As an important part of Beijing Shougang’s extreme low-cost strategy, the molten iron temperature drop is not only an integral part of implementing the national “Double Carbon” policy and adhering to the concept of green development, but also a powerful means of enhancing the core competitiveness of enterprises. For a long time, Beijing Shougang has continuously promoted research on molten iron temperature drop and improved the energy utilization rate of the whole process. With the strong cooperation of the operation department and functional departments, efficient coordination of the iron-steel rolling interface and extreme efforts of the research team, since January this year, Beijing Shougang has kept the molten iron temperature drop stable at 110℃, which is 13.38% lower than the average level of the previous year. It can effectively reduce CO2 emissions by 40,200 tons every year, and lower economic iron consumption to 930 kg/ton. It is estimated that the annual cost reduction will be RMB 72.16 million.

Setting goals, tracking processes and performing duties. Molten iron is the main raw material for steelmaking, and its chemical and physical heat are the main heat sources for converter steelmaking. The reduction of the molten iron temperature drop can not only increase the amount of steel scrap in steelmaking, but also decrease the energy consumption of the converter, which plays an important role in energy conservation and consumption reduction in the iron-making and steel-making processes. Meanwhile, the reduction of the temperature drop can greatly improve the stability of molten iron quality and provide a solid quality foundation for rolling high-end products. Beijing Shougang pointed out in its report at the 2022 Workers’ Congress that “we are determined to innovate and promote energy conservation and low carbon, maximize energy utilization efficiency, continuously promote research on the molten iron temperature drop, improve the turnover efficiency of the torpedo ladle, and strive to keep the temperature drop below 120℃.” The goal has been set, so it is time to work towards achieving it.

In order to achieve the control goal of the molten iron temperature drop, Beijing Shougang assembled a promotion team and working group to adhere to the working principles of extreme efficiency, extremely low cost and extremely high quality. The team members focus on key links such as torpedo ladle turnover, transportation organization and steelmaking production efficiency, and formulate detailed work plans so as to achieve great achievements with small goals. The team holds a monthly promotion meeting to advance the important projects that coordinate and support the molten iron temperature drop, and arrange key works in stages; the working group holds weekly meetings, tracks the implementation of tasks assigned at the monthly promotion meeting, analyzes and summarizes the molten iron temperature drop of the previous day through daily feedback, conducts operations based on wall charts, strengthens responsibilities, tracks the advancement of special research in a rolling way, coordinates and solves the problems and contradictions between processes during the advancement, and ensures that every task can be implemented and lead to practical results.

Keeping an eye on operation, planning routes and improving efficiency. Many factors affect the temperature of hot metal charging into the converter, including “increasing income” and “decreasing expenditure”. “Increasing income” means increasing the blast furnace tapping temperature, which requires a large amount of energy consumption and is contrary to the “double carbon” policy and low-cost production concept. To this end, efforts should be concentrated on “decreasing expenditure” to minimize the energy loss in the process from molten iron discharging to steelmaking transiting. Thus, the Manufacturing Department optimized the transportation mode of molten iron by opening and analyzing multiple sets of data such as molten iron output and transportation time, and adjusted the traditional transportation of two ladles for one machine to one ladle for one machine by using the No. 1 blast furnace for the pilot run in the first place. Under the organization of the Manufacturing Department, the Transportation Department quickly grasped the production mode of one ladle for one machine, overcame the difficulty of insufficient heads, and actively organized and rationally allocated to ensure the smooth development of one ladle for one machine. Relevant professionals are arranged to be on supervision and control duty 24 hours a day, go deep into the dispatching room to follow the shift realistically, and explain the change points and difficulties after the implementation of the mode of one ladle for one machine, as well as key production control links for on-site dispatchers. Full use is made of the weighing scale under the blast furnace to explore a new organization mode, increase the proportion of one ladle for one package in the No. 1 and No. 2 blast furnaces, reduce the iron-mixing operation, shorten the residence time of the torpedo ladles in the transiting station and lower the temperature loss of molten iron in the transiting process.

