阅读说明：本技术 一种电加热乙烯裂解炉 (Electric heating ethylene cracking furnace ) 是由 李保有 张磊 薄建民 詹爽 郭英锋 冯恩明 张晋华 袁睿 于 2021-09-13 设计创作，主要内容包括：本发明提供一种电加热乙烯裂解炉,属于石油化工行业中乙烯生产设备技术领域,所述电加热乙烯裂解炉包括：炉本体、设于炉本体的辐射盘管和多个电热元件、以及衬于炉本体内的耐火材料,所述电热元件布置在耐火材料内部、和/或布置在耐火材料的反射面、和/或布置在耐火材料反射面和辐射管之间,根据实际工艺需要进行以上三种方式的选择,或单独使用或组合使用。本发明的乙烯裂解炉,通过调节电热元件与耐火材料的间距、耐火材料反射面角度以及电热元件布置密度、电热元件功率得到不同的辐射范围和辐射强度,可根据工艺要求有针对性地设计,使辐射盘管受热均匀,从而提高烃类裂解反应的选择性,并提高裂解炉的运行周期。(The invention provides an electric heating ethylene cracking furnace, which belongs to the technical field of ethylene production equipment in the petrochemical industry, and comprises: the furnace comprises a furnace body, a radiation coil and a plurality of electric heating elements which are arranged on the furnace body, and refractory materials which are lined in the furnace body, wherein the electric heating elements are arranged inside the refractory materials and/or on a reflecting surface of the refractory materials and/or between the reflecting surface of the refractory materials and the radiation coil, and the three modes are selected according to actual process requirements, or are used singly or in combination. The ethylene cracking furnace can obtain 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, and can be designed in a targeted manner according to process requirements, so that the radiation coil is heated uniformly, the selectivity of hydrocarbon cracking reaction is improved, and the operation period of the cracking furnace is prolonged.)

1. An electrically heated ethylene cracking furnace, comprising at least: stove body (1), locate radiation coil (3) and a plurality of electric heating element of stove body and lining in this internal refractory material (13) of stove, its characterized in that: the electric heating elements comprise a first electric heating element (2a), and/or a second electric heating element (2b), and/or a third electric heating element (2 c);

the first electrical heating element (2a) is arranged inside the refractory (13), the second electrical heating element (2b) is arranged on the reflective surface of the refractory (13), and the third electrical heating element (2c) is arranged between the reflective surface of the refractory (13) and the radiation coil (3).

2. The electrically heated ethylene cracking furnace according to claim 1, wherein the furnace body is provided with a protective gas inlet (11) and a replaced gas outlet (12), and 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. An 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 mounting the radiant coils (3); and the arrangement density of the electric heating elements close to the inlet end is less than or equal to the arrangement density of the electric heating elements close to the outlet end;

the radiation coil (3) is 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 densely-arranged area is greater than or equal to that of the electric heating elements in the sparsely-arranged area.

4. An 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 profiled 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 degrees.

5. An 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 radiant coils (3) are mounted 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 reflecting angle of 90-180 degrees;

the reflecting surface of the refractory material (13) in the furnace body at the dense arrangement region of the radiation coil (3) is a U-shaped concave surface and/or a V-shaped concave surface with a reflecting angle of 0-90 degrees;

the reflecting surface of the refractory material (13) in the furnace body of the sparse arrangement area of the radiation coil (3) is a U-shaped concave surface and/or a V-shaped concave surface with a reflecting angle of 90-180 degrees.

6. The electrically heated ethylene cracking furnace of claim 1, further comprising 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 of claim 6, wherein the electric heating module further comprises a carrier and a connector; the refractory material is arranged in the bearing part, and the reflecting surface of the refractory material (13) faces the radiation coil (3);

the connecting piece is arranged on the bearing piece and is detachably connected with the furnace body (1).

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

9. The electrically heated ethylene cracking furnace of claim 8, wherein the electric heating elements are disposed on one or more of the six walls of the boxed enclosed furnace.

Technical Field

The invention relates to the technical field of ethylene production equipment in the petrochemical industry, in particular to an electric heating ethylene cracking furnace.

