Electric heating cracking furnace

Abstract

The utility model discloses an electric heating cracking furnace applied to ethylene production. The furnace wall of a radiation area comprises a heat storage layer, a heat insulation layer and a heat preservation layer from inside to outside. Electric heating elements are arranged in inner holes of the heat storage bricks, end faces are in sealed connection through convex-concave curved surfaces, breather pipes are arranged on the outer sides, and inert gas protects the electric heating elements. The heat insulation layer is made of pasty heat insulation materials, and the total thickness is 10-15 mm. A temperature measuring device is installed in the heat preservation layer, the thermocouple head is arranged in a groove or a pit on the outer side of the heat storage brick, a large spiral ring and a small spiral ring are arranged on the compensation wire, the large spiral ring is arranged in the ceramic tube, the small spiral ring is arranged in the outer end portion, and the large spiral ring and the outer end portion are fixedly connected into a whole in an insulation mode. The furnace wall is provided with flat flame burners which are staggered at intervals, electric heating is mainly used, and flame heating is assisted. The thermal insulation effect is good, emission of combustion tail gas is reduced, the service life of the cracking pipe is prolonged, the electric heating element can heat for a long time, and the temperature measuring device can effectively operate for a long time.

Description

Technical Field

[0001] The utility model is applied to the field of chemical high-temperature cracking and relates to a cracking furnace, in particular to a cracking furnace which adopts a mixture of gas and electricity as a heating method. Background Art

[0002] The cracking furnace is the core equipment of the ethylene production system and also a high-energy-consuming equipment. The cracking reaction needs to absorb heat, and its energy consumption accounts for more than 60% of the total energy consumption of the system. The existing ethylene cracking furnace fuel is mainly gas or oil, which provides heat for the cracking reaction after combustion, and the temperature of the cracking radiation zone is as high as 1100℃ or above. The main defects of this type of cracking furnace are: 1) The use of fossil energy, my country is a country with poor fossil energy and high energy dependence; 2) The high-temperature tail gas after combustion requires a large heat exchange device to recover, resulting in heat waste; 3) The tail gas contains a large amount of greenhouse gases and harmful gas pollutants, which need to be purified before discharge, and special purification equipment is required; 4) The combustion flame has flame licking tubes and local overheating of the radiation coil, which is not conducive to the stable operation of the cracking furnace; 5) The temperature controllability is poor. The combustion value, flow pressure, flow rate, combustion-supporting gas ratio of fossil energy directly affect the stability of the furnace temperature, and the operation status of the heat exchange system and environmental protection equipment affects the furnace temperature. The above problems can be solved by using electric heating cracking furnaces. Although more than 70% of my country's electricity comes from fossil energy, with the development of green electricity technology, fossil energy is gradually exhausted, and electric heating cracking furnaces will inevitably become the development direction of the industry.

[0003] Due to the wide range of cracking technology, there are many patent applications for electric heating cracking furnaces. For example, patent CN201254539Y discloses a tower cracking furnace, in which the electric heating device is arranged around the cracking furnace body, and the cracking temperature is only 500°C, which is not suitable for the high-temperature cracking of ethylene. Patent CN1145686C discloses an electric heating cracking furnace, in which the cracking furnace body is composed of a fixed furnace body and a movable furnace body, and the furnace temperature is controlled and adjusted by means of setting multiple furnace tiles and spacers; the fault location in the cracking furnace can be quickly and accurately detected during maintenance. The resistance wire of the cracking furnace is located in the furnace cavity. When working, it is in a high-temperature oxidizing atmosphere, which reduces the service life of the resistance wire. In order to quickly replace and repair, it is designed as a movable furnace body. Patent CN201014928Y discloses an electric heating high-temperature tubular cracking furnace, in which the inner hole of the furnace lining is placed to measure the oil product, and the high-temperature cracking is performed. The spiral resistance wire is arranged in the axial groove on the surface of the inner hole, and the thermocouple is inserted into the inner hole to measure the temperature. The cracking furnace is suitable for use in laboratories. The resistance wire and the thermocouple are both exposed to high-temperature cracking gas and will be corroded by the cracking gas, which will affect their service life.

