Verdantas Flow Labs was engaged by a confidential client to support the implementation of a wet flue gas desulfurization (FGD) system at a 4x210 MW thermal power plant in Bihar, India. The project involved a partial bypass reheat configuration, where 20% of untreated hot flue gas bypasses the absorber and mixes with the cooler, scrubbed gas before entering the stack. Initial computational fluid dynamics (CFD) modeling revealed insufficient mixing between the hot and cold gas streams, resulting in thermal stratification that extended several liner diameters into the stack. This raised concerns about potential solids buildup and stack liquid discharge (SLD), both of which could impact long-term performance.

To address these challenges, our team conducted a comprehensive study that combined CFD simulations with scaled physical flow modeling. The physical model, built at a 1:11.65 scale, replicated the absorber outlet ducting and lower portion of the stack liner, allowing for detailed observation of gas flow behavior, liquid film dynamics, and droplet re-entrainment. We evaluated baseline flow conditions and tested various configurations of liquid collectors and flow control devices to optimize performance.

The study led to the design of a robust liquid collection and drainage system, including 16 custom-engineered collectors strategically placed throughout the ductwork and stack liner. These devices were designed to capture condensate and entrained liquid, minimizing re-entrainment and preventing SLD.

To further support long-term performance, our team conducted a plume downwash analysis using CFD modeling of the upper stack and surrounding shell. Simulations under both maximum and low-load conditions confirmed that the flue gas plume remained clear of the stack shell, eliminating the need for structural modifications.