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Fuels, Combustion, and Emission Issues (13)
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The Occurrence of Inorganic Elements in Various Biofuels and Its Effect on the Formation of Melt Phases During Combustion
Sharon Falcone Miller, Bruce G. Miller
Proc. ASME. IJPGC2002, 2002 International Joint Power Generation Conference, 873-880, June 24–26, 2002
Paper No: IJPGC2002-26177
DOI: https://doi.org/10.1115/IJPGC2002-26177
The Pennsylvania State University is performing a feasibility analysis on installing a circulating fluidized bed (CFB) boiler at Penn State's University Park campus for cofiring multiple biofuels and other wastes with coal. Twenty feedstocks are being considered. Chemical fractionation analysis was performed on eleven of the fuels. It is the objective of this paper to present the results of characterizing selected biomass fuels via chemical fractionation. The chemical analysis of the fuels is then used to determine the net ash composition of possible fuel blends and their propensity to form liquid phases during combustion based on thermodynamic modeling. The FactSage equilibrium calculations suggest that a cofire of biofuels with an appropriate non-fouling coal should not pose any problems in a CFB system given that the coal makes up a majority of the thermal input. FactSage consistently predicted K 2 Si 4 O 9 (l) to be present at 1171K with biofuels having low aluminum levels and significant concentration of alkali earth elements. Only 10% of K 2 O present in a system was enough to result in the formation of K 2 Si 4 O 9 (l) at equilibrium that could compromise a CFB system.
Topics: Biofuel, Combustion, Fuels, Coal, Equilibrium (Physics), Aluminum, Biomass, Boilers, Co-firing, Feedstock
Performance of Water Cannons at Labadie
Charlie Breeding, Thomas W. Ziegler
Amerens Labadie station consists of 4 coal fired 600 megawatt size generating units. Unit 1 installed water cannon furnace cleaning devices during a spring outage this year. Water cannons were selected to clean the deposits that result from combustion of Powder River Basin (PRB) coal at the Labadie power plant. This paper describes the evaluation of methods of cleaning furnace walls and the selection, installation, and startup experience with water cannons. Cleaning the furnace results in an increase in boiler efficiency that is translated into improved heat rate and improved cost of plant operation. Benefits from water cannon installation are described along with the problems encountered. PRB fuel combustion results in tenacious deposits that inhibit heat transfer on furnace walls. PRB coal typically has a lower ash fusion temperature than bituminous coals which leads to ash slag formation in furnaces that have been changed to PRB from the fuel the boiler was originally designed for. Often the deposit from PRB fuel is of a minimal thickness, however the reflectivity of the deposit creates a high barrier to radiant heat transfer. High Furnace Exit Gas Temperature (FEGT) indicates poor heat transfer in the furnace area and this increases the formation of slag in convection passes. Cleaning of furnace surface is critical to maximizing the heat absorption of the furnace and reducing the FEGT. The increased clean capability of the water cannons compared to existing wall blowers will be compared in this paper.
