Conductive ceramic material, cracking furnace tube and reactor based on conductive ceramic material, and applications of conductive ceramic material and cracking furnace tube and reactor

Abstract

The invention relates to the technical field of petroleum cracking, and discloses a conductive ceramic material, a cracking furnace tube and a reactor based on the conductive ceramic material, and applications of the conductive ceramic material and the cracking furnace tube. The conductive ceramic material provided by the invention is conductive ceramic taking SiC as a main component, current is directly conducted to the tube wall of the cracking furnace tube made of the conductive ceramic, and petroleum hydrocarbon in the tube is heated by utilizing heat generated by short-circuit current, so that on one hand, the heat loss is small, and on the other hand, the heating efficiency is improved; on the other hand, the tube wall temperature of the radiation section furnace tube can be controlled through voltage and current, so that the depth of petroleum hydrocarbon cracking reaction can be controlled.

Description

Technical Field

[0001] This invention relates to the field of petroleum cracking technology, and more specifically, to a conductive ceramic material and cracking furnace tubes and reactors based thereon, as well as their applications. Background Technology

[0002] Petroleum cracking is one of the main methods for producing hydrocarbon compounds in industry. Traditional cracking furnaces generally use methane, hydrogen and other fuels, and provide heat for cracking by mixing in air for combustion. However, this combustion heating method produces a large amount of carbon dioxide and carbon monoxide, making it difficult for the carbon emissions of the petrochemical industry to meet the increasingly stringent energy conservation and emission reduction requirements of industrial production.

[0003] Electric heating is a common heating method in daily life. Using clean energy sources (such as electricity generated by wind, solar, and other methods) as a heat source can significantly reduce carbon emissions. For example, CN1315489A and CN113652246A respectively provide methods for heating cracking furnaces using resistance wire heating or electric heating elements for petroleum cracking. However, electric heating elements are easily damaged when heated to the temperature required for petroleum cracking, leading to unstable operation of the reaction unit and the need for frequent shutdowns and element replacements.

[0004] Therefore, there is an urgent need to develop methods and supporting equipment for petroleum cracking reactions that can operate sustainably and stably using clean energy electricity. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of high carbon emissions in fuel-heated pyrolysis furnaces used for preparing hydrocarbon compounds from petroleum, and the difficulty in long-term stable operation of electrically heated pyrolysis furnaces. This invention provides a conductive ceramic material, pyrolysis furnace reactor tubes and reactors based on the material, and their applications. The conductive ceramic material provided by this invention can be used to prepare radiant section reactor tubes for pyrolysis furnaces. Reactors using this reactor tube can utilize electric heating for petroleum pyrolysis, which is more environmentally friendly than traditional combustion heating methods, and the reaction temperature is more controllable. Furthermore, the reactor tubes prepared with this conductive ceramic material have stronger resistance to coking, enabling long-term stable operation of the pyrolysis reaction.

[0006] To achieve the above objectives, the present invention provides a conductive ceramic material, wherein the conductive ceramic material comprises SiC and a conductive material;

[0007] The conductive ceramic material contains SiC content of not less than 60 wt.%.

[0008] The resistivity of the conductive ceramic material does not exceed 100 Ω·cm.

[0009] A second aspect of the present invention provides a method for preparing a conductive ceramic material, the method comprising mixing and grinding SiC and a conductive material, pressing them into a molded shape to obtain a molded preform, and sintering the molded preform.

[0010] Wherein, the resistivity of the conductive material does not exceed 10. -3 Ω·cm;

[0011] The SiC content is not less than 60 wt.% based on the total weight of SiC and conductive materials.

[0012] The third aspect of the present invention provides the application of the conductive ceramic material described in the first aspect, or the conductive ceramic material obtained by the method described in the second aspect, in petroleum cracking, particularly in the application in the preparation of reactor tubes in cracking furnaces.

[0013] The fourth aspect of the present invention provides a radiant section reactor tube for a pyrolysis furnace, wherein the material for preparing the reactor tube is provided by the conductive ceramic material described in the first aspect, or by the conductive ceramic material prepared by the method described in the second aspect.

[0014] The fifth aspect of the present invention provides a petroleum cracking reactor, the reactor comprising an electrically heated cracking system, the electrically heated cracking system comprising the radiant section reactor tubes described in the fourth aspect.

[0015] The sixth aspect of the present invention provides a method for preparing hydrocarbon compounds by electric heating steam cracking, the method comprising feeding petroleum feedstock into the reactor described in the fifth aspect, and under electric heating conditions, promoting the cracking of the petroleum feedstock entering the radiant section reactor tube.