[0004] In order to solve the problem of service life limitation caused by oxidation or corrosion of electric heating elements, patent CN113652246A discloses an electric heating ethylene cracking furnace, which is similar to the electric heating ethylene cracking furnace device structure of patent CN113801683A. 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 protective gas (nitrogen or inert gas can be selected) is introduced into the furnace for replacement, and then the protective gas inlet and outlet valves are closed to make the furnace body in a non-oxidizing atmosphere, protect the electric heating element from oxidation, and extend the service life of the radiation coil. Since the cracking furnace cavity is large, it is difficult to completely replace it with protective gas, and the auxiliary components of the cracking furnace make it almost impossible to seal the cracking furnace body as a whole, so the electric heating ethylene cracking furnace only weakens the oxidizing atmosphere of the electric heating element, but cannot eliminate it. Utility Model Content

[0005] The technical problem solved by the utility model is to provide an electric heating cracking furnace, wherein the electric heating element is arranged in the heat storage layer of the furnace wall to isolate the atmosphere in the furnace and realize thorough oxidation and corrosion prevention. The temperature measuring device is also arranged in the furnace wall and does not contact with the gas in the furnace, thus realizing a long service life of the temperature measuring device.

[0006] The technical solution adopted by the utility model is: the furnace wall of the radiation zone of the electric heating cracking furnace includes a heat storage layer, a heat insulation layer and a thermal insulation layer from the inside to the outside; an electric heating element is arranged in the inner hole of the heat storage brick of the heat storage layer, a temperature measuring device is installed in the thermal insulation layer, and the temperature measuring point of the temperature measuring device is located on the outside of the heat storage layer. Or the heat insulation layer is divided into an outer heat insulation layer and an inner heat insulation layer, the outer heat insulation layer is arranged in the thermal insulation layer, the thermal insulation layer is divided into an inner heat insulation layer and an outer heat insulation layer, and the inner heat insulation layer is arranged between the heat storage layer and the inner heat insulation layer. The thermal conductivity of the heat insulation layer at 1000°C is not more than 0.035W / (m·K). An electric heating element is arranged in the inner hole of the heat storage brick of the heat storage layer, and a temperature measuring device is installed in the thermal insulation layer.

[0007] Preferably, in order to protect the electric heating element, a vent pipe is provided on the outside of the heat storage brick, and the connection between the vent pipe and the heat storage brick is sealed with a ceramic filter and refractory cotton. The vent pipe is connected to the inert gas pipeline, and the inert gas can be introduced into the inner hole of the heat storage brick. The mating end faces at both ends of the heat storage brick are designed with corresponding convex platforms and concave grooves, and the mating end faces of the convex platforms and concave grooves are designed with mutually matching protrusions and grooves, and the protrusions and grooves make the brick seams form a curved seal, which can isolate the furnace gas and avoid oxidation and corrosion of the electric heating element; secondly, it can save inert gas, and the inert gas retains a smaller pressure and flow rate, which can meet the requirement of furnace gas impermeability.

[0008] Preferably, the insulation layer is made of a paste-like aerogel insulation material, which can fill the brick joints of the heat storage layer and the insulation layer, so that the furnace wall is integrated. The total thickness of the insulation layer is preferably 10-15mm, the thickness of the inner insulation layer is preferably 5-8mm, and the thickness of the outer insulation layer is preferably 3-6mm.

[0009] Preferably, the temperature measuring device includes a pair head, a compensation wire, a ceramic tube, and an outer end; the pair head is arranged in a groove or a pit on the outer side of the heat storage brick, in close contact, as a temperature measuring point. A large spiral ring and a small spiral ring similar to a spiral spring are processed on the compensation wire. The large spiral ring has a large pitch and is arranged in the ceramic tube, and the small spiral ring has a small pitch and is arranged in the outer end. Insulating resin is injected into the outer end to fix the small spiral ring and the outer end as a whole.

[0010] Preferably, the two ends of the electric heating element are connected to conductive sheets, and the connection between the conductive sheets is stuffed with refractory cotton to avoid heat dissipation, and is sealed with castable or refractory mud.

[0011] Preferably, the radiation zone furnace wall is equipped with flat flame burners, which are evenly spaced and staggered. Electric heating is the main method, and flame heating is the auxiliary method.

