In the field of modern high-temperature industry, refractories play an indispensable role, and they are the key line of defense to ensure the normal operation of various high-temperature equipment. Among them, unshaped refractories, with its unique advantages, are gradually becoming the focus of attention in the industry, providing efficient, flexible and reliable high-temperature protection solutions for many industrial production processes.

I. Definition and classification of unshaped refractories

Monolithic Refractories is a kind of refractory which does not need to be fired, and is in the form of loose or slurry. Compared with traditional shaped refractories (such as refractory bricks), it has higher construction flexibility and adaptability. According to its construction methods and performance characteristics, unshaped refractories are mainly divided into the following categories:

(1) Refractory castable

Refractory castable is one of the most widely used unshaped refractories. It is a mixture of refractory aggregate, powder, binder and additive in a certain proportion, and it is molded by pouring during construction. It has high strength, high wear resistance and good corrosion resistance, and is suitable for various high-temperature environments, such as ladle, tundish, heating furnace, etc. According to different chemical composition and application requirements, refractory castable can be divided into clay castable, high alumina castable, silica castable, corundum castable and so on. For example, because of its high aluminum content, high-alumina castable has higher fire resistance and slag resistance, and is often used in parts with higher requirements on fire resistance.

(2) plastic refractory

Plastic refractory is an unshaped refractory with high plasticity, which is mainly composed of refractory aggregate, powder, plastic clay and additives. It can be formed by hand or machinery during construction, which has good construction adaptability and can meet the construction requirements of complex shape parts. Plastic refractory has high strength and good corrosion resistance after drying, and is often used for repairing and constructing furnace walls and roofs. It is characterized by convenient construction, rapid molding and stable performance at high temperature, which has important application value for some high-temperature equipment that needs rapid repair.

(3) Tamping materials

Ramming material is an unshaped refractory which needs to be compacted by strong ramming, and it is mainly composed of coarse aggregate, fine aggregate, powder and binder. It is characterized by high bulk density and good corrosion resistance, and can bear large mechanical stress and thermal stress. Tamping materials are mainly used in the parts that bear heavy load, such as the bottom of blast furnace and the bottom of hot metal ladle. During the construction process, the ramming material can be tightly filled in all parts of the equipment by strong ramming, forming a solid refractory layer, effectively preventing the high-temperature melt from eroding and damaging the equipment.

(4) paint spraying

Paint spraying is a kind of unshaped refractory which is sprayed onto the construction surface by a spray gun. It has the advantages of fast construction speed, uniform coating and adjustable thickness, and can quickly repair and protect the lining of high-temperature equipment. Paint spraying can adjust its composition and performance according to different use requirements and construction environment to meet various complicated high-temperature working conditions. For example, in the lining repair of some large industrial furnaces, paint spraying can quickly form a uniform refractory coating, which can effectively prevent the high-temperature flame and melt from eroding the lining and prolong the service life of the equipment.

II. Advantages of unshaped refractories

The reason why unshaped refractories can be widely used in high-temperature industry is mainly due to their unique advantages in the following aspects:

(1) high construction flexibility

Compared with traditional shaped refractories, unshaped refractories have higher flexibility in the construction process. They can be constructed on site according to the shape and size of the equipment, without precast bricks, and can better adapt to high-temperature equipment with complex shapes. For example, in the lining construction of some large industrial furnaces, the refractory castable can easily fill all corners of the equipment by pouring molding, forming an integral refractory layer, effectively avoiding the appearance of weak links such as brick joints, and improving the sealing performance and overall performance of the equipment. This flexibility in construction makes amorphous refractories more widely used in some special-shaped equipment and complex working conditions, and can meet the needs of different industrial production.

(2) Good overall performance

The unshaped refractory material forms an integral refractory layer after construction, and there are no weak links such as brick joints, so it has better overall performance. This integrity can effectively prevent high-temperature melt and flame from eroding the equipment through brick joints, improve the sealing and thermal insulation performance of the equipment, reduce heat loss and reduce energy consumption. At the same time, the refractory layer with good overall performance can better disperse stress and reduce stress concentration when it bears thermal stress and mechanical stress, thus prolonging the service life of equipment. For example, in the lining construction of some large ladles, the integral refractory layer formed after the construction of refractory castable can effectively withstand the high temperature and mechanical impact of molten steel, reduce the erosion and damage of ladles, and improve the service life and safety of ladles.

