A composite chromium corundum brick for a chemical salt-containing wastewater incinerator and its preparation method

Abstract

The present invention relates to a composite chromium corundum brick for a chemical salt-containing wastewater incinerator and a preparation method thereof, and belongs to the field of refractory materials. The composite chromium corundum brick is made of recycled refractory raw material fused chromium corundum with a particle size of ≤3mm, fused white corundum with a particle size of ≤3mm, chromium oxide micropowder with a particle size of ≤8μm, iron-aluminum spinel micropowder with a particle size of ≤31μm, and aluminum oxide micropowder with a particle size of ≤4μm as raw materials, and is pressed into a green body with an external binder and kept warm for 3-5h in a high-temperature furnace at 1500-1600℃ for firing. The present invention adopts recycled refractory raw material chromium corundum solid solution as raw material and utilizes corundum and chromium oxide to generate chromium corundum solid solution in situ during the firing process, introduces iron-aluminum spinel fine powder into chromium corundum to partially replace Cr2O3, and generates multinary solid solution (Al2O3) in situ inside the material. 1‑x‑y Cr x Fe y )2O3, reduce Cr2O3 content, inhibit Cr 6+ The generation of chrome corundum bricks promotes sintering, improves the high-temperature performance of chrome corundum bricks and their resistance to corrosion by sodium sulfate salt slag, increases the service life of chemical salt wastewater incinerators, and realizes the recycling of resources.

Description

Technical Field

[0001] The invention belongs to the field of refractory materials, and in particular relates to a composite chromium corundum brick for a chemical salt-containing wastewater incinerator and a preparation method thereof. Background Art

[0002] Chemical saline wastewater contains large amounts of inorganic salts and complex toxic organic compounds. If improperly handled, it can pose a serious threat to human health and the ecological environment. Incineration treatment, with its advantages of high efficiency, safety, stability, and energy recovery, is playing an increasingly important role in the treatment of chemical saline wastewater worldwide. Incinerators are key equipment for the incineration of chemical saline wastewater, and the service life of their refractory materials is crucial for their long-term safe and stable operation. However, when incinerating chemical saline wastewater, the large amount of alkali metal salts in the wastewater can cause severe erosion of the furnace lining refractory materials. The combined effects of mechanical wear, thermal stress, and chemical corrosion can easily damage the refractory materials. This requires that the refractory materials used in chemical saline wastewater incinerators possess high mechanical strength to withstand the erosion of wastewater, good thermal shock resistance to withstand drastic temperature changes, and excellent corrosion resistance to resist the chemical attack of alkali metal salts at high temperatures. The extremely low solubility of Cr2O3 in various corrosive media gives chrome corundum bricks excellent corrosion resistance. At the same time, chrome corundum bricks have high refractoriness, high mechanical strength and good wear resistance, and are expected to be used as one of the suitable working linings for chemical saline wastewater incinerators. However, under the harsh high temperature environment and alkali metal salt corrosion conditions of chemical saline wastewater incinerators, the performance of chrome corundum bricks still needs to be further improved. Ferroaluminum spinel is widely used in the field of refractory materials for cement kilns due to its excellent structural flexibility, high fracture energy, good resistance to alkaline slag corrosion and outstanding kiln lining performance. The present invention uses recycled refractory raw material chrome corundum solid solution as raw material and utilizes corundum and chromium oxide in situ to generate chrome corundum solid solution during the firing process, and introduces ferroaluminum spinel into chrome corundum bricks to partially replace Cr2O3 powder, generating in situ multinary solid solution (Al2O3) inside the material. 1-x-y Cr x Fe y )2O3, reducing the Cr2O3 content, inhibiting the formation of hexavalent chromium, and promoting sintering. Its high-temperature performance and resistance to corrosion by sodium sulfate-containing salt slag are superior to those of ordinary chrome corundum bricks. This increases the life of the refractory lining of chemical salt wastewater incinerators and enables resource recycling. Summary of the Invention

[0003] The present invention aims to provide a composite chrome corundum brick for a chemical salt wastewater incinerator and a preparation method thereof, which solves the problems of low corrosion resistance, penetration resistance and high-temperature strength of ordinary refractory bricks, and prepares a composite chrome corundum brick with excellent comprehensive properties such as corrosion resistance, penetration resistance and high-temperature strength.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] A composite chrome corundum brick for a chemical saline wastewater incinerator is prepared from the following raw materials in the following mass percentages and an external binder, aluminum dihydrogen phosphate, which accounts for 2-5% of the raw materials; wherein the raw materials include:

[0006] Recycled refractory raw material fused chromium corundum with a particle size of ≤3mm, with a mass percentage of 35-50%;

[0007] Fused white corundum with a particle size of ≤3mm, of which w(Al2O3) ≥99% and mass percentage is 20-45%;

[0008] Chromium oxide micropowder with a particle size of ≤8μm, of which w(Cr2O3)≥99% and mass percentage is 4-12%;

[0009] Ferroaluminum spinel powder with a particle size of ≤31μm: mass percentage is 3-12%;

[0010] Alumina micropowder with a particle size of ≤4μm, of which w(Al2O3) ≥99% and the mass percentage is 1-6%.

[0011] Furthermore, the recycled refractory raw material fused chrome corundum in the composite chrome corundum brick is obtained by treating the aluminum-chrome slag produced by smelting metallic chromium, wherein w(Al2O3) + w(Cr2O3)≥93%, and w(Cr2O3)≥12%.

[0012] Furthermore, the iron-aluminum spinel powder has w(Al2O3)≥55% and w(Fe2O3)≥43%, so as to improve the density, room temperature and high temperature strength and corrosion resistance of chrome corundum bricks;

[0013] A method for preparing composite chrome corundum bricks for a chemical saline wastewater incinerator comprises the following steps:

[0014] 1) Mixing: weigh the raw materials according to the ratio and mix them evenly in a mixer;

[0015] 2) Material trapping: Put the evenly mixed raw material into a sealed bag and trap it for 12-24 hours to make the binder and moisture more evenly distributed, which is more conducive to molding;

[0016] 3) Molding: The trapped material is weighed and loaded into the mold, and then molded using a hydraulic press at 120-180 MPa;

[0017] 4) Drying: After forming, the green body is dried at a temperature of 110-150°C for 24 hours;

[0018] 5) Firing: The dried sample is sintered in a high temperature furnace at 1500~1600℃ for 3-5h.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] Ferroaluminum spinel is widely used in the field of cement kiln refractory materials due to its excellent structural flexibility, high fracture energy, good resistance to alkaline slag corrosion and outstanding kiln lining performance. The present invention uses the recycled refractory raw material chromium corundum solid solution as raw material and utilizes the in-situ generation of chromium corundum solid solution by corundum and chromium oxide during the firing process. The fine powder of ferroaluminum spinel is introduced into the chromium corundum to partially replace Cr2O3, and a multi-component solid solution (Al2O3) is generated in situ inside the material. 1-x-y Cr x Fe y )2O3, reducing the Cr2O3 content, inhibiting the formation of hexavalent chromium, promoting sintering, improving the high-temperature performance of chrome corundum bricks and their resistance to corrosion by sodium sulfate salt slag, increasing the service life of chemical salt wastewater incinerators, and realizing the recycling of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a photograph of a cross-sectional view of a crucible after a sample of the composite chrome corundum brick prepared in Example 1 is corroded by sodium sulfate-containing salt slag;

[0022] Figure 2 This is a photograph of a cross-sectional view of a crucible after a sample of the composite chrome corundum brick prepared in Example 2 was corroded by sodium sulfate-containing salt slag;

[0023] Figure 3 This is a photograph of a cross-sectional view of a crucible after a sample of the composite chrome corundum brick prepared in Example 3 was corroded by sodium sulfate-containing salt slag;

[0024] Figure 4 This is the SEM image of the sample after erosion of the composite chrome corundum brick prepared in the comparative example;

[0025] Figure 5 This is an SEM image of the sample of the composite chrome corundum brick prepared in Example 2 after corrosion;

[0026] Figure 6 The relative content (wt%) of Na element at different depths in the corrosion samples of the comparative example and embodiment 2. DETAILED DESCRIPTION

[0027] The technical solutions and effects of the present invention are further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0028] Comparative Example

[0029] The composite chrome corundum bricks for the chemical salt-containing wastewater incinerator of this embodiment are prepared from the following raw materials in percentage by mass and an external binder, aluminum dihydrogen phosphate, which accounts for 3% of the raw materials; wherein the raw materials include:

[0030] Recycled refractory raw material fused chromium corundum with a particle size of ≤3mm, wherein w(Al2O3) + w(Cr2O3) ≥93%, w(Cr2O3) ≥12%, and the mass percentage is 48%;

[0031] Fused white corundum with a particle size of ≤3mm, of which w(Al2O3) ≥99% and the mass percentage is 39%;

[0032] Chromium oxide micropowder with a particle size of ≤8μm, of which w(Cr2O3)≥99%, with a mass percentage of 9%;

[0033] Alumina micropowder with a particle size of ≤4μm, of which w(Al2O3) ≥99%, the mass percentage is 4%.

