A porous fluidized bed plate for a fluidized bed boiler and a method of manufacturing

Abstract

The application discloses a kind of porous fluidized bed plate of boiling calcination kiln and preparation method, wherein, after mixing and stirring of mullite aggregate, calcium aluminate cement, water reducing agent, join proper amount of water and mix evenly, join high-temperature-resistant fiber to form castable, wherein, the high-temperature-resistant fiber includes any one of silicon carbide whisker, alumina fiber, mullite fiber, aluminum-chromium fiber;The castable is poured into the mold of porous fluidized bed plate and is shaped, after being cured at room temperature naturally, demolding is carried out and is dried, to obtain porous fluidized bed plate. Therefore, the application can effectively improve the normal temperature flexural strength, normal temperature compressive strength, high temperature flexural strength, thermal shock stability and tensile strength and other properties of the porous fluidized bed plate of boiling calcination kiln, so as to be favorable to improving the safety risk resistance and service life of the porous fluidized bed plate of boiling calcination kiln.

Description

Technical Field

[0001] This invention relates to the field of fluidized bed calcining kilns, and in particular to porous fluidized bed plates for fluidized bed calcining kilns. Background Technology

[0002] Internal circulation fluidized bed calcining kilns are key equipment in cement, chemical, and metallurgical industries. The structure and material properties of their core component, the air distribution plate, directly affect the efficiency, reliability, and safety of the production system. This component is composed of multiple sets of fluidized bed plates. Under continuous high-temperature thermal stress, it must possess excellent heat resistance, crack resistance, and mechanical stability. Its performance directly affects the operational stability and service life of the calcining system. Technically, the fluidized bed plate not only needs to ensure the uniform distribution of airflow, material concentration, and reaction atmosphere, but also needs to overcome the structural strength and thermal stability bottlenecks brought about by large-scale production. The current technical challenge lies in constructing a composite bed plate with high crack resistance, ductility, and thermomechanical stability through material system optimization and structural innovation, thereby supporting the efficient and safe operation of a 10,000-ton-level calcining system.

[0003] As a core mass transfer component in an internal circulation fluidized bed calcining kiln, the fluidized bed plate plays a decisive role in the control of fluidization quality and product homogenization within the kiln due to its thermo-mechanical coupling performance. Current research largely focuses on the macroscopic assembly optimization of the bed layer, such as patents CN118376091A and CN120008346A, while neglecting the performance of individual fluidized bed plates at high temperatures (>1350℃) and high temperature differences. The micromechanical response mechanism under the coupling of multiple physical fields leads to high local tensile stress between the holes in the bed plate, resulting in frequent failure problems such as radial through-hole cracks, interface debonding and structural fragmentation in large-scale applications.

[0004] To overcome the bottlenecks in structural strength and thermal stability brought about by large-scale production, current high-temperature mullite refractory substrate boards improve tensile strength by incorporating high-temperature resistant fibers. However, the traditional discrete random distribution or local directional arrangement method has inherent defects. When the temperature exceeds 1000℃, microcracks are generated at the fiber / matrix interface due to the difference in thermal expansion coefficients. In addition, the failure of the high-temperature bonding phase leads to the inability of the fibers to effectively transfer stress. This synergistic deterioration process causes the fiber reinforcement mechanism to completely collapse after the critical temperature. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method for preparing a porous fluidized bed plate for a fluidized bed calcining kiln.

[0006] A method for preparing a porous fluidized bed plate for a fluidized bed calcining kiln according to an embodiment of the present invention, the preparation method comprising: S1. After mixing and stirring the high-temperature resistant fiber, mullite aggregate, calcium aluminate cement and water-reducing agent, add an appropriate amount of water and wet mix evenly to form a castable. The high-temperature resistant fiber includes any one of silicon carbide whiskers, alumina fiber, mullite fiber and aluminum chromium fiber. S2. The castable material is poured into the mold of the porous fluidized bed plate and formed. After natural curing at room temperature, it is demolded and dried to obtain the porous fluidized bed plate.

[0007] Specifically, in the above steps, the mold of the porous fluidized bed plate is first placed on a vibrating table. When the casting material is poured to one-third of the volume of the mold, the vibrating table is started. During the vibration process, material is continuously added until the casting material fills the mold. Then, the cast porous fluidized bed plate is placed in the mold and naturally cured at room temperature for 24 hours before demolding. After demolding, it is placed in the air and naturally cured at room temperature for 24 hours.

