SYSTEM AND METHOD FOR COMBUSTION SYSTEM CONTROL

A combustion system includes a combustion chamber, a plurality of fuel introduction locations in the combustion chamber where fuel and air are provided to the combustion chamber for combustion, a fluid flow control device associated with each fuel introduction location, each fluid flow control device being controllable to vary an amount of the air supplied to each fuel introduction location, a plurality of sensing devices configured to monitor a plurality of operational parameters of the combustion system, and a control unit configured to control each fluid flow control device to control the amount of air supplied at each fuel introduction location independent of the amount of air supplied at the other fuel introduction locations, and to control the amount of air provided to all other air introduction locations, in dependence upon at least one of the plurality of operational parameters to minimize excess air provided to the combustion chamber.

BACKGROUND

Technical Field

Embodiments of the invention relate generally to combustion systems and, more particularly, to a system and method for optimizing the control and performance of a combustion system for boilers, furnaces and fired heaters.

Discussion of Art

A boiler typically includes a furnace in which fuel is burned to generate heat to produce steam. The combustion of the fuel creates thermal energy or heat, which is used to heat and vaporize a liquid, such as water, which makes steam. The generated steam may be used to drive a turbine to generate electricity or to provide heat for other purposes. Fossil fuels, such as pulverized coal, are typical fuels used in many combustion systems for boilers. For example, in an air-fired pulverized coal boiler, atmospheric air is fed into the furnace and mixed with the pulverized coal for combustion. In an oxy-fired pulverized coal boiler, concentrated levels of oxygen are fed into the furnace and mixed with pulverized coal for combustion.

As is known in the art, proper mixing of the fuel and air as it is introduced to the nozzle or burner for combustion is essential for efficient and clean operation of combustion systems. Under perfect combustion conditions and ideal mixing conditions it is theoretically possible to react all of the fuel with zero percent excess air. The ideal ratio of air/oxygen to fuel that burns all fuel with no excess air is referred to as the stoichiometric ratio. In practice, however, perfect mixing and temperature conditions are never achieved, necessitating the use of a certain amount of excess air to ensure complete combustion of the fuel. In particular, if excess air is not added to the combustion process, unburned carbon, soot, smoke, and carbon monoxide exhaust can create additional emissions and heat transfer surface fouling. From a safety standpoint, properly controlling excess air reduces flame instability and other hazards. Existing combustion systems may use upwards of 20-30% excess air to ensure reliable operation with a wide range of fired fuels and across all potential load and firing conditions.

Even though excess air is needed from a practical standpoint, however, too much excess air can lower boiler efficiency. Thus, a balance must be found between providing the optimal amount of excess air to achieve ideal combustion and prevent combustion issues associated with too little excess air, while not providing too much excess air that reduces efficiency and increases NOxemissions.

In view of the above, there is a need for a system and method for controlling a combustion system for a boiler that continually seeks the lowest possible excess air conditions to maximize efficiency, while maintaining optimum main burner zone stoichiometry to minimize emissions and while honoring a multitude of real-time operating process constraints required to preserve operation and safety.

BRIEF DESCRIPTION

In an embodiment, a combustion system is provided. The combustion system includes a combustion chamber, a plurality of fuel introduction locations in the combustion chamber where fuel and air are provided to the combustion chamber for combustion, a fluid flow control device associated with each fuel introduction location, each fluid flow control device being controllable to vary an amount of the air supplied to each fuel introduction location, a plurality of sensing devices configured to monitor a plurality of operational parameters of the combustion system, and a control unit configured to control each fluid flow control device to control the amount of air supplied at each fuel introduction location independent of the amount of air supplied at the other fuel introduction locations, and to control the amount of air provided to all other air introduction locations, in dependence upon at least one of the plurality of operational parameters to minimize excess air provided to the combustion chamber.

In another embodiment, a method of controlling a combustion system is provided. The method includes the steps of introducing fuel and air to a combustion chamber at a plurality of fuel introduction locations, monitoring a plurality of operational parameters of the combustion system, and minimizing an amount of excess air provided to the combustion chamber by individually controlling an amount of air supplied to the combustion chamber at each of the fuel introduction locations in dependence upon at least one of the plurality of operational parameters.

