An electrically heated fixed-bed propane dehydrogenation reaction system

Abstract

This utility model discloses an electrically heated fixed-bed propane dehydrogenation reaction system, comprising: a reactor, including a shell with a reaction chamber, and an electrically heated device and a catalyst bed disposed within the reaction chamber; and a heat exchanger, wherein the reaction outlet of the reaction chamber is connected to the inlet of a second heat exchanger to introduce the gaseous product generated by the endothermic reaction in the reactor into the second heat exchanger. The electrically heated fixed-bed propane dehydrogenation reaction system of this utility model can effectively reduce the reactor inlet temperature, the length of high-temperature pipelines within the reaction system, and the amount of coking in the side reactions. It features a large single-reactor processing capacity, controllable reaction temperature, high reaction conversion rate, high propylene selectivity, and high energy utilization efficiency. It also boasts advantages such as a short process flow, fewer pieces of equipment, low equipment investment, low energy consumption, and good economic benefits.

Description

Technical Field

[0001] This utility model relates to the technical field of propane dehydrogenation reaction equipment, and in particular to an electrically heated fixed-bed propane dehydrogenation reaction system. Background Technology

[0002] The propane dehydrogenation reaction is an endothermic reaction, and the higher the reaction temperature, the more it helps to increase the conversion rate and reaction rate of the main reaction.

[0003] Traditional propane dehydrogenation reactors are adiabatic reactors, and the reaction temperature gradually decreases during the reaction due to heat absorption. Therefore, in order to maintain a sufficient reaction temperature at the reactor outlet to meet the reaction requirements, the reactant gas is heated by a heater before entering the reactor inlet.

[0004] Excessive heating temperature in the feed heater can lead to carbon buildup, side reactions, and catalyst coking. In addition, the temperature inside the reactor decreases as the reaction progresses, making it difficult to control the temperature within the reactor within a suitable range, thereby reducing the conversion rate and selectivity of propane dehydrogenation. Utility Model Content

[0005] This invention provides an electrically heated fixed-bed reaction system suitable for propane dehydrogenation reaction, which can improve energy utilization and reduce energy consumption.

[0006] This utility model provides an electrically heated fixed-bed reaction system, which includes: The reactor includes a shell having a reaction chamber, and an electric heating device and a catalyst bed disposed within the reaction chamber; A heat exchanger includes a first heat exchange chamber and a second heat exchange chamber that are not connected to each other but can exchange heat; the inlet of the first heat exchange chamber is connected to a reaction gas source, and the outlet of the first heat exchange chamber is connected to the reaction inlet of the reaction chamber. The reaction outlet of the reaction chamber is connected to the inlet of the second heat exchange chamber so that the gaseous product generated by the endothermic reaction in the reactor is introduced into the second heat exchange chamber. The gaseous product is used as a heating medium to preheat the reaction gas source, thereby recovering and utilizing the heat of the gaseous product.

[0007] In one embodiment, the electric heating device includes: An electric heating rod extends axially through the catalyst bed, and several electric heating rods are arranged at intervals along the circumference of the shell; the electric heating rods are connected to a power source and are used to supply heat to the reaction chamber.

[0008] In one implementation, the arrangement of several electric heating rods in the reaction chamber is an equilateral triangle arrangement, a corner triangle arrangement, a square arrangement, or a corner square arrangement.

[0009] In one embodiment, one end of each of the electric heating rods is fixed to the first fixing plate, and the other end of each of the electric heating rods is fixed to the second fixing plate. The first fixing plate and the second fixing plate are respectively fixed to the housing.

[0010] In one embodiment, a support plate is provided on the inner wall of the housing at the middle of the electric heating rod, and the middle of each electric heating rod passes through the support plate.

[0011] In one embodiment, a gas distributor is provided inside the reaction chamber of the shell and near the reaction inlet.