(3) Rapid construction and repair

The construction speed of unshaped refractory is fast, and the lining construction or repair of equipment can be completed in a short time. This is of great significance for some high-temperature equipment that needs to resume production quickly. For example, in paint spraying, refractory materials can be quickly sprayed onto the surface of equipment by a spray gun to form a uniform refractory coating, which greatly shortens the construction time. At the same time, the rapid repair ability of unshaped refractories can also effectively reduce the downtime of equipment and improve production efficiency. In the case of some sudden equipment damage, such as severe local erosion of furnace wall, plastic refractory or paint spraying can quickly carry out local repair, so that the equipment can resume production as soon as possible and reduce production losses.

(4) strong customization

Unshaped refractories can be customized according to different use requirements and working conditions. By adjusting its chemical composition, particle size distribution and the type and dosage of additives, the requirements of various high-temperature equipment on fire resistance, wear resistance and corrosion resistance can be met. For example, for some parts that need high wear resistance, the wear resistance of unshaped refractories can be improved by increasing the content of wear-resistant aggregate; For some parts with high anti-erosion requirements, the anti-erosion ability can be enhanced by adding anti-erosion additives. This customization enables unshaped refractories to better meet the needs of different industrial production and provide more accurate protection for various high-temperature equipment.

III. Application fields of unshaped refractories

With its unique advantages, unshaped refractories have been widely used in many high-temperature industrial fields. The following are some main application fields:

(1) Metallurgical industry

Metallurgical industry is one of the largest application fields of unshaped refractories. In the process of iron and steel production, unshaped refractories are needed to protect equipment from high-temperature melt erosion, from the bottom and hearth of ironmaking blast furnace to the lining of steelmaking converter, and then to ladle and tundish. For example, the bottom and hearth of blast furnace are subjected to great pressure and erosion of high-temperature molten iron, and the bottom and hearth constructed by ramming materials have high volume density and corrosion resistance, which can effectively prolong the service life of blast furnace; The lining of converter mostly adopts refractory castable, which has high strength, high wear resistance and good slag resistance, and can withstand the erosion and erosion of molten steel and slag; Ladle and tundish linings need good thermal insulation and corrosion resistance to ensure the quality and temperature of molten steel. Refractory castable and paint spraying are widely used in these parts.

(2) Petrochemical industry

High temperature equipment in petrochemical industry, such as cracking furnace, reforming furnace, heating furnace, etc., also need to use amorphous refractory to protect the equipment. These equipments operate in the environment of high temperature, high pressure and corrosive gas, which requires high corrosion resistance and thermal shock resistance of refractories. Unshaped refractories can be customized according to different furnace types and working conditions to meet the special needs of petrochemical equipment. For example, on the outer wall of the furnace tube of the cracking furnace, the insulation layer constructed with refractory castable can effectively reduce heat loss and improve cracking efficiency; In the lining of the reformer, paint spraying can quickly form a uniform refractory coating to protect the lining from high temperature gas.

(3) Building materials industry

In the building materials industry, high-temperature equipment such as glass kiln and cement rotary kiln is the key equipment in the production process. Unshaped refractories have also been widely used in these equipments. For example, the melting pool and runner of glass kiln need to use unshaped refractory with high refractoriness and corrosion resistance to ensure the normal melting and molding of glass; The lining of cement rotary kiln needs to have good erosion resistance and wear resistance to withstand the erosion and erosion of high temperature clinker. Unshaped refractories can be adjusted and optimized according to different kiln types and working conditions, which provides reliable guarantee for the stable operation of high-temperature equipment in building materials industry.

(4) Other fields

In addition to the above main application fields, unshaped refractories have also been applied in ceramics, casting, machining and other industries. For example, in the ceramic firing kiln, unshaped refractory can be used for the construction of kiln car and kiln lining to ensure the firing quality of ceramic products; In the foundry industry, unshaped refractories can be used to make sand boxes, gating systems, etc., to improve casting quality and production efficiency; In the mechanical processing industry, unshaped refractories can be used to manufacture the lining of high-temperature stoves, heat treatment furnaces and other equipment to meet the high-temperature demand in the mechanical processing process.

