Preparation method of thermal insulation material prepared from waste ceramic

Abstract

The invention discloses a preparation method of a thermal insulation material prepared from waste ceramic, which specifically comprises the following steps: taking waste alumina ceramic as a raw material, taking common crop waste as a pore-forming agent, and carrying out crushing, mixing, forming and heat treatment to obtain the thermal insulation material. The used raw materials are all waste materials, so that the preparation cost is greatly saved, the ore extraction pressure is relieved, and meanwhile, a reference basis is provided for reutilization of waste aluminum oxide and crop waste materials. The prepared thermal insulation material is low in density, high in strength and excellent in thermal insulation performance, and has a wide prospect in the field of high-temperature thermal insulation.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of heat-insulating materials, and particularly relates to a preparation method of a heat-insulating material prepared from waste ceramics. Background Art

[0002] Heat-insulating materials refer to a class of materials used in high-temperature environments to block the transfer of heat flow, and have characteristics such as a high porosity, a low thermal conductivity, and a low heat capacity. Therefore, they are widely used in the field of thermal industrial furnaces. According to the different service temperatures, heat-insulating materials can be subdivided into low-temperature heat-insulating materials (<600 °C), medium-temperature heat-insulating materials (600 - 1200 °C), and high-temperature heat-insulating materials (>1200 °C). High-temperature heat-insulating materials generally include three types: alumina-based, mullite-based, and zirconia-based. Among them, alumina-based heat-insulating materials have become the most widely used high-temperature heat-insulating materials at present due to their wide range of raw material sources and diverse preparation processes.

[0003] Bauxite is the main ore raw material used to prepare alumina-based heat-insulating materials. However, due to years of disorderly exploitation, high-quality bauxite is almost exhausted, which not only causes waste of ore resources but also leads to high prices and increased raw material costs. In addition, if organic pore-forming agents are used in the most commonly used pore-forming agent method for preparing alumina-based heat-insulating materials, it will also cause problems such as environmental pollution. Summary of the Invention

[0004] The present invention aims to overcome the defects existing in the prior art. The purpose is to save bauxite ore resources, reduce the preparation cost of alumina-based heat-insulating materials, and at the same time improve the potential harm of the pore-forming agent method to the environment. Specifically, a heat-insulating material prepared from waste ceramics and its preparation method are provided. The present invention uses waste alumina as the raw material and crop waste (rice husk, straw, peanut shell, bagasse, wood chip) as the pore-forming agent, and uses the pore-forming agent method to produce low-cost and high-performance alumina-based heat-insulating materials.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] Step 1: Crush waste alumina and crop waste pore-forming agents to below 75 μm (pass through a 200-mesh sieve) respectively;

[0007] Step 2: Mix waste alumina powder and crop waste pore-forming agent evenly according to 60% - 80% and 20% - 40% by mass fraction;

[0008] Step 3: Press the mixed powder into a green body at 10 - 30 MPa;

[0009] Step 4: Calcinate the green body at 1100 - 1300 °C for 1 - 3 h, and cool it with the furnace to obtain an alumina-based heat-insulating material.

[0010] Further, the waste alumina in Step 2 is one or more of waste abrasives, waste furnace tubes, waste crucibles, waste thermocouple protection tubes, and waste electrical insulation substrates with the main component being alumina phase;

[0011] Further, the crop waste in Step 3 is one or more of rice husks, straws, peanut shells, bagasse, and wood chips;

[0012] Further, the heating rate parameters for the calcination treatment in Step 4 are specifically 10 °C / min when <400 °C, 3 °C / min when 400 - 1000 °C, and 10 °C / min when >1000 °C.