[0012] In one embodiment, the reaction inlet and reaction outlet are located on the radially opposite sidewalls of the shell; the catalyst bed is located between the reaction inlet and reaction outlet.

[0013] In one embodiment, multiple reaction inlets and outlets are provided, with each reaction inlet located on the radial side of the shell and arranged at intervals along the axial direction of the shell; Each reaction outlet is located on the other side of the shell radially and is arranged at intervals along the shell axial direction.

[0014] In one embodiment, the reaction gas source is propane, and the gaseous product is propylene; The heating temperature of the electric heating device is controlled within the range of 500℃ to 650℃.

[0015] As one embodiment, it also includes a heater having a heating chamber, the inlet of which is connected to the outlet of the first heat exchange chamber, and the outlet of which is connected to the reaction inlet of the reaction chamber. The heating temperature of the heater is higher than the preheating temperature of the heat exchanger and lower than the heating temperature of the electric heating device.

[0016] Compared with the prior art, the advantages of this utility model are: The electrically heated fixed-bed propane dehydrogenation reaction system in this embodiment is suitable for propane dehydrogenation reactions, and its basic principle is as follows: Propane gas is introduced into the first heat exchange chamber of the heat exchanger. The propane gas in the first heat exchange chamber exchanges heat with the high-temperature heating medium in the second heat exchange chamber to preheat the propane gas. The preheated propane gas is then discharged from the outlet of the first heat exchange chamber and enters the reaction chamber. Compared with directly introducing room temperature propane gas into the reaction chamber, the method of preheating the propane gas by the heat exchanger can reduce the temperature drop in the reactor and save the power consumption of the electric heating device.

[0017] The electric heating device is used to heat the propane in the reaction chamber. The heating temperature of the electric heating device is controlled within the range of 500℃ to 650℃, thereby providing the temperature conditions for the propane to carry out the endothermic dehydrogenation reaction.

[0018] The propylene produced by the dehydrogenation reaction in the reaction chamber has a high temperature. The high-temperature propylene and hydrogen are passed into the second heat exchange chamber of the heat exchanger as a heating medium to preheat the propane entering the first heat exchange chamber. This process recovers and utilizes the high-temperature heat from the propylene and hydrogen, improving energy efficiency. The cooled propylene and hydrogen are then discharged from the outlet of the second heat exchange chamber to a downstream gas separation unit for gas separation. Attached Figure Description

[0019] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings.

[0020] Figure 1 This is a flowchart of the electrically heated fixed-bed propane dehydrogenation reaction system in the first embodiment; Figure 2 This is a schematic diagram of the reactor structure; Figure 3 yes Figure 2 Cross-sectional view at section AA; Figure 4 This is a flowchart of the electrically heated fixed-bed propane dehydrogenation reaction system in the second embodiment; Figure 5 This is a flowchart of the electrically heated fixed-bed propane dehydrogenation reaction system in the third embodiment.

[0021] Figure label: 1. Heat exchanger; 11. First heat exchange chamber; 12. Second heat exchange chamber; 2. Reactor; 21. Shell; 211. Reaction chamber; 212. Reaction inlet; 213. Reaction outlet; 214. Central feed pipe; 22. Catalyst bed; 23. Electric heating rod; 24. Electrical junction box; 25. First fixing plate; 26. Second fixing plate; 27. Support plate; 28. End cap; 29. ​​Gas distributor; 3. Heater. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings.

[0023] Example 1 This utility model provides an electrically heated fixed-bed propane dehydrogenation reaction system, which includes a reactor 2 and a heat exchanger 1.

[0024] The reactor 2 includes a shell 21, an electric heating device, and a catalyst bed 22. The shell 21 is cylindrical and has a reaction chamber 211 inside. The shell 21 is provided with a reaction inlet 212 and a reaction outlet 213 that communicate with the reaction chamber 211. The electric heating device and the catalyst bed 22 are both located inside the reaction chamber 211.

