An electrically heated ethylene cracking furnace

Abstract

The present invention provides an electric heating ethylene cracking furnace, which belongs to the technical field of ethylene production equipment in the petrochemical industry. The electric heating ethylene cracking furnace comprises: a furnace body, a radiation coil and a plurality of electric heating elements arranged on the furnace body, and a refractory material lined in the furnace body. The electric heating element is arranged inside the refractory material, and / or arranged on the reflecting surface of the refractory material, and / or arranged between the reflecting surface of the refractory material and the radiation tube. The above three methods are selected according to actual process requirements, and are used alone or in combination. The ethylene cracking furnace of the present invention obtains different radiation ranges and radiation intensities by adjusting the distance between the electric heating element and the refractory material, the angle of the reflecting surface of the refractory material, the arrangement density of the electric heating element, and the power of the electric heating element. It can be designed in a targeted manner according to process requirements, so that the radiation coil is heated evenly, thereby improving the selectivity of the hydrocarbon cracking reaction and improving the operation cycle of the cracking furnace.

Description

Technical Field

[0001] The invention relates to the technical field of ethylene production equipment in the petrochemical industry, in particular to an electrically heated ethylene cracking furnace. Background Art

[0002] The cracking furnace is the core equipment of the ethylene production unit. Traditional ethylene cracking furnaces mainly provide heat by burning fuel gas or fuel oil, which releases a large amount of greenhouse gases and harmful pollutants during the combustion process. The layout of the fuel burner is limited, the radiation form is single, and the radiation intensity is difficult to accurately control. During operation, there are often phenomena such as local overheating of the radiation coil, flame licking the tube, and coking inside the tube, which makes the cracking furnace unable to operate for a long time.

[0003] In order to respond to the country's goal of promoting the proportion of non-fossil energy in primary energy consumption and reducing carbon dioxide emissions, it is imperative to upgrade the industrial technology of ethylene cracking process.

[0004] Patent CN 1315489A discloses an electric heating cracking furnace. The cracking furnace body is composed of a fixed furnace body and a movable furnace body, and the temperature in the furnace is flexibly and conveniently controlled and adjusted by means of arranging multiple furnace tiles and spacer bars in the vertical direction; and the faulty parts of the cracking furnace can be quickly and accurately detected when the inside of the cracking furnace is repaired, so as to carry out repairs. The cracking furnace is suitable for small-scale production for experimental purposes, and its movable furnace body and spacer bars and other structures cannot be enlarged for industrial application. The heat radiation of the resistance wire fixed on the furnace tile is difficult to focus.

[0005] Patent CN 112414134 A discloses a constant temperature cracking furnace. It includes a furnace body and a furnace door for closing the furnace body opening. A furnace chamber is arranged in the furnace body and is made of silicon carbide. There are rod-shaped heaters on the upper and lower sides of the furnace chamber, and also includes a base installed inside the furnace chamber for supporting a quartz tube; a temperature measuring device extends from the outside of the furnace body into the furnace chamber. It is suitable for small-scale production and does not require high uniformity of heating of the fluid in the tube.

[0006] Patent CN 213102097 U discloses a vinyl ring high-boiling material cracking furnace. The cracking furnace body is composed of a shell, a high-temperature protective liner, a heating liner, and heat-conducting bricks from the outside to the inside. A cracking furnace is installed in the middle position inside the shell, and heating heat-conducting bricks are installed on both sides of the cracking furnace. A heating plate is installed outside the heating heat-conducting brick, and an electric heating wire is installed inside the heating plate. A vacuum port is provided above one side of the cracking furnace shell. It is a single-barrel material inlet and outlet cracking furnace.

[0007] Patent CN 212432757 U discloses an improved electric pyrolysis furnace. It includes a shell, a heating tube, a protective layer, and an electric heating wire. The heating tube is designed in an N-shaped shape. The position of the heating tube located in the cracking gas chamber adopts a gradually thick tube diameter, and the inner wall is provided with concave points for generating a turbulent state. The rear gas outlet end of the heating tube located in the cracking gas chamber adopts a gradually thin tube diameter area under the same wall thickness condition. It is used for small flow gas sampling and detection.

