Energy-saving composite refractory lining system for high-temperature rotary kiln and high-temperature rotary kiln

Abstract

The application relates to an energy-saving type composite refractory lining system for a high-temperature rotary kiln and the high-temperature rotary kiln, which comprises a hot face layer, at least one transition backing layer and at least one heat insulation backing layer arranged in sequence from inside to outside along the radial direction of a furnace chamber, the hot face layer, the transition backing layer and the heat insulation backing layer constitute a stepwise thermal conductivity coefficient distribution adapted to the operation condition of 1000 DEG C to 1150 DEG C, so as to suppress local hot spots of the hot face and reduce the heat transfer to the furnace shell direction. The high-temperature rotary kiln comprises the energy-saving type composite refractory lining system. The application can solve the problems of the existing rotary nitriding furnace for lime nitrogen / cyanamide calcium production, such as large heat dissipation of the furnace shell, unstable heat field in the kiln, easy entry of materials into the sintering and bonding window, obvious tendency of skin and ring formation and relatively high unit energy consumption.

Description

Technical Field

[0001] This application relates to the technical field of industrial kilns, specifically to an energy-saving composite refractory lining system for high-temperature rotary kilns and a high-temperature rotary kiln, particularly suitable for high-temperature thermal management and energy-saving lining structure of rotary nitriding furnaces used in the production of calcium cyanamide or calcium cyanamide. Background Technology

[0002] Calcium cyanamide, or calcium cyanamide, is a crucial basic product in the nitrogen, carbon, and nitrogen (NCN) industry chain. Its production process typically requires continuous material heating, nitriding reaction, and curing under high-temperature conditions using a rotary nitriding furnace. These units generally operate at temperatures between 1000℃ and 1150℃ for extended periods, with high heat loads. Therefore, their thermal efficiency and furnace lining stability directly affect unit energy consumption, product quality, and equipment maintenance cycles.

[0003] In the current lime cyanide industry, high-temperature rotary nitriding furnaces mostly use traditional refractory linings formed by clay bricks, high-alumina bricks, aluminosilicate castables, or combinations thereof. The main design logic of this type of lining focuses on high temperature resistance and structural integrity, but it lacks specificity in heat flow distribution, furnace shell heat dissipation control, and uniform temperature of the hot surface layer. Due to the long rotary kiln shell, uneven heating, and complex heat loss paths, problems such as obvious hot spots on the outer wall of the furnace shell, excessive heat dissipation from the shell, and localized hot spots inducing crusting and ring formation are common in actual operation.

[0004] Furthermore, calcium-containing, carbon-containing, and mesophase materials in the calcium cyanamide production system are prone to softening, semi-molten adhesion, and sintering agglomeration within a specific temperature range. This unfavorable temperature range is generally regarded in the industry as the sintering "bonding window." If there are localized overheated areas on the hot surface of the kiln, or if the heat conduction path of the furnace lining is not designed properly, the material can easily enter the aforementioned bonding window, leading to phenomena such as wall adhesion, ring formation, agglomeration, and unstable material turnover. This results in a reduction of the effective reaction space, increased kiln condition fluctuations, and even forced shutdown.

[0005] On the other hand, lining solutions that solely pursue high thermal insulation performance also have drawbacks. If the thermal conductivity of the hot surface layer is insufficient, heat cannot be quickly balanced on the working surface, and local temperature peaks may further increase, which is actually detrimental to preventing adhesion. Conversely, if all materials are made of highly thermally conductive and dense materials, although the temperature uniformity of the hot surface layer is improved, more heat will be transferred to the outer shell, leading to increased heat dissipation from the furnace shell and higher energy consumption. Therefore, how to establish a controllable balance between hot surface uniformity and furnace shell insulation has always been a key challenge in the design of lime-nitrogen high-temperature rotary kiln linings.

[0006] Furthermore, traditional aluminum-silicon based materials have numerous pores on their thermal surface layer. Under the combined effects of dust erosion and chemical atmospheres, powder can easily embed itself into the surface micropores, forming a mechanical bond. This bond can then develop into a more severe adhesion layer under subsequent high temperatures. If thermal shock, wear, and corrosion are added to the mix, the surface roughness of the lining will be exacerbated, further shortening the lining's lifespan and increasing heat loss.