[0012] Preferably, the raw material inlet pipe of the cracking furnace is installed in the furnace wall, and the heat of the furnace wall is used to preheat the cracking raw material.

[0013] The beneficial effects of the utility model are: 1) the use of new insulation materials saves energy; 2) reduces tail gas emissions, saves investment in tail gas treatment equipment, and reduces tail gas treatment operating costs; 3) the electric heating element that isolates the high-temperature furnace gas meets the requirements of long-term operation of the cracking furnace; 4) the temperature measuring device that isolates the high-temperature furnace gas can accurately measure the temperature and operate effectively for a long time; 5) there is no flame licking tube phenomenon, and the service life of the cracking tube is extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of a furnace wall cross section of Example 1;

[0015] Figure 2 yes Figure 1 AA section schematic diagram;

[0016] Figure 3 yes Figure 1 Schematic diagram of the left side;

[0017] Figure 4 yes Figure 1 A partial enlarged view, which is also a schematic diagram of the temperature measuring device structure;

[0018] Figure 5 is a schematic diagram of a furnace wall cross section of Example 3;

[0019] In the figure: 1-electric heating element, 2-heat storage layer, 3-inner insulation layer, 4-inner thermal insulation layer, 5-temperature measuring device, 6-flat flame burner, 7-outer wall, 8-insulation board layer, 9-outer thermal insulation layer, 10-outer thermal insulation layer, 11-burner brick, 12-conductive sheet, 13-ventilation pipe, 14-raw material inlet pipe;

[0020] 51-head, 52-large screw ring, 53-ceramic tube, 54-small screw ring, 55-insulating resin, 56-outer end. DETAILED DESCRIPTION

[0021] The following inside and outside refers to the relative position of the furnace cavity and the furnace body, the furnace cavity is the inside, and the furnace body is the outside. Figure 1 and attached Figure 4 The left side, attached Figure 2 The upper side is inner, attached Figure 1 and attached Figure 4 On the right side, Figure 2 The lower side is outside.

[0022] The innovation of the utility model lies in the furnace wall structure of the cracking furnace radiation zone, and other structures not described in detail belong to the prior art or are applications of the prior art. Example

[0023] The structure of the electric heating cracking furnace in this embodiment is as shown in the attached figure. Figure 1-4 As shown, the furnace wall in the radiation zone is composed of a heat storage layer 2, an inner insulation layer 3, an inner thermal insulation layer 4, an outer insulation layer 10, an outer thermal insulation layer 9, a thermal insulation board layer 8, and an outer wall 7 from the inside to the outside. The electric heating element 1 is arranged in the heat storage layer 2, and the temperature measuring device 5 is installed in the thermal insulation layer to measure the temperature of the outer wall of the heat storage layer without extending into the furnace cavity. The heat storage layer 2 is used for radiation heating of the cracking tube, and the inner and outer insulation layers are made of high thermal resistance insulation materials to isolate the conduction heat transfer of the furnace wall. The inner and outer insulation layers are the main structure of the furnace wall to achieve the stability of the furnace wall. The outer wall 7 is a steel plate, which is a structural member that supports auxiliary components such as burners, temperature measuring devices, and pipelines. In this embodiment, electric heating is mainly used, and the burner heating is auxiliary. A flat flame burner 6 is installed in the furnace wall.

[0024] The heat storage layer 2 is built with heat storage bricks, the inner side of which is in direct contact with the high-temperature furnace gas, and the outer side is in close contact with the inner insulation layer 3. Requirements for heat storage bricks: 1) high temperature resistance and high high temperature strength, that is, high refractoriness and high softening point; 2) good chemical stability, that is, no chemical reaction with furnace gas; 3) good volume stability, that is, from room temperature to high temperature, it will not produce large expansion or contraction due to recrystallization or sintering; 4) have a certain heat storage capacity to ensure the stability of radiation heat transfer, and will not affect the radiation heat transfer of the heat storage layer due to the working fluctuation of the burner, that is, to ensure the hysteresis of temperature. Corundum bricks, such as chrome corundum, aluminum corundum, etc., are suitable for heat storage bricks. The heat storage brick body is square, which is convenient for furnace wall masonry. The brick body is processed with an inner hole, which is convenient for the arrangement of electric heating elements. The matching end faces at both ends of the brick body are designed with corresponding convex platforms and concave grooves. The mating end faces of the convex platform and the concave groove are designed with mating protrusions and grooves. The two are built together, and the refractory mud fills the brick joints, so that the brick joints form multiple curved seals to ensure the sealing of the inner hole of the heat storage brick, prevent the entry of furnace gas, and achieve isolation between the inner hole cavity of the heat storage brick and the furnace gas.

