Process and apparatus for dechlorination of reformer reaction products

Abstract

This invention discloses a method and apparatus for dechlorinating reaction products from a reforming unit. It includes a high-precision separator, a light hydrocarbon dechlorination tank, a reformate dechlorination tank, a circulating hydrogen compressor, a re-contact cooler, and a re-contact tank. The reforming unit reaction products, after cooling, enter the high-precision separator. The gas phase at the top of the separator is split into two streams: one stream is pressurized by the circulating hydrogen compressor and used as circulating hydrogen; the other stream is mixed with reducing hydrogen and sent to the light hydrocarbon dechlorination tank. The liquid phase at the bottom of the high-precision separator is pressurized and enters the reformate dechlorination tank. The light hydrocarbons, dechlorinated in the light hydrocarbon dechlorination tank, are pressurized and mixed with the reformate dechlorinated in the reformate dechlorination tank. After heat exchange and cooling, the mixture enters the re-contact tank for gas-liquid phase separation. The gas phase at the top of the tank is used as reformate hydrogen, and the liquid phase at the bottom of the tank is used as feed to the depentanizer. Using this invention ensures that the HCl content in the reforming reaction products and the treated reducing hydrogen does not exceed 1 ppm(v), reduces ammonium salt blockage at the inlet of the reformate hydrogen booster compressor and ammonium salt corrosion at the top of the depentanizer, and ensures safe and stable operation of the unit.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals and relates to a method for removing hydrogen chloride from hydrocarbons. Specifically, it relates to a method and apparatus for dechlorinating reaction products from a reforming unit. Background Technology

[0002] Reforming is a technology that uses a bimetallic catalyst to induce molecular rearrangement and isomerization reactions at high temperatures, increasing aromatic hydrocarbon production and improving gasoline octane number. During the reforming reaction, chlorine is continuously lost from the reforming catalyst. To maintain a certain level of acidity and high reactivity, water and organic chlorides must be continuously injected during operation to control the water-chlorine balance. Therefore, chlorine from the catalyst enters downstream along with the reforming products, leading to corrosion of downstream equipment. Simultaneously, hydrogen chloride in the reforming products reacts with trace amounts of ammonia to form ammonium chloride deposits, which not only clog pipes and equipment but also easily cause corrosion beneath the ammonium chloride scale, damaging equipment.

[0003] Currently, the method for dechlorinating reforming reaction products is as follows: the reformed oil is dechlorinated before entering the depentanizer. However, due to the low mass transfer rate in the liquid-solid reaction system, the existing liquid-phase dechlorinating agent has a low chlorine capacity, requires a large amount of dechlorinating agent, and needs to be replaced frequently. This easily causes ammonium chloride blockage and corrosion in the low-temperature part at the top of the depentanizer. The fuel gas sent from the top of the tower into the fuel gas system can also cause blockage of the heater burner nozzles, requiring a separate fuel gas dechlorination tank. The hydrogen chloride in the reformed hydrogen is pressurized by the reforming hydrogen booster and purified by re-contact before being dechlorinated. The reforming hydrogen booster and related re-contact equipment are at risk of hydrogen chloride corrosion and ammonium salt blockage, affecting the safe and stable operation of the unit. There is an urgent need to find a process flow to improve the dechlorination effect and ensure the safe and stable operation of the unit.

[0004] CN102676207A discloses a method for dechlorinating catalytic reforming reaction products, comprising directly feeding the reforming reaction products flowing out of the reforming reactor into a dechlorinating agent bed, and removing chlorine therefrom under conditions of 480~520℃, 0.35~2.0MPa, and feed volume hourly space velocity of 200~4000 h⁻¹. This method can remove chlorine from the reforming products in one step and can effectively improve the dechlorination efficiency of the dechlorinating agent. Its disadvantages are: all reaction products are dechlorinated (in conventional designs, circulating hydrogen is returned directly to the reaction section without dechlorination, which can reduce the amount of organic chlorine injected), and the entire dechlorination process is carried out at high temperature, resulting in high design conditions for the dechlorination tank and the use of high-temperature dechlorinating agents, leading to high investment.

