Electric heating structure of hot blast stove

Abstract

An electric heating structure of a hot blast stove comprises a plurality of electric heating units connected in series, a circulating fan, a hot blast heat exchanger, a high-temperature air duct connected between the electric heating units and the hot blast heat exchanger, and a low-temperature air duct connected between the hot blast heat exchanger and the circulating fan; an air outlet of the circulating fan is connected with a low-temperature air inlet of the electric heating unit; the circulating fan is a high-temperature resistant centrifugal fan; an air inlet of the circulating fan is connected with one end of the low-temperature air duct, and an air outlet of the circulating fan is connected with the low-temperature air inlet of the electric heating unit; the hot blast heat exchanger is a shell-and-tube heat exchanger made of finned tubes; a heat releasing medium flowing through a shell side of the hot blast heat exchanger is hot blast air driven by the circulating fan; a heat absorbing medium flowing through a tube side of the hot blast heat exchanger is water, CO2, air, steam, heat conducting oil, and a medium capable of flowing in a pipe and conducting heat; an air outlet of the hot blast heat exchanger is connected with the other end of the low-temperature air duct, and an air inlet is connected with a high-temperature air outlet of the electric heating unit through the high-temperature air duct.

Description

Technical Field

[0001] This invention relates to the field of hot blast stove technology, specifically to an electrically heated hot blast stove that operates in the voltage range of 0.4kV to 35kV, can output hot air below 1100℃, and has an electric heating structure that enables modular hoisting or forklifting of the equipment. Background Technology

[0002] Replacing coal-fired or gas-fired hot air furnaces with electrically heated ones presents a significant challenge: the short lifespan of the electric heating elements. This is especially true for furnaces with output hot air temperatures exceeding 700℃, where the standard for dry-burning electric heating elements specifies annual replacement. For high-power electric hot air furnaces exceeding 1000kW, hundreds to thousands of dry-burning electric heating elements are required. Replacing these elements annually would be equivalent to purchasing a new furnace. This situation limits the widespread application of electrically heated hot air furnaces. Therefore, it is necessary to develop a new electric heating element to replace existing heating elements, achieving a lifespan of over 10 years, reducing user costs, and meeting users' needs for low-carbon heating. Summary of the Invention

[0003] This invention provides an electric heating structure for a hot blast stove, aiming to solve the problem of the service life of electric heating elements in high-voltage, high-power, high-temperature hot blast stoves.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: An electric heating structure for a hot air furnace includes multiple electric heating units connected in series, a circulating fan, a hot air heat exchanger, a high-temperature air duct connecting the electric heating units and the hot air heat exchanger, and a low-temperature air duct connecting the hot air heat exchanger and the circulating fan; the air outlet of the circulating fan is connected to the low-temperature air inlet of the electric heating unit; characterized in that: the electric heating unit is composed of an insulation structure, a support plate, an electric heating element, a throttling plate, a throttling orifice, a ventilation gap, a base component, and a lead electrode; a waterproof buckle plate is also installed at the waterproof flange connection between the multiple electric heating units; The electric heating element consists of an electric heating wire, an insulating ceramic tube, an electric heating wire crimping plate, and a fixing rod; multiple electric heating elements connected in series and parallel are mounted in a parallel array on the array holes of the support plate; The support plate is made of 3 to 7 parallel plates of plate material with holes for mounting electric heating elements, capable of withstanding temperatures above 700°C and having insulation requirements to withstand working voltage. Furthermore, the circulating fan is a high-temperature resistant centrifugal fan; the air inlet of the circulating fan is connected to one end of the low-temperature air duct, and the air outlet of the circulating fan is connected to the low-temperature air inlet of the electric heating unit.

[0005] Furthermore, the hot air heat exchanger is a shell-and-tube heat exchanger made of finned tubes; the heat-releasing medium flowing through the shell side of the hot air heat exchanger is hot air driven by a circulating fan; the heat-absorbing medium flowing through the tube side of the hot air heat exchanger is water, CO2, air, steam, heat transfer oil, and other media that can conduct heat within the pipes; the air outlet of the hot air heat exchanger is connected to the other end of the low-temperature air duct, and the air inlet is connected to the high-temperature air outlet of the electric heating unit through a high-temperature air duct.

[0006] Furthermore, the heating wire is a round wire or flat strip of iron-based or nickel-based heating alloy, wound at equal intervals on an insulating ceramic tube, forming a spiral tube structure of the same length as the insulating ceramic tube.