[0013] The carbonization and decomposition of crop waste are concentrated in the temperature range of 400 - 1000 °C. If the heating rate is too fast, the process of gasification and discharge of the pore-forming agent is blocked, which easily makes the internal pore distribution and size uneven, and even forms large crack defects, ultimately resulting in insufficient product performance. If the heating rate is too slow, on the one hand, it will increase energy consumption, and on the other hand, it will prolong the process time. Therefore, considering both energy consumption and product performance, the preferred heating rate parameters for the calcination treatment in the present invention are specifically 10 °C / min when <400 °C, 3 °C / min when 400 - 1000 °C, and 10 °C / min when >1000 °C.

[0014] The present invention discloses the following technical effects:

[0015] From the perspective of resource utilization, both the raw materials and additives in the present invention are solid wastes with relatively large current production. Combining the two to make heat-insulating materials not only turns waste into treasure and saves valuable ore (bauxite) resources, but also reduces the pollution pressure of the used solid wastes on the environment and land. At the same time, it also has certain reference value for the treatment and resource utilization of industrial and agricultural solid wastes.

[0016] From the perspective of the preparation process, the preparation process and flow of the present invention are basically the same as those of the traditional pore-forming agent method, without any additional processes required, and in some aspects, it is superior to the traditional method. Firstly, the present invention uses crop waste to replace the traditional chemical reagent pore-forming agent, which is harmless to the environment and human body; secondly, the used crop waste itself has good adhesiveness, so it saves the binder cost compared with the traditional method and omits the drying and debinding process.

[0017] The performance indexes of the alumina-based heat-insulating material prepared by the present invention through national standard tests are as follows: the apparent porosity is 52% - 73%, the bulk density is 1.12 - 1.55 g / cm 3 , the cold crushing strength at room temperature is 2.4 - 13.1 MPa, and the maximum value of the thermal conductivity from 25 - 1200 °C is 0.62 - 0.95 W / (m·K). Specific Embodiments

[0018] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be construed as a limitation on the present invention, but rather as a more detailed description of certain aspects, features, and implementation schemes of the present invention.

[0019] Example 1

[0020] Step 1: Crush waste alumina (waste alumina furnace tubes) and crop waste pore-forming agent (rice husks) to below 75 μm (pass through a 200-mesh sieve) respectively;

[0021] Step 2: Mix the crushed and screened waste alumina powder and crop waste pore-forming agent evenly according to 80% and 20% by mass fraction;

[0022] Step 3: Press the mixed powder into a green body at 10 MPa;

[0023] Step 4: Heat the green body to 1100 °C at a heating rate of <400 °C at 10 °C / min, 400 - 1000 °C at 3 °C / min, and >1000 °C at 10 °C / min, and calcine for 1 h, then cool with the furnace to obtain an alumina-based thermal insulation material.

[0024] After testing, the performance indicators of the alumina-based thermal insulation material prepared in this example are as follows: apparent porosity is 73%, bulk density is 1.12 g / cm 3 , cold compressive strength is 2.4 MPa, and the maximum value of the thermal conductivity from 25 to 1200 °C is 0.62 W / (m·K).

[0025] Example 2

[0026] Step 1: Crush waste alumina (waste alumina crucibles) and crop waste pore-forming agent (a 1:1 mixture of rice husks and straw) to below 75 μm (pass through a 200-mesh sieve) respectively;

[0027] Step 2: Mix the crushed and screened waste alumina powder and crop waste pore-forming agent evenly according to 80% and 20% by mass fraction;

[0028] Step 3: Press the mixed powder into a green body at 20 MPa;

[0029] Step 4: Heat the green body to 1200 °C at a heating rate of <400 °C at 10 °C / min, 400 - 1000 °C at 3 °C / min, and >1000 °C at 10 °C / min, and calcine for 2 h, then cool with the furnace to obtain an alumina-based thermal insulation material.

[0030] After testing, the performance indicators of the alumina-based thermal insulation material prepared in this example are as follows: apparent porosity is 65%, bulk density is 1.19 g / cm 3, the normal temperature compressive strength is 4.8 MPa, and the maximum value of the thermal conductivity at 25 - 1200 °C is 0.76 W / (m·K).

