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Advantages of flat masonry structure for vault (combustion chamber) refractory of top-fired hot blast stove





Blast furnace hot blast stove is one of the main supporting equipment of the blast furnace in the ironmaking plant, and its function is to continuously provide high temperature hot air for the blast furnace. As the most widely used furnace type at present, the vault structure design is the key to the high temperature and long life of the top-fired hot blast furnace. The difficulty of the design is to combine the ceramic burner and the regenerator structure into one. At the same time, the refractory masonry material and structure design of the hot blast furnace vault (combustion chamber) can withstand the working temperature above 1400 ℃.

Since the Kalugin hot blast stove entered the country, most of the vault (combustion chamber) refractory masonry is of oblique masonry structure, I .e. the single brick joint of the masonry is perpendicular to the extension direction of the cone section of the combustion chamber. This kind of masonry structure has many defects and disadvantages from the aspects of masonry construction, force analysis and use effect.

Since 2010, Zhengzhou anike industrial co., ltd. has optimized the refractory structure of the working layer of the vault (combustion chamber) of the top-burning hot blast stove as flat masonry. at the same time, in order to strengthen the stability of the vault masonry, the vault angle and brick type have also been optimized. the single brick adopts the design of four-sided double-row sub-buckle, and applied for the utility model patent of flat masonry structure of the combustion chamber (patent (patent: 2015206539190), through the actual feedback of on-site construction and the verification of engineering practice in the past 10 years, the masonry structure has achieved good results.

The difference between flat masonry and oblique masonry for vault (combustion chamber) refractory can be summarized as follows:

(1) The flat bricklaying design is reliable, the construction method is simple, and the operation efficiency is high.

Due to the influence of sliding force in the construction process of oblique single brick, one buckle is required for every 5 bricks in vault masonry. As the slope of upward masonry increases, one buckle is required for every 2-3 bricks. At the end of the vault throat, each single brick needs to be constructed with buckle assistance. After waiting for the closing mud to form strength, the buckle is removed. The construction process is complicated, the construction is difficult, and the construction progress is slow.

(2) Better mud fullness in flat construction

The boss of the single brick of the vault (combustion chamber) is downward, the groove is upward, and the mud at the joint part of the concave-convex groove is full and firmer. However, when the single brick concave-convex groove is designed as the boss is upward, and the mud on the boss slides along the inclined plane under the influence of gravity, which is easy to cause the mud in the concave-convex groove is not full, and it is easy to cause wind leakage in the combustion chamber.

(3) When laying flat bricks, the stress of single brick is more balanced.

The stress analysis of the refractory when the vault is flat and inclined is as follows: the self-gravity of the refractory is G,FZ is the supporting force of the refractory, FN is the pressure of the vault refractory, and F is the pulling force to prevent its sliding. The stress is calculated according to the orthogonal decomposition method as follows

Force calculation of flat masonry structure: F = FN * sinθ

Calculation of force on inclined masonry structure: F = G * cos θFN

Stress analysis of flat masonry structure

Stress analysis of oblique masonry structure

According to the above formula, the sliding force generated by single brick is greater when the working layer of vault is built with refractory, especially when the hot air outlet opening is located at the variable diameter of the straight section and cone section of the vault, the upper semicircular refractory of the hot air outlet is located at the cone section, the stress is concentrated, and the structural stability is poor. This kind of structure is similar to the vault contact pipe of the external combustion hot blast stove, which is a weak and vulnerable part. Once the local refractory material of the orifice is deformed and collapsed, the refractory material of the inclined vault working layer is more likely to collapse, accelerating the damage of the refractory material of the vault working layer.

(4) the use of flat masonry structure effect is better

Baosteel Ironmaking Plant Existing 4 4000m3The above blast furnaces are all Nippon Steel's external combustion hot blast furnaces, and the use of flat-built cone-section vault refractory materials has been verified by engineering for more than 30 years in the service period of the two generations of blast furnaces. There is no overhaul or replacement, and the use effect is very good. The top-fired hot-blast stove and Nippon Steel's external-fired hot-blast stove have similar cone-section vault structures and have been included in the Technical Specification for Refractories for Top-fired Hot-blast Stoves, which is a reliable technology applicable to the vault (combustion chamber) structure of top-fired hot-blast stoves.

The vault of Nippon Steel's external combustion hot blast stove is of flat masonry structure.

Anneke cone-column composite top-fired hot-blast stove vault flat structure

To sum up, the flat masonry structure of the working layer of the vault (combustion chamber) of the top-burning hot blast stove fully reflects the following advantages: ① reducing the difficulty of on-site construction and improving the construction efficiency; ② the force is balanced and the structure is more stable, which is especially suitable for the application of masonry in the high-temperature area of the vault of the hot blast stove; ③ after 30 years of engineering verification, it is a reliable technology.