Electric heating element, electric heating kiln car, continuous kiln and method

Abstract

The present disclosure relates to an electric heating assembly for a kiln car and a kiln, an electrically heated kiln car for a kiln, an electric continuous kiln and a method. The electric heating assembly comprises a U-shaped electric heating element and a first insulating piece surrounding end pieces of a first side portion of the heating element and a second insulating piece surrounding end pieces of a second side portion of the heating element. The first side portion and the second side portion have the same or shorter length than a top portion of the U-shaped electric heating element.

Description

Technical Field

[0001] This application claims priority to European patent application EP 23205661.4, filed on October 24, 2023.

[0002] This disclosure relates to heating assemblies for kiln cars and kilns, and particularly to electrically heated kiln cars, especially electrically heated kiln cars for continuous kilns. This disclosure also relates to electric continuous kilns and methods for heating loads transported through electrically heated or non-electrically heated kiln cars in a continuous kiln. Background Technology

[0003] A kiln is a type of oven that generates sufficient temperature to complete processes such as hardening, sintering, or drying. For example, kilns are used to fire clay-based ceramic pottery. During firing, the pottery (which may be glazed) is heated for a long period according to a specific temperature profile. This temperature profile can be designed to ensure the vitrification of the pottery. The use of kilns is known, for example, in the manufacture of sanitary ware, tableware and porcelain, roofing tiles, bricks, technical ceramics, and others.

[0004] Different types of kilns are known. In a continuous kiln, kiln cars are loaded with pottery to be fired and are moved as they travel through the kiln to heat the pottery. The kiln cars can be moved "continuously" through the kiln using, for example, tracks. Continuous kilns can also be called tunnel kilns.

[0005] In these kilns, heating elements are often arranged on the inner walls of a continuous kiln, allowing the temperature of the pottery to be controlled along the entire length of the kiln. For example, gas burners can be installed so that the kiln load is heated as the kiln car passes through the continuous kiln. At the entrance, the pottery is cold, and its temperature increases as it is slowly transported through the kiln, approaching the center (often the hottest part). As the pottery continues to move through the kiln, its temperature can decrease. Cold air can be injected along different sections of the continuous kiln to ensure that the pottery undergoes a specially designed temperature profile.

[0006] In contrast, in a batch kiln, the pottery to be fired is first loaded into the kiln. The kiln is then sealed, and the internal temperature is increased according to a specific temperature profile. After firing, both the kiln and the pottery cool. Batch kilns may also rely on the use of kiln cars. In a batch kiln, heating elements are arranged on the inner walls of the kiln. A kiln car moves into or is transported into the kiln, stops, and the electric heating elements heat the load on the kiln car. After heat treatment, both the kiln and the load can cool. The load can be removed from the batch kiln, the kiln can be cleaned, and the next heating cycle can begin. Different types of heating elements can be used.

[0007] CH216256 discloses a tunnel kiln with a kiln car incorporating electric heating. Electricity is supplied to the electric heating unit via conductive tracks arranged along the tunnel floor. DE 1 558 062A also discloses a kiln car incorporating electric heating. More modern tunnel kilns typically rely on gas burners rather than electric heating, although there are CO2 reduction benefits when avoiding the use of LPG (liquefied petroleum gas) or natural gas for heating. One reason is that gas heating may be easier due to the large size of the kiln and the amount of heating power required. Furthermore, electric heating may be less efficient than gas heating in terms of heat transfer. Heat transfer in electric heating is primarily through thermal radiation, while heat transfer in conventional gas burners is primarily through thermal convection. There remains a need for electric heating solutions for ceramics that provide effective electric heating and are both efficient and economical. Summary of the Invention

[0008] In one aspect of this disclosure, an electric heating assembly is provided. The electric heating assembly includes a substantially U-shaped electric heating element comprising a first side portion, a second side portion, and a top portion connecting the first and second side portions, the top portion extending longitudinally and configured to heat ceramic. The electric heating element is mounted at end parts of the first and second side portions. The electric heating assembly also includes a first insulating member surrounding the end parts of the first side portion and a second insulating member surrounding the end parts of the second side portion, wherein the first and second end parts of the two side portions are movable longitudinally. The lengths of the first and second side portions are equal to or shorter than the length of the top portion of the U-shaped electric heating element.

[0009] Based on this aspect, an effective electric heating solution is provided for ceramic pottery in the kiln. The kiln car can support the pottery. In some examples, electric heating can be installed on individual kiln cars, making the heating suitable for the pottery placed on each individual car. In these or other examples, the electric heating can also be installed on the kiln's bottom plate.

[0010] U-shaped heating elements are generally known in the art, but often the side portions of the U are significantly longer than the bottom portion (or the "top" portion when inverted). In this disclosure, in order to provide effective heating, the portion connecting the two side portions is at least as long as or significantly longer than the side portions.