[0007] Therefore, the existing technology lacks an energy-saving composite refractory lining system that can both smooth out local hot spots on the hot surface layer and prevent materials from sintering and bonding windows, effectively block the ineffective transfer of heat to the furnace shell, and at the same time have the ability to resist wear, thermal shock, penetration and adhesion. Summary of the Invention

[0008] To address the problems existing in the prior art, this application aims to provide an energy-saving composite refractory lining system for high-temperature rotary kilns, and secondly, to provide a high-temperature rotary kiln. This application can solve the problems of high heat dissipation from the furnace shell, unstable thermal field inside the kiln, easy entry of materials into the sintering bonding window, obvious tendency for crusting and ring formation, and high unit energy consumption in existing rotary nitriding furnaces used for calcium cyanamide / calcium cyanide production.

[0009] This application describes an energy-saving composite refractory lining system for a high-temperature rotary kiln. The energy-saving composite refractory lining system includes a hot surface layer, at least one transition back lining layer, and at least one heat-insulating back lining layer arranged sequentially from the inside to the outside along the radial direction of the furnace. The hot surface layer, transition back lining layer, and heat-insulating back lining layer form a stepped thermal conductivity distribution adapted to operating conditions from 1000℃ to 1150℃, so as to smooth out local hot spots on the hot surface and reduce the transfer of heat to the furnace shell.

[0010] Preferably, the hot surface layer comprises any one or a combination of at least two of the following: silicon carbide-based anti-scabbing castable, silicon carbide-based wear-resistant castable, nitride-bonded silicon carbide shaped product, rebonded silicon carbide product, and silicon carbide-containing composite refractory material. The thickness of the heating surface layer is 30 mm to 150 mm, and the working thermal conductivity of the heating surface layer is 4.0 W / m·K to 25.0 W / m·K.

[0011] Preferably, the transition backing layer comprises any one or a combination of at least two of the following: high-alumina low-cement castable, mullite castable, spinel composite castable, high-alumina lightweight castable, and ceramic-bonded lightweight refractory layer. The thickness of the transition backing layer is 20 mm to 120 mm, and the thermal conductivity of the transition backing layer is 1.0 W / m·K to 5.0 W / m·K.

[0012] Preferably, the thermal insulation backing layer comprises any one or a combination of at least two of the following: lightweight thermal insulation castable, microporous thermal insulation material, lightweight high-alumina brick, composite structure of aluminum silicate fiber module and rigid backing, lightweight precast block, and thermal insulation board. The thickness of the thermal insulation backing layer is 40 mm to 260 mm, and the thermal conductivity of the thermal insulation backing layer is 0.15 W / m·K to 1.5 W / m·K.

[0013] Preferably, the working surface of the hot surface layer is covered with a barrier coating, which is any one of a zirconia-rich sealing coating, a zirconia-alumina composite sealing layer, a low-silica or free silica coating, or a densified anti-permeability coating; the thickness of the barrier coating is 0.5 mm to 8 mm.

[0014] Preferably, a rough interface, a mechanical interlocking interface, an expansion joint, a flexible transition pad, or an interface treatment slurry are provided between the thermal surface layer and the transition backing layer, and between the transition backing layer and the thermal insulation backing layer.

[0015] Preferably, the energy-saving composite refractory lining system is optimized through one or more methods, including thermal simulation, finite element temperature field analysis, infrared thermography, heat flow calculation, and industrial trial operation data.

[0016] This application discloses a high-temperature rotary kiln, which includes an energy-saving composite refractory lining system as described above, and the high-temperature rotary kiln is used to produce calcium cyanamide or calcium cyanamide.

[0017] The energy-saving composite refractory lining system and high-temperature rotary kiln described in this application have the following advantages: 1. By constructing a multi-layer composite lining and a stepped thermal conductivity distribution, heat dissipation from the furnace shell can be significantly reduced, and the retention of heat in the effective reaction zone can be improved.

[0018] 2. By setting a hot surface layer with high thermal conductivity, local hot spots can be effectively suppressed, and the temperature uniformity of the rotary kiln in the circumferential and axial directions can be improved, thereby reducing the risk of materials entering the sintering bonding window in local areas.