Topics: Artillery, Water, Furnaces, Coal, Fuels, Boilers, Combustion, Heat, Heat transfer, Slags
Implementation of SCR Systems for Three Boilers at the TVA Paradise Fossil Site
Donald Schreyer, Arnold Manaker, Scot Pritchard
In 1998, TVA undertook the implementation of Selective Catalytic Reduction systems at the Paradise Generating Station. The station has three fossil-fired cyclone boilers totaling 2515 Mw of power generation which have been online since the early 1960s for Paradise Units 1 and 2, and since 1970 for Unit 3. Design efforts started late 1998 with Paradise Unit 2, a 704 Mw cyclone-fired unit that went into operation for the May 2000 ozone season. This was followed by Paradise Unit 1, an identical 704 Mw unit that went into operation for the May 2001 ozone season. Paradise Unit 3, an 1107 Mw unit, is currently in manufacture and erection for placement into service for the 2003 ozone season. The Paradise Units 1 & 2 SCR modules are among the largest single modules in service for treating the entire flue gas path. The system design considered the operation of the boiler without overfire air NOx control, where the emission of NOx would be 688.5 g/GJ (1.6 lb/MMBtu) and with overfire air NOx emission of 370 g/GJ (0.86 lb/MMBtu). Paradise Units 1 & 2 are fitted with scrubbers and burn a high sulfur fuel. Paradise 3, not currently fitted with a scrubber, fires a blend of PRB and Utah bituminous coal. The SCR is configured with two modules. The SCR project guarantees are 90% NOx reduction, 2-ppm ammonia slip and a catalyst life of 20,000 hours. Each of the cyclone units retained their tubular air heaters. Each unit required the erection of either temporary or new ductwork from the air heater to the downstream equipment to allow the demolition of equipment that had been part of the gas path but is no longer in service. The old equipment had to be removed to permit the building of the SCRs. Each SCR unit is equipped with a full flow bypass and man-safe dampers. These man-safe dampers permitted the construction and maintenance of the SCR while the boiler was in operation. Paradise Unit 2's SCR was fitted with steam soot blowers. Sonic horns were tested on a section of Unit 2 and based on the results, Paradise Unit 1 was fitted only with sonic horns for catalyst cleaning. The anhydrous ammonia unloading and storage facility is more than a mile from the ammonia vaporizers that are located at grade adjacent to their respective SCR unit. The monthly ammonia consumption under full power conditions for Paradise Units 1 & 2 and 90% NOx reduction is 1,703.3 m 3 (450,000 gallons) per month with the overfire air system in service. This paper addresses the issues and decisions related to integration of the SCR systems and the experiences of manufacturing and erecting each of the SCR units.
Topics: Boilers, Nitrogen oxides, Catalysts, Dampers, Design, Emissions, Coal, Construction, Demolition, Ducts
Experimental Study on a Packed Bed Humidifier in an Evaporative Gas Turbine
Farnosh Dalili, Mats Westermark
This paper examines the performance of gas turbine cycles operating with a mixture of air and water vapor. Special attention is paid to the humidification tower, where the water vapor is added to the air. The experiments in this study have been carried out in the first evaporative gas turbine pilot plant located at Lund Institute of Technology in the southern part of Sweden. This pilot plant is based on a Volvo VT600 gas turbine with a design load of 600 kW. The compressor pressure is just above 8 bars and the intake air-flow is 3.4 kg/s. Roughly 70 percent of the compressed air is humidified in the humidification tower, which is the only humidifying device. The tower diameter is 0.7 m and the total flexible packing height is 0.9 m of a stainless steel structured packing with a specific surface area of 240 m 2 /m 3 . The number of mass transfer units in the humidifier was experimentally determined to about 3 for a packing height of 0.45 m. The height of a transfer unit from the literature data for the packing is predicted to be 0.24 m. With a packing height of 0.45 m, only about 2 transfer units are expected from the packing. However, the droplet zones above and below the packing contribute about 1 transfer unit. Thus, it is concluded that the mass transfer performance of the packing is adequately predicted by literature data. Equations are provided to adjust the height of a transfer unit for other pressures and temperatures. For full-scale plants operating at higher pressures and temperatures it is suggested that the high quality exhaust heat, (temperatures above the boiling point) is recovered in a boiler and injected as steam. The remaining part of the exhaust heat, (temperatures below the boiling point) is used to produce hot water for a relatively small humidification tower using only a portion of the compressed air flow.