[0011] When current circulates through the electric heating element, the thermal expansion of the heating element can be absorbed by allowing the U-shaped heating element to move in the longitudinal direction. This prevents damage to the U-shaped heating element, such as breakage. At the same time, because the electric heating element is (electrically) insulated, the kiln car and ceramic pottery are protected.

[0012] Throughout this disclosure, an electric heating element may refer to an element that heats up when an electric current circulates through it. As previously indicated, the electric heating element has a U-shape.

[0013] When the first and second side portions of the electric heating element are shorter than the top portion, more efficient and safer heating can be achieved because more heat can be released upwards due to the longer top portion, and fewer electric heating elements are needed in the kiln car body and / or kiln floor body.

[0014] The resistance of the side portions of a U-shaped electric heating element can differ from that of the top portion, for example, due to the introduction of materials of different densities and different conductive cross-sections, such as a hollow sleeve. In particular, the resistance of the top portion can be higher than that of the side portions. For a given current level, the top portion will become hotter, thus providing more efficient heating for the ceramic. The resistances of the two side portions can be the same or similar. Furthermore, the resistances of the two side portions can be very low or extremely low to minimize the amount of heat required to heat these side portions.

[0015] In some examples, the first and second insulators may be elastic and configured to be radially outwardly compressed as the electric heating element expands.

[0016] In some examples, the first and second insulators may comprise hollow sleeves. The sleeve can be configured to compress radially outward when a radially outward force is applied to the side portion of the U-shaped heating element, particularly along the longitudinal direction of the U-shaped heating element. In some examples, the sleeve can be tightly fitted around the side portion. That is, initially, when the heating element is cold, the inner wall of the sleeve can contact the outer surface of the side portion.

[0017] In some examples, a first gap may be provided longitudinally between the first insulator and the first side portion, and a second gap may be provided longitudinally between the second insulator and the second side portion to allow longitudinal movement of the side portion. The gaps or holes may be elongated. The first and second insulators may have elliptical or rectangular cross-sections, such as substantially racetrack-shaped ellipses, to hold the electric heating element in one direction and allow movement in the other.

[0018] The first and second insulating elements may include hollow sleeves or rings. The inner diameter of the hollow sleeve or ring may be larger than the outer diameter of the side portions of the U-shaped electric heating element along the longitudinal direction of the U-shaped electric heater, and the first and second side portions may move radially outward, particularly along the longitudinal direction, and thus be heated when current circulates through the heating element. When the side portions are cold, i.e., before current circulates through them, the initial outer diameter of the side portions may increase. The inner diameter of the hollow sleeve or ring may limit the radial expansion of the side portions along the longitudinal direction. That is, the hollow ring may be rigid. As indicated in the previous paragraphs, the hole may, for example, be elliptical or rectangular.

[0019] U-shaped electric heating elements can include, and are particularly made of, silicon carbide (SiC). Silicon carbide is a semiconductor material with high thermal conductivity and the ability to withstand harsh environments. Temperatures, for example, 1200°C or higher, can be reached in kilns used for firing ceramics such as sanitary ware.

[0020] Additional U-shaped electric heating element assemblies, similar to those described herein, can be arranged on the kiln car body or the kiln floor body. The heating element assemblies can be arranged, for example, in two (or more) rows on the kiln car body or in one row on the kiln floor body.

[0021] In another aspect of this disclosure, a kiln car for a kiln is provided. The kiln car includes a kiln car body, a support base for supporting a load to be fired, and an electric heating assembly of the previous aspect disposed below the support base. End portions of two side portions of a U-shaped electric heating element are mounted on the kiln car body, and a top portion is disposed above the kiln car body, such that the U-shaped electric heating element is configured to heat the load on the support base. One or more electric heating assemblies further include a first insulating member surrounding the end portions of a first side portion and a second insulating member surrounding the end portions of a second side portion, wherein the first and second end portions of the two side portions are mounted in the kiln car body, such that the first and second end portions are movable in a longitudinal direction.

[0022] In another aspect of this disclosure, an electric continuous kiln is provided. The electric continuous kiln includes a tunnel, one or more electrically heated kiln cars according to any of the examples described herein, and one or more tracks for guiding the electrically heated kiln cars. As the electrically heated kiln cars move along the kiln, the electric continuous kiln can heat the load on the kiln cars using electrically heated elements, such as the load on the electrically heated kiln cars disclosed herein. It should be noted that the electric continuous kiln can also be configured to additionally partially heat the load on the kiln cars. For example, in some examples, in addition to the electrically heated elements, the continuous kiln may use additional gas burners. Furthermore, as mentioned below, the electric continuous kiln can be configured to heat the load on the kiln cars (electrically heated or non-electrically heated) as the kiln cars move along the kiln, with the electrically heated elements arranged in the kiln's bottom plate body.

[0023] Different kiln cars can be used, allowing different loads to be heated and cooled simultaneously in different sections of the kiln. For example, loads on one or more kiln cars are heated in a first zone of the continuous kiln, while another load on one or more other kiln cars is cooled in a subsequent zone of the continuous kiln at the same time. The processed loads can be continuously removed from the kiln and replaced by loads in another section of the kiln, which are then heated.

