A continuous reforming recontacting process and system

Abstract

The present disclosure relates to a continuous reforming recontacting method, which comprises the following steps: S1, sending the primary supercharger outlet gas to the secondary supercharger inlet liquid separation tank after cooling by the primary supercharger outlet air cooler to obtain hydrogen-containing gas and a small amount of liquefied gas at the bottom of the tank through first gas-liquid separation; S2, pressurizing the hydrogen-containing gas by the secondary supercharger to obtain pressurized hydrogen-containing gas; S3, sending the pressurized hydrogen-containing gas to the hydrogen air cooler for cooling treatment to obtain cooled hydrogen-containing gas; S4, sending the cooled hydrogen-containing gas to the recontacting tower, and the cooled hydrogen-containing gas and the reformate tank bottom oil pressurized by the reformate tank bottom pump are recontacted on the tower plate of the recontacting tower to obtain reforming hydrogen and a tower bottom liquid phase, and the reforming hydrogen is discharged from the top of the recontacting tower. The method can improve the purity of hydrogen, increase the yield of reforming liquid products, save the investment, land occupation and energy consumption of the device.

Description

Technical Field

[0001] This disclosure relates to the field of oil refining technology, and more specifically, to a continuous reforming re-contact method and system. Background Technology

[0002] Catalytic reforming is an important petroleum processing technique. Under the action of a catalyst, the molecular structure of hydrocarbons in gasoline fractions is rearranged, transforming naphtha into high-octane reformed gasoline, liquefied petroleum gas (LPG), and reformed hydrogen rich in aromatics. This increases the yield of aromatic products while also improving the octane number of the gasoline. Catalytic reforming typically operates at lower pressures to achieve higher product yields. However, excessively low reaction pressures result in the byproduct reformed hydrogen being mixed with a large amount of light hydrocarbons under low-pressure equilibrium, leading to lower purity. This necessitates pressurization and re-contact processes to improve the liquid yield and hydrogen purity, and also results in higher investment, land occupation, and energy consumption for the equipment.

[0003] Patent documents CN108865251A and CN108774545A both disclose a reforming re-contact process to reduce energy consumption in catalytic reforming units. This process involves installing two pumps at the bottom of the primary re-contact tank. After pressurization by these pumps, the liquid streams enter the re-contact system and the reformate fractionation system respectively. This allows for flexible control of the two liquid phase ratios to optimize the re-contact effect and reduce energy consumption. However, because this process does not directly optimize the low-pressure balance between light hydrocarbons and hydrogen, the improvement in hydrogen purity is very limited. Furthermore, even with significant energy savings, the equipment investment remains high.

[0004] Patent document CN102994146A discloses a reforming re-contact process to improve the liquid yield of a catalytic reforming unit. This process utilizes a portion of the reflux from the downstream depentanizer tower, which is then fractionated through an additional C4 / C5 separator, to enhance liquid yield. While this process can improve the liquid yield, relying solely on additional fractionation methods significantly increases the operational complexity, energy consumption, investment, and floor space required for the unit. Summary of the Invention

[0005] The purpose of this disclosure is to provide a continuous reforming re-contact method and system that achieves higher reforming hydrogen purity and liquid yield than existing methods, while meeting the requirements of modern oil refining units for saving on equipment investment, land area and energy consumption.

[0006] To achieve the above objectives, the first aspect of this disclosure provides a continuous re-reconnection method, the method comprising the following steps:

[0007] S1. The outlet gas of the first-stage turbocharger is sent to the outlet air cooler of the first-stage turbocharger for cooling. The cooled gas-liquid mixture enters the inlet separator of the second-stage turbocharger for the first gas-liquid separation, and hydrogen-containing gas and a small amount of liquefied gas are obtained.

[0008] S2. The hydrogen-containing gas is fed into a secondary booster for pressurization to obtain pressurized hydrogen-containing gas;

[0009] S3. The pressurized hydrogen-containing gas is sent into a hydrogen air cooler for cooling to obtain cooled hydrogen-containing gas.

[0010] S4. The cooled hydrogen-containing gas is fed into the re-contact tower. The cooled hydrogen-containing gas and the bottom oil of the reforming product separator, which has been pressurized by the bottom pump of the reforming product separator, are re-contacted on the tower plate of the re-contact tower to obtain reformed hydrogen and bottom liquid phase. The reformed hydrogen is discharged from the top of the re-contact tower.

