A method for preparing heat-insulating refractory castable from nickel-iron slag

Abstract

The present invention belongs to the field of solid waste resource utilization, and specifically discloses a method for preparing a heat-insulating refractory castable from nickel-iron slag. A mixture is prepared by mixing nickel-iron slag particles and a binder; mixed water is added to the mixture, and after stirring, casting and molding, curing, demolding, drying, and heat treatment, the refractory castable is obtained; the nickel-iron slag particles include particle A, particle B, particle C, and particle D with a weight ratio of 11-13:21-23:30-32:19-21; 3 mm ≤ the particle size of particle A ≤ 5 mm, 1 mm ≤ the particle size of particle B < 3 mm, 0.15 mm ≤ the particle size of particle C < 1 mm, and the particle size of particle D is -0.074 mm; in the mixture, the content of nickel-iron slag particles is 80-90 wt.%; the temperature of the heat treatment is 1230-1280 °C. The preparation method proposed by the present invention can maximize the utilization of nickel-iron slag, and the production method is simple and easy to implement; the prepared refractory castable has excellent heat-insulating performance, which is conducive to realizing industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource utilization or refractory castables, and particularly relates to a method for preparing a high-performance heat-insulating refractory castable from nickel-iron slag. Background Art

[0002] Nickel-iron slag is a solid waste residue generated during the smelting process of nickel-iron alloy. With the rapid development of the stainless steel industry, the demand for nickel-iron alloy is increasing year by year, which has led to a rapid increase in the output of nickel-iron slag. It is reported that the annual output of nickel-iron slag in China will exceed 40 million tons, becoming the fourth largest metallurgical waste residue after blast furnace slag, steel slag, and red mud. At present, only less than 10% of nickel-iron slag has been utilized, and the rest is stockpiled in the open air. How to efficiently, greenly, and economically treat nickel-iron slag has become an urgent problem to be solved.

[0003] At present, the utilization of nickel-iron slag mainly focuses on the production of building materials, geopolymers, refractory materials, glass ceramics, thermal insulation materials, and the recovery of valuable metal elements, etc. Due to the complex chemical composition and low activity of nickel-iron slag, its application in building materials and geopolymers is limited. The applications in glass ceramics, thermal insulation materials, and the recovery of valuable metal elements have the disadvantages of long process, complex production process, and high energy consumption. And the treatment capacity is limited, and it cannot effectively alleviate the problem of large stockpiles of nickel-iron slag. Therefore, it is necessary to explore a new technology to greenly and efficiently treat nickel-iron slag.

[0004] Nickel-iron slag contains a large amount of forsterite phase, which has the characteristics of high melting point and excellent high-temperature resistance. Patents such as CN201510619761.X, CN106810281A, CN107285792A, etc. disclose methods for preparing shaped refractory materials from nickel-iron slag. Refractory materials have a very wide application in the high-temperature field and a large demand, and can treat a certain amount of nickel-iron slag. However, traditional shaped refractory materials need to be fired at high temperature, with high energy consumption. For products with special shapes, corresponding molds need to be manufactured, with high production costs. In recent years, unshaped refractory materials have been developed and have replaced shaped refractory materials in some fields.

[0005] Although the technology for preparing shaped refractory materials from nickel-iron slag has been relatively mature, there is no report on the application of nickel-iron slag in unshaped refractory castables. Refractory castables are made of granular and powdery materials, and a certain amount of binder and water need to be added during the production. Usually, it has a certain fluidity and is suitable for construction by pouring method. Compared with ordinary refractory materials, refractory castables have the advantages of energy conservation, good integrity, flexible adjustment of composition, high production efficiency, etc.

