Case Study: FGD Duct Lining — Long-Term Service Life

Sulfuric Acid Condensation

Occurs when flue gas temperatures fall below the acid dew point (120–150°C, SO₃-dependent), depositing acid directly on duct wall surfaces.

Chloride Attack

HCl in the flue gas compounds the chemical load on lining surfaces throughout normal operation.

Particulate Abrasion

The scrubbing process runs continuously against lining surfaces, requiring ceramic-grade abrasion resistance.

Thermal Cycling

Repeated mechanical stress from startup, shutdown, and load changes. Coatings with insufficient flexibility develop microcracks — providing acid direct access to the substrate.

Critical Variable

The Cold Wall Effect

The temperature gradient between the hot inner gas stream and the cooler outer duct wall drives acid condensation at the wall surface during normal operation. This is a continuous thermodynamic condition, not an intermittent risk. Lining systems not specified to account for it experience accelerated degradation at the substrate interface.

Chemical Resistance

Concurrent resistance in aggressive acid and alkali environments via ceramic-filled high-functionality epoxy novolac formulation.

Abrasion Resistance

Ceramic-reinforced matrix to withstand continuous particulate impingement from the scrubbing process.

Flexibility

Reactive flexibilizing agents allow the coating to accommodate substrate expansion and contraction through thermal cycling without microcracking. Primer selection varied by location based on substrate condition and exposure requirements.

The lining has been in continuous service since Spring 1994. Minor annual touchup has maintained full performance.