[0007] Furthermore, the insulating ceramic tube is made of electrical ceramic material that can horizontally support the heating wire and has a smooth or threaded surface.

[0008] Furthermore, the heating wire crimping plate is made of heat-resistant stainless steel plate, with fixing rod holes and two heating wire crimping points, and the heating wire can be welded between the two crimping points.

[0009] Furthermore, the fixing rod is a rod-shaped component made of high-temperature resistant stainless steel, with locking nuts at both ends, capable of passing through the insulating ceramic tube and connecting and fixing the insulating ceramic tube to the support plate as a whole.

[0010] Furthermore, the throttling plate is an insulating space between the insulation structure and the electric heating element, consisting of a low-temperature air passage with a central throttling hole made of mica board and the heating element.

[0011] Furthermore, the foundation components are made of fire-resistant and heat-insulating material that can withstand the weight of the electric heating unit and are located inside the steel structure shell; the foundation components are connected to the electric heating element via a throttling plate.

[0012] Furthermore, the insulation structure is installed inside the steel structure shell and is made of aluminum silicate compressed blocks and needle-punched blankets.

[0013] The technical solution adopted in this invention has the following advantages: This invention mainly improves the structure of the new electric heating element, namely, the electric heating unit. In this technical solution, if each unit contains 138 heating wires made of 3mm to 5mm diameter round wires or spiral heating alloy material made of 2mm×6mm flat strips, they can be divided into 3 groups connected in parallel and 46 groups connected in series in a resistance connection network. Each heating wire is encased in a ceramic tube made of electrical ceramic, so that the heating wires can be fixed in parallel array on the support plate to prevent them from falling off. The heating wires installed on the outer surface of the support ceramic tube are exposed to the flowing air, establishing good convective heat dissipation conditions. This avoids the defect of excessive thermal resistance of the heating wires in the electric heating tube, which easily leads to overheating and burnout, and ensures a working life of 10 years for the heating wires. This solution is designed as a unit module with a height of 2.7m, a width of 3m, and a length of 2m. The electric heating unit modules produced in the factory can be transported to the site by flatbed truck. If the equipment consists of 6 electric heating unit modules, the flanges between the electric heating unit modules need to be connected along the 2m direction. The assembled equipment forms a 12m electric heating working section, which can be delivered to the user quickly and conveniently. Attached Figure Description

[0014] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein: Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a front view schematic diagram of the electric heating unit of the present invention; Figure 3 This is a side view schematic diagram of the electric heating unit of the present invention; Figure 4 This is a top view schematic diagram of the electric heating unit of the present invention; Figure 5 This is a schematic diagram of the composition of the electric heating element of the present invention; Figure 6 This is a schematic diagram of the electric furnace wire connection of the present invention.

[0015] Explanation of icon numbers: Electric heating unit, 1-1, insulation structure, 1-2, support plate, 1-2-1, array holes, 1-3, electric heating element, 1-3-1, heating wire, 1-3-2, insulating ceramic tube, 1-3-3, heating wire crimping piece, 1-3-4, fixing rod, 1-3-5, crimping point, 1-3-6, welding point, 1-3-7, fixing rod hole, 1-4, throttling plate, 1-5, throttling orifice, 1-6, ventilation gap, 1-7, base component, 1-8, lead electrode, 2, circulating fan, 3, hot air exchanger, 4, high temperature air outlet, 5, low temperature air inlet, 6, high temperature air duct, 7, low temperature air duct, 8, waterproof buckle plate, 9, steel structure, 9-1, waterproof flange, 9-2, flange fixing hole. Detailed Implementation

[0016] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Unless otherwise specified, the techniques used in the embodiments are conventional means well known to those skilled in the art.

[0017] In this embodiment, Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a front view schematic diagram of the electric heating unit of the present invention; Figure 3 This is a side view schematic diagram of the electric heating unit of the present invention; Figure 4 This is a top view schematic diagram of the electric heating unit of the present invention; Figure 5 This is a schematic diagram of the composition of the electric heating element of the present invention; Figure 6 This is a schematic diagram of the electric furnace wire connection of the present invention.