[0006] The production raw materials of refractory castables are mostly natural materials such as bauxite. With the continuous exploitation of natural resources, the access to natural raw materials is restricted and the production cost increases. Therefore, finding alternative raw materials has become a research hotspot. At present, there are cases of using metallurgical slag to prepare refractory castables, but high dosage of metallurgical slag cannot be achieved, and additives need to be introduced to improve the performance of refractory castables. Low utilization rate and high production cost are the technical problems faced in the production of refractory castables using metallurgical slag at present. Therefore, developing a preparation technology for refractory castables with high nickel-iron slag dosage and without additives is of great significance for reducing the production cost of refractory castables and promoting the healthy and sustainable development of nickel-iron alloy smelting. Summary of the Invention

[0007] Aiming at the technical gap in preparing refractory castables with existing nickel-iron slag, the first object of the present invention is to provide a preparation method for obtaining refractory castables using nickel-iron slag, aiming to provide a refractory castable without additives and with excellent heat insulation performance under high nickel-iron slag dosage.

[0008] The second object of the present invention is to provide the refractory castable prepared by the above preparation method and its application.

[0009] It is difficult for existing nickel-iron slag refractory materials to balance high dosage and high heat insulation performance, and it is necessary to reduce the dosage of nickel-iron slag and / or add auxiliary agents to improve the performance; moreover, the existing technical ideas for preparing refractory materials using nickel-iron slag are also difficult to be directly applied to the preparation of refractory castables, and it is difficult to obtain refractory castables that meet the requirements based on the preparation methods of other known refractory materials. Aiming at this industry gap, the present invention provides the following solutions:

[0010] A method for preparing heat-insulating refractory castables with nickel-iron slag. Mix nickel-iron slag particles and a binder to obtain a mixture; add mixed water to the mixture, and after stirring, casting, curing, demolding, drying, and heat treatment, the refractory castable is obtained.

[0011] The nickel-iron slag particles include particle A, particle B, particle C, and particle D with a weight ratio of 11-13:21-23:30-32:19-21.

[0012] 3mm ≤ particle size of particle A ≤ 5mm, 1mm ≤ particle size of particle B < 3mm (materials retained on a 1mm sieve and passing through a 3mm sieve), 0.15mm ≤ particle size of particle C < 1mm (materials retained on a 0.15mm sieve and passing through a 1mm sieve), and the particle size of particle D is -0.074mm (particle size less than 0.074mm).

[0013] In the mixture, the content of nickel-iron slag particles is 80-90wt.%.

[0014] The heat treatment temperature is 1230 - 1280 °C.

[0015] In view of the preparation problems that it is difficult to selectively control the phases of clinoenstatite and forsterite during the heat treatment process required for preparing heat-insulating refractory castables from nickel-iron slag, and it is difficult to balance the heat-insulating performance and flexural strength, the present invention innovatively provides a new idea for preparing refractory castables with a high content of nickel-iron slag without auxiliary agents. It innovatively realizes synergy through the combined control of the particle size distribution, the ratio between particles, the dosage, and the heat treatment temperature of the nickel-iron slag particles A, B, C, and D. In this way, it is possible to successfully prepare refractory castables with both high flexural strength and high heat-insulating performance without auxiliary agents and with a high nickel-iron slag content.

[0016] The nickel-iron slag is water-quenched slag produced by the RKEF process, and its main chemical components are: SiO 2 content ≥ 49.56 wt.%, MgO content ≥ 29.73 wt.%, FeO content ≥ 10.95 wt.%, CaO content ≤ 4.31 wt.%, Al 2 O 3 content ≤ 1.93 wt.%, Cr 2 O 3 content ≤ 1.84 wt.%.

[0017] In the present invention, the binder is calcium aluminate cement and / or hydrated alumina.

[0018] In the present invention, the particle size of the calcium aluminate cement is -0.074 mm, and the undersize is taken; Al 2 O 3 content ≥ 60 wt.%.

[0019] In the present invention, the particle size of the hydrated alumina is -0.074 mm, and the undersize is taken; Al 2 O 3 content ≥ 90 wt.%.

[0020] In the present invention, the combined control of the particle size distribution and ratio of the particles A - D is the key to synergistically solving the problem that it is difficult to prepare refractory castables without auxiliary agents and with a high nickel-iron slag content, and the mechanical and heat-insulating properties are not ideal.

