A method for recycling waste refractory materials

Abstract

The application relates to a resource treatment method of waste refractory material, which comprises the following steps: mixing waste refractory material containing magnesium oxide and chromium oxide with sufficient carbon powder uniformly, and then pressing and forming to obtain a block; heating the block to a temperature T1 under vacuum or a protective atmosphere, so that the magnesium oxide in the block reacts with the carbon powder to generate magnesium vapor; after the reaction is completed, a residual block is obtained; during the process, the magnesium vapor is collected and condensed to obtain metallic magnesium; the residual block is heated to a temperature T2 under vacuum, and after the reaction is completed, the residual block is cooled to obtain crude chromium; after the crude chromium is crushed, the crude chromium is subjected to alkaline leaching, water washing, acid leaching, water washing and drying in sequence to obtain a metallic chromium product; the application realizes the simultaneous recovery of magnesium and chromium in the waste refractory material, has high efficiency, reduces production energy consumption, and does not generate waste water or harmful waste gas in the reaction process.

Description

TECHNICAL FIELD

[0001] The present application relates to a resource processing method of waste refractory materials, belonging to the technical field of general industrial solid waste resource environmental protection comprehensive utilization and metal smelting. BACKGROUND

[0002] High-temperature industries such as steel, cement, and glass, as well as various industrial kilns, consume a large amount of refractory materials, which will inevitably generate a large amount of waste refractory bricks, linings, and other waste materials containing magnesium and / or chromium, such as waste high-chromium bricks, magnesia-chrome bricks, and chrome corundum. In addition, magnesium and chromium refractory material production enterprises will also generate a large amount of waste containing magnesium and / or chromium during the production of the above refractory materials. The above waste materials and waste can be collectively referred to as waste refractory materials. These waste refractory materials not only have a large quantity, but also are extremely difficult to handle. Except for a small number of waste refractory materials that can be returned to the production line for reuse, most of the typical treatment methods for waste refractory materials are landfill or downgrading. Landfill treatment requires land occupation, increases costs, and causes great waste of resources and serious environmental pollution risks.

[0003] The existing recycling process of waste refractory materials mainly includes fire process and wet process. The fire process has high energy consumption and low chromium recovery rate. In addition, for refractory materials containing magnesium and chromium, the separation of magnesium and chromium is difficult, and only the recovery of a single element such as chromium can be achieved. The wet process produces a large amount of Cr 3+ waste water, and even Cr 6+ waste water, which is difficult to handle, has high cost, and is prone to environmental pollution.

[0004] Chinese patent application CN119824250A discloses a method for producing high-purity metallic chromium from waste chromium-containing refractory materials using carbon reduction, which includes the following steps: collecting waste chromium-containing refractory materials and crushing them to a particle size of 0.1-1 mm, removing impurities by magnetic separation to obtain chromium-rich materials, and then removing impurities by acid leaching to obtain chromium-rich raw materials; then, the chromium-rich raw materials, carbon powder, yttrium-stabilized zirconia, and lanthanum oxyfluoride are mixed to form a mixture; the mixture is then pressed into pellets, and then subjected to a two-stage heating reduction process to obtain a reaction product; the reaction product is then cooled to 800-1000℃, and the slag phase is removed by gravity settling, and the remaining metal phase is subjected to electroslag remelting refining treatment to obtain refined metallic chromium. The recovery of chromium from waste chromium-containing refractory materials is good, but the recovery of magnesium (with a content of 41.0-42.2%) in the waste chromium-containing refractory materials is not considered, and rare earth additives such as yttrium-stabilized zirconia and lanthanum oxyfluoride (LaOF) are needed to separate and recover chromium elements. The high price of rare earth elements will inevitably increase the treatment cost and increase the risk of fluorine and rare earth pollution to the environment. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application aims to provide a resource processing method of waste refractory material to simultaneously recover magnesium and chromium in the waste refractory material.

