Combustion Control

I. Introduction

Combustion control plays a crucial role in power plants as it ensures efficient and safe combustion of fuel. By maintaining the optimal air/fuel ratio and furnace draft, combustion control systems help maximize energy output, minimize emissions, and prevent equipment damage.

A. Importance of Combustion Control in Power Plants

Combustion control is essential in power plants for several reasons:

• Efficiency: Proper combustion control ensures that fuel is burned efficiently, maximizing energy output and reducing fuel consumption.
• Emissions: By maintaining the correct air/fuel ratio, combustion control systems help minimize harmful emissions such as nitrogen oxides (NOx) and carbon monoxide (CO).
• Equipment Protection: Combustion control prevents equipment damage by avoiding conditions like flame instability, overheating, and excessive draft.

B. Fundamentals of Combustion Control

To understand combustion control, it is important to grasp the following fundamentals:

• Air/Fuel Ratio: The air/fuel ratio refers to the ratio of air to fuel in the combustion process. It plays a crucial role in determining the efficiency and emissions of combustion.
• Furnace Draft: Furnace draft refers to the pressure difference between the furnace and the surroundings. It affects the flow of combustion air and exhaust gases, influencing combustion efficiency.

II. Air/Fuel Ratio Control

A. Definition and Importance of Air/Fuel Ratio

The air/fuel ratio is the ratio of the mass of air to the mass of fuel in a combustion process. It is a critical parameter for efficient and clean combustion.

B. Role of Air/Fuel Ratio in Combustion Efficiency

The air/fuel ratio has a direct impact on combustion efficiency. The ideal air/fuel ratio varies depending on the type of fuel being burned, but it is typically around 14.7:1 for natural gas.

C. Key Components of Air/Fuel Ratio Control System

To maintain the desired air/fuel ratio, an air/fuel ratio control system consists of several key components:

1. Oxygen Sensors: Oxygen sensors measure the oxygen content in the flue gas and provide feedback to the control system.
2. Fuel Flow Meters: Fuel flow meters measure the flow rate of fuel and provide input to the control system.
3. Control Valves: Control valves regulate the flow of fuel based on the input from the oxygen sensors and fuel flow meters.

D. Control Strategies for Air/Fuel Ratio Control

There are two main control strategies for air/fuel ratio control:

1. Feedback Control: In feedback control, the oxygen sensors continuously monitor the oxygen content in the flue gas and provide feedback to the control system. The control system adjusts the fuel flow rate based on this feedback to maintain the desired air/fuel ratio.
2. Feedforward Control: In feedforward control, the control system anticipates changes in the combustion process based on known factors such as fuel quality and load demand. It adjusts the fuel flow rate accordingly to maintain the desired air/fuel ratio.

E. Step-by-step Walkthrough of Air/Fuel Ratio Control System

To better understand how air/fuel ratio control works, let's walk through the steps involved:

1. Measurement of Oxygen Content in Flue Gas: Oxygen sensors measure the oxygen content in the flue gas and provide feedback to the control system.
2. Calculation of Air/Fuel Ratio: The control system calculates the air/fuel ratio based on the oxygen content measured by the sensors.
3. Adjustment of Fuel Flow Rate: The control system adjusts the fuel flow rate using control valves to maintain the desired air/fuel ratio.

F. Real-world Applications and Examples of Air/Fuel Ratio Control

Air/fuel ratio control is used in various combustion systems, including:

1. Gas Turbines: Gas turbines require precise control of the air/fuel ratio to ensure efficient and reliable operation.
2. Boilers: Boilers in power plants and industrial facilities rely on air/fuel ratio control to optimize combustion efficiency and reduce emissions.

G. Advantages and Disadvantages of Air/Fuel Ratio Control

Air/fuel ratio control offers several advantages, such as improved combustion efficiency, reduced emissions, and enhanced equipment protection. However, it also has some limitations, including the need for regular maintenance and calibration of sensors and control valves.

