The Use of NPV Calculations to Evaluate the Selection of FGD Technologies

摘要

Historically in the US, Wet Flue Gas Desulfurization (Wet FGD) has been used on utility projects that burn medium and high sulfur bituminous coals and Spray Dryer Absorbers (SDA) have been used on several Powder River Basin coal fired units. However, Circulating Dry Scrubbers (CDS) FGD technology and other economic factors have dramatically changed how FGD technologies are selected for the utility coal fired fleet. Economic factors such as the ability to sell gypsum, waste water discharge regulations, emission regulations for SO_3 and Hg, and shorter Return on Investments have influenced use of technologies available to utilities to meet both the Cross State Air Pollution Rule and the Mercury Air Toxic Standard. CDS technology has been proven to remove up to 98% of the SO_2 from coals with 4 to 5 lbs SO_2/MMBtu. In the past utilities would have been limited to Wet FGD technologies only for these medium sulfur coals. Now they have CDS as an alternative. The authors have applied Net Present Value (NPV) models to evaluate the most cost effective technologies to meet high removal rates of SO_2. NPV models were developed to compare the performance and economics of Spray Dryers, CDS and Wet Limestone FGDs for large coal fired power plants burning medium sulfur coals.