[0025] The inner insulation layer 3 and the outer insulation layer 10 are both made of aerogel insulation material, which is a newly developed new insulation material. The base material is resistant to high temperature, nanopore insulation is used, and the product is in paste form. During construction, the paste insulation material is scraped (equivalent to the operation of applying an insulation layer or cement layer on the wall surface) to the inner side of the insulation layer, and the water evaporates to form an insulation layer. When the material is subjected to a simple test of insulation capacity, a circular sample plate made of paste insulation material is dried to a thickness of 3.8 mm and covered on a 2kw resistance wire heating furnace. After 24 hours, the infrared temperature measuring gun measures the upper surface, which is only 87-96°C, and the insulation effect is excellent. According to the test of relevant testing agencies, the thermal conductivity at 1000°C is not greater than 0.035W / (m·K). The current disadvantage of this product is that after drying, especially at high temperatures, it cannot withstand the fluidity impact of furnace gas, is easy to powder and peel off, and gradually thins, so it is set between the heat storage layer and the inner insulation layer, and between the inner and outer insulation layers to isolate the furnace gas. Considering the air heat dissipation on the upper surface of the above test sample plate, the insulation layer in the furnace wall should be thickened to ensure the insulation effect. The thickness of the inner insulation layer should be 5-8mm, the thickness of the outer insulation layer should be 3-6mm, and the total thickness can be controlled at 10-15mm. The advantage of the paste aerogel insulation material is that it has extrusion fluidity during construction, can fill the brick joints, ensure the bite joints of the heat storage layer and the inner and outer insulation layers, thereby ensuring the integrity of the furnace wall.

[0026] The inner insulation layer 4 and the outer insulation layer 9 are built of porous lightweight refractory bricks and are the main supporting components of the furnace wall. Lightweight clay bricks or high-alumina bricks can be selected. The refractory softening point of the inner insulation layer 4 is higher than that of the outer insulation layer 9.

[0027] The insulation board layer 8 is a porous fiber material, such as an insulation asbestos board, or other insulation boards. Its main purpose is to prevent convection heat dissipation through the brick joints, while retaining a certain air permeability to facilitate the exhaust of water vapor during the drying of refractory bricks and the drying of the insulation layer.

[0028] The flat flame burners 6 are evenly arranged on the furnace wall at intervals. Figure 3 As shown, the structure of the flat flame burner 6 can be found in the "A Flat Flame Burner for Cracking Furnace" (Application No. 2023232635794) applied by the applicant. The flame of the flat flame burner can be spread along the inner wall of the heat storage layer, and its heat can quickly heat the heat storage layer. The burner brick 11 is customized, with a square outside and a round inside, matching the size of the heat storage brick. The inner end face of the flat flame burner is coated with an insulating coating. The insulating principle of the insulating coating is the same as that of the insulating layer, but the material ratio is different, and the performance emphasizes bonding ability and anti-cracking ability.

[0029] The electric heating element 1 can be made of silicon carbon rod or silicon molybdenum rod. Silicon carbon rod has a large specific resistance, with a negative characteristic curve from room temperature to 800℃ and a positive characteristic curve above 800℃. When heated in air, the surface temperature of the heating part can reach 1450℃. Silicon molybdenum rod is also a resistance heating element, which is brittle and easy to break at room temperature. The surface temperature of the heating part can reach 1900℃, and the maximum operating temperature is 1750℃ in an oxidizing atmosphere. The resistance of silicon molybdenum rod does not change with the length of use (resistance increases with increasing temperature), and new and old elements can be mixed. According to the temperature of the electric furnace and the requirements of the atmosphere medium, the heating element can use molybdenum wire or tungsten wire, but it is expensive.