Background

The cracking furnace is the core equipment of an ethylene production device. The traditional ethylene cracking furnace mainly uses fuel gas or fuel oil for supplying heat, and a large amount of greenhouse gases and harmful pollutants are released in the combustion process. The arrangement mode of the fuel burner is limited, the radiation form is single, and the radiation intensity is difficult to accurately regulate and control. The phenomena of local overheating of the radiation coil, flame lapping of the tube and coking in the tube often exist in the operation process, so that the cracking furnace can not be operated for a long time.

In order to respond to the aims of the country to promote the proportion of non-fossil energy in primary energy consumption and reduce the emission of carbon dioxide, the industrial technology of the ethylene cracking process is absolutely upgraded.

Patent CN 1315489a discloses an electrically heated cracking furnace. The cracking furnace body consists 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 a plurality of furnace tiles in the vertical direction, arranging spacing bars and the like; and can detect out the trouble position of pyrolysis furnace fast accurately when carrying out the maintenance to pyrolysis furnace inside to maintain. The cracking furnace is suitable for small-sized production aiming at experiments, and the structures of a movable furnace body, a spacing bar and the like can not be amplified for industrial application. The resistance wire is fixed on the furnace tile, and the heat radiation is difficult to focus.

Patent CN 112414134 a discloses a constant temperature cracking furnace. Comprises a furnace body and a furnace door used for sealing the opening of the furnace body. A hearth is arranged in the furnace body and is made of silicon carbide. The upper side and the lower side of the hearth are provided with rod-shaped heaters, and the hearth also comprises a base which is arranged in the hearth and used for supporting the quartz tube; the temperature measuring device extends into the hearth from the outer side of the furnace body. The device is suitable for small-sized production and has low requirement on the uniformity of the heated fluid in the tube.

Patent CN 213102097U discloses a vinyl-based ring body high-boiling-point substance cracking furnace. The cracking furnace body comprises a shell, a high-temperature resistant protective inner container, a heating inner container and heat conducting bricks from outside to inside in sequence. The inside intermediate position department of casing installs the pyrolysis furnace, and the heating heat conduction brick is all installed to the both sides of pyrolysis furnace, and the externally mounted of heating heat conduction brick has the hot plate, and the internally mounted of hot plate has the heating wire. A vacuumizing port is arranged above one side of the cracking furnace shell. Is a single-cylinder material inlet and outlet cracking furnace.

Patent CN 212432757U discloses an improved electric pyrolysis furnace. Comprises a shell, a heating pipe, a protective layer and an electric heating wire. The heating pipe is n font design, and the position that lies in the schizolysis air chamber on the heating pipe adopts the pipe diameter that becomes gradually thick, and all is provided with the concave point that is used for producing turbulent state on the inner wall, and the last rear air outlet end portion that lies in the schizolysis air chamber of heating pipe adopts the gradual change thin pipe diameter region under the same wall thickness condition. The method is applied to sampling and detecting the gas with small flow.

The prior art disclosed in the case of adopting an electric heating mode in an ethylene cracking furnace is only applied in a laboratory and is not suitable for industrial application. Other industries are not suitable for ethylene cracking furnaces due to the process principle, the structure and the like of the electric heating cracking furnace technology. Aiming at the characteristics of industrial operation of the ethylene cracking furnace, how to adopt a flexible electric heating mode to ensure that the radiation intensity is adjustable and controllable in subareas and the material is heated uniformly becomes a key problem in the technical development of the electric heating ethylene cracking furnace.

Disclosure of Invention

In view of the above-mentioned deficiencies of the prior art, the present invention aims to provide an electrically heated ethylene cracking furnace, which solves the problem of non-uniform heating of the radiant coil by controlling the heating intensity and realizes zero emission of carbon dioxide.