[0021] Preferably, the nickel-iron slag is composed of particles A, B, C, and D, and the weight ratio of particles A - D is further preferably 11.5 - 12.5:21.5 - 22.5:30.5 - 31.5:19.5 - 20.5; more preferably 12:21:31:20.

[0022] In the present invention, the mixture is composed of nickel-iron slag and a binder.

[0023] Preferably, in the mixture, the content of the nickel-iron slag can reach 84-86wt.%.

[0024] In the present invention, the mixing water is 7-14wt.% of the total weight of the mixture.

[0025] In the present invention, the processes of mixing, casting, curing, demoulding, drying, etc. can all be achieved based on known equipment and operating principles.

[0026] Preferably, the curing time is 20 to 30 hours;

[0027] Preferably, the drying temperature is 100-120°C and the drying time is 20-30 hours;

[0028] Preferably, the heat treatment temperature is 1240-1260° C., and the heat treatment time is 2-6 hours, and can further be 2-4 hours.

[0029] The invention also provides a ferronickel slag refractory castable prepared by the method.

[0030] The present invention can unexpectedly achieve synergy through the combination of the processes and parameters, and can obtain high-dosage materials without auxiliary agents. In addition, it can unexpectedly take into account excellent flexural strength and high thermal insulation performance.

[0031] The present invention also provides an application of the nickel-iron slag refractory castable prepared by the method, which is used as a refractory or heat-insulating material.

[0032] Due to the adoption of the above technical solution, the present invention has the following positive effects:

[0033] The present invention utilizes nickel-iron slag to prepare refractory castable for the first time.

[0034] The present invention innovatively controls the particle size grading mode, proportion, dosage and heat treatment temperature of the nickel-iron slag particles A, particles B, particles C and particles D, so as to achieve synergy, selectively reduce the content of high thermal conductivity phase orthoenstatite, and increase the content of forsterite. In the absence of auxiliary agents and high nickel-iron slag dosage, refractory castables with both high flexural resistance and high thermal insulation properties can be successfully prepared.

[0035] The present invention has found that the flexural strength of the prepared material can be as high as 9.30 MPa, and the thermal conductivity can be reduced to 1.68 W / m·K at 1000°C, which can unexpectedly achieve both high flexural strength and high thermal insulation capacity.

[0036] Therefore, the present invention has the characteristics of low production cost and simple process; the prepared refractory castable has good strength and excellent heat insulation performance. Description of the Drawings

[0037] Figure 1 SEM diagrams of the refractory castables after heat treatment in Example 1 and Comparative Examples 1-3;

[0038] Figure 2 Diagrams of the main phase contents of the refractory castables after heat treatment in Example 1 and Comparative Examples 1-3;

[0039] Figure 3 Diagrams of the flexural strength and thermal conductivity of the refractory castables after heat treatment in Example 1 and Comparative Examples 1-3. Detailed Description of the Invention

[0040] The present invention will be further described in detail below in conjunction with specific examples. Obviously, the described examples are only a part of the examples of the present invention, rather than all the examples. All other examples obtained by those of ordinary skill in the art based on the examples of the present invention without creative efforts belong to the scope of protection of the present invention.

[0041] To avoid repetition, the raw materials involved in this specific implementation manner are uniformly described as follows and will not be repeated in the specific examples:

[0042] In the present invention, the main chemical components of the nickel-iron slag (particles A, B, C, D) are: SiO 2 content ≥ 49.56 wt.%, MgO content ≥ 29.73 wt.%, FeO content ≥ 10.95 wt.%, CaO content ≤ 4.31 wt.%, Al 2 O 3 content ≤ 1.93 wt.%, Cr 2 O 3 content ≤ 1.84 wt.%.

[0043] In the present invention, 3 mm ≤ particle A particle size ≤ 5 mm;

[0044] 1 mm ≤ particle B particle size < 3 mm (oversize on a 1 mm sieve, undersize on a 3 mm sieve), 0.15 mm ≤ particle C particle size < 1 mm (oversize on a 0.15 mm sieve, undersize on a 1 mm sieve); particle D particle size is -0.074 mm (particle size less than 0.074 mm)

[0045] In the present invention, the calcium aluminate cement particle size is -0.074 mm, Al 2 O 3 content ≥ 60 wt.%; the hydrated alumina particle size is -0.074 mm, Al 2 O 3 content ≥ 90 wt.%.