In yet another embodiment, a boiler is provided. The boiler includes a combustion chamber, a plurality of fuel introduction locations in the combustion chamber for introducing fuel to the combustion chamber for combustion, a plurality of fluid flow control devices, each fluid flow control device being controllable to vary an amount of air supplied to the boiler, a plurality of sensing devices configured to monitor a plurality of operational parameters of the combustion system, and a control unit configured to control the amount of the air supplied to the boiler in dependence upon at least one of the plurality of operational parameters to continuously optimize an amount of excess air provided to the combustion chamber.

DETAILED DESCRIPTION

Reference will be made below in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference characters used throughout the drawings refer to the same or like parts. While embodiments of the invention are suitable for use with combustion systems, generally, a pulverized coal boiler such as for use in a pulverized coal power plant has been selected for clarity of illustration. Other combustion systems may include other types of boilers, furnaces and fired heaters utilizing a wide range of fuels including, but not limited to, coal, oil and gas. For example, contemplated boilers include, but are not limited to, may both T-fired and wall fired pulverized coal boilers, circulating fluidized bed (CFB) and bubbling fluidized bed (BFB) boilers, stoker boilers, suspension burners for biomass boilers, dutch oven boilers, hybrid suspension grate boilers, and fire tube boilers. In addition, other combustion systems may include, but are not limited to, kiln, incinerator, fired heater and glass furnace combustion systems.

As used herein, “electrical communication” or “electrically coupled” means that certain components are configured to communicate with one another through direct or indirect signaling by way of direct or indirect electrical connections. As used herein, “mechanically coupled” refers to any coupling method capable of supporting the necessary forces for transmitting torque between components. As used herein, “operatively coupled” refers to a connection, which may be direct or indirect. The connection is not necessarily being a mechanical attachment.

Embodiments of the invention relate to a combustion system and method and control scheme therefor that continually seeks the lowest possible excess air conditions to maximize system efficiency, while at the same time maintaining optimum main burner zone stoichiometry to minimize emissions and honoring a multitude of real-time operating process constraints require to preserve operation and safety. The combustion system includes a combustion chamber, a plurality of fuel introduction locations in the combustion chamber where fuel and air are provided to the combustion chamber for combustion, a fluid flow control device associated with each fuel introduction location, each fluid flow control device being controllable to vary an amount of the air supplied to each fuel introduction location, a plurality of sensing devices configured to monitor a plurality of operational parameters of the combustion system, and a control unit configured to individually control the amount of the air supplied to each of the fuel introduction locations in dependence upon at least one of the plurality of operational parameters to minimize excess air provided to the combustion chamber. In particular, the control unit is configured to individually control the amount of air provided to each air introduction location to continuously optimize the level excess air for the combustion process in real-time on a continuous operating basis.

FIG. 1illustrates a combustion system10having a boiler12. The boiler12may be a tangentially fired boiler (also known as a T-fired boiler) or wall fired boiler. T-firing is different from wall firing in that it utilizes burner assemblies with fuel admission compartments located at the corners of the boiler furnace, which generates a rotating fireball that fills most of the furnace cross-section. Wall firing, on the other hand, utilizes burner assemblies that are perpendicular to a side of the boiler.

FIG. 2depicts a tangentially fired boiler12. Tangentially fired boilers have a rectangular cross-section and have burner assemblies14defining fuel introduction locations positioned at the corners. Fuel and air are introduced into the boiler12via the burner assemblies14and/or nozzles associated therewith, and are directed tangentially to an imaginary circle located at the center of the furnace and with a diameter greater than zero. This generates a rotating fireball that fills most of the furnace cross-section. The fuel and air mixing is limited until the streams join together in the furnace volume and generate a rotation.

With further reference toFIG. 1, the combustion system10includes a fuel source such as, for example, a pulverizer16that is configured to grind fuel such as coal to a desired degree of fineness. The pulverized coal is passed from the pulverizer16to the boiler12. An air source18provides a supply of primary or combustion air to the boiler12where it is mixed with the fuel and combusted, as discussed in detail hereinafter. Where the boiler12is an oxy-fired boiler, the air source18may be an air separation unit that extracts oxygen from an incoming air stream, or directly from the atmosphere.