[0025] The heat exchanger 1 includes a first heat exchange chamber 11 and a second heat exchange chamber 12 that are not connected to each other but can exchange heat. The inlet of the first heat exchange chamber 11 is connected to the reaction gas source, and the outlet of the first heat exchange chamber 11 is connected to the reaction inlet 212 of the reaction chamber 211. The reaction outlet 213 of the reaction chamber 211 is connected to the inlet of the second heat exchange chamber 12 so that the gaseous product generated by the endothermic reaction in the reactor 2 is introduced into the second heat exchange chamber 12, and the gaseous product is used as a heating medium to preheat the reaction gas source, thereby recovering and utilizing the heat of the gaseous product.

[0026] If the reaction gas source can be propane, then the gaseous product generated by the endothermic reaction is propylene product gas.

[0027] The electrically heated fixed-bed propane dehydrogenation reaction system in this embodiment is suitable for propane dehydrogenation reactions, and its basic principle is as follows: Propane undergoes heat exchange with high-temperature reaction gases to preheat the propane gas source, which then enters the reaction chamber 211. Compared to directly introducing room-temperature propane gas into the reaction chamber 211, preheating the propane gas source by the heat exchanger 1 reduces the temperature drop within the reactor 2 and saves power consumption of the electric heating device.

[0028] The electric heating device can be a resistance heating device, which can heat the propane in the reaction chamber 211 after being electrically connected to the power supply. The heating temperature of the electric heating device is controlled within the range of 500℃~650℃, thereby providing the temperature conditions for the propane to carry out the endothermic dehydrogenation reaction.

[0029] The propylene product gas generated by the dehydrogenation reaction in reaction chamber 211 has a high temperature. This high-temperature propylene product gas is passed into heat exchanger 1 as a heating medium to preheat propane, thereby recovering and utilizing the high-temperature heat of the propylene product gas and improving energy utilization. The cooled propylene product gas is then sent to a downstream gas separation unit for gas separation.

[0030] The electric heating device in this embodiment will be described below.

[0031] The electric heating device includes an electric heating rod 23, which is a resistance heating element. The electric heating rod 23 is connected to an external junction box 24 and is connected to a power source through the junction box 24. The electric heating rod 23 provides a heat source to the reaction chamber 211 through the principle of resistance heat dissipation, which can ensure the stability of the reaction temperature in the reactor 2.

[0032] The operating temperature inside reactor 2 is controlled between 500℃ and 650℃, preferably between 550℃ and 620℃.

[0033] The reaction operating pressure in reactor 2 is controlled between -0.05 and 0.5 MPaG, preferably between -0.03 and 0.2 MPaG.

[0034] The arrangement of the electric heating rods 23 is as follows: the electric heating rods 23 extend axially along the shell 21 and pass through the catalyst bed 22, and several electric heating rods 23 are arranged at intervals along the circumference of the shell 21.

[0035] The electric heating rods 23 can be arranged in an equilateral triangle, a corner triangle, a square, or a corner square, etc. Equilateral triangle and square arrangements are preferred.

[0036] The electric heating rods 23 are arranged in the manner of reaction tubes in the field of heat exchangers, which can provide uniform heat in the reaction chamber 211 and improve the uniformity of heat in the reaction chamber 211.

[0037] The outer diameter of the electric heating rod 23 is controlled within the range of 5mm to 50mm, preferably 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, 25mm or 32mm.

[0038] The electric heating rod 23 is fixed in the following way: one end of each electric heating rod 23 is fixed to the first fixing plate 25, which is fixedly sealed at the top opening of the housing 21. The function of the first fixing plate 25 is twofold: firstly, to fix the electric heating rod 23, and secondly, to seal the top opening of the housing 21, thereby separating the reaction chamber 211 of the housing 21 from the outside. The first fixing plate 25 serves multiple purposes.

[0039] The other end of each electric heating rod 23 is fixed on the second fixing plate 26. The second fixing plate 26 is spaced below the first fixing plate 25 and fixed on the inner wall of the housing 21.