[0019] 3. By setting a barrier coating on the surface of the hot surface layer, the open pores and mechanical interlocking can be reduced, dust adhesion and chemical penetration can be reduced, thereby alleviating the phenomenon of skin adhesion.

[0020] 4. By coordinating the design of layer thickness, material thermal conductivity and construction interface, multiple objectives such as wear resistance, thermal shock resistance, heat insulation and anti-adhesion can be taken into account, thereby improving the operational stability and service life of the lining.

[0021] 5. Under partial thermal simulation and industrial trial operation conditions, compared with traditional clay or ordinary aluminum-silicon single linings, the present invention can show a more obvious trend of reduced wall heat loss and improved unit energy consumption. Attached Figure Description

[0022] Figure 1 This is a cross-sectional schematic diagram of the basic layered structure of the energy-saving composite refractory lining system of this application; Figure 2 This is a schematic diagram of the radial structure of the energy-saving composite refractory lining system of this application in a rotary nitriding furnace; Figure 3 This is a schematic diagram of the tiered thermal conductivity distribution of each layer in the energy-saving composite refractory lining system of this application; Figure 4 This is a schematic diagram comparing the energy-saving composite refractory lining system of this application with a comparative example using infrared thermal imaging. Figure 5 This is a schematic diagram comparing the energy-saving composite refractory lining system of this application with a comparative example in terms of wall heat loss and unit energy consumption.

[0023] Explanation of reference numerals in the attached drawings: 1-Hot surface layer, 2-Transition backing layer, 3-Insulating backing layer, 4-Barrier coating one, 5-Furnace shell, 6-Barrier coating two, A-Kiln chamber. Detailed Implementation

[0024] like Figures 1-2 As shown, the energy-saving composite refractory lining system for high-temperature rotary kilns described in this application includes a hot surface layer 1, at least one transition back lining layer 2, and at least one heat-insulating back lining layer 3 arranged sequentially from the inside to the outside along the radial direction of the furnace. The hot surface layer 1, the transition back lining layer 2, and the heat-insulating back lining layer 3 form a stepped thermal conductivity distribution adapted to operating conditions of 1000℃ to 1150℃, so as to smooth out local hot spots on the hot surface and reduce the transfer of heat to the furnace shell 5.

[0025] The hot surface layer 1 is made of a refractory material with high thermal conductivity, wear resistance, thermal shock resistance, and good anti-scaling properties. Preferably, it is a silicon carbide-based refractory castable, a nitride-bonded silicon carbide shaped product, a rebonded silicon carbide product, a composite refractory material containing silicon carbide particles and / or fine powder, or any combination thereof. The main function of the hot surface layer 1 is to rapidly disperse localized heat, smooth out circumferential and axial hot spots, and resist material rolling erosion and dust abrasion.

[0026] The thickness of the hot surface layer 1 is 30 mm to 150 mm, preferably 50 mm to 120 mm, and the working thermal conductivity of the hot surface layer 1 is 4.0 W / m·K to 25.0 W / m·K.

[0027] The transition backing layer 2 is disposed outside the hot surface layer 1 and is used to form a thermal buffer and a mechanical buffer between the high thermal conductivity hot surface layer 1 and the low thermal conductivity insulation layer. Its material can be selected from high alumina low cement castable, mullite castable, spinel composite castable, high alumina lightweight castable, ceramic bonded lightweight refractory layer, or any combination thereof.

[0028] The thickness of the transition backing layer 2 is 20 mm to 120 mm, and the thermal conductivity of the transition backing layer 2 is 1.0 W / m·K to 5.0 W / m·K.

[0029] The thermal insulation backing layer 3 is disposed outside the transition backing layer 2 to reduce heat transfer to the steel furnace shell 5. This layer can be made of lightweight thermal insulation castable, microporous thermal insulation material, lightweight high-alumina brick, composite structure of aluminum silicate fiber modules and rigid backing, lightweight precast blocks, thermal insulation panels, or any combination thereof. By selecting different layer thicknesses, bulk densities, apparent porosity, thermal conductivity, and construction interface conditions, a stepped distribution of thermal conductivity that gradually decreases from the hot surface to the furnace shell 5 can be achieved.

