Blast furnace maintenance technology and application of refractory materials

As the core equipment of the ironmaking industry, the stability and durability of the blast furnace are directly related to the safety and efficiency of steel production. With the advancement of blast furnace technology and the increasingly harsh smelting conditions, blast furnace maintenance technology and the application of refractory materials have become the focus of attention of steel companies. This article will deeply explore several key technologies for blast furnace maintenance and the selection and application of refractory materials, in order to provide a useful reference for the production of steel companies.

1. Overview of blast furnace maintenance technology

There are many types of blast furnace maintenance technologies, but according to the basic principles and operation methods, they can be mainly summarized into three categories: direct bricklaying method, spray repair method (gunning) and grouting repair method.

1. Direct bricklaying method

Direct bricklaying method is a traditional maintenance method that restores the lining structure by removing part or all of the refractory bricks of the blast furnace lining and rebuilding new refractory bricks. Although this method can completely restore the integrity of the lining, it is complicated to operate, time-consuming, and expensive, and requires the blast furnace to be completely cooled and the charge to be emptied, which has a great impact on production. Therefore, this method is gradually being replaced by new maintenance methods.

2. Spray repair method (gunning)

Spray repair method (gunning) is to use air to transport loose refractory materials, spray the refractory materials to the parts that need to be repaired through a spray gun, and adhere to its surface to form a refractory layer of a certain thickness. Gunning technology has the advantages of fast repair speed, good integrity, and can be carried out in a non-cool furnace state. It has become an important means of blast furnace maintenance. According to different operation methods, gunning technology can be divided into three forms: ordinary gunning, long gunning and remote control gunning.

Ordinary gunning: After the blast furnace is completely cooled, the operator enters the furnace and directly performs gunning operations.

Long gun gunning: Use a special extended gun to gun specific parts of the furnace from outside the furnace to achieve repair in a non-cool furnace state.

Remote control gunning: Put a special robot into the blast furnace, and the operator remotely controls the robot to perform gunning operations through wired monitoring equipment. This method is more flexible and efficient and is currently a commonly used gunning method.

3. Grouting repair method

Grouting repair method, also known as press-in repair method, is to drill holes in the blast furnace shell and use special press-in equipment to press refractory materials into designated parts of the furnace to achieve the purpose of filling gaps and repairing furnace linings. This method can be carried out during the blast furnace shutdown period, with little impact on production and the internal structure of the furnace body. It is an economical and reliable repair technology. Grouting repair method is mainly divided into two categories: filling repair and flow-blocking repair. The former is mainly used to fill the gaps between refractory materials, while the latter focuses on blocking the erosion of high-temperature gas and slag.

2. Selection and application of refractory materials

The working conditions and degree of erosion of various parts of the blast furnace are different, and the requirements for refractory materials are also different. Therefore, in the process of blast furnace maintenance, it is very important to choose suitable refractory materials.

1. Throat part

The throat part mainly bears the direct impact and friction of the charge, as well as the scouring of the gas flow. The temperature of this part is relatively low (400-500℃), and water-cooled or non-water-cooled steel bricks are generally used as refractory materials. The water-cooled steel bricks and the furnace shell need to be filled with castables to enhance their integrity and wear resistance.

2. The middle and upper part of the furnace body

The middle and upper part of the furnace body is the heating and reduction area of the charge, with a moderate temperature (400-800℃) and no large amount of slag formation. This part requires the refractory material to have excellent spalling resistance and wear resistance, so phosphate-bonded clay bricks, sillimanite refractory bricks and high-alumina refractory bricks are mostly used.

3. The lower part of the furnace body and the waist of the furnace

The lower part of the furnace body, the waist of the furnace and the belly of the furnace are the areas with the highest temperature and the most serious erosion in the blast furnace. These parts require the refractory material to have good slag resistance, erosion resistance and high-temperature strength. Commonly used refractory materials include high-quality clay bricks, high-alumina bricks, corundum bricks, alumina carbon bricks and silicon carbide bricks. In particular, silicon carbide bricks have been widely used in modern blast furnaces due to their excellent erosion and erosion resistance.

4. Furnace belly

The furnace belly connects the furnace hearth and the furnace waist, with extremely high temperature (1600-1650℃), and is eroded by a large amount of intermediate slag and alkali metals. This part requires the refractory material to have extremely high corrosion resistance, erosion resistance and certain thermal shock resistance. Modern large and medium-sized blast furnaces mostly use high-performance refractory materials such as fired aluminum carbon bricks and fired microporous aluminum carbon bricks.

5. Furnace hearth

The furnace hearth is the place where molten iron and slag are contained. It has the highest temperature (1700-2000℃) and is eroded by molten iron, slag and high-temperature coal gas. This part requires the refractory material to have high temperature resistance, corrosion resistance, erosion resistance and high thermal conductivity. Commonly used refractory materials include corundum-mullite bricks, brown corundum bricks, sillimanite bricks, dense carbon bricks or graphitized carbon bricks. In order to extend the life of the furnace hearth, ceramic cup + carbon brick composite technology is often used to improve the overall performance of refractory materials.