Investigation and Demonstration of Dry Carbon-Based Sorbent Injection for Mercury Control
Public Service Company of Colorado and ADA Technologies, Inc. have performed a study of the injection of activated carbon for the removal of vapor-phase mercury from coal-fired flue gas streams. The project was completed under contract to the US Department of Energy's National Energy Technology Laboratory, with contributions from EPRI and Public Service Company. The prime contractor for the project was Public Service Company, with ADA Technologies as the major subcontractor providing technical support to all aspects of the project. The research and development effort was conducted in two phases. In Phase I a pilot facility was fabricated and tests were performed using dry carbon-based sorbent injection for mercury control on a coal-fired flue gas slipstream extracted from an operating power plant. Phase II was designed to move carbon injection technology towards commercial application on coal-fired power plants by addressing key reliability and operability concerns. Phase II field work included further development work with the Phase I pilot and mercury measurements on several of PSCo's coal-fired generating units. In addition, tests were run on collected sorbent plus fly ash to evaluate the impact of the activated carbon sorbent on the disposal of fly ash. An economic analysis was performed where pilot plant test data was used to develop a model to predict estimated costs of mercury removal from plants burning western coals. Testing in the pilot plant was undertaken to quantify the effects of plant configuration, flue gas temperature, and activated carbon injection rate on mercury removal. All three variables were found to significantly impact the mercury removal efficiency in the pilot. The trends were clear: mercury removal rates increased with decreasing flue gas temperature and with increasing carbon injection rates. Mercury removal was much more efficient with reverse-gas and pulse-jet baghouse configurations than with an ESP as the particulate control device. The native fly ash of the host unit provided significant mercury removal capacity, so that the activated carbon sorbent served as an incremental mercury removal mechanism. Tests run to characterize the waste product, a combination of fly ash and activated carbon on which mercury was present, showed that mercury and other RCRA metals of interest were all below Toxic Characteristic Leaching Procedure (TCLP) regulatory limits in the leachate. The presence of activated carbon in the fly ash was shown to have an effect on the use of fly ash as an additive in the manufacture of concrete, which could limit the salability of fly ash from a plant where activated carbon was used for mercury control.
- Research Organization:
- Public Service Company of Colorado
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC22-95PC95256
- OSTI ID:
- 883038
- Country of Publication:
- United States
- Language:
- English
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