[0040] A support plate 27 is also provided on the inner wall of the housing 21 at the middle of the electric heating rod 23, and the middle of each electric heating rod 23 passes through the support plate 27.

[0041] Multiple support plates 27 are provided, and the multiple support plates 27 are arranged at intervals along the axial direction of the electric heating rod 23, and are used to provide stable support for the electric heating rod 23.

[0042] A gas distributor 29 is provided inside the reaction chamber 211 of the shell 21, near the reaction inlet 212. The gas distributor 29 allows the reaction gas to enter the catalyst bed 22 uniformly, achieving uniformity and stability of the reaction bed.

[0043] The reaction inlet 212 and the reaction outlet 213 are located on the radially opposite sidewalls of the shell 21; the catalyst bed 22 is located between the reaction inlet 212 and the reaction outlet 213.

[0044] To ensure the uniformity of gas flow within reactor 2, multiple reaction inlets 212 and reaction outlets 213 are provided. Each reaction inlet 212 is located on one radial side of the shell 21 and is arranged at intervals along the axial direction of the shell 21. Each reaction outlet 213 is located on the other radial side of the shell 21 and corresponds one-to-one with the reaction inlet 212.

[0045] The number of reaction inlets 212 and reaction outlets 213 can be 1 to 20, preferably 1 to 10.

[0046] The support plates 27 are arranged horizontally, and the number of support plates 27 can be adjusted according to the number of reaction inlets 212. Each support plate 27 is located between the upper and lower reaction inlets 212 in the longitudinal position. The support plates 27 can divide the reaction chamber 211 into zones and guide the gas in the reaction chamber 211 to improve the uniformity and flow stability of the gas.

[0047] The heat exchanger 1 can be a tubular heat exchanger, a plate heat exchanger, or other high-efficiency heat exchangers. In one embodiment, it can be divided into a first heat exchange chamber 11 and a second heat exchange chamber 12.

[0048] Existing tubular heat exchangers, such as the Chinese patent (publication number: CN112923759A) which discloses a vertical heat exchanger, include a shell side and a lower tube box disposed below the shell side. The shell side has a shell side inlet and a shell side outlet on its side wall, and the lower tube box has a tube side outlet at its bottom. An upper tube box is disposed in the inner cavity of the shell side. A heat exchange tube, a single-baffle plate, and a support plate are disposed between the upper tube box and the lower tube box. The heat exchange tube connects the upper tube box and the lower tube box. An expansion joint assembly is disposed at the top of the upper tube box, and a tube side inlet is disposed at the top of the expansion joint assembly.

[0049] For example, Chinese Patent (Publication No.: CN108981427A) discloses a shell-and-tube heat exchanger, including a shell, an upper tube sheet, a lower tube sheet, and a tube bundle. The shell includes an upper end cap, a housing, and a lower end cap arranged sequentially from top to bottom; the upper tube sheet is connected between the upper end cap and the housing; the lower tube sheet is disposed between the housing and the lower end cap and is connected to the lower end cap; the upper end of the tube bundle is connected to the upper tube sheet and communicates with the internal space of the upper end cap, and the lower end is connected to the lower tube sheet and communicates with the internal space of the lower end cap; there is a gap between the lower tube sheet and the lower end of the housing; a shell-side inlet is provided on the upper part of the housing; and a tube-side outlet and a tube-side inlet are provided on the upper end cap.

[0050] The heat exchanger 1 can be any of the above-mentioned patents. Of course, those skilled in the art can also choose according to actual needs. The specific structure of the heat exchanger 1 will not be described in detail.

[0051] The reaction conditions are explained below using a propane dehydrogenation reaction with a scale of 600,000 tons / year as an example.