[0030] In this embodiment, electric heating and combustion heating are mixed. In the low temperature stage, the resistance of non-metallic electric heating elements such as silicon carbon rods changes with temperature. At low temperatures, the resistance is small, the heat generation is small, and the heating speed is slow. Therefore, in the low temperature stage, it is appropriate to use a burner to heat the furnace wall until it turns red. When the temperature is above 800°C, the resistance of non-metallic electric heating elements such as silicon carbon rods increases, and electric heating is started. The reasons for using burner heating to assist electric heating are: 1) At present, the furnace type is in the test verification stage, and it is not appropriate to remove all the delay nozzles and directly use electric heating instead of gas heating; 2) Make full use of the existing heat exchanger and purification and environmental protection equipment, and the furnace type test does not affect normal production; 3) The development of related material technology and cost factors, such as electric heating element materials, refractory materials, etc.; 4) Customer acceptance when the furnace type is promoted.

[0031] The electrical connection of the electric heating element 1 is shown in the attached Figure 2, the two ends are connected with conductive sheets 12, and refractory cotton is inserted at the connection of the conductive sheets 12 to prevent the heat dissipation of the heat storage bricks. On the back side of the refractory cotton, castables or refractory mud are poured to seal the two ends of the heat storage bricks. The heat storage bricks in this embodiment have appropriate air permeability. In order to prevent furnace gas from penetrating into the holes of the heat storage bricks and oxidizing or corroding the electric heating elements, a vent pipe 13 is arranged on the outside of the heat storage bricks. The connection of the vent pipe 13 to the heat storage bricks is blocked with ceramic filter discs and refractory cotton to prevent heat dissipation and ensure a certain ventilation capacity. The vent pipe is connected to the inert gas pipeline outside the furnace wall (nitrogen is preferably used from a cost perspective), and a pressure reducing valve and a valve are installed on the inert gas pipeline to connect the inert gas bag. The vent pipe introduces low-pressure inert gas into the heat storage bricks to prevent the penetration of furnace gas, so that the electric heating elements work under the protection of the inert gas, and no oxidation or corrosion occurs, thereby achieving the purpose of increasing the service life of the electric heating elements, thereby ensuring the long-term smooth operation of the cracking furnace. The inert gas has low pressure and small flow rate, and as long as the furnace gas is not permeable, it will have no effect on the heat storage of the heat storage bricks and does not need to be considered in the heating simulation.

[0032] Temperature measuring device as attached Figure 4 As shown, the temperature measuring device includes a pair head 51, a compensation wire, a ceramic tube 53, an outer end, etc. The pair head 51 is a key component for temperature measurement, and is preferably made of platinum-rhodium material, and the temperature measurement capability can reach above 1300°C. The pair head 51 is directly connected to the compensation wire, and the other end of the compensation wire is electrically connected to the temperature measuring instrument. The pair head 51 is set on the outside of the heat storage brick, and the temperature of the outer side is consistent with the temperature of the inner side of the heat storage brick. The temperature detected there can be used to replace the temperature in the furnace. In order to ensure that the pair head and the heat storage brick are in good contact, a groove or pit matching the pair head is processed on the outside of the heat storage brick as a temperature measurement point. The pair head is placed in the groove or pit to increase the contact surface of the pair head and ensure the accuracy of temperature measurement. On the compensation wire, two spiral rings similar to the shape of a spring are processed, namely a large spiral ring 52 and a small spiral ring 54, wherein the large spiral ring 52 is set in the ceramic tube 53, and the ceramic tube section has the characteristics of insulation, high temperature resistance, and low thermal conductivity. Before the large spiral ring 52 is inserted into the ceramic tube 53, it is wrapped with refractory cotton. The refractory cotton is mainly used for insulation to avoid heat radiation and convection heat transfer on the outside of the heat storage brick. At the same time, it can relatively fix the compensation wire and insulate the compensation wire. The pitch of the large spiral ring is relatively long, and its main purpose is: 1) it has a certain elasticity, which can compact the head into the groove or pit of the heat storage brick to ensure the accuracy of temperature measurement; 2) increase the length of the compensation wire and reduce external conduction heat dissipation; 3) facilitate the adjustment of the length size to adapt to the different thicknesses of the furnace wall. The pitch of the small spiral ring 54 is relatively short, and the small spiral ring 54 is set in the outer end, and the outer end is fixed on the outer wall. Insulating resin 55 is injected into the outer end to fix the small spiral ring 54, and the small spiral ring 54 is fixedly connected to the outer end as a whole, and at the same time, the insulation of the two is achieved.