IV. Development trend of unshaped refractories

With the continuous development of high-temperature industry and the improvement of performance requirements for refractories, amorphous refractories are also constantly innovating and developing, showing the following development trends:

(1) high performance

In order to meet the requirements of high temperature industry for higher performance of refractories, amorphous refractories are developing towards high performance. By using high-quality raw materials, optimizing formula design and advanced production technology, the refractories' refractoriness, corrosion resistance, wear resistance and thermal shock resistance are continuously improved. For example, develop high-purity refractory aggregate and powder to improve the chemical stability and high-temperature performance of unshaped refractories; Adding nano-materials and fiber reinforced materials can improve the mechanical properties and thermal shock resistance of unshaped refractories. High-performance unshaped refractories will be able to better adapt to complex working conditions such as high temperature, high pressure and strong corrosion, prolong the service life of equipment and improve production efficiency and economic benefits.

(2) Energy conservation and environmental protection

Under the background of increasingly strict environmental protection policy, the energy-saving and environmental protection development of unshaped refractories has also become an inevitable trend. On the one hand, by optimizing the formula and production process, the energy consumption and pollution emission of unshaped refractories are reduced. For example, using low cement or cement-free binder system to reduce the heat and carbon dioxide emissions generated during cement hydration; Develop a new type of environment-friendly admixture to reduce the dust and harmful gas emission of unshaped refractories during construction and use. On the other hand, developing amorphous refractory materials with energy-saving effects, such as heat-insulating refractory castable and paint spraying, can achieve the goal of energy saving and emission reduction by improving the thermal insulation performance of equipment, reducing heat loss and energy consumption.

(3) Multifunctional

With the continuous development of high-temperature industry, the demand for multifunctional refractories is also increasing. Unshaped refractories will not only have fire resistance, but also integrate many functions, such as corrosion resistance, wear resistance, heat insulation, oxidation resistance and thermal shock resistance. For example, the development of amorphous refractories with dual functions of heat insulation and corrosion resistance can not only effectively protect equipment from corrosion by high-temperature melt, but also reduce heat loss and improve the thermal insulation performance of equipment; The development of amorphous refractories with oxidation resistance and thermal shock resistance can better adapt to the rapid heating and cooling process of high-temperature equipment and prolong the service life of the equipment. Multifunctional unshaped refractories will better meet the complex needs of high-temperature industry and provide more comprehensive protection for industrial production.

(4) Intelligent

With the continuous progress of science and technology, intelligent technology is gradually applied to the research and development and application of unshaped refractories. By adding sensors and intelligent materials to unshaped refractories, the real-time monitoring and intelligent regulation of refractories performance and equipment operation state can be realized. For example, intelligent refractories with multi-parameter monitoring functions such as temperature, stress and erosion are developed, and various parameters in the process of equipment operation are transmitted to the monitoring system in real time through sensors to realize remote monitoring and fault early warning of equipment; The intelligent unshaped refractory with self-repairing function is developed, which can automatically repair when the refractory is slightly damaged, prolong the service life of the refractory and improve the operation reliability of the equipment. Intelligent unshaped refractories will provide strong support for the intelligent development of high-temperature industry and promote the development of high-temperature industry in a more efficient, energy-saving, environmentally friendly and safe direction.

V. Conclusion

As a kind of high-temperature protective material with unique advantages, unshaped refractory is playing an increasingly important role in modern high-temperature industry. Its characteristics such as high construction flexibility, good overall performance, strong ability of rapid construction and repair, and strong customization enable it to meet the complex needs of various high-temperature equipment and provide reliable high-temperature protection for industrial production. With the continuous development of high-temperature industry and the improvement of performance requirements for refractories, amorphous refractories are developing in the direction of high performance, energy saving, environmental protection, multi-function and intelligence, and will be widely used in more fields in the future, making greater contributions to the development of high-temperature industry.