[0046] In the following cases, unless otherwise specified, the ratios between Particles A to D refer to weight ratios, and the ratio between the nickel - iron slag particles and the binder also refers to the weight ratio.

[0047] Example 1

[0048] 85% of nickel - iron slag particles (where the weight ratio of Particles A, B, C, and D is 12:22:31:20) and 15% of calcium aluminate cement were mixed evenly to obtain a mixture; then, water accounting for 12.25 wt.% of the total mass of the mixture was added thereto, stirred evenly, cast and vibration - formed, demolded after curing at room temperature for 24 h, dried at 110 °C for 24 h, and finally heated to 1250 °C (heat - treatment temperature) and held for 3 h.

[0049] The refractory castable prepared with nickel - iron slag as the main raw material in this example was measured: the bulk density was 2.45 g / cm 3 , the apparent porosity was 20.67%, the water absorption was 8.45%, the linear shrinkage rate was - 0.36%, the flexural strength was 9.30 MPa, and the thermal conductivity at 1000 °C was 1.68 W / m·K.

[0050] Example 2

[0051] Compared with Example 1, the difference is only that the preparation parameters were changed, and the experimental components were as follows:

[0052] Group A: The weight ratio of Particles A, B, C, and D was 13:21:30:21; in the mixture, the weight content of nickel - iron slag particles was 85 wt.%; the heat - treatment temperature was 1260 °C, and the time was 2.5 h;

[0053] Group B: The weight ratio of Particles A, B, C, and D was 11:23:32:19; in the mixture, the weight content of nickel - iron slag particles was 85 wt.%; the heat - treatment temperature was 1240 °C, and the time was 3.5 h;

[0054] Tested according to the method of Example 1, the results were as follows:

[0055] Group A: The flexural strength was 9.10 MPa, and the thermal conductivity at 1000 °C was 1.61 W / m·K;

[0056] Group B: The flexural strength was 8.90 MPa, and the thermal conductivity at 1000 °C was 1.69 W / m·K;

[0057] Comparative Example 1

[0058] Compared with Example 1, the difference is only that in the nickel - iron slag particles, the weight ratio of Particles A, B, C, and D was 15:27:38:5. Other operations and parameters were the same as those in Example 1.

[0059] In this embodiment, the refractory castable prepared with nickel - iron slag as the main raw material was measured: the bulk density is 2.32 g / cm 3 , the apparent porosity is 23.13%, the water absorption rate is 10.64%, the linear shrinkage rate is 0.88%, the flexural strength is 2.42 MPa, and the thermal conductivity at 1000 °C is 1.46 W / m·K. It is impossible to achieve both flexural strength and heat insulation under a large dosage without additives.

[0060] Comparative Example 2

[0061] Compared with Example 1, the difference is only that in the nickel - iron slag particles, the weight ratio of particle A, particle B, particle C, and particle D is 14:26:35:10. Other operations and parameters are the same as those in Example 1.

[0062] In this embodiment, the refractory castable prepared with nickel - iron slag as the main raw material was measured: the bulk density is 2.37 g / cm 3 , the apparent porosity is 22.75%, the water absorption rate is 9.78%, the linear shrinkage rate is 0.46%, the flexural strength is 4.29 MPa, and the thermal conductivity at 1000 °C is 1.75 W / m·K. It is impossible to achieve both flexural strength and heat insulation under a large dosage without additives.

[0063] Comparative Example 3

[0064] Compared with Example 1, the difference is only that in the nickel - iron slag particles, the weight ratio of particle A, particle B, particle C, and particle D is 13:24:33:15. Other operations and parameters are the same as those in Example 1.