[0018] In this embodiment, as Figure 1 As shown, an electric heating structure for a hot air furnace includes multiple electric heating units 1 connected in series, a circulating fan 2, a hot air heat exchanger 3, a high-temperature air duct 6 connecting the electric heating units 1 and the hot air heat exchanger 3, and a low-temperature air duct 7 connecting the hot air heat exchanger 3 and the circulating fan 2. The air outlet of the circulating fan 2 is connected to the low-temperature air inlet of the electric heating unit 1, forming a closed loop from the air outlet of the circulating fan 2 to the low-temperature air inlet 5 of the multiple combined electric heating units 1, and then from the high-temperature air outlet 4 of the multiple combined electric heating units 1 to the shell side of the hot air heat exchanger 3 via the high-temperature air duct 6. The shell side of the hot air heat exchanger 3 is then connected to the air inlet of the circulating fan 2 via the low-temperature air duct 7, forming a heat release cycle.

[0019] like Figure 2 , 3As shown in Figure 4, the electric heating unit 1 consists of an insulation structure 1-1, a support plate 1-2, an electric heating element 1-3, a throttling plate 1-4, a throttling orifice 1-5, a ventilation gap 1-6, a base component 1-7, and a connecting electrode 1-8. A waterproof fastener 8 is also installed at the connection point of the waterproof flange 9-1 between multiple electric heating units 1. The waterproof flange 9-1 has flange fixing holes 9-2 for mutual connection and fixation. Within the insulation structure 1-1 of the electric heating unit 1, two zones with different operating temperatures and functions are established by designing a low-temperature zone occupied by the throttling plate 1-4 and a high-temperature zone surrounded by the throttling plate 1-4 and containing the electric heating element 1-3. 90%–95% of the air supplied from the low-temperature air inlet 5 through the outlet of the circulating fan 2 flows through the high-temperature zone and is... When the air is heated to a high temperature, about 5% of the air enters the space of the throttling plate 1-4 and flows to the outlet through the throttling holes 1-5 on the throttling plate 1-4. Since there are no heating elements in the space of the throttling plate 1-4, it can only absorb the heat energy conducted from the high temperature area to the low temperature area. The temperature gradient of the hot air is small, which creates better insulation conditions for the insulation structure 1-1, reduces the insulation loss of the equipment, and improves the working efficiency of the hot air furnace. The space established by the throttling plate 1-4 is also the distance between the energized heating wire 1-3-1 and the insulation structure 1-1. Adjusting the width of the throttling plate 1-4 can change the working voltage of the heating wire 1-3-1. Therefore, the designed width of the throttling plate 1-4 should be greater than the safe working distance of the heating wire 1-3-1.

[0020] like Figure 5As shown, the electric heating element 1-3 consists of an electric heating wire 1-3-1, an insulating ceramic tube 1-3-2, an electric heating wire crimping plate 1-3-3, and a fixing rod 1-3-4; multiple electric heating elements 1-3 connected in series and parallel are mounted in a parallel array on the array holes 1-2-1 of the support plate 1-2. The service life of the electric heating element 1-3 should exceed that of existing electric heating tubes by more than 10 years. Firstly, the material of the electric heating wire 1-3-1 is selected according to the working air temperature of the hot air furnace; when the working air temperature is 800℃~1100℃, HRE (High Resistance Electric) is selected. For heating wire 1-3-1 made of 0Cr25Al6RE high-temperature electric heating alloy, when the working air temperature is 400℃~700℃, 216 niobium (0Cr21Al6Nb) heating wire 1-3-1 should be selected. If the circulating hot air contains gases that are corrosive to iron-chromium-aluminum heating wire 1-3-1, nickel-chromium alloy heating wire 1-3-1 can be selected. Accurate selection of the heating wire 1-3-1 material can improve its service life. Secondly, the surface heat load design of heating wire 1-3-1 should be considered. The maximum heat accumulation temperature rise of heating wire 1-3-1 at the minimum air flow rate of the hot blast stove can be determined based on whether it reaches the maximum allowable operating temperature of heating wire 1-3-1. To improve the lifespan of the heating element 1-3-1, the following measures are taken: First, reduce the surface heat load of the heating element 1-3-1 to extend its service life. Second, the material of the insulating ceramic tube 1-3-2 must be able to withstand the large temperature difference changes inside the hot air furnace and the local high-temperature radiation at the contact surface of the heating element 1-3-1 wrapped around it. It should not develop local cracks after more than 10 years of use. Third, the mechanical strength of the insulating ceramic tube 1-3-2 must meet the requirements for supporting the heating element 1-3-1. The diameter of the insulating ceramic tube 1-3-2 and the inner diameter of the heating element 1-3-1 should have a margin of 3mm to 10mm, and the fit should not be too tight or too loose. By selecting the appropriate insulating ceramic tube 1-3-2, the lifespan of the heating element 1-3-1 can be extended. The support plate 1-2 is made of 3 to 7 parallel plates with array holes 1-2-1 for mounting electric heating elements 1-3. The plate is made of a plate material that can withstand temperatures above 700°C and has insulation requirements for withstanding working voltage. The circulating fan 2 is a high-temperature centrifugal fan. The air inlet of the circulating fan 2 is connected to one end of the low-temperature air duct 7, and the air outlet of the circulating fan 2 is connected to the low-temperature air inlet 5 of the electric heating unit 1.The array of holes 1-2-1 on the two side plates of the 3-7 parallel-installed support plates 1-2 and the throttling plate 1-4 are small holes that can pass through the fixing rods 1-3-4, while the holes on the middle 1-5 plates are large holes that can pass through the spiral coil of the heating wire 1-3-1, which are 2mm-4mm larger than the diameter of the spiral coil of the heating wire 1-3-1. The fixing rods 1-3-5 installed in the small holes of the two outer support plates 1-2 should be able to support the axial direction of the heating wire 1-3-1 on the insulating ceramic tube 1-3-2 and the axial direction of the large holes of the middle 1-5 support plates 1-2, so as to keep the spiral coil of the heating wire 1-3-1 from being affected by external forces during the alternating high and low temperature operation.

