Cracking furnace and organic matter cracking method

Abstract

The present application relates to the field of organic matter cracking, and discloses a cracking furnace and an organic matter cracking method, the cracking furnace comprising: a furnace tube, the furnace tube comprising MoSi2; and an electrode connected to the outer wall of the furnace tube.The cracking furnace can generate a short-circuit current by using the electrode, so as to heat the fluid flowing into the furnace tube, and the depth of the fluid cracking reaction can be controlled by controlling the tube wall temperature of the cracking furnace tube by using the voltage and the current.

Description

Technical Field

[0001] This invention relates to the field of organic matter pyrolysis, and more specifically to pyrolysis furnaces and methods for organic matter pyrolysis. Background Technology

[0002] Industrial ethylene cracking furnaces typically use a high-temperature flame and flue gas generated by the combustion of a mixture of fuel gas (mainly methane) and air to heat the furnace tubes. This process produces large amounts of carbon monoxide and carbon dioxide. Commonly used cracking furnaces employ traditional electric heating, utilizing the heat generated by energizing a resistance wire to heat the air and refractory bricks surrounding the furnace tubes. The air and refractory bricks then further heat the furnace tubes. A significant portion of this heat is directly radiated from the resistance wire to the furnace tubes, resulting in low thermal efficiency; less than 50% of the heat actually contributes to the cracking reaction itself. Furthermore, directly energizing the metal cracking furnace tubes can lead to electrified cracking gas, compromising operational safety and causing coking on the inner wall of the furnace tubes, thus affecting heat conduction. Summary of the Invention

[0003] The purpose of this invention is to overcome the technical problems of high carbon dioxide emissions, poor safety of pyrolysis furnaces, easy coking, and low thermal efficiency in the existing technology, and to provide a pyrolysis furnace and a method for pyrolysis of organic matter.

[0004] The inventors of this invention accidentally discovered in experiments that when the MoSi2 material furnace tube is oxidized at high temperature in air, a SiO2 coating is formed on the inner and outer surfaces. The outer surface is non-conductive, while the middle substrate is conductive. After directly passing a short-circuit current, the heat utilization rate is high, the loss is low, and a very high temperature can be reached. The tube wall temperature easily exceeds 1000°C, the selectivity of pyrolysis is wider, the inner wall is not easy to coke, and no carbon dioxide is produced during the heating process. Its performance is superior to that of traditional pyrolysis furnaces.

[0005] To achieve the above objectives, a first aspect of the present invention provides a pyrolysis furnace, the pyrolysis furnace comprising:

[0006] Furnace tube, the furnace tube comprising MoSi2;

[0007] An electrode is connected to the outer wall of the furnace tube.

[0008] A second aspect of the present invention provides a method for pyrolyzing organic matter, wherein the organic matter is fed into the pyrolysis furnace described above for pyrolysis.

[0009] The pyrolysis furnace provided by the present invention can generate a short-circuit current using the electrodes to heat the fluid introduced into the furnace tube. By controlling the tube wall temperature of the pyrolysis furnace tube through voltage and current, the depth of the fluid pyrolysis reaction can be controlled.

[0010] This pyrolysis furnace has the following advantages:

[0011] (1) Using clean energy electricity as a heat source for the pyrolysis reaction can greatly reduce carbon emissions during the pyrolysis process;

[0012] (2) The pyrolysis furnace of the present invention does not require the combustion of substances containing carbon, nitrogen and sulfur during the pyrolysis process, thus reducing the emissions of carbon dioxide, nitrogen oxides and sulfides;

[0013] (3) Direct power supply results in high heat utilization and low heat loss;

[0014] (4) It has a wider selectivity for pyrolysis, the inner wall is not easy to coke, and no carbon dioxide is produced during the heating process, making it superior to traditional pyrolysis furnaces. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a pyrolysis furnace according to a preferred embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of the organic matter pyrolysis device in Comparative Examples 1-4 of the present invention.

[0017] Explanation of reference numerals in the attached figures

[0018] 100 Liquid mass flow meter, 200 Gas mass flow meter, 300 Preheating equipment, 400 Pyrolysis furnace, 500 Quenching equipment, 600 Water cooling equipment, 700 Ice cooling equipment, 800 Buffer equipment, 900 Humidification equipment, 1000 Wet gas flow meter, 401 Furnace tube, 402 Electrode, 403 Temperature detection equipment, 404 Insulation layer. Detailed Implementation

[0019] 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.