[0008] The existing public technology that uses electric heating in ethylene cracking furnaces is only used in laboratories and is not suitable for industrial applications. Electric heating cracking furnace technology in other industries is not suitable for ethylene cracking furnaces due to its process principle and structure. In view of the characteristics of industrial operation of ethylene cracking furnaces, how to use flexible electric heating methods to make the radiation intensity adjustable and controllable in different zones and to heat the materials evenly has become a key issue in the development of electric heating ethylene cracking furnace technology. Summary of the invention

[0009] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an electrically heated ethylene cracking furnace, which solves the problem of uneven heating of the radiation coil by controlling the heating intensity and achieves zero emission of carbon dioxide.

[0010] The present application belongs to the technical field of ethylene production equipment in the petrochemical industry. The cracking furnace processes a mixture of raw materials and steam into cracking gas rich in target products such as ethylene / propylene by electric heating. By supplying power to the electric heating element, the electric heating element generates heat, and provides the heat required for the cracking reaction in the tube to the radiation coil by thermal radiation. The electric heating element converts electrical energy into thermal energy, and radiates the heat to the radiation coil through reflection of refractory materials. According to the different radiation intensity requirements at different positions of the radiation coil, the arrangement density of the electric heating element can be adjusted accordingly to accurately control the heat supply at different positions of the radiation coil. The reflecting surface of the refractory material can be made into a special-shaped structure to obtain different radiation ranges and intensities. When the operating conditions of the cracking furnace change, the overall or local heat load of the cracking furnace can be changed by adjusting the power of the electric heating element.

[0011] The present invention provides an electric heating ethylene cracking furnace, which at least comprises: a furnace body, a radiation coil and a plurality of electric heating elements arranged in the furnace body, and a refractory material lining the furnace body.

[0012] The electric heating element includes a first electric heating element, and / or a second electric heating element, and / or a third electric heating element;

[0013] The first electric heating element is arranged inside the refractory material, the second electric heating element is arranged on the reflecting surface of the refractory material, and the third electric heating element is arranged between the reflecting surface of the refractory material and the radiation coil.

[0014] In some embodiments of the present invention, the furnace body is provided with a protective gas inlet and a replaced gas outlet, wherein the protective gas inlet is used to introduce protective gas; and the replaced gas outlet is used to discharge the replaced gas in the furnace body;

[0015] Preferably, the protective gas is nitrogen or an inert gas.

[0016] In some embodiments of the present invention, the furnace body is provided with an inlet end and an outlet end for installing the radiation coil; and the arrangement density of the electric heating elements near the inlet end is less than or equal to the arrangement density of the electric heating elements near the outlet end.

[0017] The arrangement of the radiation coils in the furnace body is divided into a dense arrangement area and a sparse arrangement area; and the arrangement density of the electric heating elements in the dense arrangement area is greater than or equal to the arrangement density of the electric heating elements in the sparse arrangement area.

[0018] In some embodiments of the present invention, near the inlet end, the electric heating elements are evenly arranged, and the distance between each of the electric heating elements is A;

[0019] Near the outlet end, the electric heating elements are evenly arranged, and the distance between each of the electric heating elements is B; wherein A is less than or equal to B, preferably A is less than B.

[0020] In some embodiments of the present invention, the reflective surface of the refractory material is a plane and / or a special-shaped structure;

[0021] The special-shaped structure is selected from a U-shaped concave surface, an arc-shaped concave surface or a V-shaped concave surface, and the reflection angle of the V-shaped concave surface is 0°-180°.