The application belongs to the technical field of ethylene production equipment in petrochemical industry. The cracking furnace processes the mixture of raw material and steam into cracking gas rich in target products such as ethylene/propylene in an electric heating mode. The electric heating element generates heat by supplying power to the electric heating element, and provides heat required by the cracking reaction in the pipe for the radiation coil pipe in a heat radiation mode. The electric heating element converts electric energy into heat energy, and the heat energy is radiated to the radiation coil pipe through reflection of the refractory material. According to the different radiation intensity requirements of different positions of the radiation coil, the arrangement density of the electric heating elements can be correspondingly adjusted so as to accurately control the heat supply quantity of different positions of the radiation coil. The reflecting surface of the refractory material can be made into a special-shaped structure so as to obtain different radiation ranges and intensities. When the working condition of the cracking furnace is changed, the overall or local heat load of the cracking furnace can be changed by adjusting the power of the electric heating element.

The 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 which are arranged on the furnace body, and a refractory material which is lined in the furnace body,

the electric heating elements comprise a first electric heating element, and/or a second electric heating element, and/or a third electric heating element;

the first electrical heating element is disposed within the interior of the refractory material, the second electrical heating element is disposed on the reflective surface of the refractory material, and the third electrical heating element is disposed between the reflective surface of the refractory material and the radiant coil.

In some embodiments of the present invention, the furnace body is provided with a protective gas inlet and a replaced gas outlet, and the protective gas inlet is used for introducing protective gas; the replaced gas outlet is used for discharging replaced gas in the furnace body;

preferably, the protective gas is nitrogen or an inert gas.

In some embodiments of the invention, the furnace body is provided with an inlet end and an outlet end for mounting the radiant coils; and the arrangement density of the electric heating elements close to the inlet end is less than or equal to the arrangement density of the electric heating elements close to the outlet end.

The arrangement of the radiation coil pipes 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 densely-arranged area is greater than or equal to that of the electric heating elements in the sparsely-arranged area.

In some embodiments of the invention, the electrical heating elements are uniformly arranged near the inlet end, and the distance between each of the electrical heating elements is a;

the electric heating elements are uniformly arranged close to the outlet end, and the distance between every two electric heating elements is B; wherein A is less than or equal to B, preferably A is less than B.

In some embodiments of the invention, the reflective surface of the refractory material is a planar and/or contoured 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 degrees.

In some embodiments of the invention, the reflecting surface of the refractory material (13) in the furnace body at the inlet end where the radiant coils (3) are mounted is a U-shaped concave surface and/or a V-shaped concave surface with a reflection angle of 0 ° to 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 reflecting angle of 90-180 degrees;

the reflecting surface of the refractory material (13) in the furnace body at the dense arrangement region of the radiation coil (3) is a U-shaped concave surface and/or a V-shaped concave surface with a reflecting angle of 0-90 degrees;

the reflecting surface of the refractory material (13) in the furnace body of the sparse arrangement area of the radiation coil (3) is a U-shaped concave surface and/or a V-shaped concave surface with a reflecting angle of 90-180 degrees.

In some embodiments of the invention, the refractory material and the electrical heating element are fixedly disposed within an electrically heated ethylene cracking furnace.

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

the electric heating module comprises the electric heating element and the refractory material, and the electric heating module is detachably arranged in the furnace body.

In some embodiments of the invention, the thermoelectric module further comprises a carrier and a connector; the refractory material is arranged in the bearing piece, and the reflecting surface of the refractory material faces the radiation coil;

the connecting piece is arranged on the bearing piece and is used for being detachably connected with the furnace body.

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 disposed in the module sleeve, the reflecting surface of the refractory material faces the radiation coil, and a connecting module sleeve for fixing the module sleeve and a flange cooperating with the flange cover are disposed in the furnace body of the cracking furnace.

In some embodiments of the invention, the furnace body is a square box type closed hearth; the radiation coil (3) is hung in the square box type closed hearth.

In some embodiments of the invention, the electric heating elements are arranged on one or more surfaces of six walls of the square box type closed hearth.

In some embodiments of the invention, the electrical heating element is selected from one or more of a ferro-chrome-aluminum alloy, a nickel-chrome alloy, silicon carbide, or molybdenum disilicide.

