Brad Buecker and Ron Rosinski, POWER Engineering
While many coal-fired power plants in the United States have ceased operation in the last decade, a large number remain in operation. In other parts of the world, coal-fired power continues to represent a major share of electricity production. Control of sulfur dioxide (SO2) emissions from these plants is essential for protection of air quality. As such, and particularly for wet-limestone flue gas desulfurization (FGD) systems, it is important environmentally and economically to both optimize SO2removal and minimize limestone consumption. Limestone purity and reactivity can vary widely, even within individual limestone formations. Another major variable is coal sulfur content. Use of a chemical additive is beneficial to enhance SO2-limestone reactions, however, difficulties have been encountered regarding the efficiency and availability of previous products. This article outlines the performance and cost improvements of a new compound in a full-scale application on a large coal-fired unit.
Fundamental Wet-Limestone Scrubber Chemistry
A generic flow diagram of a wet-limestone scrubber is illustrated in Figure 1. The process is a classic example of an aqueous acid-base chemistry reaction applied on a large industrial scale, where alkaline limestone slurry reacts with acidic sulfur dioxide.