[0022] In some embodiments of the present invention, the reflecting surface of the refractory material (13) in the furnace body at the inlet end where the radiation coil (3) is installed is a U-shaped concave surface and / or a V-shaped concave surface with a reflection angle of 0°-90°;

[0023] The reflecting surface of the refractory material (13) in the furnace body at the outlet end where the radiation coil (3) is installed is a U-shaped concave surface and / or a V-shaped concave surface with a reflection angle of 90°-180°;

[0024] The reflecting surface of the refractory material (13) in the furnace body at the densely arranged area of ​​the radiation coils (3) is a U-shaped concave surface and / or a V-shaped concave surface with a reflection angle of 0°-90°;

[0025] The reflecting surface of the refractory material (13) in the furnace body in the sparsely arranged area of ​​the radiation coils (3) is a U-shaped concave surface and / or a V-shaped concave surface with a reflection angle of 90°-180°.

[0026] In some embodiments of the present invention, the refractory material and the electric heating element are fixedly installed in the electrically heated ethylene cracking furnace.

[0027] In some embodiments of the present invention, the electrically heated ethylene cracking furnace further comprises an electric heating module;

[0028] The electric heating module includes the electric heating element and the refractory material, and the electric heating module is detachably arranged in the furnace body.

[0029] In some embodiments of the present invention, the electric heating module further comprises a bearing member and a connecting member; the refractory material is arranged in the bearing member, and the reflecting surface of the refractory material faces the radiation coil;

[0030] The connecting member is arranged on the bearing member and is used for being detachably connected with the furnace body.

[0031] In some embodiments of the present invention, the supporting member is a module sleeve, the connecting member is a flange cover, the refractory material is arranged in the module sleeve, and the reflecting surface of the refractory material faces the radiation coil. In addition, a connecting module sleeve for fixing the module sleeve and a flange matching the flange cover are arranged in the furnace body of the cracking furnace.

[0032] In some embodiments of the present invention, the furnace body is a square box-type closed furnace; the radiation coil (3) is hoisted in the square box-type closed furnace.

[0033] In some embodiments of the present invention, the electric heating element is arranged on one or more sides of the six walls of the square box-type closed furnace.

[0034] In some embodiments of the present invention, the electric heating element is selected from one or more of iron-chromium-aluminum alloy, nickel-chromium alloy, silicon carbide or molybdenum disilicide.

[0035] As described above, an electrically heated ethylene cracking furnace of the present invention has the following beneficial effects:

[0036] The ethylene cracking furnace of the present invention has a simple furnace body structure and adopts a fixed furnace wall, which can reach an industrial scale. In addition, by adjusting the arrangement density of the electric heating elements, the distance between the electric heating elements and the refractory material, and the special-shaped structure of the refractory material reflective surface, different radiation ranges and radiation intensities can be obtained. It can be designed specifically according to the process requirements so that the radiation coil is heated evenly, thereby improving the selectivity of the hydrocarbon cracking reaction and increasing the operation cycle of the cracking furnace. When the working condition of the cracking furnace changes, the overall or local heat load of the cracking furnace can be changed by adjusting the power of the electric heating element. At the same time, the cracking furnace is filled with protective gas, making the equipment more mature and reliable.

[0037] The present invention heats the radiation coil of the cracking furnace by heat radiation of the electric heating element. The electric heating element can be powered by clean energy such as hydropower, wind power, photovoltaic power generation, etc., to achieve zero emission of greenhouse gas and harmful gas pollutants and reduce heat loss. Different from the traditional flame heating method, the radiation coil is not affected by fire, the working environment is improved, and the service life of the coil is extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1a It is a schematic diagram of the arrangement of electric heating elements of the cracking furnace of the present invention;

[0039] Figure 1b for Figure 1a AA projection view and heating element layout diagram;

[0040] Figure 2 It is a schematic diagram of the relative positions of the first electric heating element, the second electric heating element and the third electric heating element and the refractory material of the present invention;

[0041] Figure 3a The reflecting surface of the refractory material of the present invention is a plane;

[0042] Figure 3b The reflecting surface of the refractory material of the present invention is a U-shaped concave surface;

[0043] Figure 3c The reflecting surface of the refractory material of the present invention is an arc-shaped concave surface;

[0044] Figure 3d The reflecting surface of the refractory material of the present invention is a V-shaped concave surface;

[0045] Figure 3e For the present invention Figure 3a , Figure 3b , Figure 3c , Figure 3d B-direction projection view;