[0021] The hot air heat exchanger 3 is a shell-and-tube heat exchanger made of finned tubes. The heat-releasing medium flowing through the shell side of the hot air heat exchanger 3 is hot air driven by the circulating fan 2. The heat-absorbing medium flowing through the tube side of the hot air heat exchanger 3 is water, CO2, air, steam, heat transfer oil, and other media that can flow and conduct heat within the pipes. The air outlet of the hot air heat exchanger 3 is connected to the other end of the low-temperature air duct 7, and the air inlet is connected to the high-temperature air outlet 4 of the electric heating unit 1 through the high-temperature air duct 6. The heating wire 1-3-1 is a round wire or flat strip of iron-based or nickel-based electric heating alloy, wound at equal intervals on the insulating ceramic tube 1-3-2, and forming a spiral tube structure of the same length as the insulating ceramic tube 1-3-2. The insulating ceramic tube 1-3-2 is made of electrical ceramic material with a smooth surface or a spiral coil that can horizontally support the heating wire 1-3-1. The heating element crimping plate 1-3-3 is made of heat-resistant stainless steel plate, with a fixing rod hole 1-3-7 and two crimping points 1-3-5 for the heating element 1-3-1, and the heating element 1-3-1 can be welded to the middle of the two crimping points 1-3-5. The heating element 1-3-1 is welded to the middle of the two crimping points 1-3-5 of the heating element crimping plate 1-3-3 to form a stable welding point 1-3-6. The fixing rod 1-3-4 is a rod-shaped component made of high-temperature resistant stainless steel with locking nuts at both ends, which can pass through the insulating ceramic tube 1-3-2 and connect and fix the insulating ceramic tube 1-3-2 to the support plate 1-2 into a whole. The throttling plate 1-4 is a low-temperature air channel with a throttling hole 1-5 in the center, made of mica plate, and is the insulating space between the insulation structure 1-1 and the electric heating element 1-3. The basic component 1-7 is made of refractory insulation material capable of supporting the weight of the electric heating unit 1 and is installed inside the outer shell of the steel structure 9. The basic component 1-7 is connected to the electric heating body 1-3 via the throttling plate 1-4. The insulation structure 1-1 is installed inside the outer shell of the steel structure 9 and is made of aluminum silicate compressed blocks and needle-punched blankets. The steel structure 9 is the annular outer shell of the electric heating unit 1. A ring of square waterproof flanges 9-1 is provided at each of the two end faces where the electric heating units 1 are connected in series. Flange fixing holes 9-2 are evenly distributed on the square waterproof flanges 9-1. The square waterproof flanges 9-1 are welded to the steel structure 9. When the electric heating units 1 are assembled, the waterproof flanges 9-1 are connected with bolts in sequence to complete the main electric heating structure of the hot air furnace with 3 to 30 electric heating units 1.

[0022] In practical implementation, depending on the required power, 3 to 30 electric heating units 1 can be used in series, with the number of combinations being a multiple of 3. Each electric heating unit 1 is equipped with two lead electrodes 1-8 for power supply connection. The power supply voltage can be 0.4kV, 6kV, 10kV, 22kV, or 35kV, depending on the project's power requirements. The power connection between multiple electric heating units 1 can be a star connection or a delta connection, depending on the specific circumstances.