[0016] The seventh aspect of the present invention provides the conductive ceramic material described in the first aspect, or the conductive ceramic material prepared by the method described in the second aspect; and / or, the reactor tube described in the fourth aspect; and / or, the reactor described in the fifth aspect; and / or, the method described in the sixth aspect, for application in extending the operating cycle of petroleum cracking and / or reducing carbon emissions from petroleum cracking.

[0017] Through the above technical solution, the present invention can achieve at least the following beneficial effects:

[0018] (1) The conductive ceramic material provided by the present invention has excellent mechanical and electrical properties, which can meet the requirements of the furnace tube material of the radiant section of the pyrolysis furnace. Furthermore, the preparation method is simple, the raw materials are readily available, and it is suitable for large-scale production and use.

[0019] (2) The reaction furnace tube prepared by the conductive ceramic material provided by the present invention can use clean energy electricity as the heat source for the cracking reaction, thereby greatly reducing carbon emissions in the cracking process and making the process of producing hydrocarbon compounds by cracking petroleum more in line with the requirements of green and sustainable industrial production.

[0020] (3) When using a reactor with a reaction furnace tube made of the conductive ceramic material provided by the present invention to carry out petroleum cracking, the emissions of nitrogen oxides and sulfides in the cracking furnace can be reduced;

[0021] (4) The reaction furnace tube prepared using the conductive ceramic material provided by the present invention can be directly energized during the reaction process, which has high heat utilization rate and low loss. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the conductive ceramic furnace tube structure used in the embodiment. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The inventors of this invention ingeniously discovered that a composite ceramic material obtained by mixing a material with good electrical conductivity with SiC, which is non-conductive but has good mechanical properties, and then pressing and sintering it, possesses both excellent mechanical properties and low resistivity, allowing for direct electrical heating. This composite material can be used to prepare the radiant section reactor tube of a novel pyrolysis furnace that uses electric heating as a heat source. Pyrolysis furnaces using reactor tubes made with this conductive ceramic material can effectively reduce carbon emissions from petroleum cracking by using clean energy electricity. Furthermore, since the reaction is directly heated by electricity through the reactor tube, the heat utilization rate is higher than that of traditional combustion heating methods or electric heating methods using electric heating elements. This allows for more precise control of the reaction temperature, thereby precisely controlling the reaction depth and extending the reaction cycle. In addition, compared to electric heating elements that cannot operate continuously at high temperatures for extended periods, the reactor tube made with the aforementioned composite conductive ceramic material can operate stably for a longer period, making the electrically heated petroleum cracking reaction a potential application in industrial production.

[0025] Based on this, the first aspect of the present invention provides a conductive ceramic material, the conductive ceramic material comprising SiC and a conductive material;

[0026] The conductive ceramic material contains SiC content of not less than 60 wt.%.

[0027] The resistivity of the conductive ceramic material does not exceed 100 Ω·cm.

[0028] For example, the SiC content in the conductive ceramic material can be 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, 90 wt.%, 95 wt.%, 96 wt.%, 97 wt.%, 98 wt.%, or 99 wt.%, or a range consisting of any two of the above values, or any intermediate value within that range.

[0029] Preferably, the SiC content in the conductive ceramic material is 65-95 wt.%.

[0030] According to a preferred embodiment of the present invention, the average particle size of SiC in the conductive ceramic material does not exceed 1 μm, and is preferably 0.1-0.8 μm.

[0031] According to a preferred embodiment of the present invention, the columnar SiC grains account for 70 wt.% or more of the total SiC, preferably 85 wt.% or more.

[0032] For example, in the conductive ceramic material, the columnar SiC grains can be 85wt.%, 88wt.%, 90wt.%, 91wt.%, 92wt.%, 93wt.%, 94wt.%, 95wt.%, 96wt.%, 97wt.%, 98wt.%, 99wt.%, 99.5wt.%, or 99.9wt.% of the total SiC, or a range consisting of any two of the above values, or any intermediate value within that range.

[0033] Preferably, in the conductive ceramic material, the columnar SiC grains account for 85 wt.%-99 wt.% of the total SiC content, more preferably 90-99 wt.%.

[0034] According to a preferred embodiment of the present invention, the conductive material is selected from at least one of ZrB2, Y2O3 and Al2O3.

[0035] According to a preferred embodiment of the present invention, the content of conductive material in the conductive ceramic material does not exceed 40 wt.%.

[0036] For example, the content of conductive material in the conductive ceramic material can be 1 wt.%, 5 wt.%, 8 wt.%, 10 wt.%, 12 wt.%, 14 wt.%, 16 wt.%, 18 wt.%, 20 wt.%, 22 wt.%, 24 wt.%, 26 wt.%, 28 wt.%, 30 wt.%, 32 wt.%, 34 wt.%, 36 wt.%, 38 wt.%, or 40 wt.%, or it can be a range consisting of any two of the above values, or any intermediate value within that range.

