(240d) Optimal Synthesis for the Feed-Water-Heater Network of a Pulverized Coal (PC) Power to Minimize Water Consumption



Coal-fired power plants contribute to almost 50% of the United States' total electric power production. At the same time, pulverized coal (PC) power plants are large water consumers since residual heat from the steam cycle is removed by evaporating water at the cooling tower. Therefore, reduction of such residual heat implies reduction of water consumption. A potential approach for the reduction of the residual heat in the steam cycle of the PC process is formulating an optimal design of the feed water heat exchange network (HEN). Conventional methodology for such HEN synthesis is based on equal enthalpy change on the feed water stream for each of the feed water heaters. Turbine discharge pressure and temperature as well as the mass flow rates of the steam bleeding streams are calculated based on such heat load distribution. In this work, we employ a rigorous-simulation pinch-technology refined approach for HEN synthesis. The methodology uses Aspen Energy Analyzer (AEA) to determine the mass flowrates of the bleeding streams while generating alternative designs that can potentially reduce the water consumption by reducing the total cooling requirement. The resulting alternative designs are simplified models of HENs and does not reflect realistic water consumption.  Therefore, we generated a superstructure that merges all designs in Aspen Plus to obtain the HENs rigorous simulation. Finally, the optimization approach to process synthesis is applied resulting in optimal configuration and designs.