Short-term Scheduling of Steam Power System in Iron and Steel Industry under Time-of-use Power Price

A generalized formulation for short-term scheduling of steam power system in iron and steel industry under the time-of-use（TOU）power price was presented,with minimization of total operational cost including fuel cost,equipment maintenance cost and the charge of exchange power with main grid.The model took into account the varying nature of surplus byproduct gas flows,several practical technical constraints and the impact of TOU power price.All major types of utility equipments,involving boilers,steam turbines,combined heat and power（CHP）units,and waste heat and energy recovery generators（WHERG）,were separately modeled using thermodynamic balance equations and regression method.In order to solve this complex nonlinear optimization model,a new improved particle swarm optimization（IPSO）algorithm was proposed by incorporating time-variant parameters,a selfadaptive mutation scheme and efficient constraint handling strategies.Finally,a case study for a real industrial example was used for illustrating the model and validating the effectiveness of the proposed approach.

Proposal and Assessment of an Engine-Based Distributed Steam and Power Cogeneration System Integrated with an Absorption-Compression Heat Pump

Internal combustion engine-based poly-generation systems have been widely used for energy savings and emissions reductions.To maximize their thermodynamic and environmental performance potentials,the efficient recovery of flue gas and jacket water heat is essential.In a conventional internal combustion engine-based steam and power cogeneration system,the low-temperature(less than 170°C)heat from flue gas and jacket water is usually directly discharged to the environment,which dramatically reduces the thermal and economic performance.In this work,a high-temperature heat pump is employed to recover this part of low-temperature heat for steam generation.The sensible heat of the flue gas and jacket water is cascade utilized in a steam generator and a heat pump.Simulation results show that the process steam yield of the proposed system is almost doubled(increased by 703 kg/h)compared to that of an engine-based cogeneration system without a heat pump.The proposed system can reduce natural gas consumption,C 02 and NOx emissions by approximately 199069 m3,372.64 tons and 3.02 tons per year,respectively,with a primary energy ratio and exergy efficiency of 72.52%and 46.28%,respectively.Moreover,the proposed system has a lower payback period with a value of 5.11 years,and the determining factors that affect the payback period are natural gas and electricity prices.The total net present value of the proposed system within its lifespan is 2441581 USD,and an extra profit of 785748 USD can be obtained compared to the reference system.This is a promising approach for replacing gas boilers for process steam production in industrial sectors.