As mentioned above, the electric heating ethylene cracking furnace of the invention has the following beneficial effects:

the ethylene cracking furnace has simple furnace body structure, adopts the fixed furnace wall and can reach the industrialized scale. In addition, different radiation ranges and radiation intensities can be obtained by adjusting the arrangement density of the electric heating elements, the distance between the electric heating elements and the refractory material and combining the special-shaped structure of the reflecting surface of the refractory material. Can be designed according to the process requirements, so that the radiation coil is heated uniformly, the selectivity of hydrocarbon cracking reaction is improved, and the operation period of the cracking furnace is prolonged. When the working condition of the cracking furnace is changed, the overall or local heat load of the cracking furnace can be changed by adjusting the power of the electric heating element. Meanwhile, the cracking furnace is filled with protective gas, so that the equipment is more mature and reliable.

The invention heats the radiant coil of the cracking furnace by the heat radiation of the electric heating element. The electric heating element can be powered by clean energy such as water, electricity, wind power, photovoltaic power generation and the like, zero emission of greenhouse gases and harmful gas pollutants is realized, and heat loss is reduced. Different from the traditional flame heating mode, the radiation coil pipe is not affected by fire, the working environment is improved, and the service life of the coil pipe is prolonged.

Drawings

FIG. 1a is a schematic view of the arrangement of electric heating elements of the cracking furnace of the present invention;

FIG. 1b is a schematic view of the projection from A-A to A of FIG. 1a and the arrangement of electrothermal elements;

FIG. 2 is a schematic diagram of the relative positions of a first electrothermal element, a second electrothermal element and a third electrothermal element with respect to a refractory material according to the present invention;

FIG. 3a shows the reflecting surface of the refractory of the present invention is a flat surface;

FIG. 3b shows a U-shaped concave reflecting surface of the refractory material of the present invention;

FIG. 3c shows a curved concave reflecting surface of the refractory of the present invention;

FIG. 3d shows a V-shaped concave reflecting surface of the refractory of the present invention;

FIG. 3e is a projection view of the invention from the direction B of FIGS. 3a, 3B, 3c, and 3 d;

FIG. 4a is a schematic diagram showing the arrangement of the electric heating elements in the cracking furnace according to embodiment 1 of the present invention (only example 1 is a large group of U-shaped coils, and the total number is 8);

FIG. 4b is a schematic view showing the arrangement of the bottom of the cracking furnace according to example 1 of the present invention;

FIG. 4c is a schematic diagram of the furnace tube of the first pass of the cracking furnace according to embodiment 1 of the present invention corresponding to the position of the electric heating element and the shape of the reflecting surface of the refractory material;

FIG. 4d is a schematic diagram of the position of the second-pass furnace tube of the cracking furnace according to embodiment 1 of the present invention corresponding to the electric heating element and the shape of the refractory reflective surface;

FIG. 5a is a schematic diagram of a side view of a cracking furnace and an arrangement of electric heating elements according to embodiment 2 of the present invention;

FIG. 5b is a schematic diagram of the front view of the cracking furnace and the arrangement of the electric heating elements in embodiment 2 of the present invention;

FIG. 5c 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 according to embodiment 2 of the present invention;

FIG. 5d 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 according to embodiment 2 of the present invention.

The element numbers are as follows:

1. a furnace body;

11. a protective gas inlet; 12. a displaced gas outlet; 13. a refractory material; 14. a modular sleeve; 15. connecting the module sleeve and the flange; 16 a flange cover;

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

3. radiant coils.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

Please refer to fig. 1 to 5. It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions under which the present invention can be implemented, so that the present invention has no technical significance, and any structural modification, ratio relationship change, or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention. In addition, the terms "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for clarity of description, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not to be construed as a scope of the present invention.

The electric heating cracking furnace of the present application will be described in detail with reference to fig. 1, 2 and 3.

As shown in figure 1, the electric heating ethylene thermal cracking furnace is a square box type closed hearth, and the wall of the furnace is lined with refractory materials. The furnace body is provided with a protective gas inlet and a replacement gas outlet. The radiation coil pipe is suspended in the hearth, and the cracking furnace is internally connected with an electric heating element.

Wherein, the furnace body is preferably a square box type closed hearth, and the radiation coil is hung in the square box type closed hearth.

