What is SOFA?

 ### SOFA in Power Plants

In the context of power plants—particularly coal-fired thermal power plants—**SOFA** stands for **Separated Overfire Air** (also sometimes written as Separated Over Fire Air). This is a combustion technology used in boiler systems to reduce nitrogen oxide (NOx) emissions, which are harmful pollutants formed during high-temperature fuel combustion.

#### How SOFA Works

- **Basic Principle**: In a coal-fired boiler, primary air carries pulverized coal into the furnace for burning, while secondary air supports the combustion. Overfire air (OFA) is injected above the main combustion zone to complete burning and control emissions. SOFA specifically "separates" this OFA into distinct ports or nozzles, allowing for staged combustion.

- **Staging Effect**: By delaying the introduction of some air (the separated portion), the combustion process creates oxygen-poor zones initially (reducing NOx formation) followed by oxygen-rich zones for full burnout. This lowers NOx by 20-50% without major hardware changes, making it cost-effective for retrofitting existing plants.

- **Adjustment and Optimization**: SOFA flow rates are often tuned using numerical simulations (e.g., computational fluid dynamics) to balance NOx reduction with efficiency and unburned carbon levels. For instance, increasing SOFA proportion can drop NOx concentrations significantly while maintaining boiler performance.

#### Applications in Power Plants

- **Common Use**: Widely applied in utility boilers for low-NOx compliance (e.g., under environmental regulations like the U.S. EPA standards). It's especially useful in large units (e.g., 300-600 MW).

- **Example**: In a 330 MW electric combustion boiler, SOFA adjustments based on simulations have been shown to predict and minimize NOx emissions using operational parameters like load, oxygen levels, and burner loads.

- **Related Systems**: Often combined with low-NOx burners or other air staging techniques. In some plants, like Turkey's Yatağan Thermal Power Plant, the boiler "sofa system" refers to the structural framework supporting these air injection setups, analyzed for static/dynamic loads.

This term is technical jargon in the energy sector and unrelated to furniture (like a literal "sofa") or other common meanings. If you meant something else (e.g., a specific plant, acronym variation, or even "separation of forces" in engineering), provide more details for a refined explanation!