As a subject matter expert in the field of power generation and thermodynamics, I can provide an in-depth explanation of duct firing.

Duct firing is a technique used in combined cycle power plants to enhance the thermal efficiency and output power of the plant. In a combined cycle power plant, a gas turbine generates power by burning fuel in a combustion chamber. The exhaust gases from the gas turbine, which are still at high temperature, are then used to produce steam in a heat recovery steam generator (HRSG). This steam is then used to drive a steam turbine, which generates additional power.

The concept of duct firing involves injecting additional fuel into the exhaust gas stream before it enters the HRSG. This additional fuel is burned in the duct, which is essentially a combustion chamber located in the exhaust gas path. The combustion of this fuel generates more heat, which is then absorbed by the HRSG to produce more steam or higher pressure steam.

The benefits of duct firing include:


1. Increased Thermal Efficiency: By utilizing the heat from the exhaust gases more effectively, duct firing improves the overall thermal efficiency of the power plant.


2. Higher Power Output: The additional steam or higher pressure steam produced by the HRSG allows the steam turbine to generate more electricity.


3. Flexible Operation: Duct firing provides a flexible way to adjust the power output and thermal efficiency of the plant according to the demand and operating conditions.


4. Environmental Benefits: Since duct firing allows for more efficient use of fuel, it can lead to lower emissions per unit of electricity generated.

However, there are also some considerations and challenges associated with duct firing:


1. Equipment Design: The HRSG and other components must be designed to handle the increased heat and pressure resulting from duct firing.


2. Fuel Type: The type of fuel used for duct firing must be compatible with the existing fuel and the combustion process in the HRSG.


3. Maintenance and Reliability: Additional combustion in the duct can lead to increased wear and tear on equipment, requiring more frequent maintenance and potentially affecting reliability.


4. Economic Factors: The cost of installing and operating duct firing systems must be weighed against the benefits in terms of increased power output and efficiency.

In conclusion, duct firing is a valuable technique for optimizing the performance of combined cycle power plants. It can lead to significant improvements in thermal efficiency and power output, while also offering environmental and economic benefits. However, it requires careful consideration of equipment design, fuel compatibility, and operational factors to ensure its successful implementation.

read more >>

Duct firing allows production of more and/or higher pressure steam in the heat recovery steam generator (HRSG). The additional and/or higher pressure steam produced in the HRSG allows more electricity to be produced in the steam turbine downstream of the HRSG.Feb 1, 2006read more >>