[0030] The thickness of the thermal insulation backing layer 3 is 40 mm to 260 mm, and the thermal conductivity of the thermal insulation backing layer 3 is 0.15 W / m·K to 1.5 W / m·K.

[0031] In an optional embodiment, the working surface of the hot surface layer 1, i.e., the inner surface, is further provided with a barrier coating. Figure 1 , Figure 2 The barrier coating shown is 4. The barrier coating is preferably any one of the following: a zirconia-rich sealing coating, a zirconia-alumina composite sealing layer, a low-silica or free-silica-free coating, or a densified anti-permeation coating. This barrier coating is used to seal the open pores of the hot surface layer 1, reduce dust mechanical locking, weaken chemical penetration, and improve the anti-adhesion ability of the hot surface layer 1.

[0032] The thickness of the barrier coating is 0.5 mm to 8 mm, preferably 1 mm to 5 mm.

[0033] In other alternative embodiments, a barrier coating 6 may be applied to the exterior of the furnace shell 5 to further improve the heat insulation effect of the kiln.

[0034] The lining system in this embodiment can be optimized by one or more of the following methods: thermal simulation, finite element temperature field analysis, infrared thermography measurement, furnace shell surface temperature monitoring, heat flow calculation, and industrial trial operation data. This reduces the temperature fluctuation of the working surface inside the kiln and keeps the process materials outside the sintering bonding window as much as possible.

[0035] The structure and technical effects of the energy-saving composite refractory lining system of this application will be described in detail below with reference to specific embodiments.

[0036] In this embodiment, the "tiered thermal conductivity distribution" refers to the distribution along the radial direction of the furnace, such as... Figure 3 As shown, the thermal conductivity and / or equivalent thermal conductivity of each layer of material gradually change from the hot surface to the furnace shell 5, in order to achieve a synergistic balance between the uniform temperature of the hot surface and the thermal insulation of the shell. The "sintering bonding window" refers to the unfavorable thermal range in which process materials are more prone to softening, adhesion, agglomeration, or ring formation within a certain temperature range.

[0037] Experimental Example 1: Basic Multi-layer Composite Liner This embodiment is used for a rotary nitriding furnace for calcium cyanamide production, with a designed operating temperature of 1000℃ to 1150℃. The lining structure, from the inside out, consists of a hot surface layer 1, a transition back lining layer 2, and an insulating back lining layer 3. The hot surface layer 1 uses silicon carbide-based anti-scaling castable with a thickness of 60mm to 90mm; the transition back lining layer 2 uses high-alumina, low-cement castable with a thickness of 30mm to 100mm; and the insulating back lining layer 3 uses lightweight insulating castable and / or lightweight precast blocks with a thickness of 50mm to 220mm.

[0038] The room temperature bulk density of the heated surface layer 1 can be 2.2 g / cm³. 3 Up to 2.9 g / cm 3 The thermal conductivity of the first layer is typically between 4.0 W / m·K and 25.0 W / m·K; the thermal conductivity of the second layer is typically between 1.0 W / m·K and 5.0 W / m·K; and the thermal conductivity of the third layer is typically between 0.15 W / m·K and 1.5 W / m·K. By combining these parameters, a thermal structure is formed that gradually transitions from the high thermal conductivity surface layer 1 to the low thermal conductivity backing layer.

[0039] During construction, it is preferable to first install anchors or metal connecting components on the inner side of the furnace shell 5, then construct the transition backing layer 2 and the heat insulation backing layer 3 in layers, and finally pour or build the hot surface layer 1. Each layer can be connected using one or more of the following methods: rough interface, mechanical interlocking interface, reserved expansion joint, flexible transition pad, or interface treatment grout, to improve overall stability and reduce thermal stress concentration.

[0040] After this embodiment was run, it was observed that the hot spot distribution on the surface of the furnace shell 5 was more dispersed than that of the traditional aluminum-silicon lining, the tendency of local scaling was reduced, and the fluctuation of furnace conditions was reduced.

