CFD Investigation of Hatfield 2 Slag Deposition

In April 2010, Steag Energy Services (formerly ESA) constructed a CFD model of Hatfield's Ferry Unit 2 to simulate the coal combustion and ash deposition patterns in the boiler. The model was used to analyze the combustion characteristics and temperature profiles within the boiler that lead to the accumulation of convective zone slagging and to investigate potential preventative measures to limit future slag accumulation. The model incorporated the actual coal distribution, particle size characteristics and fuel analysis measured during testing by Steag Energy Services (formerly ESA) in January, 2010. Steag Energy Services (formerly ESA) validated the model against actual boiler performance, gas temperature and emission data collected by Steag Energy Services (formerly ESA).

The results of the model indicated that measured fuel imbalances and excessive primary air when coupled with low excess air operation or windbox secondary air imbalances created a locally reducing environment that greatly accelerated the rate of slag accumulation. The burning of a PRB coal blend greatly exacerbated this problem. Based on the findings, Steag Energy Services (formerly ESA) provided several operational recommendations to limit future slag accumulation.

Permanent SNCR Upgrade at Shawville Units 1-4

In 2009, Steag Energy Services (formerly ESA) upgraded seasonal SNCR systems previously installed on Units 1-4 at RRI Energy's Shawville Station for permanent, year-round use in response to EPA's change from seasonal to annual NOx emission limits. The four coal-fired units, two wall-fired and two tangentially fired, total 700 MW net generation. The turnkey SNCR system upgrade featured two heated, insulated 20,000 gallon urea storage tanks in a concrete containment; a heat-traced, insulated urea transfer and circulation system; and multiple zones of automatic retracting injection lances on all four boilers. The control systems allow for operator control of each system from the control room as well as local injector control at each unit. The additional injection zones increased not only the load range of operation for the SNCR but also the NOx removal rate on all units. Steag Energy Services (formerly ESA) conducted optimization testing upon startup of the permanent systems and provides periodic system maintenance.

Seminole SCR Startup, Optimization & Mercury Testing

In 2009, Steag Energy Services (formerly ESA) worked with Hitachi Power Systems who recently installed SCRs on two 715 MW coal fired boilers at Seminole Electric Cooperative's Seminole Station. Steag Energy Services (formerly ESA) provided test support in the startup and tuning of the SCRs. For each unit, this involved traversing a 72-point gaseous grid at the SCR outlet for O2, NOx and SO2; multi-point measurements of ammonia slip at the SCR outlet; and determination of SO2 to SO3 conversion via inlet SO2 traverses as well as inlet and outlet SO3 traverses using the controlled condensation method. One of the boilers was found to be poorly tuned for combustion and Steag Energy Services (formerly ESA) used the gaseous data to quickly improve O2 & CO distribution with burner air damper adjustments.

Steag Energy Services (formerly ESA) also performed mercury tests at both the SCR inlet and outlet of Unit 2 using the Ontario Hydro method to determine the rate of oxidation of vapor phase mercury in the catalyst.

SNCR, OFA and FGR on Bayfront Stokers

In 2008, Steag Energy Services (formerly ESA) designed and installed combustion modifications and NOx control systems on two stoker boilers at Xcel's Bayfront station in Ashland, WI. The twin stoker units fire both coal and waste wood. The combustion modifications included an overfire air system to reduce NOx emissions, a flue-gas recirculation sytem to stabilize conditions at the stoker grate, and sweep air modifications to improve fuel delivery. A multi-zone urea SNCR system with auto-retract injectors was also installed on each unit to further reduce NOx. Steag Energy Services (formerly ESA) used CFD modeling in the design of the OFA, FGR and SNCR systems.

The extreme winter temperatures of northern Wisconsin also presented significant challenges in the design of a urea SNCR system for year-round operation. A urea storage facility was installed that included a 10,000 gallon heated urea storage tank, as well as an indoor unloading area for the delivery truck. A heat-traced urea transfer and circulation system tied the urea storage facility to the SNCR process skid.

The limited space in the boiler house presented a considerable challenge to the installation of the OFA and FGR fans and related duct work and dampers. FGR fans were installed on the rooftop; OFA fans under the boilers. Steag Energy Services (formerly ESA) provided startup commissioning, tuning, optimization testing, and operator training for each new system component to insure their smooth integration into full-time operation.