[0006] To solve the above technical problems, the technical scheme of the present application is as follows:

[0007] A resource processing method of waste refractory material, comprising the following steps:

[0008] S1, providing powder-shaped waste refractory material;

[0009] The waste refractory material contains magnesium oxide and chromium oxide.

[0010] S2, mixing the waste refractory material with sufficient carbon powder uniformly, and then pressing to form a block;

[0011] S3, heating the block to a temperature T1 under vacuum or protective atmosphere conditions, so that the magnesium oxide in the block reacts with the carbon powder to generate magnesium vapor, and after the reaction is completed, a residual body of the block is obtained;

[0012] During the process, the magnesium vapor is collected and condensed to obtain metallic magnesium;

[0013] S4, heating the residual body of the block to a temperature T2 under vacuum or protective atmosphere conditions, so that the chromium oxide in the residual body of the block reacts with the carbon powder to generate metallic chromium, and after the reaction is completed, the metallic chromium is cooled to obtain crude chromium;

[0014] Wherein, T2>T1, T2 is less than the melting point of metallic chromium; and T1 is higher than the boiling point of metallic magnesium.

[0015] S5, crushing the crude chromium, and then sequentially performing alkali leaching, water washing, acid leaching, water washing, and drying to obtain a metallic chromium product.

[0016] Thus, by the two-step carbothermal reduction process, the oxides of magnesium in the waste refractory material are preferentially reduced at a lower temperature condition to generate magnesium vapor, so that the magnesium element is separated from other elements in the waste refractory material, and a certain pore is formed in the block; on the one hand, in the first-stage carbothermal reduction process, the reaction consumption of the oxides of magnesium and the carbon powder, and the formation and escape of the magnesium vapor help to form pores in the block, promote the discharge of the magnesium vapor and CO2 and the like, and further promote the progress of the reaction of the oxides of magnesium and the carbon powder (the reaction belongs to a gas-producing reaction, and timely discharge of the gas helps to promote the forward progress of the reaction); on the other hand, the pores formed in the first-stage carbothermal reduction reaction can timely discharge the CO2 and the like generated in the carbothermal reduction reaction of the oxides of chromium and the carbon powder in the subsequent second-stage carbothermal reduction reaction, and are also beneficial to more uniform heating of the material, and help to promote the progress of the reaction of the oxides of chromium and the carbon powder in the residual body and improve the reaction rate. Subsequently, by alkali leaching and acid leaching, impurities such as aluminum oxide, silicon oxide and unreacted magnesium oxide are removed, and a high-purity chromium metal product is obtained. Therefore, the present application can realize the resource recycling of magnesium and chromium in the waste refractory material, and does not need to add additives such as rare earth fluorides, which helps to save costs and avoid secondary pollution.

[0017] Further, in S1, the waste refractory material is the waste refractory material after removal of magnetic substances by magnetic separation. Thus, the scrap iron and the like in the waste refractory material can be removed, and subsequent processing is facilitated. The collected magnetic scrap iron and the like can be further used for recycling iron, realizing resource utilization and improving processing efficiency.

[0018] Further, in S1, the particle size of the waste refractory material is 100-200 meshes, and more further is 120-180 meshes.

[0019] Further, in S1, the waste refractory material contains oxides of magnesium in an amount of ≥50wt% based on MgO. Controlling a certain amount of oxides of magnesium helps to obtain better chromium and magnesium recovery effect.

[0020] Further, in S1, the waste refractory material contains oxides of magnesium in an amount of 52-90wt% based on MgO, more further is 55-85wt%, further is 60-80wt%, and further is 65-75wt%.

[0021] Further, in S1, the waste refractory material contains oxides of chromium in an amount of 5-45wt% based on Cr2O3, more further is 8-42wt%, further is 12-38wt%, and further is 16-32wt%.

[0022] Optionally, the content of Al2O3 in the waste refractory material is 1-3wt%, and the content of SiO2 is 1-3wt%.

[0023] Optionally, the waste refractory material is composed of two or more waste refractory materials, for example, one or several of high-chromium bricks, magnesia-chrome bricks, and chrome-corundum. Optionally, magnesium oxide and / or chromium oxide can be added to the waste refractory material as needed to achieve the target content of magnesium oxide and chromium oxide in the raw material.