[0005] CN110885697A discloses a method for using waste dechlorinating agent for liquid-phase dechlorination of reforming oil. Waste dechlorinating agent with a diameter of 3-5 mm is pulverized into powder with a diameter of 5-200 μm, and then suspended and mixed with chlorinated reforming oil in a slurry bed reactor to undergo a dechlorination reaction. Due to the large specific surface area and small particle size of the powdered dechlorinating agent, the liquid-phase mass transfer resistance is low, the mass transfer rate is high, and the dechlorination efficiency and precision are higher than those of large-particle dechlorinating agents used in fixed-bed reactors. This invention achieves the reuse of waste dechlorinating agent, reducing the cost of using and disposing of dechlorinating agent. Furthermore, the waste dechlorinating agent of this invention is used for liquid-phase dechlorination of reforming oil, and the process is simple and easy to implement for industrial production. However, its disadvantage is that this invention mainly focuses on the pulverization and utilization of waste dechlorinating agent and slurry bed dechlorination, which is essentially unrelated to this invention. In addition, the reaction conditions described in the invention CN110885697A are a reaction temperature of 50-100°C and a reaction pressure of 0.1-0.5 MPa, which cannot be met directly using existing reforming processes; and since the dechlorinating agent is a powder, a filter needs to be installed at the reactor outlet, making the process relatively complex. Summary of the Invention

[0006] In order to solve the above-mentioned problems, the present invention provides a method and apparatus for dechlorination of reaction products of a reforming unit, so as to solve the problem that the reforming products cause the unit to be unable to operate stably due to chlorine corrosion.

[0007] This invention provides a method and apparatus for dechlorination of reaction products from a reforming unit, the technical solution of which is as follows.

[0008] A method for dechlorinating reaction products from a reforming unit, characterized by comprising the following steps: 1) After the reaction products of the reforming unit are cooled, they enter the high-efficiency separation tank. The gas phase at the top of the high-efficiency separation tank is divided into two streams. One stream is pressurized by the circulating hydrogen compressor and returned to the reaction section as circulating hydrogen. The other stream is mixed with reducing hydrogen and sent to the light hydrocarbon dechlorination tank. The liquid phase at the bottom of the high-efficiency separation tank is pressurized and sent to the reforming oil dechlorination tank. 2) The light hydrocarbons after dechlorination in the light hydrocarbon dechlorination tank are pressurized. The pressurized light hydrocarbons are mixed with the reformed oil after dechlorination in the reformed oil dechlorination tank and cooled after heat exchange. The cooled mixture enters the re-contact refrigeration unit for gas-liquid phase separation. 3) The gas phase at the top of the re-contact tank is fed into other units as reformed hydrogen, and the liquid phase at the bottom of the tank is fed into the depentanizer as feed to the depentanizer.

[0009] The present invention provides a method for dechlorinating reaction products of a reforming unit, further characterized in that: in step 1), the reaction products of the reforming unit are cooled by a reaction product air cooler and then enter a high-efficiency separation tank; the liquid phase at the bottom of the high-efficiency separation tank is pressurized by a high-efficiency separation tank bottom pump and then sent to a reforming oil dechlorination tank; in step 2), the light hydrocarbons after dechlorination in the light hydrocarbon dechlorination tank are pressurized by a reforming hydrogen booster.

[0010] The present invention discloses a method for dechlorination of reaction products from a reforming unit, the further technical feature of which is that the reforming unit includes a semi-regenerative reforming unit and a continuous reforming unit.

[0011] The present invention discloses a method for dechlorination of reaction products in a reforming unit, the further technical feature of which is that the operating pressure of the high-precision separator is 0.15~1.20 MPa (gauge pressure) and the operating temperature is 40~50℃.

[0012] The present invention discloses a method for dechlorinating reaction products of a reforming unit, wherein the operating pressure of the reforming oil dechlorination tank is 1.20~3.50 MPa (gauge pressure) and the operating pressure of the light hydrocarbon dechlorination tank is 0.15~1.20 MPa (gauge pressure).

[0013] The present invention discloses a method for dechlorination of reaction products of a reforming unit, the further technical feature of which is that the operating pressure of the re-contact tank is 1.5~3.0 MPa (gauge pressure) and the operating temperature is -10~40℃.

[0014] The present invention discloses a method for dechlorination of reaction products in a reforming unit, wherein the re-contact cooler contains, but is not limited to, propane, propylene, liquid ammonia, and chilled water.