SPR Coronado Baseline NOx Characerization, Acceptance Testing

On this multi-phase project, Steag Energy Services (formerly ESA) worked with Babcock Power and Salt River Project. Steag Energy Services (formerly ESA) first conducted baseline NOx characterization on both Riley turbo-fired units at Coronado, which would eventually be retrofitted with new combustion systems designed by Babcock Power. Steag Energy Services (formerly ESA) provided emissions data throughout the startup and optimization period, during which the Unit 1 combustion system caused excessively high steam temperatures. After the burner supplier left the site, Steag Energy Services (formerly ESA) continued to work with SRP operations personnel at optimizing combustion to bring steam temperatures under control.

SNCR Systems on 10 Reliant Energy Boilers

In 2005, Steag Energy Services (formerly ESA) helped Reliant Energy achieve its NOx compliance strategy by installing SNCR sytems on ten boilers at the Avon Lake, Niles, New Castle and Shawville stations. The systems, intended for temporary, seasonal NOx control, used frac tanks for urea storage and rubber hoses to transport chemical to the injection headers near the upper furnace. Reliant was given the option to purchase the PLC-controlled systems at the end of the season. Based on the systems' performance, Reliant purchased all ten systems and continued to use them during subsequent summer NOx seasons. Eventually, Reliant (now RRI Energy) chose to upgrade four of the systems for permanent, year-round operation.

SNCR at Ft. Martin Units 1 and 2

Late 2003 Steag Energy Services (formerly ESA) began engineering design of full scale SNCR systems for a 500 MW T-fired unit and a 500 MW wall fired unit at Allegheny Power's Ft. Martin Station in Maidsville, WV. Steag Energy Services (formerly ESA) initially installed temporary reagent distribution and injection equipment and successfully demonstrated SNCR technology on each unit. In early 2004, construction and installation of the engineered full-scale systems began and was completed in time for startup and commissioning at the beginning of the NOx season. Steag Energy Services (formerly ESA) subsequently provided tuning and testing services to insure optimum operation and minimal impact on plant operation.

Design and Optimization of OFA Systems on 15 Stockers

Steag Energy Services (formerly ESA) designed and recently completed the optimization of the overfire air systems installed on fifteen stoker boilers owned by Cogentrix at three generating stations. These aggressive new overfire air systems consist of two headers feeding OFA ports situated along the side walls of the furnace thus allowing better distribution and penetration than traditional front and rear port locations. The distance of the ports above the stoker bed allows for increased combustion staging, significantly reducing NOx emissions without negative impact on grate conditions or other emissions. On four of these boilers, a portion of the overfire air was used for ash reinjection while flue gas was recirculated from the ID fan inlet to the undergrate air compartments and front overfire air port, further enhancing NOx reductions.

Steag Energy Services (formerly ESA) provided the engineering design for these systems and provided parametric emissions testing on each boiler to determine optimum operational parameters.

Low NOx Burner Redesign for Gallagher Unit 4

Problem: Unit 4 at Cinergy's Gallagher station in New Albany Indiana is a 155 MW wall fired unit equipped with overfire air and recently retrofitted FW Vortex low-NOx burners. The new burners were causing various problems, including:

• NOx emissions not at target levels
• High opacity after retrofit
• Increased airflow requirements and WB pressure
• Increased superheat spray use
• Inablility to use OFA after retrofit
• Low load instability

Extensive tuning by Foster wheeler and Cinergy was unable to solve the problem.

Solution: Steag Energy Services's (formerly ESA) basic initial hypothesis was a fuel and air mixing problem. Steag Energy Services's (formerly ESA) approach was to review existing data, conduct baseline testing for a more thorough look at unit operation, build CFD models of burners, windbox and furnace to examine air and fuel mixing, to use CFD models to determine the root cause of the problem and to design and test a solution using CFD models.

Modeling results showed that a convergent fuel stream leaving the burners unbroken by secondary air caused large concentrations of fuel to proceed up the rear wall of the furnace. Overfire air was found uable to penetrate to this fuel rich zone. The fuel tip was redesigned with divergent swirling splits.

The redesigned fuel tips improved secondary air flow and mixing, reduced rear wall impingement, allowed better adjustment and tuning and enabled reduced O2 operation. With increased use of overfire air, NOx was lowered and stack opacity was no longer a problem.

Cogentrix Methane DeNOx Process Design and Installation

Steag Energy Services (formerly ESA) is the licensee of a NOx Control Technology known as METHANE de-NOX that was developed by the Gas Technology Institute (GTI). The technology is used to reduce NOx emissions from stoker-fired boilers and involves the use of flue gas recirculation, overfire air and natural gas injection. Steag Energy Services (formerly ESA) has recently completed baseline testing of Cogentrix's Hopewell Unit 2A near Richmond, Virginia as part of a Methane DeNOX system design project. As part of the work recently completed, Steag Energy Services (formerly ESA) provided test equipment, engineers and technicians to characterize the baseline emission levels and operating characteristics of the unit as a function of various operating parameters.

