Optimal synthesis for the feed-water-heater network of a Pulverized Coal (PC) power to minimize water consumption

Abstract

Abstract 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 to the point that construction and operability of PC power plants have started to be constrained by water availability in some regions of the country. Research efforts have been intensified to reduce the water usage and consumption which are closely related to the water losses associated to the cooling systems and gas purification operations. Two process systems engineering approaches have been studied to minimize the water consumption of power plants. First, a better optimization of nonlinear uncertain systems (BONUS) algorithm has provided solutions to the minimization of water consumption under uncertain atmospheric conditions. The calculated conditions for a 550 MW PC plant predicted reductions of 6.4%, 3.2%, 3.8% and 15.4% in the average water consumption for the four different seasons from fall to summer respectively. A second approach pursues the reduction of the residual heat in the steam cycle of the PC process by formulating an optimal design of the feed water heat exchange network (HEN). The proposed 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 optimization approach to process synthesis involves the selection of an optimal solution from the superstructure with a simulated annealing (SA) capability built in Aspen Plus. Results show at least a 5% reduction in water consumption for the PC power plant via this enhanced HEN synthesis technique