[0011] Optionally, the method further includes: discharging the bottom liquid phase from the bottom of the re-contact tower and mixing it with a small amount of liquefied gas to obtain mixed reforming oil.

[0012] Optionally, the outlet gas temperature of the first-stage booster is 70-150℃ and the pressure is 1.0-2.0MPa.

[0013] Optionally, the temperature of the gas-liquid mixture after cooling by the air cooler at the outlet of the first-stage booster is 20-60℃, and the pressure is 1.0-2.0MPa.

[0014] Optionally, the temperature of the hydrogen-containing gas is 20-60°C and the pressure is 1.0-2.0 MPa.

[0015] Optionally, the temperature of the pressurized hydrogen-containing gas is 70-150℃ and the pressure is 2.0-3.5MPa; the temperature of the cooled hydrogen-containing gas is 30-60℃ and the pressure is 2.0-3.5MPa.

[0016] Optionally, the temperature of the bottom oil in the reforming product separator is 20-60℃ and the pressure is 0.2-1.0MPa.

[0017] Optionally, the temperature of the bottom oil in the pressurized reforming product separator is 20-60°C, and the pressure is 2.0-3.5 MPa.

[0018] Optionally, the re-contact tower is provided with 5-15 trays, the pressure of the first tray at the top of the tower is 2.0-3.5 MPa, and the pressure of each tray decreases layer by layer with a pressure drop of 5-30 kPa.

[0019] A second aspect of this disclosure provides a continuous re-energizing re-touch system for the method described in the first aspect, the system comprising:

[0020] First-stage booster outlet air cooler, second-stage booster inlet separator, second-stage booster, hydrogen air cooler, re-contact tower, reforming product separator bottom pump;

[0021] The outlet of the primary booster air cooler is connected to the inlet of the secondary booster inlet separator; the top outlet of the secondary booster inlet separator is connected to the inlet of the secondary booster; the outlet of the secondary booster is connected to the inlet of the hydrogen air cooler; the outlet of the hydrogen air cooler is connected to the inlet of the re-contact tower; and the outlet of the reforming product separator bottom pump is connected to the inlet of the re-contact tower.

[0022] Through the above technical solution, the continuous reforming re-contact method disclosed herein, by adding a re-contact tower, allows the gas-liquid mixture to re-contact under pressurized and low-temperature conditions, establishing a new material balance to reduce the content of light hydrocarbons in gas-phase reformed hydrogen, thereby effectively improving the purity of reformed hydrogen. At the same time, light hydrocarbons, as reforming products, increase the liquid yield. Furthermore, this system can save on equipment investment, land area, and energy consumption.

[0023] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0025] Figure 1 This is a flowchart illustrating the present invention.

[0026] Figure 2 This is a schematic diagram of the existing process flow.

[0027] Explanation of reference numerals in the attached figures

[0028] 1. First-stage booster compressor outlet air cooler; 2. Second-stage booster compressor inlet separator; 3. Second-stage booster compressor; 4. Hydrogen air cooler; 5. Re-contact tower; 6. Reforming product separator bottom pump; 101. Reforming product separator bottom oil; 102. First-stage booster compressor outlet gas; 103. Gas-liquid mixture cooled by the first-stage booster compressor outlet air cooler; 104. Hydrogen-containing gas; 105. Pressurized hydrogen-containing gas; 106. Cooled hydrogen-containing gas; 107. Liquefied petroleum gas (LPG); 108. Bottom liquid phase; 109. Reformed hydrogen; 110. Mixed reformed oil; 111. Pressurized reforming product separator bottom oil.

[0029] a) Primary re-contact air cooler; b) Primary re-contact tank; c) Secondary reforming hydrogen booster; d) Secondary re-contact air cooler; e) Re-contact precooler; f) Re-contact freezer; g) Secondary re-contact tank; h) Bottom pump of reforming product separator. Detailed Implementation

[0030] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0031] The first aspect of this disclosure provides a continuous re-contact reforming method, the method comprising the following steps:

[0032] S1. The outlet gas 102 of the first-stage booster is cooled down by the outlet air cooler 1 of the first-stage booster and then sent to the inlet separator 2 of the second-stage booster for the first gas-liquid separation to obtain hydrogen-containing gas 104 and liquefied gas 107.

[0033] S2. The hydrogen-containing gas 104 is fed into the secondary booster 3 for pressurization to obtain pressurized hydrogen-containing gas 105;

[0034] S3. The pressurized hydrogen-containing gas 105 is sent into the hydrogen air cooler 4 for cooling treatment to obtain cooled hydrogen-containing gas 106.