[0046] Figure 4a This is a schematic diagram of the arrangement of electric heating elements in the cracking furnace of Example 1 of the present invention (only one large group of U-shaped coils is shown, with a total of 8 large groups);

[0047] Figure 4b This is a schematic diagram of the furnace bottom layout of the cracking furnace described in Example 1 of the present invention;

[0048] Figure 4c This is a schematic diagram of the positions of the electric heating elements corresponding to the first-pass furnace tubes of the cracking furnace described in Example 1 of the present invention and the shape of the refractory reflective surface;

[0049] Figure 4d It is a schematic diagram of the positions of the electric heating elements corresponding to the second-stage furnace tubes of the cracking furnace described in Example 1 of the present invention and the shape of the refractory reflective surface;

[0050] Figure 5a A side view of the cracking furnace and a schematic diagram of the arrangement of electric heating elements according to Example 2 of the present invention;

[0051] Figure 5b This is a front view of the cracking furnace and a schematic diagram of the arrangement of electric heating elements according to Example 2 of the present invention;

[0052] Figure 5c This is a schematic diagram of the assembly of the electric heating modules at the lower three rows of electric heating elements of the cracking furnace described in Example 2 of the present invention;

[0053] Figure 5d This is a schematic diagram of the assembly of the electric heating modules at the upper two rows of electric heating elements of the cracking furnace described in Example 2 of the present invention.

[0054] The component numbers are explained as follows:

[0055] 1. Furnace body;

[0056] 11. Protective gas inlet; 12. Displaced gas outlet; 13. Refractory material; 14. Module sleeve; 15. Connecting module sleeve and flange; 16. Flange cover;

[0057] 2a, first electric heating element; 2b, second electric heating element; 2c, third electric heating element;

[0058] 3. Radiant coil. DETAILED DESCRIPTION

[0059] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0060] Please refer to Figures 1 to 5. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantial change of the technical content.

[0061] Combined with Figure 1, Figure 2 3 describes the electrically heated cracking furnace of the present application in detail.

[0062] As shown in Figure 1, an electric ethylene thermal cracking furnace has a square box-type closed furnace chamber, and the furnace wall is lined with refractory materials. The furnace body is provided with a protective gas inlet and a replacement gas outlet. A radiation coil is suspended in the furnace chamber, and an electric heating element is connected in the cracking furnace.

[0063] The furnace body is preferably a square box-type closed furnace, and the radiation coil is hoisted in the square box-type closed furnace.

[0064] The protective gas inlet and the replacement gas outlet are arranged on the furnace body, preferably the protective gas inlet is arranged on the lower side of the furnace body, and the replacement gas outlet is arranged on the upper side of the furnace body, and the number of the protective gas inlet and the replaced gas outlet can be set to one or more according to actual needs. In actual use, the protective gas inlet can be introduced into the protective gas inlet (nitrogen or inert gas can be selected). The replaced gas is discharged from the replaced gas outlet, so that the furnace body is in a non-oxidizing atmosphere, thereby preventing the cracking gas from catching fire when leaking in the furnace, protecting the heating element from oxidation, and extending the service life of the radiation coil.

[0065] The material of the electric heating element is selected according to the working environment and process requirements. At least one or more of iron-chromium-aluminum alloy, nickel-chromium alloy, silicon carbide or molybdenum disilicide can be selected, and the electric heating element is arranged on one or more sides of the six walls of the square box-type closed furnace according to process requirements.

[0066] like Figure 2 As shown, the electric heating element can be selectively arranged inside the refractory material, and / or arranged on the reflecting surface of the refractory material, and / or arranged between the reflecting surface of the refractory material and the radiation tube. The three methods can be used alone or in combination.