[0065] In this embodiment, the refractory castable prepared with nickel - iron slag as the main raw material was measured: the bulk density is 2.43 g / cm 3 , the apparent porosity is 21.14%, the water absorption rate is 9.19%, the linear shrinkage rate is - 0.26%, the flexural strength is 7.62 MPa, and the thermal conductivity at 1000 °C is 1.92 W / m·K. It is impossible to achieve both flexural strength and heat insulation under a large dosage without additives.

[0066] Comparative Example 4

[0067] Other conditions are the same as those in Example 1, except that the heat treatment temperature is changed to 1200 °C.

[0068] The refractory castable obtained in this case was measured: the bulk density is 2.23 g / cm 3, the apparent porosity is 22.93%, the water absorption rate is 10.11%, the linear shrinkage rate is 0.42%, the flexural strength is 2.38 MPa, and the thermal conductivity at 1000 °C is 1.76 W / m·K. It is impossible to achieve both flexural strength and heat insulation under a large admixture without additives.

[0069] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced by the present invention.

[0070] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementation solutions that can be understood by those skilled in the art.

Claims

1. A method for preparing heat-insulating refractory castable from nickel-iron slag, characterized in that: Mix nickel-iron slag particles and a binder evenly to obtain a mixture composed of nickel-iron slag particles and a binder; Add mixed water to the mixture, and after stirring, casting and forming, curing, demolding, drying, and heat treatment, the refractory castable is obtained; The nickel-iron slag particles are composed of particle A, particle B, particle C, and particle D with a weight ratio of 11~13:21~23:30~32:19~21; 3mm ≤ particle A particle size ≤ 5 mm, 1mm ≤ particle B particle size < 3 mm, 0.15mm ≤ particle C particle size < 1 mm, particle D particle size ≤ 0.074 mm; In the mixture, the content of nickel-iron slag particles is 84~86 wt.%; The heat treatment temperature is 1230~1280 °C; The nickel-iron slag is water-quenched slag produced by the RKEF process, and its main chemical components are: SiO 2 content ≥ 49.56 wt.%, MgO content ≥ 29.73 wt.%, FeO content ≥ 10.95 wt.%, CaO content ≤ 4.31 wt.%, Al 2 O 3 content ≤ 1.93 wt.%, Cr 2 O 3 content ≤ 1.84 wt.%.

2. The method for preparing heat-insulating refractory castable from nickel-iron slag according to claim 1, characterized in that: In the nickel-iron slag, the weight ratio of particle A to particle D is 11.5~12.5:21.5~22.5:30.5~31.5:19.5~20.

5.

3. The method for preparing heat-insulating refractory castable from nickel-iron slag according to claim 1, characterized in that: The binder is calcium aluminate cement and / or hydrated alumina.

4. The method for preparing heat-insulating refractory castable from nickel-iron slag according to claim 3, characterized in that: The particle size of the calcium aluminate cement is ≤ 0.074 mm, and the undersize material is taken; Al 2 O 3 content ≥ 60 wt.%. The particle size of the hydrated alumina is ≤ 0.074 mm, and the material passing through the sieve is taken; the Al 2 O 3 content is ≥ 90 wt.%.

5. The method for preparing heat-insulating refractory castable from nickel-iron slag according to claim 1, characterized in that: The mixed water is 7~14 wt.% of the total weight of the mixture.

6. The method for preparing heat-insulating refractory castable from nickel-iron slag according to claim 1, characterized in that: The curing time is 20~30 hours.

7. The method for preparing heat-insulating refractory castable from nickel-iron slag according to claim 1, characterized in that: The drying temperature is 100~120 °C, and the drying time is 20~30 hours.

8. The method for preparing heat-insulating refractory castable from nickel-iron slag according to claim 1, characterized in that: The heat treatment temperature is 1240~1260 °C, and the heat treatment time is 2~6 hours.

9. A heat-insulating refractory castable prepared from nickel-iron slag, characterized in that, It is prepared by the method according to any one of claims 1~8.

10. The application of the heat-insulating refractory castable prepared by the method according to any one of claims 1~8, characterized in that, Use it as a refractory or heat-insulating material.

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