[0035] S4. The cooled hydrogen-containing gas 106 is fed into the re-contact tower 5. The cooled hydrogen-containing gas 106 and the reforming product separator bottom oil 111, which has been pressurized by the reforming product separator bottom pump 6, are re-contacted on the tower plate of the re-contact tower 5 to obtain reformed hydrogen 109 and bottom liquid phase 108. The reformed hydrogen 109 is discharged from the top of the re-contact tower 5.

[0036] Through the above technical solution, using the method described in this disclosure, the bottom oil of the reforming product separation tank and the outlet gas of the first-stage booster compressor are re-contacted in a re-contact tower from top to bottom and bottom to top, respectively, to achieve a new gas-liquid equilibrium. The light hydrocarbons in the hydrogen-containing gas at the top of the tank dissolve in the liquid oil phase. The purified reformed hydrogen is discharged from the top of the re-contact tower, while the liquid phase at the bottom goes to the fractionation section. This method can achieve higher reformed hydrogen purity and liquid yield than existing methods, while also meeting the requirements of modern oil refining units for saving on equipment investment, land area, and energy consumption.

[0037] According to this disclosure, the method further includes: discharging the bottom liquid phase 108 from the bottom of the re-contact tower 5 and mixing it with liquefied gas 107 to obtain mixed reforming oil 110.

[0038] According to this disclosure, the temperature of the top gas of the reforming reaction product separator or the outlet gas 102 of the circulating hydrogen compressor is 70-150°C and the pressure is 1.0-2.0 MPa.

[0039] According to this disclosure, the temperature of the hydrogen-containing gas 104 is 20-60°C, and the pressure is 0.2-1.0 MPa.

[0040] According to this disclosure, the temperature of the gas-liquid mixture 103 after cooling by the primary booster outlet air cooler 1 is 20-60℃, and the pressure is 1.0-2.0MPa.

[0041] According to this disclosure, the temperature of the hydrogen-containing gas 104 is 20-60°C, and the pressure is 1.0-2.0 MPa.

[0042] According to this disclosure, the temperature of the pressurized hydrogen-containing gas 105 is 70-150°C, and the pressure is 2.0-3.5 MPa.

[0043] In this disclosure, the hydrogen-containing gas is fed into a secondary booster compressor for pressurization, resulting in a pressurized hydrogen-containing gas that reaches the pressure required for the re-contact tower. The cooled hydrogen-containing gas 106 has a temperature of 30-60°C and a pressure of 2.0-3.5 MPa.

[0044] In this disclosure, the pressurized hydrogen-containing gas is sent into a hydrogen air cooler for cooling to obtain cooled hydrogen-containing gas, which can be used for low-temperature contact.

[0045] According to this disclosure, the temperature of the bottom oil 101 in the reforming product separator is 20-60°C, and the pressure is 0.2-1.0 MPa.

[0046] According to this disclosure, the temperature of the bottom oil 111 in the pressurized reforming product separator is 20-60°C, and the pressure is 2.0-3.5 MPa.

[0047] According to this disclosure, the re-contact tower 5 is provided with 5-15 layers of trays. The pressure of the first tray at the top of the tower is 2.0-3.5 MPa, and the pressure of each tray decreases layer by layer with a pressure drop of 5-30 kPa.

[0048] In this disclosure, the re-contact tower has 5-15 trays inside. The multiple trays can form gas-liquid equilibrium at different temperature layers. The appropriate trays and pressure allow the light and heavy components to re-establish equilibrium on each tray. The gaseous hydrogen-containing gas and the liquid oil re-contact each other on the trays. The purified reformed hydrogen is discharged from the top of the re-contact tower, while the liquid phase at the bottom of the tower merges with the bottom material of the separator at the inlet of the secondary booster and exits as a single stream.

[0049] A second aspect of this disclosure provides a continuous re-energizing re-touch system for the method described in the first aspect, the system comprising:

[0050] 1. Air cooler at the outlet of the first-stage booster; 2. Separating tank at the inlet of the second-stage booster; 3. Second-stage booster; 4. Hydrogen air cooler; 5. Re-contact tower; 6. Bottom pump of the reforming product separator.

