Rabigh Power Station in Saudi Arabia operates as an oil-fired facility with Pennguard® borosilicate block lining in its wet absorber outlet ductwork and stack. Under certain conditions, the plant bypasses wet absorbers, allowing flue gas at approximately 170 °C to enter the stack liner. In 2008, a thermal shock event damaged the lining, prompting Hadek to recommend installing a quench system in the bypass duct to limit gas temperatures entering the stack. The plant needed a solution to reduce flue gas temperatures from 170 °C to 100 °C during bypass operations, while preventing thermal stresses and surface wetting inside the ductwork and stack. The design had to ensure uniform cooling, rapid droplet evaporation, and minimal maintenance requirements. 

Our Solution 

Verdantas (formerly Alden Research Laboratory) was contracted to design and optimize the quench spray header system using advanced CFD simulations. Calculations were performed to determine the energy removal required based on flue gas mass flow and heat capacity, and the water injection rate was calculated using the heat of vaporization of water. Multiple nozzle types, including axial and full-cone sprays, were modeled with varying densities and grid locations to achieve the fastest droplet evaporation, avoid wall wetting, and minimize temperature gradients entering the stack. The final design provided the number, location, spacing, and nozzle specifications for the quench system, delivering the target temperature reduction with uniform distribution and minimal surface wetting. This solution ensured reliable protection of the Pennguard lining during FGD bypass mode and offered a robust, cost-effective, and maintainable design. 

Project Highlights 

• Used CFD modeling to evaluate multiple nozzle configurations and spray patterns. 

• Collaborated with Hadek to combine expertise for a robust, cost-effective, and easily maintained design. 

• Achieved target gas temperature reduction to 100 °C with uniform distribution and minimal surface wetting.