[0024] The term "load" in this document refers to a product that is being heated. These products can be, for example, hygiene products such as toilets, washbasins, or others. The terms "ceramic" and "load" are used interchangeably in this document.

[0025] In another aspect of this disclosure, an electric continuous kiln is provided. The kiln includes a tunnel, one or more tracks for guiding one or more kiln cars, and a kiln base body including an electric heating assembly as described herein. End parts of two side portions are mounted on the base body, and a top portion is arranged above the base body such that U-shaped electric heating elements are configured to heat the load on the kiln cars.

[0026] In another aspect of this disclosure, a method is provided for heating a load arranged on an electrically heated kiln car, such as one described throughout this disclosure, in a continuous kiln. The method includes moving the kiln car through the continuous kiln while simultaneously circulating an electric current through a U-shaped electric heating element as described herein for heating the load.

[0027] Therefore, as the kiln car is moved through the kiln, current can be introduced into the electric heating element through the free end of one of its side sections, circulate through its top section, and then move away through the free end of the other side section. The heat released by the electric heating element, and particularly through its top section, can be used to heat the load above the electric heating element.

[0028] In this way, the load on the electrically heated kiln car can be heated as the kiln car travels through the continuous kiln. By mounting the heating element on the kiln base body, the load on the non-electrically heated kiln car can also be heated as the kiln travels through the continuous kiln. In some examples, the electrically heated assembly, as described herein, can be mounted on both the kiln car and the kiln base body.

[0029] In some examples, the loading material can be a ceramic loading material. In other examples, the loading material can be any other suitable loading material.

[0030] Specific aspects, examples, and elements of the aspects or examples disclosed herein may be combined in any number and order to form new aspects and examples that form part of this disclosure. Attached Figure Description

[0031] Figure 1 A schematic front view of an example of an electric heating assembly including a U-shaped electric heating element is shown.

[0032] Figure 2 schematically shown Figure 1 The component's exploded view.

[0033] Figure 3 schematically shown Figure 1 A magnified cross-sectional view of the component.

[0034] Figure 4 A cross-sectional view of another example of an electric heating assembly is shown schematically.

[0035] Figure 5 , Figure 6 and Figure 7 The front view, perspective view, and side view of an example of an electrically heated kiln car including multiple U-shaped electric heating elements are schematically shown.

[0036] Figure 8 schematically shown Figures 5 to 7 A top view of the electrically heated kiln car.

[0037] Figure 9 and Figure 10 Two cross-sections of an example kiln are shown schematically. Figure 9 The cross-section is perpendicular to the direction of travel of the kiln car. Figure 9 The cross-section is the longitudinal cross-section of the kiln.

[0038] Figure 11 A flowchart is shown for a method of heating a load arranged on a kiln car, optionally on an electrically heated kiln car, in an electric continuous kiln. Detailed Implementation

[0039] Reference will now be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation only and not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure. For example, a feature shown or described as part of one embodiment may be used with another embodiment to produce yet another embodiment. Therefore, the present disclosure is intended to cover such modifications and variations within the scope of the appended claims and their equivalents.

[0040] Figure 1 A schematic front view of the electric heating assembly 3 is shown. Figure 2 You can see the exploded view of component 3 in [the image], and... Figure 3 The cross-section of the left portion of the component can be seen in the image. The electric heating assembly 3 includes a U-shaped electric heating element 2. The U-shaped electric heating element 2 includes a first side portion 4, a second side portion 5, and a top portion 6 connecting the first side portion 4 and the second side portion 5. Thus, the heating element 2 forms an inverted U. The top portion 6 extends along the longitudinal direction of the U-shaped electric heating element.

[0041] See Figure 2 and Figure 3 The electric heating assembly 3 also includes a first insulating member 8A surrounding the end part of the first side portion 4 and a second insulating member 8B surrounding the end part of the second side portion 5. The first and second end parts are mounted such that when the first side portion 4 and the second side portion 5 are mounted to the body 7 of the kiln car 1 or the bottom plate of the kiln, the first and second end parts are movable in the longitudinal direction. (As in...) Figure 1 and Figure 5 As can be seen, the lengths of the first side portion 4 and the second side portion 5 are equal to or shorter than the length of the top portion 6 of the U-shaped electric heating element 2.

[0042] In this way, the thermal expansion of the U-shaped electric heating element 2 can be controlled. In particular, damage to the heating element 2 and the kiln car body 7 can be avoided or at least reduced.

[0043] The U-shaped electric heating element 2 may include silicon carbide (SiC), and in particular may be made of silicon carbide. The resistance of the top portion 6 of the heating element 2 may be higher than the resistance of the side portions 4, 5 of the heating element 2, so that most of the heat is generated in the top portion.

