyrolysis diesel and pyrolysis fuel oil components.

8. The method according to claim 3, characterized in that, The carbon-1 cold separation unit also separates crude hydrogen and methane.

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