[0067] Specifically, Figure 1a and Figure 1b As shown, the arrangement of the radiation coil and the electric heating element are schematic representations: the arrangement of the electric heating element can be selected as follows:

[0068] First, when arranging the electric heating elements, the material cracking reaction temperature and heating rate need to be considered. For example, when the material starts to flow through the radiation coil, it needs to heat up quickly, and the cracking reaction needs to absorb a lot of heat. The arrangement of the electric heating elements is relatively dense, and the corresponding refractory reflection surface angle of the corresponding radiation coil inlet pipeline is relatively small; after N (N is greater than or equal to 1) heating, it reaches the outlet end. At this time, the primary reaction is basically completed, and the material in the tube has reached a higher temperature. If the temperature in the tube is too high, a secondary reaction will occur to reduce the ethylene yield. Therefore, the radiation coil only needs to maintain the temperature. In addition, considering the strength limit of the radiation coil, the arrangement of the electric heating elements corresponding to the radiation coil outlet pipeline is relatively sparse, and the corresponding refractory reflection surface angle is relatively large. Such an arrangement can simultaneously reduce the radiation intensity of the outlet pipeline, which is conducive to improving the operation cycle of the cracking furnace.

[0069] Second, the structure of the radiation coil is complex, and the spatial density of the arrangement is also different. In order to make the radiation coil heated evenly, in the area where the radiation coil is densely arranged, relatively dense electric heating elements are arranged, and the corresponding refractory material reflective surface shape angle is relatively small; in the area where the radiation coil is sparsely arranged, relatively sparse electric heating elements are arranged, and the corresponding refractory material reflective surface shape angle is relatively large.

[0070] Third, constrained by process requirements and engineering conditions, the space dimensions of the cracking furnace are different, especially the distances between the radiation coil and the reflecting surface of the refractory material. There are three relationships between the relative positions of the electric heating element and the refractory material: arranged inside the refractory material, arranged on the reflecting surface of the refractory material, and arranged between the reflecting surface of the refractory material and the radiation coil.

[0071] In addition, in combination with the above-mentioned arrangement, the electric heating elements can also be arranged continuously or intermittently, and can also be arranged evenly or unevenly.

[0072] Optionally, near the inlet end, the electric heating elements are evenly arranged, and the distance between each electric heating element is A; near the outlet end, the electric heating elements are evenly arranged, and the distance between each electric heating element is B; wherein A is less than or equal to B, preferably A is less than B.

[0073] The specific selection of the distances A and B between the electric heating elements is a comprehensive design based on the spatial dimensions of the cracking furnace hearth and the dimensions of the electric heating elements.

[0074] The heat energy emitted by the electric heating element is radiated to the radiation coil through the reflection of the refractory material. Figure 3a , 3b As shown in , 3c, and 3d, in conjunction with the arrangement of the above-mentioned electric heating elements, the refractory reflective surface can be selected to be a flat surface or a special-shaped structure to obtain different radiation ranges and intensities. For reflective surfaces of different shapes, the smaller the reflection angle of the reflective surface, the more concentrated the radiation energy, the greater the radiation intensity, and the faster the temperature rises. In comparison, the larger the reflection angle of the reflective surface, the more dispersed the radiation energy, the smaller the radiation intensity, and the larger the radiation range. Specifically, Figure 3a For plane, Figure 3b U-shaped concave surface, Figure 3c The curved concave surface Figure 3d It is a V-shaped concave surface.

[0075] The refractory materials include but are not limited to alumina mirror porcelain.

[0076] In an optional embodiment, in order to facilitate maintenance or replacement, the electric heating module and the refractory material can be made into an electric heating module and detachably connected to the furnace body. The electric heating module is provided with a carrier for holding the refractory material and a connector for detachably connecting to the furnace body.

[0077] In a feasible implementation, the bearing member is a module sleeve, the connecting member is a flange cover, the module sleeve is filled with refractory material, the reflective surface of the refractory material is toward the radiation coil through one end of the module sleeve, and the other end of the module sleeve is connected to the flange cover, and is fixed to the furnace body through the flange cover. The wires of the electric heating element pass through the insulation material and the flange cover in turn to connect to the power supply outside the furnace body.

[0078] Further explanation: at the location where the electric heating element is set, the refractory material and the electric heating element are integrated into a detachable and assembleable electric heating module, and the refractory material at other locations in the furnace body is lined in the furnace body.