As shown inFIG. 1, the boiler12includes a hopper zone20located below a main burner zone22from which ash can be removed, the main burner zone22(also referred to as a windbox) where the air and an air-fuel mixture is introduced into the boiler12, a burnout zone24where any air or fuel that is not combusted in the main burner zone22gets combusted, a superheater zone26where steam can be superheated to drive a turbine to generate electricity, for example, and an economizer zone28where water can be preheated prior to entering a steam drum or a mixing sphere (not shown). Combustion of the fuel with the primary air within the boiler12produces a stream of flue gases that are ultimately treated and exhausted through a stack downstream from the economizer zone28. As used herein, directions such as “downstream” means in the general direction of the flue gas flow. Similarly, the term “upstream” is opposite the direction of “downstream” going opposite the direction of flue gas flow.

As illustrated inFIGS. 1 and 2, the combustion system10includes an array of sensors, actuators and monitoring devices to monitor and control the combustion process and the resulting consequences with respect to low excess air operation, as discussed in detail hereinafter. For example, the combustion system10may include a plurality of fluid flow control devices30associated with the conduit that supplies primary air for combustion to each fuel introduction nozzle associated with the burner assemblies14. In an embodiment, the fluid flow control devices30may be electrically actuated air dampers that can be adjusted to vary the amount of air that is provided to each fuel introduction nozzle associated with each burner assembly14. As shown inFIG. 2, each corner of the boiler12includes a respective fluid flow control device30associated with each fuel introduction nozzle of each burner assembly14. The boiler12may also include other individually controllable air dampers or fluid flow control devices (not shown) at various spatial locations around the furnace. Each of the flow control devices30is individually controllable by a combustion control unit100to ensure that desired air/fuel ratios and flame temperature are achieved for each nozzle location.

The combustion system10may also include a flame scanning device32associated with each individual fuel introduction nozzle or burner assembly14. The flame scanning devices32are configured to assess the local stoichiometry (air/fuel ratio) at each respective the nozzle location within the main burner zone22. In addition to detecting the respective quantities of air and fuel at each nozzle location, the flame scanning devices32are also configured to sense the flame temperature adjacent to each burner assembly14. The flame scanning device32are electrically connected or otherwise communicatively coupled to the combustion control unit for communicating the measured stoichiometric parameters and detected temperatures to the control unit100for use in controlling the combustion process, as discussed in detail hereinafter. In an embodiment, the flame scanning devices32may instead be a single flame scanner that is configured to individually monitor and detect the local stoichiometry and temperature at each nozzle location.

With further reference toFIG. 1the combustion system10may also include a flame stability monitor34located, for example, just above the burnout zone24. The flame stability monitor34may likewise be electrically or communicatively coupled to the control unit100and is configured to measure or otherwise assess fireball stability within the boiler12. The flame stability monitor34provides feedback to enable determination of combustion stability, which is used for low excess air control and to achieve low load turndown operation, as discussed hereinafter. In addition, a 2D optical flame scanner46may also be positioned in the upper furnace for monitoring and assessing flame characteristics (e.g., temperature).

In an embodiment, the system10may further include a temperature mapping device36such as, for example, a 2D acoustic temperature mapping device for mapping a flue gas temperature at a cross-section of the backpass38of the boiler12.

FIG. 1also illustrates that the backpass38of the boiler12downstream from the temperature mapping device36and upstream from the economizer section28is fitted with a monitoring device40. In an embodiment, the monitoring device40is a laser-based monitoring device such as, for example, a tunable diode laser flue-gas monitoring device. The monitoring device40may include one or more optical sources that may, for example, pass through a portion of a flue gas duct defined by the backpass38. The optical sources provide optical beams that pass through the flue gasses within the backpass38and are detected by a corresponding plurality of detectors (not shown). As the beams pass through the flue gasses, there is absorption of various wavelengths characteristic of the constituents within the flue gasses. The optical sources are coupled to a processor to provide for characterization of received optical signals and identify the constituents, their concentrations and other physical properties or parameters of substances in the flue gasses. In other embodiments, such analysis may be performed internally by the combustion control unit100.