[0015] This invention also provides a dechlorination device for the reaction products of a reforming unit, used in the aforementioned dechlorination method for the reaction products of the reforming unit. The dechlorination device includes a high-precision separator, a light hydrocarbon dechlorination tank, a reformed oil dechlorination tank, a circulating hydrogen compressor, a re-contact cooler, and a re-contact tank. The high-precision separator has a reaction product inlet in its middle section, connected to the reaction product feed line. The bottom of the high-precision separator is connected to the inlet of the reformed oil dechlorination tank. The high-precision separator has two outlets at the top: one outlet is connected to the circulating hydrogen return line via the circulating hydrogen compressor, and the outlet line and the reducing hydrogen line of the other outlet are respectively connected to the inlet of the light hydrocarbon dechlorination tank, or the outlet line of the other outlet and the reducing hydrogen line merge and are connected to the inlet of the light hydrocarbon dechlorination tank. The outlets of the reformed oil dechlorination tank and the light hydrocarbon dechlorination tank are connected to the inlet of the re-contact cooler, and the outlet of the re-contact cooler is connected to the inlet of the re-contact tank. The top outlet of the re-contact tank is connected to the reformed hydrogen line, and the bottom outlet of the re-contact tank is connected to the feed line of the depentane tower.

[0016] The present invention discloses a dechlorination device for reaction products of a reforming unit, further characterized in that: the dechlorination device for reaction products of the reforming unit also includes a reaction product air cooler, a reforming hydrogen booster and a high-separation tank bottom pump; the reaction product air cooler is provided on the reaction product feed pipeline of the reforming unit; the outlet of the light hydrocarbon dechlorination tank is connected to the inlet of the re-contact cooler through the reforming hydrogen booster; and the bottom of the high-separation tank is connected to the inlet of the reformed oil dechlorination tank through the high-separation tank bottom pump.

[0017] This invention discloses a dechlorination device for reaction products in a reforming unit. A further technical feature is that the high-precision separator is equipped with a defoaming screen to effectively prevent liquid carryover in the circulating hydrogen compressor and the reforming hydrogen booster. Under this operating condition, 85%–95% of the fuel gas will pass through the light hydrocarbon dechlorination tank with high chlorine capacity and good dechlorination effect along with the top gas lift-off, improving the dechlorination effect of the fuel gas and mitigating subsequent pentane removal tower top ammonium salt corrosion and heater burner clogging.

[0018] The present invention discloses a dechlorination device for reaction products of a reforming unit, the further technical feature of which is that: two light hydrocarbon dechlorination tanks are provided, which can be connected in series or in parallel, and a gas-phase dechlorination agent is used, which has a good dechlorination effect and can avoid the blockage of ammonium salt at the inlet of the reforming hydrogen booster, thus ensuring the stable operation of the reforming hydrogen booster.

[0019] The present invention discloses a dechlorination device for the reaction products of a reforming unit, wherein the further technical feature is that: two dechlorination tanks for reforming oil are provided, which can be connected in series or in parallel, and can be switched according to the chlorine saturation of the dechlorinating agent without affecting the normal operation of the unit.

[0020] The present invention provides a dechlorination device for the reaction products of a reforming unit, wherein the re-contact tank is provided with a defoaming screen.

[0021] The reformed hydrogen described in this invention can be fed into other devices, either into a PSA unit for further purification or into a hydrogenation unit as a hydrogen source.

[0022] The present invention provides a method and apparatus for dechlorination of reaction products in a reforming unit, which has the following advantages compared with the prior art: 1) The present invention directly sets up a light hydrocarbon dechlorination tank on the top of the high-precision tank, and adopts gas phase dechlorination, which has a good dechlorination effect and can effectively remove chlorine from reforming hydrogen and light hydrocarbons. It avoids ammonium salt deposition caused by long-term operation and blockage of ammonium salt inlet filter of reforming hydrogen booster, thus ensuring long-term operation of the unit.

[0023] 2) Approximately 85% to 95% of the fuel gas components in the reforming products are dechlorinated in the light hydrocarbon dechlorination tank, which improves the dechlorination effect of the fuel gas and reduces the corrosion of ammonium salts at the top of the subsequent depentane dechlorination tower and the blockage of the heater burner nozzles.

[0024] 3) In this invention, when the reforming oil dechlorination tank is preferably located at the outlet of the bottom pump of the high-precision tank, there are fewer light components in the liquid phase at the bottom of the tank, which can reduce the amount of dechlorinating agent loaded in the reforming oil dechlorination tank and the amount of waste dechlorinating agent discharged.

[0025] 4) Two units are installed for both light hydrocarbon dechlorination tanks and reformate dechlorination tanks, which can be connected in series or in parallel, and the switching will not affect the normal operation of the unit.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this does not limit the scope of the invention. Attached Figure Description

[0027] Figure 1 This is a schematic flowchart of a method for dechlorination of reaction products from a reforming unit according to the present invention.

