Alkali-corrosion-resistant refractory castable for chemical waste liquid incinerator and preparation method of alkali-corrosion-resistant refractory castable

Abstract

The invention belongs to the technical field of refractory materials, and discloses an alkali-corrosion-resistant refractory castable for a chemical waste liquid incinerator and a preparation method thereof.The preparation method comprises the steps that sintered mullite, andalusite and binding clay serve as raw materials, boron-containing material powder, a dispersing agent and a coagulation accelerator are added, the mixture is mixed and then placed in a stirrer to be subjected to dry mixing, a proper amount of water is gradually added in the stirring process, and the mixture is stirred to be uniform; performing wet mixing until the aggregate and the powder are fully mixed, pouring the slurry into a mold on a vibration table, performing mold-carrying natural curing, demolding to obtain a blank, and performing drying and heat treatment on the blank to obtain the alkali-corrosion-resistant refractory castable for the chemical waste liquid furnace. The raw materials are simple, the production efficiency is high, the boron-containing material powder is introduced into the refractory castable, the viscosity of alkali-containing melt is improved by utilizing the special abnormal boron phenomenon when the boron-containing material powder makes contact with alkaline oxide, a compact high-viscosity phase formed on the surface of the refractory at the high temperature hinders erosion and permeation of the alkali melt, the excellent effect of alkali corrosion resistance is achieved, and the service life of the refractory castable is prolonged. And the service life of the lining of the incinerator is prolonged, and wide application prospects are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory materials, and in particular relates to an alkali corrosion resistant refractory castable for a chemical waste liquid incinerator and a preparation method thereof. Background Art

[0002] In my country, the huge chemical and pharmaceutical industries produce a large amount of industrial waste liquid and waste salt. When they are incinerated in high temperature furnaces, they will produce K-rich + 、Na + Molten inorganic salts can corrode and damage refractories used in high-temperature furnace linings. The alumina and mullite contained in commonly used aluminum-silicon refractories are susceptible to corrosion by the alkali ions in the molten salts, forming highly expansive nepheline. This expansion, which occurs on the surface of the refractory, causes minimal damage. However, once the molten salts penetrate the interior of the refractory, the expansion caused by the corrosive reaction can cause cracking in the lining.

[0003] Currently, a common control method involves introducing additives to form a dense layer or highly viscous phase at the interface between the refractory and the molten salt, hindering the penetration of alkaline molten salts. Studies have shown that the addition of SiC or elemental Si to refractory materials blocks surface pores, increasing the material's density while strengthening the interface between the aggregate and the matrix, thereby improving its permeability. However, the resulting SiO2 is highly susceptible to alkali ion attack, and the higher the SiO2 content, the faster the attack rate. Cr2O3 forms a structurally stable solid solution with Al2O3, forming a highly viscous phase at high temperatures that effectively improves the material's corrosion and permeation resistance. However, hexavalent chromium is environmentally hazardous. Other additives, such as ZrB2, BN, β-Sialon, and BaSO4, are also added to form a dense phase to enhance resistance to slag erosion and penetration. BaSO4 is non-wetting. ZrB2 and BN, oxidized by molten salts, fill pores and reduce slag attack. SiO2, formed by oxidized β-Sialon, inhibits the corrosion reaction.

[0004] B2O3 exhibits a boron anomaly phenomenon, which increases the viscosity of the resulting melt when it comes into contact with alkali ion oxides on the refractory surface. This helps improve the castable's resistance to alkali corrosion and penetration by alkali melts. However, excessive B2O3 produces a high-temperature liquid phase, which can negatively impact high-temperature strength. Therefore, how to appropriately incorporate boron-containing materials and leverage their boron anomaly effect to enhance the castable's resistance to alkali corrosion from high-temperature melts is a pressing issue. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides an alkali corrosion resistant refractory castable for a chemical waste liquid incinerator and a preparation method thereof. By adding boron-containing powder to the castable, the unique boron anomaly phenomenon when the boron powder comes into contact with alkaline oxides is utilized to increase the viscosity of the alkali-containing melt, and the high-temperature alkali melt is hindered from penetrating into the interior of the refractory material through adhesion, thereby achieving an alkali corrosion resistance effect.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: an alkali corrosion-resistant refractory castable for a chemical waste liquid incinerator, composed of the following raw materials in parts by weight: 35-50 parts of sintered mullite, 30-50 parts of andalusite, 5-10 parts of binding clay, plus 1.2-3.5wt% of boron-containing powder accounting for the total weight of the raw materials, 0.15wt% of a dispersant accounting for the total weight of the raw materials, and 1.5wt% of a coagulant accounting for the total weight of the raw materials, and the amount of water added accounting for 5.2-6.5wt% of the total weight of the raw materials.

