Indirect heating electric rotary kiln and method for replacing heating element of indirect heating electric rotary kiln
By designing a detachable shield module system, the downtime problem of traditional rotary kilns when replacing heating components is solved, and rapid replacement and thermal efficiency are achieved.
Patent Information
- Application Number
- CN202280097575.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-07-01
- Publication Date
- 2025-02-18
AI Technical Summary
Traditional indirectly heated rotary kilns require a lot of downtime when replacing the electric heating element, as the heating element can only be removed after cooling.
A detachable shield module system is designed to allow replacement of heating elements without stopping the entire process. The shield module can be replaced independently or replaced with a fake module to reduce heat loss and compensate for heat loss by adjusting the heat output of other modules.
The rapid replacement of heating elements without affecting process continuity is achieved, reducing kiln downtime and improving thermal efficiency.
Smart Images
Figure CN119487351A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to indirectly heated rotary kilns, and more particularly, to such rotary kilns that are electrically heated. The present disclosure further relates to methods of replacing heating elements of such indirectly heated electric rotary kilns. Background Art
[0002] Rotary kilns are used to raise materials to high temperatures in a continuous process. Typically, process materials are continuously fed through a cylindrical shell that simultaneously rotates, thereby mixing and advancing the process materials along the cylindrical shell.
[0003] In indirectly heated rotary kilns, the inner shell is usually arranged in a fixed hood which isolates the interior of the kiln from the surroundings. Furthermore, the process material in the shell is heated by introducing heat into it via the shell. That is, heat is introduced from the outside of the inner shell. Traditionally, this is achieved by arranging burners in the intermediate space between the inner shell and the hood. However, most of the heat energy is not used to heat the process material, but escapes with the exhaust gases.
[0004] In order to improve the thermal efficiency of indirect rotary kilns, electric heaters have been used instead of burners. In contrast to burners, heat is not carried away from the kiln by the exhaust gas flow. However, electric heating elements have a limited life span and need to be replaced regularly. Usually, the heating elements need to be cooled before they can be removed, which results in a lot of downtime of the kiln while the heating elements are replaced. Summary of the invention
[0005] One object of the present disclosure is to provide an indirectly heated electric rotary kiln which allows easy replacement of the electric heating elements. Another object of the present disclosure is to provide a method for replacing the heating elements of such an indirectly heated electric rotary kiln.
[0006] The objects of the present disclosure are achieved by a rotary kiln and a method which are characterized by what is stated in the independent claims. Preferred embodiments of the present disclosure are disclosed in the dependent claims.
[0007] The disclosure is based on the idea of providing the shroud surrounding the inner housing with one or more shroud modules, on which the heating elements are arranged. This allows the shroud modules to be removed without shutting down the entire process in order to replace only a part of the elements.
[0008] Thus, a shroud module with a defective or worn heating element can be replaced with another shroud module with a new or refurbished heating element with minimal impact on the overall operation of the kiln. Alternatively, a shroud module with a defective or worn heating element can be replaced with a dummy shroud module (i.e., a shroud module without a heating element) to prevent heat from escaping from within the shroud during replacement of the heating element from the removed shroud module. In addition, the missing amount of heat input from the removed shroud module can be compensated by temporarily increasing the heat output of other shroud modules.
[0009] According to a first aspect of the present disclosure, an indirectly heated electric rotary kiln is provided.
[0010] The rotary kiln comprises a longitudinal inner shell configured to convey process material (i.e. process feedstock) therethrough in use for thermal treatment. The inner shell is arranged to rotate about its longitudinal axis. Suitably, the inner shell is further configured such that when the inner shell rotates, the process material advances along the length of the inner shell.
[0011] The rotary kiln further comprises a fixed shroud arranged along the length of the inner shell and around the cross-sectional periphery of the inner shell, thereby enclosing the inner shell. The shroud acts as an insulating barrier to prevent heat from escaping from the kiln. Suitably, the shroud may be provided with a refractory lining and / or insulating material.
[0012] In particular, the rotary kiln further comprises a shroud module, which is formed as a longitudinal section and a cross-sectional peripheral section of the shroud. That is, the shroud module forms a longitudinal portion of the length of the shroud and an angular portion of the periphery of the shroud. In addition, the shroud module can be detached from the remaining shroud. Most suitably, the shroud module is detachably attached to the remaining shroud.
[0013] The rotary kiln further comprises an electric heating element disposed on the shield module on the inner side of the shield. Such heating element is configured to heat the inner shell when in use. Advantageously, such electric heating element is a non-contact type heating element, such as a radiant heater (e.g., an infrared heater) or an induction heater.
