Flue Gas Treatment

Flue gas treatment (FGT) has become a focus of electric utilities and industrial operations due to increasingly tighter air quality standards.  As companies seek to comply with air quality regulations using cost-effective fuels, the need arises for effective flue gas treatment options.

A variety of calcium-based materials are proven reagents for treating acidic air emissions.  The primary categories of calcium reagents used in FGT applications are:

• Calcium hydroxide (hydrated lime)
• Calcium oxide (quicklime)
• Calcium carbonate (limestone)

These reagents have differing characteristics and can be effectively employed at different points in the process.  Calcium-based reagents are effective at removing acid gases including:

• SO₂ – Sulfur dioxide
• H₂SO₄/SO₃ – Sulfuric acid/Sulfur trioxide
• HCl – Hydrogen chloride
• HF – Hydrogen fluoride

SO₂ treatment and SO₃ treatment are the most common needs for acid gas control.  However, recent MACT regulations for utility and industrial boilers are driving dry sorbent injection (DSI) use for multi-pollutant removal situations.

Mississippi Lime has a wide range of calcium-based reagents and the required expertise to support your application needs.

Dry Sorbent Injection

A dry sorbent injection system directly injects a fine powder of dry sorbent into the duct downstream of the combustion chamber. The alkaline sorbent reacts with acids in the flue gas and the dry reaction products are removed in the particulate collector or in the wet scrubber liquor. DSI technology was originally developed in the late 1980s to respond to the EPA regulations on emission control of acid gasses for older power plants that required low-cost, easy retrofitting solutions.

Dry sorbent injection of hydrated lime is an effective approach for acid gas control, primarily due to its simplicity in process configurations, low capital costs and in contrast to the sodium-based sorbents, the absence of ash handling concerns. Bag filters have been favored because the deposited dust layers contain unreactive sorbent that further reduces the acid gas content in the exhaust gases. DSI on ESP systems have been proven effective, especially with SO3 mitigation.

The choice of hydrated lime as a dry sorbent provides a robust, ready to use material. Mississippi Lime is an industry leader in the development of dry sorbent injection industry for hydrated lime control of acidic gases.

Mississippi Lime offers three products for DSI applications:

• Standard Hydrated Lime
• Hydrated Lime FGT
• High Reactivity Hydrated Lime

To request more information, please contact us at technicalservices@mlc.com