[0052] A gaseous propane feedstock at a temperature of 40℃, a pressure of 0.5MPaG, and a flow rate of 185000kg / h is preheated in the first heat exchange chamber 11 of heat exchanger 1. After the propane is preheated to 550℃, it is fed into reactor 2 for propane dehydrogenation reaction to obtain propylene product gas at a temperature of 600℃ and a pressure of 0.0MPaG.

[0053] The high-temperature propylene product gas discharged from the reaction outlet 213 is introduced into the second heat exchange chamber 12 of the heat exchanger 1 as a heat source to heat the raw material propane introduced into the first heat exchange chamber 11 to 550°C, thereby improving the energy utilization efficiency of the reaction system. After heat recovery, the temperature of the high-temperature propylene product gas introduced into the second heat exchange chamber 12 can be reduced to 147.1°C, and then the propylene product gas is transported to the downstream product gas separation unit.

[0054] Reactor 2 is a single vertical fixed-bed reactor with a diameter of 4.5m and a length of 8m. The operating pressure of reactor 2 is atmospheric pressure, and the operating temperature is 600℃.

[0055] The total number of electric heating rods 23 is 7000, and the core-to-core distance of the tubes is selected as 50mm. In order to ensure the uniformity of bed temperature, 10mm electric heating rods 23 are used according to the standard. The electric heating rods 23 are arranged in an equilateral triangle in reactor 2.

[0056] The reaction inlet 212 and the reaction outlet 213 are radially symmetrically designed on the shell 21. There are three reaction inlets 212 and three reaction outlets 213, so that the pressure drop of propane gas in the reactor 2 can be controlled below 5 kPa.

[0057] Example 2 The electrically heated fixed-bed propane dehydrogenation reaction system in this embodiment is basically the same as that in Embodiment 1, except that the electrically heated fixed-bed propane dehydrogenation reaction system in this embodiment also includes a heater 3 disposed between the heat exchanger 1 and the reactor 2.

[0058] The heater 3 has a heating chamber, the inlet of which is connected to the outlet of the first heat exchange chamber 11, and the outlet of which is connected to the reaction inlet 212 of the reaction chamber 211. The heating temperature of the heater 3 is higher than the preheating temperature of the heat exchanger 1 and lower than the heating temperature of the electric heating device.

[0059] Heater 3 can be an electric heater, a gas heater, an electric heater, etc.

[0060] In this embodiment, the propane gas source is first introduced into the first heat exchange chamber 11 of the heat exchanger 1 for preheating; the preheated propane is then introduced into the heater 3 for secondary preheating, so that the temperature of the propane can be further increased in stages; then the propane is introduced into the reactor 2, and under the catalytic action of the catalyst bed 22 and the heating action of the electric heating device, the propane absorbs heat and undergoes a dehydrogenation reaction in the reaction chamber 211.

[0061] The generated high-temperature propylene product gas is discharged from the reaction outlet 213 and introduced into the second heat exchange chamber 12 of the heat exchanger 1 as a heating medium to preheat the fresh propane introduced into the first heat exchange chamber 11, thereby recovering and utilizing the high-temperature heat in the propylene product gas and improving energy utilization. The cooled propylene product gas is discharged from the second heat exchange chamber 12 to the downstream gas separation device for gas separation.

[0062] Example 3 The electrically heated fixed-bed propane dehydrogenation reaction system in this embodiment is basically the same as that in Embodiment 1. The difference is that the reactor in this embodiment is an axial-radial reactor, and the reaction inlet 212 is located on the end cap 28 at one axial end of the reactor 2.

[0063] A central feed pipe 214, coaxial with reactor 2, is installed inside the center of reaction chamber 211. One end of the central feed pipe 214 is connected to reaction inlet 212, and the other end extends to the other axial end of reactor 2. Multiple channels are arranged on the peripheral wall of the central feed pipe 214 to feed propane feed material into reactor 2 after it is evenly distributed through the central pipe 214.