Topics: Gas turbines, Humidifiers, Packing (Shipments), Packings (Cushioning), Temperature, Compressed air, Exhaust systems, Heat, Mass transfer, Phase transition temperature
Peterhead Power Station: Parallel Repowering Innovative Steam Turbine Enhancement
Thomas Depolt, Edwin Gobrecht, Gu¨nter Musch
In the year 2000 one of Europe's most flexible power stations was commissioned by the authors' company. The existing fossil fired power station was modified by a "Parallel Repowering". With that concept three gas turbines (GT) in combination with three heat recovery steam generators (HRSG) were tied-in additionally to the fired boiler. This concept is compelling especially for large steam power plants and offers more flexibility than "Full Repowering" in matching GTs with the existing steam turbine (ST). The key to maintaining reliability of the repowered unit is the ST modernisation. Plant operability enhancements provide the flexibility of the fired boiler and ST for load following and peaking purposes. The authors' company was responsible for the complete conversion of the fossil fired power station into a modern combined cycle unit. This comprises the tie-in of new steam pipes, bypass stations and the upgrade of the steam turbine auxiliaries as well as the implementation of a new automation system parallel to the existing one. The "Parallel Repowering" offers a maximum of operation variations: •Conventional (Rakine cycle) mode. •Open cycle mode (only GT). •Combined cycle mode. •Hybrid mode. The non-OEM steam turbine needed to be modified for the combined cycle operation with GTs. The condenser load had to be kept as low as possible because of the existing condenser design. Auxiliary systems like the gland steam system and the drain system had to be modified for all different operating modes. Special design features, like the IP rotor cooling system and the flange heating system, had to be extended to operate under all circumstances. One essential difference to the existing operational mode is the necessity of a steam bypass operation. Existing cold reheat (CRH) piping is of carbon steel, so the ST needs to be started with an isolated HP cylinder. The following modifications for the HP turbine were necessary: •For the isolated HP cylinder operation non-return valves (NRV) were built into the CRH line at the HP turbine exhaust. •The HP cylinder will be automatically isolated by closure of the HP valves and the non-return valves in the CRH line, and the simultaneous opening of the HP vent line. •As no instrumentation was available for a reliable monitoring of the isolated operation, a controlled reverse flow from the CRH to the HP vent line was established. •The HP cylinder evacuation is controlled by a dedicated control logic.
Topics: Power stations, Steam turbines, Cylinders, Cycles, Steam, Valves, Boilers, Combined cycles, Condensers (steam plant), Design
Parametric Studies of Power Plant Performance Monitoring
Vijiapurapu Sowjanya, Robert Craven, Sastry Munukutla
Proc. ASME. IJPGC2002, 2002 International Joint Power Generation Conference, 63-70, June 24–26, 2002
Real-time performance monitoring of coal-fired power plants is becoming very important due to the impending deregulation of the electric power industry. Performance testing is made to be real-time by changing the traditional output loss method to include an estimation of coal composition based on the Continuous Emission Monitoring System (CEMS) data. This paper illustrates the robustness of the calculations by introducing a variance into each of the calculation inputs to access its effect on the final outputs of heatrate, boiler efficiency and coal flow. Though the original study was over five power plants this paper presents results for the two most diverse coals.
Topics: Power stations, Coal, Boilers, Electricity (Physics), Emissions, Flow (Dynamics), Monitoring systems, Robustness, Testing performance
Heat Transfer Characteristics of Turbulent Flames in Three-Dimensional Furnaces
Essam E. Khalil
The recent advances in numerical methods and the vast development of computers have directed the designers to better development and modifications to air-flow pattern and heat transfer in combustion chambers. Extensive efforts are exerted to adequately predict the air velocity and turbulence intensity distributions in the combustor zones, and to reduce the air pollution and noise abatement to ultimately produce quite and energy efficient combustor systems. The present work utilizes mathematical modeling techniques to primarily predict what happens in three-dimensional combustion chambers simulating boiler furnaces, and areo engines in terms of flow regimes and interactions. The present work also demonstrates the effect of chamber design and operational parameters on performance, wall shear stresses, and vorticity under various operating parameters. The governing equations of mass, momentum and energy are commonly expressed in a preset form with source terms to represent pressure radients, turbulence and viscous action. The physical and chemical characteristics of the air and fuel are obtained from tabulated data in the literature. The flow regimes and heat transfer plays an important role in the efficiency and utilization of energy. The behavior was found to be strongly dependent on turbulent shear, mixing, blockage, wall conditions and location of fuel and air inlets. Eddies can be strong enough to have higher velocities typically near reactants supply openings. Excessive transverse flow velocities cause extra macromixing; the air flow regimes are complex and of three-dimensional nature; with the advance of computational techniques it is possible to accurately simulate three-dimensional flows. The results reported in this work were obtained with the aid of the three-dimensional program 3DCOMB; applied to axisymmetrical and three-dimensional complex geometry with and without swirl. The present numerical grid comprises, typically, 144000-grid node covering the combustion chamber volume in the X, R or Y and Z coordinates directions. The numerical residual in the governing equations typically less than 0.001%. A modified grid generation formula was proposed and incorporated in the present work. Examples of large industrial furnaces are shown and were in good agreement with available measurements in the open literature. One may conclude that flow patterns, turbulence and heat transfer in combustors are strongly affected by the inlet swirl, inlet momentum ratios, combustor geometry; both micro and macro mixing levels are influential. Greater tangential velocities and turbulence characteristics are demonstrated in situations with higher swirl intensities. The present modeling capabilities can adequately predict the local flow pattern and turbulence kinetic energy levels in complex combustors.