[0014] Preferably, but not necessarily, a reflector is arranged between the heating element and the shroud module, so as to direct the heat generated by the heating element away from the shroud module. Suitably, a thermal insulation layer may also be provided between the reflector and the remaining shroud modules. Together, the reflective layer and the thermal insulation layer serve to improve the overall thermal efficiency of the kiln by promoting heat transfer in the direction of the process material and away from the surrounding environment.
[0015] The shield module may naturally include a plurality of heating elements, which are suitably arranged at a distance from the inner shell along the cross-sectional periphery of the inner shell, which enables the heating elements to cover a larger area of the inner shell than heating elements at a single angular position.
[0016] Preferably, but not necessarily, the shield module includes a plurality of sockets configured to be operably coupled to corresponding heating elements in a removable manner. Such a modular interface between the heating elements and the shield module allows both quick replacement of the heating elements and flexible customization of the shield module for different thermal power outputs. For example, a shield module at a first position of the rotary kiln may be provided with a certain number of heating elements, while other similar shield modules at a second position of the rotary kiln may be provided with another number of heating elements, thereby allowing the thermal distribution of the rotary kiln to be optimized for a specific application. Compared to the prior art, the ability to finely adjust the heat input may be particularly advantageous in applications where a specific time is required at a given temperature.
[0017] Preferably, but not necessarily, the shield module may include a detachable coupling member, the detachable coupling member allowing the shield module to be detachably coupled to a power source to provide power to the heating element. For example, the shield module may include a plug and socket interface for coupling the shield module to a power source.
[0018] Preferably, but not necessarily, the heating element extends a certain distance along the length of the inner shell. For example, the heating element may extend parallel to the inner shell, or extend horizontally (ie, parallel to the length of the rotary kiln).
[0019] In an embodiment according to the first aspect of the present disclosure, at least at the position of the shield module, the internal shape of the shield is consistent with the external shape of the inner shell at a certain distance from the inner shell. That is, the internal shape of the shield does not need to completely follow the curvature of the inner shell, but should follow the overall geometric shape of the inner shell. For example, if the internal shape of the shield is defined by a plurality of discrete planar heating elements, the inclination of the heating elements can be arranged to be consistent with the outer periphery of the inner shell. That is, the internal cross-sectional shape of the shield can be a polygonal approximation of the circular cross-sectional shape of the outer surface of the inner shell. Such an arrangement allows the heating element (one or more) to be placed closer to the inner shell while minimizing the intermediate volume between the inner shell and the shield, thereby increasing the heat transfer efficiency between the heating element and the process material in the inner shell.
[0020] In another embodiment according to the first aspect of the present disclosure, the shield module extends laterally along the bottom side of the inner shell. In other words, the shield module extends horizontally below the inner shell. Unless otherwise specified, the term "lateral" is used in the context of the present disclosure to describe a horizontal direction transverse to the longitudinal direction. Most suitably, the shield module also includes one or more heating elements arranged at a position below the inner shell. This allows the inner shell to be heated at the main position where the process material is located in the inner shell during operation, thereby minimizing heat losses.
[0021] In another embodiment according to the first aspect of the present disclosure, the shield module extends vertically along the lateral side of the inner shell (that is, the lateral side defined on the opposite side of the vertical longitudinal center plane of the inner shell). In other words, the shield module can extend upward on the lateral side of the inner shell. Unless otherwise specified, the term "vertical" is used in the context of the present disclosure to describe a direction transverse to the horizontal plane. Most suitably, the shield element includes one or more heating elements arranged at such a lateral position of the inner shell. This allows heat to be directed to the inner shell at a larger area of the inner shell.
[0022] Preferably, but not necessarily, the shield module extends vertically along the lateral side of the inner shell at least on such a side that the rotation of the inner shell pushes the process material to the side. This further allows the inner shell to be heated during operation at the main location where the process material is located inside the inner shell, thereby minimizing heat losses.
[0023] Preferably, but not necessarily, the shield module extends vertically along the lateral side of the inner shell only on such a side: the rotation of the inner shell pushes the process material to the side. Such an arrangement facilitates the removal of the shield element towards the lateral direction because the inner shell does not interfere with such removal path of the shield element.
[0024] In another embodiment according to the first aspect of the present disclosure, the shield module extends over at least a 90° cross-sectional peripheral segment of the shield below the longitudinal center axis of the inner shell. Such an arrangement is believed to provide suitable positioning of the heating element relative to the position of the process material within the inner shell and sufficient cross-sectional coverage.
