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.

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.

The thermal diagnostics of a steam power unit in the TUROW Power Station is based on the DIAGAR system and thermal and flow measurements, recorded on-line by the DCS system. Along with direct evaluation of the operating parameters of the thermal cycle, the diagnostic system evaluates degradation of the system components and prognoses economically justified repair actions.

In nuclear plants, feedwater flow is utilized to calculate the heat input to the Nuclear Steam Supply System (NSSS). The heat input, in conjunction with a heat balance around the reactor, is used to calculate the reactor core thermal power. Since a calibrated flow nozzle is used to measure feedwater flow and, the calibration assumes a clean flow section with no fouling, any deposits or fouling of the flow nozzle will result in errors in flow measurement, causing the flow to read high. This would result in a calculated reactor power higher than the true value and an attendant loss in plant capacity. The paper presents the methodology and heat balance techniques used in diagnosing the existence of feedwater flow nozzle fouling and in quantifying the capacity loss. The paper provides recommendations on how to monitor performance for tell-tale signs of feedwater flow nozzle fouling and steps to take for corrective action.

The power generation industry is currently in a very difficult period of business restructuring. All the while, the demands to reduce emissions of NO x , SO x and particulates in accordance with the Clean Air Act continue. The high capital and operating cost of post-combustion NO x controls like Selective Catalytic Reduction (SCR) is leading to greater interest in finding methods to reduce NO x formation during combustion. The most cost effective means of reducing any pollutant is to never form it in the first place. The science behind combustion NO x control uses techniques which limit the amount of air available in the high temperature combustion zones where thermal NO x forms. Minimum NO x formation occurs when fuel and air mixing are carefully controlled to maintain required stoichiometric ratios. Additionally, controlling coal and air flow minimizes excess air requirements, can reduce unburned carbon resulting in better electrostatic precipitator performance and improved overall boiler efficiency. Thus maintaining fuel and air flow at optimal levels becomes a major concern if one wishes to achieve minimum NO x formation during combustion and maintain optimum boiler performance throughout the units load range. Since pulverized coal is transported by primary air in a two phase flow it has been difficult, if not impossible, in the past to measure coal mass flow on a continuous basis. Typically, coal flow and fineness have been measured on an intermittent basis using extractive techniques. This paper serves to introduce a real-time “flow measuring system” for pulverized coal, based on the use of microwave technology. It will describe how microwaves are used to obtain very accurate coal flow measurements. Comparisons of data obtained using the microwave system will be made with measurements obtained using extractive isokinetic methods. Some relevant operational effects from both US and German installations will be discussed and projections of operational savings will be made especially when using the system on an SCR equipped installation.