In an embodiment, the monitoring device40is configured for measurement and assessment of gas species such as carbon monoxide (CO), carbon dioxide (CO2), mercury (Hg), sulfur dioxide (SO2), sulfur trioxide (SO3), nitrogen dioxide (NO2), nitric oxide (NO) and oxygen (O2) within the backpass38. SO2and SO3are collectively referred to as SOx. Similarly, NO2and NO are collectively referred to as NOx.

Downstream from the economizer section28, the combustion system10may further include a device or sensor42for measuring the amount of unburnt carbon in the fly ash within the backpass38. The device42, like monitoring device40, may be a laser-based detection device, although other types of devices capable of detecting the amount of carbon in the fly ash may also be utilized without departing from the broader aspects of the invention. The device42may likewise be electrically or communicatively coupled to the control unit100for transmitting data indicating the measured amount of unburnt carbon thereto.

As also, shown inFIG. 1, a sensor44arranged within the outlet to the stack may be utilized to monitor the concentration of oxygen within the flue gas. In an embodiment, the sensor44may be a paramagnetic sensor. The sensor44may be communicatively coupled to the control unit100for relaying the detected oxygen concentration to the control unit100. While the array of sensors and monitoring devices discussed herein may be utilized to detect, for example, carbon monoxide and other emissions, oxygen distribution, carbon in fly ash, fireball stability and the like, various other sensors and monitoring devices may also be utilized to measure pressure drop between various locations within the boiler12, temperature at various locations within the boiler, heat flux and furnace wall conditions. For example, in an embodiment, the stack may be configured with an opacity monitor to assess the degree to which visibility of a background (i.e., blue sky) is reduced by particulates for use in determining the amount or concentration of particulates within the flue gases exiting the stack. In addition, as shown inFIG. 1, the boiler12may include one or more furnace wall condition sensors46for assessing heat flux, corrosion of the furnace walls and/or deposit buildup.

In operation, a predetermined ratio of fuel and air is provided to each of the burner assemblies14for combustion. As the fuel/air mixture is combusted within the furnace and flue gases are generated, the combustion process and flue gases are monitored. In particular, as discussed above and as illustrated inFIG. 3, various parameters of the fireball and flame, conditions on the walls of the furnace, and various parameters of the flue gas are sensed and monitored. These parameters are transmitted or otherwise communicated to the combustion control unit100where they are analyzed and processed according to a control algorithm stored in memory and executed by a processor.

The control unit100is configured to control the fuel provided to the boiler12and/or the air provided to the boiler12, as shown at102and104, respectively, in dependence upon the one or more monitored combustion and flue gas parameters and furnace wall conditions. As used herein, the monitored parameters and conditions are collectively referred to as “operational parameters” of the boiler. For example, in an embodiment, the control unit100is configured to control the fluid flow control devices30associated with each burner assembly14and/or the other damper devices surrounding the main burner zone22, hopper zone20and burnout zone24of the boiler12to continuously attempt to reduce excess air provided to the boiler12to maximize efficiency, while maintaining emissions below prescribed threshold levels (and avoid other undesirable consequences that might result from any low excess air combustion conditions) and while maintaining operational performance above threshold levels. In particular, the control unit100is configured to control the damper devices12to minimize the amount of excess air provided to the boiler12and control main burner zone local stoichiometries associated with each individual fuel nozzle associated with each burner assembly14(i.e., assure that the desired air/fuel ratios are achieved for each and all nozzle locations). In this manner, the overall excess air level can be reduced to its optimum plant heat rate level without causing other issues for the equipment, process or environment, such as high CO emissions, high unburned carbon in fly ash, high opacity, high pressure drop, etc. In connection with the above, the control unit100is further configured to provide simultaneous control of the air at each fuel location to balance the air/fuel ratio based on the unique parameter measurements.