[0024] Further, in S2, the amount of carbon powder added is 1-3 times, further 1.2-2.8 times, and further 1.5-2.5 times the theoretical amount of carbon powder required to reduce all magnesium oxides and chromium oxides in the waste refractory material to metallic magnesium and chromium through carbothermic reduction reaction.

[0025] Preferably, the purity of the carbon powder is ≥99.5wt%.

[0026] Optionally, the shape of the block is one or several of a cuboid, a cube, and a cylinder.

[0027] Optionally, the block is a cube with a side length of 80-120mm.

[0028] Further, a plurality of uniformly distributed honeycomb holes are formed in the block.

[0029] Further, in S2, the pressure is 3-4MPa.

[0030] Further, 1100℃≤T1≤1200℃, and 1400℃≤T2≤1500℃.

[0031] Further, 1120℃≤T1≤1180℃, and 1420℃≤T2≤1480℃.

[0032] Further, 1140℃≤T1≤1160℃, and 1440℃≤T2≤1460℃.

[0033] Preferably, in S3, the block is heated to a temperature T1 under vacuum conditions.

[0034] Optionally, in S3, the magnesium vapor can be collected by suction and sent to a condenser for condensation to obtain metallic magnesium.

[0035] Optionally, the condensation temperature is 400-780℃, and further 420-750℃.

[0036] Further, in S3, the reaction time is 5-7h, and further 5.5-6.5h; and in S4, the reaction time is 2-3h, and further 2.2-2.8h.

[0037] Preferably, in S4, the briquettes are heated to a temperature T2 under vacuum.

[0038] Optionally, S3 and S4 are performed in a vacuum heating furnace.

[0039] Optionally, in S3 and S4, the pressure in the vacuum heating furnace is controlled to be ≤ 150 Pa, further ≤ 100 Pa, during the reaction.

[0040] Further, in S4, the furnace cooling is performed. Preferably, the furnace cooling is performed to below 100℃.

[0041] Further, in S5, after the crude chromium is broken, the crude chromium is reacted in a 80-100℃ sodium hydroxide solution for 2-4h, then solid-liquid separation is performed, then the solid phase is washed with water until the washing water is neutral, then the solid phase is reacted in a 80-100℃ sulfuric acid solution for 3-4h, then solid-liquid separation is performed, then the solid phase is washed with water until the washing water is neutral, then the solid phase is dried at 80-100℃ for 10-14h to obtain a metal chromium product; wherein the concentration of the sodium hydroxide solution is 15-40wt%, further 20-30wt%, and the concentration of the sulfuric acid solution is 5-10wt%.

[0042] Further, in S5, the crude chromium is broken to 100-200 mesh.

[0043] Compared with the prior art, the present application has the following advantages:

[0044] (1) The present application realizes the simultaneous recovery of magnesium and chromium in waste refractory materials, has high efficiency, and reduces the production energy consumption. The reaction process does not produce waste water and harmful waste gas.

[0045] (2) The present application can realize the effective recovery of magnesium and chromium, and the product purity of the metal magnesium and the metal chromium is relatively high, and has high economic value. The purity of the metal magnesium can reach 98wt%, the recovery rate of the magnesium can reach more than 80wt%, the purity of the metal chromium can reach more than 97wt%, and the recovery rate of the chromium can reach more than 79wt%.

[0046] (3) The present application does not need to add yttrium stabilized zirconium oxide and lanthanum oxyfluoride and other rare earth additives, which helps to reduce the cost and post-processing burden.

[0047] (4) The resource processing method of the waste refractory material of the present application can effectively consume the waste refractory material, realize the resource recovery of magnesium, chromium and other elements, effectively reduce the landfill pressure of the waste refractory material, and eliminate the safety hidden danger of adding the waste refractory material as a recycled aggregate to the newly built refractory material for high temperature and high pressure kiln. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 is a flow chart of a resource processing method of waste refractory material according to the present application. DETAILED DESCRIPTION

[0049] The present application will be described in detail below with reference to examples. It should be noted that the examples in the present application and the features in the examples can be combined with each other without conflict. Unless otherwise specified, the relevant percentages refer to mass percentages.