[0020] The first aspect of the present invention provides a pyrolysis furnace, with reference to Figure 1 The pyrolysis furnace includes:

[0021] Furnace tube 401, wherein the furnace tube 401 comprises MoSi2;

[0022] Electrode 402 is connected to the outer wall of furnace tube 401.

[0023] In this invention, the furnace tube 401 is preferably a conductive ceramic with MoSi2 as the main component. Specifically, alternating current is directly applied to the wall of the furnace tube 401, and the heat generated by the short-circuit current is used to heat the fluid inside the tube. The electrodes generate a short-circuit current, thereby heating the fluid flowing into the furnace tube. The temperature of the furnace tube wall is controlled by voltage and current, thereby controlling the depth of the fluid pyrolysis reaction. Since MoSi2 has high resistance, high-voltage alternating current is preferred to generate the heat required for pyrolysis.

[0024] Specifically, the furnace tube 401 is directly connected to a power source via electrode 402 and is heated when the power is turned on. When a chemical mixture is inside the furnace tube 401, the chemical mixture is heated, thereby generating a chemical reaction. The short-circuit current originates from a transformer and is connected to the pyrolysis furnace tube via an electrode. The furnace tube 401 is heated to a predetermined temperature by adjusting the electrical power applied to it, so that the fluid inside the furnace tube 401 undergoes a pyrolysis reaction.

[0025] In some embodiments of the present invention, in order to improve the thermal efficiency of the pyrolysis furnace, the length-to-diameter ratio of the furnace tube 401 is preferably 5-2000.

[0026] In some embodiments of the present invention, in order to ensure that the heat generated by the current can be effectively transferred to the internal fluid, the wall thickness of the furnace tube 401 is preferably 0.1-30 mm.

[0027] In some embodiments of the present invention, to ensure the mechanical properties of the MoSi2 material, the particle size of the MoSi2 is preferably no greater than 10 micrometers, more preferably no greater than 8 micrometers.

[0028] In this invention, MoSi2 exhibits high brittleness at room temperature and insufficient strength at high temperatures above 1300°C, particularly exhibiting low creep resistance. Alloying MoSi2 can mitigate these shortcomings, and adding Al, Mo, Re, Cr, Ta, V, Nb, Mg, and W can improve its mechanical properties. Furthermore, various strengthening methods, such as adding ceramic reinforcing agents to MoSi2, can improve the strength and toughness of the material to varying degrees. Preferably, the reinforcing agent is selected from at least one of ZrO2, SiC, TiB2, HfB2, ZrB2, TiC, and Al2O3.

[0029] In some embodiments of the present invention, in order to ensure the mechanical properties of the composite material, the particle size of the reinforcing agent is not greater than 5 micrometers, more preferably not greater than 4 micrometers.

[0030] Preferably, in order to ensure the mechanical and electrical properties of the composite material, the volume ratio of MoSi2 to the reinforcing agent is 1-9:1.

[0031] In some embodiments of the present invention, the furnace tube 401 is obtained by sequentially heat-treating and molding MoSi2 with an optional reinforcing agent. The heat treatment conditions include treatment at 1400-1600°C for 2-10 hours in an oxidizing atmosphere. Specifically, the furnace tube 401 is prepared through steps such as powdering, mixing, vacuum slurry preparation, extrusion, drying, sintering, film formation, machining, and electrode application. Preferably, the ceramic material needs to undergo air heating pretreatment (i.e., film formation) before machining, with a pretreatment temperature of 1400-1600°C and a time of 2-10 hours.

[0032] In some embodiments of the present invention, the pyrolysis furnace further includes a temperature detection device 103, which is disposed at the downstream end of the furnace tube. The present invention does not limit the specific form of the temperature detection device 103, as long as it can detect the temperature of the fluid inside the furnace tube 401. For example, it can be a thermocouple. Furthermore, in the present invention, based on relevant estimates, taking naphtha as an example, approximately 200J of heat is required for pyrolysis per gram of naphtha. Based on the resistivity of MoSi2, the cross-sectional area of ​​the furnace tube, and its length, the resistance of the furnace tube can be calculated. Therefore, it can be deduced that the range of the furnace tube current ensures sufficient heat for the pyrolysis reaction. Using a PLC to precisely control the transformer current allows the outer wall temperature of the furnace tube to be kept constant at the desired value, thereby controlling the outlet temperature of the pyrolysis gas. The PLC control system is a new generation of industrial control device formed by introducing microelectronics technology, computer technology, automatic control technology, and communication technology on the basis of a traditional sequential controller.