[0007] The main chemical components of the sintered mullite are Al2O3: 60-72wt%, SiO2: 22-37wt%, and the particle size and proportion of the sintered mullite are: 5-3mm accounts for 60%, 3-1mm accounts for 25%, and 1-0.1mm accounts for 15%.

[0008] The main chemical components of the andalusite are Al2O3: 45-59wt%, SiO2: 38-52wt%, and the particle size and proportion of the andalusite are: 1-0mm accounts for 20%, ≤0.074mm accounts for 30%, and ≤0.044mm accounts for 50%.

[0009] The main chemical components of the combined clay are Al2O3: 30-38wt%, SiO2: 50-66wt%, and a particle size of ≤0.044mm.

[0010] The boron-containing powder is boron oxide or a composite of boron oxide and boron carbide, or boron oxide and boric acid; wherein the mass ratio of boron oxide to boron carbide or boric acid in the composite is 1:1-1.5; the purity of boron oxide is ≥99.0% and the particle size is ≤0.088 mm; the purity of boron carbide is ≥90.0% and the particle size is ≤0.044 mm; and the purity of boric acid is ≥99.0% and the particle size is ≤0.088 mm.

[0011] The dispersant is sodium hexametaphosphate, the main chemical component of which is (NaPO3)6, and the purity is ≥99wt%.

[0012] The coagulant is calcium aluminate cement, the main chemical components of which are Al2O3: 59-65wt%, and CaO: 27-35wt%.

[0013] A method for preparing an alkali corrosion-resistant refractory castable for a chemical waste liquid incinerator comprises the following steps: Step 1: Weigh the required sintered mullite, andalusite, and binding clay according to weight, add the weighed boron-containing powder, dispersant, and coagulant, put them into a blender and stir for 1 minute, then add an appropriate amount of water and continue stirring for 3 minutes until the aggregate and powder are fully mixed and have a certain fluidity; Step 2: Take out the evenly stirred slurry, place the steel mold on the table of the vibration table, add the material while vibrating, and vibrate for 2-3 minutes until the surface is covered with slurry, then stop, then remove the steel mold from the vibration table and place it on the ground to cure the blank with the mold; Step 3: After curing at room temperature for 24 hours, demould, take out the green body, and then put it into an oven for drying at 110℃ for 24 hours to remove free water; Step 4: Place the dried green body in a resistance atmosphere heating furnace, heat it to 1050°C at a heating rate of 2°C / min, keep it warm for 3 hours, and obtain the alkali corrosion-resistant refractory castable for chemical waste liquid furnace after cooling.

[0014] The working mechanism of the present invention primarily utilizes the complex effects of B2O3 on silicate melts and the boron anomaly produced when B2O3 melts are exposed to alkali metal oxides such as Na2O. When a small amount of B2O3 is added to a silicate melt, boron is trapped in three-dimensionally connected boron-oxygen tetrahedra [BO4], resulting in a dense network and increased viscosity. When the alkali metal oxides come into contact with an Al2O3-SiO2 refractory material containing B2O3, the oxygen provided by the alkali metal oxides transforms the boron-oxygen trihedra [BO3] into tetrahedra [BO4], causing the B2O3 structure to partially transform from a two-dimensional layered structure to a three-dimensional framework. This strengthens the network connectivity, promotes increased melt viscosity, and enhances alkali corrosion resistance. Leveraging this principle, through material design, B2O3 is directly introduced into refractory castables, or its precursors, such as B4C and H3BO3, are introduced, where their high-temperature decomposition or oxidation produces B2O3, thereby enhancing the alkali corrosion resistance of the refractory castable. Although excessive B2O3 is detrimental to high-temperature strength due to the generation of a high-temperature liquid phase, the amount of B2O3 added to the refractory material can be controlled. Secondly, refractory castables have a temperature gradient from the working surface outward, with the temperature gradually decreasing from the inside to the outside. Therefore, introducing an appropriate amount of B2O3 or B2O3 precursor into the refractory castable will prevent the generation of excessive molten liquid phase at high temperatures. The boron anomaly effect helps improve the castable's resistance to alkaline corrosion by high-temperature melts.

