Since the 1980s, both domestically and internationally, the steel industry has vigorously developed refining technologies for steelmaking to further reduce production costs and enhance steel quality. Through years of research and practical application, significant advancements have been made in the treatment of steelmaking molten steel, leading to continuous improvement in refining techniques. Simultaneously, refining processes have not only extended the transportation time of molten steel and increased operational steps but have also considerably reduced the temperature of the molten steel. This decrease in steel temperature directly impacts the smooth operation of continuous casting and other procedures.
Modern steelmaking technologies demand that the steel ladle serves as more than just a simple transportation vessel. This necessitates the use of more modern refractory materials in steel ladles to meet the stringent requirements of the steelmaking process.
In general steelmaking plants, the permanent lining of ladles usually employs castables or refractory materials like firebricks. However, these refractory materials have high thermal conductivity. On-site measurements show that the average temperature of the ladle’s outer shell walls reaches approximately 250℃ to 330℃. This leads to significant heat loss, thermal deformation, and damage to the ladle shell. Moreover, the service life of the working and permanent linings is not high, failing to ensure the uniformity of molten steel temperature as required.
Therefore, improving ladle insulation, reducing the thickness of refractory materials in the ladle lining, increasing the effective volume of the ladle, enhancing steel ladle capacity, and enlarging the ladle’s net clear height are crucial aspects in steelmaking production.
In recent years, the emergence of nano-microporous insulation materials has played a significant role in the steel industry by replacing traditional ladle linings with high-temperature energy-saving linings. This advancement has led to reduced energy consumption, minimized the thickness of refractory materials in ladle linings, increased the effective volume of ladles, enhanced steel ladle capacity, and notably decreased or eliminated incidents of ladle slagging, thus contributing significantly to the steelmaking process.
1.Introduction to Nano-porous Insulation Materials
Nano-microporous insulation board is a newly developed, highly efficient thermal insulation material based on the principle of nano-micropores. Comprised primarily of silica dioxide particles ranging from 7 to 12 nanometers, it forms countless nanoscale micropores within, supplemented by highly efficient infrared reflective components. This material maximally suppresses heat conduction, convection, and radiation, possessing a thermal conductivity even lower than stagnant air. Its thermal insulation performance is 3 to 6 times better than traditional materials, making it one of the most efficient high-temperature thermal insulation materials available to date. This product comes in various forms such as flat panels, roll curtains, blocks, flexible blankets, etc. Flat panels are suitable for flat furnace walls or walls with less curvature, while roll curtains are mainly used in piping systems.
Figure 1:Nano-porous Insulation Material in Various Packaging Forms
2.The main characteristics of nano-porous insulation materials
Low thermal conductivity: The thermal insulation performance is 3-4 times better than traditional materials (as shown in Figure 2), which can reduce equipment energy consumption, decrease the required insulation layer thickness/weight, or provide larger equipment effective capacity.
Excellent thermal properties: It has low specific heat and minimal heat retention, withstands thermal shocks, and can be used for an extended period without external force damage.
Environmentally friendly: It does not contain harmful fiber components and complies with domestic and international environmental standards.
Ease of installation: It can be secured to the ladle using tape or refractory mortar in ladle applications.
Non-combustibility: This product is non-combustible.
3.The main role of nano-porous insulation materials in the steel industry
Reduce heat loss and energy consumption; Improve the working environment within the factory; Prolong equipment lifespan; Decrease insulation layer thickness, increase internal volume, or reduce equipment size; Minimize the heat retention of the insulation layer, enhancing the rate of temperature rise.
4.Application Introduction
4.1Steel ladle
Method of use: Clean the interior walls of the ladle and apply a layer of adhesive to the ladle wall. Apply MIP-950S first, followed by the construction of the permanent layer and working layer in sequence.
Figure 3: Installation Construction on the Ladle
The effects of use:
1）Reducing heat loss from the steel casing.
2）Lowering the temperature of steel produced from the converter.
3）Decreasing the amount of heat required for the baking process of the steel ladle.
4）Decreasing the temperature of the steel ladle shell, increasing its lifespan and safety.
5）Substituting thick insulating bricks, increasing the volume of molten steel the ladle can hold.
6）Reducing temperature changes affecting the refractory bricks, extending their lifespan.
7）Decreasing the consumption of permanent layer materials, reducing the weight of the steel ladle, thereby lessening the load on lifting devices and improving safety standards.
