In September 2023 Hot Blast Stove No. 4 (HBS No. 4) of blast furnace No. 1M was successfully put in operation after a complete overhaul at PJSC “KAMET-STEEL”.

The overhaul project for HV No. 4 was carried out by “M TECHNOLOGY” LLC in 2020 – 2021.

The main goals and objectives of this overhaul for the Client were as follows:

– proper overhaul of the HBS;

– increase in resistance and durability of the combustion chamber;

– hot blast temperature increase, both with the use of high-calorie additives and without them;

– increase of fuel efficiency.

A brief description of the current situation: HBS No.4 was built in the 1970s. It is a shaft-type HBS with an internal combustion chamber. As known, this type of HBSs  has several significant disadvantages:

– «Short-circuit» or direct gas-flows between the combustion chamber and the checker-work through cracks and seams between the bricks in the dividing wall;

– inclination of the combustion chamber towards the checker-work (“banana” effect);

– high-temperature creep of refractories under the influence of high temperatures and pressures in the lower part of the combustion chamber, which leads to deformation and bursting of brickwork of the lining, particularly in the hot blast connecting branches;

– pulsating combustion phenomenon resulting from acoustic excitation in a high combustion chamber;

– cracking of refractories in the lower part of the combustion chamber (in the area where the burner device is installed).

And indeed, all these defects were fully observed at HBS No. 4.

Within the scope of the project for complete overhaul of the Hot Blast Stove No. 4 our company performed computer modeling using a CFD (Computational Fluid Dynamics) software application. During this process, two combustion chambers were investigated: one of the oval shape and the other of lenticular shape, both equipped with a classic “tube-in-tube” type burner.

Analysis of the studied options revealed a number of significant drawbacks:

– uneven temperature pattern within the refractory lining of the combustion chamber, especially in its lower section, was observed. There were significant temperature gradients on the opposite wall of the combustion chamber along the burner axis (see Fig.1, Fig.2);

– vortex, near-wall combustion of the air-gas mixture was also identified, which leads to large temperature gradients in the refractory lining of the combustion chamber.

To minimize these phenomena we proposed replacing the standard “tube-in-tube” burner with a ceramic burner featuring an axially positioned flame jet in the combustion chamber (see Fig.3, Fig.6, Fig.7). Computational modeling demonstrated that the ceramic burner provides an elongated flame jet and directs maximum temperatures towards the upper part of the combustion chamber, where there is less refractory pressure. Consequently, the negative effect of refractory creep on the combustion chamber durability is reduced, leading to an extended service life (see Fig.4, Fig.5). The burner operates silently, with minimal gas pressure losses, the flame is well-regulated, without gas pulsations and provides better heating if compared to “tube-in-tube” burners.

The project of installation of the ceramic burner provided for retaining the HBS infrastructure to the maximum extent. This approach makes it possible to minimize costs.

Within the scope of this project, we additionally replaced the checker-work with a cell diameter of 40 mm with one having a cell diameter of 30 mm. This decision increased the heat exchange area of the HBS, consequently allowing for higher hot blast temperatures and reducing coke consumption in the blast furnace.

It is worth noting that a ceramic burner of a foreign company was used in the project. This company has extensive experience in implementing similar projects abroad. Additionally, the combustion chamber internal lining was made of modern, more durable refractories of the same company to extend the lining service life.

The photos of the burner and refractory lining in the combustion chamber are provided below (see Photo1-…Photo-9).

Thus, we succeeded in solving the following main issues within the framework of this project: extension of the combustion chamber service life, increasing the hot blast temperature, and achieving more efficient fuel utilization. We are confident that further observations of the HBS No.4 operation will confirm the correctness of the decisions made.