The operational and control approach described herein is based on a plurality of sensor-driven feedbacks and a model-based combustion control unit100. As discussed above, the combustion control unit100drives the process actuators to find the to find the lowest excess air operating conditions possible given the particular fuel utilized and other measured process conditions, e.g., unburned carbon in fly ash, furnace exit temperatures, emission profiles, corrosion rates, etc.

In an embodiment, the operational parameters may include, but are not limited to, carbon monoxide content in the flue gas, carbon in fly ash, on-line coal properties, coal flow balance, oxygen content in the backpass, gas species in the flue gas, furnace temperature, air heater basket condition, fouling of the hanging section, coal contact moisture, as well as other feedbacks from various sensors and monitoring devices such as the main burner zone flam scanner, flame stability sensor, mill sensors, a main burner zone waterwall corrosion advisor, soot blower advisor, a fly ash resistivity sensor, a primary air and forced draft fan health monitor, sulfur dioxide dew point sensor, an on-mill health monitor, a tube outside diameter corrosion probe, a waterwall tube leak sensor, and a mill and air heater fire detector.

In an embodiment, at a first level of control, the control unit100is configured to precisely control the air/fuel ratio at each fuel nozzle in dependence upon measurement signals from the optical flame scanners32associated with each nozzle/burner assembly14. In particular, the flame scanners32are configured to measure the fuel/air ratio at each fuel nozzle14and provide this information to the control unit100. The control unit100is then configured to adjust the individual dampers30associated with each fuel nozzle to bring the air/fuel ratios at each fuel nozzle into agreement with each other (i.e., so that they are all the same).

At a second level of control, the control unit100may then adjust the individual dampers30associated with each local fuel nozzle/burner assembly14(e.g., at each T-fired boiler elevation), as well as the other damper assemblies of the boiler12to optimize (minimize) excess air within the main burner zone22and maximize boiler efficiency. At this second level of control, while adjusting the amount of air at each burner assembly14and at other spatial locations of the boiler12, the control unit100simultaneously utilizes the sensor inputs and sensor constrains to ensure that emissions and other operational constraints or thresholds are not exceeded.

For example, if, upon decreasing the amount of excess air provided to the main burner zone22, the amount of unburnt carbon detected in the fly ash by sensor42exceeds a threshold stored in memory, this may indicate to the control unit100that excess air has been decreased excessively (indicating that all of the fuel provided to the main burner zone22is not being combusted). The control unit100may then increase the excess air through flow control device30and subsequently readjust the air/fuel ratio at each nozzle14through control of the individual air dampers30until the amount of unburnt carbon detected is brought within acceptable levels.

Likewise, if, upon decreasing the amount of excess air provided to the main burner zone22in an effort to increase boiler efficiency, carbon monoxide emissions exceed threshold levels, this may signal that not enough air is present to combust all of the fuel. The control unit100may then increase the excess air as described above through control of the individual air dampers30until carbon monoxide measurements are brought within acceptable levels. This control routine can be implemented based upon other sensor feedbacks, or a plurality of sensor feedbacks. In this manner, the plurality of sensors and measurement signals provided to the control unit100enable the real-time control of the combustion process (including the real-time control of excess air in dependence upon a plurality of monitored parameters).

With reference toFIG. 4, in an embodiment, a sensor priority chart400according to an embodiment of the invention is illustrated. In an embodiment, the control unit100may be programmed to prioritize the sensor feedbacks to keep monitored operation parameters within prescribed thresholds according to the chart400. For example, as illustrated therein, keeping oxygen levels, as measured by sensor44will not take precedence over keeping carbon monoxide levels, as measured by monitoring device40. As shown therein, this hierarchal control may be grouped into three or more priority levels, for example, a highest priority level410, a medium priority level412and a lowest priority level414.

As discussed above, the combustion system and control unit therefor continually seeks the lowest possible excess air conditions to maximize system efficiency (i.e., achieves total air reduction), while at the same time maintaining optimum main burner zone stoichiometry to minimize emissions and honoring a multitude of real-time operating process constraints require to preserve operation and safety (i.e., individual air balancing). In particular, the control unit is configured to individually control the amount of air provided to each air introduction location to continuously optimize the level excess air for the combustion process in real-time on a continuous operating basis. By monitoring so many operational parameters and by controlling combustion at the individual burner level, low excess air operation and target power outputs can be achieved for any particular type of fuel utilized (or variations within fuels), and at all loads and shifts.

