1. Preface

Baowu Group Echeng Iron and Steel Co., Ltd. (hereinafter referred to as Egang) No. 5 blast furnace, with an effective furnace capacity of 2600m, was originally equipped with three internal combustion hot blast furnaces, which were completed and put into operation in January 2010. In March 2014, two of the internal combustion hot blast furnaces had problems such as difficulty in burning the furnace and rapid flue temperature rise, resulting in an air supply temperature of only about 1000 ℃, decided to add a new top-fired hot blast stove. During the new hot blast stove, the blast furnace will not stop the furnace. After the completion of the blast furnace, the pipeline interface operation will be carried out during the off-wind period. After the new 4# cone column rotary cutting top-burning hot blast stove and the three internal combustion hot blast stoves are put into operation, the air supply temperature has increased by 150 ℃, and good results have been achieved in the past five years of practical operation.

2. Project Overview

The newly added No.4 hot blast stove system is designed by China Metallurgical Southern Engineering Technology Co., Ltd. The hot blast stove is of cone column rotary cutting top combustion type. The burner is independently designed and supplied by Annike Company. Three-dimensional mixed burner technology is adopted. The regenerator is designed as 37-hole d = 20mm high-efficiency lattice brick. The fuel of hot blast stove is blast furnace gas + coke oven gas, and the hot air temperature is ≥ 1250 ℃.

Detailed Design Scheme of 2.1 Hot Blast Stove

This project considers the actual operation of the original internal combustion hot blast stove, the new 4# hot blast stove adopts high-power three-dimensional mixing burner, and through a large number of CFD fluid simulation calculations in the early stage, multiple geometric models are established to carry out non-premixed combustion calculations, and the effects of air gas inlet temperature, air gas nozzle angle setting, throat diameter, etc. on the flow field, temperature field and CO concentration distribution of the hot blast stove are studied, the hot blast stove model with the best combustion effect and the most suitable for the actual working conditions is obtained, and the design parameters of the new 4# cone column rotary cutting top combustion hot blast stove are determined.

Table 1: Design Conditions of Hot Stove System

Table 2: Design parameters of hot blast stove

Layout of 2.2 hot blast stove body

Since the blast furnace does not stop heating during the new hot blast stove, the new 4# hot blast stove cannot interfere with the original hot blast stove system. Through on-site investigation and multi-scheme comparison, the new 4# hot blast stove system is selected between the existing hot blast stove and the blast furnace bridge. The 4# hot blast stove and the old 3 hot blast stoves are arranged at an included angle of 90, as shown in Figure 1.

3. Resistant material design of hot blast stove body

In view of the problems of the original internal combustion hot blast stove, such as the power drop of the burner, the low temperature of the vault, the inclination of the partition wall, the sinking of the lattice brick and the rapid heating of the flue, the newly-built 4# cone column rotary cutting top combustion hot blast stove adopts a number of patents and proprietary technologies, such as three-dimensional mixed burner, non-displacement burner anti-micro-explosion nozzle structure, vault (combustion chamber) flat structure, dense structure, dense silicon lattice brick structure.

3.1 three-dimensional hybrid burner

The burner is a cone-column composite structure, which not only reduces the height of the hot blast stove, but also improves the plane swirl mixed flow field of the traditional top-fired burner into a three-dimensional space swirl flow field. After air gas is mixed, the combustion is complete, the flame is short, and the negative pressure area formed by the mixed flow after passing through the throat rectification is small, which ensures the uniform distribution of flue gas entering the lattice brick and the lattice cross-brick, it is more conducive to the storage of heat and the release of heat to obtain high air temperature.

3.2 burner easy purging micro-explosion anti-displacement structure

The gas section of the burner mixing chamber is constructed with steel mold to support the overall pouring. The gas ring and gas nozzle are located in the cone section, and the top space is small, which is conducive to nitrogen purging. It avoids the displacement of the nozzle brick caused by the deflagration of the traditional top-fired hot blast stove, avoids the gas residue of the gas ring nitrogen purge, and avoids the deflagration of the gas nozzle. This design makes the conversion of hot blast stove air supply and burning furnace safer and more efficient.

3.3 interlocking type combustion chamber flat masonry structure

The burner combustion chamber is of flat masonry structure, so that the masonry load is evenly distributed on the horizontal plane, which is convenient for construction. The four-sided sub-female buckle is used for masonry, and the upper, lower, left and right single bricks are interlocked, which enhances the integrity and stability of the refractory masonry.

4. Use effect of 4# hot blast stove after operation

Since the 4# cone column rotary cutting top burning hot blast furnace was put into operation in 2016, the vault temperature has reached 1330 ℃-1350 ℃, and the air supply temperature measured at the temperature monitoring point on the 4# hot blast branch pipe can reach 1250 ℃, which has achieved ideal design effect.

After the newly-built 4# hot blast stove was put into operation, the damaged refractory materials of the original 2# and 3# internal combustion hot blast stove were repaired, and the ceramic wear-resistant castable for partition wall was mainly poured. After the repair, the vault temperature of the three internal combustion hot blast stoves reached above 1280 ℃-1300 ℃. In order to ensure the stable and smooth operation of the blast furnace, the vault temperature of 4# hot blast stove is currently controlled at about 1300 ℃. The hot blast stove system adopts a staggered parallel working system of "two fires and two deliveries". The 4# hot blast stove is the main air supply stove, and the air supply temperature is maintained at 1160 ℃-1200 ℃, which is more than 150 ℃ higher than the air temperature before the renovation.

5. Conclusions

(1) The technical transformation of the newly added 4# top-burning hot blast stove has achieved the set goal. The 4 hot blast stoves are operated in parallel in a staggered manner, and the air supply temperature is increased by more than 150 ℃ compared with that before the transformation. After the subsequent 1#~ 3# internal combustion type is transformed into the top-burning type, the air temperature can reach 1250 ℃.

(2) Through the good operation effect of the cone column rotary cutting top combustion hot blast furnace in the past 5 years, it is verified that the three-dimensional hybrid burner has the characteristics of high power, large load adjustment ratio and wide range of working conditions.

(3) This project provides a feasible scheme for the maintenance and transformation of internal combustion hot blast stove in the future, has certain guiding significance for similar hot blast stove projects in the future, and provides practical experience for the implementation of energy-saving, consumption-reducing and efficient technical transformation of old equipment in the iron and steel industry.