[0037] Preferably, the conductive ceramic material contains 5-40 wt.% conductive material.

[0038] According to a preferred embodiment of the present invention, the conductivity of the conductive ceramic material is 1-100 Ω·cm.

[0039] For example, the conductivity of the conductive ceramic material can be 1 Ω·cm, 5 Ω·cm, 10 Ω·cm, 11 Ω·cm, 12 Ω·cm, 13 Ω·cm, 14 Ω·cm, 15 Ω·cm, 16 Ω·cm, 17 Ω·cm, 18 Ω·cm, 19 Ω·cm, 20 Ω·cm, 22 Ω·cm, 24 Ω·cm, 26 Ω·cm, 28 Ω·cm, 30 Ω·cm, 35 Ω·cm, 40 Ω·cm, 45 Ω·cm, 50 Ω·cm, 60 Ω·cm, 70 Ω·cm, 80 Ω·cm, 90 Ω·cm, or 100 Ω·cm, or it can be a range consisting of any two of the above values, or any intermediate value within that range.

[0040] Preferably, the conductivity of the conductive ceramic material is 5-30 Ω·cm, and more preferably 10-20 Ω·cm.

[0041] According to a preferred embodiment of the present invention, the flexural strength of the conductive ceramic material is not less than 800 MPa.

[0042] For example, the flexural strength of the conductive ceramic material can be 800MPa, 820MPa, 840MPa, 860MPa, 880MPa, 900MPa, 920MPa, 940MPa, 960MPa, 980MPa, 1000MPa, 1020MPa, 1040MPa, 1060MPa, 1080MPa, 1100MPa, 1150MPa, 1200MPa, 1250MPa, or 1300MPa, or it can be a range consisting of any two of the above values, or any intermediate value within that range.

[0043] Preferably, the flexural strength of the conductive ceramic material is 800-1200 MPa;

[0044] According to a preferred embodiment of the present invention, the hardness of the conductive ceramic material is not less than 10 GPa.

[0045] For example, the hardness of the conductive ceramic material can be 10GPa, 11GPa, 12GPa, 13GPa, 14GPa, 15GPa, 16GPa, 17GPa, 18GPa, 19GPa, 20GPa, 22GPa, 24GPa, 26GPa, 28GPa, 30GPa, 35GPa, 40GPa, 45GPa, or 50GPa, or it can be a range consisting of any two of the above values, or any intermediate value within that range.

[0046] Preferably, the hardness of the conductive ceramic material is 10-20 GPa.

[0047] A second aspect of the present invention provides a method for preparing a conductive ceramic material, the method comprising mixing and grinding SiC and a conductive material, pressing them into a molded shape to obtain a molded preform, and sintering the molded preform.

[0048] Wherein, the resistivity of the conductive material does not exceed 10. -3 Ω·cm;

[0049] The SiC content is not less than 60 wt.% based on the total weight of SiC and conductive materials.

[0050] According to a preferred embodiment of the present invention, the purity of the SiC is not less than 90% and the average particle size is not more than 1 μm.

[0051] Preferably, the purity of the SiC is 95-100% and the average particle size is 0.1-0.8 μm.

[0052] Preferably, the content of isometric grains in the SiC is above 80 wt.%, and more preferably above 90 wt.%.

[0053] For example, the content of isometric grains in SiC can be 80 wt.%, 85 wt.%, 90 wt.%, 91 wt.%, 92 wt.%, 93 wt.%, 94 wt.%, 95 wt.%, 96 wt.%, 97 wt.%, 98 wt.%, 99 wt.%, 99.2 wt.%, 99.4 wt.%, 99.6 wt.%, 99.8 wt.%, or 99.9 wt.%, or a range consisting of any two of the above values, or any intermediate value within that range.

[0054] Preferably, in the conductive ceramic material, the columnar SiC grains account for 90-99.9 wt.% of the total SiC content, more preferably 95-99.9 wt.%.

[0055] According to a preferred embodiment of the present invention, the conductive material is selected from at least one of ZrB2, Y2O3 and Al2O3.

[0056] Preferably, the purity of the conductive material is not less than 95%, preferably 95-100%; the average particle size is not more than 1 μm, preferably 0.1-1 μm.

[0057] Preferably, the SiC content is 65-95 wt.%, based on the total weight of SiC and conductive materials.

[0058] More preferably, the total weight of SiC and conductive material is used as a basis, wherein the content of conductive material is 5-40 wt.%.