[0023] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An electric heating structure for a hot air furnace, comprising multiple electric heating units (1), a circulating fan (2), a hot air heat exchanger (3) connected in series, a high-temperature air duct (6) connecting the electric heating units (1) and the hot air heat exchanger (3), and a low-temperature air duct (7) connecting the hot air heat exchanger (3) and the circulating fan (2); the outlet of the circulating fan (2) is connected to the low-temperature air inlet of the electric heating unit (1), Its features are: The electric heating unit (1) is composed of a heat insulation structure (1-1), a support plate (1-2), an electric heating element (1-3), a throttling plate (1-4), a throttling hole (1-5), a ventilation gap (1-6), a base component (1-7), and a lead electrode (1-8); a waterproof buckle plate (8) shall also be installed at the connection of the waterproof flange (9-1) between multiple electric heating units (1); The electric heating element (1-3) is composed of an electric heating wire (1-3-1), an insulating ceramic tube (1-3-2), an electric heating wire pressing piece (1-3-3), and a fixing rod (1-3-4); multiple electric heating elements (1-3) connected in series and in parallel are mounted in a parallel array on the array holes (1-2-1) of the support plate (1-2); The support plate (1-2) is made of 3 to 7 parallel plates with an array of holes (1-2-1) for mounting electric heating elements (1-3) on the top, which can withstand temperatures above 700°C and have insulation requirements for withstanding working voltage.

2. The electric heating structure of a hot blast stove according to claim 1, characterized in that: The circulating fan (2) is a high-temperature resistant centrifugal fan; the air inlet of the circulating fan (2) is connected to one end of the low-temperature air duct (7), and the air outlet of the circulating fan (2) is connected to the low-temperature air inlet (5) of the electric heating unit (1).

3. The electric heating structure of a hot blast stove according to claim 1, characterized in that: The hot air heat exchanger (3) is a shell-and-tube heat exchanger made of finned tubes; the heat release medium flowing through the shell side of the hot air heat exchanger (3) is hot air driven by the circulating fan (2); the heat absorption medium flowing through the tube side of the hot air heat exchanger (3) is water, CO2, air, steam, heat transfer oil and other media that can conduct heat in the pipes; the air outlet of the hot air heat exchanger (3) is connected to the other end of the low temperature air duct (7), and the air inlet is connected to the high temperature air outlet (4) of the electric heating unit (1) through the high temperature air duct (6).

4. The electric heating structure of a hot blast stove according to claim 1, characterized in that: The heating wire (1-3-1) is made of iron-based or nickel-based electric heating alloy round wires and flat strips, which are wound at equal intervals on the insulating ceramic tube (1-3-2) and form a spiral tube structure of the same length as the insulating ceramic tube (1-3-2).

5. The electric heating structure of a hot air furnace according to claim 1, characterized in that: The insulating ceramic tube (1-3-2) is made of electrical ceramic material that can horizontally support the heating wire (1-3-1) and has a smooth or threaded surface.

6. The electric heating structure of a hot blast stove according to claim 1, characterized in that: The heating wire crimping plate (1-3-3) is made of heat-resistant stainless steel plate with a fixing rod hole (1-3-7) and two heating wire (1-3-1) crimping points (1-3-5), and the heating wire (1-3-1) can be welded between the two crimping points (1-3-5).

7. The electric heating structure of a hot air furnace according to claim 1, characterized in that: The fixing rod (1-3-4) is a rod-shaped component made of high-temperature resistant stainless steel with locking nuts at both ends. It can pass through the insulating ceramic tube (1-3-2) and connect and fix the insulating ceramic tube (1-3-2) and the support plate (1-2) into one piece.

8. The electric heating structure of a hot blast stove according to claim 1, characterized in that: The throttling plate (1-4) is an insulating space between the insulation structure (1-1) and the electric heating element (1-3), which is a low-temperature air passage with a throttling hole (1-5) in the center made of mica plate and the electric heating wire (1-3-1).

9. The electric heating structure of a hot blast stove according to claim 1, characterized in that: The basic component (1-7) is made of fire-resistant and heat-insulating material that can withstand the weight of the electric heating unit (1) and is located inside the outer shell of the steel structure (9); the basic component (1-7) is connected to the electric heating body (1-3) via the throttling plate (1-4).

10. The electric heating structure of a hot blast stove according to claim 1, characterized in that: The thermal insulation structure (1-1) is installed inside the outer shell of the steel structure (9) and is made of aluminum silicate compressed blocks and needle-punched blankets.

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