The combustion system and control therefor provided by the invention provide financial, emissions and operational benefits. In particular, fuel savings and emissions reductions can be achieved by optimizing the stoichiometric ratio at the local burner level and minimizing excess air. The combustion system provides for main burner zone emissions control by precisely controlling combustion at the individual burner level. For example, significant savings may be realized for each boiler in operation even where excess air level is simply reduced 5% from a nominal 15%-20% which is common in the industry. These cost savings can be achieved as a result of the lower amount of product gas that directly results from lower excess air operation. The lower gas flow reduces the amount of auxiliary power that is needed to operate the downstream equipment, including fans and pumps for the required air quality control equipment. The reduction in auxiliary power translates into the need for less fuel and steam to achieve a given production level which, in turn, further reduces the fuel requirements and increases efficiency.

Emissions reductions for the conventional air pollutants stem from the lower fuel requirements. In addition, lower excess air results in lower NOxformation and lower SO3formation. Lower NOxemissions further reduce the need for additives, such as ammonia, to reduce the NOxin downstream equipment. Similarly, lower SO3levels reduce the amount of corrosion experienced by the downstream equipment.

In addition to operational savings, the combustion system of the invention provides for capital cost savings on new plant or boiler design and constructions. In particular, with the control system disclosed herein, it is possible to design plan equipment for lower excess air levels from the start.

While the combustion system of the invention allows for the real-time monitoring of numerous operational parameters that are utilized by a controller to more precisely control the combustion process and to continuously drive excess air to a minimum to maximize system efficiency, the invention is not so limited in this regard. In particular, the various sensor feedbacks, in addition to being used in real-time combustion process control, can be stored and compiled for use in diagnostic and predictive analytics for asset performance and maintenance assessments of the process and equipment. That is, the data obtained from the various sensors and measurement devices can be stored or transmitted to a central controller or the like so that equipment and process performance can be assessed and analyzed. For example, the sensor feedbacks can be utilized to assess equipment health, for use in scheduling maintenance, repairs and/or replacement.

In an embodiment, a combustion system is provided. The combustion system includes a combustion chamber, a plurality of fuel introduction locations in the combustion chamber where fuel and air are provided to the combustion chamber for combustion, a fluid flow control device associated with each fuel introduction location, each fluid flow control device being controllable to vary an amount of the air supplied to each fuel introduction location, a plurality of sensing devices configured to monitor a plurality of operational parameters of the combustion system, and a control unit configured to control each fluid flow control device to control the amount of air supplied at each fuel introduction location independent of the amount of air supplied at the other fuel introduction locations, and to control the amount of air provided to all other air introduction locations, in dependence upon at least one of the plurality of operational parameters to minimize excess air provided to the combustion chamber.

In an embodiment, the plurality of sensing devices include at least one flame scanning device in communication with the control unit, the at least one flame scanning device being configured to determine a stoichiometric ratio of the fuel and the air at each fuel introduction location. The at least one operational parameter is the stoichiometric ratio at each fuel introduction location. In an embodiment, the plurality of operational parameters include at least one of an air/fuel ratio at each fuel introduction location, a flame temperature, fireball stability, flue gas temperature, flue gas species, an amount of unburnt carbon in fly ash, an oxygen concentration in a flue gas, pressure drop, opacity, and a combustion chamber wall condition. In an embodiment, the at least one operational parameter is an air/fuel ratio associated with each fuel introduction location. In an embodiment, the at least one operational parameter includes the amount of unburnt carbon in the fly ash. In an embodiment, the control unit is configured to control at least one of the fluid flow control devices to increase the amount of the air provided to at least one of the fuel introduction locations if the amount of unburnt carbon in the fly ash exceeds a threshold level. In an embodiment, the plurality of sensing devices include at least: a flame scanning device configured to determine the an air/fuel ratio at each fuel introduction location, a flame stability monitor for assessing fireball stability, a temperature mapping device for mapping a flue gas temperature at a cross-section of a flue gas passageway of the combustion system, an optical monitoring device for measuring and assessing a plurality of gas species in the flue gas, a sensing device for measuring the amount of unburnt carbon in the fly ash, and an opacity monitoring device to measure an amount of particulates in the flue gas exiting a stack of the combustion system. In an embodiment, each fuel introduction location of the plurality of fuel introduction locations includes a burner assembly. In an embodiment, the combustion system may also include a pulverizer in fluid communication with each of the fuel introduction locations for supplying pulverized coal to each of the fuel introduction locations.