Topics: Flames, Furnaces, Heat transfer, Turbulence, Combustion chambers, Flow (Dynamics), Air flow, Fuels, Geometry, Modeling
Cofiring Tire-Derived Fuel With Coal
N. Stanley Harding
Tires provide a resource of significant interest to many utilities. Tires—and tire-derived fuel (TDF)—have a high calorific value along with other favorable fuel characteristics. At the same time they present material preparation and handling issues for fuel users. For environmental reasons, they are more difficult and costly to dispose of in landfills. In 1990, only 25 million tires or 11% of the annually generated scrap tires in the U.S. were utilized (recycled, retreaded, and burned for energy). In 1994, this number increased to 138 million tires or 55% of the annually generated scrap tires with the largest increase due to tires used for energy (101 million tires). With an estimated number between 1–3 billion tires in stockpiles throughout the United States, this potential energy source is enormous. This paper will review several commercial demonstrations of tire-derived fuel cofired with coal in industrial and utility furnaces. Included will be discussions on fuel characteristics, preparation and handling of the tire-derived fuel, methods of utilization of the cofired fuel including appropriate combustion systems (e.g., cyclone boilers, stokers, fluidized bed boilers) and environmental results of the cofiring demonstrations.
Topics: Coal, Co-firing, Fuels, Tires, Boilers, Combustion systems, Fluidized beds, Furnaces, Materials preparation, Potential energy
Case History: Automation of an Existing Cogeneration Facility — Metamorphosis of an Existing Central Utility Plant Facility
Ole E. Haaland, Michael Conway
The scope was straight forward; design and install a complete SCADA system to automate as much as reasonably possible the utility plant consisting of: • One gas turbine cogeneration unit with duct firing, • Three reciprocating engine generators, • Two utility sources, • Three Absorption chillers, • Four electric chillers, • Two duel fuel boilers, and • 2 cooling towers. Prior to this project, the entire utility plant was operated manually. This included everything from chiller loading to Power Factor control.
Topics: Combined heat and power, Absorption, Boilers, Cooling towers, Design, Ducts, Firing, Fuels, Gas turbines, Generators
Advanced Steam Turbine Bypass Valve Design for Flexible Power Plants
Andreas Logar, Thomas Depolt, Edwin Gobrecht
The authors company has had extensive experience providing steam turbines including auxiliary systems as a turn key contractor for more than 40 years. Bypass systems are an integrated part of modern Combined Cycle Power Plants (CCPP) [1]. Bypass systems contribute a major part for operational flexibility. They allow the shortest start-up times by minimising mismatches between boiler/HRSG and turbine. Bypass systems also lead to predictable and repeatable start-up times, as well as reducing solid particle erosion of component, to a great extent. The functional requirements for bypass valves are: • Control mode for an accurate control of the IP and LP bypass steam flow during the unit start-up and shut-down, as well as during normal operating transients. • Fast closing mode for bypass-trip (supported by spring force) when required for condenser protection. • Combined mode for fast reaction on pressure increase to a define set point and further action in control mode. In the past, a combined stop and control valve design, each with a separate stem, was common. The challenging objective for the bypass valve design was to integrate the control function and the trip function with a single stem design. The authors company has developed this advanced steam turbine bypass valve that incorporates hydraulic actuator with a single stem design. The valve bodies have noise reduction fittings and are equipped with large extensions on the outlet side to reduce vibration throughout the bypass system. The bypass valve body has an integrated steam strainer which protects both valve parts and the condenser from external debris. The bypass design is prepared for Power Plants with elevated temperatures which allow for the highest plant efficiencies [2]. Surface coating protect moving components against oxidation and reduce friction by means of a surface coating. Steam at high temperature passes through the bypass to the condenser. An incorporated water attemporating flow control system reduces the steam temperatures before entering the condenser. Condensate water is injected through an orifice in the bypass system. The orifice is located down stream in the pipe between the bypass valve and condenser. Electro-hydraulic supply units deliver the control fluid to the bypass valves. An optimized bypass system has to provide: • Long service life with low maintenance costs; • High stroke speed; • Pressure control by unit set point; • High actuation forces; • Accurate positioning; • Very short trip time into closed position. By means of bypass station, one can get highest flexibility of power plants use of the new valve one will get highest control performance and shortest reaction time.
