A DSI System Installation at a Midwest Utility: A Low-Cost Pollutant Control Solution

摘要

Dry sorbent injection (DSI) systems have been in service for more than 20 years at coal-fired generating stations, providing an effective tool for reducing sulfur dioxide acid gas emission levels. Current and pending environmental regulations have prompted a revival of interest in DSI as a low capital-cost, multi-pollutant control solution. This paper describes the installation of a new dry sorbent injection (DSI) system at a coal-fired generating station (hereafter referred to as 'the station') owned by a cooperative (hereafter referred to as 'the utility') located in the Midwestern U.S. It also presents a before-and-after comparison of emission results. The utility did preliminary testing and proof of concept, during which it tried both 'trona' - trisodium hydrogendicarbonate dihydrate (Na_3(CO_3)(HCO_3)·2H_2O) - and sodium bicarbonate (NaHCO_3 but abbreviated here as SBC). The results showed that SBC would easily meet the utility's objective of approximately 82 percent removal of total sulfur dioxide (SO_2), so it proceeded with designing and building a system that would inject SBC. This project warrants discussion because it demonstrates an economical solution for enabling certain coal-fired energy facilities to comply with recently enacted air-quality regulations and thus remain viable. Using SBC, the DSI system achieves SO_2 removal percentages that rival the performance of scrubbers. DSI thus provides a feasible alternative for units for which it would not prove cost-effective to invest in a wet or dry flue-gas desulfurization (FGD) system.