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, the replacement gas outlet is arranged on the upper side of the furnace body, one or more protective gas inlets and one or more replaced gas outlets can be arranged according to actual requirements, and protective gas (nitrogen or inert gas can be selected) can be introduced into the protective gas inlets in actual use. The displaced gas is discharged from the displaced gas outlet, so that the interior of the furnace body is in non-oxidizing atmosphere, thereby preventing the pyrolysis gas from igniting when leaking in the hearth, protecting the heating element from being oxidized, and prolonging the service life of the radiant coil pipe.

The material of the electric heating element is selected according to the working environment and the process requirement, 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 surfaces of six walls of the square box type closed hearth according to the process requirement.

As shown in fig. 2, the electrical heating element may alternatively be arranged inside the refractory material and/or on a reflective surface of the refractory material and/or between the reflective surface of the refractory material and the radiant tube. The three methods can be used singly or in combination.

Specifically, as shown in fig. 1a and 1b, the radiant coil and the electric heating element arrangement are both represented schematically: the arrangement mode of the electric heating elements can be selected as follows:

firstly, when the electric heating element is arranged, the temperature of the material cracking reaction and the temperature rise speed need to be considered. For example, when the material starts to flow through the radiation coil, the temperature needs to be raised quickly, the cracking reaction needs to absorb a large amount of heat, the arrangement of the electric heating elements is relatively dense, and the angle between the corresponding pipeline at the inlet end of the radiation coil and the corresponding refractory material reflecting surface is relatively small; after N (N is more than or equal to 1) heating, the reaction is basically finished at the outlet end, the temperature of the materials in the pipe is high, if the temperature in the pipe is too high, secondary reaction can be carried out to reduce the ethylene yield, so that the radiation coil pipe only needs to maintain the temperature, the intensity limit of the radiation coil pipe is considered, the arrangement of the electric heating elements is relatively sparse corresponding to the pipeline at the outlet end of the radiation coil pipe, and the angle of the reflecting surface of the corresponding refractory material is relatively large. The arrangement can simultaneously reduce the radiation intensity of the outlet end pipeline, and is beneficial to improving the operation period of the cracking furnace.

Secondly, the radiant coil has a complex structure and different spatial densities. In order to heat the radiation coil uniformly, relatively dense electric heating elements are arranged in a dense area of the radiation coil, and the shape angle of the corresponding refractory material reflecting surface is relatively small; in the sparse arrangement area of the radiation coil, relatively sparse electric heating elements are arranged, and the shape angle of the corresponding refractory material reflecting surface is relatively large.

Thirdly, the size of the hearth space of the cracking furnace is different under the restriction of process requirements, engineering conditions and the like, especially the distance between the radiation coil and the reflecting surface of the refractory material is different, and the relative positions of the electric heating element and the refractory material have three relations: disposed within the refractory material, disposed on the refractory reflective surface, disposed between the refractory reflective surface and the radiant coil.

In addition, in combination with the arrangement mode, the electric heating elements can also be arranged continuously or discontinuously, and can also be arranged uniformly or non-uniformly.

Optionally, the electric heating elements are uniformly arranged near the inlet end, and the distance between the electric heating elements is a; the electric heating elements are uniformly arranged near the outlet end, and the distance between every two electric heating elements is B; wherein A is less than or equal to B, preferably A is less than B.

The specific selection of the distances A and B between the electric heating elements is designed comprehensively according to the space size of the hearth of the cracking furnace and the size of the electric heating elements.

The heat energy from the heating element is reflected by the reflecting surface of the refractory material to radiate the heat to the radiant coil. As shown in fig. 3a, 3b, 3c, and 3d, the reflecting surface of the refractory material may be a plane or a special-shaped structure to obtain different radiation ranges and intensities according to the arrangement of the electric heating elements. For the reflecting surfaces with different shapes, the smaller the reflection angle of the reflecting surface, the more concentrated the radiation energy, the higher the radiation intensity, and the rapid temperature rise. In contrast, the radiation energy is dispersed as the reflection angle of the reflection surface is larger, and the radiation range is larger as the radiation intensity is smaller. Specifically, fig. 3a is a plane, fig. 3b is a U-shaped concave surface, fig. 3c is an arc-shaped concave surface, and fig. 3d is a V-shaped concave surface.

The refractory material is selected from the group including, but not limited to, alumina mirror porcelain.