[0064] Propane, preheated by heat exchanger 1, is fed into central feed pipe 214 and enters reaction chamber 211 through vent hole on central feed pipe 214, thereby contacting catalyst bed 22 in reaction chamber 211, absorbing heat at high temperature and undergoing dehydrogenation reaction.

[0065] The gas distributor is installed outside the central feed pipe 214.

[0066] Of course, reactor 2 can be horizontal or vertical, and the feeding and discharging methods of propane in reactor 2 can also be top-in-bottom-out, bottom-in-top-out, middle-in-top-bottom-out, and top-bottom-in-middle-out, etc.

[0067] Although the present invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. An electrically heated fixed-bed propane dehydrogenation reaction system, characterized in that, include: The reactor includes a shell having a reaction chamber, and an electric heating device and a catalyst bed disposed within the reaction chamber; A heat exchanger includes a first heat exchange chamber and a second heat exchange chamber that are not connected to each other but can exchange heat; the inlet of the first heat exchange chamber is connected to a reaction gas source, and the outlet of the first heat exchange chamber is connected to the reaction inlet of the reaction chamber. The reaction outlet of the reaction chamber is connected to the inlet of the second heat exchange chamber so that the gaseous product generated by the endothermic reaction in the reactor is introduced into the second heat exchange chamber. The gaseous product is used as a heating medium to preheat the reaction gas source, thereby recovering and utilizing the heat of the gaseous product.

2. The electrically heated fixed-bed propane dehydrogenation reaction system according to claim 1, characterized in that, The electric heating device includes: An electric heating rod extends axially through the catalyst bed, and several electric heating rods are arranged at intervals along the circumference of the shell; the electric heating rods are connected to a power source and are used to supply heat to the reaction chamber.

3. The electrically heated fixed-bed propane dehydrogenation reaction system according to claim 2, characterized in that, The electric heating rods are arranged in the reaction chamber in an equilateral triangle, a corner triangle, a square, or a corner square arrangement.

4. The electrically heated fixed-bed propane dehydrogenation reaction system according to claim 2 or 3, characterized in that, One end of each of the electric heating rods is fixed to the first fixing plate, and the other end of each of the electric heating rods is fixed to the second fixing plate. The first fixing plate and the second fixing plate are respectively fixed to the housing.

5. The electrically heated fixed-bed propane dehydrogenation reaction system according to claim 4, characterized in that, A support plate is also provided on the inner wall of the housing at the middle of the electric heating rod, and the middle of each electric heating rod passes through the support plate.

6. The electrically heated fixed-bed propane dehydrogenation reaction system according to any one of claims 1-3, characterized in that, A gas distributor is provided inside the reaction chamber of the shell and near the reaction inlet.

7. The electrically heated fixed-bed propane dehydrogenation reaction system according to claim 6, characterized in that, The reaction inlet and reaction outlet are located on the radially opposite sidewalls of the shell; the catalyst bed is located between the reaction inlet and reaction outlet.

8. The electrically heated fixed-bed propane dehydrogenation reaction system according to claim 7, characterized in that, The reaction inlets and reaction outlets are each configured as multiple, with each reaction inlet located on the radial side of the shell and arranged at intervals along the axial direction of the shell; Each reaction outlet is located on the other side of the shell radially and is arranged at intervals along the shell axial direction.

9. The electrically heated fixed-bed propane dehydrogenation reaction system according to any one of claims 1-3, characterized in that, The reaction gas source is propane, and the gaseous product is propylene product gas. The heating temperature of the electric heating device is controlled within the range of 500℃ to 650℃.

10. The electrically heated fixed-bed propane dehydrogenation reaction system according to any one of claims 1-3, characterized in that, It also includes a heater with a heating chamber, the inlet of which is connected to the outlet of the first heat exchange chamber, and the outlet of which is connected to the reaction inlet of the reaction chamber. The heating temperature of the heater is higher than the preheating temperature of the heat exchanger and lower than the heating temperature of the electric heating device.

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