Williams Station Unit 1, a 610 MW coal-fired power plant owned by South Carolina Electric & Gas (SCE&G), installed a wet flue gas desulfurization (WFGD) system to remove sulfur dioxide (SO₂) from the flue gas stream. This system plays a critical role in reducing emissions and meeting environmental compliance standards. However, the design presented two major challenges: preventing liquid pullback into absorber inlet ducts, which could cause operational inefficiencies and maintenance issues, and optimizing spray coverage inside the absorber vessel to ensure uniform gas-liquid contact and maximize SO₂ removal efficiency. 

Verdantas (formerly Alden Research Laboratories) employed a dual-modeling strategy combining scaled physical flow modeling and Computational Fluid Dynamics (CFD) simulations to address these challenges. Velocity inlet profiles were derived from field measurements to ensure accurate representation of plant conditions. CFD simulations using ANSYS-Fluent® evaluated ventilation system performance under three locomotive/track configurations representing critical scenarios with trains idling at the head end of the tracks. Analyses focused on: 

• Predicting dispersion of diesel exhaust and cooling fan flows. 

• Assessing the effectiveness of proposed exhaust hoods and general ventilation systems. 

• Verifying compliance with target emission concentration limits and ambient temperature requirements. 

Performance Criteria and Metrics 

• Air Quality: Maintain NO₂ and PM concentrations below OSHA and ASHRAE thresholds (e.g., NO₂ < 3 ppm, PM₂.₅ < 35 µg/m³). 

• Temperature Control: Ensure ambient air temperature remains below 85°F under full enclosure conditions. 

• Ventilation Rates: Validate airflow rates exceeding 60,000 CFM per exhaust hood to achieve pollutant capture efficiency >90%. 

• Compliance: Confirm system meets NFPA 130 and local building code requirements for enclosed rail stations. 

Key Outcomes 

• Multiple exhaust hood configurations were tested to optimize pollutant capture and airflow distribution. 

• CFD modeling confirmed that the proposed ventilation design meets specification and code requirements for air quality and thermal conditions. 

• Robust system design accommodates variable operational scenarios, ensuring passenger and worker safety during station operations. 

This analysis provided critical validation for the South Station expansion, enabling safe enclosure of the platform areas without compromising regulatory compliance or operational efficiency.