In an alternative embodiment, the electric heating module and the refractory material may be formed as an electric heating module and removably attached to the furnace body for ease of maintenance or replacement, the electric heating module being provided with a support for holding the refractory material and a connector for removable attachment to the furnace body.

In one possible embodiment, the supporting member is a module sleeve, the connecting member is a flange cover, the module sleeve is filled with a refractory material, the reflecting surface of the refractory material faces the radiation coil pipe through one end of the module sleeve, and the other end of the module sleeve is connected with the flange cover and fixed with the furnace body through the flange cover. The lead of the electric heating element sequentially passes through the heat insulating material and the flange cover to be connected with an external power supply of the furnace body.

Further, the position of the electric heating element is arranged, the refractory material and the electric heating element are integrated into a detachable and assemblable electric heating module, and the refractory material at other positions in the furnace body is lined in the furnace body.

In addition, when the working condition of the cracking furnace is changed, the whole 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 actual conditions.

In practical industrial application, the size of the electric heating ethylene cracking furnace, the type and arrangement mode of the radiation coil, the corresponding arrangement method of the electric heating element and the selection of the refractory material are designed according to the process conditions of cracking raw materials, the feeding amount, the heat load and the like.

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

Example 1

The cracking raw material is a mixture of naphtha and dilution steam, and the feeding amount is 64 t/h.

The thermal load of the cracking furnace is 36MW, and the external dimension of the cracking furnace is 4m multiplied by 30m multiplied by 14m (H). The radiant coil 3 is 8 groups of U-shaped coils (1-1 type), each group comprises 2 groups and adopts mirror image arrangement, and each group of U-shaped coils is composed of 6 furnace tubes.

The electric heating element is made of iron-chromium-aluminum alloy and is arranged on the side wall and the bottom of the cracking furnace. 720 electric heating elements are arranged in the whole cracking furnace, the design power of a single electric heating element is 50kW, and the regulating range of the heat release power is 40-60 kW.

FIG. 4a is a schematic diagram showing the arrangement of the electric heating elements in the furnace of the cracking furnace, wherein only 1 large group of U-shaped coils is illustrated, and 8 large groups of U-shaped coils are illustrated;

arranging side wall electric heating elements: 336 electric heating elements are arranged on the side wall of the single side and divided into 7 rows (in the vertical direction of the cracking furnace), and the row spacing is 1.8 m. 48 electric heating elements are arranged in the single row in the horizontal direction, the horizontal distance between the electric heating elements corresponding to the first stroke of the furnace tube is 0.5m (vertically arranged), and the horizontal distance between the electric heating elements corresponding to the second stroke of the furnace tube is 0.9m (horizontally arranged). The electric heating element is arranged between the radiation coil and the side wall reflecting surface and is 0.7m away from the central line of the furnace tube.

FIG. 4b is a schematic view of the arrangement of the hearth of the cracking furnace; arrangement of furnace bottom electric heating elements: 48 electric heating elements are uniformly arranged on the furnace bottom and are arranged inside the refractory material 13. The electric heating element is arranged in the refractory material, and the distance between the outer surface of the electric heating element and the reflecting surface of the refractory material is 50 mm.

In order to enhance heat transfer, as shown in fig. 4c, the reflecting surface of the refractory material corresponding to the first-pass furnace tube electric heating element is made into a V-shaped concave surface, and the reflecting angle α is 86 ℃. As shown in fig. 4d, the reflecting surface of the refractory material corresponding to the second-pass furnace tube electric heating element is made into a V-shaped concave surface, and the reflecting angle α is 120 ℃. The reflecting surface of the refractory material at other positions is a plane.

The bottom of each end wall of the cracking furnace is provided with 1 protective gas inlet (ID 70mm), and the total number of the protective gas inlets is 2 protective gas inlets 11; the top of each end wall of the cracking furnace is provided with 1 replaced gas outlet 12(ID 70mm), and the total number of the replaced gas outlets 12 is 2. Argon is selected as the protective gas. Before operation, argon enters from a protective gas inlet 11, air in the furnace is discharged from a replaced gas outlet 12, gas replacement is stopped when the furnace is filled with the argon, and the protective gas inlet 11 and the replaced gas outlet 12 are sealed by blind plates, so that the environment in the furnace is in non-oxidizing atmosphere.