[0031] Example 3

[0032] Step 1: Crush waste alumina (waste alumina abrasive) and crop waste pore-forming agent (a mixture of rice husk and straw with a mass ratio of 1:1) to below 75 μm (passing through a 200-mesh sieve);

[0033] Step 2: Mix the crushed and screened waste alumina powder and crop waste pore-forming agent evenly according to 70% and 30% by mass fraction;

[0034] Step 3: Press the mixed powder into a green body at 20 MPa;

[0035] Step 4: Heat the green body to 1200 °C at a heating rate of <400 °C at 10 °C / min, 400 - 1000 °C at 3 °C / min, and >1000 °C at 10 °C / min for calcination for 2 h, and cool it in the furnace to obtain an alumina-based thermal insulation material.

[0036] After testing, the performance indexes of the alumina-based thermal insulation material prepared in this example are as follows: the apparent porosity is 69%, the bulk density is 1.17 g / cm 3 , the normal temperature compressive strength is 4.2 MPa, and the maximum value of the thermal conductivity at 25 - 1200 °C is 0.72 W / (m·K).

[0037] Example 4

[0038] Step 1: Crush waste alumina (waste thermocouple protection tube) and crop waste pore-forming agent (peanut shell) to below 75 μm (passing through a 200-mesh sieve);

[0039] Step 2: Mix the crushed and screened waste alumina powder and crop waste pore-forming agent evenly according to 70% and 30% by mass fraction;

[0040] Step 3: Press the mixed powder into a green body at 30 MPa;

[0041] Step 4: Heat the green body to 1250 °C at a heating rate of <400 °C at 10 °C / min, 400 - 1000 °C at 3 °C / min, and >1000 °C at 10 °C / min for calcination for 3 h, and cool it in the furnace to obtain an alumina-based thermal insulation material.

[0042] After testing, the performance indexes of the alumina-based thermal insulation material prepared in this example are as follows: the apparent porosity is 67%, the bulk density is 1.21 g / cm 3 , the normal temperature compressive strength is 4.9 MPa, and the maximum value of the thermal conductivity at 25 - 1200 °C is 0.74 W / (m·K).

[0043] Example 5

[0044] Step 1: Crush waste alumina (waste thermocouple protection tube) and crop waste pore former (wood chips) to below 75 μm (pass through a 200-mesh sieve);

[0045] Step 2: Mix the crushed and screened waste alumina powder and crop waste pore former evenly according to 70% and 30% by mass fraction;

[0046] Step 3: Press the mixed powder into a green body at 20 MPa;

[0047] Step 4: Heat the green body to 1300 °C at a heating rate of <400 °C at 10 °C / min, 400 - 1000 °C at 3 °C / min, and >1000 °C at 10 °C / min, and calcine for 3 h, then cool with the furnace to obtain an alumina-based thermal insulation material.

[0048] After testing, the performance indexes of the alumina-based thermal insulation material prepared in this example are as follows: apparent porosity is 61%, bulk density is 1.29 g / cm 3 , the cold crushing strength at room temperature is 6.1 MPa, and the maximum value of the thermal conductivity from 25 to 1200 °C is 0.81 W / (m·K).

[0049] Example 6

[0050] Step 1: Crush waste alumina (waste electrical insulation substrate) and crop waste pore former (bagasse) to below 75 μm (pass through a 200-mesh sieve);

[0051] Step 2: Mix the crushed and screened waste alumina powder and crop waste pore former evenly according to 60% and 40% by mass fraction;

[0052] Step 3: Press the mixed powder into a green body at 30 MPa;

[0053] Step 4: Heat the green body to 1300 °C at a heating rate of <400 °C at 10 °C / min, 400 - 1000 °C at 3 °C / min, and >1000 °C at 10 °C / min, and calcine for 1 h, then cool with the furnace to obtain an alumina-based thermal insulation material.

