A MINLP model for multi-period optimization considering couple of gas-steam-electricity and time of use electricity price in steel plant

This paper presents an optimization model for multi-period scheduling of an energy system in a steel plant. The objective function is constructed by the gasholder penalty cost (GPC), energy purchase cost (EPC) and carbon emission cost (CEC), which are used to evaluate the model. The model divides the gasholder into four operating intervals and the corresponding penalty of each interval is set. The couple of gas-steam-electricity is introduced into the model. The fitting curves are conducted to describe the operating characteristic of boilers and turbines in the self-power plants (SPPPs). The carbon emission factors supported by IPCC are used for the carbon calculation. The Optimal results showed that total cost is decreased by 2.97%, when the GPC is decreased by 52.37%, the EPC is decreased by 1.92% and the CEC is increased by 21.54%. The couple of gas-steam-electricity allows the optimization model to redistribute the energy sources to minimum the total cost. The efficiency of different type of boilers has different operation characteristics. The sensitivity analysis of the model on electricity trade price and coal purchase price are conducted. The analysis results show that the variation of those parameters would influence the electricity generation under different situation.