The power of the electric heating element is adjustable, and the whole or local heat load of the cracking furnace can be changed according to the change of the working condition of the cracking furnace.

Example 2

The cracking raw material is a mixture of propane and dilution steam, and the feeding amount is 10 t/h.

The thermal load of the cracking furnace is 7.5MW, and the external dimension of the cracking furnace is 2.8m multiplied by 8m multiplied by 13m (H). The radiant coil 3 is a single-pass pipe with lower inlet and upper outlet, is arranged along the center line of the furnace, has an outer diameter of 60.3mm, and has a total of 48 pipes.

The electric heating elements are made of silicon-molybdenum rods and are arranged on the side wall, the top surface and the bottom surface of the cracking furnace. The design power of the electric heating element is 50kW, and the regulating range of the heat release power is 40-60 kW.

FIG. 5a is a schematic diagram showing a side view of a cracking furnace and arrangement of electric heating elements, and FIG. 5b is a schematic diagram showing a front view of the cracking furnace and arrangement of electric heating elements;

arranging side wall electric heating elements: and 132 electric heating elements are arranged on the two side walls. Each side wall is arranged in 5 rows, and the row spacing is 2.35 m. The horizontal distance between the lower three rows of electric heating elements is 0.45m, and the horizontal distance between the upper two rows of electric heating elements is 0.75 m. The electric heating element is arranged between the radiation coil 3 and the reflecting surface of the refractory material 13 of the side wall, and is 0.75m away from the central line of the furnace tube.

Furnace top electric heating element arrangement: the design power of the electric heating element is 75kW, and the regulating range of the heat release power is 60-90 kW. 4 electric heating elements are uniformly distributed on the top of the furnace. The electrical heating elements are arranged on the reflecting surface of the refractory material 13 attached to the side wall.

Arrangement of furnace bottom electric heating elements: the design power of the electric heating element is 75kW, and the regulating range of the heat release power is 60-90 kW. 8 electric heating elements are uniformly distributed at the bottom of the furnace. The electrical heating elements are arranged on the reflecting surface of the refractory material 13 attached to the side wall.

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

2 protective gas inlets (ID 70mm) are arranged at the bottom of each end wall of the cracking furnace, and 4 protective gas inlets 11 are formed in total; the top of the cracking furnace was provided with 1 outlet 12 for displaced gas (ID 300 mm). Before operation, nitrogen enters from a protective gas inlet 11, the air in the furnace is discharged from a replaced gas outlet 12, gas replacement is stopped when the content of the nitrogen in the furnace is more than 95%, and the protective gas inlet 11 and the replaced gas outlet 12 are sealed by blind plates, so that the environment in the furnace is in non-oxidizing atmosphere.

In addition, in order to facilitate maintenance, the electric heating element and the corresponding refractory material in the embodiment are made into a detachable electric heating module.

FIG. 5c is a schematic diagram of the assembly of electrothermal modules at the lower three rows of electrothermal elements, and FIG. 5d is a schematic diagram of the assembly of electrothermal modules at the upper two rows of electrothermal elements;

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 refractory material is filled in the module sleeve (14), a reflecting 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 with the flange cover (16). The module sleeve (14) and the flange cover (16) are fixed with a connecting module sleeve and a flange (15) which are arranged in the furnace body 1. The lead of the electric heating element sequentially passes through the refractory material 13 and the flange cover (16) to be connected with an external power supply of the furnace body 1.

The modular design has interchangeability, and can be replaced and maintained according to the running condition of equipment.

When the electrically heated ethylene cracking furnace is in operation, the power supply of the electric heating element is switched on, and heat generated by the electric heating element is reflected to the radiation coil pipe through the reflecting surface of the refractory material. When the working condition of the cracking furnace is changed, 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, the protective gas is preferably argon, so that a hearth is in non-oxidizing atmosphere in the operation process of the cracking furnace, the cracking gas is prevented from igniting when leaking in the hearth, an electric heating element is protected from being oxidized, and the service life of the radiation coil is prolonged.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.