[0044] The first insulating member 8A and the second insulating member 8B may be elastic and configured to be radially outwardly compressed under radially outward forces from the first side portion 4 and the second portion 5, respectively (see...). Figure 2 and Figure 3 Compression can be applied specifically along the longitudinal direction of the U-shaped electric heating element.

[0045] The first insulating member 8A and the second insulating member 8B can completely surround the end parts of the corresponding side portions 4 and 5 of the heating element 2 in the tangential direction of the side portions 4 and 5.

[0046] The first insulating element 8A and the second insulating element 8B may or may not reach the ends of the side portions 4 and 5 that will be installed on the kiln car body or the kiln bottom plate body. The first insulating element 8A and the second insulating element 8A typically do not reach the opposite ends of the side portions 4 and 5, that is, the ends that contact the top portion 6 of the U-shaped electric heating element 2.

[0047] The heating assembly may also include a first limiter 9A and an optional second limiter 9B configured to respectively limit the movement of the first end part and the second end part along the longitudinal direction of the electric heating element 2. For example, a first radial gap 10 may be provided between the first limiter 9A and the first side portion 4 (see [link to relevant documentation]). Figure 3 Furthermore, the second radial clearance 10 can be provided between the second limiter and the second side portion 5. Additional limiters 9C and 9D can also be provided.

[0048] In some examples, the first insulator 8A and the second insulator 9A can be hollow bushings 8A and 8B, see [reference needed]. Figure 2 and Figure 3 The sleeve may be elastic and configured to compress in a radially outward direction when the side portions 4, 5 expand radially outward and a radial force is applied to the sleeves 8A, 9A. The force and compression may be particularly along the longitudinal direction of the U-shaped electric heating element. The sleeve may comprise a ceramic material.

[0049] The electric heating assembly 3 may also include a first outer rigid sleeve 13 and a second outer rigid sleeve 14, see [link to documentation]. Figures 1 to 3 Rigid sleeves 13 and 14 may tangentially surround compressible sleeves 8A and 8B. The inner walls of rigid sleeves 13 and 14 may radially confine and hold compressible sleeves 8A and 8B in place. Rigid sleeves 13 and 14 may comprise or be made of ceramic material. Rigid sleeves 13 and 14 may also protect the inner side of the kiln car body 7 or the kiln floor body from the heat absorbed by the compressible sleeves 8A and 8B.

[0050] In some examples, compressible sleeves 8A, 8B and outer rigid sleeves 13, 14 can be arranged between top limiters 9A, 9B and bottom limiters 9C, 9D. In the examples shown in these figures, the top and bottom limiters are configured as rigid hollow elements that have radial clearances relative to the corresponding side portions 4, 5 of the heating element 2 when the heating element is cold. The bottom limiter can help support the compressible sleeves 8A, 8B and the rigid sleeves 13, 14. A gasket 15 can be arranged between the bottom limiter and the supported sleeves 8A, 8B, 13, 14. The gasket 15 can be made of stainless steel.

[0051] See Figure 2 One or more pins 16 can be provided to hold the electric heating element 2 at a desired height relative to other parts of the assembly 3. Alternative or additional holding elements can be provided.

[0052] In some examples, a first gap may be provided longitudinally between the first insulator and the first side portion, and a second gap may be provided longitudinally between the second insulator and the second side portion. Therefore, when the U-shaped heating element is electrically heated, the first side portion 4 and the second side portion 5 can have space for movement along the longitudinal direction of the U-shaped heating element, and particularly outward movement. Furthermore, the first and second insulators can be rigid, i.e., inelastic. Therefore, when the side portions 4 and 5 of the U-shaped electric heating element are subjected to force against the rigid insulator along the longitudinal direction of the heating element, the insulator can prevent the side portions 4 and 5 from advancing further in the direction they are pushed.

[0053] Figure 4 A cross-sectional view of another example of the electric heating assembly 3 is schematically shown. The electric heating assembly 3 is similar to... Figures 1 to 3 Component 3, but the radii of the first insulator 8A and the second insulator 8B are larger along the longitudinal direction of the U-shaped electric heating element 2 than along other directions. See also Figure 4 For example, the inner and outer peripheries of the first insulator 8A and the second insulator 8B are, for example, elliptical in cross-section. Typically, the first and second insulators can have elliptical or rectangular cross-sections. In the case of a rectangular cross-section, the central segment can have a constant width between two circular portions with a constant radius. Furthermore, in... Figure 4 In the example, the first gap 27 and the second gap 28 between the side portions 4 and 5 of the U-shaped heating element 3 and the first insulating member 8A and the second insulating member 8B are arranged along the longitudinal direction of the U-shaped heating element 3.

[0054] In some examples, the first insulator 8A and the second insulator 8B can be a sleeve or a hollow ring. The first and second insulators can be elongated (e.g., in the radial direction of the sleeve or ring, and particularly in the longitudinal direction of the U-shaped heating element). The elongated inner diameter can reduce the likelihood of breakage of the U-shaped heating element 2 and help hold the heating element 2 in place by holding it along a direction perpendicular to the maximum diameter of the hole. In some examples, the inner diameter of the insulator (e.g., the sleeve or hollow ring) can have a racetrack shape or an elliptical shape.

