Uniqueness of SCR retrofits translates into broad cost variations

摘要

The growing population of U.S. SCR systems provides an opportunity to examine the impact of various factors on installed costs. This analysis is based on SCR retrofit installations on balanced draft, pulverized coal boiler units with size ranges from 150-200 to 900-1000 MW. The anonymous units are in four states, east of the Mississippi River. The cost data are from various retrofits at varying levels of completion or installation. As a whole, the cost results are at a stage of development that allows for meaningful and reasonably consistent comparison. When characterizing costs of SCR retrofits on a regional or industry basis, their uniqueness and complexity suggest that it is better to consider them as a broad range rather than as an average cost. For the more than 20 units included in this analysis, SCR retrofit costs ranged from about ＄80-160/kW, with about 70 percent of the units in this sample above ＄100/kW. The wide range of SCR retrofit costs is indicative of site-specific factors, scope differences, and site congestion. SCR retrofits are not only added to an existing plant site, but are also incorporated within the existing flue gas path, adding significant pressure drop, which increases auxiliary power requirements. While constituting a modest sample compared to the entire population of SCR retrofits, the sample size is large enough to indicate with some confidence that most previous predictions (nominally from the mid 1990s) understated SCR retrofit costs. Sites with highly congested "back end" areas will have a much higher cost than sites with little congestion. Capital costs can be as much as 35 percent higher or 30 percent lower than the regression fit of plants in the 400-900 MW size range.