The U.S. Department of Energy and EPRI have co-funded this project to improve the control of mercury emissions from coal-fired power plants equipped with wet flue gas desulfurization (FGD) systems. The project investigated catalytic oxidation of vapor-phase elemental mercury to a form that is more effectively captured in wet FGD systems. If successfully developed, the process could be applicable to over 90,000 MW of utility generating capacity with existing FGD systems and to future FGD installations.
This document is the final report for Cooperative Agreement DE-FC26-04NT42314, "Kinetics Study of Mercury Reactions in FGD Liquors." The project was co-funded by the U.S. DOE National Energy Technology Laboratory and EPRI. The objective of the project has been to determine the mechanisms and kinetics of the aqueous reactions of mercury absorbed by wet flue gas desulfurization (FGD) systems, and develop a kinetics model to predict mercury reactions in wet FGD systems. The model may be used to determine optimum wet FGD design and operating conditions to maximize mercury capture in wet FGD systems.Initially, a series of bench-top, liquid-phase reactor tests were conducted and mercury species concentrations were measured by UV/visible light spectroscopy to determine reactant and byproduct concentrations over time. Other measurement methods, such as atomic absorption, were used to measure concentrations of vapor-phase elemental mercury, that cannot be measured by UV/visible light spectroscopy.Next, a series of bench-scale wet FGD simulation tests were conducted. Because of the significant effects of sulfite concentration on mercury re-emission rates, new methods were developed for operating and controlling the bench-scale FGD experiments. Approximately 140 bench-scale wet FGD tests were conducted and several unusual and pertinent effects of process chemistry on mercury re-emissions were identified and characterized.These data have been used to develop an empirically adjusted, theoretically based kinetics model to predict mercury species reactions in wet FGD systems. The model has been verified in tests conducted with the bench-scale wet FGD system, where both gas-phase and liquid-phase mercury concentrations were measured to determine if the model accurately predicts the tendency for mercury re-emissions.This report presents and discusses results from the initial laboratory kinetics measurements, the bench-scale wet FGD tests, and the kinetics modeling efforts.v LIST OF TABLES EXECUTIVE SUMMARYThis document is the final report for DOE-NETL Cooperative Agreement DE-FC26-04NT42314, "Bench-scale Kinetics Study of Mercury Reactions in FGD Liquors." In the project, experimental methods were developed initially to use spectrophotometry to identify key reaction intermediate species in the reduction of oxidized mercury to elemental mercury under wet flue gas desulfurization (FGD) conditions, and to track their changes in concentration as the reactions proceeded. Separate but complementary methods for following the rate of evolution of mercury into the gas phase, and loss of mercury from the liquid phase were developed and applied. Using these methods, it has been determined that mercuric sulfite and chlorosulfite complexes form when oxidized mercury is absorbed by FGD systems, and correspondingly decompose to produce elemental mercury re-emissions. The rate of disappearance of the mercuric sulfite and chlorosulfite complexes and the corresponding rate of formation of elemental mercury were monitored by independent...
This document is the final technical report for Cooperative Agreement DE-FC26-04NT41992, "Pilot Testing of Mercury Oxidation Catalysts for Upstream of Wet FGD Systems," which was conducted over the time-period January 1, 2004 through December 31, 2010. The objective of this project has been to demonstrate at pilot scale the use of solid catalysts and/or fixed-structure mercury sorbents to promote the removal of total mercury and oxidation of elemental mercury in flue gas from coal combustion, followed by wet flue gas desulfurization (FGD) to remove the oxidized mercury at high efficiency. The project was co-funded by the U.S. DOE National Energy Technology Laboratory (DOE-NETL), EPRI, Great River Energy (GRE), TXU Energy (now called Luminant), Southern Company, Salt River Project (SRP) and Duke Energy. URS Group was the prime contractor.The mercury control process under development uses fixed-structure sorbents and/or catalysts to promote the removal of total mercury and/or oxidation of elemental mercury in the flue gas from coal-fired power plants that have wet lime or limestone FGD systems. Oxidized mercury not adsorbed is removed in the wet FGD absorbers and leaves with the byproducts from the FGD system.The project has tested candidate materials at pilot scale and in a commercial form, to provide engineering data for future full-scale designs. Pilot-scale catalytic oxidation tests have been completed for periods of approximately 14 to19 months at three sites, with an additional round of pilot-scale fixed-structure sorbent tests being conducted at one of those sites. Additionally, pilotscale wet FGD tests have been conducted downstream of mercury oxidation catalysts at a total of four sites. The sites include the two of three sites from this project and two sites where catalytic oxidation pilot testing was conducted as part of a previous DOE-NETL project. Pilot-scale wet FGD tests were also conducted at a fifth site, but with no catalyst or fixed-structure mercury sorbent upstream.This final report presents and discusses detailed results from all of these efforts, and makes a number of conclusions about what was learned through these efforts.
This document presents and discusses results from Cooperative Agreement DE-FC26-06NT42778, "Full-scale Testing of a Mercury Oxidation Catalyst Upstream of a Wet FGD System," which was conducted over the time-period July 24, 2006 through June 30, 2010. The objective of the project was to demonstrate at full scale the use of solid honeycomb catalysts to promote the oxidation of elemental mercury in pulverized-coal-fired flue gas. Oxidized mercury is removed downstream in wet flue gas desulfurization (FGD) absorbers and collected with the byproducts from the FGD system. The project was co-funded by EPRI, the Lower Colorado River Authority (LCRA), who also provided the host site, Great River Energy, Johnson Matthey, Southern Company, Salt River Project (SRP), the Tennessee Valley Authority (TVA), NRG Energy, Ontario Power and Westar. URS Group was the prime contractor and also provided cofunding.The scope of this project included installing and testing a gold-based catalyst upstream of one full-scale wet FGD absorber module (about 200-MW scale) at LCRA's Fayette Power Project (FPP) Unit 3, which fires Powder River Basin coal. Installation of the catalyst involved modifying the ductwork upstream of one of three wet FGD absorbers on Unit 3, Absorber C. The FGD system uses limestone reagent, operates with forced sulfite oxidation, and normally runs with two FGD modules in service and one spare. The full-scale catalyst test was planned for 24 months to provide catalyst life data. Over the test period, data were collected on catalyst pressure drop, elemental mercury oxidation across the catalyst module, and mercury capture by the downstream wet FGD absorber.The demonstration period began on May 6, 2008 with plans for the catalyst to remain in service until May 5, 2010. However, because of continual increases in pressure drop across the catalyst and concerns that further increases would adversely affect Unit 3 operations, LCRA decided to end the demonstration early, during a planned unit outage. On October 2, 2009, Unit 3 was taken out of service for a fall outage and the catalyst upstream of Absorber C was removed. This ended the demonstration after approximately 17 months of the planned 24 months of operation. This report discusses reasons for the pressure drop increase and potential measures to mitigate such problems in any future application of this technology.Mercury oxidation and capture measurements were made on Unit 3 four times during the 17-month demonstration. Measurements were performed across the catalyst and Absorber C and "baseline" measurements were performed across Absorber A or B, which did not have a catalyst upstream. Results are presented in the report from all four sets of measurements during the demonstration period. These results include elemental mercury oxidation across the catalyst, mercury capture across Absorber C downstream of the catalyst, baseline mercury capture across Absorber A or B, and mercury re-emissions across both absorbers in service. Also presented in the report are estim...
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