[0055] In the example including the first gap 27 and the second gap 28, one or more retaining elements 16 (e.g., pins, with) can also be provided. Figure 2 (Similar to the example in the example where a first gap and a second gap are provided, and in the example where the first insulating member and the second insulating member are elastic, the first insulating member and the second insulating member may be made of ceramic material.)

[0056] According to another aspect of this disclosure, a kiln car is provided. Figure 5 A schematic front view of an example kiln car 1 is shown, which includes an electric heating element assembly 3, and in particular multiple electric heating element assemblies 3.

[0057] Figure 6 The same example of a kiln car is shown in perspective. In these examples, the electric heating assembly 3 is as follows: Figures 1 to 3 The components shown are different, but in other examples, an electric heating component may be used that includes a first gap and a second gap between the U-shaped electric heating element 2 and the first and second insulators to allow longitudinal movement.

[0058] exist Figure 5 Two electric heating components of the electric heating assembly 3 of the kiln car can be seen. A portion of the main body 7 of the kiln car 1 has been removed, allowing the arrangement of the assembly 3 within the kiln car body 7 to be seen. When the electric heating assembly 3 is installed on the kiln car 1, the first insulator 8A and the second insulator 8B are arranged inside the kiln car body 7, meaning the insulators do not come into contact with the air above the kiln car body.

[0059] Multiple kiln cars can be moved along the tunnel kiln. The tunnel kiln can have a length of, for example, 60 meters, 100 meters, or greater. Suitable tracks can be arranged along the length of the tunnel kiln. In other examples, other guidance systems can be set up. In some examples, the tunnel width can be, for example, 3-5 meters.

[0060] In an example where the kiln car 1 includes multiple electric heating components 3, power can be supplied from the bottom of the kiln car using one or more conductive rails. The kiln car may include one or more contact shoes that contact the conductive rails. The kiln car may include a suitable power converter system and controls to supply current continuously or intermittently through the electric heating components.

[0061] The control system may include one or more processors and one or more memories for storing instructions that the processors can execute. The control system can be configured to set a temperature profile along the continuous kiln. The control system can be located outside the kiln, separate from the kiln car.

[0062] For example, three temperature zones can be set in a continuous kiln: a first zone where the temperature increases from the initial temperature to an intermediate temperature, a second zone where the temperature is maintained at the intermediate temperature, and a third zone where the temperature decreases from the intermediate temperature. The intermediate temperature can be the highest temperature that can be reached, and can be higher than 1000℃. Continuous kilns may include sensors for monitoring the heating process. For example, temperature sensors, pressure sensors, and others may be arranged within the kiln. Continuous kilns may also include insulation. For example, the inner wall of the continuous kiln may include an insulating coating or layer.

[0063] Continuous kilns may include suitable cooling systems. For example, multiple fans may be installed in the kiln for air injection. In some examples, air injection may be pulse-controlled, which can provide higher air velocities. Outputs for exhaust gas, such as ducts, may also be provided. One or more fans may also be used for exhaust gas removal.

[0064] The electrically heated kiln car 1 may also include a support base 11 disposed above the kiln car body 7, the support base being configured to support the load to be heated or fired in the kiln. A U-shaped electric heating element assembly 3 may be disposed below the support base 11 but not in contact with it. In some examples, the support base 11 may include a platform. The platform may be supported by a beam or rod structure.

[0065] The support base 11 may have the same or similar shape and horizontal dimensions as the kiln car body 7. See also Figure 1 and Figure 2 The support base 11 can extend over the entire or most of the top surface of the kiln car body 7.

[0066] The support base 11 can be joined to the kiln car body 7 via one or more vertical support members 12. In this example, the beam or rod structure of the platform of the support base 11 extends between the support members 12.

[0067] For loads or pottery to be fired on a kiln car, a specific temperature profile can be established. The kiln car and / or tunnel may include multiple temperature sensors, such as thermocouples. Based on temperature measurements, the current supplied to the electric heating components can be determined so that the pottery is heated according to the predetermined temperature profile.

[0068] Along the tunnel, additional heating elements (electric heaters, gas burners, or others) and / or additional cooling elements (e.g., cooling air injectors) can be installed to ensure that the predetermined temperature profile is followed as closely as possible.

[0069] In some examples, scales or other weighing systems can be installed at the entrance of the tunnel. The weight (quantity) of the pottery can be determined based on the weight of the kiln car, and this weight (quantity) can also be used as an input for controlling the electric heating components.