[0051] The outlet of the first-stage booster air cooler 1 is connected to the inlet of the second-stage booster inlet separator 2; the top outlet of the second-stage booster inlet separator 2 is connected to the inlet of the second-stage booster 3; the outlet of the second-stage booster 3 is connected to the inlet of the hydrogen air cooler 4; the outlet of the hydrogen air cooler 4 is connected to the inlet of the re-contact tower 5; and the outlet of the reforming product separator bottom pump 6 is connected to the inlet of the re-contact tower.

[0052] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0053] Example

[0054] The main raw material stream of this invention includes reforming product separator bottom oil 101 at a temperature of 46°C and a pressure of 0.24 MPa and first-stage booster outlet gas 102 at a temperature of 132°C and a pressure of 1.40 MPa. The raw material composition applicable to this embodiment is shown in Table 1 below. It should be noted that this raw material composition is exemplary and should not be limited to the composition listed herein.

[0055] Table 1. Raw material composition

[0056]

[0057] like Figure 1 As shown, the first-stage turbocharger outlet air cooler 1 cools the outlet gas of the first-stage turbocharger to a gas-liquid mixture with a temperature of 46°C and a pressure of 1.38MPa.

[0058] In the secondary booster 3, the hydrogen-containing gas from the top of the secondary booster inlet separator 2 is pressurized to 2.81 MPa and the temperature is 116℃.

[0059] In the hydrogen air cooler 4, the hydrogen-containing gas, which is pressurized to 116°C, is cooled to 45°C before entering the re-contact tower 5.

[0060] The bottom oil from the reforming product separator is pressurized to 2.94 MPa by the bottom pump 6 and then enters the re-contact tower 5.

[0061] In the re-contact tower 5, liquid oil pumped from the bottom of the reforming product separator enters the tower from the top at a temperature of 46°C and a pressure of 2.94 MPa, while hydrogen-containing gas from the top of the secondary booster inlet separator enters the tower from the bottom at a temperature of 45°C and a pressure of 2.79 MPa.

[0062] Inside the re-contact column 5, the gaseous hydrogen-containing gas and liquid oil undergo a second contact. A single-stage distillation column without a top condenser and a bottom reboiler can be used as the re-contact column 5, employing six theoretical trays. The liquid stream enters the column from the top first tray, and the gaseous stream enters from the bottom sixth tray. The pressure of the top first tray is 2.75 MPa, and the pressure drop decreases by 10 kPa for each tray. The purified reformed hydrogen exits from the top of the re-contact column 5, while the bottom liquid phase merges with a small amount of liquefied gas from the bottom of the secondary booster inlet separator 2 before exiting as a single stream.

[0063] Comparative Example

[0064] The difference from the embodiment lies in the fact that, in terms of equipment configuration, the prior art includes a re-contact precooler e, a re-contact freezer f, and a two-stage re-contact tank g; in terms of process setup, the bottom oil of the reformate separator tank is mixed with pressurized and cooled hydrogen-containing gas, and then cooled sequentially through e and f before being sent to the two-stage re-contact tank g for gas-liquid re-contact. Purified hydrogen product is obtained at the top of the tank. The liquid phase at the bottom of the tank exchanges heat with the mixture in the re-contact precooler e, and after being heated, it mixes with the top gas of the reformate separator tank before being sent to the first-stage re-contact air cooler a. The reformate oil is separated from the bottom of the first-stage re-contact tank b.

[0065] As attached Figure 2 As shown, in the first-stage re-contact air cooler a, the top gas from the top of the reforming product separator enters the first-stage re-contact air cooler a at 69°C and is cooled to 46°C by the air cooler a.

[0066] In the secondary reforming hydrogen booster compressor c, the hydrogen-containing gas from the top of the primary re-contact tank b is pressurized to 2.81 MPa at a temperature of 46°C and a pressure of 1.38 MPa.

[0067] In the secondary re-contact air cooler d, the hydrogen-containing gas, which was pressurized to 117°C, is cooled to 45°C and then mixed with the reformate separator bottom oil, which was pressurized by the bottom pump of the reformate separator to 46°C and 2.94 MPa, before entering the shell side of the re-contact precooler e.

[0068] In the re-contact precooler e, the 50°C gas-liquid mixture exchanges heat with the liquid phase material at the bottom of the 4°C secondary re-contact tank g. After the temperature of the gas-liquid mixture drops to 29°C, it enters the re-contact freezer f.

[0069] In the re-contact freezer f, the hydrogen-containing gas and liquid phase oil-gas-liquid mixture are further cooled and enter the secondary re-contact tank g at a temperature of 4°C and a pressure of 2.77 MPa to re-contact the gas and liquid.