[0025] In another embodiment according to the first aspect of the present disclosure, the shield module can be retracted from the remaining shield in a lateral direction away from the inner shell. That is, the shield module, the remaining shield, is configured so that the shield module can be removed from the remaining shield by a lateral translation movement without lifting or rotating the shield module. This further facilitates the removal and replacement of the shield module.
[0026] In another embodiment according to the first aspect of the present disclosure, the shield module includes rollers or wheels on which the shield module can be supported for retracting the shield module away from the remaining shield. Such an arrangement allows the shield module to be rolled away from the remaining shield, for example, along a factory floor or associated platform. In addition, such wheels or rollers can be configured to run on associated tracks, thereby ensuring a predetermined retraction path of the shield module and facilitating reconnection of the module.
[0027] In another embodiment according to the first aspect of the present disclosure, the pressure of the atmosphere in the intermediate space within the shield and outside the inner shell exceeds the pressure of the environment surrounding the rotary kiln. Maintaining the intermediate space under positive pressure can prevent pollutants from entering the intermediate space so as to protect the heating elements. Pollutants such as dust may sinter on the heating elements, which may reduce the efficiency of the heating elements or even damage them. To this end, the rotary kiln may further include a blower, which is configured to feed air into the intermediate space at a pressure higher than the pressure of the environment surrounding the rotary kiln. Suitably, a filter may be provided upstream of the blower.
[0028] Although embodiments and variations of the first aspect of the present disclosure have been discussed above primarily with reference to a single hood module, it should be noted that the rotary kiln is suitably provided with a plurality of hood modules.
[0029] Preferably, but not necessarily, the rotary kiln may include a plurality of hood modules arranged along the length of the kiln at appropriate intervals from each other.
[0030] Preferably, but not necessarily, the rotary kiln may comprise a pair of shroud modules disposed on opposite lateral sides of the inner shell. Suitably, the pair of shroud modules are properly aligned relative to each other along the length of the kiln.
[0031] For example, a combined pair of shroud modules may extend over at least 90°, or even up to 180°, of the cross-sectional peripheral segment of the shroud below the longitudinal centre axis of the inner casing.
[0032] Furthermore, the rotary kiln may comprise a plurality of such shroud module pairs, in which case the shroud module pairs are advantageously arranged along the length of the kiln at suitable spacings from one another.
[0033] It should be noted that, as discussed above, the first aspect of the present disclosure includes any combination of two or more embodiments or variations thereof.
[0034] According to a second aspect of the present disclosure, there is provided a method for replacing a heating element of a rotary kiln according to the first aspect of the present disclosure while operating the rotary kiln properly. That is, the method allows replacement of the heating element without stopping the feeding of the process material through the kiln.
[0035] A first shield module having at least a first heating element is removed from the remaining shield. Subsequently, the at least first heating element is replaced with at least a second heating element. Finally, the first shield module together with the at least second heating element is reattached to the remaining shield. Suitably, the rotary kilns are operated simultaneously.
[0036] Preferably, but not necessarily, after removing the first shield module, a dummy shield module may be attached to the remaining shield so as to cover its opening from which the first shield element was removed. Furthermore, before reattaching the first shield module, the dummy shield module is removed from the remaining shield so as to expose the opening, into which the first shield element may then be reattached. This prevents heat from escaping from the kiln when replacing the heating element of the first shield module.
[0037] According to a third aspect of the present disclosure, there is provided a method for replacing a heating element of a rotary kiln according to the first aspect of the present disclosure while operating the rotary kiln properly. That is, the method allows replacement of the heating element without stopping the feeding of the process material through the kiln.
[0038] A first shroud module having at least a first heating element is detached from the remaining shroud, and a second shroud module having at least a second heating element is attached to the remaining shroud.
[0039] Subsequently, one or more heating elements of the first shield module may be replaced while the second shield module is in place.The second shield module may then be detached from the remaining shield and the first shield module may be reattached to the remaining shield. BRIEF DESCRIPTION OF THE DRAWINGS
[0040] Hereinafter, the present disclosure will be described in more detail by way of preferred embodiments with reference to the accompanying drawings, in which:
[0041] Figure 1 is a schematic cross-sectional representation of a rotary kiln according to an embodiment of the present disclosure, wherein a shroud module is attached to the remaining shroud;
[0042] Figure 2 for Figure 1 A schematic cross-sectional representation of a rotary kiln with the shroud module retracted away from the remaining shroud;
[0043] Figure 3 is a schematic representation of a section of a rotary kiln according to one embodiment of the present disclosure, which is shown as a perspective view;
[0044] Figure 4a is a schematic representation of a shield module; and
[0045] Figure 4b Schematic representation of a pseudo-generation module. DETAILED DESCRIPTION
[0046] Figure 1 A schematic cross-sectional representation of a rotary kiln 1 according to an embodiment of the present disclosure is shown as seen along the length of the kiln 1. A fixed shroud 4 is arranged along the length of the inner shell 2 and around its circumference. Figure 1 The rotary kiln 1 is shown in operation, i.e. the inner shell rotates about its longitudinal axis in the direction of the arrow in the center of the inner shell. Process material 3 is fed into the inner shell 2 and advances through the inner shell 2 while being thermally treated by the heat generated by the heating elements 6. The rotation of the inner shell 2 pushes the process material 3 to the lateral sides of the inner shell 2.