[0070] See Figure 5 and Figure 6 The electrically heated kiln car 1 also includes a kiln car body 7. The kiln car body 7 may be or may include a platform or frame. The platform may be flat or have a flat top surface. The kiln car body 7 is configured to support elements arranged thereon. The two side portions 4, 5 of the electric heating element 2, particularly the end parts of the two side portions, are mounted to the kiln car body 7, and the top portion 6 of the U-shaped heating element is arranged above the kiln car body 7, such that the U-shaped electric heating element 2 heats the load (not shown) above the U-shaped electric heating element 2 while the kiln car 7 is in use and current circulates through the U-shaped electric heating element 2.

[0071] As in Figure 5 As can be seen, the top portion 6 of the heating element 2 is separated from the top surface of the kiln car body 7. The top portion 6 can be in direct contact with the surrounding air. That is, the top portion 6 can be uncoated or uncovered, so that the covering element does not contact the top portion 6. Therefore, the electric heating element 2 can effectively heat the load above the kiln car body 7.

[0072] exist Figure 2 and Figure 3 The electrical connectors 25 and 26, which are used to circulate current through the electric heating element 2, can be seen in the image.

[0073] The first side portion 4 of the U-shaped electric heating element can be closer to the side edge of the kiln car 1 than the second side portion 5, see, for example Figure 5 In such examples, the first electric heating element assembly 3 may also include a protective element 17 configured to protect the outer region of the first side portion 4. In some examples, the protective element 17 may be positioned on top of the top limiter, see [reference needed]. Figure 1 and Figure 3 .

[0074] The protective element 17 at least partially surrounds the side portion of the U-shaped heating element. The protective element 17 can be arranged to prevent cooling air from directly impacting the heating element and potentially affecting the temperature of the electric heating element. See also Figure 5 The height of the protective element 17 can be lowered towards the inside of the kiln car 1. The protective element 17 can be arranged above the kiln car body 7. In this way, the affected area of ​​the first side portion 4 can be protected from the cooling fluid transported from the inner wall of the continuous kiln.

[0075] As in Figure 3 As can be seen, a radial gap 18 can be provided between the inner wall of the protective element 17 and the outer wall of the side portions 4, 5 of the electric heating element 2. This gap may already exist when the heating element 2 is still cold. Such a gap can help direct the heat generated by the side portions 4, 5 upwards toward the load. In other examples, the protective element 17 can be provided with such a radial gap, but the height of the protective element 17 can remain unchanged, or it can be different. Figure 3 The way it changes is shown.

[0076] In an example where the first gap 27 and the second gap 28 are provided between the side portions 4 and 5 of the U-shaped electric heating element 2, a protective element 17 may also be provided.

[0077] Apart from the electric heating element, all or most of the components of the electric heating element assembly 3 can be electrically insulated. The thermal conductivity of the components surrounding the electric heating element 2 can be lower than that of the electric heating element. This allows for a safer process.

[0078] In some examples, the first and second insulating elements can be arranged entirely within the kiln car body 7. Figure 5 In the example, the compressible sleeves 8A, 8B and at least the bottom limiter are completely arranged inside the kiln car body 7.

[0079] Figure 7 and Figure 8 They are shown schematically respectively. Figure 1 Side and top views of the electrically heated kiln car. The kiln car body 7 can be configured to move on tracks. For this purpose, the kiln car 1 may include, for example, multiple wheels connected to the kiln car body 7.

[0080] As in Figure 5 and Figure 6 As can be seen, the side portions 4 and 5 of the U-shaped electric heating element can extend vertically. The top portion 6 of the electric heating element can extend substantially horizontally. This example provides a stable, simple, and efficient way to arrange the heating element relative to the kiln car body 7, the load, and the continuous kiln.

[0081] The kiln car 1 may also include multiple additional assemblies comprising U-shaped electric heating elements. The U-shaped heating element assemblies of the kiln car 1 may be arranged in at least one row 19, for example, in two rows 19, see [reference needed]. Figure 5 , Figure 6 and Figure 8 In at least some examples, row 19 may extend along the longitudinal direction of kiln car 1. The longitudinal direction of the kiln car may be the same as the longitudinal direction of the electric continuous kiln on which the kiln car is to move. The two longitudinal rows may be a suitable compromise between the large top portion 6 with electric heating elements 2 and with durable and robust heating elements.

[0082] The side portion of the heating element 2 closest to the kiln car 1, and therefore the side edge of the kiln, can be provided with a protective element 17.

[0083] The kiln car 1 may also include one or more sensors. For example, the kiln car may include one or more sensors for measuring the temperature of the U-shaped electric heating element 12. The kiln car 1 may also include a cooling system. For example, a fan may be provided on the bottom surface of the kiln car body 7. In some examples, the kiln car may be configured to be actively cooled.

[0084] On the other hand, a continuous electric kiln is provided. This kiln includes tunnels, one or more of which, as exemplified herein, are relative to... Figures 5 to 8 The electric heating kiln car 1 and one or more tracks for guiding it are described. Therefore, the kiln car can move or be moved along the continuous kiln. In some examples, electrical wiring can be arranged together with the electrical tracks, such that current drives a motor that rotates the wheels of the kiln car. A transformer can be placed between the electrical wiring and the wheels. One or more electrical lines or tracks can also be provided for electrically feeding the U-shaped electric heating elements.