[0070] In the secondary re-contact tank g, a new gas-liquid balance is established. The purified reformed hydrogen is pushed out from tank g, and the bottom liquid phase of the secondary re-contact tank g is sent back to the front of the primary re-contact air cooler a after heat exchange in the re-contact precooler e.

[0071] Table 2. Purity of reformed hydrogen (109)

[0072]

[0073]

[0074] By comparing the embodiments and comparative examples, it can be found that, compared with the existing continuous reforming unit re-contact process, the present invention can replace a series of equipment in the existing scheme, including the secondary re-contact tank, re-contact precooler, re-contact freezer and re-contact freezer compressor system, with a lower investment and simpler operation using a tower. At the same time, the results listed in Table 2 show that the present invention can effectively improve the reformed hydrogen purity and liquid yield.

[0075] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0076] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0077] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A continuous re-contact reforming method, characterized in that, The method includes the following steps: S1. The outlet gas (102) of the first-stage booster is sent to the outlet air cooler (1) of the first-stage booster to cool down and obtain a cooled gas-liquid mixture (103). This mixture enters the inlet separator (2) of the second-stage booster for the first gas-liquid separation, resulting in hydrogen-containing gas (104) and a small amount of liquefied gas (107). S2. The hydrogen-containing gas (104) is fed into the secondary booster (3) for boosting to obtain pressurized hydrogen-containing gas (105); S3. The pressurized hydrogen-containing gas (105) is sent into a hydrogen air cooler (4) for cooling treatment to obtain cooled hydrogen-containing gas (106). S4. The cooled hydrogen-containing gas (106) is fed into the re-contact tower (5). The cooled hydrogen-containing gas (106) and the reforming product separator bottom oil (111) after being pressurized by the reforming product separator bottom pump (6) are re-contacted on the tower plate of the re-contact tower (5) to obtain reformed hydrogen (109) and bottom liquid phase (108). The reformed hydrogen (109) is discharged from the top of the re-contact tower (5). The temperature of the pressurized hydrogen-containing gas (105) is 70-150℃ and the pressure is 2.81-3.5MPa; the temperature of the cooled hydrogen-containing gas (106) is 30-60℃ and the pressure is 2.81-3.5MPa. The re-contact tower (5) is equipped with 5-15 layers of tower plates. The pressure of the first layer of tower plate at the top is 2.0-3.5 MPa, and the pressure of each layer of tower plate decreases by 5-30 kPa.

2. The method according to claim 1, wherein, The method further includes: discharging the bottom liquid phase (108) from the bottom of the re-contact tower (5) and mixing it with a small amount of liquefied gas (107) to obtain mixed reforming oil (110).

3. The method according to claim 1, wherein, The temperature of the outlet gas (102) of the first-stage booster is 70-150℃ and the pressure is 1.0-2.0MPa.

4. The method according to claim 1, wherein, The temperature of the gas-liquid mixture (103) cooled by the outlet air cooler (1) of the first-stage booster is 20-60℃ and the pressure is 1.0-2.0MPa.

5. The method according to claim 1, wherein, The temperature of the hydrogen-containing gas (104) is 20-60℃ and the pressure is 1.0-2.0MPa.

6. The method according to claim 1, wherein, The temperature of the bottom oil (101) in the reforming product separator is 20-60℃ and the pressure is 0.2-1.0MPa.

7. The method according to claim 1, wherein, The temperature of the bottom oil (111) in the pressurized reforming product separator is 20-60℃, and the pressure is 2.0-3.5MPa.

8. A continuous re-reforming and re-contacting system employing the method described in any one of claims 1-7, characterized in that, The system includes: First-stage booster outlet air cooler (1), second-stage booster inlet separator (2), second-stage booster (3), hydrogen air cooler (4), re-contact tower (5), reforming product separator bottom pump (6); The outlet of the primary booster outlet air cooler (1) is connected to the inlet of the secondary booster inlet separator (2); the top outlet of the secondary booster inlet separator (2) is connected to the inlet of the secondary booster (3); the outlet of the secondary booster (3) is connected to the inlet of the hydrogen air cooler (4); the outlet of the hydrogen air cooler (4) is connected to the inlet of the re-contact tower (5); and the outlet of the reforming product separator bottom pump (6) is connected to the inlet of the re-contact tower (5).

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