As a high-quality waste heat resource, the safe and stable recovery of flue gas in the low-temperature section of the BOF has long been plagued by key technical bottlenecks such as coal gas explosion risks and smoke adhesion deposition. Although traditional spray cooling methods can effectively avoid the risk of coal gas explosions, they lead to direct waste of flue gas waste heat. The CERI's team put forward the explosion-proof concept of "active explosion prevention + passive explosion venting" in high temperature zone for the first time, developed core equipment such as high-temperature spark capture, high-temperature explosion venting and wide-channel convection heat exchange in medium and low temperature zones, built the world's first work safety process route for BOF flue gas flameproof medium and low temperature waste heat recovery, and successfully broke through the technical bottleneck of the industry. This technology recovers the sensible heat of flue gas through a wide-channel waste heat boiler, and collects dry bulk solid large particles and dry BOF coal gas with the help of a spark capture device and a flue duct along flue gas part, thereby greatly improving the heat and mass recovery efficiency of the BOF process. 

The excellent performance of the system is due to the ingenuity of developers and the wisdom and collaborative innovation of users. During the hot test, 180 heats achieved zero explosion relief throughout the process, and the steam recovery index steadily increased by more than 40%, fully verifying safety. CERI and Jianlong Xilin Steel have worked closely together to continuously optimize the system performance. Based on the comprehensive analysis of the first hot test, they focus on improving the operation stability of equipment and channels, optimizing maintenance convenience, deepening the coordinated matching between the system and BOF smelting rhythm, ensuring smooth channels after efficient gas-solid separation, stable core equipment and resistance parameters along the way, and laying a solid foundation for long-term and stable operation of the system. 

Through the innovative implementation of the "viscosity regulation - excitation to promote flow" smoke and dust control mechanism and the dry ash combined transportation solution, the system has achieved fully automatic non-manual cleaning, continuous low-resistance operation of the system, a significant reduction in maintenance points, and is highly matched with the smelting rhythm. The latest 100-day operation data shows that the average daily smelting is 43 furnaces, the average steam output per ton of steel is 148.13 kg, the average dry ash collection per ton of steel is 6.66 kg, and the calorific value of coal gas is 20% higher than the calorific value of coal gas recovered by the original LT process. The energy consumption of the BOF process is further reduced by 5.9 kgce/t steel, the carbon reduction is 13.3 kg/t steel, the dry ash is 100% recycled, the auxiliary material consumption of the BOF is reduced by 6.66 kg/t steel, and the income per ton of steel increases by about RMB 12.94, realizing the closed-loop use of dust resources, bringing significant economic and environmental benefits to steel production. 

Fig. 1 Variation of Smelting Heats and Tapping Quantity on the Current Day with Time 

Fig. 2 Variation of Steam Output and External Steam Supply Per Ton of Steel with Time 

Fig. 3 Variation of Cumulative Dry Ash Volume with Smelting Heats 

As the first user of this technology, Jianlong Xilin Steel highly praised and gave feedback on the thousand-day safe smelting achieved by No. 1 BOF. The flameproof medium and low temperature waste heat recovery technology for BOF flue gas developed by CERI has successfully achieved a leapfrog upgrade from "engineering availability" to "long-term reliability, high efficiency and low consumption, near zero operation and maintenance". Its stable improvement in steam output per ton of steel and the calorific value of recovered coal gas has refreshed the limit of BOF flue gas waste heat recovery efficiency. 100% resource recycling of dry ash per ton of steel has created an extreme energy efficiency engineering model.