Resourceful treatment method of waste refractory material

Abstract

The invention relates to a resourceful treatment method of a waste refractory material, which comprises the following steps: uniformly mixing the waste refractory material containing magnesium oxide and chromium oxide with sufficient carbon powder, and carrying out compression molding to obtain a material block; the material block is heated to the temperature T1 under the vacuum or protective atmosphere condition, so that the magnesium oxide in the material block reacts with the carbon powder to generate magnesium steam, and after the reaction is completed, a material block residual body is obtained; during the period, magnesium steam is collected and condensed to obtain metal magnesium; the material block residues are heated to the temperature T2 under the vacuum condition, after the reaction is completed, cooling is conducted, and coarse chromium is obtained; and after the coarse chromium is crushed, alkaline leaching, water washing, acid leaching, water washing and drying are conducted in sequence, and a metal chromium product is obtained. According to the invention, magnesium and chromium in the waste refractory material are recovered at the same time, the efficiency is high, the production energy consumption is reduced, and no wastewater or harmful waste gas is generated 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: A resource processing method of waste refractory material, comprising the following steps: S1, providing powder-shaped waste refractory material; Wherein, the waste refractory material contains magnesium oxide and chromium oxide; S2, mixing the waste refractory material and sufficient carbon powder uniformly, and then pressing to form a block; 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 block is obtained; During the period, the magnesium vapor is collected and condensed to obtain metallic magnesium; S4, heating the residual block to a temperature T2 under vacuum or protective atmosphere conditions, so that the chromium oxide in the residual block reacts with the carbon powder to generate metallic chromium, and after the reaction is completed, cooling to obtain crude chromium; Wherein, T2>T1, T2 is less than the melting point of metallic chromium; T1 is higher than the boiling point of 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.

[0007] Therefore, by the two-step carbothermal reduction process, the oxides of magnesium in the waste refractory material are preferentially reduced at a lower temperature 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 carbon powder, the formation and escape of magnesium vapor help to form pores in the block, promote the discharge of magnesium vapor and CO2 and other gases, and further promote the progress of the reaction of the oxides of magnesium and carbon powder (which belongs to a reaction with gas generation, timely discharge of 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 CO2 and other gases generated in the carbothermal reduction reaction of the oxides of chromium and carbon powder in the subsequent second-stage carbothermal reduction reaction, and are also beneficial to more uniform heating of the material, which helps to promote the reaction of the oxides of chromium and 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 recovery of magnesium and chromium in the waste refractory material at the same time, and does not need to add rare earth fluoride and other additives, which helps to save costs and avoid secondary pollution.

[0008] Further, in S1, the waste refractory material is the waste refractory material after the magnetic material is removed by magnetic separation. Thus, the scrap iron and other waste materials in the waste refractory material can be removed, facilitating subsequent processing, and the collected magnetic waste materials such as scrap iron can be further used for recycling iron to realize resource utilization and improve processing efficiency.

[0009] Further, in S1, the particle size of the waste refractory material is 100-200 mesh, and more further, 120-180 mesh.

[0010] 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.

[0011] Further, in S1, the waste refractory material contains oxides of magnesium in an amount of 52-90wt% based on MgO, more further, 55-85wt%, further, 60-80wt%, and further, 65-75wt%.

[0012] Further, in S1, the waste refractory material contains oxides of chromium in an amount of 5-45wt% based on Cr2O3, more further, 8-42wt%, further, 12-38wt%, and further, 16-32wt%.

[0013] Optionally, the content of Al2O3 in the waste refractory material is 1-3wt%, and the content of SiO2 is 1-3wt%.

[0014] 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.

[0015] 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.

[0016] Preferably, the purity of the carbon powder is ≥99.5wt%.

[0017] Optionally, the shape of the block is one or several of a cuboid, a cube, and a cylinder.

[0018] Optionally, the block is a cube with a side length of 80-120mm.

[0019] Further, a plurality of uniformly distributed honeycomb holes are formed in the block.

[0020] Further, in S2, the pressure for pressing and forming is 3-4MPa.

[0021] Further, 1100℃≤T1≤1200℃, and 1400℃≤T2≤1500℃.