[0041] Experimental Example 2: Zirconium-rich sealing reinforcement scheme Based on Example 1, a barrier coating 4 is added to the working surface (inner surface) of the hot surface layer 1. The thickness of the barrier coating 4 can be from 0.5 mm to 8 mm, preferably from 1 mm to 5 mm; its composition may include 20 parts by weight to 90 parts by weight of zirconium oxide component, 5 parts by weight to 60 parts by weight of alumina or other refractory fine powder component, and 0.5 parts by weight to 20 parts by weight of inorganic binder and functional additives.

[0042] The barrier coating 4 can be formed by brushing, spraying, troweling, scorching, or pre-coating followed by on-site sintering. After heating, this layer forms a relatively tight sealing layer on the surface of the hot surface layer 1, which can reduce the open pore connectivity, weaken dust embedding and chemical penetration, thereby delaying surface roughening and skinning initiation.

[0043] For working conditions where dust is fine, easily adheres, or is prone to chemical corrosion, this implementation method can further improve the anti-adhesion and anti-corrosion properties of the hot surface layer 1.

[0044] Experimental Example 3: Optimal Solution Calculated Through Thermal Simulation This embodiment corresponds to the preferred scheme obtained through joint optimization by thermal simulation, infrared thermography, and industrial trial operation. The hot surface layer 1 is made of nitride-bonded silicon carbide shaped product or rebonded silicon carbide product, with a preferred thickness of 60mm to 100mm; the transition backing layer 2 has a preferred thickness of 40mm to 80mm; and the heat insulation backing layer 3 has a preferred thickness of 80mm to 160mm. The barrier coating is preferably disposed on the working surface of the hot surface layer 1, with a thickness of 1mm to 3mm.

[0045] During the design phase, a radial heat transfer model of the furnace lining was established using the finite element method. The thermal conductivity, specific heat, thickness, and boundary conditions of different layers of materials were input, and the surface temperature of the hot surface, the interlayer heat flux density, and the outer surface temperature of the furnace shell 5 were fitted and analyzed. Then, the temperature field of the outer wall of the furnace shell 5 was checked by infrared thermography, and finally, a material combination that takes into account both the uniformity of the hot surface and the cooling of the outer wall was selected.

[0046] For example, this embodiment further illustrates the specific steps of establishing a radial heat transfer model of the furnace lining and optimizing its parameters using the finite element method.

[0047] Step 1: Establish a geometric model. Based on the inner diameter, outer diameter of the furnace shell, total lining thickness, and preset thickness of each layer of the target high-temperature rotary kiln, establish a two-dimensional axisymmetric radial section model or a three-dimensional local annular segment model. The two-dimensional axisymmetric model is used to quickly select layer thicknesses and material combinations, while the three-dimensional local annular segment model is used to verify temperature disturbances caused by anchors, joints, or local interfaces. The model should include at least the kiln chamber A, hot surface layer 1, transition back lining layer 2, heat insulation back lining layer 3, furnace shell 5, and optional barrier coating 1 4 and barrier coating 2 6.

[0048] Step 2: Determine material parameters. Input the thermal conductivity, density, specific heat, emissivity, and allowable operating temperature for the hot surface layer 1, transition backing layer 2, insulation backing layer 3, furnace shell 5, and barrier coating, respectively. For materials whose thermal conductivity changes significantly with temperature, a piecewise temperature correlation function is preferred; if a complete curve is lacking, at least the thermal conductivity at room temperature, 600℃, 900℃, and 1100℃ can be input for interpolation calculations.

[0049] Step 3: Set boundary conditions. Set the thermal boundary on the kiln side to a constant temperature boundary, equivalent convection boundary, or radiation-convection coupled boundary within the operating range of 1000℃ to 1150℃; set the outer surface of the furnace shell to a natural air convection or forced convection boundary, and superimpose a surface radiation boundary. The ambient temperature can be set according to the average ambient temperature on site or within the range of 25℃ to 45℃; the external convective heat transfer coefficient can be determined based on natural ventilation or on-site wind speed and a sensitivity analysis should be performed.

