Lightweight thermal insulation materials are materials with a porous structure, which have the characteristics of low volume density, high porosity, and low thermal conductivity, and can effectively block the transfer of heat. However, its strength is not high, and its corrosion resistance is poor. It is mostly used in non-load-bearing structures such as permanent layers and thermal insulation layers or parts that are not in contact with solutions. Lightweight thermal insulation materials were first proposed by some countries in the United States and Western Europe. Studies have found that this material can effectively improve the utilization rate of heat energy and reduce heat loss. Therefore, it has been rapidly promoted, and the research enthusiasm for it has also continued to increase.
1. Hydrophobic thermal insulation material
The thermal insulation material is a material with a porous structure. Due to different preparation processes, its pores can be divided into three types: connected pores, semi-closed pores and closed pores. The pores in most materials are connected and semi-closed, and there are few closed pores. Connected pores and semi-closed pores are easy to form capillary penetration and water absorption, resulting in moisture in the insulation material, which is difficult to remove. However, the thermal conductivity of water at normal temperature is 23 times that of air, and the thermal insulation performance of the thermal insulation material will be greatly reduced after absorbing water, and it is also very harmful to the material itself. At present, most heat insulation materials are not hydrophobic. In order to prevent the heat insulation materials from getting damp, they are often packaged specially, which invisibly increases the cost. How to make the material itself hydrophobic has become a new research trend of thermal insulation materials.
2. Environmentally friendly thermal insulation materials
With the increasing awareness of energy saving and environmental protection, higher requirements are put forward for lightweight heat insulation materials. While superior performance is required, it is also required that it will not cause harm to the human body and the environment. Environmentally friendly refractory materials are proposed under this background, which requires that refractory materials will not produce carcinogens and toxic substances that are harmful to the environment and human body during the production process and use process.
For example, magnesia-chromium material is used as the most important refractory material in the firing zone of large-scale cement rotary kiln and copper smelting industry. Although it has good performance in all aspects, in the use project, Cr3+ is converted into Cr6+, and Cr6+ is poisonous and soluble in water. It will cause harm to the human body, and it will also cause environmental pollution and groundwater pollution. In order to solve this problem, Japan has studied the use of MgO-TiO2-Al2O3 raw materials to replace magnesium-chromium materials. The performance of this material is comparable to that of magnesium-chromium materials. The ratio is not inferior, and it has an appropriate apparent porosity and better resistance to slag erosion.