[0008] Preferably, the mass fraction of the silicon carbide whiskers is in the range of 0.5% to 2%, the mass fraction of the alumina fiber is 0.5%, and the mass fraction of the aluminum chromium fiber is in the range of 4% to 10%.

[0009] In some embodiments of the present invention, the water-reducing agent is sodium tripolyphosphate and sodium hexametaphosphate, wherein the ratio of sodium tripolyphosphate to sodium hexametaphosphate is 4:3, and the total mass of the water-reducing agent accounts for 0.2% to 0.4% of the mass of water.

[0010] According to a second aspect of the present invention, a porous fluidized bed plate for a fluidized bed calcining kiln is provided, wherein the porous fluidized bed plate is prepared by any of the above-described preparation methods.

[0011] Beneficial effects

[0012] This invention effectively improves the room temperature flexural strength, room temperature compressive strength, high temperature flexural strength, thermal shock stability, and tensile strength of porous fluidized bed plates in fluidized bed calcining kilns by mixing special high temperature resistant fibers with mullite aggregates. This is beneficial to improving the safety risk resistance and service life of porous fluidized bed plates in fluidized bed calcining kilns.

[0013] High-temperature resistant fibers can form bridging at the periphery of porous structures, releasing some thermal stress through a moderate microcrack network. At the same time, they can delay the further opening of microcracks and prevent crack connection, thereby improving flexural and compressive strength and avoiding the risk of through cracks caused by stress concentration between pores. Detailed Implementation

[0014] The embodiments of the present invention are described in detail below.

[0015] Example 1

[0016] This embodiment verifies the influence of high-temperature resistant fibers on the key high-temperature properties of the mullite system, as shown in Table 1. Table 1. Key High-Temperature Properties of the Mullite System Incorporating High-Temperature Resistant Fibers ; As shown in Table 1 above, the high-temperature flexural strength of the mullite system doped with high-temperature resistant fibers increased to varying degrees. With the increase of SiC whisker and aluminum chromium fiber content, the high-temperature flexural strength increased significantly. Among them, the thermal shock retention rate of the SiC whisker mullite system decreased, and the decrease was greater with the increase of doping content. The high-temperature flexural strength and thermal shock retention rate of the mullite system doped with mullite fiber and alumina fiber were significantly improved. The high-temperature flexural strength and thermal shock retention rate of the mullite system doped with aluminum chromium fiber were significantly improved.

[0017] Example 2

[0018] In this embodiment, the effect of SiC whiskers on the high-temperature flexural strength of corundum-spinel and mullite refractory materials is verified, as shown in Table 2. Table 2. High-temperature flexural strength of refractory materials with different SiC whisker contents ; As shown in Table 2, compared to the corundum-spinel system, the incorporation of SiC whiskers is equivalent to introducing foreign impurities. Even at low doping levels, it has a significant negative impact on the high-temperature flexural strength of the system, and this negative impact gradually intensifies with increasing doping levels. Therefore, sample No. 1, with no or low SiC whisker doping, exhibits the best high-temperature flexural strength.

[0019] Furthermore, the longer the sample was exposed to air, the more significant the decrease in its high-temperature flexural strength. This phenomenon confirms that SiC whiskers gradually oxidize with prolonged exposure. In the mullite system, the high-temperature flexural strength of the sample doped with SiC whiskers was essentially equivalent to that of the sample without SiC whiskers, and changes in the SiC whisker doping amount had no significant effect on the high-temperature flexural strength of the system. This indicates that SiC whiskers are more suitable for the mullite system.

[0020] Example 3

[0021] This embodiment verifies the effect of high-temperature resistant fibers on the tensile properties of the mullite system, as shown in Table 3; Table 3 Tensile properties of the high-temperature resistant fiber-infused mullite system ; As shown in Table 3, the tensile modulus of elasticity and peak tensile stress increased after incorporating SiC whiskers and alumina fibers, but the increase was small; the tensile modulus of elasticity and peak tensile stress decreased after incorporating mullite fibers and alumina-chromium fibers; and the peak tensile strain increased slightly after incorporating mullite fibers, alumina fibers, and alumina-chromium fibers.

[0022] Example 4

[0023] This embodiment verifies the effect of stirring method on the performance of alumina fiber-mullite system, as shown in Table 4.