[0050] Step 4: Set interface conditions. The interfaces between the thermal surface layer 1 and the transition backing layer 2, and between the transition backing layer 2 and the thermal insulation backing layer 3, can be set as fully contact interfaces, or the contact thermal resistance can be set according to the construction structure. For schemes with rough interfaces, mechanical interlocking interfaces, expansion joints, flexible transition pads, or interface treatment slurries, input the equivalent interface thermal resistance or equivalent thin-layer parameters respectively to evaluate the influence of the interface structure on the temperature gradient and thermal stress.

[0051] Step 5: Mesh Generation. A locally denser mesh is applied to the hot surface layer 1, the barrier coating, and the interlayer interface area, while a relatively coarser mesh is applied to the thermal insulation backing layer 3 and the furnace shell 5. The changes in the outer surface temperature of the furnace shell 5, the working surface temperature of the hot surface layer 1, and the interlayer heat flux density are compared using at least two sets of calculation results with different mesh densities. If the differences in key results are less than the preset error range, the mesh independence is considered to meet the requirements.

[0052] Step Six: Solve the steady-state temperature field. Under steady-state conditions, solve for the temperature distribution, heat flux density, surface temperature of furnace shell 5, and interface temperatures of each layer along the radial direction. The highest temperature, lowest temperature, and temperature difference of the working surface of the hot surface layer 1 are used as indicators of the uniformity of the hot surface, and the average surface temperature and surface heat flux density of furnace shell 5 are used as indicators of heat dissipation of the outer shell.

[0053] Step 7: Perform parameter scanning. Using the thickness and thermal conductivity of the hot surface layer 1, transition backing layer 2, and insulation backing layer 3 as variables, perform combination scanning within the scope defined in the claims. For each combination, record the peak temperature of the working surface of the hot surface layer 1, the interlayer temperature, the surface temperature of the furnace shell 5, the heat flux density per unit area, and the hot surface temperature difference, and discard combinations that exceed the allowable operating temperature of the material or the allowable temperature of the furnace shell.

[0054] Step 8: Verification with Infrared Thermography. Infrared thermographic data of the furnace shell 5's exterior surface are collected on the trial run or an existing control kiln to obtain the exterior surface temperature distribution at different axial and circumferential positions. The exterior surface temperature of the furnace shell 5 calculated by the model is compared with the infrared thermographic measurement results. By correcting the surface convective heat transfer coefficient, material thermal conductivity, or interfacial thermal resistance, the simulated temperature field is made to match the measured temperature field within the engineering allowable error range.

[0055] Step 9: Assess the risk of sintering bond window. Compare the simulated working surface temperature distribution of hot surface layer 1 with the sintering bond window of calcium cyanamide or calcium cyanamide production materials, and prioritize the lining layer thickness and material combination that can reduce local overheating areas, reduce the duration of temperature peaks, and allow the material to avoid unfavorable adhesion temperature ranges as much as possible.

[0056] Step 10: Determine the optimal structure. Considering the uniformity of the hot surface, the surface temperature of the furnace shell 5, the heat flux density per unit area, the allowable temperature of each layer, construction feasibility, thermal expansion compatibility, and economy, determine the final thickness and material combination of the hot surface layer 1, the transition backing layer 2, the thermal insulation backing layer 3, and the barrier coating. The above steps can generate design calculation tables, temperature field cloud maps, heat flux density distribution maps, and infrared thermal image verification records, which serve as the basis for parameter determination in the embodiments of this application.

[0057] Based on the aforementioned finite element model and on-site infrared thermography verification, a material combination that balances hot surface uniformity and outer wall cooling can be selected. Under certain simulation and trial operation conditions, compared to traditional clay-based or ordinary aluminosilicate single-lining schemes, this embodiment exhibits a more significant trend of reduced wall heat loss and improved unit energy consumption. Under certain target conditions, the reduction in wall heat loss can reach approximately 30%, and the improvement in unit product energy consumption can reach approximately 10%; however, these results are affected by kiln size, operating procedures, batching composition, and construction quality, and should be understood as exemplary or predictive results, rather than an absolute limitation on all implementation methods.

[0058] Comparative Example The comparative example uses a traditional single alumina-silicon furnace lining structure, without a high thermal conductivity hot surface layer 1, nor a multi-layer tiered thermally conductive back lining structure or barrier coating. It is mainly composed of clay bricks, high-alumina bricks, or ordinary alumina-silicon castables, making it difficult to precisely control the overall heat conduction path, and it has many surface pores.