[0022] Further, 1120℃≤T1≤1180℃, and 1420℃≤T2≤1480℃.

[0023] Further, 1140℃≤T1≤1160℃, and 1440℃≤T2≤1460℃.

[0024] Preferably, in S3, the block is heated to a temperature T1 under vacuum conditions.

[0025] Optionally, in S3, the magnesium vapor can be collected by suction and sent to a condenser for condensation to obtain metallic magnesium.

[0026] Optionally, the condensation temperature is 400-780℃, and further 420-750℃.

[0027] 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.

[0028] Preferably, in S4, the briquettes are heated to a temperature T2 under vacuum.

[0029] Optionally, S3 and S4 are performed in a vacuum heating furnace.

[0030] Optionally, in S3 and S4, the pressure in the vacuum heating furnace is controlled to be ≤ 150 Pa, further ≤ 100 Pa, during the reaction.

[0031] Further, in S4, the furnace cooling is performed. Preferably, the furnace cooling is performed to below 100℃.

[0032] Further, in S5, after the crude chromium is crushed and reacted in a 80-100℃ sodium hydroxide solution for 2-4h, solid-liquid separation is performed, then the solid phase is washed with water until the washing water is neutral, and then reacted in a 80-100℃ sulfuric acid solution for 3-4h, solid-liquid separation is performed, then the solid phase is washed with water until the washing water is neutral, and then 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%.

[0033] Further, in S5, the crude chromium is crushed to 100-200 mesh.

[0034] Compared with the prior art, the present application has the following advantages: (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 or harmful waste gas.

[0035] (2) The present application can realize effective recovery of magnesium and chromium, and the product purity of the metal magnesium and the metal chromium is relatively high, which 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%.

[0036] (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.

[0037] (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

[0038] Figure 1is a flow chart of a resource processing method of waste refractory material. DETAILED DESCRIPTION

[0039] The application will be described in detail below with reference to the embodiments. It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict. If not otherwise specified, the relevant percentages refer to mass percentages.

[0040] Embodiment 1 The resource processing method of waste refractory material in this embodiment comprises the following steps: (1) Breaking and removing iron: the waste magnesia-chrome brick is broken to 100 mesh, and then the magnetic substances such as iron in the waste magnesia-chrome brick are removed 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%); (2) Mixing and briquetting: 100 kg of waste refractory material powder is weighed, and the corresponding carbon powder is weighed according to the carbon coefficient (i.e. the multiple of the theoretical amount of carbon powder required for reducing all MgO and Cr2O3 in the waste refractory material powder to metallic magnesium and chromium by carbon thermal reduction reaction, the same below), which is 1.00. Then the waste refractory material powder and the carbon powder are mixed uniformly, and then pressed 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; (3) Two-stage carbon reduction: the cube block is placed in a vacuum heating furnace, the furnace door is closed, vacuum is drawn, and the temperature is raised to 1150℃ under vacuum condition, and the temperature is kept for 6 h 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 the temperature is kept for 2.5 h to make chromium oxide and carbon powder react to generate metallic chromium. After the reaction is completed, the furnace is cooled to 100℃, the furnace door is opened, and the crude chromium is obtained; During the reaction, the pressure in the vacuum heating furnace is controlled to be ≤100 Pa; The magnesium vapor is sent into a condenser to be condensed to obtain metallic magnesium; wherein the condensing temperature is controlled to be ≤750℃ during condensation; (4) Impurity removal: the crude chromium is broken to 100 mesh, and then is placed in a 20wt% sodium hydroxide solution at 80℃ for 2 h, filtered to obtain solid phase 1; then the solid phase 1 is washed with deionized water until the washing water is neutral, filtered to obtain solid phase 2; then the solid phase 2 is placed in an 8wt% sulfuric acid solution at 90℃ for 3.5 h, filtered to obtain solid phase 3; then the solid phase 3 is washed with deionized water until the washing water is neutral, filtered to obtain solid phase 4; and then the solid phase 4 is dried at 80℃ for 12 h to obtain the metallic chromium product.