[0028] The reference numerals in the figure are: 1-Reformation unit reaction products, 2-Reformation product air cooler, 3-High-efficiency separation tank, 4-Circulating hydrogen compressor, 5-Circulating hydrogen, 6-Light hydrocarbon dechlorination tank, 7-Reform hydrogen booster, 8-High-efficiency separation tank bottom pump, 9-Reform oil dechlorination tank, 10-Re-contact cooler, 11-Re-contact tank, 12-Reform hydrogen, 13-Depentane tower feed, 14-Reduced hydrogen. Implementation

[0029] like Figure 1 As shown, the dechlorination unit for the reforming reaction products includes a reaction product air cooler 2, a high-efficiency separation tank 3, a light hydrocarbon dechlorination tank 6, a circulating hydrogen compressor 4, a high-efficiency separation tank bottom pump 8, a reforming oil dechlorination tank 9, a reforming hydrogen booster compressor 7, a re-contact cooler 10, and a re-contact tank 11. The high-efficiency separation tank 3 has a reforming reaction product inlet in its middle section, connected to the reforming reaction product feed line. The reaction product air cooler 2 is located on the reforming reaction product feed line. The bottom of the high-efficiency separation tank 3 is connected to the inlet of the reforming oil dechlorination tank via the high-efficiency separation tank bottom pump 8. The high-efficiency separation tank 3 has two outlets at the top. One outlet is connected to the circulating hydrogen return line via the circulating hydrogen compressor 4. The outlet line of the other outlet and the reducing hydrogen line are respectively connected to the inlet of the light hydrocarbon dechlorination tank 6, or the outlet line of the other outlet and the reducing hydrogen line merge and are connected to the inlet of the light hydrocarbon dechlorination tank 6. Figure 1 The diagram shows that the outlet pipeline of another outlet and the reduced hydrogen pipeline merge and are connected to the inlet of the light hydrocarbon dechlorination tank 6. The outlet of the light hydrocarbon dechlorination tank 6 is connected to the inlet of the reforming hydrogen booster 7. The outlet of the reforming oil dechlorination tank 9 and the outlet of the reforming hydrogen booster 7 (either separately or after merging) are connected to the inlet of the re-contact cooler 10. The outlet of the re-contact cooler 10 is connected to the inlet of the re-contact tank 11. The top outlet of the re-contact tank is connected to the reforming hydrogen pipeline, and the bottom outlet of the re-contact tank is connected to the feed pipeline of the depentanizer.

[0030] The following is a simplified description of the dechlorination method for the reaction products of the reforming unit of the present invention, with reference to the accompanying drawings.

[0031] After being cooled by the product air cooler 2, the product 1 from the reforming unit enters the high-efficiency separation tank 3. The gas phase at the top of the high-efficiency separation tank 3 is divided into two streams. One stream is pressurized by the circulating hydrogen compressor 4 and returned to the reaction section as circulating hydrogen 5. The other stream is mixed with the reducing hydrogen 14 and sent to the light hydrocarbon dechlorination tank 6 for dechlorination. The dechlorinated light hydrocarbons enter the reforming hydrogen booster 7 for pressurization.

[0032] The liquid phase at the bottom of the high-precision tank 3 is pressurized by the high-precision tank bottom pump 8 and sent to the reforming oil dechlorination tank 9 for dechlorination. After dechlorination, the reforming oil and the light hydrocarbons pressurized by the reforming hydrogen booster 7 are mixed and then enter the re-contact cooler 10 after heat exchange. The cooled mixture flows into the re-contact tank 11 for gas-liquid phase separation. The gas phase at the top of the re-contact tank 11 can be sent out as reforming hydrogen 12, and the liquid phase at the bottom of the re-contact tank 11 is fed into the depentanizer tower 13.

[0033] The high-precision tank 3 is equipped with a defoaming screen, which can effectively prevent liquid from being carried over to the circulating hydrogen compressor and the reforming hydrogen booster.

[0034] Two units are provided for both the light hydrocarbon dechlorination tank 6 and the reformate dechlorination tank 9. They can be connected in series or in parallel, and switching will not affect the normal operation of the unit. Conventional gaseous and liquid phase dechlorination agents can be used.

[0035] The above description is merely a typical embodiment of the present invention and does not impose any limitations on the present invention. Any changes or modifications made by those skilled in the art based on the above content without departing from the scope of the present invention should be considered equivalent examples of equivalent variations. Any equivalent changes made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention are all within the scope of the present invention.