It’s worth mentioning that currently in domestic steel plants, there’s also the utilization of a material known as composite nano-reflective insulation board. This material has significantly contributed to insulation and heat retention. However, compared to nano-porous insulation materials, there’s still room for improvement, especially in terms of thermal conductivity, thermal shrinkage, and specific gravity (heat capacity). Here, we’ve outlined the differences between these two materials for the reference of our customers.
Table 1: Comparison between Nanoporous Insulation Material and Composite Reflective Insulation Board
| MIP–950 | Composite Emission Insulation Board | Remarks | |
| Low Thermal Conductivity | 600℃， ≤0.029W/K.m
800℃, ≤ 0.032 W/K.m |
600℃≤0.060W/K.m
800℃, No data |
The low thermal conductivity within the application range is half of other products, meaning significantly better energy-saving effects. |
| Cost-effectiveness | Unit area cost is similar but offers better insulation effects. | >RMB 300/m2 | More cost-effective |
| Lightweight Density, Low Specific Heat | 330kg/m3
1.08KJ/kg.K @ 800℃ |
460-550kg/m3
No data |
The material exhibits very low heat storage capacity. |
| Heating Shrinkage Rate | 950℃, ≤2%
（24hr full immersion test） |
800℃, ≤2% | Less heat loss due to heat resistance and reduced thermal shrinkage gaps. |
| Insulation Principle | Nano-micropores + Efficient Opacifiers | Nano-micropores + Aluminum Foil Reflection | |
| Notable energy-saving effects | Low thermal conductivity. Low Thermal Shrinkage Rate | Less effective in temperature reduction compared to representative nano-microporous insulation products | |
| Non-Toxic and Safe | Contains no organic adhesive components, aluminum foil melting at high temperatures is non-toxic | Pressure-sensitive adhesives have some toxicity. | |
| Simple Construction | Can be applied as a single layer or alternated in two layers | Requires two layers. | |
| Application Experience | Has been used to some extent domestically and is a direction for future development; | Several applications domestically but exhibits significantly lower cooling effects compared to reported values from foreign sources. | |
| Others | Similar products are widely used in the foreign steel industry; efforts are underway for domestic production; | Developed domestically in 2004, limited applications only within the country. |
4.2 Tundish
The method of use：lay a layer of insulating board (5-10mm) on the inner side of the ladle, avoiding the steel nails on the ladle wall, and then install the castable material (Figure 5). The effect of use includes reducing heat loss during continuous casting, minimizing fluctuations in molten steel temperature, and improving the quality of continuous casting.
Figure 5: Installation Process on the Tundish
4.3 Torpedo casing
Usage: Apply a layer (5-10mm) on the inner side of the torpedo casing, then lay firebrick. (See Figure 6)
Effectiveness: Reduces heat loss during iron transportation, increases the temperature of iron reaching the converter (typically by around 40 degrees). Reduces converter energy consumption and creates conditions for the selected dephosphorization treatment during torpedo casing transportation.”
Figure 5: Installation Process on the Torpedo casing
4.4 hot air pipeline
Usage: Install several layers of roller blinds-type insulation material on the inner side of the pipeline, then install firebricks or castables.
Effectiveness: Reduces heat loss, increases the temperature of hot air entering the blast furnace, and enhances the efficiency of the hot blast stove.
4.5 RH Degassing Unit
Method of use: Affix the nano-porous insulating board to the inner side of the furnace wall (5-10mm), then install the castable material.
Effectiveness: Reduces the heat loss of the steel liquid during the circulation process.
Figure 7: RH Degassing Unit
4.6 Step-type heating furnace water-cooled column
The method of use: Wrap two layers of 5mm thick soft felt around the water-cooled pipe and secure it, then install the casting material.
The effect of use: Compared with using ceramic fiber insulation layer, the heat taken away by the cooling water is reduced by approximately 24%. As nearly 15% of the energy in the step-type heating furnace is dissipated by the cooling water, the use of nano-porous insulation material significantly improves energy efficiency.
5 Conclusion
As the application technology of nano-porous insulation materials continues to mature, their successful implementation in some foreign steel plants in recent years has proven the material’s significant role in energy conservation and emission reduction. With the decrease in material costs, enhanced awareness of energy conservation and environmental protection among enterprises, and the improvement of relevant national standards, the application of nano-porous insulation materials in the steel industry is expected to become increasingly widespread.