[0059] According to a preferred embodiment of the present invention, the mixing and grinding method includes mixing SiC and a conductive material in the presence of a solvent to form a slurry, and then grinding the slurry. The purpose of grinding is to better and more uniformly mix the raw materials.

[0060] Preferably, the solvent is selected from C 1-5 Anhydrous alcohol, preferably anhydrous ethanol.

[0061] Preferably, the amount of solvent used is such that the solid content in the slurry is not less than 50 wt.%, and more preferably 50-85 wt.%.

[0062] According to a preferred embodiment of the present invention, the compression molding process sequentially includes molding and compression steps. The molding step causes the ground and mixed composite material to initially form the desired shape, and then the compression step forms it into a dense composite material.

[0063] Preferably, the molding conditions include: pressure 20-60 MPa.

[0064] For example, the molding pressure can be 20MPa, 25MPa, 30MPa, 35MPa, 40MPa, 45MPa, 50MPa, 55MPa, or 60MPa, or it can be a range consisting of any two of the above values, or any intermediate value within that range.

[0065] For example, the compression pressure can be 100MPa, 120MPa, 140MPa, 160MPa, 180MPa, 200MPa, 220MPa, 240MPa, 260MPa, 280MPa, 300MPa, or a range consisting of any two of the above values, or any intermediate value within that range.

[0066] More preferably, the compression pressure is 2 to 15 times the molding pressure. For example, the compression pressure can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 times the molding pressure, or it can be a range consisting of any two of the above values, or any intermediate value within that range.

[0067] According to a preferred embodiment of the present invention, the sintering conditions include: a temperature of 1800-2400℃ and a time of 2-10h, wherein the preferred heating rate of the sintering treatment is 1-10℃ / min.

[0068] For example, the sintering temperature can be 1800℃, 1850℃, 1900℃, 1950℃, 2000℃, 2050℃, 2100℃, 2150℃, 2200℃, 2250℃, 2300℃, 2350℃, 2400℃, or a range consisting of any two of the above values, or any intermediate value within that range.

[0069] Preferably, the sintering process is carried out in a non-reactive atmosphere, preferably provided by nitrogen and / or an inert gas.

[0070] According to a preferred embodiment of the present invention, the method further includes a step of drying the product obtained by mixing and grinding.

[0071] Preferably, the drying conditions are such that the solvent content in the dried product does not exceed 1 wt.%.

[0072] More preferably, the drying conditions include: a temperature of 50-150°C and a time of 5-15 hours.

[0073] For example, the drying temperature can be 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, or 150℃, or it can be any range consisting of any two of the above values, or any intermediate value within that range.

[0074] According to a preferred embodiment of the present invention, the method further includes a step of cleaning the product obtained by sintering to remove adhering substances from its surface.

[0075] The third aspect of the present invention provides the application of the conductive ceramic material described in the first aspect, or the conductive ceramic material obtained by the method described in the second aspect, in petroleum cracking, particularly in the application in the preparation of reactor tubes in cracking furnaces.

[0076] The fourth aspect of the present invention provides a radiant section reactor tube for a pyrolysis furnace, wherein the material for preparing the reactor tube is provided by the conductive ceramic material described in the first aspect, or by the conductive ceramic material prepared by the method described in the second aspect.

[0077] In this invention, there are no particular limitations on the specific shape and size of the reactor tube, which can be varied according to the requirements of the pyrolysis process. For example, it can be a single-pass tube, a two-pass tube, or even a multi-pass tube. For example, the single-pass tubes and two-pass tubes commonly used in pyrolysis devices, such as type 1-1, type 2-1, type 4-1, or type 8-1, can all be prepared using the composite material of this invention.

[0078] The fifth aspect of the present invention provides a petroleum cracking reactor, the reactor comprising an electrically heated cracking system, the electrically heated cracking system comprising the radiant section reactor tubes described in the fourth aspect.

[0079] In the reactor provided by this invention, there are no particular restrictions on the specific configuration and number of the radiant section reactor tubes; any configuration commonly used in the art can be adopted. For example, the reactor tubes of this invention installed in the pyrolysis furnace can be one, or multiple tubes connected in series or parallel, and their arrangement can be horizontal or suspended, etc.

[0080] According to a preferred embodiment of the present invention, the electrically heated pyrolysis system further includes a voltage regulator connected to the connected reactor tube for adjusting the voltage to control the reaction temperature.

[0081] Preferably, the voltage regulator is a no-load voltage regulating transformer, an induction voltage regulator, a thyristor voltage regulator, or a magnetic voltage regulator, and is preferably a magnetic voltage regulator.