[0015] This invention optimizes the particle size distribution of mullite and andalusite. Given that mullite is susceptible to alkali corrosion in alkaline environments, forming nepheline, andalusite has better alkali corrosion resistance than mullite. The present invention uses andalusite powder instead of mullite powder to prevent the matrix composed of mullite powder from becoming a weak link in the corrosion process. Mullite granules are a sintered, dense material with strong corrosion resistance. By optimizing the particle size distribution range and ratio of mullite and andalusite, the material's alkali corrosion resistance is comprehensively improved.

[0016] The beneficial effects of the present invention are as follows: the raw materials are simple and the production efficiency is high. By introducing boron-containing powder into the refractory castable, the viscosity of the alkali-containing melt is increased by utilizing the unique boron anomaly when it comes into contact with alkaline oxides. The dense and highly viscous phase formed on the surface of the refractory material at high temperature hinders the erosion and penetration of the alkali melt, plays an excellent role in resisting alkali corrosion, and prolongs the service life of the incinerator lining, which has a relatively broad prospect of use. The alkali corrosion-resistant refractory castable prepared by the present invention is cast and formed, dried at 110℃×24h, and heat-treated at 1050℃×3h. The test results show that the volume density is 2.51~2.54g / cm 3 The porosity is 12.5~9.8%, the flexural strength at room temperature is 11.22~17.15MPa, the flexural strength at high temperature is 3.98~5.86MPa, and the alkali corrosion resistance is: the sample is placed in a K2CO3 melt at 950°C and kept in an eroded state for 3 hours. After being taken out, the surface of the sample is intact without any cracks. After cutting and measuring, the penetration depth of the alkali melt into the refractory material is measured to be 0.81-1.12mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional morphology photograph of the sample crucible prepared in Example 3 of the present invention after being eroded by alkaline slag at 950°C for 1 hour; Figure 2 This is a cross-sectional morphology photograph of the sample crucible prepared in Example 3 of the present invention after being eroded by alkaline slag at 950°C for 3 hours. DETAILED DESCRIPTION

[0018] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0019] To avoid repetition, the raw materials involved in this specific embodiment are first described uniformly, and no further details are given in the examples: The main chemical components of the sintered mullite are Al2O3: 60-72wt%, SiO2: 22-37wt%, and the particle sizes are 5-3mm, 3-1mm, and 1-0.1mm respectively.

[0020] The main chemical components of the andalusite are Al2O3: 45-59wt%, SiO2: 38-52wt%, and the particle sizes are 1-0mm, ≤0.074mm, and ≤0.044mm respectively.

[0021] The main chemical components of the combined clay are Al2O3: 30-38wt%, SiO2: 50-66wt%, and a particle size of ≤0.044mm.

[0022] The boron-containing powder is boron oxide or a composite of boron oxide and boron carbide, or boron oxide and boric acid; wherein the mass ratio of boron oxide to boron carbide or boric acid in the composite is 1:1-1.5; the purity of boron oxide is ≥99.0% and the particle size is ≤0.088 mm; the purity of boron carbide is ≥90.0% and the particle size is ≤0.044 mm; and the purity of boric acid is ≥99.0% and the particle size is ≤0.088 mm.

[0023] The dispersant is sodium hexametaphosphate, the main chemical component of which is (NaPO3)6, and the purity is ≥99wt%.

[0024] The coagulant is calcium aluminate cement, the main chemical components of which are Al2O3: 59-65wt%, and CaO: 27-35wt%. Example 1

[0025] An alkali corrosion-resistant refractory castable for a chemical waste liquid incinerator is composed of the following raw materials in parts by weight: 35 parts of sintered mullite, 50 parts of andalusite, 7 parts of binding clay, and additionally 0.5 wt% of boron oxide, 0.7 wt% of boric acid, 0.15 wt% of sodium hexametaphosphate, 1.5 wt% of calcium aluminate cement, and 5.2 wt% of water, based on the total weight of the raw materials.

[0026] The specific steps of preparation are as follows: Step 1: Weigh the above-mentioned parts by weight of sintered mullite, andalusite, and binder clay, add boron oxide, sodium hexametaphosphate, and calcium aluminate cement, put them into a blender and stir for 1 minute, then gradually add water during the stirring process and continue stirring for 3 minutes.

[0027] Step 2: Take out the evenly stirred slurry, place a steel mold with an inner cavity size of 40×40×160mm on the GZ-85 vibration table, add material while vibrating, stop vibrating after 3 minutes, then remove the steel mold from the vibration table and place it on the ground for static curing of the sample.

[0028] Step 3: After oxidation at room temperature for 24 hours, demould, take out the sample, and then place it in an oven for heat treatment at 110°C for 24 hours to remove free water.