[0033] In this invention, the arrangement of the pyrolysis furnaces is not limited, but is preferably selected from horizontal or suspended types.

[0034] In some embodiments of the present invention, the pyrolysis furnace further includes a heat insulation layer 404 disposed on the outer periphery of the furnace tube. Preferably, the heat insulation layer 404 is selected from asbestos and / or refractory bricks.

[0035] A second aspect of the present invention provides a method for pyrolyzing organic matter, wherein the organic matter is fed into the pyrolysis furnace described above for pyrolysis.

[0036] In this invention, the organic matter can be a hydrocarbon, such as naphtha and / or diesel oil. The cracking reaction temperature (i.e., the outlet temperature COT of the cracked gas) is preferably 810-880°C. The pressure is preferably 0.05-0.2 MPa. The mass ratio of water to organic matter is preferably 0.5-0.8.

[0037] According to a preferred embodiment, the method of the present invention includes: introducing organic matter into the aforementioned pyrolysis furnace and applying a high-voltage alternating current to the pyrolysis furnace tube to generate a short-circuit current, thereby using the heat generated by the short-circuit current to heat the organic matter to reach the pyrolysis temperature. The resistivity of the pyrolysis furnace tube at 20°C is 0.1-5 ohm-meters. The frequency of the high-voltage alternating current is preferably 50 Hz. The voltage is preferably 100-500 V. The short-circuit current is preferably 0.4-1 A. The heat generated is preferably 21000-85000 J / h.

[0038] The present invention will be described in detail below through examples. The relevant parameters of the pyrolysis furnace tubes and pyrolysis reactions used in the examples and comparative examples are shown in Tables 1 and 2.

[0039] Table 1

[0040]

[0041] Note: In Table 1, " / " indicates that there is no relevant data.

[0042] Table 2

[0043]

[0044] Note: In Table 2, " / " indicates that there is no relevant data.

[0045] Comparative Examples 1-4

[0046] All pyrolysis tests were conducted at Figure 2 The process is as follows, as shown in the diagram: First, the raw material oil and water are controlled by the liquid mass flow meter 100 to enter the constant temperature preheater 300 (resistance wire heating) at rates of 100g / h and 50g / h respectively. After vaporization, they enter the high temperature pyrolysis furnace 400. The relevant parameters of the furnace tube are shown in Table 1. The length of the constant temperature zone of the furnace tube is about 50cm. The furnace tube is heated by three sections of resistance wire. The temperature of the tube wall is kept constant at the set value by the PLC, thereby controlling the outlet temperature COT of the pyrolysis gas. The specific operating parameters are shown in Table 2. The product from the pyrolysis furnace passes through a quench cooler 500 (cooling medium: 20°C water; discharge temperature: 100-200°C), a water-cooled tank 600 (cooling medium: 20°C water; discharge temperature: 20-50°C), an ice-cooled tank 700 (cooling medium: water below 5°C), a buffer bottle 800, a humidification bottle 900 (water level in the humidification bottle is 80% of the bottle height), and a wet gas flow meter 1000 before being emptied. A pyrolysis gas sample is taken from the buffer bottle 800, and the volume percentage of each component is analyzed by gas chromatography. In Comparative Examples 1-4, the furnace tubes were all made of 2520 alloy. The heat source was the combustion of a mixture of N2 and O2, with the flow rates of N2 and O2 controlled by a gas flow meter 200. The pyrolysis results are shown in Table 3.