[0033] It should be noted that: 1) Insulating resin can also be replaced by other insulating materials, as long as it meets the purpose of insulation and fixing the small screw ring, such as rubber, plastic, mica, glass, electric porcelain, etc. 2) Ceramic tubes should be positioned and connected with multiple sections of concave and convex, which is conducive to hindering the conduction and heat transfer of ceramic tubes. 3) In the subsequent temperature measurement process, the heat transfer of the temperature measuring device is mainly the heat transfer of the temperature measuring coupler and the compensation wire. Even if the local compensation wire connected to the coupler loses its elasticity due to high temperature, the part with lower temperature at the rear end still retains its elasticity, and the part that loses elasticity is relatively fixed by the insulation layer and the thermal insulation cotton, so that the coupler can still be in full contact with the heat storage brick to ensure the accuracy of temperature measurement; 4) If the thermal expansion and contraction of the compensation wire is considered, the groove or pit should have a certain depth to avoid the coupler shrinking out of the groove or pit after the furnace is stopped; 5) There should be a gap between the steel pipe section and the ceramic pipe section. In the subsequent production and use process, the outer end and the small screw ring can be used to compress the large screw ring together by screwing the fastener, so that the compensation wire increases its elasticity again; 6) The thickness of the slurry of the paste aerogel insulation material is limited. In order to shorten the construction period of the furnace wall, the drying after slurry scraping and the refractory brick laying are carried out simultaneously, so this embodiment adopts two layers of insulation. Example

[0034] This embodiment is an improvement on embodiment 1. Figure 2 On the basis of, the ventilation pipe 13 is removed. This requires that the heat storage bricks have poor air permeability, the amount of furnace gas penetrating into the heat storage layer is small, and the heat storage bricks have good sealing when they are laid, which can meet the long-term effective operation of the electric heating element. This embodiment can save inert gas pipelines, pipeline accessories and inert gas bags, and save equipment investment. Example

[0035] This embodiment is the ultimate goal of the utility model, and the structure is as shown in the attached Figure 5 As shown. With the advancement of material technology, when new electric heating elements are substituted, the burner heating can be removed and all electric heating can be used. In this way, multiple equipment such as exhaust gas heat exchangers and exhaust gas purification equipment can be omitted, which greatly saves equipment investment and saves the operating costs of these equipment.

[0036] The radiation zone furnace wall is composed of a heat storage layer 2, a heat insulating layer 61, a heat preservation layer 62, a heat preservation board layer 8 and an outer wall 7 from the inside to the outside. The heat insulation layer in the above embodiment is divided into two layers, mainly to meet the needs of construction and the drying needs of the paste-like heat insulation material. If a single layer of the heat insulation layer can meet the needs of construction and drying, it can be simplified to a single layer.

[0037] The raw material inlet pipe 14 of the original cracking furnace convection zone is installed in the furnace wall, and the heat of the furnace wall is used to preheat the cracking raw material. This can further save space in the cracking furnace. There is no convection zone, only a cracking zone.

[0038] The utility model adopts electric heating to partially or completely replace fossil energy heating, reduce exhaust gas emissions or eliminate exhaust gas emissions, reduce the scale of exhaust gas heat exchangers or purification treatment equipment, or eliminate subsequent exhaust gas treatment equipment, reduce equipment investment, reduce land cost, and reduce operating costs. The electric heating element is installed in the heat storage layer of the cracking furnace radiation zone, and is protected by inert gas. There is no erosion by oxidizing or corrosive furnace gas, the service life of the electric heating element is extended, and the long-term effective operation of the cracking furnace is guaranteed. The temperature measuring device is arranged in the insulation layer, and the head is in close contact with the heat storage brick, the temperature measurement is accurate, the temperature measuring device is not corroded by furnace gas, and the service life is long. The furnace wall adopts a new paste-like aerogel insulation material, which not only has good thermal insulation performance and saves energy, but also can be squeezed into the brick seam to connect the heat storage layer and the insulation layer as a whole. Due to the use of a burner for auxiliary heating, the flame length is reduced, the flame licking tube phenomenon is avoided, the service life of the cracking tube is improved, and the smooth operation of the cracking tube is guaranteed. In summary, the benefits of the utility model are summarized as follows: 1) the use of new insulation materials saves energy; 2) reduces tail gas emissions, saves investment in tail gas treatment equipment, and reduces tail gas treatment operating costs; 3) the electric heating element isolates the high-temperature furnace gas, which can meet the requirements of long-term operation of the cracking furnace; 4) the temperature measuring device isolates the high-temperature furnace gas to ensure long-term effective operation; 5) the cracking is smooth and the life of the cracking tube is extended.