In another embodiment, a method of controlling a combustion system is provided. The method includes the steps of introducing fuel and air to a combustion chamber at a plurality of fuel introduction locations, monitoring a plurality of operational parameters of the combustion system, and minimizing an amount of excess air provided to the combustion chamber by individually controlling an amount of air supplied to the combustion chamber at each of the fuel introduction locations in dependence upon at least one of the plurality of operational parameters. In an embodiment, the step of monitoring the plurality of operational parameters includes determining a stoichiometric ratio of air and fuel at each of the fuel introduction locations, wherein the at least one operational parameter is the stoichiometric ratio of air and fuel at each of the fuel introduction locations. In an embodiment, the plurality of operational parameters include at least an air/fuel ratio at each fuel introduction location and at least one of a flame temperature, fireball stability, flue gas temperature, flue gas species, an amount of unburnt carbon in fly ash, an oxygen concentration in a flue gas, pressure drop, opacity, and a combustion chamber wall condition. In an embodiment, the plurality of operational parameters include at least the amount of unburnt carbon in the fly ash. In an embodiment, the method may also include the step of increasing an amount of air provided to at least one of the fuel introduction locations if the amount of unburnt carbon in the fly ash exceeds a threshold level. In the combustion system includes at least a flame scanning device configured to determine the an air/fuel ratio at each fuel introduction location, a flame stability monitor for assessing fireball stability, a temperature mapping device for mapping a flue gas temperature at a cross-section of a flue gas passageway of the combustion system, an optical monitoring device for measuring and assessing a plurality of gas species in the flue gas, a sensing device for measuring the amount of unburnt carbon in the fly ash, and an opacity monitoring device to measure an amount of particulates in the flue gas exiting a stack of the combustion system. In an embodiment, the method may include pulverizing coal in a pulverizer, supplying the pulverized coal to each of the fuel introduction locations.

In yet another embodiment, a boiler is provided. The boiler includes a combustion chamber, a plurality of fuel introduction locations in the combustion chamber for introducing fuel to the combustion chamber for combustion, a plurality of fluid flow control devices, each fluid flow control device being controllable to vary an amount of air supplied to the boiler, a plurality of sensing devices configured to monitor a plurality of operational parameters of the combustion system, and a control unit configured to control the amount of the air supplied to the boiler in dependence upon at least one of the plurality of operational parameters to continuously optimize an amount of excess air provided to the combustion chamber. In an embodiment, the plurality of sensing devices include at least one flame scanning device in communication with the control unit, the at least one flame scanning device being configured to determine a stoichiometric ratio of the fuel and the air at each fuel introduction location. The at least one operational parameter may be the stoichiometric ratio at each fuel introduction location. In an embodiment, the plurality of operational parameters include at least one of an air/fuel ratio at each fuel introduction location, a flame temperature, fireball stability, flue gas temperature, flue gas species, an amount of unburnt carbon in fly ash, an oxygen concentration in a flue gas, pressure drop, opacity, and a combustion chamber wall condition. In an embodiment, the plurality of sensing devices include at least a flame scanning device configured to determine the air/fuel ratio at each fuel introduction location, a flame stability monitor for assessing fireball stability, a temperature mapping device for mapping a flue gas temperature at a cross-section of a flue gas passageway of the boiler, an optical monitoring device for measuring and assessing a plurality of gas species in the flue gas, a sensing device for measuring an amount of unburnt carbon in fly ash, and an opacity monitoring device to measure an amount of particulate in the flue gas exiting a stack of the boiler.