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environmental screening and engineering-cost study

environmental screening and engineering-cost study
Cedar Falls Utilities
Cedar Falls, Iowa

Cedar Falls Utilities’ Streeter Station operates two older coal-fired units: a 15MW stoker unit with a fabric filter for controlling particulate matter (PM), and a 40MW pulverized-coal unit equipped with a hot-side electrostatic precipitator to control PM.

Barr’s work related primarily to the second unit, which was subject to several new air-quality regulations. We began by conducting an environmental screening study in which we created an emissions profile for the unit. Our work included characterizing the stack flow and stack constituents, as well as emissions rates and annual emissions levels. Then we ran a high-level air dispersion model (AERMOD) to confirm compliance with NAAQS requirements. The process data, new emissions-performance requirements, and modeling results allowed us to develop a set of potential compliance strategies, one of which was retrofitting both units to combust natural gas rather than coal.

After Cedar Falls Utilities reviewed the study, the company commissioned Barr to develop capital and O&M costs for five pollution-control technologies. The study had suggested that switching to natural gas would be the most economical alternative, since unlike coal, it would require control of only NOx. Barr provided detailed estimates for selective noncatalytic reduction, low-NOx burner, and overfire air system additions. We performed screening-level estimates for the other three options, which were deemed less likely to be implemented but were still necessary for our client to evaluate and compare costs for the alternatives and present the findings to the utility’s board of directors.

The utility ultimately revised its operating schedule to fire primarily natural gas, with very limited coal backup during possible curtailments.