Claims

1. A method for dechlorinating reaction products of a reforming unit, characterized in that... Includes the following steps: 1) After the reaction products of the reforming unit are cooled, they enter the high-efficiency separation tank. The gas phase at the top of the high-efficiency separation tank is divided into two streams. One stream is pressurized by the circulating hydrogen compressor and returned to the reaction section as circulating hydrogen. The other stream is mixed with reducing hydrogen and sent to the light hydrocarbon dechlorination tank. The liquid phase at the bottom of the high-efficiency separation tank is pressurized and sent to the reforming oil dechlorination tank. 2) The light hydrocarbons after dechlorination in the light hydrocarbon dechlorination tank are pressurized. The pressurized light hydrocarbons are mixed with the reformed oil after dechlorination in the reformed oil dechlorination tank and cooled after heat exchange. The cooled mixture enters the re-contact refrigeration unit for gas-liquid phase separation. 3) The gas phase at the top of the re-contact tank is fed into other units as reformed hydrogen, and the liquid phase at the bottom of the tank is fed into the depentanizer as feed to the depentanizer. In step 2), the light hydrocarbons dechlorinated in the light hydrocarbon dechlorination tank are then pressurized in the reforming hydrogen booster. The operating pressure of the high-pressure separator is 0.15~1.20 MPa (gauge pressure), and the operating temperature is 40~50℃.

2. The method for dechlorination of reaction products in a reforming unit according to claim 1, characterized in that: In step 1), the reaction products of the reforming unit are cooled by the reaction product air cooler and then enter the high-efficiency separation tank. The liquid phase at the bottom of the high-efficiency separation tank is pressurized by the high-efficiency separation tank bottom pump and then sent to the reformate dechlorination tank.

3. The method for dechlorination of reaction products in a reforming unit according to claim 1, characterized in that: The operating pressure of the reformate dechlorination tank is 1.20~3.50 MPa (gauge pressure), and the operating pressure of the light hydrocarbon dechlorination tank is 0.15~1.20 MPa (gauge pressure).

4. The method for dechlorination of reaction products in a reforming unit according to claim 1, characterized in that: The operating pressure of the re-contact tank is 1.5~3.0 MPa (gauge pressure), and the operating temperature is -10~40℃.

5. The method for dechlorination of reaction products in a reforming unit according to claim 1, characterized in that: In the re-contact cooler, the refrigerant includes, but is not limited to, propane, propylene, liquid ammonia, and chilled water.

6. A dechlorination device for the reaction products of a reforming unit, used in the dechlorination method for the reaction products of the reforming unit as described in claim 1, characterized in that: The dechlorination unit for the reforming reaction products includes a high-precision separator, a light hydrocarbon dechlorination tank, a reformed oil dechlorination tank, a circulating hydrogen compressor, a re-contact cooler, and a re-contact tank. The high-precision separator has a reforming reaction product inlet in the middle, and the reforming reaction product feed line is connected to the reforming reaction product inlet. The bottom of the high-precision separator is connected to the inlet of the reformed oil dechlorination tank. The high-precision separator has two outlets at the top. One outlet is connected to the circulating hydrogen return line via the circulating hydrogen compressor. The outlet line of the other outlet and the reducing hydrogen line are connected to the inlet of the light hydrocarbon dechlorination tank, or the outlet line of the other outlet and the reducing hydrogen line merge and are connected to the inlet of the light hydrocarbon dechlorination tank. The outlets of the reformed oil dechlorination tank and the light hydrocarbon dechlorination tank are connected to the inlet of the re-contact cooler. The outlet of the re-contact cooler is connected to the inlet of the re-contact tank. The top outlet of the re-contact tank is connected to the reformed hydrogen line, and the bottom outlet of the re-contact tank is connected to the feed line of the depentanizer.

7. A dechlorination device for the reaction products of a reforming unit according to claim 6, characterized in that: The dechlorination unit for the reaction products of the reforming unit also includes a reaction product air cooler, a reforming hydrogen booster, and a bottom pump for the high-separation tank. The reaction product air cooler is installed on the feed pipeline of the reforming unit reaction products. The outlet of the light hydrocarbon dechlorination tank is connected to the inlet of the re-contact cooler through the reforming hydrogen booster. The bottom of the high-separation tank is connected to the inlet of the reformed oil dechlorination tank through the bottom pump for the high-separation tank.

8. A dechlorination device for the reaction products of a reforming unit according to claim 6, characterized in that: Both the high-resolution tank and the re-contact tank are equipped with defoaming screens.

9. A dechlorination device for the reaction products of a reforming unit according to claim 6, characterized in that: Two units are provided for both the light hydrocarbon dechlorination tank and the reformate dechlorination tank, which can be connected in series or in parallel.

Images