[0041] The detected mass of the metal magnesium is 30.4 kg, the purity of magnesium is 89.92%, and the recovery rate of magnesium is 75.94%; the mass of the metal chromium product is 11.57 kg, the purity of chromium is 88.16%, and the recovery rate of chromium is 74.56%. Among them, the purity is obtained by inductively coupled plasma emission spectrometer (ICP-OES), and the same applies below.

[0042] Example 2 Example 1 is repeated, with the only difference being that in step (1), the mass fraction of MgO in the waste refractory material powder is 62.5%, and the mass fraction of Cr2O3 is 16%. Specifically, the waste refractory material powder is 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).

[0043] The detected mass of the metal magnesium is 32.21 kg, the purity of magnesium is 90.14%, the recovery rate of magnesium is 77.43%, the mass of the metal chromium product is 9.11 kg, the purity of chromium is 90.02%, and the recovery rate of chromium is 76.32%.

[0044] Example 3 Example 1 is repeated, with the only difference being that in step (1), the mass fraction of MgO in the waste refractory material powder is 67.5%, and the mass fraction of Cr2O3 is 14%. Specifically, the waste refractory material powder is 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.

[0045] The detected mass of the metal magnesium is 33.26 kg, the purity of magnesium is 95.76%, the recovery rate of magnesium is 78.64%, the mass of the metal chromium product is 7.86 kg, the purity of chromium is 93.2%, and the recovery rate of chromium is 76.5%.

[0046] Example 4 Example 1 is repeated, with the only difference being that in step (1), the mass fraction of MgO in the waste refractory material powder is 70%, and the mass fraction of Cr2O3 is 13%. Specifically, the waste refractory material powder is composed of magnesium-chromium brick powder 1 (MgO content 60%, Cr2O3 content 20%) and magnesium-chromium brick powder 2 (MgO content 80%, Cr2O3 content 6%) in a mass ratio of 1:1.

[0047] The detected mass of the metal magnesium is 34.89 kg, the purity of magnesium is 97.24%, the recovery rate of magnesium is 80.78%, the mass of the metal chromium product is 7.18 kg, the purity of chromium is 97.98%, and the recovery rate of chromium is 79.14%. It is calculated that the material porosity after the reaction of the metal magnesium is 60.02%.

[0048] Example 5 Example 1 is repeated, except that in step (1), the MgO content in the waste refractory material powder (magnesite-chrome brick powder) is 80%, and the Cr2O3 content is 6%.

[0049] The detected mass of the metal magnesium is 40.14 kg, the purity of magnesium is 98%, the recovery rate of magnesium is 81.96%, the mass of the metal chromium product is 3.15 kg, the purity of chromium is 94.48%, and the recovery rate of chromium is 72.46%.

[0050] Example 6 Example 1 is repeated, except that in step (1), the mass fraction of MgO in the waste refractory material powder is 66%, and the mass fraction of Cr2O3 is 13%. Specifically, the waste refractory material powder is composed of magnesite-chrome brick powder 1 (MgO content 60%, Cr2O3 content 16%) and magnesite-chrome brick powder 2 (MgO content 80%, Cr2O3 content 6%) in a mass ratio of 7:3.

[0051] The detected mass of the metal magnesium is 32.37 kg, the purity of magnesium is 95.96%, the recovery rate of magnesium is 78.45%, the mass of the metal chromium product is 7.01 kg, the purity of chromium is 96.98%, and the recovery rate of chromium is 76.43%.

[0052] Example 7 Example 2 is repeated, except that in step (1), the mass fraction of MgO in the waste refractory material powder is 52.5%, and the mass fraction of Cr2O3 is 16%. Specifically, the waste refractory material is composed of magnesite-chrome brick powder 1 (MgO content 40%, Cr2O3 content 20%) and magnesite-chrome brick powder 2 (MgO content 65%, Cr2O3 content 12%) in a mass ratio of 1:1.

[0053] The detected mass of the metal magnesium is 25.95 kg, the purity of magnesium is 86.45%, the recovery rate of magnesium is 71.23%, the mass of the metal chromium product is 8.77 kg, the purity of chromium is 87.02%, and the recovery rate of chromium is 70.98%.

[0054] Example 8 Example 2 is repeated, except that in step (1), the MgO content in the waste refractory material powder (magnesite-chrome brick powder) is 45%, and the Cr2O3 content is 16%.