[0039] It should be emphasized that the present invention takes the working environment of the ethylene cracking furnace as the research and development improvement object, and does not affect the application of the furnace wall in heating furnaces in other fields. Keywords such as ethylene and cracking shall not be regarded as limiting the scope of rights of the present invention.

Claims

1. An electrically heated cracking furnace, characterized in that: The radiation zone furnace wall comprises, from the inside to the outside, a heat storage layer (2), a heat insulation layer and a thermal insulation layer; an electric heating element (1) is arranged in the inner hole of the heat storage brick of the heat storage layer (2); a temperature measuring device (5) is installed in the thermal insulation layer, and the temperature measuring point is located outside the heat storage layer.

2. An electrically heated cracking furnace according to claim 1, characterized in that: The heat insulating layer is divided into an outer heat insulating layer (10) and an inner heat insulating layer (3); the outer heat insulating layer (10) is arranged inside the thermal insulation layer, the thermal insulation layer is divided into an inner heat insulating layer (4) and an outer heat insulating layer (9); the inner heat insulating layer (3) is arranged between the heat storage layer (2) and the inner heat insulating layer (4).

3. An electrically heated cracking furnace according to claim 2, characterized in that: The thermal insulation layer uses a paste-like aerogel thermal insulation material to fill the brick joints of the heat storage layer and the thermal insulation layer; the total thickness of the thermal insulation layer is 10-15 mm, the thickness of the inner thermal insulation layer (3) is 5-8 mm, and the thickness of the outer thermal insulation layer (10) is 3-6 mm.

4. An electrically heated cracking furnace according to claim 1 or 2, characterized in that: The temperature measuring device (5) comprises a pair head (51), a compensation wire, a ceramic tube (53), and an outer end (56); the pair head (51) is arranged in a groove or a pit on the outer side of a heat storage brick; a large spiral ring (52) and a small spiral ring (54) are processed on the compensation wire, the large spiral ring (52) is arranged in the ceramic tube (53), and the small spiral ring (54) is arranged in the outer end (56); the insulating resin injected into the outer end (56) fixes the small spiral ring (54) and the outer end (56) together.

5. An electrically heated cracking furnace according to claim 1 or 2, characterized in that: The two ends of the electric heating element (1) are connected to conductive sheets (12), and the connection between the conductive sheets (12) is filled with refractory cotton and poured with castable material or refractory mud.

6. An electrically heated cracking furnace according to claim 1 or 2, characterized in that: The radiation zone furnace wall is provided with flat flame burners (6), which are evenly distributed at intervals and in a staggered manner.

7. An electrically heated cracking furnace according to claim 1 or 2, characterized in that: The raw material inlet pipe (14) of the cracking furnace is installed in the furnace wall.

8. An electrically heated cracking furnace according to claim 1 or 2, characterized in that: A vent pipe (13) is provided on the outside of the heat storage brick, and a connection between the vent pipe (13) and the heat storage brick is sealed with a ceramic filter and refractory cotton.

9. An electrically heated cracking furnace according to claim 8, characterized in that: The mating end surfaces at both ends of the heat storage brick are designed with corresponding convex platforms and concave grooves, and the mating end surfaces of the convex platforms and concave grooves are designed with mutually matching protrusions and grooves, and the protrusions and grooves make the brick joints form a curved surface seal.

10. The electrically heated cracking furnace according to claim 8, characterized in that: The ventilation pipe (13) is connected to the inert gas pipeline.

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