Oxidized mercury species may be formed in combustion systems through gas-phase reactions between elemental mercury and halogens, such as chorine or bromine. This study examines how bromine and chlorine species affect mercury oxidation in the gas phase. Experiments were conducted in a bench-scale, laminar, methane-fired (300 W), quartz-lined reactor, in which gas composition (HCl, HBr, NO x , and SO 2 ) was varied. In the experiments, the postcombustion gases were quenched from the flame temperature to about 350°C and then speciated mercury was measured using a wet conditioning system and continuous emission monitor (CEM). Bromine was shown to be much more effective in the postflame, homogeneous oxidation of mercury than chlorine, on an equivalent molar basis. The addition of NO to the flame (up to 400 ppmv) had no impact on mercury oxidation by chlorine or bromine. The addition of SO 2 had no effect on mercury oxidation by chlorine at SO 2 concentrations below about 400 ppmv; some increase in mercury oxidation was observed at SO 2 concentrations of 400 ppmv and higher. The addition of chlorine caused minor increases in the extent of oxidation by bromine. The results of this study can be used to understand the relative importance of gasphase mercury oxidation by bromine in combustion systems.

No abstract

The analysis of gas-phase mercury speciation in combustion gases containing bromine and SO 2 was studied using a commercial mercury analyzer coupled with several different wet conditioning systems; the latter allowed the measurement of total or elemental mercury in the combustion gases. The total side of the conditioning system was modified to decrease measurement bias in total mercury by replacing an aqueous tin chloride solution (2 wt % SnCl 2 and 3 wt % HCl) with a solution of hydroxylamine hydrochloride and sodium hydroxide (4 wt % NH 2 OH−HCl and 20 wt % NaOH). This change reduced measurement bias in total mercury in the presence of 50 ppm bromine species (as HBr equivalent) from 60 to 15%. Additional improvements in total mercury recovery were obtained by frequently cleaning the glass walls of the chiller, an essential component of the mercury analysis train. The required frequency increased with increased levels of Br 2 injection through the burner. The impact of cleaning suggests that bromine species may be accumulating on the glass and subsequently heterogeneously oxidizing elemental mercury. Difficulties in recovering total mercury are not seen when using chlorine as the oxidant. The determination of elemental mercury in the presence of bromine and SO 2 yielded results that further suggest that mercury may be heterogeneously oxidized on the glass walls of the impingers and chiller. The presence of SO 2 , whether added through the burner or directly to the KCl impinger, decreased the apparent extent of oxidation of elemental mercury. This decrease may be due to the adsorption of SO 2 and possibly SO 3 on the glass surfaces, thereby preventing the adsorption of elemental mercury and bromine species and subsequent heterogeneous oxidation of elemental mercury.

This report summarizes Year 1 results of a research program designed to use multi-scale experimental studies and fundamental theoretical models to characterize and predict the impacts of retrofit of existing coal-fired utility boilers for oxy-combustion. Through the course of Year 1 activities, great progress was made toward understanding the issues associated with oxy-combustion retrofit of coal-fired boilers. All four Year 1 milestones and objectives have been, or will be, completed on schedule and within budget. Progress in the four milestone areas may be summarized as follows:• University of Utah has performed size segregated ash composition measurements in the Oxy-Fuel Combustor (OFC). These experiments indicate that oxy-combustion retrofit may impact ash aerosol mineral matter composition. Both flame temperature and flue gas composition have been observed to influence the concentration of calcium, magnesium and iron in the fine particulate. This could in turn impact boiler fouling and slagging.• Sandia National Labs has shown that char oxidation rate is dependent on particle size (for sizes between 60 and 100 microns) by performing fundamental simulations of reacting char particles. These predictions will be verified by making time-resolved optical measurements of char particle temperature, velocity and size in bench-scale experiments before the end of Year 1.• REI and Siemens have completed the design of an oxy-research burner that will be mounted on University of Utah's pilot-scale furnace, the L1500. This burner will accommodate a wide range of O 2 , FGR and mixing strategies under conditions relevant for utility boiler operation. Through CFD modeling of the different burner designs, it was determined that the key factor influencing flame stabilization location is particle heat-up rate. The new oxy-research burner and associated equipment is scheduled for delivery before the end of Year 1.• REI has completed a literature survey of slagging and fouling mechanisms in coal-fired power plants to understand key issues influencing these deposition regimes and infer their behavior under oxy-fired conditions. Based on the results of this survey, an algorithm for integrating slagging predictions into CFD models was outlined. This method accounts for ash formation, particle impaction and sticking, deposit growth and physical properties and impact of the deposit on system flow and heat transfer. A model for fouling in the back pass has also been identified which includes vaporization of sodium, deposition of sodium sulfate on fly ash particles and tube surfaces, and deposit growth rate on tubes.In Year 1, REI has also performed a review of the literature describing corrosion in order to understand the behavior of oxidation, sulfidation, chloridation, and carburization mechanisms in air-fired and oxycombustion systems. REI and Vattenfall have met and exchanged information concerning oxy-coal combustion mechanisms for CFD simulations currently used by Vattenfall. In preparation for Year 2 of this program, tw...