[0055] The detected mass of the magnesium metal 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 chromium metal product is 9.08 kg, the purity of the chromium is 80.78%, and the recovery rate of the chromium is 68.23%.

[0056] It can be seen that, by controlling the content of MgO in the waste refractory material powder in a specific range, it is helpful to obtain particularly excellent recovery rate and purity of the magnesium metal and the chromium metal, and thus obtain particularly excellent recovery benefit. The 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, and thus affects 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 chromium metal, resulting in low recovery rate and purity of the chromium metal, in addition, the purity and recovery rate of the magnesium metal are also low at this time, the possible reason is that the content of magnesium oxide in the raw material is too low, the carbon thermal reduction reaction of the magnesium oxide is not complete enough, and 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, affects the reduction of the chromium oxide, and thus causes the recovery rate of the chromium to decrease.

[0057] The above-mentioned content illustrated by the above-mentioned examples should be understood as that the examples are only used for more clearly illustrating the present application, and are not used for limiting the scope of the present application, and after reading the present application, the modification of various equivalent forms of the present application by the person skilled in the art all fall into the range defined by the claims attached to the present application.

Claims

1. A method for recycling waste refractory materials, characterized in that: The steps include: S1. Provide powdered waste refractory materials; Wherein, the waste refractory material contains magnesium oxide and chromium oxide; S2, mixing the waste refractory material and a sufficient amount of carbon powder uniformly, and pressing and forming the mixture to obtain a block; S3, heating the material block to a temperature T1 under vacuum or protective atmosphere conditions, so that the magnesium oxide in the material block reacts with the carbon powder to generate magnesium vapor, and after the reaction is completed, obtaining a material block residue; During this period, magnesium vapor is collected and condensed to obtain metallic magnesium; S4, heating the residual material block to a temperature T2 under vacuum or protective atmosphere conditions, so that the chromium oxide in the residual material block reacts with the carbon powder to form metallic chromium. After the reaction is complete, cooling is performed to obtain crude chromium; Among them, T2>T1, T2 is less than the melting point of metal chromium; T1 is higher than the boiling point of metal magnesium; S5. After crushing the crude chromium, alkali leaching, water washing, acid leaching, water washing, and drying are carried out in sequence to obtain a metallic chromium product.

2. The resource recovery method according to claim 1, characterized in that: In S1, the waste refractory materials are waste refractory materials after magnetic materials are removed by magnetic separation.

3. The resource recovery method according to claim 1, characterized in that: In S1, the content of magnesium oxide in the waste refractory material, calculated as MgO, is ≥50wt%.

4. The resource recovery method according to claim 2, characterized in that: In S1, the content of magnesium oxide in the waste refractory material, calculated as MgO, is 52-90 wt%.

5. The resource recovery method according to claim 1, characterized in that: In S1, the content of chromium oxide in the waste refractory material is 5-45wt% in terms of Cr2O3.

6. The resource recovery method according to any one of claims 1 to 5, characterized in that: In S2, the amount of carbon powder added is 1-3 times the theoretical amount of carbon powder required to reduce all magnesium oxides and chromium oxides in the waste refractory materials to metallic magnesium and metallic chromium through a carbothermic reduction reaction.

7. The resource recovery method according to any one of claims 1 to 5, characterized in that: A plurality of evenly distributed honeycomb holes are provided in the material block.

8. The resource recovery method according to any one of claims 1 to 5, characterized in that: 1100℃≤T1≤1200℃, 1400℃≤T2≤1500℃.

9. The resource recovery method according to any one of claims 1 to 5, characterized in that: In S3, the reaction time is 5-7 h; in S4, the reaction time is 2-3 h.

10. The resource recovery method according to any one of claims 1 to 5, characterized in that: In S5, the crude chromium is crushed, reacted in a sodium hydroxide solution at 80-100°C for 2-4 hours, and then separated into solid and liquid. The solid phase is washed with water until the washing water is neutral, and then reacted in a sulfuric acid solution at 80-100°C for 3-4 hours, and then separated into solid and liquid. The solid phase is washed with water until the washing water is neutral, and then dried at 80-100°C for 10-14 hours to obtain a 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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