Topics: Design, Power stations, Steam turbines, Valves, Condensers (steam plant), Steam, Coating processes, Coatings, Combined cycle power stations, Temperature
Development of the RSFC Low NOx Burner: From Fundamentals to Industrial Applications
J. M. Bee´r, M. A. Toqan, J. M. Haynes, R. W. Borio
Research and development of the low NOx Radially Stratified Flame Core (RSFC) burner is followed from its fundamental concept through prototype burner design, pilot scale experiments at MIT and scale-up and commercial design by ABB-CE (ALSTOM) to applications in industrial and utility plant boilers. The principle that turbulence can be significantly damped in a rotating flow field with a strong positive radial density gradient was used to increase the fuel rich zone residence time in internally staged low NOx burners. The continuous interaction of ideas from laboratory experimental and computational studies with those from the commercial design and industrial scale tests played a pivotal role in the development of the final product, the commercial RSFC burner. Examples of application in gas, oil, and coal fired industrial and utility boilers are discussed.
Topics: Nitrogen oxides, Design, Boilers, Coal, Density, Engineering prototypes, Flames, Flow (Dynamics), Fuels, Industrial research
Achieving Uniform Combustion Using Burner Line Orifices to Balance Coal Flow Distribution
F. P. Haumesser, R. E. Thompson, T. A. Davey, J. N. Kuipers
The combination of more stringent NO x regulations and utility heat rate improvement programs has led to an increased interest in balancing coal flow distribution to burners to improve combustion. Uniform low O 2 combustion is essential to minimizing NO x emissions without adversely impacting combustible losses (CO and LOI). Many retrofit low-NO x burner installations require balanced coal flows from each pulverizer to the burner pipes to within ± 10% of the mean in order to meet these goals. Numerous questions have arisen concerning the best methods to measure, achieve, and maintain a balanced coal flow distribution from the pulverizer to the burners. These questions concern: 1) the validity of clean air vs. "dirty" air primary air velocity measurements, 2) ASME vs. ISO "RotorProbe™" pulverized coal sampling methods, 3) fixed vs. adjustable burner line orifices, and 4) the performance of continuous on-line coal flow instrumentation. Some have questioned the need for or effectiveness of using orifices to balance coal flow distribution, while others have argued that deviations between burner line coal flows should not exceed as little as ±5% of the mean (pipe-to-pipe) within a pulverizer. This paper addresses many of the questions concerning the effectiveness of balancing coal flows with orifices. Extensive test data are presented documenting the improvement in coal flow balance using orifices on over 25 boilers. This experience covers units ranging in size from 110 to 750 MWe, equipped with roller, ball tube and exhauster type pulverizers, and for both wall-fired and T-fired burner configurations. The improvement in combustion uniformity achieved by balancing burner line coal flow distribution is illustrated by a comparison of economizer exit duct emission profiles before and after orifice application. This paper also addresses questions concerning: 1) maintaining a coal flow balance over time, 2) variations in coal flow balance with pulverizer load, and 3) recent developments in burner line continuous coal flow monitoring. Test data are included which compare coal flow measurements made with a RotorProbe™ and a microwave real-time coal flow measurement system.