[0034] The above raw materials are mixed in the required proportions, mixed evenly in a mixer, and pressed into shape using a hydraulic press at a molding pressure of 150 MPa. After molding and drying, the green body is kept warm in a high-temperature furnace at 1550°C for 4 hours and fired.

[0035] Example 1

[0036] The composite chrome corundum bricks for the chemical salt-containing wastewater incinerator of this embodiment are prepared from the following raw materials in percentage by mass and an external binder, aluminum dihydrogen phosphate, which accounts for 3% of the raw materials; wherein the raw materials include:

[0037] Recycled refractory raw material fused chromium corundum with a particle size of ≤3mm, wherein w(Al2O3) + w(Cr2O3) ≥93%, w(Cr2O3) ≥12%, and the mass percentage is 44%;

[0038] Fused white corundum with a particle size of ≤3mm, of which w(Al2O3) ≥99% and mass percentage is 40%;

[0039] Chromium oxide micropowder with a particle size of ≤8μm, of which w(Cr2O3)≥99% and mass percentage is 11%;

[0040] Ferroaluminum spinel powder with a particle size of ≤31μm: 3% by mass;

[0041] Alumina micropowder with a particle size of ≤4μm, of which w(Al2O3) ≥99% and the mass percentage is 2%.

[0042] The above raw materials are mixed in the required proportions, mixed evenly in a mixer, and pressed into shape using a hydraulic press at a molding pressure of 160 MPa. After molding and drying, the green body is kept warm in a high-temperature furnace at 1600°C for 3 hours and fired.

[0043] Example 2

[0044] The composite chrome corundum bricks for the chemical salt-containing wastewater incinerator of this embodiment are prepared from the following raw materials in percentage by mass and an external binder, aluminum dihydrogen phosphate, which accounts for 3% of the raw materials; wherein the raw materials include:

[0045] Recycled refractory raw material fused chromium corundum with a particle size of ≤3mm, wherein w(Al2O3) + w(Cr2O3) ≥93%, w(Cr2O3) ≥12%, and the mass percentage is 42%;

[0046] Fused white corundum with a particle size of ≤3mm, of which w(Al2O3) ≥99% and the mass percentage is 39%;

[0047] Chromium oxide micropowder with a particle size of ≤8μm, of which w(Cr2O3)≥99%, with a mass percentage of 9%;

[0048] Ferroaluminum spinel powder with a particle size of ≤31μm: mass percentage is 6%;

[0049] Alumina micropowder with a particle size of ≤4μm, of which w(Al2O3) ≥99%, the mass percentage is 4%.

[0050] The above raw materials are mixed in the required proportions, mixed evenly in a mixer, and pressed into shape using a hydraulic press at a molding pressure of 150 MPa. After molding and drying, the green body is kept warm in a high-temperature furnace at 1550°C for 4 hours and fired.

[0051] Example 3

[0052] The composite chrome corundum bricks for the chemical salt-containing wastewater incinerator of this embodiment are prepared from the following raw materials in percentage by mass and an external binder, aluminum dihydrogen phosphate, which accounts for 3% of the raw materials; wherein the raw materials include:

[0053] Recycled refractory raw material fused chromium corundum with a particle size of ≤3mm, wherein w(Al2O3) + w(Cr2O3) ≥93%, w(Cr2O3) ≥12%, and the mass percentage is 40%;

[0054] Fused white corundum with a particle size of ≤3mm, of which w(Al2O3) ≥99% and mass percentage is 42%;

[0055] Chromium oxide micropowder with a particle size of ≤8μm, of which w(Cr2O3)≥99% and mass percentage is 5%;

[0056] Ferroaluminum spinel powder with a particle size of ≤31μm: mass percentage is 10%;

[0057] Alumina micropowder with a particle size of ≤4μm, of which w(Al2O3) ≥99% and the mass percentage is 3%.

[0058] The above raw materials are mixed in the required proportions, mixed evenly in a mixer, and pressed into shape using a hydraulic press at a molding pressure of 150 MPa. After molding and drying, the green body is kept warm in a high-temperature furnace at 1550°C for 4 hours and fired.

[0059] The physical and chemical indicators of the composite chrome corundum bricks prepared in Examples 1 to 3 are shown in Table 1.