Steag Energy Services (formerly ESA) is currently overseeing the construction and installation of the METHANE de-NOX system at the Hopewell station. The complete installation involves installation of flue gas recirculating fan and ducts, overfire air ducts and ports, a natural gas flow-control skid and control system. Steag Energy Services (formerly ESA) environmental solutions provided the complete system design, the gas skid and the control system while Cogentrix installed the fan, duct work and field wiring. The system is scheduled for startup in early 2003.

Entergy Combustion Optimization

In the spring of 2002, Entergy hired Steag Energy Services (formerly ESA) to perform combustion tuning and optimization services on six natural gas-fired units at two generating stations. Target NOx emission rates were achieved at various loads on three CE tangential units, one B&W cell burner unit and one Foster Wheeler wall fired unit at the Willow Glen station (1,875 MW total) in St. Gagriel, LA, as well as another 550,000 lb/hr unit at the Louisiana Station in Baton Rouge, LA. NOx reductions of as much as 50% were required to achive the 0.1 lb/MMBtu emission target. The target emission rate was achieved by various techniques including burners out of service, combustion air staging, water and steam injection. The successful seven-week effort provided Entergy with a feasible low NOx baseline with which to plan their overall compliance strategy.

Kentucky Utilities Baseline Emissions Characterization

Steag Energy Services (formerly ESA) recently completed baseline performance and emissions testing for Kentucky Utilities' E.W. Brown Station, Unit 1, near Lexington, Kentucky. The owners of this coal-fired unit are beginning the preliminary evaluation of NOx control options for the unit. As part of this preparation, and potentially for future burner bid documents, Steag Energy Services (formerly ESA) was contracted to document the unit baseline emission and efficiency characteristics.

Reliant Energy

Steag Energy Services (formerly ESA) has provided engineering and NOx control expertise to the generating stations currently owned by Reliant Energy near Pittsburgh, Pennsylvania (formerly Duquesne Light). These stations include Elrama, Cheswick, Niles and Avon Lake. Steag Energy Services (formerly ESA) has worked with the operators of these stations for more than 15 years. Our work has included the supply of low NOx burner modifications, supply of overfire air systems, turnkey supply of Fuel Lean Gas Reburn (FLGR) technology, turnkey supply of Select Non Catalytic Reduction (SNCR) technology, design and supply of low temperature ammonia injection for flue gas conditioning, baseline and low NOx burner combustions optimization, low NOx burner acceptance testing and consulting on burner and boiler operating problems.

Ontario Power Generation

Steag Energy Services (formerly ESA) is the licensee of a technology known as Fuel Lean Gas Reburn (FLGR) that was invented by Steag Energy Services (formerly ESA) and developed by the Gas Research Institute (GRI). The technology involves the injection of natural gas into the upper furnace of fossil fueled boilers for the purpose of reducing NOx emissions. Steag Energy Services (formerly ESA) was awarded a contract to provide FLGR technology for Ontario Power Generation's Nanticoke Unit 6, near Hamilton, Ontario. Nanticoke is the largest fossil fueled generating station in North America, having a total generating capability of more than 4000 MW. Unit 6 is a 510 MW opposed wall fired unit. Steag Energy Services (formerly ESA) designed and supplied an FLGR system for Unit 6 in the spring of 2001. Steag Energy Services's (formerly ESA) scope of work included baseline testing, CFD design modeling, process engineering, equipment selection, procurement and fabrication, control logic engineering and configuration, system installation support, startup and about 6 weeks of on-site optimization testing.

Texas Municipal Power Agency

Steag Energy Services (formerly ESA) was contracted by the Texas Municipal Power Agency (TMPA) near College Station, Texas to provide baseline emissions and boiler efficiency testing on their Gibbons Creek Station Unit 1. Unit 1 is a 450 MW tangentially fired coal unit. Steag Energy Services (formerly ESA) was hired to evaluate existing low NOx burner equipment, optimize combustion, evaluate the potential for additional NOx reduction with this equipment and to prepare a baseline data set that could be used to bid, select and procure a new low NOx firing system. Steag Energy Services (formerly ESA) provided equipment and test personnel for two weeks of on-site testing.