Topics: Coal, Combustion, Flow (Dynamics), Orifices, Pipes, Emissions, Flow measurement, Nitrogen oxides, Boilers, Ducts
Improving Natural Draft Cooling Tower Performance With Heat Injection
Eugene Grindle, John Cooper, Roger Lawson
Proc. ASME. IJPGC2002, 2002 International Joint Power Generation Conference, 9-14, June 24–26, 2002
This paper presents an assessment of heat injection as a means of improving natural draft cooling tower performance. The concept involves injecting heat into the cooling tower exit air/vapor stream immediately above the drift eliminators in order to increase the difference between the density of the exit air/vapor stream and the ambient air. The density difference between the air/vapor in the cooling tower stack and the ambient air is the engine that drives airflow through the cooling tower. The enhancement of the airflow through the cooling tower (the natural draft) results in more evaporation and thus lowers the circulating water temperature. Because the heat is injected above the drift eliminators, it does not heat the circulating water. To evaluate the cooling tower performance improvement as a function of heat injection rate, a thermal/aerodynamic computer model of Entergy's White Bluff 1 & 2 and Independence 1 & 2 (approximately 840 MW each) natural draft cooling towers was developed. The computer model demonstrated that very substantial reductions in cold water temperature (up to 7°F) are obtainable by the injection of heat. This paper also discusses a number of possible heat sources. Sources of heat covered include extraction steam, auxiliary steam, boiler blow-down, and waste heat from a combustion turbine. The latter source of heat would create a combined cycle unit with the combination taking place in the condensing part of the cycle (bottom of the cycle) instead of the steam portion of the cycle (top of the cycle).
Topics: Cooling towers, Heat, Cycles, Vapors, Air flow, Computers, Density, Steam, Water temperature, Boilers
Hybrid Dual-Fuel Combined Cycles: General Performance Analysis
Miroslav P. Petrov, Andrew R. Martin, Laszlo Hunyadi
The hybrid dual-fuel combined cycle concept is a promising technology for increasing the energy utilization of low-grade (solid) fuels. Advantages such as enhanced electrical efficiency, favorable economics, and relative ease of construction and operation have been pointed out by various authors in previous studies. The present investigation aims to assess the performance of natural gas and coal- or biomass-fired hybrid combined cycles, with a gas turbine as topping cycle and a steam boiler as bottoming cycle. A parametric analysis considers the impact of the natural gas/solid fuel energy ratio on the electrical efficiency of various hybrid system configurations. Results show that significant performance improvements (in the order of several percentage points in electrical efficiency) can be achieved by these hybrid configurations when compared to the reference (two independent, single-fuel power plants at the given scales). In large-scale power plants with coal-fired bottoming cycle, efficiencies continuously rise as the share of natural gas fuel is increased up to the cycle integration limits, while an optimum can be seen for the small-scale biomass-fired bottoming cycles (with modest steam parameters) at a certain share of natural gas fuel input.
Topics: Combined cycles, Fuels, Cycles, Natural gas, Electrical efficiency, Biomass, Coal, Power stations, Boilers, Construction
Four Large Units at Lakeview Generating Station Achieve 50% NOx Reduction Cost Effectively With a Reduced Schedule
Kal Raman, Edmund Schindler
As part of a much larger Ontario Power Generation NOx reduction program, two separate turnkey contracts were awarded to RJM Corporation to convert the four units at the Lakeview Generating Station located on lake Ontario near downtown Toronto. Lakeview Station Units 1, 2, 5 and 6 are 300 MWe, B&W split furnace, radiant boilers firing bituminous coal. Units 1 & 2 have 24 burners and Units 5 & 6 have 18 burners all located on the front wall. The original B&W register style burners were used as a basis to reduce NOx emissions to the maximum amount possible by means of burner modifications using RJM's low NOx burner components. This upgrade reduced NO X by more than 50% from the original burner baseline, simultaneously maintained CO below 100 ppm and maintaining a reasonable increase in baseline LOI, with no effect on boiler steam temperatures or performance. RJM Corporation was selected on a competitive bid basis to perform these contracts on a turnkey basis. Stone and Webster prepared the specification and acted as the OPGI engineer throughout the project. The details of the retrofit and the results of the conversion are presented in this paper.