[0079] In addition, when the operating conditions of the cracking furnace change, the overall or local heat load of the cracking furnace can be changed by adjusting the power of the electric heating element. The power of the electric heating element is designed according to the actual situation.

[0080] In actual industrial applications, the size of the electric heating ethylene cracking furnace, the type and arrangement of the radiation coil, the corresponding arrangement method of the electric heating elements, and the selection of refractory materials are designed according to process conditions such as cracking raw materials, feed amount, and heat load.

[0081] An exemplary embodiment of the electrically heated ethylene cracking furnace of the present application is given below.

[0082] Example 1

[0083] The cracking raw material is a mixture of naphtha and dilution steam, with a feed rate of 64t / h.

[0084] The heat load of the cracking furnace is 36MW, and the overall dimensions of the cracking furnace are 4m×30m×14m(H). The radiation coil 3 is composed of 8 large groups of U-shaped coils (1-1 type), each large group includes 2 small groups and adopts a mirror image arrangement, and each small group of U-shaped coils consists of 6 furnace tubes.

[0085] The electric heating element is made of iron-chromium-aluminum alloy and is arranged on the side wall and bottom of the cracking furnace. The whole cracking furnace is equipped with 720 electric heating elements, with a single electric heating element designed to have a power of 50kW and a heat release power adjustment range of 40 to 60kW.

[0086] like Figure 4a The schematic diagram of the arrangement of electric heating elements in the cracking furnace is shown in FIG. 1 , which only shows one large group of U-shaped coils, and there are a total of eight large groups of U-shaped coils;

[0087] Arrangement of electric heating elements on the side wall: 336 electric heating elements are arranged on a single side wall, divided into 7 rows (vertical direction of the cracking furnace), with a row spacing of 1.8m. 48 electric heating elements are arranged in a single row horizontally, corresponding to the horizontal spacing of the electric heating elements of the first-pass furnace tubes of 0.5m (vertical placement), corresponding to the horizontal spacing of the electric heating elements of the second-pass furnace tubes of 0.9m (horizontal placement). The electric heating elements are arranged between the radiation coil and the side wall reflective surface, 0.7m away from the center line of the furnace tube.

[0088] Figure 4b The bottom layout of the cracking furnace is shown in the figure. The bottom electric heating element layout: 48 electric heating elements are evenly arranged on the bottom of the furnace, arranged inside the refractory material 13. The electric heating elements are arranged inside the refractory material, and the outer surface of the electric heating element is 50 mm away from the reflecting surface of the refractory material.

[0089] To enhance heat transfer, Figure 4c As shown in FIG. 1 , the refractory reflective surface corresponding to the first-pass furnace tube electric heating element is made into a V-shaped concave surface, and the reflection angle α is 86°. Figure 4d As shown, the refractory material reflecting surface corresponding to the second-pass furnace tube electric heating element is made into a V-shaped concave surface, and the reflection angle α is 120°. The refractory material reflecting surfaces at other positions are flat surfaces.

[0090] A protective gas inlet (ID 70mm) is provided at the bottom of each end wall of the cracking furnace, with a total of 2 protective gas inlets 11; a displaced gas outlet 12 (ID 70mm) is provided at the top of each end wall of the cracking furnace, with a total of 2 displaced gas outlets 12. Argon is selected as the protective gas. Before operation, argon enters from the protective gas inlet 11, and the air in the furnace is discharged from the displaced gas outlet 12. When the furnace is filled with argon, the gas replacement is stopped, and the protective gas inlet 11 and the displaced gas outlet 12 are sealed with a blind plate to make the furnace environment in a non-oxidizing atmosphere.

[0091] The power of the electric heating element is adjustable, and the overall or local heat load of the cracking furnace can be changed according to changes in the operating conditions of the cracking furnace.

[0092] Example 2

[0093] The cracking raw material is a mixture of propane and dilution steam, and the feed rate is 10t / h.