[0082] Preferably, the electric heating pyrolysis system further includes a data acquisition system and an optional computer control system. The data acquisition system is used to collect reaction temperature data inside the reactor tube during the reaction process, and the optional computer control system is used to control the pressure regulator according to the set program and the collected reaction temperature data inside the reactor tube to monitor the reaction temperature in real time.

[0083] Preferably, the outer side of the reactor tube is further covered with an insulation layer made of heat-insulating material. There are no particular limitations on the heat-insulating material used in this invention; any heat-insulating material commonly used in reactors in this art can be applied. For example, asbestos, refractory bricks, etc., can be used to make the insulation layer.

[0084] According to a preferred embodiment of the present invention, wherein, reference Figure 1In the aforementioned electrically heated pyrolysis system, the outer wall of the reactor tube 1 is wrapped with heat-insulating material to form a heat insulation layer 2. The electrode 3 (passing through the heat insulation layer 2) is connected to the reactor tube 1 and to a voltage regulator 4 connected to a power supply 5. Preferably, the voltage regulator 4 and the power supply can also be connected to a computer control system to achieve precise control of the furnace tube temperature.

[0085] The sixth aspect of the present invention provides a method for preparing hydrocarbon compounds by electric heating steam cracking, the method comprising feeding petroleum feedstock into the reactor described in the fifth aspect, and under electric heating conditions, promoting the cracking of the petroleum feedstock entering the radiant section reactor tube.

[0086] According to some preferred embodiments of the present invention, the electric heating conditions cause the temperature of the outer wall of the reactor tube to reach 1000-1600°C.

[0087] For example, the temperature of the outer wall of the reactor tube can be 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, or 1600℃, or it can be any range of any two of the above values, or any intermediate value in that range.

[0088] Preferably, the electric heating conditions result in a reactor tube outlet temperature of 800-900°C.

[0089] For example, the outlet temperature of the reactor tube can be 800℃, 805℃, 810℃, 815℃, 820℃, 825℃, 830℃, 835℃, 840℃, 845℃, 850℃, 855℃, 860℃, 865℃, 870℃, 875℃, 880℃, 885℃, 890℃, 895℃, or 900℃, or it can be a range consisting of any two of the above values, or any intermediate value within that range.

[0090] Any petroleum feedstock commonly used in the art for the cracking of hydrocarbon compounds using steam cracking can be cracked using the method provided by this invention. According to some preferred embodiments of the invention, the petroleum feedstock includes at least one of naphtha, ethane, liquefied petroleum gas, diesel oil, and hydrotreated tail oil.

[0091] The seventh aspect of the present invention provides the conductive ceramic material described in the first aspect, or the conductive ceramic material prepared by the method described in the second aspect; and / or, the reactor tube described in the fourth aspect; and / or, the reactor described in the fifth aspect; and / or, the method described in the sixth aspect, for application in extending the operating cycle of petroleum cracking and / or reducing carbon emissions from petroleum cracking.

[0092] The present invention will be described in detail below through embodiments. It should be understood that the following embodiments are only for illustrative purposes to further explain and illustrate the content of the present invention, and are not intended to limit the present invention.

[0093] Unless otherwise specified, all reagents and materials used in the following examples are commercially available products purchased from legitimate chemical reagent / material suppliers, and all reagents are of analytical grade.

[0094] Unless otherwise specified, the radiant section of the pyrolysis furnace used in the following embodiments is a single-pass furnace tube structure, which is made of a single horizontally placed conductive ceramic material or a traditional furnace tube (made of NiCr alloy).

[0095] Preparation Example

[0096] This preparation example illustrates the preparation and construction of the conductive ceramic material provided by the present invention, as well as the pyrolysis furnace containing the radiant section reactor tube of the pyrolysis furnace based on the conductive ceramic material.

[0097] (I) Preparation of conductive ceramic materials

[0098] SiC powder (approximately 97% purity) and conductive material powder (both 99% purity) were weighed according to the proportions in Table 1. Anhydrous ethanol was then added to the weighed materials to prepare a slurry with a solid content of approximately 65 ± 5 wt.%, which was then ground to ensure uniform mixing of the SiC and conductive material powders. After grinding, the product was dried (drying temperature 100℃, time approximately 10 hours, ethanol content of the dried material not exceeding 1 wt.%). Under the conditions in Table 2, the product was first shaped into rods, which were then compressed to obtain dense rods. The dense rods were sintered in an Ar atmosphere (sintering conditions detailed in Table 2). After sintering, the surface of the rods was cleaned to remove any adhering substances, yielding the conductive ceramic material.