[0085] Current can flow to these heating elements via contacts arranged, for example, on the underside of a kiln platform, which are arranged alongside or between the kiln tracks in the longitudinal direction of the kiln passage.

[0086] The continuous kiln may include a control system for controlling the U-shaped electric heating element 2 of the electrically heated kiln car 1.

[0087] In some examples, the tracks can be arranged on the kiln floor. In other examples, the tracks can be arranged below the kiln floor, for example, within the kiln floor body.

[0088] In another aspect of this disclosure, a different type of continuous kiln using electric heating is provided. The kiln includes a tunnel, one or more tracks for guiding one or more kiln cars, and a base plate body including an electric heating assembly as described herein. End parts of two side portions are mounted on the base plate body, and a top portion is arranged above the base plate body such that U-shaped electric heating elements are configured to heat the load on the kiln cars.

[0089] In these examples, the kiln car does not include the electric heating components described in other examples.

[0090] Figure 9 and Figure 10 An example of a kiln according to this aspect is schematically shown. Kiln 30 includes a base plate 31, a top wall, and two side walls 33 and 34. See also Figure 9 The first electric heating assembly 3 is mounted on the base plate body 31. The top portion 6 of the U-shaped heating element 2 is parallel to the horizontal transverse direction of the kiln 30, and in particular parallel to the direction in which the width of the kiln is measured.

[0091] The base plate body 31 may include more than one electric heating assembly 3. For example, a row including multiple electric heating assemblies may be provided. Since multiple electric heating assemblies are arranged along the longitudinal direction of the kiln, the U-shaped electric heating elements can release heat when the kiln car travels over the corresponding portion of the base plate body of the kiln. The electric heating assemblies may be sized and arranged such that a vertical gap can be provided between the top portion 6 of the U-shaped heating element 2 and the bottom of the kiln car body when the kiln car body is located above the heating assemblies. Typically, the first insulator 8A and the second insulator 8B will be arranged inside the base plate body 31.

[0092] The electric heating element 3 can be arranged between the two tracks 35 of the kiln 30. That is, the length of the heating element 3 can be shorter than the distance between the two tracks. In this way, the kiln car body can travel above the heating element when it moves along the tracks. The bottom plate body 31 can include a top portion 36 and a bottom portion 37. The electric heating element can be arranged in the top portion 36, and the tracks 35 can be arranged in the bottom portion 37. The bottom portion 37 may also include electrical components, such as wires, for circulating current through the U-shaped heating element 2.

[0093] The kiln 30 may also include additional electric heating components. For example, additional electric heating components similar to the heating components 3 described herein may be arranged on the base plate body 31, for example, facing the side of the kiln, for example, between the corresponding rails 35 and the kiln side walls 33, 34. In some examples, there may therefore be at least three rows of electric heating components 3 or the like arranged on the base plate body 31. For example, providing additional electric heating components on the base plate body can help to better heat the load.

[0094] Alternatively or additionally, other types of electric heating elements may be provided. For example, instead of arranging the electric heating assembly between the track 35 and the side walls 33, 34, other U-shaped electric heating elements 38 may be arranged. Figure 9 In the example, U-shaped electric heating elements 38 can be seen arranged on the side walls 33 and 34 of the kiln. Some of them extend below the kiln car body 7, while others extend above the load for heating the load from above. Those arranged on the bottom portions of the side walls 33 and 34 can be supported on the kiln bottom plate body 31, while those arranged on the top portions of the side walls 33 and 34 can be supported on the kiln top wall 32. Suitable supports 39 are provided for this purpose.

[0095] The U-shaped electric heating element 38 may have side portions 40 (i.e., legs) configured to heat up when current circulates through them. Connecting portions engage the side portions of the heating element 38. These connecting portions may, for example, be bridges made of low-resistivity SiC. Figure 9 In the example, because the connecting portion extends in the longitudinal direction of the kiln, only one leg 40 of these elements 38 is visible. Therefore, these elements 38 can be heated to aid in heating the loads on the kiln car. In some examples, the connecting portion of these heating elements 38 may be shorter than its side portion.

[0096] Leg 40 can pass through the side walls 33 and 34 of the kiln and be supported within the side walls. Electrical connections can be made at the side of the kiln.

[0097] In another aspect, a method 20 is provided for heating in an electric continuous kiln a load arranged on a kiln car, optionally on an electrically heated kiln car 1 as described herein. Figure 11 The method is illustrated in the flowchart. The previous details and explanations of the kiln car and the kiln apply to this method, and vice versa. The method includes, at box 21, continuously moving the kiln car 1 through the continuous kiln. The method also includes, at box 22, simultaneously circulating current through the U-shaped electric heating element 2 of the electric heating assembly 3 as described herein for heating the load.

