Research On Operation Optimization For Low Carbon Steel Mill Gas Utilization System

The iron and steel industry is the highest carbon emission industrial sector,its decarbonization is impervative to achieve the carbon peak and carbon neutrality target of China.As the most important secondary energy,steel mill gases are the largest carbon emission source in the conventional iron and steel industry.The efficient and low-carbon utilization of steel mill gases provides a vital pathway to reduce the unitary CO₂ emission.Therefore,this study concentrates on the utilization of steel mill gases.A low-carbon steel mill gases utilization model is developed with the integration of solvent-based carbon capture,methanol-based carbon utilization and renewable power.A comprehensive study from scheduling to control and then to low-carbon planning is presented to gain indepth knowledge on different timescales for the transition of conventional iron and steel industry towards carbon neutrality.The main contributions of this paper are as follows:（1）The first-principle model of steel mill gas low-carbon utilization system consisted by the gas power plant,carbon capture and utilization and renewable power is established.A simultaneous design and operation parametric optimization method is proposed for the solvent-based carbon capture plant to better match with the flue gas emitted form steel mill gas-fired power plant.（2）A two-layer scheduling shceme for low-carbon steel mill gas utilization system is proposed.The day-ahead scheduling implements a stochastic optimization to provide hourly operating instructions for the next 24 hours for the target of low carbon and economic operation;The intraday scheduling exploites flexibility supporting function of carbon capture besides decarbonization,in which a novel index reflecting the power adjustment contribution of carbon capture is introduced to enhance the small-timescale flexibility of the mill gas utilization system.The case studies show that the proposed scheduling scheme can realize low-carbon,economical and flexible operation of the system.（3）Based on the dynamic characteristic analysis of gas power plant-carbon capture system,feedforward model predictive controllers are designed to deal with frequent disturbances of steel mill gases and flue gas.Meanwhile,a novel cooperative predictive control method is proposed for the integrated system based on the“heat storage”characteristic of carbon capture plant.Multiple flexible operation modes serving different power-carbon demand are also presented.The simulation results verify the efficacy and advantages of the proposed control approach.（4）A two-stage low carbon planning model is established for steel mill gas utilization system towards 2050.The upper stage implements configuration optimization under the varations of technology costs and carbon trading market conditions;the lower stage carries out a robust scheduling considering the uncertainty of renewable power;Comprehensive discussion is then presented to offer an insight into the low-carbon transition of the steel industry.