[0099] Table 1

[0100]

[0101] Table 2

[0102] Material Number raw material Molding pressure / MPa Compression pressure / MPa Sintering temperature / °C Sintering time / h A1-1 1# 30 200 2000 5 A1-2 1# 35 150 1800 1 A1-3 1# 40 100 1850 2 A1-4 1# 45 250 1900 3 A1-5 1# 50 200 1950 4 A1-6 1# 55 300 2050 4.5 A1-7 1# 60 180 2100 6 A1-8 1# 65 120 2250 6.5 A1-9 1# 70 280 2300 7 A2 2# 40 150 2200 6 A3 3# 50 250 2100 8 A4 4# 25 300 2250 9 A5 5# 30 220 1900 10 A6 6# 35 180 1950 9.5 A7 7# 40 150 2000 4.5

[0103] The mechanical properties of the obtained conductive ceramic material were tested by Steel Research Institute Nake Testing Co., Ltd. The resistivity of the obtained conductive ceramic material was measured using a resistivity meter (Ningbo Ruike Micro Intelligent Technology Co., Ltd.). The SiC and conductive material content in the conductive ceramic material was calculated based on the slurry composition. The content of equiaxed and columnar SiC grains in the conductive ceramic material was detected by XRD and electron microscopy. The results are detailed in Table 3.

[0104] Table 3

[0105]

[0106] Note: The content of SiC equiaxed grains and columnar grains in Table 3 refers to the percentage of SiC in these two types of grains based on the total weight of SiC in the conductive ceramic material.

[0107] (II) Construction of the pyrolysis furnace

[0108] The conductive ceramic material prepared above was cut into a reaction furnace tube with a length of 12m, an outer diameter of 18cm, and an inner diameter of 12cm using electrical discharge machining.

[0109] refer to Figure 1 About 5cm of asbestos is wrapped around the outside of the reactor tube wall 1 as an insulation layer 2. The outer wall 1 of the reactor tube is connected to an electrode 3, which is connected to a voltage regulator 4 (a magnetic voltage regulator purchased from Yixing Xingyi Special Transformer Co., Ltd.). The voltage regulator 4 is connected to a power supply 5, forming a conductive ceramic furnace tube in the radiant section of the pyrolysis furnace.

[0110] By replacing the radiant section furnace tubes in a traditional cracking furnace with the aforementioned ceramic furnace tubes, a cracking furnace that uses electrical energy for petroleum cracking can be formed. A PLC is used to precisely control the voltage regulator current, thereby maintaining the outer wall temperature of the furnace tubes at a constant set temperature, and consequently controlling the outlet temperature of the cracked gas.

[0111] Example 1

[0112] In this embodiment, ethane is used as the cracking feedstock.

[0113] The radiant section furnace tubes of the traditional pyrolysis furnace were replaced with SiC-ZrB2 conductive ceramic furnace tubes made of conductive ceramic material A1-1 as shown in Table 3. The convection section remained unchanged, and the outlet temperature of the convection section furnace tubes was maintained at 600℃. The radiant section furnace tubes used a single-phase AC 220V power supply as the heating power source, and the outlet temperature of the radiant section furnace tubes was controlled at 862℃ through an electric heating system.

[0114] (1) The dilution steam and ethane are directly fed into the traditional preheating section at a weight ratio of 0.3 for mixing and preheating. The temperature of the preheated mixed gas is 600℃.

[0115] (2) The mixed gas obtained from the preheating section is introduced into the conductive ceramic furnace tube (radiation section). The outlet temperature of the radiation section furnace tube is controlled at 862℃, the outlet pressure is 0.17MPa, the residence time is 0.29s, and the ethane feed rate is 110kg / hour. After cracking, cracked gas is obtained.

[0116] Example 2

[0117] Naphtha was used as the pyrolysis feedstock in this embodiment.

[0118] The radiant section furnace tubes of the traditional pyrolysis furnace were replaced with SiC-ZrB2 conductive ceramic furnace tubes made of conductive ceramic material A2 as shown in Table 3. The convection section remained unchanged, and the outlet temperature of the convection section furnace tubes was maintained at 603℃. The radiant section furnace tubes used a three-phase AC 380V power supply as the heating power source, and the outlet temperature of the radiant section furnace tubes was controlled at 838℃ through an electric heating system.

[0119] (1) The dilution steam and naphtha are directly fed into the traditional preheating section at a weight ratio of 0.5 for mixing and preheating. The temperature of the preheated mixture is 603℃.

[0120] (2) The mixed gas obtained from the preheating section is introduced into the conductive ceramic furnace tube (radiation section). The outlet temperature of the radiation section furnace tube is 838℃, the outlet pressure of the pyrolysis section of the pyrolysis furnace is 0.17MPa, the residence time is 0.28s, the naphtha feed rate is 3.3 tons / hour, and the pyrolysis gas is obtained after pyrolysis.