[0060] Table 1 Physical and chemical indicators of composite chrome corundum bricks prepared in Examples 1 to 3

[0061]

[0062] As shown in Table 1, the composite chrome corundum bricks of Examples 1, 2 and 3 have low porosity, high bulk density, high flexural strength and compressive strength at room temperature, and excellent high-temperature flexural strength at 1300°C.

[0063] Depend on Figure 1-3 It can be seen that the materials of Examples 1, 2 and 3 were subjected to corrosion experiments using a static crucible method with sodium sulfate-containing salt slag at 1200° C. for 12 hours. After corrosion, the crucible outlines were clear and complete, with no obvious corrosion phenomenon.

[0064] Depend on Figure 4 and 5 It can be seen that both the sample without FeAl2O4 and the sample from Example 2 consist of two parts: the erosion and penetration layer (CPL) and the original brick layer (UL). The erosion and penetration layer becomes denser due to the erosion and penetration of the original slag (Na2SO4), and the original brick layer has a relatively high porosity. With the addition of FeAl2O4, the depth of the erosion and penetration layer of the sample decreases from 5.4mm to 2.4mm. This shows excellent resistance to corrosion by sodium sulfate-containing salt slag.

[0065] Figure 6 is the relative content of Na at different depths in the eroded sample (wt%). The distribution of Na at different locations in the eroded samples of the comparative example (without the addition of ferroaluminum spinel) and Example 2 was analyzed by energy dispersive spectrometer (EDS) to indicate the penetration depth of the slag in the refractory material. Figure 6 It can be seen that the sodium content in the erosion penetration layer of Example 2 is relatively low, the erosion depth is relatively small, and the corrosion resistance to sodium sulfate-containing salt slag is relatively good.

[0066] The present invention uses the recycled refractory raw material fused chromium corundum obtained by treating the aluminum chromium slag used to produce metallic chromium as the raw material, adds a certain amount of corundum fine powder or micro powder and chromium oxide micro powder into the batching, and generates the chromium corundum solid solution in situ during the firing process, and simultaneously introduces the iron aluminum spinel fine powder to generate the multicomponent solid solution (Al2O3) during the firing process. 1-x-y Cr x Fe y )2O3 prepared composite chromium corundum bricks, reducing Cr 6+The production of molten salt promotes sintering, resulting in good density, high strength at both room and high temperatures, and excellent resistance to corrosion from sodium sulfate-containing salt slag. This extends the service life of chemical salt wastewater incinerators, while also achieving resource recycling and cost savings, resulting in good economic and social benefits.

[0067] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A composite chromium corundum brick for a chemical saline wastewater incinerator, characterized in that: The composite chrome corundum brick is prepared from the following raw materials in the following mass percentages and an external binder, aluminum dihydrogen phosphate, which accounts for 3% of the raw materials; wherein the raw materials include: Recycled refractory raw material fused chromium corundum with a particle size of ≤3mm, wherein w(Al2O3) + w(Cr2O3) ≥93%, w(Cr2O3) ≥12%, and the mass percentage is 42%; Fused white corundum with a particle size of ≤3mm, of which w(Al2O3) ≥99% and the mass percentage is 39%; Chromium oxide micropowder with a particle size of ≤8μm, of which w(Cr2O3)≥99%, with a mass percentage of 9%; Ferroaluminum spinel powder with a particle size of ≤31μm: mass percentage is 6%; Alumina powder with a particle size of ≤4μm, of which w(Al2O3) ≥99%, mass percentage is 4%; The preparation method of the composite chrome corundum brick for the chemical salt wastewater incinerator is as follows: the above raw materials are mixed according to the required ratio, mixed evenly in a mixer, pressed into shape by a hydraulic press at a molding pressure of 150MPa, and after molding and drying, the green body is kept warm in a high-temperature furnace at 1550°C for 4 hours and fired; The material prepared by the above preparation method was subjected to an erosion test using a static crucible method with sodium sulfate-containing salt slag at 1200°C for 12 hours. The results showed that the crucible had a clear and complete outline after erosion, and there was no obvious erosion phenomenon. The erosion sample consists of two parts: the erosion penetration layer and the original brick layer. The erosion penetration layer becomes denser due to the erosion and penetration of the original slag Na2SO4, and the porosity of the original brick layer is relatively high. With the addition of FeAl2O4, the depth of the erosion penetration layer of the sample is reduced from 5.4mm to 2.4mm, and the sample has excellent resistance to the erosion of sodium sulfate-containing salt slag.

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