[0050] Example 1

[0051] The resource processing method of waste refractory material of the present embodiment comprises the following steps:

[0052] (1) Breaking and removing iron: break the waste magnesia-chrome brick to 100 mesh, and then remove the magnetic substances such as iron in it by magnetic separation to obtain magnesia-chrome brick powder (i.e. waste refractory material powder, wherein the MgO content is 60% and the Cr2O3 content is 20%);

[0053] (2) Mixing and briquetting: take 100 kg of waste refractory material powder, and weigh the corresponding carbon powder according to the carbon coefficient (i.e. the multiple of the theoretical amount of carbon powder required to reduce all MgO and Cr2O3 in the waste refractory material powder to metallic magnesium and chromium by carbon thermal reduction reaction, the same below) of 1.00, and then mix the waste refractory material powder and carbon powder uniformly, and press into a cube block with a side length of 100 mm (wherein the cube block has 36 honeycomb holes with a diameter of 8 mm) at a pressure of 3.4 MPa to better ensure good permeability and reactivity;

[0054] (3) Two-stage carbon reduction: place the cube block in a vacuum heating furnace, close the door, and then vacuumize, and then heat to 1150℃ under vacuum, and keep the temperature for 6h to make magnesium oxide and carbon powder react to generate magnesium vapor, during which the magnesium vapor is collected; then the temperature is raised to 1450℃, and kept for 2.5h to make chromium oxide react with carbon powder to generate metallic chromium, after the reaction is completed, the furnace is cooled to 100℃, then the door is opened, and the crude chromium is obtained;

[0055] During the reaction, the pressure in the vacuum heating furnace is controlled to be ≤100 Pa;

[0056] The magnesium vapor is sent into a condenser to condense and obtain metallic magnesium; wherein during the condensation, the condensation temperature is controlled to be ≤750℃;

[0057] (4) Impurity removal: the crude chromium was crushed to 100 mesh, and then was reacted in a 20wt% sodium hydroxide solution at 80°C for 2h, and then was filtered to obtain solid phase 1; then the solid phase 1 was washed with deionized water until the washing water was neutral, and then was filtered to obtain solid phase 2; then the solid phase 2 was reacted in a 8wt% sulfuric acid solution at 90°C for 3.5h, and then was filtered to obtain solid phase 3; then the solid phase 3 was washed with deionized water until the washing water was neutral, and then was filtered to obtain solid phase 4; then the solid phase 4 was dried at 80°C for 12h to obtain the metal chromium product.

[0058] It was detected that the mass of the metal magnesium was 30.4kg, the purity of the magnesium was 89.92%, and the recovery rate of the magnesium was 75.94%; the mass of the metal chromium product was 11.57kg, the purity of the chromium was 88.16%, and the recovery rate of the chromium was 74.56%. The purity was obtained by inductively coupled plasma optical emission spectrometer (ICP-OES), and the same was true for the following.

[0059] Example 2

[0060] Example 1 was repeated, except that in step (1), the mass fraction of MgO in the waste refractory material powder was 62.5%, and the mass fraction of Cr2O3 was 16%. Specifically, the waste refractory material powder was composed of magnesium-chromium brick powder 1 (MgO content 60%, Cr2O3 content 20%) and magnesium-chromium brick powder 2 (MgO content 65%, Cr2O3 content 12%) in a mass ratio of 1:1 (i.e., composed of two kinds of waste magnesium-chromium brick powders with different contents of magnesium oxide and chromium oxide).

[0061] It was detected that the mass of the metal magnesium was 32.21kg, the purity of the magnesium was 90.14%, the recovery rate of the magnesium was 77.43%, the mass of the metal chromium product was 9.11kg, the purity of the chromium was 90.02%, and the recovery rate of the chromium was 76.32%.