[0029] Step 4: Place the dried green body in a resistive atmosphere heating furnace, heat it to 1050°C at a heating rate of 2°C / min, and hold it for 3 hours. After cooling, a sample of the alkali corrosion-resistant refractory castable for chemical waste liquid furnace is obtained.

[0030] The volume density of the sample was found to be 2.51 g / cm 3 The porosity is 12.3%, the room temperature flexural strength is 16.32MPa, and the high temperature flexural strength is 5.12MPa. After alkali etching, the surface of the sample is intact without any cracks. After cutting and measuring, the penetration depth of the alkali melt into the refractory material is measured to be 1.02mm. Example 2

[0031] An alkali corrosion-resistant refractory castable for a chemical waste liquid incinerator is composed of the following raw materials in parts by weight: 50 parts of sintered mullite, 30 parts of andalusite, 10 parts of binding clay, and additionally 2 wt% of boron oxide, 0.15 wt% of sodium hexametaphosphate, 1.5 wt% of calcium aluminate cement, and 6.5 wt% of water, based on the total weight of the raw materials.

[0032] The specific steps of preparation are as follows: Step 1: Weigh the above-mentioned parts by weight of sintered mullite, andalusite, and binder clay, add boron carbide, sodium hexametaphosphate, and calcium aluminate cement, put them into a blender and stir for 1 minute, then gradually add water during the stirring process and continue stirring for 3 minutes.

[0033] Step 2: Take out the evenly stirred slurry, place a steel mold with an inner cavity size of 40×40×160mm on the GZ-85 vibration table, add material while vibrating, stop vibrating after 3 minutes, then remove the steel mold from the vibration table and place it on the ground for static curing of the sample.

[0034] Step 3: After oxidation at room temperature for 24 hours, demould, take out the sample, and then place it in an oven for heat treatment at 110°C for 24 hours to remove free water.

[0035] Step 4: Place the dried green body in a resistive atmosphere heating furnace, heat it to 1050°C at a heating rate of 2°C / min, and hold it for 3 hours. After cooling, a sample of the alkali corrosion-resistant refractory castable for chemical waste liquid furnace is obtained.

[0036] The volume density of the sample was 2.52 g / cm 3 The porosity is 11.5%, the room temperature flexural strength is 14.13MPa, and the high temperature flexural strength is 4.21MPa. After alkali etching, the surface of the sample is intact without any cracks. After cutting and measuring, the penetration depth of the alkali melt into the refractory material is measured to be 0.86mm. Example 3

[0037] An alkali-corrosion-resistant refractory castable for a chemical waste liquid incinerator and a preparation method thereof are composed of the following raw materials in parts by weight: 42 parts of sintered mullite, 40 parts of andalusite, 5 parts of binding clay, and additionally 1.5 wt% of boron oxide, 2 wt% of boron carbide, 0.15 wt% of sodium hexametaphosphate, 1.5 wt% of calcium aluminate cement, and 5.5 wt% of water, based on the total weight of the raw materials.

[0038] The specific steps of preparation are as follows: Step 1: Weigh the above-mentioned parts by weight of sintered mullite, andalusite, and binder clay, add boron oxide, sodium hexametaphosphate, and calcium aluminate cement, put them into a blender and stir for 1 minute, then gradually add water during the stirring process and continue stirring for 3 minutes.

[0039] Step 2: Take out the evenly stirred slurry, place a steel mold with an inner cavity size of 40×40×160mm on the GZ-85 vibration table, add material while vibrating, stop vibrating after 3 minutes, then remove the steel mold from the vibration table and place it on the ground for static curing of the sample.

[0040] Step 3: After oxidation at room temperature for 24 hours, demould, take out the sample, and then place it in an oven for heat treatment at 110°C for 24 hours to remove free water.

[0041] Step 4: Place the dried green body in a resistive atmosphere heating furnace, heat it to 1050°C at a heating rate of 2°C / min, and hold it for 3 hours. After cooling, a sample of the alkali corrosion-resistant refractory castable for chemical waste liquid furnace is obtained.

[0042] The volume density of the sample was 2.52 g / cm 3 The porosity is 10.1%, the room temperature flexural strength is 11.98 MPa, and the high temperature flexural strength is 5.30 MPa. After alkali etching, the surface of the sample is intact without any cracks. After cutting and measuring, the penetration depth of the alkali melt into the refractory material is measured to be 0.93 mm.