[0047] The rotary kiln 1 comprises a shroud element 5 forming a cross-sectional peripheral section of the shroud 4. Figure 1 Shield element 5 is not visible in the figure, but also forms a longitudinal section of shield 4. Furthermore, shield element 5 extends laterally below the lateral sides of inner housing 2, towards which the rotation of inner housing 2 pushes the process material, and vertically along said lateral sides. Figure 1 In the arrangement of, the internal shape of the shield 4 (including the internal shape of the shield module 5) is consistent with the external shape of the inner shell 2. Figure 1 In the arrangement of , the shield element 5 extends over a 90° circumferential section of the shield 4 .
[0048] The shield element 5 includes a plurality of heating elements 6 along the cross-sectional periphery of the inner shell 2 at a distance from the inner shell 2. Figure 1 Not shown in the drawing, the heating element 6 is suitably operatively coupled to a corresponding socket arranged on the shield element 5. Figure 1 Also not visible in the drawing is that the heating element 6 extends a certain distance along the length of the inner housing 2 .
[0049] Figure 2 Further showing Figure 1 Schematic cross-sectional representation of a rotary kiln shown in , wherein the hood module 5 is retracted away from the remaining hood 4. In particular, the hood module 5 has been retracted away from the remaining hood 4 in the lateral direction. Figure 2 Also shown are rollers 7, on which the shroud module 5 can be supported during retraction. For example, such rollers 7 can be fixed to the shroud module 5, or alternatively, temporarily attached to the shroud module 5 for its removal.
[0050] Figure 3 A schematic representation of a section of a rotary kiln according to one embodiment of the present disclosure is shown as a perspective view. The inner shell 2 of the rotary kiln 1 is housed in a hood 4 in a manner similar to that of the figures discussed above. The rotary kiln 1 comprises a plurality of hood modules 5 arranged longitudinally one after the other, each hood module 5 forming a longitudinal section and a cross-sectional peripheral section of the hood 4. In particular, Figure 3 One of the shield modules 5 is shown being detached from the remaining shield 4 and retracted away from it. The shield module 5 is supported on rollers 7 ( Figure 3 The rollers 7 allow the shield module 5 to be easily pulled out of the remaining shield 4. In addition, the shield module 5 is provided with a flange 8 for positioning and fixing the shield module 5 to the remaining shield 4. For example, the flange may have an opening through which a pin protruding from the remaining shield 4 extends when the shield module 5 is correctly positioned in the appropriate position.
[0051] although Figure 3 The arrangement shows that the shield modules 5 are positioned one after another along the length of the rotary kiln 1, but the shield modules 5 can be spaced apart from each other instead or in addition. In such a case, the remaining shields 4 can advantageously extend into the space between the spaced shield modules 5. In addition, although Figure 3 The arrangement of FIG. 5 shows that the shroud modules 5 are arranged on a single lateral side of the rotary kiln 1, but the shroud modules 5 may be provided on both lateral sides of the rotary kiln 1. In such a case, the shroud modules may be arranged in pairs on laterally opposite sides of the rotary kiln 1.
[0052] It should also be noted that, for the sake of clarity, Figure 3 The heating elements of the hood module 5 are not shown.