[0062] Example 3

[0063] Example 1 was repeated, except that in step (1), the mass fraction of MgO in the waste refractory material powder was 67.5%, and the mass fraction of Cr2O3 was 14%. Specifically, the waste refractory material powder was composed of magnesium-chromium brick powder 1 (MgO content 60%, Cr2O3 content 20%) and magnesium-chromium brick powder 2 (MgO content 75%, Cr2O3 content 8%) in a mass ratio of 1:1.

[0064] It was detected that the mass of the metal magnesium was 33.26kg, the purity of the magnesium was 95.76%, the recovery rate of the magnesium was 78.64%, the mass of the metal chromium product was 7.86kg, the purity of the chromium was 93.2%, and the recovery rate of the chromium was 76.5%.

[0065] Example 4

[0066] Example 1 was repeated, except that in step (1), the MgO content of the waste refractory material powder (magnesite-chrome brick powder) was 80%, and the Cr203content was 6%.

[0067] The detected mass of the metallic magnesium was 40.14 kg, the purity of the magnesium was 98%, the recovery rate of the magnesium was 81.96%, the mass of the metallic chromium product was 3.15 kg, the purity of the chromium was 94.48%, and the recovery rate of the chromium was 72.46%.

[0068] Example 5

[0069] Example 1 was repeated, except that in step (1), the MgO content of the waste refractory material powder (magnesite-chrome brick powder) was 80%, and the Cr203content was 6%.

[0070] The detected mass of the metallic magnesium was 40.14 kg, the purity of the magnesium was 98%, the recovery rate of the magnesium was 81.96%, the mass of the metallic chromium product was 3.15 kg, the purity of the chromium was 94.48%, and the recovery rate of the chromium was 72.46%.

[0071] Example 6

[0072] Example 1 was repeated, except that in step (1), the MgO content of the waste refractory material powder (magnesite-chrome brick powder) was 80%, and the Cr203content was 6%.

[0073] The detected mass of the metallic magnesium was 40.14 kg, the purity of the magnesium was 98%, the recovery rate of the magnesium was 81.96%, the mass of the metallic chromium product was 3.15 kg, the purity of the chromium was 94.48%, and the recovery rate of the chromium was 72.46%.

[0074] Example 7

[0075] Example 2 was repeated, except that in step (1), the MgO content of the waste refractory material powder was 52.5%, and the Cr203content was 16%. Specifically, the waste refractory material was composed of magnesite-chrome brick powder 1 (MgO content 40%, Cr203content 20%) and magnesite-chrome brick powder 2 (MgO content 65%, Cr203content 12%) in a mass ratio of 1:1.

[0076] The detected mass of the metallic magnesium is 25.95 kg, the purity of the magnesium is 86.45%, the recovery rate of the magnesium is 71.23%, the mass of the metallic chromium product is 8.77 kg, the purity of the chromium is 87.02%, and the recovery rate of the chromium is 70.98%.

[0077] Example 8

[0078] Example 2 is repeated, with the only difference being that in step (1), the content of MgO in the waste refractory material powder (magnesite-chrome brick powder) is 45%, and the content of Cr2O3 is 16%.

[0079] The detected mass of the metallic magnesium is 22.75 kg, the purity of the magnesium is 83.23%, the recovery rate of the magnesium is 70.13%, the mass of the metallic chromium product is 9.08 kg, the purity of the chromium is 80.78%, and the recovery rate of the chromium is 68.23%.

