Marsulex Environmental Technologies (MET) contracted Alden to re-engineer a heat recovery system for flue gas reheat at Great River Energy Coal Creek Generating Station. The goal of the system was to ensure that no condensation would be present in the flue gas system as it enters the stack and vents to ambient conditions. The reheat was provided through the use of multiple available heat sources within the existing facility. A Computational Fluid Dynamics (CFD) Model Study was also peformed to simulate the operation of the system.

With the available heat from various locations in the plant analyzed, our flow experts designed the final system to remove ambient air from the boiler house and to heat that air through contact with the economizer ductwork prior to the re-heat fans. Two separate CFD models—that included convective and radiative heat transfer—were then used for final evaluation of the design. The first model included the Reheat Air System and Wet Flue Gas Desulfurization inlet ductwork. The second model was for the reheat ducting and mixing chamber, in which the reheated air mixed with the flue gas.

CFD results showed that the project goals for pressure drop, temperature rise, and mixing of ambient air with flue gas were all met.