FIELD TEST PROGRAM TO DEVELOP COMPREHENSIVE DESIGN, OPERATING, AND COST DATA FOR MERCURY CONTROL SYSTEMS
Brayton Point Unit 1 was successfully tested for applicability of activated carbon injection as a mercury control technology. Test results from this site have enabled a thorough evaluation of the impacts of future mercury regulations to Brayton Point Unit 1, including performance, estimated cost, and operation data. This unit has variable (29-75%) native mercury removal, thus it was important to understand the impacts of process variables and activated carbon on mercury capture. The team responsible for executing this program included: (1) Plant and PG&E National Energy Group corporate personnel; (2) Electric Power Research Institute (EPRI); (3) United States Department of Energy National Energy Technology Laboratory (DOE/NETL); (4) ADA-ES, Inc.; (5) NORIT Americas, Inc.; (6) Apogee Scientific, Inc.; (7) TRC Environmental Corporation; (8) URS Corporation; (9) Quinapoxet Solutions; (10) Energy and Environmental Strategies (EES); and (11) Reaction Engineering International (REI). The technical support of all of these entities came together to make this program achieve its goals. Overall, the objectives of this field test program were to determine the impact of activated carbon injection on mercury control and balance-of-plant processes on Brayton Point Unit 1. Brayton Point Unit 1 is a 250-MW unit that fires a low-sulfur eastern bituminous coal. Particulate control is achieved by two electrostatic precipitators (ESPs) in series. The full-scale tests were conducted on one-half of the flue gas stream (nominally 125 MW). Mercury control sorbents were injected in between the two ESPs. The residence time from the injection grid to the second ESP was approximately 0.5 seconds. In preparation for the full-scale tests, 12 different sorbents were evaluated in a slipstream of flue gas via a packed-bed field test apparatus for mercury adsorption. Results from these tests were used to determine the five carbon-based sorbents that were tested at full-scale. Conditions of interest that were varied included SO{sub 3} conditioning on/off, injection concentrations, and distribution spray patterns. The original test plan called for parametric testing of NORIT FGD carbon at 1, 3, and 10 lbs/MMacf. These injection concentrations were estimated based on results from the Pleasant Prairie tests that showed no additional mercury removal when injection concentrations were increased above 10 lbs/MMacf. The Brayton Point parametric test data indicated that higher injection concentrations would achieve higher removal efficiencies and should be tested. The test plan was altered to include testing at 20 lbs/MMacf. The first test at this higher rate showed very high removal across the second ESP (>80%). Unlike the ''ceiling'' phenomenon witnessed at Pleasant Prairie, increasing sorbent injection concentration resulted in further capture of vapor-phase mercury. The final phase of field-testing was a 10-day period of continuous injection of NORIT FGD carbon. During the first five days, the injection concentration was held at 10 lbs/MMacf, followed by nominally five days of testing at an injection concentration of 20 lbs/MMacf. The mercury removal, as measured by the semi-continuous emission monitors (S-CEM), varied between 78% and 95% during the 10 lbs/MMacf period and increased to >97% when the injection concentration was increased to 20 lbs/MMacf. During the long-term testing period, mercury measurements following EPA's draft Ontario Hydro method were conducted by TRC Environmental Corporation at both 10 and 20 lbs/MMacf test conditions. The Ontario Hydro data showed that the particulate mercury removal was similar between the two conditions of 10 or 20 lbs/MMacf and removal efficiencies were greater than 99%. Elemental mercury was not detected in any samples, so no conclusions as to its removal can be drawn. Removal of oxidized mercury, on the other hand, increased from 68% to 93% with the higher injection concentration. These removal rates agreed well with the S-CEM results.
- Research Organization:
- ADA Environmental Solutions (US)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- FC26-00NT41005
- OSTI ID:
- 839121
- Resource Relation:
- Other Information: PBD: 17 Mar 2005
- Country of Publication:
- United States
- Language:
- English
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