[0047] Examples 1-4

[0048] The embodiments of the present invention will Figure 2 The electric heating furnace 400 of the device shown is in operation. Figure 1 The modification shown replaces the resistance wire heating method with direct low-voltage alternating current flowing onto the wall of the conductive ceramic furnace tube. The heat generated by the short-circuit current heats the fluid inside the tube, and the resistance of the current controls the temperature of the furnace tube wall, thereby controlling the depth of the fluid pyrolysis reaction. An embodiment of this invention is implemented on this device. Specifically, the raw material oil and water are first fed into the constant-temperature preheater 300 (resistance wire heating) at the mass ratios specified in Table 2, controlled by the liquid mass flow meter 100. After vaporization, they enter the pyrolysis furnace 400. The relevant parameters of the furnace tube are shown in Table 1. The length of the constant-temperature zone of the furnace tube is approximately 50 cm. High-voltage alternating current is provided by a transformer; the AC parameters are shown in Table 2. The PLC maintains the tube wall temperature at a set value, thereby controlling the outlet temperature (COT) of the pyrolysis gas. Specific operating parameters are shown in Table 2. The product from the pyrolysis furnace passes through a quench cooler 500 (cooling medium is 20℃ water, discharge temperature is 100-200℃), a water-cooled tank 600 (cooling medium is 20℃ water, discharge temperature is 20-50℃), an ice-cooled tank 700 (cooling medium is water at a temperature below 5℃), a buffer bottle 800, a humidification bottle 900 (the water level in the humidification bottle is 80% of the bottle height), and a wet gas flow meter 1000 before being emptied. A pyrolysis gas sample is taken at the buffer bottle 800, and the volume percentage of each component is analyzed by gas chromatography.

[0049] By using a PLC to precisely control the transformer current, the outer wall temperature of the furnace tube can be kept constant at the required value, thereby controlling the outlet temperature (COT) of the pyrolysis gas, as shown in Table 2. The results obtained after pyrolysis are shown in Table 3.

[0050] Table 3

[0051]

[0052] In addition, in Examples 1-4, the resistivity of MoSi2 at around 1000℃ is approximately 1 ohm-meter. Combined with the cross-sectional area and length of the furnace tube, the resistance of the furnace tube can be calculated to be approximately 425 ohms. By controlling the current flowing through the furnace tube, approximately 244,800-1,530,000 J of heat can be obtained per hour. According to relevant estimates, approximately 200 J of heat is required for the cracking of each gram of naphtha. This experiment, processing 100 grams of naphtha per hour, requires approximately 20,000 J of heat (excluding heat loss). Therefore, controlling the current between 0.4-1 A provides sufficient heat for the cracking reaction. According to relevant estimates, with a furnace tube inner diameter of 10 mm and a wall thickness of 20 mm, the temperature difference between the inner and outer walls is approximately 500℃ when current flows through the tube. Therefore, if the inner wall needs to reach approximately 850℃ (close to COT), the outer wall needs to reach approximately 1350℃. The heat utilization rates achieved in the examples and comparative examples are shown in Table 4.

[0053] Table 4

[0054]

[0055] As can be seen from Tables 3 and 4, the pyrolysis furnace of the present invention achieves a pyrolysis depth comparable to that of a conventional pyrolysis furnace. However, Examples 1-4 do not produce carbon dioxide or exhibit coking during the pyrolysis process, demonstrating good equipment safety and high thermal efficiency. In contrast, Comparative Examples 1-4 all exhibit varying degrees of coking.

[0056] 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 method for pyrolyzing organic matter, characterized in that, The method includes: passing organic matter into a pyrolysis furnace for pyrolysis; wherein the pyrolysis furnace includes: Furnace tube, wherein the furnace tube is a conductive ceramic with MoSi2 as the main component; An electrode is connected to the outer wall of the furnace tube.

2. The method according to claim 1, characterized in that, The length-to-diameter ratio of the furnace tube is 5-2000.

3. The method according to claim 1, characterized in that, The wall thickness of the furnace tube is 0.1-30mm.

4. The method according to claim 1, characterized in that, The particle size of the MoSi2 is no greater than 10 micrometers.

5. The method according to claim 1, characterized in that, The furnace tube also includes a reinforcing agent.

6. The method according to claim 5, characterized in that, The particle size of the reinforcing agent is no greater than 5 micrometers; And / or, the volume ratio of MoSi2 to the reinforcing agent is 1-9:1; And / or, the reinforcing agent is selected from at least one of ZrO2, SiC, TiB2, HfB2, ZrB2, TiC and Al2O3.

7. The method according to claim 1, characterized in that, The pyrolysis furnace also includes a temperature detection device, which is located at the downstream end of the furnace tube.

8. The method according to any one of claims 1-7, characterized in that, The arrangement of the pyrolysis furnaces is selected from horizontal or suspended types.

9. The method according to any one of claims 1-7, characterized in that, The pyrolysis furnace also includes a heat insulation layer, which is disposed on the outer periphery of the furnace tube.

10. The method according to claim 9, characterized in that, The insulation layer is selected from asbestos and / or refractory bricks.

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