[0053] Figure 4a Shown in side view Figure 3 The shield module 5 is arranged in a manner as described above. In particular, the shield module 5 is equipped with a heating element 6. Figure 4bFurthermore, a dummy module 5' is shown, which can be used to cover the opening of the shield element 5 when the disassembled shield element 5 is being repaired. In particular, the dummy module 5' is not equipped with a heating element. Reference numerals list
[0054] 1 Rotary kiln
[0055] 2 Inner shell
[0056] 3 Process Materials
[0057] 4 Shield
[0058] 5 Shield module
[0059] 5' pseudogene module
[0060] 6 Heating element
[0061] 7 Rollers
[0062] 8 Flange
Claims
1. An indirectly heated electric rotary kiln (1), comprising: a longitudinal inner casing (2) configured, in use, for conveying a process material (3) therethrough for undergoing a heat treatment, the inner casing (2) being rotatable about its longitudinal axis, a fixed shield (4), the fixed shield (4) being arranged along the length of the inner shell (2) and around the cross-sectional periphery of the inner shell (2) so as to surround the inner shell (2), The rotary kiln (1) comprises a hood module (5), which is formed as a longitudinal section and a cross-sectional peripheral section of the hood (4), wherein the hood module (5) can be detached from the rest of the hood (4), and The rotary kiln (1) further comprises an electric heating element (6) arranged on the shield module at the inner side of the shield, and the heating element (6) is configured to heat the inner shell when in use.
2. The rotary kiln (1) according to claim 1, characterized in that: The shield module (5) comprises a plurality of heating elements (6), wherein the plurality of heating elements (6) are arranged along the periphery of the cross section of the inner shell (2) at a certain distance from the inner shell (2).
3. The rotary kiln (1) according to claim 2, characterized in that: The shield module (5) comprises a plurality of sockets configured to be detachably operatively coupled to corresponding heating elements (6).
4. The rotary kiln (1) according to claim 2 or 3, characterized in that: The heating element (6) extends a certain distance along the length of the inner shell (2).
5. The rotary kiln (1) according to any one of the preceding claims 1 to 4, characterized in that At least at the position of the shield module (5), the internal shape of the shield (4) is consistent with the external shape of the inner shell (2) at a certain distance from the inner shell (2).
6. The rotary kiln (1) according to any one of the preceding claims 1 to 5, characterized in that The shield module (5) extends laterally along the bottom side of the inner casing (2).
7. The rotary kiln (1) according to any one of the preceding claims 1 to 6, characterized in that The shield module extends vertically along the lateral side of the inner casing (2).
8. The rotary kiln (1) according to claim 7, characterized in that: The shield module (5) extends vertically along the lateral side of the inner housing (2), at least on the side toward which the rotation of the inner housing (2) pushes the process material (3).
9. The rotary kiln (1) according to claim 8, characterized in that: The shield module (5) extends vertically along the lateral side of the inner housing (2) only on the side to which the rotation of the inner housing (2) pushes the process material (3).
10. The rotary kiln according to any one of the preceding claims 1 to 9, characterized in that The shield module (5) extends below the longitudinal center axis of the inner casing over a cross-sectional peripheral section of at least 90° of the shield (4).
11. The rotary kiln (1) according to any one of the preceding claims 1 to 10, characterized in that The shield module (5) is retractable from the remainder of the shield (4) in a lateral direction away from the inner casing (2).
12. The rotary kiln (1) according to any one of the preceding claims 1 to 11, characterized in that The shield module (5) comprises rollers (7) or wheels on which the shield module (5) can be supported for retracting the shield module (5) away from the remainder of the shield (4).
13. The rotary kiln (1) according to any one of the preceding claims 1 to 12, characterized in that It further comprises a plurality of shield modules (5) arranged along the length of the rotary kiln (1) at appropriate intervals from each other.
14. The rotary kiln according to any one of the preceding claims 1 to 13, characterized in that It further comprises a pair of shroud modules (5) disposed on opposite lateral sides of the inner shell (2), the pair of shroud modules being properly aligned relative to each other along the length of the rotary kiln (1).
15. A method for replacing a heating element (6) of a rotary kiln (1) according to any one of the preceding claims 1 to 14, characterized in that The following steps are involved: While operating the rotary kiln (1), - removing a first shield module (5) from the remainder of the shield (4), said first shield module (5) having at least a first heating element (6); - replacing said at least first heating element (6) with at least a second heating element (6), and - Reattaching the first shroud module (5) with the at least second heating element (6) to the remaining part of the shroud (4).
16. The method according to claim 15, characterized in that After removing the first shield module (5) and before reattaching the first shield module (5), the following steps are further included: - attaching a dummy shield module to the remaining part of the shield (4) so as to cover its opening, the first shield element (5) being detached from said opening, and - Disassembling the dummy shield module from the remainder of the shield (4) so as to reveal the opening into which the first shield element (5) can be reattached.
17. A method for replacing a heating element (6) of a rotary kiln (1) according to any one of the preceding claims 1 to 14, comprising the following steps: While operating the rotary kiln (1), - removing the first shroud module (5) having at least the first heating element (6) from the remainder of the shroud (4), and - Attaching a second shroud module (5) having at least a second heating element (6) to the remainder of the shroud (4).