Topics: Nitrogen oxides, Power stations, Boilers, Coal, Emissions, Energy generation, Engineers, Firing, Furnaces, Lakes
Petroleum Coke as a Supplementary Fuel for Cyclone Boilers: Characteristics and Test Results
David A. Tillman
Petroleum coke is periodically tested and used as a supplementary fuel for cyclone boilers. Its high heat content and low cost make it an attractive fuel for power generation. In cyclone boiler firing, it also has environmental advantages. While it is high in sulfur content, it can be used to reduce NO x emissions along with such trace metal emissions as mercury and arsenic. Successful firing of petroleum coke in cyclone boilers, however, requires considerable attention to fuel properties of the coal and the opportunity fuel including fuel structure and reactivity, and ash chemistries. This paper reviews selected properties of petroleum coke including traditional analyses plus structural characterization using 13 Carbon Nuclear Magnetic Resonance (NMR), drop tube reactor (DTR) characterization for kinetics and volatility evaluation, and thermogravimetric analysis (TGA) for char oxidation kinetics. The paper then summarizes results of petroleum coke firing at the Paradise Fossil Plant of TVA, and Bailly Generating Station of Northern Indiana Public Service Company (NIPSCO). Results presented include impacts of cofiring on boiler efficiency, NO x emissions, and the fate of selected trace metals including arsenic, mercury, nickel, and vanadium. It documents the overall benefits and issues associated with cofiring petroleum coke with coal in cyclone boilers as a significant opportunity fuel.
Topics: Boilers, Coke, Fuels, Petroleum, Emissions, Firing, Coal, Co-firing, Metals, Nitrogen oxides
NO x Reduction of a 165 MW Wall-Fired Boiler Utilizing Air and Fuel Flow Measurement and Control
Marion Cherry, Dave Earley, David Silzle
As a result of increasingly stringent emissions limitations being imposed on coal-fired power plants today, electric utilities are faced with having to make major compliance related modifications to their existing power plants. While many utilities have elected to implement expensive post-combustion NO x reduction programs on their largest generating units, infurnace NO x reduction offers a less expensive alternative suitable to any size boiler, to reduce NO x while also improving overall combustion. In-furnace NO x reduction strategies have proven that, when used with other less expensive approaches (Overfire air, fuel switching, and/or SNCR), levels less than 0.15 lb./MMBtu can be economically achieved. Furthermore, when implemented in conjunction with an expensive post-combustion SCR program, initial capital requirements and ongoing operating costs can be cut to save utilities millions of dollars. For the purpose of developing a system-wide NO x reduction strategy, Santee Cooper, a southeastern U.S. utility applied pulverized coal flow and individual burner airflow measurement systems to Unit 3 at its Jefferies Station, a 165MW, 16-burner front wall-fired boiler. The airflow measurement system, in service for many years, applied a well-proven averaging Pitot tube technology to measure individual burner secondary airflow. The coal flow measurement system utilized low energy microwaves to accurately measure coal density and coal velocity in individual coal pipes. The combination of these two systems provided the accurate measurements necessary for controlled manipulation of individual burner stoichiometries, giving the plant the ability to improve burner combustion, yielding a reduction in NO x levels approaching 20%. Optimized burner combustion also resulted in a leveling of the excess O 2 profile, which will enable the plant to pursue further reductions in excess air as well as staged combustion, thus allowing for further NO x reductions in the future. How this program produced a significant NO x reduction will be presented in detail in this paper. The paper will also discuss the effects on excess O 2 , opacity, and unburned carbon. In addition, this program will allow for future system-wide planning with regard to possible SCR implementation.