[0054] After testing, the performance indexes of the alumina-based thermal insulation material prepared in this example are as follows: apparent porosity is 63%, bulk density is 1.25 g / cm 3 , the cold crushing strength at room temperature is 5.4 MPa, and the maximum value of the thermal conductivity from 25 to 1200 °C is 0.77 W / (m·K).

[0055] Example 7

[0056] Step 1: Crush waste alumina (a 1:1 mass ratio mixture of waste electrical insulation substrates and waste furnace tubes) and the pore-forming agent made from agricultural waste (bagasse) to below 75 μm (passing through a 200-mesh sieve).

[0057] Step 2: Mix the crushed and screened waste alumina powder and the agricultural waste pore-forming agent evenly at 80% and 20% by mass fraction.

[0058] Step 3: Press the mixed powder into a green body at 10 MPa.

[0059] Step 4: Heat the green body to 1300 °C at a heating rate of <400 °C at 10 °C / min, 400 - 1000 °C at 3 °C / min, and >1000 °C at 10 °C / min, and calcine for 2 h, then cool with the furnace to obtain the alumina-based thermal insulation material.

[0060] After testing, the performance indicators of the alumina-based thermal insulation material prepared in this example are as follows: the apparent porosity is 55%, the bulk density is 1.51 g / cm 3 , the normal temperature compressive strength is 10.2 MPa, and the maximum value of the thermal conductivity from 25 to 1200 °C is 0.91 W / (m·K).

[0061] Example 8

[0062] Step 1: Crush waste alumina (waste electrical insulation substrates) and the pore-forming agent made from agricultural waste (a 1:1 mass ratio mixture of bagasse and rice husk) to below 75 μm (passing through a 200-mesh sieve).

[0063] Step 2: Mix the crushed and screened waste alumina powder and the agricultural waste pore-forming agent evenly at 80% and 20% by mass fraction.

[0064] Step 3: Press the mixed powder into a green body at 30 MPa.

[0065] Step 4: Heat the green body to 1300 °C at a heating rate of <400 °C at 10 °C / min, 400 - 1000 °C at 3 °C / min, and >1000 °C at 10 °C / min, and calcine for 3 h, then cool with the furnace to obtain the alumina-based thermal insulation material.

[0066] After testing, the performance indicators of the alumina-based thermal insulation material prepared in this example are as follows: the apparent porosity is 52%, the bulk density is 1.55 g / cm 3 , the normal temperature compressive strength is 13.1 MPa, and the maximum value of the thermal conductivity from 25 to 1200 °C is 0.95 W / (m·K).

[0067] In addition, the above embodiments are examples to illustrate the technical content of the present invention, rather than limiting the implementation manners of the present invention. Any technical extension or re-creation made according to the present invention falls within the protection scope of the present invention.

Claims

1. A method for preparing a thermal insulation material using waste ceramics, characterized in that: The following steps are involved: (1) crushing the waste alumina and the crop waste pore-forming agent to less than 75 μm respectively; (2) mixing waste alumina powder and crop waste pore-forming agent in mass fractions of 60% to 80% and 20% to 40% respectively; (3) pressing the mixed powder into a green compact at 10-30 MPa; (4) calcining the green body at 1100-1300° C. for 1-3 h and cooling the furnace to obtain an alumina thermal insulation material.

2. The preparation method according to claim 1, characterized in that: The waste alumina in step (1) is one or more of waste abrasives, waste furnace tubes, waste crucibles, waste thermocouple protection tubes, and waste electrical insulating substrates whose main components are alumina phase.

3. The preparation method according to claim 1, characterized in that: The crop waste in step (1) is one or more of rice husks, straws, peanut shells, bagasse, and sawdust.

4. The preparation method according to claim 1, characterized in that: The heating parameters of the calcination treatment in step (4) are: 10°C / min for temperatures <400°C, 3°C / min for temperatures between 400 and 1000°C, and 10°C / min for temperatures >1000°C.