This report summarizes Year 1 results of a research program designed to use multi-scale experimental studies and fundamental theoretical models to characterize and predict the impacts of retrofit of existing coal-fired utility boilers for oxy-combustion. Through the course of Year 1 activities, great progress was made toward understanding the issues associated with oxy-combustion retrofit of coal-fired boilers. All four Year 1 milestones and objectives have been, or will be, completed on schedule and within budget. Progress in the four milestone areas may be summarized as follows:• University of Utah has performed size segregated ash composition measurements in the Oxy-Fuel Combustor (OFC). These experiments indicate that oxy-combustion retrofit may impact ash aerosol mineral matter composition. Both flame temperature and flue gas composition have been observed to influence the concentration of calcium, magnesium and iron in the fine particulate. This could in turn impact boiler fouling and slagging.• Sandia National Labs has shown that char oxidation rate is dependent on particle size (for sizes between 60 and 100 microns) by performing fundamental simulations of reacting char particles. These predictions will be verified by making time-resolved optical measurements of char particle temperature, velocity and size in bench-scale experiments before the end of Year 1.• REI and Siemens have completed the design of an oxy-research burner that will be mounted on University of Utah's pilot-scale furnace, the L1500. This burner will accommodate a wide range of O 2 , FGR and mixing strategies under conditions relevant for utility boiler operation. Through CFD modeling of the different burner designs, it was determined that the key factor influencing flame stabilization location is particle heat-up rate. The new oxy-research burner and associated equipment is scheduled for delivery before the end of Year 1.• REI has completed a literature survey of slagging and fouling mechanisms in coal-fired power plants to understand key issues influencing these deposition regimes and infer their behavior under oxy-fired conditions. Based on the results of this survey, an algorithm for integrating slagging predictions into CFD models was outlined. This method accounts for ash formation, particle impaction and sticking, deposit growth and physical properties and impact of the deposit on system flow and heat transfer. A model for fouling in the back pass has also been identified which includes vaporization of sodium, deposition of sodium sulfate on fly ash particles and tube surfaces, and deposit growth rate on tubes.In Year 1, REI has also performed a review of the literature describing corrosion in order to understand the behavior of oxidation, sulfidation, chloridation, and carburization mechanisms in air-fired and oxycombustion systems. REI and Vattenfall have met and exchanged information concerning oxy-coal combustion mechanisms for CFD simulations currently used by Vattenfall. In preparation for Year 2 of this program, tw...

This report summarizes Year 1 results of a research program designed to use multi-scale experimental studies and fundamental theoretical models to characterize and predict the impacts of retrofit of existing coal-fired utility boilers for oxy-combustion. Through the course of Year 1 activities, great progress was made toward understanding the issues associated with oxy-combustion retrofit of coal-fired boilers. All four Year 1 milestones and objectives have been, or will be, completed on schedule and within budget. Progress in the four milestone areas may be summarized as follows:• University of Utah has performed size segregated ash composition measurements in the Oxy-Fuel Combustor (OFC). These experiments indicate that oxy-combustion retrofit may impact ash aerosol mineral matter composition. Both flame temperature and flue gas composition have been observed to influence the concentration of calcium, magnesium and iron in the fine particulate. This could in turn impact boiler fouling and slagging.• Sandia National Labs has shown that char oxidation rate is dependent on particle size (for sizes between 60 and 100 microns) by performing fundamental simulations of reacting char particles. These predictions will be verified by making time-resolved optical measurements of char particle temperature, velocity and size in bench-scale experiments before the end of Year 1.• REI and Siemens have completed the design of an oxy-research burner that will be mounted on University of Utah's pilot-scale furnace, the L1500. This burner will accommodate a wide range of O 2 , FGR and mixing strategies under conditions relevant for utility boiler operation. Through CFD modeling of the different burner designs, it was determined that the key factor influencing flame stabilization location is particle heat-up rate. The new oxy-research burner and associated equipment is scheduled for delivery before the end of Year 1.• REI has completed a literature survey of slagging and fouling mechanisms in coal-fired power plants to understand key issues influencing these deposition regimes and infer their behavior under oxy-fired conditions. Based on the results of this survey, an algorithm for integrating slagging predictions into CFD models was outlined. This method accounts for ash formation, particle impaction and sticking, deposit growth and physical properties and impact of the deposit on system flow and heat transfer. A model for fouling in the back pass has also been identified which includes vaporization of sodium, deposition of sodium sulfate on fly ash particles and tube surfaces, and deposit growth rate on tubes.In Year 1, REI has also performed a review of the literature describing corrosion in order to understand the behavior of oxidation, sulfidation, chloridation, and carburization mechanisms in air-fired and oxycombustion systems. REI and Vattenfall have met and exchanged information concerning oxy-coal combustion mechanisms for CFD simulations currently used by Vattenfall. In preparation for Year 2 of this program, tw...

Oxidized mercury species may be formed in combustion systems through gas-phase reactions between elemental mercury and halogens, such as chorine or bromine. This study examines how bromine species affect mercury oxidation in the gas phase and examines the effects of mixtures of bromine and chlorine on extents of oxidation. Experiments were conducted in a bench-scale, laminar flow, methane-fired (300 W), quartz-lined reactor in which gas composition (HCl, HBr, NO x , SO 2 ) and temperature profile were varied. In the experiments, the post-combustion gases were quenched from flame temperatures to about 350 o C, and then speciated mercury was measured using a wet conditioning system and continuous emissions monitor (CEM). Supporting kinetic calculations were performed and compared with measured levels of oxidation.