III. Furnace Draft Control

A. Definition and Importance of Furnace Draft

Furnace draft refers to the pressure difference between the furnace and the surroundings. It plays a crucial role in ensuring proper combustion and heat transfer.

B. Role of Furnace Draft in Combustion Efficiency

Furnace draft affects the flow of combustion air and exhaust gases, influencing combustion efficiency. Insufficient draft can lead to incomplete combustion and increased emissions, while excessive draft can cause flame instability and equipment damage.

C. Key Components of Furnace Draft Control System

To control furnace draft, a furnace draft control system typically includes the following components:

1. Draft Sensors: Draft sensors measure the pressure difference between the furnace and the surroundings and provide feedback to the control system.
2. Damper Actuators: Damper actuators adjust the position of dampers in the air supply and exhaust systems to control the flow of combustion air and exhaust gases.

D. Control Strategies for Furnace Draft Control

There are two main control strategies for furnace draft control:

1. Manual Control: In manual control, the damper position is adjusted manually based on operator experience and judgment.
2. Automatic Control: In automatic control, the control system adjusts the damper position based on feedback from the draft sensors to maintain the desired furnace draft.

E. Step-by-step Walkthrough of Furnace Draft Control System

To better understand how furnace draft control works, let's walk through the steps involved:

1. Measurement of Furnace Draft Pressure: Draft sensors measure the pressure difference between the furnace and the surroundings and provide feedback to the control system.
2. Adjustment of Damper Position: The control system adjusts the position of dampers using damper actuators to maintain the desired furnace draft.

F. Real-world Applications and Examples of Furnace Draft Control

Furnace draft control is used in various combustion systems, including:

1. Industrial Boilers: Industrial boilers require precise control of furnace draft to ensure efficient combustion and prevent equipment damage.
2. Incinerators: Incinerators use furnace draft control to maintain the proper flow of combustion air and exhaust gases for effective waste disposal.

G. Advantages and Disadvantages of Furnace Draft Control

Furnace draft control offers several advantages, such as improved combustion efficiency, enhanced equipment protection, and reduced emissions. However, it also has some limitations, including the need for regular maintenance and calibration of draft sensors and damper actuators.

IV. Conclusion

In conclusion, combustion control is crucial in power plants to ensure efficient and safe combustion of fuel. Air/fuel ratio control and furnace draft control are two key aspects of combustion control systems.

A. Recap of the Importance and Fundamentals of Combustion Control

Combustion control is essential for maximizing energy output, minimizing emissions, and preventing equipment damage. It involves maintaining the optimal air/fuel ratio and furnace draft.

B. Summary of Air/Fuel Ratio Control and Furnace Draft Control

Air/fuel ratio control involves maintaining the desired ratio of air to fuel in the combustion process. It relies on oxygen sensors, fuel flow meters, and control valves to adjust the fuel flow rate. Furnace draft control involves maintaining the proper pressure difference between the furnace and the surroundings. It relies on draft sensors and damper actuators to adjust the damper position.

C. Future Developments in Combustion Control Technology

The field of combustion control is continuously evolving, with ongoing research and development focused on improving control strategies, enhancing sensor technology, and integrating advanced automation techniques.

Summary

Combustion control is crucial in power plants to ensure efficient and safe combustion of fuel. It involves maintaining the optimal air/fuel ratio and furnace draft. Air/fuel ratio control maintains the desired ratio of air to fuel, while furnace draft control maintains the proper pressure difference between the furnace and the surroundings. Both control systems rely on sensors and actuators to adjust the fuel flow rate and damper position, respectively. Combustion control offers numerous benefits, including improved efficiency, reduced emissions, and enhanced equipment protection. However, regular maintenance and calibration are necessary for optimal performance.

Analogy

Combustion control in power plants is like maintaining the perfect balance of ingredients in a recipe. Just as the right amount of each ingredient is crucial for a delicious dish, the optimal air/fuel ratio and furnace draft are essential for efficient and safe combustion. Too much or too little of any ingredient can ruin the recipe, just as incorrect air/fuel ratio or furnace draft can lead to inefficient combustion and equipment damage.