[0080] It can be seen that by controlling the content of MgO in the waste refractory material powder within a specific range, particularly excellent recovery rates and purities of the metallic magnesium and the metallic chromium can be obtained, thereby obtaining particularly excellent recovery benefits. A possible reason is that the content of MgO in the waste refractory material powder affects the porosity or looseness of the block residue after the first carbon thermal reduction, thereby affecting the carbon thermal reduction reaction process of the chromium oxide. Specifically, when the content of MgO in the waste refractory material powder is low, the porosity of the pores of the block residue is low, the gas generated by the carbon thermal reduction reaction of the chromium oxide is difficult to discharge in time, and the heat transfer is weak, which is not conducive to the generation of the metallic chromium, resulting in low recovery rate of the metallic chromium and low purity of the chromium. In addition, the purity of the metallic magnesium and the recovery rate of the magnesium are also low at this time. A possible reason is that the content of magnesium oxide in the raw material is too low, and the carbon thermal reduction reaction of the magnesium oxide is not complete, so the relative content of magnesium in the collected magnesium vapor (with dust) is reduced. When the content of MgO in the waste refractory material powder is too high, the porosity of the pores of the block residue is too high, which causes the local collapse of the block residue, affecting the reduction of the chromium oxide, and thereby causing the recovery rate of the chromium to decrease.

[0081] The above-mentioned content illustrated by the examples should be understood as the examples being used only for more clearly illustrating the present application, and not for limiting the scope of the present application. After reading the present application, various equivalent modifications of the present application made by those skilled in the art all fall within the scope defined by the claims attached to the present application.

Claims

1. A method for resource recovery of spent refractories, characterized by, The method comprises the following steps: S1, providing waste refractory material in powder form; The waste refractory material contains magnesium oxide and chromium oxide; the content of the magnesium oxide in the waste refractory material is 50-90wt% in terms of MgO; S2, uniformly mixing the waste refractory material with sufficient carbon powder, and then pressing to obtain a block; S3, heating the block to a temperature T1 under vacuum or in a protective atmosphere, so that the magnesium oxide in the block reacts with the carbon powder to generate magnesium vapor; after the reaction is completed, a residual block is obtained; During the process, the magnesium vapor is collected and condensed to obtain metallic magnesium; S4, heating the residual block to a temperature T2 under vacuum or in a protective atmosphere, so that the chromium oxide in the residual block reacts with the carbon powder to generate metallic chromium; after the reaction is completed, the residual block is cooled to obtain crude chromium; T2>T1, and T2 is less than the melting point of the metallic chromium; T1 is higher than the boiling point of the metallic magnesium; S5, crushing the crude chromium, and then sequentially performing alkali leaching, water washing, acid leaching, water washing, and drying to obtain a metallic chromium product.

2. The method of claim 1, wherein, In S1, the waste refractory material is the waste refractory material after removing magnetic substances through magnetic separation.

3. The method of claim 1, wherein, In S1, the content of the magnesium oxide in the waste refractory material is 52-90wt% in terms of MgO.

4. The method of claim 1, wherein, In S1, the content of the chromium oxide in the waste refractory material is 5-45wt% in terms of Cr2O3.

5. The method of resourceful processing according to any one of claims 1-4, wherein, In S2, the addition amount of the carbon powder is 1-3 times the theoretical amount of the carbon powder required for reducing all the magnesium oxide and chromium oxide in the waste refractory material into metallic magnesium and metallic chromium through carbothermic reduction reaction.

6. The method of resourceful processing according to any one of claims 1-4, wherein, The block is provided with a plurality of uniformly distributed honeycomb holes.

7. The method of resourceful processing according to any one of claims 1-4, wherein, 1100℃≤T1≤1200℃, and 1400℃≤T2≤1500℃.

8. The method of resourceful processing according to any one of claims 1-4, wherein, In S3, the reaction time is 5-7h; and in S4, the reaction time is 2-3h.

9. The method of resourceful processing according to any one of claims 1-4, wherein, In S5, after the crude chromium is crushed, the crushed crude chromium is reacted in a 80-100℃ sodium hydroxide solution for 2-4h, and then solid-liquid separation is performed; the solid phase is then washed with water until the washing water is neutral; the solid phase is then reacted in a 80-100℃ sulfuric acid solution for 3-4h, and then solid-liquid separation is performed; the solid phase is then washed with water until the washing water is neutral; and then the solid phase is dried at 80-100℃ for 10-14h to obtain the metallic chromium product; wherein the concentration of the sodium hydroxide solution is 15-40wt%, and the concentration of the sulfuric acid solution is 5-10wt%.

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