For large traffic density after the implementation of transportation of one ladle for one machine, the Manufacturing Department and Transportation Department cooperate with each other, grasp the root of the matter, organize and rearrange the release of the weighing road area of the raw material station, reserve the marching route in advance by mastering the rhythm of ironmaking, steel tapping and iron casting, and drive according to the map to ensure a quick entrance and exit from the No. 1 blast furnace to the first steel-making mill. Meanwhile, in order to adapt to the quick iron casting rhythm in the first steel-making mill, the engine is adjusted to wait for cast iron at the mill rather than the south of the railroad , and trailers are available at any time, so as to reduce operating steps and time. Engine operation control methods and measures are formulated to clarify the acceleration and deceleration operation stands of watched and unwatched road entrances and other areas, and guide workers to speed up immediately after passing dangerous and speed limit point locations, which not only ensures safety but also improves efficiency. 

Enhancing coordination, fully tapping potential and solidifying the foundation. Research on molten iron temperature drop is not a simple single breakthrough but an efficient multi-point cooperation. This is because coordination and organization between departments and seamless connection between working procedures can minimize the waiting time and heat loss of molten iron in the process of tapping, transportation and transiting. On the basis of ensuring safe, smooth and stable company production, the Manufacturing Department strengthens the top-level design, constructs “chess game” thinking between the Ironmaking Operation Department and Steelmaking Operation Department, scientifically arranges and coordinates the production and maintenance plans of each process, and ensures the same frequency of resonance between departments and efficient and unified production. Through the real-time linkage of ironmaking and transportation scheduling, the Steelmaking Operation Department can distribute molten iron reasonably, reduce cross-supply, shorten the transportation time and improve the connection efficiency of the iron-steel interface. In order to ensure the smooth and efficient transportation of torpedo ladles and develop rapid iron tapping technology, the No. 3 iron feeding pit is built to ensure that the arrival, transit and departure of torpedo ladles can be completed. Meanwhile, research on process technology, optimization of cast production scheduling and comprehensive balance of production rhythm is carried out to keep the casting machine production at constant speed, avoid iron foam on the torpedo ladles, realize casting without accumulation and drive the turnover efficiency of iron packages and torpedo ladles.

The Ironmaking Operation Department optimizes the tapping mode of the provided ladles under the blast furnace, introduces the blast furnace liquid level metering system, grasps the tapping situation in real time, reduces the contact time between dispatching and field operators, and improves the turnover efficiency of the torpedo ladles. Meanwhile, it strengthens contact and communication with the Transportation Department, and conducts the real-time scheduling of the operation of online torpedo ladles, thereby minimizing their turnover quantity and improving their turnover efficiency. With the cooperation of various departments, the turnover of the torpedo ladles has decreased from 42 in 2018 to 22 now, and their turnover rate has increased from 2.8 times/day to 5.0 times/day.

Working together for research, improving performance and promoting applications. In order to ensure that the online torpedo ladles have higher safety and heat preservation under high frequency use, the Ironmaking Operation Department optimizes and reforms the refractory material of the torpedo ladle linings, improves the masonry method of the torpedo ladles and simultaneously revises the material standard to standardize the masonry operation. It also perfects the permanent layer structure of the torpedo ladles, agalmatolite brick masonry and isolation layer. Masonry and supervision methods are expanded for the joints, impacted areas and other weak parts of the cones, cylinders and toroids of the ladles. During the masonry work, professionals conduct online quality inspections 24 hours a day, upload on-site quality photos and progress information to the WeChat working group of torpedo ladles’ refractory material quality every hour, and provide timely feedback when problems are found. They also design the capped heat insulating apparatus for the torpedo ladles. Relevant professionals of the Manufacturing Department, Ironmaking Department, Steelmaking Department and Dingshengcheng cooperate with each other and discuss the shape, size and material of the insulation covers so as to form a feasible plan. In order to master the heat preservation effect of torpedo ladles with asbestos coverings, the Manufacturing Department and Qianshun Technology Center organize the natural temperature drop test of empty torpedo ladles with and without covers at the iron casting machine station. The temperature drop of empty torpedo ladles with covers is significantly lower than those without covers, and the heat preservation effect is remarkable.