DRI and HBI continuous loading experience have proved that the new concept of electric arc furnace process control system proposed by Danieli Automation has achieved good results.
Thanks to continuous monitoring of the entire smelting process – from electric arc furnace preparation to tapping, the control system enables continuous charge management of different charge materials, including DRI direct reduction of hot and cold materials, HBI charge, Even two kinds of charge are installed at the same time. The control system divides the charging process into several steps, enabling it to gradually achieve intermediate process objectives.
In the charging step using the electric arc furnace, different stages can be further subdivided. Each phase represents a basic unit of the process. The entire smelting process can be divided into the following stages: electric arc furnace preparation, batch melting, DRI direct reduction iron continuous charging, refining, tapping.
The process control system and the basic automation system continue to work together to obtain real-time process data and report parameter settings (fixed and calculated), including power input, continuous charging, and all other equipment conditions (module, burning) Mouth, oxygen lance…).
The endpoint control for each phase is achieved by the relevant rules established according to the following process parameters: energy (electric energy, molten pool enthalpy); time (power-on time); electrode position (relative to the arcing point).
The amount of DRI direct reduced iron charge is varied to maintain the molten pool within a predetermined temperature range. Then gradually increase the bath temperature to achieve the required tap superheat.
At the end of the continuous charge, it begins to enter the refining stage. During the refining process, the key parameters of the bath temperature are continuously monitored until the tapping is performed.
The target bath enthalpy is determined based on the weight and type of charge. Current enthalpy estimates are based on an energy balance model. The model calculates the difference between the input energy (electric energy and/or chemical energy) and various energy losses (heat radiation, heat taken away by the flue gas, and loss of electrical energy) at regular intervals. Based on the current molten pool thermal state, the process control system can predict its theoretical average temperature. In particular, the repeated calculation of the continuous charge amount is based on the extrapolation of these calculation results as a basis for repeated iterative prediction of the molten steel in the latter several minutes.
This new EAF process control method has the following significant features and advantages: It can improve process control accuracy and reduce energy consumption per ton of steel without affecting the quality of molten steel by linking energy input to the charged charge; The balance model can automatically optimize the recovery of various power-off delays; it can predict the future thermal state of the molten pool, thereby optimizing the control of the continuous charge; predicting the tapping time, thereby optimizing the tapping process management, and making it subsequent refining The equipment is kept in sync; the difference between the actual tapping temperature and the target temperature is reduced, thereby improving the ladle refining process.