Topics: Boilers, Combustion, Flow measurement, Fuels, Nitrogen oxides
CAREM-25: Energy and Safety for the Future
La´zaro E. Pomier Ba´ez
Proc. ASME. IJPGC2002, 2002 International Joint Power Generation Conference, 1047-1054, June 24–26, 2002
The CAREM-25 is an advanced small nuclear power plant being jointly developed by CNEA (Comisio´n Nacional de Energi´a Ato´mica) and INVAP S. E. in Argentina. CAREM is a modular 100 MWt pressurized water reactor with integral steam generators designed to be used for electricity generation (25 MW e ) or as a research reactor or for water desalination. The plant has its entire primary coolant system within the reactor pressure vessel (hence 'integral' PWR), self-pressurized and relying entirely on natural convection. Fuel is standard 3.4% enriched PWR fuel, with burnable poison, and is refueled annually. It is a mature design, which could be deployed within a decade. The CAREM reactor shows itself as a design capable to fill the existing gap between a research reactor and a full-scale commercial nuclear power plant. From this point of view, CAREM is a very attractive option for countries who have not yet developed technical capabilities, human resources, and an industrial infrastructure needed for a medium or large size nuclear units. Advanced nuclear reactor designs, such as the CAREM reactor, include several improvements related to safety issues either enhancing the passive safety functions or allowing plant operators more time to undertake different management actions against radioactive releases to the environment The enhancement and development of safety measures for this type of system are a top priority of designers. In the development of the nuclear power plant CAREM, the possibility of including a passive metallic in-vessel container in its design is being considered, to arrest the reactor pressure vessel meltdown sequence during a core damaging event, and thereof prevent its failure. The present paper will provide an overview of the CAREM-25 technology as a general purpose generation unit, and highlight the work on safety measure's enhancements, including design modifications aiming to improve overall safety targets of the plant.
Topics: Safety, Design, Nuclear power stations, Pressurized water reactors, Fuels, Reactor vessels, Boilers, Containers, Coolants, Electric power generation
Numerical Investigation on Premixed Combustion Using a Fiber Mat Burner With a Boiler
T. Golder, O. Kawaguchi
This paper presents a numerical study of combustion and multi mode heat transfer in inert porous media. In this case a sintered fiber mat is used. From this work it is understood that the premixed flame is stabilized on the downstream surface of the fiber mat burner. The influence of the flame location, the radiative properties of the porous material, the solid thermal conductivity, and stoichiometry on the flame speed and flame stability are determined using a one-dimensional conduction, convection, radiation, and combustion model. The fiber mat is allowed to emit, absorb, and scatter radiant energy. Non-local thermal equilibrium between the solid and gas was taken into account. Here, separate energy equations for the two phases are introduced, i.e. gas energy equation for the entire system and solid energy equation for the fiber mat. The results indicate that stable combustion can be maintained near the downstream surface of the fiber mat which is mostly controlled by solid-phase radiation.
Topics: Boilers, Combustion, Fibers, Flames, Porous materials, Radiation (Physics), Convection, Electromagnetic scattering, Heat conduction, Heat transfer
Low Solids Coal Water Slurry Cofiring for NOx Trim
Joseph J. Battista, Evan E. Hughes
Over the past decade, members of the Upgraded Coal Interest Group and EPRI, the Department of Energy, the Energy and Environmental Research Corporation (GE-EER), Washington Energy Processing (WEP), Penn State University and the previous owners and operators of Seward Station located in western Pennsylvania, conducted a series of formulation and combustion tests using coal waste fines as a low solids coal water slurry cofiring fuel for electric power generation. The fine coal was recovered from coal fines impoundments and fresh coal cleaning plant fines that were cleaned, thickened and then cofired with pulverized coal in utility scale boilers. This paper explains the need for a program to eliminate these impoundments and describes the results of some of the tests conducted on the technology that demonstrate the effectiveness of trimming NOx emissions by the use of slurry cofiring. This method of trimming NOx emission has been shown to have the capability of reducing NOx emissions by 20% to 35% below the levels achieved by some low NOx burners and selective non-catalytic reduction systems (SNCRs).
Topics: Coal, Co-firing, Nitrogen oxides, Slurries, Solids, Water, Emissions, Boilers, Combustion, Electric power generation
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