[0059] like Figure 4 As shown, Figure 4 The left image shows an infrared thermal imaging schematic of a conventional furnace lining, while the right image shows an infrared thermal imaging schematic of Experimental Example 3 of this application.

[0060] Figure 5 This further shows the comparison between the comparative example and Experimental Example 3 in terms of wall heat loss and unit product energy consumption.

[0061] Under similar operating conditions, the comparative model is more likely to experience concentrated hot spots on the furnace shell, localized overheating of the hot surface, increased crusting and wall adhesion, and higher unit energy consumption.

[0062] Comparison data table of the effects of the comparative example and experimental example 3 In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application.

[0063] For those skilled in the art, various other corresponding changes and modifications can be made based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of this application.

Claims

1. An energy-saving composite refractory lining system for high-temperature rotary kilns, characterized in that, The energy-saving composite refractory lining system includes a hot surface layer, at least one transition back lining layer, and at least one heat insulation back lining layer arranged radially from the inside to the outside of the furnace. The hot surface layer, transition back lining layer, and heat insulation back lining layer form a stepped thermal conductivity distribution adapted to operating conditions from 1000℃ to 1150℃, so as to smooth out local hot spots on the hot surface and reduce the transfer of heat to the furnace shell.

2. The energy-saving composite refractory lining system for high-temperature rotary kilns according to claim 1, characterized in that, The hot surface layer includes any one or a combination of at least two of the following: silicon carbide-based anti-scabbing castable, silicon carbide-based wear-resistant castable, nitride-bonded silicon carbide shaped product, rebonded silicon carbide product, and silicon carbide-containing composite refractory material. The thickness of the heating surface layer is 30 mm to 150 mm, and the working thermal conductivity of the heating surface layer is 4.0 W / m·K to 25.0 W / m·K.

3. The energy-saving composite refractory lining system for high-temperature rotary kilns according to claim 1, characterized in that, The transition backing layer includes any one or a combination of at least two of the following: high-alumina low-cement castable, mullite castable, spinel composite castable, high-alumina lightweight castable, and ceramic-bonded lightweight refractory layer. The thickness of the transition backing layer is 20 mm to 120 mm, and the thermal conductivity of the transition backing layer is 1.0 W / m·K to 5.0 W / m·K.

4. The energy-saving composite refractory lining system for high-temperature rotary kilns according to claim 1, characterized in that, The thermal insulation backing layer includes any one or a combination of at least two of the following: lightweight thermal insulation castable, microporous thermal insulation material, lightweight high-alumina brick, composite structure of aluminum silicate fiber module and rigid backing, lightweight precast block, and thermal insulation board. The thickness of the thermal insulation backing layer is 40 mm to 260 mm, and the thermal conductivity of the thermal insulation backing layer is 0.15 W / m·K to 1.5 W / m·K.

5. The energy-saving composite refractory lining system for high-temperature rotary kilns according to claim 1, characterized in that, The working surface of the hot surface layer is covered with a barrier coating, which is any one of the following: a zirconia-rich sealing coating, a zirconia-alumina composite sealing layer, a low-silica or free silica-free coating, or a densified anti-permeability coating; the thickness of the barrier coating is 0.5 mm to 8 mm.

6. The energy-saving composite refractory lining system for high-temperature rotary kilns according to claim 1, characterized in that, A rough interface, a mechanical interlocking interface, an expansion joint, a flexible transition pad, or an interface treatment slurry are provided between the thermal surface layer and the transition backing layer, and between the transition backing layer and the thermal insulation backing layer.

7. The energy-saving composite refractory lining system for high-temperature rotary kilns according to claim 1, characterized in that, The energy-saving composite refractory lining system is optimized through one or more methods, including thermal simulation, finite element temperature field analysis, infrared thermography, heat flow calculation, and industrial trial operation data.

8. A high-temperature rotary kiln, characterized in that, Includes the energy-saving composite refractory lining system as described in any one of claims 1-7, wherein the high-temperature rotary kiln is used to produce calcium cyanamide or calcium cyanamide.

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