[0094] The heat load of the cracking furnace is 7.5MW, and the overall dimensions of the cracking furnace are 2.8m×8m×13m (H). The radiation coil 3 is a bottom-in and top-out one-way tube, arranged along the center line of the furnace, with an outer diameter of 60.3mm, and a total of 48 tubes.

[0095] The electric heating element is made of silicon molybdenum rods and is arranged on the side walls, top and bottom of the cracking furnace. The design power of the electric heating element is 50kW, and the heat release power adjustment range is 40-60kW.

[0096] like Figure 5a This is a side view of the cracking furnace and a schematic diagram of the layout of the electric heating elements. Figure 5b This is a schematic diagram of the front view of the cracking furnace and the layout of the electric heating elements;

[0097] Arrangement of electric heating elements on the side walls: A total of 132 electric heating elements are arranged on the two side walls. Five rows are arranged on each side wall, with a row spacing of 2.35m. The horizontal spacing of the lower three rows of electric heating elements is 0.45m, and the horizontal spacing of the upper two rows of electric heating elements is 0.75m. The electric heating elements are arranged between the radiation coil 3 and the reflective surface of the refractory material 13 of the side wall, 0.75m away from the center line of the furnace tube.

[0098] Arrangement of electric heating elements on the furnace roof: The design power of the electric heating elements is 75kW, and the heat release power adjustment range is 60-90kW. Four electric heating elements are evenly distributed on the furnace roof. The electric heating elements are arranged on the reflective surface of the refractory material 13 attached to the side wall.

[0099] Arrangement of electric heating elements at the bottom of the furnace: The design power of the electric heating elements is 75kW, and the heat release power adjustment range is 60-90kW. Eight electric heating elements are evenly distributed at the bottom of the furnace. The electric heating elements are arranged on the reflective surface of the refractory material 13 attached to the side wall.

[0100] In order to enhance heat transfer, the reflecting surface of the refractory material 13 on the side wall corresponding to the electric heating elements is selected as a special-shaped surface: the reflecting surface corresponding to the lower three rows of electric heating elements is selected as a U-shaped concave surface, and the reflecting surface corresponding to the upper two rows of electric heating elements is selected as an arc-shaped concave surface.

[0101] Two protective gas inlets (ID 70mm) are arranged at the bottom of each end wall of the cracking furnace, and there are four protective gas inlets 11 in total; one replaced gas outlet 12 (ID 300mm) is arranged at the top of the cracking furnace. Before operation, nitrogen enters from the protective gas inlet 11, and the air in the furnace is discharged from the replaced gas outlet 12. When the nitrogen content in the furnace is greater than 95%, the gas replacement is stopped, and the protective gas inlet 11 and the replaced gas outlet 12 are sealed with a blind plate to make the furnace environment in a non-oxidizing atmosphere.

[0102] In addition, for the convenience of maintenance, the electric heating elements and the corresponding refractory materials in the above embodiments are made into a detachable electric heating module.

[0103] Figure 5c This is a schematic diagram of the assembly of the electric heating module at the lower three rows of electric heating elements. Figure 5d It is a schematic diagram of the assembly of the electric heating module at the upper two rows of electric heating elements;

[0104] Specifically, the electric heating module comprises an electric heating element 2c, a refractory material 13, a module sleeve (14) and a flange cover (16). The module sleeve (14) is filled with refractory material, and the reflective surface of the refractory material 13 faces the radiation coil 3 through one end of the module sleeve (14), and the other end of the module sleeve (14) is connected to the flange cover (16). The module sleeve (14) and the flange cover (16) are fixed to the connecting module sleeve and the flange (15) arranged in the furnace body 1. The wires of the electric heating element pass through the refractory material 13 and the flange cover (16) in sequence to connect to the power supply outside the furnace body 1.

[0105] Modular design, interchangeable, can be replaced and repaired according to the equipment operation status.