[0024] The conventional mixing method for high-temperature resistant fibers is as follows: mechanically mix alumina fibers, mullite aggregate, calcium aluminate cement, and water-reducing agent for 2 minutes, mix evenly, then add water and mix for 3 minutes to form the final product.

[0025] The mixing method for alumina fiber is as follows: first, mechanically mix mullite aggregate, calcium aluminate cement and water-reducing agent for 2 minutes, then add water and mix for about 1 minute after mixing evenly, and then slowly and evenly add high-temperature resistant fiber and mix for 2 minutes.

[0026] Table 4. Performance of the alumina fiber-mullite system under different stirring methods ; As shown in Table 4, compared with the stirring method, the room temperature flexural strength, room temperature compressive strength, high temperature flexural strength and thermal shock retention rate of the alumina fiber-mullite system are all higher than those of the conventional stirring method.

[0027] Example 5

[0028] The effect of high-temperature resistant fibers on the conventional properties of the mullite system at room temperature was verified, as shown in Table 5. Table 5. Room temperature conventional properties of the mullite system incorporating high-temperature resistant fibers ; As shown in Table 5, the linear shrinkage rate at 1500℃ of the mullite system decreases when less than 2% of SiC whiskers, mullite fibers, alumina fibers, and aluminum chromium fibers are added. When 3% and 4% aluminum chromium fibers are added, the linear shrinkage rate at 1500℃ increases significantly, approaching 1%. The bulk density of the mullite system does not change much after the addition of high-temperature resistant fibers, and remains at around 2.80. The room temperature flexural strength, room temperature compressive strength, and elastic modulus of the mullite system are significantly improved after the addition of SiC whiskers, and the improvement effect is more significant with the increase of the doping amount. The room temperature flexural strength, room temperature compressive strength, and elastic modulus of the mullite system with 0.5% mullite fiber, alumina fiber, and 2% aluminum chromium fiber doped did not change significantly. When the content of aluminum chromium fiber reached 3% and 4%, the room temperature flexural strength and room temperature compressive strength increased significantly, while the elastic modulus decreased significantly.

[0029] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0030] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a porous fluidized bed plate for a fluidized bed calcining kiln, characterized in that, The preparation method includes the following steps: S1. After mixing mullite aggregate, calcium aluminate cement and water-reducing agent, add an appropriate amount of water for wet mixing, and then uniformly add high-temperature resistant fiber to form a castable. The high-temperature resistant fiber includes silicon carbide whiskers, alumina fibers, mullite fibers or aluminum chromium fibers. S2. The castable material is poured into the mold of the porous fluidized bed plate and formed. After natural curing at room temperature, it is demolded and dried to obtain the porous fluidized bed plate.

2. The method for preparing a porous fluidized bed plate for a fluidized bed calcining kiln according to claim 1, characterized in that, Step S2 includes: S21. Place the mold of the porous fluidized bed plate on the vibration table. When the casting material is poured to one-third of the volume of the mold, start the vibration table and continuously add material during the vibration until the casting material fills the mold. S22. After placing the cast porous fluidized bed plate in a mold and curing it naturally at room temperature for 24 hours, demold it and then place it in the air to cure it naturally at room temperature for 24 hours.

3. The method for preparing a porous fluidized bed plate for a fluidized bed calcining kiln according to claim 1 or 2, characterized in that, The mass fraction of the silicon carbide whiskers is in the range of 0.5% to 2%.

4. The method for preparing a porous fluidized bed plate for a fluidized bed calcining kiln according to claim 1, characterized in that, The mass fraction of alumina fiber and mullite aggregate is 0.5%.

5. The method for preparing a porous fluidized bed plate for a fluidized bed calcining kiln according to claim 1, characterized in that, The mass fraction of the aluminum chromium fiber is in the range of 4% to 10%.

6. The method for preparing a porous fluidized bed plate for a fluidized bed calcining kiln according to claim 5, characterized in that, The aluminum-chromium fiber content is 10% by mass.

7. The method for preparing a porous fluidized bed plate for a fluidized bed calcining kiln according to claim 1, characterized in that, The water-reducing agent is sodium tripolyphosphate and sodium hexametaphosphate, and the mass of the water-reducing agent accounts for 0.2% to 0.4% of the mass of water.

8. A porous fluidized bed plate for a fluidized bed calcining kiln, characterized in that, The porous fluidized bed plate is prepared by the method for preparing a porous fluidized bed plate for a fluidized bed calcining kiln as described in any one of claims 1 to 7.