[0121] Example 3

[0122] In this embodiment, diesel oil is used as the pyrolysis feedstock.

[0123] The radiant section furnace tubes of the traditional pyrolysis furnace were replaced with SiC-Y2O3-A12O3 conductive ceramic furnace tubes made of conductive ceramic material A3 as shown in Table 3. The convection section remained unchanged, and the outlet temperature of the convection section furnace tubes was maintained at 600℃. The radiant section furnace tubes used a single-phase DC 220V power supply as the heating power source, and the outlet temperature of the radiant section furnace tubes was controlled at 812℃ through an electric heating system. The pyrolysis section consisted of six pyrolysis furnace tubes, divided into two groups of three for each group to be electrically heated.

[0124] (1) The dilution steam and diesel are directly fed into the traditional preheating section at a weight ratio of 0.8 for mixing and preheating. The temperature of the preheated mixture is 600℃.

[0125] (2) The mixed gas obtained from the preheating section is introduced into the conductive ceramic furnace tube (radiation section). The outlet temperature of the radiation section furnace tube is 812℃, the outlet pressure of the pyrolysis section of the pyrolysis furnace is 0.17MPa, the residence time is 0.28s, the diesel feed rate is 6.6 tons / hour, and pyrolysis gas is obtained after pyrolysis.

[0126] Example 4

[0127] Using the methods and conditions in Example 1, ceramic furnace tubes made of the composite materials listed in Table 3 were used as the radiant section furnace tubes of the pyrolysis furnace to perform ethane pyrolysis.

[0128] Comparative Example

[0129] Ethane cracking to olefins is carried out in a conventional cracking furnace, with the furnace tubes in the radiant section made of NiCr alloy. Methane and hydrogen combustion provides heat to the cracking section. The high-temperature flue gas in the combustion chamber preheats the cracking feedstock and produces ultra-high-pressure steam through heat exchange in the convection section. The specific process is as follows:

[0130] (1) A dilution vapor / ethane with a weight ratio of 0.3 is mixed and preheated in the convection section, and the temperature of the preheated mixed gas is 600℃;

[0131] (2) The mixed gas, after being preheated in the convection section, is introduced into the cracking section. The mixed gas in the cracking tube undergoes a cracking reaction. The outlet temperature of the cracking furnace tube is 862℃, the outlet pressure of the cracking furnace tube is 0.17MPa, the residence time is 0.28s, the ethane feed rate is 1.1 tons / hour, and cracked gas is obtained after cracking.

[0132] Test case

[0133] The pyrolysis furnaces in each embodiment and comparative example were operated continuously until the tube wall temperature reached 1100°C. The continuous operating time (i.e., operating cycle) of each pyrolysis furnace was recorded, and the results are detailed in Table 4. The pyrolysis gases obtained from the above embodiments and comparative examples were separated by a subsequent system, and the composition of the pyrolysis gases was analyzed using gas chromatography. The average product yield (wt.%) within the operating cycle was calculated, and the results are detailed in Table 4.

[0134] Table 4

[0135]

[0136]

[0137] Note: In Table 4, * represents the test results of Example 1; ** represents the test results of Example 2; *** represents the test results of Example 3; the furnace tube material "NiCr" represents the test results of the comparative example, and the rest are the test results of Example 4.

[0138] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A conductive ceramic material, characterized in that, The conductive ceramic material includes SiC and conductive materials; The conductive ceramic material contains SiC content of not less than 60 wt.%. The resistivity of the conductive ceramic material does not exceed 100 Ω·cm.

2. The conductive ceramic material according to claim 1, wherein, The conductive material is selected from at least one of ZrB2, Y2O3 and Al2O3; Preferably, in the conductive ceramic material, the average particle size of SiC does not exceed 1 μm; Preferably, the SiC content in the conductive ceramic material is 65-95 wt.%. More preferably, the columnar SiC grains account for 70 wt.% or more of the total SiC, and more preferably 85 wt.% or more; Preferably, the conductive ceramic material contains no more than 40 wt.% conductive material, and more preferably 5-40 wt.% conductive material. Preferably, the conductivity of the conductive ceramic material is 1-100 Ω·cm; Preferably, the flexural strength of the conductive ceramic material is not less than 800 MPa, and more preferably 800-1200 MPa; Preferably, the hardness of the conductive ceramic material is not less than 10 GPa, and more preferably 10-20 GPa.