[0106] According to the electric heating ethylene cracking furnace of the present invention, when in operation, the power of the electric heating element is turned on, and the heat generated by the electric heating element is reflected to the radiation coil through the reflection surface of the refractory material. When the working condition of the cracking furnace changes, the overall or local heat load of the cracking furnace can be changed by adjusting the power of the electric heating element. The cracking furnace is provided with a protective gas inlet and a replacement gas outlet, and the protective gas is preferably argon gas, so that the furnace is in a non-oxidizing atmosphere during the operation of the cracking furnace, so as to prevent the cracking gas from catching fire when leaking in the furnace, protect the electric heating element from oxidation, and prolong the service life of the radiation coil.

[0107] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An electrically heated ethylene cracking furnace, the electrically heated ethylene cracking furnace comprising at least: A furnace body (1), a radiation coil (3) and a plurality of electric heating elements arranged in the furnace body, and a refractory material (13) lined in the furnace body, characterized in that the electric heating elements include a first electric heating element (2a), and / or a second electric heating element (2b), and / or a third electric heating element (2c); The first electric heating element (2a) is arranged inside the refractory material (13), the second electric heating element (2b) is arranged on the reflecting surface of the refractory material (13), and the third electric heating element (2c) is arranged between the reflecting surface of the refractory material (13) and the radiation coil (3).

2. The electrically heated ethylene cracking furnace according to claim 1, characterized in that: The furnace body is provided with a protective gas inlet (11) and a replaced gas outlet (12); the protective gas inlet (11) is used for introducing protective gas; the replaced gas outlet (12) is used for discharging the replaced gas in the furnace body (1).

3. The electrically heated ethylene cracking furnace according to claim 1, characterized in that: The furnace body (1) is provided with an inlet end and an outlet end for installing the radiation coil (3); and the arrangement density of the electric heating elements near the inlet end is less than or equal to the arrangement density of the electric heating elements near the outlet end; The radiation coils (3) are arranged in a dense arrangement area and a sparse arrangement area in the furnace body (1); the arrangement density of the electric heating elements in the dense arrangement area is greater than or equal to the arrangement density of the electric heating elements in the sparse arrangement area.

4. The electrically heated ethylene cracking furnace according to claim 1, characterized in that: The reflecting surface of the refractory material (13) is a plane and / or a special-shaped structure; The special-shaped structure is selected from a U-shaped concave surface, an arc-shaped concave surface or a V-shaped concave surface, and the reflection angle of the V-shaped concave surface is 0°-180°.

5. The electrically heated ethylene cracking furnace according to claim 3, characterized in that: The reflecting surface of the refractory material (13) in the furnace body at the inlet end where the radiation coil (3) is installed is a U-shaped concave surface and / or a V-shaped concave surface with a reflection angle of 0°-90°; The reflecting surface of the refractory material (13) in the furnace body at the outlet end where the radiation coil (3) is installed is a U-shaped concave surface and / or a V-shaped concave surface with a reflection angle of 90°-180°; The reflecting surface of the refractory material (13) in the furnace body at the densely arranged area of ​​the radiation coils (3) is a U-shaped concave surface and / or a V-shaped concave surface with a reflection angle of 0°-90°; The reflecting surface of the refractory material (13) in the furnace body in the sparsely arranged area of ​​the radiation coils (3) is a U-shaped concave surface and / or a V-shaped concave surface with a reflection angle of 90°-180°.

6. The electrically heated ethylene cracking furnace according to claim 1, characterized in that: Also includes an electric heating module; The electric heating module comprises the electric heating element and the refractory material (13), and the electric heating module is detachably arranged in the furnace body.

7. The electrically heated ethylene cracking furnace according to claim 6, characterized in that: The electric heating module further comprises a bearing member and a connecting member; the refractory material is arranged in the bearing member, and the reflecting surface of the refractory material (13) faces the radiation coil (3); The connecting member is arranged on the supporting member and is used for being detachably connected to the furnace body (1).

8. The electrically heated ethylene cracking furnace according to any one of claims 1 to 7, characterized in that: The furnace body (1) is a square box-type closed furnace; the radiation coil (3) is hoisted in the square box-type closed furnace.

9. The electrically heated ethylene cracking furnace according to claim 8, characterized in that: The electric heating elements are arranged on one or more sides of the six walls of the square box-type closed furnace.

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