[0043] from Figure 1 It can be seen that after 1 hour of alkali etching with K2CO3 melt, the crucible sample did not crack, but there was residue inside, and the penetration depth of the alkali melt was between 0.8mm and 1mm. Figure 2 It can be seen that even when the erosion time is extended to 3 hours, the crucible sample still does not crack, the residue adheres to the inner wall of the crucible, and the melt penetration depth remains between 0.8mm and 1mm, showing no increase. The material demonstrates good resistance to alkali melt penetration.

[0044] The above embodiments are merely examples of the explanation, specific embodiments, and implementation effects of the present invention, and are not intended to limit the present invention. Based on the present disclosure, some modifications or improvements without creative contributions may be made thereto, which will be apparent to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present disclosure are intended to fall within the scope of protection claimed in the present disclosure.

Claims

1. An alkali corrosion resistant refractory castable for a chemical waste liquid incinerator, characterized in that: The invention is composed of the following raw materials in parts by weight: 35-50 parts of sintered mullite, 30-50 parts of andalusite, 5-10 parts of binding clay, 1.2-3.5 wt% of boron-containing powder accounting for the total weight of the raw materials, 0.15 wt% of a dispersant accounting for the total weight of the raw materials, 1.5 wt% of a coagulant accounting for the total weight of the raw materials, and 5.2-6.5 wt% of water added to the total weight of the raw materials.

2. The alkali corrosion resistant refractory castable for a chemical waste liquid incinerator according to claim 1, characterized in that: The main chemical components of sintered mullite are Al2O3: 60~72wt%, SiO2: 22~37wt%; the particle size and proportion of sintered mullite are: 5-3mm accounts for 60%, 3-1mm accounts for 25%, and 1-0.1mm accounts for 15%.

3. The alkali corrosion resistant refractory castable for a chemical waste liquid incinerator according to claim 1, characterized in that: The main chemical components of andalusite are Al2O3: 45~59wt%, SiO2: 38~52wt%; the particle size and proportion of andalusite are: 1-0mm accounts for 20%, ≤0.074mm accounts for 30%, and ≤0.044mm accounts for 50%.

4. The alkali corrosion resistant refractory castable for a chemical waste liquid incinerator according to claim 1, characterized in that: The main chemical components of the bonded clay are Al2O3: 30~38wt%, SiO2: 50~66wt%, and the particle size is ≤0.044mm.

5. The alkali corrosion resistant refractory castable for a chemical waste liquid incinerator according to claim 1, characterized in that: The boron-containing powder is boron oxide or a composite of boron oxide and boron carbide, or boron oxide and boric acid; wherein the mass ratio of boron oxide to boron carbide or boric acid in the composite is 1:1-1.5; the purity of boron oxide is ≥99.0% and the particle size is ≤0.088 mm; the purity of boron carbide is ≥90.0% and the particle size is ≤0.044 mm; and the purity of boric acid is ≥99.0% and the particle size is ≤0.088 mm.

6. The alkali corrosion resistant refractory castable for a chemical waste liquid incinerator according to claim 1, characterized in that: The dispersant is sodium hexametaphosphate, the main chemical component of which is (NaPO3)6, and the purity is ≥99%.

7. The alkali corrosion resistant refractory castable for a chemical waste liquid incinerator according to claim 1, characterized in that: The coagulant is calcium aluminate cement, the main chemical components of which are Al2O3: 59~65wt%, CaO: 27~35wt%.

8. A method for preparing the alkali corrosion resistant refractory castable for a chemical waste liquid incinerator according to claim 1, characterized in that: The following steps are involved: Step 1: Weigh the required sintered mullite, andalusite, and binding clay according to weight, add the weighed boron-containing powder, dispersant, and coagulant, put them into a blender and stir for 1 minute, then add an appropriate amount of water and continue stirring for 3 minutes until the aggregate and powder are fully mixed and have a certain fluidity; Step 2: Take out the evenly stirred slurry, place the steel mold on the table of the vibration table, add the material while vibrating, and vibrate for 2-3 minutes until the surface is covered with slurry, then stop, then remove the steel mold from the vibration table and place it on the ground to cure the blank with the mold; Step 3: After curing at room temperature for 24 hours, demould, take out the green body, and then put it into an oven for drying at 110°C for 24 hours to remove free water; Step 4: Place the dried green body in a resistance atmosphere heating furnace, heat it to 1050°C at a heating rate of 2°C / min, keep it warm for 3 hours, and obtain the alkali corrosion-resistant refractory castable for chemical waste liquid furnace after cooling.

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