[0098] In some examples, the electric heating assembly 3 can be arranged on the kiln car body 7. In other examples, the electric heating assembly 3 can be arranged on the kiln bottom plate body 31.

[0099] In some examples, the kiln car body 7 and / or the kiln floor body may include multiple electric heating components 3.

[0100] In some examples, the loading material can be a ceramic loading material. In some of these examples, the loading material can be sanitary pottery.

[0101] In an example where the kiln car includes multiple electric heating element assemblies 3, some of the electric heating elements 2 can be heated at different times than the other heating elements. For example, alternating heating elements 2 in a row can be heated at a first time, and the remaining heating elements 2 in that row can be heated at a second time after the first time. This can extend the lifespan of the electric heating assembly and the kiln car. In this regard, the electric heating elements can be heated using current pulses. Even if all electric heating elements 2 are heated at the same time, current pulses can still be used.

[0102] This written description uses examples to disclose teachings including preferred embodiments and also enables any person skilled in the art to put those teachings into practice, including making and using any apparatus or system and performing any combined methods. The scope of patentability is defined by the claims and may include other examples that would occur to a person skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims. Those skilled in the art can mix and match aspects of the various embodiments described, as well as other known equivalents of each such aspect, to construct additional embodiments and techniques within the scope of this disclosure. If reference numerals associated with the drawings are enclosed in parentheses in the claims, they are merely for the purpose of increasing the comprehensibility of the claims and should not be construed as limiting the scope of the claims.

Claims

1. An electric heating assembly for a kiln, the electric heating assembly comprising: The electric heating element is essentially U-shaped, comprising a first side portion, a second side portion, and a top portion connecting the first side portion and the second side portion and extending along a longitudinal direction. The lengths of the first side portion and the second side portion are equal to or shorter than the length of the top portion of the U-shaped electric heating element; and wherein, The electric heating element is mounted at the end parts of both side portions, and the top portion is arranged such that the U-shaped electric heating element is configured to heat the load; and A first insulating member surrounding the end part of the first side portion and a second insulating member surrounding the end part of the second side portion, wherein the first end part and the second end part are mounted such that the first end part and the second end part are movable along the longitudinal direction.

2. The electric heating assembly according to claim 1, wherein, The first and second insulating elements are elastic and configured to be compressed radially outward.

3. The electric heating assembly according to claim 2, further comprising a limiter configured to limit the movement of the first end part and the second end part along the longitudinal direction.

4. The electric heating assembly according to claim 1, wherein, A first gap is disposed between the first insulating member and the first side portion along the longitudinal direction, and a second gap is disposed between the second insulating member and the second side portion along the longitudinal direction.

5. The electric heating assembly according to any one of claims 1 to 4, wherein, The first insulating element and the second insulating element have an elliptical cross-section or a rectangular cross-section.

6. The electric heating assembly according to any one of claims 1 to 5, wherein, The U-shaped electric heating element comprises silicon carbide, and is specifically made of silicon carbide.

7. The electric heating assembly according to any one of claims 1 to 6, wherein, The first insulating element and the second insulating element are made of ceramic material.

8. A kiln car, said kiln car comprising: Kiln car body; Support base used to support the load to be fired; as well as The electric heating assembly according to any one of claims 1 to 7 is arranged below the support base; wherein, The end parts of the two side portions are mounted on the kiln car body, and the top portion is arranged above the kiln car body, such that the U-shaped electric heating element is configured to heat the load on the support base.

9. The kiln car according to claim 8, wherein, The first side portion is closer to the side edge of the kiln car than the second side portion, and the first electric heating element assembly also includes a protective element configured to protect the outer area of ​​the first side portion.

10. The kiln car according to claim 9, wherein, The height of the protective element decreases towards the inside of the kiln car.

11. The kiln car according to any one of claims 8 to 10, wherein the kiln car comprises a plurality of electrically heated components, wherein, The U-shaped heating elements of the heating assembly are arranged in one or more rows.

12. An electric continuous kiln, the electric continuous kiln comprising a tunnel, one or more electrically heated kiln cars according to any one of claims 8 to 11, and one or more tracks for guiding the electrically heated kiln cars.

13. An electric continuous kiln, the electric continuous kiln comprising a tunnel, one or more tracks for guiding one or more kiln cars, and a kiln floor body, the kiln floor body comprising an electric heating assembly according to any one of claims 1 to 7; in, The end parts of the two side portions are mounted on the base plate body, and the top portion is arranged above the base plate body, such that the U-shaped electric heating element is configured to heat the load on the kiln car.

14. A method for heating, in an electric continuous kiln, a load arranged on a kiln car, particularly on a kiln car according to any one of claims 8 to 11, the method comprising: The kiln car moves continuously through the continuous kiln; as well as Simultaneously, current is circulated through the U-shaped electric heating element of the electric heating assembly according to any one of claims 1 to 7 for heating the load.

15. The method according to claim 14, wherein, The loading material is a ceramic loading material.

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