3. A method for preparing conductive ceramic materials, characterized in that, The method includes mixing and grinding SiC and conductive materials, pressing them into a molded shape to obtain a molded preform, and then sintering the molded preform. Wherein, the resistivity of the conductive material does not exceed 10. -3 Ω·cm; The SiC content is not less than 60 wt.% based on the total weight of SiC and conductive materials.

4. The method according to claim 3, wherein, The purity of the SiC is not less than 90%; the average particle size does not exceed 1 μm. Preferably, the purity of the SiC is 95-100% and the average particle size is 0.1-0.8 μm. Preferably, the content of isometric grains in the SiC is 80 wt.% or more, and more preferably 90 wt.% or more; And / or, the conductive material is selected from at least one of ZrB2, Y2O3 and Al2O3; Preferably, the purity of the conductive material is not less than 95%, and more preferably 95-100%; the average particle size does not exceed 1 μm. More preferably, based on the total weight of SiC and conductive materials, the content of SiC is 65-95 wt.%. More preferably, the total weight of SiC and conductive material is used as a basis, wherein the content of conductive material is 5-35 wt.%.

5. The method according to claim 3 or 4, wherein, The mixed grinding method includes mixing SiC and conductive materials in the presence of a solvent to form a slurry, and then grinding the slurry. Preferably, the solvent is selected from C 1-5 Anhydrous alcohol, preferably anhydrous ethanol; Preferably, the amount of solvent used is such that the content of solid matter in the slurry is not less than 50 wt.%, and more preferably 50-85 wt.%. And / or, the compression molding process includes the steps of molding and compression in sequence; Preferably, the molding conditions include: a pressure of 20-60 MPa; Preferably, the compression conditions include: a pressure of 100-300 MPa; More preferably, the compression pressure is 2-15 times the molding pressure; And / or, the conditions for the sintering treatment include: a temperature of 1800-2400℃ and a time of 2-10h, preferably a heating rate of 1-10℃ / min; Preferably, the sintering process is carried out in a non-reactive atmosphere, preferably provided by nitrogen and / or an inert gas.

6. The method according to any one of claims 3-5, wherein, The method further includes a step of drying the product obtained by mixing and grinding; Preferably, the drying conditions are such that the solvent content in the dried product does not exceed 1 wt.%; preferred drying conditions include: temperature 50-150°C, time 5-15 h; And / or, the method further includes the step of cleaning the product obtained from the sintering process to remove any adhering substances from its surface.

7. The application of the conductive ceramic material according to claim 1 or 2, or the conductive ceramic material obtained by the method of any one of claims 3-6, in petroleum cracking, especially in the preparation of reactor tubes in cracking furnaces.

8. A reactor tube for the radiant section of a pyrolysis furnace, characterized in that, The material used to prepare the reactor tube is the conductive ceramic material as described in claim 1 or 2, or the conductive ceramic material prepared by any one of claims 3-6.

9. A petroleum cracking reactor, characterized in that, The reactor includes an electrically heated pyrolysis system, which includes the radiant section reactor tube as described in claim 8.

10. The reactor according to claim 9, wherein, The electric heating pyrolysis system also includes a voltage regulator connected to the connected reactor tube, used to adjust the voltage to control the reaction temperature; Preferably, the voltage regulator is a no-load voltage regulating transformer, an induction voltage regulator, a thyristor voltage regulator, or a magnetic voltage regulator, and is preferably a magnetic voltage regulator. Preferably, the electric heating pyrolysis system further includes a data acquisition system and an optional computer control system. The data acquisition system is used to collect reaction temperature data inside the reactor tube during the reaction process, and the optional computer control system is used to control the pressure regulator according to the set program and the collected reaction temperature data inside the reactor tube to monitor the reaction temperature in real time. Preferably, the outer side of the reactor tube is also covered with an insulation layer made of heat-insulating material.

11. A method for preparing hydrocarbon compounds by electric heating steam cracking, characterized in that, The method includes feeding petroleum feedstock into the reactor of claim 9 or 10, and under electrically heated conditions, causing the petroleum feedstock entering the radiant section reactor tube to crack.

12. The method according to claim 11, wherein, The electric heating conditions cause the temperature of the outer wall of the reactor tube to reach 1000-1600℃; Preferably, the electric heating conditions result in a reactor tube outlet temperature of 800-900°C; And / or, the petroleum feedstock includes at least one of naphtha, ethane, liquefied petroleum gas, diesel oil, and hydrotreated tail oil.

13. The conductive ceramic material of claim 1 or 2, or the conductive ceramic material prepared by the method of any one of claims 3-6; and / or the reactor tube of claim 8; and / or the reactor of claim 9 or 10; and / or the method of claim 11 or 12, for application in extending the operating cycle of petroleum cracking and / or reducing carbon emissions from petroleum cracking.

Images